Method and device for measuring and repairing concentricity and out-of-roundness of optical fiber preform

Abstract

The invention relates to the technical field of preparation of optical fiber preforms, and aims to solve the technical problem of large economic loss caused by lack of repair methods and means. In order to solve the technical problem, the invention provides the method and the device for measuring and repairing the concentricity and the out-of-roundness of the optical fiber preform. The method comprises the following steps: rotating a to-be-measured preform to measure a plurality of cladding outer diameters D; the out-of-roundness of the preform to be measured is calculated; if the out-of-roundness is unqualified, calculating a critical cladding outer diameter D0 corresponding to a critical value of the out-of-roundness control range, and repairing the to-be-detected preform; after light enters the preform, emergent light is emitted to form two cladding projections and a core projection; identifying the width of the two cladding projections and the width of the core projection, and calculating the concentricity of the optical fiber preform; if the concentricity is not qualified, calculating to obtain a critical value LDC-LAB0 corresponding to the boundary value of the concentricity control range, and repairing the preform to be detected. According to the invention, the out-of-roundness and concentricity of the preform are accurately tested before wire drawing.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber preform preparation, in particular to a method and a device for measuring and repairing the concentricity and out-of-roundness of an optical fiber preform. Background Art

[0002] The fully synthetic optical fiber preform is to first make the preform core rod, and then make the outer cladding outside the core rod. The outside vapor deposition (OVD) process uses one or more core rods to rotate along the longitudinal axis on a horizontal lathe, and the blowtorch platform moves back and forth along the core rod. High-purity raw material compounds (such as SiCl4, GeCl4, etc.) are sprayed onto the core rod through an oxyhydrogen flame or a methane flame torch. The oxide glass particles SiO2 dust produced by hydrolysis at high temperature are deposited on the core rod, and finally a porous preform loose body is formed. After sintering and annealing processes, a transparent optical fiber preform is obtained.

[0003] Whether the parameters of the preform are qualified can only be verified when the optical fiber is drawn. The geometric parameters and optical parameters of the optical fiber are mainly determined by the optical fiber preform and are less affected by the optical fiber drawing. There is a lack of effective solutions and repair methods for preforms with unqualified drawing geometric parameters. Therefore, a small number of preforms are scrapped by various optical fiber preform manufacturers.

[0004] The core-cladding concentricity of optical fiber is one of the important parameters of optical fiber. If the core and cladding have poor concentricity, during fusion splicing, only the cladding will be aligned but the core will not be aligned. At this time, the core connection after fusion splicing will be bent or not connected at all, causing joint loss.

[0005] The non-circularity of optical fiber, including the core non-circularity and cladding non-circularity, has a significant impact on the performance of optical fiber. The core non-circularity refers to the ratio of the difference between the diameter of the circumscribed circle and the inscribed circle of the core boundary to the core diameter, expressed as a percentage. When the core non-circularity of the optical fiber is too large, it may cause a large relative displacement at the joint, which in turn affects the characteristics of the optical fiber. In order to improve production efficiency and reduce production costs, effective means must be used to check the core cladding concentricity and non-circularity of the finished rod.

[0006] In the actual production process, the existing testing equipment cannot check the concentricity of the finished optical fiber preform rod, and the optical fiber needs to be checked after drawing. Preform rods with poor concentricity will cause a large amount of raw materials to be scrapped during drawing, increasing production costs.

[0007] With the improvement of preform preparation technology, the diameter of preforms has gradually increased, the weight of preform loose bodies has increased, the time required for deposition has gradually increased, and the requirements for deposition equipment have gradually increased. In the mass production of preforms, there is a lack of repair methods and means for preforms with unqualified geometric parameters such as out-of-roundness and concentricity, which causes great economic losses and is not conducive to reducing production costs and improving market competitiveness. Summary of the invention

[0008] Therefore, the technical problem to be solved by the present invention is to overcome the above-mentioned problems existing in the prior art.

[0009] In order to solve the above technical problems, the present invention provides a method for measuring and repairing the concentricity and out-of-roundness of an optical fiber preform, which moves along the axial direction to measure and repair the concentricity and out-of-roundness of the preform to be measured at different positions on the axis of the preform to be measured; the steps include: Out-of-roundness measurement and repair: Rotate the preform to be tested to measure multiple cladding outer diameters D; calculate the out-of-roundness of the preform to be tested based on the cladding outer diameter D; if the out-of-roundness is unqualified, calculate the critical cladding outer diameter D0 corresponding to the critical value of the out-of-roundness control range, move and fix the cutter head at the position corresponding to the critical cladding outer diameter D0, and rotate the preform to be tested for repair; Concentricity measurement and repair: After the light enters the preform, it is refracted in the cladding and core layers and then emitted from the preform. Two cladding projections and a core projection located between the two cladding projections are formed in the emitted light. The cladding projection and the core projection have different brightness. The cladding projection includes the first cladding projection and the second cladding projection. By identifying the width L of the first cladding projection AB , the width of the second projection of the cladding L DC And the width L of the core layer projection BC , and measure the outer diameter OD of the cladding to calculate the core-cladding concentricity of the optical fiber preform; if the concentricity is unqualified, calculate the first projection L of the cladding corresponding to the boundary value of the concentricity control range AB The second projection L of the cladding DC The critical value of the width difference |L DC -LAB|0, fix the cutter head at the critical value|LDC-LAB |0 At the corresponding position, the preform to be tested is rotated to perform repair processing.

[0010] In one embodiment of the present invention, the width L of the first projection AB , the width of the second projection of the cladding L DC , the width of the core layer projection L BC , cladding outer diameter OD, core-to-cladding ratio M, core diameter d, and concentricity are expressed as: d=OD / M ---------------------------Formula 1 K=L BC / d------------------------------Formula 2 Concentricity = | L DC -L AB | / K-----------Formula 3 Where: K is the magnification.

[0011] In one embodiment of the present invention, the expression of the outer diameter D of the cladding and the out-of-roundness is: Out-of-roundness = |Dmax- Dmin| / (Dmax+Dmin)×100%-------Formula 4 Wherein, Dmax is the maximum value of the cladding outer diameter D; Dmin is the minimum value of the cladding outer diameter D.

[0012] The present invention also provides a device for measuring and repairing the concentricity and out-of-roundness of an optical fiber preform, comprising: Test platform; The rotary clamping assembly comprises two clamping jaws rotatably connected to the test platform, at least one of the two clamping jaws has a power unit; the clamping jaws are used to clamp the preform to be tested and drive the preform to be tested to rotate, and the distance between the two clamping jaws is adjustable; A diameter measuring assembly is slidably connected to the test platform along the X direction, and the diameter measuring assembly is located at one side of the preform to be tested, and is used to measure the outer diameter of the preform to be tested; The illumination assembly is slidably connected above the test platform along the X direction; the light of the illumination assembly is emitted from above the preform to be tested into the preform to be tested, forming a projection on the test platform; The repair component is connected to the test platform by sliding along the X direction and the Y direction. The repair component is located at one side of the preform to be tested and is used to repair unqualified preform to be tested.

[0013] In one embodiment of the present invention, the present application also includes a photoresistor for identifying the brightness of the projection.

[0014] In one embodiment of the present invention, the diameter measuring assembly and the repairing assembly are arranged on both sides of the preform rod to be measured.

[0015] In one embodiment of the present invention, the diameter measuring assembly includes a diameter measuring bracket and a laser diameter measuring instrument connected to the top of the diameter measuring bracket.

[0016] In one embodiment of the present invention, the illumination component is connected to one side of the diameter measuring component.

[0017] In one embodiment of the present invention, the repair component includes a grinding component and a grinding bracket connected to the bottom of the grinding component; the grinding bracket is slidably connected to the top of the test platform.

[0018] In one embodiment of the present invention, the present application also includes a first movable component, a second movable component, a third movable component and a fourth movable component; the repair component is slidably connected to the test platform through the first movable component and the second movable component; the diameter measuring component is slidably connected to the test platform through the third movable component; the claw is slidably connected to the test platform through the fourth movable component, for adjusting the distance between the two claws.

[0019] The above technical solution of the present invention has the following advantages compared with the prior art: The method and device for measuring and repairing the concentricity and non-circularity of optical fiber preforms of the present invention have a high degree of automation, accurate and efficient repair, and greatly reduce the optical fiber loss caused by unqualified parameters. Before the preforms of the present application are drawn from the factory, the non-circularity and core package concentricity of the preforms can be accurately tested, while in the past, the non-circularity and core package concentricity data of the preforms needed to be obtained during the drawing process, thereby avoiding the scrapping loss caused by the non-circularity and concentricity exceeding the standard after the preforms are put on the line for drawing, reducing safety risks, and being highly efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein: Figure 1 is a cross-sectional view of an optical fiber preform; Figure 2 It is a three-dimensional schematic diagram of a device for measuring and repairing the concentricity and out-of-roundness of an optical fiber preform in a preferred embodiment of the present invention; Figure 3 yes Figure 1 The main view; Figure 4 yes Figure 1 Side view of Figure 5 yes Figure 1 A top view of Figure 6 It is a schematic diagram of the principle of concentricity measurement using the device and method of the present application; Figure 7 It is a projection schematic diagram of performing concentricity measurement and repair measurement at the axial P0 position using the device and method of the present application; Description of the accompanying drawings in the specification: 100, test platform; 200, rotating clamping assembly; 210, claw; 300, diameter measuring assembly; 310, diameter measuring bracket; 320, laser diameter measuring instrument; 400, illumination assembly; 410, cladding projection; 420, core projection; 500, repair component; 510, grinding component; 520, grinding bracket; 600, preform to be tested; 610, cladding; 620, core layer; 700, photoresistor; 800, moving assembly; 810, first moving assembly; 820, second moving assembly; 830, third moving assembly; 840, fourth moving assembly. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0022] During the OVD deposition process, the height difference between the core rod handle and the flame torch is fixed. During the deposition process, the core rod rotates at a fixed rate. Since the handle and the core rod are not concentric, the height difference between the core rod and the flame torch is constantly changing during the deposition process. When the distance between the core rod and the torch becomes smaller, more loose bodies are deposited on the target rod. When the distance between the core rod and the torch becomes larger, less loose bodies are deposited on the target rod. Since the loose bodies are deposited axially layer by layer during the OVD deposition process, the loose bodies deposited on the target rod will have a directional offset over time. Figure 1 As shown, A is the center of the cladding loose body (i.e., cladding 610), and B is the center of the core layer 620. Due to the non-concentricity of the handle and the core rod, A and B will gradually deviate after the deposition is completed, resulting in the concentricity of the final optical fiber core package exceeding the standard.

[0023] The optical fiber preform of the present application is an ultra-large diameter and ultra-heavy preform, which weighs more than 60kg and has a diameter of more than 200mm. Because the preform is long, the diameter of the preform varies at different positions. When repairing the preform whose out-of-roundness or concentricity exceeds the required standard, it is necessary to set the grinding interval and grinding depth (radial direction of the preform, i.e. Y direction) for different positions (axial position of the preform, i.e. X direction), which has high requirements for operation and the measurement accuracy cannot be guaranteed.

[0024] Reference Figure 2~Figure 5 As shown, an embodiment of the present invention provides a device for measuring and repairing the concentricity and out-of-roundness of an optical fiber preform, comprising: Test platform 100; The rotating clamping assembly 200 includes two clamping claws 210 rotatably connected to the test platform 100, at least one of the two clamping claws 210 has a power unit; the clamping claws 210 are used to clamp the preform rod 600 to be tested and drive the preform rod 600 to be tested to rotate, and the distance between the two clamping claws 210 is adjustable; The diameter measuring assembly 300 is slidably connected to the test platform 100 along the X direction. The diameter measuring assembly 300 is located on one side of the preform rod 600 to be tested and is used to measure the outer diameter of the preform rod 600 at different axial positions. The illumination assembly 400 is connected above the test platform 100 in a sliding manner along the X direction; the light of the illumination assembly 400 is emitted from above the preform rod 600 to be tested, and forms a projection on the test platform 100; the illumination assembly 400 moves above the test platform 100 to improve the light source when measuring different axial positions of the preform rod 600 to be tested.

[0025] The repair assembly 500 is slidably connected to the test platform 100 along the X direction and the Y direction. The repair assembly 500 is located at one side of the preform rod 600 to be tested and is used to repair different axial positions of the unqualified preform rod 600 to be tested.

[0026] Furthermore, the present application also includes a photoresistor 700 for identifying the brightness of the projection. Specifically, the photoresistor 700 in this embodiment can accurately identify the cladding projection 410 and the core layer projection 420 of different brightness, that is, the boundary of the cladding projection 410 and the core layer projection 420 can be accurately measured, which improves the measurement accuracy of the core cladding concentricity and out-of-roundness, thereby providing accurate data for the preform grinding process.

[0027] Furthermore, the diameter measuring assembly 300 and the repairing assembly 500 are arranged on both sides of the preform rod to be measured 600. Specifically, the repairing and measuring are performed in this way without interference.

[0028] Furthermore, the diameter measuring assembly 300 includes a diameter measuring bracket 310 and a laser diameter measuring instrument 320 connected to the top of the diameter measuring bracket 310. The diameter measuring bracket 310 supports the laser diameter measuring instrument 320.

[0029] Further, the illumination component 400 is connected to one side of the diameter measuring component 300. In some embodiments, the illumination component 400 can be an LED light source. Specifically, the illumination component 400 and the diameter measuring component 300 can share a moving component 800, which is low in cost.

[0030] Furthermore, the repair assembly 500 includes a grinding component 510 and a grinding bracket 520 connected to the bottom of the grinding component 510; the grinding bracket 520 is slidably connected to the top of the test platform 100. In this embodiment, the grinding component 510 is used to grind and repair the unqualified preform 600 to be tested.

[0031] Further, the present application also includes a moving assembly 800, which is divided into a first moving assembly 810, a second moving assembly 820, a third moving assembly 830 and a fourth moving assembly 840; the repair assembly 500 is slidably connected to the test platform 100 through the first moving assembly 810 and the second moving assembly 820; the diameter measuring assembly 300 is slidably connected to the test platform 100 through the third moving assembly 830; the claw 210 is slidably connected to the test platform 100 through the fourth moving assembly 840, and is used to adjust the distance between the two claws 210. The first moving assembly 810 is connected to the top of the working platform; the second moving assembly 820 is connected to the top of the first moving assembly 810, and the repair assembly 500 is connected to the top of the second moving assembly 820. The first moving assembly 810 is configured to drive the repair assembly 500 to move on the test platform 100 along the X direction; the second moving assembly 820 is configured to drive the repair assembly 500 to move on the test platform 100 along the Y direction.

[0032] In some embodiments, the first moving assembly 810, the second moving assembly 820, the third moving assembly 830 and the fourth moving assembly 840 have the same structure, and all of them include a bottom plate and a base, and the base is slidably connected to the top of the bottom plate through an electric slide rail.

[0033] The method for measuring and repairing the concentricity and out-of-roundness of the optical fiber preform using the above device is as follows: moving along the axial direction, measuring and repairing the concentricity and out-of-roundness at different positions of the axis of the preform 600 to be measured; after moving the diameter measuring component 300, the illumination component 400 and the repair component 500 to a certain position P0 and fixing them, the steps of measuring and repairing at the position P0 include: See also Figure 2~Figure 7 , Non-circularity measurement and repair: Rotate the preform 600 to be tested to measure multiple cladding outer diameters D. For example, measure one cladding outer diameter D at every α angle interval, α can be 90°, and upload multiple cladding outer diameters D to the control computer. The non-circularity of the preform 600 to be tested is obtained by calculating formula 4, which is: non-circularity = |Dmax- Dmin| / (Dmax+Dmin)×100%, where Dmax is the maximum value of the cladding outer diameter D; Dmin is the minimum value of the cladding outer diameter D. For example, the control range of non-circularity is less than 1%.

[0034] If the out-of-roundness of the preform 600 to be tested is qualified (ie, the out-of-roundness is less than 1%), the preform 600 to be tested is removed and the next preform 600 to be tested is measured.

[0035] If the out-of-roundness of the preform 600 to be tested is unqualified (i.e., the out-of-roundness is greater than 1%), the preform 600 to be tested is rotated, and its cladding outer diameter is measured by the laser diameter gauge 320 until the minimum cladding outer diameter is found, and the minimum cladding outer diameter is substituted into the calculation formula 4 to obtain the critical cladding outer diameter D0 corresponding to the critical value of the out-of-roundness control range. The tool head of the grinding component 510 is moved along the Y direction to the position corresponding to the critical cladding outer diameter D0 and fixed, and the preform 600 to be tested with a diameter greater than D0 is ground, so as to ensure that the out-of-roundness of the preform 600 to be tested at the position P0 after grinding is less than 1%.

[0036] See also Figure 2~Figure 7 , Concentricity measurement and repair: turn off other light sources around the equipment, and only turn on the LED light source of the illumination component 400. After the light from the LED light source enters the preform, it is refracted by the cladding and the core layer and then emits outgoing light from the preform. The outgoing light forms two cladding projections 410 and a core projection 420 located between the two cladding projections 410 on the test platform 100; due to the difference in refractive index between the core layer and the cladding, the brightness of the cladding projection 410 and the core projection 420 presented on the test table is different; the cladding projection 410 includes a first cladding projection and a second cladding projection. The photoresistor 700 is very sensitive to the intensity of the projected light and can accurately identify and read the width L of the first cladding projection. AB , the width of the second projection of the cladding L DC and the width L of the core layer projection 420 BC The laser diameter gauge 320 measures the outer diameter OD of the cladding (i.e. the outer diameter of the preform). The core-to-cladding ratio M of the preform is known. The core-to-cladding concentricity of the optical fiber preform can be accurately calculated by calculating formulas 1 to 3; the calculation formula is: d=OD / M (Formula 1), K=L BC / d(Formula 2), concentricity = |L DC -L AB | / K (Formula 3), where: d is the core diameter; OD is the measured outer diameter of the cladding; M is the core-to-cladding ratio; K is the magnification; L BC is the width of the core layer projection 420; |L DC -L AB | is the first projection L of the cladding AB The second projection of the cladding L DC The width difference.

[0037] For example, the control range of concentricity is less than 0.6%.

[0038] When the calculated concentricity is less than 0.6%, the preform 600 to be tested is qualified, the preform is discarded, and the next preform is tested and repaired.

[0039] When the calculated concentricity is greater than 0.6%, the preform 600 to be tested is unqualified. The first projection L of the cladding corresponding to the boundary value of the concentricity control range is calculated by formula 1 to formula 3. AB The second projection L of the cladding DC The critical value of the width difference (i.e. the critical difference) |L DC -L AB |0, that is, the critical difference value |L when the concentricity is equal to 0.6% is calculated DC -L AB |0. Rotate the preform to be tested 600 to find the critical difference |L DC -L AB |0 corresponding to the two end points on the preform rod 600 to be tested, and the two end points are marked and recorded. Move the grinding component 510 until the grinding head is at the critical difference value |L DC -L AB |0 is closely fitted to one of the two end points corresponding to the preform rod, and the preform rod located between the two marked end faces is ground to ensure that the concentricity at the P0 position after grinding is less than 0.6%.

[0040] The ground preform can be re-tested by laser diameter gauge 320 and LED light source projection to see if the concentricity and out-of-roundness of the preform core package meet the qualified standards.

[0041] The preform is divided into three parts: cladding and core. The cladding includes an outer cladding and an inner cladding. The rod body of the preform is a transparent cylindrical glass. The inner and outer cladding are high-purity silica layers, and the core layer is a high-purity silica layer doped with a small amount of germanium dioxide. When a beam of parallel light passes through the preform from top to bottom, it will be deflected or refracted. Since the inner cladding and the outer cladding in the cladding have the same refractive index, there will be no obvious difference in the light in the inner cladding and the outer cladding. However, due to the different refractive indices of silicon dioxide and germanium dioxide, there is a significant difference between the light deflection at the cladding and the light deflection at the core layer. And the projection of the core layer will become larger after refraction. Therefore, when the light enters the preform 600 to be tested and refracts, the outgoing light emitted from the preform 600 to be tested will form projections of different brightness levels. Due to the difference in refractive index between the core layer and the cladding layer, a cladding layer projection 410 and a core layer projection 420 are formed, and the brightness of the cladding layer projection 410 and the core layer projection 420 are different. Therefore, by identifying the brightness of the projection, the cladding layer projection 410 and the core layer projection 420 can be distinguished, and the width of the corresponding projection can be obtained. The concentricity of the core layer and the cladding of the optical fiber preform can be inferred from the width of the projection.

[0042] After the preform is sintered and vitrified, it is annealed and subjected to auxiliary treatment. The preform 600 to be tested is rotated at a certain axial position, and the outer diameter of the preform 600 to be tested is measured at different angles along the circumferential direction by the diameter measuring assembly 300 of the present application, and the data is calculated and summarized to obtain the out-of-roundness curve of the preform at different axial positions, and the out-of-roundness is calculated; and unqualified products can be repaired in real time. Due to the difference in refractive index between the core layer and the cladding of the preform of the present application, when the light enters the preform, the path experienced by the light will be different due to the different materials of the optical rods passed through. The light emitted from the preform will form a projection on the equipment table. Due to the difference in refractive index between the core layer and the cladding, projections of different brightness will be formed on the equipment table. By accurately reading the width of each interval of the preform projection, the core-cladding concentricity of the optical fiber preform can be inferred, and unqualified products can be repaired in real time.

[0043] It can be seen that it has a high degree of automation, accurate and efficient repair, and greatly reduces the loss of optical fiber caused by unqualified parameters. Before the preform rod of the present application is drawn, the out-of-roundness and core package concentricity of the preform rod can be accurately tested, while in the past, the out-of-roundness and core package concentricity data of the preform rod needed to be obtained during the drawing process, thereby avoiding the scrap loss caused by the out-of-roundness and concentricity exceeding the standard after the preform rod is put on the line for drawing, reducing safety risks and high efficiency.

[0044] The present application provides a method for measuring and effectively repairing preformed rods with unqualified parameters such as out-of-roundness and concentricity during the production process.

[0045] The present invention can also be equipped with a grinding and water washing device, so that the preformed rods with out-of-roundness, concentricity and other appearance defects can be accurately repaired. The water washing device can ensure that the surface of the preformed rod after grinding is clean and flat.

[0046] The present invention can also grind preformed rods with appearance problems, and the repair efficiency is high. The device can also be simply transformed into a welding lathe, which is convenient and simple to operate.

[0047] Obviously, the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A method for measuring and repairing the concentricity and out-of-roundness of an optical fiber preform, characterized in that: Moving along the axial direction, measuring and repairing the concentricity and out-of-roundness at different positions of the axis of the preform to be measured; the steps include: Out-of-roundness measurement and repair: rotating the preform to be tested to measure multiple cladding outer diameters D, and calculating the out-of-roundness of the preform to be tested through the cladding outer diameter D; if the out-of-roundness is unqualified, the critical cladding outer diameter D0 corresponding to the critical value of the out-of-roundness control range is calculated, the cutter head is moved and fixed at the position corresponding to the critical cladding outer diameter D0, and the preform to be tested is rotated for repair processing; Concentricity measurement and repair: After the light enters the preform, it is refracted by the cladding and the core layer and then emitted from the preform. Two cladding projections and a core projection located between the two cladding projections are formed in the emitted light. The cladding projection and the core projection have different brightness. The cladding projection includes a first cladding projection and a second cladding projection. By identifying the width L of the first cladding projection AB , the width of the second projection of the cladding L DC And the width L of the core layer projection BC , measure the outer diameter OD of the cladding, and calculate the core-cladding concentricity of the optical fiber preform; if the concentricity is unqualified, calculate the first projection L of the cladding corresponding to the boundary value of the concentricity control range AB The second projection L of the cladding DC The critical value of the width difference |L DC -LAB|0, fix the cutter head at the position corresponding to the critical value |LDC-LAB|0, and rotate the preform to be tested for repairing.

2. The method for measuring and repairing the concentricity and out-of-roundness of an optical fiber preform according to claim 1, characterized in that: The width of the first projection is L AB , the width of the second projection of the cladding L DC , the width of the core layer projection L BC , cladding outer diameter OD, core-to-cladding ratio M, core diameter d, and concentricity are expressed as: d=OD / M ---------------------------Formula 1 K=L BC / d------------------------------Formula 2 Concentricity = | L DC -L AB | / K-----------Formula 3 Where: K is the magnification.

3. The method for measuring and repairing the concentricity and out-of-roundness of an optical fiber preform according to claim 2, characterized in that: The expression of cladding outer diameter D and non-circularity is: Out-of-roundness = |Dmax- Dmin| / (Dmax+Dmin)×100%-------Formula 4 Wherein, Dmax is the maximum value of the cladding outer diameter D; Dmin is the minimum value of the cladding outer diameter D.

4. A device for measuring and repairing the concentricity and out-of-roundness of an optical fiber preform, characterized in that: A device for measuring and repairing the concentricity and out-of-roundness of an optical fiber preform as claimed in any one of claims 1 to 3; the device comprises: Test platform; A rotary clamping assembly, comprising two clamping jaws rotatably connected to the test platform, at least one of the two clamping jaws having a power unit; the clamping jaws are used to clamp the preform to be tested and drive the preform to be tested to rotate, and the spacing between the two clamping jaws is adjustable; A diameter measuring assembly is slidably connected to the test platform along the X direction, the diameter measuring assembly is located at one side of the preform to be tested, and is used to measure the outer diameter of the preform to be tested; An illumination assembly is slidably connected above the test platform along the X direction; the light of the illumination assembly is emitted from above the preform to be tested into the preform to be tested, forming a projection on the test platform; A repair component is slidably connected to the test platform along the X direction and the Y direction. The repair component is located at one side of the preform to be tested and is used to repair unqualified preform to be tested.

5. The device for measuring and repairing the concentricity and out-of-roundness of an optical fiber preform according to claim 4, characterized in that: A photoresistor for identifying the brightness of the projection is also included.

6. The device for measuring and repairing the concentricity and out-of-roundness of an optical fiber preform according to claim 4, characterized in that: The diameter measuring assembly and the repairing assembly are arranged on both sides of the preform rod to be measured.

7. The device for measuring and repairing the concentricity and out-of-roundness of an optical fiber preform according to claim 4, characterized in that: The diameter measuring assembly comprises a diameter measuring bracket and a laser diameter measuring instrument connected to the top of the diameter measuring bracket.

8. The device for measuring and repairing the concentricity and out-of-roundness of an optical fiber preform according to claim 4, characterized in that: The illumination component is connected to one side of the diameter measuring component.

9. The device for measuring and repairing the concentricity and out-of-roundness of an optical fiber preform according to claim 4, characterized in that: The repair component comprises a grinding component and a grinding bracket connected to the bottom of the grinding component; the grinding bracket is slidably connected to the top of the test platform.

10. The device for measuring and repairing the concentricity and out-of-roundness of an optical fiber preform according to claim 4, characterized in that: It also includes a first movable component, a second movable component, a third movable component and a fourth movable component; the repair component is slidably connected to the test platform via the first movable component and the second movable component; the diameter measuring component is slidably connected to the test platform via the third movable component; the claw is slidably connected to the test platform via the fourth movable component, for adjusting the distance between the two claws.

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