A low-stress fiber loop design method based on finite element simulation

Abstract

The application discloses a low-stress fiber loop design method based on finite element simulation and belongs to the technical field of computer-aided design. The low-stress fiber loop design method of the application is aimed at the jump-turn transition area of an octupole symmetrical winding method fiber loop, constructs a jump-turn geometric model containing cross-layer jump-turn optical fibers and regular layer winding optical fibers, establishes a local Cartesian coordinate system and adopts a sweeping method to perform structured grid division, applies a fixed constraint to the regular layer winding optical fibers, applies tension and opposite displacement loads to the cross-layer jump-turn optical fibers to simulate jump-turn deformation, considers the nonlinear mechanical behavior of the optical fibers, solves equivalent stress distribution by adopting a nonlinear finite element algorithm, obtains an optimal transition path based on the equivalent stress distribution fitting, and adjusts the jump-turn angle and wrapping buffer materials. The application can truly restore the local stress state under the jump-turn scene, effectively reduces the stress concentration of the jump-turn transition area, and improves the design reliability and mechanical stability of the fiber loop.

Description

Technical Field

[0001] This invention belongs to the field of computer-aided design technology, specifically relating to a low-stress fiber optic ring design method based on finite element simulation. Background Technology

[0002] As a core component of high-precision optical sensing devices such as fiber optic gyroscopes and fiber optic hydrophones, the manufacturing precision of fiber optic rings directly determines the measurement accuracy and stability of these devices. The octet symmetrical winding method (ABBABAAB) is widely used in the winding process of high-precision fiber optic rings due to its excellent temperature compensation performance and anti-interference capabilities.

[0003] In the winding process of an octet symmetric fiber optic ring, the skip-turn transition region is an unavoidable critical area. When the fiber skips from one layer to another, stress concentration is easily generated. The stress distribution in the skip-turn transition region directly affects the mechanical stability and optical performance of the fiber optic ring. If the stress is too high or unevenly distributed, it will lead to increased fiber transmission loss, changes in polarization state, and even microcracks in the fiber, severely reducing the service life and measurement accuracy of the fiber optic ring and subsequent sensing equipment.

[0004] In engineering practice, computer simulation technology has become an important tool for the design and performance analysis of fiber optic ring structures. By establishing a finite element model of the fiber optic ring, designers can simulate the stress distribution during the winding process, predict potential failure risks, and optimize winding parameters in a virtual environment. However, current simulation studies on the skipped-turn transition region of octet symmetric fiber optic rings still have significant shortcomings: on the one hand, existing simulation models are mostly for regular winding regions, lacking accurate geometric models that can accurately characterize the spatial attitude of the fiber and its positional relationship with surrounding fibers during the skipped-turn process; on the other hand, the skipped-turn transition region presents significant challenges to mesh generation and load application due to abrupt changes in fiber path and complex contact relationships. Conventional simplification methods cannot accurately reflect the local stress state under skipped-turn scenarios, resulting in significant deviations between simulation results and actual working conditions; furthermore, existing research has failed to fully consider the nonlinear mechanical behavior of fibers under bending and compression in terms of material property settings and boundary condition definitions, further affecting the reliability of the designed fiber optic rings. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a low-stress fiber optic ring design method based on finite element simulation. This method solves the technical problems in existing technologies, such as the lack of accurate geometric representation of the transition zone simulation model for the octagonal symmetric fiber optic ring, large simulation deviations caused by unreasonable meshing and load application, and insufficient design reliability due to the failure to consider the nonlinear mechanical behavior of the fiber.

[0006] This invention discloses a low-stress fiber optic ring design method based on finite element simulation, comprising the following steps: Step 1: Use the octet symmetric winding method to wind multiple optical fibers to obtain an optical fiber loop coil; construct a jump-turn geometric model for the jump-turn transition region of the optical fiber coil; The multiple optical fibers include multiple regularly wound optical fibers and one cross-layer jump-turn optical fiber; The jump-turn transition zone is the area where cross-layer jump-turn optical fibers jump from the bottom layer to the middle layer. Step 2: Establish a local Cartesian coordinate system with one end face of the cross-layer jump-turn fiber in the jump-turn geometric model as the origin; Step 3: Use the sweep method to perform structured mesh generation for each fiber in the jump-turn geometric model; Step 4: Apply fixed support constraints to both ends of the multiple regular layer-wound optical fibers, except for the cross-layer jump-turn fiber; Step 5: Apply a tensile load to one end face of the cross-layer jumper fiber, and then apply opposing displacement loads to both ends of the cross-layer jumper fiber to simulate the jumper deformation process. Step 6: Use the nonlinear finite element algorithm to perform equivalent stress simulation and solve the cross-layer skip-turn fiber to obtain the equivalent stress distribution; Step 7: Fit the skip-turn path based on the equivalent stress distribution to obtain the optimal transition path; Step 8: Based on the optimal transition path, adjust the jump-turn angle of the cross-layer jump-turn fiber and wrap the cross-layer jump-turn fiber with buffer material to complete the fiber ring design.

[0007] Optionally, when performing structured mesh generation in step 3, the ratio of the side length of the mesh cell in the corresponding jumper transition zone of each optical fiber to the side length of the mesh cell on the circumference of the circular end face of the corresponding optical fiber is 3~5:5~8; the number of axial sweep layers is divided into 20~30 layers per 1mm length.

[0008] Optionally, when performing equivalent stress simulation on the cross-layer skipped-turn fiber using the nonlinear finite element algorithm in step 6, the nonlinear mechanical behavior of the cross-layer skipped-turn fiber under bending and extrusion is considered, and the nonlinear elastic parameters of the fiber core, cladding and coating are entered when setting the material properties.

[0009] Optionally, the regular layer is configured with 7 optical fibers; the intermediate layer is the fourth layer.

[0010] Optionally, when obtaining the optimal transition path in step 7, the bending radius of the cross-layer jumper fiber is greater than the minimum bending radius of the cross-layer jumper fiber (1) itself.

[0011] Optionally, adjusting the jump-turn angle in step 8 specifically involves using a spiral transition method to control the progressive offset angle corresponding to the unit arc length of the cross-layer jump-turn fiber circumferentially within the range of 15° to 20°.

[0012] Compared with the prior art, the present invention has at least the following beneficial effects: 1. The low-stress fiber optic ring design method of the present invention solves the problem of inaccurate simulation model of the jump-turn transition zone of the fiber optic ring in the prior art. By constructing an accurate three-dimensional geometric model, the spatial orientation of the jump-turn fiber and the positional relationship with the surrounding fibers are clarified. The method abandons the rough mode of simple straight line or circular arc fitting, truly restores the jump-turn scenario, avoids simulation deviation caused by model simplification, and makes the stress analysis more in line with the actual working conditions.

[0013] 2. The low-stress fiber optic ring design method of the present invention optimizes the simulation accuracy and reliability. For the skip-turn transition zone, it adopts fine mesh generation and stress monitoring, which solves the problem of inaccurate stress calculation caused by coarse mesh and unreasonable load application in the prior art. It ensures that the simulation results can truly reflect the actual stress situation and provide reliable data support for low-stress design.

[0014] 3. The low-stress fiber ring design method of the present invention makes up for the shortcomings of the prior art in not fully considering the nonlinear mechanical characteristics of optical fibers. It fully combines the material properties of optical fibers in the simulation process, and at the same time, by optimizing the jumper path and parameter settings, it effectively reduces the stress concentration in the jumper transition zone, reduces the risk of optical fiber damage, and improves the stability and service life of the fiber ring.

[0015] 4. The low-stress fiber optic ring design method of the present invention takes into account both practicality and efficiency. Through accurate modeling and reasonable parameter settings, it not only ensures the scientific nature of the design but also avoids redundant calculations. Compared with the existing simplified model, it improves the design accuracy while reducing potential problems in subsequent production and use, and is more in line with the needs of actual engineering applications. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly introduced below. The features and advantages of the present invention can be more clearly understood by referring to the accompanying drawings. The accompanying drawings are schematic and should not be construed as limiting the present invention in any way. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the geometric model of the skip-turn transition region of the optical fiber wound using the octet symmetric winding method in the low-stress optical fiber ring design method of the present invention. Figure 2 This is a schematic diagram illustrating the definition of the local Cartesian coordinate system in the low-stress fiber optic ring design method of the present invention; Figure 3 This is a schematic diagram of the element division of the skipped-turn geometric model in the low-stress fiber optic ring design method of the present invention; Figures 4(a)-(b) are schematic diagrams of the method of applying fixed support constraints to the two end faces of the other seven optical fibers in the low-stress optical fiber ring design method of the present invention. Figure 5(a) is a schematic diagram of applying tension to a single optical fiber in the low-stress optical fiber ring design method of the present invention; Figure 5(b) is a schematic diagram of applying displacement to one end face of the optical fiber in the low-stress optical fiber ring design method of the present invention; Figure 5(c) is a schematic diagram of applying displacement to the other end face of the optical fiber in the low-stress optical fiber ring design method of the present invention.

[0018] Explanation of reference numerals in the attached figures: 1-Interlayer skipped-turn fiber; 2-Regular layer wound fiber. Detailed Implementation

[0019] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0020] A specific embodiment of the present invention, such as Figure 1 Figure 5(c) shows a low-stress fiber optic ring design method based on finite element simulation, which includes the following steps: Step 1: Use the octet symmetric winding method to wind multiple optical fibers to obtain an optical fiber loop coil; for the jump-turn transition region of the optical fiber coil, construct the jump-turn geometric model of the jump-turn scenario area where the cross-layer jump-turn fiber jumps from the bottom layer to the middle layer. Furthermore, the fiber coil of the fiber ring is formed by winding an optical fiber with a diameter of 135μm.

[0021] Further, see Figure 3The specific steps for constructing the tripping geometric model are as follows: Matching an octagonal symmetric winding (ABBABAAB) structure, containing eight cylindrical optical fibers, including seven regular layer-wound fibers 2 and one cross-layer jumper fiber 1. Precisely defining the spatial attitude of the cross-layer jumper fiber: For example, setting the axial tilt angle of the cross-layer jumper fiber at the starting position of the first layer to 3°–5° and the circumferential deflection angle to 8°–12°; the axial tilt angle at the ending position of the fourth layer to 2°–4° and the circumferential deflection angle to 6°–10°; controlling the spatial rise angle of the cross-layer oblique transition section to 18°–25°; and maintaining the spatial angle between the jumper fiber axis and the regular layer-wound fiber axis at 12°–18°. These angle parameters quantitatively constrain the three-dimensional spatial orientation of the jumper fiber, achieving precise attitude characterization. The cross-layer jump-turn fiber crosses from the first layer to the fourth layer at a preset tilt angle, forming a spatial oblique transition section. The middle section of the cross-layer jump-turn fiber forms a 2-3 mm line contact with the other seven regular layer winding fibers. The model is set to a non-penetrating and non-initial compression contact constraint to restore the real spatial orientation of the cross-layer jump-turn fiber and its relative position with the other seven regular layer winding fibers during the jump-turn process. The overall length of the model is 8-12 mm, and the diameter envelope size matches the inner diameter of the fiber ring skeleton. Only the jump-turn transition area is extracted for detailed modeling, balancing simulation accuracy and computational efficiency. This completely solves the problem of existing simplified models being out of touch with actual working conditions, ensuring computational accuracy while improving simulation efficiency.

[0022] The accurate three-dimensional solid geometric model of the jump-turn transition region constructed in this invention solves the problem that existing models only target regular winding regions and cannot characterize the jump-turn attitude and fiber position relationship.

[0023] Furthermore, this invention constructs a precise three-dimensional solid geometric model of the jump-turn transition zone through multi-dimensional quantitative constraints, realistic contact relationship replication, and refined modeling of local features: First, it accurately matches the octagonal symmetrical winding sequence and interlayer positional relationship, quantitatively defining the spatial tilt angle, circumferential deflection angle, and interlayer crossing trajectory of the cross-layer jump-turn fiber, achieving a parameterized and precise representation of the jump-turn attitude; Second, it accurately restores the line contact bonding shape, bonding length, and initial compression constraint relationship between the cross-layer jump-turn fiber and the surrounding regular layer-wound fiber, truly reflecting the relative position and spatial interference state between fibers; Third, it accurately extracts the jump-turn transition area and matches the inner diameter of the skeleton, ensuring that the model is highly consistent with the actual working conditions while avoiding positional distortion and attitude deviation caused by simplified modeling, thus solving the technical problem that existing models only target the jump-turn transition zone and cannot accurately represent the jump-turn attitude and fiber positional relationship.

[0024] Step 2: Establish a local Cartesian coordinate system (e.g., using one end face of the interlayer jump-turn fiber in the jump-turn geometric model as the origin) Figure 2 As shown in the figure, it is used to accurately locate the spatial position of each optical fiber.

[0025] Step 3: Use the sweep method to perform structured mesh generation for each fiber in the jump-turn geometric model.

[0026] For example, the optical fiber is a cylindrical entity with a diameter of 135 μm and a circular cross-section. To ensure the simulation accuracy of the skipped turn transition region, the mesh edge size is adjusted across the entire circumferential contour of the optical fiber's circular end face to ensure sufficient mesh refinement in the skipped turn transition region: the side length of the mesh cells on the circumference of the end face is set to 5 μm to 8 μm, and the side length of the mesh cells in the skipped turn transition region is set to 3 μm to 5 μm, ensuring that the number of mesh cells on a single optical fiber end face is no less than 120 to 160 cells. The axial sweep layer number is set at 20 to 30 layers per 1 mm length, achieving a uniform and dense mesh distribution along the fiber axis. The mesh cell division of the skipped turn geometry model can accurately characterize the local structural features of the optical fiber, improving simulation accuracy.

[0027] Step 4: Apply fixed support constraints to both ends of the seven regular layer-wound optical fibers other than the cross-layer skip-turn fiber to simulate the limiting effect of the surrounding optical fibers on the cross-layer skip-turn fiber during the actual winding process. Referring to Figures 4(a) and 4(b), with the fixed support constraint applied at the position, the seven regular layer-wound optical fibers are arranged in a close arrangement. Only the two ends of the seven regular layer-wound optical fibers are constrained, and no fixed support is applied to the cross-layer jump-turn optical fibers.

[0028] Step 5: Apply a tension load to one end face of the cross-layer jump-turn fiber to simulate the tension state during the fiber winding process; then apply opposing displacement loads to both ends of the cross-layer jump-turn fiber to gradually bring the two ends closer to other regular layer-wound fibers in the surrounding area, simulating the deformation process of the cross-layer jump-turn fiber during the jump-turn process. Referring to Figures 5(a)-5(c), Figure 5(a) is a schematic diagram of the application of tension load. A tension load is applied axially to one end face of the cross-layer jump-turn fiber to simulate the tension preload state of the fiber in the actual winding process, ensuring the straightness and tension control of the fiber winding process; Figure 5(b) is a schematic diagram of the application of the first-end displacement load. A displacement boundary condition is applied to one end face of the cross-layer jump-turn fiber to simulate the progressive movement path of the first end relative to the skeleton during the fiber jump-turn process; Figure 5(c) is a schematic diagram of the application of the last-end displacement load. An opposing displacement load is applied to the other end face of the cross-layer jump-turn fiber. Through the displacement coordination of the two end faces gradually approaching each other, the spatial deformation trajectory of the cross-layer jump-turn fiber during the process of crossing to the fourth layer is realistically restored, accurately replicating the actual working condition deformation of the fiber during the jump-turn process.

[0029] The simulation of the turn-skipping process in this invention avoids the stress simulation deviation caused by conventional simplified load application, and truly restores the local stress state under the turn-skipping scenario.

[0030] Step 6: Using a nonlinear finite element method, perform equivalent stress simulation on the cross-layer skipped-turn fiber to obtain the equivalent stress distribution of the cross-layer skipped-turn fiber. Specifically: Considering the nonlinear mechanical behavior of cross-layer skipped-turn optical fibers under bending and compression, nonlinear elastic parameters (such as nonlinear elastic modulus and Poisson's ratio) of the fiber core, cladding, and coating are entered when setting material properties to replace the linear material assumptions in existing studies. A nonlinear finite element algorithm is used to accurately calculate the equivalent stress distribution of cross-layer skipped-turn optical fibers, providing data support for subsequent low-stress design.

[0031] Step 7: Ensure that the bending radius of the cross-layer jumper fiber is greater than the minimum bending radius of the fiber used, and obtain the optimal transition path based on the equivalent stress distribution obtained in Step 6.

[0032] Specifically, based on the equivalent stress distribution of the cross-layer skipped-turn fiber obtained in step 6, a catenary model is used to fit the skipped-turn path to ensure a smooth bending transition. At the same time, the minimum bending radius is accurately determined according to the fiber type, further improving the reliability of the fiber ring design and solving the design defects caused by the failure to consider nonlinear behavior in existing studies.

[0033] For example, when using G.657.A type optical fiber, the minimum local bending radius of the cross-layer jumper fiber on the transition path must be ≥10mm; Furthermore, a catenary model is used to fit the transition path of the cross-layer skipped-turn fiber, so that the bending transition of the cross-layer skipped-turn fiber is smooth and the bending stress is reduced; according to the equivalent stress distribution obtained in step 6, the optimal transition path with the maximum stress value lower than the allowable stress threshold of the fiber is selected; when using fiber other than G.657.A type, the minimum bending radius rating is not less than the minimum bending radius specified in the technical specifications of the fiber.

[0034] Step 8: Based on obtaining the optimal transition path, adjust the jump-turn angle of the cross-layer jump-turn fiber; Specifically, a spiral transition method is adopted, and the skipping of the fiber is achieved by gradually changing the winding angle of the cross-layer skipping fiber. The progressive offset angle corresponding to the unit arc length of the cross-layer skipping fiber in the circumferential direction is controlled within the range of 15°~20°, reducing stress concentration caused by sudden angle changes. The progressive offset angle is adjusted in real time through a high-precision winding device to ensure that the actual deviation of the progressive offset angle is controlled within ±1°, thus ensuring adjustment accuracy.

[0035] Step 9: Wrap the cross-layer jumper with fiber buffer material to obtain the final designed fiber coil, and use the designed fiber coil to prepare the final fiber ring; Specifically, a low-modulus buffer material is wrapped around the surface of the cross-layer jumper fiber to absorb mechanical stress and reduce stress transmission. The low-modulus buffer material can be silicone, polyurethane, etc., with a Shore hardness of A20~A40. The wrapping thickness is controlled at 0.8~2mm, and the wrapping area needs to cover the entire length of the jumper transition section and the fiber extension area of ​​1~2mm on both sides of the transition section. Before wrapping the buffer material, the fiber surface at the jumper needs to be degreased and cleaned to remove surface oil, dust and impurities, ensuring that the buffer material is tightly attached to the fiber surface and that there are no air bubbles remaining at the bonding interface, thus ensuring the buffering effect.

[0036] The stress distribution in the skipped-turn transition region of the prepared fiber ring was measured using a white light interferometer. The measurement results show that the fiber ring designed in this invention has a uniform stress distribution in the skipped-turn transition region with no obvious stress concentration points, and the maximum equivalent stress is reduced by more than 30% compared with the traditional design scheme.

[0037] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A low-stress fiber optic ring design method based on finite element simulation, characterized in that, Includes the following steps: Step 1: Use the octet symmetric winding method to wind multiple optical fibers to obtain an optical fiber loop coil; construct a jump-turn geometric model for the jump-turn transition region of the optical fiber coil; The multiple optical fibers include multiple regular layer-wound optical fibers (2) and one cross-layer skip-turn optical fiber (1). The jump-turn transition zone is the area where cross-layer jump-turn optical fibers jump from the bottom layer to the middle layer. Step 2: Establish a local Cartesian coordinate system with one end face of the cross-layer jump-turn fiber (1) in the jump-turn geometric model as the origin; Step 3: Use the sweep method to perform structured mesh generation for each fiber in the jump-turn geometric model; Step 4: Apply fixed support constraints to both ends of the multiple regular layer-wound optical fibers (2) except for the cross-layer jump-turn fiber (1); Step 5: Apply a tensile load to one end face of the cross-layer jump-turn fiber (1), and then apply opposing displacement loads to both ends of the cross-layer jump-turn fiber (1) to simulate the jump-turn deformation process; Step 6: Use the nonlinear finite element algorithm to perform equivalent stress simulation on the cross-layer skip-turn fiber (1) to obtain the equivalent stress distribution; Step 7: Fit the skip-turn path based on the equivalent stress distribution to obtain the optimal transition path; Step 8: Based on the optimal transition path, adjust the jump-turn angle of the cross-layer jump-turn fiber (1) and wrap the cross-layer jump-turn fiber (1) with buffer material to complete the fiber ring design.

2. The low-stress fiber optic ring design method based on finite element simulation according to claim 1, characterized in that, When performing structured mesh generation in step 3, the ratio of the side length of the mesh cell in the jumper transition zone of each optical fiber to the side length of the mesh cell on the circumference of the circular end face of the corresponding optical fiber is 3~5:5~8; the number of axial sweep layers is divided into 20~30 layers per 1mm length.

3. The low-stress fiber optic ring design method based on finite element simulation according to claim 1, characterized in that, In step 6, when using the nonlinear finite element algorithm to perform equivalent stress simulation on the cross-layer skipped-turn fiber (1), the nonlinear mechanical behavior of the cross-layer skipped-turn fiber under bending and extrusion is considered. When setting the material properties, the nonlinear elastic parameters of the fiber core, cladding and coating are entered.

4. The low-stress fiber optic ring design method according to claim 1, characterized in that, The regular layer is configured with 7 optical fibers; the intermediate layer is the fourth layer.

5. The low-stress fiber optic ring design method based on finite element simulation according to claim 1, characterized in that, When the optimal transition path is obtained in step 7, the bending radius of the cross-layer jumper fiber (1) is greater than the minimum bending radius of the cross-layer jumper fiber (1) itself.

6. The low-stress fiber optic ring design method based on finite element simulation according to claim 1, characterized in that, In step 8, adjusting the jump-turn angle specifically involves using a spiral transition method to control the progressive offset angle of the cross-layer jump-turn fiber (1) within the range of 15° to 20°, corresponding to the unit arc length of the circumferential loop.

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