Optical fiber device for laser recovery, preparation method thereof and optical fiber laser module

Abstract

According to the optical fiber device for laser recovery, the preparation method thereof and the optical fiber laser module provided by the invention, the second output part, the plurality of multimode optical fiber arms and the quartz tube are subjected to a melting process to form the optical fiber bundle, and return light firstly passes through the quartz end cap and then enters the optical fiber bundle; the return light entering the plurality of multimode fiber arms at the periphery is transmitted along a loop formed by the bending part and then enters the quartz end cap in a forward transmission direction, and the return light entering the second output part is coupled with a second fiber core layer in the multimode fiber arms with high refractive index at the periphery in the transmission process; and after being transmitted along a loop formed by the bending part, the laser enters the quartz end cap in the forward transmission direction and then becomes forward transmission laser. Therefore, the energy of the return light entering the optical fiber laser module again is greatly reduced, the damage of the return light to a front-end device in the optical fiber laser module is further reduced, and the energy utilization rate of the optical fiber laser module is finally improved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber laser modules, and in particular to an optical fiber device for laser recovery and a preparation method thereof, and an optical fiber laser module. Background Art

[0002] Fiber laser modules are widely used in industrial processing, military defense and other fields due to their excellent beam quality, high conversion efficiency and high compactness. Fiber laser modules are usually composed of optical fibers and various fiber optic devices that match them. Its output end is often formed by welding a section of passive optical fiber with a quartz end cap coated with an anti-reflection film on the output end face, which is used to reduce the power density of the output laser at the output end face and suppress the end face return light generated by Fresnel reflection at the quartz-air interface. However, when the high-power laser emitted by the quartz end cap acts on metal and other objects, reflected light is often generated. This part of the reflected light reaches the quartz end cap after propagating through the air. Since the refractive index of the quartz end cap is higher than that of air, part of the reflected light returns to the fiber laser system through the quartz end cap, increasing the thermal burden of the fiber optic devices in the system, thereby increasing the risk of burning the entire system. Therefore, in order to prevent this part of the return light from causing adverse effects on the fiber optic devices at the front end of the system, or even worse, it is of great significance to reuse this part of the return light.

[0003] Therefore, there is an urgent need for an optical fiber device for laser recycling and a preparation method thereof, as well as an optical fiber laser module to solve the above-mentioned technical problems. Summary of the invention

[0004] The purpose of the present invention is to provide an optical fiber device for laser recovery and a preparation method thereof, and an optical fiber laser module, which are used to improve the technical problem of the laser module in the prior art that the risk of burning of the entire laser module is increased due to the return light.

[0005] In order to solve the above technical problems, the present invention provides an optical fiber device for laser recovery, comprising an output optical fiber, a plurality of large-core multimode optical fibers, a quartz tube and a quartz end cap, wherein the output optical fiber comprises a first output portion and a second output portion connected along the axial direction, the second output portion is arranged close to the quartz end cap, each large-core multimode optical fiber comprises a bending portion arranged corresponding to the first output portion and multimode optical fiber arms located at both ends of the bending portion, and the plurality of multimode optical fiber arms and the second output portion are completely sleeved in the quartz tube along the axial direction; The second output part, the multiple multimode optical fiber arms and the quartz tube are formed into an optical fiber bundle after a melting process; and one end of the optical fiber bundle away from the bending part is fused with the input end face of the quartz end cap.

[0006] Preferably, the output optical fiber is a passive optical fiber; the working band of the output signal optical fiber includes any one of the 1.0µm band, the 1.5µm band and the 2.0µm band; the output end face of the quartz end cap is coated with an anti-reflection film.

[0007] Preferably, the first output portion comprises a first core layer, a first cladding layer and a first coating layer which are sequentially arranged from the inside to the outside in the radial direction, and the second output portion comprises a first core layer and a first cladding layer which are sequentially arranged from the inside to the outside in the radial direction; The refractive index of the first core layer is n2, the refractive index of the first cladding layer is n1, and the refractive index of the quartz tube is n0. Then n0, n1 and n2 satisfy the following relationship: n0<n1<n2.

[0008] Preferably, the bending portion includes a second core layer, a second cladding layer and a second coating layer sequentially arranged from the inside to the outside in the radial direction, and the multimode optical fiber arm includes a second core layer and a second cladding layer sequentially arranged from the inside to the outside in the radial direction; The refractive index of the second core layer is n3, and the refractive index of the second cladding layer is n1, then n0, n1 and n3 satisfy the following relationship: n0<n1<n3.

[0009] Preferably, the material of the second core layer is germanium-doped silica, the material of the second cladding layer is silica, and the material of the quartz tube is fluorine-doped silica.

[0010] Preferably, in the optical fiber bundle: the second output portion is located at the center of the optical fiber bundle in the radial direction, and two multimode optical fiber arms of the same large-core multimode optical fiber are symmetrical about the second output portion.

[0011] Preferably, the inner wall diameter of the quartz tube is larger than the sum of the cladding diameters of the two multimode optical fiber arms and the above three in the second output part; the second output part is gap-matched with the adjacent multiple multimode optical fiber arms, and the multiple multimode optical fiber arms are gap-matched with the inner wall of the quartz tube.

[0012] Accordingly, the present invention also provides a method for preparing an optical fiber device for laser recycling as described above, the method comprising the following steps: S10, completely sleeve the second output portion and two multimode optical fiber arms corresponding to each large-core multimode optical fiber in the quartz tube along the axial direction; S20, melting the second output portion, the plurality of multimode optical fiber arms and the quartz tube to obtain an optical fiber bundle; S30, axially aligning one end of the optical fiber bundle away from the bending portion with the quartz end cap and fusing the end end face of the quartz end cap.

[0013] Preferably, before step S10, the method further includes: removing the second coating layer of the multimode optical fiber arm and the first coating layer of the second output portion respectively.

[0014] Correspondingly, the present invention further provides a fiber laser module, comprising any one of the fiber optic devices for laser recovery as described above, or, comprising an fiber optic device for laser recovery made by any one of the methods for preparing the fiber optic device for laser recovery as described above.

[0015] The beneficial effects of the present invention are as follows: Different from the prior art, the present invention provides an optical fiber device for laser recovery and a preparation method thereof, and an optical fiber laser module. The optical fiber device for laser recovery forms an optical fiber bundle by melting the second output part, multiple multimode optical fiber arms and a quartz tube. The return light first enters the optical fiber bundle after passing through the quartz end cap. The return light in the multiple multimode optical fiber arms in the periphery is transmitted along the loop composed of the bending part and enters the quartz end cap in the forward transmission direction. The return light entering the second output part will couple with the second fiber core layer in the multimode optical fiber arm with a high refractive index in the periphery during the transmission process, and then enter the quartz end cap in the forward transmission direction after being transmitted along the loop composed of the bending part and becoming a forward transmission laser. In this way, the energy of the return light re-entering the optical fiber laser module is greatly reduced, and it is recycled and reused, thereby reducing the harm of the return light to the front-end device in the optical fiber laser module, and finally improving the energy utilization rate of the optical fiber laser module. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a radial structural schematic diagram of an optical fiber device for laser recovery provided in Example 1 of the present invention; Figure 2 is a schematic diagram of the three-dimensional structure of an optical fiber device for laser recovery provided in Example 1 of the present invention; Figure 3 is an end view of the first output portion of the optical fiber device for laser recovery provided in Example 1 of the present invention; Figure 4 is an end view of an optical fiber bundle in an optical fiber device for laser recovery provided in Example 1 of the present invention; Figure 5 It is a schematic diagram of the radial structure of a quartz end cap in an optical fiber device for laser recovery provided in Example 1 of the present invention; Figure 6 is a flow chart of a method for preparing an optical fiber device for laser recovery provided in Example 1 of the present invention; In the attached drawings: 100 - optical fiber device for laser recovery; 10 - output optical fiber; 11 - first output part; 111 - first core layer; 112 - first cladding; 113 - first coating layer; 12 - second output part; 20 - large core multimode optical fiber; 21 - bending part; 22 - multimode optical fiber arm; 221 - second core layer; 222 - second cladding; 30 - optical fiber bundle; 31 - quartz tube; 40 - quartz end cap; 41 - input end face; 42 - output end face. 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 address the defects of the prior art and provide an optical fiber device 100 for laser recovery and a preparation method thereof, and an optical fiber laser module, which can reuse the return light generated by the above-mentioned optical fiber laser module at the quartz end cap 40 and reduce the risk of unstable operation of the optical fiber laser module.

[0019] The technical solution of the present invention is now described in conjunction with specific embodiments.

[0020] Embodiment 1: See also Figure 1 as well as Figure 2 , Figure 1 is a radial structural schematic diagram of an optical fiber device 100 for laser recovery provided in Embodiment 1 of the present invention; Figure 2 3D is a schematic diagram of the three-dimensional structure of an optical fiber device 100 for laser recovery provided in Example 1 of the present invention; specifically, the present invention provides an optical fiber device 100 for laser recovery, comprising an output optical fiber 10, a plurality of large-core multimode optical fibers 20, a quartz tube 31 and a quartz end cap 40, the output optical fiber 10 comprises a first output portion 11 and a second output portion 12 connected along the axial direction, the second output portion 12 is arranged close to the quartz end cap 40, each large-core multimode optical fiber 20 comprises a bending portion 21 arranged corresponding to the first output portion 11 and multimode optical fiber arms 22 located at both ends of the bending portion 21, and the plurality of multimode optical fiber arms 22 and the second output portion 12 are completely sleeved in the quartz tube 31 along the axial direction; The second output portion 12 , the multiple multimode optical fiber arms 22 and the quartz tube 31 are melted to form an optical fiber bundle 30 ; one end of the optical fiber bundle 30 away from the bending portion 21 is welded to the input end face 41 of the quartz end cap 40 .

[0021] In the present embodiment 1, the output optical fiber 10 is a passive optical fiber; the working band of the output signal optical fiber includes any one of the 1.0µm band, the 1.5µm band and the 2.0µm band.

[0022] See also Figure 3 , Figure 3It is an end view of the first output part 11 in the optical fiber device 100 for laser recovery provided in Example 1 of the present invention; in this Example 1, the first output part 11 includes a first core layer 111, a first cladding 112 and a first coating layer 113 arranged in sequence from the inside to the outside along the radial direction, and the second output part 12 includes a first core layer 111 and a first cladding 112 arranged in sequence from the inside to the outside along the radial direction; wherein, the refractive index of the first core layer 111 is n2, the refractive index of the first cladding 112 is n1, and the refractive index of the quartz tube 31 is n0, then n0, n1 and n2 satisfy the following relationship: n0<n1<n2.

[0023] Specifically, by removing the first coating layer 113 of the second output portion 12 , the second output portion 12 can more effectively interact with other optical fibers for optical signals, thereby reducing problems such as signal attenuation and low coupling efficiency caused by the presence of the first coating layer 113 .

[0024] Specifically, n1<n2 can cause total reflection of light at the interface between the first core layer 111 and the first cladding layer 112, thereby limiting the transmission of light within the first core layer 111; the refractive index relationship of n0<n1 can enable the quartz tube 31 to play a certain blocking role, further ensuring that light is effectively transmitted within the structure of the second output part 12, reducing light leakage, and thus improving the efficiency and stability of optical fiber transmission.

[0025] In the present embodiment 1, the diameter of the first core layer 111 is preferably 20 μm, and the diameter of the first cladding layer 112 is preferably 400 μm.

[0026] See also Figure 1 as well as Figure 4 , Figure 4 It is an end view of the optical fiber bundle 30 in the optical fiber device 100 for laser recovery provided in Example 1 of the present invention; wherein, the second output part 12, the multiple multi-mode optical fiber arms 22 and the quartz tube 31 form the optical fiber bundle 30 after a melting process.

[0027] In this embodiment 1, each large-core multimode optical fiber 20 includes a bending portion 21 corresponding to the first output portion 11 and multimode optical fiber arms 22 located at both ends of the bending portion 21. The multiple multimode optical fiber arms 22 and the second output portion 12 are completely axially arranged in the quartz tube 31.

[0028] Specifically, the bending portion 21 includes a second core layer 221, a second cladding 222 and a second coating layer which are arranged in sequence from the inside to the outside along the radial direction, and the multimode optical fiber arm 22 includes a second core layer 221 and a second cladding 222 which are arranged in sequence from the inside to the outside along the radial direction; wherein, the refractive index of the second core layer 221 is n3, and the refractive index of the second cladding 222 is n1, then n0, n1 and n3 satisfy the following relationship: n0<n1<n3.

[0029] Specifically, the bending portion 21 is designed to be an arc shape, which can facilitate the return light entering the peripheral multiple multi-mode optical fiber arms 22 to be transmitted along the loop formed by the bending portion 21 and then enter the quartz end cap 40 in the forward transmission direction.

[0030] In this embodiment 1, the material of the second core layer 221 is germanium-doped silica, and the material of the second cladding 222 is silica; the diameter of the second core layer 221 is 220 μm, and the diameter of the second cladding 222 is 242 μm, or the diameter of the second core layer 221 is 200 μm, and the diameter of the second cladding 222 is 220 μm.

[0031] In the first embodiment, in the optical fiber bundle 30 , the second output portion 12 is located at the center of the optical fiber bundle 30 in the radial direction, and the two multimode optical fiber arms 22 of the same large-core multimode optical fiber 20 are symmetrical about the second output portion 12 .

[0032] Specifically, from the perspective of light field distribution, the return light can form a relatively uniform light field around the second output portion 12. If the two multimode fiber arms 22 are asymmetrical, the intensity of the return light on one side may be much higher than that on the other side, resulting in a significant imbalance in the light field around the second output portion 12, which is not conducive to the processing of optical signals and the stability of the entire system. At the same time, this symmetrical setting also plays a balancing role. When the pump light provides energy to the gain medium to amplify the signal light, the uniform light field distribution can ensure that the gain medium at each position can absorb the return light energy in a relatively balanced manner, avoiding the occurrence of local energy excess or deficiency.

[0033] In the present embodiment 1, the inner wall diameter of the quartz tube 31 is larger than the sum of the cladding diameters of the two multimode optical fiber arms 22 and the second output portion 12 .

[0034] Specifically, this size design provides necessary space margin for placing the second output part 12 and the multimode optical fiber arm 22 in the quartz tube 31. It ensures that the second output part 12 and the multimode optical fiber arm 22 can be smoothly installed in the quartz tube 3140, avoiding the difficulty of installing the second output part 12 and the multimode optical fiber arm 22 due to too narrow space, and even the possibility of squeezing and damaging the second output part 12 and the multimode optical fiber arm 22, thereby affecting the performance of the second output part 12 and the multimode optical fiber arm 22 and the subsequent light transmission.

[0035] In the present embodiment 1, the second output portion 12 is gap-matched with the adjacent plurality of multi-mode optical fiber arms 22 , and the plurality of multi-mode optical fiber arms 22 are gap-matched with the inner wall of the quartz tube 31 .

[0036] Specifically, the second output portion 12 is gap-matched with the adjacent plurality of multimode optical fiber arms 22, which means that there is a certain small gap between them, rather than being tightly fitted together. From an optical point of view, the existence of the gap is conducive to reducing the optical interference that may be caused by direct contact between optical fibers.

[0037] Specifically, the plurality of multimode optical fiber arms 22 are matched with the inner wall gap of the quartz tube 31, which facilitates the installation and positioning of the multimode optical fiber arms 22 in the quartz tube 31, so that the multimode optical fiber arms 22 can be easily passed through the quartz tube 31 along the axial direction and be in a suitable position, thereby avoiding damage to the multimode optical fiber arms 22 due to interference fit (i.e., the outer diameter of the multimode optical fiber arm 22 is almost equal to or even slightly larger than the inner diameter of the quartz tube 31, and it needs to be forcibly squeezed into it during installation), thereby ensuring that the structural integrity of the multimode optical fiber arm 22 and its function of transmitting pump light are not affected.

[0038] See also Figure 5 , Figure 5 It is a schematic diagram of the radial structure of the quartz end cap 40 in the optical fiber device 100 for laser recovery provided in Example 1 of the present invention; wherein the quartz end cap 40 is a quartz cylinder with a uniformly distributed refractive index and a cone angle, and the size of its input end face 41 matches the optical fiber bundle 30 and is fused with the optical fiber bundle 30.

[0039] Specifically, the input end face 41 of the quartz end cap 40 is a non-coated surface, and the output end face 42 of the quartz end cap 40 is coated with an anti-reflection film.

[0040] Accordingly, see Figure 6 Embodiment 1 of the present invention further provides a method for preparing an optical fiber device 100 for laser recycling as described above, the method comprising the following steps: S10, completely sleeve the second output portion 12 and the two multimode optical fiber arms 22 corresponding to each large-core multimode optical fiber 20 in the quartz tube 31 along the axial direction; Specifically, step S10 also includes: See also Figure 1 , Figure 2 as well as Figure 4 , the second output portion 12 obtained by removing the first coating layer 113 from the first output optical fiber 10 is inserted into the center of the quartz tube 31; at the same time, the multimode optical fiber arms 22 at both ends of N large-core multimode optical fibers 20 (N≥1) are removed from the second coating layer and inserted into the quartz tube 31, so that multiple multimode optical fiber arms 22 are arranged around the second output portion 12. Among them, 4 large-core multimode optical fibers 20 are selected in this embodiment 1.

[0041] S20 , melting the second output portion 12 , the plurality of multimode optical fiber arms 22 , and the quartz tube 31 to obtain an optical fiber bundle 30 .

[0042] Specifically, step S20 also includes: See also Figure 1 , Figure 2 as well as Figure 4 The second output part 12, the multiple multimode optical fiber arms 22 and the quartz tube 31 are melted to obtain the optical fiber bundle 30; the melting method for the optical fiber bundle 30 includes but is not limited to hydrogen-oxygen flame melting, graphite melting, laser melting and electrode melting.

[0043] Specifically, the melting process is to change the structure of the optical fiber to optimize the transmission and coupling of light in the optical fiber. The optical fiber is softened by heating and then formed into an optical fiber bundle 30. This process can adjust the diameter, refractive index distribution, and light field mode of the optical fiber. At the same time, the melting of multiple multimode optical fiber arms 22, the second output part 12, and the quartz tube 31 together can make their structures change synchronously, thereby forming an integral environment that is conducive to light interaction in the optical fiber bundle 30. The quartz tube 31 can stabilize the optical fiber structure during the melting process, and the change in its own shape also helps to optimize the light field distribution.

[0044] In practical applications, after the optical fiber bundle 30 is arranged into a specified shape, it is necessary to heat the optical fibers in the optical fiber bundle 30 at a high temperature so that each part of the optical fibers is in a molten state. At the same time, one end is sealed with a low-refractive index glue and then a vacuum pump is used to evacuate the other end so that the air in the quartz tube 31 is extracted. When each part of the optical fiber is melted and tightly attached, the air gap between the optical fibers is reduced, making the arrangement of the optical fiber bundle 30 more compact.

[0045] S30 , axially aligning one end of the optical fiber bundle 30 away from the bending portion 21 with the quartz end cap 40 and fusing the end end face 41 of the quartz end cap 40 .

[0046] See also Figure 1 as well as Figure 5 , one end of the optical fiber bundle 30 away from the bending portion 21 is axially opposite to the quartz end cap 40 and is fused to the input end face 41 of the quartz end cap 40 .

[0047] In the present embodiment 1, the first output portion 11 and the optical fiber bundle 30, the optical fiber bundle 30 and the quartz end cap 40, and the large-core multimode optical fiber 20 in the optical fiber bundle 30 are all connected by thermal melting.

[0048] Correspondingly, the present invention further provides a fiber laser module, comprising an optical fiber device 100 for laser recovery as described in any one of the above items, or an optical fiber device 100 for laser recovery made by the preparation method of an optical fiber device 100 for laser recovery as described in any one of the above items.

[0049] Specifically, the specific process of the method for preparing the optical fiber device 100 for laser recycling provided in this embodiment 1 is as follows: When the laser light transmitted forward in the optical fiber passes through the first output part 11, the second output part 12 and the quartz end cap 40 in sequence, it acts on the object; when the incident angle of the laser light relative to the object is small, the laser light will be reflected at the interface between the object and the air, and a part of the reflected light will re-enter the optical fiber laser module through the quartz end cap 40. After being uniformly transmitted through the quartz end cap 40, this part of the returned light enters the regularly arranged optical fiber bundle 30. At this time, this part of the returned light can be divided into two parts. One part is the returned light that enters the large-core multimode optical fiber 20 (multimode optical fiber arm 22) located on the periphery. This part of the returned light is transmitted along the large-core multimode optical fiber 20. Since the core part of the large-core multimode optical fiber 20 has a large area and a high refractive index, this part of the returned light is gradually coupled into the second core layer 221 of the multimode optical fiber arm 22 as the transmission distance increases, and continues to be transmitted along the second core layer 221, and then becomes a forward-transmitting laser through the loop of the bending portion 21, and finally output through the quartz end cap 40; the other part is the returned light that enters the large-core multimode optical fiber 20 (multimode optical fiber arm 22). As for the return light entering the second output part 12 located at the center of the optical fiber bundle 30, since the core area of ​​the second output part 12 accounts for a small proportion, most of the energy in this part of the return light (experiments have shown that this proportion is about 97%) is still transmitted in its first cladding 112. Since the refractive index of its first cladding 112 is the same as the refractive index of the second cladding 222 of the large-core multimode optical fiber 20 located around it, this part of the return light will gradually couple into the large-core multimode optical fiber 20 during the transmission process, and become a forward-transmitting laser along the loop formed by the bending part 21 in the large-core multimode optical fiber 20. In this way, the energy of the return light re-entering the optical fiber laser system is greatly reduced, and it is recycled, reducing the harm of the return light to the front-end optical fiber laser system and improving energy utilization.

[0050] In the optical fiber device 100 for laser recovery provided in Embodiment 1 of the present invention, after the return light enters the quartz end cap 40, it enters the optical fiber bundle 30 after several reflections; most of the return light enters the multimode optical fiber arm 22 of the large-core multimode optical fiber 20, and is transmitted in its second core layer 221, and after passing through the bending portion 21 with a loop in the large-core multimode optical fiber 20 connected thereto, it becomes a cladding laser propagating in the forward direction, and finally outputs through the quartz end cap 40. Through this method, while greatly reducing the return light power, this part of the return light can be reused as output laser.

[0051] The optical fiber device 100 for laser recovery provided in Embodiment 1 of the present invention can improve the reuse rate of the returned light by increasing the number of large-core multimode optical fibers 20, thereby achieving the effect of returning light recovery.

[0052] Specifically, when the number of large-core multimode optical fibers 20 is increased, it means that there are more channels to introduce the returned light into the fiber laser module used in the optical fiber device 100 for laser recovery, which can provide more "raw materials" for the recycling and reuse of the returned light, thereby improving the reuse rate of the returned light and better achieving the effect of recycling the returned light.

[0053] The optical fiber device 100 for laser recovery provided in Example 1 of the present invention has the advantages of simple operation, compact structure, low price, high reliability, etc. The present invention can not only greatly reduce the return light generated by the optical fiber laser on the object, and reduce the adverse effects of the return light on the front-end device in the optical fiber laser module, but also reuse this part of the return light on the object, thereby improving energy utilization.

[0054] Of course, the above is only a preferred embodiment of the present case, and there may be more variations in specific applications. For example, the number of large-core multimode optical fibers 20 in the above-mentioned optical fiber device 100 for laser recovery is 4. Theoretically, the number of large-core multimode optical fibers 20 only needs to be greater than or equal to 1. As the number of large-core multimode optical fibers 20 increases, the recovery rate of the returned light will increase.

[0055] In summary, the present invention provides an optical fiber device 100 for laser recovery and a preparation method thereof, and an optical fiber laser module. The optical fiber device 100 for laser recovery forms an optical fiber bundle 30 by melting the second output part 12, multiple multimode optical fiber arms 22, and a quartz tube 31. The return light first enters the optical fiber bundle 30 after passing through the quartz end cap 40. The return light entering the multiple multimode optical fiber arms 22 in the periphery is transmitted along the loop formed by the bending part 21 and enters the quartz end cap 40 in the forward transmission direction. The return light entering the second output part 12 will couple with the second fiber core layer 221 in the multimode optical fiber arm 22 with a high refractive index in the periphery during the transmission process, and then enter the quartz end cap 40 in the forward transmission direction after being transmitted along the loop formed by the bending part 21 and becoming a forward transmission laser. In this way, the energy of the return light re-entering the optical fiber laser module is greatly reduced, and it is recycled, thereby reducing the harm of the return light to the front-end device in the optical fiber laser module, and finally improving the energy utilization rate of the optical fiber laser module.

[0056] It should be noted that the above embodiments all belong to the same inventive concept, and the descriptions of the embodiments have different focuses. For the parts not described in detail in the individual embodiments, reference can be made to the descriptions in other embodiments. The above embodiments only express the implementation methods of the present invention, and the descriptions 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 ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. An optical fiber device for laser recovery, characterized in that: It comprises an output optical fiber, a plurality of large-core multimode optical fibers, a quartz tube and a quartz end cap, wherein the output optical fiber comprises a first output portion and a second output portion connected in an axial direction, the second output portion is arranged close to the quartz end cap, each of the large-core multimode optical fibers comprises a bending portion arranged corresponding to the first output portion and multimode optical fiber arms located at both ends of the bending portion, and the plurality of multimode optical fiber arms and the second output portion are completely sleeved in the quartz tube in an axial direction; The second output portion, the plurality of multimode optical fiber arms and the quartz tube are formed into an optical fiber bundle through a melting process; and one end of the optical fiber bundle away from the bending portion is fused to the input end face of the quartz end cap.

2. The optical fiber device for laser recovery according to claim 1, characterized in that: The output optical fiber is a passive optical fiber; the working band of the output signal optical fiber includes any one of the 1.0µm band, the 1.5µm band and the 2.0µm band; the output end face of the quartz end cap is coated with an anti-reflection film.

3. The optical fiber device for laser recovery according to claim 1, characterized in that: The first output portion includes a first core layer, a first cladding layer and a first coating layer which are sequentially arranged from the inside to the outside in the radial direction, and the second output portion includes the first core layer and the first cladding layer which are sequentially arranged from the inside to the outside in the radial direction; The refractive index of the first core layer is n2, the refractive index of the first cladding layer is n1, and the refractive index of the quartz tube is n0. Then n0, n1 and n2 satisfy the following relationship: n0<n1<n2.

4. The optical fiber device for laser recovery according to claim 3, characterized in that: The bending portion includes a second core layer, a second cladding layer and a second coating layer which are sequentially arranged from the inside to the outside in the radial direction, and the multimode optical fiber arm includes the second core layer and the second cladding layer which are sequentially arranged from the inside to the outside in the radial direction; The refractive index of the second core layer is n3, the refractive index of the second cladding layer is n1, and n0, n1 and n3 satisfy the following relationship: n0<n1<n3.

5. The optical fiber device for laser recovery according to claim 4, characterized in that: The material of the second core layer is germanium-doped silica, the material of the second cladding layer is silica, and the material of the quartz tube is fluorine-doped silica.

6. The optical fiber device for laser recovery according to claim 1, characterized in that: In the optical fiber bundle: the second output portion is located at the center of the optical fiber bundle along the radial direction, and two multimode optical fiber arms of the same large-core multimode optical fiber are symmetrical about the second output portion.

7. The optical fiber device for laser recovery according to claim 6, characterized in that: The inner wall diameter of the quartz tube is larger than the sum of the cladding diameters of the two multimode optical fiber arms and the above three in the second output part; the second output part is gap-matched with the multiple multimode optical fiber arms adjacent to it, and the multiple multimode optical fiber arms are gap-matched with the inner wall of the quartz tube.

8. A method for preparing an optical fiber device for laser recycling according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: S10, completely sleeve the second output portion and the two multimode optical fiber arms corresponding to each of the large-core multimode optical fibers in the quartz tube along the axial direction; S20, melting the second output portion, the plurality of multimode optical fiber arms, and the quartz tube to obtain the optical fiber bundle; S30, axially aligning one end of the optical fiber bundle away from the bending portion with the quartz end cap and fusing the end end face of the quartz end cap.

9. The method for preparing an optical fiber device for laser recycling according to claim 8, characterized in that: Before the step S10, the method further includes: removing the second coating layer of the multimode optical fiber arm and the first coating layer of the second output portion respectively.

10. A fiber laser module, characterized in that: An optical fiber device for laser recovery comprising the optical fiber device for laser recovery as described in any one of claims 1 to 7, or an optical fiber device for laser recovery made by the preparation method of the optical fiber device for laser recovery as described in any one of claims 8 to 9.

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