Optical fiber shape sensing method, system, and electronic device

Abstract

The application discloses an optical fiber shape sensing method, system and electronic equipment, relates to the technical field of optical fiber shape sensing, and divides a bound section of an optical fiber shape sensor through a clamp holder, respectively collects a reference spectrum and a measurement spectrum, and calculates an initial strain distribution, forces the curvature of the bound section to be zero after solving the curvature and the orthogonal curvature component, and reconstructs a three-dimensional shape curve based on the curvature distribution data after zeroing by using a relative parallel frame. The scheme no longer performs direction vector recursive iteration on the bound section, reduces the effective sensing length participating in the integral operation, reduces the accumulation number of strain, curvature and numerical integral three types of errors from the source, suppresses the tip positioning cumulative error under long distance measurement, only increases the processing step after the curvature zeroing, improves the three-dimensional shape reconstruction accuracy, completely adapts to the optical fiber shape sensor with at least three cores, and the output three-dimensional shape curve can accurately restore the three-dimensional appearance of the optical fiber to be measured.

Description

Technical Field

[0001] This application relates to the field of fiber optic shape sensing technology, and in particular to a fiber optic shape sensing method, system and electronic device. Background Technology

[0002] With the increasing demand for structural health monitoring in large-scale infrastructure projects (such as long-span bridges, high dams, offshore wind turbine blades, and aircraft wings), distributed fiber optic shape sensing technology has gradually become an important technical means for monitoring deformation of large-size structures due to its advantages such as resistance to electromagnetic interference, corrosion resistance, and embedding within structures. Fiber optic shape sensing technology based on optical frequency domain reflectometers can continuously measure strain distribution along the sensing fiber and reconstruct the two-dimensional or three-dimensional deformation state of the structure through curve reconstruction algorithms. It has broad application prospects in fields such as bridge deflection monitoring, wind turbine blade bending detection, and aircraft wing deformation measurement.

[0003] However, in long-distance (typically several meters to tens of meters) and large-scale structure shape monitoring scenarios, existing fiber optic shape sensors face a significant technical bottleneck—accumulated error. Currently widely used unit orthogonal frame curve reconstruction algorithms are all recursive integral type, meaning the position of the next spatial point depends on the position and direction vector of the previous point. This implies that strain measurement error, curvature calculation error, and numerical integration error accumulate point by point as the sensing length increases. For long-distance applications such as bridge structure monitoring (sensing length often exceeds 10 meters), even if the single-point strain measurement accuracy reaches the micro-strain level, the accumulated tip position error can still reach decimeter or even meter levels, failing to meet the engineering requirements for deformation monitoring accuracy.

[0004] To reduce accumulated errors, existing technologies mainly focus on two aspects: first, improving strain measurement accuracy, such as employing high signal-to-noise ratio optical path design, laser frequency modulation nonlinear correction, and phase noise compensation; second, improving reconstruction algorithms to avoid torsion calculation errors or reduce local truncation errors. However, none of these methods can fundamentally reduce the number of recursive steps, and the accumulated error still increases with the sensing length. While shape reconstruction methods based on neural networks, which have emerged in recent years, avoid recursive integration, they require a large amount of training data and have limited generalization ability. Summary of the Invention

[0005] This application provides a fiber optic shape sensing method, system, and electronic device to at least solve the problem that fiber optic shape sensors in the related art cannot effectively reduce accumulated errors.

[0006] This application provides an optical fiber shape sensing method, including:

[0007] An optical path for an optical frequency domain reflectometer shape sensing system is constructed, including an optical fiber shape sensor; the optical fiber shape sensor has at least three fiber cores;

[0008] Several clamps are assembled at specified sensing length coordinate positions along the axial direction of the shape sensor. The restraint section of the fiber optic shape sensor with the clamps is extended to the strain-free reference state. The restraint section is marked on the axial coordinate of the fiber optic shape sensor, and the beat signal of each fiber core in the fiber optic shape sensor under the reference state is collected to obtain the reference spectrum.

[0009] The fiber optic shape sensor with the clamp is bent to the three-dimensional shape to be measured, and the beat signal of each fiber core in the fiber optic shape sensor is collected in the measurement state to obtain the measurement spectrum;

[0010] For each fiber core, a sliding rectangular window is used to perform cross-correlation calculations between the reference spectrum and the measured spectrum to obtain the initial strain distribution along the sensing length;

[0011] Using the strain data of the three fiber cores, the curvature and orthogonal curvature components along the sensing length of each sensing point are calculated based on the relationship between fiber bending strain and curvature. The curvature and orthogonal curvature components of the bound section are then forcibly set to zero to obtain the curvature distribution data after zeroing.

[0012] Based on the zeroed curvature distribution data, shape reconstruction is performed using a relative parallel frame. The three-dimensional coordinates of each sensor point obtained from the reconstruction are connected to form a three-dimensional shape curve, and the three-dimensional shape curve is output.

[0013] Furthermore, marking the confinement segment on the axial coordinate of the fiber optic shape sensor includes:

[0014] Obtain the starting and ending coordinates of each gripper on the sensing length axis, and determine the coordinate area of ​​the restraint segment corresponding to each gripper based on the starting and ending coordinates of each gripper.

[0015] The coordinate region of the confinement segment is marked on the axial coordinate of the fiber optic shape sensor to generate coordinate calibration information of the confinement segment.

[0016] Furthermore, the step of performing a cross-correlation operation between the reference spectrum and the measured spectrum to obtain the initial strain distribution along the sensing length includes:

[0017] The spectral offset of each sensing point is obtained by performing cross-correlation calculation between the reference spectrum and the measured spectrum at the same axial sensing position.

[0018] The spectral offset is converted into strain data to generate an initial strain distribution that is continuously distributed along the sensing length.

[0019] Furthermore, by utilizing the strain data of the three fiber cores and based on the relationship between fiber bending strain and curvature, the curvature and orthogonal curvature components along the sensing length at each sensing point are calculated, including:

[0020] The curvature and orthogonal curvature components along the sensing length of each sensing point are obtained from the solution, and their expressions are as follows:

[0021] ;

[0022] ;

[0023] In the formula, s is the axial position coordinate of the optical fiber shape sensor, and position s represents the position of the sensing point. Let represent the strain of the i-th fiber core at position s, M represent the total number of fiber cores used to solve for the curvature, d be the center-to-center distance of each fiber core on the cross-section of the fiber shape sensor, and α be the strain of the i-th fiber core at position s. i α represents the fixed polar angle of the i-th fiber core on the cross-section of the optical fiber shape sensor. i (s) represents the fixed polar angle of the i-th fiber core at position s on the cross section, θ b (s) represents the polar angle of the overall bending direction of the optical fiber at position s. and Let represent the orthogonal curvature components in two orthogonal directions at position s, respectively. This represents the curvature along the sensing length at position s.

[0024] Furthermore, the step of reconstructing the shape using a relative parallel frame based on the zeroed curvature distribution data, connecting the reconstructed three-dimensional coordinates of each sensing point into a three-dimensional shape curve, and outputting the three-dimensional shape curve includes:

[0025] The tangent vector of the sensing point The initial value is set to (1,0,0), based on the polar angle θ of the overall bending direction of the optical fiber at position s. b (s) Initialize a pair of orthogonal normal vectors at position s that satisfy the condition of relative parallelism. and ;

[0026] The orthogonal curvature components of each sensing point at position s after the curvature distribution data is zeroed are read sequentially along the sensing length. and ;

[0027] Using the zeroed-out orthogonal curvature components and the initial direction vector, the tangent vector of each sensing point is calculated iteratively point by point. Orthogonal normal vector and The spatial coordinates are solved by integration, and the spatial coordinates of all sensor points are summarized to obtain the set of three-dimensional coordinates of all sensor points.

[0028] The three-dimensional coordinates of each sensor point are obtained by shape reconstruction using a relative parallel frame based on the set of three-dimensional coordinates of all sensor points. The expression for the three-dimensional coordinates of the sensor point at position s obtained by shape reconstruction is as follows: ;

[0029] The reconstructed three-dimensional coordinates of each sensing point are sequentially stitched together along the sensing length to form a three-dimensional shape curve, and the three-dimensional shape curve is output.

[0030] This application also provides an optical fiber shape sensing system, including:

[0031] The optical path of the optical frequency domain reflectometer shape sensing system includes an optical fiber shape sensor; the optical fiber shape sensor has at least three fiber cores;

[0032] Several grippers are assembled to a sensing length coordinate position along the axial direction of the shape sensor;

[0033] The data processing unit is used to mark the restraint section of the optical fiber shape sensor on the axial coordinate of the optical fiber shape sensor, and to acquire the beat signal of each fiber core in the optical fiber shape sensor in the reference state to obtain the reference spectrum, and to acquire the beat signal of each fiber core in the optical fiber shape sensor in the measurement state to obtain the measurement spectrum. For each fiber core, a sliding rectangular window is used to perform cross-correlation calculations between the reference spectrum and the measurement spectrum to obtain the initial strain distribution along the sensing length. Using the strain data of the three fiber cores, the curvature and orthogonal curvature components of each sensing point position along the sensing length are solved according to the relationship between optical fiber bending strain and curvature. The curvature and orthogonal curvature components of the restraint section are forcibly set to zero to obtain the zeroed curvature distribution data. The shape is reconstructed using a relative parallel frame based on the zeroed curvature distribution data. The three-dimensional coordinates of each sensing point obtained by reconstruction are connected to form a three-dimensional shape curve, and the three-dimensional shape curve is output.

[0034] Furthermore, the optical path of the optical frequency domain reflectometer shape sensing system includes a tunable laser, coupler one, coupler two, coupler three, coupler four, coupler five, coupler six, coupler seven, coupler eight, coupler nine, coupler ten, circulator one, circulator two, circulator three, balanced detector one, balanced detector two, balanced detector three, balanced detector four, auxiliary interferometer, measuring interferometer, and fiber optic shape sensor.

[0035] The tunable laser outputs a linear frequency sweep optical signal, which is input to coupler one for beam splitting; coupler one splits into two beams, the first beam is connected to the auxiliary interferometer to correct the frequency modulation nonlinearity of the tunable laser, and the second beam is input to coupler two.

[0036] The output light from coupler two is sent to the measurement interferometer, which further splits the incident light to form a local oscillator optical path and a measurement optical path; the local oscillator optical path is connected to coupler three and coupler eight respectively; the output light from the measurement optical path is sequentially sent to coupler four and coupler five;

[0037] The output light of the coupler five is connected to the circulator one. The output end of the circulator one is connected to the fiber shape sensor. The backscattered Rayleigh light reflected by the fiber shape sensor is transmitted back to the coupler three via the circulator one. The coupler three combines the returned light with the local oscillator light output by the measuring interferometer and then connects it to the balanced detector one to complete the photoelectric conversion.

[0038] The output light of the coupler four is connected to the circulator two, the output light of the circulator two is connected to the fiber optic shape sensor, the reflected light of the fiber optic shape sensor is transmitted back to the coupler eight via the circulator two, and the coupler eight combines the reflected light with the local oscillator light and then connects it to the balanced detector two to complete the photoelectric conversion.

[0039] Coupler six is ​​connected in series with the optical path of circulator three. The output light of circulator three is connected to the optical fiber shape sensor. The optical fiber shape sensor reflects the light back and transmits it back to coupler nine through circulator three. Coupler nine combines the light and connects it to the balanced detector three. Coupler seven and coupler ten cooperate with the multi-core optical path of the optical fiber shape sensor to complete the beam splitting and beam combining. The combined light is connected to the balanced detector four.

[0040] The interference electrical signals output by the first, second, third, and fourth balance detectors are transmitted to the data processing unit for calculating the beat signals corresponding to each fiber core.

[0041] Furthermore, the optical path of the optical frequency domain reflectometer shape sensing system further includes:

[0042] The first-in-first-out connector has its input end connected to the circulator one, the circulator two, and the circulator three, and its output end connected to the fiber optic shape sensor.

[0043] Furthermore, the clamp includes a first clamping plate and a second clamping plate arranged symmetrically. The first clamping plate and the second clamping plate have screw holes on both sides and are locked by fasteners. The first clamping plate and the second clamping plate have a straight clamping hole in the middle. The inner diameter of the straight clamping hole is 0.1~0.2mm larger than the outer diameter of the fiber optic shape sensor.

[0044] This application also provides an electronic device, including:

[0045] Memory, used to store computer programs;

[0046] A processor, used to execute computer programs, implements the following steps:

[0047] Mark the restraint section of the optical fiber shape sensor with the clamp mounted on the optical fiber shape sensor on the axial coordinate, and collect the beat signal of each fiber core in the optical fiber shape sensor under the reference state to obtain the reference spectrum.

[0048] The fiber optic shape sensor with the clamp is bent to the three-dimensional shape to be measured, and the beat signal of each fiber core in the fiber optic shape sensor is collected in the measurement state to obtain the measurement spectrum;

[0049] For each fiber core, a sliding rectangular window is used to perform cross-correlation calculations between the reference spectrum and the measured spectrum to obtain the initial strain distribution along the sensing length;

[0050] Using the strain data of the three fiber cores, the curvature and orthogonal curvature components along the sensing length of each sensing point are calculated based on the relationship between fiber bending strain and curvature. The curvature and orthogonal curvature components of the bound section are then forcibly set to zero to obtain the curvature distribution data after zeroing.

[0051] Based on the zeroed curvature distribution data, shape reconstruction is performed using a relative parallel frame. The three-dimensional coordinates of each sensor point obtained from the reconstruction are connected to form a three-dimensional shape curve, and the three-dimensional shape curve is output.

[0052] This application utilizes a clamp to divide the constrained section of an optical fiber shape sensor. Reference and measurement spectra are collected separately, and the initial strain distribution is calculated. After solving for the curvature and orthogonal curvature components, the curvature of the constrained section is forcibly set to zero. Then, based on the zeroed curvature distribution data, a three-dimensional shape curve is reconstructed using a relatively parallel frame. This scheme eliminates the need for recursive direction vector iteration in the constrained section, reducing the effective sensing length involved in integration calculations. This reduces the accumulation of strain, curvature, and numerical integration errors from the source, suppressing the cumulative error in tip positioning during long-distance measurements. This method requires no modification to the optical path and original strain demodulation logic of the optical frequency domain reflectometer shape sensing system. Only a curvature zeroing post-processing step is added to improve the accuracy of three-dimensional shape reconstruction. It is fully compatible with optical fiber shape sensors with at least three fiber cores, and the output three-dimensional shape curve accurately restores the three-dimensional morphology of the optical fiber under test. Attached Figure Description

[0053] To more clearly illustrate the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0054] Figure 1 This is a structural block diagram of an optical fiber shape sensing system in one embodiment of this application;

[0055] Figure 2 This is a flowchart illustrating an embodiment of the fiber optic shape sensing method in this application.

[0056] Figure 3 This is a schematic cross-sectional view of a clamp mounted on an optical fiber shape sensor in one embodiment of this application;

[0057] Figure 4 This is a schematic diagram of the curvature distribution of the fiber optic shape sensor not set to zero in one embodiment of this application;

[0058] Figure 5 This is a schematic diagram showing the calculation results of the three direction vectors after the curvature is set to zero in one embodiment of this application;

[0059] Figure 6 This is a schematic diagram of the shape of a three-dimensional shape curve output in one embodiment of this application;

[0060] Figure 7 This is an internal structural diagram of a computer device in one embodiment of this application. Detailed Implementation

[0061] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this application.

[0062] It should be noted that, in the description of this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. The terms "first," "second," etc., in this application are used to distinguish similar objects and are not used to describe a specific order or sequence.

[0063] To enable those skilled in the art to better understand the present application, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0064] The fiber optic shape sensing method provided in this application can be applied to, for example... Figure 1The diagram shows the optical path for constructing an optical frequency domain reflectometer (OFDR) shape sensing system. This optical path includes a tunable laser, a coupler, an auxiliary interferometer, a measuring interferometer, a circulator, a balanced detector, and an optical fiber shape sensor.

[0065] like Figure 2 As shown, an embodiment of this application provides an optical fiber shape sensing method, including the following steps:

[0066] Step S1: Construct the optical path of the optical frequency domain reflectometer shape sensing system, including an optical fiber shape sensor; the optical fiber shape sensor has at least three fiber cores;

[0067] Step S2: Assemble several clamps at the specified sensing length coordinate position along the axial direction of the shape sensor, extend the restrained section of the fiber shape sensor with the clamps attached to it to the strain-free reference state, mark the restrained section on the axial coordinate of the fiber shape sensor, and collect the beat signal of each fiber core in the fiber shape sensor under the reference state to obtain the reference spectrum.

[0068] Step S3: Bend the fiber shape sensor with the clamp to the three-dimensional shape to be measured, and collect the beat signal of each fiber core in the fiber shape sensor under the measurement state to obtain the measurement spectrum;

[0069] Step S4: For each fiber core, a sliding rectangular window is used to perform cross-correlation calculations between the reference spectrum and the measured spectrum to obtain the initial strain distribution along the sensing length;

[0070] Step S5: Using the strain data of the three fiber cores, based on the relationship between fiber bending strain and curvature, the curvature and orthogonal curvature components along the sensing length of each sensing point are calculated, and the curvature and orthogonal curvature components of the bound section are forcibly set to zero to obtain the curvature distribution data after zeroing.

[0071] Step S6: Based on the zeroed curvature distribution data, shape reconstruction is performed using a relatively parallel (Bishop) frame. The three-dimensional coordinates of each sensor point obtained by reconstruction are connected into a three-dimensional shape curve, and the three-dimensional shape curve is output.

[0072] This method involves dividing the fiber optic shape sensor into a confined section using a clamp, acquiring reference and measurement spectra separately, calculating the initial strain distribution, solving for curvature and orthogonal curvature components, and then forcibly zeroing the curvature of the confined section. Based on the zeroed curvature distribution data, a three-dimensional shape curve is reconstructed using a relatively parallel frame. This approach eliminates the need for recursive direction vector iteration in the confined section, reducing the effective sensing length involved in integration calculations and minimizing the accumulation of strain, curvature, and numerical integration errors at the source, thus suppressing accumulated tip positioning errors during long-distance measurements. This method requires no modification to the optical path of the optical frequency domain reflectometer shape sensing system or the existing strain demodulation logic; simply adding a curvature zeroing post-processing step improves the accuracy of three-dimensional shape reconstruction. It is fully compatible with fiber optic shape sensors with at least three fiber cores, and the output three-dimensional shape curve accurately reproduces the three-dimensional morphology of the fiber being measured.

[0073] like Figure 3 As shown, Figure 3 A schematic diagram of the cross-sectional structure for mounting the clamp on the optical fiber shape sensor.

[0074] In this embodiment, marking the confinement segment on the axial coordinate of the optical fiber shape sensor includes:

[0075] Obtain the starting and ending coordinates of each gripper on the sensing length axis, and determine the coordinate area of ​​the restraint segment corresponding to each gripper based on the starting and ending coordinates of each gripper.

[0076] The coordinate region of the confinement segment is marked on the axial coordinate of the fiber optic shape sensor to generate coordinate calibration information of the confinement segment.

[0077] In this embodiment, the step of obtaining the initial strain distribution along the sensing length by performing a cross-correlation operation between the reference spectrum and the measured spectrum includes:

[0078] The spectral offset of each sensing point is obtained by performing cross-correlation calculation between the reference spectrum and the measured spectrum at the same axial sensing position.

[0079] The spectral offset is converted into strain data to generate an initial strain distribution that is continuously distributed along the sensing length.

[0080] In this embodiment, the step of using the strain data of the three fiber cores to solve for the curvature and orthogonal curvature components along the sensing length at each sensing point position based on the relationship between fiber bending strain and curvature includes:

[0081] The curvature and orthogonal curvature components along the sensing length of each sensing point are obtained from the solution, and their expressions are as follows:

[0082] ;

[0083] ;

[0084] In the formula, s is the axial position coordinate of the optical fiber shape sensor, and position s represents the position of the sensing point. Let represent the strain of the i-th fiber core at position s, M represent the total number of fiber cores used to solve for the curvature, d be the center-to-center distance of each fiber core on the cross-section of the fiber shape sensor, and α be the strain of the i-th fiber core at position s. i α represents the fixed polar angle of the i-th fiber core on the cross-section of the optical fiber shape sensor. i (s) represents the fixed polar angle of the i-th fiber core at position s on the cross section, θ b (s) represents the polar angle of the overall bending direction of the optical fiber at position s. and Let represent the orthogonal curvature components in two orthogonal directions at position s, respectively. This represents the curvature along the sensing length at position s.

[0085] θ b (s)=arctan( / ).

[0086] In this embodiment, the step of reconstructing the shape using a relative parallel frame based on the zeroed curvature distribution data, connecting the reconstructed three-dimensional coordinates of each sensing point into a three-dimensional shape curve, and outputting the three-dimensional shape curve includes:

[0087] The tangent vector of the sensing point The initial value is set to (1,0,0), based on the polar angle θ of the overall bending direction of the optical fiber at position s. b (s) Initialize a pair of orthogonal normal vectors at position s that satisfy the condition of relative parallelism. and ;

[0088] The orthogonal curvature components of each sensing point at position s after the curvature distribution data is zeroed are read sequentially along the sensing length. and ;

[0089] Using the zeroed-out orthogonal curvature components and the initial direction vector, the tangent vector of each sensing point is calculated iteratively point by point. Orthogonal normal vector and The spatial coordinates are solved by integration, and the spatial coordinates of all sensor points are summarized to obtain the set of three-dimensional coordinates of all sensor points.

[0090] The three-dimensional coordinates of each sensor point are obtained by shape reconstruction using a relative parallel frame based on the set of three-dimensional coordinates of all sensor points. The expression for the three-dimensional coordinates of the sensor point at position s obtained by shape reconstruction is as follows: ;

[0091] The reconstructed three-dimensional coordinates of each sensing point are sequentially stitched together along the sensing length to form a three-dimensional shape curve, and the three-dimensional shape curve is output.

[0092] Specifically, the curvature and orthogonal curvature components of the constrained section are forcibly set to zero. When obtaining the zero-set curvature distribution data, the constrained section can be determined based on the recorded gripper position coordinates. Locating the sensing area corresponding to each gripper in the curvature distribution data defines the constrained section. The curvature and orthogonal curvature components of the constrained section are then forcibly modified to 0. The curvature of the area not held by the gripper remains unchanged. The curvature of the fiber optic shape sensor, which is not zeroed, is as follows: Figure 4 As shown.

[0093] For regions where curvature is zero, the direction vector remains unchanged during the recursive calculation, and this part does not introduce accumulated error. The curve extends along the direction of the last tangent vector before entering this region. The actual sensing length involved in the recursive calculation is equal to the total length minus the sum of the lengths of all bound segments. At position s=1, the results of the three direction vectors after setting the curvature to zero during the calculation are as follows: Figure 5 As shown.

[0094] The shape of the output three-dimensional shape curve is as follows Figure 6 As shown.

[0095] In the aforementioned fiber optic shape sensing method, a clamp is used to divide the constrained section of the fiber optic shape sensor. Reference and measurement spectra are collected and the initial strain distribution is calculated. After solving for the curvature and orthogonal curvature components, the curvature of the constrained section is forcibly set to zero. Then, based on the zeroed curvature distribution data, a three-dimensional shape curve is reconstructed using a relatively parallel frame. This scheme eliminates the need for recursive direction vector iteration in the constrained section, reducing the effective sensing length involved in integration calculations. This reduces the accumulation of strain, curvature, and numerical integration errors from the source, suppressing the cumulative error in tip positioning under long-distance measurements. This method does not require modification to the optical path and original strain demodulation logic of the optical frequency domain reflectometer shape sensing system. Only a curvature zeroing post-processing step is added to improve the accuracy of three-dimensional shape reconstruction. It is fully compatible with fiber optic shape sensors with at least three fiber cores, and the output three-dimensional shape curve can accurately restore the three-dimensional morphology of the fiber under test.

[0096] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods according to the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method.

[0097] In one embodiment, such as Figure 1 As shown, this application also provides an optical fiber shape sensing system, including:

[0098] The optical path of the optical frequency domain reflectometer shape sensing system includes an optical fiber shape sensor; the optical fiber shape sensor has at least three fiber cores;

[0099] Several grippers are assembled to a sensing length coordinate position along the axial direction of the shape sensor;

[0100] The data processing unit is used to mark the restraint section of the optical fiber shape sensor on the axial coordinate of the optical fiber shape sensor, and to acquire the beat signal of each fiber core in the optical fiber shape sensor in the reference state to obtain the reference spectrum, and to acquire the beat signal of each fiber core in the optical fiber shape sensor in the measurement state to obtain the measurement spectrum. For each fiber core, a sliding rectangular window is used to perform cross-correlation calculations between the reference spectrum and the measurement spectrum to obtain the initial strain distribution along the sensing length. Using the strain data of the three fiber cores, the curvature and orthogonal curvature components of each sensing point position along the sensing length are solved according to the relationship between optical fiber bending strain and curvature. The curvature and orthogonal curvature components of the restraint section are forcibly set to zero to obtain the zeroed curvature distribution data. The shape is reconstructed using a relative parallel frame based on the zeroed curvature distribution data. The three-dimensional coordinates of each sensing point obtained by reconstruction are connected to form a three-dimensional shape curve, and the three-dimensional shape curve is output.

[0101] In this embodiment, the optical path of the optical frequency domain reflectometer shape sensing system includes a tunable laser, coupler one, coupler two, coupler three, coupler four, coupler five, coupler six, coupler seven, coupler eight, coupler nine, coupler ten, circulator one, circulator two, circulator three, balanced detector one, balanced detector two, balanced detector three, balanced detector four, auxiliary interferometer, measuring interferometer, and fiber optic shape sensor.

[0102] The tunable laser outputs a linear frequency sweep optical signal, which is input to coupler one for beam splitting; coupler one splits into two beams, the first beam is connected to the auxiliary interferometer to correct the frequency modulation nonlinearity of the tunable laser, and the second beam is input to coupler two.

[0103] The output light from coupler two is sent to the measurement interferometer, which further splits the incident light to form a local oscillator optical path and a measurement optical path; the local oscillator optical path is connected to coupler three and coupler eight respectively; the output light from the measurement optical path is sequentially sent to coupler four and coupler five;

[0104] The output light of the coupler five is connected to the circulator one. The output end of the circulator one is connected to the fiber shape sensor. The backscattered Rayleigh light reflected by the fiber shape sensor is transmitted back to the coupler three via the circulator one. The coupler three combines the returned light with the local oscillator light output by the measuring interferometer and then connects it to the balanced detector one to complete the photoelectric conversion.

[0105] The output light of the coupler four is connected to the circulator two, the output light of the circulator two is connected to the fiber optic shape sensor, the reflected light of the fiber optic shape sensor is transmitted back to the coupler eight via the circulator two, and the coupler eight combines the reflected light with the local oscillator light and then connects it to the balanced detector two to complete the photoelectric conversion.

[0106] Coupler six is ​​connected in series with the optical path of circulator three. The output light of circulator three is connected to the optical fiber shape sensor. The optical fiber shape sensor reflects the light back and transmits it back to coupler nine through circulator three. Coupler nine combines the light and connects it to the balanced detector three. Coupler seven and coupler ten cooperate with the multi-core optical path of the optical fiber shape sensor to complete the beam splitting and beam combining. The combined light is connected to the balanced detector four.

[0107] The interference electrical signals output by the first, second, third, and fourth balance detectors are transmitted to the data processing unit for calculating the beat signals corresponding to each fiber core.

[0108] In this embodiment, the optical path of the optical frequency domain reflectometer shape sensing system further includes:

[0109] The first-in-first-out (FIFO) connector has its input end connected to the circulator one, the circulator two, and the circulator three, and its output end connected to the fiber optic shape sensor.

[0110] like Figure 3 As shown, in this embodiment, the clamp includes a symmetrically arranged first clamping plate 1 and a second clamping plate 2. Screw holes are pre-drilled on both sides of the first clamping plate 1 and the second clamping plate 2, and they are locked together by fasteners 3. A straight clamping hole 4 is provided in the middle of the first clamping plate 1 and the second clamping plate 2. The inner diameter of the straight clamping hole 4 is 0.1~0.2mm larger than the outer diameter of the fiber optic shape sensor. The length of the clamp is set to 10cm, and the symmetrically arranged first clamping plate 1 and second clamping plate 2 are fabricated using 3D printing. The fasteners 3 include screws, nuts, or clips.

[0111] The gripper has a simple structure and low cost, and can be rapidly prototyping using 3D printing. It features a detachable connection to the sensor, allowing for flexible installation without affecting the sensor's optical performance or mechanical integrity. The number, length, and installation spacing of the grippers can be adjusted to suit different measurement scenarios (such as different radii of curvatures and different sensing lengths), demonstrating excellent adaptability.

[0112] This application actively restrains a portion of the sensor using an external clamp, zeroing the curvature of the corresponding segment during data processing. This fundamentally reduces the actual sensing length involved in the recursive calculation, directly reducing accumulated errors compared to simply improving the algorithm or increasing measurement accuracy. Without altering the existing OFDR optical path or conventional strain demodulation algorithm, only adding a region zeroing operation in the post-processing curvature data stage, it is easily compatible with existing shape sensing systems, requiring no additional hardware investment or complex signal processing.

[0113] In the aforementioned fiber optic shape sensing device, a clamp divides the fiber optic shape sensor into a confined section. Reference and measurement spectra are collected and calculated to obtain the initial strain distribution. After solving for the curvature and orthogonal curvature components, the curvature of the confined section is forcibly set to zero. Then, based on the zeroed curvature distribution data, a three-dimensional shape curve is reconstructed using a relatively parallel frame. This scheme eliminates the need for recursive direction vector iteration in the confined section, reducing the effective sensing length involved in integration calculations. This reduces the accumulation of strain, curvature, and numerical integration errors from the source, suppressing the cumulative error in tip positioning during long-distance measurements. This method requires no modification to the optical path and original strain demodulation logic of the optical frequency domain reflectometer shape sensing system. Only a curvature zeroing post-processing step is added to improve the accuracy of the three-dimensional shape reconstruction. It is fully compatible with fiber optic shape sensors with at least three fiber cores, and the output three-dimensional shape curve accurately restores the three-dimensional morphology of the fiber under test.

[0114] For a description of the features in the embodiment corresponding to the fiber optic shape sensing device, please refer to the relevant description of the embodiment corresponding to the fiber optic shape sensing method, which will not be repeated here.

[0115] This application is not only applicable to fiber optic shape sensors, but can also be extended to other types of fiber optic shape sensors such as multi-core optical fibers and helical multi-core optical fibers. It is only necessary to design a corresponding clamp according to the outer diameter of the sensor.

[0116] Embodiments of this application also provide an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to perform the steps in any of the above embodiments of the fiber optic shape sensing method:

[0117] Mark the restraint section of the optical fiber shape sensor with the clamp mounted on the optical fiber shape sensor on the axial coordinate, and collect the beat signal of each fiber core in the optical fiber shape sensor under the reference state to obtain the reference spectrum.

[0118] The fiber optic shape sensor with the clamp is bent to the three-dimensional shape to be measured, and the beat signal of each fiber core in the fiber optic shape sensor is collected in the measurement state to obtain the measurement spectrum;

[0119] For each fiber core, a sliding rectangular window is used to perform cross-correlation calculations between the reference spectrum and the measured spectrum to obtain the initial strain distribution along the sensing length;

[0120] Using the strain data of the three fiber cores, the curvature and orthogonal curvature components along the sensing length of each sensing point are calculated based on the relationship between fiber bending strain and curvature. The curvature and orthogonal curvature components of the bound section are then forcibly set to zero to obtain the curvature distribution data after zeroing.

[0121] Based on the zeroed curvature distribution data, shape reconstruction is performed using a relative parallel frame. The three-dimensional coordinates of each sensor point obtained from the reconstruction are connected to form a three-dimensional shape curve, and the three-dimensional shape curve is output.

[0122] In one embodiment, the electronic device may be a server, and its internal structure diagram may be as follows: Figure 7 As shown, the electronic device includes a processor, memory, network interface, and database connected via a system bus. The processor provides computational and control capabilities. The memory includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores the operating system, computer programs, and database. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The database stores fiber optic shape sensing data. The network interface communicates with external terminals via a network connection. When the computer program is executed by the processor, it implements a fiber optic shape sensing method.

[0123] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0124] The foregoing has provided a detailed description of the fiber optic shape sensing method, system, and electronic device provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only intended to aid in understanding the methods, systems, and core ideas of this application. It should be noted that those skilled in the art can make various improvements and modifications to this application without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A fiber optic shape sensing method, characterized in that, include: An optical path for an optical frequency domain reflectometer shape sensing system is constructed, including an optical fiber shape sensor; the optical fiber shape sensor has at least three fiber cores; Several clamps are assembled at specified sensing length coordinate positions along the axial direction of the shape sensor. The restraint section of the fiber optic shape sensor with the clamps is extended to the strain-free reference state. The restraint section is marked on the axial coordinate of the fiber optic shape sensor, and the beat signal of each fiber core in the fiber optic shape sensor under the reference state is collected to obtain the reference spectrum. The fiber optic shape sensor with the clamp is bent to the three-dimensional shape to be measured, and the beat signal of each fiber core in the fiber optic shape sensor is collected in the measurement state to obtain the measurement spectrum; For each fiber core, a sliding rectangular window is used to perform cross-correlation calculations between the reference spectrum and the measured spectrum to obtain the initial strain distribution along the sensing length; Using the strain data of the three fiber cores, the curvature and orthogonal curvature components along the sensing length of each sensing point are calculated based on the relationship between fiber bending strain and curvature. The curvature and orthogonal curvature components of the bound section are then forcibly set to zero to obtain the curvature distribution data after zeroing. Based on the zeroed curvature distribution data, shape reconstruction is performed using a relative parallel frame. The three-dimensional coordinates of each sensor point obtained from the reconstruction are connected to form a three-dimensional shape curve, and the three-dimensional shape curve is output.

2. The fiber optic shape sensing method according to claim 1, characterized in that, Marking the confinement segment on the axial coordinate of the fiber optic shape sensor includes: Obtain the starting and ending coordinates of each gripper on the sensing length axis, and determine the coordinate area of ​​the restraint segment corresponding to each gripper based on the starting and ending coordinates of each gripper. The coordinate region of the confinement segment is marked on the axial coordinate of the fiber optic shape sensor to generate coordinate calibration information of the confinement segment.

3. The fiber optic shape sensing method according to claim 1, characterized in that, The step of obtaining the initial strain distribution along the sensing length by performing a cross-correlation operation between the reference spectrum and the measured spectrum includes: The spectral offset of each sensing point is obtained by performing cross-correlation calculation between the reference spectrum and the measured spectrum at the same axial sensing position. The spectral offset is converted into strain data to generate an initial strain distribution that is continuously distributed along the sensing length.

4. The fiber optic shape sensing method according to claim 1, characterized in that, The method utilizes strain data from three fiber cores to determine the curvature and orthogonal curvature components along the sensing length at each sensing point location based on the relationship between fiber bending strain and curvature. This includes: The curvature and orthogonal curvature components along the sensing length of each sensing point are obtained from the solution, and their expressions are as follows: ； ； In the formula, s is the axial position coordinate of the optical fiber shape sensor, and position s represents the position of the sensing point. Let represent the strain of the i-th fiber core at position s, M represent the total number of fiber cores used to solve for the curvature, d be the center-to-center distance of each fiber core on the cross-section of the fiber shape sensor, and α be the strain of the i-th fiber core at position s. i α represents the fixed polar angle of the i-th fiber core on the cross-section of the optical fiber shape sensor. i (s) represents the fixed polar angle of the i-th fiber core at position s on the cross section, θ b (s) represents the polar angle of the overall bending direction of the optical fiber at position s. and Let represent the orthogonal curvature components in two orthogonal directions at position s, respectively. This represents the curvature along the sensing length at position s.

5. The fiber optic shape sensing method according to claim 4, characterized in that, The step of reconstructing the shape using a relative parallel frame based on the zeroed curvature distribution data, connecting the three-dimensional coordinates of each sensor point obtained from the reconstruction into a three-dimensional shape curve, and outputting the three-dimensional shape curve includes: The tangent vector of the sensing point The initial value is set to (1,0,0), based on the polar angle θ of the overall bending direction of the optical fiber at position s. b (s) Initialize a pair of orthogonal normal vectors at position s that satisfy the condition of relative parallelism. and ; The orthogonal curvature components of each sensing point at position s after the curvature distribution data is zeroed are read sequentially along the sensing length. and ; Using the zeroed-out orthogonal curvature components and the initial direction vector, the tangent vector of each sensing point is calculated iteratively point by point. Orthogonal normal vector and The spatial coordinates are solved by integration, and the spatial coordinates of all sensor points are summarized to obtain the set of three-dimensional coordinates of all sensor points. The three-dimensional coordinates of each sensor point are obtained by shape reconstruction using a relative parallel frame based on the set of three-dimensional coordinates of all sensor points. The expression for the three-dimensional coordinates of the sensor point at position s obtained by shape reconstruction is as follows: ; The reconstructed three-dimensional coordinates of each sensing point are sequentially stitched together along the sensing length to form a three-dimensional shape curve, and the three-dimensional shape curve is output.

6. A fiber optic shape sensing system, characterized in that, include: The optical path of the optical frequency domain reflectometer shape sensing system includes an optical fiber shape sensor; the optical fiber shape sensor has at least three fiber cores; Several grippers are assembled to a sensing length coordinate position along the axial direction of the shape sensor; The data processing unit is used to mark the binding section of the clamp mounted on the optical fiber shape sensor on the axial coordinate of the optical fiber shape sensor, and to collect the beat signal of each fiber core in the optical fiber shape sensor in the reference state to obtain the reference spectrum, and to collect the beat signal of each fiber core in the optical fiber shape sensor in the measurement state to obtain the measurement spectrum. For each fiber core, a sliding rectangular window is used to perform cross-correlation calculations between the reference spectrum and the measured spectrum to obtain the initial strain distribution along the sensing length. Using the strain data of the three fiber cores, the curvature and orthogonal curvature components along the sensing length at each sensing point are calculated based on the relationship between fiber bending strain and curvature. The curvature and orthogonal curvature components of the bound section are then forcibly set to zero to obtain the zeroed curvature distribution data. Based on the zeroed curvature distribution data, a shape reconstruction is performed using a relative parallel frame. The reconstructed three-dimensional coordinates of each sensing point are connected to form a three-dimensional shape curve, which is then output as the three-dimensional shape curve.

7. The fiber optic shape sensing system according to claim 6, characterized in that, The optical path of the optical frequency domain reflectometer shape sensing system includes a tunable laser, coupler 1, coupler 2, coupler 3, coupler 4, coupler 5, coupler 6, coupler 7, coupler 8, coupler 9, coupler 10, circulator 1, circulator 2, circulator 3, balanced detector 1, balanced detector 2, balanced detector 3, balanced detector 4, auxiliary interferometer, measuring interferometer, and fiber optic shape sensor. The tunable laser outputs a linear frequency sweep optical signal, which is input to coupler one for beam splitting; coupler one splits into two beams, the first beam is connected to the auxiliary interferometer to correct the frequency modulation nonlinearity of the tunable laser, and the second beam is input to coupler two. The output light from coupler two is sent to the measurement interferometer, which further splits the incident light to form a local oscillator optical path and a measurement optical path; the local oscillator optical path is connected to coupler three and coupler eight respectively; the output light from the measurement optical path is sequentially sent to coupler four and coupler five; The output light of the coupler five is connected to the circulator one. The output end of the circulator one is connected to the fiber shape sensor. The backscattered Rayleigh light reflected by the fiber shape sensor is transmitted back to the coupler three via the circulator one. The coupler three combines the returned light with the local oscillator light output by the measuring interferometer and then connects it to the balanced detector one to complete the photoelectric conversion. The output light of the coupler four is connected to the circulator two, the output light of the circulator two is connected to the fiber optic shape sensor, the reflected light of the fiber optic shape sensor is transmitted back to the coupler eight via the circulator two, and the coupler eight combines the reflected light with the local oscillator light and then connects it to the balanced detector two to complete the photoelectric conversion. Coupler six is ​​connected in series with the optical path of circulator three. The output light of circulator three is connected to the optical fiber shape sensor. The optical fiber shape sensor reflects the light back and transmits it back to coupler nine through circulator three. Coupler nine combines the light and connects it to the balanced detector three. Coupler seven and coupler ten cooperate with the multi-core optical path of the optical fiber shape sensor to complete the beam splitting and beam combining. The combined light is connected to the balanced detector four. The interference electrical signals output by the first, second, third, and fourth balance detectors are transmitted to the data processing unit for calculating the beat signals corresponding to each fiber core.

8. The fiber optic shape sensing system according to claim 7, characterized in that, The optical path of the optical frequency domain reflectometer shape sensing system further includes: The first-in-first-out connector has its input end connected to the circulator one, the circulator two, and the circulator three, and its output end connected to the fiber optic shape sensor.

9. The fiber optic shape sensing system according to claim 6, characterized in that, The clamp includes a first clamping plate and a second clamping plate arranged symmetrically. The first clamping plate and the second clamping plate have screw holes on both sides and are locked by fasteners. The first clamping plate and the second clamping plate have a straight clamping hole in the middle. The inner diameter of the straight clamping hole is 0.1~0.2mm larger than the outer diameter of the fiber optic shape sensor.

10. An electronic device, characterized in that, include: Memory, used to store computer programs; A processor, used to execute computer programs, implements the following steps: Mark the restraint section of the optical fiber shape sensor with the clamp mounted on the optical fiber shape sensor on the axial coordinate, and collect the beat signal of each fiber core in the optical fiber shape sensor under the reference state to obtain the reference spectrum. The fiber optic shape sensor with the clamp is bent to the three-dimensional shape to be measured, and the beat signal of each fiber core in the fiber optic shape sensor is collected in the measurement state to obtain the measurement spectrum; For each fiber core, a sliding rectangular window is used to perform cross-correlation calculations between the reference spectrum and the measured spectrum to obtain the initial strain distribution along the sensing length; Using the strain data of the three fiber cores, the curvature and orthogonal curvature components along the sensing length of each sensing point are calculated based on the relationship between fiber bending strain and curvature. The curvature and orthogonal curvature components of the bound section are then forcibly set to zero to obtain the curvature distribution data after zeroing. Based on the zeroed curvature distribution data, shape reconstruction is performed using a relative parallel frame. The three-dimensional coordinates of each sensor point obtained from the reconstruction are connected to form a three-dimensional shape curve, and the three-dimensional shape curve is output.

Images