JPH03214681A - Fiber type light amplifier - Google Patents

Abstract

PURPOSE:To get unidirectionally the same amplification properties with high amplification gain by equipping an optical fiber with plural pieces of optical couplers connected to different places of the same optical fiber. CONSTITUTION:The pumping light outputted from the pumping light source 2 driven by a driving circuit 4 is divided in two with an optical branching filter 7 after passing through an optical isolator 6, and one pumping light is inputted in the left direction into a rare earth optical fiber 1 through the optical coupler 3a provided in a signal light I/O terminal 5a. The other excitation light is inputted in the left direction into the earth optical fiber 1 through the optical coupler 3b provided in a signal light I/O terminal 5b. The rare earth optical fiber 1, to which the pumping lights are input in right and left direction, becomes inverted population state, but the state of inverted population becomes more uniform as compared with the case where it is excited only from one place. Hereby, the signal light inputted from the signal light I/O terminal 5a or the signal light I/O terminal 5b is amplified with higher efficiency, and further unidirectionally the same properties can be gotten.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fiber-type optical amplifier using an optical fiber used, for example, in an optical communication system, and in particular to a fiber-type optical amplifier that pumps a signal light with a plurality of pumping lights. It concerns amplifiers.

[Conventional technology]

Conventionally, there has been a fiber type optical amplifier of this type as shown in FIG. This third figure is written by Yoshinobu Shimada, 'Er.
Impact of doped fiber optical amplifiers on optical communications
・”, Q pl+xs E-.NO.113, pp
．． 75-82, 1989J, in FIG. 3, 2 is a rare earth-doped optical fiber that is an optical amplification medium, and 2 is a pump that outputs pumping light that excites the signal light of optical fiber 1. A light source, 3a is an optical coupler that transmits light, and 4 is a drive circuit that drives excitation light B2.

5a and 5b are signal light input/output terminals.

Next, the operation of this conventional example will be explained. The rare earth doped optical fiber 1 is a single mode optical fiber having a length of several meters to several tens of meters doped with, for example, erbium, which is a rare earth element. An optical coupler 3a is connected to the rare earth doped optical fiber 1. The excitation light source 2 has a wavelength of, for example, 1.
A 48 μm semiconductor laser is driven by a drive circuit 4 to achieve a stable DC oscillation state. When pump light of several mW to several tens of mW output from the pump light source 2 is input to the rare earth doped optical fiber 1 through the optical coupler 3a, the rare earth doped optical fiber 1 enters a population inversion state, and the signal light is input from the signal light input/output terminal 5a. In addition, the wavelength was 1.53 μm or 1.53 μm.
The 55 μm signal light is amplified by stimulated emission and output to the signal light input/output terminal 5b.

[Problem to be solved by the invention]

As described above, conventional fiber-type optical amplifiers are configured to input pump light into a rare earth-doped optical fiber from only one point, so as the pump light moves away from the input point, the fiber-type optical amplifier Since the amplification gain decreases, there is a problem in that efficient optical amplification cannot be performed throughout the rare earth doped optical fiber.

This invention was made to solve the above-mentioned problems, and aims to obtain a fiber-type optical amplifier with higher amplification gain by using rare earth doped optical fibers of the same length and pumping light sources of the same output level. With the goal.

[Means for Solving the Problems] A fiber-type optical amplifier according to the present invention is characterized in that it includes a plurality of optical couplers 3a and 3b connected to different locations of an optical fiber 1.

[Effect]

The excitation light from the excitation light source 2 is transmitted through a plurality of optical couplers 3a, 3.
The signal is input to the optical fiber 1 via b.

〔Example〕

FIG. 1 is a block diagram of a fiber type optical amplifier according to an embodiment of the present invention. In FIG. 1, components corresponding to those shown in FIG. 3 are designated by the same reference numerals, and their explanations will be omitted. In FIG. 1, 3a and 3b are two optical couplers connected to different points of the rare earth doped optical fiber 1,
6 connects the excitation light from the excitation light source 2 to two lights, a coupler 3a,
An optical isolator 7 is used to transmit the light to the rare earth doped optical fiber 1 via the optical isolator 3b, and an optical demultiplexer 7 separates the excitation light from the optical isolator 6 into the optical coupler 3a and the optical coupler 3b. This optical demultiplexer 7 can be realized using, for example, a 3 dB optical fiber coupler or an optical waveguide type Y branch circuit.

Next, the operation of this embodiment will be explained. Similar to the conventional example shown in FIG. 3, the excitation light source 2 driven by the drive circuit 4 stably outputs constant excitation light. The output pumping light passes through an optical isolator 6 and is divided into two by a demultiplexer 7. One of the distributed pumping lights is input rightward into the rare earth doped optical fiber l through the optical coupler 3a provided at the signal light input/output terminal 5a. The other equally distributed pumping light is input to the left into the rare earth doped optical fiber 1 through the optical coupler 3b provided at the signal light input/output terminal 5b. The rare-earth-doped optical fiber 1 that receives excitation light from both the left and right directions is in a population inversion state, but the population inversion state is more uniform compared to the conventional example shown in Fig. 3, in which the pump light is pumped from only one location. . Therefore, the signal light input from the signal light input/output terminal 5a or the signal light input/output terminal 5b is amplified with higher efficiency, and the same characteristics can be obtained in both directions. Note that a part of the signal light input from the signal light input/output terminal 5a goes toward the excitation light source 2 through the optical coupler 3b, but this is blocked by the optical isolator 5 and has no harmful effect on the excitation light source 2. Not affected. Similarly, a part of the signal light input from the signal light input/output terminal 5b is sent to the excitation light source 2 through the optical coupler 3a.
However, this is also blocked by the optical isolator 6 and does not have a harmful effect on the excitation light ajX2.

FIG. 2 is a block diagram of a fiber type optical amplifier according to another embodiment of the present invention. In FIG. 2, components corresponding to those shown in FIG. 1 are designated by the same reference numerals, and their explanations will be omitted. In FIG. 2, 6a is an optical isolator for transmitting the excitation light from the excitation light source 2 to the optical coupler 3a, and 6b is an optical isolator for transmitting the excitation light from the excitation light source 2 to the optical coupler 3b.
This is an optical isolator for transmitting data to

Next, the operation of this embodiment will be explained. The excitation light source 2 outputs two lights, a front light and a back light, as excitation light. One of the excitation lights passes through the optical isolator 6a and is input to the left side into the rare earth doped optical fiber l via the optical coupler 3a.

The other excitation light passes through the optical isolator 6b and enters the rare earth doped optical fiber 1 in the left direction via the light 6 coupler 3b. After that, the process is similar to the embodiment shown in FIG.

With the configuration shown in FIG. 2, pumping light can be input into the optical fiber 1 from two locations on the rare earth doped optical fiber 1 without the optical demultiplexer 7 shown in FIG. 1, and the pumping light source 2 This has the effect of increasing the utilization efficiency of the fiber-type optical amplifier and reducing the power consumption of the entire fiber-type optical amplifier.

In the above embodiment, two optical couplers are provided at two different locations on the optical fiber, but the invention is not limited thereto, and a plurality of optical couplers may be provided at multiple different locations on the optical fiber.

〔Effect of the invention〕

As described above, according to the present invention, since the configuration includes a plurality of optical couplers connected to different locations of the optical fiber,
Pumping light is input from different points in the optical fiber, which creates a more uniform population inversion state in the optical fiber than when pumping from only one point, which increases the efficiency of the utilization of the amplification medium and therefore results in higher amplification. It is possible to realize a bidirectional fiber-type optical amplifier that exhibits the same gain and amplification characteristics regardless of which signal light input/output terminal at both ends of the optical fiber is input.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a fiber-type optical amplifier according to one embodiment of the present invention, FIG. 2 is a configuration diagram of a fiber-type optical amplifier according to another embodiment, and FIG. 3 is a configuration diagram of a conventional fiber-type optical amplifier. It is a diagram. 1... Rare earth doped optical fiber, 2... Excitation light source, 3
a, 3b = optical coupler, 6, 6a6b... optical isolator.

Claims (1)

[Claims] A fiber-type optical amplifier comprising an optical fiber as a light amplification medium and a pumping light source for pumping signal light of the optical fiber, comprising a plurality of optical couplers connected to different points of the optical fiber. A fiber-type optical amplifier characterized in that the optical coupler is used to input excitation light from the excitation light source from a plurality of points of a doped optical fiber.