WO2007063931A1

WO2007063931A1 - Monitor circuit

Info

Publication number: WO2007063931A1
Application number: PCT/JP2006/323896
Authority: WO
Inventors: Mitsuru Nagano; Tomoyuki Yamada; Mikitaka Ito; Toshio Watanabe; Shin Kamei; Takayuki Mizuno; Akimasa Kaneko
Original assignee: Nippon Telegraph And Telephone Corporation; Ntt Electronics Corporation
Priority date: 2005-11-30
Filing date: 2006-11-30
Publication date: 2007-06-07
Also published as: JP2007155777A

Abstract

Provided is a monitor circuit which has a small number of part items and is easily assembled. The monitor circuit for a multiplexer multiplexes optical signals having different wavelengths and outputs wavelength multiplexed signals. The monitor circuit is provided with an optical coupler (202) connected to the output of the multiplexer (201); a branching filter (204) connected to one of the outputs from the optical coupler (202) and branches the wavelength multiplexed signals and outputs the signals; and optical signal detecting means (203-1 to 203-n) connected to each output from the branching filter (204).

Description

Specification

Monitor circuit

Technical field

TECHNICAL FIELD [0001] The present invention relates to a monitor circuit, and more specifically, a multiplexer that multiplexes optical signals of different wavelengths and outputs a wavelength multiplexed signal, or a wavelength multiplexed signal into optical signals of different wavelengths. The present invention relates to a monitor circuit for a duplexer that outputs a wave.

Background art

In recent years, a wavelength division multiplexing transmission system has been used as a system for realizing a large-capacity optical transmission system. In a wavelength division multiplexing transmission system, it is necessary to accurately control not only the wavelength-multiplexed optical signal output from the multiplexer but also the optical intensity of each of the different wavelengths input to the multiplexer. There is. Specifically, the feedback control is performed so that the light intensity of the optical signal of each wavelength is monitored and the output light intensity of each light source is maintained at a predetermined intensity. In addition, in the receiving apparatus, it is necessary to monitor not only the wavelength multiplexed optical signal input to the duplexer but also the optical intensity of optical signals of different wavelengths output from the duplexer.

FIG. 1 shows a configuration of a conventional monitor circuit. Figure 1A shows the configuration on the transmitter side. The output of each channel of the optical transmitter power having a different wavelength is connected to the optical power plugs 102-l to 102-n. One output of the optical power plastics 102— 1 to 102—n is connected to the input of the multiplexer 101, and the other output is a photodiode (PD) 103 — 1 to 103— that monitors the light intensity of the optical signal. connected to n.

[0004] FIG. 1B shows a configuration on the receiving device side. The output for each channel from the duplexer 121 is connected to the optical power couplers 122-1 to 122-n. One of the optical power plugs 122-1 to 122-n is connected to the input of the optical receiver, and the other output is a photodiode (PD) 123-1 to 123 that monitors the optical intensity of the optical signal. — Connected to n!

[0005] For example, a directional coupler in which an optical fiber or a core of an optical waveguide is brought close to each other is used as the optical power bra. As the multiplexer / demultiplexer, for example, a first slab waveguide connected to the input waveguide, a second slab waveguide connected to the output waveguide, a first slab waveguide, and In addition, an AWG (Arrayed Waveguide Grating) type optical multiplexer / demultiplexer composed of an array waveguide connecting between the second slab waveguide and the second slab waveguide is used.

[0006] However, the conventional monitor circuit has a problem in that the number of parts is increased and the assembly process of the transmitter is complicated because the optical power bra is connected to each channel.

[0007] Furthermore, the number of parts has been reduced by using a tap monitor in which an optical power bra and a PD are integrated. However, since it is necessary to connect each channel with a high component unit price, there was a problem that the component cost was high.

[0008] An object of the present invention is to provide a monitor circuit having a small number of parts and a simple assembly process.

Patent Document 1: Japanese Patent Laid-Open No. 3-39905

Patent Document 2: Japanese Patent Laid-Open No. 2002-341165

Disclosure of the invention

In order to achieve the above object, the present invention provides an output connection of the multiplexer in a monitor circuit of the multiplexer that multiplexes optical signals of different wavelengths and outputs a wavelength multiplexed signal. Connected to one output of the optical power bra, a demultiplexer for demultiplexing and outputting the wavelength multiplexed signal, and an optical signal detection connected to each output of the demultiplexer It is characterized by having means.

[0011] The multiplexer and the duplexer can be configured by two waveguide type optical multiplexers / demultiplexers formed on the same substrate. Furthermore, the optical power bra can be formed on the substrate as a waveguide type optical power bra.

[0012] On the other hand, in the monitor circuit of the demultiplexer that demultiplexes the wavelength multiplexed signal into optical signals of different wavelengths and outputs the optical signal, the optical power bra that inputs the wavelength multiplexed signal and one of the optical power bras A first demultiplexer connected to the output of the second optical demultiplexer, a second demultiplexer connected to the other output of the optical power bra, and an optical signal detecting means connected to the output of each of the second demultiplexers It is characterized by having.

[0013] The first duplexer and the second duplexer can be constituted by two waveguide type optical multiplexers / demultiplexers formed on the same substrate. Furthermore, the optical power bra can be formed on the substrate as a waveguide type optical power bra. Brief Description of Drawings

FIG. 1A is a block diagram showing a configuration of a conventional monitor circuit (transmitting device side),

[FIG. 1B] FIG. 1B is a block diagram showing a configuration of a conventional monitor circuit (receiving device side),

[FIG. 2A] FIG. 2A is a block diagram showing a configuration of a monitor circuit (transmitting device side) according to an embodiment of the present invention.

[FIG. 2B] FIG. 2B is a block diagram showing a configuration of a monitor circuit (receiving device side) that works in one embodiment of the present invention.

FIG. 3A is a diagram showing a first embodiment of the multiplexer / demultiplexer of the monitor circuit (transmitting device side);

[FIG. 3B] FIG. 3B is a diagram showing Example 1 of the multiplexer / demultiplexer of the monitor circuit (receiving device side);

FIG. 4 is a diagram showing a second embodiment of the multiplexer / demultiplexer of the monitor circuit,

FIG. 5 is a diagram showing a third embodiment of the multiplexer / demultiplexer of the monitor circuit,

FIG. 6 is a diagram showing a fourth embodiment of the multiplexer / demultiplexer of the monitor circuit,

FIG. 7 is a diagram showing a fifth embodiment of the multiplexer / demultiplexer of the monitor circuit,

FIG. 8 is a diagram showing a sixth embodiment of the multiplexer / demultiplexer of the monitor circuit,

FIG. 9 is a diagram showing a seventh embodiment of the multiplexer / demultiplexer of the monitor circuit,

FIG. 10 is a diagram of an eighth embodiment of the multiplexer / demultiplexer of the monitor circuit.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 shows a configuration of a monitor circuit according to an embodiment of the present invention. Figure 2A shows the configuration on the transmitter side. The output for each channel from the optical transmitters having different wavelengths is connected to the input of the multiplexer 201. The wavelength multiplexed signal output from the multiplexer 201 is input to the optical power bra 202. One output of the optical power bra 202 is connected to the optical transmission line, and the other output is connected to the input of the duplexer 204. The demultiplexer 204 demultiplexes the wavelength multiplexed signal into optical signals for each channel, and detects the optical signal detection means, that is, the light intensity of the optical signal. Photodiode (PD) 203-1 to 203-n Output.

With such a configuration, the monitor circuit can monitor the light intensity for each channel with only one optical power bra and one duplexer. Therefore, the number of parts can be reduced and the assembling process of the transmitting apparatus can be simplified. FIG. 2B shows a configuration on the receiving device side. The optical power bra 222 connected to the optical transmission line has one output connected to the input of the duplexer 221 and the other output connected to the input of the duplexer 224. The output for each channel from the demultiplexer 221 is connected to the input of the optical receiver, and the output for each channel from the demultiplexer 224 is an optical signal detection means, that is, a photodiode that monitors the light intensity of the optical signal ( PD) connected to 223-l to 223-n.

With such a configuration, the monitor circuit can monitor the light intensity for each channel with only one optical power bra and one duplexer. Therefore, the number of parts can be reduced and the assembly process of the receiving apparatus can be simplified.

Here, since the optical power bras 202 and 222 branch the optical intensities of optical signals having different wavelengths, it is desirable that the branching ratio is constant regardless of the wavelength in the wavelength range to be multiplexed / demultiplexed. As such a wavelength-independent light power bra, light power composed of two 2-input 2-output directional couplers and two waveguide force delay lines connecting the two directional couplers. Bra is known (for example, see Patent Document 1). Also, by using such a light power bra, it is possible to reduce the deviation of the branching ratio due to a manufacturing error as compared with a normal light power bra. Of course, other directional couplers, X-branch force bras, Y-branch force bras, multi-mode interference (MMI) type force bras, etc. can be used. If a waveguide type optical power bra is used, it can be integrated on a PLC (P1 aner light-wave circuit) substrate.

In addition, it is desirable that the branching ratio of the optical power plastics 202 and 222 is asymmetric. That is, the optical transmission line and the optical receiver side branch within an appropriate branching ratio within a range of 50% to less than 99.9% and the monitor side within a range of 0.1% to less than 50%. . The optimal branching ratio to the monitor side is about 5%. It is desirable that the wavelength of the optical signal transmitted / received via the optical transmission line is substantially the same as the wavelength of the optical signal to be monitored. However, when the transmission band of the optical signal is flat and the wavelength band is wide, it is possible to monitor any wavelength within the transmission band, not necessarily the center wavelength of the transmission band.

[0022] In addition to the above-described AWG type optical multiplexer / demultiplexer, the demultiplexers 204 and 224 include an optical multiplexer / demultiplexer in which a Mach-Zehnder interferometer is connected in multiple stages (see, for example, Patent Document 2), a filter-type optical multiplexer / demultiplexer. A fiber grating type optical multiplexer / demultiplexer, a waveguide grating type optical multiplexer / demultiplexer, a diffraction grating type optical multiplexer / demultiplexer, a lens type optical multiplexer / demultiplexer, or the like can be used. In addition, As the duplexer 201 and the duplexer 221, the same optical multiplexer / demultiplexer as the duplexers 204 and 224 can be used. By using the same configuration for the former and the latter, it is possible to reduce circuit design and manufacturing costs.

Example 1

FIG. 3 shows a first embodiment of the multiplexer / demultiplexer of the monitor circuit. In the configuration of Fig. 2, an AWG type optical multiplexer / demultiplexer is used as the optical multiplexer / demultiplexer and a directional coupler is used as the optical power bra. Fig. 3A shows the configuration on the transmitter side. The multiplexer 201 and the duplexer 204 are composed of an AWG type optical multiplexer / demultiplexer, and are integrated on one PLC substrate 211. The output of each channel of the optical transmitter having different wavelengths is connected to the input of the multiplexer 201. An optical power bra 202 is connected to the output of the multiplexer 201, one output of the optical power bra 202 is connected to the optical transmission line, and the other output is connected to the input of the duplexer 204. . The output of the duplexer 204 is connected to photodiodes (PD) 203-1 to 203-n that monitor the light intensity of the optical signal.

[0024] According to this configuration, the monitor circuit can be miniaturized by integrating the multiplexer / demultiplexer on one substrate. Further, by integrating the optical power plug 202, which is a directional coupler having optical fibers close to each other, as a waveguide type directional coupler on the PLC substrate 211, the size can be further reduced. Of course, even if an optical power bra composed of two 2-input 2-output directional couplers and two waveguide force delay lines connecting the two directional couplers are integrated on the PLC board 211, Yo! /

FIG. 3B shows a configuration on the receiving device side. The multiplexer 221 and the demultiplexer 224 are composed of an AWG type optical demultiplexer and are integrated on one PLC substrate 231. One of the optical power bras 222 connected to the optical transmission line is connected to the input of the demultiplexer 221, and the other output is connected to the input of the demultiplexer 224. The output for each channel from the demultiplexer 221 is connected to the input of the optical receiver, and the output for each channel from the demultiplexer 224 is a photodiode (PD) that monitors the optical intensity of the optical signal. Connected to 223-n.

According to this configuration, the monitor circuit can be reduced in size by integrating the multiplexer / demultiplexer on one substrate. Further, the optical power bra 222 can be integrated on the PLC substrate 231. [0027] In the AWG type optical multiplexer / demultiplexer, a groove is provided in the center of the arrayed waveguide connecting the first slab waveguide and the second slab waveguide, and a wave plate that eliminates polarization dependence is provided. It ’s all about people.

Example 2

FIG. 4 shows a second embodiment of the multiplexer / demultiplexer of the monitor circuit. An application example of the AWG optical multiplexer / demultiplexer on the transmitter side shown in Fig. 3A is shown. Two AWG-type optical multiplexer / demultiplexer forces are integrated on one PLC substrate 211, and the multiplexer 201 and duplexer 204 are formed with the bending direction of the arrayed waveguides reversed. . According to this configuration, the area of the substrate can be further reduced as compared with the PLC substrate shown in FIG. 3A. Further, the optical power bra 202 can also be integrated on the PC board 211.

Example 3

FIG. 5 shows a third embodiment of the multiplexer / demultiplexer of the monitor circuit. An application example of the AWG optical multiplexer / demultiplexer on the transmitter side shown in Fig. 3A is shown. One AWG type optical multiplexer / demultiplexer 251 is integrated on one PLC substrate 211, and the multiplexer and the demultiplexer share the arrayed waveguide 254, respectively. That is, an input waveguide 252 connected to the first slab waveguide 253 and an output waveguide 256 connected to the second slab waveguide 255 are formed according to the multiplexer and the demultiplexer, respectively. Yes.

[0030] According to this configuration, the size can be further reduced as compared with the PLC substrate shown in FIG. 3A. Furthermore, by integrating the optical power bra 202 on the PLC board 211, a monitor circuit with a small number of parts and an easy assembly process can be realized.

Example 4

FIG. 6 shows a fourth embodiment of the multiplexer / demultiplexer of the monitor circuit. In the configuration shown in FIG. 2A, a case where a Mach-Zehnder interferometer type optical multiplexer / demultiplexer is used as the optical multiplexer / demultiplexer and a waveguide type directional coupler is used as the optical power bra is described. The multiplexer 201 and the demultiplexer 204 are Mach-Zehnder interferometer type optical multiplexers / demultiplexers, and are integrated on one PLC substrate 211. The output of each channel of the optical transmitter having different wavelengths is connected to the input of the multiplexer 201. An optical power bra 202 is connected to the output of the multiplexer 201, one output of the optical power bra 202 is connected to the optical transmission line, and the other output is connected to the input of the duplexer 204. . Min The output of the waver 204 is connected to a photodiode (PD) 203-1-2-03-n that monitors the light intensity of the optical signal.

According to this configuration, the monitor circuit of the transmission device can be reduced in size by integrating the two multiplexers / demultiplexers and the optical power bra on one substrate.

Example 5

FIG. 7 shows a fifth embodiment of the multiplexer / demultiplexer of the monitor circuit. In the configuration of FIG. 2A, a case where a filter-type optical multiplexer / demultiplexer is used as the optical multiplexer / demultiplexer and a half mirror is used as the optical power bra is described. The multiplexer 201 and the demultiplexer 204 are constituted by a filter type optical demultiplexer and are integrated on one substrate 211. The output for each channel from the optical transmitters having different wavelengths is connected to the input of the multiplexer 201. A half mirror 202 is connected to the output of the multiplexer 201, one output is connected to the optical transmission line, and the other output is connected to the input of the duplexer 204. The output of the duplexer 204 is connected to a photodiode (PD) 203-1 to 203-n that monitors the light intensity of the optical signal.

[0034] The multiplexer 201 and the demultiplexer 204 include lens arrays 711 and 721, wavelength filters 712 and 722 that transmit optical signals of wavelengths for each channel, and reflect optical signals of other wavelengths, It consists of mirrors 71 3 and 723.

Example 6

FIG. 8 shows a sixth embodiment of the multiplexer / demultiplexer of the monitor circuit. In the configuration of FIG. 2A, a case where a fiber grating type optical multiplexer / demultiplexer is used as an optical multiplexer / demultiplexer and a fiber type directional coupler is used as an optical power bra is described. The multiplexer 201 and the demultiplexer 204 are composed of fiber grating type optical multiplexers / demultiplexers. The output for each channel from the optical transmitters having different wavelengths is connected to the input of the multiplexer 201. An optical power bra 202 is connected to the output of the multiplexer 201, one output is connected to the optical transmission line, and the other output is connected to the input of the duplexer 204. The output of the duplexer 204 is connected to photodiodes (PD) 203-1 to 203-n that monitor the light intensity of the optical signal.

[0036] The multiplexer 201 and the demultiplexer 204 are configured by fiber gratings 811, 821 that reflect the optical signals of the respective wavelengths and transmit optical signals of other wavelengths, and circulators 812, 822. Has been. Example 7

FIG. 9 shows a seventh embodiment of the multiplexer / demultiplexer of the monitor circuit. In the configuration of FIG. 2A, a case where a diffraction grating type optical multiplexer / demultiplexer is used as the optical multiplexer / demultiplexer and a half mirror is used as the optical power bra is described. The multiplexer 201 and the demultiplexer 204 are constituted by a diffraction grating type optical multiplexer / demultiplexer. The output of each channel of the optical transmitter having different wavelengths is connected to the input of the multiplexer 201. A half mirror 202 is connected to the output of the multiplexer 201, one output is connected to the optical transmission line, and the other output is connected to the input of the duplexer 204. The output of the duplexer 204 is connected to photodiodes (PD) 203-1 to 203-n that monitor the light intensity of the optical signal.

[0038] The multiplexer 201 and the demultiplexer 204 are the lens arrays 911 and 921, the diffraction gratings 912 and 922 that separate the optical paths according to the wavelengths of the respective channels, and the optical signals of the respective channels. The lens is composed of 913 and 923!

Example 8

FIG. 10 shows an eighth embodiment of the multiplexer / demultiplexer of the monitor circuit. In the first to seventh embodiments, the multiplexer 201 and the demultiplexer 221 and the demultiplexers 204 and 224 are configured using the same optical multiplexer / demultiplexer. In Example 8, a waveguide grating type optical multiplexer / demultiplexer was used as the multiplexer 201, and an AWG type optical multiplexer / demultiplexer was used as the duplexer 204. In this way, different types of optical multiplexer / demultiplexers having the same multiplexing / demultiplexing characteristics may be combined.

Claims

The scope of the claims

[1] In the monitor circuit of the multiplexer that multiplexes the optical signals of different wavelengths and outputs the wavelength multiplexed signal,

A light bra connected to the output of the multiplexer;

A demultiplexer connected to one output of the optical power bra and demultiplexing and outputting the wavelength multiplexed signal;

Optical signal detection means connected to each output of the duplexer;

A monitor circuit comprising:

[2] The optical multiplexer / demultiplexer according to claim 1, wherein the optical multiplexer / demultiplexer includes two waveguide-type optical multiplexers / demultiplexers formed on the same substrate. Monitor circuit.

3. The monitor circuit according to claim 2, wherein the light power bra is a waveguide-type light power bra and is formed on the substrate.

[4] In the monitor circuit of the demultiplexer that demultiplexes the wavelength multiplexed signal into optical signals of different wavelengths and outputs them.

An optical power bra that inputs the wavelength multiplexed signal;

A first duplexer connected to one output of the light bra;

A second duplexer connected to the other output of the light power bra;

Optical signal detection means connected to the respective outputs of the second duplexer;

A monitor circuit comprising:

5. The first demultiplexer and the second demultiplexer are constituted by two waveguide type optical multiplexers / demultiplexers formed on the same substrate. Monitor circuit described in

6. The monitor circuit according to claim 5, wherein the optical power bra is a waveguide type optical power bra, and is formed on the substrate.