JPH05232527A - Optical fiber amplifier - Google Patents

Abstract

PURPOSE:To eliminate a fusion-joint part between optical fibers of the optical fiber amplifier and an optical system which uses lenses. CONSTITUTION:An optical isolator 1 is connected to the input of an erbium- doped optical fiber (EDF) 2 and signal light is inputted from the input side of the optical isolator 1. The polarization maintaining optical fiber output of an exciting light source 5 and the polarization maintaining optical fiber output light of an exciting light source 6 after being converted into parallel light are coupled by a polarizing filter 69, reflected by a dielectric filter 70, and inputted to the EDF 2, wherein the signal light is optically amplified. The optically amplified light from the EDF 2 after being converted into parallel light is transmitted through a dielectric filter 70, an optical isolator 71, and a dielectric filter 72 in the state of the parallel light and outputted from an optical fiber 26. Part of the optically amplified light is branched by a dielectric filter 72 in the form of the parallel light, part of it is outputted as monitor light, and the rest is outputted as light for output control over the optical fiber amplifier. Reflected light from an optical connector 29 at the output terminal of the optical fiber 26 is converted into parallel light, which is reflected by the dielectric filter 72 and outputted from an optical fiber 28.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical fiber amplifier used in an optical communication device or the like.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram showing a configuration of a conventional optical fiber amplifier. In the figure, 13 is an input optical fiber, which is connected to the optical isolator 1. The optical isolator 1 is provided for blocking the reflected return light to the input side. Reference numeral 2 denotes an erbium-doped optical fiber in which the optical fiber is doped with erbium, and the input side is fused with the output optical fiber 14 of the optical isolator 1. Reference numeral 12 indicates a fused portion, and the same applies to all nine locations hereinafter. Reference numeral 3 denotes an optical multiplexer / demultiplexer, which outputs light having a wavelength of 1.48 μm input from the optical fiber 16 to the optical fiber 15 and outputs light having a wavelength of 1.55 μm input from the optical fiber 15 to the optical fiber 17. To do. The optical fiber 15 is fused with the erbium-doped optical fiber 2. Reference numerals 5 and 6 denote pumping light sources having a wavelength of 1.48 μm, which are output from the polarization maintaining fibers 21 and 22, respectively. Reference numeral 4 denotes a polarization beam coupler, which is composed of polarization maintaining fibers 19 and 20.
The two orthogonal polarizations input from the optical fiber 18 are combined and output from the optical fiber 18. Optical fibers 21 and 19 and 22
And 20 are fused together, and the excitation light sources 5 and 6 are
The light having a wavelength of 1.48 μm is coupled by the polarization beam coupler 4 and output from the optical fiber 18. Optical fiber 1
8 is fused with the optical fiber 16, so that the light having a wavelength of 1.48 μm output from the pumping light sources 5 and 6 is transmitted by the optical multiplexer / demultiplexer 3 to the erbium-doped optical fiber 2
To excite erbium atoms in the fiber.
At this time, when 1.55 μm light is input to the erbium-doped optical fiber 2, stimulated emission occurs and optical amplification of 1.55 μm light is performed. The 1.55 μm optically amplified light passes through the optical multiplexer / demultiplexer 3 and is input to the optical isolator 7. The optical isolator 7 is provided to prevent reflected return light from the optical component connected to the output side thereof. The optical multiplexer / demultiplexer 3 and the optical isolator 7 are connected by fusing the output fiber 17 of the optical multiplexer / demultiplexer 3 and the input optical fiber 23 of the optical isolator 7. Reference numeral 8 denotes an optical branching / coupling device, which converts the light input from the optical fiber 25 into the optical fiber 26.
And 27, and the light input from the optical fiber 26 is branched and output to the optical fibers 25 and 28. The optically amplified light that has passed through the optical isolator 7 is output from the optical fiber 24. The optical fibers 24 and 25 are fused, and one of the amplified light is output from the optical fiber 26 as the output of the optical fiber amplifier, and the other is output from the optical fiber 27 for controlling the output of the pumping light source. Reference numeral 29 is an output optical connector of the optical amplifier. The optical fiber 28 is for monitoring the return light from the connector end surface of the output optical connector 29. The light output from the optical fiber 27 is connected to the input optical fiber 30 of the second optical branching / coupling device 9 by fusion. The optical branching / coupling device 9 splits the input light, one of which is output from the optical fiber 31 as a monitor output of the optical amplifier, and the other of which is output from the optical fiber 32.
The optical fiber 32 is fused with the input optical fiber of the light receiving element 10, and the output light of the optical fiber 32 is converted into a current 34 by the light receiving element 10. The converted current 34 is input to the automatic light output control circuit 11. The automatic light output control circuit 11 controls the bias currents 35 and 36 of the pumping light sources 5 and 6 so that the current 34 becomes constant.

The optical system inside the optical isolators 1 and 7, the optical multiplexer / demultiplexer 3, the polarization beam coupler 4, and the optical branching / coupling devices 8 and 9 will be described with reference to FIG. 3 by taking the optical multiplexer / demultiplexer 3 as an example. To do. FIG. 3 is a plan view showing the outline of the structure of the optical multiplexer / demultiplexer. 41 reflects light of 1.48 μm, and 1.5
It is a dielectric filter that transmits light of 5 μm, and is vapor-deposited on one surface of the optical glass 42. The 1.48 μm light emitted from the optical fiber 16 is converted into parallel light by the lens 43 and reflected by the dielectric filter 41. The reflected light is condensed on the optical fiber 15 by the lens 44 and input. On the other hand, the 1.55 μm light emitted from the optical fiber 15 is converted into parallel light by the lens 44, and the dielectric filter 41
Through the lens 45, is focused on the optical fiber 17 by the lens 45, and is input. The light is multiplexed and demultiplexed as described above. Further, the component shown by one block as described above also has the same number of lenses as the optical fibers inside.

As described above, the conventional optical fiber amplifier can optically amplify the input light to obtain a constant output light.

[0005]

However, the above-mentioned conventional optical fiber amplifier uses many optical components such as an optical multiplexer / demultiplexer having an optical fiber for input and output, a polarization beam coupler, an optical isolator, and an optical branching / coupling device. Therefore, since there are a large number of fused portions for joining the optical fibers, there is a problem in that the loss due to the fused portions is large and the assembly takes a long time.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide an optical fiber amplifier in which the number of fused portions between optical fibers and the number of lenses are reduced.

[0007]

In order to achieve the above object, the optical fiber amplifier of the present invention uses a lens and optical glass which are used in a plurality of optical components in common and parallelizes the coupling of light between the optical components. The light is coupled as it is.

[0008]

With this structure, since the optical components are not coupled to each other through the optical fiber, the number of fused portions can be reduced and the assembling time can be shortened.

[0009]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention. In FIG. 1, a portion surrounded by a dotted line is a conventional example shown in FIG.
It corresponds to the dotted line part of. In FIG. 1, 1 is an optical isolator, 2 is an erbium-doped optical fiber, 5 and 6 are excitation light sources, 10 is a light receiving element, 11 is an automatic optical output control circuit, 1
Reference numeral 2 denotes a fusion splicing part in which optical fibers are joined together, 1
3, 14, 15 are optical fibers, 19, 20, 21, 22
Is a polarization maintaining optical fiber, 26 and 28 are optical fibers, 29
Is an optical connector, 31 is an optical fiber, 34 is an electric current, 35,
36 is a bias current, 51, 52, 53, 54, 55,
56 and 57 are lenses, 61, 62, 63, 64, 65,
66, 67, 68 are optical glass, 69 is a polarizing filter,
70 is a dielectric filter, 71 is an optical isolator, 72,
73 is a dielectric filter.

The operation of the optical fiber amplifier configured as described above will be described with reference to FIG. First, the optical fiber 13 is the entrance of the signal input, and the optical isolator 1
It is connected to the. The optical isolator 1 is provided for blocking the reflected return light to the input side. The erbium-doped optical fiber 2 is an optical fiber doped with erbium, and its input side is fused with the output optical fiber 14 of the optical isolator 1. Reference numeral 12 denotes a fusion-bonded portion, and the same applies to all four locations hereinafter. The pumping light sources 5 and 6 having a wavelength of 1.48 μm are polarization maintaining optical fibers 21 and 2, respectively.
It is output from 2. Polarization maintaining optical fibers 19 and 20
Are fused with the polarization maintaining optical fibers 21 and 22. The light emitted from the polarization-maintaining optical fiber 19 has its plane of polarization parallel to the plane of the paper and is converted into parallel light by the lens 51. The light emitted from the polarization-maintaining optical fiber 20 has its plane of polarization perpendicular to the plane of the paper and is converted into parallel light by the lens 52. The polarization filter 69 is the optical glass 61 and 6
Between the two, it is adhered to both optical glasses. The polarization filter 69 transmits light whose polarization plane is parallel to the paper surface and reflects light whose polarization plane is perpendicular to the paper surface. Therefore, the 1.48 μm wavelength light of the excitation light source 5 emitted from the polarization maintaining optical fiber 19 is transmitted, and the 1.48 μm wavelength light of the excitation light source 6 emitted from the polarization maintaining optical fiber 20 is reflected. The dielectric filter 70 reflects light of 1.48 μm,
Optical glass 63 or 6 that transmits 1.55 μm light
4 is vapor-deposited on one side. The 1.48 μm light of the excitation light sources 5 and 6 transmitted and reflected by the polarization filter 69 is reflected by the dielectric filter 70, is condensed by the lens 53 to the optical fiber 15, and excites the erbium atom in the erbium-doped optical fiber 2. To do. At this time, when 1.55 μm light is input to the erbium-doped optical fiber 2, stimulated emission occurs and optical amplification of 1.55 μm light is performed. 1.
The 55 μm optically amplified light passes through the dielectric filter 70 and is input to the optical isolator 71. The optical isolator 71 is provided to block reflected return light from the optical component connected to the output side thereof. Dielectric filters 72, 73
Transmits a part of light and reflects a part of the light, and is provided between the optical glasses 65 and 66 and the optical glasses 67 and 68 by vapor deposition. A part of the amplified light that has passed through the optical isolator 71 passes through the dielectric filter 72 and is condensed by the lens 55 onto the optical fiber 26.
It is output as the output of the optical fiber amplifier. The light reflected by the end face of the optical connector 29 is reflected by the dielectric filter 72, is focused on the optical fiber 28 by the lens 54, and can be monitored by the optical fiber 28. The light passing through the optical isolator is partially reflected by the dielectric filter 72,
Further, a part of the light is reflected by the dielectric filter 73, and the light reflected by the dielectric filter 73 is condensed on the optical fiber 31 by the lens 56 and output as monitor light. The light transmitted through the dielectric filter 73 is condensed on the light receiving element 10 by the lens 57. The light receiving element 10 converts the input light into a current 34. The converted current 34 is the automatic light output control circuit 1
Input to 1. The automatic light output control circuit 11 uses this current 3
The bias currents 35 and 36 of the pump light sources 5 and 6 are controlled so that 4 becomes constant.

As described above, according to the above-described embodiment, the portion corresponding to the function of the conventional polarization beam coupler, the portion corresponding to the function of the optical multiplexer / demultiplexer, the portion corresponding to the function of the optical isolator, and the portion corresponding to the optical branching coupler 2 are used. By combining and integrating the points, an optical fiber amplifier can be realized with a configuration in which the number of input / output optical fibers in each optical component is reduced.

[0012]

As is apparent from the above-described embodiment, the present invention reduces the number of optical fibers between a plurality of optical components, and can reduce the number of fused portions between the optical fibers. The assembly time of the optical fiber amplifier can be shortened. Further, according to the present invention, since the number of input / output optical fibers to / from each optical component is reduced, the number of optical components such as lenses can be reduced, and the material and assembling time of the optical fiber amplifier can be reduced. Furthermore, since the fusion and the number of optical components are reduced, a low loss optical fiber amplifier can be realized.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a schematic configuration of a conventional optical fiber amplifier.

FIG. 3 is a diagram showing an optical system of a main part of the optical fiber amplifier.

[Explanation of symbols]

 1 Optical Isolator (First Optical Isolator) 2 Erbium Doped Optical Fiber 5 Excitation Light Source (First Excitation Light Source) 6 Excitation Light Source (Second Excitation Light Source) 10 Photodetector 21, 22 Polarization-Maintaining Optical Fiber 26 Optical Fiber ( First optical fiber 28 Optical fiber (second optical fiber) 29 Optical connector 31 Optical fiber (third optical fiber) 34 Current 35, 36 Bias current 53, 54, 55, 56, 57 Lens 69 Polarizing filter 70 Dielectric Filter (First Dielectric Filter) 71 Optical Isolator (Second Optical Isolator) 72 Dielectric Filter (Second Dielectric Filter) 73 Dielectric Filter (Third Dielectric Filter)

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Claims (1)

[Claims] 1. A polarization maintaining optical fiber output of a first pumping light source, wherein a first optical isolator is connected to an input side of an erbium-doped optical fiber, signal light is input from an input side of the first optical isolator. After converting the light and the polarization-maintaining optical fiber output light of the second pumping light source into parallel light, they are combined by a polarization filter, and the combined light is reflected by the first dielectric filter as parallel light and reflected light Is input to the erbium-doped optical fiber by a lens, the signal light is optically amplified in the erbium-doped optical fiber, and the optical amplified light output from the erbium-doped optical fiber is converted into parallel light by a lens, and parallel light is emitted. As it is, the first dielectric filter, the second optical isolator, and the second dielectric filter are transmitted, and the lens is used as the output of the optical fiber amplifier by the first optical fiber. Output from the optical connector provided in the first optical fiber, reflected by the second dielectric filter and output from the second optical fiber by a lens, the second optical isolator The light transmitted through the second dielectric filter is reflected by the third dielectric filter and is output from the third optical fiber by the lens as the monitor light of the optical fiber amplifier, and the third dielectric filter is The transmitted light is focused on a light receiving element by a lens, converted into a current, the bias current of the pumping light source is controlled so that the current is constant, and the polarization-maintaining optical fiber output light of the pumping light source is controlled. An optical fiber amplifier that keeps the output of the optical fiber amplifier constant.