A high-power narrow-linewidth Raman fiber amplifier

Abstract

The present invention discloses a high-power narrow-linewidth Raman fiber amplifier, which uses a narrow-linewidth signal source to provide a low-power narrow-linewidth signal, and then uses a pump source to provide a high-power pump light, and then the low-power narrow-linewidth signal and the high-power pump light are coupled to a phosphorus-doped fiber through a fiber combiner, and finally a Raman gain peak with a frequency shift of about 40THz in the Raman gain spectrum of the phosphorus-doped fiber is used to provide a narrow-linewidth gain, and the pump light is converted into a narrow-linewidth signal for power amplification to achieve high-power narrow-linewidth Raman laser output. Compared with pure silica-based optical fiber, the amplifier provided by the present invention uses the Raman gain peak with a frequency shift of about 40THz in the phosphorus-doped fiber to provide gain to achieve narrow-linewidth Raman laser output.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber lasers, in particular to a high-power narrow-linewidth Raman optical fiber amplifier. Background Art

[0002] Fiber lasers are widely used in various fields such as optical communication, industrial processing, biomedicine, and sensor detection due to their simple structure, good beam quality, and high conversion efficiency. With the rapid development of the process level of optical fiber manufacturing and the high-brightness semiconductor laser diode pump source, the output power of fiber lasers has been rapidly improved. However, most conventional high-power fiber lasers are based on rare earth ion-doped optical fibers to provide gain. Limited by the energy level structure of rare earth ions, lasers can only work in a specific band, which is difficult to meet the application requirements of special wavelength lasers in fields such as sodium guide stars and atmospheric remote sensing. Raman fiber lasers based on stimulated Raman scattering have the advantages of gain spectrum width, cascade operation, and no need for phase matching. As long as there is a pump laser of suitable wavelength, laser output of any wavelength within the transparent range of the optical fiber can be generated. In addition, the line width of general high-power fiber lasers / amplifiers is usually from a few nanometers to tens of nanometers. In special application fields such as spectrum synthesis, lidar, and nonlinear frequency conversion, there are high requirements for the line width of the light source, and wide-spectrum fiber lasers are difficult to meet application requirements. Therefore, narrow linewidth fiber Raman fiber lasers have extremely high research value and application prospects. Most traditional Raman fiber amplifiers provide gain based on the Raman gain peak with a frequency shift of about 13.2THz in silicon-based optical fibers. The gain peak has a wide linewidth, with a 3dB linewidth of about 7.79THz, which is not conducive to achieving narrow linewidth Raman laser output. Summary of the invention

[0003] The present invention provides a high-power narrow-linewidth Raman optical fiber amplifier, which is used to overcome the defects of the amplifier gain peak linewidth being relatively wide in the prior art.

[0004] To achieve the above object, the present invention provides a high-power narrow-linewidth Raman fiber amplifier, comprising: a narrow-linewidth signal source, a pump source, a fiber combiner and a phosphorus-doped fiber;

[0005] The output end of the narrow linewidth signal source and the output end of the pump source are fused with the input end of the optical fiber combiner respectively to provide a narrow linewidth signal;

[0006] The fiber combiner comprises a plurality of input ends and one output end, the number of the input ends of the fiber combiner is equal to the sum of the number of the output ends of the narrow linewidth signal source and the number of the output ends of the pump source, and the output end of the fiber combiner is fused with one end of the phosphorus-doped optical fiber;

[0007] The other end of the phosphorus-doped optical fiber serves as the output end of the high-power narrow-linewidth Raman optical fiber amplifier, and is used to output high-power narrow-linewidth Raman laser.

[0008] Compared with the prior art, the present invention has the following beneficial effects:

[0009] The high-power narrow-linewidth Raman fiber amplifier provided by the present invention uses a narrow-linewidth signal source to provide a low-power narrow-linewidth signal, then uses a pump source to provide a high-power pump light, then the low-power narrow-linewidth signal and the high-power pump light are coupled to a phosphorus-doped fiber through a fiber combiner, and finally a Raman gain peak with a frequency shift of about 40 THz in the Raman gain spectrum of the phosphorus-doped fiber is used to provide a narrow-linewidth gain. When the low-power narrow-linewidth signal provided by the narrow-linewidth signal source and the high-power pump light provided by the pump source propagate in the phosphorus-doped fiber at the same time, the narrow-linewidth Raman gain peak is used to provide gain. Based on the stimulated Raman scattering effect, the high-power pump light provided by the pump source can be converted into a narrow-linewidth signal, thereby realizing power amplification and outputting a high-power narrow-linewidth Raman laser. Compared with pure silica-based optical fiber, in the Raman gain spectrum of the phosphorus-doped optical fiber used in the amplifier provided by the present invention, there is a Raman gain peak with a narrow line width near the frequency shift of 40 THz, and its 3dB line width is about 1.24 THz. The 3dB line width is significantly smaller than the existing 3dB line width of the Raman gain peak near the frequency shift of 13.2 THz (about 7.79 THz). By using the Raman gain peak with a frequency shift of about 40 THz in the phosphorus-doped optical fiber to provide gain, narrow-linewidth Raman laser output can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0011] Figure 1 A structural diagram of a high-power narrow-linewidth Raman fiber amplifier provided by the present invention;

[0012] Figure 2 A comparison chart of the Raman gain spectrum of the phosphorus-doped optical fiber used in the present invention and the Raman gain spectrum of the pure silica-based optical fiber;

[0013] Figure 3 A structural diagram of a high-power narrow-linewidth Raman fiber amplifier provided in Example 1 of the present invention;

[0014] Figure 4 This is a structural diagram of a high-power narrow-linewidth Raman fiber amplifier provided in Example 2 of the present invention.

[0015] Explanation of the accompanying drawings: 1: narrow linewidth signal source; 11: seed source laser; 12: FP cavity narrow linewidth filter; 13: fiber isolator; 14: fiber circulator; 15: first port; 16: second port; 17: third port; 18: narrow linewidth fiber Bragg grating; 2: fusion point; 3: pump source; 4: fiber combiner; 5: phosphorus-doped fiber; 6: 8° bevel.

[0016] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0019] The present invention provides a high-power narrow-linewidth Raman fiber amplifier, such as Figure 1 As shown, it includes: a narrow linewidth signal source 1, a pump source 3, a fiber combiner 4 and a phosphorus-doped fiber 5;

[0020] The output end of the narrow linewidth signal source 1 and the output end of the pump source 3 are respectively fused with the input end of the optical fiber combiner 4 to form three fusion points 2. The narrow linewidth signal source 1 is used to provide a narrow linewidth signal.

[0021] The optical fiber combiner 4 includes a plurality of input ends and an output end. The number of the input ends of the optical fiber combiner 4 is equal to the sum of the number of the output ends of the narrow linewidth signal source 1 and the number of the output ends of the pump source 3. The output end of the optical fiber combiner 4 is fused with one end of the phosphorus-doped optical fiber 5 to form a fusion point 2.

[0022] The other end of the phosphorus-doped optical fiber 5 serves as the output end of the high-power narrow-linewidth Raman optical fiber amplifier, and is used to output high-power narrow-linewidth Raman laser.

[0023] The high-power narrow-linewidth Raman fiber amplifier provided by the present invention uses a narrow-linewidth signal source to provide a low-power narrow-linewidth signal, then uses a pump source to provide a high-power pump light, then the low-power narrow-linewidth signal and the high-power pump light are coupled to a phosphorus-doped fiber through a fiber combiner, and finally a Raman gain peak with a frequency shift of about 40 THz in the Raman gain spectrum of the phosphorus-doped fiber is used to provide a narrow-linewidth gain. When the low-power narrow-linewidth signal provided by the narrow-linewidth signal source and the high-power pump light provided by the pump source propagate in the phosphorus-doped fiber at the same time, the narrow-linewidth Raman gain peak is used to provide gain. Based on the stimulated Raman scattering effect, the high-power pump light provided by the pump source can be converted into a narrow-linewidth signal, thereby realizing power amplification and outputting a high-power narrow-linewidth Raman laser. Compared with pure silica-based optical fiber, in the Raman gain spectrum of the phosphorus-doped optical fiber used in the amplifier provided by the present invention, there is a Raman gain peak with a narrow line width near the frequency shift of 40 THz, and its 3dB line width is about 1.24 THz. The 3dB line width is significantly smaller than the existing 3dB line width of the Raman gain peak near the frequency shift of 13.2 THz (about 7.79 THz). By using the Raman gain peak with a frequency shift of about 40 THz in the phosphorus-doped optical fiber to provide gain, narrow-linewidth Raman laser output can be achieved.

[0024] Preferably, the frequency shift between the narrow linewidth signal output by the narrow linewidth signal source 1 and the optical signal output by the pump source 3 is equal to the frequency shift of the narrow linewidth gain peak in the Raman gain spectrum of the phosphorus-doped fiber 5, and the value of the shift is 40 THz. Under this condition, the gain coefficient of the signal light (narrow linewidth signal) is the highest, the pump light is converted more fully, and the output power of the signal light is the highest.

[0025] Preferably, the narrow linewidth signal source 1 comprises a seed source laser 11 and a FP cavity narrow linewidth filter 12;

[0026] The output end of the seed source laser 11 is fused with the input end of the FP cavity narrow linewidth filter 12 to generate an initial signal;

[0027] The output end of the FP cavity narrow linewidth filter 12 is fused with the input end of the optical fiber combiner 4 to filter the initial signal to generate a narrow linewidth signal.

[0028] Preferably, the narrow linewidth signal source 1 further comprises an optical fiber isolator 13, and the optical signal in the optical fiber isolator 13 is unidirectionally transmitted to prevent the backscattered light in the amplifier from entering the narrow linewidth signal source 1 and destroying the narrow linewidth signal;

[0029] The optical fiber isolator 13 is arranged between the FP cavity narrow linewidth filter 12 and the optical fiber combiner 4 , the input end of the optical fiber isolator 13 is fused with the output end of the FP cavity narrow linewidth filter 12 , and the output end of the optical fiber isolator 13 is fused with the input end of the optical fiber combiner 4 .

[0030] Preferably, the narrow linewidth signal source 1 comprises a seed source laser 11, a fiber circulator 14 and a narrow linewidth fiber grating 18;

[0031] The optical fiber circulator 14 includes a first port 15, a second port 16 and a third port 17 in sequence, and the optical signal is unidirectionally transmitted from the first port 15 to the third port 17 to prevent the backscattered light in the amplifier from entering the narrow linewidth signal source 1 and destroying the narrow linewidth signal;

[0032] The output end of the seed source laser 11 is fused with the first port 15 to generate an initial signal;

[0033] One end of the narrow linewidth fiber grating 18 is fused with the second port 16 to reflect the initial signal to generate a narrow linewidth signal;

[0034] The third port 17 serves as an output end of the narrow linewidth signal and is fused with the input end of the optical fiber combiner 4 .

[0035] The initial signal provided by the seed source laser 11 is transmitted via the first port 15 of the fiber circulator 14 to the second port 16 and reaches the narrow linewidth fiber grating 18. Under the action of the narrow linewidth fiber grating 18, a narrow linewidth reflected light signal is generated and re-enters the second port 16 of the fiber circulator 14 and is finally output from the third port 17.

[0036] Preferably, the other end of the narrow linewidth fiber grating 18 is beveled to suppress end face feedback and increase output power.

[0037] Preferably, the output end of the high-power narrow-linewidth Raman fiber amplifier is beveled to suppress end face feedback and increase output power.

[0038] Preferably, the inclination angle of the bevel is 8°, at which the effect of suppressing end surface feedback is optimal.

[0039] Preferably, the high-power narrow-linewidth Raman fiber amplifier comprises two pump sources 3; and the fiber combiner 4 is a (2+1)×1 fiber combiner.

[0040] If there are N pump sources 3, the fiber combiner 4 is a (N+1)×1 fiber combiner. The number of pump sources 3 is selected according to actual conditions to meet different application requirements.

[0041] Preferably, the pump source 3 is one of a fiber laser, a semiconductor laser, and a gas laser. A common laser is selected as the pump source because it is low in cost and easy to obtain.

[0042] Preferably, the phosphorus-doped optical fiber 5 is a single-clad optical fiber or a multi-clad optical fiber. Commonly used phosphorus-doped optical fibers are selected, which are low in cost and easy to obtain.

[0043] Preferably, the narrow linewidth signal source 1 is one of a fiber laser, a semiconductor laser and a gas laser. A common laser is selected as the narrow linewidth signal source because it is low in cost and easy to obtain.

[0044] Preferably, the 3dB linewidth of the narrow linewidth signal output by the narrow linewidth signal source 1 is ≤0.2nm, so as to ensure that the 3dB linewidth of the laser output after amplification is significantly narrower than that of the prior art.

[0045] The amplifier provided by the present invention adopts phosphorus-doped optical fiber to perform gain amplification on the signal. The phosphorus-doped optical fiber can achieve non-broadening of narrow linewidth signals while performing gain amplification on the signal, thereby outputting narrow linewidth Raman laser.

[0046] Example 1

[0047] This embodiment provides a high-power narrow-linewidth Raman fiber amplifier, such as Figure 3 As shown, it includes a narrow linewidth signal source 1, two pump sources 3, a (2+1)×1 optical fiber combiner 4 and a phosphorus-doped optical fiber 5;

[0048] The narrow linewidth signal source 1 includes a seed source laser 11, a fiber isolator 13 and an FP cavity narrow linewidth filter 12. The fiber isolator 13 is arranged between the FP cavity narrow linewidth filter 12 and the fiber combiner 4. The input end of the fiber isolator 13 is fused with the output end of the FP cavity narrow linewidth filter 12, and the output end of the fiber isolator 13 is fused with the input end of the fiber combiner 4. The seed source laser 11 is used to generate an initial signal; the FP cavity narrow linewidth filter 12 is used to filter the initial signal to generate a narrow linewidth signal.

[0049] The output end of the narrow linewidth signal source 1 and the output end of the pump source 3 are respectively fused with the input end of the optical fiber combiner 4 to form three fusion points 2. The narrow linewidth signal source 1 is used to provide a narrow linewidth signal.

[0050] The optical fiber combiner 4 includes three input ends (one of which is used to be fused with the output end of the narrow linewidth signal source 1, and the other two are used to be fused with the output ends of the pump source 3) and an output end. The output end of the optical fiber combiner 4 is fused with one end of the phosphorus-doped optical fiber 5 to form a fusion point 2;

[0051] The other end of the phosphorus-doped fiber 5 is used as the output end of the high-power narrow-linewidth Raman fiber amplifier to output narrow-linewidth Raman laser light. The output end of the high-power narrow-linewidth Raman fiber amplifier is cut at an angle of 8° to suppress end face feedback.

[0052] The central wavelength of the FP cavity filter 12 is the same as the central wavelength of the seed source laser 11, and the 3dB line width is ≤0.2nm.

[0053] Example 2

[0054] This embodiment provides a high-power narrow-linewidth Raman fiber amplifier, such as Figure 3 As shown, it includes a narrow linewidth signal source 1, two pump sources 3, a (2+1)×1 optical fiber combiner 4 and a phosphorus-doped optical fiber 5;

[0055] The narrow linewidth signal source 1 includes a seed source laser 11, a fiber circulator 14 and a narrow linewidth fiber Bragg grating 18; the fiber circulator 14 includes a first port 15, a second port 16 and a third port 17 in sequence, and the optical signal is unidirectionally transmitted from the first port 15 to the third port 17 to prevent the backscattered light in the amplifier from entering the narrow linewidth signal source 1 and destroying the narrow linewidth signal; the output end of the seed source laser 11 is fused with the first port 15 to generate an initial signal; one end of the narrow linewidth fiber Bragg grating 18 is fused with the second port 16 to reflect the initial signal to generate a narrow linewidth signal; the third port 17, as the output end of the narrow linewidth signal, is fused with the input end of the fiber combiner 4. The initial signal provided by the seed source laser 11 is transmitted to the second port 16 via the first port 15 of the fiber circulator 14 and reaches the narrow linewidth fiber Bragg grating 18. Under the action of the narrow linewidth fiber Bragg grating 18, a narrow linewidth reflected light signal is generated and re-enters the second port 16 of the fiber circulator 14, and finally outputs from the third port 17.

[0056] The output end of the narrow linewidth signal source 1 and the output end of the pump source 3 are respectively fused with the input end of the optical fiber combiner 4 to form three fusion points 2. The narrow linewidth signal source 1 is used to provide a narrow linewidth signal.

[0057] The optical fiber combiner 4 includes three input ends (one of which is used to be fused with the output end of the narrow linewidth signal source 1, and the other two are used to be fused with the output ends of the pump source 3) and an output end. The output end of the optical fiber combiner 4 is fused with one end of the phosphorus-doped optical fiber 5 to form a fusion point 2;

[0058] The other end of the phosphorus-doped fiber 5 is used as the output end of the high-power narrow-linewidth Raman fiber amplifier to output narrow-linewidth Raman laser light. The output end of the high-power narrow-linewidth Raman fiber amplifier is cut at an angle of 8° to suppress end face feedback.

[0059] The central wavelength of the narrow linewidth fiber grating 18 is the same as the central wavelength of the seed source laser 11, and the 3dB linewidth is ≤0.2nm.

[0060] The frequency shift between the narrow linewidth signal output by the narrow linewidth signal source 1 and the optical signal output by the pump source 3 is equal to the frequency shift of the narrow linewidth gain peak in the Raman gain spectrum of the phosphorus-doped optical fiber 5, and the value of the shift is 40 THz.

[0061] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A high-power narrow-linewidth Raman fiber amplifier, characterized in that: include: Narrow linewidth signal sources, pump sources, fiber combiners and phosphorus-doped fibers; The output end of the narrow linewidth signal source and the output end of the pump source are fused with the input end of the optical fiber combiner respectively to provide a narrow linewidth signal; The fiber combiner comprises a plurality of input ends and one output end, the number of the input ends of the fiber combiner is equal to the sum of the number of the output ends of the narrow linewidth signal source and the number of the output ends of the pump source, and the output end of the fiber combiner is fused with one end of the phosphorus-doped optical fiber; The other end of the phosphorus-doped optical fiber serves as the output end of the high-power narrow-linewidth Raman optical fiber amplifier, and is used to output high-power narrow-linewidth Raman laser. The 3dB linewidth of the narrow linewidth signal output by the narrow linewidth signal source is ≤0.2nm.

2. The high-power narrow-linewidth Raman fiber amplifier according to claim 1, characterized in that: The narrow linewidth signal source includes a seed source laser and an FP cavity narrow linewidth filter; The output end of the seed source laser is fused with the input end of the FP cavity narrow linewidth filter to generate an initial signal; The output end of the FP cavity narrow linewidth filter is fused with the input end of the optical fiber combiner to filter the initial signal to generate a narrow linewidth signal.

3. The high-power narrow-linewidth Raman fiber amplifier according to claim 2, characterized in that: The narrow linewidth signal source further comprises an optical fiber isolator, in which the optical signal is transmitted unidirectionally; The optical fiber isolator is arranged between the FP cavity narrow linewidth filter and the optical fiber combiner, the input end of the optical fiber isolator is fused with the output end of the FP cavity narrow linewidth filter, and the output end of the optical fiber isolator is fused with the input end of the optical fiber combiner.

4. The high-power narrow-linewidth Raman fiber amplifier according to claim 1, characterized in that: The narrow linewidth signal source includes a seed source laser, a fiber circulator and a narrow linewidth fiber grating; The optical fiber circulator comprises a first port, a second port and a third port in sequence, and the optical signal is transmitted unidirectionally from the first port to the third port; The output end of the seed source laser is fused with the first port to generate an initial signal; One end of the narrow linewidth fiber Bragg grating is fused with the second port to reflect the initial signal to generate a narrow linewidth signal; The third port serves as the output end of the narrow linewidth signal and is fused with the input end of the optical fiber combiner.

5. The high-power narrow-linewidth Raman fiber amplifier according to claim 4, characterized in that: The other end of the narrow linewidth fiber grating is beveled.

6. The high-power narrow-linewidth Raman fiber amplifier according to claim 1, characterized in that: The output end of the high-power narrow-linewidth Raman optical fiber amplifier is cut at an angle.

7. The high-power narrow-linewidth Raman fiber amplifier according to claim 5 or 6, characterized in that: The inclination angle of the bevel is .

8. The high-power narrow-linewidth Raman fiber amplifier according to claim 1, characterized in that: The high-power narrow-linewidth Raman fiber amplifier includes two pump sources; the fiber combiner is a (2+1)×1 fiber combiner.

9. The high-power narrow-linewidth Raman fiber amplifier according to claim 8, characterized in that: The pump source is one of a fiber laser, a semiconductor laser, and a gas laser.

10. The high-power narrow-linewidth Raman fiber amplifier according to claim 1, characterized in that: The phosphorus-doped optical fiber is a single-clad optical fiber or a multi-clad optical fiber.

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