Method for fusion-splicing of optical fiber

Abstract

Provided is a method for fusion-splicing of an optical fiber (10), comprising the following steps: at a preset stripping length of an optical fiber (10) to be fusion-spliced, performing an operation of making a slit (14) on a coating layer (13); soaking said optical fiber (10) on which the slit (14) has been made in a softening liquid to soften the coating layer (13); taking out said optical fiber (10) and applying an axial force along said optical fiber (10) to strip the softened coating layer (13); cutting the end of said optical fiber (10) from which the coating layer (13) has been stripped to form a fusion-splicing end face; fusion-splicing two fusion-splicing end faces; and sleeving a light-transmissive tube (41) at a fusion-splicing point, filling the light-transmissive tube (41) with a coating adhesive and then vacuumizing same, and using an ultraviolet lamp to irradiate the light-transmissive tube (41) to cure the coating adhesive in the light-transmissive tube (41). According to the provided method for fusion-splicing of the optical fiber (10), the axial force is applied to the optical fiber (10) after the optical fiber (10) is subjected to physical slitting and chemical soaking for softening; the optical fiber (10) is cut off at the position of the slit (14), so that there is no damage caused by hard debris friction on a cladding, and a stripping opening of the optical fiber (10) is flat and smooth. The light-transmissive tube (41) is used to support and protect a fusion-spliced part, and the light-transmissive tube (41) is filled with the coating adhesive, achieving a good coating effect.

Description

Optical fiber fusion splicing method

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application number 202310891492.7, filed with the Chinese Patent Office on July 19, 2023, entitled “A Method for Fusion Splicing Optical Fibers,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the technical field of optical fiber fusion splicing, and in particular to an optical fiber fusion splicing method. Background Art

[0004] Fiber lasers typically consist of multiple passive optical components and a pump source. Each component is connected via fiber fusion splicing, making the fiber fusion point the weakest link in the system. The quality of the fusion splice determines the stability of the system. The fusion splice process generally involves five steps: fiber stripping, fiber cleaning, fiber cleaving, fiber fusion splicing, and fiber coating. Existing fiber stripping techniques typically use Miller pliers, thermal stripping pliers, blades, or fiber stripping equipment to physically remove the fiber coating. Lasers are also sometimes used for stripping.

[0005] In the existing technology, optical fiber stripping still has the following disadvantages: optical fiber stripping adopts the physical contact stripping method of a blade, which can easily scratch the optical fiber cladding during the stripping process, causing defects such as fine cracks, easy breakage, cladding light will overflow, and heat accumulation will burn the fusion splice; optical fiber stripping adopts the laser stripping method, which is complicated to operate, and the laser is thermal stripping, which can easily damage the optical fiber cladding.

[0006] Application Contents

[0007] The present application provides a fiber fusion splicing method to solve the technical problem in the prior art of using physical contact stripping method or laser stripping method to strip the fiber, which easily causes damage to the fiber cladding.

[0008] The present application provides a method for optical fiber fusion splicing, wherein the optical fiber to be fused includes, radially from the inside to the outside, a core, a cladding, and a coating layer, the method comprising the following steps:

[0009] Coating stripping: Slit the coating of the optical fiber to be spliced ​​at a preset stripping length; immerse the slitted optical fiber in a softening liquid to soften the coating, with the slit flush with the highest level of the softening liquid; after soaking for a predetermined time, remove the optical fiber to be spliced ​​and apply force along the axial direction of the optical fiber to strip the softened coating to expose the cladding;

[0010] Fiber cutting: cutting the end of the optical fiber to be fused, from which the coating layer has been stripped, to obtain a fusion-bonded end face;

[0011] Fiber fusion splicing: fusing the two fusion end faces obtained in the coating stripping and fiber cutting steps; and,

[0012] Coating at the welding point: A light-transmitting tube is placed at the welding point, the light-transmitting tube is filled with the coating glue and then vacuumed, and the light-transmitting tube is irradiated with an ultraviolet lamp to cure the coating glue in the light-transmitting tube.

[0013] The optical fiber fusion splicing method provided in the present application, when stripping the coating layer, adopts physical cutting and chemical immersion to soften it, and then applies axial force to the optical fiber to strip the coating layer to expose the cladding. Compared with the physical contact stripping in the prior art, the coating layer is softened after immersion and is disconnected at the cutting gap position, and there is no phenomenon of hard debris rubbing the cladding to cause damage, and the optical fiber stripping end is flat and smooth; when coating the fusion point, on the one hand, a transparent tube is used to cover the fusion part, and the transparent tube can provide a certain mechanical strength support for the fusion part, avoid bending of the fusion part, and play a protective role for the fusion part; on the other hand, the coating glue is poured into the transparent tube and then vacuumed, so the coating effect is good, the coating glue is transparent and has no defects, and the temperature rise is low during operation.

[0014] Optionally, after the coating stripping step, the method further includes: optical fiber cleaning: cleaning and drying the optical fiber to be fused after the coating is stripped.

[0015] Optionally, the optical fiber cleaning method includes cleaning with dust-free paper dipped in anhydrous alcohol; or cleaning with dust-free cotton dipped in anhydrous alcohol; or ultrasonic cleaning, wherein the solvent for ultrasonic cleaning is anhydrous ethanol.

[0016] Optionally, in the step of performing a slit operation on the coating layer at a preset stripping length of the optical fiber to be fused, the slit is a circular slit or an arc slit.

[0017] Optionally, in the step of performing a slit operation on the coating layer at a preset stripping length of the optical fiber to be fused, the number of the slits is at least 2, and the slits are arranged at intervals on the same cut surface of the optical fiber to be fused.

[0018] Optionally, in the step of slitting the coating at a predetermined stripping length of the optical fiber to be spliced, the diameter of the cladding is D1, the diameter of the coating is D2, and the depth of the slit is between (0, (D2-D1) / 2). This limited slit depth prevents the fiber stripping tool from contacting the cladding of the optical fiber to be spliced, thereby damaging the cladding.

[0019] Optionally, in the step of immersing the slitted optical fiber in a softening liquid to soften the coating, the softening liquid is anhydrous ethanol, the concentration of which is greater than or equal to 99.5%, and the immersion time is greater than or equal to 6 hours. This choice is because, compared to acetone and toluene, anhydrous ethanol is virtually non-toxic, more environmentally friendly and safe, and is gentler on the coating during immersion and softening, without corrosive effects on the optical fiber cladding. The coating remains intact during stripping, breaking at the slits. After removal, the coating forms a complete tubular structure, eliminating the risk of debris rubbing against the cladding and causing damage. Furthermore, compared to strong acids, this solution avoids the undesirable localized roughening of the optical fiber cladding that can occur due to strong acid corrosion.

[0020] Optionally, the softening liquid is contained in a container having a cover plate, the cover plate of the container having an opening, and the slit end of the optical fiber to be fused is passed through the opening and immersed in the softening liquid. The optical fiber fusion splicing method provided in this application performs an immersion softening treatment on the coating layer, and a cover plate is provided on the container to seal the container and prevent the softening liquid from evaporating.

[0021] Optionally, the optical fiber cutting step includes: using a first clamp to clamp one end of the optical fiber to be fused, after the coating has been stripped; using a second clamp to clamp the portion of the optical fiber to be fused having the coating; cutting the optical fiber to be fused, after the coating has been stripped, between the first clamp and the second clamp to form a slit; and using the first clamp and the second clamp to apply axial tension in opposite directions to the optical fiber to be fused, respectively, to sever the optical fiber to be fused. In this manner, the cladding remaining portion is free of contact contamination, thereby preventing damage to the cladding remaining portion.

[0022] Optionally, the fiber fusion splicing step includes: securing the two optical fibers to be fused to a positioning structure of a fusion splicing device, aligning the fusion end faces of the two optical fibers to be fused, and then performing discharge fusion splicing; the positioning structure of the fusion splicing device focuses on the portion of the two optical fibers to be fused that has the coating layer. This placement avoids direct contact between the positioning structure and the cladding of the optical fibers to be fused, preventing particles, debris, and other impurities on the positioning structure from damaging the cladding of the optical fibers to be fused during alignment or even rotation of the optical fibers to be fused.

[0023] Optionally, the positioning structure includes a V-shaped groove and a pressure foot, and the fiber fusion splicing step includes: placing the coating layer parts of the two optical fibers to be fused in the V-shaped groove, the pressure foot facing the V-shaped groove and abutting against the coating layer parts of the optical fibers to be fused, and discharge-fusing the end faces of the cut optical fibers to be fused.

[0024] Optionally, the steps of putting a light-transmitting tube on the fusion point, filling the light-transmitting tube with coating glue and then performing vacuum treatment include: using coating glue to seal between the first end of the light-transmitting tube and the coating layer; placing the light-transmitting tube vertically, and filling the light-transmitting tube with coating glue from the second end of the light-transmitting tube; placing the optical fiber to be fused covered with the light-transmitting tube in a vacuum box and evacuating for 10 minutes to 60 minutes.

[0025] The optical fiber fusion splicing method provided in the present application, when performing optical fiber coating, on the one hand, a transparent tube is used to cover the fusion splicing part, and the transparent tube can provide a certain mechanical strength support for the fusion splicing part, avoid bending of the fusion splicing part, and play a protective role for the fusion splicing part; on the other hand, the coating glue is poured into the transparent tube and then vacuumed, so the coating effect is good, the coating glue is transparent and has no defects, and the temperature rise is low during operation.

[0026] Optionally, in the step of coating the fusion joint, the light-transmitting tube is configured as a glass capillary tube.

[0027] Optionally, in the step of coating the welding points, the coating glue is a low-refractive-index UV glue having a refractive index lower than 1.40.

[0028] Optionally, in the step of coating the welding points, the power of the ultraviolet lamp is less than or equal to 1W and the irradiation time of the ultraviolet lamp is configured to be 30s to 300s.

[0029] Optionally, the predetermined time is between 6 hours and 10 hours. By limiting the predetermined time in this way, it is ensured that the coating layer is fully softened, which facilitates the subsequent stripping of the coating layer and prevents damage to the cladding. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG1 is a schematic diagram of the seed source structure of a fiber laser in the prior art;

[0031] FIG2 is a schematic diagram of the structure of an amplifier of a fiber laser in the prior art;

[0032] FIG3 is a schematic diagram of a process flow of an optical fiber fusion splicing method provided in an embodiment of the present application;

[0033] FIG4 is a first schematic diagram of a cross-sectional view of an optical fiber slit in the optical fiber fusion splicing method provided in an embodiment of the present application;

[0034] FIG5 is a second schematic diagram of a cross-sectional view of an optical fiber slit in the optical fiber fusion splicing method provided in an embodiment of the present application;

[0035] FIG6 is a third schematic diagram of a cross-sectional view of an optical fiber slit in the optical fiber fusion splicing method provided in an embodiment of the present application;

[0036] FIG7 is a schematic diagram of the structure of optical fiber cutting in the optical fiber fusion splicing method provided in an embodiment of the present application;

[0037] FIG8 is a schematic diagram of the structure of optical fiber fusion splicing in the optical fiber fusion splicing method provided in an embodiment of the present application;

[0038] Figures 9(a) to 9(c) are schematic diagrams of the optical fiber coating state in the optical fiber fusion splicing method provided in an embodiment of the present application;

[0039] Description of reference numerals:

[0040] 1-1, first pump source; 1-2, first pump combiner; 1-3, high-reflection grating; 1-4, first gain fiber; 1-5, low-reflection grating; 1-6, first melting point; 1-7, second melting point;

[0041] 2-1, second pump source; 2-2, second pump combiner; 2-3, third melting point; 2-4, second gain fiber;

[0042] 10. Optical fiber to be spliced; 11. Fiber core; 12. Cladding; 13. Coating; 14. Slit; 15. Arc slit; 16. Ring slit; 21. First clamp; 22. Second clamp; 23. Optical fiber cutter; 31. V-groove; 32. Presser foot; 41. Light-transmitting tube; 42. Coating glue. DETAILED DESCRIPTION

[0043] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the application background and specific embodiments of the present application are described in detail below with reference to Figures 1-9.

[0044] Figure 1 shows the seed source structure of an existing general fiber laser, including a first pump source 1-1, a first pump combiner 1-2, a high-reflection grating 1-3, a first gain fiber 1-4 and a low-reflection grating 1-5. Among them, the first melting point 1-6 between the first pump combiner 1-2 and the high-reflection grating 1-3, and the second melting point 1-7 between the high-reflection grating 1-3 and the first gain fiber 1-4, the first melting point 1-6 and the second melting point 1-7 constitute the key melting points of this seed source structure and are the weakest links.

[0045] FIG2 shows the amplifier structure of an existing general fiber laser, including a second pump source 2-1, a second pump combiner 2-2, and a second gain fiber 2-4. The third melting point 2-3 of the second pump combiner 2-2 and the second gain fiber 2-4 is the key melting point of the amplifier and is also the weakest link.

[0046] The optical fiber fusion splicing method provided in the embodiment of the present application is suitable for being configured as the fusion splicing of the key melting points in the above-mentioned Figures 1 and 2 .

[0047] On the other hand, existing high-power fiber lasers generally use cladding pumping. A pump combiner directs pump light into the passive fiber cladding, which is then fused to the gain fiber and directed back into the gain fiber cladding. High-power pumping fills the cladding with pump light. If the cladding is damaged or contaminated, some of the cladding light will be extracted or absorbed, causing heat generation. If the threshold is exceeded, a burnout may occur.

[0048] 3 and 4, the embodiment of the present application provides a method for optical fiber fusion splicing, wherein the optical fiber 10 to be fused includes a core 11, a cladding 12 and a coating 13 in order from the inside to the outside in radial direction, and the method includes the following steps: coating stripping: cutting a slit 14 on the coating at a preset stripping length of the optical fiber 10 to be fused; immersing the optical fiber 10 to be fused after the slit 14 is cut in a softening liquid to soften the coating 13, and the slit 14 is flush with the highest level of the softening liquid; after immersing for a predetermined time, taking out the optical fiber 10 to be fused and applying The softened coating 13 is stripped off by applying force along the axial direction of the optical fiber 10 to be fused, exposing the cladding 12; optical fiber cutting: cutting one end of the optical fiber 10 to be fused from which the coating 13 has been stripped off to obtain a fusion end face; optical fiber fusion splicing: fusing the two fusion end faces obtained in sequence through the coating stripping and optical fiber cutting steps; and fusion point coating: placing a light-transmitting tube 41 on the fusion point, filling the light-transmitting tube 41 with coating glue, and then evacuating the tube, and irradiating the light-transmitting tube 41 with an ultraviolet lamp to cure the coating glue in the tube 41.

[0049] It should be noted that a fiber stripping tool is used to cut a slit 14 at a predetermined stripping length in the optical fiber 10 to be fused. During the slit 14, the fiber stripping tool does not contact the cladding 12 of the optical fiber 10 to be fused, thereby preventing damage to the cladding 12. The fiber stripping tool can be a blade or a Miller pliers. If a Miller pliers is used to cut the slit 14, the limit screw can be adjusted to control the Miller pliers' blade aperture to be slightly smaller than the diameter of the coating 13 to ensure that the Miller pliers does not get stuck in the optical fiber cladding 12.

[0050] It should be noted that the preset stripping length is between 3 cm and 4 cm.

[0051] It should be noted that the predetermined time is between 6 hours and 10 hours, preferably 8 hours. The predetermined time is limited in this way to ensure that the coating layer 13 is fully softened, which is convenient for subsequent stripping of the coating layer 13 and prevents damage to the cladding layer 12.

[0052] It should be noted that the gap 14 is flush with the highest level of the softening liquid, ensuring that the coating layer 13 of the preset stripping length is completely immersed in the softening liquid, facilitating subsequent complete stripping; and preventing the coating layer 13 outside the preset stripping length from being softened.

[0053] It should be noted that the soaked optical fiber 10 to be fused is taken out, the soaked coating layer is clamped with dust-free paper, and a force is applied to the coating layer along the axial direction of the optical fiber 10 to be fused, and the soaked coating layer 13 is stripped off to expose the cladding 12.

[0054] Therefore, the optical fiber fusion splicing method provided in the embodiment of the present application adopts physical cutting of the slit 14 and chemical soaking to soften the optical fiber and then applies axial force to the optical fiber to strip off the coating layer 13 to expose the cladding 12. Compared with the physical contact stripping adopted in the prior art, the coating layer 13 of the present application is softened after soaking and is disconnected at the position of the cutting slit 14. There is no phenomenon of damage to the cladding 12 caused by friction of hard debris, and the optical fiber stripping end is flat and smooth. When coating the fusion point, on the one hand, a transparent tube is used to cover the fusion part. The transparent tube can provide a certain mechanical strength support for the fusion part, avoid bending of the fusion part, and protect the fusion part. On the other hand, the coating glue is poured into the transparent tube and then vacuumed. The coating effect is good, the coating glue is transparent and has no defects, and the temperature rise is low during operation.

[0055] The embodiment of the present application further includes, after the coating stripping step, optical fiber cleaning: cleaning and drying the optical fiber 10 to be fused after the coating 13 is stripped. This configuration prevents cleaning liquid from remaining.

[0056] It should be noted that, in a specific embodiment, the optical fiber can be cleaned by using dust-free paper or dust-free cotton dipped in anhydrous alcohol. This method is convenient and economical, but if the cleaning force is too strong, it is easy to cause debris to scratch the cladding 12 of the optical fiber 10 to be fused, causing cracks in the cladding 12, affecting the service life of the optical fiber. Therefore, when using dust-free paper or dust-free cotton dipped in anhydrous alcohol for cleaning, it is necessary to adopt a one-way gentle wiping method to avoid repeated use of a single piece of dust-free paper or a single piece of dust-free cotton to prevent friction damage to the cladding 12.

[0057] In another specific embodiment, the optical fiber cleaning method can also be ultrasonic cleaning, and the ultrasonic cleaning solvent uses anhydrous ethanol, the cleaning power is 2w~5w, and the cleaning time is between 20s~40s. By limiting the cleaning power and cleaning time to meet a certain range, the ultrasonic cleaning is ensured to be thorough and stubborn stains are prevented from remaining on the optical fiber 10 to be fused.

[0058] Preferably, the cleaning power of ultrasonic cleaning is 3W and the cleaning time is 30s.

[0059] It should be noted that the drying method may be air drying. Specifically, pure compressed nitrogen is used to dry the optical fiber 10 to be fused after the coating layer 13 is stripped.

[0060] 4-6 , in the embodiment of the present application, in the step of cutting a slit 14 into the coating layer at a predetermined stripping length of the optical fiber 10 to be fused, the slit 14 is a circular slit 16 or an arc slit 15. It should be noted that the optical fiber stripping tool is used to cut one circular slit 16, one arc slit 15, two arc slits 15, three arc slits 15, four arc slits 15, or other multiple arc slits 15 along the same cut surface of the coating layer 13.

[0061] In the embodiment of the present application, in the step of cutting slits 14 in the coating layer at a preset stripping length of the optical fiber 10 to be fused, the number of slits 14 is at least two, and the slits 14 are arranged at intervals on the same cut surface of the optical fiber 10 to be fused.

[0062] In the embodiment of the present application, the slots 14 are arranged at equal intervals on the same cut surface of the optical fiber 10 to be fused.

[0063] Referring to Figure 4, in an embodiment of the present application, the diameter of the cladding 12 is D1, the diameter of the coating layer 13 is D2, and the depth t of the gap 14 is between (0, (D2-D)1 / 2). The depth of the gap 14 is limited in this way to prevent the optical fiber stripping tool from contacting the cladding 12 of the optical fiber 10 to be fused and causing damage to the cladding 12.

[0064] It should be noted that the material of the coating layer 13 is rubber, and the softening liquid can be ethanol, acetone or toluene. In the embodiment of the present application, in the step of immersing the optical fiber 10 to be fused after the slit 14 is cut in the softening liquid to soften the coating layer 13, preferably, the softening liquid is anhydrous ethanol, the concentration of anhydrous ethanol is greater than or equal to 99.5%, and the immersion time is greater than or equal to 6 hours. In this way, compared with acetone and toluene, anhydrous ethanol is almost non-toxic, more environmentally friendly and safe, and the immersion softening of the coating layer 13 is gentler, and has no corrosive effect on the optical fiber cladding 12, so that the coating layer 13 remains a complete cylinder during the stripping process, is disconnected at the slit position, and is a tubular structure after being pulled out, and there is no phenomenon of debris rubbing against the cladding 12 to cause damage; in addition, compared with strong acid, it avoids the undesirable phenomenon of local hairiness of the optical fiber cladding 12 caused by strong acid corrosion.

[0065] In the embodiment of the present application, the softening liquid is contained in a container with a cover plate. The cover plate of the container is provided with an opening. The end of the optical fiber 10 to be fused, which has been slit 14, passes through the opening and is immersed in the softening liquid.

[0066] It should be noted that the container can be a glass beaker or a plastic bottle.

[0067] In the optical fiber fusion splicing method provided in the embodiment of the present application, the coating layer 13 is immersed in a softening treatment, and a cover plate is provided on the container to seal the container and prevent the softening liquid from volatilizing.

[0068] In one embodiment of the present application, a clamp may be provided on the cover plate, the clamp being collinear with the axis of the opening and configured to clamp the optical fiber 10 to be spliced. This arrangement facilitates clamping the optical fiber 10 to be spliced ​​and adjusting the depth of the optical fiber 10 to be spliced ​​into the softening liquid.

[0069] In another embodiment of the present application, the optical fiber 10 to be fused is bonded to the cover plate by adhesive tape.

[0070] Referring to FIG. 7 , in the embodiment of the present application, the fiber cleaving step includes: using a first clamp 21 to clamp one end of the optical fiber 10 to be spliced, after the coating 13 has been stripped; using a second clamp 22 to clamp the portion of the optical fiber 10 to be spliced, with the coating 13 still present; cleaving the optical fiber 10 to be spliced, after the coating 13 has been stripped, between the first clamp 21 and the second clamp 22 to form a cleavage; and applying axial tension in opposite directions to the optical fiber 10 to be spliced, respectively, using the first clamp 21 and the second clamp 22 to sever the optical fiber 10 to be spliced. The portion of the cladding 12 near the coating 13 is the remaining portion of the cladding 12. This cleavage prevents contact contamination and damage to the remaining portion of the cladding 12.

[0071] Specifically, the optical fiber cutter 23 is used to cut the cladding 12 of the optical fiber 10 to be fused.

[0072] Referring to FIG8 , in one embodiment of the present application, the fiber fusion splicing step includes: securing two optical fibers 10 to be fused to a positioning structure of a fusion splicing device, aligning the fusion end faces of the two optical fibers 10 to be fused, and then performing discharge fusion splicing; the positioning structure of the fusion splicing device focuses on the portion of the two optical fibers 10 to be fused that has the coating layer 13. This placement prevents direct contact between the positioning structure and the cladding of the optical fibers to be fused, preventing particles, debris, and other impurities on the positioning structure from damaging the cladding of the optical fibers to be fused during alignment or even rotation of the optical fibers to be fused.

[0073] In the embodiment of the present application, specifically, the positioning structure includes a V-groove 31 and a pressure foot 32. The fiber fusion splicing step includes: placing the coating 13 of two optical fibers 10 to be fused in the V-groove 31 of the fusion splicer, with the pressure foot 32 of the fusion splicer facing the V-groove 31 and abutting against the coating 13 of the optical fibers 10 to be fused, and performing discharge welding on the end faces of the cut optical fibers 10 to be fused. Such placement prevents the V-groove 31 and the pressure foot 32 from directly contacting the cladding 12 of the optical fibers 10 to be fused, and prevents impurities such as particles and debris from being present on the V-groove 31 and the pressure foot 32, which could damage the cladding 12 of the optical fibers 10 to be fused when the optical fibers 10 to be fused are aligned or even rotated.

[0074] 9a to 9c, in an embodiment of the present application, a light-transmitting tube 41 is put on the fusion splicing point, and the steps of filling the light-transmitting tube 41 with coating glue and then evacuating the light-transmitting tube 41 include: sealing the first end of the light-transmitting tube 41 with coating glue and the coating layer 13; placing the light-transmitting tube 41 vertically and filling the light-transmitting tube 41 with coating glue from the second end of the light-transmitting tube 41; placing the optical fiber 10 to be fused with the light-transmitting tube 41 in a vacuum box and evacuating the light-transmitting tube 41 for 10 to 60 minutes.

[0075] It should be noted that the use of optical fiber coating machines is prone to air holes, glue shortages, coating fractures, or dust spots and air holes caused by unclean coating grooves, which are not easy to detect and will greatly affect the stability of the laser. In the optical fiber fusion splicing method provided in the embodiment of the present application, when performing optical fiber coating, on the one hand, a light-transmitting tube 41 is used to cover the fusion splicing part. The light-transmitting tube 41 can provide a certain mechanical strength support for the fusion splicing part, prevent the fusion splicing part from bending, and play a protective role for the fusion splicing part; on the other hand, the optical fiber coating glue 42 is poured into the light-transmitting tube 41 and then vacuumed, which has a good coating effect. The optical fiber coating glue 42 is transparent and has no defects, and the temperature rise is low during operation.

[0076] In the embodiment of the present application, in the step of coating the fusion point, the light-transmitting tube 41 is configured as a glass capillary tube.

[0077] It should be noted that the light transparent tube 41 is placed vertically, the first end of the light transparent tube 41 is the bottom end of the light transparent tube 41, and the second end of the light transparent tube 41 is the upper end of the light transparent tube 41. The optical fiber coating glue is poured into the upper end of the light transparent tube 41 until it is completely filled.

[0078] In the embodiment of the present application, the coating glue 42 is a UV coating glue, and the coating glue adopts a low-refractive-index UV glue with a refractive index lower than 1.40.

[0079] In the embodiment of the present application, the power of the ultraviolet lamp is optionally less than or equal to 1W, and the irradiation time is between 30s and 300s. Since high-power ultraviolet lamp irradiating the optical fiber coating glue in the light-transmitting tube 41 will cause the optical fiber coating glue 42 to turn yellow, a low-power ultraviolet lamp is used for irradiation.

[0080] Preferably, the power of the ultraviolet lamp is 10 mW, and the irradiation time is 40 s.

[0081] Specific embodiments of this application

[0082] The laser of this embodiment includes a high-reflection grating fiber and a gain fiber. The output power of the laser is 1500W and the wavelength is 1080nm. The core 11 of the high-reflection grating fiber has a diameter of 20μm, the cladding 12 has a diameter of 400μm, and the coating 13 has a diameter of 550μm. The core 11 of the gain fiber has a diameter of 20μm, the cladding 12 has a diameter of 400μm, and the coating 13 has a diameter of 550μm. The optical fiber fusion splicing method includes the following steps:

[0083] Coating stripping:

[0084] (1) Cutting slits 14: The preset stripping length of the high-reflection grating fiber and the gain fiber is 4 cm. The diameter of the Miller clamp is adjusted to 500 μm. Vertical slits 14 are cut at the preset stripping length of the high-reflection grating fiber and the gain fiber. The slits 14 are arc slits 15. There are four arc slits 15, and the four arc slits 15 are arranged at intervals on the same section.

[0085] (2) Soaking and softening treatment: Add 5 cm of anhydrous ethanol to a glass cup, cover it with a cover plate, and pass the high-reflection grating fiber and the gain fiber behind the slit 14 through the opening of the cover plate so that the slit 14 is flush with the upper surface of the anhydrous ethanol. Fix the high-reflection grating fiber and the gain fiber after the slit 14 operation to the cover plate and soak for 8 hours before taking them out.

[0086] (3) Stripping off the coating layer 13: Applying an axial force to the soaked high-reflection grating fiber and the soaked gain fiber to remove the coating layer 13 of the high-reflection grating fiber and the gain fiber.

[0087] Fiber cleaning: Use an ultrasonic cleaner to clean the high-reflection grating fiber and gain fiber after stripping the coating layer 13. The cleaning agent is anhydrous ethanol. The cleaning power is 3W and the cleaning time is 30s.

[0088] Fiber drying: Use a clean compressed nitrogen tank to blow dry the cleaned high-reflection grating fiber and the soaked gain fiber to prevent anhydrous ethanol residue.

[0089] Fiber cutting: The first clamp 21 is used to clamp one end of the high-reflection grating optical fiber with the coating layer 13 stripped, and the second clamp 22 is used to clamp the portion of the high-reflection grating optical fiber with the coating layer 13. The high-reflection grating optical fiber with the coating layer 13 stripped between the first clamp 21 and the second clamp 22 is cut to form a crack. The first clamp 21 and the second clamp 22 respectively apply axial tension in opposite directions to the high-reflection grating optical fiber to break the high-reflection grating optical fiber.

[0090] A first clamp 21 is used to clamp one end of the gain fiber from which the coating 13 has been stripped, and a second clamp 22 is used to clamp a portion of the gain fiber from which the coating 13 has been stripped. The gain fiber from which the coating 13 has been stripped, which is located between the first clamp 21 and the second clamp 22, is cut to form a slit. The first clamp 21 and the second clamp 22 apply axial tension in opposite directions to the gain fiber, respectively, to break the gain fiber.

[0091] The tensile force is 1000 psi and the cutting length is 4 mm.

[0092] Fiber fusion splicing: Place the coating 13 of the high-reflection grating fiber in the V-groove 31 of the fusion splicer, with the pressure foot 32 of the fusion splicer facing the V-groove 31 and abutting against the coating 13 of the high-reflection grating fiber; Place the coating 13 of the gain fiber in the V-groove 31 of the fusion splicer, with the pressure foot 32 of the fusion splicer facing the V-groove 31 and abutting against the coating 13 of the gain fiber; Align the end faces of the cladding 12 of the high-reflection fiber Bragg grating and the gain fiber, and perform discharge fusion splicing, wherein the discharge duration is 10000ms.

[0093] Fiber Coating: Wipe the fiber coating after the fusion splicing process with a dust-free tissue dampened with alcohol. Then, place a light-transmitting tube 41 over the fusion splice. The glass tube has an inner diameter of 0.8 mm, an outer diameter of 1.5 mm, and a length of 15 mm. The coating 13 of some high-reflectivity grating fibers and some gain fibers is located within the light-transmitting tube 41. The light-transmitting tube 41 is positioned vertically. UV glue is used to seal the bottom of the light-transmitting tube 41 with the coating 13. The glue is poured into the light-transmitting tube 41 from the top. The tube is placed in a vacuum chamber and evacuated for 30 minutes. A UV lamp is used to illuminate the light-transmitting tube 41 to cure the glue within. The refractive index of the glue is 1.373.

[0094] In a specific embodiment of this application, the gain fiber is coiled into a high-reflectivity grating fiber slot, with the slot size in the melting point region matching the dimensions of the glass tube. A coating adhesive is then applied to the fusion zone. At a measured laser output of 1500W, the fusion zone exhibits no noticeable bright spots, exhibits uniform heating, and a melting point of only 40°C, well below the 80°C threshold. If applied using a coating machine, the temperature would be between 50°C and 60°C due to the whitening of the coating surface. This coating method significantly reduces the melting point.

[0095] The scope of application of this application includes but is not limited to the high-power continuous 1080nm laser mentioned in the specific embodiments of this application, and is also applicable to the treatment method of the weld part using continuous, quasi-continuous or pulsed lasers of other wavelengths.

[0096] Although the present application is disclosed as above, the present application is not limited thereto. Any person skilled in the art may make various changes and modifications without departing from the spirit and scope of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined by the claims. Industrial Applicability

[0097] The optical fiber fusion splicing method provided in the embodiment of the present application, when stripping the coating layer, adopts physical cutting and chemical immersion to soften it, and then applies axial force to the optical fiber to strip the coating layer to expose the cladding. Compared with the physical contact stripping in the prior art, the coating layer of the present application is softened after immersion and is disconnected at the gap position. There is no phenomenon of hard debris rubbing the cladding to cause damage, and the optical fiber stripping end is flat and smooth; when coating the fusion point, on the one hand, a transparent tube is used to cover the fusion part, and the transparent tube can provide a certain mechanical strength support for the fusion part, avoid bending of the fusion part, and play a role in protecting the fusion part; on the other hand, the coating glue is poured into the transparent tube and then vacuumed, the coating effect is good, the coating glue is transparent and has no defects, and the temperature rise is low during operation; thereby improving the quality of optical fiber splicing and ensuring smooth communication.

Claims

1. A method for optical fiber fusion splicing, characterized in that: The optical fiber (10) to be fused comprises a core (11), a cladding (12) and a coating layer (13) in order from the inside to the outside in radial direction, and the method comprises the following steps: Stripping the coating layer: cutting a slit (14) on the coating layer at a preset stripping length of the optical fiber (10) to be fused; immersing the optical fiber (10) to be fused after the slit (14) is cut in a softening liquid to soften the coating layer (13), with the slit (14) being flush with the highest level of the softening liquid; after immersing for a predetermined time, taking out the optical fiber (10) to be fused and applying a force along the axial direction of the optical fiber (10) to be fused to strip off the softened coating layer (13), so that the cladding (12) is exposed; Optical fiber cutting: cutting one end of the optical fiber (10) to be fused, from which the coating layer (13) has been stripped, to obtain a fusion end face; Optical fiber fusion splicing: fusing the two fusion end faces obtained in sequence through the coating stripping and optical fiber cutting steps; and, Coating at the welding point: a light-transmitting tube (41) is placed at the welding point, the light-transmitting tube (41) is filled with coating glue and then vacuumed, and an ultraviolet lamp is used to irradiate the light-transmitting tube (41) to solidify the coating glue in the light-transmitting tube (41).

2. The optical fiber fusion splicing method according to claim 1, characterized in that: After the coating layer stripping step, the method further comprises: Optical fiber cleaning: cleaning and drying the optical fiber (10) to be fused after the coating layer (13) is stripped off.

3. The optical fiber fusion splicing method according to claim 2, characterized in that: The optical fiber cleaning method includes cleaning with dust-free paper dipped in anhydrous alcohol; or cleaning with dust-free cotton dipped in anhydrous alcohol; or ultrasonic cleaning, wherein the solvent for ultrasonic cleaning is anhydrous ethanol.

4. The optical fiber fusion splicing method according to any one of claims 1 to 3, characterized in that: In the step of performing a slit (14) operation on the coating layer at a preset stripping length of the optical fiber (10) to be fused, the slit (14) is a circular ring slit (16) or an arc slit (15).

5. The optical fiber fusion splicing method according to any one of claims 1 to 4, characterized in that: In the step of cutting slits (14) into the coating layer at a preset stripping length of the optical fiber (10) to be fused, the number of the slits (14) is at least 2, and the slits (14) are arranged at intervals on the same cut surface of the optical fiber (10) to be fused.

6. The optical fiber fusion splicing method according to any one of claims 1 to 5, characterized in that: In the step of performing a slit (14) operation on the coating layer (13) at a preset stripping length of the optical fiber (10) to be fused, the diameter of the cladding (12) is D1, the diameter of the coating layer (13) is D2, and the depth t of the slit (14) is between (0, (D2-D1) / 2).

7. The optical fiber fusion splicing method according to any one of claims 1 to 6, characterized in that: In the step of immersing the optical fiber (10) to be fused after the slit (14) is cut into a softening liquid to soften the coating layer (13), the softening liquid is anhydrous ethanol, the concentration of the anhydrous ethanol is greater than or equal to 99.5%, and the immersion time is greater than or equal to 6 hours.

8. The optical fiber fusion splicing method according to any one of claims 1 to 7, characterized in that: The softening liquid is contained in a container with a cover plate, the cover plate of the container is provided with an opening, and one end of the optical fiber (10) to be fused, which has been subjected to the slit (14) operation, passes through the opening and is immersed in the softening liquid.

9. The optical fiber fusion splicing method according to any one of claims 1 to 8, characterized in that: The optical fiber cutting step comprises: using a first clamp (21) to clamp one end of the optical fiber (10) to be fused from which the coating layer (13) has been stripped; using a second clamp (22) to clamp a portion of the optical fiber (10) to be fused having the coating layer (13); cutting the optical fiber (10) to be fused from which the coating layer (13) has been stripped and which is located between the first clamp (21) and the second clamp (22) to form a crack; and the first clamp (21) and the second clamp (22) respectively apply axial tension in opposite directions to the optical fiber (10) to be fused, so that the optical fiber (10) to be fused is disconnected.

10. The optical fiber fusion splicing method according to any one of claims 1 to 9, characterized in that: The optical fiber fusion splicing step comprises: fixing the two optical fibers (10) to be fused on the positioning structure of the fusion splicing equipment, aligning the fusion end faces of the two optical fibers (10) to be fused and then performing discharge fusion splicing; the positioning structure of the fusion splicing equipment focuses on the parts of the two optical fibers (10) to be fused that have the coating layer (13).

11. The optical fiber fusion splicing method according to claim 10, characterized in that: The positioning structure comprises a V-shaped groove (31) and a pressure foot (32), and the optical fiber fusion splicing step comprises: placing the coating layer (13) portions of the two optical fibers (10) to be fused in the V-shaped groove (31), the pressure foot (32) facing the V-shaped groove (31) and abutting against the coating layer (13) portions of the optical fibers (10) to be fused, and performing discharge fusion splicing on the end faces of the cut optical fibers (10) to be fused.

12. The optical fiber fusion splicing method according to any one of claims 1 to 11, characterized in that: The steps of putting a light-transmitting tube (41) on the fusion point, filling the light-transmitting tube (41) with coating glue and then performing vacuum treatment include: using coating glue to seal between the first end of the light-transmitting tube (41) and the coating layer (13); placing the light-transmitting tube (41) vertically and filling the light-transmitting tube (41) with coating glue from the second end of the light-transmitting tube (41); placing the optical fiber (10) to be fused with the light-transmitting tube (41) in a vacuum box and evacuating the box for 10 minutes to 60 minutes.

13. The optical fiber fusion splicing method according to any one of claims 1 to 12, characterized in that: In the step of welding point coating, the light-transmitting tube (41) is configured as a glass capillary tube.

14. The optical fiber fusion splicing method according to any one of claims 1 to 13, characterized in that: In the step of coating the welding points, the coating glue is a low-refractive-index ultraviolet glue having a refractive index lower than 1.

40.

15. The optical fiber fusion splicing method according to any one of claims 1 to 14, characterized in that: In the step of coating the welding point, the power of the ultraviolet lamp is less than or equal to 1W and the irradiation time of the ultraviolet lamp is configured to be 30s to 300s.

16. The optical fiber fusion splicing method according to any one of claims 1 to 15, characterized in that: The predetermined time is between 6h-10h.

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