JPH08234029A - Optical star coupler - Google Patents

Abstract

(57) [Summary] [Purpose] To provide an optical star coupler with a small loss, a small size, and a low cost, which has a demultiplexing function and an equal distribution function. An input waveguide 102 formed of at least one channel waveguide formed on a substrate 101, and a signal light 12 of a certain wavelength band connected to the input waveguide 102.
In an optical star coupler including a slab waveguide 103 for evenly distributing 0 and an output waveguide 105 connected to the slab waveguide 103 and including at least one channel waveguide, in the slab waveguide 103, An arrayed waveguide diffraction grating 104 composed of a plurality of channel waveguides 115 is connected, and the signal light 12 of another wavelength band from the input waveguide 102 is connected.
The feature is that 1 is demultiplexed for each wavelength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical star coupler, and more particularly to an optical star coupler for equally distributing or multiplexing signal lights.

[0002]

2. Description of the Related Art Conventionally, there has been no device having a function of equally distributing signal light in a certain wavelength band and a function of multiplexing / demultiplexing signal light in another wavelength band by wavelength.

Therefore, in order to realize an optical star coupler having an equal distribution function and a multiplexing / demultiplexing function, an optical star coupler for equally distributing the signal light and a signal light are combined and demultiplexed in a narrow band. The narrow-band optical wavelength demultiplexer / demultiplexer and the wavelength demultiplexer / demultiplexer for multiplexing / demultiplexing the equally distributed signal light and the narrow-band demultiplexed signal light can be connected by optical fiber etc. I was broken.

FIG. 8 shows an example of a conventional optical star coupler with equal distribution and demultiplexing functions, which combines the above-mentioned devices.

This optical star coupler comprises an optical fiber type wavelength multiplexer / demultiplexer 201 on the incident side, a Y-branch waveguide type optical star coupler 202, and an arrayed waveguide diffraction grating type optical wavelength multiplexer / demultiplexer 203 (special (See "Waveguide type diffraction grating" in Japanese Patent Laid-Open No. 2-244105), an optical fiber type optical wavelength multiplexer / demultiplexer 204 on the output side, and an optical fiber 205 for connecting these.
It consists of and.

The operating principle of a conventional optical star coupler having a wavelength multiplexing / demultiplexing function will be described below with reference to FIG. Incidentally, 1300 nm band or a signal light lambda ₀ of 1550nm band N equal parts, a case of demultiplexing a signal light lambda ₁ to [lambda] _N of 1650nm band for each wavelength will be described as an example.

Signal light 2 from the optical fiber 206 on the incident side
07 (wavelength λ ₀ ) and signal light 208 (wavelengths λ _{1 to} λ _N )
Is incident on the fiber type optical wavelength multiplexer / demultiplexer 201. Here, the fiber-type optical wavelength multiplexer / demultiplexer 201 uses signal light of different wavelength bands (for example, 1300 nm band or 1550 n).
This is a device for multiplexing and demultiplexing the m-band signal light and the 1650 nm band signal light. Therefore, the signal light 207 and the signal light 2
08 is demultiplexed into a signal light 207 in the 1300 nm band or the 1550 nm band and a signal light 208 in the 1650 nm band, and respectively into a Y-branch waveguide type optical star coupler 202 and an arrayed waveguide diffraction grating type optical wavelength multiplexer / demultiplexer 203. Propagated. Here, the Y-branch waveguide type star coupler 202 is a device that equally distributes the incident signal light, and the arrayed waveguide diffraction grating type optical wavelength multiplexer / demultiplexer has a narrow band and outputs the signal light of several n.
It is a device that multiplexes and demultiplexes at intervals of about m.

Therefore, the 1300 nm band or 1550
The signal light 207 in the nm band is equally divided into N by the Y-branch waveguide type star coupler 202, and is propagated to the fiber-type optical wavelength multiplexer / demultiplexer 204 on the emission side.

Accordingly, the signal light 207 of N equally divided 1300nm band or 1550nm band, the signal light lambda ₁ of demultiplexed 1650nm band at a wavelength, lambda _2, ..., lambda _N are fiber type optical wavelength division The wave filters 204 respectively output the optical fibers 209 on the output side in pairs.

[0010]

By the way, a conventional optical star coupler having an optical wavelength multiplexing / demultiplexing function includes an optical star coupler,
It was necessary to combine an optical wavelength multiplexer / demultiplexer with a narrow band and an optical wavelength multiplexer / demultiplexer with a wide band, and it was necessary to connect each device with an optical fiber. As a result, the number of connected parts increases and the loss increases. There is also a problem that the size is large and the cost is high.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide an optical star coupler having a demultiplexing function and a uniform distribution function, which has a small loss, a small size, and a low cost.

[0012]

In order to achieve the above object, the present invention provides an input waveguide comprising at least one channel waveguide formed on a substrate, and connected to the input waveguide. In an optical star coupler including a slab waveguide for equally distributing signal light in a certain wavelength band and an output waveguide connected to the slab waveguide and including at least one channel waveguide, An arrayed waveguide diffraction grating composed of a plurality of channel waveguides is connected to separate the signal light of another wavelength band from the input waveguide for each wavelength.

In addition to the above construction, the present invention provides a slab waveguide with a wavelength filter so that the signal light from the input waveguide is demultiplexed or equally distributed and output from the output waveguide.

In addition to the above structure, the present invention allows a wavelength filter to transmit signal light of a certain wavelength band and reflect signal light of another wavelength band, or to reflect signal light of a certain wavelength band and The signal light of the wavelength band is transmitted.

In addition to the above configuration, the present invention is one in which the arrayed waveguide diffraction grating is composed of channel waveguides having different lengths and arranged in order of length.

In addition to the above structure, the present invention provides an arrayed waveguide diffraction grating in which the waveguide length difference ΔL between the channel waveguides adjacent to each other is expressed by equation (1).

[0017]

## EQU1 ## ΔL = λ · m / n _eff (where λ is the wavelength used, n _eff is the effective refractive index, and m is a positive integer).

In addition to the above configuration, the present invention is one in which an input waveguide, an output waveguide, and an input portion and an output portion of an arrayed waveguide are arranged along the end face of the slab waveguide.

In addition to the above construction, the present invention is one in which the input waveguide and the input portion of the arrayed waveguide diffraction grating are arranged opposite to each other at the end of the slab waveguide.

In addition to the above construction, the present invention is one in which the output waveguide and the output portion of the arrayed waveguide diffraction grating are arranged opposite to each other at the end portion of the slab waveguide.

In addition to the above structure, the present invention forms the connecting end faces of the input waveguide and the slab waveguide and the connecting end faces of the output waveguide and the slab waveguide in an arc shape, respectively, and
The input waveguide and the output waveguide are arranged in a fan shape from the respective centers of curvature.

In addition to the above structure, the present invention forms the connecting end face between the input part of the arrayed waveguide diffraction grating and the slab waveguide and the connecting end face between the output part of the arrayed waveguide diffraction grating and the slab waveguide in an arc shape. In addition, the input waveguide and the output waveguide are arranged in a fan shape from the respective centers of curvature.

In addition to the above structure, the present invention is such that the central axis of the input waveguide arranged in a fan shape and the input part of the slab waveguide arranged in a fan shape are aligned with each other.

In addition to the above configuration, the present invention is such that the central axis of the output waveguide arranged in a fan shape and the output part of the slab waveguide arranged in a fan shape are aligned with each other.

In addition to the above structure, the present invention provides an angle between the central axis of the input waveguide arranged in a fan shape and the wavelength filter,
The wavelength filter is provided so that the angle formed by the central axis of the output waveguide arranged in a fan shape and the angle of the interference film filter are matched.

In addition to the above structure, the present invention has a wavelength of 1300n.
The signal light of m band and the signal light of wavelength 1550 nm band are equally distributed, and the signal light of wavelength 1650 nm band is demultiplexed for each wavelength.

In addition to the above structure, the present invention has a wavelength of 1300n.
The signal light in the m band is equally distributed and the signal light in the wavelength band of 1550 nm is demultiplexed for each wavelength.

In addition to the above structure, the present invention has a wavelength of 1550n.
The signal light in the m band is equally distributed, and the signal light in the wavelength band of 1300 nm is demultiplexed for each wavelength.

[0029]

According to the above construction, since the slab waveguide has no light confining structure in the direction parallel to the surface of the substrate, when the signal light in the wavelength band in the input waveguide is input, it spreads out in a fan shape for output. Each channel of the waveguide is equally distributed and output. When the signal light of another wavelength band is input to the input waveguide, it spreads in the slab waveguide and is input to the arrayed waveguide diffraction grating. In the arrayed waveguide diffraction grating, the wavelengths are demultiplexed, input to the slab waveguide again, and then demultiplexed to each channel waveguide of the spreading output waveguide and output.

By providing the slab waveguide with a wavelength filter so that the signal light from the input waveguide is demultiplexed or equally distributed and output from the output waveguide, equal distribution and demultiplexing are performed depending on the wavelength band. It can be switched freely.

[0031]

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a diagram showing an embodiment of the optical star coupler of the present invention. 2A is a sectional view taken along the line AA of FIG.
2B is a sectional view taken along line BB of FIG. 1, and FIG. 2C is FIG.
6 is a cross-sectional view taken along the line CC of FIG.

As shown in FIG. 1, the optical star coupler comprises a single input waveguide 10 on a substrate 101 made of glass.
2 and a slab waveguide 1 connected to the input waveguide 102
03, a plurality of output waveguides 105 connected to the slab waveguide 103, and an annular arrayed waveguide diffraction grating 104 having both ends connected to the slab waveguide 103. Slit 10 formed in part
6 has an interference film filter 107 embedded therein.

As shown in FIGS. 2A to 2C, the optical star coupler has a buffer layer 108 formed on a substrate 101 and is made of a material having a refractive index slightly higher than that of the buffer layer 108. A waveguide (core) is formed, and a core 109 is further formed.
A clad 110 having a slightly lower refractive index than the core 109
It has a structure embedded in.

The structure of each portion will be described below with reference to FIGS. 1 and 2A to 2C.

The slab waveguide 103 has a flat plate structure having no light confining structure in the lateral direction (direction parallel to the surface of the substrate), and is connected to the input waveguide and the output waveguide. Connection part, input part 111 of arrayed waveguide diffraction grating 104
And the output section 11 of the arrayed waveguide diffraction grating 104
The connecting portion with 2 has an arc shape.

Input waveguide 102 and output waveguide 10
Reference numeral 5 is a channel waveguide having a rectangular cross section, and has dummy ports 113 and 114, respectively. The input waveguide 102 and the output waveguide 105 are arranged along the end face of the slab waveguide 103 so as to have a fan shape (radial shape).

The arrayed waveguide diffraction grating 104 is composed of a plurality of channel waveguides 115 each having a rectangular cross section. The length of each channel waveguide 115 differs by ΔL (constant value), and they are arranged in the order of length. The dimensions of these channel waveguides 115 are designed so as to satisfy the single mode condition in the wavelength band of the signal light used.

The input section 111 and the output section 112 of the arrayed waveguide diffraction grating 104 are arranged radially along the end face of the slab waveguide 103, respectively, and have their centers of curvature 11 respectively.
6, 117 are arranged in a fan shape.

The input waveguide 102 and the input portion 111 of the arrayed waveguide diffraction grating 104 are the slab waveguide 103.
The output waveguide 105 and the output section 112 of the arrayed waveguide diffraction grating 104 are arranged to face each other with the slab waveguide 103 interposed therebetween.

In the interference film filter 107, the angle formed by the interference film filter 107 and the central axis 118 of the input waveguide 102 and the angle formed by the interference film filter 107 and the central axis 119 of the output waveguide 105 are the same. It is arranged to.

Here, the characteristic (1300
nm band (1270 to 1340 nm) or 1550n
Reflects light in the m band (1550 to 1560 nm), 1650
The interference film filter 107 having a wavelength band (1640 to 1700 nm) is used to equally distribute the signal light in the 1300 nm band or the 1550 nm band to obtain 1650 nm.
The operation principle of the optical star coupler in the case of multiplexing and demultiplexing the band signal light in a narrow band will be described.

FIGS. 4 (a) and 4 (b) are explanatory views for explaining the operation principle of the optical star coupler shown in FIG.

FIG. 4A shows the 1300 nm band or 15
It is shown that the signal light 120 in the 50 nm band is distributed to the output waveguide 105.

Signal light 120 (wavelength λ ₀ ) in the 1300 nm band or 1550 nm band is input from the input waveguide 102 to the slab waveguide 103 and propagates in the slab waveguide 103.

Here, the interference film filter 107 is 1300.
Since the light in the nm band or the 1550 nm band is reflected, the signal light 120 is reflected at the same angle as the incident angle and propagates in the direction of the output waveguide 105. At this time, since the slab waveguide 103 has no lateral confinement effect and the spot size of the signal light 120 increases with propagation, the signal light 120 is distributed to the output waveguide 105 arranged in a fan shape. .

FIG. 4B shows that the signal light (wavelengths λ _{1 to} λ _N ) 121 of 1650 nm is demultiplexed according to the wavelength. Signal light 121 in the 1650 nm band is also 1300
As with the signal light 120 in the nm band or 1550 nm band,
The slab waveguide 103 is input from the input waveguide 102 and propagates through the slab waveguide 103. However, since the interference film filter 107 transmits light in the 1650 nm band, the signal light 121 further propagates in the slab waveguide 103 while increasing the spot size. At this time, the input unit 1 of the slab waveguide 103 and the arrayed waveguide diffraction grating 104
Since the connection surface with 11 is formed in an arc shape having a center of curvature 116 at the connection point between the input waveguide 102 and the slab waveguide 103, this signal light 121 is in phase with the arrayed waveguide diffraction. The light enters the grating 104 and is distributed to the respective channel waveguides 115.

Since the plurality of channel waveguides 115 forming the arrayed waveguide diffraction grating 104 have different lengths, the phase of each channel waveguide 115 at the output section of the arrayed waveguide diffraction grating 104 is different. Assuming that the waveguide length difference of the arrayed waveguide diffraction grating 104 is ΔL, the phase difference φ between the adjacent channel waveguides is expressed by the equation 2, and it can be seen that it depends on the wavelength of the signal light.

[0049]

## EQU2 ## φ = 2πn _e ΔL / λ (where n _e is the effective refractive index of the channel waveguide) When Equation 2 is differentiated by the wavelength λ, it is expressed by Equation 3 and the wavelength dependence of the phase difference δφ Is proportional to the wavelength change δλ.

[0050]

Equation 3] .delta..phi = signal light 121 subjected to the phase change in -2πn _e ΔLδλ / λ ² arrayed waveguide grating 104, the output unit 112 of the arrayed waveguide grating 104
From the slab waveguide 103. At this time, since there is a phase difference between the channel waveguides, the equiphase surface 122 is inclined with respect to the end face of the slab waveguide 103. Further, since the phase difference φ has wavelength dependence, the equal phase plane 122
Of the arrayed waveguide diffraction grating 10 also has a wavelength dependence.
If the interval on the circular arc of each channel waveguide 115 constituting 4 is s, the inclination δθ of the phase plane between each wavelength (δλ).
Is from Equation 3 to Equation 4.

[0051]

## EQU4 ## δθ = −tan ⁻¹ {ΔLδλ / (sλ)} Therefore, the 1650 nm signal light 121 having the wavelength interval δλ.
(Wavelengths λ _{1 to} λ _N ) are propagated in different directions by the angular interval δθ. At this time, the interference film filter 107 has 16
1650 nm because it is transparent to 50 nm band light
Signal light of the above passes through the interference film filter 107. further,
The end face of the slab waveguide 103 at the output portion 112 of the arrayed waveguide diffraction grating 104 has an arc shape and its center of curvature 117
Is on the end face of the slab waveguide 103, the wavelength-multiplexed lights λ _{1 to} λ _N are condensed on the end face of the slab waveguide 103, and are output from the respective output waveguides 105.

FIGS. 5A and 5B are diagrams showing loss wavelength characteristics of the 1 × 8 optical star coupler. In both figures, the horizontal axis represents wavelength and the vertical axis represents loss.

From both figures, the 1300 nm band or 1550 nm
It can be seen that the signal light is equally distributed in the nm band, and the signal light is demultiplexed every 1.0 nm in the 1650 nm band.

FIG. 6 is a diagram showing a modification of the optical star coupler of the present invention.

The difference from the optical star coupler shown in FIG. 1 is that the shape of the slab waveguide, the mounting position of the input / output waveguide, the shape of the slit, and the characteristics of the interference film filter are changed.

As shown in the figure, an input waveguide 131, a substantially V-shaped slab waveguide 132 connected to the input waveguide 131, and an input waveguide 131 are provided on a substrate 130.
An output waveguide 133 connected to the slab waveguide 132 so as to face each other and an annular arrayed waveguide diffraction grating 134 having both ends connected to the slab waveguide 132 are formed. An inverted V-shaped slit 135 is formed in the slab waveguide 132, and two interference film filters 136 and 137 are inserted in the inverted V-shaped slit to form an optical star coupler.

FIG. 7 is a diagram showing the characteristics of the interference film filter used in the optical star coupler shown in FIG. In the figure, the horizontal axis represents wavelength and the vertical axis represents transmittance.

In this optical star coupler, 1300n
The signal light 120 in the m band or 1550 nm band is transmitted through the interference film filter and equally distributed. The signal light 121 in the 1650 nm band is reflected in the direction of the arrayed waveguide diffraction grating by the interference film filter, undergoes a phase shift according to the wavelength in the arrayed waveguide diffraction grating, and is output by the second interference film filter. It is reflected in the direction of the optical waveguide and is demultiplexed for each wavelength. In this way, the optical star coupler shown in FIG. 6 can obtain the same characteristics as those of the optical star coupler shown in FIG.

Therefore, the optical star coupler of this modification can obtain the same characteristics even if the shape of the slab waveguide, the mounting position of the input / output waveguide, and the forming / inserting position of the interference film filter are changed. .

As described above, according to the present embodiment, it is possible to realize an optical star coupler with a low loss, a small size, and a low cost, which has a demultiplexing function and an equal distribution function.

The optical star coupler described above can be changed by changing the characteristics and the mounting position of the interference film filter.
It is possible to freely set the wavelength band in which the signal light is desired to be equally distributed and the wavelength band in which the signal light is desired to be multiplexed / demultiplexed.

Further, the optical star coupler can be formed not only on the glass substrate but also on the semiconductor substrate or the like. Further, the core, the clad, and the buffer layer may be formed using not only a glass-based material but also an optically transparent material such as a semiconductor material.

The number of input waveguides is not limited to one and may be plural, and the number of output waveguides may be one instead of plural.

Further, in the present embodiment, the case where the signal light in the 1300 nm band or the 1550 nm band is equally distributed and the signal light in the 1650 nm band is multiplexed / demultiplexed in a narrow band has been described, but the present invention is not limited to this. Evenly distribute the light, 1
The signal light in the 550 nm band may be multiplexed / demultiplexed.

[0065]

In summary, according to the present invention, the following excellent effects are exhibited.

Signal light of a certain wavelength band from the input waveguide is equally distributed by the slab waveguide, and signal light of another wavelength from the input waveguide is multiplexed / demultiplexed for each wavelength by the arrayed waveguide diffraction grating. Therefore, it is possible to realize an optical star coupler having a demultiplexing function and a uniform distribution function, which has a small loss, a small size, and a low cost.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an optical star coupler of the present invention.

2 (a) is an AA of the optical star coupler shown in FIG.
A line sectional view, (b) is a BB line sectional view, and (c) is a CC line sectional view.

FIG. 3 is a diagram showing characteristics of an interference film filter of the optical star coupler shown in FIG.

4A and 4B are explanatory diagrams for explaining the operation principle of the optical star coupler shown in FIG.

5A and 5B are diagrams showing loss wavelength characteristics of a 1 × 8 optical star coupler.

FIG. 6 is a diagram showing a modification of the optical star coupler of the present invention.

7 is a diagram showing characteristics of an interference film filter used in the optical star coupler shown in FIG.

FIG. 8 is an example of a conventional optical star coupler with equal distribution and demultiplexing functions.

[Explanation of symbols]

 101 substrate 102 input waveguide 103 slab waveguide 104 array waveguide diffraction grating 105 output waveguide 120 signal light in a certain wavelength band 121 signal light in another wavelength band

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoto Uezuka 5-1-1 Hidaka-cho, Hitachi-shi, Ibaraki Hitachi Cable Co., Ltd.

Claims (16)

[Claims] 1. An input waveguide comprising at least one channel waveguide formed on a substrate, and a slab waveguide connected to the input waveguide for equally distributing signal light in a certain wavelength band. And an output waveguide connected to this slab waveguide and comprising an output waveguide comprising at least one channel waveguide, an array waveguide diffraction grating comprising a plurality of channel waveguides is provided in the slab waveguide. An optical star coupler, which is configured to connect and demultiplex the signal light of another wavelength band from the input waveguide for each wavelength. 2. The optical star coupler according to claim 1, wherein the slab waveguide is provided with a wavelength filter so that the signal light from the input waveguide is demultiplexed or equally distributed and output from the output waveguide. 3. The wavelength filter transmits signal light of a certain wavelength band and reflects signal light of another wavelength band, or reflects signal light of a certain wavelength band and signals of another wavelength band. The optical star coupler according to claim 2, wherein light is transmitted. 4. The optical star coupler according to claim 1, wherein the arrayed waveguide diffraction grating is composed of channel waveguides having different lengths and arranged in order of length. 5. The arrayed-waveguide diffraction grating has a waveguide length difference ΔL between adjacent channel waveguides expressed by the following equation (1): ΔL = λ · m / n _eff (where λ is a used wavelength, n The optical star coupler according to claim 4, wherein _eff is an effective refractive index and m is a positive integer. 6. The input waveguide, the output waveguide, the input portion and the output portion of the arrayed waveguide are arranged along the end face of the slab waveguide, respectively. Optical star coupler as described in the item. 7. The optical star according to claim 1, wherein the input waveguide and the input portion of the arrayed-waveguide diffraction grating are arranged opposite to each other at the end portion of the slab waveguide. Coupler. 8. The optical star according to claim 1, wherein the output waveguide and the output section of the arrayed waveguide diffraction grating are arranged opposite to each other at the end of the slab waveguide. Coupler. 9. The input end waveguide and the slab waveguide and the connection end face between the output waveguide and the slab waveguide are each formed in an arc shape, and the input waveguide and the slab waveguide are formed. 9. The optical star coupler according to claim 1, wherein the output waveguides are arranged in a fan shape from each curvature center. 10. The connection end face between the input part of the arrayed waveguide diffraction grating and the slab waveguide and the connection end facet between the output part of the arrayed waveguide diffraction grating and the slab waveguide are each formed in an arc shape. 10. The optical star coupler according to claim 1, wherein the input waveguide and the output waveguide are arranged in a fan shape from their respective centers of curvature. 11. The optical star coupler according to claim 9, wherein the central axis of the input waveguide arranged in a fan shape and the input part of the slab waveguide arranged in a fan shape are aligned with each other. 12. The optical star coupler according to claim 9, wherein a central axis of the output waveguide arranged in a fan shape and an output part of the slab waveguide arranged in a fan shape are aligned with each other. . 13. The angle formed by the center axis of the input waveguide arranged in a fan shape and the wavelength filter and the angle formed by the center axis of the output waveguide arranged in a fan shape and the interference film filter are matched. 13. The optical star coupler according to claim 2, wherein the wavelength filter is provided. 14. A signal light having a wavelength of 1300 nm and a signal light having a wavelength of 1550 nm are equally distributed to obtain a wavelength of 1650 nm.
The signal light of the band is demultiplexed for each wavelength.
13. The optical star coupler according to any one of 13 above. 15. The optical star coupler according to claim 1, wherein the signal light in the wavelength band of 1300 nm is equally distributed, and the signal light in the wavelength band of 1550 nm is demultiplexed for each wavelength. 16. The optical star coupler according to claim 1, wherein the signal light in the wavelength band of 1550 nm is equally distributed, and the signal light in the wavelength band of 1300 nm is demultiplexed for each wavelength.