JPH07327024A - Frequency selective optical filter - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a frequency selective optical filter that does not generate unnecessary optical output and has little crosstalk light. [Configuration] Arrayed waveguide diffraction grating type optical multiplexer / demultiplexer (21)
The input optical path (1) and the output optical path (2) are connected to the waveguide pair in the first input / output waveguide group (23), The optical path (2
8) was connected, and an optical switch (9) was inserted in the middle of each folding optical path (28). [Effect] Since the optical signal input from the input optical path is not directly output to the output optical path,
The above object is achieved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency selective optical filter for selecting and extracting an optical signal of a desired optical frequency from a plurality of frequency multiplexed optical signals in an optical frequency division multiplexing transmission system.

[0002]

2. Description of the Related Art Conventionally, a Fabry-Perot interferometer or a Mach-Zehnder interferometer has been used as a frequency selective optical filter for selecting and extracting only an optical signal of a desired optical frequency from a plurality of frequency-multiplexed (synonymous with wavelength-multiplexed) optical signals. An optical filter applying the above principle has been used.

This type of frequency selective optical filter is constructed, for example, by cutting an optical fiber and polishing both cut surfaces so as to face each other, so that light is multiply reflected between both cut surfaces. . At the time of this multiple reflection, only the light of a certain specific wavelength (optical frequency) is in phase with each other among the multiple reflected lights, strengthens each other, and is transmitted through the optical filter.
Here, the value of the transmitted wavelength (optical frequency) continuously changes depending on the distance between the two cut surfaces. Therefore, by changing this distance, it is possible to select only the optical signal of the desired wavelength (optical frequency).

However, in the above-mentioned frequency selective optical filter, the value of the wavelength (optical frequency) to be transmitted is continuous (analog).
Since it can only be controlled in a targeted manner, there is an essential drawback that analog control with high accuracy is required when the number of frequency multiplexing is large. In order to solve this drawback, a circuit including an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer having a loopback optical path and an optical switch has been proposed.
A frequency selective optical filter using this arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path is shown in FIG.
This will be described with reference to FIG.

For details of this conventional example, Japanese Patent Application No. 5-233874 (Tachikawa, Kawauchi, Takahashi, Inoue, "Array waveguide diffraction grating type optical multiplexer / demultiplexer with loopback optical path" September 20, 1993) Submission, Japanese Patent Application No. 4-260222 (1992)
Priority claim based on September 29, 2009).

FIG. 17 shows the operating principle of a conventional frequency selective optical filter. In the figure, reference numerals 1 and 2 denote optical fiber transmission lines. In the optical fiber transmission line 1, n-wave signal lights having optical frequencies f ₁ , f ₂ , ..., F _n are frequency-multiplexed and propagated. . In the frequency selective optical filter 3, the incoming multiplexed optical signal is first separated by the demultiplexer 4 into n signal lights having different optical frequencies (wavelengths), and the corresponding optical fibers 8a,
8b, ..., 8n are propagated. Here, the optical fiber 8
Optical switches 9 are provided in the middle of a, 8b, ..., 8n.
, 9n are provided, and only the optical switch 9i corresponding to the selected optical frequency f _i is turned on. The signal light of the optical frequency f _i thus selected is output to the optical fiber transmission line 2 through the multiplexer 5.

In the above-mentioned patent application, Tachikawa et al. Disclose a technique in which the demultiplexer 4 and the multiplexer 5 according to this principle are configured by one arrayed waveguide diffraction grating type optical demultiplexer. . Based on this technique, a conventional frequency selective optical filter used for realizing the principle shown in FIG. 17 is shown in FIG.
Shown in. In FIG. 18, reference numeral 21 denotes an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer, which includes a first input / output waveguide group 23 including a plurality of waveguides 23a to 23p, a slab waveguide 24,
The arrayed waveguide diffraction grating 26, the slab waveguide 25, and the second input / output waveguide group 27 including a plurality of waveguides 27a to 27p are formed on the same substrate. Also,
Reference numeral 18 is an optical fiber group composed of optical fibers 18a to 18p, and 9 is an optical switch group composed of optical switches 9a to 9p. In FIG. 18, reference numerals 23a to 23p indicating the respective waveguides of the first input / output waveguide group 23 are followed by I1 to I16.
Although the symbols up to are added in parentheses, these I1 to I16 are indexes that indicate the order of the waveguide in the first input / output waveguide group 23. Further, indexes J1 to J16, K1 to K16, and S having the same purpose as these indexes I1 to I16.
1 to S16 denote the waveguides 27a to 27p, and
After the reference numerals 18a to 18p indicating the optical fiber and the reference numerals 9a to 9p indicating the optical switch, they are respectively added in parentheses. For convenience of explanation, for example, when specifying the waveguide 23g, the waveguide 23g (I7) or 23 (I
As in 3), the waveguide is specified by the notation using the index.

Describing according to the above notation, each optical fiber 18 (Kj) is connected to each waveguide 27 (Jj) of the second input / output waveguide group 27 and each waveguide of the first input / output waveguide group 23. It connects to the waveguide (Ij), and the waveguide 27
The signal light output from (Jj) is transmitted to the waveguide 27 (J
It plays a role as a loop-back optical path returning to the waveguide 23 (Ij) corresponding to j). In addition, an optical switch 9 (S) is provided in the middle of each optical fiber 18 (Kj).
j) is provided. The optical fiber transmission line 1 plays a role as an input optical path. The optical fiber transmission line 2 also serves as an output optical path.

Generally, the number of waveguides M and N of the first input / output waveguide group 23 and the second input / output waveguide group 27 of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21 is arbitrary, but here Then, for simplicity, M = N = 16, and the optical fiber transmission line 1 has 16
Each waveguide 23a (I of the first first input / output waveguide group 23)
1), 23b (I2), ..., 23p (I16), which is connected to the waveguide 23h (18), and the optical fiber transmission line 2 is similarly formed by each waveguide of the 16 second input / output waveguide group 27. Two
7a (J1), 27b (J2), ..., 27p (J16)
Of these, it is connected to the waveguide 27h (J8).

[0010] In the conventional example shown in FIG. 18, an optical frequency f _1, f _2, ..., 16-wave frequency-multiplexed optical signal of f _16, an array waveguide diffraction grating type after propagating through the optical fiber transmission line 1 Medium It is input to the waveguide 23h corresponding to the index I8 in the first input / output waveguide group of the optical multiplexer / demultiplexer 21. In the slab waveguide 24, this frequency-multiplexed optical signal spreads due to diffraction and is input to a plurality of waveguides forming the arrayed waveguide diffraction grating 26.

The frequency-multiplexed optical signal is condensed by the slab waveguide 25 after propagating through the arrayed waveguide diffraction grating 26. The convergence position will differ depending on the optical frequency. The arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21 shown in FIG. 18 is an application of this principle, and is designed to exhibit the frequency multiplexing / demultiplexing characteristics as shown in FIG.

For example, when a frequency-multiplexed optical signal consisting of optical signals of optical frequencies f _{1 to} f ₁₆ is input to the waveguide 23h (I8) of the first input / output waveguide group 23, as shown in FIG. , The optical signal of the optical frequency f ₁ is the second input / output waveguide group 2
7 from the waveguide 27a (J1), the optical signal with the optical frequency f ₂ from the waveguide 27b (J2), ..., The optical signal with the optical frequency f ₁₆ from the waveguide 27p (J16), and so on. fj (j = 1, 2, ..., 16) is the corresponding waveguide 2
7 (Jj).

When a frequency-multiplexed optical signal is input to the waveguide 23i (I9) having an index larger than that of the waveguide 23h (I8) by one, each optical signal (optical Frequencies f _{1 to} f ₁₆ ) and the respective waveguides 27 in the second input / output waveguide group 27 for outputting these
The relationship with (Jj) is shifted by one waveguide as shown in FIG. 23, and the optical signal of the optical frequency f ₂ is transmitted from the waveguide 27a (J1) to the optical signal of the optical frequency f _16. It is taken out from the waveguide 27o (J15).

Further, since the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21 has a symmetrical structure, the frequency multiplexing / demultiplexing characteristic also exhibits reversibility as shown in FIG. That is, for example, a frequency-multiplexed optical signal composed of optical signals of optical frequencies f _{1 to} f _{16 is} a waveguide 27h (J
8), the optical signal of the optical frequency f ₂ is from the waveguide 23b (I2), ..., The optical signal of the optical frequency f ₁₆ is from the waveguide 23p (I16), as shown in FIG. Thus, the optical frequency fj (j = 1, 2, ..., 16) is taken out from the corresponding waveguide 23 (Ij).

When a frequency-division-multiplexed optical signal is input to the waveguide 27i (J9) whose index is larger than that of the waveguide 27h (J8) by one, each optical signal (optical Frequencies f _{1 to} f ₁₆ ) and the respective waveguides 23 in the first input / output waveguide group 23 for outputting these
Becomes the relationship between (Ij) is shifted waveguide one roll as shown in FIG. 23, the optical signal of the optical frequency f ₂ from the waveguide 23a (I1), ..., the optical signals of the optical frequency f ₁₆ is It is taken out from the waveguide 23o (I15).

The signal light of the optical frequency fj extracted from each of the waveguides 27 (Jj) of the second input / output waveguide group 27 is an optical fiber (loopback optical path) 18 (K).
j) Propagate through. Here, the optical switch 9 (Sj) provided in the middle of each optical fiber (loopback optical path) 18 (Kj) is either in an ON state in which light is transmitted or in an OFF state in which light is blocked based on a command from the outside. Take that state. The optical signal propagating through the loopback optical path in which this optical switch is in the ON state is transmitted from the first input / output waveguide 23 to the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 2.
It is input to 1 again.

The signal light returned to the first input / output waveguide group 23 is output to the second input / output waveguide group 27 by the same action as that of the first time. What is important here is that the j-th optical fiber (loopback optical path) 18 (Kj) is connected to the j-th waveguide 23 (Ij) in the first input / output waveguide group 23. Since the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21 is designed so as to exhibit the frequency multiplexing / demultiplexing characteristics as shown in FIG. 19, the waveguide 23 (I
The signal light of the optical frequency fj input from j) is output from 27 (J8) in the second input / output waveguide. Thus
Optical fiber (loopback optical path) 18 (Kj) (j =
1, 2, ..., 16) and the switch 9 (S
The signal light of the optical frequency fj re-inputted to the waveguide 23 (Ij) via j) is sent to the optical fiber transmission line 2 from the same line 27 (J8) regardless of the value of the index j.

On the other hand, since the optical signal propagating in the loopback optical path in which the optical switch 9 (Sj) is in the OFF state is not re-input to the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21, it is sent to the optical fiber transmission path 2. It will not be sent out.

Therefore, only the optical switch 9 (Si) provided in the optical fiber (loop pack optical path) 18 (Kj) through which the light of the desired optical frequency propagates is turned on,
When the other optical switch 9 is turned off, only the light of the desired optical frequency is output to the optical fiber transmission line 2 among the frequency-multiplexed signal lights propagating in the optical fiber transmission line 1. FIG. 20 shows an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21.
23 shows the relationship between the optical switch 9 (Sj) to be turned on and the selected optical frequency fj when the frequency multiplexing / demultiplexing characteristic of is designed as shown in FIG.

Thus, in the conventional frequency selective optical filter shown in FIG. 18, the signal light of a desired optical frequency can be selected by digital control in which only the corresponding optical switch 9 (Sj) is turned on. It is possible and does not require high-precision analog control even when the number of frequency multiplexes increases.

If the optical switch 9 is constructed as shown in FIG. 21 and the loopback optical path 18 is formed by a waveguide, all the frequency selective optical switches shown in FIG. 18 are formed on a single waveguide substrate. It is also possible to integrate. Here, the 2 × 2 optical switch 51 shown in FIG. 21 has a 3 dB coupler 51 formed by a quartz waveguide on a quartz waveguide substrate 512.
4, 515 form a two-beam interference system. Here, an electric current is passed through the heater 513 to change the temperature of a specific portion of the waveguide, and the ON / OFF switch operation between the input / output optical paths 517 and 519 is realized by the change in the refractive index due to the temperature change.

In FIG. 21, the input / output optical path 51
The reason why 7,519 is connected to the diagonal position of the 2 × 2 optical switch 51 is to obtain an ON / OFF switch operation with a high extinction ratio. For details of this fact, see the literature (Kominato et al., IEICE Transactions CI, vol. J73-C-
I, No. 5, pp. 354-359, 1990 5
Month).

[0023]

However, the conventional frequency selective optical filter described with reference to FIG. 18 has the following problems. <Problem 1> Light of a specific optical frequency is always output. <Problem 2> Leakage (crosstalk) light cannot be removed. <Problem 3> Optical switches are required for the number of frequency division multiplexing. The above problems will be described in detail below.

<Problem 1> Regarding “The light of a specific optical frequency is always output”, in the conventional example shown in FIG. 18, the optical frequency is included in the frequency-multiplexed optical signal propagated through the optical fiber transmission line 1. When the light of f ₈ is included, only the light of the optical frequency f ₈ does not pass through the optical fiber (loopback optical path) 18, and 23h (18) in the first input / output waveguide 23, the array waveguide Waveguides 27h in the second input / output waveguide group 27 in the diffraction grating 2
(J8) is output to the optical fiber transmission line 2 via each (see FIG. 19). Therefore, the light having the optical frequency f ₈ is always output to the optical fiber transmission line 2 regardless of the state of the 15 optical switches 9. FIG. 22
FIG. 22 is a diagram showing an example of measurement of transmission characteristics of the conventional frequency selective optical filter shown in FIG. 18, and FIG. 22 (1) shows a case where all the optical switches 9 (Sj) are in the OFF state.

Therefore, if the light of the optical frequency f ₈ is mixed and transmitted in the optical fiber transmission line 1, even if the desired optical frequency f _j (j ≠ 8) is selected, the signal light of the fj is obtained. At the same time, the light of f ₈ is also output. In particular, the optical frequency f
signal light j is because the light of the optical frequency f ₈ relative to pass through the arrayed waveguide grating type optical demultiplexer 21 twice not pass once, the optical frequency f ₈ as the interference of light There is less loss. Therefore, the S / N of the desired signal light is significantly deteriorated. FIG. 22 (2) shows a desired optical frequency f ₁₃
It is an example of measurement of filter characteristics when selected. The transmission loss at f ₈ which is the interfering light is smaller by 7 dB.

<Problem 2>"Leakage(Crosstalk)"
`` Cannot remove light '' In a frequency selective optical filter that extracts only the signal light of the desired optical frequency from the frequency-multiplexed signal light, when light of the unselected optical frequency leaks into the output, it becomes noise as crosstalk light. Is a factor that deteriorates the S / N of the desired signal light. When the total optical power of the leaked light becomes 0.4 times (-4 dB) of the desired signal light, the reception sensitivity deteriorates by 3 dB (for example, K. Oda and
H. Toba, IEEE Journal of L
lightwave Technology, Vol. n
o 5/6, 1993, pp, 809, Fig. 10). This is extremely inconvenient because it requires transmitting a signal with twice the optical power in order to realize the same code error rate.

However, the frequency multiplexing / demultiplexing characteristic (see FIG. 19) of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21 used in the conventional frequency selective optical filter described with reference to FIG. This can only be achieved incompletely in an actual device due to the precision with which the waveguide diffraction grating 26 is created. Therefore, for example, 23h (I8) in the first input / output waveguide 23
The optical frequencies f ₁ , f ₂ , ..., F ₁₆ (where f ₈
The signal light of the 15 waves of frequency multiplexing (excluding
It is directly output to 27h (J8) in the input / output waveguide 27 of.

For example, in the measurement example shown in FIG.
Since all the optical switches 9 (Sj) are in the OFF state,
Originally, it should not transmit any light except for transmitting the light having the optical frequency f ₈ generated in the above-mentioned first defect. However, in practice, light other than f ₈ is -33 to -36.
A transmittance of about dB has been observed.

Therefore, for example, when the light of the optical frequency f ₁₃ is selected as shown in FIG. 22 (2), crosstalk of about -23 dB occurs for each signal light. Since the crosstalk can be generated by the signal light of all optical frequencies other than the selected optical frequency, the total optical power of the crosstalk light (leakage light) is (N-2) times (N is the frequency multiplex number). Become. Therefore, if the frequency multiplexing number increases and becomes N = 100, for example, the total optical power of the crosstalk light becomes approximately −3 dB, and the reception sensitivity becomes 3 as described above.
It deteriorates by more than dB.

In addition, with respect to the signal light of the selected optical frequency, there is crosstalk due to the similar mechanism.
For example, consider the case of FIG. 22 (2), that is, the case where the signal light of the optical frequency f ₁₃ is selected. The signal light of the optical frequency f ₁₃ input to the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21 through the optical fiber transmission line 1 and the waveguide 23h (I8) is originally the waveguide 27m (J13) and the optical switch 9m.
(S13), through the waveguide 23m (I13), and through the waveguide 27h (J8), output to the optical fiber transmission line 2. However, a small part of the signal light having the optical frequency f ₁₃ input from the waveguide 23h (I8) is directly transmitted to the waveguide 27h.
(J8) is output as crosstalk light. For example, referring to FIG. 22A, −36 dB of the signal light of the optical frequency f ₁₃ is directly output to the optical fiber transmission line 2. As shown in FIG. 22 (2), the intensity of the signal light of the optical frequency f ₁₃ output through the original path is −1.
Since it is 3 dB, there is a crosstalk of subtraction -23 dB.

Unfortunately, since this crosstalk light has the same optical frequency as the signal light to be selected, it interferes coherently. That is, not the light intensity but the optical electric field is added. Therefore, for example, even with a crosstalk of only -23 dB (0.005 times),
If the light intensity is used, an intensity fluctuation of −11.5 dB may occur, which is a factor that significantly deteriorates the S / N of the signal light, which is very inconvenient.

<Problem 3> In the conventional frequency selective optical filter described with reference to FIG. 18 regarding “the optical switch is required for the number of frequency multiplexing”, as shown in FIG. 20, the optical frequency to be selected is selected. For each, one corresponding ON / OFF type optical switch is required. In other words, N optical switches are required in order to extract any optical signal from the multiplexed light of the frequency multiplexing number N. Therefore, when the frequency multiplexing number N increases, it is necessary to provide an extremely large number of optical switches, which is costly. Further, it may cause a decrease in reliability.

The present invention has been made in view of the above circumstances, in which there is no unnecessary light output, crosstalk (leakage) light is small, and in some cases, the number of optical switches required for control is small. It is an object of the present invention to provide a frequency selective optical filter that can be used.

[0034]

In order to solve the above problems, the present invention provides a frequency selective optical filter using an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer,
The input optical path and the output optical path to the filter are connected to the input / output waveguides on the same side of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer, while the other side of the arrayed waveguide diffraction grating optical multiplexer / demultiplexer is connected. The most important feature is to connect a folded optical path equipped with an optical switch to the input / output waveguide. Hereinafter, the invention according to each claim of the present application as a means for solving the above problems will be sequentially described.

First, the invention according to claim 1 discloses a typical configuration example thereof in FIG. The present invention can be expressed as follows when the reference numerals of corresponding parts in FIG. N (N
The first input / output waveguide group (2
3) and a second input / output waveguide group (2
7) and an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer (2
1), at least one input optical path (1) connected to the waveguide of the first input / output waveguide group, and a waveguide adjacent to the waveguide to which the input optical path is connected, respectively. At least one output optical path (2) connected to each other and two waveguides adjacent to each other in the second input / output waveguide group (27), at least not including overlapping waveguides. It has at least one folded optical path (28) for connecting between two waveguides of a pair of waveguides, and an optical switch (9) arranged in the middle of said at least one folded optical path. Characteristic frequency selective optical filter.

According to the present invention, the input optical path and the output optical path to the filter are connected to the input / output waveguide group on the same side of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer. The light directly output from the optical path to the output optical path does not exist in principle. Therefore, unlike the conventional example in which the input optical path and the output optical path are connected to different input / output waveguides, light of a specific frequency is always output regardless of the ON / OFF state of the optical switch. The situation that would end up is avoided. At the same time, the crosstalk light, which is unavoidable due to the imperfections in the fabrication accuracy of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer, does not have a component directly coupled from the input optical path to the output optical path. Thus, by providing a plurality of folding optical paths each having an optical switch in the input / output waveguides on the opposite side of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer, there is no unnecessary optical output, which is an object of the present invention, and crossing is performed. Talk (leakage)
It becomes possible to construct a frequency selective optical filter with less light.

Next, the invention according to claim 2 discloses a typical configuration example thereof in FIG. The present invention can be expressed as follows when the reference numerals of corresponding parts in FIG. N (N
The first input / output waveguide group (2
3) and a second input / output waveguide group (2
7) and an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer (2
1), an input optical path (1) connected to the v-th (v is an integer) waveguide of the first input / output waveguide group, and the w-th (w) of the first input / output waveguide group. Is an integer) and the output optical path (2) is connected to the waveguide, and Mod [w-v +
N, N] = Mod [ts + N, N] or Mod [v
At least one set of s selected from a combination of integers s and t satisfying −w + N, N] = Mod [ts−N, N],
At least one folded optical path (2 for transmitting a light signal from the sth waveguide to the tth waveguide of the second input / output waveguide group, which is a folded optical path corresponding to t.
8) and an optical switch (9) disposed in the middle of the at least one folding optical path, a frequency selective optical switch.

In the invention of claim 1, the folded optical path is connected to two adjacent waveguides in the second input / output waveguide group, and the input optical path and the output optical path are the first optical path.
The two input / output waveguide groups are connected to the adjacent two waveguides. However, in the invention according to claim 2, the limitation of the “adjacent two waveguides” is removed, and the second input / output waveguide is formed. A waveguide that connects two waveguides separated by at least one waveguide in the waveguide group by a folded optical path, and accordingly connects the input optical path and the output optical path in the first input / output waveguide group. Is a change. According to the invention of claim 2, the same operation as that of the invention of claim 1 can be obtained, and the transmission loss can be made uniform for each optical frequency.
Because, according to the present invention, an optical signal of a certain optical frequency in the frequency-multiplexed signal reaches the return optical path from the input optical path through the first input / output waveguide group and the second input / output waveguide group. Even if the path up to is a path with a large transmission loss, this optical signal is returned by the return optical path and then output through the second input / output waveguide group and the first input / output waveguide group. This is because it is possible to follow a path with a small transmission loss when returning to the optical path.

Next, the invention according to claim 3 discloses a typical configuration example thereof in FIG. 6, and in the configuration according to claim 2, the absolute value of the t-s is particularly N / S. It is characterized by being limited to 2.

According to the present invention, by limiting the above t-s, compared to the case where this limiting is not performed,
The optical frequency interval of the frequency-multiplexed optical signal input from the input optical path can be halved.

Next, the invention according to claim 4 discloses a typical configuration example thereof in FIG. 8 or FIG. The present invention can be expressed as follows when the reference numerals of the corresponding parts in FIG. 8 or FIG. Array waveguide diffraction grating having a first input / output waveguide group (23) composed of N waveguides (N is an integer) and a second input / output waveguide group (27) composed of N waveguides Type optical multiplexer / demultiplexer (21), a first input optical path (1) connected to the v-th (v is an integer) waveguide of the first input / output waveguide group, and the first input / output optical path. W-th output waveguide group (w
Is a first output optical path (2) connected to the waveguide
And a second input optical path (1 ′) connected to the v′-th (v ′ is an integer) waveguide of the second input / output waveguide group.
And a second output optical path (2 ′) connected to the w′-th (w ′ is an integer) waveguide of the second input / output waveguide group, and Mod [v′− v + N, N] = Mod [s−s ′ + N,
N] is satisfied, and Mod [w−v + N, N] = Mod
[Ts−N, N] or Mod [v−w + N, N]
= Mod [ts−N, N], and Mod
[W'-v '+ N, N] = Mod [t'-s' + N,
N] or Mod [v'-w '+ N, N] = Mod [t'-s' +
N, N] is an optical path whose connection position is determined according to each combination of integers s and t and each combination of integers s ′ and t ′,
At least one first folded optical path (28) for transmitting an optical signal from the s-th waveguide to the t-th waveguide of the second input / output waveguide group, and the first input / output waveguide group A second folded optical path (28 ') for transmitting an optical signal from the s'th waveguide to the t'th waveguide of
2. A frequency selective optical filter, comprising: at least one optical switch (29) for connecting optical paths of optical signals of the same optical frequency propagating in the return optical path and the second return optical path.

The present invention can function not only as a frequency selective optical filter but also as an optical add / drop circuit.

A frequency selective optical filter according to claim 5 is
FIG. 10 discloses a typical configuration example thereof.
The present invention can be expressed as follows when the reference numerals of corresponding portions in FIG. Array waveguide diffraction grating having a first input / output waveguide group (23) composed of N (N is an integer) waveguides and a second input / output waveguide group (27) composed of N waveguides In an optical path having a type optical multiplexer / demultiplexer (21), and the connection position is determined according to each integer v, w, u satisfying Mod [w−v + N, N] = Mod [v−u + N, N]. And an input optical path (1) connected to the v-th waveguide of the first input / output waveguide group and a first optical path (1) connected to the w-th waveguide of the first input / output waveguide group. 1 output optical path (32g) and a second output optical path (32i) connected to the u-th waveguide of the first input / output waveguide group, and further Mod [wv + N , N] = Mod [v−u + N, N] = Mod [ts−N + N] An optical path whose position is determined, having at least one folded optical path (28) for transmitting an optical signal from the s-th waveguide to the t-th waveguide of the second input / output waveguide group, Furthermore, an optical switch (9) arranged in the middle of the at least one folding optical path, and at least one of the output from the first output optical path and the output from the second output optical path Optical path connecting means for outputting to the third output optical path (3
9) A frequency-selective optical switch having:

According to the present invention, the optical frequency of the optical signal output to the output optical path (2) is determined by the combination of the ON / OFF state of the optical switch (9) and the connection state of the optical path connecting means (39). It Therefore, even when there are many types of optical frequencies to be selected, the number of switches required is small.

The frequency selective optical filter according to claim 6 is
FIG. 13 discloses a typical configuration example thereof.
The present invention can be expressed as follows when the reference numerals of corresponding parts in FIG. Array waveguide diffraction grating having a first input / output waveguide group (23) composed of N waveguides (N is an integer) and a second input / output waveguide group (27) composed of N waveguides Type optical multiplexer / demultiplexer (21), a first input optical path (1) connected to the v-th (v is an integer) waveguide of the first input / output waveguide group, and the first input / output optical path. First output optical path (32g) connected to the w-th (w is an integer) waveguide of the output waveguide group
And a second output optical path (32i) connected to the u-th (u is an integer) waveguide of the first input / output waveguide group, and the v′-th of the second input / output waveguide group. The second input optical path (1 ′) connected to the (v ′ is an integer) waveguide and the w′-th (w ′ is an integer) waveguide of the second input / output waveguide group. A third output optical path (32g ') and a fourth output optical path (32i') connected to the u'th (u 'is an integer) waveguide of the second input / output waveguide group. Have
Further, v, w, u and v ′, w ′, u ′ are Mod
[W−v + N, N] = Mod [v−u + N, N] and M
od [w'-v '+ N, N] = Mod [v'-u' +
N [N]], and Mod [v'-v + N, N] = Mod [s-s' + N,
N], and Mod [w−v + N, N] = Mod [v−u + N, N] = Mod [ts−N, N] or Mod [w′−v ′ + N, N] = Mod [v ′ -U '+ N, N] = Mod [t'-s' + N, N] An optical path whose connection position is determined according to each combination of integers s and t and each combination of integers s'and t', wherein
A first folded optical path (2) for transmitting an optical signal from the s-th waveguide to the t-th waveguide of the second input / output waveguide group.
8) and a second folded optical path (28 ') for transmitting an optical signal from the s'th waveguide to the t'th waveguide of the first input / output waveguide group, and further First optical path connection means (39) for outputting at least one of the output from the first output optical path and the output from the second output optical path to the fifth output optical path (2), Second optical path connecting means (39 ') for outputting at least one of the output from the third output optical path and the output from the fourth output optical path to the sixth output optical path (2'). ), And further has at least one optical switch (29) for connecting optical paths in which optical signals of the same optical frequency propagate in the first and second returning optical paths. Is characterized by.

The present invention has the same operational effect as the invention according to claim 5, and also has the operational effect of being usable as an optical add / drop circuit.

A frequency selective optical filter according to claim 7 is
FIG. 14 discloses a typical configuration example thereof.
The present invention can be expressed as follows when the reference numerals of the corresponding portions in FIG. Array waveguide diffraction grating having a first input / output waveguide group (23) composed of N waveguides (N is an integer) and a second input / output waveguide group (27) composed of N waveguides Optical multiplexer / demultiplexer (21) and v1 of the first input / output waveguide group
A first input optical path (31d) connected to the th (v1 is an integer) waveguide and a first input optical path (31d) connected to the w1th (w1 is an integer) waveguide of the first input / output waveguide group. Output optical path (31c), a second output optical path (31m) connected to the u1th (u1 is an integer) waveguide of the first input / output waveguide group, and the first input / output The second input optical path (31l) connected to the v2th (v2 is an integer) waveguide of the waveguide group and the w2th (w2 is an integer) waveguide of the first input / output waveguide group. A third output optical path (32e) connected and a fourth output optical path (32k) connected to the u3th (u3 is an integer) waveguide of the first input / output waveguide group. , The absolute value of v1-v2 is N / 2
And v1, w1, u1, v2, w2, u2 are Mod [w1-v1 + N, N] = Mod [v1-u1 + N, N] = Mod [w2-v2 + N, N] = Mod [v2-u2 + N, N] ] Mod [w1-v1 + N, N] = Mod [v1-u1 + N, N] = Mod [w2-v2 + N, N] = Mod [v2-u2 + N, N] = Mod [t-s + N] , N] is an optical path whose connection position is determined according to each combination of integers s and t, and an optical signal is transmitted from the sth waveguide to the tth waveguide of the second input / output waveguide group. An optical switch (9) having a return optical path (28) for switching, and further arranged at least in the middle of the return optical path.
And a first optical path connecting means (39a) for distributing the output of the third input optical path (1) to at least one of the first input optical path (31d) and the second input optical path (31l).
And the first to fourth output optical paths (32c, 32)
m, 32e, 32k), and at least one output from the second optical path connecting means (39b) for outputting to the fifth output optical path (2).

According to the present invention, the number of switches can be further reduced as compared with the invention according to the fifth aspect.

The following may be considered as preferable modes for carrying out each of the inventions described above. (1) In the frequency selective optical filter according to any one of claims 4 and 6, the optical switch connects the first folding optical path and the second folding optical path according to an external signal. The state is a 2 × 2 optical switch that selects either the cross state or the bar state (claim 8). (2) In the frequency selective optical filter according to claim 4 or 6, the optical switch is configured by a 1 × 2 optical switch having first to third ports, and the first port is the first port. Connected to either one of the return optical path or the second return optical path, and connecting the second port and the third port to the first return optical path and the second return optical path, respectively. 9).

(3) In the frequency selective optical filter described in claim 5, the optical path connecting means is constituted by a 1 × 2 optical switch (claim 10). (4) In the frequency selective optical filter according to claim 6, at least one of the first optical path connecting means and the second optical path connecting means is configured by a 1 × 2 optical switch (claim 11). (5) In the frequency selective optical filter according to claim 5, the optical path connecting means is configured by a 1 × 2 optical coupler (claim 12). (6) In the frequency selective optical filter according to claim 6, at least one of the first optical path connecting means and the second optical path connecting means is configured by a 1 × 2 optical coupler (claim 13).

(7) In the frequency selective optical filter according to claim 7, the first optical path connecting means is constituted by a 1 × 2 optical switch (claim 14). (8) In the frequency selective optical filter according to claim 7, the first optical path connecting means is configured by a 1 × 2 optical coupler (claim 15). (9) In the frequency selective optical filter according to claim 7, the second optical path connecting means is constituted by a 1 × 4 optical switch (claim 16). (10) In the frequency selective optical filter according to claim 7, the second optical path connecting means is configured by a 1 × 4 optical coupler (claim 17).

(11) In the frequency selective optical filter according to claim 7, the first 1 × 2 optical path connecting means and the second 1 × 2 optical path connecting means.
× 2 optical path connecting means are arranged in parallel, and the first and second
The second optical path connecting means is constructed by inputting the output of the 1 × 2 optical path connecting means of (3) to the third 1 × 2 optical path connecting means (claim 18). (12) In the frequency selective optical filter according to claim 18, at least one of the first to third optical path connecting means is configured by a 1 × 2 optical switch (claim 19). (13) In the frequency selective optical filter according to claim 18, at least one of the first to third 1 × 2 optical path connecting means is configured by a 1 × 2 optical coupler (claim 20).

(14) In the frequency selective optical filter according to any one of claims 2, 3, 5 or 12, the input optical path and the output optical path are provided in the first input / output waveguide. A plurality of combinations are provided (claim 21). (15) In the frequency selective optical filter according to any one of claims 4, 6, 8, 9, 11 or 13, the input optical path and the output optical path are provided in the first input / output waveguide group. A plurality of combinations of optical paths are provided, and a plurality of combinations of the input optical path and the output optical path are provided in the second input / output waveguide group (claim 22). (16) In the frequency selective optical filter according to any one of claims 12, 13, 15, 17 or 20, the 1 × 2 optical coupler is constituted by a Mach-Zehnder type optical multiplexer (claim 23). ). (17) In the frequency selective optical filter according to any one of claims 1 to 23, at least one of the input optical path, the output optical path, and the folding optical path is an optical fiber transmission path (claim Item 24). (18) In the frequency selective optical filter according to any one of claims 1 to 23, an optical waveguide in which at least one of the input optical path, the output optical path and the folding optical path is formed on a substrate. (Claim 25). (19) In the frequency selective optical filter according to any one of claims 1 to 25, the first and second waveguide groups are replaced by the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer. An arrayed waveguide diffraction grating type optical multiplexer / demultiplexer composed of only waveguides connected to the input optical path, the output optical path or the folded optical path is used.

[0054]

Embodiments of the frequency selective optical filter according to the present invention will be described below in detail with reference to the drawings. In the following embodiments, the array waveguide diffraction grating type optical multiplexer / demultiplexer has the same number of input / output waveguides, or unused input / output waveguides may be deleted. However, when counting the waveguide numbers, it is assumed that there are also deleted waveguides.

(Embodiment 1) FIG. 1 is a configuration diagram showing a first embodiment of a frequency selective optical filter according to the present invention. This frequency selective optical filter has 16 waveguides for each of the first input / output waveguide 23 group and the second input / output waveguide 27 group as in the conventional example described with reference to FIG. An arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21 having a frequency multiplexing number of 16 (N = 16) is used. In this arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21, 24 and 25 are slab waveguides, and 26 is an arrayed waveguide diffraction grating. Further, it is assumed that the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21 is designed to exhibit the frequency multiplexing / demultiplexing characteristic shown in FIG. 23 as in the conventional example.

In FIG. 1, reference numerals 1 and 2 denote optical fiber transmission lines corresponding to an input optical path and an output optical path, respectively, and a waveguide 23h (I
8) and 23g (I7), respectively.

On the other hand, in each of the waveguides 27 (Jj (j = 1, 2, ..., 16)) of the second input / output waveguide group 27, an optical fiber 28 (Fj (j = 1, 1) corresponding to a folded optical path is provided. 3 ...
15)) are connected as follows. That is, the optical fiber 28a (F1) is connected to the waveguides 27a (J1) and 27b (J2), and so on.
c (J3) and 27d (J4) to the optical fiber 28c (F
3), ..., Waveguides 27o (J15) and 27p (J1)
The optical fiber 28o (F15) is connected to 6).

The optical fiber 28 (Fj (j = 1, 3
..., 15)), the optical switch 9 (Sj
(J = 1, 3, ..., 15)) is provided and takes either an ON state in which light is transmitted or an OFF state in which light is blocked based on a command from the outside.

Next, the operation of the frequency selective optical filter of the first embodiment shown in FIG. 1 will be described with reference to FIGS. 23 and 2. Optical frequency f _1, f _3, ..., 8-wave frequency-multiplexed optical signal of f _15, the first output guide of the arrayed waveguide grating type optical demultiplexer 21 after propagating through the optical fiber transmission line 1 Medium Input to 23h (I8) in the waveguide 23. Here, since the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21 exhibits the frequency multiplexing / demultiplexing characteristic shown in FIG. 23, the optical signal of the optical frequency f ₁ is the second
It propagates through the optical fiber 28a (F1) via 27a (J1) in the input / output waveguide 27. Similarly, according to FIG. 23, the optical signal of the optical frequency f ₃ is the optical fiber 28c (F3).
Inside the optical fiber 28o, the optical signal of the optical frequency f15
Each is propagated through (F15).

Here, the eight optical switches 9a (S1),
9c (S3), ..., 9o (S15) are all in the ON state, the optical fibers Fx (x = 1, 3, ..., 1)
5) The light having the optical frequency fx propagating in the inside is input to J (x + 1) in the second input / output waveguide 27, respectively. That is, the optical signal of the optical frequency f ₁ is input to J2 via the optical fiber F1 and the optical switch S1.
The optical signal of ₃ is sent through the optical fiber F3 and the optical switch S3 to J
4, the optical signal of the optical frequency f15 is the optical fiber F1.
5, input to J16 via the optical switch S15. Here, the light of the optical frequency fx input to J (x + 1) is output to the waveguide 23g (I7) in the first input / output waveguide group 23 regardless of the value of x according to FIG. It That is, the signal light having the optical frequency f ₁ input to J2, the optical signal having the optical frequency f 3 input to J4, and the optical signal having the optical frequency f ₁₅ input to J16 are all guided through the waveguide 23g.
It is output to (I7) and sent out to the optical fiber transmission line 2 connected to this waveguide 23g (I7).

Therefore, the eight optical switches 9a, 9
If only one of the optical switches c, ..., 9o, for example, the optical switch 9a (S1) is turned on and the other optical switches are turned off, only the signal light of the optical frequency f ₁ is transmitted through the optical fiber. It is output in the path 2. That is, only the optical signal of the optical frequency f ₁ is selected from the eight frequency-multiplexed lights propagating in the optical fiber transmission line 1 and output to the optical fiber transmission line 2. Similarly, if only the optical switch Sx (where x = 1, 3, ..., 15) is turned on, the optical signal of the optical frequency fx is selected. This state,
It is shown as a table in FIG.

Next, the effect of the frequency selective optical filter according to the first embodiment shown in FIG. 1 will be described with reference to FIG. FIG. 3 shows an example of measurement of optical filter characteristics when the frequency selective optical filter of the first embodiment shown in FIG. 1 is actually configured using an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with 16 wavelength multiplexing. is there. The arrayed waveguide diffraction grating type optical multiplexer / demultiplexer used in the experiment is the same as the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer used when measuring the characteristics of the conventional frequency selective optical filter shown in FIG. Is.

In FIG. 3, (1) is the transmission characteristic when all eight optical switch groups 9 are in the OFF state, and is a measurement example of the characteristic of the conventional frequency selective optical filter shown in FIG. 22 (1). Also, FIG. 3 (2)
Is an optical switch 9 (S13) of the eight optical switches.
FIG. 22 (2) shows the filter characteristics in the case of selecting the light of the optical frequency f ₁₃ in the measurement example in the case where only the light is turned on.
Corresponding to. In the frequency selective optical filter of the first embodiment, both the input optical path and the optical fiber transmission paths 1 and 2 which are the output optical paths are included in the first group of input / output waveguides 23 of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer. Since they are connected, the light of the optical frequency f ₈ is not directly output with a low loss as in the conventional example. Further, since the non-selected light does not reach the output optical path 2, as is clear from a comparison between FIG. 22 (1) and FIG. 3 (1), the non-selected light leak (crosstalk) is reduced. There is. The transmittance of the strongest crosstalk light is −33 dB in the conventional filter, but is improved to −40 dB in the filter of the first embodiment. Therefore, it is possible to improve the crosstalk by at least 7 dB as compared with the conventional example while using the same arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer, and even if the frequency multiplexing number is increased to 5 times that of the conventional example. It is possible to suppress the deterioration of reception sensitivity to the same extent as.

The crosstalk of -40 dB is
It is the residual reflection component at the birefringent medium portion inserted in the middle of the arrayed waveguide diffraction grating 26 in order to eliminate the polarization dependence of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21.

As described above, in the frequency selective optical filter of the first embodiment, the input optical path 1 and the output optical path 2 to the filter are provided.
And are connected to the input / output waveguides on the same side of the arrayed-waveguide diffraction grating optical multiplexer / demultiplexer, while the optical switches are connected to the opposite input-output waveguides of the arrayed waveguide diffraction grating-type optical multiplexer / demultiplexer. Thanks to the skillful configuration of connecting the folded optical paths, the excellent characteristics that there is no unnecessary light output and less crosstalk (leakage) light are realized.

Further, in the present embodiment 1 and the following embodiments, optical fibers are used as the folding optical path 28 and the input / output optical paths 1, 2, etc., but these are waveguides on the waveguide substrate as in the conventional example. Of course, it may be configured as.

In the first embodiment shown in FIG. 1,
An optical switch is provided by connecting a folded optical path to all the waveguides of the second input / output waveguide 27.
It is also possible to provide only a folding optical path and an optical switch corresponding to the optical frequency that needs to be selected from the eight waves of ₁ , f ₃ , ..., F ₁₅ . For example, when it is necessary to select only one of the optical frequencies f1, f3, f5, the folding optical paths 28 (F7), 28 (F9), ..., 2
8 (F15) and optical switches 9 (S7), 9 (S9),
..., 9 (S15) may be omitted. The folding optical path and part of the optical switch may be omitted in the same manner in the following embodiments.

In the first embodiment and the following embodiments, the array waveguide diffraction grating type optical multiplexer / demultiplexer with the frequency multiplex number N = 16 is used, but the array waveguide diffraction grating type with different multiplex numbers is used. Of course, an optical multiplexer / demultiplexer may be used. Generally, the frequency multiplex number of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer can be designed arbitrarily. Therefore, in this embodiment, for example, an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer of N = 2M (M is a natural number) is used. If used, it is possible to configure a frequency selective optical filter that selects any one wave from the frequency multiplexed lights of maximum M waves.

In this embodiment and the following embodiments, the arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer can have a periodicity that is an integral multiple of the wavelength multiplexing number. That is, the 16 × 16 arrayed waveguide diffraction grating type optical multiplexer / demultiplexer is
For example, it can be designed so as to exhibit a frequency multiplexing / demultiplexing characteristic as shown in FIG. 19 having a periodicity equal to the wavelength multiplexing number 16. By using the arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer designed in this way, for example, in addition to the eight waves of optical frequencies f ₁ , f ₃ , and f ₁₅ , in the optical fiber transmission line 1, the optical frequency f ₁₇ , The optical switch 9
a (S1) at the same time you can select f ₁ and f ₁₇ by the ON state.

In this embodiment, the optical fiber transmission line 2 is connected to the waveguide 23g (I7) of the first input / output waveguide 23, but instead of this, the optical fiber transmission line 1 is connected. The optical fiber transmission line 2 is inserted into the waveguide 23i (I9) located symmetrically with respect to the existing waveguide 23h (I8).
May be connected. In this case, the optical switch Sx (x =
By turning on 1, 3, ..., 15), the signal light of the optical frequency f _{x + 1} is selected. That is, the optical switch 9
The signal light having the optical frequency f ₂ is selected by a (S1), the optical frequency f ₄ is selected by the optical switch 9c (S3), ..., And the signal light having the optical frequency f ₁₆ is selected by the optical switch 9o (S15).

Further, in the present embodiment, the optical fiber transmission line 1 as the input optical line is connected to the waveguide 23h (I8) of the first input / output waveguide 23, but the optical fiber transmission line 1 is It may be connected to any one of the one input / output waveguide 23. For example, when the optical fiber transmission line 1 is connected to the waveguide Ii (i is a natural number of 1 ≦ i ≦ N), the optical fiber transmission line 2 is the waveguide I (i + 1) or the waveguide I.
It may be connected to (i-1).

Further, in the present embodiment, the input optical path and the output optical path are respectively one of the optical fiber transmission paths 1 and 2, but a plurality of input optical paths or output optical paths may of course be provided. . For example, in the embodiment of FIG. 1, in addition to the optical fiber transmission lines 1 and 2 respectively connected to the waveguides 23h (I8) and 23g (I7), the waveguide 23f (I
If the optical fiber transmission line 1'is connected to 6) and the frequency multiplexed signal light having the optical frequencies f ₀ , f ₂ , f ₄ , ..., F ₁₄ is propagated as the second input optical path, the optical switch Sx ( x = 1,
By turning on 3, ..., 15), the optical frequency f _x ,
The optical signal of f _x-1 can be selected.

Similarly, in the embodiment of FIG. 1, the waveguide 23
In addition to the optical fiber transmission lines 1 and 2 respectively connected to h (I8) and 23g (I7), for example, the waveguide 23d (I
4) and 23c (I3) are connected to the optical fiber transmission lines 1'and 2 ', respectively, and are used as the second input optical path and the second output optical path, respectively, two frequency selective optical filters are simultaneously provided. Composed. In this case, for example, the optical switch S
If only 1 is turned on, the optical signal of optical frequency f ₁ is selected from the frequency-multiplexed optical signal propagating through the optical fiber transmission line 1 and output from the optical fiber transmission line 2, while the optical fiber transmission line 2 is transmitted. Optical fiber transmission line 1'from line 2 '
Of the frequency-multiplexed optical signals propagated through
_-3 optical signals are selected and output.

Incidentally, a plurality of input / output optical paths may be provided in the same manner in the following embodiments.

Furthermore, in the present embodiment, two adjacent waveguides of the second input / output waveguide 27 are connected by the folded optical path 28, but two distant waveguides are connected by the folded optical path. It may be configured to do so. in this case,
Since the effect that the frequency dependence of the filter transmission characteristic can be reduced by appropriately selecting the interval between the waveguides connected by the folded optical path will be described in detail below as Example 2.

(Embodiment 2) FIG. 4 is a block diagram showing a second embodiment of the frequency selective optical filter according to the present invention. The second embodiment differs from the first embodiment described with reference to FIG. 1 above in that the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21 has a periodicity equal to the wavelength multiplex number 16 as shown in FIG. An optical fiber (folded optical path) 28 (Fx, where x = x) that connects the waveguide pair in the second input / output waveguide group 27 is used.
1, 3, ..., 15) are non-adjacent waveguide pairs (J5, J1).
4), (J7, J16), (J9, J2), (J11,
J4), (J13, J6), (J15, J18), (J
1, J10) and (J3, J12), respectively. Along with this, the waveguides in the first input / output waveguide 23 to which the optical fiber transmission lines 1 and 2 are connected are also changed to 23k (I11) and 23d (I4), respectively.

Next, the operation according to the second embodiment will be described focusing on the part different from the first embodiment. Optical frequency f ₁ ,
The frequency-multiplexed optical signals of 8 waves of f ₃ , ..., F ₁₅ are propagated through the optical fiber transmission line 1 and then 23 k in the first input / output waveguide 23 of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21. (I
Enter in 11). Here, since the arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer 21 exhibits the frequency multiplexing / demultiplexing characteristics shown in FIG. 23, the optical signal of the optical frequency f ₁ is transmitted to the second input / output waveguide 27.
Optical fiber 28a (F1) through 27n (J14) inside
Propagate inside. Similarly, an optical signal of optical frequency f ₃ propagates in the optical fiber 28c (F3), ..., An optical signal of optical frequency f ₁₅ propagates in the optical fiber 28o (F15).

Here, the eight optical switches 9a (S1),
9c (S3), ..., 9o (S15) are all in the ON state, the optical fibers Fx (x = 1, 3, ..., 1)
5) The light having the optical frequency fx propagating through the inside is input to J (1 + Mod [x + 3,16]) in the second input / output waveguide 27, respectively. However, Mod [x, y] represents the remainder when x is divided by y. That is, the optical signal of the optical frequency f ₁ is input to J5 via the optical fiber F1 and the optical switch S1, and similarly, the optical signal of the optical frequency f ₃ is input to the optical fiber F 1.
3, through the optical switch S3 to J7, ..., The optical signal of the optical frequency f ₁₅ is passed through the optical fiber F15 and the optical switch S15 to J
Input to 3. Where J (1 + Mod [x + 3,1
6]), the light having the optical frequency fx is input to the second input / output waveguide 23 regardless of the value of x according to FIG.
It is output to 3d (I4). That is, the optical signal of optical frequency f ₁ input to J5, the optical signal of optical frequency f ₃ input to J7, ..., The optical signal of optical frequency f ₁₅ input to J3 are all 14 It is output and sent out into the optical fiber transmission line 2 connected to I4.

Therefore, as in the first embodiment described with reference to FIGS. 1 and 2, the optical switch Sx (where x = 1,
If only 3, ..., 15) are turned on, the optical frequency fx
The signal light of can be selected.

Thus, the frequency selective optical filter of the second embodiment can obtain the same effect as that of the first embodiment described with reference to FIG. In addition, the folded optical path 28 is formed by a pair of non-adjacent waveguides (Js, Jt) (1 ≦ s, t = ≦ 16, where 〓
The configuration provided between s-t 〓> 1) also has an excellent effect of reducing variation in filter transmission loss due to optical frequency. The new effect will be described below.

Generally, in the first and second input / output waveguides 23 and 27 of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21, waveguides near both ends, for example, I1, I16, J1 and J16 are passed. The loss incurred by the signal light is about 2-3 dB greater than the loss incurred by the signal light passing through the waveguide near the center, for example, 18, 19, J8, J9. Therefore, in the first embodiment described with reference to FIG. 1, for example, the transmission loss in the filter is different when the signal light of the optical frequency f ₁ is selected and when the signal light of the optical frequency f ₇ is selected. The difference is 4 to 6 dB. This is because the signal light of the optical frequency f ₁ passes through the waveguides J1 and J2 with large loss, while the signal light of the optical frequency f ₇ passes through the waveguides J7 and J8 with small loss.

FIG. 5A shows an example of measurement in Example 1 of FIG. Although the light of f ₇ and f _{9 with} the least loss is not selected, the loss difference of 4 dB is still observed between the optical frequency f ₅ and the optical frequency f ₁₅ .

However, in the second embodiment described with reference to FIG. 4, the signal light of the optical frequency f ₃ passing through the waveguide J16 having a large loss passes through the optical fiber 28c (F3) and the optical switch 9c (S3). Waveguide J with small loss after passing
Via 7. The same applies to signal lights of other optical frequencies. That is, the transmission loss can be averaged by connecting the folded optical path between the waveguide with large loss and the waveguide with small loss. FIG. 5 (2) shows a measurement example in Example 2 shown in FIG. 4, and the transmission loss difference is reduced to 1.5 dB. A new effect obtained by the second embodiment is apparent when compared with FIG.

In this embodiment, the optical fiber transmission lines 1 and 2 are connected to the waveguide 23 of the first input / output waveguide 23.
I connected to k (I11) and 23d (I4) respectively,
Generally, the waveguides Iv and Iw (1 ≦ v, w = ≦ N,
However, the same effect can be obtained by connecting v and w to Mod [w-v + N, N] = 9). Here, N is the frequency multiplex number of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21, and is 16 in the second embodiment. Of course, the optical fiber transmission lines 1 and 2 may be connected to Iw and Iv, respectively.

Furthermore, in the second embodiment, the folding optical path 28 is used.
Waveguide pair (Js, Jt) (1 ≦ s, t ≦ N)
As the above, a waveguide pair in which the value y defined by y = Mod [ts−N, N] is 9 is used, but any natural number y satisfying 1 ≦ y ≦ N−1 may be used. In this case, the waveguides Iv, Iw (1 ≦
v, w ≦ N) may be selected so as to satisfy Mod [w−v + N, N] = y or Mod [v−w + N, N] = y.

Summarizing the above, when the input waveguide is Iv, the output waveguide is Iw, and the optical signal travels from Js to Jt in the folding optical path, Mod [w-v + N, N] = M
It suffices to select v, w, s, and t that satisfy od [v−w + N, N] = Mod [ts−N, N]. If Iv and Iw are known, y = Mod [wv
+ N, N] and s = Mod [t + y, n], the set of (s, t) can be obtained.

Here, when y = N / 2 is set,
In addition to the effects of the second embodiment described above, there is an advantage that the frequency multiplexing interval can be halved, and the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21 does not necessarily require periodicity. Therefore, the third embodiment will be described in detail below.

(Embodiment 3) FIG. 6 is a block diagram showing a third embodiment of the frequency selective optical filter of the present invention. The third embodiment differs from the second embodiment described with reference to FIG. 4 in that a waveguide pair (Js, Jt) (1 ≦ s in the second input / output waveguide connected to each other by the folded optical path 28). , T ≦ N), a waveguide pair with | ts− = N / 2 is used. Since N = 16 here, the waveguide pair (J1, J
9), (J2, J10), ..
F5 is connected. Along with this, the optical fiber transmission lines 1 and 2 are respectively waveguides 23m (I13) and 23e (I
It has been changed to 5). Next, the operation according to the third embodiment will be described focusing on the part different from the second embodiment.

[0089] optical frequency f _1, f _2, ..., 8-wave frequency multiplexed optical signals of F _8, the first array waveguide grating multiplexer-demultiplexer 21 after propagating through the optical fiber transmission line 1 Medium Input to 23 m (I13) in the input / output waveguide 23. here,
Since the arrayed waveguide grating type optical demultiplexer 21 showing a frequency multiplexing-demultiplexing characteristic shown in FIG. 19, the optical signal of the optical frequency f ₁ is in the second input-output waveguides 27 27l a (J12) And propagates through the optical fiber 28a (F1). Similarly, an optical signal of optical frequency f ₂ is transmitted through the optical fiber 28b (F2),
The optical signal of the optical frequency f ₈ is the optical fiber 28h (F8)
Propagate through each.

Here, the eight optical switches 9a (S1),
9b (S2), ..., 9h (S8) are all in the ON state, the optical fibers Fy (y = 1, 2, ..., 8)
The light having the optical frequency fy propagating inside is input to J (1 + Mod [y + 2,16]) in the second input / output waveguide 27, respectively. That is, the optical signal of the optical frequency f ₁ is input to J4 via the optical fiber F1 and the optical switch S1, and similarly, the optical signal of the optical frequency f ₂ is input to J5 via the optical fiber F2 and the optical switch S2. The optical signal of optical frequency f8 is input to J11 via the optical fiber F8 and the optical switch S8. Here, the light of the optical frequency fy input to J (1 + Mod [y + 2,16]) is, according to FIG. 19, 23e (I5) in the first input / output waveguide 23 regardless of the value of y.
And is propagated through the optical fiber transmission line 2.

Therefore, the optical switch Sy (however, y
= 1, 2, ..., 8) is turned on, the signal light of the optical frequency fy can be selected. The relationship between the state of the optical switch and the optical frequency of the selected optical signal is shown as a table in FIG. In this way, the frequency selective optical filter of the third embodiment has the same effect as that of the second embodiment described with reference to FIG. In particular, the folding optical path 28 has | ts− = N /
Since it is connected to two waveguide pairs (Js, Jt),
The signal light passing through the waveguides J1 and J16 with the largest loss is folded back to the waveguide J9 with the smallest loss.
Pass J8. As a result, the effect of loss averaging described in the second embodiment can be most remarkably obtained.

Further, the folded optical path 28 is formed by using a waveguide pair (Js, Jt) (1 ≦ s, t ≦ 16, where | t−s |
= N / 2), there is also an advantage that the frequency multiplexing interval can be designed to be half that of the second embodiment. This can increase the frequency utilization efficiency in the optical frequency region, and it is possible to narrow the optical frequency range of the laser light sources that should be aligned when constructing a system with the same multiplex number. .

In this embodiment, the optical fiber transmission lines 1 and 2 are connected to the waveguide 23 of the first input / output waveguide 23.
I (I12) and 23e (I5) were connected,
Generally, the waveguides Iv and Iw (1≤v, w≤N, respectively)
However, the same effect can be obtained by connecting | v−w | = N / 2. Here, N is the frequency multiplex number of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21, and is 16 in the second embodiment.

(Fourth Embodiment) FIG. 8 is a configuration diagram showing a fourth embodiment of the frequency selective optical filter of the present invention. The fourth embodiment is different from the first embodiment described with reference to FIG. 1 in that the folded optical path is also provided on the first input / output waveguide 23 side,
By providing a 2 × 2 optical switch 29 capable of switching the path between two folded optical paths instead of the ON / OFF optical switch 9, an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21 is provided.
The input / output optical paths can be connected to either side of the first and second input / output waveguides.

In FIG. 8, 1'and 2'are the second, respectively.
Is an optical fiber transmission line corresponding to the input optical path and the second output optical path, and is connected to 27h (J8) and 27g (J7) of the second input / output waveguide 27, respectively.
Therefore, unlike the first embodiment shown in FIG. 1, the folding optical path F7 is not formed.

On the other hand, the first input / output waveguide 23 (Ii (i
= 1, 2, ..., 16)), the optical fiber transmission line 1,
The optical fiber 28 '(F'i (i = 1, 3, ..., 1
5)) is connected as follows. That is, the waveguide 2
Optical fiber 28'a on 3a (I1) and 23b (I2)
(F′1) is connected to the waveguide 23c (I
3) and 23d (I4) to the optical fiber 28'c (F ')
3), ..., Waveguides 23o (I15) and 23p (I1
The optical fiber 28'o (F'15) is connected to 6).

Further, an optical fiber (folded optical path) Fj,
In the middle of F′j (j = 1, 3, ..., 15), 2 × 2 optical switches 29 (Tj (j = 1, 3, ..., 1
5)) is provided and takes either a bar state in which the folding optical paths Fj and F'j are in a transmissive state or a cross state in which Fj and F'j are interchanged based on a command from the outside.

Next, the operation according to the fourth embodiment will be described focusing on the part different from the first embodiment. Optical frequencies f ₁ , f ₃ , f ₅ , f ₉ , f propagated through the optical fiber transmission line 1
Of the seven frequency multiplexed optical signals of ₁₁ , f ₁₃ , and f _15, the optical signal of optical frequency f ₁ is 27 a in the second input / output waveguide 27.
It propagates through the optical fiber 28a (F1) via (J1). Similarly, according to FIG. 23, an optical signal of optical frequency f ₃ propagates in the optical fiber 28c (F3), ..., An optical signal of optical frequency f ₁₅ propagates in the optical fiber 28o (F15).

Here, seven 2 × 2 optical switches 29a are provided.
If (T1), 29c (T3), ..., 29o (T15) are all in the bar state, the optical fiber Fx (x =
The light of the optical frequency fx propagating in 1, 3, ..., 15) is
The signals are respectively input to J (x + 1) in the second input / output waveguide 27. That is, the optical signal of the optical frequency f ₁ is input to J2 via the optical fiber F1 and the optical switch T1, and similarly, the optical signal of the optical frequency f ₃ is input to J4 via the optical fiber F3 and the optical switch T3. optical signal of frequency f ₁₅ is the optical fiber F15, is input through the optical switch T15 to J16. Thus, similarly to the first embodiment described with reference to FIG. 1, the signal lights of all the optical frequencies are sent out to the optical fiber transmission line 2 connected to I7.

On the other hand, seven 2 × 2 optical switches 29a (T
1), 29c (T3), ..., 29o (T15) are all in the cross state, the optical fiber Fx (x =
The light having the optical frequency fx propagating through 1, 3 ..., 15) is input to I (x + 1) in the first input / output waveguide 23, respectively. That is, the optical signal of the optical frequency f ₁ is transmitted to the optical switch T
1, the optical signal of the optical frequency f ₃ is input to I4 via the optical switch T3, ..., And the optical signal of the optical frequency f ₁₅ is input to 116 via the optical switch T15.
Thus, the signal lights of all the optical frequencies are sent out into the optical fiber transmission line 2 ′ connected to J7.

Therefore, seven 2 × 2 optical switches 29
If only one of the optical switches a, 29c, ... Optical frequency f of the frequency multiplexed light of
Only the signal light of ₁ is output to the optical fiber transmission line 2, and the remaining signal light is output to the optical fiber transmission line 2 '. Similarly, the optical switch Tx (where x = 1, 3, ..., 1
If only 5) is brought into the bar state, the signal light having the optical frequency f _X is selected.

The optical frequencies f ₁ , f ₃ , f ₅ , f ₉ , f ₁₁ , f ₁₃ , f ₁₅ propagating in the optical fiber transmission line 1 '.
The 7-wave frequency-multiplexed optical signal also functions in exactly the same way due to the symmetry. That is, if only the optical switch Tx (where x = 1, 3, ..., 15) is in the bar state,
Of the 7 waves of frequency-multiplexed light propagating in the optical fiber transmission line 1 ′, only the signal light of the optical frequency f is output to the optical fiber transmission line 2 ′, and the remaining signal light is in the optical fiber transmission line 2. Is output to.

In this way, a frequency selective optical filter having the same effect as that of the first embodiment described with reference to FIG. 1 is constructed for the frequency-multiplexed optical signal propagating on either the optical fiber transmission line 1 or 1 '. can do. However, folded optical path F7, F7 'because not configured, it can not be selected for the signal light of the optical frequency f _7. Regarding crosstalk, for example, the signal light input from the optical fiber transmission line 1 and output from the optical fiber transmission line 2 can be reduced to the same level as that of the embodiment, but the signal output from the optical fiber transmission line 2 '. Light is at the level of conventional technology.

The fourth embodiment shown in FIG. 8 also has the advantage of functioning also as an optical add / drop circuit. That is, in FIG. 8, the path from the optical fiber transmission line 1 to the optical fiber transmission line 2 may be the main transmission line, the optical fiber transmission line 2 ′ may be the branch output, and the optical fiber transmission line 1 ′ may be the insertion input. That is, the signal light of the optical frequency corresponding to the optical switch in the bar state of the 2 × 2 optical switch 29 propagates through the main transmission line as it is, while the signal light of the optical frequency corresponding to the optical switch in the cross state is transmitted. The signal light of the same optical frequency that is branched from the main transmission line and output to the branch output and that is input from the add input is merged into the main transmission line.

As described in detail in the first embodiment, the optical add / drop circuit to which the present embodiment shown in FIG. 8 is applied has no unnecessary optical output with respect to the light propagating through the main transmission line and crosstalk. (Leakage) Excellent characteristics of little light can be realized.

In the fourth embodiment, as in the second embodiment, the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21 having the periodicity described above is used.
It is possible to change the input / output waveguide connecting the two and the optical fiber transmission lines 1 ', 2'. That is, the input / output waveguide on the side of the input / output waveguide 23 is Iv, the output waveguide is Iw, and in the case where the optical signal travels from Js to Jt in the corresponding folded optical path of the input / output waveguide 27, Mod [w -V + N, N] = Mod [v-w + N, N] = Mod [ts-N, N] v, w, s, t may be selected. Similarly, the input waveguide on the input / output waveguide 27 side is Jv 'and the output waveguide is Jw'.
In the case where the optical signal travels from Is ′ to It ′ in the folded optical path of the input / output waveguide 23 with respect to these, Mod [w′−v ′ + N, N] = Mod [v′−w ′ + N, N] = It suffices to select v ′, w ′, s ′, and t ′ satisfying Mod [t′−s ′ + N, N]. In this embodiment, the optical switch Ti is provided between the folded optical path Fi that connects the waveguide pair (Js, Jt) and the folded optical path Fi ′ that connects the waveguide pair (Is ', It').
Since optical signals of the same optical frequency must be propagated to i and Fi ′, it is necessary to satisfy Mod [v′−v + N, N] = Mod [s−s ′ + N, N].

Further, by using a 1 × 2 optical switch instead of the 2 × 2 optical switch, it is possible to form a dedicated optical branching circuit or a dedicated optical insertion circuit. For example, in FIG. 8, instead of the 2 × 2 optical switch 29a (T1), 27a (J1) to 2
If the 1 × 2 optical switch connected to either 3b (I2) or 27b (J2) is replaced, the optical frequency F1
An optical branch circuit in which the optical signal of 1 is output to either the optical fiber transmission line 2 or 2'is formed by switching the 1 × 2 optical switch. In this case, even if an optical signal is output from 23a, there is no place to go, so there is no problem even if 23a is omitted.
In addition, set all 2 × 2 optical switches 29 to 1 as described above.
When replaced with a × 2 optical switch, the circuit shown in FIG. 8 becomes an optical branching dedicated circuit. In this case, the optical fiber transmission line 1'can also be omitted. 2x2 optical switch 23a (I1)
Alternatively, if any of 27a (J1) is replaced with a 1 × 2 optical switch connected to 27b (J2), 27b (J
An optical adder circuit can be provided in which the input port of the optical signal output to 2) can be selected as 23a (I1) or 27a (J1), that is, the optical fiber transmission line 1 or 1 '. Also in this case, the unused waveguide 23b (I2) can be omitted. Plus, all 2x
When the 2 optical switch 29 is replaced with the 1 × 2 optical switch as described above, the circuit shown in FIG. 8 becomes an optical insertion dedicated circuit. In this case, the optical fiber transmission line 2'can also be omitted.

Further, in the same way that the new effect is obtained by the third embodiment with respect to the second embodiment, by combining the fourth embodiment with the skillful configuration described in the third embodiment, an optical add / drop circuit is obtained. It is possible to obtain a circuit that is extremely effective as a frequency selective optical filter that can also be used. A configuration example thereof will be described below as a fifth embodiment.

(Embodiment 5) FIG. 9 is a block diagram showing the fifth embodiment of the present invention. The fifth embodiment differs from the fourth embodiment described with reference to FIG. 8 in that the returning optical paths 28 and 28 'are different.
Waveguide pairs (Js, Jt), (Is,
It) is designed to satisfy the relationship (| ts− = N / 2) described in the third embodiment, not the adjacent waveguide pair (y = 1, 3, 4, 5,). 6, 7, 8).

The operation of the fifth embodiment will be described below, focusing on the points different from the fourth embodiment. Optical frequencies f ₁ , f ₃ , f ₄ , f ₅ , f propagated through the optical fiber transmission line 1
Among the seven frequency-multiplexed optical signals of ₆ , f ₇ , and f _8, the optical signal of the optical frequency f ₁ propagates in the optical fiber 28a (F1) through the waveguide 27 '(J12). Similarly, the optical frequency f
The optical signals of y (y = 1, 3, 4, 5, 6, 7, 7, 8) respectively propagate in the optical fiber Fy.

Here, seven 2 × 2 optical switches T1, T
If 3, T4, ..., T8 are all in the bar state,
Light having an optical frequency fy propagating through the optical fiber Fy (y = 1, 3, 4, ..., 8) is guided by the waveguide J (1 + Mod [y + 2,2
16]) and is output to the optical fiber transmission line 2 via the waveguide 23e (I5) regardless of the value of y.

In addition, seven 2 × 2 optical switches T1 and T
When T3, T4, ..., T8 are all in the cross state,
Similarly, all of the seven frequency-multiplexed optical signals of the optical frequencies f ₁ , f ₃ , f ₄ , f ₅ , f ₆ , f ₇ , f ₈ propagated through the optical fiber transmission line 1 are transmitted through the optical fiber transmission line 2. 'Sent out inside.

Therefore, the seven 2 × 2 optical switches T
Only one optical switch among 1, T3, T4, ..., T8,
For example, if only T1 is in the bar state and the other optical switches are in the cross state, only the signal light of the optical frequency f1 out of the seven-wave frequency multiplexed light propagating in the optical fiber transmission line 1 is transmitted through the optical fiber transmission line. 2 and the rest of the signal light is output to the optical fiber transmission line 2 '. Similarly, if only the optical switch Ty (y = 1, 3, 4, ..., 8) is in the bar state, the signal light of the optical frequency fy is selected. In addition, the optical frequencies f ₁ , f ₃ , and f propagating in the optical fiber transmission line 1 ′ are
The frequency-multiplexed optical signals of 7 waves of ₄ , f ₅ , f ₆ , f ₇ , and f ₈ function in exactly the same way due to the symmetry.

The fifth embodiment described above has the advantages described in the third embodiment in addition to the various advantages described in the fourth embodiment.

(Sixth Embodiment) FIG. 10 is a block diagram showing an embodiment. The present embodiment is different from the first embodiment described with reference to FIG. 1 in that the optical fiber transmission lines 32g and 32i, which are a plurality of output optical paths, are the first of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21. 23g (I in the input / output waveguide
7), 23i (I9), and the optical fiber transmission line 3
The point is that the 1 × 2 optical switch 39 connected to 2g and 32i selects one of them as the actually used output optical path.

Next, the operation according to the sixth embodiment shown in FIG. 10 will be described with reference to FIGS. 23 and 11 for the parts different from the first embodiment. The 16 frequency-multiplexed optical signals of optical frequencies f ₁ , f ₂ and f ₁₆ propagate through the optical fiber transmission line 1 and then the first input / output waveguide 23 of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21. Input to 23h (18). Here, since the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21 exhibits the frequency multiplexing / demultiplexing characteristic shown in FIG. 23, the optical signal of the optical frequency f ₁ is 27a ( J
1) propagates in the optical fiber 28a (F1), while the optical signal of the optical frequency f ₂ passes through 27b (J2) in the second input / output waveguide 27 and reverses in the optical fiber 28a (F1). Propagate in the direction. Similarly, the optical signals of the optical frequencies f ₃ and f ₄ propagate in opposite directions in the optical fiber 28c (F3), and the optical signals of the optical frequencies f ₁₅ and f ₁₆ propagate to the optical fiber 28.
O (F15) propagates in the opposite direction.

Here, the eight optical switches 9a (S1),
If 9c (S3), ..., 9o (S15) are all in the ON state, the optical fiber Fx (x = 1, 3, 15)
The light having the optical frequency fx + 1 propagating in the inside is input to J (x + 1) and Jx in the second input / output waveguide 27, respectively. That is, the optical signals of the optical frequencies f ₁ and f ₂ are both input to J2 and J1 via the optical switch S1, and similarly, the optical signals of the optical frequencies f ₃ and f ₄ are input to J4 and J3 via the optical switch S3. The optical signals of optical frequencies f ₁₅ and f ₁₆ are input to J16 and J15 via the optical switch S15. Here, referring to FIG. 23, the light of the optical frequency fx input to J (x + 1) is output to 23g (I7) in the first input / output waveguide 23 regardless of the value of x, and , J
The light having the optical frequency f _{x + 1} input to x is output to 23i (I9) regardless of the value of x. That is, the optical signal of optical frequency f ₁ input to J2, the optical signal of optical frequency f 3 input to J4, ..., The optical frequency f input to J16
_{All the 15} optical signals are output to 17 and sent to the optical fiber transmission line 32g. On the other hand, an optical signal of optical frequency f2 input to J1 and an optical signal of optical frequency f4 input to J3
, And the optical signal of optical frequency f ₁₆ input to J15 are all output to I9, and the optical fiber transmission line 3
It is sent out during 2i.

Therefore, the eight switches 9a, 9c,
..., only one optical switch of 9o, eg 9a
Only (S1) is turned on and other optical switches are turned off
In this state, only the signal light having the optical frequency f ₁ is output to the optical fiber transmission line 32g, and at the same time, only the signal light having the optical frequency f ₂ is output to the optical fiber transmission line 32i. At this time, the 1 × 2 optical switch 39 is used for the optical fiber transmission line 32g.
If is selected, the signal that has propagated through the optical fiber transmission line 1
Of the 6 waves of frequency multiplexed light, only the optical signal of the optical frequency f ₁ is selected and output to the optical fiber transmission line 2. When only the optical signal of the optical frequency f ₂ is selected, the 1 × 2 optical switch 39 may be used to select the optical fiber transmission line 32i side. Similarly, the optical switch Sx (where x = 1, 3,
..., 15) is turned on, and the optical switch 39 is set to 32.
On the g side or the 32i side, the optical frequency f
Signal lights of x and f _{x + 1} are selected. The optical frequencies of the optical signals selected with respect to the state of the optical switch are summarized in a table in FIG.

Next, the effect of the frequency selective optical filter of the sixth embodiment shown in FIG. 10 will be described. First, from the operation of the sixth embodiment described in detail above, the effect that the first embodiment described with reference to FIG. 1 has, that is, an excellent characteristic that there is no unnecessary light output and less crosstalk (leakage) light is obtained. It is clear to show.

In addition, compared with the first embodiment shown in FIG.
It is possible to handle frequency-multiplexed light of a multiplex number. That is, for example, if an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a multiplex number of 16 is used as shown in FIG. 10, any one or a plurality of signal lights can be selected from 16 frequency multiplexed lights. This is improved by one wave as compared with the case of 15 waves in the conventional example described with reference to FIG. Further, in the sixth embodiment, the number of optical switches required to select an arbitrary signal light of one wave from 16 frequency-multiplexed lights is 8 ON / OFF optical switches and 1 × optical switch 1.
There are only 9 in total. This is about half that in the conventional example, which requires ON / OFF optical switches for the number of multiplexed lights. As a result, not only the number of parts is reduced and the cost is reduced, but also the effects such as improvement of reliability and reduction of control circuit scale are remarkable.

In other words, in addition to the effects described in the first embodiment, the sixth embodiment uses the optical switch 9 for the light propagating in the opposite direction, so that the optical switch required for the control can be controlled. The great effect is that the number can be reduced to about half.

As the 1 × 2 optical switch 39 in FIG. 10, for example, a mechanical optical switch may be used. Further, by using the 2 × 2 optical switch 51 shown in FIG. 21, it becomes possible to integrate the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21 on the same substrate. Further ON / OFF
By combining two optical switches with an optical coupler or a Mach-Zehnder interferometer, a 1 × 2 optical switch that can be integrated and has an excellent extinction ratio may be realized. An example of this configuration will be described with reference to FIG.

FIG. 12 is a diagram for explaining an example of the structure of the 1 × 2 optical switch 39, in which 91 and 92 are ON / OFF optical switches, 514 and 515 are optical couplers, and 60 is a multiplexer (Mach-Zehnder interferometer). ). If the ON / OFF optical switches 91 and 92 are configured to use the opposite terminals of the waveguide type 2 × 2 optical switch shown in FIG. 21, for example, and the optical switches 91 and 92 are operated in a complementary manner. A 1 × 2 optical switch that can be integrated on the same waveguide substrate and has an excellent extinction ratio can be configured. In the configuration of FIG. 12A, the optical coupler 515 causes a loss of 3 dB in principle. However, by adopting the configuration of FIG. 12 (2) and appropriately designing the Mach-Zehnder interferometer 60 so that the period of the multiplexing characteristic thereof coincides with twice the frequency multiplex interval, there is theoretically no loss of 1 ×. A two-optical switch 39 can be realized.

In the sixth embodiment shown in FIG. 10, the frequency-multiplexed signal light may be input from the optical fiber transmission line 2 and the selected signal light may be extracted from the optical fiber transmission line 1. .

Further, in the present embodiment, the optical fiber transmission line 1 as the input optical line is connected to the waveguide 23h (I8) of the first input / output waveguide 23, but the optical fiber transmission line 1 is the first optical fiber transmission line. Any of the input / output waveguides 23 may be connected. For example, when the optical fiber transmission line 1 is connected to the waveguide Ii (i is a natural number of 1 ≦ i ≦ 16), the optical fiber transmission lines 32g and 32i are connected to the waveguide 23 (I (i-
1)) and the waveguide 23 (I (i + 1)).

As described in the first embodiment, it is of course possible to provide a plurality of input optical paths and simultaneously configure a plurality of frequency selective optical filters.

Further, as described in the second embodiment, if the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21 having the above-mentioned periodicity is used, the pair of waveguides 27 (Js) connected by the folded optical path 28 is used. , Jt) (1 ≦ s, t ≦ N),
The value y defined by y = Mod [ts−N, N] is 2 ≦
It is of course possible to select a waveguide pair that is a natural number that satisfies y ≦ N−2 (where y ≠ N / 2). In this case, the waveguide 2 to which the optical fiber transmission lines 1, 32g, 32i are connected
3 (Iv, Iw, Iu) (1 ≦ v, w, u, ≦ N) is M
od [w−v + N, N] = y, Mod [v−u + N,
It may be selected so as to satisfy N] = y. For example, N = 1
6, when y = 9 and v = 11, the optical fiber transmission line 32
g and 32i are waveguides 23 (I4) and 23 (I
2). In this case, it is possible to obtain the effect of suppressing the variation in loss due to the optical frequency as described in the second embodiment with reference to FIG.

As described in the fourth embodiment with reference to FIG. 8, in the frequency selective optical filter according to the present embodiment, the folded optical paths are provided in both the first and second input / output waveguides 23 and 27. , 2 × 2 between the corresponding optical paths
With the configuration in which the optical switch 29 is installed, it is possible to configure a filter having the effects of both the sixth embodiment and the fourth embodiment. An example thereof is shown in FIG.

(Embodiment 7) FIG. 14 is a block diagram showing Embodiment 7. The present embodiment differs from the sixth embodiment described with reference to FIG. 10 in that the optical fiber transmission lines 31d and 31l, which are a plurality of input optical paths, are waveguides 23d (I4),
23l (I12) connected to the optical fiber transmission line 3
The point is that the 1 × 2 optical switch 39a connected to 1d and 31l is configured to select either one as the actually used input optical path. Along with this, the optical fiber transmission lines 32c and 32e, which are output optical paths corresponding to the optical fiber transmission line 31d, are respectively guided to the waveguide 23c (I
3) and 23 (I5), while the optical fiber transmission lines 32k and 32m, which are the optical paths for output corresponding to the optical fiber transmission line 31l, are respectively waveguides 23k (I11) and 2k.
It is connected to 3 m (I13). Further, it is provided with optical couplers 41a and 41b to which optical fiber transmission lines 32c, 32m and 32e, 32k are respectively connected, and one of the combined outputs of the optical cabs 41a and 41b is 1 ×.
It is selected by the two optical switch 39b and output to the optical fiber transmission line 2. In addition, the folding optical path Fx and the optical switch Sx (x = 1, 1) provided in the fourth embodiment shown in FIG.
3, ..., 15), the part of x = 1, 3, 13, 15 is removed.

Next, the operation of the seventh embodiment shown in FIG. 14 different from that of the sixth embodiment will be described with reference to FIGS. 23 and 15. Optical frequencies f ₁ , f ₂ , ..., F ₁₆
The 16-wave frequency-multiplexed optical signal is input to the 1 × 2 optical switch 39a after propagating in the optical fiber transmission line 1 and guided through either the optical fiber transmission line 31d or 31l according to a control signal from the outside. Input to the waveguide 23d (I4) or 23l (I12).

Since the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer 21 exhibits the frequency multiplexing / demultiplexing characteristic shown in FIG.
If the optical switch 39a is connected to the d side, the optical signal of the optical frequency f ₁ propagates in the optical switch 28e (F5) via the waveguide 27e (J5), while the optical signal of the optical frequency f2 is transmitted. The signal propagates in the opposite direction in the optical fiber 28e (F5) via the waveguide 27f (J6). Similarly, the optical signals of the optical frequencies f ₃ and f ₄ propagate in the optical fiber 28g (F7) in opposite directions, and the optical signals of the optical frequencies f ₇ and f ₈ propagate in the optical fiber 28k (F11). Each propagates in the opposite direction.

On the other hand, if the optical switch 39a is connected to the 31l side, an optical signal of optical frequency f ₉ propagates in the optical fiber 28e (F5) via the waveguide 27e (J5), The optical signal of optical frequency f10 is the waveguide 27f
It propagates in the opposite direction through the optical fiber 28e (F5) via (J6). Similarly, the optical signals of the optical frequencies f ₁₁ and f ₁₂ propagate in the optical fiber 28g (F7) in opposite directions, ...
The optical signals of the optical frequencies f ₁₅ and f ₁₆ are transmitted through the optical fiber 28k (F1
1) Propagate in the opposite direction in each direction.

Here, the four optical switches 9e (S5),
It is assumed that 9g (S7), 9i (S9), and 9k (S11) are all in the ON state. At this time, the optical fiber F
Optical frequency f propagating in x (x = 5, 7, 9, 11)
Lights of _x-4 and f _x-3 are emitted from J (x in the second input / output waveguide 27).
+1) and Jx, respectively. That is, the optical signals of the optical frequencies f ₁ and f ₂ are input to J6 and J5 via the optical switch S5, respectively, and similarly, the optical frequencies f ₃ and f ₂ are input.
The optical signal of f ₄ is sent to J8 and J7 via the optical switch S7, and the optical signals of optical frequencies f ₅ and f ₆ are sent to J1 via the optical switch S9.
0, J9, optical signals of optical frequencies f ₇ , f ₈ are sent to the optical switch S.
It is input to J12 and J11 via 11 respectively. Here, referring to FIG. 23, the light of the optical frequency f _X-4 input to J (x + 1) does not depend on the value of x, and the waveguide 23c (I
The optical frequency f output to 3), while being input to Jx
The light of _X-3 is output to 23e (I5) regardless of the value of x.

Similarly, the optical fiber 28 (Fx) (x =
5, 7, 9, 11) optical frequencies f _{X + 4} , f _{X + 5} propagating in
Light is input to the waveguides J (x + 1) and Jx, respectively. Here, the optical frequency f input to J (x + 1)
The light of _{X + 4} is output to the waveguide 23k (I11) regardless of the value of x, while the light of optical frequency f _{X + 5} input to Jx is 23 m (I13) regardless of the value of x. Is output to.

Therefore, the four optical switches 9e (S
5), 9g (S7), 9i (S9), and 9k (S11), only one optical switch, for example, 9e (S5) is turned on, and the d side is selected by the optical switch 39a. , Only the signal light of the optical frequency f ₁ is output to the optical fiber transmission line 32c, and at the same time, only the signal light of the optical frequency f ₂ is output to the optical fiber transmission line 32e. here,
The signal lights having the optical frequencies f ₁ and f ₂ are respectively supplied to the optical coupler 41.
Since it reaches the 1 × 2 optical switch 39b via b and 41a, for example, if the optical switch 39b selects the 32c & m side, only the signal light of the optical frequency f1 is output to the optical fiber transmission line 2.

The correspondence between various optical switch state combinations and selected optical frequencies is summarized in the table of FIG.
For example, if you want to select an optical signal with optical frequency f ₈ ,
1x2 optical switches 39a and 39b are provided on the 31d side,
The 32e & k side may be selected, and only 9k (S11) of the ON / OFF optical switches 9 may be turned on. In the seventh embodiment shown in FIG. 14, the optical coupler 41a combines the optical signals in the optical fiber transmission lines 32e and 32k, while the optical coupler 41b combines the optical signals in the optical fiber transmission lines 32c and 32m. The optical coupler 41a multiplexes the optical signals in the optical fiber transmission lines 32e and 32m, and the optical coupler 41b multiplexes the optical signals in the optical fiber transmission lines 32c and 32e.

When an optical coupler is used as a multiplexer, as in the seventh embodiment shown in FIG. 14, a loss of 3 dB is generated in principle, but the Mach-Zehnder interferometer shown in FIG. In principle, it is possible to make lossless if the multiplexer 60 used is properly designed and used. because,
For example, an optical fiber transmission line optical frequency f ₁ is the a of 32c could propagate, f _3, f _5, the signal light f ₇ 14, whereas, possible to propagate an optical fiber transmission path 32m The signal light having the optical frequencies f ₁₀ , f ₁₂ , f ₁₄ , and f ₁₆ is effective. Therefore, for example, the frequency multiplexing interval is 1
If it is set to 00 GHz, it is possible to obtain lossless multiplexing characteristics by using a Mach-Zehnder interferometer with a period of 200 GHz.

Further, when the optical couplers 41a and 41b used as the multiplexer are provided with 1 × 2 optical switches respectively and are configured to switch according to the optical frequency to be selected, the multiplexing means with less loss is configured. can do. Also, instead of the optical couplers 41a and 41b and the optical switch 39b, a 1 × 4 optical switch is used to select one of the optical fiber transmission lines 32c, 32e, 32k, and 32m and connect it to the optical fiber transmission line 2. Of course, you can configure it.

Next, the effect of the frequency selective optical filter of the seventh embodiment shown in FIG. 14 will be described. First, from the operation of the seventh embodiment described in detail above, the effect of the first embodiment described with reference to FIG. 1 is obtained, that is, the excellent characteristic that the crosstalk (leakage) light is small without unnecessary optical output. It is clear to show.

Furthermore, in the seventh embodiment, the number of optical switches required to select an arbitrary signal light of one wave from the frequency multiplexed light of 16 waves is 4 ON / OFF optical switches and 1 optical switch.
There are only two x2 optical switches for a total of six. In the conventional example described with reference to FIG. 18, this is ON / OFF by the number of multiplexed lights.
Approximately 1/4 compared with the case where an OFF optical switch was required
It's done. FIG. 16 is a table showing the number of optical switches required when a similar frequency selective optical filter is configured using arrayed waveguide diffraction grating type optical multiplexers / demultiplexers with various frequency multiplexing numbers. For example, when an optical filter for selecting one wave from 63 to 64 multiplexed light is formed by using an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a frequency multiplexing number of 64, 63 optical switches are required in the conventional example. There was this Example 7
With the configuration, only 18 pieces are required. The sixth embodiment described with reference to FIG. 10 also requires 33 optical switches, and the effects such as cost reduction, reliability improvement, and control circuit scale reduction are extremely remarkable.

In addition, in the seventh embodiment shown in FIG. 14, of the first and second input / output waveguides 23 and 27, only the waveguide near the center is used, and I1, I16, J1,
The waveguide near both ends such as J16 is not used. Generally, the input and output waveguides near both ends of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer have a larger loss and a larger loss difference between the waveguides than the waveguides near the center. Therefore, in the seventh embodiment,
It also has an effect of improving the loss and the variation of the loss difference due to the optical frequency.

In summary, the seventh embodiment is similar to the sixth embodiment.
In addition to the effects described in Section 1, the input optical path and the output optical path can be selected from a plurality of ones, so that the optical switch 9 is bidirectionally propagating in two different optical frequencies. Due to the skillful configuration of utilizing it for light, it is possible to further reduce the number of optical switches required for control, and it is possible to obtain a composite and extremely remarkable effect that a frequency selective optical filter with less loss and loss difference can be configured.

The optical circuit shown in FIG. 14 may also be configured to input the frequency-multiplexed signal light from the optical fiber transmission line 2 and take out the selected signal light from the optical fiber transmission line 1. Further, in the seventh embodiment shown in FIG. 14, x = as the return optical path Fx and the optical switch Sx.
Four optical paths 5, 7, 9, and 11 and an optical switch are provided, but instead of this, for example, x = 1, 3, 1 of the folded optical path Fx and the optical switch Sx shown in FIG.
It is possible to construct an optical fiber having the same function even if four optical paths 3, 15 and an optical switch are provided.

In the seventh embodiment, the waveguide 23d
(I4) and 23l (I12) are connected to the optical fiber transmission lines 31d and 31l which are the input optical paths, but may be connected to other waveguides of the first input / output waveguide 23. For example, the optical fiber transmission lines 31d and 31l are connected to the waveguides Ii and I (i + (N / 2)) (i is a natural number of 1 ≦ i ≦ N / 2 and N is the frequency multiplex number), and the optical fibers are connected. By connecting the transmission lines 32c, 32d, 32k, and 32m to the corresponding waveguides of the first input / output waveguide 23, respectively, it is possible to configure a frequency selective optical filter having a similar function.

As described in the first embodiment, it is of course possible to simultaneously configure a plurality of frequency selective optical filters. Further, as described in the second embodiment, the waveguide pair (Js, Jt) (1 ≦ s, t ≦ that is connected by the folded optical path 28).
As N), it is of course possible to select a waveguide pair in which the value y defined by y = Mod [ts−N, N} is a natural number satisfying 1 ≦ y ≦ N−1.

[0146]

As described in detail above, according to the present invention,
The input optical path and the output optical path to the filter are connected to the input / output waveguides on the same side of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer, while the other side of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer is connected. With the configuration in which the folded optical paths each having an optical switch are connected to the input / output waveguide, the excellent characteristics that there is no unnecessary optical output and less crosstalk (leakage) light are realized. In addition, according to the inventions of the present invention in which the folded optical path and the optical switch are also used for light propagating in the opposite direction, such a duplexed optical switch is used. As a result, a great effect that the number of optical switches required for control can be reduced can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a frequency selective optical filter according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a frequency selection operation according to the first embodiment of the present invention.

FIG. 3 is a measurement example of filter characteristics according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram showing a frequency selective optical filter according to a second embodiment of the present invention.

FIG. 5 is a measurement example of filter characteristics according to the second embodiment of the present invention.

FIG. 6 is a configuration diagram showing a frequency selective optical filter according to a third embodiment of the present invention.

FIG. 7 is a diagram illustrating a frequency selection operation according to the third embodiment of the present invention.

FIG. 8 is a configuration diagram showing a frequency selective optical filter according to a fourth embodiment of the present invention.

FIG. 9 is a configuration diagram showing a frequency selective optical filter according to a fifth embodiment of the present invention.

FIG. 10 is a configuration diagram showing a frequency selective optical filter according to a sixth embodiment of the present invention.

FIG. 11 is a diagram illustrating a frequency selection operation according to the sixth embodiment of the present invention.

FIG. 12 is a diagram illustrating a configuration of a 1 × 2 optical switch used in Example 6 of the present invention.

FIG. 13 is a configuration diagram showing a frequency selective optical filter similar to that of Embodiment 6 of the present invention.

FIG. 14 is a configuration diagram showing a frequency selective optical filter according to a seventh embodiment of the present invention.

FIG. 15 is a diagram illustrating a frequency selection operation according to the seventh embodiment of the present invention.

FIG. 16 is a diagram for explaining the effect of reducing the number of optical switches obtained in Examples 6 and 7 of the present invention.

FIG. 17 is a diagram illustrating the principle of a conventional frequency selective optical filter.

FIG. 18 is a configuration diagram showing a conventional frequency selective optical filter.

FIG. 19 is a diagram showing frequency multiplexing / demultiplexing characteristics of an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer with a frequency multiplexing number of 16;

FIG. 20 is a diagram illustrating a frequency selection operation in a conventional frequency selection optical filter.

FIG. 21 is a diagram illustrating a configuration example of a waveguide type optical switch.

FIG. 22 is a measurement example of characteristics of a conventional frequency selective optical filter.

FIG. 23 is a diagram showing frequency multiplexing / demultiplexing characteristics of a 16 × 16 arrayed waveguide diffraction grating type optical multiplexer / demultiplexer.

[Explanation of symbols]

1, 2, 1 ', 2'optical fiber transmission line 9a-9p optical switch 29a-29p 2x2 optical switch 21 array waveguide diffraction grating type optical multiplexer / demultiplexer 23a-23p first input / output waveguide 24, 25 Slab waveguide 26 Arrayed waveguide Diffraction grating 27a to 27p Output waveguide 18a to 18p Optical fiber (loop back optical path) 28a to 28p, 28'a to 28'p Optical fiber (folded optical path) 31d, 31l, 32c, 32e, 32g, 32i, 3
2k, 32m, optical fiber transmission line 39, 39a, 39b 1x2 optical switch 41a, 41b optical coupler

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location G02B 6/12 H04B 10/02 G02B 6/12 F H04B 9/00 T (72) Inventor Yasuyuki Inoue 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (26)

[Claims] 1. A first waveguide comprising N waveguides (N is an integer)
Array waveguide diffraction grating type optical multiplexer / demultiplexer having a second input / output waveguide group consisting of N input / output waveguide groups, and a waveguide of the first input / output waveguide group. At least one input optical path connected, and at least one output optical path connected to a waveguide adjacent to the waveguide to which the input optical path is connected, respectively, the second input / output At least one folded optical path that is formed by two waveguides adjacent to each other in the waveguide group and that connects between the two waveguides of at least one pair of waveguides that does not include overlapping waveguides; A frequency selective optical filter, comprising: an optical switch disposed in the middle of one folded optical path. 2. A first waveguide comprising N waveguides (N is an integer)
Array waveguide diffraction grating type optical multiplexer / demultiplexer having a second input / output waveguide group including N input / output waveguide groups, and a v-th array of the first input / output waveguide group. v is an integer), an input optical path connected to the waveguide, and an output optical path connected to the w-th (w is an integer) waveguide of the first input / output waveguide group, and Mod [w −v + N, N] = Mod [ts−s +
N, N] or Mod [v−w + N, N] = Mod [t
-S + N, N], which is a folded optical path corresponding to at least one set of s and t selected from the combination of integers s and t, each of which is s-th of the second input / output waveguide group. A frequency selective optical filter comprising: at least one folded optical path for transmitting an optical signal from the waveguide to the t-th waveguide; and an optical switch arranged in the middle of the at least one folded optical path. 3. The frequency selective optical filter according to claim 2, wherein the absolute value of t-s is N / 2. 4. A first waveguide comprising N waveguides (N is an integer)
Array waveguide diffraction grating type optical multiplexer / demultiplexer having a second input / output waveguide group including N input / output waveguide groups, and a v-th array of the first input / output waveguide group. a first input optical path connected to the (v is an integer) waveguide, and a first output optical path connected to the w-th (w is an integer) waveguide of the first input / output waveguide group. , A second input optical path connected to the v′-th (v ′ is an integer) waveguide of the second input / output waveguide group, and the w′-th (w 'Is an integer) and a second output optical path connected to the waveguide, and Mod [v'-v + N, N] = Mod [s-s' + N,
N] is satisfied, and Mod [w−v + N, N] = Mod [ts−N, N]
Alternatively, Mod [v−w + N, N] = Mod [ts−s +
N, N], and further, Mod [w'-v '+ N, N] = Mod [t'-s' +
N, N] or Mod [v'-w '+ N, N] = Mo
An optical path provided corresponding to each combination of integers s and t and each combination of integers s ′ and t ′ satisfying d [t′−s ′ + N, N], wherein the second input / output waveguide is provided. At least one first folded optical path for transmitting an optical signal from the sth waveguide to the tth waveguide of the group, and t'from the s'th waveguide of the first input / output waveguide group
A second folded optical path for transmitting an optical signal to the second waveguide, and optical paths for propagating optical signals of the same optical frequency in the first folded optical path and the second folded optical path. And at least one optical switch for connecting to the frequency selective optical filter. 5. A first waveguide comprising N waveguides (N is an integer)
And an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer having a second input / output waveguide group consisting of N waveguides, and each of which is Mod [wv + N, N]. = Mod [v−u + N, N] which is an optical path whose connection position is determined according to each integer v, w, u, and which is an input connected to the v-th waveguide of the first input / output waveguide group. Optical path, a first output optical path connected to the w-th waveguide of the first input / output waveguide group, and a u-th waveguide of the first input / output waveguide group And a second output optical path, and further connected according to each combination of integers s and t satisfying: Mod [w−v + N, N] = Mod [v−u + N, N] = Mod [t−s + N, N] An optical path whose position is determined, wherein the optical path is the s-th waveguide from the s-th waveguide of the second input / output waveguide group. An optical switch having at least one return optical path for transmitting an optical signal to the optical path, the optical switch disposed in the middle of the at least one return optical path, the output from the first output optical path, and the second output. And an optical path connecting means for outputting at least one of the output from the output optical path to the third output optical path. 6. A first waveguide comprising N waveguides (N is an integer)
Array waveguide diffraction grating type optical multiplexer / demultiplexer having a second input / output waveguide group including N input / output waveguide groups, and a v-th array of the first input / output waveguide group. a first input optical path connected to the (v is an integer) waveguide, and a first output optical path connected to the w-th (w is an integer) waveguide of the first input / output waveguide group. A second output optical path connected to the u-th (u is an integer) waveguide of the first input / output waveguide group, and the v′-th (v ′ is the A second input optical path connected to the (integer) waveguide, and a third output optical path connected to the w'th (w 'is an integer) waveguide of the second input / output waveguide group. , A fourth output optical path connected to the u'th (u 'is an integer) waveguide of the second input / output waveguide group, and further includes v, w, u and v', w ', U' is Mo [W-
v + N, N] = Mod [v−u + N, N] and Mod
[W'-v '+ N, N] = Mod [v'-u' + N,
N], and further Mod [v'-v + N, N] = Mod [s-s' + N,
N], and Mod [w−v + N, N] = Mod [v−u + N, N] = Mod [ts−N, N] or Mod [w′−v ′ + N, N] = Mod [v ′ -U '+ N, N] = Mod [t'-s' + N, N] An optical path whose connection position is determined according to each combination of integers s and t and each combination of integers s'and t', wherein A first folded optical path for transmitting an optical signal from the sth waveguide of the second input / output waveguide group to the tth waveguide, and an s'th waveguide of the first input / output waveguide group To t '
A second folded optical path for transmitting an optical signal to the th waveguide, and further at least one of the output from the first output optical path and the output from the second output optical path. A sixth optical path for outputting at least one of the output from the first optical path connecting means for outputting to the fifth optical path for output, the output from the third optical path for output, and the output from the fourth optical path for output. And a second optical path connecting means for outputting to at least one optical switch for connecting optical paths for propagating optical signals of the same optical frequency in the first returning optical path and the second returning optical path. A frequency-selective optical filter having two sets. 7. A first waveguide comprising N waveguides (N is an integer)
Array waveguide diffraction grating type optical multiplexer / demultiplexer having a second input / output waveguide group consisting of N input / output waveguide groups, and the first input / output waveguide group v1 ( a first input optical path connected to the (v1 is an integer) waveguide, and a first output optical path connected to the w1th (w1 is an integer) waveguide of the first input / output waveguide group. , A second output optical path connected to the u1th (u1 is an integer) waveguide of the first input / output waveguide group, and the v2nd (v2 is an integer) of the first input / output waveguide group A second input optical path connected to the first waveguide, a third output optical path connected to the w2th (w2 is an integer) waveguide of the first input / output waveguide group, and the first input optical path And a fourth output optical path connected to the u3th (u3 is an integer) waveguide of the input / output waveguide group, the absolute value of v1-v2 is N / 2, and v1, w1, u1, v2, w2, u2 are Mod [w1-v1 + N, N] = Mod [v1-u1 + N, N] = Mod [w2-v2 + N, N] = Mod [v2- u2 + N, N], and Mod [w1-v1 + N, N] = Mod [v1-u1 + N, N] = Mod [w2-v2 + N, N] = Mod [v2-u2 + N, N] = Mod [ [t-s + N, N] is an optical path whose connection position is determined according to each combination of integers s and t, and the light is transmitted from the s-th waveguide to the t-th waveguide of the second input / output waveguide group. An optical switch having a return optical path for transmitting a signal, and further comprising at least one optical switch arranged in the middle of the return optical path; and an output of a third input optical path from the first input optical path and the second input optical path. Less input light path And a second optical path connecting means for distributing at least one of the outputs from the first to fourth output optical paths to a fifth output optical path. A frequency selective optical filter characterized by. 8. The 2 × 2 optical switch, wherein the optical switch selects either a cross state or a bar state as a connection state between the first folding optical path and the second folding optical path according to an external signal. The frequency selective optical filter according to claim 4, wherein the frequency selective optical filter is provided. 9. The optical switch comprises a first port and a second port.
1 × 2 optical switch for connecting the first port and the third port, wherein the first port is connected to either one of the first return optical path and the second return optical path, and the second port 7. The frequency selective optical filter according to claim 4, wherein the third port and the third port are 1 × 2 optical switches respectively connected to the first folded optical path and the second folded optical path. 10. The frequency selective optical filter according to claim 5, wherein the optical path connecting means is a 1 × 2 optical switch. 11. The frequency selective optical filter according to claim 6, wherein at least one of the first optical path connecting unit and the second optical path connecting unit is a 1 × 2 optical switch. 12. The frequency selective optical filter according to claim 5, wherein the optical path connecting means is a 1 × 2 optical coupler. 13. The frequency selective optical filter according to claim 6, wherein at least one of the first optical path connecting unit and the second optical path connecting unit is a 1 × 2 optical coupler. 14. The frequency selective optical filter according to claim 7, wherein the first optical path connecting unit is a 1 × 2 optical switch. 15. The frequency selective optical filter according to claim 7, wherein the first optical path connecting unit is a 1 × 2 optical coupler. 16. The frequency selective optical filter according to claim 7, wherein the second optical path connecting unit is a 1 × 4 optical switch. 17. The frequency selective optical filter according to claim 7, wherein the second optical path connecting unit is a 1 × 4 optical coupler. 18. The first optical path connecting means comprises:
The two optical path connecting means and the second 1 × 2 optical path connecting means are arranged in parallel, and the outputs of the first and second 1 × 2 optical path connecting means are input to the third 1 × 2 optical path connecting means. The frequency selective optical filter according to claim 7, which is characterized in that. 19. The frequency selective optical filter according to claim 18, wherein at least one of the first to third optical path connecting units is a 1 × 2 optical switch. 20. The frequency selective optical filter according to claim 18, wherein at least one of the first to third 1 × 2 optical path connecting units is a 1 × 2 optical coupler. 21. The one of claim 2, 3, 5 or 12, wherein the first input / output waveguide has a plurality of combinations of the input optical path and the output optical path. A frequency selective optical filter according to item. 22. The first input / output waveguide group has a plurality of combinations of the input optical path and the output optical path, and the second input / output waveguide group has the input optical path and the output. The frequency selective optical filter according to any one of claims 4, 6, 8, 9, 11 or 13, having a plurality of combinations with a use optical path. 23. The optical multiplexer according to claim 12, wherein the 1 × 2 optical coupler is a Mach-Zehnder type optical multiplexer.
The frequency selective optical filter according to any one of claims 3, 15, 17 and 20. 24. The frequency according to claim 1, wherein at least one of the input optical path, the output optical path, and the folding optical path is an optical fiber transmission path. Selective light filter. 25. The optical waveguide according to claim 1, wherein at least one of the input optical path, the output optical path, and the folding optical path is an optical waveguide formed on a substrate. The frequency selective optical filter described in. 26. A waveguide in which the first and second waveguide groups are connected to the input optical path, the output optical path or the folded optical path instead of the arrayed waveguide diffraction grating type optical multiplexer / demultiplexer. An arrayed-waveguide diffraction grating type optical multiplexer / demultiplexer configured by only one is provided.
The frequency selective optical filter according to claim 25.