A method of manufacturing a photonic crystal fiber

Abstract

This invention relates to the field of optical fiber fabrication technology, and provides a method for fabricating photonic crystal fibers, comprising: fabricating a capillary rod, an outer sheath, a tail tube, and at least one type of capillary tube, wherein the number of tail tubes is the same as the number of capillary tubes of different specifications; stacking the capillary rod, the outer sheath, and at least one type of capillary tube to obtain a preform, ensuring that one end of the preform is flush; connecting the unflush end of the preform to a tail tube; drawing the preform; applying a first negative pressure to the outer sheath and a first positive pressure to the tail tube; adjusting the magnitudes of the first positive and first negative pressures to obtain the photonic crystal fiber; wherein the first positive pressure includes at least one pressure value, and the number of pressure values ​​is the same as the number of tail tubes. The photonic crystal fiber fabrication method provided by this invention achieves coordinated regional control of the preform through different pressure controls, achieving high-precision controllability of the end-face structure of the photonic crystal fiber.

Description

Technical Field

[0001] This invention relates to the field of optical fiber fabrication technology, and in particular to a method for fabricating photonic crystal optical fibers. Background Technology

[0002] Photonic crystal fibers (PCFs) are a new type of optical fiber with unique optical properties. The characteristic of PCFs is that the refractive index distribution at the cross-section perpendicular to its longitudinal axis has a two-dimensional periodic structure that remains unchanged along the longitudinal axis of the fiber. They possess unique and novel physical properties, such as cutoff-free single-mode, tunable dispersion, and effective large mode area. They have broad application prospects in fields such as biomedicine, precision manufacturing, and optical fiber communication.

[0003] Photonic crystal fibers are generally fabricated using a stacking-drawing method, which involves arranging capillaries with the same outer diameter according to a designed geometry, then transferring a set of stacked capillaries with the desired geometry into a suitable sleeve, and filling and fixing them with quartz wire to form a preform of the photonic crystal fiber. Subsequently, the photonic crystal fiber is fabricated at high temperature by controlling the drawing parameters during the drawing process.

[0004] The air holes in the cross-section of photonic crystal fibers are on the order of micrometers and are not necessarily all the same size. During the fabrication process, air holes at different locations may deform or collapse to varying degrees, damaging the structure of the photonic crystal fiber and directly affecting its performance. Summary of the Invention

[0005] This invention provides a method for fabricating photonic crystal fibers, which solves the problem of unstable product quality caused by deformation or collapse of air holes in the fabrication of photonic crystal fibers in the prior art.

[0006] This invention provides a method for fabricating a photonic crystal fiber, comprising:

[0007] Prepare capillary rods, outer tubes, tail tubes, and at least one type of capillary tube, wherein the number of tail tubes is the same as the number of capillary tubes of each type.

[0008] The capillary rod, the outer tube, and the at least one type of capillary tube are stacked to obtain a preform, ensuring that one end of the preform is flush.

[0009] Perform a tail tube connection operation on the unaligned end of the preform to ensure that capillary tubes of the same specification are inserted into the same tail tube;

[0010] The preform is drawn into a fiber, a first negative pressure is applied to the outer tube, a first positive pressure is applied to the tail tube, and the magnitudes of the first positive pressure and the first negative pressure are adjusted to obtain a photonic crystal fiber.

[0011] The first positive pressure includes at least one pressure value, and the number of pressure values ​​is the same as the number of tailpipes.

[0012] According to a method for fabricating a photonic crystal fiber provided by the present invention, the steps of fabricating a capillary rod, an outer sheath, a tail tube, and at least one type of capillary tube include:

[0013] Prepare a core capillary rod and several filler capillary rods with different outer diameters;

[0014] Prepare one of the outer tubes;

[0015] Prepare a plurality of the capillary tubes and prepare a tail tube of the same specifications and quantity as the capillary tubes;

[0016] Among them, the capillaries of different specifications have the same outer diameter but different inner diameters, and are the same as the outer diameter of the fiber core capillary rod.

[0017] According to a method for fabricating a photonic crystal fiber provided by the present invention, the step of stacking the capillary rod, the outer sheath, and at least one type of capillary tube to obtain a preform includes:

[0018] The capillary rod and the capillary tube are compactly stacked to obtain a preform, the cross-section of which is a regular polygon;

[0019] The preform is inserted into the outer tube, ensuring that the preform and the outer tube are coaxially arranged.

[0020] The capillary rod is filled into the gap between the outer wall of the preform and the inner wall of the outer sleeve.

[0021] According to a method for fabricating a photonic crystal fiber provided by the present invention, when the number of capillary tubes is 1, the step of splicing a tail tube to the unaligned end of the preform includes:

[0022] Connect the tailpipe to the preformed bar;

[0023] The connection between the outer tube and the tail tube is heated, a second negative pressure is provided to the outer tube, and a second positive pressure is provided to the tail tube. The magnitudes of the second negative pressure and the second positive pressure are adjusted to fuse the joint between the outer tube and the tail tube.

[0024] According to a method for fabricating a photonic crystal fiber provided by the present invention, the tail tube is connected to the outer tube, and both the outer tube and the tail tube are provided with corresponding pressure channels, which are used to connect to corresponding pressure sources.

[0025] According to a method for fabricating a photonic crystal fiber provided by the present invention, when the number of capillary gauges is greater than 1, the number of capillary gauges is N, and the step of splicing a tail tube to the unaligned end of the preform includes:

[0026] Connect the first tailpipe to the preformed rod;

[0027] The connection between the outer tube and the first tail tube is heated, a third negative pressure is provided to the outer tube, and a third positive pressure is provided to the first tail tube. The magnitudes of the third negative pressure and the third positive pressure are adjusted to fuse the joint between the outer tube and the first tail tube.

[0028] Connect the remaining N-1 tailpipes sequentially to the first tailpipe;

[0029] The connection between the Nth tailpipe and the (N-1)th tailpipe is heated, a fourth negative pressure is provided to the (N-1)th tailpipe, and a fourth positive pressure is provided to the Nth tailpipe. The magnitudes of the fourth positive pressure and the fourth negative pressure are adjusted to fuse the joint between the Nth tailpipe and the (N-1)th tailpipe.

[0030] According to a method for fabricating a photonic crystal fiber provided by the present invention, the lengths and numbers of the first to Nth capillaries are different, with the first capillaries having the largest number and the shortest length, and the Nth capillaries having the smallest number and the longest length.

[0031] The length of the filling capillary rod is the same as the length of the first capillary tube;

[0032] The Nth tailpipe is sleeve-shaped;

[0033] The first tail tube to the (N-1)th tail tube are in the shape of a cover, and the bottom end of the first tail tube to the (N-1)th tail tube is provided with an opening. The opening of the (N-1)th tail tube is used for the Nth capillary tube to pass through.

[0034] The Nth tail tube is used to connect to the bottom end of the (N-1)th tail tube, and the cover end of the (N-1)th tail tube is used to connect to the bottom end of the (N-2)th tail tube.

[0035] The outer diameters of the first tailpipe to the Nth tailpipe are the same.

[0036] According to a method for fabricating a photonic crystal fiber provided by the present invention, the outer sheath, the first tail tube to the Nth tail tube are each provided with a corresponding pressure channel, and the pressure channel is used to connect to a corresponding pressure source.

[0037] According to the method for fabricating a photonic crystal fiber provided by the present invention, the step of performing a tailing tube connection operation on the unfurled end of the preform further includes:

[0038] A sleeve is installed at the joint between the Nth tailpipe and the (N-1)th tailpipe.

[0039] According to a method for fabricating a photonic crystal fiber provided by the present invention, between obtaining the preform and performing a tailing operation on the preform, the method further includes:

[0040] The flush end of the preform is tapered or tapered.

[0041] Between the tail pipe connection operation of the preform and the wire drawing process of the preform, the following steps are also included:

[0042] The preformed rods are dried after the tailpipe docking operation.

[0043] The photonic crystal fiber fabrication method provided by this invention involves stacking capillary rods, cladding tubes, and capillaries of at least one specification to form a preform. Ensuring one end of the preform is flush, the other end is connected to a tail tube. Since the number of tail tubes is the same as the number of capillaries of the same specification, capillaries of the same specification are inserted into the same tail tube at the tail tube end of the preform. During the preform drawing process, a first negative pressure is applied to the cladding tube to eliminate gaps between the structures, and a first positive pressure is applied to the tail tubes. The pressure value of the first positive pressure is determined by the number of tail tubes, ensuring that capillaries of the same specification within each tail tube are drawn under the same positive pressure. This allows for coordinated, regional control of the pressure between capillaries of different sizes, between capillaries, and between capillaries and the cladding tube during the preform drawing process. This achieves high-precision control of the photonic crystal fiber end-face structure, meeting the needs of diverse photonic crystal fiber fabrication. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0045] Figure 1 This is one of the flowcharts illustrating the fabrication method of photonic crystal fiber provided by the present invention.

[0046] Figure 2 This is a schematic diagram of the process for preparing capillary rods, outer tubes, tail tubes, and at least one type of capillary provided by the present invention.

[0047] Figure 3This is a schematic diagram of the process provided by the present invention of stacking capillary rods, outer tubes and at least one type of capillary tube to obtain preforms.

[0048] Figure 4 This is one of the flowcharts illustrating the process of connecting a tail tube to the unaligned end of a preform when the number of capillary tubes provided by this invention is one.

[0049] Figure 5 This is a schematic diagram of the process of connecting the end of the preform rod that is not flush with the capillary tube when the number of capillary tube specifications provided by the present invention is greater than 1.

[0050] Figure 6 This is the second schematic diagram of the process for connecting the unaligned end of the preform to the tail pipe, provided by the present invention.

[0051] Figure 7 This is the second schematic diagram of the process for fabricating photonic crystal fibers provided by the present invention.

[0052] Figure 8 This is a schematic diagram of the main structure of the preform provided by the present invention.

[0053] Figure 9 This is a three-dimensional structural schematic diagram of the first tailpipe provided by the present invention.

[0054] Figure 10 This is a three-dimensional structural schematic diagram of the second tailpipe provided by the present invention.

[0055] Figure 11 This is one of the schematic diagrams provided by the present invention for the tail pipe connection operation of the preform.

[0056] Figure 12 This is the second schematic diagram of the preform rod tail pipe connection operation provided by the present invention.

[0057] Figure 13 This is the third schematic diagram of the preform rod tail pipe connection operation provided by the present invention.

[0058] Figure label:

[0059] 1. Preform; 11. Core capillary rod; 12. Outer tube; 13. Capillary; 14. Filler capillary rod; 131. First capillary; 132. Second capillary;

[0060] 2. Tailpipe; 21. First tailpipe; 22. Second tailpipe;

[0061] 3. Pressure channel. Detailed Implementation

[0062] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described 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.

[0063] The following is combined Figures 1-13 The preparation method of photonic crystal fiber provided in this invention will be described in detail through specific embodiments and application scenarios.

[0064] In some embodiments, such as Figure 1 , Figure 8 , Figure 11 , Figure 12 and Figure 13 As shown, this embodiment provides a method for fabricating a photonic crystal fiber, including the following steps:

[0065] Step 111: Prepare capillary rods, outer tubes 12, tail tubes 2, and at least one type of capillary tube 13, wherein the number of tail tubes 2 is the same as the number of capillary tubes 13 of the same type.

[0066] Step 112: Stack the capillary rod, the outer tube 12, and at least one type of capillary tube 13 to obtain the preform 1, ensuring that one end of the preform 1 is flush.

[0067] Step 113: Connect the tail tube to the unaligned end of the preform 1 to ensure that capillary tubes 13 of the same specification are inserted into the same tail tube 2.

[0068] Step 114: The preform 1 is drawn into fibers, a first negative pressure is applied to the outer tube 12, a first positive pressure is applied to the tail tube 2, and the magnitudes of the first positive pressure and the first negative pressure are adjusted to obtain a photonic crystal fiber.

[0069] The first positive pressure includes at least one pressure value, and the number of pressure values ​​is the same as the number of tailpipes 2.

[0070] Understandably, the capillary rod is usually made of quartz, and the outer sheath 12 is usually made of quartz. The capillary 13 is usually made of quartz. The specifications of the capillary 13 can be of only one type or multiple types, depending on the specific requirements of the photonic crystal fiber, and are not limited here.

[0071] Correspondingly, the number of tail tubes 2 is the same as the number of specifications included in capillary tube 13. That is, when capillary tube 13 has only one specification, the number of tail tubes 2 is 1, and when capillary tube 13 has N specifications, the number of tail tubes 2 is N.

[0072] The capillary rod, capillary tube 13 and outer tube 12 are stacked to form a preform 1. One end of the preform 1 is set flat to prepare for the subsequent wire drawing process, and the other end of the preform 1 is the tail tube end, which is used for the tail tube processing.

[0073] When connecting the tailpipe, it is necessary to ensure that the internal spaces of the outer sleeve 12 and the tailpipe 2 are isolated from each other, providing operational space for subsequent segmented pressurization. Furthermore, capillary tubes 13 of the same specification should be inserted into the same tailpipe 2 to facilitate corresponding pressure control.

[0074] The preform 1, with one end flat, is drawn into wires. During this high-temperature heating process, a first negative pressure is applied to the outer tube 12 to eliminate the gaps between the capillary rods and capillary tubes 13 within the outer tube 12, allowing the gaps to completely fuse. A first positive pressure is applied to the tail tube 2. The value of the first positive pressure is related to the number of tail tubes 2. For example, if there is only one tail tube 2, only one first positive pressure is applied; if there are multiple tail tubes 2, multiple different pressure values ​​are applied to different tail tubes 2 to control the size of different types of capillary tubes 13. During the drawing process of the preform 1, the coordinated control of the first negative pressure and the first positive pressure eliminates the gaps between the outer tube 12 and the capillary rods, between the capillary rods and capillary tubes 13, between adjacent capillary rods, and between adjacent capillary tubes 13. Furthermore, different pressure values ​​can be used to control the size of capillary tubes 13 of different specifications based on their different specifications.

[0075] The method for fabricating photonic crystal fibers provided by this invention involves stacking capillary rods, outer sheaths 12, and capillary tubes 13 of at least one specification to form a preform 1. While ensuring one end of the preform 1 is flush, the other end of the preform 1 is connected to a tail tube. Since the number of tail tubes 2 and the number of capillary tubes 13 of the same specification are the same, capillary tubes 13 of the same specification are inserted into the same tail tube 2 at the tail tube end of the preform 1. During the fiber drawing process of the preform 1, a first negative pressure is applied to the outer sheath 12 to eliminate gaps between the structures, and a first positive pressure is applied to the tail tubes 2. The pressure value of the first positive pressure is determined by the number of tail tubes 2, so that the capillary tubes 13 of the same specification in each tail tube 2 are drawn under the same positive pressure. This allows the preform 1 to achieve coordinated regional control of the pressure between capillaries 13 of different sizes, between capillaries 13, and between capillaries 13 and the sleeve during the fiber drawing process through different pressure control. This achieves the goal of high-precision control of the end face structure of the photonic crystal fiber and meets the needs of diverse photonic crystal fiber fabrication.

[0076] In some embodiments, such as Figure 2 , Figure 8 , Figure 9 and Figure 10As shown, the steps for preparing the capillary rod, outer tube 12, tail tube 2, and at least one type of capillary tube 13 in this embodiment include the following steps:

[0077] Step 211: Prepare a core capillary rod 11 and several filler capillary rods 14 with different outer diameters.

[0078] Step 212: Prepare an outer tube 12.

[0079] Step 213: Prepare a number of capillary tubes 13 and a number of tail tubes 2 of the same specifications as the capillary tubes 13.

[0080] Among them, the capillary tubes 13 of different specifications have the same outer diameter but different inner diameters, and have the same outer diameter as the fiber core capillary rod 11.

[0081] Understandably, the capillary rods are divided into core capillary rods 11 and filler capillary rods 14. There is one core capillary rod 11 and multiple filler capillary rods 14, with different outer diameters. The outer diameter of the capillary tube 13 is the same as that of the core capillary rod 11, so that the core capillary rod 11 and the capillary tube 13 can be stacked at equal intervals.

[0082] The fiber core capillary rod 11 can be active or passive. Optionally, the fiber core capillary rod 11 can also be replaced by a capillary tube with the same outer diameter.

[0083] Multiple capillary tubes 13 are provided, with different specifications having the same outer diameter but different inner diameters. This facilitates the control of the gaps between the multiple capillary tubes 13 within the outer sheath 12 when they are stacked. The different inner diameters of the capillary tubes 13 can be used for different optical fiber applications, thus expanding the application range of photonic crystal fibers.

[0084] Accordingly, the number of tail tubes 2 is the same as the number of capillary tubes 13 of different specifications, so as to facilitate pressure control of capillary tubes 13 of different specifications within a tail tube 2.

[0085] Specifically, the cross-sectional shape of the capillary 13 can be circular or regular hexagonal.

[0086] In some embodiments, such as Figure 3 and Figure 8 As shown, in this embodiment, the capillary rod, the outer sheath 12, and at least one type of capillary tube 13 are stacked to obtain the preform 1, including the following steps:

[0087] Step 311: The capillary rod and capillary tube 13 are compactly stacked to obtain a preform with a cross-section of a regular polygon.

[0088] Step 312: Insert the preform into the outer sleeve 12, ensuring that the preform and the outer sleeve 12 are coaxially aligned.

[0089] Step 313: Fill the gap between the outer wall of the preform and the inner wall of the outer sleeve 12 with capillary rods 14.

[0090] Understandably, capillary rods and capillary tubes 13 are compactly stacked within the mold. Since the outer diameters of different types of capillary tubes 13 are the same and are also the same as the outer diameters of the core capillary rods 11, the core capillary rods 11 and capillary tubes 13 can be stacked into a regular polygonal structure.

[0091] Specifically, in this embodiment, the fiber core capillary rod 11 and the capillary tube 13 are stacked into a regular hexagon.

[0092] A preform with a regular polygonal cross-section is inserted into the outer sleeve 12. Both the preform and the outer sleeve 12 have an axis of symmetry; aligning these axes ensures the preform is centered within the outer sleeve 12. Multiple filler capillary rods 14 are then inserted between the inner wall of the outer sleeve 12 and the outer wall of the preform to tightly fill the gap between them. To ensure proper assembly, the inner diameter of the outer sleeve 12 is slightly larger than the diameter of the circumscribed circle of the preform.

[0093] Furthermore, the outer tube 12 is aligned with one end of the preform, so that one end of the outer tube 12, the fiber core capillary rod 11, the filling capillary rod 14, and the capillary tube 13 are all aligned, which facilitates the connection of the tail tube to the other end of the preform rod 1.

[0094] In some embodiments, such as Figure 4 As shown, in this embodiment, when the number of capillary tubes 13 is one, the tail tube connection operation for the unaligned end of the preform 1 includes the following steps:

[0095] Step 411: Connect the tailpipe 2 to the preform 1.

[0096] Step 412: Heat the connection between the outer tube 12 and the tail tube 2, provide a second negative pressure to the outer tube 12 and a second positive pressure to the tail tube 2, and adjust the magnitude of the second negative pressure and the second positive pressure to fuse the joint between the outer tube 12 and the tail tube 2.

[0097] Understandably, when the number of capillary tubes 13 is one, the number of tail tubes 2 is also one. The tail tube 2 is connected to the tail tube end of the preform 1, and the connection is heated. A second negative pressure is applied to the outer sleeve 12, and a second positive pressure is provided to the tail tube 2. Since all capillary tubes 13 extend into the tail tube 2, it is ensured that while the capillary tubes 13 can achieve controlled dimensions without shrinking or collapsing, all gaps are fused together, resulting in a tight connection between the outer sleeve 12 and the tail tube 2. This creates independent spaces within the outer sleeve 12 and the tail tube 2, providing space for subsequent wire drawing and facilitating pressure application. Furthermore, during the connection process between the tail tube and the outer sleeve, it is ensured that all capillary tubes 13 do not close.

[0098] In some embodiments, the tail tube 2 of this embodiment is connected to the outer tube 12. Both the outer tube 12 and the tail tube 2 are provided with corresponding pressure channels 3, which are used to connect to the corresponding pressure source.

[0099] Understandably, in the case of only one tail tube 2, a small section of quartz tube is provided on both the outer tube 12 and the tail tube 2, and the quartz tube is formed during the fabrication of the tail tube 2 and the outer tube 12. Different pressure sources can apply positive or negative pressure to the tail tube 2 and the outer tube 12 through the quartz tube to meet the pressure requirements during the fabrication of photonic crystal fibers.

[0100] In some embodiments, such as Figure 5 , Figure 11 , Figure 12 and Figure 13 As shown, in this embodiment, when the number of capillary tube 13 specifications is greater than 1, the number of capillary tube 13 specifications is N. The tail tube connection operation for the unaligned end of the preform 1 includes the following steps:

[0101] Step 511: Connect the first tail tube 21 to the preform 1.

[0102] Step 512: Heat the connection between the outer sleeve 12 and the first tail tube 21, provide a third negative pressure to the outer sleeve 12 and a third positive pressure to the first tail tube 21, and adjust the magnitude of the third negative pressure and the third positive pressure to fuse the joint between the outer sleeve 12 and the first tail tube 21.

[0103] Step 513: Connect the remaining N-1 tailpipes 2 sequentially to the first tailpipe 21.

[0104] Step 514: Heat the connection between the Nth tail tube and the (N-1)th tail tube, provide a fourth negative pressure to the (N-1)th tail tube, provide a fourth positive pressure to the Nth tail tube, and adjust the magnitude of the fourth positive pressure and the fourth negative pressure to fuse the joint between the Nth tail tube and the (N-1)th tail tube.

[0105] Understandably, when the number of capillary tube 13 specifications is greater than 1, the number of capillary tube 13 specifications is N, and the number of tail tubes 2 is also N. The number of tail tubes 2 ranges from 1 to N, namely the first tail tube 21, the second tail tube 22, and so on up to the Nth tail tube.

[0106] The outer tube 12 is connected to the first tail tube 21. The connection between the outer tube 12 and the first tail tube 21 is heated. A third positive pressure is applied to the first tail tube 21 and a third negative pressure is applied to the outer tube 12. Since the first capillary tube 131 extends into the first tail tube 21, it is ensured that the first capillary tube 131 can achieve the controlled size without shrinking or collapsing, while all gaps are fused together, so that the outer tube 12 and the first tail tube 21 are tightly connected. Thus, independent spaces are formed inside the outer tube 12 and the first tail tube 21, providing space for subsequent wire drawing processing to facilitate pressure application.

[0107] Further, the remaining N-1 tail tubes 2 are connected sequentially. Specifically, the second tail tube 22 is connected to the first tail tube 21, the third tail tube 2 is connected to the second tail tube 22, and so on, until the Nth tail tube is connected to the N-1th tail tube. Heating is performed at the connection points of adjacent tail tubes 2. A fourth negative pressure is applied to the N-1th tail tube, and a fourth positive pressure is applied to the Nth tail tube. Since the N-1th capillary extends into the N-1th tail tube, it is ensured that the N-1th capillary can achieve controlled dimensions without shrinking or collapsing, while all gaps are fused together, resulting in a tight connection between the Nth and N-1th tail tubes. This creates independent spaces within the Nth and N-1th tail tubes, providing space for subsequent wire drawing and facilitating pressure application. Furthermore, during the connection process between the Nth and N-1th tail tubes, it is ensured that all capillaries 13 do not close.

[0108] Specifically, since the Nth tailpipe and the (N-1)th tailpipe together contain N tailpipes, the fourth positive pressure of each Nth tailpipe and the fourth negative pressure of the (N-1)th tailpipe are set in pairs and adjusted according to different tailpipe specifications.

[0109] In some embodiments, such as Figure 11 , Figure 12 and Figure 13 As shown, the lengths and numbers of the first capillary 131 to the Nth capillary in this embodiment are different. The first capillary 131 has the largest number and the shortest length, while the Nth capillary has the smallest number and the longest length.

[0110] The length of the filling capillary rod 14 is the same as the length of the first capillary tube 131.

[0111] The Nth tailpipe is sleeve-shaped.

[0112] The first tail tube 21 to the N-1 tail tube are in the shape of a cover. The bottom end of the first tail tube 21 to the N-1 tail tube is provided with an opening. The opening of the N-1 tail tube is used for the Nth capillary tube to pass through.

[0113] The Nth tailpipe is used to connect to the bottom end of the (N-1)th tailpipe, and the cover end of the (N-1)th tailpipe is used to connect to the bottom end of the (N-2)th tailpipe.

[0114] The outer diameters of the first tail tube 21 to the Nth tail tube are the same.

[0115] Understandably, in order to individually control the pressure applied to each capillary tube 13, different lengths of capillary tubes 13 are set so that capillary tubes 13 of different lengths can extend into different tail tubes 2. To control costs, the most numerous type of capillary tube 13 is set to the shortest length and pressure is applied in the first tail tube 21. As the number decreases, the length of the capillary tube 13 is extended. In this way, the least numerous capillary tubes 13 are the longest, saving material for the capillary tubes 13.

[0116] The length of the (N-1)th tail tube is less than the difference between the length of the Nth capillary and the length of the (N-1)th capillary, to ensure that the Nth capillary can extend into the Nth tail tube for pressure control within the Nth tail tube.

[0117] During the heating process, at the opening where the Nth capillary passes through the (N-1)th tail tube, it is necessary to ensure that the outer wall of the Nth capillary is in close contact with the inner wall of the opening of the (N-1)th tail tube, so as to form a sealed space inside the (N-1)th tail tube to facilitate pressure application.

[0118] The outer diameter of the first tailpipe 21 to the Nth tailpipe differs from the outer diameter of the outer sleeve 12 by no more than ±3mm.

[0119] In one embodiment, such as Figure 11 , Figure 12 and Figure 13 As shown, the capillary 13 in this embodiment includes two specifications. There are several first capillary 131s, and the length of the first capillary 131 is the same as the length of the core capillary rod 11 and the filler capillary rod 14. There are two second capillary 132s, and the second capillary 132s are longer and have a larger inner diameter than the inner diameter of the first capillary 131s.

[0120] The length of the outer tube 12 determines the effective length of the preform 1. The length of the outer tube 12 is L mm, the length of the first capillary 131 is (L+50) mm, and the length of the second capillary 132 is (L+250) mm.

[0121] There are also two tail tubes 2. The first tail tube 21 corresponds to the first capillary tube 131, and the second tail tube 22 corresponds to the second capillary tube 132. The outer diameters of the first tail tube 21 and the second tail tube 22 are the same. The length of the first tail tube 21 is slightly less than the length difference between the second capillary tube and the first capillary tube 131. The length of the second tail tube 22 is slightly greater than the difference between the length of the second capillary tube and the sum of the lengths of the first capillary tube 131 and the first tail tube 21. The first tail tube 21 is in the shape of a cover, and the second tail tube 22 is in the shape of a sleeve. The bottom end of the first tail tube 21 is provided with two openings. The two second capillary tubes 132 pass through the two openings and extend into the second tail tube 22.

[0122] Thus, when the first tail tube 21 is connected to the outer tube 12 and heated, the first capillary tube 131 extending into the first tail tube 21 is subjected to a third positive pressure, and the outer tube 12 is subjected to a third negative pressure. By adjusting the magnitude of the third positive pressure and the third negative pressure, the joint between the outer tube 12 and the first tail tube 21 is fused together, and the first capillary tube 131 maintains its design dimensions while the rest of the structure is tightly fused together.

[0123] When the second tail tube 22 is connected to the first tail tube 21 and heated, the second capillary tube 132 extending into the second tail tube 22 is subjected to a fourth positive pressure, and the first tail tube 21 is subjected to a fourth negative pressure. By adjusting the magnitude of the fourth positive pressure and the fourth negative pressure, the joint between the first tail tube 21 and the second tail tube 22 is fused together, and the second capillary tube 132 maintains its design dimensions while the rest of the structure is tightly fused together.

[0124] After the preform 1 is connected to the first tail tube 21 and the second tail tube 22, the preform 1 is drawn into fibers. A first negative pressure is applied to the outer tube 12, a first positive pressure is applied to the first tail tube 21, and a second positive pressure is applied to the second tail tube 22. The magnitudes of the first negative pressure and the first positive pressure are adjusted so that the fiber drawing process is carried out under the condition of regional pressure control in the outer tube 12, the first tail tube 21 and the second tail tube 22, thereby obtaining a photonic crystal fiber and enabling precise control of the end face size of the photonic crystal fiber.

[0125] In some embodiments, such as Figure 11 , Figure 12 and Figure 13 As shown, in this embodiment, the outer sleeve 12, the first tail tube 21 to the Nth tail tube are all provided with corresponding pressure channels 3, and the pressure channels 3 are used to connect to the corresponding pressure sources.

[0126] Understandably, in the case of N tail tubes 2, a small section of quartz tube is respectively provided on the outer tube 12, the first tail tube 21 to the Nth tail tube, and the quartz tube is formed during the fabrication of the N tail tubes 2 and the outer tube 12. Different pressure sources can apply positive or negative pressure to the N tail tubes 2 and the outer tube 12 through the quartz tubes to meet the pressure requirements during the fabrication of photonic crystal fibers.

[0127] In some embodiments, such as Figure 6 As shown, the tail pipe connection operation for the un-aligned end of the preform 1 in this embodiment also includes the following steps:

[0128] Step 611: Perform sleeve treatment at the joint between the Nth tail tube and the (N-1)th tail tube.

[0129] Understandably, if the outer diameter of the joint between the Nth tail pipe and the (N-1)th tail pipe differs significantly from the outer diameter of the tail pipes 2 on both sides of the joint, a separate sleeve can be installed at the joint and heated to ensure a smooth transition between the joint and the tail pipes 2 on both sides. This is to prevent the gas pressure in the drawing tower furnace from becoming unstable due to excessive changes in the diameter of the preform 1 during the drawing process.

[0130] In some embodiments, such as Figure 7 As shown, this embodiment includes the following steps between obtaining the preform 1 and connecting the preform 1 to the tail tube 2:

[0131] Step 711: Taper the flat end of the preform 1.

[0132] Between the tailpipe connection operation of preform 1 and the wire drawing process of multiple preform 1, the following steps are also included:

[0133] Step 712: Dry the preform 1 after the tailpipe connection operation.

[0134] Understandably, the tapering process is performed on the flat end of the preform 1 after it has been made and one end of the preform 1 is flush, in preparation for the subsequent wire drawing process of the preform 1.

[0135] Furthermore, the preform 1 after the tail tube connection operation is dried to remove the moisture introduced into the preform 1 and tail tube 2 due to the connection and tapering operations, thereby optimizing the quality of the preform 1 and helping to improve the optical performance of the subsequently prepared photonic crystal fiber.

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for fabricating a photonic crystal fiber, characterized in that, include: Prepare capillary rods, outer tubes, tail tubes, and at least one type of capillary tube, wherein the number of tail tubes is the same as the number of capillary tubes of each type. The capillary rod, the outer tube, and the at least one type of capillary tube are stacked to obtain a preform, ensuring that one end of the preform is flush. Perform a tail tube connection operation on the unaligned end of the preform to ensure that capillary tubes of the same specification are inserted into the same tail tube; The preform is drawn into a fiber, a first negative pressure is applied to the outer tube, a first positive pressure is applied to the tail tube, and the magnitudes of the first positive pressure and the first negative pressure are adjusted to obtain a photonic crystal fiber. The first positive pressure includes at least one pressure value, and the number of pressure values ​​is the same as the number of tailpipes.

2. The method for fabricating photonic crystal fiber according to claim 1, characterized in that, The steps for preparing the capillary rod, outer sheath, tail tube, and at least one type of capillary include: Prepare a core capillary rod and several filler capillary rods with different outer diameters; Prepare one of the outer tubes; Prepare a plurality of the capillary tubes and prepare a tail tube of the same specifications and quantity as the capillary tubes; Among them, the capillaries of different specifications have the same outer diameter but different inner diameters, and are the same as the outer diameter of the fiber core capillary rod.

3. The method for fabricating photonic crystal fiber according to claim 1, characterized in that, The step of stacking the capillary rod, the outer sheath, and at least one type of capillary tube to obtain a preform includes: The capillary rod and the capillary tube are compactly stacked to obtain a preform, the cross-section of which is a regular polygon; The preform is inserted into the outer tube, ensuring that the preform and the outer tube are coaxially arranged. The capillary rod is filled into the gap between the outer wall of the preform and the inner wall of the outer sleeve.

4. The method for fabricating photonic crystal fiber according to claim 1, characterized in that, When the number of capillary tubes is 1, the steps for connecting the unfurled end of the preform include: Connect the tailpipe to the preformed bar; The connection between the outer tube and the tail tube is heated, a second negative pressure is provided to the outer tube, and a second positive pressure is provided to the tail tube. The magnitudes of the second negative pressure and the second positive pressure are adjusted to fuse the joint between the outer tube and the tail tube.

5. The method for fabricating photonic crystal fiber according to claim 4, characterized in that, The tailpipe is connected to the outer tube, and both the outer tube and the tailpipe are provided with corresponding pressure channels, which are used to connect to the corresponding pressure source.

6. The method for fabricating photonic crystal fiber according to claim 1, characterized in that, When the number of capillary tube specifications is greater than 1, and the number of capillary tube specifications is N, the steps for connecting the tail tube to the unfurled end of the preform include: Connect the first tailpipe to the preformed rod; The connection between the outer tube and the first tail tube is heated, a third negative pressure is provided to the outer tube, and a third positive pressure is provided to the first tail tube. The magnitudes of the third negative pressure and the third positive pressure are adjusted to fuse the joint between the outer tube and the first tail tube. Connect the remaining N-1 tailpipes sequentially to the first tailpipe; The connection between the Nth tailpipe and the (N-1)th tailpipe is heated, a fourth negative pressure is provided to the (N-1)th tailpipe, and a fourth positive pressure is provided to the Nth tailpipe. The magnitudes of the fourth positive pressure and the fourth negative pressure are adjusted to fuse the joint between the Nth tailpipe and the (N-1)th tailpipe.

7. The method for fabricating photonic crystal fiber according to claim 6, characterized in that, The lengths and numbers of the first to Nth capillaries are different. The first capillaries have the most numbers and the shortest length, while the Nth capillaries have the fewest numbers and the longest length. The length of the filling capillary rod is the same as the length of the first capillary tube; The Nth tailpipe is sleeve-shaped; The first tail tube to the (N-1)th tail tube are in the shape of a cover, and the bottom end of the first tail tube to the (N-1)th tail tube is provided with an opening. The opening of the (N-1)th tail tube is used for the Nth capillary tube to pass through. The Nth tail tube is used to connect to the bottom end of the (N-1)th tail tube, and the cover end of the (N-1)th tail tube is used to connect to the bottom end of the (N-2)th tail tube. The outer diameters of the first tailpipe to the Nth tailpipe are the same.

8. The method for fabricating photonic crystal fiber according to claim 7, characterized in that, Each of the outer sleeve, the first tail tube to the Nth tail tube is provided with a corresponding pressure channel, which is used to connect to the corresponding pressure source.

9. The method for fabricating a photonic crystal fiber according to claim 6, characterized in that, The step of connecting the unaligned end of the preformed bar to the tail pipe further includes: A sleeve is installed at the joint between the Nth tailpipe and the (N-1)th tailpipe.

10. The method for fabricating a photonic crystal fiber according to claim 1, characterized in that, Between obtaining the preform and performing the tailpipe connection operation on the preform, the method further includes: The flush end of the preform is tapered or tapered. Between the tail-end pipe operation of the preform and the wire drawing process of the preform, the method further includes: The preformed rods are dried after the tailpipe docking operation.

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