JP2540166Y2 - Optical signal receiver - Google Patents

Description

[Detailed description of the invention]

[0001]

The present invention relates to an optical fiber for receiving an optical signal transmitted through an optical fiber without cutting the optical fiber at an arbitrary position other than an optical signal transmitting end and a receiving end. The present invention relates to a signal receiving device. More specifically, in measuring the transmission characteristics of the optical fiber and searching for the position of the break point,
An optical pulse tester (OTDR) is used. When a PCM signal is transmitted via the optical fiber, a waveform distortion may occur due to a wavelength dispersion phenomenon of light. Although there is a demand to know where in the optical fiber the waveform distortion is occurring, the above-mentioned OTDR does not meet this requirement. Therefore, the present invention relates to a technique for efficiently receiving a part of an optical signal being transmitted through an optical fiber and monitoring a transmission state of the optical fiber.

[0002]

2. Description of the Related Art A so-called core sensor is known as a method for measuring the power of an optical signal propagating through an optical fiber without cutting the optical fiber. In the case of a germanium photodiode (hereinafter, referred to as PD) used for a core wire contrast sensor, a photodiode having a light receiving diameter of φ1 mm to 2 mm is used to receive light leaking from a bent portion of an optical fiber. The electrical characteristics of such a PD are such that a capacitance corresponding to the light receiving area is large, so that a high-speed response at a response frequency of 1 MHz or more cannot be performed, and an optical signal modulated at a high frequency such as PCM modulation is converted into an electrical signal. That was impossible.

[0003] As a technology of a core contrast sensor, for example,
No. 40906/57. The technical gist will be described with reference to FIG. One end 6 of optical fiber 61
The optical signal A incident from No. 2 propagates in the optical fiber at an angle smaller than the critical angle for total reflection. When the optical fiber is bent (66) beyond the total reflection critical angle, the optical signal A appears as leaked light 63 outside the optical fiber. If the light receiving surface of the photodetector 64 is placed on an extension of the leak light, the leak light can be detected.

(Case of Communication Using Optical Fiber) FIG. 5 is a diagram showing a basic concept of a communication system using an optical fiber. At the transmitting end 20, a signal to be transmitted is converted into an optical signal by an electric-to-optical converter (E / O converter) 21 and output to an optical fiber 21. At the receiving end 30, an optical signal propagating through the optical fiber is demodulated into an electric signal by an optical-to-electrical converter (O / E converter) 31. In communication using optical fibers, high-speed, large-capacity, low-loss transmission is possible. In particular, if the optical fiber is laid on a substantially straight line, the optical signal does not leak out of the optical fiber, so that low loss, that is, long-distance transmission can be realized. The fact that the optical signal does not leak outside means that the optical signal cannot be received in the middle of the optical fiber. That is, if an optical branching means is provided in the middle of the optical transmission system, an optical signal can be received in the middle of the optical transmission system. However, in other methods, the optical signal is received unless the optical fiber is cut. Can not do. For example, the same applies when a bit error rate measuring device, an optical power measuring device, or the like is used to monitor a change in transmission state due to deformation of an optical fiber.

[0005]

However, the prior art using a core contrast sensor has the following disadvantages. As shown in FIG. 4, the leak light 63 has a spread. In order to efficiently receive the leaked light, the area of the light receiving surface of the photodetector 64 must be increased (generally, the light receiving diameter is 1 mm to 2 mm). When the area of the light receiving surface is increased,
There is a disadvantage that the frequency response speed of the photodetector 64 is reduced.
For example, the response frequency of a light receiving element having a light receiving surface with a diameter of 1 mm is limited to 1 MHz. In the case of simply detecting the average value of leaked light appearing at the bending point of the optical fiber as in the case of a fiber optic sensor, even a photodetector having a large light receiving surface can sufficiently achieve the initial purpose. . But,
For example, P handling a high-speed signal such as several gigabits / second
In the case of CM transmission, a conventional light receiving element having a large light receiving surface area has a drawback that the modulated signal waveform cannot be reproduced because the frequency response speed is low. Further, according to the conventional technique, the optical signal incident on one end 62 of the optical fiber 61 has a photodetector 64 provided on an extension of the bending point 66 in the traveling direction. The other end of the optical fiber 6
The leakage light 63a of the optical signal B incident from the
4 cannot be detected.

An object of the present invention is as follows: (1) An optical signal modulated at a high frequency without cutting an optical fiber at an arbitrary position between a transmitting end and a receiving end performing PCM communication using an optical fiber. And (2) inputting an optical signal received without cutting the optical fiber to a bit error rate measuring device, an optical power measuring device, or the like, and monitoring the optical fiber for abnormalities.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned drawbacks, the optical signal receiving apparatus of the present invention handles a high-frequency modulated optical signal emitted from a bending point of an optical fiber, for example, a high-speed signal. As a means for efficiently receiving leaked light of a signal such as PCM transmission, an optical fiber transmitting an optical signal is bent at a plurality of locations, and leaked light is formed on an extension of the leaked light 63 emitted from the bending point 66. A plurality of light receiving means 1 arranged so as to cover the beam of light and converting the optical signal of the leaked light into an electric signal, and a delay means 2 for adjusting the timing of each electric signal output from the plurality of light receiving means.
And signal synthesizing means 3 for synthesizing a plurality of electric signals whose timings have been adjusted by the delay means.

Also, a signal reproducing means 4 for receiving the electric signal output from the signal synthesizing means and restoring the electric signal into a modulated signal is added, and receiving the output signal, a communication evaluation device for an optical fiber, for example, a code A waveform evaluation means 8 is provided for inputting to an error rate measuring device, an optical power measuring device, or the like, and monitoring abnormalities such as breakage or deformation of the optical fiber.

[0009]

A light receiving element having a small light receiving area with a high frequency response speed is used to detect leaked light of an optical signal modulated at a high frequency emitted from a bending point of a bent optical fiber. Also, it is necessary to receive a small amount of leaked light so as not to affect optical communication during transmission. Therefore, in order to improve the light receiving sensitivity, a plurality of light receiving elements having a small light receiving area are used. Using the received signal, a process for monitoring an abnormality such as breakage or deformation of the optical fiber is performed.

[0010]

FIG. 1 shows the configuration of a first embodiment of the present invention. The following description is made by taking the case where the optical fiber 61 is used for PCM communication as an example. The first optical fiber pressing means 67 and the second optical fiber pressing means 68 have an uneven shape opposite to each other, and when the optical fiber 61 is placed between them and the interval is reduced, the optical fiber along the unevenness is reduced. Is bent to form a bending point 66. The optical signal A incident on the optical fiber end 62 of the optical fiber 61 leaks light 6 from the bending point 66 in the traveling direction.
3 is emitted. The amount of this light leakage is determined by the radius of the bend. Normally, weak leakage light is emitted so as not to hinder the transmission system. In order to efficiently receive the leaked light, a plurality of light receiving units 1 are arranged so as to cover the output beam width. In the case where the passing optical signal is modulated at a high frequency as in PCM communication, a photodiode (not shown) having a small light receiving area is used as the light receiving means 1 in order to increase the frequency response speed. As an example of the frequency response speed of the germanium photodiode used here, the maximum response frequency when the light receiving diameter φ is 0.1 mm is about 10 MHz.
(The rise time is 0.5 μs). In this embodiment, three light receiving units 1 are used, but the number of light receiving units may be increased or decreased according to the beam width of the leaked light and the intensity of the leaked light.

The signal detected by the light receiving means 1 is input to the delay means 2. The timing of the signal input to each delay unit 2 varies depending on the detection position of the photodiode incorporated in each light receiving unit 1 even if the pulse signal is the same. For this purpose, the delay means 2 outputs the delay time between the photodiodes from the leak point of the optical fiber with the same delay time.

The signal synthesizing means 3 is for adding the input signals. The signals with the same timing output from the respective delay means 2 are input to the signal synthesis means 3 and added. The output of the signal synthesizing means 3 is input to the signal reproducing means 4 at the next stage. The signal reproducing means 4 is for amplifying and shaping the pulse signal output from the signal synthesizing means 3 and restoring it to a modulated signal. The restored signal is input to the next-stage optical fiber communication waveform evaluation means, for example, a bit error rate measuring device, and the transmission characteristics are measured to monitor the deformation of the optical fiber. By measuring power fluctuations, it is possible to monitor an increase in optical fiber transmission loss and disconnection.

(Second Embodiment) FIG. 2 shows the configuration of a second embodiment of the present invention when signals A and B are incident from both directions of an optical fiber. In FIG. 2, the light leaked from the bending point 66 of the fiber 61 is detected by the light receiving means 1 in the same manner as in the first embodiment. The signal B incident on the other end 65 is detected by the light receiving means 1a provided on the extension of the traveling direction. Each of the detected signals is, as in the first embodiment, a delay means 2, 2a, a signal combining means 3,
3a, the signal is processed by the signal reproducing means 4, 4a. Thereafter, the processing by the evaluation means is the same as in the first embodiment.

(Third Embodiment) This embodiment also shows a case where it is used for PCM communication as in the above embodiment. As shown in FIG. 3, the first optical fiber pressing means 5, the second optical fiber pressing means 6, and the plurality of optical fiber bending means 7 are used to bend the optical fiber 61 to generate leakage light 66. It is configured. First
The optical fiber 61 is placed between the optical fiber 61 and a second optical fiber pressing means, for example, a flat plate, and the bending means 7, for example, a cylindrical rod is alternately placed on the first and second optical fiber pressing means sides with respect to this optical fiber. And the distance between the first and second optical fiber holding means is reduced. At this time, the number of folding means 7
The outer diameter and the interval may be selected so that light leakage does not affect the transmission system.

Leaked light 6 emitted from each bending point 66
In the method of detecting 3, the same light receiving means 1 as in the first embodiment is provided corresponding to each bending point. Since the respective delays of the same signal by the plurality of light receiving means 1 differ depending on the detection position, the delay means 2 is provided as in the above-described embodiment to deal with the subsequent signal processing. The signal processing after the delay means 2 is the same as in the above embodiment. In this embodiment, each light 63
If the beam width is small, the number of light receiving means (photodiodes) may be one, and the number can be increased or decreased as needed according to the beam width. Also,
As in the second embodiment, the light receiving means 2a and subsequent parts may be provided on the emission line of the bidirectional leaked light.

[0016]

As described above, in order to detect the leaked light by bending the optical fiber transmitting the optical signal to be modulated at a high frequency, a plurality of light receiving elements having a small light receiving area having a high frequency response speed are used. The following effects are obtained by providing and coping with them. (1) A high-speed optical signal during transmission such as PCM communication can be received without cutting the optical fiber. (2) Since the reception efficiency can be increased, an optical signal in an optical fiber can be received without affecting signal transmission between transmission and reception. (3) Since the light receiving means is provided on the outgoing line of the leak light, the optical signal in the optical fiber can be received regardless of the transmission direction of the optical signal. (4) In addition to the above effects, the transmission state of light in the optical fiber can be monitored using the above received signal.

[0017]

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of an optical signal receiving apparatus according to the present invention.

FIG. 2 is a block diagram showing a second embodiment of the optical signal receiving apparatus according to the present invention;

FIG. 3 is a block diagram showing a third embodiment of the optical signal receiving apparatus according to the present invention;

FIG. 4 is a conventional optical signal receiving circuit.

FIG. 5 is a configuration diagram of a communication system using an optical fiber.

[Explanation of symbols]

 1, 1a light receiving means 2, 2a delay means 3, 3a signal synthesizing means 4, 4a signal reproducing means 5 first optical fiber pressing means 6 of the third embodiment 6 second optical fiber pressing means 7 of the third embodiment 7 Optical fiber bending means of three embodiments 8 Waveform evaluation means 20 PCM communication transmitting side 21 E / O converter 30 PCM communication receiving side 31 O / E converter 61 Optical fiber 62 Optical fiber input end 63 Leakage light 64 Conventional Example light receiving means 65 The other input end of optical fiber 66 Bending point 67 First optical fiber pressing plate 68 Second optical fiber pressing plate

Claims (2)

(57) [Scope of request for utility model registration] 1. An inflection point (6) of an optical fiber transmitting an optical signal.
A plurality of light receiving means (1) arranged on an extension of the leaked light (63) emitted from 6) for converting an optical signal of the leaked light into an electrical signal, and respective light output means output from the plurality of light receiving means. Delay means for adjusting the timing of electric signals (2)
An optical signal receiving apparatus comprising: a plurality of electric signals whose timings are adjusted by the delay unit; 2. An inflection point (6) of an optical fiber transmitting an optical signal.
A plurality of light receiving means (1) arranged on an extension of the leaked light (63) emitted from 6) for converting an optical signal of the leaked light into an electrical signal, and respective light output means output from the plurality of light receiving means. A plurality of delay means for adjusting the timing of the electric signal; a signal synthesizing means for synthesizing the plurality of electric signals whose timing is adjusted by the delay means; and an electric signal output from the signal synthesizing means. Signal recovery means (4) for restoring the electric signal to the original signal upon receiving the signal, and waveform evaluation for constantly monitoring the transmission state of the optical fiber based on the signal output from the signal reproduction means (4). Means (8)
An optical signal receiving apparatus for restoring a signal and monitoring a transmission state of light in an optical fiber.