Device and method for measuring numerical aperture of optical fiber and application

Abstract

The invention relates to a device and method for measuring the numerical aperture of an optical fiber and application, and the device comprises a laser which outputs a first laser beam; the light isolation plate is provided with a light through hole, the light through hole vertically penetrates through the upper bottom surface and the lower bottom surface of the light isolation plate, and the first laser beam irradiates the light isolation plate and penetrates through the light through hole to form a second laser beam which irradiates the input end surface of the to-be-detected optical fiber and penetrates through an optical fiber filament of the to-be-detected optical fiber; the diameter of the light through hole is matched with the diameter of an optical fiber filament of the to-be-measured optical fiber; the second laser beam and the optical fiber are coaxial; the light isolation plate is made of a lightproof material; the second laser beam penetrates through the optical fiber and then vertically falls on the receiving end face of the laser detector, and light spots are formed. According to the far-field light spot measurement method, the uncertainty of numerical aperture calculation is greatly reduced, and the full-spectrum detection requirement from a conventional image transmitting optical fiber to a special microstructure optical fiber can be met.

Description

Technical Field

[0001] This application relates to the field of optical fiber parameter measurement technology, and in particular to an apparatus, method and application for measuring the numerical aperture of an optical fiber. Background Technology

[0002] Fiber optic image arrays are optical components made of tens of millions of micron-sized optical fibers arranged and fused together in a regular pattern. They are widely used in the field of high-precision optical transmission. Their working principle mainly includes three key steps: input, distribution, and output of optical signals. Each fiber acts as an independent image transmission unit, featuring high light transmission efficiency, low coupling loss, clear and realistic images, and zero optical thickness.

[0003] Numerical aperture (NA), a key parameter in fiber optic imaging arrays, is defined as the product of the sine of the maximum angle of incidence (i.e., the acceptance angle) at which the fiber can receive and transmit light, and the refractive index of the fiber end face. Its magnitude depends on the refractive index difference between the core and cladding, reflecting the fiber's ability to receive and transmit light. In imaging applications using fiber optic imaging arrays, NA significantly impacts image sharpness and resolution. Specifically, a larger NA increases image brightness but also increases light loss during propagation within the fiber. Therefore, a balance must be struck between receiving capability and transmission loss in practical applications. The selection of NA needs to be optimized based on specific requirements to consider factors such as receiving capability, image quality, and transmission loss. However, traditional NA measurement methods typically rely on complex optical systems and cumbersome operating procedures, and their measurement accuracy is limited.

[0004] Therefore, developing a high-precision and easy-to-operate fiber optic image array numerical aperture measurement device is of great practical significance. Summary of the Invention

[0005] The main objective of this application is to provide an apparatus, method, and application for measuring the numerical aperture of optical fibers. The technical problem to be solved is to develop a high-precision and easy-to-operate optical fiber imaging array numerical aperture measuring device to improve measurement efficiency and accuracy, thereby making it more suitable for practical use.

[0006] The objective of this application and the technical problem it solves are achieved by the following technical solution. According to this application, an apparatus for measuring the numerical aperture of an optical fiber includes: The laser, as described above, outputs a first laser beam; A light-blocking plate, having light-permeable holes perpendicularly penetrating its upper and lower surfaces, wherein a first laser beam irradiates the light-blocking plate and passes through the light-permeable holes, forming a second laser beam that irradiates the input end face of the optical fiber under test and passes through the fiber filament; the diameter of the light-permeable holes matches the diameter of the fiber filament; the second laser beam and the fiber filament are coaxial; the light-blocking plate is made of an opaque material; and... The laser detector, in which the aforementioned second laser beam passes through the aforementioned optical fiber and falls vertically onto the receiving end face of the aforementioned laser detector, forms a light spot.

[0007] The purpose of this application and the technical problems to be solved can also be further achieved by the following technical measures.

[0008] Preferably, in the aforementioned apparatus for measuring the numerical aperture of an optical fiber, the laser is controlled in a closed loop and the power fluctuation does not exceed 0.5%; the beam width of the aforementioned first laser beam is 1μm~2mm and the power is 1~500mW.

[0009] Preferably, the aforementioned apparatus for measuring the numerical aperture of an optical fiber further includes: a displacement platform on which the aforementioned light-blocking plate, the aforementioned optical fiber under test, and the aforementioned laser detector are mounted, and the positions and angles of the aforementioned light-blocking plate, the aforementioned optical fiber under test, and the aforementioned laser detector can be adjusted.

[0010] Preferably, in the aforementioned apparatus for measuring the numerical aperture of an optical fiber, the displacement platform on which the optical fiber under test is mounted is a high-precision displacement platform with a displacement accuracy of 0.1~1μm.

[0011] Preferably, the aforementioned apparatus for measuring the numerical aperture of an optical fiber further includes: an ambient light shield with an extinction ratio >60dB; the aforementioned ambient light shield covers the aforementioned laser, the aforementioned light-blocking plate, the aforementioned optical fiber under test, and the aforementioned laser detector.

[0012] Preferably, in the aforementioned apparatus for measuring the numerical aperture of an optical fiber, the laser detector is formed by coupling an optical fiber imaging array with a complementary metal-oxide-semiconductor detector.

[0013] The objective of this application and the solution to its technical problem are further achieved by the following technical solution. According to the method for measuring the numerical aperture of an optical fiber proposed in this application, it is implemented using any of the aforementioned devices for measuring the numerical aperture of an optical fiber, and the steps include: Turn on the aforementioned laser and output the aforementioned first laser beam; Adjust the positions of the aforementioned light-blocking plate, the aforementioned optical fiber under test, and the aforementioned laser detector so that the center of the aforementioned light spot formed on the aforementioned laser detector is bright and the edges are clear; The distance L between the output end face of the optical fiber under test and the aforementioned light spot and the diameter D of the aforementioned light spot are obtained, and the numerical aperture of the aforementioned optical fiber under test is calculated. ; ; Where θ is the divergence angle and NA is the numerical aperture.

[0014] The purpose of this application and the technical problem it solves are also achieved by the following technical solution. According to the method for measuring the numerical aperture of an optical fiber proposed in this application, the steps include: The laser beam irradiates the input end face of the optical fiber under test, passes through the fiber filament of the optical fiber under test, exits from the output end face of the optical fiber under test, and falls vertically onto the receiving end face to form a light spot; the laser beam and the fiber filament are coaxial, and the diameter of the laser beam matches the diameter of the fiber filament. The distance L between the output end face of the optical fiber under test and the aforementioned light spot and the diameter D of the aforementioned light spot are obtained, and the numerical aperture of the aforementioned optical fiber under test is calculated. ; ; Where θ is the divergence angle and NA is the numerical aperture.

[0015] The purpose of this application and the solution to its technical problems are also achieved by the following technical solutions. This application proposes the application of any of the aforementioned devices for measuring the numerical aperture of optical fibers in the fields of optical fiber numerical aperture measurement or optical fiber imaging.

[0016] The purpose of this application and the solution to its technical problems are also achieved by the following technical solutions. This application proposes the application of any of the aforementioned methods for measuring the numerical aperture of optical fibers in the fields of optical fiber numerical aperture measurement or optical fiber imaging.

[0017] By employing the above technical solution, the apparatus, method, and application for measuring the numerical aperture of optical fibers disclosed in this application have at least the following advantages: The method for measuring the numerical aperture of optical fibers proposed in this application uses a laser with a diameter matching that of the fiber filament under test. The laser passes through the fiber filament and diverges in the far field to form a light spot. The divergence distance is determined by the spot diameter. The divergence angle is calculated using the distance between the output end of the fiber under test and the light spot, along with the spot diameter, and the numerical aperture is then calculated. The far-field spot measurement method used in this application significantly reduces the uncertainty in numerical aperture calculation and can meet the full-spectrum testing needs, from conventional imaging fibers to special microstructure fibers.

[0018] The device for measuring the numerical aperture of optical fibers proposed in this application reduces the requirements for laser equipment by using a light-blocking plate with a light-passing hole to form a second laser beam that matches the diameter of the fiber filament under test. The device has a simple structure, is easy to operate, and is readily automated. It is suitable for measuring the numerical aperture of various types of optical fibers and has broad application prospects. Furthermore, the accuracy of the measurement results is further improved by employing a high-precision displacement platform and a CMOS coupled detector.

[0019] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, the preferred embodiments of this application are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the apparatus for measuring numerical aperture in some embodiments of this application; Figure 2 This is a schematic diagram illustrating the mechanism of measuring numerical aperture in some embodiments of this application; Explanation of reference numerals in the attached figures: 1-Laser; 2-First laser beam; 3-Light shield; 4-Light passage; 5-Second laser beam; 6-Fiber optic cable under test; 7-CMOS coupler detector; 71-CMOS detector; 72-Fiber optic imaging array; 8-First displacement platform; 9-High-precision displacement platform; 10-Second displacement platform; 11-Ambient light shield; 12-Fiber optic filament; - Divergence angle. Detailed Implementation

[0021] To further illustrate the technical means and effects adopted by this application to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of an apparatus, method, and application for measuring the numerical aperture of an optical fiber according to this application. In the following description, different "embodiments" or "embodiments" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable manner.

[0022] Traditional optical fiber numerical aperture is mainly calculated based on the refractive indices of the core and cladding. The formula based on the refractive indices of the core and cladding is as follows: ; Where n1 is the refractive index of the fiber core; n2 is the refractive index of the cladding.

[0023] The refractive index difference between the core and cladding determines the size of the numerical aperture. A larger refractive index difference results in a larger numerical aperture and a stronger light-receiving capability. However, because fiber filaments undergo multiple processes of fiber assembly, melting, and drawing to obtain the desired fiber imaging element, the core and cladding undergo interpenetration during this process, altering the degree of refractive index gradient between the cladding and core. Therefore, theoretical characterization of the fiber's numerical aperture based on the refractive indices of the core and cladding glass will deviate somewhat from the actual effective numerical aperture.

[0024] The measurement principle of this application is based on the relationship between the divergence angle θ at the fiber output end and the numerical aperture (NA): ; This application calculates the fiber divergence angle based on the far-field spot method. First, it ensures that the beam at the fiber output is perpendicular to the receiver of the optical power meter. The geometric calculation of the divergence angle θ is based on the following formula: ; Where D is the distance the beam deviates from the original measurement position (i.e., the diameter of the imaging spot on the laser detector), and L is the distance from the fiber output end to the laser detector receiver end.

[0025] because , Where D0 is the initial diameter of the incident laser beam (the modulated beam width), and λ is the wavelength of the incident laser.

[0026] That is, the propagation distance L is significantly greater than Furthermore, the laser beam used has a Gaussian distribution, which meets the conditions for calculating the fiber divergence angle using the far-field (Fraunhofer, diffraction region) spot method.

[0027] This application proposes a device for measuring the numerical aperture of an optical fiber, such as... Figure 1-2 As shown, it includes: Laser 1, the aforementioned laser 1 outputs a first laser beam 2; A light-blocking plate 3 has a light-transmitting hole 4, which vertically penetrates the upper and lower surfaces of the light-blocking plate 3. A first laser beam 2 irradiates the light-blocking plate 3 and passes through the light-transmitting hole 4, forming a second laser beam 5 that irradiates the input end face of the optical fiber 6 under test and passes through the fiber filament 12 of the optical fiber 6 under test. The diameter of the light-transmitting hole 4 matches the diameter of the fiber filament 12 of the optical fiber 6 under test. The second laser beam 5 and the fiber filament 12 are coaxial. The light-blocking plate 3 is made of an opaque material. The laser detector, the aforementioned second laser beam 5 passes through the aforementioned optical fiber 12 and falls vertically onto the receiving end face of the aforementioned laser detector to form a light spot.

[0028] Specifically, due to the use of the light-blocking plate 3, the limitations on beam width and power of the laser 1 used in this application are reduced, allowing for a wider range of beam width and power selection. Preferably, the aforementioned laser 1 employs closed-loop control, with power fluctuations not exceeding 0.5%; the beam width of the first laser beam 2 output by the aforementioned laser 1 is 1μm~2mm, and the power is 1~500mW.

[0029] The light-blocking plate 3 is made of an opaque material, such as an alloy. The alloy material of the light-blocking plate 3 effectively reduces the energy of the laser passing through the light-transmitting hole 4, preventing damage to the fiber 6 under test due to excessive laser power. It also allows for a higher power limit for the selected laser 1, a wider range of laser types, and relatively lower equipment costs. The edge of the light-transmitting hole 4 is smooth, with a diameter error of less than 0.1 μm. Preferably, the aperture of the light-transmitting hole 4 is adjustable. The aperture of the light-transmitting hole 4 should match the diameter of the fiber filament 12 of the fiber 6 under test; that is, the aperture of the light-transmitting hole 4 should be the same as the diameter of the fiber filament 12. For example, when the diameter of the fiber filament 12 of the fiber 6 under test is 5 μm, a light-transmitting hole 4 with a diameter of 5 μm is selected. Of course, the beam width of the first laser beam 2 is greater than or equal to the diameter of the fiber filament 12 of the fiber 6 under test. The fiber filament 12 of the fiber 6 under test refers to the imaging unit of the fiber 6 under test, whose structure includes a core layer and a sheath layer. The fiber under test 6 can be a fiber optic panel, a fiber optic image inverter, or a fiber optic taper, etc.

[0030] The second laser beam 5 and the optical fiber filament 12 are coaxial. Preferably, the aforementioned device for measuring the numerical aperture of an optical fiber further includes a displacement platform on which the aforementioned light-blocking plate 3, the aforementioned optical fiber under test 6, and the aforementioned laser detector are mounted. The position and angle of the aforementioned light-blocking plate 3, the aforementioned optical fiber under test 6, and the aforementioned laser detector can be adjusted. More preferably, the aforementioned displacement platform on which the optical fiber under test 6 is mounted is a high-precision displacement platform 9 with a displacement accuracy of 0.1~1μm. After the first laser beam 2 and the light-passing aperture 4 are made coaxial through optical axis calibration, a second laser beam 5 with a specified beam width is generated. The second laser beam 5 irradiates the input end face of the optical fiber under test 6. The position of the optical fiber under test 6 can be finely adjusted by the high-precision moving platform on which the optical fiber under test 6 is located to perform the measurement.

[0031] Preferably, the distance from the output end of the fiber under test 6 to the receiving end of the laser detector does not exceed 1000mm, to avoid excessive distance, which would degrade the imaging effect and affect the measurement accuracy.

[0032] Preferably, the aforementioned apparatus for measuring the numerical aperture of an optical fiber further includes an ambient light shield 11 with an extinction ratio >60dB; the aforementioned ambient light shield 11 covers the aforementioned laser 1, the aforementioned light-blocking plate 3, the aforementioned optical fiber under test 6, and the aforementioned laser detector.

[0033] Preferably, the aforementioned laser detector is a complementary metal-oxide-semiconductor (CMOS) detector 71. The CMOS detector 71 allows multiple functional modules, such as an image sensor and a signal processor, to be integrated onto the same chip. It enables random pixel readout and rapid data transmission of image data, facilitating the quick and accurate acquisition of the spot diameter data. More preferably, the aforementioned laser detector is formed by coupling a fiber optic image transmission array 72 to the CMOS detector 71. On one hand, coupling the fiber optic image transmission array 72 makes the spot more uniform and the spot edges clearer. Using grayscale values ​​to set the effective spot size is more accurate, further reducing measurement errors. On the other hand, coupling the fiber optic image transmission array 72 can mitigate minor fluctuations in the laser beam, making the spot shape more stable and further reducing measurement errors.

[0034] The device for measuring the numerical aperture of optical fibers proposed in this application has a simple structure, is easy to operate, and is readily automated. It is suitable for measuring the numerical aperture of various types of optical fibers 6 and has broad application prospects. Furthermore, this application employs a high-precision displacement platform 9 and a CMOS coupled detector 7 to ensure the accuracy of the measurement results.

[0035] This application proposes a method for measuring the numerical aperture of an optical fiber, implemented using any of the aforementioned devices for measuring the numerical aperture of an optical fiber, comprising the following steps: Turn on the aforementioned laser 1 and output the aforementioned first laser beam 2; Adjust the positions of the aforementioned light-blocking plate 3, the aforementioned optical fiber 6 to be tested, and the aforementioned laser detector so that the center of the aforementioned light spot formed on the aforementioned laser detector is bright and the edges are clear; The distance L between the output end face of the aforementioned optical fiber 6 under test and the aforementioned light spot and the diameter D of the aforementioned light spot are obtained, and the numerical aperture of the aforementioned optical fiber 6 under test is calculated. ; ; Where θ is the divergence angle and NA is the numerical aperture.

[0036] Specifically, when the second laser beam 5 illuminates the input end face of the fiber 6 under test, if it hits the junction of the fiber filament 12, the center of the resulting light spot will be mottled and the edges will be unclear. By adjusting the position of the fiber 6 under test so that the center of the resulting light spot is bright and the edges are clear, the second laser beam 5 and the fiber filament 12 will be coaxial.

[0037] Preferably, multiple numerical aperture measurements are performed on multiple fiber filaments 12 on the fiber under test 6, and the average value is calculated to reduce errors. When changing the fiber filament 12 being measured, this can be achieved by translating or rotating the fiber under test 6 within the plane of its cross-section.

[0038] This application proposes a method for measuring the numerical aperture of an optical fiber, such as... Figure 2 As shown, the steps include: The laser irradiates the input end face of the fiber optic cable 6 under test, passes through the fiber filament 12 of the fiber optic cable 6 under test, exits from the output end face of the fiber optic cable 6 under test, and falls vertically onto the receiving end face to form a light spot; the laser and the fiber filament 12 are coaxial, and the diameter of the laser matches the diameter of the fiber filament 12. The distance L between the output end face of the aforementioned optical fiber 6 under test and the aforementioned light spot and the diameter D of the aforementioned light spot are obtained, and the numerical aperture of the aforementioned optical fiber 6 under test is calculated. ; ; Where θ is the divergence angle and NA is the numerical aperture.

[0039] Specifically, the laser beam with the required diameter matching the diameter of the fiber optic cable 12 can be generated directly by the laser 1, or it can be generated by focusing a laser beam with a wider beam width through a lens or filtering through a pinhole.

[0040] This application proposes the application of any of the aforementioned devices for measuring the numerical aperture of optical fibers in the fields of optical fiber numerical aperture measurement or optical fiber imaging.

[0041] This application proposes the application of any of the aforementioned methods for measuring the numerical aperture of an optical fiber in the fields of optical fiber numerical aperture measurement or optical fiber imaging.

[0042] The present application will be further described below with reference to specific embodiments, but this should not be construed as a limitation on the scope of protection of the present application. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present application are still within the scope of protection of the present application.

[0043] Unless otherwise specified, all materials and reagents mentioned below are commercially available products well known to those skilled in the art; unless otherwise specified, all methods described are methods known in the art. Unless otherwise defined, the technical or scientific terms used should have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains.

[0044] In the following examples and comparative examples, the fiber under test 6 uses a standard fiber panel with fiber diameters of 5.0 μm, panel thickness of 2.5 mm, core refractive index n1 of 1.62, and skin refractive index n2 of 1.50. Using near-field refractive index imaging (RNF), the actual NA values ​​of standard fiber panels 1, 2, and 3 were measured to be 0.54, 0.53, and 0.57, respectively.

[0045] Example 1 This embodiment provides a device for measuring the numerical aperture of an optical fiber, such as... Figure 1-2 As shown, it includes: a laser 1, a light-shielding plate 3, an optical fiber under test 6, a CMOS coupling detector 7, a first displacement platform 8, a high-precision displacement platform 9, a second displacement platform 10, and an ambient light shield 11.

[0046] Laser 1 outputs a first laser beam 2. A light-blocking plate 3 has a light-passing hole 4, which vertically penetrates the upper and lower surfaces of the plate. The first laser beam 2 passes through the light-passing hole 4, forming a second laser beam 5 that illuminates the input end face of the fiber optic cable 6 under test and passes through the fiber filament 12. The second laser beam 5 and the fiber filament 12 are coaxial. The light-blocking plate 3 is made of an alloy material. After passing through the fiber filament 12, the second laser beam 5 falls vertically onto the receiving end face of the CMOS coupler detector 7, forming a light spot. The CMOS coupler detector 7 consists of a CMOS detector 71 and a fiber optic imaging array 72.

[0047] A light-blocking plate 3 is mounted on a first displacement platform 8, which can adjust the position and angle of the light-blocking plate 3. The optical fiber under test 6 is mounted on a high-precision displacement platform 9, which can also adjust the position and angle of the light-blocking plate 3. A CMOS coupler detector 7 is mounted on a second displacement platform 10, which can also adjust the position and angle of the CMOS coupler detector 7.

[0048] The first laser beam 2 output by laser 1 has a wavelength of 1310nm, a beamwidth of 20μm, and an output power set to 150mW. The diameter of the light-passing hole 4 in the light-blocking plate 3 is 5μm, and the distance between the emitting end of laser 1 and the light-blocking plate 3 is adjusted to 5mm, forming a coaxial optical path system. The high-precision displacement platform 9 uses piezoelectric ceramic drive, with a displacement accuracy of 0.1μm and a travel range of ±10cm. The CMOS detector 71 has a pixel size of 3.45μm and is paired with a 10-megapixel sensor. The fiber optic image transmission array 72 is a lightweight, large-size fiber optic panel with a diameter of 500mm and a thickness of 5mm.

[0049] An ambient light shield 11 covers the laser 1, the light-blocking plate 3, the optical fiber under test 6, and the CMOS coupled detector 7. The extinction ratio of the ambient light shield 11 is 60 dB.

[0050] Example 2 This embodiment provides a method for measuring the numerical aperture of an optical fiber, implemented using the apparatus described in Embodiment 1. The specific steps are as follows: (1) Open the ambient light shield 11, place the fiber 6 to be tested on the high-precision displacement platform 9, and close the ambient light shield 11. The fiber 6 to be tested uses the standard fiber optic panel sample 1.

[0051] (2) Turn on the first laser beam 2 with a beam width of 20μm output from the laser 1. Adjust the first displacement platform 8 so that the first laser beam 2 passes through the 5μm light-passing hole 4 on the light-blocking plate 3 to form a second laser beam 5 with a beam width of 5μm. Adjust the high-precision displacement platform 9 to form a bright spot with clear edges on the CMOS coupled detector 7. At this time, the second laser beam 5 and the fiber optic cable 12 are coaxial.

[0052] (3) Adjust the second displacement platform 10 so that the distance L from the output end face of the fiber under test 6 to the receiving end of the CMOS coupled detector 7 is 200mm, and measure the spot diameter D 10 times. Adjust the position of the fiber under test 6 using the high-precision optical displacement platform 9, replace the fiber filament 12 under test, and measure the spot diameter D 10 times. In the above steps, the temperature fluctuation is controlled within ±0.1℃ / h.

[0053] Calculate the mean value of the spot diameter D from the above 20 measurements. and variance σ 2 , =255.60mm, σ 2 =0.44. The divergence angle θ and numerical aperture NA of the tested optical fiber were calculated. The calculation results and process are as follows: ; .

[0054] Example 3 The difference between this embodiment and embodiment 2 is that in step (1), the fiber optic panel sample 2 is used as the standard sample fiber optic panel 6, and in step (3), the distance L from the output end face of the fiber optic panel 6 to the receiving end of the CMOS coupling detector 7 is 250mm.

[0055] Calculate the mean value of the spot diameter D from 20 measurements. and variance σ 2 , =311.38mm, σ 2 =1.27. The divergence angle θ and numerical aperture NA of the tested optical fiber were calculated. The calculation results and process are as follows: ; .

[0056] Example 4 The difference between this embodiment and embodiment 2 is that in step (1), the fiber optic panel sample 3 is used as the standard sample fiber optic panel 6, and in step (3), the distance L from the output end face of the fiber optic panel 6 to the receiving end of the CMOS coupling detector 7 is 300mm.

[0057] Calculate the mean value of the spot diameter D from 20 measurements. and variance σ2 , =352.65mm, σ 2 =1.19. The divergence angle θ and numerical aperture NA of the tested optical fiber were calculated. The calculation results and process are as follows: ; .

[0058] Example 5 The difference between this embodiment and embodiment 2 is that the fiber optic image array 72 on the CMOS coupled detector 7 is removed, and a CMOS detector 71 is used instead.

[0059] Calculate the mean value of the spot diameter D from 20 measurements. and variance σ 2 , =257.10mm, σ 2 =3.89. The divergence angle θ and numerical aperture NA of the tested optical fiber were calculated. The calculation results and process are as follows: ; .

[0060] Comparative Example 1 The numerical aperture NA of a standard fiber optic panel was calculated using traditional methods. The core refractive index of the standard fiber optic panel is n1 = 1.62, and the skin refractive index is n2 = 1.50. .

[0061] Examples 1-5 and Comparative Example 1 show that, compared with the ±5% error of the traditional refractive index method, the uncertainty of the numerical aperture NA of the optical fiber under test in this application, using the far-field spot measurement method, is significantly reduced, meeting the full spectrum detection needs from conventional imaging optical fibers to special microstructure optical fibers.

[0062] The above description is merely a preferred embodiment of this application and is not intended to limit this application in any way. Although this application has disclosed the preferred embodiment as above, it is not intended to limit this application. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the content of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. An apparatus for measuring the numerical aperture of an optical fiber, characterized in that, It includes: A laser that outputs a first laser beam; A light-blocking plate has a light-transmitting hole that vertically penetrates the upper and lower surfaces of the light-blocking plate. A first laser beam irradiates the light-blocking plate and passes through the light-transmitting hole, forming a second laser beam that irradiates the input end face of the optical fiber under test and passes through the fiber filament of the optical fiber under test. The diameter of the light-transmitting hole matches the diameter of the fiber filament of the optical fiber under test. The second laser beam and the fiber filament are coaxial. The light-blocking plate is made of an opaque material. as well as, The laser detector is used to detect the second laser beam as it passes through the optical fiber and falls vertically onto the receiving end face of the laser detector, forming a light spot.

2. The apparatus according to claim 1, characterized in that, The laser is controlled in a closed loop, with power fluctuation not exceeding 0.5%; the beam width of the first laser beam is 1μm~2mm, and the power is 1~500mW.

3. The apparatus according to claim 1, characterized in that, It also includes: a displacement platform on which the light-blocking plate, the optical fiber under test and the laser detector are mounted, and the position and angle of the light-blocking plate, the optical fiber under test and the laser detector can be adjusted.

4. The apparatus according to claim 3, characterized in that, The displacement platform on which the optical fiber under test is installed is a high-precision displacement platform with a displacement accuracy of 0.1~1μm.

5. The apparatus according to claim 1, characterized in that, It also includes: an ambient light shield with an extinction ratio >60dB; the ambient light shield covers the laser, the light shield, the optical fiber under test, and the laser detector.

6. The apparatus according to claim 1, characterized in that, The laser detector is composed of an optical fiber imaging array coupled with a complementary metal-oxide-semiconductor detector.

7. A method for measuring the numerical aperture of an optical fiber, implemented using the apparatus for measuring the numerical aperture of an optical fiber as described in any one of claims 1-6, characterized in that, The steps include: The laser is turned on, and the first laser beam is output; Adjust the positions of the light-blocking plate, the optical fiber under test, and the laser detector so that the center of the light spot formed on the laser detector is bright and the edges are clear. The distance L between the output end face of the optical fiber under test and the light spot and the diameter D of the light spot are obtained, and the numerical aperture of the optical fiber under test is calculated. ； ； Where θ is the divergence angle and NA is the numerical aperture.

8. A method for measuring the numerical aperture of an optical fiber, characterized in that, The steps include: A laser beam illuminates the input end face of the optical fiber under test, passes through the fiber filament of the optical fiber under test, exits from the output end face of the optical fiber under test, and falls perpendicularly onto the receiving end face, forming a light spot; the laser beam is coaxial with the fiber filament, and the diameter of the laser beam matches the diameter of the fiber filament. The distance L between the output end face of the optical fiber under test and the light spot and the diameter D of the light spot are obtained, and the numerical aperture of the optical fiber under test is calculated. ； ； Where θ is the divergence angle and NA is the numerical aperture.

9. The application of the apparatus according to any one of claims 1-6 in the field of fiber optic numerical aperture measurement or fiber optic imaging.

10. The application of the method according to any one of claims 7-8 in the field of fiber optic numerical aperture measurement or fiber optic imaging.

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