JPH07114300B2 - Optical fiber 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 direct amplifier for effectively improving the receiving sensitivity in optical fiber communication and optical measurement, and to an optical amplifier capable of obtaining a stable signal light gain.

[0002]

2. Description of the Related Art An optical fiber doped with a rare earth element (hereinafter referred to as a rare earth optical fiber) has characteristics as a laser active medium, and an optical fiber amplifier using this is realized. For example, 1 microwatt (μW)
Signal light and 100 mWatt (mW) pump light are incident on the same rare earth optical fiber and propagated for about 10 m (m), the signal light is easily amplified to about 1 mW.

FIG. 3 shows the basic configuration of a known optical fiber amplifier. Reference numeral 301 is an optical connector which is an incident end of signal light, 302 is an optical code, and 303 is for multiplexing signal light and pumping light. , An optical coupler 304, a rare earth optical fiber, an optical filter 305 for removing noise, an optical connector 306 for outputting a signal light, optical cords 307 and 308, an optical isolator 309 for blocking return light,
310 is an optical code, 311 is a pumping semiconductor laser, 31
Reference numeral 2 is an optical code for monitoring the light intensity of the pumping semiconductor laser 311. Reference numeral 313 is a power supply line for supplying a current to the pumping semiconductor laser 311. Reference numeral 314 is for controlling the current of the pumping light source according to the light intensity monitor. It is a control current supply device.

The rare earth optical fiber 304 is generally an erbium optical fiber doped with erbium as a rare earth element. In this case, the pumping semiconductor laser 3 is used.
A semiconductor laser having an emission wavelength of 1.48 μm (μm) is used for 11. The wavelength of the signal light is 1.55μ
m is suitable. Optical coupler 303 is 1.48μm and 1.55
A μm multiplexer is used, and the center wavelength of the optical filter 305 is 1.55 μm.

In the example of FIG. 3, when the pumping semiconductor laser 311 is deteriorated or damaged and its optical output is reduced, the amplification gain of the signal light is reduced, which causes a serious obstacle to optical communication and optical measurement.

Conventionally, in an optical communication system such as a submarine optical repeater which requires high reliability, one spare semiconductor laser is incorporated in advance, and when the main semiconductor laser is deteriorated, it is spared. The method of switching has been put to practical use. However, this method relates to the signal light source, and is merely a switching method, not a method in which the main and standby semiconductor lasers of two systems operate simultaneously.

In an optical fiber amplifier, two pump light sources are used.
Although a method of systematic use has been proposed so far, a method or apparatus for use as a dual light source for improving reliability has not been proposed for the purpose of additively increasing pump light intensity.

[0008]

SUMMARY OF THE INVENTION Therefore, the present invention uses two systems of pumping light sources, and by controlling the optical outputs of these systems in cooperation with each other, it is possible to obtain a stable signal light gain against deterioration or damage of the pumping light source. The challenge is to provide an amplifier.

[0009]

In order to achieve the above object, the present invention provides an optical fiber doped with a rare earth element,
Two systems of pumping semiconductor laser light sources for optically pumping the optical fiber, an optical coupler for making output light and signal light of the pumping semiconductor laser light source enter the optical fiber, and the pumping In an optical fiber amplifier comprising a control current supply device for supplying a current to a semiconductor laser light source, the control current supply device inputs the output light intensity of each of the two pump semiconductor laser light sources and inputs each of the two semiconductor laser pumps. The supply current to the light source is used as the output, and the relationship between the input and the output is that the output of one system decreases but the output of the other system increases.
By supplementing with one in which signal light gain is configured to operate according to a program which is a predetermined constant value.

[0010]

1 is a schematic diagram of the configuration of a first embodiment of the present invention. Reference numeral 101 denotes an optical connector serving as an incident end of signal light, 10
2 is an optical code, 103 is an optical coupler that combines signal light and pumping light, 104 is a rare earth optical fiber, 105 is an optical filter, 106 is an optical connector that outputs signal light, 107, 1
08 109 is an optical code, 110 is an optical isolator for blocking return light, 111 is an optical code, 11
2 is a pumping semiconductor laser with a center wavelength of 1.48 μm, 113
Is an optical code for monitoring the optical output of the pumping semiconductor laser 112, 114 is a power supply line to the pumping semiconductor laser 112, 1
Reference numeral 15 is an optical code, 116 is an optical isolator, 117 is an excitation semiconductor laser having a center wavelength of 1.48 μm, 118 is an optical output monitor optical code of the excitation semiconductor laser 117, 11
Reference numeral 9 is a power supply line to the pumping semiconductor laser 117, 120 is a control current supply device, 121 is an optical code, and 122 is an optical coupler for multiplexing pumping lights of two systems.

Since the central wavelengths of the pumping semiconductor lasers 112 and 117 are the same, two pumping semiconductor lasers 1 are provided.
The optical couplers 1 and 2 are configured by making the polarization planes of the optical outputs 12 and 117 orthogonal to each other.
Combine at 22. Since the signal light and the pump light have different wavelengths,
As the optical coupler 103, a wavelength multiplex wave device having no polarization dependence is used.

Since the semiconductor laser normally outputs light in both the front and back directions, the output light behind the pumping semiconductor lasers 112 and 117 may be propagated to the optical codes 113 and 118, respectively. In a semiconductor laser that emits light only in one direction,
The output in the forward direction can be branched into monitor light. Since the signal light gain of the rare earth optical fiber 104 does not depend on the polarization state of the pump light, if the output sum of the two pump light sources is constant, the signal light gain does not depend on the individual pump light intensity.
Therefore, the current control program of the control current supply device 120 may be set so that the sum of the pump light source monitor light outputs of the two systems becomes constant.

[0013]

In the embodiment of FIG. 1, it is also possible to adopt a configuration in which the central wavelengths of the two systems of pumping semiconductor lasers are different. That is, the wavelength of the excitation light source is 1.48 μm
In addition, 0.98 μm or 0.82 μm is known to be suitable. As an example, a semiconductor laser for excitation 1
12 has a center wavelength of 0.98 μm and 117 has a center wavelength of 1.4
A configuration of 8 μm is conceivable. In this case, the optical coupler 122 may be a wavelength division multiplexer. When the wavelength of the pumping light is different, the relationship between the pumping light intensity and the signal light gain is different, so the program is not such that the simple addition of the monitor light intensity is constant as in the previous example.

However, from the viewpoint of obtaining the same amplification gain, 0.9
It is possible to measure in advance how many times the light intensity of 8 μm corresponds to the light intensity of 1.48 μm. By storing the relationship in the control current supply device, the current supplied to each semiconductor laser can be easily adjusted. Will be able to control.

FIG. 2 shows the configuration of an optical fiber amplifier according to another embodiment of the present invention, in which one of the pumping light sources propagates in the opposite direction to the signal light. Reference numeral 201 is an optical connector that is an incident end of signal light, 202 is an optical code, 203 is an optical coupler that multiplexes signal light and excitation light, 204 is a rare earth optical fiber, 20
5 is an optical filter, 206 is an optical connector for outputting signal light, 207 is an optical coupler for making excitation light incident on the erbium optical fiber, 208 and 209 are optical codes, 210 is an optical isolator, 211 is an optical code, 21
2 is a semiconductor laser for excitation with a central wavelength of 1.48 μm, 213
Is an optical code for monitoring the optical output of the pumping semiconductor laser 212, 214 is a power supply line to the pumping semiconductor laser 212, 2
Reference numeral 15 is an optical code, 216 is an optical isolator, 217 is an excitation semiconductor laser having a center wavelength of 1.48 μm, 218 is an optical output monitor optical code of the excitation semiconductor laser 217, 21
Reference numeral 9 is a power supply line to the pumping semiconductor laser 217, 220 is a control current supply device, and 221 and 222 are optical cords. Wavelength multiplexing multiplexers having no polarization dependence are used as the optical couplers 203 and 207.

When the embodiment of FIG. 2 is compared with the embodiment of FIG. 1, one system of pump light propagates in the opposite direction to the signal light,
That is, it is reverse pumping, and the optical coupler is different accordingly.

However, since it is well known that there is almost no difference in the relationship between the pumping light intensity and the signal light gain between the same-direction pumping and the reverse-direction pumping, the same current control as in the embodiment shown in FIG. 1 is performed. The program of can be applied.

An optical fiber amplifier combining the embodiments of FIGS. 1 and 2 or an optical fiber amplifier combining pumping light sources of different wavelengths can be considered. In these cases as well, an optical fiber amplifier having a constant signal light gain can be configured by the control current supply device based on the current control method described above.

Although the embodiments of FIGS. 1 and 2 are intended to amplify weak signal light, the present invention is also effective when optical power amplification is performed by optical fiber amplification.

[0021]

As described above, according to the present invention, in the optical fiber amplifier, the supply currents to the two pumping light sources are controlled in cooperation with each other, so that one of the pumping light sources deteriorates and the optical output decreases. However, the signal light gain as a whole is constant, and it is useful for an optical communication system that requires high reliability.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of another embodiment of the present invention.

FIG. 3 is a basic configuration diagram of a conventional optical fiber amplifier.

[Explanation of symbols]

 101 Optical Connector 102 Optical Code 103 Optical Coupler 104 Rare Earth Optical Fiber 105 Optical Filter 106 Optical Connector 107 Optical Code 108 Optical Code 109 Optical Code 110 Optical Isolator 111 Optical Code 112 Excitation Semiconductor Laser 113 Optical Code 114 Feed Line 115 Optical Code 116 Optical isolator 117 Excitation semiconductor laser 118 Optical code 119 Feed line 120 Control current supply device 121 Optical code 122 Optical coupler 201 Optical connector 202 Optical code 203 Optical coupler 204 Rare earth optical fiber 205 Optical filter 206 Optical connector 207 Optical coupler 208 Optical code 209 Optical code 210 Optical isolator 211 Optical code 212 Excitation semiconductor laser 213 Optical code 214 Feed line 215 Optical code 216 Optical isolator 217 Excitation Semiconductor Laser 218 Optical Code 219 Feed Line 220 Control Current Supply Device 221 Optical Code 222 Optical Code 301 Optical Connector 302 Optical Code 303 Optical Coupler 304 Rare Earth Optical Fiber 305 Optical Filter 306 Optical Connector 307 Optical Code 308 Optical Code 309 Optical Isolator 310 Optical code 311 Excitation semiconductor laser 312 Optical code 313 Feed line 314 Control current supply device

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Claims (1)

[Claims] 1. An optical fiber doped with a rare earth element,
Two systems of pumping semiconductor laser light sources for optically pumping the optical fiber, an optical coupler for making output light and signal light of the pumping semiconductor laser light source enter the optical fiber, and the pumping In an optical fiber amplifier comprising a control current supply device for supplying a current to a semiconductor laser light source, the control current supply device inputs the output light intensity of each of the two pump semiconductor laser light sources and inputs each of the two semiconductor laser pumps. The supply current to the light source is used as the output, and the relationship between the input and the output is that the decrease in the output light intensity of one system is the output of the other system.
By supplementing with increase in light intensity, an optical fiber amplifier signal Mitsutoshi obtained is characterized by that operates according to a program which is a predetermined constant value.