Optical fiber positioning and common-mode noise suppression integrated device based on time-frequency joint coding

Abstract

The invention relates to the technical field of optical fiber sensing and signal processing, and discloses an optical fiber positioning and common-mode noise suppression integrated device based on time-frequency joint coding, which comprises a time-frequency coding modulation module, a common-mode noise suppression module is mounted at the bottom of the time-frequency coding modulation module, and a common-mode noise suppression module is mounted at the bottom of the common-mode noise suppression module. An optical fiber sensing link is installed in the common-mode noise suppression module. According to the optical fiber positioning and common-mode noise suppression integrated device based on time-frequency joint coding, the time-frequency coding modulation module deeply fuses frequency hopping spread spectrum coding and a heterodyne detection technology, and the encoder encodes a positioning signal and a noise suppression signal into a composite waveform, so that the probability of being interfered is reduced, and the positioning precision is improved. Positioning signal transmission and common-mode noise suppression can be achieved through the same optical fiber, the common-mode noise suppression module can dynamically adjust the noise suppression ratio and the accurate positioning precision according to the environment, a learning-adjustment-optimization closed loop is achieved, and the reliability of the system in complex environments such as traffic, outdoor and mine environments is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical fiber sensing and signal processing, and specifically to an integrated device for optical fiber positioning and common-mode noise suppression based on time-frequency joint coding. Background Art

[0002] An optical fiber positioning system is a distributed monitoring device based on optical fiber sensing technology. Its core function is to detect changes in the transmission characteristics of optical signals in the optical fiber, real-time locate the position of physical disturbance events, and synchronously monitor the state changes of the environment or target. It can be applied in security monitoring, pipeline safety, transportation infrastructure, geological disaster warning, and power facilities.

[0003] The optical fiber itself is non-conductive and non-radiative, suitable for flammable and explosive environments. The optical fiber positioning system in coal mines can penetrate the gas environment to achieve equipment positioning. However, traditional optical fiber positioning devices rely on the intensity of backscattered light for positioning, but interference such as environmental vibration and temperature drift will introduce common-mode noise, causing the target signal to overlap in the time domain and frequency domain, resulting in an increase in positioning error. In oil pipeline monitoring, the vibration noise generated by mechanical construction may cover up the real leakage signal, leading to incorrect actual positioning.

[0004] Therefore, there is an urgent need for an integrated device for optical fiber positioning and common-mode noise suppression based on time-frequency joint coding. Summary of the Invention

[0005] The purpose of the present invention is to provide an integrated device for optical fiber positioning and common-mode noise suppression based on time-frequency joint coding to solve the problem that traditional optical fiber positioning devices rely on the intensity of backscattered light for positioning, but interference such as environmental vibration and temperature drift will introduce common-mode noise, causing the target signal to overlap in the time domain and frequency domain, resulting in an increase in positioning error. In oil pipeline monitoring, the vibration noise generated by mechanical construction may cover up the real leakage signal, leading to incorrect actual positioning as mentioned in the above background art.

[0006] To solve the above technical problems, the present invention provides the following technical solution: An integrated device for optical fiber positioning and common-mode noise suppression based on time-frequency joint coding, including a time-frequency coding modulation module. A common-mode noise suppression module is installed at the bottom of the time-frequency coding modulation module, and an optical fiber sensing link is installed inside the common-mode noise suppression module; The time-frequency coding modulation module includes a narrow linewidth laser, an acousto-optic modulator, and an encoder. The narrow linewidth laser outputs continuous light with a wavelength of 1550 nm and a linewidth ≤ 1 MHz. The acousto-optic modulator generates heterodyne pulse pairs with a frequency shift range of 50 kHz to 100 kHz and a pulse width of 10 ns to 1 μs. The encoder combines pseudo-random sequence coding and frequency hopping spread spectrum, and the coding sequence length ≥ 1024 bits.

[0007] Preferably, a plurality of common-mode noise suppression modules are provided. The common-mode noise suppression module includes a differential detection structure and an adaptive filter. The differential detection structure uses dual-detector balanced reception, and the two detectors are electrically connected to each other. The adaptive filter uses the LMS algorithm, and the adaptive filter is electrically connected to the differential detection mechanism.

[0008] Preferably, the LMS algorithm is the core algorithm of adaptive filtering. It iteratively optimizes the filter coefficients through the gradient descent method to minimize the mean square error between the output signal and the desired signal. At initialization, the filter coefficients w(0) and the step size factor μ are set. During iterative update, for each time step n, the filter output is calculated as: y(n) = wT(n)x(n), where x(n) is the input signal vector and w(n) is the coefficient vector; the error is calculated as: e(n) = d(n) - y(n), where d(n) is the desired signal; the coefficients are updated as: w(n + 1) = w(n) + 2μe(n)x(n). The convergence condition is: stop when the error e(n) or the coefficient change amount is less than the threshold.

[0009] Preferably, the LMS algorithm also includes dynamic adjustment for noise reduction. In the fiber optic positioning system, environmental vibration causes common-mode noise, and the frequency changes with time. Initialize the filter coefficients w(0) = [0, 0, …, 0]T, and collect the input noisy signal x(n) and the desired signal d(n) (i.e., the pure signal) in real time. Calculate the error e(n), and update w(n) according to the LMS formula. As the iteration progresses, the filter gradually learns the noise pattern, the output y(n) approaches d(n), and the adaptive filter is adjusted.

[0010] Preferably, the fiber optic sensing link includes a single-mode fiber, a circulator, and a photodetector. The length of the single-mode fiber is 10 km to 50 km, which is used for distributed sensing and serves as the transmission medium for signals.

[0011] Preferably, the circulator separates the incident light and the backscattered light, and the isolation degree is ≥60 dB, which prevents the incident light from entering the receiving channel of the backscattered light.

[0012] Preferably, the photodetector uses an avalanche photodiode, with a bandwidth ≥100 MHz and a noise equivalent power ≤10 pW / √Hz. The photodetector is installed with the circulator to convert the backscattered light into an electrical signal.

[0013] Preferably, a signal demodulation and processing unit is further included. The signal demodulation and processing unit is electrically connected to the fiber optic sensing link. The signal demodulation and processing unit includes a high-speed data acquisition card with a sampling frequency ≥100 MHz and a sampling depth ≥10^6 points. The high-speed data acquisition card is electrically connected to the time-frequency coding modulation module.

[0014] Preferably, the signal conditioning and processing unit further includes a DSP algorithm, which acts on positioning. Through the cooperation of three stages: demodulation - filtering - positioning, the original electrical signal is converted into a high-precision positioning result.

[0015] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: First, in the present invention, the single-mode optical fiber is used as the signal transmission medium to achieve long-distance distributed sensing. The single-mode optical fiber has the characteristics of low loss and high bandwidth, which can ensure less attenuation of the signal during transmission, improve the sensing distance and accuracy of the system. The circulator can effectively prevent the incident light from entering the receiving channel of the backscattered light, ensuring the purity of the received signal. The photodetector converts the backscattered light into an electrical signal for subsequent signal processing. The time-frequency coding modulation module is the core basis. By connecting with the fiber optic sensing link, a narrow-linewidth laser provides a stable and monochromatic light source for the system. The narrow-linewidth characteristic helps to reduce phase noise, improve the signal-to-noise ratio and positioning accuracy of the system. The acousto-optic modulator modulates the continuous light into heterodyne pulse pairs, and by changing the frequency shift range and pulse width, flexible coding of the signal is achieved. The laser outputs continuous light, which is modulated by the acousto-optic modulator to generate heterodyne pulse pairs (Δf = f1 - f2). The pulse pairs are injected into the optical fiber after time-frequency coding, and the encoder encodes the positioning signal and the noise suppression signal into a composite waveform, improving the anti-interference ability and confidentiality of the signal. The pseudo-random sequence coding increases the randomness of the signal, and the frequency-hopping spread-spectrum technology disperses the signal in the frequency domain, reducing the probability of being interfered. The time-frequency coding modulation module deeply integrates the frequency-hopping spread-spectrum coding and the heterodyne detection technology, and can realize the transmission of the positioning signal and the common-mode noise suppression through the same optical fiber.

[0016] Second, in the present invention, the differential detection structure suppresses the common-mode interference through balanced reception by two detectors. When environmental vibration and temperature drift cause common-mode noise, the common-mode noise signals received by the two detectors are equal in magnitude and the same in phase, while the effective signals are different. Through differential operation, the common-mode noise can be suppressed, improving the anti-interference ability of the system. The adaptive filter is based on the LMS algorithm, which adjusts the filter coefficients in real time to dynamically suppress noise. The reference optical fiber noise signal is collected, and the noise power spectral density is calculated. The LMS algorithm iteratively optimizes the filter coefficients through the gradient descent method to minimize the mean square error between the output signal and the desired signal. When environmental vibration and temperature drift cause common-mode noise to be mixed into the backscattered signal of the optical fiber, the noisy signal x(n) output from the input photodetector is used, and the pure positioning signal generated by the time-frequency coding modulation module is set as the desired signal. Finally, through the adaptive filter, the coefficients are dynamically adjusted by the LMS algorithm, and the signal y(n) after noise suppression is output, which can dynamically adjust the noise suppression ratio according to the environment, accurately position the accuracy, and realize a closed loop of learning - adjustment - optimization, improving the reliability of the system in complex environments such as traffic, outdoor, and mine environments.

[0017] Thirdly, in the present invention, a high-speed data acquisition card performs high-speed acquisition on the electrical signals output by a photodetector to obtain sufficient data points for subsequent signal processing and analysis. The DSP algorithm demodulates, filters, and processes the acquired signals to achieve high-precision positioning and effective noise suppression. The signal demodulation and processing unit extracts the positioning signal and the noise suppression signal from the composite waveform of the time-frequency coding modulation module. Among them, the DSP algorithm is synchronized with the data of the LMS algorithm in the common-mode noise suppression module and matches the corresponding filtering algorithm, enabling the composite waveform emitted by the frequency coding modulation module to be quickly decoded with the signal demodulation and processing unit, and being synchronized in real time according to the change of the dynamically adjusted LMS algorithm data, updating the variable items related to filtering in the DSP algorithm, reducing the difference between the data obtained during decoding and the original pure data, and further improving the accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the working process of the structure of the present invention; Figure 2 It is a three-dimensional overall schematic diagram of the structure of the present invention.

[0019] Wherein: 1. Time-frequency coding modulation module; 2. Common-mode noise suppression module; 3. Optical fiber sensing link. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0021] The present invention provides the following technical solutions: Embodiment 1 Please refer to Figure 1 , Figure 2 , an integrated device for optical fiber positioning and common-mode noise suppression based on time-frequency joint coding, including a time-frequency coding modulation module 1. A common-mode noise suppression module 2 is installed at the bottom of the time-frequency coding modulation module 1, and an optical fiber sensing link 3 is installed inside the common-mode noise suppression module 2; The time-frequency coding modulation module 1 includes a narrow-linewidth laser, an acousto-optic modulator, and an encoder. The narrow-linewidth laser outputs continuous light with a wavelength of 1550 nm and a linewidth ≤ 1 MHz. The acousto-optic modulator generates heterodyne pulse pairs with a frequency shift range of 50 kHz to 100 kHz and a pulse width of 10 ns to 1 μs. The encoder combines pseudo-random sequence coding and frequency-hopping spread spectrum, and the coding sequence length ≥ 1024 bits.

[0022] The fiber optic sensing link 3 includes a single-mode optical fiber, a circulator, and a photodetector. The length of the single-mode optical fiber is 10 km to 50 km and is used for distributed sensing as a signal transmission medium.

[0023] The circulator separates the incident light from the backscattered light, with an isolation degree ≥ 60 dB, preventing the incident light from entering the receiving channel of the backscattered light.

[0024] The photodetector uses an avalanche photodiode, with a bandwidth ≥ 100 MHz and a noise equivalent power ≤ 10 pW / √Hz. The photodetector is installed with the circulator to convert the backscattered light into an electrical signal.

[0025] Through the above technical solutions, where the single-mode optical fiber serves as the signal transmission medium to achieve long-distance distributed sensing. The single-mode optical fiber has the characteristics of low loss and high bandwidth, which can ensure less attenuation of the signal during transmission, improve the sensing distance and accuracy of the system. The circulator can effectively prevent the incident light from entering the receiving channel of the backscattered light, ensuring the purity of the received signal. The photodetector converts the backscattered light into an electrical signal for subsequent signal processing. The time-frequency coding modulation module 1 is the core foundation. By connecting with the fiber optic sensing link 3, a narrow linewidth laser provides a stable and monochromatic light source for the system. The narrow linewidth characteristic helps reduce phase noise and improve the signal-to-noise ratio and positioning accuracy of the system. The acousto-optic modulator modulates the continuous light into heterodyne pulse pairs. By changing the frequency shift range and pulse width, flexible coding of the signal is achieved. The laser outputs continuous light, which is modulated by the acousto-optic modulator to generate heterodyne pulse pairs (Δf = f1 - f2). The pulse pairs are injected into the optical fiber after time-frequency coding, and the encoder encodes the positioning signal and the noise suppression signal into a composite waveform to improve the anti-interference ability and confidentiality of the signal. The pseudo-random sequence coding increases the randomness of the signal, and the frequency hopping spread spectrum technology disperses the signal in the frequency domain, reducing the probability of being interfered. The time-frequency coding modulation module 1 deeply integrates the frequency hopping spread spectrum coding and the heterodyne detection technology, and can achieve the transmission of the positioning signal and the common-mode noise suppression through the same optical fiber.

[0026] Embodiment 2 Please refer to Figure 1 、 Figure 2 , an integrated device for fiber optic positioning and common-mode noise suppression based on time-frequency joint coding. There are multiple common-mode noise suppression modules 2. The common-mode noise suppression module 2 includes a differential detection structure and an adaptive filter. The differential detection structure uses dual-detector balanced reception, and the two detectors are electrically connected to each other. The adaptive filter uses the LMS algorithm, and the adaptive filter is electrically connected to the differential detection mechanism.

[0027] The LMS algorithm is the core algorithm of adaptive filtering. It iteratively optimizes the filter coefficients through the gradient descent method to minimize the mean square error between the output signal and the desired signal. At initialization, the filter coefficients w(0) and the step size factor μ are set. During iterative update, for each time step n, the filter output is calculated as: y(n) = wT(n)x(n), where x(n) is the input signal vector and w(n) is the coefficient vector; the error is calculated as: e(n) = d(n) - y(n), where d(n) is the desired signal; the coefficients are updated as: w(n + 1) = w(n) + 2μe(n)x(n). The convergence condition is to stop when the error e(n) or the coefficient change amount is less than the threshold value.

[0028] The LMS algorithm also includes dynamic adjustment, which is used for noise reduction. In a fiber optic positioning system, environmental vibration causes common mode noise, and the frequency changes with time. The filter coefficients w(0) = [0, 0, …, 0]T are initialized, and the noisy input signal x(n) and the desired signal d(n) (i.e., the pure signal) are collected in real time. The error e(n) is calculated, and w(n) is updated according to the LMS formula. As the iteration progresses, the filter gradually learns the noise pattern, the output y(n) approaches d(n), and the adaptive filter is adjusted.

[0029] Through the above technical solutions, the differential detection structure balances the reception through two detectors to suppress common mode interference. When environmental vibration and temperature drift cause common mode noise, the common mode noise signals received by the two detectors are of equal magnitude and the same phase, while there are differences in the effective signals. Through differential operation, the common mode noise can be suppressed, improving the anti-interference ability of the system. The adaptive filter is based on the LMS algorithm, which adjusts the filter coefficients in real time to dynamically suppress noise. The reference fiber optic noise signal is collected, and the noise power spectral density is calculated. The LMS algorithm iteratively optimizes the filter coefficients through the gradient descent method to minimize the mean square error between the output signal and the desired signal. When environmental vibration and temperature drift cause common mode noise to be mixed into the fiber optic backscattering signal, the noisy signal x(n) output from the input optoelectronic detector is used, and the pure positioning signal generated by the time-frequency coding modulation module is set as the desired signal. Finally, the adaptive filter dynamically adjusts the coefficients according to the LMS algorithm, and outputs the signal y(n) after noise suppression, which can dynamically adjust the noise suppression ratio according to the environment, accurately position the accuracy, realize a closed loop of learning - adjustment - optimization, and improve the reliability of the system in complex environments such as traffic, outdoor, and mine environments.

[0030] Embodiment III Please refer to Figure 1 、 Figure 2, an integrated device for fiber optic positioning and common mode noise suppression based on time-frequency joint coding, further includes a signal demodulation and processing unit. The signal demodulation and processing unit is electrically connected to the fiber optic sensing link 3. The signal demodulation and processing unit includes a high-speed data acquisition card with a sampling frequency ≥ 100 MHz and a sampling depth ≥ 10^6 points. The high-speed data acquisition card is electrically connected to the time-frequency coding modulation module 1.

[0031] The signal conditioning and processing unit also includes a DSP algorithm. The DSP algorithm is used for positioning. Through the coordination of three stages: demodulation - filtering - positioning, the original electrical signal is converted into a high-precision positioning result.

[0032] Through the above technical solution, the high-speed data acquisition card performs high-speed acquisition on the electrical signal output by the photodetector to obtain sufficient data points for subsequent signal processing and analysis. The DSP algorithm demodulates, filters, and processes the acquired signal to achieve high-precision positioning and effective noise suppression. The signal demodulation and processing unit is used to extract the positioning signal and noise suppression signal from the composite waveform of the time-frequency coding modulation module 1. Among them, the DSP algorithm is synchronized with the data of the LMS algorithm in the common mode noise suppression module 2 and matches the corresponding filtering algorithm, enabling the composite waveform sent by the frequency coding modulation module 1 to be quickly decoded with the signal demodulation and processing unit, and being synchronized in real time according to the dynamic adjustment of the LMS algorithm data change, updating the variable items related to filtering in the DSP algorithm, reducing the difference between the data obtained during decoding and the original pure data, and further improving the accuracy.

[0033] In use, a single-mode optical fiber serves as the signal transmission medium to achieve long-distance distributed sensing. The single-mode optical fiber has the characteristics of low loss and high bandwidth, which can ensure less attenuation of the signal during transmission, improve the sensing distance and accuracy of the system. The circulator can effectively prevent the incident light from entering the receiving channel of the backscattered light, ensuring the purity of the received signal. The photodetector converts the backscattered light into an electrical signal for subsequent signal processing. The time-frequency coding modulation module 1 is the core foundation. By connecting to the fiber optic sensing link 3, a narrow-linewidth laser provides a stable and monochromatic light source for the system. The narrow-linewidth characteristic helps reduce phase noise, improve the signal-to-noise ratio and positioning accuracy of the system. The acousto-optic modulator modulates the continuous light into heterodyne pulse pairs, and by changing the frequency shift range and pulse width, flexible coding of the signal is achieved. The laser outputs continuous light, which is modulated by the acousto-optic modulator to generate heterodyne pulse pairs (Δf = f1 - f2). The pulse pairs are injected into the optical fiber after time-frequency coding. The encoder encodes the positioning signal and the noise suppression signal into a composite waveform, improving the anti-interference ability and confidentiality of the signal. The pseudo-random sequence coding increases the randomness of the signal, and the frequency-hopping spread-spectrum technology disperses the signal in the frequency domain, reducing the probability of being interfered. The time-frequency coding modulation module 1 deeply integrates the frequency-hopping spread-spectrum coding and the heterodyne detection technology, and can realize the transmission of the positioning signal and the common-mode noise suppression through the same optical fiber. The differential detection structure suppresses the common-mode interference through balanced reception by two detectors. When environmental vibration and temperature drift cause common-mode noise, the common-mode noise signals received by the two detectors are of equal magnitude and the same phase, while the effective signals are different. Through differential operation, the common-mode noise can be suppressed, improving the anti-interference ability of the system. The adaptive filter is based on the LMS algorithm, adjusts the filter coefficients in real time, and dynamically suppresses noise. It collects the reference optical fiber noise signal and calculates the noise power spectral density. The LMS algorithm iteratively optimizes the filter coefficients through the gradient descent method to minimize the mean square error between the output signal and the desired signal. When environmental vibration and temperature drift cause common-mode noise to be mixed into the fiber backscattered signal, the noisy signal x(n) output by the input photodetector is set as the desired signal by the pure positioning signal generated by the time-frequency coding modulation module. Finally, through the adaptive filter dynamically adjusting the coefficients in the LMS algorithm, the signal y(n) after noise suppression is output, which can dynamically adjust the noise suppression ratio according to the environment, accurately position the accuracy, realize the closed-loop of learning - adjustment - optimization, and improve the reliability of the system in complex environments such as traffic, outdoor, and mine environments.The high-speed data acquisition card performs high-speed acquisition on the electrical signals output by the photodetector to obtain sufficient data points for subsequent signal processing and analysis. The DSP algorithm demodulates, filters, and processes the acquired signals to achieve high-precision positioning and effective noise suppression. The signal demodulation and processing unit extracts the positioning signal and the noise suppression signal from the composite waveform of the time-frequency coding modulation module 1. Among them, the DSP algorithm is synchronized with the LMS algorithm data in the common-mode noise suppression module 2 and matches the corresponding filtering algorithm, enabling the composite waveform sent by the frequency coding modulation module 1 to be quickly decoded with the signal demodulation and processing unit, and being synchronized in real time according to the dynamic adjustment of the LMS algorithm data change, updating the variable items related to filtering in the DSP algorithm, reducing the difference between the data obtained during decoding and the original pure data, and further improving the accuracy.

[0034] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An integrated device for fiber optic positioning and common mode noise suppression based on time-frequency joint coding, characterized in that: It includes a time-frequency coding and modulation module (1). A common-mode noise suppression module (2) is installed at the bottom of the time-frequency coding and modulation module (1), and an optical fiber sensing link (3) is installed inside the common-mode noise suppression module (2). The time-frequency coding and modulation module (1) includes a narrow-linewidth laser, an acousto-optic modulator, and an encoder. The narrow-linewidth laser outputs continuous light with a wavelength of 1550 nm and a linewidth ≤ 1 MHz. The acousto-optic modulator generates heterodyne pulse pairs with a frequency shift range of 50 kHz to 100 kHz and a pulse width of 10 ns to 1 μs. The encoder combines pseudo-random sequence coding and frequency-hopping spread spectrum, and the coding sequence length ≥ 1024 bits.

2. The integrated device for fiber optic positioning and common mode noise suppression based on time-frequency joint coding according to claim 1, characterized in that: A plurality of the common-mode noise suppression modules (2) are provided. The common-mode noise suppression module (2) includes a differential detection structure and an adaptive filter. The differential detection structure uses dual-detector balanced reception, and the two detectors are electrically connected to each other. The adaptive filter uses the LMS algorithm, and the adaptive filter is electrically connected to the differential detection mechanism.

3. An integrated device for fiber optic positioning and common mode noise suppression based on time-frequency joint coding according to claim 3, characterized in that: The LMS algorithm is the core algorithm of adaptive filtering. It iteratively optimizes the filter coefficients through the gradient descent method to minimize the mean square error between the output signal and the desired signal. At initialization, the filter coefficients w(0) and the step size factor μ are set. During iterative update, for each time step n, the filter output is calculated: y(n) = wT(n)x(n), where x(n) is the input signal vector and w(n) is the coefficient vector; the error is calculated: e(n) = d(n) - y(n), where d(n) is the desired signal. Update the coefficients: w(n + 1) = w(n) + 2μe(n)x(n). Convergence condition: Stop when the error e(n) or the coefficient change amount is less than the threshold.

4. An integrated device for fiber optic positioning and common mode noise suppression based on time-frequency joint coding according to claim 3, characterized in that: The LMS algorithm also includes dynamic adjustment for noise reduction. In an optical fiber positioning system, environmental vibration causes common-mode noise, and the frequency changes with time. Initialize the filter coefficients w(0) = [0, 0,..., 0]T, and collect the input noisy signal x(n) and the desired signal d(n) in real time, which is the pure signal. Calculate the error e(n), update w(n) according to the LMS formula. As the iteration progresses, the filter gradually learns the noise pattern, the output y(n) approaches d(n), and the adaptive filter is adjusted.

5. An integrated device for fiber optic positioning and common mode noise suppression based on time-frequency joint coding according to claim 1, characterized in that: The optical fiber sensing link (3) includes a single-mode optical fiber, a circulator, and a photodetector. The length of the single-mode optical fiber is 10 km to 50 km, which is used for distributed sensing and serves as the transmission medium of the signal.

6. The integrated device for fiber optic positioning and common mode noise suppression based on time-frequency joint coding according to claim 5, characterized in that: The circulator separates the incident light and the backscattered light, and the isolation degree ≥ 60 dB, preventing the incident light from entering the receiving channel of the backscattered light.

7. An integrated device for fiber optic positioning and common mode noise suppression based on time-frequency joint coding according to claim 5, characterized in that: The photodetector uses an avalanche photodiode with a bandwidth ≥ 100 MHz and a noise equivalent power ≤ 10 pW / √Hz. The photodetector is installed with the circulator to convert the backscattered light into an electrical signal.

8. An integrated device for fiber optic positioning and common mode noise suppression based on time-frequency joint coding according to claim 1, characterized in that: It further includes a signal demodulation and processing unit, which is electrically connected to the fiber optic sensing link (3). The signal demodulation and processing unit includes a high-speed data acquisition card with a sampling frequency ≥ 100 MHz and a sampling depth ≥ 10^6 points. The high-speed data acquisition card is electrically connected to the time-frequency coding modulation module (1).

9. An integrated device for fiber optic positioning and common mode noise suppression based on time-frequency joint coding according to claim 8, characterized in that: The signal conditioning and processing unit further includes a DSP algorithm. The DSP algorithm is used for positioning. Through the coordinated operation of three stages: demodulation - filtering - positioning, the original electrical signal is converted into a high-precision positioning result.

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