U-band fiber laser module

Abstract

The invention provides a U-band optical fiber laser module which comprises a first distributed feedback laser source and a backward pumping structure which are sequentially connected in the transmission direction from a signal input end to a signal output end, and the backward pumping structure comprises a first gain optical fiber, a first wavelength division multiplexer and a multi-stage amplification pumping source which are sequentially connected in the transmission direction, the first distributed feedback laser source is used for providing U-band signal light, the first gain optical fiber is a bismuth-germanium co-doped silica optical fiber, and the multi-stage amplification pumping source is used for providing C-band pumping light subjected to multi-stage amplification. The U-band fiber laser module provided by the invention adopts the backward pumping structure to amplify U-band signal light, the bismuth-germanium co-doped silica fiber can realize gain amplification of the U-band signal light, and the C-band pumping light subjected to multi-stage amplification and the backward pumping structure can further output U-band signal light with relatively high power. And finally, high-power and high-quality U-waveband continuous laser is output.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber laser technology, and in particular to a U-band optical fiber laser module. Background Art

[0002] With the large-scale deployment and large-scale application of 5G networks, global network data traffic is growing rapidly. The rise of technologies such as artificial intelligence, autonomous driving, the metaverse, and extended reality has put forward higher requirements on the data transmission capacity of existing fiber-optic communication networks, and they need to be upgraded to meet future challenges. At present, the fiber amplifiers used in fiber-optic communication networks are mainly erbium-doped quartz fiber amplifiers (EDFAs). However, their gain bandwidth only covers the conventional C-band and part of the L-band in the low-loss transmission band of quartz optical fiber, which seriously limits the further expansion of commercial communication bands. Making full use of communication bands other than the C-band and L-band is an effective way to increase the communication capacity of fiber-optic networks, such as the U-band. Therefore, it is of great significance to develop fiber laser modules that can work in the U-band.

[0003] Therefore, there is an urgent need for a U-band fiber laser module to solve the above technical problems. Summary of the invention

[0004] The object of the present invention is to provide a U-band fiber laser module for improving the technical problem that it is difficult to amplify U-band laser in the prior art.

[0005] In order to solve the above technical problems, the present invention provides a U-band fiber laser module, comprising a first distributed feedback laser source and a backward pumping structure connected in sequence along the transmission direction from a signal input end to a signal output end, wherein the backward pumping structure comprises a first gain fiber, a first wavelength division multiplexer and a multi-stage amplification pump source connected in sequence along the transmission direction; The first distributed feedback laser source is used to provide U-band signal light, the first gain fiber is bismuth-germanium co-doped quartz fiber, and the multi-stage amplification pump source is used to provide C-band pump light after multi-stage amplification.

[0006] Preferably, the molar fraction of GeO2 in the first gain fiber is 20% to 45%.

[0007] Preferably, the length of the first gain optical fiber is 200-300 m.

[0008] Preferably, the backward pumping structure comprises a first isolator, an input end of the first isolator is connected to a first distributed feedback laser source, and an output end of the first isolator is fused to a first end of a first gain optical fiber.

[0009] Preferably, the Pass end of the first wavelength division multiplexer is connected to the multi-stage amplification pump source, and the Common end of the first wavelength division multiplexer is fused to the second end of the first gain optical fiber.

[0010] Preferably, the U-band fiber laser module further includes a fiber Bragg grating and a second isolator, the Reflect end of the first wavelength division multiplexer is connected to the input end of the fiber Bragg grating, and the output end of the fiber Bragg grating is connected to the second isolator.

[0011] Preferably, the multi-stage amplification pump source includes a second distributed feedback laser source, a first forward pumping structure and a second forward pumping structure, the input end of the first forward pumping structure is connected to the second distributed feedback laser source, the output end of the first forward pumping structure is connected to the input end of the second forward pumping structure, and the output end of the second forward pumping structure is connected to the Pass end of the first wavelength division multiplexer.

[0012] Preferably, the first forward pumping structure comprises a third isolator, a first pump source, a second wavelength division multiplexer and a second gain fiber; Among them, the input end of the third isolator is connected to the second distributed feedback laser source, and the output end of the third isolator is connected to the Reflect end of the second wavelength division multiplexer; the Pass end of the second wavelength division multiplexer is connected to the first pump source, and the Common end of the second wavelength division multiplexer is fused with the first end of the second gain optical fiber.

[0013] Preferably, the second forward pumping structure comprises a fourth isolator, a second pump source, a beam combiner, a third gain fiber and a fifth isolator; Among them, the input end of the fourth isolator is fused with the second end of the second gain fiber, and the output end of the fourth isolator is connected to the first input end of the combiner; the second input end of the combiner is connected to the second pump source, and the output end of the combiner is fused with the first end of the third gain fiber; the second end of the third gain fiber is fused with the input end of the fifth isolator; and the output end of the fifth isolator is connected to the Pass end of the first wavelength division multiplexer.

[0014] Preferably, the second gain fiber is an erbium-doped silica fiber, and the third gain fiber is an erbium-ytterbium co-doped silica fiber.

[0015] The beneficial effects of the present invention are as follows: Different from the prior art, the present invention provides a U-band fiber laser module, comprising a first distributed feedback laser source and a backward pumping structure connected in sequence along the transmission direction from the signal input end to the signal output end, the backward pumping structure comprising a first gain fiber, a first wavelength division multiplexer and a multi-stage amplification pumping source connected in sequence along the transmission direction, wherein the first distributed feedback laser source is used to provide U-band signal light, the first gain fiber is a bismuth-germanium co-doped quartz fiber, and the multi-stage amplification pumping source is used to provide C-band pumping light amplified by multiple stages. The U-band fiber laser module provided by the present invention adopts a backward pumping structure in which bismuth-germanium co-doped quartz fiber is a gain fiber and multi-stage amplified C-band pumping light is a pumping source to amplify the U-band signal light, the bismuth-germanium co-doped quartz fiber can achieve gain amplification of the U-band signal light, the multi-stage amplified C-band pumping light and the backward pumping structure can further output a higher-power U-band signal light, and finally output a high-power, high-quality U-band continuous laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of the connection of a U-band fiber laser module provided in an embodiment of the present invention; Figure 2 Output spectrum diagram of the U-band fiber laser module provided in Example 1 of the present invention; Figure 3 The output slope efficiency diagram of the U-band fiber laser module provided in Example 1 of the present invention; In the figure: 1000-U band fiber laser module; 101-first distributed feedback laser source; 102-first isolator; 103-first gain fiber; 104-first wavelength division multiplexer; 105-fiber Bragg grating; 106-second isolator; 200-backward pumping structure; 20-multi-stage amplification pump source; 21-first forward pumping structure; 22-second forward pumping structure; 201-second distributed feedback laser source; 202-third isolator; 203-first pumping source; 204-second wavelength division multiplexer; 205-second gain fiber; 206-fourth isolator; 207-second pumping source; 208-combiner; 209-third gain fiber; 210-fifth isolator. DETAILED DESCRIPTION

[0017] The following will be combined with 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] The purpose of the present invention is to provide a U-band fiber laser module 1000 to address the defects of the prior art, which can output high-power, high-quality U-band continuous laser.

[0019] See also Figure 1 , Figure 1 A connection diagram of a U-band fiber laser module 1000 provided in an embodiment of the present invention; the present invention provides a U-band fiber laser module 1000, comprising a first distributed feedback laser source 101 and a backward pumping structure 200 connected in sequence along a transmission direction from a signal input end to a signal output end, the backward pumping structure 200 comprising a first gain fiber 103, a first wavelength division multiplexer 104 and a multi-stage amplification pump source 20 connected in sequence along the transmission direction; The first distributed feedback laser source 101 is used to provide U-band signal light, the first gain fiber 103 is bismuth-germanium co-doped quartz fiber, and the multi-stage amplified pump source 20 is used to provide multi-stage amplified C-band pump light to the backward pump structure 200 .

[0020] In the embodiment of the present invention, the grating pitch of the first distributed feedback laser source 101 is very small, forming a micro-resonant cavity with good wavelength selectivity, so that the threshold gain of the main mode and the side mode is relatively large, thereby obtaining a line width much narrower than that of a Fabry-Perot (FP) cavity laser module and maintaining dynamic single longitudinal mode output.

[0021] Specifically, the first distributed feedback laser source 101 (Distributed Feedback Laser, DFB) is used to provide U-band signal light; preferably, the first distributed feedback laser source 101 is used to provide 1653nm signal light.

[0022] In the embodiment of the present invention, the backward pumping structure 200 transmits the C-band (1530-1565nm) pump light and the U-band (1625-1675nm) signal light in the reverse direction after multi-stage amplification, so that the C-band pump light can continue to provide energy to the U-band signal light while the U-band signal light is gradually weakened. This can more effectively excite the particles in the first gain fiber 103, improve the energy transfer efficiency, and thus enhance the amplification effect of the U-band signal light.

[0023] At the same time, the reverse transmission of C-band pump light and U-band signal light reduces the accumulation of noise such as spontaneous radiation in the transmission direction of U-band signal light. This makes the backward pumping structure 200 have obvious advantages in reducing amplifier noise and can improve the signal-to-noise ratio of the output signal.

[0024] In addition, in the backward pumping structure 200, the pump light is injected from the output end, so that the temperature of the input end is relatively low, which helps to reduce the impact of temperature changes on the performance of the optical fiber and improve the temperature stability of the system.

[0025] In the embodiment of the present invention, the backward pumping structure 200 includes a first isolator 102 , the input end of the first isolator 102 is connected to the first distributed feedback laser source 101 , and the output end of the first isolator 102 is fused to the first end of the first gain fiber 103 .

[0026] Specifically, an isolator (ISO) is a passive optical isolator device that only allows one-way light to pass through. Its working principle is based on the non-reciprocity of Faraday rotation. An isolator is a passive device that allows light to pass in one direction but prevents it from passing in the opposite direction. Its function is to limit the direction of light so that light can only be transmitted in one direction. The light reflected by the optical fiber echo can be well isolated by the isolator, improving the efficiency of light wave transmission.

[0027] Furthermore, the isolator is used to isolate the reverse light transmitted by the first gain optical fiber 103 .

[0028] In the embodiment of the present invention, the first gain fiber 103 is a bismuth-germanium co-doped silica fiber, and the molar fraction of GeO2 in the first gain fiber 103 is 20% to 45%; wherein, the doping of bismuth can give the fiber unique optical properties, such as broadband luminescence. Bismuth may form different types of luminescence centers in the optical fiber, interact with other elements, and affect the luminescence characteristics of the optical fiber. The introduction of germanium can change the refractive index of the optical fiber and improve the transmission performance of light.

[0029] Specifically, when the molar fraction of GeO2 is less than 20%, it is difficult for Ge-associated bismuth active centers (Ge-BACs) to appear in the germanium-bismuth co-doped quartz fiber, making it difficult for the germanium-bismuth co-doped quartz fiber to exhibit luminescence characteristics in the U band; when the molar fraction of GeO2 is higher than 45%, the high content of GeO2 may cause the optical fiber to absorb and scatter more light of a specific wavelength, which will reduce the transmission efficiency of the optical fiber and reduce the intensity of the optical signal.

[0030] Specifically, the length of the first gain optical fiber 103 is 200-300 m; the first gain optical fiber 103 of 200-300 m can compensate for the loss of the signal during the transmission process, ensuring that the signal still maintains sufficient strength after long-distance transmission.

[0031] In the embodiment of the present invention, the U-band fiber laser module 1000 also includes a first wavelength division multiplexer 104 and a fiber Bragg grating 105. The Pass end (transmission end) of the first wavelength division multiplexer 104 is connected to the multi-stage amplification pump source 20, the Common end (common end) of the first wavelength division multiplexer 104 is fused with the second end of the first gain fiber 103, and the Reflect end (reflection end) of the first wavelength division multiplexer 104 is connected to the input end of the fiber Bragg grating 105.

[0032] Specifically, the first wavelength division multiplexer 104 is a reflective wavelength division multiplexer (R-WDM for short), which is a device used in optical communication systems. Its main principle is to use reflection and diffraction phenomena to achieve multiplexing and demultiplexing of optical signals of different wavelengths. A reflective wavelength division multiplexer is usually composed of one or more gratings, reflectors or other optical elements. When optical signals of different wavelengths are incident on the reflective wavelength division multiplexer, they will be reflected and diffracted inside the device, so that optical signals of different wavelengths are separated or multiplexed; in an embodiment of the present invention, the first wavelength division multiplexer 104 is used to couple the multi-stage amplified C-band pump light and 1653nm signal light into the first gain fiber 103, and output the coupled light after filtering through the fiber Bragg grating 105.

[0033] Specifically, the fiber Bragg grating 105 has a high reflectivity (greater than 90%), can filter out the remaining C-band pump light reflected by the optical path, and output the U-band signal light after gain.

[0034] In the embodiment of the present invention, the U-band fiber laser module 1000 further includes a second isolator 106 , the output end of the fiber Bragg grating 105 of the first wavelength division multiplexer 104 is connected to the second isolator 106 , and the second isolator 106 is used to isolate the reverse light.

[0035] In the embodiment of the present invention, the multi-stage amplification pump source 20 includes a second distributed feedback laser source 201, a first forward pumping structure 21 and a second forward pumping structure 22, the input end of the first forward pumping structure 21 is connected to the second distributed feedback laser source 201, the output end of the first forward pumping structure 21 is connected to the input end of the second forward pumping structure 22, and the output end of the second forward pumping structure 22 is connected to the Pass end of the first wavelength division multiplexer 104.

[0036] Specifically, the first forward pumping structure 21 and the second forward pumping structure 22 belong to the forward pumping structure, which connects the pumping fiber to the inlet end of the signal fiber so that the pumping light is transmitted along the propagation direction of the signal light. The pumping light is reflected multiple times in the optical fiber, and a large number of erbium-doped ions are cumulatively excited, thereby realizing the amplification of the signal light. The advantages of the forward pumping structure are simple structure and low noise index, and the disadvantage is low output power, which is suitable for pre-amplification of the signal source.

[0037] In the embodiment of the present invention, the second distributed feedback laser source 201 is used to provide C-band signal light; preferably, the first distributed feedback laser source 101 is used to provide 1550 nm signal light.

[0038] In the embodiment of the present invention, the first forward pump structure 21 includes a third isolator 202, a first pump source 203, a second wavelength division multiplexer 204 and a second gain fiber 205; Among them, the input end of the third isolator 202 is connected to the second distributed feedback laser source 201, and the output end of the third isolator 202 is connected to the Reflect end of the second wavelength division multiplexer 204; the Pass end of the second wavelength division multiplexer 204 is connected to the first pump source 203, and the Common end of the second wavelength division multiplexer 204 is fused with the first end of the second gain fiber 205.

[0039] Specifically, the third isolator 202 is used to isolate the reverse light reflected by the second wavelength division multiplexer 204; the second wavelength division multiplexer 204 is used to couple the 1550nm signal light and the first pump light emitted by the first pump source 203 into the second gain fiber 205 to achieve the first gain amplification of the 1550nm signal light.

[0040] Specifically, the first pump source 203 is used to provide a first pump light; preferably, the first pump source 203 is used to provide a 980 nm pump light.

[0041] Specifically, the second gain fiber 205 is an erbium-doped quartz fiber, which serves as a gain medium. When light is incident on the erbium-doped quartz fiber, the electrons of the erbium element are excited to a high energy level, and the erbium element is in an excited state. When the signal light passes through the erbium-doped quartz fiber, the excited erbium element emits photons to the signal light, and stimulated radiation occurs, thereby increasing the energy of the signal light and amplifying the signal light.

[0042] In the embodiment of the present invention, the second forward pump structure 22 includes a fourth isolator 206, a second pump source 207, a combiner 208, a third gain fiber 209 and a fifth isolator 210; Among them, the input end of the fourth isolator 206 is fused with the second end of the second gain fiber 205, and the output end of the fourth isolator 206 is connected to the first input end of the combiner 208; the second input end of the combiner 208 is connected to the second pump source 207, and the output end of the combiner 208 is fused with the first end of the third gain fiber 209; the second end of the third gain fiber 209 is fused with the input end of the fifth isolator 210; the output end of the fifth isolator 210 is connected to the Pass end of the first wavelength division multiplexer 104.

[0043] Specifically, the fourth isolator 206 is used to isolate the reverse light reflected by the combiner 208; the second pump source 207 is used to provide the second pump light; preferably, the second pump source 207 is used to provide 940nm pump light; the fifth isolator 210 is used to isolate the reverse light reflected by the first wavelength division multiplexer 104.

[0044] Specifically, the beam combiner 208 is usually composed of multiple input ends and an output end. The input end is used to receive different light beams, and the output end outputs the combined light beam; wherein the beam combiner 208 is used to couple the 1550nm signal light after the first amplification and the 940nm pump light emitted by the second pump source 207 into the third gain fiber 209 to achieve the second gain amplification of the 1550nm signal light.

[0045] Specifically, the third gain fiber 209 is an erbium-ytterbium co-doped silica fiber; the erbium-ytterbium co-doped silica fiber has a unique absorption and emission spectrum within a specific wavelength range. Ytterbium ions strongly absorb pump light with a wavelength near 940nm, and then transfer energy to erbium ions, which emit light at a wavelength near 1550nm.

[0046] The technical solution of the present invention is now described in conjunction with specific embodiments.

[0047] Embodiment 1: Embodiment 1 of the present invention provides a U-band fiber laser module 1000, comprising a first distributed feedback laser source 101 and a backward pumping structure 200 connected in sequence along the transmission direction from a signal input end to a signal output end, and the backward pumping structure 200 comprises a first isolator 102, a first gain fiber 103, a first wavelength division multiplexer 104 and a multi-stage amplification pump source 20 connected in sequence along the transmission direction.

[0048] Specifically, the first distributed feedback laser source 101 is used to provide 1653 nm signal light.

[0049] Specifically, the first gain fiber 103 is a 4 / 125 bismuth-germanium co-doped quartz fiber (core diameter is 4 μm, cladding diameter is 125 μm), the molar fraction of GeO2 in the first gain fiber 103 is 42%, and the mass fraction of bismuth ions in the first gain fiber 103 is 0.02%; the length of the first gain fiber 103 is 250 m.

[0050] In Embodiment 1 of the present invention, the U-band fiber laser module 1000 further includes a first wavelength division multiplexer 104 and a fiber Bragg grating 105 , and the reflectivity of the fiber Bragg grating 105 is 95%.

[0051] In Embodiment 1 of the present invention, the U-band fiber laser module 1000 further includes a second isolator 106 , the output end of the fiber Bragg grating 105 of the first wavelength division multiplexer 104 is connected to the second isolator 106 , and the second isolator 106 is used to isolate the reverse light.

[0052] In Embodiment 1 of the present invention, the multi-stage amplification pump source 20 includes a second distributed feedback laser source 201, a first forward pumping structure 21 and a second forward pumping structure 22, the input end of the first forward pumping structure 21 is connected to the second distributed feedback laser source 201, the output end of the first forward pumping structure 21 is connected to the input end of the second forward pumping structure 22, and the output end of the second forward pumping structure 22 is connected to the Pass end of the first wavelength division multiplexer 104.

[0053] In Embodiment 1 of the present invention, the second distributed feedback laser source 201 is used to provide 1550 nm signal light.

[0054] In Embodiment 1 of the present invention, the first forward pumping structure 21 includes a third isolator 202, a first pump source 203, a second wavelength division multiplexer 204 and a second gain fiber 205; Among them, the input end of the third isolator 202 is connected to the second distributed feedback laser source 201, and the output end of the third isolator 202 is connected to the Reflect end of the second wavelength division multiplexer 204; the Pass end of the second wavelength division multiplexer 204 is connected to the first pump source 203, and the Common end of the second wavelength division multiplexer 204 is fused with the first end of the second gain fiber 205.

[0055] Specifically, the first pump source 203 is used to provide 980 nm pump light; the second gain fiber 205 is a 6 / 125 erbium-doped co-doped silica fiber (core diameter is 6 μm, cladding diameter is 125 μm), and the length is 5 m.

[0056] In Embodiment 1 of the present invention, the second forward pumping structure 22 includes a fourth isolator 206, a second pump source 207, a beam combiner 208, a third gain fiber 209 and a fifth isolator 210; Among them, the input end of the fourth isolator 206 is fused with the second end of the second gain fiber 205, and the output end of the fourth isolator 206 is connected to the first input end of the combiner 208; the second input end of the combiner 208 is connected to the second pump source 207, and the output end of the combiner 208 is fused with the first end of the third gain fiber 209; the second end of the third gain fiber 209 is fused with the input end of the fifth isolator 210; the output end of the fifth isolator 210 is connected to the Pass end of the first wavelength division multiplexer 104.

[0057] Specifically, the second pump source 207 is used to provide 940 nm pump light; the third gain fiber 209 is a 6 / 125 Erbium-Ytterbium co-doped silica fiber (core diameter is 6 μm, cladding diameter is 125 μm), and the length is 5 m.

[0058] See also Figure 2 , Figure 2The output spectrum diagram of the U-band fiber laser module 1000 provided in Example 1 of the present invention; Figure 2 It can be seen that when the second distributed feedback laser source 201 provides 3.5W of 1550nm signal light, the U-band fiber laser module 1000 provided in Example 1 of the present invention can output higher power (450mW) 1650nm signal light; this shows that the U-band fiber laser module 1000 provided in Example 1 of the present invention can output high-power, high-quality U-band continuous laser.

[0059] See also Figure 3 , Figure 3 The output slope efficiency diagram of the U-band fiber laser module 1000 provided in Example 1 of the present invention; wherein, Figure 3 It can be seen that the horizontal axis x is the input pump power, the vertical axis y is the output optical power, and the relationship between y and x satisfies the following formula: y=0.1274x-22.892. From the above formula, it can be obtained that the output slope efficiency of the U-band fiber laser module 1000 provided in Example 1 of the present invention is 12%. Higher output slope efficiency means that the U-band fiber laser module 1000 provided in Example 1 of the present invention can convert the input pump energy into output optical energy more efficiently. This makes it possible to obtain a higher output optical power under the same pump power, thereby improving the energy utilization rate.

[0060] The present invention discloses a U-band fiber laser module 1000, which is mainly implemented by using independently developed and prepared bismuth-germanium co-doped quartz fiber as a gain medium, utilizing its amplification characteristics in the U-band, and adopting an all-fiber amplifier structure to achieve 1653nm high-power continuous laser output.

[0061] The present invention adopts a master oscillator power amplifier (MOPA) structure, uses a self-built 1550nm pump light source (i.e., a multi-stage amplification pump source 20), and is implemented in a two-stage amplification structure. The first stage adopts an erbium-doped quartz fiber amplification structure, and the second stage adopts an erbium-ytterbium co-doped quartz fiber amplification structure. Together with the 1653nm DFB signal light, it is input into the bismuth-germanium co-doped quartz fiber through the first wavelength division multiplexer 104 to amplify the signal light, and finally outputs a high-power, high-quality 1653nm continuous laser.

[0062] In summary, different from the prior art, the present invention provides a U-band fiber laser module 1000, comprising a first distributed feedback laser source 101 and a backward pumping structure 200 connected in sequence along the transmission direction from the signal input end to the signal output end, the backward pumping structure 200 comprises a first gain fiber 103, a first wavelength division multiplexer 104 and a multi-stage amplification pump source 20 connected in sequence along the transmission direction, wherein the first distributed feedback laser source 101 is used to provide U-band signal light, the first gain fiber 103 is a bismuth-germanium co-doped quartz fiber, and the multi-stage amplification pump source 20 is used to provide C-band pump light after multi-stage amplification. The U-band fiber laser module 1000 provided by the present invention adopts a bismuth-germanium co-doped quartz fiber as a gain fiber and a backward pumping structure 200 with multi-stage amplified C-band pump light as a pump source to amplify the U-band signal light. The bismuth-germanium co-doped quartz fiber can achieve gain amplification of the U-band signal light. The multi-stage amplified C-band pump light and the backward pumping structure 200 can further output higher-power U-band signal light, and finally output high-power, high-quality U-band continuous laser.

[0063] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For matters that are not described in detail in some embodiments, reference may be made to the description in other embodiments.

[0064] The above embodiments only express the implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A U-band fiber laser module, characterized in that: It includes a first distributed feedback laser source and a backward pumping structure connected in sequence along the transmission direction from the signal input end to the signal output end, and the backward pumping structure includes a first gain optical fiber, a first wavelength division multiplexer and a multi-stage amplification pump source connected in sequence along the transmission direction; The first distributed feedback laser source is used to provide U-band signal light, the first gain fiber is bismuth-germanium co-doped quartz fiber, and the multi-stage amplification pump source is used to provide C-band pump light after multi-stage amplification.

2. The U-band fiber laser module according to claim 1, characterized in that: The molar fraction of GeO2 in the first gain optical fiber is 20% to 45%.

3. The U-band fiber laser module according to claim 1, characterized in that: The length of the first gain optical fiber is 200-300 m.

4. The U-band fiber laser module according to claim 1, characterized in that: The backward pumping structure includes a first isolator, an input end of the first isolator is connected to the first distributed feedback laser source, and an output end of the first isolator is fused to a first end of the first gain optical fiber.

5. The U-band fiber laser module according to claim 4, characterized in that: The Pass end of the first wavelength division multiplexer is connected to the multi-stage amplification pump source, and the Common end of the first wavelength division multiplexer is fused to the second end of the first gain optical fiber.

6. The U-band fiber laser module according to claim 5, characterized in that: The U-band fiber laser module also includes a fiber Bragg grating and a second isolator. The Reflect end of the first wavelength division multiplexer is connected to the input end of the fiber Bragg grating, and the output end of the fiber Bragg grating is connected to the second isolator.

7. The U-band fiber laser module according to claim 1, characterized in that: The multi-stage amplification pump source includes a second distributed feedback laser source, a first forward pumping structure and a second forward pumping structure, the input end of the first forward pumping structure is connected to the second distributed feedback laser source, the output end of the first forward pumping structure is connected to the input end of the second forward pumping structure, and the output end of the second forward pumping structure is connected to the Pass end of the first wavelength division multiplexer.

8. The U-band fiber laser module according to claim 7, characterized in that: The first forward pumping structure includes a third isolator, a first pump source, a second wavelength division multiplexer and a second gain fiber; Among them, the input end of the third isolator is connected to the second distributed feedback laser source, and the output end of the third isolator is connected to the Reflect end of the second wavelength division multiplexer; the Pass end of the second wavelength division multiplexer is connected to the first pump source, and the Common end of the second wavelength division multiplexer is fused with the first end of the second gain fiber.

9. The U-band fiber laser module according to claim 8, characterized in that: The second forward pumping structure includes a fourth isolator, a second pump source, a beam combiner, a third gain fiber and a fifth isolator; The input end of the fourth isolator is fused with the second end of the second gain fiber, and the output end of the fourth isolator is connected to the first input end of the combiner; the second input end of the combiner is connected to the second pump source, and the output end of the combiner is fused with the first end of the third gain fiber; the second end of the third gain fiber is fused with the input end of the fifth isolator; and the output end of the fifth isolator is connected to the Pass end of the first wavelength division multiplexer.

10. The U-band fiber laser module according to claim 9, characterized in that: The second gain fiber is an erbium-doped silica fiber, and the third gain fiber is an erbium-ytterbium co-doped silica fiber.

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