Method for improving stress symmetry of fiber-optic gyroscope interferometer

Abstract

The invention discloses a method for improving stress symmetry of a fiber-optic gyroscope interferometer, which is characterized by comprising the following steps: 1) processing a stress compensation module; 2) assembling a light source, an optical fiber coupler, a photoelectric detector and a Y waveguide; (3) one tail fiber of the optical fiber ring penetrates through the through hole of the stress block, and then epoxy resin is poured; 4) connecting the other tail fiber of the optical fiber ring with an extinction ratio tester; electrifying the light source; 5) tightening the adjusting bolt between the two pressing plates; 6) comparing extinction ratio values output by the extinction ratio tester before and after tightening the adjusting bolt; if the extinction ratio value is increased, continuously tightening the adjusting bolt; if the numerical value is reduced, the adjusting bolt is unscrewed; according to the method for assembling the fiber-optic gyroscope interferometer, the stress symmetry in the interferometer composed of the fiber ring and the Y waveguide can be improved, and the refractive index and the polarization coupling degree of the fiber can be kept relatively stable.

Description

Technical Field

[0001] This invention relates to the field of fiber optic gyroscope technology, and in particular to a method for improving the stress symmetry of a fiber optic gyroscope interferometer. Background Technology

[0002] A fiber optic gyroscope is an inertial instrument that measures angular velocity. It is highly autonomous and can be used in inertial navigation systems. Due to its all-solid-state structure, wide dynamic range, short startup time, and strong shock resistance, it has been widely used in modern aviation, aerospace, and defense industries.

[0003] See Figure 1 A fiber optic gyroscope requires five types of optoelectronic devices: a light source, an optical fiber coupler, a multi-functional phase modulator (Y-waveguide), a photodetector, and an optical fiber ring. These optoelectronic devices are spliced ​​together to form a complete optical path. Among them, the optical fiber ring and the optical fiber in the Y-waveguide are the main transmission and interference points of optical signals, and are sensitive to angular velocity. Together, they form the interferometer of the fiber optic gyroscope.

[0004] The Y-waveguide in the interferometer has two sets of optical fibers, each approximately 1–6 m long. One set contains only one fiber, fused to the fiber coupler; the other set contains two fibers, fused to the two fibers of the fiber ring. The fiber ring is constructed using panda-type polarization-maintaining fiber. The fiber length outside the ring body is typically only about 2 m, but the fiber wound around the ring body is usually in the range of 200 m–3000 m. Because the panda-type polarization-maintaining fiber is designed with two stress zones with very high coefficients of thermal expansion, it is extremely sensitive to external environmental factors such as temperature and stress. To reduce the impact of temperature and stress on the interferometer, techniques such as four-pole symmetrical winding, eight-pole symmetrical winding, and sixteen-pole symmetrical winding are typically used during fiber winding to achieve neat fiber arrangement and high symmetry.

[0005] To achieve this technology, tension needs to be applied during the winding process to ensure the fibers are aligned neatly. When this tension is applied to an fiber with an outer diameter of only 135 μm, it causes changes in the fiber's refractive index and polarization coupling. During the long winding process, tension fluctuations lead to varying stresses on the fiber, disrupting the stress symmetry of the fiber ring and causing deviations in the refractive index and polarization coupling at different points within the ring. Simultaneously, due to the long length of the wound fiber, the process of splitting the fiber from the fiber barrel to the fiber distributor and then winding it onto the fiber ring causes varying degrees of twisting. This torsional stress also acts on the fiber, affecting its stress symmetry. Furthermore, during fiber winding, bending stress is generated in the small space due to the layering effect; bending stress also occurs when the fiber ring and Y-waveguide fiber are fused and wound together. Since these bending stresses are random and uncontrollable, they also affect the fiber's stress symmetry. In addition, during the curing process of the adhesive binding the optical fiber after winding, the curing of the adhesive is a phase transition process, during which significant curing stress is generated, which will also affect the stress symmetry of the optical fiber.

[0006] The combined effect of the above stresses can cause the stress symmetry in the fiber optic ring to fall short of the ideal level. Even if stress is released after winding, the release effect cannot ensure that the stress is completely eliminated. This results in insufficient suppression of errors caused by stress, leaving residual errors. These residual errors will reach the fiber optic gyroscope, ultimately causing a decline in the performance of the fiber optic gyroscope.

[0007] To further improve the stress symmetry in the interferometer composed of fiber optic rings and Y-waveguides, ensure that the refractive index and polarization coupling of the fiber do not change significantly, and improve the performance of fiber optic gyroscopes, it is urgent to develop an improved method for enhancing the stress symmetry of fiber optic gyroscope interferometers. Summary of the Invention

[0008] In view of the above-mentioned shortcomings of the existing technology, the purpose of this invention is to solve the problem of poor stress symmetry in the interferometer composed of fiber optic ring and Y-waveguide, and to provide a method to improve the stress symmetry of fiber optic gyroscope interferometer, which can improve the stress symmetry in the interferometer composed of fiber optic ring and Y-waveguide, so that the refractive index and polarization coupling of the fiber optic remain relatively stable, thereby improving the accuracy of the gyroscope.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for improving the stress symmetry of a fiber optic gyroscope interferometer, characterized by comprising the following steps:

[0010] 1) Processing stress compensation module, the stress compensation module includes stress block and two pressure plates, a through hole is provided on the stress block, the through hole passes through the opposite sides of the stress block; the two pressure plates are distributed on both sides of the through hole in the axial direction, and fit against the opposite sides of the stress block, and are connected by adjusting bolts;

[0011] 2) Assemble the light source, fiber coupler, photodetector, and Y-waveguide, and splice the optical fibers according to the optical path;

[0012] 3) Pass one of the fiber optic loop pigtails through the through hole of the stress block, then fusion splice it with one of the pigtails of the Y waveguide, then inject epoxy resin into the through hole of the stress block and wait for it to cure.

[0013] 4) Connect the other pigtail of the fiber optic ring to the fiber optic adapter, and then connect the fiber optic adapter to the corresponding interface on the extinction ratio tester; then power on the light source and observe the extinction ratio value output by the extinction ratio tester.

[0014] 5) Tighten the adjusting bolts between the two pressure plates to increase the clamping force exerted by the two pressure plates on the stress block;

[0015] 6) Compare the extinction ratio values ​​output by the extinction ratio tester before and after tightening the adjusting bolt; if the extinction ratio value increases, continue to tighten the adjusting bolt until the extinction ratio value no longer increases or decreases; if the value decreases, loosen the adjusting bolt to increase the extinction ratio value until the extinction ratio value no longer increases or decreases.

[0016] 7) Keep the adjusting bolt in its current state and pour epoxy resin into the adjusting part of the adjusting bolt. Wait for the epoxy resin to cure so that the compensation stress applied by the stress compensation module remains stable.

[0017] 8) Finally, fusion splice the pigtail of the fiber optic ring with another pigtail of the Y-waveguide to complete the assembly of the fiber optic gyroscope interferometer.

[0018] Furthermore, in step 1), in the initial state, under the action of the adjusting bolt, the two pressure plates are pressed tightly onto the stress block, so that the stress block has initial prestress.

[0019] Furthermore, in step 1), there are multiple adjusting bolts, which are symmetrically distributed on both sides of the axis of the through hole.

[0020] Furthermore, in step 1), the adjusting bolt passes through one of the pressure plates and is threadedly connected to the other pressure plate.

[0021] Furthermore, in step 1), the end of the screw of the adjusting bolt is connected to a nut after passing through two pressure plates.

[0022] Furthermore, in step 1), the adjusting part of the adjusting bolt includes the external thread of the screw and a screw hole or nut that mates with the screw.

[0023] Compared with the prior art, the present invention has the following advantages: The solution is simple and quick to operate. By adding a reverse stress to the optical fiber at the end of the interferometer, stress symmetry on the optical fiber is achieved, thereby ensuring that the refractive index and polarization coupling of the optical fiber remain relatively stable. This avoids the complex and repeated stress release process in conventional methods, thereby improving the accuracy of the gyroscope and improving assembly efficiency. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the optical path principle of a fiber optic gyroscope.

[0025] Figure 2 This is a schematic diagram of the stress compensation module.

[0026] In the diagram: 1—pressure plate, 2—stress block, 3—tail fiber, 4—epoxy resin. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to represent selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0029] It should be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship commonly used when the product is in use. They are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance. In addition, the terms "horizontal," "vertical," etc., do not indicate that the component is required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted. In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0030] Example: See Figure 1 , Figure 2 A method for improving the stress symmetry of a fiber optic gyroscope interferometer includes the following steps:

[0031] 1) A stress compensation module is fabricated, comprising a stress block 2 and two pressure plates 1. A through hole is provided on the stress block 2, extending through both opposite sides of the stress block 2; the diameter of the through hole is larger than the diameter of the optical fiber. The two pressure plates 1 are distributed on both sides of the through hole along its axial direction and fit against the opposite sides of the stress block 2, connected by adjusting bolts. In implementation, multiple adjusting bolts are used, symmetrically distributed on both sides of the through hole's axis; this makes the clamping force adjustment of the pressure plates 1 (i.e., the stress adjustment of the stress block 2) more balanced and stable. As one embodiment, the adjusting bolt passes through one pressure plate 1 and is threadedly connected to the other pressure plate 1; this method makes pressure adjustment more convenient. As another embodiment, the end of the adjusting bolt's screw passes through both pressure plates 1 and is connected to a nut; this makes the fabrication and assembly of the stress compensation module more convenient. In the initial state, under the action of the adjusting bolts, the two pressure plates 1 are pressed tightly against the stress block 2, giving the stress block 2 initial prestress.

[0032] 2) Assemble the light source, fiber coupler, photodetector and Y waveguide, and splice the fiber according to the optical path; in this step, the fiber, fiber coupler, photodetector and Y waveguide are all assembled and spliced ​​according to the conventional assembly and splicing process (method); the fiber ring is also installed according to the conventional method (pigtails are not spliced).

[0033] 3) Pass one of the fiber optic loop pigtails 3 through the through hole of the stress block 2, then fuse it with one of the pigtails 3 of the Y waveguide, and then inject epoxy resin 4 into the through hole of the stress block 2 and wait for it to cure.

[0034] 4) Connect the other pigtail of the fiber optic ring to the fiber optic adapter, and then connect the fiber optic adapter to the corresponding interface of the extinction ratio tester; then power on the light source and observe the extinction ratio value output by the extinction ratio tester.

[0035] 5) Tighten the adjusting bolt between the two pressure plates 1 to increase the clamping force exerted by the two pressure plates 1 on the stress block 2. Since the stress block 2, epoxy resin 4 and the pigtail 3 are bonded together after the through hole is filled with epoxy resin 4, the clamping force increases during the tightening of the adjusting bolt, applying compressive stress to the stress block 2, which gradually increases and is applied to the pigtail 3; during the loosening process, the clamping force decreases, applying tensile stress to the stress block 2, which gradually increases and is applied to the pigtail 3.

[0036] 6) Compare the extinction ratio values ​​output by the extinction ratio tester before and after tightening the adjusting bolt. If the extinction ratio value increases, continue tightening the adjusting bolt until the extinction ratio value no longer increases or decreases. If the value decreases, loosen the adjusting bolt to increase the extinction ratio value until the extinction ratio value no longer increases or decreases. This balances the stress generated by other factors, thereby ensuring the stability of the stress on the pigtail 3.

[0037] 7) Maintain the state of the adjusting bolt and pour epoxy resin into the adjusting portion of the adjusting bolt. Specifically, the adjusting portion of the adjusting bolt includes the external thread of the screw and the threaded hole or nut that mates with the screw. Therefore, when pouring epoxy resin, the resin is poured into the exposed portion of the adjusting bolt screw, and simultaneously, epoxy resin is also poured between the adjusting bolt screw and pressure plate 1 or the nut. This ensures that the position of the adjusting bolt is fixed after the epoxy resin cures. After the epoxy resin cures, the compensation stress applied by the stress compensation module remains stable.

[0038] 8) Finally, fusion splice the pigtail of the fiber optic ring with another pigtail of the Y-waveguide to complete the assembly of the fiber optic gyroscope interferometer.

[0039] This solution achieves stress symmetry in the fiber by adding a reverse stress to the fiber at the end of the interferometer, thereby ensuring that the refractive index and polarization coupling of the fiber remain relatively stable. This avoids the complex and repeated stress release process in conventional methods, thus improving the accuracy of the gyroscope and increasing assembly efficiency.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A method of improving stress symmetry of a fiber optic gyroscope interferometer, characterized by, The method comprises the following steps: 1) processing a stress compensation module, which comprises a stress block and two pressing plates, a through hole is arranged on the stress block, the through hole penetrates through opposite sides of the stress block, the two pressing plates are distributed on the two sides of the through hole in the axial direction and are attached to the opposite sides of the stress block, and the two pressing plates are connected through adjusting bolts; 2) assembling a light source, a fiber coupler, a photodetector and a Y waveguide, and fusing optical fibers according to an optical path; 3) passing one of the tail fibers of an optical fiber coil through the through hole of the stress block, then fusing the tail fiber with one of the tail fibers of the Y waveguide, pouring epoxy resin into the through hole of the stress block, and waiting for the epoxy resin to solidify; 4) connecting the other tail fiber of the optical fiber coil to an optical fiber adapter, then connecting the optical fiber adapter to a corresponding interface on an extinction ratio tester, then powering on the light source, and observing the extinction ratio value output by the extinction ratio tester; 5) tightening the adjusting bolts between the two pressing plates to increase the clamping force of the two pressing plates on the stress block; 6) comparing the extinction ratio values output by the extinction ratio tester before and after the adjusting bolts are tightened; if the extinction ratio value increases, continue to tighten the adjusting bolts until the extinction ratio value no longer increases or decreases; if the value decreases, loosen the adjusting bolts to increase the extinction ratio value until the extinction ratio value no longer increases or decreases; 7) maintaining the state of the adjusting bolts, pouring epoxy resin into the adjusting part of the adjusting bolts, and waiting for the epoxy resin to solidify to stabilize the compensation stress applied by the stress compensation module; 8) finally, fusing the tail fiber of the optical fiber coil with the other tail fiber of the Y waveguide to complete the assembly of the fiber-optic gyroscope interferometer.

2. The method of claim 1, wherein the method further comprises: In step 1), the initial state, under the action of the adjusting bolts, the two pressing plates are tightly pressed on the stress block, so that the stress block has an initial prestress.

3. The method of claim 1, wherein the method further comprises: In step 1), the adjusting bolts are a plurality of adjusting bolts and are symmetrically distributed on the two sides of the axial center line of the through hole.

4. The method of claim 1, wherein the method further comprises: In step 1), the adjusting bolts pass through one of the pressing plates and are connected to the other pressing plate in threaded cooperation.

5. The method of claim 1, wherein the method further comprises: In step 1), the end of the screw rod of the adjusting bolt is connected to a nut after passing through the two pressing plates.

6. The method of claim 1, wherein the method further comprises: In step 1), the adjusting part of the adjusting bolt comprises the outer thread of the screw rod and the screw hole or nut matched with the screw rod.

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