An apparatus and method for testing optical fiber geometry parameters

Abstract

This application discloses a testing device and method for optical fiber geometric parameters, belonging to the field of optical fiber manufacturing technology. In the testing device of this application, the illumination unit is at a certain angle to the exit face of the optical fiber under test, illuminating the exit face so that it is clearly imaged in the image acquisition unit. The parameter calculation unit is used to determine the boundary of the core and cladding layers based on whether the difference in grayscale values ​​between adjacent pixels in the end-face image is greater than a preset grayscale threshold, thereby deriving the optical fiber geometric parameters. This application's testing device improves the imaging effect of the optical fiber end-face image by improving the illumination unit that illuminates the exit face of the optical fiber, and further improves the algorithm for testing optical fiber geometric parameters based on the end-face imaging effect. Therefore, it is unnecessary to set an incident light source at the incident end of the optical fiber under test to obtain the optical fiber geometric parameters. Compared with the prior art, this application's device reduces a series of components such as the incident light source and the incident collimating lens, thereby reducing the complexity of the device.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of optical fiber manufacturing, and more particularly relates to a testing device and method for optical fiber geometric parameters. BACKGROUND

[0002] Optical fiber geometric parameter testing is one of the important means for evaluating the performance of optical fiber, which mainly focuses on the geometric characteristics of optical fiber, such as cladding diameter, cladding non-circularity, core diameter, core non-circularity, core spacing, etc. These geometric characteristics have an important influence on the transmission performance of optical fiber. Through optical fiber geometric testing, we can understand the quality of optical fiber, judge whether the optical fiber meets the use requirements, and provide important reference for the production and manufacturing of optical fiber.

[0003] At present, the structures of optical fiber geometric testing equipment at home and abroad are similar, and there are problems of complex structure, large size, many components, high cost and difficult maintenance. At the same time, there are certain requirements for the length of the optical fiber to be tested, and the testing of optical fiber geometric parameters under specific conditions cannot be realized. Moreover, the existing testing equipment and testing method have few and complex algorithms for testing multi-core optical fiber, and the technical problem of core missing detection is easy to occur. SUMMARY

[0004] In view of the above defects or improvement needs of the prior art, the present application provides a testing device and method for optical fiber geometric parameters, which aims to solve the technical problem that the existing testing equipment and testing method are too complex.

[0005] To achieve the above-mentioned purpose, in a first aspect, the present application provides a testing device for optical fiber geometric parameters, which comprises an illumination unit, an image acquisition unit and a parameter solving unit.

[0006] The illumination unit is located between the image acquisition unit and the optical fiber to be tested, and is used to illuminate the exit end face of the optical fiber to be tested. The irradiation direction of the illumination unit and the exit end face form an included angle of 30°-60°, so that the exit end face is clearly imaged in the image acquisition unit.

[0007] The image acquisition unit is used to acquire the end face image of the exit end face.

[0008] The parameter solving unit is used to determine the boundary of the core layer and the cladding layer according to whether the difference between the gray values of adjacent pixel points in the end face image is greater than a preset gray threshold, and to derive the geometric parameters of the optical fiber.

[0009] Preferably, the irradiation direction of the illumination unit and the exit end face form an included angle of 45±5°.

[0010] Preferably, the illumination unit is ring-shaped, and the center of the ring-shaped and the extension line of the axis of the exit end face coincide.

[0011] Preferably, the parameter calculation unit is specifically used for:

[0012] Draw multiple core-finding circles with gradually increasing diameters, using the center of the end face image as the center.

[0013] Find the adjacent pixels on the core-finding circle whose grayscale value difference is greater than the grayscale threshold;

[0014] Judge each group of adjacent pixels found on the core-finding circle in clockwise or counterclockwise order: if the gray value of a group of adjacent pixels increases from small to large, and the gray value of the next group of adjacent pixels decreases from large to small, then connect the midpoints of the two groups of adjacent pixels, and determine a fiber core by the midpoint of the line connecting them.

[0015] An ellipse fitting algorithm is used to obtain the geometric parameters of all identified fiber cores.

[0016] Preferably, the parameter calculation unit is used to find the core-finding circle with the most determined fiber cores, and the fiber cores located on the core-finding circle are all the fiber cores in the optical fiber under test.

[0017] Preferably, the parameter calculation unit is specifically used for:

[0018] Obtain the grayscale value of all pixels in the end face image. If the difference in grayscale value between adjacent pixels is greater than the grayscale threshold, then the midpoint of the line connecting the adjacent pixels is the boundary point.

[0019] Connect the boundary points that are less than a preset distance threshold to obtain the boundary lines between the core layer and the cladding layer;

[0020] Based on the boundary line, an ellipse fitting algorithm was used to fit the geometric parameters of all the core and cladding layers.

[0021] Preferably, the testing device further includes a fixing unit for fixing the optical fiber under test, such that the outgoing end face of the optical fiber under test faces the center of the image acquisition unit.

[0022] Secondly, this application provides a method for testing the geometric parameters of an optical fiber, the method comprising the following steps:

[0023] Adjust the tilt angle of the illumination unit so that the angle between the illumination direction and the output end face of the optical fiber under test is 30° to 60° until the output end face is clearly imaged in the image acquisition unit.

[0024] Acquire end-face images of the exiting end face;

[0025] Draw multiple core-finding circles with gradually increasing diameters, using the center of the end face image as the center.

[0026] Find the adjacent pixels on the core-finding circle whose grayscale value difference is greater than a preset grayscale threshold;

[0027] Judge each group of adjacent pixels found on the core-finding circle in clockwise or counterclockwise order: if the gray value of a group of adjacent pixels increases from small to large, and the gray value of the next group of adjacent pixels decreases from large to small, then connect the midpoints of the two groups of adjacent pixels, and determine a fiber core by the midpoint of the line connecting them.

[0028] An ellipse fitting algorithm is used to obtain the geometric parameters of all identified fiber cores.

[0029] Preferably, in the test method, the tilt angle of the illumination unit is adjusted so that the illumination direction and the output end face of the optical fiber under test form an angle of 45±5° until the output end face is clearly imaged in the image acquisition unit.

[0030] Preferably, the method further includes the step of: finding the core-finding circle with the most cores, then the cores located on the core-finding circle are all the cores in the optical fiber to be tested.

[0031] Thirdly, this application provides an electronic device, comprising: a memory for storing a program; and a processor for executing the program stored in the memory, wherein when the program stored in the memory is executed, the processor is configured to execute the method described in any possible implementation of the second aspect.

[0032] Fourthly, this application provides a computer-readable storage medium storing a computer program that, when run on a processor, causes the processor to perform the method described in any possible implementation of the second aspect.

[0033] Fifthly, this application provides a computer program product that, when run on a processor, causes the processor to perform the method described in any possible implementation of the second aspect.

[0034] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art:

[0035] (1) The testing device of this application tilts the illumination unit used to illuminate the output end face of the optical fiber at a certain angle, thereby eliminating reflection, reducing shadows, brightening the core layer and enhancing the imaging effect, so that the core cladding boundary of the output end face of the optical fiber produces obvious light and dark difference. Therefore, the boundary identification and detection of the optical fiber core layer can be directly performed based on the imaging of the output end face. Therefore, the device of this application does not need to set an incident light source at the input end of the optical fiber under test. Compared with the existing optical fiber geometric parameter testing device, the device of this application reduces a series of components such as the incident light source and the incident collimating lens, thereby reducing the complexity of the device.

[0036] (2) Based on the improvement of the testing device, this application has made corresponding improvements to the testing method of optical fiber geometric parameters. The fiber core is determined by whether the difference between the gray values ​​of adjacent pixels in the acquired optical fiber end face image is greater than a preset gray value threshold. The fiber core circle is further fitted to obtain the core layer size. The testing method of this application is simple and effective, especially suitable for multi-core optical fibers. It can realize the synchronous detection of geometric parameters of all fiber cores in multi-core optical fibers without worrying about the possibility of missing fiber cores.

[0037] (3) Since the test device of this application simplifies and optimizes the light source located at the incident end of the optical fiber under test in the conventional test device, there is no need to consider the influence of the excessive length of the optical fiber under test on the light source, and there is no requirement for the length of the optical fiber under test, thereby expanding the adaptability of the test device and method of this application to the usage conditions. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of a device structure for testing optical fiber geometric parameters provided in an embodiment of this application.

[0039] Figure 2 This is a schematic diagram of an optical fiber core positioning method provided in an embodiment of this application.

[0040] Figure 3 This is a schematic diagram of the ellipse fitting algorithm provided in the embodiments of this application.

[0041] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, including: 1, three-axis displacement stage; 2, LED light strip; 3, telescope; 4, camera; 5, parameter calculation unit. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0043] The terms "first" and "second," etc., used in the specification and claims herein are used to distinguish different objects, not to describe a specific order of the objects. For example, "first fiber core" and "second fiber core," etc., are used to distinguish different fiber cores, not to describe a specific order of the fiber cores.

[0044] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0045] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more, for example, multiple core-finding circles refer to two or more core-finding circles, multiple fiber cores refer to two or more fiber cores, etc.

[0046] Next, the technical solutions provided in the embodiments of this application will be described.

[0047] Example 1:

[0048] The optical fiber geometric parameter testing device proposed in this application is used to test the geometric parameters of multi-core optical fibers.

[0049] like Figure 1 The diagram shown is a schematic diagram of a device for testing optical fiber geometric parameters provided in Embodiment 1 of this application. It includes a three-axis displacement stage 1 as a fixed unit, an LED light strip 2 as an illumination unit, a cylindrical lens 3 as a magnification unit, a camera 4 as an image acquisition unit, and a parameter calculation unit 5.

[0050] The three-axis displacement stage 1 is used to fix the optical fiber under test. Simultaneously, by adjusting the front-back, left-right, and vertical directions of the three-axis displacement stage 1, the exit end face of the optical fiber fixed within it (it should be noted that in this invention, the "exit" end face is not a functional limitation on the fiber end face, but only serves to distinguish the two ends of the fiber, and is different from the prior art where testing of optical fiber geometric parameters requires introducing test devices at both ends of the fiber) is directly aligned with the center of the image acquisition unit, that is, the extended line of the axis of the exit end face coincides with the center of the image acquisition unit. In this embodiment, the center of the image acquisition unit is also the center of the viewfinder of the camera 4.

[0051] LED strip 2 is located between the triaxial displacement stage 1 and the cylindrical mirror 3, used to illuminate the output end face. LED strip 2 is ring-shaped, forming a ring-shaped light circle during illumination. The illumination direction of LED strip 2 forms a 45° angle with the output end face of the optical fiber under test. The tilt angle of the plane on which LED strip 2 is located can be finely adjusted by ±5°. Furthermore, the center of LED strip 2 coincides with the extension line of the axis of the output end face of the optical fiber under test.

[0052] In this embodiment, tilting the lighting unit, i.e., the LED light strip 2, at 45±5° can bring the following advantages:

[0053] 1. Eliminate reflection: Direct sunlight may cause high-gloss reflection on the end face surface, obscuring the core layer's features. By tilting the LED light, the angle of the reflected light can avoid directly hitting the camera's line of sight, thereby reducing the impact of reflection;

[0054] 2. Reduce shadows: It can reduce the shadow effects produced by the end face or the surrounding environment;

[0055] 3. High-brightness core layer: Its function is to allow light hitting the end face of the optical fiber to enter the cladding and core layers at different angles. Due to the different refractive indices of the core and cladding glass, some of the light entering the cladding will be refracted into the core layer. The light entering the core layer will not return to the cladding due to total internal reflection, thus illuminating both the core and cladding layers and making the core layer brighter. The end face image acquired by the camera will then clearly show the images of the cladding and core layers.

[0056] 4. Enhanced effect: Tilted illumination can highlight the texture and contour of the sample surface, enhance the sense of depth and three-dimensionality in the image, make the core features more obvious, and facilitate subsequent analysis and processing.

[0057] Therefore, camera 4 can acquire clear end-face images with distinct core and cladding layers, and directly perform fiber geometry detection based on the end-face images, thereby eliminating the need for light sources that illuminate the incident end of the fiber under test and related collimating lenses and other components.

[0058] Since the LED light strip 2, which serves as the lighting unit, is supported by a mechanical structure, there may be some mechanical error. Therefore, it is necessary to adjust the tilt angle of the LED light strip 2 by ±5° according to the clarity of the image of the output end face in the camera, so that the output end face can be clearly imaged in the camera 4.

[0059] The telescope 3 is located between the LED light strip 2 and the camera 4. It is used to magnify the end-face imaging of the exit face. In this embodiment, the magnification of the telescope 3 is adjustable.

[0060] Camera 4 is located at the rear end of the tube lens 3 and is used to acquire the magnified image of the exit end face;

[0061] The parameter calculation unit 5 reads the end-face image from the camera 4, performs noise reduction preprocessing on the end-face image, and then completes the fiber geometric parameter test based on the end-face image, specifically as follows: Figure 2 As shown:

[0062] Draw multiple core-finding circles with gradually increasing diameters, using the center of the end face image as the center.

[0063] Find adjacent pixels on the core-finding circle whose grayscale value difference is greater than a preset grayscale threshold; for example... Figure 2 There are multiple groups of adjacent pixels A1, B1, A2, B2, A3, B3, A4 and B4, where the difference in grayscale value between two adjacent pixels in each group is greater than a preset grayscale threshold.

[0064] The adjacent pixels found on the core-finding circle are judged sequentially in a clockwise or counterclockwise order: if the gray value of one group of adjacent pixels increases and the gray value of the next group of adjacent pixels decreases, then the midpoint of the two groups of adjacent pixels is connected, and a fiber core is determined by the midpoint of the connecting line. For example... Figure 2As shown, each group of adjacent pixels found on the core-finding circle is judged in clockwise order: the gray values ​​of adjacent pixels in group A1 increase from small to large, and the gray values ​​of adjacent pixels in the next group, group B1, decrease from large to small. Therefore, the midpoint C1 of the line connecting the midpoints a1 and b1 of the two groups of adjacent pixels A1 and B1 must lie within a fiber core. Thus, point C1 determines the first fiber core.

[0065] Similarly, the second fiber core is determined by the two sets of adjacent pixels A2 and B2. The third fiber core is determined by the two sets of adjacent pixels A3 and B3. The fourth fiber core is determined by the two sets of adjacent pixels A4 and B4.

[0066] Repeat the above core-locating operation in multiple core-finding circles to find the core-finding circle with the most identified cores to determine all cores in a multi-core fiber. Then, use an ellipse fitting algorithm to fit all the core circles and obtain geometric parameters such as the center coordinates and core diameter.

[0067] The following describes how to fit the core circle containing point C1 using point C1:

[0068] In this embodiment, the image acquisition unit, i.e., the camera, has a resolution of 5 megapixels. Figure 3 In images captured by the camera, the area of ​​a pixel is much smaller than the area of ​​the fiber core. This means that the higher the pixel count, the higher the accuracy of the proposed solution. Therefore, image acquisition units with the highest possible pixel count can be selected based on the required testing accuracy. After imaging by the image acquisition unit, the area of ​​the fiber core in the image is at least 100 times the area of ​​the pixels.

[0069] like Figure 3 As shown: First, draw a green circle containing the fiber core, with green point C1 as the center and the preset radius value as the radius;

[0070] Draw 16 blue radii in a perfect circle, with the same angle between adjacent radii;

[0071] On each radius, adjacent pixels are judged sequentially from the center outward. If the difference in gray value between adjacent pixels is greater than the preset gray value threshold for the first time, and the gray value of adjacent pixels decreases from large to small, then the pixel with the larger gray value is recorded as X1.

[0072] Similarly, find 16 yellow pixels from the 16 radii: X1 to X16;

[0073] Ellipse fitting is performed on the 16 yellow pixels X1 to X16, and the resulting ellipse is the fiber core circle.

[0074] Example 2:

[0075] The geometric parameters of a multi-core optical fiber are tested using a similar optical fiber geometric parameter testing device as in Example 1. The difference between this device and the device in Example 1 is that the illumination direction of the LED light strip 2 forms a 30° angle with the exit end face of the optical fiber under test.

[0076] Example 3:

[0077] The geometric parameters of a multi-core optical fiber are tested using a similar optical fiber geometric parameter testing device as in Example 1. The difference between this device and the device in Example 1 is that the illumination direction of the LED light strip 2 forms a 60° angle with the exit end face of the optical fiber under test.

[0078] Example 4:

[0079] The geometric parameters of multi-core optical fibers are tested using a fiber optic geometric parameter testing method proposed in this application. This embodiment of the method includes the following steps:

[0080] S1. Adjust the tilt angle of the illumination unit so that the angle between the illumination direction and the output end face of the optical fiber under test is 45±5° until the output end face is clearly imaged in the image acquisition unit.

[0081] S2. Acquire the end face image of the exiting end face;

[0082] S3. Draw multiple core-finding circles with gradually increasing diameters, using the center of the end face image as the center.

[0083] S4. Find the adjacent pixels on the core-finding circle whose grayscale value difference is greater than a preset threshold.

[0084] S5. Judge each group of adjacent pixels found on the core-finding circle in clockwise or counterclockwise order: if the gray value of a group of adjacent pixels increases from small to large, and the gray value of the next group of adjacent pixels decreases from large to small, then connect the midpoints of the two groups of adjacent pixels, and determine a fiber core by the midpoint of the line.

[0085] S6. Find the core-finding circle with the most fiber cores. The fiber cores located on this core-finding circle are all the fiber cores in the fiber under test.

[0086] S7. Use an ellipse fitting algorithm on all located fiber cores to obtain the geometric parameters of all fiber cores.

[0087] Example 5:

[0088] The geometric parameters of the multi-core optical fiber are tested using a similar optical fiber geometric parameter testing method as in Example 4. The difference between this method and the method in Example 4 is that the tilt angle of the illumination unit is adjusted so that the angle between the illumination direction and the output end face of the optical fiber under test is 60°, and the output end face is imaged in the image acquisition unit.

[0089] Example 6:

[0090] The geometric parameters of the multi-core optical fiber are tested using a similar optical fiber geometric parameter testing method as in Example 4. The difference between this method and the method in Example 4 is that the tilt angle of the illumination unit is adjusted so that the angle between the illumination direction and the output end face of the optical fiber under test is 30°, and the output end face is imaged in the image acquisition unit.

[0091] It should be understood that the methods in the above embodiments can be applied to the apparatus described in Embodiment 1. They can also be used in other optical fiber geometric parameter testing apparatuses.

[0092] Based on the methods in the above embodiments, this application provides an electronic device that may include a processor, a communications interface, a memory, and a communication bus, wherein the processor, communications interface, and memory communicate with each other via the communication bus. The processor may invoke logical instructions in the memory to execute the methods in the above embodiments.

[0093] Furthermore, the logical instructions in the aforementioned memory can be implemented as software functional units and, when sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application.

[0094] Based on the methods in the above embodiments, this application provides a computer-readable storage medium storing a computer program that, when run on a processor, causes the processor to execute the methods in the above embodiments.

[0095] Based on the methods in the above embodiments, this application provides a computer program product that, when run on a processor, causes the processor to execute the methods in the above embodiments.

[0096] It is understood that the processor in the embodiments of this application may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. A general-purpose processor may be a microprocessor or any conventional processor.

[0097] The method steps in the embodiments of this application can be implemented in hardware or by a processor executing software instructions. The software instructions can consist of corresponding software modules, which can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, portable hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can reside in an ASIC.

[0098] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a storage medium or transmitted through the storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state disk (SSD)).

[0099] It is understood that the various numerical designations used in the embodiments of this application are merely for descriptive convenience and are not intended to limit the scope of the embodiments of this application.

[0100] The above content is readily understood by those skilled in the art. The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A testing device for optical fiber geometric parameters, characterized in that, The testing device includes an illumination unit, an image acquisition unit, and a parameter calculation unit; The illumination unit is located between the image acquisition unit and the optical fiber under test, and is used to illuminate the emitting end face of the optical fiber under test. The illumination direction of the illumination unit is perpendicular to the emitting end face. This results in a significant difference in brightness between the core and cladding boundaries at the output end, allowing for clear imaging in the image acquisition unit; there is no need to set an incident light source at the input end of the optical fiber under test. The image acquisition unit is used to acquire the end face image of the exiting end face; The parameter calculation unit is used to determine the boundary of the core cladding based on whether the difference in gray values ​​of adjacent pixels in the end face image is greater than a preset gray value threshold, thereby deriving the optical fiber geometric parameters.

2. The testing apparatus according to claim 1, characterized in that, The illumination direction of the lighting unit and the emission end face are at an angle. .

3. The testing apparatus according to claim 1, characterized in that, The lighting unit is ring-shaped, and the center of the ring coincides with the extension line of the axis of the emission end face.

4. The testing apparatus according to claim 1, characterized in that, The parameter calculation unit is specifically used for: Draw multiple core-finding circles with gradually increasing diameters, using the center of the end face image as the center. Find the adjacent pixels on the core-finding circle whose grayscale value difference is greater than the grayscale threshold; Judge each group of adjacent pixels found on the core-finding circle in clockwise or counterclockwise order: if the gray value of a group of adjacent pixels increases from small to large, and the gray value of the next group of adjacent pixels decreases from large to small, then connect the midpoints of the two groups of adjacent pixels, and determine a fiber core by the midpoint of the line connecting them. An ellipse fitting algorithm is used to obtain the geometric parameters of all identified fiber cores.

5. The testing apparatus according to claim 4, characterized in that, The parameter calculation unit is used to find the core-finding circle with the most cores. The cores located on the core-finding circle are all the cores in the optical fiber under test.

6. The testing apparatus according to claim 1, characterized in that, The parameter calculation unit is specifically used for: Obtain the grayscale value of all pixels in the end face image. If the difference in grayscale value between adjacent pixels is greater than the grayscale threshold, then the midpoint of the line connecting the adjacent pixels is the boundary point. Connect the boundary points that are less than a preset distance threshold to obtain the boundary lines between the core layer and the cladding layer; Based on the boundary line, an ellipse fitting algorithm was used to fit the geometric parameters of all the core and cladding layers.

7. The testing apparatus according to claim 1, characterized in that, The testing device also includes a fixing unit, which is used to fix the optical fiber under test so that the outgoing end face of the optical fiber under test is facing the center of the image acquisition unit.

8. A method for testing the geometric parameters of an optical fiber, characterized in that, The testing method specifically includes the following steps: Adjust the tilt angle of the illumination unit so that the illumination direction and the output end face of the optical fiber under test are aligned. Until the exit end face is clearly imaged in the image acquisition unit; Acquire end-face images of the exiting end face; Draw multiple core-finding circles with gradually increasing diameters, using the center of the end face image as the center. Find the adjacent pixels on the core-finding circle whose grayscale value difference is greater than a preset grayscale threshold; Judge each group of adjacent pixels found on the core-finding circle in clockwise or counterclockwise order: if the gray value of a group of adjacent pixels increases from small to large, and the gray value of the next group of adjacent pixels decreases from large to small, then connect the midpoints of the two groups of adjacent pixels, and determine a fiber core by the midpoint of the line connecting them. An ellipse fitting algorithm is used to obtain the geometric parameters of all identified fiber cores.

9. The test method according to claim 8, characterized in that, In the aforementioned testing method, the tilt angle of the illumination unit is adjusted so that the illumination direction and the output end face of the optical fiber under test are aligned. Until the exit face is clearly imaged in the image acquisition unit.

10. The test method according to claim 8, characterized in that, The method further includes the step of: finding the core-finding circle with the most cores, and then the cores located on the core-finding circle are all the cores in the optical fiber under test.

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