JP2707892B2 - Optical wavelength division multiplexing - 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 wavelength division multiplex system in the field of optical communications, and more particularly to an optical wavelength division multiplex system for stabilizing the output of an optical wavelength division multiplex system using an optical fiber amplifier.

[0002]

2. Description of the Related Art A conventional optical wavelength division multiplexing system employs two or more types of optical transmitters having different optical wavelengths, an optical coupler for multiplexing the outputs of the respective optical transmitters, and an optical signal synthesized by the optical coupler. Is provided with an optical fiber amplifier for amplifying.

[0003]

In this conventional optical wavelength division multiplexing system, when the optical output of each optical transmission board is reduced (deteriorated) for some reason, when there is no output stabilization control circuit in the optical amplifier, or However, when the gain is controlled to be constant, there is a problem that the optical output power output to the transmission line is reduced by an amount corresponding to the reduction of the optical transmission board.

[0004]

SUMMARY OF THE INVENTION An optical wavelength division multiplexing system according to the present invention uses two different wavelengths for converting an electric signal into an optical signal.
More than two types of optical transmitters, an optical splitter that splits the optical output of the optical transmitter, and an optical output power
A photodetector that converts the output light into an electrical signal, an optical coupler that multiplexes the other output light of the optical branching unit, an optical fiber amplifier that directly amplifies the output light of the optical coupler , The second excitation light source and the first and second excitation light sources
A first and a second excitation light source driving circuit to be driven respectively;
The output of the pump light source is input to the front of the optical fiber amplifier.
The output of the first WDM coupler and the output of the second pump
A second WDM coupler input after the fiber amplifier;
The information of the optical output power output from the photodetector is input and
So that the output of the optical fiber amplifier is constant.
The first and second control units respectively control the first excitation light source driving circuit.
And a second gain control circuit .

[0005]

According to the present invention, when the optical fiber amplifier is used in the optical wavelength division multiplexing system, the output of the optical fiber amplifier is controlled to be constant in order to compensate for the optical output fluctuation of the optical transmitter.

[0006]

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, reference numerals 1 and 2 denote optical transmitters having different optical wavelengths for converting electric signals into optical signals, reference numerals 3 and 4 denote optical splitters for branching optical outputs of the optical transmitters 1 and 2, and reference numerals 5 and 5, respectively.
Reference numeral 6 denotes a photodetector that monitors each branch output of the optical branching units 3 and 4, and reference numeral 7 denotes an optical coupler that combines the other output lights of the optical branching units 3 and 4. Reference numeral 8 denotes a rare-earth-doped optical fiber. The rare-earth-doped optical fiber 8 constitutes an optical fiber amplifier for directly amplifying the output light of the optical coupler 7. Here, the optical coupler 7 and the rare-earth-doped optical fiber 8 constitute an optical multiplexing board. Reference numerals 9 and 10 denote gain control circuits for controlling the output of the rare-earth-doped optical fiber 8 as an optical fiber amplifier to a constant value, 11 and 12 denote excitation light sources (lasers), and 13 and 14 denote excitation light sources 11 and 12. , And 16 and 15 are WDM couplers, and 17, 18 and 19 are optical fibers.

Next, the operation of the embodiment shown in FIG. 1 will be described. First, an electric signal is converted into an optical signal by the optical transmitters 1 and 2 having two different wavelengths. Then, the optical output is split by the optical splitters 3 and 4, and one of the splitters is split by the photodetectors 5 and 5.
6 and each is again converted into an electric signal corresponding to the optical output power. Information on the optical output power from the photodetectors 5 and 6 is sent to gain control circuits 9 and 10, respectively. The other optical outputs of the optical branching units 3 and 4 are combined by the optical coupler 7 via the optical fibers 17 and 18.

Next, the optical signal synthesized by the optical coupler 7 passes through the WDM coupler 15 to the rare-earth-doped optical fiber 8.
The light is directly amplified. This rare earth doped optical fiber 8
The optical signal amplified by is transmitted through the WDM coupler 16 and the optical fiber 19 to the transmission line. Further, the drive currents of the excitation light source driving circuits (laser driving circuits) 13 and 14 are controlled by the gain control circuits 9 and 10, respectively, that is, the outputs of the excitation light sources (lasers) 11 and 12 are controlled, respectively.
The configuration is such that the gain of the rare-earth-doped optical fiber 8 is controlled. By adopting such a configuration, the optical transmitter 1,
When there is a change in the optical output of No. 2, the gain of the rare-earth-doped optical fiber (optical fiber amplifier) 8 can be controlled in accordance with the change, and a constant stable output can always be transmitted to the transmission line.

[0009]

As described above, according to the present invention, when an optical fiber amplifier is used in an optical wavelength division multiplexing system, the output of the optical fiber amplifier is controlled to be constant in order to compensate for the optical output fluctuation of the optical transmitter. Therefore, when the optical output of the optical transmission board fluctuates, the pump light output can be controlled by the gain control circuit, the gain of the rare-earth-doped optical fiber can be controlled, and a stable (constant) optical output is always transmitted to the transmission line. It has the effect that it can be done.

[Brief description of the drawings]

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

[Explanation of symbols]

 1, 2 optical transmission board 3, 4 optical branching unit 5, 6 photodetector 7 optical coupler 8 rare earth doped optical fiber (optical fiber amplifier) 9, 10 gain control circuit 11, 12 pumping light source (laser) 13, 14 pumping light source Drive circuit (laser drive circuit) 15, 16 WDM coupler 17-19 Optical fiber

Claims (1)

(57) [Claims] 1. A two or more light transmitting plate and having different optical wavelength for converting an electric signal into an optical signal, an optical branching section that branches the light output of the light transmitting plate, a light branching output of the optical branching section output
A photodetector for converting to an electric signal corresponding to power, and an optical coupler for multiplexing the other output light of the optical branching unit,
An optical fiber amplifier for directly amplifying the output light of the optical coupler, first and second excitation light sources, and first and second excitation light
First and second excitation light source driving circuits for driving respective light sources
And the output of the first pumping light source in front of the optical fiber amplifier.
Input first WDM coupler and output of second pump light source
Input to the rear of the optical fiber amplifier
And information on the optical output power output from the photodetector.
Force so that the output of the optical fiber amplifier is constant.
To control the first and second excitation light source driving circuits, respectively.
An optical wavelength division multiplexing system comprising first and second gain control circuits .