A collapsed air-clad, columnar dispersion optical fiber and a method of manufacturing the same

Abstract

The application discloses a kind of collapsed air cladding columnar dispersion optical fiber and its manufacturing method, belong to optical fiber technical field.A kind of manufacturing method of columnar dispersion optical fiber, comprising: providing an air cladding optical fiber, the air cladding optical fiber is quartz core, air cladding and quartz cladding in turn from inside to outside;The predetermined section of the air cladding optical fiber is locally heated, and simultaneously air cladding optical fiber is stretched, and then the air cladding optical fiber is cut at the dispersion section, and a layer of material layer with refractive index greater than quartz refractive index is arranged on the outer surface of the dispersion section.The application also discloses the columnar dispersion optical fiber prepared by the method.The application forms dispersion section in an integrated manner by local collapsing treatment of air cladding optical fiber, and the process is simple, the cost is low, easy to mass production, and the prepared optical fiber has high mechanical strength and reliable structure, and is suitable for medical lighting, photodynamic therapy and other fields.

Description

Technical Field

[0001] This invention relates to the field of optical fiber technology, specifically to a columnar diffuse optical fiber with a collapsed air cladding for medical lighting or photodynamic therapy, and a method for manufacturing the same. Background Technology

[0002] Cylindrical diffused fiber is a special type of functional fiber that allows light, which would normally travel axially within the fiber core, to leak uniformly from the sides of the fiber, forming a linear light source similar to a "lamp tube." Due to its unique light emission pattern, cylindrical diffused fiber has significant application value in fields such as photodynamic therapy (PDT), interstitial laser thermotherapy, biophotonics, and special lighting.

[0003] A typical cylindrical diffused optical fiber usually consists of three parts: a transmission section responsible for low-loss transmission of laser energy, a diffused section for achieving lateral uniform emission, and an end reflection structure to prevent energy leakage from the end and improve light energy utilization. Among these, the fabrication of the diffused section is the core and most challenging aspect that determines the performance of the optical fiber.

[0004] Currently, there are two main technical methods for achieving the diffusion segment function. The first method involves microstructure fabrication on the fiber surface, such as using femtosecond lasers to etch a series of microgrooves or scattering points on the core or cladding surface. By precisely controlling the density and shape of the microstructure, light scattering can be modulated. However, this method introduces microcracks into the fiber surface, significantly reducing the fiber's tensile strength and bending fatigue resistance, making it prone to breakage in clinical applications. Furthermore, femtosecond laser processing equipment is expensive, has a narrow process window, and is extremely sensitive to parameters, making it difficult to achieve low-cost, high-yield mass production.

[0005] The second method involves doping the optical fiber material with scattering particles. For example, high-refractive-index nanoparticles such as titanium dioxide (TiO2) and alumina (Al2O3) can be incorporated into the region corresponding to the diffusion section, forming a diffusion section containing scattering centers after tapering. The challenge of this method lies in the fact that if the scattering particles are uniformly distributed, the light intensity will decrease exponentially along the fiber axis, resulting in excessive brightness at the near end and excessive darkness at the far end, failing to meet the uniform dose requirements of medical applications. To achieve uniform light output, the concentration of scattering particles must be gradient-distributed along the axial direction, but this is extremely difficult to control precisely in the manufacturing process. In addition, if the diffusion section and the transmission section are fused together using different optical fibers, the fusion point will become a stress concentration point and hot spot, posing a risk of breakage and burn-out.

[0006] Therefore, existing methods for manufacturing columnar diffused optical fibers generally suffer from problems such as complex processes, high costs, low mechanical strength of finished products, or difficulty in ensuring uniform light output. There is an urgent need for a new manufacturing solution that is simple in process, cost-controllable, and structurally reliable. Summary of the Invention

[0007] In view of this, the present invention aims to provide a columnar diffuse optical fiber with a collapsed air cladding and a method for manufacturing the same, so as to solve the technical problems of complex manufacturing process, high cost, low mechanical strength and poor reliability of the finished product in the prior art.

[0008] To achieve the above objectives, the present invention provides a method for manufacturing a columnar diffuse optical fiber with a collapsed air cladding, comprising: An air-clad optical fiber is provided, wherein the air-clad optical fiber consists of a quartz core, an air cladding, and a quartz cladding from the inside out. A predetermined section of the air-clad optical fiber is locally heated, and the air-clad optical fiber is simultaneously stretched to cause the air cladding in the predetermined section to collapse, thereby forming a solid diffusion section. The air-clad optical fiber is then cut at the diffusion section, and the uncollapsed portion of the air-clad optical fiber constitutes the transmission section, and the diffusion section is integrally connected with the transmission section. A material layer with a refractive index greater than that of quartz is disposed on the outer surface of the dispersion section; An end-reflection structure is provided at the far end of the diffusion segment.

[0009] By performing localized collapse treatment on the air-clad optical fiber to form a diffused section in an integrated manner, the splicing process is avoided, ensuring the overall mechanical strength and structural integrity of the optical fiber.

[0010] In one embodiment, the localized heating is achieved using a carbon dioxide laser with a heating power of 15.5 watts to 17 watts and a heating time of 20 to 40 seconds. This parameter range effectively and stably causes the air cladding to collapse while avoiding thermal damage to the optical fiber, ensuring process repeatability.

[0011] Furthermore, the localized heating is achieved by scanning the spot of the carbon dioxide laser along the axial direction of the air-clad fiber, and by reducing the scanning speed of the spot or allowing the spot to remain in the waist region of the predetermined segment for a preset time. This method can provide energy compensation in the waist region, ensuring more complete and uniform collapse, thereby improving the consistency of optical performance in the diffusion section.

[0012] Optionally, during the stretching process, when the predetermined segment is stretched to a predetermined waist diameter, the output power of the carbon dioxide laser is simultaneously increased. This diameter-feedback-based power control method allows for more precise control of the collapse process, further improving process stability and yield.

[0013] In one embodiment, the application of tension includes: clamping the air-clad optical fiber with a clamping force of 4000 gf to 5000 gf using the left and right clamps of a tensioning device, and stretching it with a tensile force of 2000 gf to 3000 gf, wherein the stretching is performed uniformly at a stretching speed of 0.45 μm / ms to 0.55 μm / ms. Precise control of mechanical parameters helps to achieve controllable, slight stretching, ensuring minimal change in the fiber's outer diameter while the air cladding collapses, thus maintaining good structural integrity.

[0014] Furthermore, the left and right clamps of the tensioning device are respectively mounted on the left and right tracks. The tensioning is achieved by fixing one of the left and right tracks and moving the other at a constant tensioning speed. This unilateral movement method simplifies equipment control and facilitates a stable tensioning process.

[0015] In one embodiment, the step of cutting the air-clad optical fiber at the diffusion section includes cutting it at the middle position of the diffusion section to obtain two columnar diffusion optical fibers at once. This "split-into-two" process allows two finished products to be produced in a single processing flow, greatly improving production efficiency and reducing the unit manufacturing cost.

[0016] Furthermore, the step of cutting at the middle position of the diffusion section is implemented using a fiber optic cleaver, wherein: the optical fiber is held by the left and right clamps of the fiber optic cleaver, the clamping force of the left clamp is 2000 gf to 2700 gf, and the clamping force of the right clamp is 1500 gf to 1800 gf; the fiber optic cleaver cuts the optical fiber by applying forces of 3.4 N to 4 N multiple times; and the cutting is performed under a cutting tension of 1300 gf to 1350 gf, at a cutting speed of 2500 μm / s to 3100 μm / s. Using specific cutting parameters, a smooth and flat cutting end face can be obtained, providing a good foundation for subsequent installation of the end reflection structure and ensuring the reliability of the cutting process.

[0017] Preferably, the diameter of the quartz fiber core is between 200 micrometers and 600 micrometers. Optical fibers within this size range can meet the transmission requirements of high-power lasers and are also suitable for miniaturized applications in fields such as medicine.

[0018] This invention also provides a columnar diffusion optical fiber with a collapsed air cladding, comprising a quartz core, an air cladding, and a quartz cladding, and divided into a transmission section and a diffusion section, wherein the air cladding in the diffusion section collapses to form a solid structure; the columnar diffusion optical fiber further includes: a material layer disposed on the outer surface of the diffusion section, the refractive index of the material layer being greater than that of quartz; and an end-reflection structure disposed at the distal end of the diffusion section. The transmission section and the diffusion section of this optical fiber are different segments of the same optical fiber, forming an integrated structure with excellent mechanical strength and structural reliability.

[0019] Compared with the prior art, the present invention has the following beneficial effects: 1. Simple process and low cost. This invention utilizes local heating and micro-stretching of air-clad optical fibers to cause the air holes to collapse and form a diffuse section. This process can be completed using existing special optical fiber fusion splicing tables, without the need for expensive femtosecond laser etching equipment or complex doped preform drawing processes, greatly reducing manufacturing costs and technical barriers.

[0020] 2. High mechanical strength and reliable structure. The transmission section and diffusion section of this invention are integrally formed from the same optical fiber, eliminating the fragile splice points introduced by traditional splicing processes, fundamentally avoiding the risks of breakage and high-power overheating caused by poor splicing. The solid quartz structure formed after the diffusion section collapses has mechanical properties far superior to optical fibers with etched surfaces.

[0021] 3. High production efficiency. By creating a diffusion section in the middle of a longer optical fiber and then cutting it in the middle, two finished optical fibers can be obtained in one process, doubling the production efficiency compared to the single-fiber production method.

[0022] 4. Stable and controllable performance. By precisely controlling process parameters such as heating power, stretching speed, and force, diffuse optical fibers with consistent performance can be manufactured stably and repeatedly. The collapse of the air cladding reliably disrupts the total internal reflection condition, and combined with the external high-refractive-index material layer, it ensures effective leakage of light energy from the side, achieving a diffuse light emission effect. Attached Figure Description

[0023] Figure 1 This is a flowchart of the method for manufacturing columnar diffused optical fibers according to the present invention.

[0024] Figure 2 This is a schematic diagram of the overall structure of the columnar diffused optical fiber of the present invention.

[0025] Figure 3 A schematic diagram of the cross-sectional structure of the air-clad optical fiber used in this invention.

[0026] Figure 4 This is a schematic diagram of the tapered region of the columnar diffused optical fiber of the present invention.

[0027] The reference numerals in the attached figures are explained as follows: 10 Transmission section; 20 Dispersion section; 110 Quartz fiber core; 120 Air cladding; 130 Quartz cladding; 210 Left cone region; 220 Waist region; 230 Right cone region. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0029] This invention employs a specially structured air-clad optical fiber. By locally heating and stretching the fiber, the original air-hole structure inside collapses, thus forming a single, solid diffusion segment. This diffusion segment and the transmission segment are continuous portions of the same optical fiber, not spliced ​​together later. This method avoids any damaging processing on the fiber surface and eliminates the need for complex doping processes. It offers significant advantages such as a unified structure, high mechanical strength, simple fabrication process, low cost, and easily controllable luminescent performance.

[0030] Reference Figure 1 One aspect of the present invention provides a method for manufacturing a columnar diffuse optical fiber with a collapsed air cladding. The method first includes step S1, which involves providing an air-clad optical fiber, referring to an optical fiber with a special structure, the cross-sectional structure of which is as follows... Figure 3 As shown, from the inside out, it consists of a quartz fiber core 110, an air cladding 120, and a quartz cladding 130. The air cladding 120 is the air region between the quartz fiber core 110 and the outer quartz cladding 130. This air region is typically composed of multiple axially spaced air channels distributed circumferentially, as shown in the attached diagram. Figure 3 As shown, a thin quartz wall is provided between adjacent axial air channels, connecting the quartz fiber core 110 and the quartz cladding 130 to support the quartz cladding 130. The quartz fiber core 110 is the main channel for light energy transmission. The extremely low refractive index (close to 1) of the air cladding 120 and the refractive index (approximately 1.45) of the quartz fiber core 110 create a large refractive index difference, thereby achieving efficient total internal reflection and firmly confining the light energy inside the quartz fiber core 110 for low-loss transmission.

[0031] Next, step S2 is performed, in which a predetermined section of the air-clad optical fiber is locally heated while simultaneously being stretched. Under the combined action of high temperature and tensile force, the axial air channels of the air cladding 120 close and disappear, i.e., collapse occurs. This process transforms the internal structure of the predetermined section into a homogeneous solid structure; that is, the air cladding 120 between the quartz core 110 and the quartz cladding 130 collapses, and the quartz core 110 and the quartz cladding 130 adhere to each other, forming a solid structure. This collapsed section forms the diffuse section 20, while the portion of the air-clad optical fiber that has not undergone this treatment and retains its original structure constitutes the transmission section 10. Since the diffuse section 20 is directly transformed from the transmission section 10, the two are integrated structures on the same optical fiber without any splicing points, thus ensuring the continuity of the overall structure and excellent mechanical strength.

[0032] To significantly improve production efficiency, a cutting step is performed at the middle position of the diffusion segment 20. Specifically, after preparing a relatively long diffusion segment 20 (e.g., 3 to 5 cm in length), step S3 is executed, followed by precise cutting at the middle position of the diffusion segment 20 using a fiber optic cleaver. (Refer to...) Figure 2 Through this step, two identical semi-finished cylindrical diffused optical fibers can be obtained simultaneously in a single heating and stretching operation, each containing a transmission segment 10 and a diffusion segment 20. This manufacturing method directly doubles the output per unit time, greatly reducing the manufacturing cost and time per unit.

[0033] After precise cutting at the middle position of the diffusion section 20, step S4 is performed to apply a material layer to the outer surface of the diffusion section 20. The refractive index of this material layer is greater than that of quartz. In the transmission section 10, light is confined by the air cladding 120; however, in the diffusion section 20, the air cladding 120 disappears, and the conditions for total internal reflection are disrupted. At this time, if the diffusion section 20 is directly exposed to air, the interface between quartz and air can still form a certain degree of total internal reflection. By coating this material layer, the conditions for total internal reflection at the quartz-air interface are completely disrupted, allowing light to effectively leak out from the side of the diffusion section 20, thereby achieving the effect of columnar diffused light emission.

[0034] Finally, step S5 is performed, where an end-reflection structure is installed at the distal end of the diffusion section 20. This reflection structure is located at the very end of the diffusion section 20. The reflection structure reflects the light transmitted through the optical fiber to the end face back into the optical fiber, allowing it to leak out again from the side of the diffusion section 20. This not only prevents high-energy laser light from directly escaping from the end face and damaging normal tissue outside the target area, but also effectively improves the utilization rate of light energy, allowing more energy to be output from the side in the form of diffused light, thus enhancing the overall luminous efficiency.

[0035] Based on the above scheme, the local heating is preferably achieved using a carbon dioxide laser. (Refer to...) Figure 4 The laser beam emitted by the carbon dioxide laser is focused onto a predetermined section of the optical fiber. As a preferred embodiment, the heating power can be set to 15.5 watts to 17 watts, and the heating time to 20 to 40 seconds. This power and time range has been experimentally verified to effectively heat the quartz to above its softening point (approximately 1500-1600°C), sufficient to cause the air cladding 120 to collapse under tensile force, while avoiding excessive temperature that could lead to fiber fusion or unnecessary deformation, thus ensuring the stability and repeatability of the process.

[0036] As a specific heating method, the localized heating can be achieved by scanning the spot of the carbon dioxide laser along the axial direction of the air-clad fiber. To form a longer, uniformly sized diffuse segment 20, the scanning speed of the spot can be reduced or the spot can be briefly paused at the waist region 220 of the predetermined segment. (Refer to...) Figure 4 When stretching an optical fiber, the stretching region typically includes a left conical region 210, a waist region 220, and a right conical region 230. By applying more heat to the waist region 220, it is ensured that the air cladding 120 of the waist region 220 completely collapses, forming a cylindrical region with a uniform diameter. The conical regions 210 and 230 on both sides form a smooth transition, which helps reduce optical loss and stress concentration. The reason for applying more heat to the waist region 220 is that during the tapering process, the middle waist region is stretched thinner, resulting in a smaller diameter. Under the same laser power, the waist region 220 absorbs less heat, which may lead to insufficient temperature and incomplete air cladding collapse. Therefore, additional power is needed to compensate for heat loss and ensure that the waist region 220 is also sufficiently heated and collapsed.

[0037] In another alternative implementation, during the stretching process, when the predetermined segment is stretched to a predetermined waist diameter, the output power of the carbon dioxide laser can be increased simultaneously. This power adjustment method based on real-time geometric feedback allows for more precise control of the collapse process and the final diameter of the diffuse segment 20. It is particularly suitable for applications requiring extremely high uniformity of the diffuse segment 20, as it compensates for changes in heat loss during the stretching process by dynamically adjusting the heat input, thereby achieving a more ideal collapse effect.

[0038] Regarding the stretching step, in a preferred embodiment, the stretching includes: clamping the air-clad optical fiber with a clamping force of 4000 gf to 5000 gf using the left and right clamps of the stretching device. Such a large clamping force ensures that the optical fiber will not slip in the clamps during stretching, guaranteeing precise control of the stretching displacement. Simultaneously, stretching is performed with a stretching force of 2000 gf to 3000 gf, which is sufficient to overcome the viscous resistance of quartz in its softened state, allowing the air cladding 120 to collapse smoothly, but not enough to break the optical fiber.

[0039] To ensure a smooth and uniform stretching process, the stretching is preferably performed at a uniform speed of 0.45 μm / ms to 0.55 μm / ms. Too high a speed may cause the air holes to stretch before they can close, resulting in incomplete collapse; too slow a speed may lead to excessive heat accumulation, causing uneven changes in the fiber diameter. The selected speed range is the ideal range for achieving uniform and complete collapse.

[0040] Specifically, the left and right clamps of the stretching device are fixedly mounted on the left and right tracks, respectively. The stretching is achieved by fixing one of the left and right tracks and moving the other at a uniform stretching speed. For example, on a special optical fiber splicing table, the left track remains stationary while the right track moves to the right at a preset speed. This unilateral movement simplifies the control system and effectively applies uniform axial stretching to the heated area of ​​the optical fiber, thereby stably producing a high-quality diffusion segment 20.

[0041] The cutting step is preferably performed using a professional fiber optic cleaver to ensure the flatness and perpendicularity of the cut end face. In a specific embodiment, the cutting parameters are precisely controlled: the optical fiber is held by the left and right clamps of the fiber optic cleaver, with the clamping force of the left clamp set to 2000gf to 2700gf and the clamping force of the right clamp set to 1500gf to 1800gf. The reason for setting different clamping forces for the left and right clamps is that in the cutting process, one end needs to provide stronger fixation, while the other end, in conjunction with tension, achieves precise breakage. In this setup, the left clamp with a larger clamping force acts as a stable anchoring end, preventing the optical fiber from slipping under force; while the right clamp with a slightly smaller clamping force works together with the cutting tension to guide the crack to expand cleanly from the cleaver's scribe point, thereby obtaining a high-quality flat end face. During cutting, the fiber optic cleaver applies a force of 3.4 N to 4 N multiple times to form a tiny initial crack on the surface of the optical fiber. Meanwhile, the entire cutting process is carried out under a cutting tension of 1300 gf to 1350 gf, with the cutting speed controlled between 2500 micrometers / second and 3100 micrometers / second. This precisely controlled tension allows the crack to propagate stably, ultimately resulting in a mirror-smooth cut surface.

[0042] In a preferred embodiment, the diameter of the quartz fiber core 110 is between 200 micrometers and 600 micrometers. This diameter range covers the large-core-diameter power transmission fiber specifications commonly used in medical, industrial, and other fields, ensuring a sufficiently large aperture to withstand high-power lasers while maintaining the flexibility of the fiber to a certain extent, facilitating operation and use.

[0043] Accordingly, the present invention also provides a columnar diffuse optical fiber with a collapsed air cladding prepared by the above method. This optical fiber is an integrated structure comprising a transmission section 10 and a diffuse section 20. The optical fiber includes a quartz core 110, an air cladding 120, and a quartz cladding 130. In the transmission section 10, these three layers are fully present, with the air cladding 120 ensuring efficient light transmission; while in the diffuse section 20, the air cladding 120 collapses to form a solid structure. Furthermore, a material layer is disposed on the outer surface of the diffuse section 20. The refractive index of this material layer is greater than that of quartz (approximately 1.45), for example, a UV-curable adhesive with a refractive index of 1.55 can be used. This completely disrupts the conditions for total internal reflection of light at the interface between the quartz and the external environment, causing light to leak uniformly from the sidewalls of the diffuse section 20, forming a columnar luminescence effect. An end-reflective structure, such as a highly reflective metal film, is disposed at the distal end of the diffuse section 20. This structure can reflect the light transmitted to the end of the optical fiber back, thereby improving the efficiency of light utilization and avoiding potential safety hazards caused by light emanating from the end face.

[0044] The technical solution of the present invention will be described in more detail below through a specific manufacturing embodiment. This embodiment integrates the aforementioned preferred technical features.

[0045] First, prepare the optical fiber. Prepare an air-clad optical fiber approximately 6 meters long, with a quartz core (110) diameter of 300 micrometers and an overall outer diameter (including the quartz cladding (130)) of 440 micrometers. Carefully strip approximately 5 centimeters of the outer protective coating at the midpoint of the fiber's length, exposing the bare fiber. Then, place this fiber on the track of the special fiber fusion splicing stage, ensuring the area where the coating has been stripped is located in the laser heating zone at the center of the stage. Clamp both ends of the fiber to keep it taut. Before the actual processing, perform a concentric alignment procedure on the special fiber fusion splicing stage to ensure the left and right tracks are strictly coaxial, preventing bending during the stretching process.

[0046] Specialized fiber optic fusion splicing workstations are existing technologies. For example, several existing technologies, such as CN122172385A (publication number: CN122172385A, patent name: A fully automatic fiber optic fusion tapering machine) and CN101672951B (publication number: CN101672951B, patent name: Fiber optic fusion tapering machine), disclose that these workstations possess heating and stretching functions. In the market, various commercial processing equipment with fiber optic fusion splicing, tapering, and dicing functions already exist. For instance, the LDS 2.5 fiber optic processing workstation produced by 3SAE Technologies, Inc. (USA) integrates fusion splicing, tapering, online dicing, bundling, and end cap fabrication. Domestically, Shenzhen OSCOM Technology Co., Ltd.'s XQ7210 series CO2 laser large-diameter fiber optic fusion splicing system also possesses multiple operation functions, including fusion splicing and tapering.

[0047] Next, a heating and stretching process is performed. Heating and stretching parameters are set in the control software of the special fiber optic fusion splicing stage, with a carbon dioxide laser as the heating source. The actual power of the special fiber optic fusion splicing stage is set to 15.5W, and the total heating power for the waist section 220 is set to 17W. The clamping force is set to 4500gf, and the stretching force to 2500gf. The stretching method is set to right track movement, left track fixed, and stretching speed set to 0.49 μm / ms. After the parameters are set, the program is started. The carbon dioxide laser begins to heat the predetermined section of the fiber, while the right track begins to move at a constant speed, applying stretching to the fiber. The entire heating and stretching process lasts approximately 20 seconds, ultimately forming a diffused section 20 with a length of approximately 30 mm. The online measurement function of the stage shows that the fiber outer diameter only decreases slightly, for example, from the original 440 μm to 434 μm.

[0048] Next, the fiber is cleaved. The fiber is carefully removed from the fusion splicing table and transferred to the fiber optic cleaving equipment. The fiber is placed on the cleaving equipment's track, and its position is adjusted so that the cleaving blade is aligned with the center of the formed diffusion section 20. The cleaving parameters are set as follows: left clamping force 2500 gf, right clamping force 1600 gf, cleaving tension 1320 gf, and cleaving speed 2800 micrometers / second. The cleaving program is started, and the equipment automatically completes the scoring and breakage operations, precisely cleaving one fiber from the center of the diffusion section 20 into two identical semi-finished products.

[0049] Finally, the finished product is processed. At this point, two semi-finished columnar diffused optical fibers are obtained, each with a diffused section 20 approximately 15 mm long. For each fiber, a layer of UV-curable adhesive with a refractive index of 1.55 is uniformly coated onto the outer surface of the diffused section 20 as a material layer, and then cured using a UV lamp. Next, a thin silver film is deposited on the farthest end face of the diffused section 20 of each fiber using a magnetron sputtering process to form an end-reflective structure. Thus, two fully functional columnar diffused optical fibers are manufactured.

[0050] Those skilled in the art will understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. For example, the material layer can be any polymer or sol-gel material with a refractive index greater than quartz and transparent to the working wavelength, in addition to using a UV-curable adhesive. Similarly, the end-reflective structure can be achieved not only by sputtering a metal film, but also by fusing a pre-fabricated end-reflective structure or by coating a high-reflectivity dielectric film stack. These modifications and substitutions do not depart from the core technical concept of the present invention.

Claims

1. A method for manufacturing a columnar diffuse optical fiber with a collapsed air cladding, characterized in that, include: An air-clad optical fiber is provided, wherein the air-clad optical fiber consists of a quartz core, an air cladding, and a quartz cladding from the inside out. A predetermined section of the air-clad optical fiber is locally heated, and the air-clad optical fiber is simultaneously stretched to cause the air cladding in the predetermined section to collapse, thereby forming a solid diffusion section. The air-clad optical fiber is then cut at the diffusion section, and the uncollapsed portion of the air-clad optical fiber constitutes the transmission section, and the diffusion section is integrally connected with the transmission section. A material layer with a refractive index greater than that of quartz is disposed on the outer surface of the dispersion section; An end-reflection structure is provided at the far end of the diffusion segment.

2. The method for manufacturing a columnar diffuse optical fiber with a collapsed air cladding according to claim 1, characterized in that, The localized heating is achieved using a carbon dioxide laser with a heating power of 15.5 watts to 17 watts and a heating time of 20 to 40 seconds.

3. The method for manufacturing a columnar diffuse optical fiber with a collapsed air cladding according to claim 2, characterized in that, The localized heating is achieved by scanning the spot of the carbon dioxide laser along the axial direction of the air-clad fiber, and by reducing the scanning speed of the spot or allowing the spot to remain in the waist region of the predetermined segment for a preset time.

4. The method for manufacturing a columnar diffuse optical fiber with a collapsed air cladding according to claim 2, characterized in that, During the stretching process, when the predetermined segment is stretched to a predetermined waist diameter, the output power of the carbon dioxide laser is simultaneously increased.

5. The method for manufacturing a columnar diffuse optical fiber with a collapsed air cladding according to claim 1, characterized in that, The application of tension includes: clamping the air-clad optical fiber with a clamping force of 4000 gf to 5000 gf by the left and right clamps of the tensioning device, and stretching it with a tensile force of 2000 gf to 3000 gf, and the stretching is performed at a uniform speed of 0.45 micrometers / millisecond to 0.55 micrometers / millisecond.

6. The method for manufacturing a columnar diffuse optical fiber with a collapsed air cladding according to claim 5, characterized in that, The left and right clamps of the stretching device are respectively installed on the left and right tracks. The stretching is achieved by fixing one of the left and right tracks and moving the other track at a constant speed at the stretching speed.

7. The method for manufacturing a columnar diffuse optical fiber with a collapsed air cladding according to claim 1, characterized in that, The step of cutting the air-clad optical fiber at the diffusion section includes cutting it at the middle position of the diffusion section to obtain two columnar diffusion optical fibers at one time.

8. The method for manufacturing a columnar diffuse optical fiber with a collapsed air cladding according to claim 7, characterized in that, The step of cutting at the middle position of the diffusion segment is implemented by an optical fiber cleaver, wherein: the optical fiber is held by the left and right clamps of the optical fiber cleaver, the clamping force of the left clamp is 2000gf to 2700gf, and the clamping force of the right clamp is 1500gf to 1800gf; the optical fiber cleaver cuts the optical fiber by applying a force of 3.4N to 4N multiple times; and the cutting is performed under a cutting tension of 1300gf to 1350gf, and the cutting speed is 2500μm / s to 3100μm / s.

9. The method for manufacturing a columnar diffuse optical fiber with a collapsed air cladding according to claim 1, characterized in that, The diameter of the quartz fiber core is between 200 micrometers and 600 micrometers.

10. A columnar diffuse optical fiber with a collapsed air cladding, characterized in that, It includes a quartz fiber core, an air cladding, and a quartz cladding, and is divided into a transmission section and a diffusion section, wherein the air cladding in the diffusion section collapses to form a solid structure; The columnar diffused optical fiber further includes: A material layer disposed on the outer surface of the dispersion section, wherein the refractive index of the material layer is greater than that of quartz; as well as An end-reflection structure is located at the far end of the diffusion segment.

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