JPH0697885A - System and device for optical amplification and repeating - Google Patents

Abstract

PURPOSE:To improve the stability of modulation degree control and to simplify the circuit by adopting PSK modulation in the modulation system for monitor and control signal insertion. CONSTITUTION:The output signal of a subcarrier generating circuit 7 is subjected to PSK modulation in accordance with the monitor and control signal outputted from a monitor and control circuit 5 by a PSK modulation circuit 6 and passes through an AGC 4 and is inputted to the modulation input terminal of an optical amplifier 1. The optical amplifier 1 is the repeating amplifier which amplifies the optical main signal from one transmission line to send it to the other, transmission line, and a part of this output light is branched by an optical branching device 9 and is converted from light to electricity by a PD 2 and is inputted to a modulation degree control circuit 3. The output of this circuit 3 is inputted to the gain control terminal of the AGC 4, and the output signal level of the AGC 4 is controlled to stabilize the degree of modulation. A figure (b) shows the state of PSK modulation of the subcarrier superposed on the main signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical amplification repeater system and apparatus, and more particularly to a subcarrier used for transmission of a supervisory control signal and an optical direct amplifier for amplifying and repeating an optical main signal. The present invention relates to an optical amplification repeater system and an optical amplification repeater device in which a supervisory signal is superimposed on a main signal and transmitted.

[0002]

2. Description of the Related Art Conventionally, an optical amplification repeater of this type employs a subcarrier modulation method as a method of transmitting a supervisory control signal to a terminal device or the like. This sub-carrier modulation method is mainly amplitude-shift keying (AS) because of its ease of construction.
K; Amplitude Shift Keying)
Frequency shift keying (FSK; Frequency Shift Keying) to improve sensitivity.
t Keying) is used.

FIG. 2 shows (a) a block diagram and (b) a waveform diagram of subcarriers showing the configuration of a conventional example by amplitude shift keying. In FIG. 2A, the output signal of the subcarrier generation circuit 7 is sent to the ASK modulation circuit 6 by the monitor control circuit 5.
ASK modulation according to the supervisory control signal output from
It is input to the modulation input terminal of the optical amplifier 1 through a GC (Auto Gain Control) 4. Optical amplifier 1
Is a relay amplifier that inputs an optical main signal from one transmission line, amplifies it, and sends it out to the other transmission line. A part of the output light is branched by the optical branching device 9 and PD (Photo Dio).
de) In 2 the light is converted into the electric signal and the modulation degree control circuit 3
Entered in. The output signal of the modulation degree control circuit 3 is AGC4.
Is input to the gain control terminal of and the level of the output signal of the AGC 4 is controlled to be constant. This stabilizes the modulation degree of the subcarrier. Since this modulation degree stabilization control is performed only while the subcarrier is being output, the output signal of the modulation degree control circuit 3 is ON / OFF controlled by the timing circuit 8 by the monitoring control signal from the monitoring control circuit 5.

FIG. 2B shows a state in which the subcarrier superimposed on the optical main signal is ASK-modulated. The optical amplifier 1
In the optical direct amplifier, the excitation current is controlled by the modulation input applied to the modulation input terminal, and the optical output power changes.

[0005]

In the conventional optical amplification repeater, the subcarrier ASK method is used to modulate the subcarrier by turning it on and off, so that the degree of modulation is stabilized and controlled only when the subcarrier is on. Was difficult and required a special timing circuit. Further, even in the FSK system, since the optical amplifier has frequency characteristics, it is difficult to stabilize the modulation degree at the time of modulation, and a difference occurs in the modulation degree when multi-repeater transmission is performed. When the modulation degree becomes unstable in this way, there is a problem that the optical main signal is adversely affected and it becomes difficult to demodulate the optical main signal on the receiving side.

[0006]

In the optical amplification repeater system of the present invention, the pump light of the optical direct amplifier is modulated by the subcarrier modulated by the supervisory control signal, and the subcarrier is amplified and relayed by the optical direct amplifier. In an optical amplifier relay system in which an optical main signal is superimposed and transmitted, the subcarrier is PSK-modulated by the supervisory signal.

Further, the optical amplification repeater of the present invention controls a subcarrier generator for generating a subcarrier, a modulation circuit for PSK modulating the subcarrier with a supervisory control signal, and an amplitude of an output signal of the modulation circuit. A controlled by signal
A GC circuit, an optical direct amplifier in which pump light is modulated by the output signal of the AGC circuit, and an optical main signal that is amplified is shallowly modulated; and an optical branching device that branches the output light of the optical direct amplifier,
An optical element that converts one optical output signal of the optical branching device into an electrical signal and a control circuit that generates the control signal based on the output signal of the optical element and outputs the control signal to the AGC are provided.

[0008]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of (a) of this embodiment,
(B) It is a waveform diagram of a subcarrier.

In FIG. 1A, the output signal of the subcarrier generation circuit 7 is PSK modulated by the PSK modulation circuit 6 according to the baseband signal output from the monitor control circuit 5,
It is input to the modulation input terminal of the optical amplifier 1 through the AGC 4. The optical amplifier 1 is a relay amplifier that amplifies an optical main signal input from one transmission line and sends it out to the other transmission line. A part of the output light is branched by the optical branching device 9 and converted from light to electricity by the PD 2 and input to the modulation degree control circuit 3. The output signal of the modulation degree control circuit 3 is input to the gain control terminal of the AGC 4, and the level of the output signal of the AGC 4 is controlled to be constant to stabilize the modulation degree.

FIG. 1B shows a state in which the subcarrier superimposed on the optical main signal is PSK-modulated. The phase of the subcarrier is inverted by the monitor control signal from the monitor control circuit 5. Further, in the optical amplifier 1, the modulation current applied to the modulation input terminal of the optical direct amplifier, that is, the excitation current is controlled by the sub-carrier to change the optical output power, and the sub-carrier is superimposed on the optical main signal.

[0011]

As described above, according to the present invention, since the PSK is adopted as the modulation system of the monitor control subcarrier, the timing circuit is not required, so that the stability of the modulation control is improved. is there.

[Brief description of drawings]

FIG. 1A is a block diagram of an embodiment of the present invention, FIG.
It is a wave form diagram of a subcarrier.

2A is a block diagram of a conventional example, and FIG. 2B is a waveform diagram of a subcarrier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical amplifier 2 PD (photodiode) 3 Modulation degree control circuit 4 AGC 5 Supervisory control circuit (SV) 6 PSK modulation circuit 7 Subcarrier generation circuit 9 Optical brancher

Claims (2)

[Claims] 1. An optical amplifier repeating system in which pump light of an optical direct amplifier is modulated by a subcarrier modulated by a supervisory control signal, and the subcarrier is superimposed on an optical main signal amplified and relayed by the optical direct amplifier for transmission. In the optical amplification repeater system, the subcarrier is PSK-modulated by the supervisory signal. 2. A subcarrier generator for generating a subcarrier, a modulation circuit for PSK modulating the subcarrier with a supervisory control signal, an AGC circuit for controlling the amplitude of an output signal of the modulation circuit by a control signal, An optical direct amplifier in which pumping light is modulated and amplified by an output signal of an AGC circuit and an optical main signal is shallowly modulated, an optical branching device for branching output light of the optical directing amplifier, and one optical output of the optical branching device An optical amplification repeater comprising: an optical element that converts a signal into an electric signal; and a control circuit that generates the control signal from an output signal of the optical element and outputs the control signal to the AGC.