JP2000059338A - Wavelength multiplexer circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the wavelength multiplexer circuit with a small size at a low cost by employing an AWG that is easily integrated with semiconductor components so as to reduce number of components. SOLUTION: Input signal lights with 8 different wavelength components λ1-λ8 are given to different input ports of a 9×9 AWG 30, A multiplex light combining the signal lights with wavelength components is outputted from any of output ports by utilizing a combination characteristic of the AWG 30. Part of the multiplex light is branched and given to the remaining input ports of the AWG 30 to which no input signal light is given. This multiplexed light is outputted as a branch light having the different wavelength components λ1-λ8 from the remaining output ports of the AWG 30 other than the output port from which the multiplex light is outputted by using the synthesis characteristic of the AWG 30 as a branch light. Then a PD detects each wavelength component to detect the presence of the signal light with each wavelength component given to the AWG 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength division multiplexing circuit, and more particularly to a wavelength division multiplexing circuit for reducing the cost by reducing the number of parts.

[0002]

2. Description of the Related Art Conventionally, a plurality of optical signals having different wavelengths are multiplexed and simultaneously transmitted as a plurality of channels using an optical fiber, thereby increasing the transmission capacity.
x: hereinafter abbreviated as WDM. ) There is a method. This WDM system is receiving attention as one of the optical transmission technologies that will be the core of future long-distance, large-capacity optical communication systems. In a WDM system that multiplexes and divides an optical signal having a plurality of wavelength components, an optical wavelength multiplexing / demultiplexing device that multiplexes and demultiplexes an optical signal having a very narrow wavelength interval affects the performance of the communication system.
An arrayed waveguide diffraction grating as a planar lightwave circuit formed on a planar substrate as such an optical wavelength multiplexer / demultiplexer.
d-Waveguide Grating: Hereinafter, abbreviated as AWG. ) Is W
It is expected to be applied not only to the optical wavelength multiplexer / demultiplexer in the DM system but also to an optical communication device such as a wavelength router and a wavelength selecting element for a multi-wavelength laser.

FIG. 5 schematically shows the structure of such an AWG. This AWG has an input waveguide 11 composed of a plurality of waveguides arranged at equal intervals on a substrate 10.
The waveguides are formed so as to be bent so as to have different lengths. The other end, which is different from the input end of each waveguide formed to have a different length in this way, is
Each of the first slab waveguides 12 is connected to an input terminal. The output end of the first slab waveguide 12 is connected to one end of a connection waveguide 13 composed of a plurality of waveguides arranged at regular intervals in a U-shape. The other end of the connection waveguide 13 is connected to an input end of the second slab waveguide 14. These first and second slab waveguides 12 and 14 function as a collimator and a condenser lens. The slab waveguide has a sector shape in which each waveguide has an end of the input or output waveguide as a center of curvature, and a light collecting function similar to a concave mirror can be provided by directing the axis of the waveguide to the center of curvature. That is, when input wavelength multiplexed light having a plurality of wavelength components λ ₁ ,..., Λ _N different from each other is input to one waveguide of the input waveguide 11, the lengths formed on the substrate 10 are different. In order to generate the same dispersibility as the diffraction grating due to the phase shift generated between the waveguides, the wavelength multiplexed light from the input waveguide 11 is demultiplexed, and different wavelength components λ ₁ ,.
The split light having λ _N can be extracted from the output waveguide 15, and the first slab waveguide 12 corresponds to this. By the way, if you input this in the opposite direction,
The second slab waveguide 14 corresponds to an optical multiplexer.

Further, by inputting wavelength multiplexed light input from one input waveguide from another adjacent input waveguide, split light having completely different wavelength components is extracted from each of the output waveguides 15. be able to. By inputting signal light having different wavelength components from each input waveguide, it is also possible to output a multiplexed signal obtained by multiplexing each signal light.

The wavelength interval Δλ between the wavelength components λ ₁ ,..., Λ _N of the signal light input to the AWG is one of the important parameters of the AWG. The pitch d of each waveguide,
The length difference ΔL of the waveguide, the focal length f determined by the radius of curvature of the ends of the first and second slab waveguides, the spacing Δx between the input and output waveguides, and the effective refractive index n _s of the first slab waveguide The wavelength interval Δλ can be changed. The wavelength λ ₀ obtained from the output waveguide at the center of the AWG is the center wavelength of the AWG,
The n _c and effective refractive index of the waveguide, when a numerical value that indicates whether the phase of light is shifted several wavelengths between adjacent waveguides m on diffraction orders of the AWG, the diffraction order m wavelength interval Δλ and AWG by the following equation Can be expressed as

[0006] Δλ = Δx / (f · m ) / (n s · d) ··· (1) m = n c · ΔL / λ 0 ··· (2)

By adjusting the design parameters in the AWG configuration, a desired AWG optical multiplexer / demultiplexer can be realized. Such AWG-related technology is disclosed, for example, in "Latest Data Collection 2 on Optical Communication Technology" (published by Optronics Co., Ltd.).

[0008] By the way, signal light having at least two wavelengths and different wavelength components is multiplexed, transmitted as a wavelength multiplexed optical signal through one optical fiber, and then demultiplexed into each wavelength again, thereby obtaining an optical fiber. There is a wavelength division multiplexing optical transmission device that enables effective utilization. In such a wavelength division multiplexing optical transmission device, it is necessary to recognize the number of multiplexed signals when wavelength multiplexing signal lights having different wavelength components. This is because the information is useful for setting a gain when collectively amplifying multiplexed optical signals such as an optical booster amplifier, an optical in-line amplifier, and an optical preamplifier included in the wavelength division multiplexing optical transmission device. Information on the number of signals to be multiplexed can be obtained by using an additional device that detects light intensity for each wavelength, such as an optical spectrum analyzer or a wavelength meter, or by counting the number of optical signals to be multiplexed in a wavelength multiplexing circuit. Is commonly done.

FIG. 6 shows a wavelength multiplexing circuit using the above-described AWG.
This shows an outline of the road configuration. This wavelength multiplexing
The paths have different wavelength components λ₁, Λ_Two, ...
・, Λ ₈Signal light 20 having₁, 20_Two, ..., 2
0₈Is input, and the wavelength component λ is output by the 8 × 8 AWG 21.₁
~ Λ₈Output a multiplexed light 22 in which the signal lights are multiplexed.
And can be. Input to the wavelength multiplexing circuit
Input signal light 20₁~ 20₈Is for each input signal light
Optical splitter 23 provided in₁~ 23₈Has been entered.
Optical splitter 23₁Then, the wavelength component λ₁Signal light 2 having
0₁AWG input light 24₁And monitor light 25₁Branch into two
You. Other optical splitter 23_Two~ 23₈But the optical splitter 23_TwoIs
Wavelength component λ_TwoSignal light 20 having_TwoTo AWG input light 2
4_TwoAnd monitor light 25_TwoAnd the optical branching record 23_ThreeIs the wavelength component λ_Three
Signal light 20 having_ThreeAWG input light 24_ThreeAnd monitor
Light 25_ThreeTo, the optical splitter 23₈Is the wavelength component λ₈To
Input signal light 20 having₈AWG input light 24₈And monitor light
25₈And two branches.

Each of the AWG input lights 24 _{1 to} 24 ₈ is input to _eight input ports I _{1 to} I ₈ of the 8 × ₈ AWG 21 respectively. Furthermore, each monitor light 25 _to 253 ₈ are each photodiode (Photo Diode:. Hereinafter abbreviated as PD) is input to the 26 ₁ to 26 _8. 8 × 8 AWG2
In 1, multiplexes the signal light having the input port I ₁ ~I ₈ different wavelength components lambda ₁ to [lambda] ₈ mutually inputted from so can be output from the output port O ₁ as a multiplexed optical 22 Has become. Also, each PD 26 _{1 to} 26 ₈
Detects signal lights having the respective wavelength components λ _{1 to} λ ₈ and counts the detected signal lights to recognize the number of wavelength multiplexed light signals.

By recognizing the number of wavelengths of each signal light to be multiplexed in this manner, it becomes possible to perform an optimum level adjustment for an amplifier such as an optical booster amplifier, an optical in-line amplifier, or an optical preamplifier having wavelength dependency. .

Also, the above-mentioned “Latest Data Collection 2 on Optical Communication Technology” (published by Optronics, Inc.) includes one AW
A band in which a plurality of wavelengths can be used without overlap due to a plurality of center wavelengths λ ₀ (Free Spectral Range: FS)
R), an ADM (Add / Drop Multi) that incorporates an AWG multiplexer / demultiplexer utilizing the repetition of the wavelength that repeats every R) into the WDM system.
plexer) is disclosed.

Japanese Patent Application Laid-Open No. 9-73107 discloses a "variable channel optical drop filter" which has approximately the same number of input / output ports as the number of selectable wavelengths, which is conventionally indispensable by using an input / output unit defined by the AWG. A technique that eliminates the number and optical semiconductor amplifier is disclosed.

[0014]

In such a conventional wavelength multiplexing circuit, an optimum level adjustment can be performed on a multiplexed optical signal amplified by an optical booster amplifier, an optical in-line amplifier, or an optical preamplifier. However, in order to recognize the signal light of each wavelength component included in the multiplexed light, an additional device for detecting the light intensity for each wavelength such as an optical spectrum analyzer or a wavelength meter is required, or the wavelength multiplexing shown in FIG. The circuit was arranged. However, in such an additional device, there is a problem that the wavelength multiplexing optical transmission device becomes very large and the cost increases.

Further, the wavelength division multiplexing circuit shown in FIG. 6 has a problem that the number of optical splitters required for the number of signals to be wavelength multiplexed is required to recognize the number of signals. This leads to a problem of lowering reliability.

Further, in the technique disclosed in Japanese Patent Application Laid-Open No. 9-73107, only by reducing the number of input / output ports to be used, the wavelength dependence inherent in an amplifier for amplifying multiplexed light to be transmitted to a transmission path or the like is known. There is a problem that it is not possible to perform control to avoid the problem.

Since the above-mentioned AWG can be integrated with a semiconductor device, it is desired to realize a lower-cost wavelength multiplexing circuit using such an AWG.

An object of the present invention is to provide a wavelength division multiplexing circuit that uses an AWG that can be integrated with a semiconductor element and that can reduce the number of components as much as possible to reduce the size and cost.

[0019]

According to the first aspect of the present invention, (a) a plurality of input ports, a plurality of output ports,
An optical multiplexing means for multiplexing a plurality of signal lights having different wavelength components input from the respective input ports and outputting the multiplexed light from one of the plurality of output ports; The multiplexed light input from one input port different from the input port to which the plurality of signal lights is input is split for each wavelength component, and the split light is output from the plurality of output ports to output the multiplexed light among the plurality of output ports. An optical multiplexing / demultiplexing means including optical demultiplexing means for outputting from a plurality of output ports different from the above; and (b) splitting a part of the multiplexed light output from one output port after being multiplexed by the optical multiplexing means. An optical splitting means for inputting the split light to one of the plurality of input ports different from the input port to which the plurality of signal lights are input; And it is provided to the wavelength division multiplexer circuit and a plurality of signal light detection means for detecting the presence or absence of the signal light for each of the plurality of demultiplexed light output from the plurality of output ports is branched into each wavelength component by.

That is, according to the first aspect of the present invention, the optical multiplexing / demultiplexing means provided with a plurality of input ports and output ports includes:
An optical multiplexing means for outputting multiplexed light of a plurality of signal lights having different wavelength components input from each of the input ports from one output port of the plurality of output ports, and a plurality of signal lights of the plurality of input ports The multiplexed light input from one input port different from the input port to which the multiplexed light is input is output from the plurality of output ports different from the output port from which the multiplexed light is output among the plurality of output ports. Optical demultiplexing means. Then, the split light obtained by splitting a part of the multiplexed light output from one output port of the optical multiplexing means is converted into an input port which is not used again for inputting any signal light among the plurality of input ports of the optical multiplexing means. From the multiplexed light. The split light input to the optical multiplexing means in this way is demultiplexed for each wavelength component by the optical demultiplexing means and output as demultiplexed light from a plurality of output ports. Is used to detect the presence or absence of signal light. Thus, when detecting the signal light for each wavelength component included in the multiplexed light having different wavelength components from each other, the optical branching unit, which is conventionally required by the number of the wavelength components included in the multiplexed light, is branched. Since only one light branching unit for generating light is required, the wavelength multiplexing circuit can be easily reduced in size and cost.

According to a second aspect of the present invention, in the wavelength multiplexing circuit of the first aspect, the signal light detecting means is a photodiode.

That is, according to the second aspect of the present invention, by using a photodiode as the signal light detecting means, the presence or absence of the signal light for each wavelength component included in the multiplexed light having different wavelength components can be easily detected. This makes it possible to appropriately change the gain of the subsequent optical amplifier having wavelength dependency.

According to a third aspect of the present invention, in the wavelength multiplexing circuit according to the first aspect, the optical multiplexing / demultiplexing means is an array waveguide diffraction grating.

That is, according to the third aspect of the present invention, the optical multiplexing / demultiplexing means is constituted by an array waveguide diffraction grating, the optical multiplexing means and the optical demultiplexing means are reduced in size, and signal light of each component wavelength is input. An input port, an output port for outputting multiplexed light, an input port for inputting the multiplexed light as return light, and an output port for outputting split light for each wavelength component are appropriately selected. Thus, by reducing the required number of light branching means and adopting the arrayed waveguide diffraction grating, a remarkable effect can be obtained in reducing the size of the wavelength division multiplexing circuit.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments.

FIG. 1 shows an outline of the configuration of a wavelength division multiplexing circuit according to an embodiment of the present invention. This wavelength multiplexing circuit multiplexes signal light of eight wavelength components,
9 × 9 AWG 30, optical splitter 31, and multiple PDs 32
It is characterized by and a _{1-32 8.} 9x9
The AWG 30 has nine input ports I _{1 to} I ₉ and nine output ports O _{1 to} O ₉ . In the 9 × 9 AWG 30, eight input ports I _{2 to} I ₉ are transmitted from an optical transmitter (not shown).
Signal light 32 ₁ having a predetermined wavelength input to each of them.
To 32 _8, it is outputted from the output port O ₁ as an output signal light 34 are multiplexed by the multiplexing characteristics of the AWG. The multiplexed output signal light 34 having a plurality of wavelength components is input to the optical splitter 31 and is split into an output light 35 and a return light 36. Returning light 36 which is branched by the optical splitter 31 is input to the input port I ₁ of 9 × 9AWG30 as multiplexed light having a plurality of wavelength components. The return light 36 is adapted to output as the demultiplexed light 37 _{1-37 8} having a predetermined wavelength components from the output port O ₂ ~ O _9, respectively, by demultiplexing property of AWG30. Each demultiplexed light 37 _{1-37 8} is inputted to the PD 32 ₁ to 32 _8, which are provided in correspondence to each output port, respectively, the presence or absence of the signal light of each wavelength component is detected.

Next, an AWG having such multiplexing and demultiplexing characteristics will be described.

FIG. 2 shows the input ports and output ports of the 9 × 9 AWG 30 shown in FIG. The 9 × 9 AWG 30 has a first input port I ₁ , a second input port I ₂ ,..., And a ninth input port I ₉ , similarly to the multiplexing and demultiplexing characteristics of the conventional AWG. The output signal light output from the first output port O ₁ , the second output port O ₂ ,..., The ninth output port O _9, respectively, according to the wavelength component of the signal light input thereto. Have different wavelength components.

FIG. 3 is a wavelength characteristic table for explaining the multiplexing characteristic of the AWG 30. That is, different wavelength components to the first input port _{I 1 λ a, λ 1,} ···,
When the input multiplexed signal light having a lambda ₈ is input, a first output port O ₁ from the wavelength components lambda _a, a second output port O ₂ wavelength components from lambda _1, · · ·, the output port O of the 9 ₉ indicates that the split light having the wavelength component λ ₈ is output. The second input port I ₂ in mutually different wavelength components lambda _a, lambda _1, · · ·, the input multiplexed signal light having a lambda ₈ is input, the wavelength component from the first output port O ₁ lambda ₈ , the second output port O ₂ from the wavelength components lambda _a, a third output port O ₃ wavelength components from lambda _1, · · ·, a ninth output port O ₉ demultiplexed light output having respective wavelength components lambda ₇ from It is shown that it is. Similarly, wavelength components λ different from each other are output from the third input port I ₃ to the seventh input port I _7.
Also , when an input multiplexed signal light having _a , λ ₁ ,..., λ ₈ is input, a demultiplexed light having a wavelength component as shown in FIG. 3 is output. Ninth input port I ₉ in mutually different wavelength components lambda _a of, lambda _1, · · ·, the input multiplexed signal light having a lambda ₈ is input, the wavelength components lambda ₁ from the first output port O _1, the 2
Output port O ₂ wavelength components from λ _2, ···, demultiplexed light is output with a ninth wavelength component lambda _a from the output port O _9, respectively.

Focusing on the signal light of each wavelength component inputted from the input port, if an input signal light having _a wavelength component λa is inputted from the first input port I ₁ , the wavelength is outputted from the first output port O _1. demultiplexed light is obtained having components lambda _a.
When input signal light having a wavelength component λ ₁ is input from the second input port I _2, split light having a wavelength component λ ₁ is obtained from the third output port O ₃ . When an input signal light having a wavelength component λ ₂ is input from the third input port I ₃ ,
The split light having the wavelength component λ ₂ is obtained from the fifth output port O ₅ . Similarly, the wavelength component λ ₃ from the _fourth input port I ₄ is output from the seventh output port O ₇ , and the wavelength component λ ₄ from the _fifth input port I ₅ is output from the ninth output port O ₉
The wavelength component λ ₅ from the _sixth input port I ₆ is transmitted from the second output port O ₂ to the wavelength component λ ₆ from the _seventh input port I _7.
From the fourth output port O _4, the wavelength component lambda ₇ from the input port I ₈ of the eighth output port O ₆ of the sixth, the wavelength component lambda ₈ from the input port I ₉ of a ninth eighth from the output port O _8, it can be seen that respectively obtained. By inputting the signal light having only one wavelength component from each input port in this manner, output light corresponding to the wavelength component of the input signal light from the input port can be obtained from each output port of the AWG 30.

[0032] FIG. 4 is a diagram showing an wavelength characteristics focusing on output signal light output from the first output port O _1. That is, the wavelength component λ ₈ from the second input port I ₂ ,
The third input port I ₃ wavelength components from lambda _7, the fourth input port I ₄ wavelength component from lambda _6, a fifth input port I ₅ wavelength component from lambda _5, the wavelength components from the input port I ₆ of the 6 lambda _4th , 7th
Wavelength component λ ₃ from the input port I _{7 of the}
Wavelength component lambda ₂ to _8, when the ninth input from port I ₉ wavelength components lambda ₉ entered simultaneously AWG30 signal light having each first as is clear from the wavelength characteristic shown in FIG. 4
Wavelength multiplexed light having wavelength components λ _{1 to} λ ₈ can be obtained from the output port O ₁ .

By devising a method of inputting signal light having each wavelength component from each input port in this manner, an optical multiplexer / demultiplexer having desired multiplexing characteristics and demultiplexing characteristics can be realized. .

Therefore, in the wavelength division multiplexing circuit according to the present embodiment, the first to ninth input ports I _{1 to} I ₉ are such that the input signal light wavelength matches the filter center wavelength, and the first output port port O ₁ is so as to have a multiplexing characteristics as multiplexed optical signal is output. Then, in such a wavelength multiplexing circuit, to the input port I ₂ an input signal light 33 ₁ of the second, respectively the signal light has a wavelength component lambda ₈ having different wavelength components lambda ₁ to [lambda] ₈ together, the wavelength component lambda an input signal light 33 ₂ having ₇ to the third input port I _3, an input signal light 33 ₃ having a wavelength component lambda ₆ to the fourth input port I _4, the wavelength component lambda
_The input signal light 33 ₄ having _{5 is applied} to a fifth input port I ₅ ,
Input signal light 33 ₅ having wavelength component λ ₄ is supplied to sixth input port I ₆ , and input signal light 33 ₆ having wavelength component λ ₃ is supplied to seventh input port I ₆ .
The input port I ₇ of the input signal light 3 having the wavelength component lambda ₂
3 ₇ to the input port I ₈ of the eighth to input the input signal light 33 ₈ having wavelength components lambda ₁ to the input port I ₉ ninth. 9
The × 9 AWG 30 outputs the multiplexed light having the wavelength components λ _{1 to} λ ₈ from the first output port O ₁ as the output signal light 34 as shown in FIG. The output signal light 34 is input to the optical splitter 31 and is split into an output light 35 having wavelength components λ _{1 to} λ ₈ and a return light 36. Output light 35
Is output as it is to the outside of the wavelength division multiplexing circuit and sent to a transmission line (not shown) or an optical booster amplifier.

Return light 36 having wavelength components λ _{1 to} λ ₈ is
It is input to the _first input port I ₁ of the 9 × 9 AWG 30. Then, as is apparent from the demultiplexing characteristics shown in FIG. 3, the components having the wavelength components λ ₁ , λ ₂ ,..., Λ ₈ from the second output port O ₂ to the ninth output port O ₉ , respectively. Wave light 37 ₁
To 37 ₈ is output. Each demultiplexed light 37 _{1-37 8} is input to each PD 32 ₁ to 32 _8, the presence or absence of the signal light of each wavelength component is detected. Thus, in accordance with the signal component detected by the PD, it is possible to perform optimal level adjustment of various amplifying devices for amplifying a transmission signal such as an optical booster amplifier to which the above-described output light 35 is transmitted. .

As described above, in this embodiment,
The wavelength multiplexing circuit has eight different wavelength components λ₁,
λ_Two, ..., λ₈Input signal light with different
Input to 9 × 9 AWG30 from input port, AWG30
From one of the output ports using the multiplexing characteristics of
To output a multiplexed light that combines the component signal lights.
I have. Therefore, a part of the multiplexed light is branched and the input signal is
Input to the remaining input ports of AWG30 where light is not input
Let it. Branch in this way and input from the remaining input ports
The multiplexed light is combined in the AWG 30 by the AWG 30.
Output port of AWG30 that outputs multiplexed light using the wave characteristics
Demultiplexing characteristics of AWG30 from the remaining output ports other than the port
Using the wavelength components λ different from each other₁, Λ_Two,
..., λ ₈Is output as demultiplexed light having Soshi
By detecting each wavelength component with PD, A
Detects the presence or absence of signal light of each wavelength component input to WG30
I am trying to do it. As a result, using the conventional AWG
To monitor the signal light of each wavelength component with a wavelength multiplexed circuit
To reduce the number of optical splitters required for each wavelength component to one
Will be able to

The wavelength division multiplexing circuit in this embodiment can supply useful wavelength number information to an optical amplifier connected after the optical ADM. In general, when an optical ADM is configured, a wavelength-multiplexed optical signal is branched by an optical demultiplexer or the like, and a wavelength component assigned to each node is extracted and received. Will be sent. In such a case as well, information on the number of signals of multiplexed wavelengths is useful for an optical amplifier connected after the optical ADM, and it is possible to perform optimal level adjustment.

Although the wavelength spacing between a plurality of signal lights having different wavelength components in the present embodiment is not particularly described, it is easily optimized by changing various AWG design parameters in the present embodiment. AW
The multiplexing and demultiplexing characteristics of G can be realized.

Although the AWG in this embodiment is 9 × 9 AWG in order to handle eight wavelength components, the invention is not limited to this. When dealing with N (N is plural) wavelength components, using (N + 1) × (N + 1) AWG,
By inputting an optimal input signal light as shown in this embodiment, a low-cost wavelength multiplexing circuit can be realized.

The AWG and PD according to the present embodiment,
It is obvious that the wavelength division multiplexing circuit can be reduced in size and improved in reliability by integrating the optical branching device.

[0041]

As described above, according to the first aspect of the present invention, when detecting the signal light for each wavelength component included in the multiplexed light having different wavelength components, the conventional multiplexed light is used. Since the number of wavelength components included in the optical branching unit is required, only one optical branching unit for generating the branched light is required, so that it is possible to easily realize the miniaturization and cost reduction of the wavelength division multiplexing circuit. become able to.

According to the second aspect of the present invention, the presence or absence of signal light for each wavelength component included in the multiplexed light having different wavelength components can be easily detected by using a photodiode as the signal light detecting means. By counting the detection results, it becomes possible to appropriately change the gain of the subsequent-stage optical amplifier having wavelength dependency.

Further, according to the third aspect of the present invention, a remarkable effect can be obtained in reducing the size of the wavelength multiplexing circuit by reducing the required number of light branching means and employing the array waveguide diffraction grating.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an outline of a configuration of a wavelength division multiplexing circuit according to an embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating a 9 × 9 AWG in the present embodiment.

FIG. 3 is an explanatory diagram for explaining a demultiplexing characteristic of an AWG in the present embodiment.

FIG. 4 is an explanatory diagram for explaining the multiplexing characteristics of the AWG in the present embodiment.

FIG. 5 is a plan view showing a structure of a conventional AWG.

FIG. 6 is a block diagram showing an outline of a configuration of a conventionally proposed wavelength division multiplexing circuit.

[Explanation of symbols]

30 9 × 9AWG 31 optical splitter _{32 1 ~32 8 PD 33 1 ~33} 8 input signal light 34 output signal light 35 output light 36 returning light 37 _{1-37 8} demultiplexed light

Claims (3)

[Claims] 1. A plurality of input ports, a plurality of output ports, and a plurality of signal lights having different wavelength components input from the respective input ports are multiplexed, and the multiplexed light is combined with the plurality of output ports. Optical multiplexing means for outputting from one output port, and multiplexed light input from one of the plurality of input ports different from the input port to which the plurality of signal lights are input, for each of the wavelength components. Optical demultiplexing means comprising: demultiplexing means for demultiplexing and outputting these demultiplexed lights from a plurality of output ports different from the output port outputting the multiplexed light among the plurality of output ports; and A part of the multiplexed light that is multiplexed by the one output port and is output from the one output port is split, and the split light is split into the plurality of signals of the plurality of input ports. Optical branching means for inputting to one input port different from the input port to which the light is input, and a signal for each of a plurality of demultiplexed lights output from the plurality of output ports after being split for each wavelength component by the optical splitting means. A wavelength multiplexing circuit comprising: a plurality of signal light detecting means for detecting the presence or absence of light. 2. The wavelength multiplexing circuit according to claim 1, wherein said signal light detecting means is a photodiode. 3. The wavelength multiplexing circuit according to claim 1, wherein said optical multiplexing / demultiplexing means is an array waveguide diffraction grating.