Dual-band resonant fiber amplifier and co-band ASE suppression method

Abstract

The application discloses a double-sideband resonance optical fiber amplifier and a same-band ASE suppression method. The optical fiber amplifier comprises a narrow-line-width seed light source, a narrow-line-width laser pre-amplification system, a main amplification system, a seventh single-mode optical fiber, a mode field adapter, a first large-mode-field optical fiber, a laser collimating lens and a transmission diffraction grating. The final pre-amplification signal light output from the narrow-line-width laser pre-amplification system passes through FBGs of a first LWS resonant cavity, a second LWS resonant cavity, a first SWS resonant cavity and a second SWS resonant cavity in the main amplification system, and long-wave and short-wave sideband lasers are obtained, respectively. The main amplifier gain optical fiber absorbs pump light, the pump light and the sideband laser pass through the processing of a laser output end cap, and a divergent laser beam is obtained. After the processing of the laser collimating lens and the transmission diffraction grating, amplified signal laser is obtained. The application can reduce the influence on signal laser gain to the maximum and can be applied to a higher-power main amplification stage.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser technology, in particular to a double sideband resonance fiber amplifier and a co-band ASE suppression method. BACKGROUND

[0002] In the amplification process of narrow linewidth laser, ASE (Amplified Spontaneous Emission), especially co-band ASE, is a very serious main factor restricting the power improvement of the amplifier. Specifically, the co-band ASE makes the laser spectrum contrast of the fiber amplifier quickly reach saturation with the power improvement. Further increasing the pump strength may also lead to parasitic self-oscillation in the time domain, which not only further reduces the spectral contrast, makes the spectral profile more complex and unstable, but also easily causes damage to the gain fiber itself.

[0003] At present, the suppression of co-band ASE mainly adopts spectral filtering technology. In addition, there is almost no more practical technology used for its effective suppression. However, the traditional all-fiber spectral filter device can generally only be used in the pre-amplification stage of lower power, and there is still a lack of related technology in the main amplification stage of higher power of hundreds of watts or even kilowatts. SUMMARY

[0004] The technical problem to be solved by the present application is to solve the adverse effects of co-band ASE in the current high-power narrow linewidth fiber amplifier, and to provide a double sideband resonance fiber amplifier and a co-band ASE suppression method, to realize high spectral contrast and low ASE level laser amplification.

[0005] In order to solve the above technical problems, the present application adopts the following technical solutions:

[0006] A double sideband resonance fiber amplifier, comprising:

[0007] a narrow linewidth seed light source, a narrow linewidth laser pre-amplification system, a main amplification system, a seventh single-mode optical fiber, a mode field adapter, a first large-mode optical fiber, a laser collimating lens and a transmission diffraction grating.

[0008] The output end of the narrow linewidth laser pre-amplification system is connected with one end of the mode field adapter through the seventh single-mode optical fiber, and the other end of the mode field adapter is connected with the input end of the main amplification system through the first large-mode optical fiber.

[0009] The input narrow linewidth seed light source is processed by the narrow linewidth laser pre-amplification system, the main amplification system and the mode field adapter, and a divergent laser beam is output. The divergent laser beam is transmitted into the laser collimating lens for collimation to obtain a collimated beam. The collimated beam is separated by the transmission diffraction grating to obtain an amplified signal laser.

[0010] Further, the narrow linewidth seed light source is a full-fiber structure narrow linewidth seed light source or a single-frequency semiconductor laser diode seed light source.

[0011] Further, the narrow linewidth laser pre-amplification system is used for providing narrow linewidth light power, and the system comprises a first single-mode optical fiber, a second single-mode optical fiber, a third single-mode optical fiber, a fourth single-mode optical fiber, a fifth single-mode optical fiber, a sixth single-mode optical fiber, a first-stage pre-amplifier, a second-stage pre-amplifier, a third-stage pre-amplifier, a first band-pass filter, a second band-pass filter and a third band-pass filter.

[0012] The narrow linewidth seed light source is connected with one end of the first-stage pre-amplifier through the first single-mode optical fiber, the other end of the first-stage pre-amplifier is connected with one end of the first band-pass filter through the second single-mode optical fiber, the other end of the first band-pass filter is connected with one end of the second-stage pre-amplifier through the third single-mode optical fiber, the other end of the second-stage pre-amplifier is connected with one end of the second band-pass filter through the fourth single-mode optical fiber, the other end of the second band-pass filter is connected with one end of the third-stage pre-amplifier through the fifth single-mode optical fiber, and the other end of the third-stage pre-amplifier is connected with one end of the third band-pass filter through the sixth single-mode optical fiber.

[0013] Further, the main amplification system is used for realizing high-power laser output, and the system comprises a second large-mode-field optical fiber, a third large-mode-field optical fiber, a fourth large-mode-field optical fiber, a fifth large-mode-field optical fiber, a sixth large-mode-field optical fiber, a seventh large-mode-field optical fiber, an eighth large-mode-field optical fiber, a FBG (Fiber Bragg Grating) of a first LWS (Long-wave Sideband) resonant cavity, a FBG of a second LWS resonant cavity, a FBG of a first SWS (Short-wave Sideband) resonant cavity, a FBG of a second SWS resonant cavity, a forward-pumping LD (Laser Diode), a backward-pumping LD, a forward-pumping / signal combiner, a backward-pumping / signal combiner, a main amplifier gain optical fiber and a laser output end cap.

[0014] The other end of the mode field adapter is connected with one end of the FBG of the first LWS resonant cavity through the first large-mode-field fiber, the other end of the FBG of the first LWS resonant cavity is connected with one end of the FBG of the first SWS resonant cavity through the second large-mode-field fiber, the other end of the FBG of the first SWS resonant cavity is connected with one end of the forward pump / signal combiner through the third large-mode-field fiber, one end of the forward pump / signal combiner is connected with one end of the forward pump LD through the multimode tail fiber, the other end of the forward pump / signal combiner is connected with one end of the main amplifier gain fiber through the fourth large-mode-field fiber, the other end of the main amplifier gain fiber is connected with one end of the backward pump / signal combiner through the fifth large-mode-field fiber, one end of the backward pump / signal combiner is connected with the backward pump LD through the multimode tail fiber, the other end of the backward pump / signal combiner is connected with one end of the FBG of the second SWS resonant cavity through the sixth large-mode-field fiber, the other end of the FBG of the second SWS resonant cavity is connected with one end of the FBG of the second LWS resonant cavity through the seventh large-mode-field fiber, the other end of the FBG of the second LWS resonant cavity is connected with one end of the laser output end cap through the eighth large-mode-field fiber.

[0015] Further, the FBG of the first LWS resonant cavity, the FBG of the second LWS resonant cavity, the FBG of the first SWS resonant cavity and the FBG of the second SWS resonant cavity are all FBGs with a reflectivity greater than 99%.

[0016] Further, the FBG of the first LWS resonant cavity and the FBG of the first SWS resonant cavity are both FBGs with a reflectivity greater than 99%, and the FBG of the second LWS resonant cavity and the FBG of the second SWS resonant cavity are both FBGs with a reflectivity greater than 10%.

[0017] Further, the single-mode fiber and the large-mode-field fiber are connected in a fusion manner.

[0018] Further, the application further provides a same-band ASE suppression method for a double-sideband resonant optical fiber amplifier, comprising:

[0019] S1, input the narrow linewidth seed light source into the narrow linewidth laser preamplification system, in which the signal light is transmitted in a single mode through a single-mode fiber, and sequentially passes through a first-stage preamplifier, a second-stage preamplifier and a third-stage preamplifier for one-stage, two-stage and three-stage preamplification respectively, a first band-pass filter filters out the same-band ASE of the signal light after one-stage preamplification, a second band-pass filter filters out the same-band ASE of the signal light after two-stage preamplification, and a third band-pass filter filters out the same-band ASE of the signal light after three-stage preamplification, to obtain the final preamplified signal light.

[0020] S2, the mode field adapter transitions the final pre-amplified signal light from the single mode fiber to the large mode area fiber with low loss, at this time the final pre-amplified signal light enters the main amplifier system, in which the final pre-amplified signal light is transmitted in the form of near single mode and large mode field through the large mode area fiber, the final pre-amplified signal light forms long wave sideband laser at the long wave sideband when passing through the FBG of the first LWS resonant cavity and the FBG of the second LWS resonant cavity, and forms short wave sideband laser at the short wave sideband when passing through the FBG of the first SWS resonant cavity and the FBG of the second SWS resonant cavity, namely LWS and SWS.

[0021] S3, the forward pumping LD provides forward pumping light, the reverse pumping LD provides reverse pumping light, the forward pumping / signal combiner combines the forward pumping light into the subsequent large mode area fiber, the reverse pumping / signal combiner combines the reverse pumping light into the front large mode area fiber, the main amplifier gain fiber absorbs the pumping light, and the pumping light and the sideband laser are processed through the laser output end cap to obtain a divergent laser beam.

[0022] S4, the laser collimating lens is used for collimating the divergent laser beam to obtain a collimated light beam; the collimated light beam is separated through the transmission type diffraction grating to obtain amplified SL (Signal Laser) after filtering out LWS and SWS, and the same band ASE suppression is completed.

[0023] Further, the process of the laser output end cap is as follows: the sideband laser is transmitted in the quartz column for about 3-5 mm, the light beam gradually diverges, the light beam diameter changes from 20-30 microns to more than 1 mm when reaching the quartz / air interface, the quartz / air interface is cut at an angle of 8° and coated with an antireflection film.

[0024] Compared with the prior art, the above technical scheme has the following technical effects:

[0025] The sideband resonance of the application can effectively reduce the ratio of ASE and improve the spectral contrast of SL, and the small gain of the sideband resonance can minimize the influence on the gain of SL. In addition, the application can be applied to a higher power main amplification stage, especially suitable for ASE suppression in a high power amplifier, and the application can be applied to various different wavelengths and different rare earth doped fiber amplifiers, including erbium doped, ytterbium doped, thulium doped, holmium doped and other fiber amplifiers. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is a whole structure diagram of the fiber amplifier of the application.

[0027] Figure 2 It is a typical position distribution diagram of SWS, SL and LWS on the ASE spectrum of the erbium doped fiber of the embodiment of the application.

[0028] Figure 3 is a spectral distribution and shape feature map of SWS, SL and LWS of an embodiment of the present application. DETAILED DESCRIPTION

[0029] The present application will be further described below with reference to the drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and cannot be used to limit the protection scope of the present application.

[0030] To achieve the above-mentioned purpose, the present application provides a double-sideband resonance optical fiber amplifier, as shown in the figure, comprising: Figure 1

[0031] a narrow linewidth seed light source, a narrow linewidth laser pre-amplification system, a main amplification system, a seventh single-mode optical fiber 2g, a mode field adapter 5, a first large-mode optical fiber 6a, a laser collimating lens 14 and a transmission diffraction grating 16.

[0032] The output end of the narrow linewidth laser pre-amplification system is connected with one end of the mode field adapter 5 through the seventh single-mode optical fiber 2g, and the other end of the mode field adapter 5 is connected with the input end of the main amplification system through the first large-mode optical fiber 6a.

[0033] The input narrow linewidth seed light source is processed by the narrow linewidth laser pre-amplification system, the main amplification system and the mode field adapter 5, and an output divergent laser beam 13 is obtained, which is transmitted into the laser collimating lens 14 for collimation to obtain a collimated light beam 15, which is separated by the transmission diffraction grating 16 to obtain the amplified SL (Signal Laser, signal laser) 18 after filtering out the LWS (Long-wave Sideband, long-wave sideband) 17 and the SWS (Short-wave Sideband, short-wave sideband) 19.

[0034] Among them, the narrow linewidth seed light source is a full-fiber structure narrow linewidth seed light source 1a or a single-frequency semiconductor laser diode seed light source 1b.

[0035] The narrow linewidth laser pre-amplification system comprises a first single-mode optical fiber 2a, a second single-mode optical fiber 2b, a third single-mode optical fiber 2c, a fourth single-mode optical fiber 2d, a fifth single-mode optical fiber 2e, a sixth single-mode optical fiber 2f, a first-stage pre-amplifier 3a, a second-stage pre-amplifier 3b, a third-stage pre-amplifier 3c, a first band-pass filter 4a, a second band-pass filter 4b and a third band-pass filter 4c, which are used to provide sufficient narrow linewidth optical power for the main amplifier.

[0036] ​The main amplification system comprises a second large-mode-field fiber 6b, a third large-mode-field fiber 6c, a fourth large-mode-field fiber 6d, a fifth large-mode-field fiber 6e, a sixth large-mode-field fiber 6f, a seventh large-mode-field fiber 6g, an eighth large-mode-field fiber 6h, a FBG (Fiber Bragg Grating) 7a of the first LWS resonator, a FBG 7b of the second LWS resonator, a FBG 8a of the first SWS resonator, a FBG 8b of the second SWS resonator, a forward-pumping LD (Laser Diode) 9a, a backward-pumping LD 9b, a forward-pumping / signal combiner 10a, a backward-pumping / signal combiner 10b, a main amplifier gain fiber 11, and a laser output end cap 12, for realizing high-power laser output.

[0037] The all-fiber structure narrow linewidth seed light source 1a or the single-frequency semiconductor laser diode seed light source 1b is connected with one end of the first-stage pre-amplifier 3a through the first single-mode optical fiber 2a, the other end of the first-stage pre-amplifier 3a is connected with one end of the first band-pass filter 4a through the second single-mode optical fiber 2b, the other end of the first band-pass filter 4a is connected with one end of the second-stage pre-amplifier 3b through the third single-mode optical fiber 2c, the other end of the second-stage pre-amplifier 3b is connected with one end of the second band-pass filter 4b through the fourth single-mode optical fiber 2d, the other end of the second band-pass filter 4b is connected with one end of the third-stage pre-amplifier 3c through the fifth single-mode optical fiber 2e, the other end of the third-stage pre-amplifier 3c is connected with one end of the third band-pass filter 4c through the sixth single-mode optical fiber 2f, the other end of the third band-pass filter 4c is connected with one end of the mode field adapter 5 through the seventh single-mode optical fiber 2g, the other end of the mode field adapter 5 is connected with one end of the FBG 7a of the first LWS resonant cavity through the first large-mode optical fiber 6a, the other end of the FBG 7a of the first LWS resonant cavity is connected with one end of the FBG 8a of the first SWS resonant cavity through the second large-mode optical fiber 6b, the other end of the FBG 8a of the first SWS resonant cavity is connected with one end of the forward pumping / signal combiner 10a through the third large-mode optical fiber 6c, one end of the forward pumping / signal combiner 10a is connected with one end of the forward pumping LD 9a through a multimode tail fiber, the other end of the forward pumping / signal combiner 10a is connected with one end of the main amplifier gain optical fiber 11 through the fourth large-mode optical fiber 6d, the other end of the main amplifier gain optical fiber 11 is connected with one end of the backward pumping / signal combiner 10b through the fifth large-mode optical fiber 6e, one end of the backward pumping / signal combiner 10b is connected with the backward pumping LD 9b through a multimode tail fiber, the other end of the backward pumping / signal combiner 10b is connected with one end of the FBG 8b of the second SWS resonant cavity through the sixth large-mode optical fiber 6f, the other end of the FBG 8b of the second SWS resonant cavity is connected with one end of the FBG 7b of the second LWS resonant cavity through the seventh large-mode optical fiber 6g, the other end of the FBG 7b of the second LWS resonant cavity is connected with one end of the laser output end cap 12 through the eighth large-mode optical fiber 6h, and the laser collimating lens 14 and the transmission type diffraction grating 16 process the light beam.

[0038] The first single-mode optical fiber 2a, the second single-mode optical fiber 2b, the third single-mode optical fiber 2c, the fourth single-mode optical fiber 2d, the fifth single-mode optical fiber 2e and the sixth single-mode optical fiber 2f are generally tail fibers of the device, and they can be polarization-maintaining or non-polarization-maintaining, depending on the specific fiber system adopted.

[0039] The FBG 7a of the first LWS resonant cavity and the FBG 8a of the first SWS resonant cavity are both FBGs with a reflectivity greater than 99%, and the FBG 7b of the second LWS resonant cavity and the FBG 8b of the second SWS resonant cavity are both FBGs with a reflectivity greater than 10%.

[0040] Both single-mode fiber and large-mode-area fiber are connected by fusion splicing.

[0041] The sideband resonance is realized by a resonant cavity composed of FBGs with central wavelength at the gain edge. The sidebands include LWS and SWS, which are at the long-wave edge and short-wave edge of the gain spectrum of the active fiber, respectively.

[0042] The working principle of the co-directional ASE suppression method of the dual-sideband resonance fiber amplifier is as follows:

[0043] S1, input the narrow linewidth seed light source into the narrow linewidth laser pre-amplification system, in which the signal light is transmitted in a single mode through a single-mode fiber, sequentially passes through the first-stage pre-amplifier 3a, the second-stage pre-amplifier 3b and the third-stage pre-amplifier 3c, and is pre-amplified in one stage, two stages and three stages, respectively. The first band-pass filter 4a filters out the co-directional ASE of the signal light after one-stage pre-amplification, the second band-pass filter 4b filters out the co-directional ASE of the signal light after two-stage pre-amplification, and the third band-pass filter 4c filters out the co-directional ASE of the signal light after three-stage pre-amplification, to obtain the final pre-amplified signal light.

[0044] S2, the mode field adapter 5 transitions the final pre-amplified signal light from the single-mode fiber to the large-mode-area fiber with low loss, at which time the final pre-amplified signal light enters the main amplification system. In the system, the final pre-amplified signal light is transmitted in a near-single mode and a larger mode field through a large-mode-area fiber. When the final pre-amplified signal light passes through the FBG 7a of the first LWS resonant cavity, it provides high reflectivity (>99%) for the light at the long-wave sideband. When the final pre-amplified signal light passes through the FBG 7b of the second LWS resonant cavity, it provides partial reflectivity (>10%) for the light at the long-wave sideband, forming long-wave sideband laser, i.e. LWS, at the long-wave sideband. When the final pre-amplified signal light passes through the FBG 8a of the first SWS resonant cavity, it provides high reflectivity (>99%) for the light at the short-wave sideband. When the final pre-amplified signal light passes through the FBG 8b of the second SWS resonant cavity, it provides partial reflectivity (>10%) for the light at the short-wave sideband, forming short-wave sideband laser, i.e. SWS, at the short-wave sideband.

[0045] S3, the forward pumping LD 9a provides forward pumping light, the backward pumping LD 9b provides backward pumping light, the forward pumping / signal combiner 10a combines the forward pumping light into the subsequent large-mode-area fiber, the backward pumping / signal combiner 10b combines the backward pumping light into the front large-mode-area fiber, the pumping light provides sufficient optical power and is further converted into signal light in the active fiber through stimulated radiation process, thereby increasing the power of the signal light; the main amplifier gain fiber 11 absorbs the pumping light to provide gain for the LWS, the SWS and the SL, the pumping light and the sideband laser are processed by the laser output end cap 12 to reduce the power density at the quartz / air interface and at the same time avoid light reflection back into the amplifier, and a divergent laser beam 13 is obtained.

[0046] S4, the laser collimating lens 14 is used to collimate the divergent laser beam 13 to obtain a collimated light beam 15; the collimated light beam 15 is separated by the transmission diffraction grating 16, and after the LWS 17 and the SWS 19 are filtered out, the amplified SL 18 is obtained, and the same-band ASE suppression is completed.

[0047] The process of the laser output end cap 12 is as follows: the sideband laser is transmitted in the quartz column for about 3-5 mm, the beam is gradually divergent, and when reaching the quartz / air interface, the beam diameter can be changed from 20-30 microns to more than 1 mm. The quartz / air interface is generally cut at an angle of 8° and coated with an antireflection film, so as to avoid backward reflection of light.

[0048] Figure 2 and Figure 3 The results of the embodiment based on the EDF (Erbium-Ddoped Fiber, erbium-doped fiber) amplifier are given. Figure 2 The ASE spectrum of the EDF is given. The EDF used is a polarization maintaining single-mode fiber, the specific model is EDF50-PM EC, and it is produced by OFS Fitel LLC. The center wavelength of the single-mode pumping LD used in the measurement is 976 nm, and the pumping power is 100 mW. The spectrum used in the spectrum measurement is AQ6374, produced by Yokogawa Electric Corporation. The SL is at the center wavelength with large gain, and the LWS and the SWS are at the ASE edge with small gain.

[0049] Figure 3In the experiment, the seed light source is a single-frequency semiconductor LD with a line width of <100 kHz, the amplifier uses a 3-m-long polarization-maintaining erbium-ytterbium co-doped fiber as a gain fiber, and a 910-nm multimode semiconductor LD as a pump source. The specific model of the gain fiber is DCF-EY-10 / 128-PM, which is produced by CorActive Company. The model of the spectrometer used for spectrum measurement is AQ6374, which is produced by Yokogawa Electric Corporation. The center wavelengths of the LWS, the SL and the SWS are respectively at 1520.21 nm, 1550.49 nm and 1580.92 nm. The wavelength positions and the line widths of the LWS and the SWS are determined by the FBGs written. Compared with no sideband resonance, the spectral contrast of the center wavelength to the ASE is increased from 37.643 dB to 42.826 dB.

[0050] The above only describes the preferred embodiments of the present application, and it should be noted that, for those skilled in the art, some improvements and modifications can be made without departing from the technical principles of the present application, and these improvements and modifications should also be considered as the protection scope of the present application.

Claims

1. A double sideband resonant fiber optical amplifier characterized by, Comprise: A narrow linewidth seed light source, a narrow linewidth laser pre-amplification system, a main amplification system, a seventh single-mode optical fiber (2g), a mode field adapter (5), a first large-mode optical fiber (6a), a laser collimating lens (14) and a transmission diffraction grating (16); Wherein, the main amplification system is used to realize high-power laser output, and the system comprises a second large-mode optical fiber (6b), a third large-mode optical fiber (6c), a fourth large-mode optical fiber (6d), a fifth large-mode optical fiber (6e), a sixth large-mode optical fiber (6f), a seventh large-mode optical fiber (6g), an eighth large-mode optical fiber (6h), an FBG (7a) of a first LWS resonant cavity, an FBG (7b) of a second LWS resonant cavity, an FBG (8a) of a first SWS resonant cavity, an FBG (8b) of a second SWS resonant cavity, a forward pumping LD (9a), a reverse pumping LD (9b), a forward pumping / signal combiner (10a), a reverse pumping / signal combiner (10b), a main amplifier gain optical fiber (11) and a laser output end cap (12); The other end of the mode field adapter (5) is connected with one end of the FBG (7a) of the first LWS resonant cavity through the first large-mode optical fiber (6a), the other end of the FBG (7a) of the first LWS resonant cavity is connected with one end of the FBG (8a) of the first SWS resonant cavity through the second large-mode optical fiber (6b), the other end of the FBG (8a) of the first SWS resonant cavity is connected with one end of the forward pumping / signal combiner (10a) through the third large-mode optical fiber (6c), one end of the forward pumping / signal combiner (10a) is connected with one end of the forward pumping LD (9a) through a multimode tail fiber, the other end of the forward pumping / signal combiner (10a) is connected with one end of the main amplifier gain optical fiber (11) through the fourth large-mode optical fiber (6d), the other end of the main amplifier gain optical fiber (11) is connected with one end of the reverse pumping / signal combiner (10b) through the fifth large-mode optical fiber (6e), one end of the reverse pumping / signal combiner (10b) is connected with the reverse pumping LD (9b) through a multimode tail fiber, the other end of the reverse pumping / signal combiner (10b) is connected with one end of the FBG (8b) of the second SWS resonant cavity through the sixth large-mode optical fiber (6f), the other end of the FBG (8b) of the second SWS resonant cavity is connected with one end of the FBG (7b) of the second LWS resonant cavity through the seventh large-mode optical fiber (6g), the other end of the FBG (7b) of the second LWS resonant cavity is connected with one end of the laser output end cap (12) through the eighth large-mode optical fiber (6h); The output end of the narrow linewidth laser pre-amplification system is connected with one end of the mode field adapter (5) through the seventh single-mode optical fiber (2g), and the other end of the mode field adapter (5) is connected with the input end of the main amplification system through the first large-mode optical fiber (6a); The input narrow linewidth seed light source is processed by a narrow linewidth laser pre-amplification system, a main amplification system and a mode field adapter (5), and an output divergent laser beam (13) is obtained. The divergent laser beam (13) is transmitted into a laser collimating lens (14) for collimation, and a collimated light beam (15) is obtained. The collimated light beam (15) is separated by a transmission diffraction grating (16), and an amplified signal laser (18) is obtained.

2. The dual-bandpass resonant fiber-optic amplifier of claim 1, wherein, The narrow linewidth seed light source is a full-fiber structure narrow linewidth seed light source (1a) or a single-frequency semiconductor laser diode seed light source (1b).

3. The dual-bandpass resonant fiber-optic amplifier of claim 1, wherein, The narrow linewidth laser pre-amplification system is used for providing narrow linewidth optical power, and the system comprises a first single-mode optical fiber (2a), a second single-mode optical fiber (2b), a third single-mode optical fiber (2c), a fourth single-mode optical fiber (2d), a fifth single-mode optical fiber (2e), a sixth single-mode optical fiber (2f), a first-stage pre-amplifier (3a), a second-stage pre-amplifier (3b), a third-stage pre-amplifier (3c), a first band-pass filter (4a), a second band-pass filter (4b) and a third band-pass filter (4c). The narrow linewidth seed light source is connected with one end of the first-stage pre-amplifier (3a) through the first single-mode optical fiber (2a). The other end of the first-stage pre-amplifier (3a) is connected with one end of the first band-pass filter (4a) through the second single-mode optical fiber (2b). The other end of the first band-pass filter (4a) is connected with one end of the second-stage pre-amplifier (3b) through the third single-mode optical fiber (2c). The other end of the second-stage pre-amplifier (3b) is connected with one end of the second band-pass filter (4b) through the fourth single-mode optical fiber (2d). The other end of the second band-pass filter (4b) is connected with one end of the third-stage pre-amplifier (3c) through the fifth single-mode optical fiber (2e). The other end of the third-stage pre-amplifier (3c) is connected with one end of the third band-pass filter (4c) through the sixth single-mode optical fiber (2f).

4. The dual-bandpass resonant fiber-optic amplifier of claim 1, wherein, The FBG (7a) of the first LWS resonant cavity, the FBG (7b) of the second LWS resonant cavity, the FBG (8a) of the first SWS resonant cavity and the FBG (8b) of the second SWS resonant cavity are FBGs with a reflectivity greater than 99%.

5. The dual-bandpass resonant fiber-optic amplifier of claim 1, wherein, The FBG (7a) of the first LWS resonant cavity and the FBG (8a) of the first SWS resonant cavity are FBGs with a reflectivity greater than 99%, and the FBG (7b) of the second LWS resonant cavity and the FBG (8b) of the second SWS resonant cavity are FBGs with a reflectivity greater than 10%.

6. The dual-bandpass resonant fiber-optic amplifier of claim 1, wherein, The single-mode optical fiber and the large-mode-area optical fiber are connected in a fusion manner.

7. The co-ASE suppression method applied to the dual-band resonant fiber amplifier of claim 1, characterized in that, The method comprises the following steps: S1, inputting the narrow linewidth seed light source into a narrow linewidth laser pre-amplification system, in which the signal light is transmitted in a single-mode form through a single-mode optical fiber, sequentially passes through a first-stage pre-amplifier, a second-stage pre-amplifier and a third-stage pre-amplifier, and is pre-amplified in one stage, two stages and three stages respectively. A first band-pass filter filters out the same-band ASE of the signal light after one-stage pre-amplification. A second band-pass filter filters out the same-band ASE of the signal light after two-stage pre-amplification. A third band-pass filter filters out the same-band ASE of the signal light after three-stage pre-amplification, and finally obtains pre-amplified signal light; S2, the mode field adapter transitions the final pre-amplified signal light from the single-mode fiber to the large-mode-area fiber with low loss, at this time the final pre-amplified signal light enters the main amplifier system, in which the final pre-amplified signal light is transmitted in the form of near single-mode and large mode field through the large-mode-area fiber, the final pre-amplified signal light forms long-wave sideband laser at the long-wave sideband when passing through the FBG of the first LWS resonant cavity and the FBG of the second LWS resonant cavity, and forms short-wave sideband laser at the short-wave sideband when passing through the FBG of the first SWS resonant cavity and the FBG of the second SWS resonant cavity; S3, the forward pumping LD provides forward pumping light, the backward pumping LD provides backward pumping light, the forward pumping / signal combiner combines the forward pumping light into the subsequent large-mode-area fiber, the backward pumping / signal combiner combines the backward pumping light into the front large-mode-area fiber, the main amplifier gain fiber absorbs the pumping light, the pumping light and the sideband laser are processed by the laser output end cap to obtain a divergent laser beam; S4, the laser collimating lens is used to collimate the divergent laser beam to obtain a collimated beam; the collimated beam is separated by a transmission diffraction grating to obtain amplified signal laser after filtering out the long-wave sideband and the short-wave sideband, and the same-band ASE suppression is completed.

8. The method of claim 7, wherein the dual-bandpass resonant fiber-optic amplifier is a dual-bandpass resonant fiber-optic amplifier with a center wavelength of 1310 nm and a bandwidth of 100 nm. The process of the laser output end cap processing is as follows: the sideband laser is transmitted in the quartz column for about 3-5 mm, the beam gradually diverges, and when reaching the quartz / air interface, the beam diameter changes from 20-30 microns to more than 1 mm, the quartz / air interface is cut at an angle of 8° and coated with an antireflection film.

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