JPS5873249A - Optical transmission monitoring device - Google Patents

Abstract

PURPOSE:To detect the transmission error due to the increased loss in the optical transmission, by providing an optical branching filter branching a part of an optical signal prior to a photoelectric converter at the reception side, a power meter detecting the power of the optical signal, and a level discriminator. CONSTITUTION:An optical signal from a transmission section 5 is transmitted to a reception section 10 via an optical fiber 11. An optical branching filter 6 such as half miror which branches the power of an incident optical signal to a prescribed ratio is provided at the pre-stage of an photoelectric converter 7 of the reception section 10 and the branched optical signal is inputted to a power meter 8. The optical signal power measured at the power meter 8 is detected at a level discriminator 9 to discriminate whether or not the incident optical signal power is a minimum reception level or over of the converter 7.

Description

[Detailed description of the invention] 1ml Technical distribution This invention Optical transmission monitoring 1i1E4 that constantly monitors the attenuation of the transmitting power during optical transmission during overconfidence at the transmitter side 1i1E4
-It is related to

4t+1 Conventional technology Optical communication using Optical 7-IPA has been widely adopted in recent years, taking advantage of its characteristics of non-interrogation, signal insulation, and wideband transmission.However, this optical communication also There are some disadvantages and restrictions on application.

One of the problems with ft communication is the increase in transmission loss due to radiation of optical fibers. This is the glass used in the transmission part of the original fiber and the transmission 11 that utilizes that glass.
This is a problem caused by 11142.

11th shows the transmission aI Tachibana of Hikari 7 AIPA. Figure 1 4: In the central core l that transmits yt, V, quartz glass and G/P are chemically combined with 4 = refraction 1 which is higher than the refractive index of silica glass alone. A cladding of quartz glass 2v is used around the core l, and the light is totally reflected at the interface between the core and the cladding, which have different refractive indexes, and the light is trapped inside the core.・In this way, the T7 Eyepa has a transmission mechanism that utilizes total internal reflection between the core and cladding, which have different refractive indexes, and in order to achieve this refractive index of 11V, it is
1'' chemical bonding expansion method is used.

This refractive index! It is called a 1V dopant in Ge to attach a dopant, but when a high-energy irradiation is applied to a quartz glass containing a dopant, an absorbing part called a color center is generated as a dopant nucleus. The original signal transmitted through the core in the AIPA is absorbed at this color center, resulting in an increase in transmission loss.

An example of this state is shown in 2g. The increase in transmission loss due to the color center is related to the amount of radiation irradiated to the optical fiber, and as the amount of radiation increases, the transmission loss also increases. Although the transmission loss of the irradiation-irradiation 111Wf7 AIPA is decreasing, it takes a considerable amount of time until the loss returns to the level before irradiation. Therefore, when the Hikari 7 Eyeper is used in a place where radiation is irradiated, transmission loss increases both during and after irradiation.

On the other hand, the optical signal is input into the first fiber.
This is a likelihood converter (hereinafter referred to as I10).

This Ilo is an electric signal v'yt, which is converted into a signal and is input into the original fiber as an optical signal l.The conversion element is usually a laser diode (hereinafter referred to as LD) or a light emitting diode (hereinafter referred to as LDI). Used・I, D
The power of the incident light incident on the optical fiber is usually a few watts or about 0.01 mW, and is determined by the performance of the conversion element and the type of optical fiber.

The original-to-electrical converter (hereinafter referred to as 0/l) receives the original signal output from the optical fiber and converts it into an electrical signal. ] and photodiode (hereinafter referred to as I'D)
) is used. One of the important performances of O/M is the minimum reception level, which means that in the case of digital signals, if the pulse of the original signal is below a certain bit error rate, it is #0- or 1.
-v is the lowest original signal power level that can be determined. It is about value. That is, o
/1 or reliable replacement Il capability requires receiving the original signal power at or above the minimum reception level. This minimum reception level varies depending on the type of FD or PD, but it ranges from a normal number W to several nW, and is a constant value determined by the performance of the conversion element.

Here, the conventional original communication method is that whether it is an input electrical signal, a digital signal, or an analog signal, the original signal power converted by the VO and the input signal power are input to the 7-channel 7-iper, and the 7-channel 7-iper V has a certain transmission loss. This is a method of replacing the optical signal power t' QA≦2 which is higher than the lowest reception level after transmission, and extracting the input electrical signal and the output electrical signal. Here, even if a constant output source signal from Ilo is input into the optical fiber.

If the transmission loss of an optical fiber becomes a temporal ζ device, it is no longer possible to guarantee that the received optical signal at 0/1 will exceed the minimum reception level.In other words, when optical transmission is performed using conventional optical communication methods In order for the O/L on the receiver side to perform reliable electrical conversion, it is necessary to input the original signal at a level higher than the required minimum reception level. A condition is required that the transmission loss in the fiber is a constant value after installation and does not change over time.

This means that the transmission loss of the IPA changes in places where radiation is likely to be irradiated, so the conventional i:Jm communication system lacks III-III characteristics and is difficult to apply. In addition, a radiation-resistant optical fiber is being considered that suppresses the increase in transmission loss due to radiation exposure. There is a method of completely shielding the beam from radiation, but this method increases the cost of wiring the optical fiber, so it cannot be said to be a realistic method. , in optical communication systems where the transmission loss of optical fibers changes, the receiving side O/
An optical transmission monitoring device t's is provided to detect whether or not a likely signal of a minimum damage level or higher is input to B.

(11 Structure of the Invention The present invention will be explained below with reference to the drawings. Fig. 3 is a diagram of a boot 1 showing an embodiment of the present invention. The electric signal transmitter 3 transmits an electric signal to be transmitted. In the case of normal measurement, this is a device such as a replacer that matches the senna and the input signal vm10 from the senna to the IIl! level.The electrical signal output from the electrical signal transmitter 3 is input to 1704.

This 1104 incorporates the above-mentioned conversion element, etc., and converts the input electric signal vfta to the party 7.
0 or more electrical signal transmitters 3 and m that output to the AIPA 11
1041', the combined part is the transmitter 5. overconfidence
The original signal outputted from the optical fiber is transmitted through the original fiber and input to the receiving section 101: an optical branching device 6. Light minutes #ILs6
is a device that splits the input source signal power into a fixed splitting ratio, and is usually used as a half filter.

One of the original signals branched by the optical splitter 6 is 07m1-
Here, the original signal is converted into an electric signal, and the electric signal output by the electric signal transmitter 3 of the transmitter 5 and the electric signal output from the ceramic etc. are measured. If it is an analog signal, it can be recorded using a recording needle etc.
Or, if it is a control signal, it is output to the first controller and each device is controlled.

The other original signal branched by the optical splitter 6 is input to the power meter 8. That is, out of the original signal power received by the receiving section 10, the receiving source signal power k/< which is branched at a constant ratio by the optical splitter 6 is measured by the power meter 8. The value measured by this power meter 8 is input to the level difference determiner 9.

Determine whether the original signal power input to the optical splitter 6 is equal to or higher than the O/I minimum reception level (・) Function of the invention Here, the operation of the optical splitter 6, power meter 8, and level difference determiner 9 is determined. This will be explained in detail.

The half mirror splits the light into transmitted light and reflected light, and this splitting ratio can be continuously changed depending on the degree of coating on the half mirror.

For example, if you set the fart ratio of transmitted light and reflected light vs: tt: and combine it with the transmitted light side QO/) 7, and connect the reflected light measurement with the power meter 8, the optical signal power input at the optical splitter 6 will be The optical fiber can be used for normal communication, and the loss as an optical transmission line will not be too great.

On the other hand, the original signal power input to the power meter 8 is 1 of the original signal power input at the optical splitter 6, but the lowest constant range of the power meter 8 is usually 0.1 nW.
Even with such a low signal power, it is possible to sufficiently measure the signal power. This means that the 9 times the original signal power measured by the power meter 8 is manually input, and the level difference determiner 9 directly outputs the output value from the power meter 8: whereas the 9 times the integrated value and 0/17 e It can be compared with the original signal power of the lowest received level determined by the replacement element used.

The i7 eyeglass connecting the optical splitter 6 and the O/M'l't' and the original 7 eyeglass connecting the optical splitter 5 and the power meter 8v have the same transmission loss, and if the length is made m-, the transmission line becomes a highly accurate transmission line. Moreover, since this yt7 eyebar can be made very short, the transmission loss here can be ignored.

Next, the function of the level 1 determiner 9 will be explained using FIG. 4. The signal value measured by the power meter 8 is input to the integrator 12 and outputted to the 9 times integrated value 1 subtracter 13. This integrated value is the original signal power input at 0/17,
The subtracter 13 separately inputs the Ik low reception level of O/17, and subtracts the output value of the integrator 12 minus the lowest reception level, and if this value is negative, outputs a borrow signal of 14V.

The level at which the borrow signal 14 is output is the original signal power received at 0/17, which is below the lowest reception level of O/]c7, and the one-source transmission system is (11+1). The state of being 1isv is small.

There are many ways to use this P-signal, but an example is shown in the fifth example. In other words, when the level difference judger 9 outputs a L-low signal 14, the signal is moved at the m-point 15. relay
Stop the plant in operation using

Such a protective sequence [If used, it may be considered to be radiation irradiation. If the plan is controlled using the JFrj dual transmission system V) 6: On the other hand, if the optical transmission system is operating normally - I: The power is set to 1kTIj, and if there is an abnormality, it will automatically issue a warning and maintain 111V.
I'll be able to realize five scratches.

Also, use this transmission step t-tt-form for convenience, and the time when the level difference judger 9 outputs the error value 141'. It is also possible to use this data to distinguish between unreliable tl and tl data. Even if this happens, the level difference determiner 9 & 2 can detect the abnormality.

lfl Combined Effects As explained above, according to the present invention, in an optical communication system, an increase in the transmission loss of optical fibers due to radiation etc., malfunction of IC10 in the transmitting section, bending of the original fiber, etc. can occur. Even in the receiving department! Since it is constantly monitored to see if ¥iJi+power is equal to or higher than the minimum reception level of 0/l, and this can be detected as an abnormality in the original transmission path, a reliable optical communication system can be realized.

[Brief explanation of drawings]

Figure 1 is a diagram showing the general structure of the original fiber, the second factor is a graph showing the transmission loss due to radiation in the original fiber, and the third
The figure shows the inside of a block showing one embodiment of the present invention, and FIG.
FIG. 5 is a block diagram showing the function of the level difference determiner in the present invention. 4; Electricity-source converter; 6; Optical weapon. 7; Photo-electrical converter, 8; Bawame! , 9; Level 11 judge. lzs'full calculator. 13; ratio aS. (7317) Agent Patent Attorney Noriyuki Chika (and 1 others)
Name Figure 1 / ( 〉 Figure 2 Myo ℃ 〒 〒 〒

Claims (1)

[Claims] In an optical transmission system in which an optical signal is transmitted to a YT/electrical converter on a receiving side via a 1-source 7-aiper [1GK signal side optical/electrical converter], A branching light beam gun, a power meter for detecting the power of the optical signal branched by the splitter, and a level judger for comparing the output of the power meter with a predetermined level, and according to the output of the level judger. W of optical transmission characterized by two optical/electrical exchangers on the receiving side to check whether or not the input original signal is full or not.
l vision device.