JP2004064031A - Optical amplifier and light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical amplifier and a light source device in which the pumping efficiency of a rare-earth-doped optical fiber is enhanced. <P>SOLUTION: The ASE light source device comprises a pumping source 2 composed of a 0.98 μm laser diode (LD), an optical multiplexer 3, an Yb-doped optical fiber 4 which is pumped by the pumping light introduced via the optical multiplexer 3, a reflecting mirror 5 that reflects the ASE from the Yb-doped optical fiber 4 or the pumping light, an optical isolator 6, and a temperature controlling means 7 that controls the temperature of the pumping source 2 to shift the oscillation wavelength band to a short wavelength side. A higher output power level of the ASE light source than those of conventional ones is obtained by reducing the pumping light component that is not absorbed in a longer wavelength side than 980 nm where the absorption quantity of the Yb-doped optical fiber 4 abruptly decreases while increasing the absorption efficiency of the pumping light in a shorter wavelength side than 980 nm. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical amplification device including an optical fiber doped with a rare earth element and a light source device.
[0002]
[Prior art]
Conventionally, a Yb-doped optical fiber doped with a rare earth element, for example, Yb (ytterbium) having an emission band in the 1 μm band, outputs a 1 μm band optical amplifier or an 1 μm band ASE (spontaneous emission light). Used in light source devices.
[0003]
Since such a Yb-doped optical fiber has a narrow absorption wavelength band at 980 nm as shown by the solid line in FIG. 9, the excitation light source is an Erbium-doped optical fiber (EDF). The laser diode (LD) of 0.98 μm (980 nm), which is widely used for exciting the laser, is used. In FIG. 9, the imaginary line is an example of the spectrum of the laser diode of 0.98 μm, but since it overlaps the absorption wavelength band of Yb of 980 nm, the output of the laser diode of 0.98 μm is directly used as the excitation light of Yb. We are using.
[0004]
[Problems to be solved by the invention]
The absorption wavelength band around 980 nm of the Yb-doped optical fiber has a narrow full width at half maximum of about 1 nm, whereas the full width at half maximum in the oscillation wavelength band of a general 0.98 μm laser diode is 5 nm to 5 nm. It is about 10 nm, which is wider than the absorption wavelength band of the Yb-doped optical fiber as shown by the imaginary line in FIG. 9, so that it is not possible to absorb the pump light having a wide oscillation wavelength band, and the pump efficiency is poor. Was something. ,
As shown in FIG. 9, the absorption amount of the Yb-doped optical fiber sharply decreases on the longer wavelength side than 980 nm. Therefore, in a conventional example using a 0.98 μm laser diode as an excitation light source, excitation light having a wavelength longer than 980 nm is emitted without being absorbed by Yb, and there is a problem that the excitation efficiency is poor.
[0005]
The present invention has been made in view of such circumstances, and has as its main object to provide an optical amplifying device and a light source device in which the excitation efficiency of a rare-earth-doped optical fiber is increased.
[0006]
[Means for Solving the Problems]
The present invention is configured as follows to achieve the above object.
[0007]
That is, an optical amplification device or a light source device according to the present invention is an optical amplification device including a rare earth-doped optical fiber doped with a rare earth element and an excitation light source, and an oscillation wavelength band for controlling an oscillation wavelength band of the excitation light source. It has control means.
[0008]
According to the present invention, since the oscillation wavelength band control means for controlling the oscillation wavelength band of the excitation light source is provided, it is possible to control the oscillation wavelength band to a wavelength at which the excitation light absorption efficiency of the rare-earth-doped optical fiber is high. In addition, the gain of the optical amplifier or the output of the light source device can be increased.
[0009]
In addition, since the oscillation wavelength band of the pump light source can be controlled, the pump wavelength can be varied according to the application, thereby expanding the amplification band as an optical amplifier or the high output band as a light source. can do.
[0010]
In one embodiment of the present invention, the oscillation wavelength band control means controls an oscillation wavelength band by controlling a temperature of the pump light source.
[0011]
According to the present invention, since the oscillation wavelength band is controlled by controlling the temperature of the excitation light source, the oscillation wavelength band of the excitation light source can be controlled with a relatively simple configuration.
[0012]
In another embodiment of the present invention, the oscillation wavelength band control means is a fiber Bragg grating.
[0013]
According to the present invention, the oscillation spectrum in which the oscillation wavelength band is controlled by the fiber Bragg grating has a full width at half maximum narrowed to about 1 nm or less, so that, for example, the excitation light not absorbed in the narrow absorption wavelength band of 980 nm of Yb. The component can be greatly reduced to increase the absorption efficiency of the pump light, thereby increasing the gain as an optical amplifier or increasing the output as a light source device.
[0014]
In a preferred embodiment of the present invention, the fiber Bragg grating is made by irradiation on a coating.
[0015]
According to the present invention, by controlling the reflection wavelength by applying tension to the fiber Bragg grating, the oscillation wavelength band of the excitation light source can be controlled, so that the excitation wavelength can be varied depending on the application, for example, By controlling the oscillation wavelength to the excitation wavelength having the highest gain in the amplification band, the gain of the optical amplifier can be increased, or the peak wavelength of the light source device can be controlled.
[0016]
In another embodiment of the present invention, the rare earth element is Yb, and according to the present invention, in the narrow absorption wavelength band of 980 nm of Yb, the unabsorbed excitation light component is significantly reduced to reduce the excitation light component. The absorption efficiency can be increased, thereby increasing the gain as an optical amplifying device or increasing the output as a light source device.
[0017]
In another embodiment of the present invention, the oscillation wavelength band control means shifts the oscillation wavelength band to a shorter wavelength side than the absorption wavelength band of the rare earth-doped optical fiber.
[0018]
According to the present invention, the oscillation wavelength band of the pumping light source is shifted to a shorter wavelength side than the rare-earth-doped optical fiber, for example, the absorption wavelength band of Yb, so that the wavelength is shorter than the absorption peak wavelength of Yb. The pumping light absorption efficiency on the wavelength side can be increased, thereby increasing the gain as an optical amplifying device or the output as a light source device.
[0019]
In still another embodiment of the present invention, the rare earth element is Yb, and the oscillation wavelength band control means shifts the oscillation wavelength band to a shorter wavelength side than the absorption wavelength band of 980 nm. Things.
[0020]
Here, the oscillation wavelength band is, for example, 974 to 984 nm.
[0021]
According to the present invention, when exciting Yb, which has a narrow absorption wavelength band in the 980 nm band and the absorption amount sharply decreases on the longer wavelength side than the absorption peak wavelength, the oscillation wavelength band of the excitation light source is shifted to the shorter wavelength side. By shifting, the excitation light absorption efficiency of Yb can be increased, thereby increasing the gain as an optical amplifying device or the output as a light source device.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0023]
(Embodiment 1)
FIG. 1 is a diagram showing an overall configuration of an ASE light source device according to one embodiment of the present invention.
[0024]
The ASE light source device 1 of this embodiment is of a backward pumping type in which pumping light is incident from a direction opposite to the output of the ASE, and includes a pumping light source 2 composed of a 0.98 μm laser diode (LD) and an optical multiplexer. 3, an Yb-doped optical fiber 4 as a rare earth-doped optical fiber excited by the pump light introduced through the optical multiplexer 3, and an ASE or pump light from the Yb-doped optical fiber 4 is indicated by an arrow A. And a 1 μm band optical isolator 6 provided on the output side of the ASE.
[0025]
In the ASE light source device 1, when the excitation light from the excitation light source 2 enters the Yb-doped optical fiber 4, the ASE is emitted, and the ASE propagated to the optical isolator 6 is output or propagated to the reflection mirror 5. The ASE is returned to the Yb-doped optical fiber 4 and output via the optical isolator 6.
[0026]
The ASE light source device 1 is used, for example, when measuring a loss wavelength characteristic of an optical component in combination with a measuring instrument such as an optical spectrum analyzer.
[0027]
Conventionally, the center wavelength of the oscillation wavelength band of the pumping light source 2 composed of a 0.98 μm laser diode (LD) is substantially equal to the absorption peak wavelength of the Yb-doped optical fiber 4. Since the absorption amount of the Yb-doped optical fiber 4 is sharply reduced, the excitation light on the longer wavelength side than 980 nm is not sufficiently absorbed and is emitted as it is, resulting in poor excitation efficiency.
[0028]
Therefore, in the ASE light source device 1 of this embodiment, a temperature control means 7 for controlling the temperature of the excitation light source 2 is provided as an oscillation wavelength band control means for controlling the oscillation wavelength band of the excitation light source 2. The control means 7 controls the temperature of the pump light source 2 to shift the oscillation wavelength band to a shorter wavelength side than the conventional output wavelength.
[0029]
The excitation light source 2 has a laser and a resonator section fixed on a temperature control element such as a Peltier element (not shown) via a metal block having good thermal conductivity, and a temperature control means 7 is not shown. The excitation light source 2 is controlled to a desired temperature by controlling a Peltier element or the like based on the output of the temperature sensor.
[0030]
In this embodiment, the temperature of the excitation light source 2 is controlled to, for example, 0 ° C. in order to shift the oscillation wavelength band of the 0.98 μm laser diode, which is the excitation light source, to the shorter wavelength side.
[0031]
FIG. 2 is a spectrum for explaining the shift of the oscillation wavelength band of the pump light source 2 due to the temperature control. A broken line is a spectrum at a normal temperature, for example, 30 ° C. which is a conventional example. 5 is a spectrum at 0 ° C. according to the embodiment.
[0032]
In the conventional example, the center wavelength of the oscillation wavelength band of the pumping light source 2 (for example, the center wavelength of two wavelengths that is 3 dB lower (half value) from the output peak) is near 981 nm as shown by the phantom line in FIG. On the other hand, in the embodiment in which the temperature of the excitation light source 2 is controlled to 0 ° C., the center wavelength of the oscillation wavelength band of the excitation light source 2 is near 974 nm, and is shifted to the shorter wavelength side by about 7 nm.
[0033]
FIG. 3 is a diagram showing the spectrum C and the absorption loss D of the Yb-doped optical fiber when the temperature of the pumping light source 2 is controlled to 0 ° C., and shows the center of the oscillation wavelength band of the pumping light source 2. By shifting the wavelength to a shorter wavelength side, for example, 974 nm, it is possible to reduce the amount of the excitation light component that is not absorbed on the longer wavelength side than 980 nm, where the absorption amount of the Yb-doped optical fiber sharply decreases, as compared with the related art. Excitation light absorption efficiency on the shorter wavelength side than 980 nm can be increased.
[0034]
As a result, in the ASE light source device 1, the excitation efficiency of Yb is improved and the output of the ASE is increased. (Comma) It was confirmed that the ASE output increased by about several dB.
[0035]
Although this embodiment is of a backward pumping type, it may be applied to a forward pumping type or a bidirectional pumping type.
[0036]
(Embodiment 2)
FIG. 4 is a diagram illustrating an overall configuration of an optical amplifying device according to one embodiment of the present invention.
[0037]
The optical amplifying device 8 of this embodiment is a backward pumping type in which pumping light is incident from the opposite direction to the signal light in the 1 μm band, and includes a pumping light source 9 composed of a 0.98 μm laser diode and a pumping light source 9. An optical multiplexer 10 for multiplexing the pump light and the signal light, a Yb-doped fiber 11 as a rare earth-doped fiber excited by the pump light, and a 1 μm band optical isolator 12 provided on the output side of the signal light. It has.
[0038]
In the optical amplifying device 8 of this embodiment, similarly to the ASE light source device 1 described above, a temperature control means 13 for controlling the temperature of the pump light source 9 to control the oscillation wavelength band is provided.
[0039]
The temperature control means 13 controls the temperature of the excitation light source 9 to, for example, 0 ° C. by controlling a Peltier element or the like based on the output of a temperature sensor (not shown), thereby controlling the oscillation wavelength band of the excitation light source 9. It is shifted to the short wavelength side.
[0040]
Therefore, according to the optical amplifying device 8 of this embodiment, as in the case of the ASE light source device 1 described above, the pump light that is not absorbed on the longer wavelength side than 980 nm where the absorption amount of the Yb-doped optical fiber rapidly decreases. While the component can be reduced, the absorption efficiency on the shorter wavelength side than 980 nm can be increased, whereby the pumping efficiency of Yb increases and the amplification gain of the signal light increases.
[0041]
Although this embodiment has been described with reference to the backward pumping type, it may be applied to the forward pumping type or the bidirectional pumping type.
[0042]
(Embodiment 3)
The present invention is not limited to the ASE light source device 1 of FIG. 1, but can also be applied as a light source device such as the fiber laser shown in FIG.
[0043]
That is, the fiber laser 14 includes a pumping light source 15 composed of a 0.98 μm laser diode, an optical multiplexer 16 that combines pumping light from the pumping light source 15 with ASE, and a rare-earth-doped pumping pumping light. A Yb-doped optical fiber 18 as an optical fiber, a 1 μm band optical isolator 20 for determining the direction of light circulation as indicated by an arrow B, a band pass filter 17 for transmitting 1 μm band excitation light, and a laser beam This is a ring-type forward-pumped fiber laser including a 1 μm-band coupler 19 that outputs light. Since the optical isolator 20 is disposed between the Yb-doped optical fiber 18 and the 1 μm-band coupler 19, the return light (reflected light) from the laser output end is incident on the Yb-doped optical fiber 18 in reverse. And the output of the laser can be stabilized.
[0044]
This fiber laser 14 also has a temperature control means 21 for controlling the temperature of the excitation light source 2 to control the oscillation wavelength band, similarly to the ASE light source device 1 described above. The band is shifted to the shorter wavelength side.
[0045]
That is, also in this embodiment, the oscillation wavelength band of the excitation light source 15 is shifted to the shorter wavelength side by controlling the temperature of the excitation light source 15 to, for example, 0 ° C.
[0046]
As a result, the excitation efficiency of Yb increases, and the laser output increases. In this embodiment, the noise figure is good because of forward excitation.
[0047]
As another embodiment of the present invention, the position of the optical multiplexer 16 is changed between the Yb-doped optical fiber 18 and the optical isolator 20, and the pump light is incident from behind the Yb-doped optical fiber 18 in a ring type. A backward-pumped fiber laser may be used, in which case the laser output is improved.
[0048]
In this embodiment, the present invention is applied to a fiber laser using a ring-type resonator, but as another embodiment of the present invention, it may be applied to a fiber laser using various reflecting mirrors.
[0049]
(Embodiment 4)
FIG. 6 is a diagram showing an overall configuration of an ASE light source device 1 'according to still another embodiment of the present invention. The same reference numerals are used for parts corresponding to the first embodiment shown in FIG. Add a sign.
[0050]
In the first embodiment, as the oscillation wavelength band control means for controlling the oscillation wavelength band of the excitation light source 2, a temperature control means 7 for controlling the temperature of the excitation light source 2 is provided. While the temperature is controlled to shift the oscillation wavelength band to the shorter wavelength side, in this embodiment, the oscillation wavelength band control means for controlling the oscillation wavelength band of the excitation light source 2 is manufactured by irradiating the coating. A fiber Bragg grating (FBG) 30 is provided.
[0051]
The fiber Bragg grating 30 is one in which the refractive index of the core portion of the fiber is periodically changed, and can reflect light of a specific wavelength (Bragg wavelength) arbitrarily. Thus, the oscillation wavelength band of the pump light source 2 is controlled.
[0052]
By applying tension to the fiber Bragg grating, the reflection wavelength can be shifted to, for example, a longer wavelength side by 10 nm or more as compared with a non-tension state.
[0053]
Normally, in order to obtain a high reflectance, the fiber Bragg grating is manufactured by directly irradiating the glass portion with ultraviolet rays in order to obtain a high reflectance. Even if the fiber is not damaged, and a relatively low reflectance of, for example, about 10% or less is sufficient, a fiber produced by irradiation on the coating is used.
[0054]
In this embodiment, the fiber Bragg grating 30 is stretched between a fixed drum 31 and a rotating drum 32, and the rotating drum 32 is rotationally driven by a driving means such as a stepping motor, and is further manually finely rotated. It is configured to be adjusted to adjust to a desired reflection wavelength.
[0055]
In the fiber Bragg grating 30, if the reflection wavelength at the time of manufacture is, for example, 965 nm, the reflection wavelength can be varied by about 965 to 995 nm. In this embodiment, the reflection wavelength is, for example, Yb absorption. The wavelength is adjusted to 977 nm, which is the peak wavelength, so that the oscillation wavelength of the excitation light source 2 obtained through the fiber Bragg grating 30 substantially matches the absorption peak wavelength of Yb.
[0056]
Other configurations are the same as those in the first embodiment.
[0057]
In the ASE light source device 1 ′ of this embodiment, since the oscillation wavelength band of the pump light source 2 is controlled using the fiber Bragg grating 30, the full width at half maximum of the output of the pump light source 2 obtained via the fiber Bragg grating 30 is: As compared with the conventional range of about 5 nm to 10 nm shown by the imaginary line in FIG. 9, the width is narrowed to about 1 nm or less, thereby significantly reducing the unabsorbed excitation light component in the narrow absorption wavelength band of Yb of 980 nm. As a result, the pump light absorption efficiency can be increased, and the ASE output can be increased.
[0058]
Although this embodiment is of a backward pumping type, it may be applied to a forward pumping type or a bidirectional pumping type.
[0059]
(Embodiment 5)
FIG. 7 is a diagram showing an overall configuration of an optical amplifying device 8 ′ according to still another embodiment of the present invention, and portions corresponding to the above-described second embodiment shown in FIG. Add a sign.
[0060]
In the second embodiment, as the oscillation wavelength band control means for controlling the oscillation wavelength band of the excitation light source 9, the temperature control means 13 for controlling the temperature of the excitation light source 9 is provided. While the wavelength band is shifted to the shorter wavelength side, in the present embodiment, a fiber Bragg grating (FBG) made by irradiating on the coating is used as an oscillation wavelength band control means for controlling the oscillation wavelength band of the pump light source 9. ) 30 is provided.
[0061]
The fiber Bragg grating 30 is stretched between the fixed drum 31 and the rotating drum 32 in the same manner as in the fourth embodiment, and the rotating drum 32 is rotationally driven by driving means such as a stepping motor. It is configured to finely adjust manually to adjust to a desired reflection wavelength.
[0062]
Other configurations are the same as those of the second embodiment.
[0063]
In the optical amplifying device 8 'of this embodiment, similarly to the ASE light source device 1' described above, the tension of the fiber Bragg grating 30 is adjusted to control the reflection wavelength, so that the oscillation wavelength of the pump light source 2 is adjusted to the absorption of Yb. The peak wavelength is adjusted to 977 nm.
[0064]
According to the optical amplifying device 8 'of this embodiment, since the oscillation wavelength band is controlled using the fiber Bragg grating 30, the full width at half maximum of the output of the pump light source 9 obtained via the fiber Bragg grating 30 is about 1 nm. In the narrow absorption wavelength band of Yb of 980 nm, the unabsorbed pump light component can be greatly reduced to increase the pump light absorption efficiency, thereby increasing the signal light amplification gain.
[0065]
Although this embodiment has been described with reference to the backward pumping type, it may be applied to the forward pumping type or the bidirectional pumping type.
[0066]
(Embodiment 6)
FIG. 8 is a diagram showing an overall configuration of a fiber laser 14 'according to still another embodiment of the present invention, and the same reference numerals are used for parts corresponding to the third embodiment shown in FIG. Is attached.
[0067]
In the above-described third embodiment, as the oscillation wavelength band control means for controlling the oscillation wavelength band of the excitation light source 15, the temperature control means 21 for controlling the temperature of the excitation light source 15 is provided. While the wavelength band is shifted to the shorter wavelength side, in this embodiment, a fiber Bragg grating (FBG) made by irradiating on the coating is used as an oscillation wavelength band control means for controlling the oscillation wavelength band of the pump light source 15. ) 30 is provided.
[0068]
The fiber Bragg grating 30 is stretched between the fixed drum 31 and the rotating drum 32 in the same manner as in the fourth embodiment, and the rotating drum 32 is rotationally driven by driving means such as a stepping motor. It is configured to finely adjust manually to adjust to a desired reflection wavelength.
[0069]
Other configurations are the same as those of the third embodiment.
[0070]
According to the fiber laser 14 'of this embodiment, since the oscillation wavelength band is controlled using the fiber Bragg grating 30, the full width at half maximum of the output of the pump light source 15 obtained via the fiber Bragg grating 30 is about 1 nm or less. In the narrow absorption wavelength band of Yb of 980 nm, the unabsorbed excitation light component can be greatly reduced to increase the excitation light absorption efficiency, and the laser output increases.
[0071]
As another embodiment of the present invention, the position of the optical multiplexer 16 is changed between the Yb-doped optical fiber 18 and the optical isolator 20, and the pump light is incident from behind the Yb-doped optical fiber 18 in a ring type. The present invention may be applied to a backward-pumped fiber laser, and is not limited to a fiber laser using a ring-type resonator, and may be applied to a fiber laser using various reflecting mirrors.
[0072]
(Other embodiments)
As another embodiment of the present invention, the amount of shift of the oscillation wavelength of the pump light source due to temperature control or tension adjustment is such that when the spectrum of the pump light source and the absorption loss of the Yb-doped optical fiber are overlapped, the overlapping area is the largest May be determined in advance.
[0073]
Although the above embodiment has been described with reference to the optical fiber doped with Yb, the present invention may be applied to an optical fiber doped with another rare earth element such as Er or Nd.
[0074]
In the above-described embodiment, the fiber Bragg grating manufactured by irradiation on the coating is used. However, the fiber Bragg grating may be manufactured by removing the coating material and directly irradiating ultraviolet laser light.
[0075]
【The invention's effect】
As described above, according to the present invention, since the oscillation wavelength band control means for controlling the oscillation wavelength band of the excitation light source is provided, it is possible to control the oscillation wavelength band to a wavelength where the excitation light absorption efficiency of the rare-earth-doped optical fiber is high. Alternatively, the full width at half maximum of the output of the pump light source can be narrowed, whereby the amplification gain of the optical amplifier or the output of the light source device can be increased.
[0076]
In addition, since the oscillation wavelength band of the pump light source can be controlled, the pump wavelength can be varied according to the application, thereby expanding the amplification band as an optical amplifier or the high output band as a light source device. Can be.
[0077]
Further, by controlling the temperature of the pump light source to control the oscillation wavelength band, the oscillation wavelength band of the pump light source can be controlled with a relatively simple configuration to increase the amplification gain or output.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an ASE light source device according to one embodiment of the present invention.
FIG. 2 is a spectrum showing a shift of an oscillation wavelength of an excitation light source due to temperature control.
FIG. 3 is a diagram showing the spectrum C and the absorption loss D of the Yb-doped optical fiber when the temperature of the excitation light source is controlled to 0 ° C.
FIG. 4 is a configuration diagram of an optical amplifying device according to one embodiment of the present invention.
FIG. 5 is a configuration diagram of a fiber laser according to one embodiment of the present invention.
FIG. 6 is a configuration diagram of an ASE light source device according to another embodiment of the present invention.
FIG. 7 is a configuration diagram of an optical amplifying device according to another embodiment of the present invention.
FIG. 8 is a configuration diagram of a fiber laser according to another embodiment of the present invention.
FIG. 9 is a diagram showing the absorption loss of a Yb-doped optical fiber.
[Explanation of symbols]
1,1 'ASE light source 2,9,15 Excitation light source 4,11,18 Yb-doped optical fiber 5 Reflection mirror 6,12,20 Optical isolator 7,13,21 Temperature control means 8,8' Optical amplifier 14,14 '' Fiber laser 30 Fiber Bragg grating 31 Fixed drum 32 Rotary drum

Claims (8)

An optical amplifier comprising a rare earth-doped optical fiber doped with a rare earth element and an excitation light source,
An optical amplifying device comprising: an oscillation wavelength band control unit that controls an oscillation wavelength band of the pump light source. 2. The optical amplifying device according to claim 1, wherein said oscillation wavelength band control means controls an oscillation wavelength band by controlling a temperature of said pump light source. 2. The optical amplifying device according to claim 1, wherein said oscillation wavelength band control means is a fiber Bragg grating. 4. The optical amplifying device according to claim 3, wherein the fiber Bragg grating is produced by irradiation on a coating. The optical amplifier according to claim 1, wherein the rare earth element is Yb. 3. The optical amplifying device according to claim 1, wherein the oscillation wavelength band control means shifts the oscillation wavelength band to a shorter wavelength side than an absorption wavelength band of the rare earth-doped optical fiber. 7. The optical amplifying device according to claim 6, wherein the rare-earth element is Yb, and the oscillation wavelength band control means shifts the oscillation wavelength band to a shorter wavelength side than the 980 nm band, which is the absorption wavelength band. A rare-earth-doped optical fiber doped with a rare-earth element, and a light source device including an excitation light source,
A light source device comprising: an oscillation wavelength band control unit that controls an oscillation wavelength band of the excitation light source.

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