Preparation method of photonic crystal fiber

Abstract

The invention relates to the technical field of optical fiber preparation, and provides a preparation method of a photonic crystal fiber, which comprises the following steps: preparing a capillary rod, an outer sleeve, tail tubes and capillary tubes of at least one specification, the number of the tail tubes being the same as the number of the capillary tubes; stacking the capillary rod, the outer sleeve and at least one type of capillary tube to obtain a prefabricated rod, and ensuring that one end of the prefabricated rod is flush; carrying out tail pipe connection operation on the non-flush end of the preform; performing wire drawing treatment on the preform, providing first negative pressure for the outer sleeve, providing first positive pressure for the tail pipe, and adjusting the first positive pressure and the first negative pressure to obtain a photonic crystal fiber; wherein the first positive pressure comprises at least one pressure value, and the number of the pressure values is the same as that of the tail pipes. According to the preparation method of the photonic crystal fiber provided by the invention, cooperative regional control of the preform is realized through different pressure control, and the purpose of high-precision controllability of the end face structure of the photonic crystal fiber is achieved.

Description

Technical Field

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

[0002] Photonic crystal fibers (PCF) are a new type of optical fiber with unique optical properties. The characteristic of photonic crystal fibers 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. It has unique and novel physical properties, such as endless single mode, adjustable dispersion and effective large mode area. It has broad application prospects in biomedicine, precision processing and optical fiber communications.

[0003] Photonic crystal fibers are generally prepared by the stacking-drawing method, that is, capillaries with the same outer diameter are arranged according to the designed geometric shape, and then a group of stacked capillaries with a good geometric shape are transferred to a suitable sleeve, and filled and fixed with quartz wire to form a preform rod of the photonic crystal fiber. Subsequently, the photonic crystal fiber is prepared at high temperature by controlling the drawing parameters during the drawing process.

[0004] The size of the air holes in the cross section of a photonic crystal fiber is in the micron range, and the sizes are not necessarily exactly the same. During the preparation process, air holes at different positions may deform or collapse to varying degrees, destroying the structure of the photonic crystal fiber and directly affecting its performance. Summary of the invention

[0005] The invention provides a method for preparing a photonic crystal optical fiber, which is used to solve the problem of unstable product quality caused by deformation or collapse of air holes when preparing the photonic crystal optical fiber in the prior art.

[0006] The present invention provides a method for preparing a photonic crystal optical fiber, comprising: Prepare a capillary rod, an outer sleeve, a tail tube and at least one specification of a capillary tube, wherein the number of the tail tube is the same as the number of specifications of the capillary tube; The capillary rod, the outer sleeve and the at least one type of capillary tube are stacked to obtain a preformed rod, and one end of the preformed rod is ensured to be flush; Performing a tail pipe connection operation on the end of the preform rod that is not flush, ensuring that the capillaries of the same specification extend into the same tail pipe; Performing a wire drawing process on the preform rod, providing a first negative pressure on the outer sleeve, providing a first positive pressure on the tail tube, and adjusting the first positive pressure and the first negative pressure to obtain a photonic crystal optical fiber; The first positive pressure includes at least one pressure value, and the number of the pressure values ​​is the same as the number of the tail pipes.

[0007] According to a method for preparing a photonic crystal optical fiber provided by the present invention, the steps of preparing a capillary rod, an outer sleeve, a tail tube and at least one type of capillary tube include: A core capillary rod and a plurality of filling capillary rods with different outer diameters are prepared; Prepare an outer sleeve; Prepare a plurality of the capillaries and prepare the tail pipes of the same number as the specifications of the capillaries; The capillaries of different specifications have the same outer diameter and different inner diameters, and are the same as the outer diameter of the core capillary rod.

[0008] According to a method for preparing a photonic crystal optical fiber provided by the present invention, the step of stacking the capillary rod, the outer sleeve and the at least one type of capillary to obtain a preform rod comprises: The capillary rod and the capillary tube are compactly stacked to obtain a preform, wherein the cross section of the preform is a regular polygon; Loading the preform into the outer sleeve, ensuring that the preform is coaxially arranged with the outer sleeve; The gap between the outer wall of the preform and the inner wall of the outer sleeve is filled with the capillary rod.

[0009] According to a method for preparing a photonic crystal optical fiber provided by the present invention, when the number of the capillary tube specifications is 1, the step of performing a tail tube connection operation on the uneven end of the preform rod comprises: Connecting the tail pipe to the preform rod; The connection between the outer sleeve and the tail pipe is heated, a second negative pressure is provided to the outer sleeve, a second positive pressure is provided to the tail pipe, and the magnitudes of the second negative pressure and the second positive pressure are adjusted to fuse the joint between the outer sleeve and the tail pipe.

[0010] According to the method for preparing a photonic crystal optical fiber provided by the present invention, the tail tube is connected to the outer sleeve, and the outer sleeve and the tail tube are both provided with corresponding pressure channels, and the pressure channels are used to be connected to the corresponding pressure source.

[0011] According to a method for preparing a photonic crystal optical fiber provided by the present invention, when the number of specifications of the capillary tube is greater than 1, the number of specifications of the capillary tube is N, and the step of performing a tail tube connection operation on the uneven end of the preform rod comprises: Connecting the first tail pipe to the preform rod; Heating the connection between the outer sleeve and the first tail pipe, providing a third negative pressure to the outer sleeve, providing a third positive pressure to the first tail pipe, and adjusting the third negative pressure and the third positive pressure to fuse the connection between the outer sleeve and the first tail pipe; Connecting the remaining N-1 tail pipes to the first tail pipe in sequence; A connection between the Nth tail pipe and the N-1th tail pipe is subjected to a heating treatment, a fourth negative pressure is provided to the N-1th tail pipe, a fourth positive pressure is provided to the Nth tail pipe, and the magnitudes of the fourth positive pressure and the fourth negative pressure are adjusted to fuse a connection between the Nth tail pipe and the N-1th tail pipe.

[0012] According to a method for preparing a photonic crystal fiber provided by the present invention, the lengths and quantities of the first capillary to the Nth capillary are different, the first capillary has the largest quantity and the shortest length, and the Nth capillary has the smallest quantity and the longest length; The length of the filling capillary rod is the same as the length of the first capillary tube; The Nth tail pipe is in a sleeve shape; The first tail pipe to the N-1th tail pipe are in a cover shape, and the bottom ends of the first tail pipe to the N-1th tail pipe are all provided with openings, and the openings of the N-1th tail pipe are used for the Nth capillary to pass through; The Nth tail pipe is used to connect to the bottom end of the N-1th tail pipe, and the cover end of the N-1th tail pipe is used to connect to the bottom end of the N-2th tail pipe; The outer diameters of the first tail pipe to the Nth tail pipe are the same.

[0013] According to a method for preparing a photonic crystal optical fiber provided by the present invention, the outer sleeve and the first to Nth tail tubes are all provided with corresponding pressure channels, and the pressure channels are used to be connected to corresponding pressure sources.

[0014] According to a method for preparing a photonic crystal optical fiber provided by the present invention, the step of performing a tail pipe connection operation on the uneven end of the preform rod further comprises: A casing treatment is performed on the joint between the Nth tail pipe and the N-1th tail pipe.

[0015] According to a method for preparing a photonic crystal optical fiber provided by the present invention, between obtaining the preform and performing a tail tube connection operation on the preform, the method further includes: Performing a taper or a taper treatment on the flush end of the preform; Between the tail pipe connection operation on the preform rod and the wire drawing operation on the preform rod, the method further includes: The preform rod after the tail tube docking operation is dried.

[0016] The preparation method of the photonic crystal optical fiber provided by the present invention is to stack a capillary rod, an outer sleeve and a capillary of at least one specification to form a preform rod, and to connect the tail tube to the other end of the preform rod while ensuring that one end of the preform rod is flush. Since the number of tail tubes is the same as the number of specifications of the capillary tubes, the capillaries of the same specification are extended into the same tail tube at the tail tube end of the preform rod. When the preform rod is subjected to the wire drawing process, the outer sleeve is provided with a first negative pressure to eliminate the gap between the structures, and the tail tube is provided with a first positive pressure, and the number of pressure values ​​of the first positive pressure is determined by the number of tail tubes, so that the capillaries of the same specification in each tail tube are drawn under the same positive pressure. In the wire drawing process of the preform rod, the pressure of capillaries of different sizes, between capillaries and between capillaries and between capillaries and sleeves is controlled in a coordinated and divided area by different pressure controls, so as to achieve the purpose of high-precision control of the end face structure of the photonic crystal optical fiber and meet the requirements of diversified photonic crystal optical fiber preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction will be 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.

[0018] Figure 1 This is one of the flow diagrams of the method for preparing the photonic crystal optical fiber provided by the present invention.

[0019] Figure 2 It is a schematic diagram of the process of preparing a capillary rod, an outer sleeve, a tail tube and at least one type of capillary provided by the present invention.

[0020] Figure 3 It is a schematic diagram of a process for obtaining a preformed rod by stacking a capillary rod, an outer sleeve and at least one type of capillary tube provided by the present invention.

[0021] Figure 4 It is one of the flow diagrams of connecting the tail tube to the uneven end of the preform rod when the number of the capillary tube specifications provided by the present invention is 1.

[0022] Figure 5 It is a schematic flow chart of the process of connecting the tail tube to the uneven end of the preform rod when the number of the capillary tube specifications provided by the present invention is greater than 1.

[0023] Figure 6 This is the second schematic diagram of the process of connecting the tail pipe to the uneven end of the preform provided by the present invention.

[0024] Figure 7 This is the second schematic diagram of the process of preparing the photonic crystal optical fiber provided by the present invention.

[0025] Figure 8 It is a schematic diagram of the main structure of the preform provided by the present invention.

[0026] Fig. 9 It is a schematic diagram of the three-dimensional structure of the first tail pipe provided by the present invention.

[0027] Fig.10 It is a schematic diagram of the three-dimensional structure of the second tail pipe provided by the present invention.

[0028] Fig.11 This is one of the schematic diagrams of the tail pipe connection operation for the preform provided by the present invention.

[0029] Fig.12 This is the second schematic diagram of the tail pipe connection operation for the preform rod provided by the present invention.

[0030] Fig.13 This is the third schematic diagram of the tail pipe connection operation for the preform rod provided by the present invention.

[0031] Reference numerals: 1. preform rod; 11. core capillary rod; 12. outer sleeve; 13. capillary tube; 14. filling capillary rod; 131. first capillary tube; 132. second capillary tube; 2. tail pipe; 21. first tail pipe; 22. second tail pipe; 3. Pressure channel. DETAILED DESCRIPTION

[0032] 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.

[0033] Combine the following Figure 1-Figure 13 , the preparation method of the photonic crystal fiber provided by the embodiment of the present invention is described in detail through specific embodiments and application scenarios.

[0034] In some embodiments, Figure 1 , Figure 8 , Fig.11 , Fig.12 and Fig.13 As shown, this embodiment provides a method for preparing a photonic crystal fiber, comprising the following steps: Step 111 , preparing a capillary rod, an outer sleeve 12 , a tail tube 2 and at least one specification of capillary tubes 13 , wherein the number of the tail tubes 2 is the same as the number of specifications of the capillary tubes 13 .

[0035] Step 112 , stacking the capillary rod, the outer sleeve 12 and at least one type of capillary tube 13 to obtain a preform rod 1 , and ensuring that one end of the preform rod 1 is flush.

[0036] Step 113 , performing a tail pipe connection operation on the uneven end of the preform rod 1 to ensure that the capillaries 13 of the same specification extend into the same tail pipe 2 .

[0037] Step 114, drawing the preform rod 1, providing a first negative pressure to the outer tube 12, providing a first positive pressure to the tail tube 2, adjusting the first positive pressure and the first negative pressure, and obtaining a photonic crystal fiber.

[0038] The first positive pressure includes at least one pressure value, and the number of the pressure values ​​is the same as the number of the tail pipes 2 .

[0039] It is understandable that the capillary rod is usually made of quartz, and the outer tube 12 is usually made of quartz. The capillary 13 is usually made of quartz. The specification of the capillary 13 can be only one or multiple, which is selected according to the specific requirements of the photonic crystal fiber and is not limited here.

[0040] Correspondingly, the number of tail tubes 2 is the same as the number of specifications included in the capillary 13, that is, when the capillary 13 has only one specification, the number of tail tubes 2 is 1, and when the capillary 13 has N specifications, the number of tail tubes 2 is N.

[0041] The capillary rod, the capillary tube 13 and the outer sleeve 12 are stacked to form a preform rod 1. One end of the preform rod 1 is flush with each other to prepare for the subsequent wire drawing process. The other end of the preform rod 1 is a tail tube end for tail tube processing.

[0042] When connecting the tail pipe, it is necessary to ensure that the inner spaces of the outer sleeve 12 and the tail pipe 2 are isolated from each other to provide operating space for subsequent segmented pressure application. In addition, the capillaries 13 of the same specifications extend into the same tail pipe 2 to facilitate corresponding pressure control.

[0043] The preform rod 1 with one end flush is subjected to wire drawing. During the high-temperature heating process, a first negative pressure is applied to the outer sleeve 12 to eliminate the gaps between the capillary rods and the capillary tubes 13 in the outer sleeve 12 so that the gaps can be completely fused. A first positive pressure is applied to the tail tube 2. The number of values ​​of the first positive pressure is related to the number of tail tubes 2. For example, if the number of tail tubes 2 is 1, only one first positive pressure is applied. If the number of tail tubes 2 is multiple, multiple different pressure values ​​are applied to different tail tubes 2 to control the size of different types of capillaries 13. In the wire drawing process of the preform rod 1, the first negative pressure and the first positive pressure are coordinated to eliminate the gaps between the outer sleeve 12 and the capillary rods, the capillary rods and the capillary tubes 13, the adjacent capillary rods and the adjacent capillary tubes 13, and the sizes of the capillaries 13 of different specifications can be controlled by using different pressure values ​​based on the different specifications of the capillaries 13.

[0044] The preparation method of the photonic crystal optical fiber provided by the present invention is to stack a capillary rod, an outer sleeve 12 and a capillary tube 13 of at least one specification to form a preform rod 1, and to connect the tail tube to the other end of the preform rod 1 while ensuring that one end of the preform rod 1 is flush. Since the number of tail tubes 2 is the same as the number of specifications of the capillary tubes 13, the capillaries 13 of the same specification are extended into the same tail tube 2 at the tail tube connection end of the preform rod 1. When the preform rod 1 is subjected to the drawing process, the outer sleeve 12 is provided with a first negative pressure to eliminate the gaps between the structures, and the tail tube 2 is provided with a first positive pressure, and the number of pressure values ​​of the first positive pressure is determined by the number of tail tubes 2, so that the capillaries 13 of the same specification in each tail tube 2 are drawn under the same positive pressure. During the drawing process of the preform rod 1, different pressure controls are used to realize coordinated and regional control of the pressures of capillaries 13 of different sizes, between capillaries 13 and 13, and between capillary 13 and sleeve, so as to achieve high-precision control of the end face structure of the photonic crystal fiber and meet the needs of diversified photonic crystal fiber preparation.

[0045] In some embodiments, Figure 2 , Figure 8 , Fig. 9 and Fig.10 As shown, the steps of preparing the capillary rod, the outer sleeve 12, the tail tube 2 and at least one type of capillary 13 in this embodiment include the following steps: Step 211, preparing a core capillary rod 11 and a plurality of filling capillary rods 14 with different outer diameters.

[0046] Step 212, preparing an outer sleeve 12.

[0047] Step 213 , preparing a plurality of capillaries 13 and preparing the same number of tail pipes 2 as the specifications of the capillaries 13 .

[0048] The capillaries 13 of different specifications have the same outer diameter but different inner diameters, and are the same as the outer diameter of the core capillary rod 11 .

[0049] It is understandable that the capillary rods are divided into a core capillary rod 11 and a filling capillary rod 14. There is one core capillary rod 11 and multiple filling capillary rods 14, and the outer diameters of the multiple filling capillary rods 14 are different. The outer diameter of the capillary 13 is the same as the outer diameter of the core capillary rod 11, so that the core capillary rod 11 and the capillary 13 can be stacked equidistantly.

[0050] The core capillary rod 11 may be active or passive. Optionally, the core capillary rod 11 may also be replaced by a capillary tube with the same outer diameter.

[0051] There are multiple capillaries 13, and the capillaries 13 of different specifications have the same outer diameter and different inner diameters, so that when the capillaries 13 of different specifications are stacked in the outer sleeve 12, it is beneficial to control the gap between the capillaries 13 in the outer sleeve 12. The different inner diameters of the capillaries 13 can be used for different optical fiber usage requirements, expanding the application range of photonic crystal optical fibers.

[0052] Correspondingly, the number of the tail pipes 2 is the same as the number of specifications of the capillary tubes 13 , so that the pressure of the capillary tubes 13 of different specifications can be controlled in one tail pipe 2 .

[0053] Specifically, the cross-sectional shape of the capillary 13 may be a circle or a regular hexagon.

[0054] In some embodiments, Figure 3 and Figure 8 As shown, in this embodiment, the capillary rod, the outer sleeve 12 and at least one type of capillary tube 13 are stacked to obtain the preform rod 1, which includes the following steps: Step 311 , compactly stack the capillary rods and the capillary tubes 13 to obtain a preform, wherein the cross section of the preform is a regular polygon.

[0055] Step 312 , loading the preform into the outer sleeve 12 , ensuring that the preform and the outer sleeve 12 are coaxially arranged.

[0056] Step 313 , filling the gap between the outer wall of the preform and the inner wall of the outer sleeve 12 with the capillary rod 14 .

[0057] It is understandable that the capillary rods and capillaries 13 are compactly stacked in the mold. Since different types of capillaries 13 have the same outer diameter, which is also the same as the outer diameter of the core capillary rod 11, the core capillary rod 11 and the capillary 13 can be stacked into a regular polygonal structure.

[0058] Specifically, in this embodiment, the core capillary rod 11 and the capillary tube 13 are stacked into a regular hexagon.

[0059] A preform with a regular polygonal cross section is loaded into an outer sleeve 12. The preform has a symmetry axis, and the outer sleeve 12 also has a symmetry axis. The two symmetry axes are overlapped to ensure that the preform is loaded into the center of the outer sleeve 12. A plurality of filling capillary rods 14 are filled between the inner wall of the outer sleeve 12 and the outer wall of the preform to fill the gap between the preform and the outer sleeve 12 tightly. In order to ensure the assembly of the outer sleeve 12 and the preform, the inner diameter of the outer sleeve 12 is slightly larger than the diameter of the circumscribed circle of the preform.

[0060] Furthermore, the outer sleeve 12 is adjusted to be flush with one end of the preform, that is, the outer sleeve 12, the core capillary rod 11, the filling capillary rod 14, and one end of the capillary 13 are all flush, which facilitates the operation of connecting the tail tube to the other end of the preform rod 1.

[0061] In some embodiments, Figure 4 As shown, in this embodiment, when the number of the capillary tube 13 is 1, the tail tube connection operation for the uneven end of the preform rod 1 includes the following steps: Step 411 , connecting the tail tube 2 to the preform rod 1 .

[0062] Step 412, heat the connection between the outer sleeve 12 and the tail pipe 2, provide a second negative pressure to the outer sleeve 12, provide a second positive pressure to the tail pipe 2, adjust the second negative pressure and the second positive pressure, and fuse the joint between the outer sleeve 12 and the tail pipe 2.

[0063] It is understandable that when the number of capillary tubes 13 is 1, the number of tail tubes 2 is also 1. The tail tube 2 is connected to the tail tube end of the preform rod 1, 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 the capillary tubes 13 are all extended into the tail tube 2, it can be ensured that the capillary tubes 13 can reach the controlled size without shrinking and collapsing, and the gaps are all fused, so that the outer sleeve 12 is tightly connected to the tail tube 2, and then independent spaces are formed inside the outer sleeve 12 and the tail tube 2, respectively, which provides space for subsequent wire drawing processing to facilitate pressure application. In addition, in the process of connecting the tail tube with the outer sleeve, ensure that all capillaries 13 are not closed.

[0064] In some embodiments, the tail pipe 2 of this embodiment is connected to the outer sleeve 12. The outer sleeve 12 and the tail pipe 2 are both provided with corresponding pressure channels 3. The pressure channels 3 are used to be connected to corresponding pressure sources.

[0065] It is understandable that, in the case of only one tail tube 2, a small section of quartz tube is respectively provided on the outer tube 12 and the tail tube 2, and the quartz tube is formed during the manufacturing process of the tail tube 2 and the outer tube 12. Different pressure sources can apply positive pressure or negative pressure to the tail tube 2 and the outer tube 12 respectively through the quartz tube to meet the pressure requirements during the preparation process of the photonic crystal fiber.

[0066] In some embodiments, Figure 5 , Fig.11 , Fig.12 and Fig.13 As shown, in the case where the number of specifications of the capillary tube 13 of this embodiment is greater than 1, the number of specifications of the capillary tube 13 is N, and the tail pipe connection operation for the uneven end of the preform rod 1 includes the following steps: Step 511 , connecting the first tail pipe 21 to the preform rod 1 .

[0067] Step 512, heat the connection between the outer sleeve 12 and the first tail pipe 21, provide a third negative pressure to the outer sleeve 12, provide a third positive pressure to the first tail pipe 21, adjust the third negative pressure and the third positive pressure, and fuse the joint between the outer sleeve 12 and the first tail pipe 21.

[0068] Step 513 , connecting the remaining N−1 tail pipes 2 to the first tail pipe 21 in sequence.

[0069] Step 514, heat the connection between the Nth tail pipe and the N-1th tail pipe, provide a fourth negative pressure to the N-1th tail pipe, provide a fourth positive pressure to the Nth tail pipe, adjust the magnitudes of the fourth positive pressure and the fourth negative pressure, and fuse the connection between the Nth tail pipe and the N-1th tail pipe.

[0070] It is understandable that when the number of specifications of the capillary tube 13 is greater than 1, the number of specifications of the capillary tube 13 is N, and the number of tail pipes 2 is also N. The number of tail pipes 2 ranges from 1 to N, namely the first tail pipe 21, the second tail pipe 22, and the Nth tail pipe.

[0071] The outer sleeve 12 is connected to the first tail pipe 21, and the connection between the outer sleeve 12 and the first tail pipe 21 is heated, a third positive pressure is applied to the first tail pipe 21, and a third negative pressure is applied to the outer sleeve 12. Since the first capillary 131 extends into the first tail pipe 21, it is ensured that the first capillary 131 can reach a controlled size without shrinking or collapsing, and all the gaps are fused, so that the outer sleeve 12 is tightly connected to the first tail pipe 21, and independent spaces are formed inside the outer sleeve 12 and the first tail pipe 21, respectively, which provides space for subsequent wire drawing processing and facilitates pressure application.

[0072] Further, the remaining N-1 tail pipes 2 are connected in sequence, specifically, the second tail pipe 22 is connected to the first tail pipe 21, the third tail pipe 2 is connected to the second tail pipe 22, until the Nth tail pipe is connected to the N-1th tail pipe. A heating treatment is performed at the connection of two adjacent tail pipes 2, and a fourth negative pressure is applied to the N-1th tail pipe, and a fourth positive pressure is applied to the Nth tail pipe. Since the N-1th capillary extends into the N-1th tail pipe, it is ensured that the N-1th capillary can reach the controlled size without shrinking and collapsing, and all the gaps are fused, so that the Nth tail pipe is tightly connected to the N-1th tail pipe, and then independent spaces are formed inside the Nth tail pipe and the N-1th tail pipe, respectively, which provides space for subsequent wire drawing processing to facilitate pressure application. In addition, in the process of connecting the Nth tail pipe to the N-1th tail pipe, it is ensured that all capillaries 13 are not closed.

[0073] Specifically, since the Nth tail pipe and the N-1th tail pipe include N tail pipes in total, the fourth positive pressure of each Nth tail pipe and the fourth negative pressure of the N-1th tail pipe are arranged in pairs and adjusted according to different tail pipe specifications.

[0074] In some embodiments, Fig.11 , Fig.12 and Fig.13 As shown, the lengths and quantities of the first capillaries 131 to the Nth capillaries in this embodiment are different. The first capillaries 131 have the largest quantity and the shortest length, and the Nth capillaries have the smallest quantity and the longest length.

[0075] The length of the filling capillary rod 14 is the same as that of the first capillary tube 131 .

[0076] The Nth tail pipe is in a sleeve shape.

[0077] The first to N-1 tail pipes 21 to 21 are in a cover shape, and the bottom ends of the first to N-1 tail pipes 21 to 21 are all provided with openings, and the openings of the N-1 tail pipe are used for the N-1 capillary tube to pass through.

[0078] The Nth tail pipe is used to butt joint with the bottom end of the N-1th tail pipe, and the cover end of the N-1th tail pipe is used to butt joint with the bottom end of the N-2th tail pipe.

[0079] The first tail pipe 21 to the Nth tail pipe have the same outer diameter.

[0080] It is understandable that, in order to control the pressure of each specification of the capillary tube 13 separately, the capillary tubes 13 of different specifications are set to different lengths so that the capillary tubes 13 of different lengths can be extended into different tail pipes 2. In order to control the cost, the capillary tubes 13 of the largest specification are set to be the shortest, and the pressure is applied in the first tail pipe 21. According to the decrease in the number, the length of the capillary tubes 13 is respectively extended. In this way, the capillary tubes 13 with the smallest number have the longest length, saving the material of the capillary tubes 13.

[0081] The length of the N-1th tail tube is smaller than the difference between the length of the Nth capillary tube and the length of the N-1th capillary tube, so as to ensure that the Nth capillary tube can extend into the Nth tail tube, so as to control the pressure of the Nth capillary tube in the Nth tail tube.

[0082] When the Nth capillary tube passes through the opening of the N-1th tail tube, during the heating process, it is necessary to ensure that the outer wall of the Nth capillary tube fits tightly with the inner wall of the opening of the N-1th tail tube, so that a closed space is formed in the N-1th tail tube to facilitate pressure application.

[0083] The difference between the outer diameters of the first tail pipe 21 to the Nth tail pipe and the outer diameter of the outer sleeve 12 does not exceed ±3 mm.

[0084] In one embodiment, if Fig.11 , Fig.12 and Fig.13 As shown, the capillary 13 of this embodiment includes two specifications, the number of first capillaries 131 is a plurality, and the length of the first capillary 131 is the same as the length of the core capillary rod 11 and the filling capillary rod 14. The number of second capillaries 132 is two, and the length of the second capillary 132 is longer, and the inner diameter of the second capillary 132 is greater than the inner diameter of the first capillary 131.

[0085] The length of the outer sleeve 12 determines the effective length of the preform 1 . The length of the outer sleeve 12 is L mm. The length of the first capillary 131 is (L+50) mm. The length of the second capillary 132 is (L+250) mm.

[0086] There are also two tail pipes 2, the first tail pipe 21 corresponds to the first capillary tube 131, and the second tail pipe 22 corresponds to the second capillary tube 132. The outer diameters of the first tail pipe 21 and the second tail pipe 22 are consistent, the length of the first tail pipe 21 is slightly smaller than the difference between the lengths of the second capillary tube and the first capillary tube 131, and the length of the second tail pipe 22 is slightly larger 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 pipe 21. The first tail pipe 21 is in a cover shape, and the second tail pipe 22 is in a sleeve shape. Two openings are provided at the bottom end of the first tail pipe 21, and the two second capillaries 132 pass through the two openings respectively and extend into the second tail pipe 22.

[0087] In this way, when the first tail pipe 21 is connected to the outer sleeve 12 and heated, the first capillary 131 extending into the first tail pipe 21 is applied with a third positive pressure, and the outer sleeve 12 is applied with a third negative pressure. By adjusting the magnitude of the third positive pressure and the third negative pressure, the joint between the outer sleeve 12 and the first tail pipe 21 is fused, and the first capillary 131 maintains the designed size while the remaining structures are tightly fused.

[0088] When the second tail pipe 22 is connected to the first tail pipe 21 and heated, the second capillary 132 extending into the second tail pipe 22 is applied with a fourth positive pressure, and the first tail pipe 21 is applied with a fourth negative pressure. By adjusting the magnitudes of the fourth positive pressure and the fourth negative pressure, the joint between the first tail pipe 21 and the second tail pipe 22 is fused, and the second capillary 132 maintains the designed size while the remaining structures are tightly fused.

[0089] After the connection between the preform rod 1 and the first tail tube 21 and the second tail tube 22 is completed, the preform rod 1 is subjected to a wire drawing process, a first negative pressure is applied to the outer sleeve 12, a first pressure value of a first positive pressure is applied to the first tail tube 21, and a second pressure value of the first positive pressure is applied to the second tail tube 22. The two pressure values ​​of the first negative pressure and the first positive pressure are adjusted so that the wire drawing process is performed under the condition of regional pressure control in the outer sleeve 12, the first tail tube 21 and the second tail tube 22 to obtain a photonic crystal fiber, so that the end face size of the photonic crystal fiber is accurately controlled.

[0090] In some embodiments, Fig.11 , Fig.12 and Fig.13 As shown, the outer sleeve 12 and the first tail pipe 21 to the Nth tail pipe of this embodiment are all provided with corresponding pressure channels 3, and the pressure channels 3 are used to be connected to corresponding pressure sources.

[0091] It is understandable that, in the case of N tail tubes 2, a small section of quartz tube is respectively provided on the outer tube 12 and the first to Nth tail tubes, and the quartz tube is formed during the manufacturing process of the N tail tubes 2 and the outer tube 12. Different pressure sources can apply positive pressure or negative pressure to the N tail tubes 2 and the outer tube 12 through the quartz tube to meet the pressure requirements during the preparation process of the photonic crystal fiber.

[0092] In some embodiments, Figure 6 As shown, in this embodiment, the tail pipe connection operation for the uneven end of the preform rod 1 also includes the following steps: Step 611, performing casing treatment on the joint between the Nth tail pipe and the N-1th tail pipe.

[0093] It is understandable that if the outer diameter of the joint between the Nth tail tube and the N-1th tail tube is significantly different from the outer diameter of the tail tubes 2 on both sides of the joint, a separate sleeve can be installed at the joint and heat treated to achieve a smooth transition between the joint and the tail tubes 2 on the front and rear sides, so as to avoid unstable gas pressure in the heating furnace of the drawing tower due to excessive changes in the diameter of the preform rod 1 during the drawing process.

[0094] In some embodiments, Figure 7 As shown, in this embodiment, between obtaining the preform rod 1 and connecting the tail tube 2 to the preform rod 1, the following steps are also included: Step 711, performing a taper process on the flat end of the preform rod 1.

[0095] Between the tail pipe connection operation for the preform rod 1 and the wire drawing operation for the multiple preform rods 1, the following steps are also included: Step 712, performing a drying operation on the preform rod 1 after the tail tube docking operation.

[0096] It is understandable that the taper treatment is performed on the flat end of the preform rod 1 after the preform rod 1 is produced and one end of the preform rod 1 is flat, so as to prepare for the subsequent wire drawing treatment of the preform rod 1 .

[0097] Furthermore, the preform 1 is dried after the tail tube connection operation to remove moisture introduced into the preform 1 and the tail tube 2 due to the connection and taper operation, thereby optimizing the quality of the preform 1 and helping to improve the optical performance of the subsequently prepared photonic crystal fiber.

[0098] 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 photonic crystal optical fiber, characterized in that: include: Prepare a capillary rod, an outer sleeve, a tail tube and at least one specification of a capillary tube, wherein the number of the tail tube is the same as the number of specifications of the capillary tube; The capillary rod, the outer sleeve and the at least one type of capillary tube are stacked to obtain a preformed rod, and one end of the preformed rod is ensured to be flush; Performing a tail pipe connection operation on the end of the preform rod that is not flush, ensuring that the capillaries of the same specification extend into the same tail pipe; Performing a wire drawing process on the preform rod, providing a first negative pressure on the outer sleeve, providing a first positive pressure on the tail tube, and adjusting the first positive pressure and the first negative pressure to obtain a photonic crystal optical fiber; The first positive pressure includes at least one pressure value, and the number of the pressure values ​​is the same as the number of the tail pipes.

2. The method for preparing a photonic crystal optical fiber according to claim 1, characterized in that: The steps of preparing the capillary rod, the outer sleeve, the tail tube and at least one type of capillary tube include: A core capillary rod and a plurality of filling capillary rods with different outer diameters are prepared; Prepare an outer sleeve; Prepare a plurality of the capillaries and prepare the tail pipes of the same number as the specifications of the capillaries; The capillaries of different specifications have the same outer diameter and different inner diameters, and are the same as the outer diameter of the core capillary rod.

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

4. The method for preparing a photonic crystal optical fiber according to claim 1, characterized in that: When the number of the capillary tube specifications is 1, the step of performing a tail tube connection operation on the uneven end of the preform rod comprises: Connecting the tail pipe to the preform rod; The connection between the outer sleeve and the tail pipe is heated, a second negative pressure is provided to the outer sleeve, a second positive pressure is provided to the tail pipe, and the magnitudes of the second negative pressure and the second positive pressure are adjusted to fuse the joint between the outer sleeve and the tail pipe.

5. The method for preparing a photonic crystal optical fiber according to claim 4, characterized in that: The tail pipe is butt-jointed with the outer sleeve. The outer sleeve and the tail pipe are both provided with corresponding pressure channels, and the pressure channels are used to be connected with corresponding pressure sources.

6. The method for preparing a photonic crystal fiber according to claim 1, characterized in that: When the number of specifications of the capillary tube is greater than 1, the number of specifications of the capillary tube is N, and the step of performing a tail tube connection operation on the uneven end of the preform rod comprises: Connecting the first tail pipe to the preform rod; Heating the connection between the outer sleeve and the first tail pipe, providing a third negative pressure to the outer sleeve, providing a third positive pressure to the first tail pipe, and adjusting the third negative pressure and the third positive pressure to fuse the connection between the outer sleeve and the first tail pipe; Connecting the remaining N-1 tail pipes to the first tail pipe in sequence; A connection between the Nth tail pipe and the N-1th tail pipe is subjected to a heating treatment, a fourth negative pressure is provided to the N-1th tail pipe, a fourth positive pressure is provided to the Nth tail pipe, and the magnitudes of the fourth positive pressure and the fourth negative pressure are adjusted to fuse a connection between the Nth tail pipe and the N-1th tail pipe.

7. The method for preparing a photonic crystal optical fiber according to claim 6, characterized in that: The lengths and numbers of the first capillary to the Nth capillary are different, the first capillary has the largest number and the shortest length, and the Nth capillary has the smallest number and the longest length; The length of the filling capillary rod is the same as the length of the first capillary tube; The Nth tail pipe is in a sleeve shape; The first tail pipe to the N-1th tail pipe are in a cover shape, and the bottom ends of the first tail pipe to the N-1th tail pipe are all provided with openings, and the openings of the N-1th tail pipe are used for the Nth capillary to pass through; The Nth tail pipe is used to connect to the bottom end of the N-1th tail pipe, and the cover end of the N-1th tail pipe is used to connect to the bottom end of the N-2th tail pipe; The outer diameters of the first tail pipe to the Nth tail pipe are the same.

8. The method for preparing a photonic crystal optical fiber according to claim 7, characterized in that: The outer sleeve and the first to the Nth tail pipes are all provided with corresponding pressure channels, and the pressure channels are used to be connected to corresponding pressure sources.

9. The method for preparing a photonic crystal optical fiber according to claim 6, characterized in that: The step of performing a tail pipe connection operation on the uneven end of the preform rod further comprises: A casing treatment is performed on the joint between the Nth tail pipe and the N-1th tail pipe.

10. The method for preparing a photonic crystal optical fiber according to claim 1, characterized in that: The process of obtaining the preform rod and connecting the tail pipe to the preform rod further includes: Performing a taper or a taper treatment on the flush end of the preform; Between the tail pipe connection operation on the preform rod and the wire drawing operation on the preform rod, the method further includes: The preform rod after the tail tube docking operation is dried.

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