JPH042016B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a method for monitoring optical repeaters constituting an optical digital repeater system, and more specifically, the present invention relates to a method for monitoring optical repeaters constituting an optical digital repeater system, and more specifically, the present invention relates to a method for monitoring optical repeaters that constitute an optical digital repeater system, and more specifically, for monitoring optical input power and optical output power of an optical repeater remotely at a terminal station. Regarding the method of measurement.

(Background Art) Once an optical submarine cable system is installed on the ocean floor, it requires a large amount of money to recover from a failure, so it is required to have extremely high reliability. For this reason, each component that makes up the relay system is required to have high reliability, and during and after construction of the system, it is necessary to closely monitor whether the relay system is operating at the level diagram originally designed. is desired. In particular, it is desirable that the optical input power and optical output power of each repeater can be measured remotely at the terminal station. For measuring the optical input power, as shown in Figure 1, the avalanche
Bias voltage 2 of photodiode (APD) 1
Utilizing the fact that the voltage corresponds to the optical input power through the functions of the AGC loop 3 and the bias generation circuit 4, this bias voltage is passed through the code converter 5 and modulated by the modulation circuit 6 to modulate the main transmission signal, and the laser diode (LD) 7 to the terminal station, and by demodulating this signal at the terminal station, remote measurement is possible.
On the other hand, it is difficult to simply and directly measure optical output power. Therefore, conventionally, it has been considered to convert the code of the bias current of a laser diode, which is a light emitting element, in the same manner as in the measurement of the optical input power shown in FIG. 1, and send it to the terminal station.

However, since the bias current of the laser diode is not directly related to the optical output power, it is impossible to know the optical output power from this information.

(Objective of the Invention) The present invention has been made by focusing on such conventional problems, and provides a method for remotely measuring the optical input power and optical output power of an optical repeater at a terminal station with a simple configuration. The purpose is to

(Structure and operation of the invention) The present invention will be explained below based on the drawings. Second
The figure is a block diagram showing one embodiment of the present invention.
This is for measuring the optical input power and optical output power of a one-way optical repeater. In the same figure, 1,
1' is the avalanche photodiode which is the light receiving element, 2, 2' is the bias voltage of the avalanche photodiode 1, 1', 3, 3' is the AGC loop, 4, 4' is the DC-DC converter, etc. Bias generation circuit, 5, 5' code converter, 6, 6' modulation circuit, 7, 7' laser diode (LD) which is a light emitting element, 8, 8' optical fiber 11, which will be described later, from the terminal station. 11' is an optical switch that is driven by a remote control signal and connects the laser diodes 7, 7' and the optical fibers 9, 9' or the optical fibers 10, 10', each installed in the electrical circuit of the optical repeater. and 9, 9' are laser diodes 7,
An optical fiber that returns each output light of 7' to an avalanche photodiode 1, 1', respectively.
10' is an optical fiber for outputting the main line, 11,1
1' is an optical fiber for inputting the main line. In addition,
Optical fibers 9 and 11' are bundled and input to avalanche photodiode 1', and optical fibers 9' and 11 are bundled and input to avalanche photodiode 1. As mentioned above, in response to an instruction from the terminal station, the bias voltages 2, 2' of the avalanche photodiodes 1, 1' created by the bias generation circuits 4, 4' are transferred through the code converters 5, 5'. The main transmission signal composed of a digital signal inputted and converted into an electric signal by avalanche photodiodes 1 and 1' is modulated (for example, mark rate modulation), and is transmitted to the laser diode 7,
Output to 7'. The optical return circuit is composed of optical switches 8, 8' and optical fibers 9, 9'. Here, the optical switch is driven, for example, as follows. If a code (remote control signal) that repeats the density of the mark rate of the digital signal at a period matching the tuning frequency of the receiving filter (not shown) of the optical repeater is transmitted from the terminal station via the optical fiber 11, the transmission is completed. A frequency component equal to the above-mentioned tuning frequency is generated at the output of the filter. By applying this output to the optical switch 8 via a detection circuit and an amplifier (both not shown), the optical switch 8
to drive.

Next, measurement of optical input power will be explained. The optical switch 8 normally connects the laser diode 7 and the optical fiber 10, and no output light is generated in the optical fiber 9. When measuring optical input power, the optical switch 8 connects the laser diode 7 and the optical fiber 9 in response to a remote control signal from the terminal station via the optical fiber 11. In this state, the modulation circuit 6 is turned on by the remote control signal from the terminal station via the optical fiber 11, and the input light input from the optical fiber 11 is converted into an electrical signal by the avalanche photodiode 1, and this electric signal is A bias voltage is generated from the signal by a bias generation circuit 4, and the electric signal is further modulated by a modulation circuit 6 via a code converter 5 using the bias voltage. The modulated electrical signal (input power information) is converted into an optical signal by the laser diode 7, and then the optical switch 8, the optical fiber 9, the avalanche photodiode 1', and the modulation circuit 6'.
(modulation circuit), a laser diode 7', and an optical fiber 10'. The optical signal having the optical input power information remotely measured in this way is demodulated at the terminal station and converted into the bias voltage of the avalanche photodiode 1, and the optical input power corresponding to this bias voltage can be determined. .

Next, measurement of the optical output power of the optical repeater will be explained. When measuring the optical output power, the laser diode 7 and the optical fiber 9 are connected by the optical switch 8 at the same time as when measuring the optical input power described above. In this state, the modulation circuit 6 is turned off by a remote control signal from the terminal station via the optical fiber 11, the modulation circuit 6' is turned on, and the output light from the laser diode 7 is transferred to the optical switch 8 and the optical fiber 9. is converted into an electric signal by an avalanche photodiode 1', a bias voltage is generated from this electric signal by a bias generation circuit 4', and the electric signal is further converted by the bias voltage to a sign converter 5'. The signal is then modulated by the modulation circuit 6'. The modulated electrical signal is converted into an optical signal by a laser diode 7',
The signal is received at the terminal station via the optical switch 8' and the optical fiber 10'. By calibrating the optical power thus measured with the optical power output from the laser diode 7 to the main optical fiber 10 in advance, the optical output of the repeater can be determined. Calibration here refers to changing the optical power and measuring the frequency, and at this time, changing the temperature and power supply voltage of the optical repeater to obtain several types of characteristic curves.

In this way, the optical input power and optical output power of the optical repeater can be measured remotely. Note that these measurements are performed in the absence of any signal from the optical fiber 11'.

Although the above description has been made in one direction, the same applies to the opposite direction by providing an optical switch and an optical fiber between the laser diode 7' and the avalanche photodiode 1.

(Effects of the Invention) As explained above, according to the present invention, optical input power and optical output power of a repeater can be remotely measured at a terminal station with a simple configuration, and an optical submarine that requires high reliability can be used. This is highly effective in realizing cables.

[Brief explanation of drawings]

FIG. 1 shows a conventional optical input power measuring circuit, and FIG. 2 shows an embodiment of the present invention. 1,1'...Avalanche photo diode,
2, 2'...Bias voltage, 3, 3'...AGC loop, 4, 4'...Bias generation circuit, 5, 5'...
...Code converter, 6,6'...Modulation circuit, 7,7'...
...laser diode, 8,8'...optical switch,
9, 9', 10, 10', 11, 11'...optical fiber.

Claims (1)

[Scope of Claims] 1. In an optical repeater constituting an optical digital repeater system arranged between terminal stations, there is provided a light-receiving element that receives input light and converts it into an electrical signal, and an electrical signal that is the output of the light-receiving element. a modulation circuit that modulates the output of the light-receiving element by a bias voltage of the light-receiving element; a light-emitting element that converts an electrical signal, which is the output of the light-receiving element modulated by the modulation circuit, into an optical signal; an uplink transmission line and a downlink transmission line comprising an optical switch for switching, and a link between the output side of the optical switch of the uplink transmission line and the input side of the light receiving element of the downlink transmission line, and of the downlink transmission line. first and second optical folding circuits respectively provided between the output side of the optical switch and the input side of the light receiving element of the upstream transmission line, one end of the input side of the upstream transmission line; When determining the optical input power of the input light on the upstream transmission path at the station, turn on the modulation circuit on the upstream transmission path,
The optical switch of the upstream transmission line is switched to the first folding circuit side, and the optical input power information of the input light of the upstream transmission line, which is the electric power modulated by the modulation circuit of the upstream transmission line, is The signal is transmitted to one terminal station via the first folding circuit and the downlink transmission line, and the optical output power of the output light of the uplink transmission line is determined at one terminal station on the input side of the uplink transmission line. When the modulation circuit of the downlink transmission path is turned on,
The optical switch of the uplink transmission line is switched to the first optical folding circuit side, and the optical output power information of the output light of the uplink transmission line is modulated by the modulation circuit of the downlink transmission line. An electrical signal is transmitted to one terminal station via the downlink transmission path, and when determining the optical input power of the input light of the downlink transmission path at the other terminal station on the input side of the downlink transmission path, the downlink transmission turning on the modulation circuit of the
The optical switch of the downlink transmission path is switched to the second folding circuit side, and the optical input power information of the input light of the downlink transmission path, which is the electric power modulated by the modulation circuit of the downlink transmission path, is The signal is transmitted to the other terminal station via the second folding circuit and the uplink transmission line, and the optical output power of the output light of the downlink transmission line is determined at the other terminal station on the input side of the downlink transmission line. when the modulation circuit of the upstream transmission path is turned on,
The optical switch of the downlink transmission path is switched to the second optical folding circuit side, and the downlink transmission path is outputted with optical output power information of the output light modulated by the modulation circuit of the uplink transmission path. An optical submarine repeater monitoring system characterized in that an electrical signal is transmitted to the other terminal station via the uplink transmission path.