Energy delivery fiber and method of making same, fiber laser

Abstract

The application provides an energy transmission optical fiber, a preparation method thereof and a fiber laser. The energy transmission optical fiber comprises a core layer and a cladding layer. The core layer comprises an inner core layer, an inner recess layer and an outer core layer which are sequentially covered, and the cladding layer is covered on the outer wall of the outer core layer. The shape of the section of the inner core layer is circular, the shape of the section of the inner recess layer is annular, the inner wall of the section of the outer core layer is circular annular, and the outer wall of the section of the outer core layer is rectangular annular along the extension direction of the energy transmission optical fiber. The inner core layer and the inner recess layer are concentrically arranged, and the outer core layer is centrally symmetric along the center of the inner core layer. The refractive indexes of at least two of the inner core layer, the inner recess layer and the outer core layer are different. The energy transmission optical fiber has good uniformity of the energy of the light beam output by the energy transmission optical fiber, and the fiber laser using the energy transmission optical fiber is not easy to cause damage to the plate when cutting the plate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical fiber technology, and in particular to an energy transmission optical fiber, a preparation method thereof and an optical fiber laser. BACKGROUND

[0002] The optical fiber laser refers to a laser using a glass optical fiber doped with a rare earth element as a gain medium. In recent years, continuous high-power optical fiber lasers have been widely used in the field of metal cutting and welding. The output light of the optical fiber laser is output through an energy transmission optical fiber.

[0003] In the related art, the energy transmission optical fiber includes a core layer and a cladding layer, and the cladding layer is arranged around the core layer. The cross-sectional shape of the core layer is circular, and the cross-sectional shape of the cladding layer is a circular ring.

[0004] However, the energy of the light beam output by the energy transmission optical fiber presents a Gaussian distribution, and the optical fiber laser using the energy transmission optical fiber is prone to causing damage to the cutting plate. SUMMARY

[0005] The present application provides an energy transmission optical fiber, a preparation method thereof and an optical fiber laser, the uniformity of the energy of the light beam output by the energy transmission optical fiber is better, and the optical fiber laser using the energy transmission optical fiber is less likely to cause damage to the plate when cutting the plate.

[0006] In a first aspect, the present application provides an energy transmission optical fiber, including a core layer and a cladding layer, along the center of the energy transmission optical fiber to the outer wall of the energy transmission optical fiber, the core layer includes an inner core layer, an inner depression layer and an outer core layer which are sequentially covered, and the cladding layer is covered on the outer wall of the outer core layer;

[0007] Along the direction perpendicular to the extension direction of the energy transmission optical fiber, the cross-sectional shape of the inner core layer is circular, the cross-sectional shape of the inner depression layer is annular, the inner wall of the cross section of the outer core layer is circular ring, the outer wall of the cross section of the outer core layer is rectangular ring, the inner core layer and the inner depression layer are concentrically arranged, and the outer core layer is centrally symmetric along the center of the inner core layer;

[0008] The refractive indexes of at least two of the inner core layer, the inner depression layer and the outer core layer are different.

[0009] In a possible implementation manner, the first difference between the refractive index of the inner core layer and the refractive index of the outer core layer is not greater than 0.002, the second difference between the refractive index of the inner depression layer and the refractive index of the outer core layer is not greater than 0 to 0.003, and the refractive index of the inner depression layer is not greater than the refractive index of the outer core layer.

[0010] In a possible implementation manner, along the direction perpendicular to the extension direction of the energy transmission optical fiber, the outer wall of the cross section of the outer core layer includes a plurality of straight edges which are sequentially connected in a head-to-tail manner, and at least two adjacent straight edges are connected through an arc segment.

[0011] In a possible implementation, the energy transmission fiber provided by the present application, the cladding comprises a first cladding and a second cladding coated on the outer wall of the first cladding, the first cladding is coated on the outer wall of the outer core layer, the difference between the refractive index of the first cladding and the refractive index of the outer core layer is 0.003 to 0.012, and the refractive index of the first cladding is less than the refractive index of the outer core layer;

[0012] The difference between the refractive index of the second cladding and the refractive index of the outer core layer is greater than 0.075, and the refractive index of the second cladding is less than the refractive index of the outer core layer.

[0013] In a possible implementation, the energy transmission fiber provided by the present application, the inner core layer is a silicon dioxide layer;

[0014] The outer core layer is a silicon dioxide layer;

[0015] The inner recess layer is a fluorine-doped silicon dioxide layer.

[0016] In a possible implementation, the energy transmission fiber provided by the present application, the inner core layer is a germanium-fluorine co-doped silicon dioxide layer;

[0017] The outer core layer is a silicon dioxide layer;

[0018] The inner recess layer is a silicon dioxide layer.

[0019] In a possible implementation, the energy transmission fiber provided by the present application, further comprising an outer coating layer, the outer coating layer is coated on the outer wall of the second cladding;

[0020] The first cladding is a fluorine-doped silicon dioxide layer;

[0021] The second cladding is an acrylic resin layer;

[0022] The outer coating layer is an acrylic resin layer.

[0023] In a possible implementation, the energy transmission fiber provided by the present application, the diameter of the inner core layer is 6 μm to 50 μm;

[0024] The diameter of the outer wall of the inner recess layer is 7 μm to 55 μm;

[0025] The outer wall of the cross section of the outer core layer is in a square ring shape along the direction perpendicular to the extension direction of the energy transmission fiber, and the distance between the opposite straight edges of the outer wall of the cross section of the outer core layer is 30 μm to 600 μm;

[0026] The diameter of the outer wall of the first cladding is 90 μm to 1000 μm;

[0027] The diameter of the outer wall of the second cladding is 170 μm to 1200 μm;

[0028] The diameter of the outer wall of the outer coating layer is 250 μm to 1400 μm.

[0029] In a possible implementation, the energy transmission fiber provided by the present application, the arc-shaped section is a circular arc section, the radius of the circular arc section is 5-15 μm, and the ratio of the distance between the opposite straight edges of the outer core layer to the radius of the circular arc section is 5-15.

[0030] In a second aspect, the present application provides a method for manufacturing an energy transmission fiber, which is used to manufacture the energy transmission fiber provided in the first aspect, and the method comprises the following steps:

[0031] forming an inner recess layer and an inner core layer on the inner wall of the base pipe to form a first preform, wherein the inner recess layer is coated on the outer wall of the inner core layer;

[0032] forming an outer core layer on the outer wall of the first preform;

[0033] polishing the outer wall of the outer core layer into a rectangular ring along a section perpendicular to the extension direction of the energy transmission fiber to form a second preform;

[0034] forming a cladding layer on the outer wall of the second preform.

[0035] In a possible implementation, the method for manufacturing an energy transmission fiber provided by the present application, the cladding layer is formed on the outer wall of the second preform, and the method comprises the following steps:

[0036] depositing the cladding layer on the outer wall of the second preform by using a plasma external deposition method.

[0037] In a possible implementation, the method for manufacturing an energy transmission fiber provided by the present application, the cladding layer is formed on the outer wall of the second preform, and the method comprises the following steps:

[0038] inserting the second preform into a fluorine-doped sleeve, and performing fusion shrinking on the second preform and the fluorine-doped sleeve;

[0039] polishing the fluorine-doped sleeve into a circular ring along a section perpendicular to the extension direction of the energy transmission fiber.

[0040] In a third aspect, the present application provides an optical fiber laser, which comprises an optical fiber laser body and the energy transmission fiber provided in the first aspect and connected to the optical fiber laser body.

[0041] The application provides an energy transmission optical fiber, a preparation method thereof and an optical fiber laser. BRIEF DESCRIPTION OF DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0043] Figure 1 A structural schematic diagram of the energy transmission optical fiber provided by the embodiment of the present application;

[0044] Figure 2 A contrast schematic diagram of the refractive indexes of the inner core layer, the inner depression layer, the outer core layer, the first cladding layer and the second cladding layer in the energy transmission optical fiber provided by the embodiment of the present application;

[0045] Figure 3 A structural schematic diagram of the core layer in the energy transmission optical fiber provided by the embodiment of the present application;

[0046] Figure 4 A flowchart of the preparation method of the energy transmission optical fiber provided by the embodiment of the present application.

[0047] Legend of the drawings:

[0048] 100 - core layer;

[0049] 110 - inner core layer;

[0050] 120 - inner depression layer;

[0051] 130 - outer core layer;

[0052] 200 - cladding layer;

[0053] 210 - first cladding layer;

[0054] 220 - second cladding layer;

[0055] 300 - outer coating layer. DETAILED DESCRIPTION

[0056] In the description of the application, unless otherwise clearly specified and limited, the terms "mounting", "connection", "connecting" should be understood in a broad sense, for example, can be fixed connection, can also be indirectly connected through an intermediate medium, can be internal communication of two elements or interaction relationship of two elements. For those skilled in the art, the specific meaning of the above terms in the application can be understood according to the specific circumstances.

[0057] In the description of the application, the terms "upper", "lower", "front", "back", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application.

[0058] The terms "first", "second", "third" (if any) in the specification and claims of the application and the above drawings are used to distinguish similar objects, and do not necessarily describe a particular order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the application described herein can be implemented in an order other than that illustrated or described herein.

[0059] In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or maintenance tool including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or maintenance tools.

[0060] In order to make the purpose, technical scheme and advantages of the embodiments of the application more clear, the technical scheme in the embodiments of the application will be described clearly and completely in combination with the drawings in the embodiments of the application. Obviously, the described embodiments are part of the embodiments of the application, not all embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0061] In the related art, the energy transmission fiber includes a core layer and a cladding layer, and the cladding layer is arranged around the core layer. The cross-sectional shape of the core layer is circular, and the cross-sectional shape of the cladding layer is circular. However, the energy of the light beam output by the energy transmission fiber presents a Gaussian distribution, and when cutting a material, the Gaussian light beam with high energy concentration is extremely easy to cause damage to the cutting plate, resulting in an enlarged cutting heat affected zone, and further causing the splashing of metal residues to injure the laser output lens. Therefore, the high-power laser is converted into a flat-top light beam from a Gaussian light beam by different ways, so as to improve the cutting quality of the high-power laser.

[0062] In order to solve the above technical problems, the core layer of the energy transmission fiber is improved, and the core layer is arranged as an inner core layer, an inner depression layer and an outer core layer which are sequentially covered, wherein the inner wall of the cross section of the outer core layer is circular along the direction perpendicular to the extension direction of the energy transmission fiber, the outer wall of the cross section of the outer core layer is rectangular, and the refractive indexes of at least two of the inner core layer, the inner depression layer and the outer core layer are different. In this way, the circular symmetry structure of the energy transmission fiber can be destroyed while the core layer has different refractive indexes, so that the core layer is in a chaotic state, thereby more high-order modes can be excited, the mode coupling between the high-order modes is stronger, and the energy at the center of the core layer can be dispersed to the periphery, so that the Gaussian light beam is converted into a flat-top light beam. Therefore, the uniformity of the energy of the light beam output by the energy transmission fiber is better, and when cutting a plate, the cutting heat affected zone is smaller, and it is not easy to cause damage to the plate.

[0063] Figure 1 A structural schematic diagram of the energy transmission fiber provided by the embodiment of the present application is provided, Figure 2 A comparison schematic diagram of the refractive indexes of the inner core layer, the inner depression layer, the outer core layer, the first cladding layer and the second cladding layer in the energy transmission fiber provided by the embodiment of the present application is provided.

[0064] Referring to Figure 1 and Figure 2 As shown in the figures, the energy transmission fiber provided by the present application includes a core layer 100 and a cladding layer 200, and along the center of the energy transmission fiber 500 to the outer wall of the energy transmission fiber 500, the core layer 100 includes an inner core layer 110, an inner depression layer 120 and an outer core layer 130 which are sequentially covered, and the cladding layer 200 covers the outer wall of the outer core layer 130.

[0065] The cross-sectional shape of the inner core layer 110 is circular, the cross-sectional shape of the inner depression layer 120 is circular ring, the inner wall of the cross section of the outer core layer 130 is circular ring, and the outer wall of the cross section of the outer core layer 130 is rectangular ring along the direction perpendicular to the extension direction of the energy transmission fiber 500. The inner core layer 110 and the inner depression layer 120 are concentrically arranged, and the outer core layer 130 is centrally symmetric along the center of the inner core layer. The refractive indexes of at least two of the inner core layer 110, the inner depression layer 120 and the outer core layer 130 are different.

[0066] It should be noted that, referring to Figure 2 As shown in the figure, n0 is the refractive index of the outer core layer 130, the value of which is equal to the refractive index of silica quartz glass, n1 is the refractive index of the inner core layer 110, n2 is the refractive index of the inner depression layer 120, n4 is the refractive index of the first cladding layer, and n5 is the refractive index of the second cladding layer.

[0067] Among them, the cross section of the outer core layer 130 is a rectangular ring, which can have a better homogenization effect on the Gaussian light beam, has a better homogenization mode disturbance characteristic, and the refractive indexes of at least two of the inner core layer 110, the inner depression layer 120 and the outer core layer 130 are different, which also has a better homogenization effect.

[0068] Among them, the inner core layer 110 and the inner depression layer 120 are concentrically arranged, and the outer core layer 130 is centrally symmetric along the center of the inner core layer 110. In this way, compared with the conventional core layer arranged in a rectangular shape, the inner core layer 110 or the inner depression layer 120 of the energy transmission optical fiber provided by the embodiment can be used as a reference during optical fiber fusion, so that the coaxiality of the energy transmission optical fiber and the passive optical fiber during fusion is higher.

[0069] It should be noted that, from the energy homogenization effect, the energy transmission optical fiber in the related art is lower than the energy transmission optical fiber provided by the embodiment in the case that the refractive index of the inner core layer 110 is higher than the refractive index of the outer core layer 130, lower than the energy transmission optical fiber provided by the embodiment in the case that the refractive index of the inner core layer 110 is equal to the refractive index of the outer core layer 130, and lower than the energy transmission optical fiber provided by the embodiment in the case that the refractive index of the inner core layer 110 is less than the refractive index of the outer core layer 130. That is, in the case that the refractive index of the inner core layer 110 is less than the refractive index of the outer core layer 130, the energy homogenization effect of the energy transmission optical fiber provided by the embodiment is the best.

[0070] From the cutting ability of the energy transmission optical fiber, the energy transmission optical fiber provided by the embodiment in the case that the refractive index of the inner core layer 110 is higher than the refractive index of the outer core layer 130 is better than the energy transmission optical fiber provided by the embodiment in the case that the refractive index of the inner core layer 110 is equal to the refractive index of the outer core layer 130, and better than the energy transmission optical fiber provided by the embodiment in the case that the refractive index of the inner core layer 110 is less than the refractive index of the outer core layer 130. That is, in the case that the refractive index of the inner core layer 110 is greater than the refractive index of the outer core layer 130, the cutting ability of the energy transmission optical fiber provided by the embodiment is the best.

[0071] In addition, compared with the conventional core layer arranged in a rectangular shape, the cross-sectional size of the outer core layer 130 is smaller, which can improve the energy density of the final laser and improve the laser cutting quality.

[0072] It can be understood that when the refractive indexes of the inner recess layer 120 and the outer core layer 130 are the same, the inner recess layer 120 and the outer core layer 130 can be provided as one layer or two layers. That is, the core layer 100 can only include the inner core layer 110 and the outer core layer 130.

[0073] Wherein, since the refractive index of the core layer 100 is greater than the refractive index of the cladding layer 200, the cladding layer 200 can confine the light in the core layer 100, so that the light beam is transmitted in the core layer 100.

[0074] The energy transmission optical fiber provided by the embodiment is provided with the core layer 100 and the cladding layer 200. Along the center of the energy transmission optical fiber 500 to the outer wall of the energy transmission optical fiber 500, the core layer 100 includes the inner core layer 110, the inner recess layer 120 and the outer core layer 130 which are sequentially covered, and the cladding layer 200 covers the outer wall of the outer core layer 130. Along the extension direction perpendicular to the energy transmission optical fiber 500, the shape of the cross section of the inner core layer 110 is circular, the shape of the cross section of the inner recess layer 120 is circular ring, the inner wall of the cross section of the outer core layer 130 is circular ring, and the outer wall of the cross section of the outer core layer 130 is rectangular ring. The inner core layer 110 and the inner recess layer 120 are concentrically arranged, and the outer core layer 130 is centrally symmetric along the center of the inner core layer. The refractive indexes of at least two of the inner core layer 110, the inner recess layer 120 and the outer core layer 130 are different. In this way, the circular symmetry structure of the energy transmission optical fiber can be destroyed while the core layer has different refractive indexes, so that the core layer is in a chaotic state, thereby more high-order modes can be excited, the mode coupling between the high-order modes is stronger, the energy at the center of the core layer can be dispersed to the periphery, and thus the Gaussian light beam can be converted into a flat-top light beam. Therefore, the energy uniformity of the light beam output by the energy transmission optical fiber is better, the cutting heat affected zone is smaller when the plate material is cut, and the plate material is not easy to be damaged.

[0075] In a possible implementation, a first difference between the refractive index of the inner core layer 110 and the refractive index of the outer core layer 130 is not greater than 0.002, a second difference between the refractive index of the inner recess layer 120 and the refractive index of the outer core layer 130 is not greater than 0.003, and the refractive index of the inner recess layer 120 is not greater than the refractive index of the outer core layer 130. In this way, the homogenization effect can be improved, and the light beam can be dispersed and transmitted between the inner core layer 110, the inner recess layer 120 and the outer core layer 130.

[0076] Wherein, the first difference is equal to |n1-n0|, and the second difference is equal to |n2-n0|.

[0077] Specifically, the value of n1-n0 is -0.002 to 0.001, and the value of n2-n0 is -0.003 to 0.

[0078] For example, the first difference is 0, and the second difference is 0.001, or the first difference is 0.001, and the second difference is 0.002.

[0079] In order to facilitate processing and simplify processing difficulty, the outer wall of the cross section of the outer core layer 130 includes a plurality of straight edges connected in sequence along the extension direction perpendicular to the energy transmission optical fiber 500, and at least two adjacent straight edges are connected by an arc segment.

[0080] In some embodiments, the cladding 200 includes a first cladding 210 and a second cladding 220 coated on the outer wall of the first cladding 210, the first cladding 210 is coated on the outer wall of the outer core layer 130, the difference between the refractive index of the first cladding 210 and the refractive index of the outer core layer 130 is 0.003 to 0.012, and the refractive index of the first cladding 210 is less than the refractive index of the outer core layer 130. In this way, the difference between the refractive index of the first cladding 210 and the refractive index of the outer core layer 130 is small, which can effectively avoid the leakage of the light beam output and cause the fiber to burn out.

[0081] For example, the difference between the refractive index of the first cladding 210 and the refractive index of the outer core layer 130 is 0.01 or 0.006.

[0082] The difference between the refractive index of the second cladding 220 and the refractive index of the outer core layer 130 is greater than 0.075, and the refractive index of the second cladding 220 is less than the refractive index of the outer core layer 130.

[0083] The difference between the refractive index of the second cladding 220 and the refractive index of the outer core layer 130 can be 0.01 or 0.02.

[0084] In a possible implementation, the inner core layer 110 is a silica layer. The outer core layer 130 is a silica layer. The invaginated layer 120 is a fluorine-doped silica layer.

[0085] In another possible implementation, the inner core layer 110 is a germanium-fluorine co-doped silica layer, the outer core layer 130 is a silica layer, and the invaginated layer 120 is a silica layer.

[0086] In some embodiments, the energy transmission optical fiber further includes an outer coating layer 300 coated on the outer wall of the second cladding 220.

[0087] The outer coating layer 300 not only has the functions of maintaining the strength of the energy transmission optical fiber, preventing the micro-bending loss of the energy transmission optical fiber, and preventing the energy transmission optical fiber from being damp, but also can reduce the mechanical damage of the energy transmission optical fiber.

[0088] Specifically, the first cladding 210 is a fluorine-doped silica layer, the second cladding 220 is an acrylic resin layer, and the outer coating layer 300 is an acrylic resin layer.

[0089] It should be noted that the refractive index of the acrylic resin coating of the second cladding 220 is lower than the refractive index of the acrylic resin coating of the outer coating layer 300.

[0090] It can be understood that, along the extension direction perpendicular to the energy transmission optical fiber, the outer wall of the cross section of the outer core layer 130 can be a square ring or a rectangular ring. For the convenience of description, the outer wall of the cross section of the outer core layer 130 is described as a square ring below.

[0091] Figure 3 A structure diagram of the core layer in the energy transmission optical fiber provided by the embodiment of the present application is shown.

[0092] Referring to Figure 3 In a possible implementation, the diameter a1 of the inner core layer 110 is 6 μm to 50 μm.

[0093] The diameter a2 of the inner recess layer 120 is 7 μm to 55 μm.

[0094] Along the extension direction perpendicular to the energy transmission optical fiber 500, the outer wall of the cross section of the outer core layer 130 is a square ring, and the distance a3 between the opposite straight edges of the outer wall of the cross section of the outer core layer 130 is 30 μm to 600 μm.

[0095] The diameter of the outer wall of the first cladding layer 210 is 90 μm to 1000 μm.

[0096] The diameter of the outer wall of the second cladding layer 220 is 170 μm to 1200 μm.

[0097] The diameter of the outer wall of the outer coating layer 300 is 250 μm to 1400 μm.

[0098] In a possible implementation, the arc-shaped segment is a circular arc segment, the radius r3 of the circular arc segment is 5 μm to 15 μm, and the ratio of the distance a3 between the opposite straight edges of the outer wall of the cross section of the outer core layer 130 to the radius r3 of the circular arc segment is 5 to 15.

[0099] Figure 4 A flowchart of a preparation method of the energy transmission optical fiber provided by the embodiment of the present application is shown.

[0100] The present application also provides a preparation method of an energy transmission optical fiber, which is used for preparing the energy transmission optical fiber provided by the above embodiments, and the preparation method of the energy transmission optical fiber comprises the following steps:

[0101] S101, sequentially forming the inner recess layer 120 and the inner core layer 110 on the inner wall of the base pipe to form a first preform, wherein the inner recess layer 120 is coated on the outer wall of the inner core layer 110.

[0102] Specifically, the inner recess layer 120 and the inner core layer 110 can be prepared by using a modified chemical vapor deposition (MCVD, Modified Chemical Vapor Deposition) method.

[0103] S102, forming an outer core layer 130 on the outer wall of the first preform rod.

[0104] Specifically, the outer core layer 130 can be prepared by an external vapor deposition (OVD) or a vapor axial deposition (VAD) method.

[0105] S103, polishing the outer wall of the outer core layer 130 along a cross section perpendicular to the extension direction of the energy transmission optical fiber 500 into a rectangular ring shape to form a second preform rod.

[0106] It can be understood that the outer wall of the cross section of the outer core layer 130 is polished into a rectangular ring shape, which is convenient for processing and has high processing accuracy.

[0107] S104, forming a cladding layer 200 on the outer wall of the second preform rod.

[0108] Finally, the preform rod is drawn to the required size, and low refractive index acrylic resin paint and high refractive index acrylic resin paint are applied in sequence.

[0109] The drawing temperature is 1700-2200°C, the drawing speed is 3-30 m / min, and the drawing tension is 0.5-2 N.

[0110] In one possible implementation, the cladding layer 200 is formed on the outer wall of the outer core layer 130, comprising:

[0111] The cladding layer 200 is deposited on the outer wall of the outer core layer 130 by a plasma external deposition method.

[0112] Specifically, a fluorine-doped layer meeting the size requirements is prepared by a plasma external deposition (POD) method to form the cladding layer 200.

[0113] In one possible implementation, the cladding layer 200 is formed on the outer wall of the outer core layer 130, comprising:

[0114] The cross section of the outer core layer 130 is polished into a rectangular preform rod, which is inserted into a fluorine-doped sleeve, and the preform rod is shrinked with the fluorine-doped sleeve.

[0115] The fluorine-doped sleeve is polished into a circular ring shape along a cross section perpendicular to the extension direction of the energy transmission optical fiber 500.

[0116] Specifically, the fluorine-doped sleeve is prepared by a PCVD process, and a fluorine-doped layer is deposited on the inner surface of the silica-based tube.

[0117] It should be noted that after melting and shrinking, the silica layer on the surface of the preform needs to be polished clean.

[0118] To facilitate understanding, the fabrication process and performance parameters of square-core power transmission optical fiber are described in detail below.

[0119] Example 1

[0120] Step 1: Install the base tube on an MCVD lathe, and deposit SiCl4 (tetrachlorosilane) and SF6 (sulfur hexafluoride) inside the base tube to prepare an indentation layer 120. Based on the deposited indentation layer 120, continue to deposit SiCl4, GeCl4 (germanium tetrachloride) and SF6 to prepare the inner core layer 110, thereby forming the first preform.

[0121] The SiCl4 deposition rate was 0.8 g / min, and the SF6 flow rate was 50 sccm. A first preform containing an inner core layer 110 and an inner recess layer 120 was obtained by base tube melting and shrinkage.

[0122] Step 2: The first preform is mounted on a VAD lathe, and SiCl4 gas is introduced through a flame torch to deposit a silica porous body on the outer wall of the first preform. The porous body is 40 mm thick and the deposition rate is 10 g / min. After the porous body is deposited, the first preform with the attached white porous body is placed in a sintering furnace for degassing and sintering. Finally, it is extended to a diameter of 15 mm on the lathe, thereby forming an outer core layer 130 on the outer wall of the first preform.

[0123] Step 3: Grind the outer wall of the outer core layer 130 along the cross-section perpendicular to the extension direction of the power transmission fiber 500 to a square shape to form the second preform.

[0124] The distance between the opposite straight edges of the outer wall of the outer core layer 130 is 9mm, and the radius of the arc segment is 0.9mm.

[0125] After grinding and shaping, the second preform is subjected to acid washing, alkali washing and water washing.

[0126] Step 4: A SiO2 (silicon dioxide) fluorine-doped layer is deposited on the outer wall of the second preform using POD. The SiCl4 flow rate is 10 g / min, and the SF6 flow rate is 50 mL / min. The preform is then sintered into a solid third preform, which is rectangular with a distance of 26 mm between the opposite straight edges of its outer wall. The third preform is then polished into a circle with a diameter of 22.6 mm to form the first cladding layer 210.

[0127] Step 5: Connect the third preform to the tailstock and perform wire drawing.

[0128] Before the wire drawing process, the first preform is subjected to acid washing, alkali washing, and water washing. During the wire drawing process, the wire drawing temperature is controlled at 1950℃, the wire drawing speed is 20m / min, and the wire drawing tension is 1.2N.

[0129] After the wire drawing process, a low-refractive-index acrylic resin coating and an outer coating 300 are applied sequentially. The refractive index of the low-refractive-index acrylic resin coating is 1.37.

[0130] The specifications of the power transmission optical fiber prepared in the above embodiments are shown in Table 1 below.

[0131] Table 1. Specifications of the power transmission optical fiber prepared in Example 1

[0132] The diameter a1 of the inner core layer 110 20 μm First difference 0.0005 the diameter a2 of the outer wall of the inner layer 120 22 μm Second difference 0.0007 the distance a3 between opposite straight sides of the outer wall of the cross section of the outer core layer 130 50 μm radius r3 of the circular segment 5 μm Diameter of the outer wall of the first cladding layer 210 125 Difference between the refractive index of the first cladding layer 210 and the refractive index of the outer core layer 130 0.01

[0133] Example 2

[0134] Step 1: Install the base tube on an MCVD lathe, and deposit SiCl4 and SF6 inside the tube to prepare an indentation layer 120. Based on the deposited indentation layer, continue to deposit SiCl4, GeCl4 and SF6 to prepare the inner core layer 110, thereby forming the first preform.

[0135] The SiCl4 deposition rate was 1.5 g / min, and the SF6 flow rate was 20 sccm. A first preform containing an inner core layer 110 and an inner recessed layer was obtained by base tube melting and shrinkage.

[0136] Step 2: The first preform is mounted on a VAD lathe, and SiCl4 gas is introduced through a flame torch to deposit a silica porous body on the surface of the first preform. The porous body deposition thickness is controlled at 45 mm, and the deposition rate is controlled at 15 g / min. After the porous body deposition is completed, the first preform with the attached white porous body is placed in a sintering furnace for degassing and sintering. Finally, the transparent preform is extended to a diameter of 12 mm on the lathe, thereby forming an outer core layer 130 on the outer wall of the first preform.

[0137] Step 3: Grind the cross-section of the outer core layer 130 into a square shape to form the second preform.

[0138] The distance between the opposite straight edges of the outer wall of the square cross-section is 8mm, and the radius of the arc segment is 0.5mm.

[0139] After grinding and shaping, the second preform is subjected to acid washing, alkali washing and water washing.

[0140] Step 4: The second preform and the prepared fluorine-doped sleeve are melted together to form the third preform.

[0141] Before melting and shrinking, the fluorine-doped sleeve needs to be acid-washed, alkali-washed, and water-washed respectively. The melting and shrinking flow rate is 100 slm, and the melting and shrinking speed is 5 mm / min. After melting and shrinking, the third preform is ground into a circle with an outer diameter of 25.2 mm to form the first cladding layer 210.

[0142] Step 5: Connect the third preform to the tailstock and perform wire drawing.

[0143] Before the wire drawing process, the third preform is subjected to acid washing, alkali washing and water washing.

[0144] The drawing temperature is 2050℃, the drawing speed is 30m / min, and the drawing tension is 1.5N.

[0145] After the wire drawing process, a low-refractive-index acrylic resin coating and an outer coating 300 are applied sequentially. The refractive index of the low-refractive-index acrylic resin coating is 1.37.

[0146] The properties of the power transmission optical fiber prepared in the above embodiments are shown in Table 2 below.

[0147] Table 2. Specifications of the energy transfer optical fiber prepared in Example 2

[0148] The diameter a1 of the inner core layer 110 25 μm First difference 0.001 The diameter a2 of the inner layer 120 27 μm Second difference 0.0015 the distance a3 between opposite straight sides of the outer wall of the cross section of the outer core layer 130 100 μm radius r3 of the circular segment 20 μm Diameter of the outer wall of the first cladding layer 210 250 μm Difference between the refractive index of the first cladding layer 210 and the refractive index of the outer core layer 130 0.008

[0149] Example 3

[0150] Step 1: Install the base tube on an MCVD lathe, and deposit SiCl4 and SF6 inside the tube to prepare an indentation layer 120. Based on the deposited indentation layer 120, continue to deposit SiCl4, GeCl4 and SF6 to prepare the inner core layer 110, thereby forming the first preform.

[0151] The SiCl4 deposition rate was 2.5 g / min, and the SF6 flow rate was controlled at 100 sccm. A first preform containing an inner core layer 110 and an inner recessed layer was obtained by base tube melting and shrinkage.

[0152] Step 2: The first preform is mounted on a VAD lathe, and SiCl4 gas is introduced through a flame torch to deposit a silica porous body on the surface of the first preform. The porous body deposition thickness is 55 mm, and the deposition rate is 18 g / min. After the porous body deposition is completed, the first preform with the white porous body attached is placed in a sintering furnace for degassing and sintering. Finally, the transparent preform is extended to a diameter of 18 mm on the lathe, thereby forming an outer core layer 130 on the outer wall of the first preform.

[0153] Step 3: Grind the cross-section of the outer core layer 130 into a square shape to form the second preform.

[0154] The distance between the opposite straight edges of the outer wall of the outer core layer 130 is 12mm, and the radius of the arc segment is 0.6mm.

[0155] In the grinding and shaping process, the second preform is subjected to acid washing, alkali washing and water washing.

[0156] Step 4: The second preform and the prepared fluorine-doped sleeve are melted together to form the third preform.

[0157] Before melting and shrinking, the fluorine-doped sleeve needs to be acid-washed, alkali-washed, and water-washed.

[0158] The melting flow rate is 125 slm, and the melting speed is 18 mm / min. After melting, the third preform is ground into a circle with an outer diameter of 18.2 mm to form the first cladding layer 210.

[0159] Step 5: Connect the third preform to the tailstock and perform wire drawing.

[0160] Before the wire drawing process, the third preform is subjected to acid washing, alkali washing and water washing.

[0161] The drawing temperature is 2020℃, the drawing speed is 25m / min, and the drawing tension is 2N.

[0162] After the wire drawing process, a low-refractive-index acrylic resin coating and an outer coating 300 are applied sequentially. The refractive index of the low-refractive-index acrylic resin coating is 1.375.

[0163] The specifications of the power transmission optical fiber prepared in the above embodiments are shown in Table 3 below.

[0164] Table 3. Specifications of the power transmission optical fiber prepared in Example 3

[0165]

[0166]

[0167] The present invention also provides a fiber laser, including a fiber laser body and a power transmission fiber 500 provided in the above embodiments connected to the fiber laser body.

[0168] The structure and principle of the power transmission fiber 500 have been described in detail in the above embodiments, and will not be repeated here.

[0169] 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 or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power transmission optical fiber, characterized in that, The fiber includes a core layer and a cladding layer, extending from the center of the power-transmitting fiber to the outer wall of the power-transmitting fiber. The core layer includes an inner core layer, an inner core layer, and an outer core layer that are sequentially clad together, and the cladding layer covers the outer wall of the outer core layer. Along the extension direction perpendicular to the power transmission optical fiber, the cross-sectional shape of the inner core layer is circular, the cross-sectional shape of the recessed layer is annular, the inner wall of the cross-section of the outer core layer is annular, and the outer wall of the cross-section of the outer core layer is rectangular. The inner core layer and the recessed layer are concentrically arranged, and the outer core layer is centrally symmetrical about the center of the inner core layer. At least two of the inner core layer, the recessed layer, and the outer core layer have different refractive indices; The first difference between the refractive index of the inner core layer and the refractive index of the outer core layer is no greater than 0.002, the second difference between the refractive index of the recessed layer and the refractive index of the outer core layer is no greater than 0.003, and the refractive index of the recessed layer is no greater than the refractive index of the outer core layer; When the refractive indices of the recessed layer and the outer core layer are the same, the recessed layer and the outer core layer are either one layer or two layers; along the extension direction perpendicular to the power transmission optical fiber, the outer wall of the cross-section of the outer core layer includes a plurality of straight edges connected end to end in sequence, and at least two adjacent straight edges are connected by an arc segment. The arc segment is a circular arc segment with a radius of 5μm to 15μm, and the ratio of the distance between the opposite straight edges of the outer wall of the cross-section of the outer core layer to the radius of the circular arc segment is 5 to 15.

2. The power transmission optical fiber according to claim 1, characterized in that, The cladding includes a first cladding and a second cladding covering the outer wall of the first cladding. The first cladding covers the outer wall of the outer core layer. The difference between the refractive index of the first cladding and the refractive index of the outer core layer is 0.003 to 0.012, and the refractive index of the first cladding is less than the refractive index of the outer core layer. The difference between the refractive index of the second cladding layer and the refractive index of the outer core layer is greater than 0.075, and the refractive index of the second cladding layer is less than the refractive index of the outer core layer.

3. The power transmission optical fiber according to claim 1, characterized in that, The inner core layer is a silicon dioxide layer; The outer core layer is a silicon dioxide layer; The recessed layer is a fluorine-doped silicon dioxide layer.

4. The power transmission optical fiber according to claim 1, characterized in that, The inner core layer is a germanium-fluorine co-doped silicon dioxide layer; The outer core layer is a silicon dioxide layer; The recessed layer is a silicon dioxide layer.

5. The power transmission optical fiber according to claim 2, characterized in that, It also includes an outer coating layer, which covers the outer wall of the second cladding layer; The first cladding layer is a fluorine-doped silicon dioxide layer; The second cladding layer is an acrylic resin layer; The outer coating is an acrylic resin layer.

6. The power transmission optical fiber according to claim 5, characterized in that, The diameter of the inner core layer is 6 μm to 50 μm; The diameter of the outer wall of the indentation layer is 7 μm to 55 μm; Along the extension direction perpendicular to the power transmission optical fiber, the outer wall of the cross-section of the outer core layer is square annular, and the distance between the opposite straight edges of the outer wall of the cross-section of the outer core layer is 30μm to 600μm. The diameter of the outer wall of the first cladding layer is 90 μm to 1000 μm; The diameter of the outer wall of the second cladding layer is 170 μm to 1200 μm; The diameter of the outer wall of the outer coating is between 250 μm and 1400 μm.

7. A method for fabricating a power-transmitting optical fiber, used to fabricate the power-transmitting optical fiber according to any one of claims 1 to 6, characterized in that, The method for preparing the energy-transmitting optical fiber includes: An indented layer and an inner core layer are sequentially formed on the inner wall of the base tube to form a first preform, wherein the indented layer covers the outer wall of the inner core layer; An outer core layer is formed on the outer wall of the first preform; The outer wall of the outer core layer along the cross-section perpendicular to the extension direction of the power transmission optical fiber is ground into a rectangular ring to form a second preform. A cladding layer is formed on the outer wall of the second preform.

8. The method for preparing the power transmission optical fiber according to claim 7, characterized in that, The step of forming a cladding layer on the outer wall of the second preform includes: The cladding is deposited on the outer wall of the second preform using plasma external deposition.

9. The method for preparing the power transmission optical fiber according to claim 7, characterized in that, The step of forming a cladding layer on the outer wall of the second preform includes: The second preform is inserted into the fluorine-doped sleeve, and the second preform and the fluorine-doped sleeve are melted together. The fluorine-doped sleeve is ground into a ring shape along a cross section perpendicular to the extension direction of the power transmission optical fiber.

10. A fiber laser, characterized in that, The fiber laser body includes a power transmission fiber as described in any one of claims 1 to 6 connected to the fiber laser body.

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