Optical fiber shape reconstruction method and system

Abstract

The invention provides an optical fiber shape reconstruction method and system. The method comprises the following steps: acquiring an optical fiber reference signal and an optical fiber measurement signal; respectively processing the obtained optical fiber reference signal and the optical fiber measurement signal to obtain an optical fiber reference spectrum and an optical fiber measurement spectrum; based on the optical fiber reference spectrum and the optical fiber measurement spectrum, using a preset deviation operation algorithm to obtain a wavelength offset containing noise; carrying out noise reduction processing on the wavelength offset through a wavelength offset denoising model to obtain denoised strain information; and based on the strain information, reconstructing the shape of the optical fiber through a shape reconstruction algorithm. According to the optical fiber shape reconstruction method and system provided by the invention, good optical fiber three-dimensional shape reconstruction precision can be realized, the optical fiber three-dimensional shape reconstruction speed can be effectively improved, and the real-time requirement of optical fiber three-dimensional shape reconstruction application can be met.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber sensing technology, and in particular to an optical fiber shape reconstruction method and system. Background Art

[0002] Multi-core fiber shape sensing is a sensing method based on multi-core fiber technology. It realizes the three-dimensional shape reconstruction of optical fiber by utilizing the strain distribution at different positions of multiple fiber cores. It is widely used in structural health monitoring, medical surgical robots and other fields.

[0003] In the prior art, Optical Frequency Domain Reflectometry (OFDR) is a high-precision distributed fiber optic sensing technology, which is often used in fiber optic 3D shape reconstruction. For fiber optic 3D shape reconstruction, it is necessary to obtain both high 3D shape reconstruction accuracy and fast 3D shape reconstruction speed. The existing fiber optic shape reconstruction method based on OFDR system cannot meet both requirements at the same time. Especially in the case of high precision requirements, the speed of fiber optic 3D shape reconstruction is often slow, which seriously affects the real-time performance of fiber optic 3D shape reconstruction. Therefore, there are many limitations in practical application. Summary of the invention

[0004] The purpose of the present invention is to propose a fiber shape reconstruction method and system to address the problem that the existing fiber shape reconstruction method based on OFDR system pursues high shape reconstruction accuracy but cannot take into account the real-time performance of shape reconstruction. The fiber shape reconstruction implemented by this method can not only achieve the accuracy of the traditional cross-correlation demodulation algorithm, but also greatly improve the demodulation speed, thereby realizing fast and accurate fiber shape reconstruction.

[0005] In order to achieve the above objectives, the present invention proposes a method and system for reconstructing the shape of an optical fiber. The specific implementation method is to first use an OFDR shape sensing device to collect information on the shape of the optical fiber; then use a deviation operation and a wavelength offset denoising model to process the strain data, and finally use a shape reconstruction algorithm to reconstruct the shape of the optical fiber.

[0006] A method for reconstructing an optical fiber shape, the method comprising:

[0007] When the optical fiber has no shape change, a reference signal of the optical fiber is obtained, and when the optical fiber has shape change, a measurement signal of the optical fiber is obtained;

[0008] Respectively processing the acquired optical fiber reference signal and the optical fiber measurement signal to obtain an optical fiber reference spectrum and an optical fiber measurement spectrum;

[0009] Based on the optical fiber reference spectrum and the optical fiber measurement spectrum, a preset deviation calculation algorithm is used to obtain a wavelength offset containing noise information;

[0010] The wavelength offset is subjected to denoising processing by using a pre-trained wavelength offset denoising model to obtain denoised strain information;

[0011] Based on the strain information, the shape of the optical fiber is reconstructed through a shape reconstruction algorithm.

[0012] In some embodiments, the obtained optical fiber reference signal and the optical fiber measurement signal are processed separately to obtain an optical fiber reference spectrum and an optical fiber measurement spectrum, specifically including:

[0013] Performing fast Fourier transform processing on the obtained optical fiber reference signal and the obtained optical fiber measurement signal to obtain a reference time domain result and a measurement time domain result respectively;

[0014] Selecting the reference time domain result and the measurement time domain result at the same position through a sliding window;

[0015] The reference time domain result and the measurement time domain result of the selected same position are respectively converted into the wavelength domain by inverse Fourier transformation to obtain a local reference spectrum and a local measurement spectrum respectively;

[0016] Repeat the above steps of selecting the reference time domain result and the measurement time domain result at the same position through the sliding window, and arrange all the local reference spectra in sequence to obtain the fiber reference spectrum, and arrange all the local measurement spectra in sequence to obtain the fiber measurement spectrum.

[0017] In some embodiments, the expression formula of the optical fiber reference signal includes:

[0018]

[0019] The expression formula of the optical fiber measurement signal includes:

[0020]

[0021] Among them, σ represents the responsivity of the detector, E0 represents the intensity of light, R Z represents the backscattering coefficient of the multi-core optical fiber at position Z, γ represents the tuning rate of the light source, f0 represents the initial frequency of the light source, τ z represents the transmission delay, Φ z represents the phase noise of the light source, represents the phase difference due to strain.

[0022] In some embodiments, due to the strain ε z The calculation formula for the resulting phase difference includes:

[0023] Δλ=λ c(1-P e )ε z ;

[0024] Among them, P e represents the photoelastic coefficient of the material of the multi-core optical fiber, c represents the propagation speed of light in vacuum, and λ c Indicates the central wavelength.

[0025] In some embodiments, the wavelength shift expression formula includes:

[0026] Δλ=λ c (1-P e )ε z ;

[0027] Where Δλ represents the wavelength shift, λ c represents the central wavelength, P e Represents the photoelastic coefficient of the material of the multi-core optical fiber; ε z Indicates the strain on the optical fiber.

[0028] In some embodiments, establishing the preset wavelength offset denoising model includes:

[0029] Acquire a sample set for pre-training a neural network model, the sample set comprising a plurality of training samples and a verification sample, the training samples and the verification sample both comprising noise data and strain data;

[0030] If the loss value calculated by the preset target of the strain data output by the neural network model and the noise data tends to be stable, the wavelength offset denoising model is obtained;

[0031] The pre-trained wavelength offset denoising model is used to denoise input data, the input data is strain data containing phase noise, and the output data is strain data after the noise is removed;

[0032] The input data of the wavelength offset denoising model is expressed as follows:

[0033]

[0034] Where α0 represents the amplitude of the strain, X1 represents a random signal below the fundamental frequency, α1 and α2 represent parameters used to adjust the variation of the strain signal, Γ0 represents the spin rate of the helical fiber, and X2 represents Φ z Random frequency jitter after Fourier transform.

[0035] In some embodiments, the framework of the wavelength offset denoising model includes any one or more of DPDNet, MWCNN, RIDNet, Unet and RFDNet;

[0036] The optical fiber corresponding to the optical fiber reference signal and the optical fiber measurement signal includes one or any combination of a multi-core straight optical fiber, a multi-core spiral optical fiber, a multi-core weak grating array optical fiber, a multi-core spiral weak grating array optical fiber, and an optical fiber bundle;

[0037] The shape reconstruction algorithm includes any one of an arc length splicing method, a Frenet frame and a minimum rotation frame.

[0038] In some embodiments, the obtaining of the optical fiber reference signal and the optical fiber measurement signal comprises:

[0039] The main interferometer of the OFDR shape sensing device is used to obtain the signal when the optical fiber is in different shapes;

[0040] Obtaining the absolute wavelength of the light output by the light source through the wavelength calibration module of the OFDR shape sensing device;

[0041] Acquiring a phase change of an output light of a light source through an auxiliary interferometer of the OFDR shape sensing device;

[0042] The signal acquisition module of the OFDR shape sensing device acquires the signal when the optical fiber is in different shapes, the absolute wavelength of the output light of the light source, and the phase change of the output light of the light source to obtain an optical fiber reference signal and an optical fiber measurement signal;

[0043] The light source of the OFDR shape sensing device is connected to the first fiber coupler through a first isolator, and the first fiber coupler is respectively connected to the main interferometer module and the auxiliary interferometer module; the auxiliary interferometer is connected to the wavelength calibration module; the main interferometer module, the auxiliary interferometer module and the wavelength calibration module are respectively connected to the signal acquisition module.

[0044] In some embodiments, the auxiliary interferometer module includes: a second fiber coupler, a third fiber coupler, a second isolator, a first photodetector, a fiber delay line, a first Faraday rotator mirror, and a second Faraday rotator mirror, wherein the first photodetector is connected to the signal acquisition module;

[0045] The main interferometer module includes: a fourth optical fiber coupler, a circulator, an optical switch, a polarization beam splitter, a first balanced photodetector, a second balanced photodetector and a sensing optical fiber, wherein the first balanced photodetector and the second balanced photodetector are respectively connected to the signal acquisition module;

[0046] The wavelength calibration module comprises: a hydrogen cyanide gas chamber and a second photoelectric detector, the hydrogen cyanide gas chamber is connected to the second photoelectric detector, and the second photoelectric detector is connected to the signal acquisition module;

[0047] The first fiber coupler is respectively connected to the second fiber coupler and the fourth fiber coupler; the second fiber coupler is respectively connected to the hydrogen cyanide gas chamber and the second isolator; the second isolator is connected to the third fiber coupler, the third fiber coupler is respectively connected to the fiber delay line, the first Faraday rotator mirror and the first photodetector, and the fiber delay line is connected to the second Faraday rotator mirror;

[0048] The fourth optical fiber coupler is connected to the circulator and the polarization beam splitter respectively, the circulator is connected to the first balanced photodetector and the optical switch respectively, the optical switch is connected to the sensing optical fiber, and the polarization beam splitter is connected to the second photodetector.

[0049] An optical fiber shape reconstruction system, used to execute an optical fiber shape reconstruction method described in any one of the first part, comprising:

[0050] A signal acquisition part, used to acquire optical fiber reference signals and optical fiber measurement signals;

[0051] A spectrum generating part, used for processing the acquired optical fiber reference signal and the acquired optical fiber measurement signal respectively, to obtain an optical fiber reference spectrum and an optical fiber measurement spectrum;

[0052] A deviation calculation part, used for obtaining a wavelength offset including noise by using a preset deviation calculation algorithm based on the optical fiber reference spectrum and the optical fiber measurement spectrum;

[0053] The denoising processing part is used to perform denoising processing on the wavelength offset through a pre-trained wavelength offset denoising model to obtain denoised strain information;

[0054] The shape reconstruction part is used to reconstruct the shape of the optical fiber through a shape reconstruction algorithm based on the strain information.

[0055] The beneficial effects of the present invention are as follows: Different from the prior art, the optical fiber shape reconstruction method and system provided by the present invention can achieve good optical fiber three-dimensional shape reconstruction accuracy and effectively improve the optical fiber three-dimensional shape reconstruction speed, which helps to meet the real-time requirements of optical fiber three-dimensional shape reconstruction applications;

[0056] Specifically, the wavelength offset caused by the change in the optical fiber shape is obtained by using a deviation operation algorithm, and the required demodulation time is significantly reduced, thereby improving the speed of optical fiber 3D shape reconstruction; on the basis of obtaining the wavelength offset through the deviation operation algorithm, the preset wavelength offset denoising model is used to remove the residual nonlinear tuning phase noise in the wavelength offset, thereby reducing the impact of noise. While improving the demodulation speed, the reconstruction accuracy is also improved, which helps to achieve real-time optical fiber 3D shape reconstruction. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0058] Figure 1 is a flow chart of a method for reconstructing an optical fiber shape according to an embodiment;

[0059] Figure 2 A flow chart for establishing a preset wavelength offset denoising model of an embodiment;

[0060] Figure 3 A system diagram for optical fiber shape reconstruction of an embodiment;

[0061] Figure 4 It is a composition structure diagram of the OFDR shape sensing device of an embodiment;

[0062] Figure 5 A schematic diagram of the steps of the optical fiber shape reconstruction method of an embodiment;

[0063] Figure 6 The wavelength offset denoising model composition and denoising effect diagram of the embodiment;

[0064] Figure 7 A schematic diagram of the wavelength offset denoising model composition of an embodiment;

[0065] Figure 8 A schematic diagram of an optical fiber measurement spectrum and an optical fiber reference spectrum of an embodiment;

[0066] Fig. 9 A schematic diagram of wavelength offset after the deviation calculation algorithm of the embodiment;

[0067] Fig.10 3D shape reconstruction effect comparison diagram of optical fiber according to the embodiments.

[0068] Reference numerals:

[0069] 1-signal acquisition part; 2-spectrum generation part; 3-deviation calculation part; 4-denoising processing part; 5-shape reconstruction part; 1a-optical fiber; 11a-first optical fiber coupler; 2a-auxiliary interferometer module; 21a-second optical fiber coupler; 22a-third optical fiber coupler; 23a-second isolator; 24a-first photodetector; 25a-optical fiber delay line; 26a-first Faraday rotation mirror; 27a-second Faraday rotation mirror; 3a-main interferometer module; 31a-fourth optical fiber coupler; 32a-circulator; 33a-optical switch; 34a-polarization beam splitter; 35a-first balanced photodetector; 36a-second balanced photodetector; 37a-sensing optical fiber; 4a-wavelength calibration module; 41a-hydrogen cyanide gas chamber; 42a-second photodetector; 5a-signal acquisition module; 6a-light source; 61a-first isolator. DETAILED DESCRIPTION

[0070] In the following, various embodiments of the present disclosure will be described more fully. The present disclosure may have various embodiments, and adjustments and changes may be made therein. However, it should be understood that there is no intention to limit the various embodiments of the present disclosure to the specific embodiments disclosed herein, but rather the present disclosure should be understood to cover all adjustments, equivalents and / or alternatives that fall within the spirit and scope of the various embodiments of the present disclosure.

[0071] Hereinafter, the terms "include" or "may include" used in various embodiments of the present disclosure indicate the presence of disclosed functions, operations, or elements, and do not limit the addition of one or more functions, operations, or elements. In addition, as used in various embodiments of the present disclosure, the terms "include", "have", and their cognates are intended only to indicate specific features, numbers, steps, operations, elements, components, or a combination of the foregoing, and should not be understood as first excluding the presence of one or more other features, numbers, steps, operations, elements, components, or a combination of the foregoing or the possibility of adding one or more features, numbers, steps, operations, elements, components, or a combination of the foregoing.

[0072] In various embodiments of the present disclosure, the expression "or" or "at least one of A or / and B" includes any combination or all combinations of the words listed at the same time. For example, the expression "A or B" or "at least one of A or / and B" may include A, may include B, or may include both A and B.

[0073] The expressions (such as "first", "second", etc.) used in the various embodiments of the present disclosure may modify the various constituent elements in the various embodiments, but may not limit the corresponding constituent elements. For example, the above expressions do not limit the order and / or importance of the elements. The above expressions are only used for the purpose of distinguishing one element from other elements. For example, the first user device and the second user device indicate different user devices, although both are user devices. For example, without departing from the scope of the various embodiments of the present disclosure, the first element may be referred to as the second element, and similarly, the second element may also be referred to as the first element.

[0074] It should be noted that if it is described that one component element is “connected” to another component element, the first component element may be directly connected to the second component element, and a third component element may be “connected” between the first component element and the second component element. Conversely, when one component element is “directly connected” to another component element, it can be understood that there is no third component element between the first component element and the second component element.

[0075] The term “user” used in various embodiments of the present disclosure may indicate a person using an electronic device or a device (eg, an artificial intelligence electronic device) using the electronic device.

[0076] The terms used in the various embodiments of the present disclosure are only used for the purpose of describing specific embodiments and are not intended to limit the various embodiments of the present disclosure. As used herein, the singular form is intended to also include the plural form, unless the context clearly indicates otherwise. Unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the meanings commonly understood by ordinary technicians in the field to which the various embodiments of the present disclosure belong. The terms (such as the terms defined in the generally used dictionary) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning, unless clearly defined in the various embodiments of the present disclosure.

[0077] Example 1

[0078] The present application embodiment proposes a method for reconstructing the shape of an optical fiber, such as Figure 1 As shown, including:

[0079] S100, obtaining an optical fiber reference signal and an optical fiber measurement signal;

[0080] Specifically, in some embodiments of the present application, the reference signal is an optical signal generated when light passes through the multi-core optical fiber in a stress-free state, that is, when the multi-core optical fiber has no shape change;

[0081] The optical fiber measurement signal is the optical signal generated when the multi-core optical fiber is under stress and the light passes through the multi-core optical fiber in this state;

[0082] S200, respectively processing the acquired optical fiber reference signal and optical fiber measurement signal to obtain an optical fiber reference spectrum and an optical fiber measurement spectrum;

[0083] Specifically, in some embodiments of the present application, Figure 8 As shown, the fiber reference spectrum is obtained after processing the fiber reference signal, and the fiber measurement spectrum is obtained after processing the fiber measurement signal. The spectrum refers to the optical signal related to the physical properties of the fiber shape, stress, temperature, etc. by analyzing the propagation, scattering or absorption of light in the fiber.

[0084] S300, based on the optical fiber reference spectrum and the optical fiber measurement spectrum, uses a preset deviation calculation algorithm to obtain the wavelength offset containing noise information;

[0085] Through the deviation calculation algorithm, the difference between the fiber measurement signal at each time point and each position point in the fiber measurement spectrum and the corresponding fiber reference signal in the fiber reference spectrum can be measured, so as to obtain the difference value between the fiber measurement signal in the fiber measurement spectrum and the corresponding fiber reference signal in the fiber reference spectrum, and then obtain the wavelength offset and the change trend of the wavelength offset. Specifically, Fig. 9 shown.

[0086] More specifically, in some embodiments of the present application, the difference between the optical fiber measurement spectrum and the optical fiber reference spectrum can be obtained by a preset deviation operation algorithm. Of course, there is no limitation on the specific deviation operation algorithm.

[0087] S400, performing denoising processing on the wavelength offset through a wavelength offset denoising model to obtain denoised strain information;

[0088] Specifically, in some embodiments of the present application, the strain information includes or relates to strain data output by a wavelength offset denoising model.

[0089] It can be understood that the wavelength offset obtained by the deviation calculation algorithm still has residual phase noise of the nonlinear tuning of the tunable laser. The existence of phase noise will affect the accuracy of the three-dimensional shape reconstruction of the optical fiber. Therefore, it is necessary to perform noise reduction processing on the wavelength offset to obtain the strain information of the optical fiber.

[0090] The pre-trained wavelength shift denoising model is a neural network model proposed based on the characteristics of optical fiber strain changes during optical fiber shape sensing to improve the accuracy and demodulation speed of shape sensing.

[0091] S500, based on the strain information, the shape of the optical fiber is reconstructed by a shape reconstruction algorithm.

[0092] Specifically, in some embodiments of the present application, the optical fiber shape is reconstructed through a shape reconstruction algorithm based on the demodulated strain information.

[0093] Strain information specifically refers to the response or feedback of the propagation characteristics of light to the external stress on the optical fiber when the light propagates in the optical fiber. These responses or feedbacks are sensed and collected by the optical fiber sensor to form a collection of information;

[0094] Optionally, the propagation characteristics of light may be reflection, refraction, propagation speed or scattering of light, etc. Of course, there is no limitation on the specific propagation characteristics of light sensed by the optical fiber sensor;

[0095] Based on the strain information, the position and extent of external stress on the optical fiber can be obtained, thereby reconstructing the three-dimensional shape of the optical fiber.

[0096] Furthermore, if Figure 5 As shown, the obtained optical fiber reference signal and optical fiber measurement signal are processed respectively to obtain an optical fiber reference spectrum and an optical fiber measurement spectrum, which specifically includes:

[0097] The obtained optical fiber reference signal and optical fiber measurement signal are processed by fast Fourier transform respectively, so as to obtain reference time domain result and measurement time domain result respectively;

[0098] Select the reference time domain result and the measurement time domain result at the same position through a sliding window;

[0099] The reference time domain result and the measurement time domain result of the same selected position are respectively subjected to inverse Fourier transform processing to obtain a local reference spectrum and a local measurement spectrum respectively;

[0100] Repeat the above steps of selecting the reference time domain result and the measurement time domain result at the same position through the sliding window, and arrange all the local reference spectra in sequence to obtain the fiber reference spectrum, and arrange all the local measurement spectra in sequence to obtain the fiber measurement spectrum.

[0101] Specifically, in some embodiments of the present application, the multi-core optical fiber includes a plurality of cores, and one or more cores for which strain needs to be solved are selected;

[0102] The entire signal of the optical fiber is divided into n segments through a sliding window. It can be understood that the larger the value of n, the more detailed the division of the entire optical fiber signal is, and the more helpful it is to improve the accuracy of the reconstruction of the three-dimensional morphology of the optical fiber; the reference time domain results and the measurement time domain results of the signal segments of each optical fiber are respectively subjected to inverse Fourier transform processing to obtain a local reference spectrum and a local measurement spectrum.

[0103] Furthermore, the expression formula of the optical fiber reference signal includes:

[0104]

[0105] The expression formulas of optical fiber measurement signals include:

[0106]

[0107] Among them, σ represents the responsivity of the detector, E0 represents the intensity of light, R Z represents the Rayleigh backscattering coefficient at position Z on the multi-core optical fiber, γ represents the tuning rate of the light source, f0 represents the initial frequency, τ z represents the transmission delay, Φ z represents the phase noise of the light source, represents the phase difference due to strain.

[0108] Wherein, the light source is a tunable light source (TLS);

[0109] The optical fiber reference signal and the optical fiber measurement signal are calculated respectively mainly through the detector's responsiveness, the propagation characteristics of light in the optical fiber, the state of the light source, etc. The propagation characteristics of light in the optical fiber mainly involve the intensity of light, the scattering coefficient, etc. The calculation of the optical fiber reference signal and the optical fiber measurement signal through these influencing factors can more accurately reflect the strain information of the optical fiber, so as to further improve the accuracy of the reconstruction of the three-dimensional morphology of the optical fiber.

[0110] Furthermore, due to the strain ε z The calculation formula for the resulting phase difference includes:

[0111]

[0112] Among them, P e represents the photoelastic coefficient of the material of the multi-core optical fiber, c represents the propagation speed of light in vacuum, and λ c Indicates the central wavelength.

[0113] The phase difference caused by strain is affected by many factors, including the central wavelength of the multi-core optical fiber, the photoelastic coefficient of the material of the multi-core optical fiber, and the propagation speed of light in vacuum;

[0114] Among them, the phase difference is positively correlated with the refractive index of the multi-core optical fiber, and negatively correlated with the refractive index of the multi-core optical fiber and the wavelength of light in vacuum;

[0115] In the calculation of the phase difference, a variety of relevant influencing factors are fully considered, which helps to improve the accuracy of the phase difference calculation and further improve the accuracy of the three-dimensional morphology reconstruction of the optical fiber.

[0116] Furthermore, the wavelength shift expression formula includes:

[0117] Δλ=λ c (1-P e )ε z ;

[0118] Where Δλ represents the wavelength shift, λ c represents the central wavelength, P e Represents the photoelastic coefficient of the material of the multi-core optical fiber; ε z Indicates the strain on the optical fiber.

[0119] The wavelength offset between the optical fiber reference spectrum and the optical fiber measurement spectrum can be obtained through the difference calculation algorithm, and the difference between the optical fiber reference spectrum and the optical fiber measurement spectrum can be compared. It can more clearly reflect the position where the optical fiber is affected by external stress and the changing trend of the stress magnitude, and improve the demodulation speed, which is helpful to improve the real-time performance of the optical fiber three-dimensional shape reconstruction.

[0120] Furthermore, if Figure 2 As shown, the establishment of the preset wavelength offset denoising model includes:

[0121] S401, obtaining a sample set for pre-training a neural network model, the sample set including a plurality of training samples and verification samples, both of which include noise data and strain data;

[0122] Specifically, in some embodiments of the present application, the training sample is expressed in the form of a simulation curve, and the data involved in the simulation curve includes noise, strain data without phase noise, and strain data containing phase noise;

[0123] Among them, strain data refers to the deformation of the multi-core optical fiber, that is, the signal generated under the action of external stress; in order to fully simulate the actual strain information in the experiment, the initial part of the optical fiber is not subject to stress when it is shaping.

[0124] Specifically, the strain data may also reflect the position where the optical fiber is subjected to stress and the magnitude of the stress, etc. The specific strain data is not limited here.

[0125] S402, if the loss value calculated by the preset target of the strain data output by the neural network model and the noise data tends to be stable, then the wavelength offset denoising model is obtained;

[0126] When the loss value calculated by the preset target of the strain data and noise data output by the neural network model tends to be stable, it means that the training of the wavelength offset denoising model is completed.

[0127] S403, the pre-trained wavelength offset denoising model is used to denoise input data, the input data is strain data containing phase noise, and the output data is the denoised strain data.

[0128] Furthermore, the input data is expressed as follows:

[0129]

[0130] Where α0 represents the amplitude of the strain, X1 represents a random signal below the fundamental frequency, α1 and α2 represent parameters used to adjust the variation of the strain signal, Γ0 represents the spin rate of the helical fiber, and X2 represents Φ z Random frequency jitter after Fourier transform; z represents the position coordinate.

[0131] Specifically, in some embodiments of the present application, the mean square error between the actual output data and the preset output data in the training sample is defined as the loss, a data sample set including 10,000 data samples is used for training in the wavelength offset denoising model, and the optimizer used is Adaptive Moment Estimation with a learning rate of 10-3; the Python version used for the wavelength offset denoising model is 3.8, the Pytorch version is 2.1.0, and the wavelength offset model is trained for 200 rounds using NVIDIA RTX A5000 GPU.

[0132] Furthermore, the framework of the wavelength offset denoising model includes any one or more of DPDNet, MWCNN, RIDNet, Unet and RFDNet;

[0133] The optical fiber corresponding to the optical fiber reference signal and the optical fiber measurement signal includes one or any combination of a multi-core straight optical fiber, a multi-core spiral optical fiber, a multi-core weak grating array optical fiber, a multi-core spiral weak grating array optical fiber, and an optical fiber bundle;

[0134] The shape reconstruction algorithm includes any one of the arc length splicing method, Frenet frame and minimum rotation frame.

[0135] Furthermore, there is no limitation on the architecture of the specific wavelength offset denoising model, the type of optical fiber, and the specific shape reconstruction algorithm;

[0136] Furthermore, in the wavelength offset denoising model, the encoder is responsible for extracting key features, and the decoder is used to restore data details and perform dimensionality reduction processing to remove redundant information and retain the core content of the data. In addition, the nonlinear transformation of the activation layer further enhances the network's ability to identify and suppress noise, allowing CNN to demonstrate excellent performance and accuracy when processing complex spectral data. Combining the spectral features of OFDR with deep learning can not only effectively remove noise and improve the demodulation rate and accuracy, but also provide strong technical support for the automation and intelligent development of spectral analysis.

[0137] For example, Figure 6 and Figure 7 As shown, the wavelength offset denoising model takes the Unet model architecture as an example, including an encoder and a decoder;

[0138] The main task of the encoder is feature extraction, capturing the comprehensive information of the spectrum from the deviation operation result (wavelength offset); the role of the decoder is mainly feature fusion and dimensionality recovery; after the upsampling layer, dimensional splicing and convolution, the fusion features of the spectrum can be obtained, and the denoised wavelength offset result can be output.

[0139] More specifically, in some embodiments of the present application, the wavelength offset denoising model includes an encoder and a decoder;

[0140] The encoder comprises: four encoder modules connected in sequence, each of the encoder modules comprising a convolutional layer, a batch normalization layer and a pooling layer connected in sequence;

[0141] The decoder comprises: four decoder modules connected in sequence, each of which comprises a convolutional layer, a batch normalization layer and a sampling layer connected in sequence.

[0142] Furthermore, if Figure 4 As shown, a fiber reference signal and a fiber measurement signal are obtained to improve the accuracy of obtaining the fiber reference signal and the fiber measurement signal, thereby improving the accuracy of the fiber reference spectrum and the fiber measurement spectrum, and further facilitating the improvement of the accuracy of the wavelength offset obtained by using a deviation operation in a fiber reconstruction method in an embodiment of the present application, so as to improve the authenticity of the fiber morphology reconstruction.

[0143] The OFDR shape sensing device comprises: a light source 6a, an optical fiber 1a, a main interferometer module 3a, an auxiliary interferometer module 2a, a wavelength calibration module 4a and a signal acquisition module 5a;

[0144] Obtain fiber reference signals and fiber measurement signals, including:

[0145] The main interferometer 3a of the OFDR shape sensing device is used to obtain the signal of the optical fiber 1a when it is in different shapes;

[0146] Obtaining the absolute wavelength of the light output by the light source 6a through the wavelength calibration module 4a of the OFDR shape sensing device;

[0147] Acquiring the phase change of the output light of the light source 6a through the auxiliary interferometer 2a of the OFDR shape sensing device;

[0148] The signal acquisition module 5a of the OFDR shape sensing device acquires the signal of the optical fiber 1a when it is in different shapes, the absolute wavelength of the output light of the light source 6a, and the phase change of the output light of the light source 6a to obtain the optical fiber reference signal and the optical fiber measurement signal;

[0149] The light source 6a is connected to the optical fiber 1a through the first isolator 61a, and the optical fiber 1a is respectively connected to the main interferometer module 3a and the auxiliary interferometer module 2a; the auxiliary interferometer module 2a is connected to the wavelength calibration module 4a;

[0150] The main interferometer module 3a, the auxiliary interferometer module 2a and the wavelength calibration module 4a are respectively connected to the signal acquisition module 5a.

[0151] Among them, the light source 6a is a tunable laser source, which is used to emit light signals and provide stable light signals for the optical fiber whose three-dimensional shape is to be reconstructed; the optical fiber 1a is used to transmit the light signal from the light source 6a; the first isolator 61a connects the light source 6a and the first optical coupler 11a, which is used to reduce the interference of the external environment on the stability of the light source 6a signal, thereby improving the measurement accuracy; the main interferometer module 3a is used to obtain the signal when the optical fiber is in different shapes, and the auxiliary interferometer module 2a is used to obtain the phase change of the output light of the tunable laser; the wavelength calibration module 4a is used to obtain the absolute wavelength of the light output by the light source, so as to improve the accuracy and consistency of the wavelength of the light source 6a.

[0152] Furthermore, if Figure 4 As shown, the optical fiber 1a includes: a first optical fiber coupler 11a, the first optical fiber coupler 11a is a 90:10 optical fiber coupler, the output end with an optical signal output accounting for 90% is connected to the main interferometer module 3a, and the output end with an optical signal output accounting for 10% is connected to the auxiliary interferometer module 2a;

[0153] The auxiliary interferometer module 2a includes: a second fiber coupler 21a, a third fiber coupler 22a, a second isolator 23a, a first photodetector 24a, a fiber delay line 25a, a first Faraday rotator mirror 26a, and a second Faraday rotator mirror 27a;

[0154] The second fiber coupler 21a and the third fiber coupler 22a are both 50:50 fiber couplers, and the fiber delay line 25a is 50 meters long;

[0155] The main interferometer 3a module includes: a fourth fiber coupler 31a, a circulator 32a, an optical switch 33a, a polarization beam splitter 34a, a first balanced photodetector 35a, a second balanced photodetector 36a and a sensing fiber 37a;

[0156] The fourth optical fiber coupler 31a is a 90:10 optical fiber coupler, wherein the output end with an optical signal output accounting for 90% is connected to the circulator 32a, and the output end with an optical signal output accounting for 10% is connected to the polarization beam splitter 34a;

[0157] The wavelength calibration module 4a includes: a hydrogen cyanide gas chamber 41a and a second photodetector 42a, the hydrogen cyanide gas chamber 41a is connected to the second photodetector 42a, and the second photodetector 42a is connected to the signal acquisition module 5a;

[0158] The first fiber coupler 11a is respectively connected to the second fiber coupler 21a and the fourth fiber coupler 31a; the second fiber coupler 21a is respectively connected to the hydrogen cyanide chamber 41a and the second vibration isolator 23a; the second vibration isolator 23a is connected to the third fiber coupler 22a, the third fiber coupler 22a is respectively connected to the fiber delay line 25a, the first Faraday rotation mirror 26a and the first photodetector 24a, the fiber delay line 25a is connected to the second Faraday rotation mirror 27a, and the first photodetector 24a is connected to the signal acquisition module 5a;

[0159] The beat signal generated by the two light beams of the third fiber coupler 22a is detected by the first photodetector 24a and used as an external clock of the data acquisition component to compensate for the influence of the nonlinear tuning of the light source 6a.

[0160] The fourth fiber coupler 31a is respectively connected to the circulator 32a and the polarization beam splitter 34a, the circulator 32a is respectively connected to the first balanced photodetector 35a and the optical switch 33a, the optical switch 33a is connected to the sensing optical fiber 37a, the polarization beam splitter 34a is connected to the second photodetector 42a, and the first balanced photodetector 35a and the second balanced photodetector 36a are respectively connected to the signal acquisition module 5a.

[0161] The main interferometer module 3a is divided into a reference arm and a measuring arm by a 10:90 fourth optical fiber coupler 31a. 90% of the light reaches the measuring arm and is transmitted to the sensing optical fiber 37a after passing through the circulator and the optical switch 33a. The back Rayleigh scattering signal from the sensing optical fiber 37a returns to the circulator 32a and the polarization beam splitter 34a. The polarization beam splitter 34a divides the light into s-light and p-light, and uses the first balanced photodetector 35a and the second balanced photodetector 36a to collect them respectively. The four signals of the auxiliary interferometer 2a and the main interferometer 3a are all collected by the four-channel signal acquisition component 5a.

[0162] There are no requirements for the collection position and specific polarization direction of the s-light and p-light.

[0163] The optical fiber shape reconstruction method proposed in the present invention reconstructs the three-dimensional shape of the optical fiber and verifies the reconstruction effect. The experimental content and experimental results are as follows:

[0164] A multi-core optical fiber with a length of 31.14 cm was wound around a cylinder with a radius of 5 cm. The spectral information of each core was collected using an OFDR device, and a standard group, a control group, and an experimental group were set up. The strain information was demodulated by cross-correlation calculation and the optical fiber shape reconstruction method of the present application, respectively. Finally, based on the two sets of strain information obtained by processing, the shape of the optical fiber at this time was reconstructed by a shape reconstruction algorithm.

[0165] The reconstruction result is as follows Fig.10 As shown, the dotted line is the cylindrical model curve, which is Figure 2, the dashed line is the reconstructed curve after the cross-correlation operation, which is Figure 3, and the solid line is the reconstructed curve obtained after the optical fiber shape reconstruction method of the present application is processed, which is Figure 1;

[0166] Depend on Fig.10 It can be seen that the overlap between the dotted line and the solid line is higher than the overlap between the dotted line and the dashed line. Therefore, it can be seen that the deviation calculation algorithm and the wavelength offset denoising model preset in the optical fiber shape reconstruction method of the present application are used to process and obtain strain information, which significantly improves the accuracy of optical fiber three-dimensional shape reconstruction;

[0167] In terms of demodulation speed, it takes 211.392605 seconds for the cross-correlation operation to process one strain data, and 0.006045 seconds for the deviation strain fast demodulation operation to process one strain data. The root mean square error of the Euclidean distance of the curve after the cross-correlation operation is 0.0935 cm, and the root mean square error of the Euclidean distance of the curve after the deviation strain fast demodulation operation is 0.0755 cm.

[0168] In summary, in the optical fiber shape reconstruction method proposed in the present invention, the demodulation method using the deviation operation and the offset denoising model can effectively replace the cross-correlation operation, which not only reduces the demodulation time but also improves the demodulation accuracy.

[0169] The embodiments of the present invention have at least the following beneficial effects:

[0170] The embodiment of the present invention provides a method for reconstructing the shape of an optical fiber, which can achieve good optical fiber three-dimensional shape reconstruction accuracy and effectively improve the speed of optical fiber three-dimensional shape reconstruction, thereby helping to meet the real-time requirements of optical fiber three-dimensional shape reconstruction applications;

[0171] Specifically, the preset deviation operation algorithm is used to obtain the wavelength offset caused by the change in the optical fiber shape. The required demodulation time is significantly reduced, thereby improving the speed of optical fiber three-dimensional shape reconstruction and enhancing real-time performance. On the basis of obtaining the wavelength offset through the deviation operation algorithm, the preset wavelength offset denoising model is used to remove the residual nonlinear tuning phase noise in the wavelength offset, reducing the influence of phase noise. While improving the demodulation speed, the reconstruction accuracy is also improved, which helps to achieve real-time optical fiber three-dimensional shape reconstruction.

[0172] Example 2

[0173] The embodiment of the present invention provides a fiber shape reconstruction system, which is used to execute a fiber shape reconstruction method of embodiment 1, such as Figure 3 As shown, including:

[0174] A signal acquisition part 1, used for acquiring an optical fiber reference signal and an optical fiber measurement signal;

[0175] The spectrum generating part 2 is used to process the acquired optical fiber reference signal and optical fiber measurement signal respectively to obtain the optical fiber reference spectrum and the optical fiber measurement spectrum;

[0176] The deviation calculation part 3 is used to obtain the wavelength offset including noise by using a preset deviation calculation algorithm based on the optical fiber reference spectrum and the optical fiber measurement spectrum;

[0177] A denoising processing part 4 is used to perform denoising processing on the wavelength offset through a pre-trained wavelength offset denoising model to obtain denoised strain information;

[0178] The shape reconstruction part 5 is used to reconstruct the shape of the optical fiber through a shape reconstruction algorithm based on the strain information.

[0179] The rest of the contents are the same or similar to those in Example 1 and are not described in detail here.

[0180] Those skilled in the art will appreciate that the modules in the device in the implementation scenario can be distributed in the device in the implementation scenario according to the implementation scenario description, or can be changed accordingly and located in one or more devices different from the implementation scenario. The modules in the above implementation scenario can be combined into one module, or can be further split into multiple sub-modules.

[0181] The above serial numbers of the present invention are only for description and do not represent the advantages or disadvantages of the implementation scenarios.

[0182] The above disclosure is only a few specific implementation scenarios of the present invention, but the present invention is not limited thereto, and any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for reconstructing an optical fiber shape, characterized in that: include: Obtaining optical fiber reference signal and optical fiber measurement signal; Respectively processing the acquired optical fiber reference signal and the optical fiber measurement signal to obtain an optical fiber reference spectrum and an optical fiber measurement spectrum; Based on the optical fiber reference spectrum and the optical fiber measurement spectrum, a preset deviation calculation algorithm is used to obtain a wavelength offset containing noise information; The wavelength offset is subjected to denoising processing by a wavelength offset denoising model to obtain denoised strain information; Based on the strain information, the shape of the optical fiber is reconstructed through a shape reconstruction algorithm.

2. A method for reconstructing an optical fiber shape according to claim 1, characterized in that: The obtained optical fiber reference signal and the optical fiber measurement signal are processed respectively to obtain an optical fiber reference spectrum and an optical fiber measurement spectrum, specifically including: Performing fast Fourier transform processing on the obtained optical fiber reference signal and the obtained optical fiber measurement signal to obtain a reference time domain result and a measurement time domain result respectively; Selecting the reference time domain result and the measurement time domain result at the same position through a sliding window; The reference time domain result and the measurement time domain result of the selected same position are respectively converted into the wavelength domain by inverse Fourier transformation to obtain a local reference spectrum and a local measurement spectrum respectively; Repeat the above steps of selecting the reference time domain result and the measurement time domain result at the same position through the sliding window, and arrange all the local reference spectra in sequence to obtain the fiber reference spectrum, and arrange all the local measurement spectra in sequence to obtain the fiber measurement spectrum.

3. The optical fiber shape reconstruction method according to claim 2, characterized in that: The expression formulas of optical fiber reference signals include: The expression formula of the optical fiber measurement signal includes: Among them, σ represents the responsivity of the detector, E0 represents the intensity of light, R Z represents the backscattering coefficient of the multi-core optical fiber at position Z, γ represents the tuning rate of the light source, f0 represents the initial frequency of the light source, τ z represents the transmission delay, Φ z represents the phase noise of the light source, represents the phase difference due to strain.

4. The optical fiber shape reconstruction method according to claim 3, characterized in that: Due to the strain ε z The calculation formula of the phase difference caused by include: Among them, P e represents the photoelastic coefficient of the material of the multi-core optical fiber, c represents the propagation speed of light in vacuum, and λ c Indicates the central wavelength.

5. The optical fiber shape reconstruction method according to claim 1, characterized in that: The wavelength shift expression formula includes: Dλ=λ c (1-P e )e z ; Where Δλ represents the wavelength shift, λ c represents the central wavelength, P e Represents the photoelastic coefficient of the material of the multi-core optical fiber; ε z Indicates the strain on the optical fiber.

6. The optical fiber shape reconstruction method according to claim 1, characterized in that: The establishment of the preset wavelength offset denoising model includes: obtaining a sample set for pre-training a neural network model, the sample set includes a plurality of training samples and a verification sample, and the training sample and the verification sample both include noise data and strain data; If the loss value calculated by the preset target of the strain data output by the neural network model and the noise data tends to be stable, the wavelength offset denoising model is obtained; The pre-trained wavelength offset denoising model is used to denoise input data, the input data is strain data containing phase noise, and the output data is strain data after the noise is removed; The input data of the wavelength offset denoising model is expressed as follows: Where α0 represents the amplitude of the strain, X1 represents a random signal below the fundamental frequency, α1 and α2 represent parameters used to adjust the variation of the strain signal, Γ0 represents the spin rate of the helical fiber, and X2 represents Φ z Random frequency jitter after Fourier transform.

7. The optical fiber shape reconstruction method according to claim 1, characterized in that: The framework of the wavelength offset denoising model includes any one or more of DPDNet, MWCNN, RIDNet, Unet and RFDNet; The optical fiber corresponding to the optical fiber reference signal and the optical fiber measurement signal includes one or any combination of a multi-core straight optical fiber, a multi-core spiral optical fiber, a multi-core weak grating array optical fiber, a multi-core spiral weak grating array optical fiber, and an optical fiber bundle; The shape reconstruction algorithm includes any one of an arc length splicing method, a Frenet frame and a minimum rotation frame.

8. The optical fiber shape reconstruction method according to claim 1, characterized in that: It is characterized in that The obtaining of the optical fiber reference signal and the optical fiber measurement signal comprises: The main interferometer of the OFDR shape sensing device is used to obtain the signal when the optical fiber is in different shapes; Obtaining the absolute wavelength of the light output by the light source through the wavelength calibration module of the OFDR shape sensing device; Acquiring a phase change of an output light of a light source through an auxiliary interferometer of the OFDR shape sensing device; The signal acquisition module of the OFDR shape sensing device acquires the signal when the optical fiber is in different shapes, the absolute wavelength of the output light of the light source, and the phase change of the output light of the light source to obtain an optical fiber reference signal and an optical fiber measurement signal; The light source of the OFDR shape sensing device is connected to the first fiber coupler through a first isolator, and the first fiber coupler is respectively connected to the main interferometer module and the auxiliary interferometer module; the auxiliary interferometer is connected to the wavelength calibration module; the main interferometer module, the auxiliary interferometer module and the wavelength calibration module are respectively connected to the signal acquisition module.

9. The optical fiber shape reconstruction method according to claim 8, characterized in that: The auxiliary interferometer module includes: a second fiber coupler, a third fiber coupler, a second isolator, a first photodetector, a fiber delay line, a first Faraday rotator mirror and a second Faraday rotator mirror, wherein the first photodetector is connected to the signal acquisition module; The main interferometer module includes: a fourth optical fiber coupler, a circulator, an optical switch, a polarization beam splitter, a first balanced photodetector, a second balanced photodetector and a sensing optical fiber, wherein the first balanced photodetector and the second balanced photodetector are respectively connected to the signal acquisition module; The wavelength calibration module comprises: a hydrogen cyanide gas chamber and a second photoelectric detector, the hydrogen cyanide gas chamber is connected to the second photoelectric detector, and the second photoelectric detector is connected to the signal acquisition module; The first fiber coupler is respectively connected to the second fiber coupler and the fourth fiber coupler; the second fiber coupler is respectively connected to the hydrogen cyanide gas chamber and the second isolator; the second isolator is connected to the third fiber coupler, the third fiber coupler is respectively connected to the fiber delay line, the first Faraday rotator mirror and the first photodetector, and the fiber delay line is connected to the second Faraday rotator mirror; The fourth optical fiber coupler is connected to the circulator and the polarization beam splitter respectively, the circulator is connected to the first balanced photodetector and the optical switch respectively, the optical switch is connected to the sensing optical fiber, and the polarization beam splitter is connected to the second photodetector.

10. An optical fiber shape reconstruction system, characterized in that: A method for reconstructing an optical fiber shape according to any one of claims 1 to 7, comprising: A signal acquisition part, used to acquire optical fiber reference signals and optical fiber measurement signals; A spectrum generating part, used for processing the acquired optical fiber reference signal and the acquired optical fiber measurement signal respectively, to obtain an optical fiber reference spectrum and an optical fiber measurement spectrum; A deviation calculation part, used for obtaining a wavelength offset including noise by using a preset deviation calculation algorithm based on the optical fiber reference spectrum and the optical fiber measurement spectrum; The denoising processing part is used to perform denoising processing on the wavelength offset through a pre-trained wavelength offset denoising model to obtain denoised strain information; The shape reconstruction part is used to reconstruct the shape of the optical fiber through a shape reconstruction algorithm based on the strain information.

Images