JPH02250437A - Diagnostic method for optical communication system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for diagnosing an optical communication system, and more particularly to a method for easily diagnosing whether or not the system is being operated within a specified system margin.

(Prior art and issues to be solved) In optical communication systems, by combining low-loss, broadband optical fibers with high-output, highly sensitive light-emitting and light-receiving elements, the relay distance of transmission lines can be increased from several kilometers to several kilometers. It is possible to make it as long as 10 km. For this reason, compared to communication systems using conventional metallic cables, it is possible to significantly reduce the number of repeaters or connect telephone stations without repeaters, making communication systems more economical and highly efficient. , construction, maintenance, etc. will also be easier.

By the way, in such an optical communication system, it is necessary to check whether or not it is being operated within a specified system margin or whether it can be operated. Conventionally, methods for testing whether such systems are operating within a specified margin include measuring the optical reception level using an optical power meter, or installing a signal level detection circuit within the optical receiver. or by adding a light emission level detection circuit inside the optical transmitter.

However, the method of measuring the optical reception level using an optical power meter requires a lot of time and effort, and moreover, the system must be stopped while the inspection is being performed, which can cause problems due to communication being unavailable during this time. many. Furthermore, the methods of adding a signal level detection circuit within the optical receiver or adding a light emitting and bell detection circuit within the optical transmitter require complicated and expensive structures of the optical transmitter or optical receiver. There is also a problem that detection cannot be performed until the level drops to the set value.

The present invention has been made in view of the above-mentioned points.
An object of the present invention is to provide a method for diagnosing an optical communication system, which reduces the level by a specified system margin and confirms that the system operates normally.

(Intelligence A to be Solved by the Invention) According to the present invention, in order to achieve the above object, at least one of the optical transmission level on the optical transmitter side or the optical reception level on the optical receiver side of an optical communication system is set to a predetermined value. The system is designed to check whether the optical communication system is operating within a specified system margin.

(Function) During or before and after operation of the optical communication system,
The system margin specified for the optical communication system is reduced at either the optical transmitter or optical receiver side. That is, on the optical transmitter side, the optical transmission level is lowered by the system margin, and on the optical receiver side, the incoming signal level is lowered by the system margin. In this state, it is checked whether the optical communication system is operating normally.

(Example) An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows the simplest circuit configuration of an optical communication system to which the present invention is applied, and the optical communication system 1 includes an optical transmitter 2,
The optical transmitter 2 is composed of an optical transmission line 3 and an optical receiver 4, and the optical transmitter 2 is equipped with a light emitting diode (LED), etc., and changes the strength of the light corresponding to the change in the strength of the electric signal e inputted from the input terminal 2a. is converted into an optical signal and sent to the optical transmission line 3 via a lens system.

The optical transmitter 2 further includes a transmission light level control circuit, and the diagnostic signal S input from the signal input terminal 2b allows
It is configured to reduce the level of the transmission signal by a predetermined level and output the signal at a lower level. The signal level to be reduced is, for example, a system margin of 3 dB,
The warning level is set to 1.5 dB, and the danger level is set to 0.5 dB. Then, when the optical transmitter 2 receives Sl as a diagnostic signal, it changes the light emission level to the signal S! with the system margin subtracted. When S is input, the light emission level is controlled to a level with the warning level reduced, and when S is input, the light emission level is controlled to a level with the danger level reduced. Then, when the signal S0 is input, the light emission level returns to the original level.

The optical receiver 4 converges the optical signal transmitted from the optical transmission path 3, that is, the intensity of light, through a lens system, irradiates it onto a light receiving element, converts it into a corresponding electrical signal, and outputs it from an output terminal 4a. This is what is output. Examples of light receiving elements include photodiodes that utilize the photoelectric effect to directly convert optical signals into electrical signals.

The action will be explained below.

In the optical communication system 1, when performing optical communication, when an electrical signal e is input from the input terminal 2a of the optical transmitter 2, the optical transmitter 2 outputs a corresponding optical signal and transmits it to the optical transmission line 3. Send. This optical signal is transmitted through the optical transmission line 3 to the optical receiver 4 . The optical receiver 4 converts the received (incoming) optical signal into a corresponding electrical signal and outputs it from the output terminal 4a. Thereby, information is transmitted from the optical transmitter 2 to the optical receiver.

Now, when inspecting whether or not the optical communication system 1 is operated within the specified system margin or whether it can be operated, a diagnostic signal SL is sent to the optical transmitter 2 before the operation of the system 1. Manually increase the light emission level by 3 dB
normal signal transmission. If the optical receiver 4 receives the optical signal accurately without causing any error or distortion, and passes the standard, it gives the optical transmitter 2 a signal S0 to return the light emission level to the original level, and Finish the diagnosis.

If the above inspection fails, we will notify you to that effect,
Or display the diagnostic signal St to the optical transmitter 2 at the same time.
and set the light emission level to 1.5 from the system margin.
Return only dB to the original level and set it to the warning level. Then, it is diagnosed whether the system 1 operates normally at this warning level. If this warning level diagnosis is passed, a notification or display to that effect is provided.

If this warning level test fails, the optical transmitter 2
A diagnostic signal S is input to the device, and the light emission level is further returned by 1.0 dB from the warning level to set it to the dangerous level. Then, it is diagnosed whether the system 1 operates normally at this danger level. If this warning level diagnosis is passed, that effect is notified or displayed.

In this way, the system margin, warning level, and danger level are diagnosed while operating the communication system 1, and it is confirmed that the system 1 operates normally.

FIG. 2 shows another embodiment of the present invention, in which a variable optical attenuator 5 is connected to the output side of the optical transmitter 2. When a diagnostic signal S is input from the signal input terminal 5a, this variable optical attenuator 5 operates according to the diagnostic signal, for example, transmittance (
The level of the output optical signal passing through the variable optical attenuator 5 is attenuated to each level such as the system margin, warning level, or danger level, and the attenuated optical signal is transmitted to the optical transmission line. 3 is output.

FIG. 3 shows another embodiment of the present invention, in which a variable optical attenuator 5 is connected to the input side of the optical receiver 4, and the level of the optical signal transmitted to the optical transmission line 3 is adjusted by the system margin. Alternatively, the signal is input to the optical receiver 4 after being attenuated to a warning level or a dangerous level.

(Effects of the Invention) As explained above, according to the present invention, at least one of the optical transmission level on the optical transmitter side or the optical reception level on the optical receiver side of an optical communication system is reduced by a predetermined level, and the optical By inspecting whether the communication system is operating within the specified system margin, it becomes possible to inspect and predict the decrease in the system 4° margin before system operation. Since the operation mode of the system can be used as is, there is no need to change or switch the system, or it can be done to a minimum extent. In addition, no special method is required for inspection, and it is only necessary to know whether the system is operating normally when the optical transmission level or optical reception level is reduced, thereby reducing diagnostic time and diagnostic labor. There are effects such as being able to.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the method for diagnosing an optical communication system according to the present invention, and FIGS. 2 and 3 are block diagrams showing other embodiments of the method for diagnosing an optical communication system according to the present invention. It is. 1... Optical communication system, 2... Optical transmitter, 3...
Optical transmission line, 4... optical receiver, 5... optical variable attenuator. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] Reduce at least one of the optical transmission level on the optical transmitter side or the optical reception level on the optical receiver side of the optical communication system by a predetermined level, and check whether the optical communication system is operated within a specified system margin. A method for diagnosing an optical communication system, the method comprising: inspecting an optical communication system;