JP3019566B2 - Optical amplifier - 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 amplifier, and more particularly, to an optical amplifier.
It relates to control of an optical amplifier.

[0002]

2. Description of the Related Art Conventionally, an amplifier using a plurality of pumping light sources is known as an optical amplifier. In this type of optical amplifier, the output of each pumping light source is controlled so that the intensity of an optical output signal is constant. I have. When controlling the intensity of the optical output signal to be constant, it is necessary to consider the characteristics of each excitation light source and drive circuit.

[0003]

However, in the conventional optical amplifier, it is difficult to control the intensity of the optical output signal to be constant due to the difference between the characteristics of each pumping light source and the driving circuit. There is a problem that it is extremely difficult to variably control the output of the device.

An object of the present invention is to provide an optical amplifier capable of uniformly and variably controlling the outputs of a plurality of pump light sources.

[0005]

An optical amplifier according to the present invention comprises: an optical fiber for optically amplifying an input optical signal input from an input terminal to which an amplification additive is added and transmitting an output optical signal from an output terminal; A first excitation light source that applies a first excitation light to the optical fiber to excite the amplification additive, a second excitation light source that provides a second excitation light to the optical fiber at the output end to excite the amplification additive, A driving circuit for driving the first and second excitation light sources, a driving pulse generating circuit for generating a driving pulse signal for driving and controlling the driving circuit, and a photodetector for detecting a transmission signal level of the output optical signal. Have. The drive pulse generation circuit changes the duty ratio of the drive pulse signal according to a difference between the transmission signal level and a preset value, and shares the drive pulse signal with the first and second excitation light sources. And give the first and second
Is characterized in that the output of the excitation light is uniformly variably controlled.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

Referring to FIG. 1, an optical signal (input optical signal) input from connector a is provided to Er-doped optical fiber 12 via coupler 11. The input optical signal transmitted through the optical fiber 12 is combined with the coupler 13 and the splitter 14.
Is output from the connector b as an output optical signal.

The coupler 11 has an excitation light source 15.
The excitation light source 16 is similarly connected to the coupler 13. Then, these excitation light sources 15 and 16
Are driven and controlled by drive circuits 17 and 18, respectively. On the other hand, a photodetector 19 is connected to the branching device 14. A variable duty ratio circuit 20 is connected to the photodetector 19. The duty ratio variable circuit 20 is driven by a high-frequency pulse signal from a high-frequency pulse generator 21 and generates a driving pulse signal based on a detection output of the photodetector 19 as described later. 17 and 18. This means that the drive circuits 17 and 18 drive control the excitation light sources 15 and 16 based on the drive pulse signals.

Light from the excitation light sources 15 and 16 (hereinafter referred to as light source light) is supplied to the optical fiber 12 via the couplers 11 and 13, respectively. Will be amplified. Then, the amplified optical signal is output as an output optical signal. The output optical signal is split by the splitter 14 and provided to the photodetector 19. The photodetector 19 detects the output optical signal and outputs an electric signal corresponding to the output optical signal. Then, the electric signal is provided to the duty ratio variable circuit 20. The duty ratio variable circuit 20 changes the duty ratio of the drive pulse signal in accordance with the level of the electric signal, and supplies the drive pulse signal to the drive circuits 17 and 18. As a result, the drive circuits 17 and 18 control the excitation light sources 15 and 16 in accordance with the level of the output optical signal, and the output optical signal level is controlled to be constant.

Here, the configuration of the drive circuit will be described with reference to FIG.

The drive circuit has first to fifth terminals c to g. A voltage having a predetermined voltage level is applied to each of the first and second terminals c and d and the fourth terminal f. You. The third terminal e is supplied with a driving pulse signal, and the fifth terminal g is connected to an excitation light source.

The driving circuit comprises a resistor 22, a transistor 23
And 24, and constant current sources 25 and 26.
As shown, the collector of transistor 23 is connected to resistor 2
2 to the first terminal c, the base of which is the fourth terminal c.
Is connected to the terminal f. The emitter of the transistor 23 is connected to the second terminal d via the constant current source 26. On the other hand, the collector of the transistor 24 is connected to the fifth terminal g and is connected to the second terminal g through the constant current source 25.
Is connected to the terminal d. The base of the transistor 25 is connected to the third terminal e. Further, the emitter of the transistor 24 is connected to the second terminal g via the constant current source 26.

Referring to FIGS. 1 and 2, when the level of the optical signal (transmitted optical signal) detected by photodetector 19 deviates from a preset value, variable duty ratio circuit 20 drives Change the duty ratio of the pulse signal. For example, when the transmission signal level is lower than a preset value, the duty ratio variable circuit 20 increases the duty ratio of the drive pulse signal according to the difference (deviation) between the transmission signal level and the preset value. As a result, the drive circuits 17 and 18 increase the drive current (average value) applied to the excitation light sources 15 and 16, and the transmission optical signal is controlled to a preset level. On the other hand, if the transmission signal level is higher than a preset value,
The duty ratio variable circuit 20 reduces the duty ratio of the drive pulse signal according to the difference (deviation) between the transmission signal level and a preset value. As a result, the drive circuits 17 and 18 reduce the drive current (average value) supplied to the excitation light sources 15 and 16, and the transmission optical signal is controlled to a preset level.

As described above, in the above-described amplifier, by changing the duty ratio of the drive pulse signal, the output light from the plurality of pump light sources can be uniformly varied, and the level of the transmission light signal can be controlled to be constant.

[0015]

As described above, according to the present invention, the duty ratio of the drive pulse signal for driving the pump light source is changed in accordance with the level of the transmission signal. It has the effect of being able to change.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of an optical amplifier according to the present invention.

FIG. 2 is a circuit diagram showing an example of a drive circuit used in the optical amplifier shown in FIG.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 coupler 12 Er-doped optical fiber 13 coupler 14 brancher 15 excitation light source 16 excitation light source 17 drive circuit 18 drive circuit 19 photodetector 20 duty ratio variable circuit 21 high frequency pulse generator

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01S 3/10 H01S 3/131 H01S 3/0941 H01S 3/06-3/07 G02F 1/35 H04B 10 / 00-10/28

Claims (2)

(57) [Claims] 1. An optical fiber to which an amplification additive is added, which optically amplifies an input optical signal input from an input terminal and sends an output optical signal from an output terminal; and a first pump light to the optical fiber at the input terminal. And a second excitation light source for providing the second excitation light to the optical fiber at the output end to excite the amplification additive; and a first excitation light source for applying the second excitation light to the optical fiber at the output end to excite the amplification additive. a drive circuit for driving the an excitation light source a second excitation light source, a drive pulse generating circuit for generating a driving pulse signal for driving and controlling the drive circuit, a light detector for detecting the level of said output optical signal An optical amplifier comprising: wherein the drive pulse generation circuit is preset with the level.
Depending on the difference between the value to change the duty ratio of the drive pulse signal given in common the driving pulse signal to said second excitation light source and the first pumping light source the first excitation
An optical amplifier , wherein the output of the light emission and the output of the second pump light are variably controlled equally . 2. An optical amplifier according to claim 1, wherein Er (erbium) is used as said amplification additive, and said Er is added to a core of said optical fiber.