JP2004087687A - High output ase light source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high output ASE light source that has a simple structure using a common stimulation light source in C band (1530-1560nm) and L band (1560-1600nm). <P>SOLUTION: A stimulation light source 6 and an output end 1 are connected with one end of an Erbium added fibre 4, one end of a reflection body 7 or an Erbium added fiber 8 is selectively connected with the other end thereof by means of an optical switch 5, and a reflection body 9 is connected with the other end of the Erbium added fiber 8. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a high-power ASE light source that generates spontaneous emission light (ASE light) generated from an amplification optical fiber to which a rare earth element such as erbium is added, and is suitable for use as a light source for optical measurement and the like. Things.
[0002]
[Prior art]
An erbium-doped optical fiber (hereinafter referred to as EDF) has a characteristic that a large gain can be obtained for a certain wavelength by injecting pumping light in a certain wavelength range. Therefore, by transmitting signal light in a wavelength band having a gain into the EDF, the light intensity of the signal light can be extremely increased, and is currently used as an optical amplifier in the field of optical communication.
[0003]
On the other hand, when the pumping light is incident on the EDF, the EDF generates the gain of the signal light and also generates the spontaneous emission light. The light output of the generated spontaneous emission light increases under the influence of the gain. The light generated in this manner is referred to as amplified spontaneous emission light (hereinafter, referred to as ASE light).
[0004]
The EDF can emit ASE light by its own large gain, and can be used as a high-output broadband light source. In recent years, with the expansion of communication capacity, wavelength division multiplexing optical communication systems for multiplexing and transmitting and receiving optical signals having different wavelengths using a wide wavelength band have been actively studied. A high-power broadband light source using ASE light is used as an incoherent WDM light source, and also as a sensing light source using an optical fiber as well as a test light source for an optical component for a WDM system.
[0005]
In optical fiber sensing, an FBG (fiber Bragg grating) and an ASE light source are combined and used for strain measurement of a structure. The FBG reflects specific light determined by the grating interval, but the stress is applied to the FBG and the FBG is contracted (the FBG is distorted), so that the reflection wavelength of the FBG changes. If this FBG is attached to a measurement point of a structure, ASE light is incident, and the reflection wavelength is measured with a wavelength meter or the like, the distortion of the FBG, that is, the distortion of the structure can be measured.
[0006]
In the above-described optical fiber sensing, an optical fiber is stretched around a distance of about 30 km, and the amount of distortion at that point can be measured. Since there is a transmission loss and an FBG loss of an optical fiber, an ASE light source having a high output and a wide band is required to extend the measurement distance and further increase the number of measurement points.
[0007]
FIG. 4 is a configuration diagram of a conventional broadband ASE light source disclosed in JP-A-2001-135880. It comprises an EDF 105 serving as an amplification optical fiber, an excitation light source 103 composed of a semiconductor laser in the 1480 nm band, a fiber fusion-stretched type multiplexer 104, a reflector 106, and an optical isolator 102 provided at an ASE output terminal 101. By appropriately selecting the length of the EDF 105 and the power of the pumping light source 103, ASE light including a band of 1530 to 1600 nm can be obtained.
[0008]
FIG. 5 shows the spectrum waveform of the ASE light thus obtained. The output near 1530 nm is low, and ASE light including the 1530 to 1600 nm band (C + L band) having a peak near 1560 nm is obtained.
[0009]
[Problems to be solved by the invention]
However, the output of the conventional ASE light source around 1530 nm to 1550 nm in the C band is low, and the output around 1560 nm to 1590 nm in the L band is large. Since the output of the C band is low as a light source for optical fiber sensing, it becomes a bottleneck in measurement. Therefore, there is a need for an ASE light source for optical fiber sensing in which the output in the C band and the L band is increased without increasing the pump power.
[0010]
If the outputs in the C to L band range are output collectively, the output (spectrum density) in the wavelength range is reduced. Instead, the output is concentrated in the C band or the L band to increase the output, and either one is further increased. Provide a high-output light source that can be selectively output.
[0011]
[Means for Solving the Problems]
The present invention has been made to solve these problems. In an ASE light source configured to input excitation light to a rare-earth-doped fiber and output ASE light from one end, a plurality of wavelength band ASE lights are selected. It has a means for outputting.
[0012]
In addition, the present invention connects a plurality of rare-earth-doped fibers via an optical switch, and switches the optical switch to change the substantial length of the rare-earth-doped fiber, thereby selecting ASE light of a plurality of wavelength bands. Output.
[0013]
Further, the present invention is characterized in that there is provided means for reflecting the ASE light output to the other end of the rare earth-doped fiber.
[0014]
Further, the present invention is characterized in that the plurality of wavelength bands include a first wavelength band having a wavelength of 1530 to 1560 nm and a second wavelength band having a wavelength of 1560 to 1600 nm.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a broadband ASE light source according to the present invention will be described.
[0016]
FIG. 1 is a configuration diagram showing an embodiment of the present invention.
[0017]
An output optical terminal 1 for ASE light, an optical isolator 2 for passing an optical signal in only one direction, a multiplexer 3 for multiplexing ASE light and pump light, and a first erbium-doped optical fiber as an amplification optical fiber ( An EDF) 4, a second erbium-doped optical fiber (EDF) 8, an optical switch 5, an excitation light source 6, a reflector 7, and a reflector 9.
[0018]
An optical switch 5 is connected to one end of the first EDF 4, a reflector 7 is connected to a first port of the optical switch 5, and one end of a second EDF 8 is optically connected to a second port of the optical switch 5. The reflector 9 is connected to the other end of the EDF 8. An excitation light source 6 is connected to the other end of the EDF 4 via an excitation port of the multiplexer 3, and an output terminal 1 is connected to a signal port of the multiplexer 3 via an optical isolator 2. The optical isolator 2 functions to pass an optical signal only in one direction, and uses a Faraday rotator in principle.
[0019]
EDF4 and EDF8 are silica-based optical fibers doped with erbium, which is a rare earth element, and have the function of amplifying signal light. ASE light in the 1530 to 1600 nm band is output from one end as described in the related art by appropriately selecting. In the present invention, the 1530 to 1560 nm band of the C band output here is referred to as a first wavelength band, and the 1560 to 1600 nm band of the L band is referred to as a second wavelength band.
[0020]
The multiplexer 3 is made by fusing and stretching an optical fiber. The excitation light source 6 excites erbium ions of the EDFs 4 and 8. The pump light output from the pump light source 6 has a wavelength of 1480 nm and is guided to the EDF 4 via the multiplexer 3. The reflectors 7 and 9 are formed by bonding and connecting a total reflection mirror composed of a dielectric multilayer film to an end face of an optical fiber so as to reflect an optical signal.
[0021]
First, a case in which ASE light of the first wavelength band is output using the ASE light source of the present invention will be described.
[0022]
When outputting the first wavelength band ASE light, the optical switch 5 is selected to the reflector 7 side, and the EDF 8 side is cut off. When the excitation light from the excitation light source 6 enters, the ASE light of the first wavelength band is emitted from the EDF 4 and propagates to both sides of the EDF 4. The ASE light propagated to the multiplexer 3 is output from the output terminal 1 via the isolator 2. Further, the ASE propagating to the reflector 7 side is reflected by the reflector 7 and returns to the EDF 4, where it is amplified in the EDF 4 and output from the output terminal 1, and the ASE light of the first wavelength band of the C band is output. Is done.
[0023]
Next, a case where ASE light of the second wavelength band is output will be described.
[0024]
When outputting the ASE light of the second wavelength band, the optical switch 5 is selected to the EDF 8 side, and the reflector 7 side is cut off. In this state, EDF4 and EDF8 behave together like one long EDF. That is, the wavelength band of the output light can be changed by changing the substantial length of the EDF.
[0025]
When the excitation light from the excitation light source 6 enters, the ASE light of the first wavelength band is first emitted from the EDF 4 and propagates to both sides of the EDF 4. The ASE light propagated to the multiplexer 3 is output from the output terminal 1 in the first wavelength band. Further, the ASE light of the first wavelength band, which propagates to the EDF 8 side, becomes ASE light of the second wavelength band by being absorbed by the EDF 8 part in the middle, and the ASE light of the second wavelength band is reflected by the reflector 9. After being returned, the signal is amplified in the EDF 8 and the EDF 4 and output from the output terminal 1. In this state, the ASE light of the first wavelength band and the ASE light of the second wavelength band are combined from the output terminal 1, but the output of the second wavelength band is larger than the output of the first wavelength band by the amount amplified. Therefore, ASE light of the second wavelength band is substantially output.
[0026]
By switching the optical switch 5 as described above, it is possible to selectively output high-output first wavelength band ASE light and second wavelength band ASE light.
[0027]
Here, the reflectors 7 and 9 are used to obtain high-output ASE light, but when these are not used, the output of the ASE light decreases.
[0028]
Next, a case where the ASE light source of the present invention is used as a sensing light source will be described with reference to FIG.
[0029]
It comprises a high output ASE light source 10, a wavelength meter 11, an optical circulator 12, an optical fiber 13, and FBGs 14 to 23 of the present invention. The ASE light output from the high-power ASE light source passes through the optical circulator 12 and the light of a specific wavelength is reflected from each of the FBGs 14 to 23 connected to the optical fiber 13. Here, the reflection wavelengths of the FBGs are designed to be different from each other. The reflected light is guided to the wavelength meter 11 via the optical circulator 12, the wavelength of which is measured, and converted into an FBG distortion amount by the measurement computer 24. For example, the length of the optical fiber 13 is 30 km, the number of FBGs is 10 (FBG14 to FBG23), the optical fiber transmission loss is 0.3 dB / km, and the FBG transmission loss is 0.3 dB / piece. When the FBGs are installed in series in the longitudinal direction of the optical fiber as shown in FIG. 3, the intensity of the ASE light reaching the FBG 23 installed far away decreases to 11.7 dB on the outward path and decreases 23.4 dB on the round trip. Higher output ASE light is required.
[0030]
Therefore, the ASE light of the first wavelength band is selected by the high-power ASE light source 10 of the present invention for the FBG located far away, and the ASE light of the second wavelength band is selected for the FBG located on the near side. Variation in the intensity of the reflected light from the FBGs 14 to 23 measured by the wavelength meter 11 can be suppressed.
[0031]
【Example】
As an example of the high output ASE light source of the present invention, a prototype of the ASE light source shown in FIG. 1 was manufactured. Each component and configuration will be described below.
[0032]
The excitation light source 6 has a wavelength of 1480 nm and an excitation output of 200 mW. EDF4 and EDF8 use commercially available silica-based erbium-doped optical fibers. %. The length of the EDF 4 is such that the ASE light in the 1530 to 1560 nm band is easily output, and the total length of the EDF 4 and the EDF 8 is such that the ASE light in the 1530 to 1600 nm band is output.
[0033]
FIG. 2 shows output characteristics of the ASE light source of the present embodiment.
[0034]
The ASE light in the first wavelength band is 0 dBm / nm or more at 1530 nm and about -10 dBm / nm in the case of the ASE light in the second wavelength band, and the ASE light in the first wavelength band is larger by about 10 dB. Up to 1560 nm, the output of the ASE light in the first wavelength band is larger than the output of the ASE light in the second wavelength band.
[0035]
As a result, by selectively outputting the ASE light of the first wavelength band and the ASE light of the second wavelength band, it is possible to provide a high-output ASE light source from the first wavelength band to the second wavelength band.
[0036]
【The invention's effect】
As described above, according to the present invention, in an ASE light source configured to input excitation light to a rare-earth-doped fiber and output ASE light from one end, a means for selecting and outputting ASE light in a plurality of wavelength bands. , High-output ASE light can be obtained in a wavelength range of 1530 to 1560 nm and a wavelength of 1560 to 1600 nm.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of a high output ASE light source according to the present invention.
FIG. 2 is a graph showing an ASE spectrum of the high-power ASE light source of the present invention.
FIG. 3 is a diagram showing an example in which the high-power ASE light source of the present invention is applied to sensing.
FIG. 4 is a diagram showing a conventional ASE light source.
FIG. 5 is a graph showing an ASE spectrum of a conventional ASE light source.
[Explanation of symbols]
1: output end 2: optical isolator 3: multiplexer 4: erbium-doped optical fiber (EDF)
5: Optical switch 6: Excitation light source 7: Reflector 8: Erbium-doped optical fiber (EDF)
9: reflector 10: high-power ASE light source 11: wavelength meter 12: optical circulator 13: optical fiber 14 to 23: FBG
24: Computer for measurement

Claims (4)

A high-power ASE light source, comprising: an ASE light source configured to input excitation light to a rare-earth-doped fiber and to output ASE light from one end, and to select and output ASE light in a plurality of wavelength bands. . A plurality of rare-earth-doped fibers are connected via an optical switch, and the optical switch is switched to change the substantial length of the rare-earth-doped fiber, thereby selecting and outputting ASE light in a plurality of wavelength bands. 2. The high-power ASE light source according to claim 1, wherein: 3. The high-output ASE light source according to claim 1, further comprising means for reflecting the ASE light output to the other end of the rare-earth-doped fiber. The high-power ASE light source according to any one of claims 1 to 3, wherein the plurality of wavelength bands include a first wavelength band having a wavelength of 1530 to 1560 nm and a second wavelength band having a wavelength of 1560 to 1600 nm. .

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