JPH0579905A - Signal processing module for two-way transmission - Google Patents

Abstract

PURPOSE:To test and monitor each of a pair of optical fibers for two-way transmission with a small device by selectively switching the test light fed from a light pulse tester with a light switching circuit. CONSTITUTION:A light transmission line 8-1 sends the signal light from a transmitter 1 to an optical fiber 5-1. A light transmission line 8-2 sends the arriving signal light lambda, to a receiver 2 via an optical fiber 5-2. The test light lambda2 transmitted from a pulse tester 3 is guided to a light switching circuit 13 via a light transmission line 8-5 and selectively switched, and it is sent to a light transmission line 8-3 or 8-4 and the transmission line 8-1 or 8-2 via a merging/diverging unit 6-1 or 6-2. The light lambda2 enters the fiber 5-1 or 5-2 and is propagated, it is reflected by a demarcating unit provided near the mating terminal, then it retrogresses on the line and is returned to the tester 3. When the reflected light quantity value is monitored, the deterioration of the transmission characteristic of the fiber 5-1 or 5-2 can be evaluated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical signal processing module suitable for use in bidirectional transmission using a pair of optical fibers, and more particularly to an optical system for test monitoring of an optical fiber transmission line. The present invention relates to an optical signal processing module incorporating the.

[0002]

2. Description of the Related Art In general, when transmitting an optical signal using an optical fiber transmission line, from the viewpoint of improving the reliability of the line, sufficient preventive maintenance against disconnection or deterioration of the optical fiber is an important issue. Become. Moreover, in order to perform preventive maintenance of the transmission line, it is necessary to test or monitor the characteristics of the optical fiber in use without affecting the communication quality. There is a method shown below (see Tomita et al., "Automatic Fault Isolation Method for Optical Lines", Spring National Convention of the Institute of Electronics, Information and Communication Engineers, 1990, B-890).

In FIG. 3, 31 is an optical transmitter (for example, a light emitting element) on the terminal A side, 32 is an optical receiver (for example, a light receiving element) on the terminal B side, and 33 is an optical transmitter 31 for the terminal A side. Optical fibers for coupling between the optical receiver 32 on the terminal B side and the optical receiver 32 on the terminal B side are shown. In this example, the optical coupler 34 is provided on the terminal A side, and the divider 35 is provided on the terminal B side. Divider 35
Is composed of, for example, an interference film filter, the communication light (wavelength λ ₁ ) passes through as it is, and the test light (wavelength λ 1
₂ ) has the property of reflecting.

The test or monitoring is performed by sending pulsed test light (wavelength λ ₂ ) from the optical pulse tester 36 through the optical coupler 34 to the optical fiber 33. The test light is
After propagating to the sever 35 on the other end side, it is reflected by the slicing device 35 and returns to the optical pulse tester 36 via the optical coupler 34. Therefore, by measuring the reflected light and comparing it with a normal value measured in advance, it is possible to determine whether or not the optical fiber 33 is broken, the degree of deterioration, and the like. Since the wavelength λ _{2 of the} test light is different from the wavelength λ _{1 of the} signal light, the normal optical signal transmission function will not be disturbed even if the test or the monitoring is performed during the line use.

However, in the case of bidirectional transmission using a pair of optical fibers, it is necessary to test and monitor each fiber. For that purpose, two sets of optical pulse testers 36 having the same performance are prepared. There is a need. This tester
Since it is necessary to use a semiconductor laser that emits extremely stable and high-power light, an attempt to satisfy such a condition results in a very expensive system.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art and to realize a compact and high performance in which a test monitoring function of an optical fiber and a signal light transmitting / receiving function are integrated together. An object is to provide an optical signal processing module.

[0007]

An optical signal processing module according to the present invention includes a first optical transmission line for coupling an optical transmitter and an optical fiber, and an optical receiver and another optical fiber. A second optical transmission line for coupling with the fiber, and an optical switch circuit for switching and controlling the test light,
A first optical transmission line is provided between the third optical transmission line for coupling the switch circuit and the optical pulse tester and the first optical transmission line.
A fourth optical transmission line that forms the optical multiplexer / demultiplexer and forms a light path between the optical multiplexer / demultiplexer and the switch circuit;
A fifth optical transmission line that forms a second multiplexer / demultiplexer with the second optical transmission line and that also forms a light path between the multiplexer / demultiplexer and the switch circuit is provided. It is characterized by The switch circuit switches the test light from the optical pulse tester and selectively supplies the test light to either one of the optical fibers, and the test light reflected from the optical fiber side is returned to the pulse tester. Function to introduce.

The optical signal processing module of the present invention can be applied to the case where a plurality of optical transmitters and optical receivers having different wavelengths are used. However, in this case, on the optical transmitter side or the optical receiver side, the first and second optical transmission lines are branched into at least two optical transmission lines, and the optical transmitter or the optical receiver is coupled to each of them. There is a need. Further, since the optical signal processing module of the present invention has a structure that can be integrated on a substrate, by configuring each of the above optical transmission lines with a thin film type optical waveguide, the size of the device can be reduced. Alternatively, high functionality can be realized.

[0009]

The first transmission line is used by being inserted between one of the pair of optical fibers and the optical transmitter so that the signal light (transmission light) from the optical transmitter is sent to the optical fiber. Function. The second transmission line is used by being inserted between the other optical fiber and the optical receiver, and functions to transmit the signal light (received light) arriving via the optical fiber to the optical receiver. To do.

The test light emitted from the optical pulse tester is
After being guided to the optical switch circuit via the third optical transmission line and selectively switched by the switch circuit,
Alternatively, it enters either one of the first and second optical transmission lines via the fifth optical transmission line and the first or second multiplexer / demultiplexer. As a result, the test light enters and propagates in one of the pair of optical fibers, is reflected by the slicing device provided in the vicinity of the other terminal, and then propagates back in the optical fiber and returns.
The reflected light is guided to the optical switch circuit by the reverse route,
After passing through the switch circuit, it reaches the optical pulse tester via the third optical transmission line and is received by the tester.

[0011]

【Example】

<Embodiment 1> FIG. 1 shows an embodiment of the optical signal processing module of the present invention. In this embodiment, a pair of optical fibers 5-1 and 5
This is a module for transmitting information bidirectionally by using -2 and signal light of wavelength λ ₁ . The test light of wavelength λ ₂ supplied from the optical pulse tester 3 is selectively distributed to either one of the optical fibers 5-1 and 5-2 by the optical switch circuit 13, and the optical fiber is used in the state of using the line. It is possible to evaluate the transmission characteristics (transmission loss) and test or monitor the state of breakage and deterioration.

The optical signal processing module 10 has a low refractive index layer 7a (refractive index _nb ) formed on the surface of a substrate 9 as shown in the sectional view taken along the line AA ', and an optical signal is formed on the low refractive index layer. After forming the core layer 8 (refractive index n _w ) that functions as a transmission line of a circular cross section or a rectangular cross section, the entire structure is covered with a cladding layer 7 b (refractive index n _c ) to form an embedded waveguide structure. Make up. The substrate 9 is made of pure silica glass or silica glass containing an appropriate refractive index controlling additive, as well as silicon or GaAs.
A semiconductor material such as LiNbO ₃ , LiTaO ₃ or the like, a magnetic material such as Y ₃ Fe ₅ O _12, or a polymer material such as polyurethane or epoxy can be appropriately selected and used.

The embedded waveguide is constructed so as to be a single-mode transmission line for the wavelengths λ ₁ and λ ₂ , and the relative refractive index difference Δ = (n _w −n _c ) / n _w [ Or Δ = (n _w −n _b ) / n _w ]
The value of Δ defined by is set so as to fall within the range of 0.2% to 0.8%. The thickness and width of the core layer 8 are several μm to 1
Set in the range of 2 μm. Since the thicker the low refractive index layer 7a, the more the propagation loss can be reduced,
Usually, it is desirable that the thickness is 10 μm or more. Similarly, the thicker the clad layer 7a is, the more preferable it is. Usually, the thickness is set in the range of 15 μm to several tens of μm. As the material of the low refractive index layer 7a, the core layer 8 and the clad layer 7b, it is desirable to use low loss material such as quartz glass, polymer material, multi-component glass, or the like.

The core layer 8 is formed so as to have the pattern shown in FIG. In the figure, the core 8-1 is the optical transmitter 1.
And the optical fiber 5-1 function as an optical transmission path, and the core 8-2 functions as an optical transmission path for connecting the optical receiver 2 and the optical fiber 5-2. To do. Therefore,
Wavelength lambda ₁ of the signal light from the optical transmitter 1 (transmitting light), arrows
As shown by 11-1, it propagates in the core 8-1 and enters the optical fiber 5-1 and propagates in the fiber toward the partner terminal. On the other hand, the signal light (received light) of the wavelength λ ₁ from the partner terminal that has propagated in the optical fiber 5-2 propagates in the core 8-2 as indicated by an arrow 11-4, and the optical receiver Received by 2.

A directional coupler type optical switch circuit 13 is formed in advance in the optical signal processing module 10. This kind of optical switch circuit is known per se, and for example, the one described in "Optical Integrated Circuit" by Nishihara et al. (Published on February 25, 1960 by Ohmsha) can be used. The optical switch circuit 13 is connected to a core 8-5 that constitutes an optical transmission line with the optical pulse tester 3.

To the output side of the optical switch circuit 13, cores 8-3 and 8-4 functioning as another optical transmission line are connected.
The tips of both cores are arranged at appropriate intervals in parallel with the cores 8-1 and 8-2, respectively, and a directional coupling type multiplexer / demultiplexer is provided between the cores 8-1 and 8-2. 6-1 and 6-2 are formed. This type of multiplexer / demultiplexer is also known per se, and is described in, for example, Imoto et al., "Waveguide type optical multiplexer / demultiplexer", "Qigaku Technical Report", OQE87-7 (pp. 47-53), published by The Institute of Electronics, Information and Communication Engineers. It is possible to use the existing one. That is, the wavelength λ _{1 of the} signal light is 1.3 μm and the wavelength λ _{2 of the} test light is 1.5 μm.
When the thickness is 5 μm, the thickness of the core layer 8 is 8 μm, the width is 10 μm, the core 8-1 (or 8-2) and the core 8-3 (or 8-4)
It is possible to configure the multiplexer / demultiplexer by selecting 3.2 μm as the interval, the coupling section length as 4.965 mm, and the relative refractive index difference Δ as 0.25%.

The test light emitted from the optical pulse tester is the core 8-
Propagating in 5 and enters the optical switch circuit 13 of the directional coupler type. Here, if a voltage V is applied between the electrodes 14-1 and 14-2 on both sides of the optical switch circuit 13 from the terminals P and P ′ and the value is adjusted so as to satisfy the equation (1), The test light enters the core 8-3 side and is combined by the multiplexing / demultiplexing unit 6-1 into the core 8-1.
After being coupled inside, it propagates in the optical fiber 5-1 toward the partner terminal.

[Equation 1]

The test light of wavelength λ ₂ propagating in the optical fiber 5-1 is provided with a splitter (a function of reflecting only the light of wavelength λ ₂ and allowing the other light to pass) provided near the terminal of the other party. An interference film filter that has (not shown), propagates in the opposite direction in the optical fiber 5-1 and enters the core 8-1 again, and is coupled to the core 8-3 side by the multiplexer / demultiplexer 6-1. After being demultiplexed, it returns to the optical pulse tester 3 through the optical switch circuit 13 as indicated by arrow 12-6.

Therefore, by measuring the light quantity of the reflected light when the optical fiber 5-1 is normally operating, and checking how much the actual reflected light quantity changes, the optical fiber 5 It is possible to evaluate the degree of deterioration of the transmission characteristic of -1. Also, by measuring the delay time between the sent test light and its reflected light,
It is possible to judge the deterioration position or break position of 5-1 and the degree of deterioration.

When testing or monitoring the transmission characteristics of the optical fiber 5-2, the voltage V applied between PP and P'is adjusted to a value satisfying the expression (2). Then, the optical pulse tester 3
The test light from is switched to the core 8-4 side as shown by the arrow 12-7 and propagated in the core, and then the optical fiber 5-through the multiplexer / demultiplexer 6-2 and the core 8-2. It is sent out within 2. Then, by returning the reflected light reflected from a slicing device (not shown) provided in the vicinity of the other party's terminal to the optical pulse tester 3, the transmission characteristics of the optical fiber are evaluated, and the state of deterioration or breakage is evaluated. Etc. can be checked.

[Equation 2]

<Embodiment 2> FIG. 2 shows another embodiment of the optical signal processing module of the present invention. In the present embodiment, a devise is made for bidirectional transmission using another signal light of wavelength λ ₃ in addition to the signal light of wavelength λ ₁ . In other words, in the present embodiment, the optical signal processing module is configured so that a plurality of optical transmitters and optical receivers can be used, and in order to achieve such an object,
Cores 8-6 and 8-7 forming an additional optical transmission line are formed.

Signal light of wavelength λ ₃ from the optical transmitter 15 (second
Transmitted through the core 8-6 as indicated by an arrow 18-1 and the multiplexer / demultiplexer 17-1 formed between the core and the core 8-1.
Is coupled (combined) with the signal light of the wavelength λ ₁ (first transmission light) from the optical transmitter 1, and then propagates in the optical fiber 5-1 toward the partner terminal. On the other hand, optical fiber 5-2
The signal light having the wavelength λ ₁ (first received light) and the signal light having the wavelength λ ₃ (second received light) propagating in the inside are formed between the core 8-2 and the core 8-7. The signals are demultiplexed by the multiplexer / demultiplexer 17-2 and received by the optical receiver 2 and the optical receiver 16 as indicated by arrows 11-4 and 18-6, respectively.

The demultiplexer 17-1 and 17-2, the signal light of the wavelength lambda ₃ are multiplexed or demultiplexed signal light of the wavelength lambda ₁ is of configuration to pass it, lambda ₁ and lambda _Once the value of ₃ is determined, the thickness, width, core spacing, joint length, and Δ of the core 8 can be determined. The design can be realized by citing the above references. The module of the present embodiment is configured to propagate two signal lights having different wavelengths to each of a pair of optical fibers. However, an optical transmitter and an optical receiver are additionally installed, and three or more optical fibers are provided. It is also possible to use the signal light of.

According to the optical signal processing module of the present invention, a single optical pulse tester can be used to test and monitor a pair of optical fiber transmission lines, and a thin film suitable for integration and mass production. Since it is possible to adopt a waveguide structure, it is possible to economically construct an optical communication system that is small in size, has high performance, and has high reliability.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a first embodiment of an optical signal processing module for bidirectional transmission of the present invention.

FIG. 2 is a schematic view showing a second embodiment of the optical signal processing module for bidirectional transmission of the present invention.

FIG. 3 is a system diagram for explaining a conventional optical fiber test method.

[Explanation of symbols]

1 ... Optical transmitter, 2 ... Optical receiver, 3 ... Optical pulse tester, 5
... optical fiber, 6 ... multiplexer / demultiplexer, 7a ... low refraction layer, 7b ...
Cladding layer, 8 ... Core layer, 9 ... Substrate, 13 ... Optical switch circuit, 14 ... Electrode, 15 ... Optical transmitter, 16 ... Optical receiver, 17 ... Multiplexer / demultiplexer, 31 ... Optical transmitter, 32 ... Optical Receiver, 33 ... Optical fiber,
34 ... Optical coupler, 35 ... Divider, 36 ... Optical pulse tester.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location H04B 10/08

Claims (3)

[Claims] 1. A first optical transmission line for coupling between an optical transmitter and one optical fiber, and a second optical transmission for coupling between an optical receiver and another optical fiber. A path, an optical switch circuit for switching and controlling the test light, a third optical transmission path for coupling the switch circuit and the optical pulse tester, and a first optical transmission path. And a fourth optical transmission line that forms a first optical multiplexer / demultiplexer and an optical path between the optical multiplexer / demultiplexer and the switch circuit, and a second optical transmission line. A fifth optical path forming the optical multiplexer / demultiplexer and an optical path between the optical multiplexer / demultiplexer and the switch circuit;
And an optical transmission line of
It functions to switch the test light from the optical pulse tester and selectively supply it to one of the optical fibers, and to introduce the test light reflected and returned from the optical fiber side into the pulse tester. An optical signal processing module for bidirectional transmission, which is characterized in that 2. Each of the first and second optical transmission lines is branched into at least two optical transmission lines on the optical transmitter side or the optical receiver side, and a plurality of optical transmitters or optical receivers having different wavelengths are provided. The optical signal processing module for bidirectional transmission according to claim 1, wherein the optical signal processing module is formed so as to be capable of coupling with each other. 3. The first to fifth optical transmission lines are constituted by thin film type optical waveguides which are integrated and arranged on one substrate, and both of them are set forth in claim 1. Optical signal processing module for bidirectional transmission.