JP2000180910A - Light amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light amplifier in which amplification factor is high and an amplifying wavelength band can be changed. SOLUTION: Each of input/output ports P2 to Pn-1 of a wave length multiple coupler 1 and P1 to Pn-1 of a wave length multiple coupler 2 are total- reflection-terminated, an optical fiber 3 is connected between common ports P0 and P0 of couplers 1, 2, exciting light of wavelength λ1 is given to the input/output port P1 of the coupler 1, Raman divergence is serially caused, and Raman divergence light of wavelength λn is generated. Signal light of wavelength λn is made incident on the input/output port Pn of the coupler 1, and amplified signal light is taken out from the input/output port Pn of the coupler 2. An amplifying band can be changed by changing connection of a signal light source and a total reflection terminal part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical amplifier,
In particular, it relates to an optical amplifier for amplifying signal light.

[0002]

2. Description of the Related Art Conventionally, there has been known a method of performing optical amplification using stimulated Raman scattering. In this optical amplification method, excitation light having a wavelength λ is incident on an optical fiber, and the excitation light generates Raman scattered light (hereinafter referred to as Raman scattered light) due to stimulated Raman scattering at wavelengths λ + a1 and λ-a1 in the optical fiber. Is done. By making the signal light having the wavelength λ + a1 incident on the optical fiber in such a state, the signal light can be amplified.

[0003]

However, the conventional optical amplification method has a low amplification factor and cannot be put to practical use in fields such as optical communication and optical measurement.

Recently, by combining a plurality of types of fiber-type optical couplers or by connecting a plurality of types of fiber Bragg gratings (FBGs), the pumping light is confined in the optical fiber for Raman scattered light generation to improve the amplification factor. Methods have been proposed, but special couplers and FBs
The implementation is not easy because a plurality of types of G are required, and the amplification wavelength range is fixed.

[0005] Therefore, a main object of the present invention is to provide an optical amplifier having a high amplification factor and capable of changing an amplification wavelength range.

[0006]

An optical amplifier according to the present invention is an optical amplifier for amplifying signal light.
And a second wavelength division multiplexing coupler, an optical fiber, an excitation light source and a reflection unit. The first wavelength multiplexing coupler includes a common port and first to n-th input / output ports each provided corresponding to light of the first to n-th wavelengths (where n is an integer of 2 or more). And the first to first incident on the common port
The light of the n-th wavelength is emitted to the first to n-th input / output ports, respectively, and the light of the first to n-th wavelengths incident on the first to n-th input / output ports is multiplexed and shared. Output to port. The second wavelength multiplex coupler has the same configuration as the first wavelength multiplex coupler. The optical fiber comprises first and second optical fibers.
Are connected between the common ports of the wavelength division multiplexing coupler, and the Raman scattered light of the second to n-th wavelengths is generated by the excitation light of the first to n-1st wavelengths. The pump light source emits a pump light of a first wavelength to a first input / output port of the first wavelength division multiplex coupler. The reflecting means is a second to n-th wavelength multiplexing coupler.
-1 input / output port and the first of the second wavelength division multiplexing coupler.
The light of the first to (n-1) th wavelengths incident from the optical fiber side through the (n-1) th input / output port is reflected and returned to the optical fiber side. N-th of the first or second wavelength division multiplexing coupler
The signal light of the n-th wavelength incident from the input / output port of
The signal is amplified in the optical fiber and output from the n-th input / output port of the second or first wavelength division multiplex coupler.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS When light having a wavelength .lambda. Is incident on an optical fiber, the incident light is used as pumping light and wavelengths .lambda. + A1, .lambda.-.
Raman scattered light is generated in the wavelength range of a1. When, for example, a signal light having a wavelength λ + a1 is incident on the optical fiber in such a state, the signal light is amplified.

When excitation light having a high light intensity is incident on the optical fiber, the light intensity of the scattered light having the wavelengths λ + a1 and λ-a1 increases, and the scattered light is used as the excitation light to further increase the wavelength λ + a1 + a2, λ. -A1-a2 scattered light is generated. For example, the wavelength λ
When the signal light of + a1 + a2 enters, the signal light is amplified. That is, under these conditions, light amplification in a wavelength range considerably separated from the original pump light becomes possible. The present invention
Optical amplification is performed using such a chained Raman amplification.

FIG. 1 is a block diagram showing a configuration of a Raman optical amplifier according to one embodiment of the present invention. In FIG. 1, the Raman optical amplifier includes wavelength multiplexing couplers 1, 2,
Optical fiber 3, a plurality of total reflection ends 4.1 to 4.. n-2,
5.1-5. n-1 and a light source 6 for amplifying the signal light of wavelength λn emitted from the signal light source 7.

The wavelength division multiplexing coupler 1 has one common port P
0 and n (where n is an integer of 2 or more) input / output ports P1 to Pn. Light of wavelengths λ1 to λn is assigned in advance to each of the input / output ports P1 to Pn. Where λ1 = λ, λ2 = λ + a1, λ3 =
λ + a1 + a2,..., λn = λ + a1 +... + a (n−
1), for example, λ1 to λ5,... = 1.06 μm,
1.12 μm, 1.18 μm, 1.24 μm, 1.30
μm,. The wavelength division multiplexing coupler 1 multiplexes light having wavelengths λ1 to λn incident from outside via the input / output ports P1 to Pn and emits the light from the common port P0.
The wavelength λ1- input from outside via the common port P0
λn is emitted from the input / output ports P1 to Pn, respectively.

More specifically, the wavelength division multiplexing coupler 1 comprises:
As shown in FIG. 2, in addition to the ports P1 to Pn, a reflector 8 and n + 1 condensing lenses L0 to Ln are included. Reflector 8
The diffraction grating 8a is formed on one surface. The diffraction grating 8a reflects the incident light of the wavelengths λ1 to λn at a reflection angle corresponding to each wavelength. Condensing lenses L0-L
n is provided corresponding to the ports P0 to Pn, respectively, and is arranged at a predetermined angle with respect to the diffraction grating 8a. Light of wavelengths λ1 to λn incident from the outside via the input / output ports P1 to Pn respectively passes through the condenser lenses L1 to Ln and is reflected by the diffraction grating 8a.
Through the common port P0. Conversely, light of wavelengths λ1 to λn incident from the outside via the common port P0 both pass through the condenser lens L0, are reflected by the diffraction grating 8a, and are input / output via the condenser lenses L1 to Ln, respectively. Light is input to ports P1 to Pn. The wavelength multiplex coupler 2
The configuration is the same as that of the wavelength multiplex coupler 1.

The optical fiber 3 is connected between the common port P0 of the wavelength multiplex coupler 1 and the common port P0 of the wavelength multiplex coupler 2. The light of wavelengths λ1 to λn-1 is
, Raman scattered light having a wavelength of λ2 to λn is generated in the optical fiber 3. In order to generate Raman scattered light efficiently, the optical fiber 3 is selected to have a high nonlinear constant and a low optical loss.

The total reflection ends 4.1 to 4. n-2, 5.1-
5. n-1 are provided at the input / output ports P2 to Pn-1 of the wavelength division multiplexing coupler 1 and the input / output ports P1 to Pn-1 of the wavelength division multiplexing coupler 2, respectively. 3. Total reflection end
1-4. n-2, 5.1 to 5. Each of n-1 completely reflects the light incident from the optical fiber 3 side via the corresponding input / output port and returns the light to the optical fiber 3 side.

The light source 6 emits the excitation light having the wavelength λ1 to the input / output port P1 of the wavelength multiplex coupler 1. The signal light source 7
The signal light of wavelength λn is input / output port P of wavelength multiplex coupler 1
to n. The amplified signal light having the wavelength λn is emitted from the input / output port Pn of the wavelength division multiplexing coupler 2.

Next, the operation of the Raman optical amplifier will be described. The excitation light of wavelength λ1 = λ emitted from the light source 6 enters the optical fiber 3 via the wavelength multiplexing coupler 1 and generates the Raman scattered light of wavelength λ2 = λ + a1 in the optical fiber 3 while generating the Raman scattered light. Input / output port P
1 and is reflected at the total reflection end 5.1 to generate again Raman scattered light having the wavelength λ2 = λ + a1 in the optical fiber 3.

The wavelength λ2 = λ + generated in the optical fiber 3
The Raman scattered light a1 is confined in the optical fiber 3 by being reflected at the total reflection ends 4.1 and 5.2 of the input / output ports P2 and P2 of the wavelength division multiplex couplers 1 and 2, and the wavelength λ3 = λ + a1 + a2. Continue to generate Raman scattered light.

Hereinafter, similarly, the wavelength λn-1 = λ + a
+ A (n−2) Raman scattered light is generated, and the Raman scattered light generates a wavelength λn = λ + a1 +... + A (n−
1) Raman scattered light is generated, and this wavelength λn becomes the gain band of the Raman amplifier. When signal light having a wavelength λn enters the optical fiber 3 from the signal light source 7 via the wavelength multiplexing coupler 1, the signal light is amplified in the optical fiber 3 and emitted from the input / output port Pn of the wavelength multiplexing coupler 2. .

In this embodiment, each of the input / output ports P2 to Pn-1 of the wavelength division multiplexing coupler 1 and the input / output ports P1 to Pn-1 of the wavelength division multiplexing coupler 2 is terminated by total reflection. The optical fiber 3 is connected between the common ports P0 and P0 of the
To generate Raman scattering light having a wavelength of λn. And
The signal light having the wavelength λn is made incident on the input / output port Pn of the wavelength division multiplexing coupler 1 to extract the amplified signal light from the input / output port Pn of the wavelength division multiplexing coupler 2. Therefore, since the Raman scattered light is confined in the optical fiber 3, a higher amplification factor can be obtained as compared with the conventional example 1 in which the optical amplification is performed without confining the Raman scattered light in the optical fiber.

On the wavelength multiplexing coupler 1 side, a signal light source 6 'of a desired wavelength (for example, λ3) is connected to an input / output port (in this case, P3), and the input / output port Pn is connected to a total reflection end (in this case, P3). 4.2), and by moving the total reflection end 5.3 of the input / output port (P3 in this case) corresponding to the signal light source 6 'to the input / output port Pn on the wavelength multiplexing coupler 2 side. It becomes possible to amplify the signal light of the wavelength λ3. That is, the amplification wavelength range can be arbitrarily changed.

On the wavelength multiplexing coupler 1 side, a light source 6 'of a desired wavelength (for example, λ3) is connected to an input / output port (in this case, P3), and a total reflection end (in this case, 4) is connected to the input / output port P1. .2), the wavelength of the pump light can be changed without changing the amplification wavelength range.

The wavelength multiplexing couplers 1 and 2 serving as key devices can be easily manufactured by existing techniques such as a diffraction grating and can be easily realized.

In this embodiment, the signal light is input from the signal light source 7 to the input / output port Pn of the wavelength multiplex coupler 1 and the amplified signal light is extracted from the input / output port Pn of the wavelength multiplex coupler 2. Conversely, the signal light may be input from the signal light source 7 to the input / output port Pn of the wavelength division multiplexing coupler 2 and the amplified signal light may be extracted from the input / output port Pn of the wavelength division multiplexing coupler 1.

It should be understood that the embodiments disclosed herein are illustrative in all respects and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0024]

As described above, in the optical amplifier according to the present invention, the second to (n-1) th input / output ports of the first wavelength multiplex coupler and the first to n-th ports of the second wavelength multiplex coupler are provided. Each of the input / output ports is terminated by total reflection, and an optical fiber is connected between the common ports of the first and second wavelength division multiplexing couplers. Then, excitation light of the first wavelength is supplied to the optical fiber through the first input / output port of the first wavelength division multiplexing coupler to cause chained Raman scattering to generate Raman scattered light of the nth wavelength. Let it. The signal light of the n-th wavelength incident on the n-th input / output port of the first or second wavelength division multiplexing coupler is
The signal is amplified in the optical fiber and output from the n-th input / output port of the second or first wavelength division multiplex coupler. Therefore, since the Raman scattered light is confined in the optical fiber, a higher amplification factor can be obtained as compared with Conventional Example 1 in which the Raman scattered light is amplified without being confined in the optical fiber.

The amplification wavelength range can be easily changed by changing the number n of input / output ports.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a configuration of the wavelength division multiplexing coupler illustrated in FIG. 1;

[Explanation of symbols]

1, 2 wavelength multiplex coupler 3 optical fiber 4.1-4. n-2, 5.1 to 5. n-1 Total reflection termination 6 Light source 7 Signal light source 8 Reflector 8a Diffraction grating P0 Common port P1 to Pn Input / output port L0 to L1 Condensing lens

Claims (1)

[Claims] 1. An optical amplifier for amplifying a signal light, wherein each of the optical amplifiers is a common port and each of the first to n-th (where,
n is an integer of 2 or more) and first to n-th input / output ports provided corresponding to the light having the wavelengths of 1 to n. First to first
The light is emitted to the n-th input / output port, and
First and second light beams of the first to n-th wavelengths that have entered the n-th input / output port are multiplexed and output to the common port.
A wavelength multiplexing coupler connected between a common port of the first and second wavelength multiplexing couplers, and a second
To an optical fiber for generating Raman scattered light having an nth wavelength, an excitation light source for emitting an excitation light having a first wavelength to the first input / output port of the first wavelength multiplex coupler, and the first The first light incident from the optical fiber side via the second to (n-1) th input / output ports of the wavelength multiplex coupler and the first to (n-1) th input / output ports of the second wavelength multiplex coupler.
A reflecting means for reflecting light of wavelengths n to n-1 and returning the light to the optical fiber side, the n-th light input from the n-th input / output port of the first or second wavelength division multiplexing coupler. An optical amplifier, wherein a signal light having a wavelength is amplified in the optical fiber and emitted from an n-th input / output port of the second or first wavelength division multiplexing coupler.