JPH04258036A - Automatic optical output control system - Google Patents

Abstract

PURPOSE:To prevent overload, to make the installation work and the maintenance efficient and to improve the reliability by controlling automatically the optical input to an APD. CONSTITUTION:An O/E conversion circuit 3 is provided with an alarm circuit outputting an alarm signal when a reverse bias voltage of an APD is decreased to a prescribed value or below, an E/O conversion circuit 4 is provided with an alarm transmission means inserting the alarm signal to an overhead bit of a transmission signal and sending the result to an opposite station, an O/E conversion circuit 2 is provided with an alarm reception means receiving the alarm signal and outputting it, and an EGO conversion circuit 1 is provided with an optical output attenuation means decreasing a sender side optical output level automatically by a prescribed quantity by means of the alarm signal.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic optical output control system, and more particularly to an automatic optical output control system used to prevent overloading of a light receiving element APD on the receiving side.

0002

2. Description of the Related Art On the receiving side of optical communication equipment, an APD is generally used as a light receiving element in an O/E conversion circuit that converts a received optical signal into an electrical signal. However, if the optical input level of this APD is excessive, Problems such as deterioration of the output characteristics of the APD and shortening of the life span occur. For this reason, it is necessary to control the optical input level to prevent overload.

Conventionally, in this type of optical output control system, a fixed optical attenuator was inserted on the receiving side, that is, on the optical input side of the APD, to adjust the optical input level. This adjustment is done using an optical power meter.
The optical level was measured, and the optimal fixed attenuator was selected based on this measured value and inserted into the line. That is, the light level was controlled manually. Note that this adjustment is generally performed at the time of initial adjustment of the line.

0004

[Problems to be Solved by the Invention] As mentioned above, the conventional optical output control method manually controls the optical input level on the receiving side, which has the disadvantage that it takes time and labor to control. there were.

[0005]

[Means for Solving the Problems] The optical output control method according to the present invention provides an optical communication device that uses an APD as a light-receiving element on the receiving side of a transmission line, when the reverse bias voltage of the APD drops below a predetermined value. an alarm circuit that outputs an alarm signal at the time of transmission, an alarm transmitting means that inserts the alarm signal into an overhead bit of a transmission line signal and transmits it to the other station, and an alarm circuit that outputs the alarm signal at the other station; - optical output attenuation means for receiving the system signal and lowering the transmitting side optical output level by a predetermined amount.

[0006]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment, and FIG. 2 is a characteristic diagram showing the relationship between the reverse bias voltage and optical input power of the APD used in the embodiment.

In FIG. 2, the reverse bias voltage varies according to the level of optical input power as shown in the curve. Point a is the lowest reverse bias voltage at which the APD can operate, and point b is the optical input power at that time. That is, it is shown that the maximum allowable value of optical input power can be controlled by detecting the lowest reverse bias voltage at point a.

In FIG. 1, an optical signal on an optical fiber 5 from the A station to the B station enters the receiving side O/E conversion circuit 3 of the B station, where it is input to the APD and converted into an electrical signal. At this time, if the optical input power exceeds point b shown in Figure 2 because the line length is short and line loss is very small, the O/E conversion circuit 2 detects point a of the reverse bias voltage and alarms. -Music signal 1
Generates 2. This alarm signal is transmitted to the E/O conversion circuit 4 on the transmitting side. The E/O conversion circuit 4 converts this alarm signal into an overdrive signal placed in the pulse train of the transmission line signal.
It is inserted into the head bit, converted into an optical signal together with the main signal, and transmitted to station A via optical fiber 6.

[0009] At station A, the O/E conversion circuit 2 on the receiving side
receives this optical signal, converts it to an electrical signal, and then sends an alarm.
extracts the system signal 12 and sends it to the E/O conversion circuit 1 on the transmitting side.
tell to. The E/O conversion circuit 1 attenuates the optical transmission power to a predetermined amount by controlling the driving current of the light emitting element using this signal. This predetermined amount is nothing but the amount from point b to point c shown in FIG. 2 in terms of the optical reception power of station B. Since this optical transmission power attenuation circuit controls the amount of electricity, the control is easier and can be automated compared to the case where the amount of light is directly controlled. Furthermore, since the alarm signal disappears by lowering the optical output, this circuit has a latch function.

The above explanation is for the case from the A station to the B station, but the same applies to the case from the B station to the A station.

[0011]

Effects of the Invention As explained above, the present invention automatically controls the optical output on the transmitting side to prevent overloading of the optical input of the photodetector APD, so that it can be done quickly without requiring any human intervention. , and can be carried out reliably, which has a great effect on facilitating installation work and maintenance and improving reliability.

[Brief explanation of the drawing] [Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a characteristic diagram of a light receiving element APD used in an example of the present invention.

[Explanation of symbols]

1, 4 E/O conversion circuit 2, 3 O/E conversion circuit 5, 6 Optical fiber 11, 12 Alarm signal

Claims (1)

[Claims] 1. An alarm circuit that outputs an alarm signal when a reverse bias voltage of the APD drops below a predetermined value in an opposing optical communication device using an APD as a light receiving element on a receiving side of a transmission line. , an alarm transmitting means for inserting the alarm signal into an overhead bit of a transmission line signal and transmitting it to a partner station; An automatic light output control method characterized by comprising a light output attenuation means for quantitatively reducing the light output.