Vortex-based vector stress sensing system and method based on hollow-core Bragg fiber

Abstract

This invention discloses a vortex-based vector stress sensing system and method based on hollow-core Bragg fiber, relating to fiber optic sensing technology. A hollow-core Bragg fiber is incorporated into the object under test, along with a light source modulation module, a fiber coupling module, and a stress sensing module. The light source modulation module comprises a laser, a fiber polarization controller, a fiber collimator, a polarization beam splitter, and a spatial light modulator connected in sequence. The fiber coupling module comprises a near-infrared microscope objective and a fiber-coupled displacement stage connected in sequence. The stress sensing module comprises a stress loading platform, a charge-coupled element, and a computer connected in sequence. The light source modulation module, fiber coupling module, hollow-core Bragg fiber, and stress sensing module are sequentially connected. This invention utilizes the anisotropic response of the helical phase wavefront of a vortex beam to the stress direction to achieve vector stress sensing in a hollow-core Bragg fiber, offering advantages such as compact structure, high sensitivity, and the ability to distinguish stress directions.

Description

Technical Field

[0001] This invention relates to the field of optical field manipulation and fiber optic sensing technology, and in particular to a vortex vector stress sensing system and method based on hollow Bragg fiber, which is applicable to multi-parameter optical sensing, optical communication and optical information processing. Background Technology

[0002] In recent years, vortex beams carrying orbital angular momentum have shown great application potential in the field of fiber optic sensing due to their unique helical phase structure. The wavefront of a vortex beam is helically distributed, and its intensity pattern has a central dark core. It is highly sensitive to stress-induced wavefront distortion and mode coupling, providing a new technical path for high-precision stress sensing.

[0003] Currently, vortex fiber stress sensing solutions can be mainly divided into the following three categories: I. Stress Sensing Scheme Based on Fiber Bragg Grating. This scheme senses stress magnitude by writing a periodic refractive index modulation structure into the fiber core and utilizing the Bragg wavelength shift phenomenon caused by stress. Its core advantage lies in its mature technology and ability to achieve quasi-distributed measurement. However, it essentially only detects stress magnitude and lacks sensitivity to stress direction. To obtain stress direction information, existing technologies typically require multi-core fibers, off-axis grating writing, or complex packaging structures, which undoubtedly significantly increases system complexity and application cost.

[0004] II. Stress Sensing Schemes Based on Interferometers. These schemes utilize Mach-Zehnder interferometers, Fabry-Perot interferometers, and Sagnac interferometers as core components. They achieve stress sensing by detecting drift or fringe changes in the interference spectrum, exhibiting high sensitivity. However, these schemes also lack stress direction resolution and are susceptible to temperature crosstalk, typically requiring additional temperature compensation mechanisms to ensure measurement accuracy, further increasing the system design complexity.

[0005] III. Distributed stress sensing schemes based on Brillouin or Rayleigh scattering. These schemes utilize the frequency shift or phase change of backscattered light in optical fibers to achieve continuous stress sensing along the fiber's length, offering advantages in long-distance, large-scale monitoring scenarios. However, these systems typically require expensive microwave modulation modules and rely on complex demodulation algorithms. Furthermore, their ability to identify the direction of lateral stress is limited, restricting their application in high-precision vector stress monitoring scenarios.

[0006] However, existing vortex optical sensing schemes mainly rely on few-mode fiber or ring fiber as the transmission and sensing medium, which still has obvious limitations: on the one hand, the light field is mainly confined inside the quartz material, and the interaction with the external object to be measured is weak, which seriously restricts the further improvement of sensing sensitivity; on the other hand, the process of vortex light coupling into the optical fiber requires extremely high spatial alignment accuracy. Traditional coupling methods rely on repeated manual trial and error, which is not only inefficient but also has poor measurement repeatability, making it difficult to meet the needs of engineering applications.

[0007] In summary, among existing fiber optic stress sensing technologies, there is still a lack of a fiber optic vector stress sensing system that is structurally simple, can simultaneously and accurately sense the magnitude and direction of stress, and has an efficient and predictable vortex optical coupling alignment process. This has become a key technical challenge that urgently needs to be solved in the current field of fiber optic sensing. Summary of the Invention

[0008] The purpose of this invention is to address the problems existing in fiber optic stress sensing technology, such as the lack of direction sensing capability or the need to rely on complex multi-core structures to achieve vector detection, the low efficiency of vortex light coupling to hollow fiber and the need for repeated manual trial and error in the debugging process, and the limitation of sensing sensitivity by the inherent elastic-optic coefficient of solid fiber material. The invention provides a vortex light vector stress sensing system and method based on hollow Bragg fiber.

[0009] This invention utilizes the inherent sensitivity of the spiral phase wavefront of a vortex beam to the anisotropy of stress direction, combined with the high-fidelity transmission and stress enhancement characteristics of hollow Bragg fiber, to achieve synchronous sensing of stress magnitude and direction in a single fiber, enabling vector stress measurement without complex discrete structures; at the same time, by configuring a graphical user interface with advance prediction function, the optimal coupling coordinates are given before coupling alignment, thereby achieving efficient coupling of vortex light.

[0010] The present invention also provides a vector stress sensing method, which is applied to the vortex optical vector stress sensing system based on hollow-core Bragg fiber. The sensing system includes a light source modulation module, an optical fiber coupling module and a stress sensing module. Through steps such as prediction-assisted alignment, vortex mode excitation and transmission, optical feature extraction and vector calculation under stress disturbance, the vector information of the measured stress is finally output.

[0011] To achieve the above objectives, the present invention provides the following technical solution: I. Vortex Vector Stress Sensing System Based on Hollow-Core Bragg Fiber Hollow-core Bragg fiber is installed in the object under test, along with a light source modulation module, an optical fiber coupling module, and a stress sensing module. The light source modulation module includes a laser, an optical fiber polarization controller, an optical fiber collimator, a polarization beam splitter, and a spatial light modulator connected in sequence. The fiber optic coupling module includes a near-infrared microscope objective and a fiber optic coupling displacement stage connected in sequence. The stress sensing module includes a stress loading platform, a charge-coupled device, and a computer connected in sequence. The light source modulation module, fiber optic coupling module, hollow Bragg fiber, and stress sensing module are connected in sequence.

[0012] ① Light source modulation module: After the laser outputs laser light of a specific wavelength and power, the fiber polarization controller adjusts the polarization state of the light at the output end of the fiber. After the divergence angle is adjusted by the fiber collimator, the divergent beam output by the fiber is collimated into a spatial parallel beam, and a suitable spot size is ensured to match the effective working area of ​​the subsequent spatial light modulator. The polarization state of the light is further adjusted by the polarization beam splitter, and then incident on the spatial light modulator loaded with a specific phase distribution, outputting vortex light with orbital angular momentum characteristics. ② Fiber Optic Coupling Module: The vortex beam output by the spatial light modulator is focused by a 20x near-infrared microscope objective and then efficiently coupled into a hollow Bragg fiber for transmission under the precise adjustment of a six-dimensional fiber coupling displacement stage. Based on the system architecture designed in this invention, the hollow Bragg fiber is highly sensitive to changes in external stress. External stress causes deformation of the fiber cross-section, which leads to changes in the refractive index distribution within the fiber core, thereby generating detectable modulation of the phase and mode characteristics of the transmitted vortex beam, thus realizing stress sensing. ③ Stress sensing module: After the hollow Bragg beam is subjected to stress by the stress loading platform, the output vortex beam is captured by the charge-coupled device to obtain the light intensity distribution image. The captured light spot intensity pattern is transmitted to the computer for calculation. The computer inverts the magnitude and direction of the stress at this time based on the topological charge change and light intensity distribution characteristics, and displays the monitoring results in real time.

[0013] II. Vortex Vector Stress Detection Method Based on Hollow-Core Bragg Fiber ① After the laser in the light source modulation module outputs a laser with a wavelength of 1550nm and a power of 25dBm, the fiber polarization controller adjusts the polarization state of the light at the output end of the fiber. After the divergence angle is adjusted by the fiber collimator, the divergent beam output by the fiber is collimated into a spatial parallel beam. The polarization state of the light is further adjusted by the polarization beam splitter, and then incident on the spatial light modulator loaded with a specific phase distribution, outputting vortex light with orbital angular momentum characteristics. ② The vortex beam output by the spatial light modulator is focused by a 20x near-infrared microscope objective and then efficiently coupled into a hollow Bragg fiber for transmission under the precise adjustment of a six-dimensional fiber coupling displacement stage. Before the coupling operation, the operator inputs the vortex beam parameters, objective parameters, and fiber parameters through a graphical user interface configured on a computer. The interface performs simulation calculations and predicts the optimal coupling position in advance. The operator then manually adjusts the fiber coupling displacement stage according to the predicted coordinates to complete the alignment. The hollow Bragg fiber is highly sensitive to changes in external stress. External stress causes deformation of the fiber cross-section, which leads to changes in the refractive index distribution within the fiber core, thereby producing detectable modulation of the phase and mode characteristics of the transmitted vortex beam, thus realizing stress sensing. ③ After the hollow Bragg fiber is subjected to stress by the stress loading platform, the output vortex beam is captured by the charge-coupled device to obtain the light intensity distribution image. The captured light spot intensity pattern is transmitted to the computer for calculation. Based on the topological charge change and light intensity distribution characteristics, the magnitude and direction of the stress at this time are inverted, and the monitoring results are displayed in real time.

[0014] Compared with the prior art, the present invention has the following advantages and positive effects: ① This invention utilizes the anisotropic response characteristics of the spiral phase wavefront of a vortex beam to the stress direction. It can simultaneously acquire stress magnitude and direction information using only a single hollow Bragg fiber, which significantly simplifies the sensor probe structure, reduces system complexity and manufacturing costs, and is more suitable for application scenarios with limited space or strict requirements on probe size. ② This invention uses hollow Bragg fiber as a sensing medium, which is more sensitive to force. Compared with the scheme in solid fiber where the light field is confined inside the quartz material and only relies on the elasto-optic effect, its air core significantly enhances the energy overlap between the light field and the cladding microstructure and the area under external stress. ③ This invention designs a graphical user interface with advance prediction function in the optical fiber coupling module. The operator can know the predicted optimal coupling coordinates before starting physical adjustment. This fundamentally solves the problem that traditional vortex optical coupling requires repeated manual trial and error, is inefficient, and is prone to damaging the optical fiber end face. It significantly improves the efficiency and repeatability of system construction and debugging. ④ The sensing probe of this invention has an all-fiber structure with no electrical signal transmission. It has the inherent advantages of fiber optic sensing, such as resistance to electromagnetic interference, corrosion resistance, and intrinsic safety. By changing the vortex mode of different topological charges, introducing multiple hollow Bragg fiber sensing segments, or combining optical time-domain / frequency-domain reflection technology, it can be flexibly expanded into a quasi-distributed or distributed vector stress sensing network to meet the needs of multi-point or long-distance monitoring.

[0015] In summary, this invention utilizes the anisotropic response of the helical phase wavefront of a vortex beam to the stress direction to achieve vector stress sensing in a hollow Bragg fiber, offering advantages such as compact structure, high sensitivity, and the ability to distinguish stress directions. Combined with a designed graphical user interface, the optimal coupling position can be predicted in advance through simulation calculations, significantly improving the system's coupling efficiency and repeatability. Attached Figure Description

[0016] Figure 1 This is a block diagram of the sensor system. 8—Hollow-core Bragg fiber; A—Light source modulation module, 1—Laser, 2—Fiber polarization controller, 3—Fiber collimator, 4—Polarization beam splitter, 5—Spatial light modulator; B—Fiber optic coupling module, 6—Near-infrared microscope objective; 7—Fiber-coupled displacement stage; C—Stress sensing module, 9—Stress loading platform, 10—Charge-coupled device, 11—Computer.

[0017] Figure 2 This is a schematic diagram of the graphical user interface of this sensing system. In the diagram: A—Parameter configuration area, B—Multi-tab visualization area, C—Status bar area. Detailed Implementation

[0018] The following detailed description is provided in conjunction with the accompanying drawings and embodiments.

[0019] I. System 1. Overall like Figure 1 Hollow-core Bragg fiber 8 is installed in the object under test, and a light source modulation module A, an optical fiber coupling module B and a stress sensing module C are also installed. The light source modulation module A includes a laser 1, an optical fiber polarization controller 2, an optical fiber collimator 3, a polarization beam splitter 4, and a spatial light modulator 5 connected in sequence. The fiber optic coupling module B includes a near-infrared microscope objective 6 and a fiber optic coupling displacement stage 7 connected in sequence. The stress sensing module C includes a stress loading platform 9, a charge coupling element 10, and a computer 11 connected in sequence. The light source modulation module A, the fiber coupling module B, the hollow Bragg fiber 8, and the stress sensing module C are connected in sequence.

[0020] 2. Functional components 1) Laser 1 Laser 1 is a narrow linewidth tunable light source, consisting of an external cavity laser and a precision control system, which can ensure high stability of output wavelength and optical power.

[0021] This laser combines high output power with a high side-mode suppression ratio. Its core working principle is based on stimulated emission amplification. Particles in the working medium achieve population inversion under the excitation of the pump source. When spontaneous emission photons induce stimulated emission, photons with the same frequency, phase, polarization, and propagation direction as the incident photons are generated. Under the positive feedback of the optical resonator, they form continuous oscillations and finally output a fundamental Gaussian beam with high monochromaticity, high directionality, and high coherence. In this system, the 1550nm near-infrared light source generated by laser 1 provides the basis for the subsequent generation of a high-quality vortex beam at the spatial light modulator 5.

[0022] 2) Fiber polarization controller 2 The fiber polarization controller 2 consists of three rotatable fiber rings, which are equivalent to a quarter-wave plate, a half-wave plate, and a quarter-wave plate, respectively. By independently adjusting the angle of each ring, any input polarization state can be converted into the linear polarization state required by the spatial light modulator 5.

[0023] Its working principle is based on the stress birefringence effect of optical fiber: when the fiber ring is subjected to mechanical stress such as bending, the local refractive index distribution of the fiber core changes anisotropically, introducing a controllable phase delay, thereby achieving precise control of the polarization state of the transmitted beam.

[0024] 3) Fiber optic collimator 3 The fiber collimator 3 is used to collimate the diverging beam of the fiber output from the fiber polarization controller 2 into a spatially parallel beam and ensure a suitable spot size.

[0025] Its working principle is as follows: Based on the collimation characteristics of the lens, the end face of the optical fiber is placed at the focal plane of the collimating lens. The diverging spherical wave emitted from the optical fiber is refracted by the lens and output in the form of an approximately parallel plane wave. The collimated beam has a uniform wavefront and a moderate spot diameter, which can effectively match the effective working area of ​​the spatial light modulator 5, thereby improving the efficiency and uniformity of spatial light modulation.

[0026] 4) Polarizing beam splitter 4 It is made of two right-angled prisms bonded together, and the bonded surface is coated with a multi-layer dielectric polarization beam splitter film; the polarization beam splitter 4 is used to further purify the polarization state of the beam after it has been collimated by the fiber collimator 3.

[0027] The working principle is as follows: Based on the polarization-selective reflection and transmission characteristics of the thin film, when an unpolarized or partially polarized beam is incident on the beam splitter at a 45-degree angle, the S-polarized component is efficiently reflected, while the P-polarized component is efficiently transmitted. In this system, after the incident beam passes through the polarization beam splitter prism 4, only the P-polarized component is transmitted to the spatial light modulator 5. After being modulated and reflected by the spatial light modulator 5, the polarization state of the beam rotates, and the S-polarized component is reflected by the polarization beam splitter prism 4 to the output optical path, thereby achieving spatial separation of the incident light and the modulated output light and avoiding feedback interference.

[0028] 5) Spatial light modulator 5 Spatial light modulator 5 is a reflective liquid crystal spatial light modulator.

[0029] Its core principle is the electro-controlled birefringence effect of liquid crystals. During operation, the molecules in the liquid crystal layer undergo different degrees of orientation deflection according to the applied driving voltage, thereby changing the effective refractive index of the incident light polarization component in real time, achieving precise control of the phase delay of each pixel. After the computer-generated spiral phase hologram is loaded into this spatial light modulator, each pixel applies a corresponding phase modulation amount to the incident plane wave according to the gray value of the hologram, reshaping its wavefront into a spiral phase distribution. After reflection, the outgoing beam carries a preset orbital angular momentum, ultimately forming a vortex beam characterized by a central phase singularity and a ring-shaped intensity distribution.

[0030] 6) Near-infrared microscope objective 6 The near-infrared microscope objective 6 is used to focus and couple the vortex beam emitted from the spatial light modulator 5 to the hollow Bragg fiber 8. Its core principle is based on Fourier transform and mode-matching focusing of the lens. During operation, the vortex beam carrying orbital angular momentum is refracted by the 20x magnified near-infrared microscope objective 6 with a numerical aperture of 0.35, converging to form a focused spot at the focal plane that has a Fourier transform relationship with the incident light field. The beam waist diameter of the spot precisely matches the mode field diameter of the target transmission mode of the hollow Bragg fiber 8, maximizing the overlap integration efficiency between the spatial light field and the fiber's intrinsic modes. Through this mode-matching focusing method, the helical phase wavefront of the vortex beam is efficiently injected into the core of the hollow Bragg fiber 8, exciting the required orbital angular momentum mode with low loss.

[0031] 7) Fiber-coupled displacement stage The fiber optic coupling displacement stage 7 is used to hold the input end of the hollow Bragg fiber 8 and provides high-precision multi-dimensional spatial position adjustment.

[0032] Its core principle is precision mechanical transmission and closed-loop feedback positioning. During operation, the input end of the hollow Bragg fiber 8 is fixed in the fixture of the fiber coupling displacement stage 7. The displacement stage, driven by a piezoelectric ceramic driver or a high-precision stepper motor, uses a precision lead screw or flexible hinge mechanism to achieve translational adjustment in the X, Y, and Z axes, as well as angular attitude adjustment in the pitch, yaw, and rotation axes, thus forming a six-dimensional precision alignment capability. In actual operation, the operator manually adjusts the fiber coupling displacement stage 7 based on the optimal coupling coordinates predicted in advance by the graphical user interface of the system. This ensures that the focused vortex beam is precisely incident on the preset position of the hollow Bragg fiber 8 core, achieving spatial alignment with sub-micron precision, thereby ensuring efficient coupling and stable transmission of the vortex beam.

[0033] 8) Hollow-core Bragg fiber Hollow-core Bragg fiber 8 is used simultaneously as a transmission medium for vortex beams and a stress sensing probe. Its core principle is: high-fidelity mode transmission of hollow waveguide and stress-induced cross-sectional deformation modulation; during operation, the vortex beam carrying orbital angular momentum is transmitted with low loss in the air core of the hollow Bragg fiber 8, and its helical phase wavefront is stably maintained; when external stress is applied to the hollow Bragg fiber 8, the fiber cross-section undergoes asymmetric deformation, causing anisotropic changes in the geometry and refractive index distribution of the air core, which in turn applies direction-dependent phase perturbation to the transmitted vortex beam, causing the optical characteristics of the vortex beam, such as mode purity, dark nucleus position, and interference pattern, to change in a one-to-one correspondence with the magnitude and direction of stress; through this stress-induced mode modulation method, the measured vector stress information is directly encoded in the orbital angular momentum characteristics of the vortex beam, providing a physical basis for subsequent feature extraction and vector calculation by the computer 11.

[0034] 9) Stress loading platform 9 The stress loading platform 9 is used to apply controllable vector stress to the hollow Bragg fiber 8, serving as an excitation source to simulate external mechanical forces. Its core function is to apply adjustable transverse or axial stress to a specific region of the hollow Bragg fiber 8, causing asymmetric deformation of the fiber cross-section. The stress loading platform 8 consists of a precision displacement stage, a force sensor, and fiber clamps. It applies a preset stress vector to the hollow Bragg fiber 8 by applying weights. During operation, the external stress causes anisotropic changes in the cross-sectional shape and refractive index distribution of the air core of the hollow Bragg fiber 8, thereby applying a helical phase perturbation to the propagating vortex beam. The measured stress information is encoded in the beam's orbital angular momentum characteristics, providing a physical basis for subsequent vector calculations.

[0035] 10) Charge-coupled device 10 The charge-coupled device 10 is used to acquire in real time the intensity distribution image of the vortex beam emitted from the hollow Bragg fiber 8 after stress disturbance.

[0036] Its core principle is based on the photoelectric effect and charge-coupled transport mechanism. The pixel array on the detector surface converts incident photons into charge packets, which are then read out sequentially by vertical and horizontal shift registers to form a digital image signal. In this system, the charge-coupled element 10 is placed after the output end of the hollow Bragg fiber 8 to capture in real time the changes in optical characteristics of the vortex beam caused by stress, such as dark nucleus shift, spot distortion, and mode coupling. It also transmits high-resolution light intensity distribution data to the computer 11, providing raw image data for subsequent feature extraction and vector calculation.

[0037] 11) Computer Science Computer 11, as the core of the system's control and data processing, undertakes three functions: signal processing, interface interaction, and system control. In signal processing, computer 11 receives the light spot intensity distribution image acquired by charge-coupled device 10, runs image processing algorithms to extract optical characteristic parameters such as dark kernel offset vector, topological charge component purity, and interference pattern rotation angle, and, based on a pre-calibrated sensing model, derives the magnitude and direction of stress from these parameters, achieving quantitative output of vector stress information. Regarding interface interaction, computer 11 is equipped with a graphical user interface, providing predictive alignment based on simulation calculations during the coupling phase and visual display and data recording functions for stress monitoring results during the sensing phase. In system control, the computer is responsible for loading the spiral phase hologram onto the spatial light modulator 5 and coordinating the timing and parameter settings of each module to ensure stable system operation.

[0038] 3. Graphical User Interface like Figure 2 This user interface includes a parameter configuration area A, a multi-tab visualization area B, and a status bar area C.

[0039] 1) Parameter configuration area A The parameter configuration area A, located on the left side of the interface, is used to input and adjust the physical parameters required for the simulation. The vortex beam parameter setting area includes numerical input controls for wavelength, beam waist radius, topological charge (l), radial index (p), and input power; the objective / lens system parameter setting area includes numerical input controls for equivalent focal length, numerical aperture (NA), medium refractive index, objective-to-beam waist distance, and fiber-to-objective distance; the fiber parameter setting area includes fiber type selection controls (supporting single-mode fiber and hollow-core Bragg fiber, etc.), and dynamically displays the corresponding mode field diameter (MFD) or hollow-core radius input controls according to the selected type; the simulation control area includes function buttons for "Start Simulation Calculation," "Optimize Coupling Efficiency," "Export Data," and "Save Image." The real-time results display area includes a multi-line text box for displaying detailed text results, and a progress bar control for visually displaying the current coupling efficiency percentage.

[0040] 2) Multi-tab visualization area B The multi-tab visualization area B is located on the right side of the interface, allowing users to switch between tabs to display simulation results from different dimensions. The "Optical Field Distribution" tab displays the intensity distribution of the optical field in front of the objective lens, the phase distribution of the optical field in front of the objective lens, the intensity distribution of the optical field at the fiber end face (with a superimposed fiber core outline), and the phase distribution of the optical field at the fiber end face (with a superimposed fiber core outline) using a 2x2 grid layout. The "Fiber Coupling Analysis" tab displays the intensity distribution of the fiber fundamental mode (with a superimposed core boundary), the overlap integral intensity distribution, a comparison curve of the one-dimensional normalized intensity profile of the incident light field and the fiber fundamental mode, and a histogram comparing the total incident power, core power, and coupling power. The "System Schematic" tab displays a schematic diagram of the propagation path of the vortex beam from the source end to the fiber end face, including the beam envelope, beam waist position marker, objective lens position and parameter labels, focal point position marker, and fiber end face position and parameter labels, dynamically displaying the current coupling efficiency value in the graph.

[0041] 3) Status bar area C The status bar area is located at the bottom of the interface and is used to display the current status information of the system (such as "Ready" or "Simulation Calculation Completed") and operation feedback messages.

[0042] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A vortex optical vector stress sensing system based on hollow-core Bragg fiber, characterized in that: Hollow-core Bragg fiber (8) is installed in the object under test, and a light source modulation module (A), an optical fiber coupling module (B) and a stress sensing module (C) are also installed. The light source modulation module (A) includes a laser (1), an optical fiber polarization controller (2), an optical fiber collimator (3), a polarization beam splitter (4), and a spatial light modulator (5) connected in sequence. The fiber optic coupling module (B) includes a near-infrared microscope objective (6) and a fiber optic coupling displacement stage (7) connected in sequence. The stress sensing module (C) includes a stress loading platform (9), a charge coupling element (10), and a computer (11) connected in sequence. The light source modulation module (A), the fiber coupling module (B), the hollow Bragg fiber (8), and the stress sensing module (C) are connected in sequence.

2. The detection method of the vortex vector stress sensing system based on hollow-core Bragg fiber according to claim 1, characterized in that: ① After the laser (1) in the light source modulation module (A) outputs a laser with a wavelength of 1550nm and a power of 25dBm, the fiber polarization controller (2) adjusts the polarization state of the light at the output end of the fiber. After the divergence angle is adjusted by the fiber collimator (3), the diverging beam output by the fiber is collimated into a spatial parallel beam. The polarization state of the light is further adjusted by the polarization beam splitter (4), and then incident on the spatial light modulator (5) loaded with a specific phase distribution, outputting vortex light with orbital angular momentum characteristics. ②The vortex beam output by the spatial light modulator (5) is focused by the 20x near-infrared microscope objective (6) and then efficiently coupled into the hollow Bragg fiber (8) for transmission under the precise adjustment of the six-dimensional fiber coupling displacement stage (7). Before the coupling operation, the operator inputs the vortex beam parameters, objective parameters and fiber parameters through the graphical user interface configured on the computer. The interface performs simulation calculations and predicts the best coupling position in advance. The operator manually adjusts the fiber coupling displacement stage (7) according to the predicted coordinates to complete the alignment. Hollow-core Bragg fiber (8) is highly sensitive to changes in external stress. External stress causes deformation of the fiber cross section, which leads to changes in the refractive index distribution in the fiber core, thereby generating detectable modulation of the phase and mode characteristics of the transmitted vortex beam, thus realizing stress sensing. ③ After the hollow Bragg fiber (8) is subjected to stress by the stress loading platform, the output vortex beam is captured by the charge coupling element (10) to obtain the light intensity distribution image. The captured light spot intensity pattern is transmitted to the computer (11) for calculation. Based on the topological charge change and light intensity distribution characteristics, the magnitude and direction of the stress at this time are inverted, and the monitoring results are displayed in real time.

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