JP2002174741A - Optical multiplexer / demultiplexer - Google Patents

Abstract

(57) Abstract: An optical multiplexer / demultiplexer capable of miniaturizing a planar waveguide type optical circuit used for multiplexing / demultiplexing each signal light included in multi-wavelength signal light is provided. SOLUTION: An optical multiplexer / demultiplexer A is provided with an optical multiplexer / demultiplexer waveguide part B.
And a first input / output waveguide section C and a second input / output waveguide section D. Then, the first signal light group having the frequency interval Δν ₁ inputted by the first channel waveguide 1 and the second channel waveguide 2 of the first input / output waveguide section C is converted into two signal lights having the frequency interval Δν _2. A Mach-Zehnder type optical circuit that performs group demultiplexing into groups is formed, and two group-demultiplexed signal light groups are passed through the arrayed waveguide grating type optical circuit of the optical multiplexing / demultiplexing waveguide section B in the opposite direction. As a result, the signal light is demultiplexed for each signal light, and output from the third channel waveguide 3 and the fourth channel waveguide 4 of the second input / output waveguide section D.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical multiplexer / demultiplexer used for multiplexing or demultiplexing each signal light of multi-wavelength signal light in a wavelength division multiplexing transmission system.

[0002]

2. Description of the Related Art Wavelength multiplexing (WDM)
The n Multiplexing) communication system performs high-speed and large-capacity optical communication by transmitting multi-wavelength signal light (a plurality of signal lights having different wavelengths) through an optical fiber line. Such wavelength division multiplexing transmission systems are being developed and introduced in response to social needs due to the advent of the advanced information society and in response to the rapid increase in communication demands in recent years such as the Internet.

In such a wavelength division multiplexing transmission system, each signal light having a different wavelength contained in the multi-wavelength signal light is compared with the multi-wavelength signal light transmitted on an optical transmission line such as an optical fiber transmission line. May need to be multiplexed or demultiplexed. For such multiplexing and demultiplexing of multi-wavelength signal light, for example, a planar waveguide type optical circuit including a planar optical waveguide formed on a substrate with a predetermined waveguide pattern is used.

[0004]

As an optical multiplexer / demultiplexer constituted by the above-mentioned planar waveguide type optical circuit, there is, for example, an arrayed waveguide diffraction grating type optical multiplexer / demultiplexer (for example, Japanese Patent Laid-Open No. 4-326308). Reference). In an arrayed waveguide grating type optical multiplexer / demultiplexer, an arrayed waveguide section including a plurality of channel waveguides having different optical path lengths is formed on a substrate. Then, when the multi-wavelength signal light (signal light group) is transmitted through the arrayed waveguide section, the multi-wavelength signal light is multiplexed / demultiplexed using the phase difference generated in each signal light.

[0005] In such an optical multiplexer / demultiplexer such as an arrayed waveguide diffraction grating type, the channel interval (frequency interval, wavelength interval) of each signal light in the multi-wavelength signal light to be multiplexed / demultiplexed becomes small. When the number of signal lights for a certain wavelength band increases, it becomes difficult to secure a sufficient signal light wavelength band with a normal optical circuit configuration. Further, problems such as occurrence of crosstalk between signal lights of respective channels at small channel intervals occur.

[0006] The securing of the signal light wavelength band and the suppression of the occurrence of crosstalk can be realized to some extent by expanding the configuration of a normal optical circuit. However, in this case, it is necessary to increase the area of the array waveguide in the array waveguide diffraction grating type optical circuit.
A problem is the increase in the size of the planar waveguide type optical circuit used as the optical multiplexer / demultiplexer.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to reduce the size of a planar waveguide type optical circuit used for multiplexing / demultiplexing each signal light included in a multi-wavelength signal light. It is an object of the present invention to provide an optical multiplexer / demultiplexer capable of performing the following.

[0008]

In order to achieve the above object, an optical multiplexer / demultiplexer according to the present invention comprises a substrate and an optical waveguide formed on the substrate, wherein each of the multi-wavelength signal light is provided. An optical multiplexer / demultiplexer for multiplexing or demultiplexing signal light, comprising: (1) an array waveguide section including a plurality of channel waveguides having different optical path lengths, and connected to one end of the array waveguide section; An optical multiplexing / demultiplexing waveguide section having a first slab waveguide and a second slab waveguide connected to the other end of the arrayed waveguide section; and (2) one end of the first slab waveguide. And a second channel waveguide having one end connected to the second slab waveguide.
The other end of each of the channel waveguide and the second channel waveguide is connected to a first input / output waveguide that forms a first input / output port, and (3) one end is connected to the first slab waveguide. A plurality of third channel waveguides, and a plurality of fourth channel waveguides each having one end connected to the second slab waveguide, wherein the plurality of third channel waveguides and the plurality of fourth channel waveguides are provided. A second input / output waveguide section having the other end of each of the waveguides forming a second input / output port; and (4) the first input / output waveguide section has a first input / output port. When a first signal light group consisting of a plurality of signal lights having a frequency interval Δν ₁ is input from the port, the first signal light is transmitted from the first channel waveguide to the first signal light group.
Frequency interval Δν ₂ output to the slab waveguide (Δν ₂ =
2 × Δν ₁ ) and a third signal shifted by Δν _{1 with} respect to the second signal light group at a frequency interval Δν ₂ output from the second channel waveguide to the second slab waveguide. (5) The second signal light group input to the first slab waveguide is demultiplexed by the optical multiplexing / demultiplexing waveguide unit, and each of the first signal light group is demultiplexed into the light group. The signal light is output from the second input / output port through each of the plurality of fourth channel waveguides, and the third signal light group input to the second slab waveguide is separated by the optical multiplexing / demultiplexing waveguide unit. The signal light is demultiplexed, and each signal light is output from the second input / output port via each of the plurality of third channel waveguides.

In the above-described optical multiplexer / demultiplexer, a first input / output waveguide section including a first input / output port for an optical multiplexer / demultiplexer waveguide section constituting an arrayed waveguide grating optical circuit; The second input / output waveguide section including the second input / output port is connected to the channel waveguide connected to the first slab waveguide and the second slab waveguide of the optical multiplexing / demultiplexing waveguide section, respectively. Channel waveguide. And
One of these two input / output waveguide sections, one of the first input / output waveguide sections is a light having a function of group-dividing the multi-wavelength signal light into the first slab waveguide and the second slab waveguide. It is formed so as to constitute a circuit (interleaver).

[0010] Thus, as described above, the signal light groups of frequency intervals .DELTA..nu ₁ input as multi-wavelength signal light, first
Two signal light groups (for example, a signal light group consisting of even-numbered signal lights of the input signal light group and an odd-numbered signal light group) having two times the frequency interval Δν ₂ via the input / output waveguide unit. ). Then, each of the group-demultiplexed signal light groups is demultiplexed for each signal light by passing through the arrayed waveguide grating optical circuit in opposite directions.

At this time, the input signal light group has the number of channels N,
If the frequency spacing .DELTA..nu _1, as the optical multiplexing and demultiplexing waveguide section, the number of channels N / 2, so that may be used arrayed waveguide grating optical circuit of the frequency interval .DELTA..nu _2. Therefore, even if the frequency interval between adjacent channels in the multi-wavelength signal light to be multiplexed / demultiplexed is reduced, it is possible to sufficiently reduce the size of the planar waveguide type optical circuit used for multiplexing / demultiplexing. Become. Further, since the frequency interval of the signal light group to be multiplexed / demultiplexed by the arrayed waveguide diffraction grating type optical circuit can be increased,
The occurrence of crosstalk between the signal lights of the respective channels is suppressed. Also, by simplifying the configuration of the optical circuit,
The production yield is also improved.

In the first input / output waveguide section, the first channel waveguide and the second channel waveguide constitute a Mach-Zehnder optical circuit having an interference frequency period Δν ₂ for group-splitting the first signal light group. It is characterized by doing.

As described above, the group demultiplexing function of the first input / output waveguide section is realized by configuring the Mach-Zehnder type optical circuit, so that light can be transmitted only by the planar optical waveguide without using additional optical elements. A circuit can be configured.

The other end of each of the first channel waveguide and the second channel waveguide forming the first input / output port, and a plurality of third channels forming the second input / output port The other end of each of the waveguide and the plurality of fourth channel waveguides is formed on the same side of the substrate.

According to such a configuration, since all input / output ports are on the same side of the board, connection of an optical transmission line for inputting or outputting multi-wavelength signal light is facilitated. .

Further, the frequency interval Δν of the first signal light group
₁ is characterized by being 50 GHz or less.

The enlargement of the planar waveguide type optical circuit becomes a problem particularly when the frequency interval of the multi-wavelength signal light to be multiplexed / demultiplexed becomes a small frequency interval of 50 GHz or less.
On the other hand, according to the optical multiplexer / demultiplexer configured as described above, for example, the frequency interval Δν ₁ = 50 GHz (the wavelength interval Δλ ₁ =
0.4nm) for a multi-wavelength signal light.
An arrayed-waveguide grating type optical circuit capable of demultiplexing at ₂ = 100 GHz (wavelength interval Δλ ₂ = 0.8 nm) can be used. Therefore, even when the channel spacing is reduced as described above, it is possible to sufficiently reduce the size of the planar waveguide optical circuit.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an optical multiplexer / demultiplexer according to the present invention will be described below in detail with reference to the drawings.
In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description. Also, the dimensional ratios in the drawings do not always match those described.

FIG. 1 is a plan view showing the configuration of an embodiment of an optical multiplexer / demultiplexer according to the present invention. This optical multiplexer / demultiplexer A is
It has a substrate W and a planar optical waveguide formed on the substrate W with a predetermined waveguide pattern, and can multiplex or demultiplex each signal light included in the multi-wavelength signal light with a predetermined channel interval. It is configured as follows.

The planar optical waveguide formed on the substrate W and constituting an optical circuit having a function of multiplexing / demultiplexing multi-wavelength signal light includes an optical multiplexer for multiplexing or demultiplexing each signal light of the multi-wavelength signal light. It is configured to include a demultiplexing waveguide section B, a first input / output waveguide section C including a first input / output port, and a second input / output waveguide section D including a second input / output port. I have.

The optical multiplexing / demultiplexing waveguide section B includes an array waveguide section 6 composed of a plurality of channel waveguides having different optical path lengths, and one end of the array waveguide section 6 (left side in FIG. 1). Slab waveguide 5 connected to the other end (right end) of the arrayed waveguide section 6, and a second slab waveguide 7 connected to the other end (right end) of the arrayed waveguide section 6. It is formed so as to constitute a diffraction grating type optical circuit (AWG: Arrayed Waveguide Grating).

With respect to the optical multiplexing / demultiplexing waveguide portion B, the input port and the output port of the multi-wavelength signal light serve as 2 ports.
Two input / output ports (a first input / output port and a second input / output port) are provided in the first input / output waveguide section C and the second input / output waveguide section D, respectively.

The first input / output waveguide section C including the first input / output port of the optical multiplexing / demultiplexing waveguide section B to the arrayed waveguide diffraction grating type optical circuit is connected to the first slab waveguide 5 at one end. And a second input / output channel waveguide 2 having one end connected to the second slab waveguide 7. It is formed.

Here, the end of the first channel waveguide 1 opposite to the first slab waveguide 5 and the end of the second channel waveguide 2 opposite to the second slab waveguide 7 are: It is formed on a predetermined side (lower side in FIG. 1) S of the substrate W. Thus, the ends of these waveguides 1 and 2 are the first input / output ports P of the optical multiplexer / demultiplexer A, respectively.

Further, in the first input / output waveguide section C of the present embodiment, the first channel waveguide 1 and the second channel waveguide 2 are formed by a Mach-Zehnder type optical circuit (M
ZI: Mach Zender Interferometer).

On the other hand, the second input / output waveguide section D including the second input / output port of the optical multiplexing / demultiplexing waveguide section B to the arrayed waveguide grating type optical circuit is connected to the first slab waveguide 5 by one end. Third input / output channel waveguides 3 to which the ends of are connected.
And a plurality of fourth input / output channel waveguides 4 each having one end connected to the second slab waveguide 7. In FIG. 1, L (L ≧ 2) third channel waveguides 3 ₁ to 3 are used as the plurality of third channel waveguides 3.
3 _L is shown. Also, as the plurality of fourth channel waveguides 4, M (M ≧ 2) fourth channel waveguides 4 ₁
~4 _M is shown.

Here, the ends of the third channel waveguides 3 _{1 to} 3 _L on the side opposite to the first slab waveguide 5 and the second slab waveguides 7 of the fourth channel waveguides 4 ₁ to 4 _M are The other end is formed on the side S of the substrate W. Thus, the ends of these waveguides _{3 1 ~3 L, 4 1 ~4} M has become a second output port Q of the optical coupler A, respectively.

Optical multiplexer / demultiplexer A according to the embodiment shown in FIG.
The operation and the specific function will be described with reference to FIG. FIG. 2 shows a portion including a first input / output waveguide portion C and a second input / output waveguide portion D in the planar waveguide type optical circuit constituting the optical multiplexer / demultiplexer A shown in FIG. It is a top view which expands and shows.

In the following, the first input / output port P provided on the first input / output waveguide section C is provided on the input port for multi-wavelength signal light and the second input / output waveguide section D is provided on the second input / output waveguide section D. The case where the second input / output port Q is used as an output port for multi-wavelength signal light and the optical multiplexer / demultiplexer A is used as an optical demultiplexer will be described. However, the optical multiplexer / demultiplexer A shown in FIG. 1 can function as an optical multiplexer by exchanging the input port and the output port.

[0030] In the optical multiplexer A shown in FIGS. 1 and 2, as an input port (first output port) P, 1 or between the input port P ₁ of the first channel waveguide 1, the second channel one input port P ₂ of the waveguide 2 is provided. Further, the output port (second output port) Q, and L output ports Q ₃ of the third channel waveguide 3 ₁ to 3 _L of L present, fourth channel waveguide ₄₁ to the M _M output ports Q ₄ at M are provided.

In the first input / output waveguide section C of the present embodiment, the first channel waveguide 1 is arranged in order from the input port P ₁ which is the end on the side S of the substrate W, It is composed of three waveguide portions, a group splitting waveguide 12 and an output waveguide 13. The end of the output waveguide 13 is connected to the first slab waveguide 5.

Similarly, the second channel waveguide 2 is connected to the substrate W
Port P which is the end on the side S of _TwoFor input
Waveguide 21, group branching waveguide 22, and output waveguide 2
3 is composed of three waveguide portions. And out
The end of the force waveguide 23 is connected to the second slab waveguide 7.
Have been.

Waveguide 1 for group splitting of first channel waveguide 1
2 and the group branching waveguide 22 of the second channel waveguide 2, as shown in FIG.
2 and 83 constitute a Mach-Zehnder optical circuit.

Thus, the signal light group (first signal light group) of the multi-wavelength signal light input from the input port P is divided into two signal light groups by the Mach-Zehnder type optical circuit of the first input / output waveguide section C. (Second signal light group, third signal light group). Further, the second signal light group and the third signal light group, which have been group-demultiplexed, are demultiplexed for each signal light by the arrayed waveguide diffraction grating type optical circuit of the optical multiplexing / demultiplexing waveguide section B, respectively. The signal is output from the output port Q via the input / output waveguide section D.

The preceding Mach-Zehnder type optical circuit (MZ
I) and a subsequent stage arrayed waveguide grating optical circuit (AW
The demultiplexing of the multi-wavelength signal light according to G) will be described more specifically.

Here, the first input from the input port P
For the signal light group, the number of signal lights included in the first signal light group
(The number of channels) is set to N (N ≧ 2;
Channels, etc.), each signal
The wavelength of the light is λ ₁, Λ_Two, Λ_Three, Λ_Four,…,
λ_N-1, Λ_NAnd In addition, adjacent signal light (channel)
Δν is the frequency interval (channel interval) between₁(Corresponding
Wavelength interval Δλ₁= Λ_i−λ_{i -1}).

The specific configuration of the optical multiplexer / demultiplexer A corresponds to the first input / output waveguide corresponding to the first signal light group which is the multi-wavelength signal light to be multiplexed / demultiplexed. The Mach-Zehnder type optical circuit of the part C has an interference frequency period Δν ₂ = 2 × Δ
ν ₁ (wavelength period Δλ ₂ = 2 × Δλ ₁ ). The array waveguide diffraction grating type optical circuit of the optical multiplexing / demultiplexing waveguide section B and each of the channel waveguides 3 and 4 of the second input / output waveguide section D set the demultiplexing channel interval to the frequency interval Δν ₂ (Wavelength interval Δλ ₂ ).

First, among the input ports P, a first signal light group including a plurality of signal lights having a frequency interval Δν ₁ is input to an input port P ₁ of the first channel waveguide 1. The input first signal light group is converted to a frequency Δν ₁ (wavelength Δν ₁ ) by a Mach-Zehnder optical circuit having an interference frequency period Δν ₂ = 2 × Δν ₁ composed of the group branching waveguide 12 and the group branching waveguide 22.
λ ₁ ).

[0039] The first one signal light group that is the group demultiplexing the input and output waveguide section C, the first channel waveguide 1 of the output waveguide 13, the wavelength _{λ 2, λ 4, ...,} λ N Is output as a second signal light group (the number of signal lights N / 2) composed of even-numbered signal lights of the above, and is input to the first slab waveguide 5. The frequency interval between adjacent signal lights in the second signal light group is:
Δν equal to the interference frequency period of a Mach-Zehnder optical circuit
₂

For the second signal light group input from the first channel waveguide 1 to the first slab waveguide 5, the first slab waveguide 5, the array waveguide section 6, the second slab waveguide 7,
The optical circuit composed of the plurality of fourth channel waveguides 4 functions as an arrayed waveguide grating optical circuit in which the number of channels is N / 2 and the frequency interval of the splitting channels is Δν ₂ . Then, each signal light of the second signal light group demultiplexed by the optical circuit is branched and guided to the fourth channel waveguide 4 corresponding respectively, each output from the corresponding output port of the output port Q ₄ Is done.

The other group of signal lights is supplied from the output waveguide 23 of the second channel waveguide 2 to the odd _- numbered signal lights of wavelengths λ ₁ , λ ₃ ,. The third consisting of
The signal is output as a signal light group (the number of signal lights N / 2) and is input to the second slab waveguide 7. The frequency interval between adjacent signal lights in the third signal light group is Δν ₂ which is equal to the interference frequency period of the Mach-Zehnder optical circuit, as in the second signal light group. Each signal light of the third signal light group is the second signal light.
The frequency is shifted by Δν _{1 with} respect to each signal light of the signal light group.

For the third signal light group input from the second channel waveguide 2 to the second slab waveguide 7, the second slab waveguide 7, the array waveguide section 6, the first slab waveguide 5,
The optical circuit including the plurality of third channel waveguides 3 functions as an arrayed waveguide grating type optical circuit in which the number of channels is N / 2 and the frequency interval of the splitting channels is Δν ₂ . Then, each signal light of the third optical signal group which is demultiplexed by the optical circuit is branched and guided to the third channel waveguide 3 respectively corresponding, respectively output from the corresponding output port of the output port Q ₃ Is done.

The effect of the optical multiplexer / demultiplexer A of this embodiment will be described.

In the optical multiplexer / demultiplexer A described above, the array
Waveguide for optical multiplexing / demultiplexing constituting a waveguide grating type optical circuit
For the first input / output including the first input / output port P for the road section B
For the second input / output including the waveguide section C and the second input / output port Q
The waveguide section D and the optical multiplexing / demultiplexing waveguide section B are respectively
Channel waveguides 1, 3 connected to one slab waveguide 5 ₁
~ 3_LAnd a channel conductor connected to the second slab waveguide 7.
Wave paths 2, 4₁~ 4_MIt is composed of And these
First input / output of one of the two input / output waveguide sections C and D
The force waveguide section C is connected to the first slab waveguide 5 and the second slab.
Light having a function of group-demultiplexing multi-wavelength signal light into the waveguide 7
Circuit (interleaver)
You.

Thus, as described above, the first signal light group having the frequency interval Δν ₁ input to the optical multiplexer / demultiplexer A as multi-wavelength signal light passes through the first input / output waveguide section C, Even-numbered and odd-numbered ₂ with double frequency spacing Δν 2
It is split into two signal light groups. Then, the second signal light group and the third signal light group, which have been group-demultiplexed, are connected to the optical multiplexing / demultiplexing waveguide section B.
Are passed through the arrayed waveguide diffraction grating type optical circuit in opposite directions, and are demultiplexed for each signal light.

At this time, with respect to the number of channels N and the frequency interval Δν _{1 of} the first signal light group to be inputted, the array section having the number of channels N / 2 and the frequency interval Δν ₂ is used as the optical multiplexing / demultiplexing waveguide section B. What is necessary is just to use a waveguide grating optical circuit. Therefore, even if the frequency interval between adjacent channels in the multi-wavelength signal light to be multiplexed / demultiplexed is reduced, it is possible to sufficiently reduce the size of the planar waveguide type optical circuit used for multiplexing / demultiplexing. Become. In addition, since the configuration of the optical circuit is simplified, the production yield is improved.

FIG. 3 is a graph for explaining the group splitting and splitting of the signal light group by the optical multiplexer / demultiplexer A. This figure 3
In the graph, the transmission characteristic curves G _{1 to} G ₆ of the signal light by the optical circuit having the above configuration are shown, with the horizontal axis representing the wavelength λ of the signal light and the vertical axis representing the signal light transmittance of the optical circuit. These transmission characteristic curves G _{1 to} G ₆ correspond to each output port (each third channel waveguide 3) included in the output port Q.
And transmission characteristics (output characteristics of signal light) in the fourth channel waveguide 4), and output signal lights of wavelengths λ _{1 to} λ ₆ included in the input first signal light group, respectively. Transmission characteristics.

Among the transmission characteristic curves G _{1 to} G ₆ , the characteristic curves G ₂ , G ₄ , and G ₆ shown by solid lines are input from the first channel waveguide 1 and the first slab waveguide 5 shows transmission characteristic curves of signal light that is split by the array waveguide section 6 and the second slab waveguide 7 and output from each of the fourth channel waveguides 4. On the other hand, the characteristic curve G ₁ indicated by a dashed line, G _3, and G ₅ is input from the second channel waveguides 2, the second slab waveguide 7, array waveguide portion 6, and the first slab waveguide 5 shows a transmission characteristic curve of signal light branched by 5 and output from each of the third channel waveguides 3.

As shown by these transmission characteristic curves G _{1 to} G ₆ , the arrayed waveguide diffraction grating type optical circuit of the optical multiplexing / demultiplexing waveguide section B has a frequency separation Δν ₂ (wavelength interval Δλ ₂ ). Waves are configured to be possible. Furthermore, the signal light is input from the first channel waveguide 1 and output to the fourth channel waveguide 4, and the signal light is input from the second channel waveguide 2 and output to the third channel waveguide 3, Each transmission characteristic is shifted by a frequency interval Δν ₁ (wavelength interval Δλ ₁ ). Such transmission characteristics are specifically, for example, the third channel waveguide 3 and the fourth channel waveguide 4.
This is realized by appropriately setting the connection position and the connection interval to the first slab waveguide 5 and the second slab waveguide 7.

As described above, with respect to the arrayed waveguide grating type optical circuit configured so that the transmission characteristic is shifted by the frequency interval Δν ₁ when the multi-wavelength signal light is transmitted in the opposite direction at the frequency interval Δν _2. In the Mach-Zehnder optical circuit of the first input / output waveguide section C, the first signal light group having the frequency interval Δν ₁ is converted into the frequency ΔΔ ₂ at the frequency interval Δν ₂ as described above.
To the group demultiplexing to the second signal light group and the third signal light group shifted by [nu _1.

Thus, as a whole of the planar waveguide type optical circuit of the optical multiplexer / demultiplexer A, the characteristic curve G indicated by the solid line in FIG.
_2, G _4, and G _6, and the characteristic curve G ₁ indicated by a broken line,
G _3, and the transmission characteristics of the frequency interval .DELTA..nu ₁ the combined G ₅ (demultiplexing property) becomes the input WDM signal light can be demultiplexed.

The signal lights of the adjacent channels at the frequency interval Δν ₁ pass through the arrayed waveguide grating optical circuit in the opposite direction. Therefore, the frequency interval of the signal light group that is demultiplexed after passing through the optical circuit is substantially 2
Since it can be twice as large as Δν ₂ , occurrence of crosstalk between signal lights of each channel is suppressed.

[0053] Here, in the above embodiment, the first signal light group as a first output waveguide section C of the group branching, are used Mach-Zehnder type optical circuit of the interference frequency period .DELTA..nu _2. At this time, without using additional optical elements,
An optical circuit can be constituted only by the planar optical waveguide.

The ends (ports) P ₁ , P _{2 of} the first channel waveguide 1 and the second channel waveguide 2 constituting the first input / output port P, and the second input / output port Q End (port) of each of the plurality of third channel waveguides 3 and the plurality of fourth channel waveguides 4 constituting
Q ₃ and Q ₄ are provided on the same side S of the substrate W.

According to such a configuration, since all the input / output ports are on the same side of the substrate, connection of the optical transmission line for inputting or outputting multi-wavelength signal light is facilitated. . For example, an optical transmission line for input / output of signal light
It is only necessary to connect from the side S side via the connector, and the mounting of the optical multiplexer / demultiplexer A in the wavelength division multiplexing transmission system is simplified. Also, the number of components required for connection to the optical transmission line is reduced.

The specific channel interval of the multi-wavelength signal light is determined by the frequency interval Δ of the input first signal light group.
ν ₁ is preferably set to 50 GHz or less. That is, the enlargement of the planar waveguide type optical circuit becomes a problem particularly when the frequency interval of the multi-wavelength signal light to be multiplexed / demultiplexed becomes a small frequency interval of 50 GHz or less.

On the other hand, according to the optical multiplexer / demultiplexer A having the above configuration, for example, as shown in FIG.
For a multi-wavelength signal light with ν ₁ = 50 GHz (wavelength interval Δλ ₁ = 0.4 nm), frequency interval Δν ₂ = 100 GHz
An arrayed waveguide grating optical circuit capable of multiplexing / demultiplexing (wavelength interval Δλ ₂ = 0.8 nm) can be used. Therefore, even when the channel spacing is reduced as described above, it is possible to sufficiently reduce the size of the planar waveguide optical circuit.

The document "2000 IEICE Electronics Society Conference C-3-10"
An optical multiplexer / demultiplexer combining a Mach-Zehnder optical circuit and an arrayed waveguide grating optical circuit is described. However, in the optical multiplexer / demultiplexer described in the above document, two array waveguide diffraction grating type optical circuits are formed on the substrate, and the two signal light groups that are group-demultiplexed by the Mach-Zehnder type optical circuit are respectively used. Demultiplexing is performed by another array waveguide diffraction grating type optical circuit. With such a configuration, it is impossible to reduce the size of the planar waveguide type optical circuit.

On the other hand, the optical multiplexer / demultiplexer according to the present invention is provided with a single arrayed waveguide grating type optical circuit after the Mach-Zehnder type optical circuit. Then, the two signal light groups group-demultiplexed by the Mach-Zehnder type optical circuit are respectively demultiplexed by passing through the arrayed waveguide grating optical circuit in opposite directions, thereby demultiplexing the multi-wavelength signal light. This realizes both miniaturization of the planar waveguide type optical circuit.

The optical multiplexer / demultiplexer according to the present invention is not limited to the above embodiment, and various modifications are possible. For example, the optical circuit having the group demultiplexing function in the first input / output waveguide section is not limited to the Mach-Zehnder type optical circuit having the three directional couplers described above, but may be the Mach-Zehnder having the two directional couplers. A type optical circuit may be used. Alternatively, an optical element other than the planar optical waveguide may be provided to perform group branching using a polarizer, a mirror, a diffraction grating, or the like.

The arrangement of the two input / output ports with respect to the planar waveguide type optical circuit is not limited to the configuration provided on the same side as described above, and may be provided on different sides.

[0062]

The optical multiplexer / demultiplexer according to the present invention has the following effects as described in detail above. That is, an optical circuit such as a Matter-Zehnder type optical circuit at the previous stage for group-multiplexing the multi-wavelength signal light to be multiplexed / demultiplexed into two signal light groups, and two group-demultiplexed signal light groups, respectively. According to the optical multiplexer / demultiplexer including the array waveguide diffraction grating type optical circuit at the subsequent stage that demultiplexes each signal light by passing in the opposite direction, the input multi-wavelength signal light having the frequency interval Δν ₁ It is possible to use an arrayed waveguide diffraction grating type optical circuit having twice the frequency interval Δν ₂ . Therefore, even if the frequency interval between adjacent channels in the multi-wavelength signal light to be multiplexed / demultiplexed is reduced, it is possible to sufficiently reduce the size of the planar waveguide type optical circuit used for multiplexing / demultiplexing. Become.

[Brief description of the drawings]

FIG. 1 is a plan view showing the configuration of an embodiment of an optical multiplexer / demultiplexer.

FIG. 2 shows first and second optical multiplexers / demultiplexers shown in FIG.
It is a top view which expands and shows the part containing the waveguide part for input / output.

FIG. 3 is a graph illustrating demultiplexing of signal light by the optical multiplexer / demultiplexer illustrated in FIG. 1;

[Explanation of symbols]

A: optical multiplexer / demultiplexer, W: substrate, B: waveguide for optical multiplexer / demultiplexer,
C: first input / output waveguide, D: second input / output waveguide, P: first input / output port, Q: second input / output port, 1
... first input / output channel waveguide, 11 ... input waveguide,
12: waveguide for group splitting, 13: waveguide for output, 2: second
Input / output channel waveguides, 21 ... Input waveguides, 22 ...
Group branching waveguide, 23 ... output waveguide, 3 ... third input / output channel waveguide, 4 ... fourth input / output channel waveguide,
5 ... first slab waveguide, 6 ... array waveguide part, 7 ... second
Slab waveguide.

Claims (4)

[Claims] 1. A substrate and an optical waveguide formed on the substrate.
And multiplexes or demultiplexes each signal light of the multi-wavelength signal light.
Comprising a plurality of channel waveguides having different optical path lengths.
Ray waveguide connected to one end of the array waveguide
Of the first slab waveguide and the arrayed waveguide portion
Optical coupling having a second slab waveguide connected to the other end
A demultiplexing waveguide portion, and a first chip having one end connected to the first slab waveguide.
One end to the channel waveguide and the second slab waveguide.
A second channel waveguide connected to the first channel;
The channel waveguide and the second channel waveguide, respectively.
A first input / output conductor whose one end constitutes a first input / output port
A plurality of waveguides each having one end connected to the first slab waveguide;
One of the third channel waveguide and the second slab waveguide
Having a plurality of fourth channel waveguides connected at one end.
The plurality of third channel waveguides and the plurality of fourth channel waveguides;
The other end of each channel waveguide is connected to a second input / output port.
And a second input / output waveguide part constituting
The first input / output waveguide section is formed from the first input / output port.
Frequency interval Δν₁Signal light comprising a plurality of signal lights
When a group is input, the first channel waveguide
The frequency interval Δν output to the first slab waveguide
_Two(Δν_Two= 2 × Δν ₁), And the second signal light group.
Output from the channel waveguide to the second slab waveguide
Frequency interval Δν_TwoAnd Δν with respect to the second signal light group.₁Only
The first signal light group is split into a third signal light group which is shifted.
And the second signal light group input to the first slab waveguide.
Are demultiplexed by the optical multiplexing / demultiplexing waveguide, and
The signal light passes through each of the plurality of fourth channel waveguides.
Output from the second input / output port and the second
The third signal light group input to the slab waveguide is
Demultiplexed by the multiplexing / demultiplexing waveguide section, each signal light is
The second channel waveguide is provided through each of the plurality of third channel waveguides.
Optical multiplexer / demultiplexer output from an input / output port
vessel. 2. The first input / output waveguide section, wherein the first channel waveguide and the second channel waveguide are:
Demultiplexer according to claim 1, characterized in that it constitutes a Mach-Zehnder type optical circuit of the interference frequency period .DELTA..nu ₂ to the group demultiplexing said first signal light group. 3. The other end of each of the first channel waveguide and the second channel waveguide forming the first input / output port, and the second input / output port. The other end of each of the plurality of third channel waveguides and the plurality of fourth channel waveguides is
The optical multiplexer / demultiplexer according to claim 1, wherein the optical multiplexer / demultiplexer is formed on the same side of the substrate. 4. The frequency interval Δν of the first signal light group
_{2. The method according} to claim 1, wherein ₁ is 50 GHz or less.
An optical multiplexer / demultiplexer as described in the above.