JP2940194B2 - Optical direct amplification method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical direct amplification system,
In particular, it relates to an optical direct amplification system capable of controlling the gain of an optical fiber amplifier.

[0002]

2. Description of the Related Art In this type of conventional optical direct amplification system, a pilot signal is superimposed on a signal at a transmitting terminal at a specified level, and a level variation of a pilot signal in a transmission line is detected by each optical amplifier circuit. The gain of the optical fiber amplifier is variably controlled by varying the optical output level of the pump laser diode according to the amount of deviation from the initial value.

FIG. 3 shows a configuration example of such an optical amplifier circuit. The optical signal sent from the terminal is optically amplified by the rare-earth doped fiber 22, then split by the optical splitter 31, and photoelectrically converted by the photodiode (PD) 32. The pilot signal in the electric signal is extracted by the filter 33, amplified by the amplifier 34, and compared with the output voltage of the reference voltage circuit 35 by the comparison circuit 36.
Laser diode (LD) 2 for excitation in D drive circuit 28
3 to control the amount of light to be excited,
This is passed through an optical splitter 21 to a rare earth doped fiber 22.
To change the optical amplification gain. That is, when the level of the extracted pilot signal is smaller (greater) than the specified value, the current flowing from the LD drive circuit 28 to the LD 23 is increased (decreased), and the optical amplification gain is increased (decreased).
I'll do it.

[0004]

However, in this conventional system, in each optical amplifier circuit, the output level obtained at the output terminal 2 is reduced by the insertion loss of the optical demultiplexer 31, and the demultiplexed signal is output. Since the optical signal is subjected to photoelectric conversion and the pilot signal is further extracted, the PD 32 and the filter 33 are required, and there are problems such as an increase in circuit size and complexity.

[0005]

According to the present invention, there is provided an optical direct amplification system comprising: a transmitting terminal for transmitting an optical signal in which a pilot signal is superimposed on a transmission signal to a transmission line; a level of the pilot signal received from the optical transmission line; And a receiving terminal having a power supply device for varying the power supply current to the optical transmission line in accordance with a change in the level, and detecting the magnitude of the power supply current which is disposed in the middle of the optical transmission line. Current detection circuit, a drive circuit for issuing a current signal for setting the magnitude of the excitation light signal in accordance with the current detection result, a light emitting element for emitting an excitation light signal in response to the current signal, and the excitation light An optical amplifier circuit having an optical fiber amplifier for amplifying an optical signal received from the optical transmission line in accordance with a signal and transmitting the amplified signal to the optical transmission line.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of a configuration example of an optical amplifier circuit 13 in the present embodiment. The terminal station 12A superimposes a pilot signal emitted from the oscillator 16 on the data signal from the input terminal 10, converts the data signal into an electric signal, and sends the electric signal to the transmission line including the optical fiber of the optical fiber cable 14 and the optical amplifier circuit 13.
The transmission line transmits the optical signal attenuated by the loss of the optical fiber to the terminal station 12B while amplifying the optical signal with the optical amplifier circuit 13.
The terminal station 12B detects the pilot signal level after photoelectric conversion of the received optical signal and, based on the deviation of the signal level from the initial value, determines a part of the power supply current of the power supply devices 15A and 15B, for example, as a reference. Is varied within the range of ± 0.1 A in accordance with the variation of the pilot level with respect to the current 1A.

On the other hand, in the optical amplifying circuit 13 in the transmission line, as shown in FIG. 2, the above-mentioned change in the supply current is detected by the current detection circuit 26 and converted into a voltage signal. Is compared with the output voltage of
Excitation laser diode (LD) 2 from D drive circuit 28
The optical amplification gain of the rare-earth-doped fiber 22 is changed by changing the current flowing to 3 and changing the optical output power of the LD 23.

As described above, the optical amplification gain of each optical amplifier circuit 13 is changed according to the change of the power supply current given by the terminal station.
Control can be performed so that the reception pilot level at the terminal station 12B becomes a preset value. This allows
Each optical amplifier circuit 13 does not need to be provided with a photodiode and a filter for detecting the pilot level.

[0010]

As described above, according to the present invention, the terminal supplies a change in the power supply current in accordance with the change in the pilot reception level, and each optical amplifier circuit detects the change in the power supply current. By controlling the gain, a demultiplexer is not required in each optical amplifier circuit, thereby preventing a decrease in gain,
Also, there is no need for photoelectric conversion, simplifying the circuit configuration,
Miniaturization can improve reliability and transmission characteristics.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of an optical amplifier circuit according to the embodiment of the present invention.

FIG. 3 is a block diagram of a conventional optical amplifier circuit.

[Explanation of symbols]

 12A, 12B Terminal station 13 Optical amplifier circuit 15A, 15B Power supply device 14 Optical fiber cable 16 Oscillator 21 Optical multiplexer 22 Rare earth doped fiber 23 Laser diode (LD) 24 Reference voltage circuit 25 Comparison circuit 26 Current detection circuit 27 Power supply circuit 28 LD Drive circuit

Claims (1)

(57) [Claims] A transmitting terminal for transmitting an optical signal in which a pilot signal is superimposed on a transmission signal to a transmission line; detecting a level of the pilot signal received from the optical transmission line; A receiving terminal having a power supply device for varying the power supply current to the transmission line, a current detection circuit disposed in the middle of the optical transmission line and detecting the magnitude of the power supply current, and A drive circuit that emits a current signal for setting the magnitude of the excitation light signal, a light emitting element that emits an excitation light signal in response to the current signal, and reception light from the optical transmission line according to the excitation light signal An optical amplifier circuit having an optical fiber amplifier for amplifying a signal and sending the amplified signal to the optical transmission line.