JPH0521881A - Optical fiber amplifier - Google Patents

Abstract

PURPOSE:To provide an optical fiber amplifier capable of ensuring a maximum amplification by independently separately adjusting excitation laser diodes even when variations of characteristics of those laser diodes take place. CONSTITUTION:(n-1) Excitation laser diodes 4, 5, 6 connected to rare-earth doped fibers 3 are controlled constantly at their output levels by APC circuits 9, 10, 11, respectively. An output of an optical fiber amplifier is monitored, with reference to which output the output level of a remaining one excitation laser diode 7 is controlled constantly by a constant output control circuit 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical amplifier for amplifying and outputting an input optical signal as it is, and more particularly to an optical fiber amplifier for amplifying an optical signal by using a rare earth doped fiber.

[0002]

2. Description of the Related Art For example, when amplifying an input optical signal using a rare earth-doped fiber, a plurality of pumping laser diodes are connected to the fiber, and all output levels of these laser diodes are individually set. It is possible to adjust manually.

[0003]

However, it is difficult to obtain a desired result only by adjusting all the laser diodes in the same manner. That is, the excitation laser
If the characteristics of the diodes vary, the desired amplification cannot be obtained.

Therefore, the object of the present invention is to
It is an object of the present invention to provide an optical fiber amplifier capable of obtaining the maximum amplification degree by adjusting each of the diodes independently even if the characteristics of the diodes vary.

[0005]

According to the present invention, a rare earth-doped fiber and n (n is 2) connected to the fiber.
(N is a positive integer above), and an output level of each of (n-1) pumping laser diodes in an optical fiber amplifier that amplifies an input optical signal as it is and outputs it. Control means for controlling the output of the optical fiber amplifier and a monitor means for monitoring the output of the optical fiber amplifier, and the output level of the remaining one pumping laser diode is controlled to be constant with reference to the output of the monitoring means. An optical fiber amplifier including a sub-control unit is obtained.

[0006]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram of an optical fiber amplifier according to an embodiment of the present invention. The optical fiber amplifier of this embodiment includes two polarization-combining WDM couplers 1 and 2, a rare earth-doped fiber 3, four pump laser diodes 4, and a laser diode 4.
It includes 5, 6, and 7.

In FIG. 1, first, the optical input signal input to the input terminal 13 enters the rare earth-doped fiber 3 via the first polarization combining WDM coupler 1. The output of the first pumping laser diode 4 is kept constant by the first APC circuit 9 and enters the rare earth-doped fiber 3 via the first polarization combining WDM coupler 1. The output of the second pumping laser diode 5 is kept constant by the second APC circuit 10 and enters the rare earth-doped fiber 3 via the first polarization combining WDM coupler 1. Further, the output of the third pumping laser diode 6 is kept constant by the third APC circuit 11, and enters the rare earth-doped fiber 3 via the second polarization combining WDM coupler 2. In this way, the optical input signal is amplified and passes through the 10: 1 splitter 8 to the output terminal 1
It is output as an optical output signal from 4. Here, the first, second and third APC circuits 9, 10 and 11 are collectively referred to as main control means.

The amplified optical signal is partially branched by the 10: 1 branching device 8 and input to the constant output control circuit 12 as a sub control circuit. That is, the 10: 1 branching device 8 functions as a monitoring means for monitoring the output of the optical fiber amplifier.
Then, the output of the fourth laser diode 7 is controlled by the control signal from the constant output control circuit 12. Therefore, the optical output signal output from the output terminal 14 is kept constant.

[0009]

As described above, according to the present invention,
Even if the characteristics of the pumping laser diode vary, each can be adjusted independently to obtain the maximum amplification, which is useful when using the booster amplifier with the maximum output level. Is.

[Brief description of drawings]

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

[Explanation of symbols]

1 First polarization combining WDM coupler 2 Second polarization combining WDM coupler 3 Rare earth doped fiber 4 First laser diode for pumping 5 Second pump laser diode 6 Third pump laser diode 7 Fourth laser diode for pumping 8 10: 1 switch 9 First APC circuit 10 Second APC circuit 11 Third APC circuit 12 output constant control circuit 13 Optical input signal 14 Optical output signal

Claims (2)

[Claims] 1. A rare earth-doped fiber and n (n is a positive integer of 2 or more) pumping laser diodes connected to the fiber, and an input optical signal is amplified as it is and output. In an optical fiber amplifier, main control means for controlling the output level of each of (n-1) pumping laser diodes to be constant, monitoring means for monitoring the output of the optical fiber amplifier, and output of the monitoring means. And an auxiliary control means for controlling the output level of the remaining one pumping laser diode to a constant level. 2. The main control means controls each of the (n-1) pump laser diodes (n-1).
The optical fiber amplifier according to claim 1, including an individual APC circuit.