A method for preparing a tapered optical fiber and a tapered optical fiber

Abstract

The present invention relates to the technical field of optical fiber preparation, and provides a method for preparing a tapered optical fiber and a tapered optical fiber. The method for preparing a tapered optical fiber comprises depositing a core layer on the inner wall of a first quartz tube; performing a rod shrinking operation on the first quartz tube on which the core layer is deposited to obtain a cylindrical core rod; using a second quartz tube to perform a sleeve operation on the cylindrical core rod, and extending the cylindrical core rod during the sleeve operation to obtain a conical optical fiber preform rod; and sequentially drawing and coating the optical fiber preform rod to produce a tapered optical fiber with a double cladding and a gradual core-cladding ratio. The present invention has a simple preparation process for the tapered optical fiber, can realize one-time molding of the tapered optical fiber, does not require multiple polishing during the entire process, reduces the processing difficulty of the tapered optical fiber, can save costs, shorten preparation time, and improves the preparation efficiency and precision of the tapered optical fiber.

Description

Technical Field

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

[0002] Compared to conventional optical fibers with uniform cores and claddings, tapered fibers, by introducing a large core diameter end, can increase the effective mode area of the fiber, effectively suppressing nonlinear effects. Furthermore, tapered fibers also offer excellent performance in suppressing mode instabilities, maintaining beam quality, and suppressing amplified spontaneous emission (ASE), showing great potential in the high-power laser field.

[0003] Tapered optical fibers are usually produced by melt tapering, mechanical polishing, or chemical etching. By changing the radius of the optical fiber in the axial direction and forming a tapered region, applications such as optical coupling, optical sensing, nonlinear optics, micro-nano optics, optical fiber devices, and other research fields can be achieved.

[0004] However, during the processing of existing tapered optical fibers, the core rod and glass rod need to be ground separately, and the preparation process is complicated and tedious, 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 internal grinding also limits the length of the glass rod, and has disadvantages such as poor adaptability. Summary of the Invention

[0005] The present invention provides a method for preparing a tapered optical fiber and the tapered optical fiber, which are used to solve the problem that during the processing of the existing tapered optical fiber, the core rod and the glass rod need to be ground separately, resulting in a complicated and tedious preparation process.

[0006] The present invention provides a method for preparing a tapered optical fiber, comprising:

[0007] Depositing a core layer on the inner wall of the first quartz tube;

[0008] performing a rod shrinking operation on the first quartz tube on which the core layer is deposited to obtain a cylindrical core rod;

[0009] Using a second quartz tube to perform a casing operation on the cylindrical core rod, and during the casing operation, extending the cylindrical core rod to obtain a conical optical fiber preform;

[0010] The optical fiber preform rod is drawn and coated in sequence to produce a tapered optical fiber with a core-cladding ratio gradient and double cladding.

[0011] According to a method for preparing a tapered optical fiber provided by the present invention, the step of depositing a core layer on the inner wall surface of the first quartz tube includes:

[0012] Pickling the first quartz tube;

[0013] A loose layer of glass particles is deposited on the inner wall surface of the first quartz tube, and the loose layer of glass particles is doped with rare earth ions.

[0014] According to a method for preparing a tapered optical fiber provided by the present invention, the step of doping the loose layer of glass particles with rare earth ions comprises:

[0015] Passing a solution containing the rare earth ions into the first quartz tube;

[0016] After soaking for a preset time, the remaining solution containing the rare earth ions is discharged.

[0017] According to a method for preparing a tapered optical fiber provided by the present invention, the rare earth ion is Nd 3+ 、Yb 3+ 、Er 3+ 、Tm 3+ Any one or a combination of at least two of .

[0018] According to a method for preparing a tapered optical fiber provided by the present invention, the step of performing a rod shrinking operation on the first quartz tube on which the core layer is deposited to obtain a cylindrical core rod comprises:

[0019] sintering the first quartz tube on which the core layer is deposited, so that the loose layer of glass particles is vitrified;

[0020] The first quartz tube and the vitrified loose layer of glass particles are melted and shrunk into the solid cylindrical core rod.

[0021] According to a method for preparing a tapered optical fiber provided by the present invention, the step of using a second quartz tube to perform a casing operation on the cylindrical core rod, and extending the cylindrical core rod during the casing operation to obtain a tapered optical fiber preform rod includes:

[0022] Inserting the cylindrical core rod into the second quartz tube along the axial direction of the second quartz tube;

[0023] After the cylindrical core rod and the second quartz tube are fitted together to form an assembly, the end of the assembly is heated and shrunk, while the cylindrical core rod is driven to move toward the shrunk end away from the second quartz tube. The cylindrical core rod is then extended to form the assembly into a conical optical fiber preform. The extension operation can be continuous or segmented.

[0024] According to a method for preparing a tapered optical fiber provided by the present invention, before drawing the optical fiber preform, the method further comprises:

[0025] Polishing the outer wall surface of the conical optical fiber preform to obtain a cylindrical optical fiber preform;

[0026] Accordingly, the step of drawing the optical fiber preform includes:

[0027] The cylindrical optical fiber preform is placed on a drawing tower, and the tapered optical fiber is drawn by adjusting the drawing parameters.

[0028] According to a method for preparing a tapered optical fiber provided by the present invention, the drawing parameters include heating rate, drawing temperature, drawing tension, drawing atmosphere and drawing gas flow rate.

[0029] According to a method for preparing a tapered optical fiber provided by the present invention, the step of coating the optical fiber preform comprises:

[0030] The peripheral wall of the drawn optical fiber preform is coated twice in sequence to form an optical fiber coating.

[0031] The present invention also provides a tapered optical fiber, which is prepared by the tapered optical fiber preparation method described above.

[0032] The present invention provides a method for preparing a tapered optical fiber and a tapered optical fiber. By depositing a core layer on the inner wall of a first quartz tube, the first quartz tube can be subjected to a rod shrinking operation to obtain a cylindrical core rod. During the process of sleeve-forming the cylindrical core rod, the cylindrical core rod is extended to obtain a conical optical fiber preform rod. The optical fiber preform rod is then sequentially drawn and coated to conveniently obtain a tapered optical fiber with double cladding and a gradient cladding ratio.

[0033] As can be seen from the above, the present invention has a simple preparation process for the tapered optical fiber, can realize the one-time molding of the tapered optical fiber, does not require multiple polishing during the entire process, reduces the processing difficulty of the tapered optical fiber, saves costs, shortens the preparation time, and improves the preparation efficiency and precision of the tapered optical fiber. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction is given below to 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 any creative work.

[0035] Figure 1 1 is a schematic flow chart of a method for preparing a tapered optical fiber provided by the present invention;

[0036] Figure 2 1 is a schematic structural diagram of a first quartz tube provided by the present invention;

[0037] Figure 31 is a schematic structural diagram of a first quartz tube with a core layer deposited thereon provided by the present invention;

[0038] Figure 4 Schematic diagram of the structure of the cylindrical core rod provided by the present invention;

[0039] Figure 5 1 is a schematic structural diagram of an optical fiber preform provided by the present invention;

[0040] Figure 6 It is a schematic structural diagram of the tapered optical fiber provided by the present invention.

[0041] Reference numerals:

[0042] 1. First quartz tube; 2. Core layer; 3. Cylindrical core rod; 4. Second quartz tube; 5. Optical fiber preform;

[0043] 6. Tapered optical fiber; 61. Fiber core; 62. Optical fiber cladding. DETAILED DESCRIPTION

[0044] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0045] The following combination Figures 1-6 , the preparation method of the tapered optical fiber and the tapered optical fiber provided by the embodiment of the present invention are described in detail through specific embodiments and their application scenarios.

[0046] In the first aspect, Figure 1 As shown, an embodiment of the present invention provides a method for preparing a tapered optical fiber, comprising the following steps:

[0047] In step 110 , a core layer is deposited on the inner wall of the first quartz tube.

[0048] It is understandable that if Figure 2 As shown, the first quartz tube 1 is cylindrical, and the inner wall and outer wall of the first quartz tube 1 are coaxially arranged. Along the axial direction of the first quartz tube 1, the outer diameter of each position of the first quartz tube 1 remains consistent, and the inner diameter of each position of the first quartz tube 1 also remains consistent.

[0049] According to actual needs, a quartz tube material with matching thermal properties and optical properties that meet the requirements can be selected to prepare the first quartz tube 1 shown in this embodiment.

[0050] Furthermore, after the preparation of the first quartz tube 1 is completed, the first quartz tube 1 can be placed on a deposition lathe. During the process of driving the first quartz tube 1 to rotate by the deposition lathe, a gas raw material is introduced into the first quartz tube 1 to deposit a core layer 2 of a preset thickness on the inner wall surface of the first quartz tube 1, as shown in FIG. Figure 3 shown.

[0051] In this embodiment, the thickness of the deposited core layer 2 can be determined according to the size parameters of the core of the pre-fabricated tapered optical fiber.

[0052] Step 120 , performing a rod shrinking operation on the first quartz tube on which the core layer is deposited to obtain a cylindrical core rod.

[0053] It is understood that after the core layer is deposited on the inner wall of the first quartz tube, the first quartz tube is placed on a lathe, and the first quartz tube and the core layer on the inner wall are melted and sintered to form a quartz tube. Figure 4 The cylindrical core rod 3 shown completes the shrinking operation of the first quartz tube.

[0054] like Figure 4 As shown, cylindrical core rod 3 is solid and has a cylindrical outer structure. Its outer diameter remains consistent at all locations along its axial direction. Cylindrical core rod 3 structurally comprises a core corresponding to core layer 2 and a cladding corresponding to first quartz tube 1, with the cladding surrounding the core.

[0055] The core of the cylindrical core rod 3 is prepared by a drawing process to form the core of the tapered optical fiber, and the cladding of the cylindrical core rod 3 is prepared by a drawing process to form the optical fiber cladding of the tapered optical fiber.

[0056] Step 130: Use a second quartz tube to perform a casing operation on the cylindrical core rod, and extend the cylindrical core rod during the casing operation to obtain a conical optical fiber preform.

[0057] It is understandable that in this embodiment, a second quartz tube adapted to the cylindrical core rod can be prepared according to the core-to-cladding ratio of the pre-prepared tapered optical fiber and the geometric parameters of the cylindrical core rod, and then the second quartz tube can be sleeved on the circumferential wall of the cylindrical core rod.

[0058] At the same time, this embodiment can perform a sleeve operation on the cylindrical core rod in a heating field such as an electric heating furnace and an oxyhydrogen flame, so that the second quartz tube and the cylindrical core rod are melted together during the sleeve operation. In the heating scenario, this embodiment can also perform an extension operation on the cylindrical core rod at the same time, so as to draw the assembly formed by the melted second quartz tube and the cylindrical core rod into a conical optical fiber preform rod.

[0059] like Figure 5As shown, after the cylindrical core rod is sleeved, the second quartz tube 4 is sleeved on the peripheral wall of the original first quartz tube 1 and fused therewith to form the cladding of the optical fiber preform 5, and the core layer 2 deposited on the inner wall of the original first quartz tube 1 forms the core of the optical fiber preform 5.

[0060] The cross-sectional area of the core of the optical fiber preform 5 gradually decreases from one end to the other end, and the cladding diameter of the optical fiber preform 5 gradually decreases.

[0061] Step 140 , drawing and coating the optical fiber preform in sequence to produce a tapered optical fiber with a double cladding and a gradient core-to-cladding ratio.

[0062] After the optical fiber preform is produced, it is placed on a drawing tower, and the drawing parameters are set according to actual needs. The optical fiber preform is drawn, and then the peripheral wall of the drawn optical fiber preform is coated to obtain a tapered optical fiber with a gradual core-to-clad ratio.

[0063] like Figure 6 As shown, the tapered optical fiber 6 includes a core 61 for guiding light along the axial direction of the tapered optical fiber and a fiber cladding 62 surrounding the core 61 .

[0064] Specifically, the core-cladding ratio of the tapered optical fiber 6 is gradually changed. The tapered optical fiber 6 has gradually changed core diameter and cladding diameter. The core-cladding ratio of the tapered optical fiber 5 gradually changes along its axial direction.

[0065] Among them, according to actual needs, the core-to-clad ratio of the tapered optical fiber can be controlled within a certain range, and can be specifically adjusted according to the requirements of passive optical fiber devices and optical systems.

[0066] The diameter of the optical fiber cladding of the tapered optical fiber can be 200 to 450 μm, and the diameter of the core of the tapered optical fiber gradually changes from 0 to 200 μm.

[0067] The preparation method shown in the present invention deposits a core layer on the inner wall of a first quartz tube, and then performs a rod shrinking operation on the first quartz tube to obtain a cylindrical core rod. During the process of sleeve-forming the cylindrical core rod, the cylindrical core rod is extended to obtain a conical optical fiber preform rod. The optical fiber preform rod is then sequentially drawn and coated to conveniently obtain a tapered optical fiber with a double cladding and a gradient cladding ratio.

[0068] As can be seen from the above, the present invention has a simple preparation process for the tapered optical fiber, can realize the one-time molding of the tapered optical fiber, does not require multiple polishing during the entire process, reduces the processing difficulty of the tapered optical fiber, saves costs, shortens the preparation time, and improves the preparation efficiency and precision of the tapered optical fiber.

[0069] It should be noted here that the tapered optical fiber prepared in this embodiment can be either an active optical fiber doped with rare earth ions or a passive optical fiber not doped with rare earth ions, and there is no specific limitation on this.

[0070] In some embodiments, the steps of depositing the core layer on the inner wall of the first quartz tube as shown in this embodiment include:

[0071] The first quartz tube is acid-washed.

[0072] A loose layer of glass particles is deposited on the inner wall surface of the first quartz tube, and the loose layer of glass particles is doped with rare earth ions.

[0073] It is understandable that after the first quartz tube is selected or prepared, acid washing of the first quartz tube can effectively reduce the introduction of impurities and ensure the processing quality of the tapered optical fiber.

[0074] In some examples, the present embodiment may immerse the first quartz tube in a hydrofluoric acid solution for a immersion time greater than or equal to 200 minutes to remove impurities.

[0075] After the first quartz tube is pickled, a rotary joint is installed at the air inlet end of the first quartz tube. The first quartz tube is installed on a deposition lathe. A modified chemical vapor deposition (MCVD) method is used to deposit a loose layer of glass particles on the inner wall of the first quartz tube, and then the loose layer of glass particles is doped with rare earth ions.

[0076] Specifically, first, the first quartz tube is externally preheated using an oxyhydrogen flame. During the preheating process, the temperature of the first quartz tube is gradually increased to 1200°C.

[0077] Then, a gas feedstock is introduced into the first quartz tube at a preset flow rate. The gas feedstock can be any one of SiCl₄, BCl₃, GeCl₄, or POCl₃, or a combination of at least two. Prior to this, SF₆ is introduced into the first quartz tube, and the inner wall of the first quartz tube is etched several times. The first quartz tube is then heated and the gas feedstock is introduced again.

[0078] When the gas raw material is introduced, the temperature of the first quartz tube is controlled to be heated to 1500° C. to 1800° C., and the first quartz tube is controlled to rotate until a loose layer of glass particles of a specified thickness is deposited on the inner wall surface of the first quartz tube.

[0079] During the deposition of the loose layer of glass particles, or after the deposition of the loose layer of glass particles is completed, rare earth ions may be doped into the loose layer of glass particles.

[0080] It should be noted that, according to actual needs, outside vapor deposition (OVD), axial chemical vapor deposition (VAD) or plasma chemical vapor deposition (PCVD) can also be used to deposit a loose layer of glass particles, and rare earth ions can be doped into the loose layer of glass particles.

[0081] In some embodiments, the step of doping the loose layer of glass particles with rare earth ions as shown in this embodiment includes:

[0082] A solution containing rare earth ions is passed into the first quartz tube.

[0083] After soaking for a preset time, the remaining solution containing rare earth ions is discharged to obtain a loose layer of glass particles containing rare earth ions.

[0084] Specifically, a solution containing rare earth doping ions is introduced into the first quartz tube and soaked for a preset time, for example, more than 30 minutes, to dope the loose layer of glass particles with rare earth ions.

[0085] Furthermore, in this embodiment, rare earth doping ions and a dissolving solution can be mixed in a preset ratio to obtain a solution containing rare earth doping ions. 3+ 、Yb 3+ 、Er 3+ 、Tm 3+ Any one or a combination of at least two of the following: the dissolving liquid is a chloride solution or a nitrate solution.

[0086] After preparing the solution containing rare earth doping ions, the first quartz tube is taken out and then immersed in the solution of rare earth doping ions of a specified concentration. After the immersion is completed, the solution containing rare earth ions can be discharged and dried to obtain a loose layer of glass particles containing rare earth ions on the inner wall surface of the first quartz tube.

[0087] In some embodiments, the step of performing a rod shrinking operation on the first quartz tube having the core layer deposited thereon to obtain a cylindrical core rod as shown in this embodiment includes:

[0088] The first quartz tube with the core layer deposited thereon is sintered to vitrify the loose layer of glass particles. The sintering temperature of the first quartz tube with the core layer deposited thereon is 1200° C. to 2000° C.

[0089] Then, the first quartz tube and the vitrified glass particle loose layer are melted and shrunk, and the melting and shrinking temperature is controlled to be 1400° C. to 2200° C., so as to effectively remove the gap between the glass particle loose layer and the first quartz tube by shrinking the rod to obtain a solid cylindrical core rod.

[0090] In some embodiments, the steps of using a second quartz tube to perform a casing operation on a cylindrical core rod, and extending the cylindrical core rod during the casing operation to obtain a conical optical fiber preform as shown in this embodiment include:

[0091] Insert the cylindrical core rod into the second quartz tube along the axial direction of the second quartz tube.

[0092] After the cylindrical core rod and the second quartz tube are fitted together to form an assembly, the end of the assembly is heated and shrunk, and the cylindrical core rod is driven to move toward the shrunk end away from the second quartz tube, and the cylindrical core rod is extended to form the assembly into a conical optical fiber preform rod.

[0093] Specifically, in this embodiment, the cylindrical core rod can be clamped and fixed by a first clamp, and the second quartz tube can be clamped and fixed by a second clamp, so as to ensure that the cylindrical core rod and the second quartz tube are coaxially arranged.

[0094] Then, while the second quartz tube remains stationary, the cylindrical core rod is controlled to be inserted into the second quartz tube along the axial direction of the second quartz tube. An axially movable heating source is provided under the second quartz tube, and the first clamp can drive the core rod to rotate axially, and the second clamp can drive the second quartz tube to rotate in place.

[0095] After the cylindrical core rod and the second quartz tube are fitted together to form an assembly, the end of the assembly is heated and shrunk, while the cylindrical core rod is driven to move toward the shrunk end away from the second quartz tube. The cylindrical core rod is then extended to form the assembly into a conical optical fiber preform. The extension operation can be continuous or segmented.

[0096] In some embodiments, before drawing the optical fiber preform, the method further includes: polishing the outer wall surface of the conical optical fiber preform to obtain a cylindrical optical fiber preform.

[0097] Accordingly, the step of drawing the optical fiber preform includes placing the cylindrical optical fiber preform on a drawing tower and drawing a tapered optical fiber by adjusting drawing parameters.

[0098] It is understandable that after the optical fiber preform is produced, this embodiment can first polish the conical optical fiber preform into a cylindrical optical fiber preform according to the core-to-clad ratio requirements of the pre-prepared tapered optical fiber, and then draw the cylindrical optical fiber preform into a tapered optical fiber.

[0099] Furthermore, in this embodiment, a cylindrical optical fiber preform can be placed on a drawing tower, and a resistance wire furnace can be used to heat and soften the optical fiber preform. Then, the softened optical fiber preform can be drawn using the drawing tower to draw a tapered optical fiber.

[0100] like Figure 6 As shown, after the optical fiber preform is drawn and coated by a drawing tower, the obtained tapered optical fiber 6 includes a core 61 for transmitting light along the axial direction of the tapered optical fiber 6 and an optical fiber cladding 62 surrounding the core 61 .

[0101] In some examples, the adjustable drawing parameters during the wire drawing operation include heating rate, drawing temperature, drawing tension, drawing atmosphere, drawing gas flow rate, etc.

[0102] Specifically, among the above-mentioned drawing parameters, the heating rate is 10°C / min to 25°C / min; the drawing temperature is 300°C to 1000°C; the drawing tension is 0.5g to 50g; the drawing atmosphere is a high-purity single reactive gas, a single inert gas or a high-purity gas mixture made of the above gases in a certain proportion, the single reactive gas includes oxygen and nitrogen, the single inert gas includes argon and helium, the high-purity gas mixture includes a gas mixture of nitrogen and oxygen, and a gas mixture of helium and oxygen; the drawing gas flow rate is 0.5L / min to 5L / min.

[0103] In some embodiments, the steps of coating the optical fiber preform shown in this embodiment include:

[0104] The peripheral wall of the drawn optical fiber preform rod is coated twice in sequence to form an optical fiber coating, wherein the optical fiber coating includes an inner coating and an outer coating.

[0105] It is understandable that the peripheral wall of the drawn optical fiber preform is coated for the first time to form an optical fiber inner coating; and the peripheral wall of the optical fiber inner coating is coated for the second time to form an outer coating.

[0106] In the above-mentioned preparation process, this embodiment essentially applies an inner coating to the peripheral wall of the optical fiber cladding. The inner coating is a low-refractive-index coating, and the refractive index of the inner coating is lower than that of the optical fiber cladding to ensure the reliability of the tapered optical fiber.

[0107] Furthermore, the outer coating formed by the coating process on the peripheral wall of the optical fiber inner coating is specifically a polymer protective layer, which can be used to protect the internal structure of the tapered optical fiber. In addition, the present invention also provides the following two specific embodiments to specifically describe the method for preparing the tapered optical fiber.

[0108] Example 1:

[0109] A double-clad ytterbium-doped tapered optical fiber is prepared using the following steps:

[0110] Step 1: Place a cylindrical quartz tube on a deposition lathe, and evenly deposit a core layer of a set thickness on the inner wall of the quartz tube.

[0111] Step 2: Place the quartz tube with the core layer deposited thereon on a lathe, and perform a rod shrinking operation on the quartz tube to obtain a cylindrical core rod.

[0112] Step 3: performing a casing operation on the cylindrical core rod. During the casing operation, the cylindrical core rod is extended to prepare a conical optical fiber preform.

[0113] Step 4: Place the optical fiber preform on a drawing tower, perform a drawing operation by setting different drawing parameters, and coat the drawn optical fiber to produce a tapered optical fiber with double cladding.

[0114] The core diameter of the tapered optical fiber ranges from 150 to 200 μm, and the cladding diameter ranges from 400 to 600 μm.

[0115] Example 2:

[0116] A double-clad ytterbium-doped tapered optical fiber is prepared using the following steps:

[0117] Step 1: Place a cylindrical quartz tube on a deposition lathe, and evenly deposit a core layer of a set thickness on the inner wall of the quartz tube.

[0118] Step 2: Place the quartz tube with the core layer deposited thereon on a lathe, and perform a rod shrinking operation on the quartz tube to obtain a cylindrical core rod.

[0119] Step 3: performing a casing operation on the cylindrical core rod. During the casing operation, the cylindrical core rod is extended to prepare a conical optical fiber preform.

[0120] Step 4: Polish the conical optical fiber preform into a cylindrical optical fiber preform with the same diameter to facilitate subsequent drawing operations.

[0121] In step 5, the cylindrical optical fiber preform is placed on a drawing tower, and a drawing operation is performed by setting different drawing parameters. After the drawn optical fiber is coated, a tapered optical fiber with a double cladding is produced.

[0122] The core diameter of the tapered optical fiber ranges from 150 to 200 μm, and the cladding diameter ranges from 400 to 600 μm.

[0123] In the second aspect, Figure 6As shown, an embodiment of the present invention further provides a tapered optical fiber, which is prepared by the tapered optical fiber preparation method as described above.

[0124] Specifically, the tapered optical fiber 6 includes a core 61 and a fiber cladding 62. The fiber cladding 62 is coated on the outside of the core 61. The outside of the fiber cladding 62 is coated with an inner fiber coating and an outer fiber coating in sequence. The refractive index of the inner fiber coating is lower than that of the fiber cladding.

[0125] Since the tapered optical fiber is prepared using the tapered optical fiber preparation method described in the above embodiment, the tapered optical fiber of this embodiment includes all the technical solutions of the above embodiment. Therefore, it has at least all the beneficial effects achieved by all the technical solutions of the above embodiment, which will not be described one by one here.

[0126] 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 various embodiments of the present invention.

Claims

1. A method for preparing a tapered optical fiber, characterized in that: include: Depositing a core layer on the inner wall of the first quartz tube; performing a rod shrinking operation on the first quartz tube on which the core layer is deposited to obtain a cylindrical core rod; Using a second quartz tube to perform a casing operation on the cylindrical core rod, and during the casing operation, extending the cylindrical core rod to obtain a conical optical fiber preform; Polishing the outer wall surface of the conical optical fiber preform to obtain a cylindrical optical fiber preform; The cylindrical optical fiber preform is placed on a drawing tower, and a drawing operation is performed by adjusting drawing parameters. After the drawn optical fiber is coated, a tapered optical fiber with a double cladding is produced.

2. The method for preparing a tapered optical fiber according to claim 1, wherein: The step of depositing the core layer on the inner wall of the first quartz tube includes: Pickling the first quartz tube; A loose layer of glass particles is deposited on the inner wall surface of the first quartz tube, and the loose layer of glass particles is doped with rare earth ions.

3. The method for preparing a tapered optical fiber according to claim 2, wherein: The step of doping the loose layer of glass particles with rare earth ions comprises: Passing a solution containing the rare earth ions into the first quartz tube; After soaking for a preset time, the remaining solution containing the rare earth ions is discharged.

4. The method for preparing a tapered optical fiber according to claim 2, wherein: The rare earth ion is Nd 3+ 、Yb 3+ 、Er 3+ 、Tm 3+ Any one or a combination of at least two of .

5. The method for preparing a tapered optical fiber according to claim 2, wherein: The step of performing a rod shrinking operation on the first quartz tube on which the core layer is deposited to obtain a cylindrical core rod comprises: sintering the first quartz tube on which the core layer is deposited, so that the loose layer of glass particles is vitrified; The first quartz tube and the vitrified loose layer of glass particles are melted and shrunk into the solid cylindrical core rod.

6. The method for preparing a tapered optical fiber according to any one of claims 1 to 5, characterized in that: The step of using a second quartz tube to perform a casing operation on the cylindrical core rod, and extending the cylindrical core rod during the casing operation to obtain a conical optical fiber preform rod comprises: Inserting the cylindrical core rod into the second quartz tube along the axial direction of the second quartz tube; After the cylindrical core rod and the second quartz tube are fitted together to form an assembly, the end of the assembly is heated and shrunk, and the cylindrical core rod is driven to move toward the shrunk end away from the second quartz tube, and the cylindrical core rod is extended to form the assembly into a conical optical fiber preform rod.

7. The method for preparing a tapered optical fiber according to claim 1, wherein: The drawing parameters include heating rate, drawing temperature, drawing tension, drawing atmosphere and drawing gas flow rate.

8. A tapered optical fiber, characterized in that: The tapered optical fiber is prepared by the method for preparing a tapered optical fiber according to any one of claims 1 to 7.

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