Method and device for identifying stress range of polarization maintaining optical fiber

Abstract

The invention relates to the technical field of optical fiber communication, in particular to a stress range identification method and device of a polarization maintaining optical fiber. The stress range identification device of the polarization maintaining optical fiber is used for measuring the stress range of an optical fiber to be measured and comprises a light source used for providing a detection light signal; the light-in optical fiber is located on the light-out side of the light source and used for receiving and transmitting the detection light signals, and the optical fiber to be detected and the light-in optical fiber are arranged in parallel and fixed in relative position; the polaroid is located at the output end of the incident optical fiber and the input end of the to-be-measured optical fiber; the reflector is located on the side, away from the incident optical fiber, of the polarizer; and the test equipment is located at the output end of the to-be-tested optical fiber and used for analyzing the test optical signal output by the to-be-tested optical fiber to obtain a stress range. The test method provided by the invention is simple and high in test efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber communications, and in particular to a method and device for identifying the stress range of a polarization-maintaining optical fiber. Background Art

[0002] Polarization-maintaining fiber components are widely used in fields such as optical fiber communications due to their unique polarization-maintaining properties. However, during actual installation and use, these components often require operations such as fixing, bending, or squeezing. These mechanical stresses can significantly affect the performance of polarization-maintaining fibers, particularly their polarization-maintaining properties.

[0003] At the same time, measuring the parameters of polarization-maintaining fibers faces numerous challenges. Firstly, performance indicators (such as polarization extinction ratio and polarization state preservation) require extremely high-precision measurement equipment. Only high-precision equipment can accurately capture subtle changes in these parameters, thereby truly reflecting the fiber's performance. Secondly, existing measurement processes are often complex, involving multiple steps, including precise fiber alignment, setting measurement parameters, and obtaining stable data through multiple measurements. Summary of the Invention

[0004] The embodiments of the present invention provide a method and device for identifying the stress range of a polarization-maintaining optical fiber, so as to solve the problem that the parameter measurement process of the polarization-maintaining optical fiber is relatively complicated.

[0005] The present invention discloses a stress range identification device for a polarization-maintaining optical fiber, which is used to measure the stress range of an optical fiber to be tested, comprising: a light source, for providing a detection light signal; An input optical fiber is located at the light output side of the light source and is used to receive and transmit the detection light signal. The optical fiber to be tested is arranged in parallel with the input optical fiber and their relative positions are fixed; a polarizer, located at the output end of the incident optical fiber and the input end of the optical fiber to be tested; a reflector, located on a side of the polarizer away from the input optical fiber; The testing device is located at the output end of the optical fiber to be tested and is used to analyze the test optical signal output by the optical fiber to be tested to obtain the stress range.

[0006] Optionally, the input optical fiber and the optical fiber to be tested are cut from the same optical fiber.

[0007] Optionally, the light source is an incoherent light source; and the main polarization direction of the incident optical fiber is aligned with the transmission axis of the polarizer.

[0008] Optionally, when the polarization direction of the optical signal input into the polarizer is the same as the transmission axis direction, the extinction ratio exceeds 35 dB.

[0009] Optionally, the device for identifying the stress range of the polarization-maintaining optical fiber further includes: A collimating lens, wherein the polarizer is attached to a side of the collimating lens facing the reflector; A capillary tube is wrapped around the light-input optical fiber and the optical fiber to be tested, and is used to fix the relative positions of the light-input optical fiber and the optical fiber to be tested.

[0010] The present invention also discloses a method for identifying the stress range of a polarization-maintaining optical fiber, which is applied to the device for identifying the stress range of a polarization-maintaining optical fiber as described above; The method for identifying the stress range of the polarization-maintaining optical fiber includes: Synchronously rotating the input optical fiber and the optical fiber to be tested to obtain insertion loss values ​​corresponding to various rotation angles, and setting the rotation angle with the minimum insertion loss value as the target angle; Taking the target angle as the starting point, the input optical fiber and the optical fiber to be tested are synchronously rotated to obtain the polarization extinction ratio corresponding to each rotation angle, obtain an extinction ratio-angle curve, and obtain the stress range of the polarization-maintaining optical fiber based on the extinction ratio-angle curve.

[0011] Optionally, the step of obtaining the insertion loss value corresponding to each rotation angle includes: The insertion loss value is obtained according to the following formula:

[0012] in, is the insertion loss value, is the actual deflection angle.

[0013] Optionally, the step of obtaining the polarization extinction ratio corresponding to each rotation angle includes: The polarization extinction ratio corresponding to each rotation angle is expressed by the following formula:

[0014] in, is the polarization extinction ratio, is the actual deflection angle.

[0015] Optionally, before the step of synchronously rotating the input optical fiber and the optical fiber to be tested, the method further comprises: The cat's eye adjustment is performed on the input optical fiber and the optical fiber to be tested so that the cat's eyes of the input optical fiber and the optical fiber to be tested are located on the same straight line.

[0016] Optionally, the step of synchronously rotating the input optical fiber and the optical fiber to be tested with the target angle as the starting point includes: Taking the target angle as a starting point, the light input optical fiber and the optical fiber to be tested are synchronously rotated in a clockwise direction and a counterclockwise direction respectively.

[0017] The beneficial effects of a stress range identification method and device for a polarization-maintaining optical fiber provided by an embodiment of the present invention are as follows: the optical fiber to be tested is arranged in parallel with the input optical fiber and their relative positions are fixed, the polarizer is located at the output end of the input optical fiber and the input end of the optical fiber to be tested, and the reflector is located on the side of the polarizer away from the input optical fiber. In this way, the detection light signal of natural light is output to the polarizer through the input optical fiber and converted into a polarized light signal. After being reflected by the reflector, the polarized light signal is converted into a secondary polarized light signal of pure polarized light. After the secondary polarized light signal is transmitted through the optical fiber to be tested, it changes due to the rotation of the optical fiber to be tested and becomes a test light signal output. In this way, the test equipment can obtain the stress range of the optical fiber to be tested by measuring the test light signal. The test method is simple and the test efficiency is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments, in which: Figure 1 1 is a schematic structural diagram of an embodiment of a device for identifying a stress range of a polarization-maintaining optical fiber provided by the present invention; Figure 2 1 is a flow chart of an embodiment of a method for identifying a stress range of a polarization-maintaining optical fiber provided by the present invention; Figure 3 It is a rotational schematic diagram of the input optical fiber and the optical fiber to be tested provided by the present invention; Figure 4 Schematic diagram of the effect of cat's eye adjustment of the input optical fiber and the optical fiber to be tested provided by the present invention; Figure 5 It is a schematic diagram of a curve showing that the extinction ratio and insertion loss value vary with the rotation angle provided by the present invention.

[0019] The reference numerals in the figures are: 10. Polarization-maintaining optical fiber stress range identification device; 11. Light source; 12. Light input optical fiber; 13. Polarizer; 14. Reflector; 15. Test equipment; 16. Collimating lens; 17. Capillary tube; 20. Optical fiber to be tested. DETAILED DESCRIPTION

[0020] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. Now, in conjunction with the accompanying drawings, the preferred embodiments of the present invention will be described in detail.

[0021] See also Figure 1 , Figure 1FIG1 is a schematic diagram illustrating the structure of an embodiment of a device for identifying the stress range of a polarization-maintaining optical fiber provided by the present invention. Device 10 is used to measure the stress range of a polarization-maintaining optical fiber under test. Device 10 includes a light source 11, an input optical fiber 12, a polarizer 13, a reflector 14, and a test device 15.

[0022] The light source 11 is used to provide a detection light signal. In one implementation scenario, the light source 11 is an incoherent light source 11, such as a natural light ASE light source 11. It can provide wide-spectrum, low-coherence natural light (unpolarized light) as a detection light signal, covering the operating wavelength range of polarization-maintaining optical fiber (such as the 1310nm or 1550nm band), and has stable output light power and low noise. This wide-spectrum characteristic can avoid measurement errors caused by interference effects of single-wavelength lasers. At the same time, natural light can generate pure linearly polarized light after passing through a polarizer, providing a high signal-to-noise ratio input signal for subsequent polarization extinction ratio (PER) testing, thereby ensuring the accuracy and repeatability of stress area detection.

[0023] The input optical fiber 12 is located on the light-emitting side of the light source 11, so that the detection light signal can be input into the input optical fiber 12 and transmitted in the input optical fiber 12. The optical fiber to be tested 20 is arranged in parallel with the input optical fiber 12, and the relative positions of the input optical fiber 12 and the optical fiber to be tested 20 are fixed, so the input optical fiber 12 and the optical fiber to be tested 20 can move synchronously. For example, the relative positions of the two are fixed by a mechanical structure to ensure that the two move at exactly the same angle, curvature and direction (for example, synchronous twisting of 30° or bending radius of 5mm), so that the stress environment to which the optical fiber to be tested 20 is subjected can be accurately reproduced and controlled. The two optical fibers move as a whole, and the stress state at the connection remains consistent, eliminating boundary interference caused by relative displacement. In addition, the motion states of the two optical fibers are completely consistent, and the changes in the optical signal output by the optical fiber to be tested 20 only reflect its own stress response, eliminating non-target variables such as docking offset.

[0024] In one implementation scenario, the stress range identification device 10 for a polarization-maintaining optical fiber further includes a capillary 16 , which is wrapped around the input optical fiber 12 and the optical fiber to be tested 20 to fix the relative positions of the input optical fiber 12 and the optical fiber to be tested 20 .

[0025] In one implementation scenario, the input fiber 12 and the fiber under test 20 are cut from the same fiber. This eliminates the impact of individual fiber variations on the test results, ensuring that the measured data reflects only the true polarization characteristics of the segment of fiber under test 20. Because the two fibers are sourced from the same material batch and possess identical stress zone structures, geometric dimensions, and optical parameters, systematic errors introduced by intrinsic PER differences, slow-axis misalignment, or end-face coupling loss between fibers are avoided, significantly improving the accuracy and repeatability of stress zone detection. This homologous design ensures that experimental results are determined solely by the stress zone performance of the fiber under test 20, rather than by deviations in the test system itself.

[0026] The polarizer 13 is located at the output end of the input optical fiber 12 and the input end of the optical fiber to be tested 20, and the reflectors 1·4 are located on the side of the polarizer 13 away from the input optical fiber 12 and the optical fiber to be tested 20; in this way, the detection light signal of natural light output from the input optical fiber 12 is converted into a polarized light signal after being filtered by the polarizer 13. The polarized light signal will be emitted to the reflector 14 along the original transmission direction (the extension direction of the input optical fiber), and after being reflected by the reflector 14, it will pass through the polarizer 13 again. After being polarized by the polarizer 13, the pure, direction-fixed polarized light secondary polarization signal is emitted into the optical fiber to be tested 20 and transmitted in the optical fiber to be tested 20.

[0027] The principal polarization direction of the input optical fiber 12 is aligned with the transmission axis of the polarizer 13. This ensures that the polarized light signal emitted by the polarizer 13 is high-intensity and stable linearly polarized light, providing a reliable input for subsequent stress detection. Ignoring this alignment can result in a weak signal or noise that overwhelms the true stress response, invalidating the test results.

[0028] When the polarization direction of the optical signal input to polarizer 13 aligns with the transmission axis of polarizer 13, the extinction ratio exceeds 35dB. This 35dB extinction ratio equates to a 1 / 3162 suppression capability of polarizer 13 for light polarized along its non-transmission axis, providing a high signal-to-noise ratio foundation for detecting minute stress changes in the fiber 20 under test. Even when stress on the fiber 20 causes a 0.1° polarization shift, this high extinction ratio system can still detect a PER change of approximately 0.03dB. In this embodiment, the optical signal passes through the same polarizer 13 twice (polarization + analysis), theoretically achieving a total system extinction ratio of 70dB (35dB x 2). This is limited in practice by the fiber's intrinsic PER (typically 25-40dB) and end-face reflection losses, but it still ensures that stress-induced PER changes are not overwhelmed by system noise. In subsequent simultaneous bending / torsion testing, the initial 35dB extinction ratio provides sufficient dynamic range for stress detection. For example, when stress is applied to reduce the PER by 20 dB, the system still maintains an effective extinction ratio of 15 dB, preventing the signal from entering the detector noise floor.

[0029] In one implementation scenario, the stress range identification device 10 for a polarization-maintaining optical fiber also includes a collimating lens 16. A polarizer 13 is attached to the side of the collimating lens 16 facing the reflector 14. The detection light signal output by the input optical fiber 12 is first collimated by the collimating lens 16 and then filtered by the polarizer 13. This converts the divergent Gaussian beam into parallel light, eliminating the edge filtering effect of the polarizer 13 caused by the beam divergence and ensuring the accuracy of the polarization extinction ratio (PER) test. The polarized light signal reflected by the reflector 14 passes through the polarizer 13 to generate a secondary polarized light signal. This signal is then passed through the collimating lens 16 again and transmitted to the optical fiber under test 20. After passing through the polarizer 13 a second time, it undergoes secondary collimation, allowing the secondary polarized light signal to be accurately coupled back to the optical fiber under test 20, reducing polarization state distortion caused by Fresnel reflection at the end face. The collimating lens 16 and the attached polarizer 13 form an integrated optical module that synchronously controls the spot size and polarization direction, preventing interference from discrete component assembly errors on systems with a high extinction ratio of 35 dB or more.

[0030] In one implementation scenario, collimating lens 16 is a G-lens (gradient-index lens). Its flat end face allows for seamless, planar bonding with polarizer 13, eliminating the complex angular adjustments required for conventional spherical lenses and limiting the mounting tolerance of polarizer 13 to within ±0.1°. Its radially graded refractive index profile decouples beam collimation / focusing from polarization direction, ensuring that the transmission axis of polarizer 13 is strictly orthogonal to the optical axis (deviation <0.05°), thereby maintaining the demanding system extinction ratio requirement of >35dB. The integrated design of collimating lens 16 and polarizer 13 eliminates air-lens interface reflections, reduces end-face loss by approximately 2.3dB, and improves optical power stability in the closed optical path.

[0031] The test equipment 15 is located at the output end of the optical fiber 20 to be tested. After the polarized light signal is transmitted in the optical fiber 20 to be tested, it undergoes a certain change due to the stress of the optical fiber 20 to be tested and becomes a test light signal. The test equipment 15 analyzes the test light signal to obtain the stress range.

[0032] Specifically, the configuration of the input optical fiber 12 can provide an input signal without stress interference (ie, a secondary polarized light signal), which is compared with the test optical signal affected by stress, so as to obtain the stress range of the optical fiber 20 to be tested.

[0033] It can be seen from the above description that in this embodiment, the optical fiber to be tested and the input optical fiber are arranged in parallel and their relative positions are fixed, the polarizer is located at the output end of the input optical fiber and the input end of the optical fiber to be tested, and the reflector is located on the side of the polarizer away from the input optical fiber. In this way, the detection light signal of natural light is output to the polarizer through the input optical fiber and converted into a polarized light signal. After being reflected by the reflector, the polarized light signal is converted into a secondary polarized light signal of pure polarized light. After the secondary polarized light signal is transmitted through the optical fiber to be tested, it will change due to the rotation of the optical fiber to be tested and become a test light signal output. In this way, the test equipment can obtain the stress range of the optical fiber to be tested by measuring the test light signal. The test method is simple and the test efficiency is high.

[0034] Please refer to Figure 1 and Figure 2 , Figure 2 FIG1 is a flow chart of an embodiment of a method for identifying the stress range of a polarization-maintaining optical fiber provided by the present invention. The method for identifying the stress range of a polarization-maintaining optical fiber provided by the present invention comprises the following steps: S101: Synchronously rotate the input optical fiber and the optical fiber to be tested to obtain insertion loss values ​​corresponding to various rotation angles, and set the rotation angle with the minimum insertion loss value as the target angle.

[0035] In a specific implementation scenario, since the input optical fiber 12 and the optical fiber to be tested 20 are fixed relative to each other by a mechanical component, when the input end of the input optical fiber 12 is rotated, the output end of the optical fiber to be tested 20 will also deflect accordingly. Figure 3 , Figure 3 It is a rotational schematic diagram of the input optical fiber and the optical fiber to be tested provided by the present invention.

[0036] In other implementation scenarios, before rotating the input optical fiber 12 and the optical fiber to be tested 20, the cat's eye adjustment of the input optical fiber 12 and the optical fiber to be tested 20 is first performed so that the cat's eyes of the input optical fiber 12 and the optical fiber to be tested 20 are located on the same straight line. The cat's eye refers to the concentric ring reflection image (similar to the cat's eye reflection) presented by the optical fiber end face under a microscope, which is formed by the core / cladding interface. Under the microscope field of view, the position of the input optical fiber 12 and / or the optical fiber to be tested 20 is fine-tuned so that the cores are completely coaxial, that is, the concentric rings presented by the input optical fiber 12 and the optical fiber to be tested 20 are located on the same straight line. Please refer to Figure 4 , Figure 4 It is a schematic diagram of the effect of cat's eye adjustment of the input optical fiber and the optical fiber to be tested provided by the present invention.

[0037] Furthermore, the consistency of the cat's eye direction of the input optical fiber 12 and the optical fiber to be tested 20 reaches the second level, 1 second = 1 / 3600 degrees ≈ 4.85×10⁻ 6For an optical fiber with a diameter of 125 μm, the 1-second angular deviation is approximately 0.3 nm (calculated as: 125 μm × sin(1″) ≈ 0.3 nm). Second-level directional consistency ensures that the mechanical states of the input optical fiber 12 and the optical fiber under test 20 are completely consistent during motion, strictly controlling the stress environment of the optical fiber under test 20 and increasing the accuracy and reliability of stress range measurement results.

[0038] In a specific implementation scenario, the insertion loss values ​​corresponding to various rotation angles of the input optical fiber 12 and the optical fiber under test 20 can be measured and obtained. The rotation angle α at which the insertion loss value is minimized is determined and used as the target angle. For each unit rotation angle (which can be set based on actual needs, for example, 0.1°), the output power of the probe light signal output by the light source 11 and the test power of the test light signal received by the test device 15 are obtained. Based on the output power and the test power, the insertion loss value corresponding to each rotation angle can be calculated.

[0039] Assuming the slow axis of input fiber 12 is aligned with the transmission axis of polarizer 13, the probe light signal is output from input fiber 12. Light along the slow axis is filtered twice by polarizer 13 to generate a secondary polarization signal of linearly polarized light. After cat's eye calibration, the principal axes of the fiber under test 20 and the input fiber 12 should be aligned (slow axis to slow axis, fast axis to fast axis). At this point, the angle between the principal axes of the two fibers is zero, allowing the secondary polarization signal to be losslessly coupled into the slow axis of the fiber under test 20.

[0040] In one implementation scenario, the relationship between the rotation angle and insertion loss of the optical fiber is obtained according to the following formula:

[0041] in, is the insertion loss value, is the actual rotation angle of the optical fiber 。 It represents the projection component of the secondary polarized optical electric field vector in the slow axis direction of the optical fiber to be tested. The optical power is proportional to the square of the electric field intensity. Indicates the ratio of optical power that can be coupled into the slow axis of the optical fiber under test. It converts the power ratio into an insertion loss value in decibels (dB).

[0042] According to the above formula, it can be inferred that when θ=0°, cos(0°)=1, cos(0°)²=1, IL=-10·log 10(1) = 0dB, so when the insertion loss value is the smallest, the actual rotation angle of the optical fiber is 0°. However, due to details such as the installation of the optical fiber, the rotation angle α at this time may not be 0. Therefore, if it can be ensured that the optical fiber does not deflect during installation, the non-rotated angle 0° can be directly used as the initial angle. Alternatively, as described above, the ends of the optical fiber 20 to be tested and the input optical fiber 12 can be rotated for measurement. When the insertion loss value is the smallest, it proves that the optical fiber 20 to be tested and the input optical fiber 12 are not deflected at this moment, and the optical fiber 20 to be tested and the input optical fiber 12 achieve optimal coupling. The angle at this time is the target angle.

[0043] S102: Starting from the target angle, synchronously rotate the input optical fiber and the optical fiber to be tested, obtain the polarization extinction ratio corresponding to each rotation angle, obtain an extinction ratio-angle curve, and obtain the stress range of the polarization-maintaining optical fiber based on the extinction ratio-angle curve.

[0044] In a specific implementation scenario, the polarization extinction ratio (PER) is measured at a target angle, representing the PER in a stress-free or axis-aligned region. As the input fiber 12 and the fiber under test 20 are rotated, the actual rotation angle θ of the fibers gradually increases. Under optimal coupling conditions, artificially rotating the fiber angle will degrade the PER. In one embodiment, starting from the target angle, the input fiber 12 and the fiber under test 20 are synchronously rotated in clockwise and counterclockwise directions, respectively.

[0045] In one implementation scenario, the relationship between the rotation angle and the polarization extinction ratio is obtained according to the following formula:

[0046] in, is the polarization extinction ratio, is the actual deflection angle.

[0047] When the optical fiber 20 to be tested rotates by an angle of θ, the angle between its fast axis and the polarization direction of the secondary polarized light (the original slow axis direction) becomes (90-θ)°. According to Malus's law, Represents the ratio of optical power that can be coupled into the fast axis of the fiber under test (relative to the intensity of the incident polarized light). PER (Polarization Extinction Ratio) is defined as the ratio of the optical power coupled into the slow axis (P_slow) to the optical power coupled into the fast axis (P_fast), usually expressed in decibels: PER = 10∙log 10 (P_slow / P_fast)dB.

[0048] In rotation After the angle, P_slow∝ , P_fast∝ = , PER=10∙log 10 (P_slow / P_fast), when the incident power is fixed and P_slow changes relatively slowly with θ (especially when θ is small), PER is mainly affected by P_fast (i.e. )). Therefore, PER is inversely proportional to , or PER is proportional to -log 10 ( ), which is proportional to Based on the above analysis, we can see that PER decreases sharply as θ increases. In particular, when θ deviates from 0°, the increase in sin²(θ) leads to a deterioration in PER.

[0049] By obtaining the polarization extinction ratio corresponding to each rotation angle, the extinction ratio-angle curve is obtained, and the stress range of the polarization-maintaining fiber is obtained based on the extinction ratio-angle curve. Figure 5 , Figure 5 This is a schematic diagram of a curve showing how the extinction ratio and insertion loss vary with the rotation angle, provided by the present invention. The stress region of the optical fiber to be tested can be defined based on the curve.

[0050] Specifically, if the PER value remains above a certain acceptable threshold, the current deflection angle is in the safe stress zone. If the PER value begins to decline significantly and rapidly, the current deflection angle is in the transition zone. If the PER value drops sharply to a very low level, the current deflection angle is in the failure zone. Simultaneously monitoring the PER and IL (Insertion Loss) provides more comprehensive information. A sudden drop in PER coupled with a stable IL indicates a polarization performance failure, while a sudden drop in PER coupled with a sharp increase in IL indicates physical fiber damage.

[0051] As can be seen from the above description, in this embodiment, the input light fiber and the fiber under test are synchronously rotated to obtain insertion loss values ​​corresponding to various rotation angles. The rotation angle at which the insertion loss value is minimized is defined as the target angle. At this time, the actual rotation angle of the fiber under test is 0. Starting from the target angle (that is, the position at which the polarization extinction ratio is optimal), the input light fiber and the fiber under test are synchronously rotated to obtain the polarization extinction ratio corresponding to each rotation angle, and an extinction ratio-angle curve is obtained. Based on the extinction ratio-angle curve, the stress range of the polarization-maintaining fiber is determined. The synchronous rotation of the two fibers ensures that the principal axis direction of the entire system (except for stress points within the fiber under test) is globally consistent. Changes in the PER purely reflect local principal axis direction deflections caused by internal factors (primarily stress areas) within the fiber under test, thereby improving the accuracy and reliability of the stress range.

[0052] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Those skilled in the art may modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein; and all these modifications and replacements should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A device for identifying the stress range of a polarization-maintaining optical fiber, characterized in that: Used to measure the stress range of the optical fiber under test, including: a light source, for providing a detection light signal; An input optical fiber is located at the light output side of the light source and is used to receive and transmit the detection light signal. The optical fiber to be tested is arranged in parallel with the input optical fiber and their relative positions are fixed; a polarizer, located at the output end of the incident optical fiber and the input end of the optical fiber to be tested; a reflector, located on a side of the polarizer away from the input optical fiber; The testing device is located at the output end of the optical fiber to be tested and is used to analyze the test optical signal output by the optical fiber to be tested to obtain the stress range.

2. The stress range identification device for polarization-maintaining optical fiber according to claim 1, characterized in that: The light input optical fiber and the optical fiber to be tested are formed by cutting off the same optical fiber.

3. The stress range identification device for polarization-maintaining optical fiber according to claim 1, characterized in that: The light source is an incoherent light source; the main polarization direction of the input optical fiber is aligned with the transmission axis of the polarizer.

4. The stress range identification device for polarization-maintaining optical fiber according to claim 3, characterized in that: When the polarization direction of the optical signal input to the polarizer is the same as the transmission axis direction, the extinction ratio exceeds 35 dB.

5. The stress range identification device for polarization-maintaining optical fiber according to claim 1, characterized in that: The stress range identification device of the polarization-maintaining optical fiber further includes: A collimating lens, wherein the polarizer is attached to a side of the collimating lens facing the reflector; A capillary tube is wrapped around the light-input optical fiber and the optical fiber to be tested, and is used to fix the relative positions of the light-input optical fiber and the optical fiber to be tested.

6. A method for identifying the stress range of a polarization-maintaining optical fiber, characterized in that: A stress range identification device for a polarization-maintaining optical fiber according to any one of claims 1 to 5; The method for identifying the stress range of the polarization-maintaining optical fiber includes: Synchronously rotating the input optical fiber and the optical fiber to be tested to obtain insertion loss values ​​corresponding to various rotation angles, and setting the rotation angle with the minimum insertion loss value as the target angle; Taking the target angle as the starting point, the input optical fiber and the optical fiber to be tested are synchronously rotated to obtain the polarization extinction ratio corresponding to each rotation angle, obtain an extinction ratio-angle curve, and obtain the stress range of the polarization-maintaining optical fiber based on the extinction ratio-angle curve.

7. The method for identifying the stress range of a polarization-maintaining optical fiber according to claim 6, wherein: The step of obtaining the insertion loss value corresponding to each rotation angle includes: The insertion loss value is obtained according to the following formula: in, is the insertion loss value, is the actual deflection angle.

8. The method for identifying the stress range of a polarization-maintaining optical fiber according to claim 7, wherein: The step of obtaining the polarization extinction ratio corresponding to each rotation angle includes: The polarization extinction ratio corresponding to each rotation angle is expressed by the following formula: in, is the polarization extinction ratio, is the actual deflection angle.

9. The method for identifying the stress range of a polarization-maintaining optical fiber according to claim 6, wherein: Before the step of synchronously rotating the input optical fiber and the optical fiber to be tested, the method includes: The cat's eye adjustment is performed on the input optical fiber and the optical fiber to be tested so that the cat's eyes of the input optical fiber and the optical fiber to be tested are located on the same straight line.

10. A stress range identification system for polarization-maintaining optical fiber, characterized in that: The steps of synchronously rotating the input optical fiber and the optical fiber to be tested with the target angle as the starting point include: Taking the target angle as a starting point, the light input optical fiber and the optical fiber to be tested are synchronously rotated in a clockwise direction and a counterclockwise direction respectively.

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