A tapered optical fiber and a method for preparing the same

Abstract

The present invention provides a tapered optical fiber and a preparation method thereof, the preparation method of the tapered optical fiber comprising: placing a first cylindrical quartz tube provided with a first through hole on a deposition lathe; depositing a core layer in the first through hole, and gradually adjusting the deposition amount along the direction of the first through hole during the deposition of the core layer; shrinking the first cylindrical quartz tube for depositing the core layer to prepare a tapered preform rod; drawing the tapered preform rod into a tapered optical fiber, the tapered optical fiber comprising a core for conducting light along the axial direction of the tapered optical fiber and a cladding surrounding the core. The preparation method of the tapered optical fiber provided by the present invention does not require multiple polishing during the entire process, is formed in one step, has a simple process, greatly reduces the processing difficulty of the tapered optical fiber, and improves the preparation efficiency and precision of the tapered optical fiber.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber preparation, and in particular to a method for preparing a tapered optical fiber. Background Art

[0002] Compared with ordinary fibers with uniform core cladding, tapered fibers can increase the effective mode field area of ​​the fiber by introducing a large core diameter end, which has the advantage of effectively suppressing nonlinear effects. At the same time, tapered fibers also have excellent mode instability suppression performance, beam quality maintenance characteristics, and amplified spontaneous emission (ASE) suppression effects, and have great potential in the field of high-power lasers.

[0003] Tapered optical fibers are often made by melting and taper methods, mechanical polishing methods, or chemical etching methods. By changing the radius of the optical fiber in the axial direction, a tapered region is formed to achieve applications such as optical coupling, optical sensing, nonlinear optics, micro-nano optics, optical fiber devices, and other research fields. However, during the processing of existing tapered optical fibers, the core rod and the glass rod need to be ground separately. The preparation process is complicated and cumbersome, especially the grinding of the inner wall of the glass rod, which is difficult to process and has low precision. At the same time, the inner grinding also limits the length of the glass rod and has disadvantages such as poor adaptability. Summary of the invention

[0004] The invention provides a method for preparing a tapered optical fiber, which is used to solve the problem that in the processing of the existing tapered optical fiber, a core rod and a glass rod need to be ground and processed separately, and the preparation process is complicated and cumbersome.

[0005] In a first aspect, the present invention provides a method for preparing a tapered optical fiber, comprising:

[0006] placing a first cylindrical quartz tube having a first through hole on a deposition lathe;

[0007] Depositing a core layer in the first through hole, and gradually adjusting a deposition amount along a direction of the first through hole during the deposition of the core layer;

[0008] shrinking the first cylindrical quartz tube on which the core layer has been deposited to prepare a tapered preform;

[0009] The tapered preform is drawn into a tapered optical fiber, which includes a core for guiding light along the axial direction of the tapered optical fiber and a cladding surrounding the core.

[0010] According to a method for preparing a tapered optical fiber of the present invention, the step of depositing a core layer in the first through hole and gradually adjusting the deposition amount along the direction of the first through hole during the process of depositing the core layer comprises:

[0011] acid washing the first cylindrical quartz tube;

[0012] The deposited loose layer is gradually increased or decreased along the direction of the first through hole, and rare earth ions are doped into the deposited loose layer.

[0013] According to a method for preparing a tapered optical fiber of the present invention, a core layer is deposited in the first through hole, and during the process of depositing the core layer, a step of gradually adjusting the deposition amount along the direction of the first through hole comprises:

[0014] acid washing the first cylindrical quartz tube;

[0015] The deposited loose layer is gradually increased or decreased along the direction of the first through hole, and rare earth ions are doped into the deposited loose layer.

[0016] According to a method for preparing a tapered optical fiber of the present invention, the step of doping the deposited loose layer with rare earth ions comprises:

[0017] Passing a solution containing the rare earth ions into the first through hole;

[0018] After soaking for a preset time, the remaining solution containing the rare earth ions is discharged.

[0019] According to a method for preparing a tapered optical fiber of the present invention, the rare earth ion is Nd 3+ , Yb 3+ , Er 3+ 、Tm 3+ Any one or combination of the following.

[0020] According to a method for preparing a tapered optical fiber of the present invention, the step of shrinking the first cylindrical quartz tube for depositing the core layer to prepare a tapered preform comprises:

[0021] The first cylindrical quartz tube and the deposited loose layer are sintered to melt and shrink the first cylindrical quartz tube and the deposited loose layer into the tapered preform rod.

[0022] According to a method for preparing a tapered optical fiber of the present invention, the step of drawing the tapered preform into a tapered optical fiber comprises:

[0023] The tapered preform rod is placed on a drawing tower and drawn into the tapered optical fiber.

[0024] According to a method for preparing a tapered optical fiber of the present invention, the step of drawing the tapered preform into a tapered optical fiber comprises:

[0025] Assembling the second quartz tube and the tapered preform rod, and sleeve-forming the rod on a sleeve lathe to obtain a solid tapered optical fiber preform rod;

[0026] The tapered optical fiber preform is placed on a drawing tower and drawn into the tapered optical fiber.

[0027] According to a method for preparing a tapered optical fiber of the present invention, after the step of drawing the tapered preform into a tapered optical fiber, the method further comprises:

[0028] The outer periphery of the cladding is coated twice to form an optical fiber coating.

[0029] In a second aspect, the present invention further provides a tapered optical fiber, wherein the tapered optical fiber is manufactured by any of the methods for preparing a tapered optical fiber as described above.

[0030] The method for preparing a tapered optical fiber provided by the present invention provides a first through hole in a first cylindrical quartz tube, and in the process of depositing a core layer in the first through hole, gradually adjusts the deposition amount along the direction of the first through hole, so that the thickness of the core layer gradually changes along the direction of the first through hole, so as to shrink the rod to form a tapered preform rod, and finally draws the tapered preform rod into a tapered optical fiber. The whole process does not require multiple polishing, and the molding is carried out in one time. The process is simple, which greatly reduces the processing difficulty of the tapered optical fiber and improves the preparation efficiency and accuracy of the tapered optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 This is one of the schematic flow diagrams of the method for preparing a tapered optical fiber provided in an embodiment of the present invention;

[0033] Figure 2 is a schematic diagram of a first cylindrical quartz tube provided in an embodiment of the present invention;

[0034] Figure 3 is a schematic diagram of a first cylindrical quartz tube after a core layer is deposited provided by an embodiment of the present invention;

[0035] Figure 4 is a schematic diagram of a tapered preform provided by an embodiment of the present invention;

[0036] Figure 5 is one of the schematic diagrams of the tapered optical fiber provided in an embodiment of the present invention;

[0037] Figure 6 This is a second schematic flow chart of a method for preparing a tapered optical fiber provided in an embodiment of the present invention;

[0038] Figure 7 This is a third schematic diagram of the process of preparing a tapered optical fiber provided by an embodiment of the present invention;

[0039] Figure 8 is a schematic diagram of a tapered optical fiber preform provided by an embodiment of the present invention;

[0040] Fig. 9 This is the second schematic diagram of the tapered optical fiber provided by the embodiment of the present invention;

[0041] Reference numerals:

[0042] 1. a first cylindrical quartz tube; 10. a first through hole;

[0043] 2. Core layer;

[0044] 3. Conical preform;

[0045] 4. tapered optical fiber; 41. core; 42. cladding;

[0046] 5. The second quartz tube. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are 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.

[0048] In the description of the embodiments of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "front", "back", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the devices or elements referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0049] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0050] Combine the following Figure 1The method for preparing the tapered optical fiber provided by the present invention comprises the following steps:

[0051] Step S101: placing a first cylindrical quartz tube having a first through hole on a deposition lathe.

[0052] First, if Figure 2 As shown, a first cylindrical quartz tube 1 having matching thermal properties and satisfying optical properties and provided with a first through hole 10 is selected, and the first cylindrical quartz tube 1 is placed on a deposition lathe.

[0053] In this embodiment, the first through hole 10 is disposed at the center of the first cylindrical quartz tube 1 , and the first through hole 10 extends from one end of the first cylindrical quartz tube 1 to the other end of the first cylindrical quartz tube 1 .

[0054] Step S102: depositing a core layer in the first through hole, and gradually adjusting the deposition amount along the direction of the first through hole during the process of depositing the core layer.

[0055] After the first cylindrical quartz tube 1 having the first through hole 10 is manufactured, the first cylindrical quartz tube 1 can be rotated while the gas or liquid raw material can be introduced through the first through hole 10, and the gas or liquid raw material is deposited on the inner wall of the first through hole 10 to form the core layer 2; during the deposition process, the introduction speed of the gas or liquid raw material is gradually adjusted to adjust the deposition amount of the core layer 2 along the direction of the first through hole 10, such as Figure 3 shown.

[0056] Optionally, the introduction speed of the gas or liquid raw material can be changed continuously, so that the deposition amount of the core layer 2 along the direction of the first through hole 10 changes continuously to form an inclined surface; or, the introduction speed of the gas or liquid raw material can also be changed in sections, so that the deposition amount of the core layer 2 along the direction of the first through hole 10 changes in sections to form a multi-section step surface.

[0057] Step S103: shrinking the first cylindrical quartz tube on which the core layer is deposited to prepare a tapered preform.

[0058] The deposition amount of the raw material in the first through hole 10 changes gradually along the direction of the first through hole 10. After the core layer 2 with a gradually changing thickness is deposited in the first through hole 10 of the first cylindrical quartz tube 1, the first cylindrical quartz tube 1 is shrunk. Since the thickness of the core layer 2 changes gradually, it will melt and shrink to form a conical core layer 2 during the shrinking process, that is, melt and shrink to form a conical preform 3, such as Figure 4 shown.

[0059] During the shrinking process, oxygen is introduced to purge the core layer 2 and the first cylindrical quartz tube 1, and the temperature is raised to 1700° C. The temperature is continued to rise, and the moving speed of the heat source is reduced to 2.5 to 20 mm / min, the pressure difference between the gas outlet end and the atmospheric pressure is maintained, and the temperature is controlled at 1850 to 2150° C. The first cylindrical quartz tube 1 on which the core layer 2 is deposited is made into a conical preform 3.

[0060] S104: Drawing the tapered preform into a tapered optical fiber.

[0061] After the conical preform rod 3 is manufactured, the conical preform rod 3 is placed on a drawing tower. Figure 5 As shown, a tapered optical fiber 4 with a core-to-cladding ratio is drawn. The tapered optical fiber 4 includes a core 41 for guiding light along the axial direction of the tapered optical fiber 4 and a cladding 42 surrounding the core 41.

[0062] The tapered optical fiber 4 has a constant cladding diameter and a gradually changing core 41 diameter. The core-to-cladding ratio of the optical fiber gradually changes with the length of the optical fiber. Moreover, the diameter of the core 41, the core-to-cladding ratio and the cone angle can be controlled within a certain range according to the needs, and can be specifically adjusted according to the requirements of the passive optical fiber device and the optical system.

[0063] The method for preparing a tapered optical fiber provided by the present invention provides a first through hole 10 in a first cylindrical quartz tube 1, and in the process of depositing a core layer 2 in the first through hole 10, gradually adjusts the deposition amount along the direction of the first through hole 10, so that the thickness of the core layer 2 gradually changes along the direction of the first through hole 10, so as to shrink the rod to form a tapered preform rod 3, and finally draws the tapered preform rod 3 into a tapered optical fiber 4. The entire process does not require multiple polishing, and the molding is performed in one time. The process is simple, which greatly reduces the processing difficulty of the tapered optical fiber 4 and improves the preparation efficiency and accuracy of the tapered optical fiber.

[0064] In another specific embodiment, after selecting a cylindrical quartz tube with matching thermal properties, satisfying optical properties and having a first through hole 10, the outer wall of the cylindrical quartz tube can also be etched or polished into a conical surface to obtain a conical quartz tube, and the first conical quartz tube is placed on a deposition lathe, and the first through hole 10 extends from one end of the first conical quartz tube to the other end of the first conical quartz tube.

[0065] After the first conical quartz tube with the first through hole 10 is manufactured, the gas or liquid raw material can be introduced through the first through hole 10 while the first conical quartz tube is controlled to rotate, and the gas or liquid raw material is deposited on the inner wall of the first through hole 10 to form the core layer 2; during the deposition process, the introduction speed of the gas or liquid raw material is gradually adjusted to adjust the deposition amount of the core layer 2 along the direction of the first through hole 10. Specifically, the deposition amount of the core layer 2 increases with the contraction of the outer cone surface of the first conical quartz tube.

[0066] Optionally, the introduction speed of the gas or liquid raw material can be changed continuously, so that the deposition amount of the core layer 2 along the direction of the first through hole 10 changes continuously to form an inclined surface; or, the introduction speed of the gas or liquid raw material can also be changed in sections, so that the deposition amount of the core layer 2 along the direction of the first through hole 10 changes in sections to form a multi-section step surface.

[0067] The deposition amount of the raw material in the first through hole 10 changes gradually along the direction of the first through hole 10. After the core layer 2 with a gradually changing thickness is deposited in the first through hole 10 of the first conical quartz tube, the first conical quartz tube is shrunk. Since the thickness of the core layer 2 changes gradually, it will melt and shrink to form a conical core layer 2 during the shrinking process, and the first through hole 10 will melt and shrink to form a conical hole that wraps the core layer 2, so as to construct a conical preform 3 with a conical hole inside.

[0068] During the process of melting and shrinking the rod, oxygen is introduced to purge the core layer 2 and the first conical quartz tube, and the temperature is gradually raised to 1700° C. The temperature is continued to rise, and the moving speed of the heat source is reduced to 2.5 to 20 mm / min, the pressure difference between the gas outlet end and the atmospheric pressure is maintained, and the temperature is controlled at 1850 to 2150° C. The first conical quartz tube on which the core layer 2 is deposited is made into a conical preform rod 3.

[0069] After the tapered preform rod 3 is manufactured, the tapered preform rod 3 is placed on a drawing tower and drawn into a tapered optical fiber 4 with a gradually changing core-to-cladding ratio. The tapered optical fiber 4 includes a core 41 for guiding light along the axial direction of the tapered optical fiber 4 and a cladding 42 surrounding the core 41.

[0070] The tapered optical fiber 4 has a gradually changing cladding diameter and a reversely changing core 41 diameter. The core-to-cladding ratio of the optical fiber gradually changes with the length of the optical fiber, and the core-to-cladding ratio per unit length varies more, which is conducive to meeting the actual design and use requirements. At the same time, the diameter of the core 41, the cladding diameter, the core-to-cladding ratio, etc. can be adjusted within a certain range according to the requirements, and can be specifically adjusted according to the requirements of the passive optical fiber device and the optical system.

[0071] Optionally, in another specific embodiment, a cylindrical quartz tube with matching thermal properties and satisfying optical properties and having a through hole is selected, and the inner wall of the through hole is etched or polished to form a tapered through hole, thereby obtaining a first tapered quartz tube. The first tapered quartz tube is placed on a deposition lathe, and the tapered through hole extends from one end of the first tapered quartz tube to the other end of the first tapered quartz tube, and the aperture of the tapered through hole gradually decreases from one end to the other end, forming a truncated cone shape.

[0072] After the first tapered quartz tube with a tapered through hole is manufactured, the gas or liquid raw material can be introduced through the tapered through hole while the first tapered quartz tube is controlled to rotate, and the gas or liquid raw material is deposited on the inner wall of the tapered through hole to form the core layer 2; during the deposition process, the introduction speed of the gas or liquid raw material is gradually adjusted to adjust the deposition amount of the core layer 2 along the tapered through hole. Specifically, the deposition amount of the core layer 2 decreases as the tapered through hole shrinks.

[0073] Optionally, the introduction speed of the gas or liquid raw material can be changed continuously, so that the deposition amount of the core layer 2 along the direction of the tapered through hole changes continuously to form an inclined surface; or, the introduction speed of the gas or liquid raw material can also be changed in sections, so that the deposition amount of the core layer 2 along the direction of the tapered through hole changes in sections to form a multi-section step surface.

[0074] Optionally, the deposition amount of the raw material in the tapered through hole changes gradually along the direction of the tapered through hole, and after the raw material is deposited in the tapered through hole of the first tapered quartz tube to form a core layer 2 with a gradually changing thickness, the first tapered quartz tube is shrunk. Since the thickness of the core layer 2 changes gradually, it will melt and shrink to form a tapered core layer 2 during the shrinking process, and the tapered through hole will melt and shrink to form a tapered hole that wraps the core layer 2, so as to construct a tapered preform 3 with a tapered hole inside.

[0075] During the shrinking process, oxygen is introduced to purge the core layer 2 and the first tapered quartz tube, and the temperature is gradually raised to 1700° C. The temperature is continued to rise, and the moving speed of the heat source is reduced to 2.5 to 20 mm / min, the pressure difference between the gas outlet end and the atmospheric pressure is maintained, and the temperature is controlled at 1850 to 2150° C. The first tapered quartz tube on which the core layer 2 is deposited is made into a tapered preform 3.

[0076] After the tapered preform rod 3 is manufactured, the tapered preform rod 3 is placed on a drawing tower and drawn into a tapered optical fiber 4 with a gradual core-to-cladding ratio. The tapered optical fiber 4 includes a core 41 for conducting light along the axial direction of the tapered optical fiber 4 and a cladding 42 surrounding the core 41.

[0077] The tapered optical fiber 4 has a constant cladding diameter and a gradually changing core 41 diameter, and the core-to-cladding ratio of the optical fiber gradually changes with the length of the optical fiber to meet the actual design and use requirements. At the same time, the diameter of the core 41 and the core-to-cladding ratio can be adjusted within a certain range according to the requirements, and can be specifically adjusted according to the requirements of the passive optical fiber device and the optical system.

[0078] In one embodiment, step S102: depositing a core layer in the first through hole, and gradually adjusting the deposition amount along the first through hole during the deposition of the core layer, such as Figure 6 As shown, the following steps are included:

[0079] Step S1021: pickling the first cylindrical quartz tube.

[0080] Step S1022: gradually increasing or decreasing the deposited loose layer along the direction of the first through hole, and doping rare earth ions in the deposited loose layer.

[0081] Specifically, if Figure 3 As shown, after the first cylindrical quartz tube 1 with the first through hole 10 is manufactured, the first cylindrical quartz tube 1 is first cleaned by pickling. For example, the entire first cylindrical quartz tube 1 can be pickled with a hydrofluoric acid solution. The impurities in the first cylindrical quartz tube 1 are effectively removed by pickling, thereby ensuring the processing quality.

[0082] After pickling, the air inlet section of the first cylindrical quartz tube 1 is equipped with a rotary joint, and the first cylindrical quartz tube 1 is installed on a deposition lathe. Modified Chemical Vapor Deposition (MCVD) can be used to deposit a loose layer, and rare earth ions are doped in the deposited loose layer.

[0083] Specifically, the first cylindrical quartz tube 1 is preheated externally by an oxyhydrogen flame, and during the preheating process, the temperature of the first cylindrical quartz tube 1 is gradually increased to 1200°C. Then, a gas raw material is introduced into the first cylindrical quartz tube 1 according to a preset flow rate. The gas raw material is any one or a combination of SiCl4, BCl3, GeCl4, and POCl3. Prior to this, SF6 and O2 need to be introduced into the first cylindrical quartz tube 1 to perform several passes of etching on the inner side wall of the first cylindrical quartz tube 1, and the first cylindrical quartz tube 1 is continuously heated and the gas raw material is introduced. Among them, when the gas raw material is introduced, the temperature of the reaction tube needs to be heated to 1500°C to 1800°C. During the repeated rotation of the first cylindrical quartz tube 1, the introduction speed of the gas raw material is gradually changed, and the deposition loose layer is gradually increased or decreased along the direction of the first through hole 10, so that the deposition loose layer gradually becomes thicker or thinner along the direction of the first through hole 10, which is convenient for subsequent rod shrinking to form a conical preform 3. During the deposition process or after the deposition is completed, the deposited loose layer may be doped with rare earth ions.

[0084] It should be noted that, according to actual needs, the loose layer can also be deposited by outside vapor deposition (OVD), axial chemical vapor deposition (VAD) or plasma chemical vapor deposition (PCVD), and rare earth ions can be doped into the deposited loose layer.

[0085] Optionally, in another embodiment, step S102: depositing a core layer in the first through hole, and gradually adjusting the deposition amount along the first through hole during the deposition of the core layer, such as Figure 7 As shown, the following steps are included:

[0086] Step S1021: pickling the first cylindrical quartz tube.

[0087] Step S1022: increasing or decreasing the deposited loose layer section by section along the direction of the first through hole, and doping the deposited loose layer with rare earth ions.

[0088] In this embodiment, the specific implementation of step S1021 and the method of introducing the gas raw material in step S1022 are similar to the above-mentioned embodiments, and will not be described in detail here. It should be noted that in step S1022, when the gas raw material is introduced into the first through hole 10, the first cylindrical quartz tube 1 is repeatedly rotated, and the introduction speed of the gas raw material is changed step by step, so that the deposited loose layer can be increased or decreased step by step along the direction of the first through hole 10, thereby forming a stepped deposited loose layer that becomes thicker or thinner step by step along the direction of the first through hole 10, which is convenient for subsequent rod shrinking to form a conical preform rod 3. Rare earth ions can be doped in the deposited loose layer during the deposition process or after the deposition is completed.

[0089] In this embodiment, during the process of doping rare earth ions, a solution containing rare earth ions may be first introduced into the first through hole 10 , and after soaking for a preset time, the remaining solution containing rare earth ions is discharged to obtain a deposited loose layer containing rare earth ions.

[0090] Specifically, a solution containing rare earth doping ions is introduced into the first cylindrical quartz tube 1 and soaked for a preset time, which is more than 30 minutes, to dope the deposited loose layer with rare earth ions. Specifically, the rare earth doping ions and the dissolving solution are mixed according to a preset ratio to obtain a rare earth doping ion solution, wherein the rare earth ions are Nd 3+ , Yb 3+ , Er 3+ 、Tm 3+ Any one or a combination of the above. The dissolving liquid is a chloride solution or a nitrate solution. After the solution containing rare earth doping ions is prepared, the first cylindrical quartz tube 1 is taken out, and then the first cylindrical quartz tube 1 is immersed in the solution of rare earth doping ions of a specified concentration. After the immersion, the solution containing rare earth ions can be discharged and dried, so that a deposited loose layer containing rare earth ions can be obtained in the first through hole 10.

[0091] Optionally, in some embodiments, according to actual needs, rare earth ions may not be doped into the deposited loose layer, so as to produce a passive optical fiber without rare earth ions. Based on the above embodiments, in some embodiments, step S103: shrinking the first cylindrical quartz tube of the deposited core layer to prepare a tapered preform includes: sintering the first cylindrical quartz tube and the deposited loose layer, so that the first cylindrical quartz tube and the deposited loose layer are melted and shrunk into a tapered preform.

[0092] like Figure 4 As shown, after the core layer 2 is deposited, the first cylindrical quartz tube 1 and the deposited loose layer are sintered at high temperature to vitrify the deposited loose layer containing rare earth ions, and then the vitrified deposited loose layer and the first cylindrical quartz tube 1 are melted and shrunk into a solid conical preform rod 3, and the gap between the deposited loose layer and the first cylindrical quartz tube 1 is effectively removed by shrinking the rod.

[0093] Based on the above embodiments, in some embodiments, step S104: drawing the tapered preform into a tapered optical fiber specifically includes: after the tapered preform is manufactured, Figure 4 As shown, the conical preform rod 3 can be placed on a drawing tower, and a high temperature furnace is used to heat and soften the conical preform rod 3. The adjustable experimental parameters include heating rate, drawing temperature, drawing tension, etc. The conical preform rod 3 is softened by a high temperature furnace and then drawn to form a conical optical fiber 4. Figure 5 As shown, the tapered optical fiber 4 includes a core 41 that conducts light along the axial direction of the tapered optical fiber 4 and a cladding 42 surrounding the core 41. The tapered optical fiber 4 with a core-to-cladding ratio gradient has a gradually varying core 41 diameter and a constant cladding diameter. The core-to-cladding ratio of the optical fiber gradually changes with the length of the optical fiber, and the diameter of the core 41, the core-to-cladding ratio and the taper angle can be adjusted within a certain range according to requirements, and can be specifically adjusted according to the requirements of passive optical fiber devices and optical systems.

[0094] Based on the above embodiments, in other embodiments, step S104: drawing the tapered preform into a tapered optical fiber specifically includes: after the tapered preform is made, if it is found that the tapered preform does not meet the specifications and requires a sleeve, such as Figure 8As shown, firstly, a second quartz tube 5 is selected whose thermal properties match and whose optical properties meet the requirements. The second quartz tube 5 has a second through hole that matches the tapered preform rod 3, and the second through hole extends from one end of the second quartz tube 5 to the other end. Then, the second quartz tube 5 is assembled with the tapered preform rod 3, and the tube is sleeved on a sleeve lathe to obtain a solid tapered optical fiber preform rod, thereby obtaining a tapered optical fiber preform rod that meets the requirements. The tapered optical fiber preform rod is then placed on a drawing tower, and a high-temperature furnace is used to heat and soften the tapered optical fiber preform rod. Adjustable experimental parameters include heating rate, drawing temperature, drawing tension, etc. The tapered optical fiber preform rod is softened in a high-temperature furnace and then drawn to form a tapered optical fiber 4. By drawing after the sleeve, the sealing performance can be fully guaranteed, the drawing can be more easily controlled, and the concentricity error can be suppressed. As shown Figure 5 As shown, the tapered optical fiber 4 includes a core 41 that conducts light along the axial direction of the tapered optical fiber 4 and a cladding 42 surrounding the core 41; wherein the cladding 42 is formed by the second quartz tube 5 and the first cylindrical quartz tube 1 being sleeved. The tapered optical fiber 4 has a gradually changing core 41 diameter and a constant cladding diameter, and the core-to-cladding ratio of the optical fiber gradually changes with the length of the optical fiber. Moreover, the diameter of the core 41, the core-to-cladding ratio, the taper angle, etc. can be adjusted within a certain range according to the requirements, and can be specifically adjusted according to the requirements of the passive optical fiber device and the optical system.

[0095] Finally, if Fig. 9 As shown, the outer periphery of the cladding 42 may be coated with a low-refractive coating twice, thereby forming an optical fiber coating outside the cladding 42 .

[0096] Specifically, the first coating is performed to form an inner coating of the optical fiber; and the second coating is performed on the peripheral wall of the inner coating of the optical fiber to form an outer coating.

[0097] In the above-mentioned preparation process, the embodiment is essentially to apply the inner coating of the optical fiber to the peripheral wall of the optical fiber cladding. The inner coating of the optical fiber is a low-refractive index coating, and the refractive index of the inner coating of the optical fiber is lower than the refractive index of the optical fiber cladding to ensure the reliability of the tapered optical fiber.

[0098] In addition, the present application also provides two specific embodiments.

[0099] Example 1:

[0100] A double-clad ytterbium-doped tapered optical fiber is prepared using the following steps:

[0101] Step 1: Place a cylindrical high purity quartz tube on a deposition lathe.

[0102] Step 2: Deposit the core layer on a lathe, gradually increase it in the axial direction, and shrink the rod into a tapered optical fiber preform after the core layer is deposited. Specifically, a high-temperature lamp moves at a constant speed under the quartz tube, gradually increasing the amount of silicon tetrachloride introduced into the tube in the axial direction, and forming a deposition layer with a tapered cross-section and increasing thickness in the axial direction of the tube.

[0103] Step 3: Place the deposited core rod on a lathe to shrink it into a tapered optical fiber preform rod.

[0104] Step 4: Place the tapered optical fiber preform on a drawing tower and draw it into a tapered optical fiber.

[0105] Example 2:

[0106] A double-clad ytterbium-doped tapered optical fiber is prepared using the following steps:

[0107] Step 1: Place a cylindrical high purity quartz tube on a deposition lathe.

[0108] Step 2: Deposit the core layer on a lathe, gradually change it in sections along the axial direction, and shrink the rod into a tapered optical fiber preform after the core layer is deposited. Specifically, a high-temperature lamp moves at a constant speed under the quartz tube, and increases the amount of silicon tetrachloride introduced into the tube in sections along the axial direction, so that the core layer deposited in the tube gradually thickens, and finally forms multiple sections of deposited layers with tapered cross-sections along the axial direction.

[0109] Step 3: Place the deposited core rod on a lathe to shrink it into a tapered optical fiber preform rod.

[0110] Step 4: Place the tapered optical fiber preform on a drawing tower and draw it into a tapered optical fiber.

[0111] On the other hand, in some embodiments of the present application, a tapered optical fiber is provided, which is made by the method for preparing a tapered optical fiber as provided in any of the above embodiments. Therefore, the tapered optical fiber also includes all the beneficial effects of the method for preparing a tapered optical fiber as provided in any of the above embodiments. To avoid repetition, they will not be repeated here.

[0112] The device embodiments described above are merely illustrative, and some or all of the modules may be selected according to actual needs to achieve the purpose of the present embodiment. A person skilled in the art may understand and implement the present invention without creative effort.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a tapered optical fiber, characterized in that: include: placing a first cylindrical quartz tube having a first through hole on a deposition lathe; Depositing a core layer in the first through hole, and gradually adjusting a deposition amount along a direction of the first through hole during the deposition of the core layer; The first cylindrical quartz tube on which the core layer is deposited is shrunk to prepare a tapered optical fiber preform; Drawing the tapered optical fiber preform into a tapered optical fiber, wherein the tapered optical fiber includes a core for guiding light along the axial direction of the tapered optical fiber and a cladding surrounding the core; The step of gradually adjusting the deposition amount along the direction of the first through hole comprises: controlling the introduction speed of the gas or liquid raw material to continuously change, so that the deposition amount of the core layer along the direction of the first through hole continuously changes to form an inclined surface; Alternatively, the introduction speed of the gas or liquid raw material is controlled to change in stages, so that the deposition amount of the core layer along the first through hole direction changes in stages, thereby forming a multi-stage stepped surface.

2. The method for preparing a tapered optical fiber according to claim 1, characterized in that: The step of depositing a core layer in the first through hole and gradually adjusting a deposition amount along the direction of the first through hole during the process of depositing the core layer comprises: acid washing the first cylindrical quartz tube; The deposited loose layer is gradually increased or decreased along the direction of the first through hole, and rare earth ions are doped into the deposited loose layer.

3. The method for preparing a tapered optical fiber according to claim 1, characterized in that: The step of depositing a core layer in the first through hole and gradually adjusting a deposition amount along the direction of the first through hole during the process of depositing the core layer comprises: acid washing the first cylindrical quartz tube; The deposited loose layer is gradually increased or decreased along the direction of the first through hole, and rare earth ions are doped into the deposited loose layer.

4. The method for preparing a tapered optical fiber according to any one of claims 2 or 3, characterized in that: The step of doping rare earth ions in the deposited loose layer comprises: Passing a solution containing the rare earth ions into the first through hole; After soaking for a preset time, the remaining solution containing the rare earth ions is discharged.

5. The method for preparing a tapered optical fiber according to claim 3, characterized in that: The rare earth ion is Nd 3+ , Yb 3+ , Er 3+ 、Tm 3+ Any one or combination of the following.

6. The method for preparing a tapered optical fiber according to any one of claims 1 to 3, characterized in that: The step of shrinking the first cylindrical quartz tube for depositing the core layer to prepare a tapered preform comprises: The first cylindrical quartz tube and the deposited loose layer are sintered to melt and shrink the first cylindrical quartz tube and the deposited loose layer into the tapered preform rod.

7. The method for preparing a tapered optical fiber according to claim 6, characterized in that: The step of drawing the tapered preform into a tapered optical fiber comprises: The tapered preform rod is placed on a drawing tower and drawn into the tapered optical fiber.

8. The method for preparing a tapered optical fiber according to any one of claims 1 to 3, characterized in that: The step of drawing the tapered optical fiber preform into a tapered optical fiber comprises: Assembling the second quartz tube and the tapered preform rod, and sleeve-forming the rod on a sleeve lathe to obtain a solid tapered optical fiber preform rod; The tapered optical fiber preform is placed on a drawing tower and drawn into the tapered optical fiber.

9. The method for preparing a tapered optical fiber according to any one of claims 1 to 3, characterized in that: After the step of drawing the tapered optical fiber preform into a tapered optical fiber, the method further comprises: The outer periphery of the cladding is coated twice to form an optical fiber coating.

10. A tapered optical fiber, characterized in that: The tapered optical fiber is manufactured by the method for manufacturing a tapered optical fiber according to any one of claims 1 to 9.

Images