JPH05323389A - Optical variable branching filter device - Google Patents

Abstract

(57) [Summary] (Modified) [Objective] To provide an optical variable demultiplexer that demultiplexes a frequency-multiplexed optical signal for each frequency with no loss and with a simple configuration. [Structure] Outgoing optical paths 15A to 15 by demultiplexing light of a predetermined frequency out of frequency multiplexed optical signals input from an input optical path 5
In the variable optical demultiplexer 1 for outputting on D, the ring-shaped optical paths 7A to 7D and the first optical coupling means 9A to 9 for optically coupling the ring-shaped optical paths 7A to 7D and the input optical path 5 respectively.
D, second optical coupling means 11A to 11D for optically coupling this and the output optical paths 15A to 15D, and adjusting means 13A to 13D provided in the ring-shaped optical paths 7A to 7D and adjusting the optical path length. Have and.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field of optical frequency multiplex communication, and more particularly to an optical variable demultiplexer used for frequency multiplex type optical switching.

[0002]

2. Description of the Related Art In recent years, optical frequency multiplex communication for multiplexing and transmitting and exchanging a large number of optical signals at a frequency interval of about 5 GHz using an optical transmission medium such as a silica optical fiber is a future large capacity optical communication. It is attracting attention as the main method of web.

An optical variable demultiplexer can be mentioned as one of the optical circuits that enables such optical frequency multiplex communication. The variable optical demultiplexer spatially separates and extracts the multiplexed optical signals of a plurality of frequency channels into an arbitrary output optical path.

As a typical example for realizing such a variable demultiplexer, as shown in FIG. 4, an optical signal on the input optical path is once branched by an optical branching device 101, and then each output optical path 105A, Frequency filters 103A, 103B, 103 provided for each of 105B, 105C, 105D
It is known that a desired channel is selected by C and 103D and output to the output optical paths 105A to 105D. As the frequency filter used here, various frequency filters using a resonator structure of a bulk type, a fiber type, a plane waveguide type, etc. can be applied. In the example shown in FIG. 4, as an operation example, the optical signal f1, on the input optical path is
, F4 are demultiplexed to output optical path 105A f2, output optical path 105B f4, output optical path 105C f1, output optical path 1
The case where f3 is output to 05D is shown. In addition, each frequency filter 103A, 103B, 103C,
By adjusting 103D, an optical signal having an arbitrary frequency can be output to an arbitrary output optical path.

[0005]

However, in the conventional optical demultiplexer described above, as is apparent from FIG. 4, the optical signal of each frequency channel is processed by the optical branch circuit before being selected by the frequency filter. Since it is divided into four, the optical power becomes 1/4 in principle. That is, in general, when branching into n lines, the optical power becomes 1 / n in principle. Therefore, there is a drawback that the loss becomes large when the scale is increased and n is increased.

The present invention has been made in view of the above problems, and provides an optical variable demultiplexing device which has no loss due to a branch circuit unlike the conventional optical variable demultiplexing circuit and has a low loss in principle. With the goal.

[0007]

According to a first aspect of the present invention, there is provided an optical variable demultiplexing device for demultiplexing a frequency-multiplexed optical signal inputted from an input optical path for each frequency and outputting the demultiplexed optical signals on a plurality of output optical paths. A plurality of ring-shaped optical paths formed in an annular shape having a predetermined optical path length, a plurality of first optical coupling means for optically coupling the ring-shaped optical path and the input optical path, and the ring-shaped optical path. It is a gist to have a plurality of second optical coupling means for respectively optically coupling the output optical path.

A second aspect of the present invention is an optical variable demultiplexing device that demultiplexes a predetermined frequency light of a frequency-multiplexed optical signal input from an input optical path and outputs the demultiplexed optical signal on an output optical path. A ring-shaped optical path, a plurality of first optical coupling means for optically coupling the ring-shaped optical path and the input optical path, and a plurality of second optical couplings for optically coupling the ring-shaped optical path and the output optical path. The gist of the invention is to have means and an adjusting means that is provided in the ring-shaped optical path and adjusts the optical path length.

A third invention of the present application is that the ring-shaped optical path according to the above-mentioned claim 1 or 2 has a waveguide-type optical amplification means in which at least a part of the ring-shaped optical path is provided with rare earth ions. Use as a summary.

[0010]

The variable optical demultiplexer according to the first aspect of the present invention has a predetermined optical path length for optically coupling the frequency-multiplexed optical signal input from the input optical path with the input optical path by the first optical coupling means. Then, the light is guided to a plurality of ring-shaped optical paths formed in an annular shape, and is further demultiplexed for each frequency and output to the output optical paths optically coupled with the ring-shaped optical path and the second optical coupling means.

In the optical variable demultiplexer according to the second aspect of the present invention, a predetermined frequency light of the frequency multiplexed optical signal input from the input optical path is optically coupled to the input optical path by the first optical coupling means. The light having the desired frequency is demultiplexed and output to the ring-shaped optical path formed in the above step, and the output optical path optically coupled with the ring-shaped optical path by the second optical coupling means.
At this time, since the ring-shaped optical path is provided with the adjusting means for adjusting the optical path length, the light obtained from the output optical path can be made to have a desired frequency by finely adjusting the optical path length.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a block diagram showing a configuration of an optical variable demultiplexer 1 according to the present invention, which is an example in the case where the number of output optical paths is 4 and the input frequency signals are f1, f2, f3 and f4.

A silica single mode optical waveguide formed on the substrate 3 is used for each optical path, and four output optical paths 15A, 15B, 15C and 15D are provided for one input optical path 5. Further, the input optical path 5 and the output optical paths 15A, 15
The first couplers 9A, 9B, 9C, 9D and the second couplers 11A, 11 are respectively connected to B, 15C, 15D.
Ring-shaped optical paths 7A, 7B, through B, 11C, 11D,
7C and 7D are arranged. These ring-shaped optical paths 7A, 7
B, 7C, and 7D are appropriately set according to the output frequency signal whose optical length is desired by changing the actual physical length or the refractive index. When changing the optical length, the phase shifters 13A, 1 as adjusting means are used.
3B, 13C, 13D may be used, and in this case, the light obtained from the output optical path can be easily set to a desired frequency.

The phase shifters 13A, 13B, 13C and 13
For D, a thin film heater that induces a change in the refractive index due to the thermo-optic effect is used. In the figure, the phase shifters 13A, 13
B, 13C, 13D are adjusted by the heater voltage, f1 is selected as the output optical path 15C, f2 is selected as the output optical path 15A, f3 is selected as the output optical path 15D, and f4 is selected as the output optical path 15B. Of the frequency-multiplexed optical signals f1, f2, f3, f4 on the input optical path 5, the ring-shaped optical path 7A
Since the resonance frequency of is set to f2, only f2 is output to the output optical path 15A, and f1, f3, and f4 propagate as they are on the input optical path. Hereinafter, similarly, the resonance frequencies of the ring-shaped optical paths 7B, 7C, and 7D are f4, f, respectively.
1 and f3, the output optical paths 15B,
It is output to 15C and 15D.

In the optical variable demultiplexer 1 according to this embodiment, four ring-shaped optical paths 7A, 7B, 7C, 7 are provided on the input optical path 5.
D is arranged, and the frequency characteristic of each ring-shaped optical path is as shown in FIGS. 2 and 3, the so-called FSR (Fre (Fre)
e Spectrum Range) which is repeated at regular frequency intervals.

Also, from the input optical path 5 to the output optical paths 15A, 1
As shown in FIG. 2, the frequency characteristics up to 5B, 15C, and 15D are transmission at the resonance frequency f0 of the ring and cutoff characteristics at other than the resonance frequency f0. On the other hand, as shown in FIG. 3, the frequency characteristic with respect to the optical signal propagating through the input optical path 5 as it is is cut off at the resonance frequency f0 and the resonance frequency f0.
In other cases, the pass characteristic is obtained, which is complementary to that in FIG. The pass band width Δf indicating the steepness of the filter characteristic at the resonance frequency f0 can be adjusted by setting the coupling coefficient of the first optical coupler 9 and the second optical coupler 11.

When a particularly steep filter characteristic is required, the patent by Kawauchi et al.
-306801), it is realized by providing an asymmetric Mach-Zehnder interferometer circuit in the optical path of the ring-shaped optical path 7. Also, the resonance frequency f of the ring
0 can be finely adjusted by adjusting the phase shifter provided on the ring, and can be adjusted to an arbitrary frequency by shifting the frequency within the FSR range. That is, in each ring resonator, only one arbitrary frequency is selected from a plurality of frequency-multiplexed optical signals and output to the output optical path, and optical signals of other frequencies are theoretically transmitted on the input optical path. It propagates as it is with low loss.

That is, in the variable optical demultiplexer according to the present embodiment, the phase shifter is adjusted in each of the plurality of ring resonators provided on the input optical path to select an arbitrary frequency signal and output it to an arbitrary output optical path. Can be output.

Further, a steep filter characteristic can be realized by providing a waveguide type optical amplifier in a part of the ring-shaped optical path. As such a waveguide type amplifier, optical amplification in which rare earth ions are added to the waveguide is known.

[0021]

As described above, in the variable optical branch circuit according to the present invention, the variable branch is realized without branching the input signal. Therefore, the branch loss due to the branch when the number of output optical paths is increased. It is possible to realize a variable optical branch with low loss.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an optical variable demultiplexer having four output optical paths according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining an optical frequency characteristic of a ring-shaped optical path in FIG.

FIG. 3 is a diagram for explaining an optical frequency characteristic of the ring-shaped optical path in FIG.

FIG. 4 is a diagram showing a configuration of a conventional variable optical branching device.

[Explanation of symbols]

 1 optical variable demultiplexer, 3 substrate, 5 input optical path, 7 ring optical path, 9 first optical coupler, 11 second optical coupler, 13 phase shifter, 15 output optical path,

Claims (3)

[Claims] 1. An optical variable demultiplexing device that demultiplexes a frequency-multiplexed optical signal input from an input optical path for each frequency and outputs it on a plurality of output optical paths, each having a predetermined optical path length and formed into an annular shape. A plurality of ring-shaped optical paths to be formed, a plurality of first optical coupling means for optically coupling the ring-shaped optical path and the input optical path, respectively, and a plurality of optical coupling means for optically coupling the ring-shaped optical path and the output optical path. An optical variable demultiplexing device having a second optical coupling means. 2. An optical variable demultiplexing device for demultiplexing a predetermined frequency light of a frequency-multiplexed optical signal input from an input optical path and outputting it on an output optical path, wherein a ring-shaped optical path formed in an annular shape, First optical coupling means for optically coupling the ring-shaped optical path and the input optical path with each other, second optical coupling means for optically coupling the ring-shaped optical path and the output optical path with each other, and provided in the ring-shaped optical path. And an adjusting means for adjusting the optical path length of the optical variable demultiplexing device. 3. The variable optical component according to claim 1, wherein the ring-shaped optical path has a waveguide-type optical amplification means in which at least a part of the ring-shaped optical path is provided with rare earth ions. Wave device.