A high-resolution, large-capacity optical fiber quasi-distributed sensing system and demodulation method

Abstract

This invention relates to the field of fiber optic sensing technology, specifically to a high-resolution, high-capacity fiber optic quasi-distributed sensing system and demodulation method. The system includes: an optical emission and pulse modulation module that emits narrowband laser light at a set step size, performs pulse chopping and optical amplification, and outputs optical pulses; an optical transmission and amplification module that isolates the reflected light, and guides the amplified optical pulses into a non-identical weak fiber Bragg grating array, extracting the signal light reflected from the array; within the same partition of the non-identical weak fiber Bragg grating array, signals are transmitted using wavelength division multiplexing (WDM), while between different partitions, signals are transmitted using time division multiplexing (TDM); a photoelectric conversion and data acquisition module converts the reflected optical signal into an electrical signal, performs A / D sampling and synchronous acquisition on the electrical signal; and a control processing module sends a synchronous control signal, performs time-domain signal filtering, spectral sliding filtering, and peak-finding demodulation on the acquired signal, and inverts the wavelength information of each weak fiber Bragg grating. This solves the problems of high transmission loss and low reliability in existing technologies.

Description

Technical Field

[0001] This invention relates to the field of fiber optic sensing technology, specifically to a high-resolution, high-capacity fiber optic quasi-distributed sensing system and demodulation method. Background Technology

[0002] With the continuous expansion of intelligent application scenarios, fiber optic sensing technology has attracted widespread market attention due to its unique advantages. Currently, fiber optic sensing is mainly divided into two categories based on measurement point resolution: point sensing and fully distributed sensing. Point sensing is deployed in a series-parallel manner, offering fast response speed but a limited number of sensing units. Fully distributed sensing is deployed in a series manner, where the entire optical cable can be used as a sensing unit, resulting in extremely high spatial resolution but slower response speed. Weak fiber Bragg grating array detection technology, as a novel solution integrating the advantages of both types of sensing technologies, adopts a networking method combining time-division multiplexing with identical weak fiber Bragg grating arrays. This enables measurement effects such as ultra-long-distance transmission, high spatial resolution, multi-point coverage, and fast response, adapting to the needs of more sensing application scenarios.

[0003] Existing fiber optic sensing technologies cannot simultaneously achieve high spatial resolution, large measurement point capacity, and fast response capabilities. Spatial resolution is strictly limited by the laser pulse modulation width; improving resolution requires compressing the pulse width, leading to a decrease in laser power and a significant reduction in effective sensing distance. Alternatively, pulse coding can result in stringent control requirements and complex demodulation processes. Multiplexing networking methods are limited, identical gratings are prone to wavelength crosstalk, partitioning multiplexing capabilities are weak, and measurement point capacity is difficult to increase on a large scale. There is no unified synchronization mechanism for optical emission, pulse modulation, and data acquisition, resulting in poor signal timing coordination and insufficient acquisition stability. The lack of effective isolation of the return light can easily damage the transmitting device, and the optical signal lacks efficient C-band amplification and stable unidirectional loop transmission, resulting in high transmission loss and low reliability. Signal processing does not integrate time-domain filtering, spectral sliding filtering, and precise peak-finding demodulation, resulting in poor wavelength inversion accuracy and low demodulation efficiency, failing to meet the requirements of high-performance sensing applications. Summary of the Invention

[0004] This application provides a high-resolution, high-capacity fiber optic quasi-distributed sensing system and demodulation method to solve the problems of high transmission loss and low reliability in the prior art.

[0005] The first aspect of this application provides a high-resolution, high-capacity fiber optic quasi-distributed sensing system, comprising: an optical emission and pulse modulation module, an optical transmission and amplification module, a non-identical weak fiber Bragg grating array, a photoelectric conversion and data acquisition module, and a control and processing module; wherein, the optical emission and pulse modulation module is used to emit narrowband laser at a set step size, and to pulse-chop and optically amplify the narrowband laser to output an optical pulse; the optical transmission and amplification module is used to isolate the return light, amplify the optical pulse in the C-band, and perform unidirectional loop transmission of the optical signal, guiding the amplified optical pulse into the non-identical weak fiber Bragg grating array, while simultaneously exporting the signal light reflected from the array; the non-identical weak... The fiber grating array is divided into N partitions, each containing M weak fiber gratings with different center wavelengths. Wavelength division multiplexing is used to transmit signals within the same partition, while time division multiplexing is used between different partitions. The photoelectric conversion and data acquisition module converts the reflected light signal into an electrical signal and performs A / D sampling and synchronous acquisition on the electrical signal. The control processing module sends synchronization control signals to the light emission and pulse modulation module and the photoelectric conversion and data acquisition module to synchronize light emission, pulse chopping, and data acquisition. It also performs time-domain signal filtering, spectral sliding filtering, and peak-finding demodulation on the acquired signals to retrieve the wavelength information of each weak fiber grating.

[0006] Preferably, the optical emission and pulse modulation module includes a tunable laser unit and an optical pulse modulation unit. The tunable laser unit emits narrowband laser light in a set step size using an electrically tunable method, performing continuous wavelength scanning and rapid switching. The optical pulse modulation unit is used to pulse chop and pre-amplify the narrowband laser light to output optical pulses. The pulse width can be adaptively adjusted according to the sensing distance and spatial resolution requirements.

[0007] Preferably, the optical transmission and amplification module includes an optical isolator, a C-band optical amplifier, and a three-port optical circulator. The optical isolator is used to completely isolate the reflected light returning from the sensing link, preventing the reflected light from interfering with the stable operation of the laser or even causing damage to the device. The C-band optical amplifier is used to amplify the power of the optical pulses passing through the isolator, compensating for losses during optical transmission and extending the sensing distance. The three-port optical circulator receives the amplified optical pulses at its first port and outputs them to the non-identical weak fiber Bragg grating array from its second port. Simultaneously, it unidirectionally exports the reflected signal returned from the second port to the photoelectric conversion and data acquisition module from its third port, performing unidirectional loop transmission and transceiver separation of the optical signal.

[0008] Preferably, the non-identical weak fiber Bragg grating array includes a partitioned time-division multiplexing unit, a co-partitioned wavelength-division multiplexing unit, and a wavelength-sensitive sensing unit. The partitioned time-division multiplexing unit divides the entire sensing fiber into N independent sensing partitions, achieving spatial separation of signals from different partitions through time-division multiplexing. The co-partitioned wavelength-division multiplexing unit deploys M weak fiber Bragg gratings with different center wavelengths within each sensing partition, distinguishing signals from multiple measurement points within the same partition through wavelength-division multiplexing. The wavelength-sensitive sensing unit uses weak fiber Bragg gratings as the basic sensing element, utilizing their wavelength-sensitive characteristics to sense changes in external physical quantities and reflect signal light of the corresponding wavelength. Simultaneously, a low reflectivity design is employed to reduce channel crosstalk between gratings.

[0009] Preferably, the photoelectric conversion and data acquisition module includes a C-band photoelectric conversion unit and a high-speed data acquisition unit. The C-band photoelectric conversion unit linearly converts weak reflected light signals in the C-band range into analog electrical signals, ensuring the fidelity of the signal conversion. The high-speed data acquisition unit performs A / D sampling on the analog electrical signals, and the sampling rate can be flexibly adjusted according to the requirements of light pulse width and spatial resolution.

[0010] Preferably, the control processing module includes a signal synchronization control unit and a signal demodulation processing unit. The signal synchronization control unit generates timing synchronization control signals, which are sent to the optical emission and pulse modulation module and the photoelectric conversion and data acquisition module, respectively, to perform timing matching of optical wavelength emission, pulse chopping, and data acquisition. The signal demodulation processing unit processes the acquired raw electrical signals, removes baseline drift and random noise, performs time-domain signal filtering to separate the effective spectral information of weak fiber grating locations, performs multi-point sliding filtering on the effective spectrum to smooth the spectral curve and reduce the influence of occasional discrete acquisition points on the peak finding results, and fits the peak position of the spectral response curve through a peak finding algorithm to obtain the center wavelength information of each weak fiber grating.

[0011] A second aspect of this application provides a demodulation method for a high-resolution, high-capacity fiber optic quasi-distributed sensing system, comprising: acquiring a scanning wavelength signal and a spatial position sequence; determining a first array based on the wavelength signal and the spatial position sequence; superimposing each column of the first array to obtain a second array; judging the second array, wherein if the second array exceeds a noise floor threshold, it is judged that there is a fiber grating at the corresponding spatial position, otherwise it is judged that there is no fiber grating; when it is judged that there is a fiber grating, acquiring the index of the spatial position information; extracting data at the corresponding index position in the first array based on the index to obtain a third array; and fitting the third array with a Gaussian fitting algorithm to demodulate the center wavelength of the actual fiber grating.

[0012] Preferably, before determining the first array based on the wavelength signal and spatial position sequence, the method includes: transmitting multiple consecutive scanning wavelengths according to a synchronization signal; chopping the current wavelength after it stabilizes to form a light pulse with a preset pulse width; the light pulse enters a weak fiber grating array; if the incident wavelength is within the wavelength bandwidth of a certain fiber grating, the fiber grating reflects the signal light of the corresponding wavelength and performs data acquisition; if the incident wavelength is not within the wavelength bandwidth of any fiber grating, the signal light is directly transmitted to the next fiber grating until the light pulse signal completes one round trip transmission, and then the next wavelength is switched.

[0013] Preferably, the first array is: ; in, The acquired light signal intensity / voltage amplitude value; The sequence number for the scanning wavelength; The sequence number is used to collect data at spatial locations;

[0014] The second array is: ; in, For the first The wavelength, the first The light signal intensity / voltage amplitude values ​​were collected at each location; For the same spatial location All scanning wavelengths signal The total signal value after column-by-column summation;

[0015] The third array is: ; in This is the index of the effective raster positions after filtering; The wavelength-spatial signal array is re-extracted to retain only the spatial locations of weak fiber Bragg gratings.

[0016] Preferably, after performing sliding filtering on each column of the third array, a Gaussian fitting algorithm is used to find the peak to obtain the index of the center wavelength, and the center wavelength of the actual fiber optic grating is calculated based on the current value of the light source. This includes: after performing sliding filtering on each column of the third array, a Gaussian fitting algorithm is used to find the peak to obtain the index of the center wavelength, and the center wavelength of the actual fiber optic grating is calculated based on the index of the center wavelength.

[0017] Therefore, this application has the following beneficial effects:

[0018] The optical emission and pulse modulation module in this embodiment can rapidly emit narrowband lasers and output nanosecond-level optical pulses according to a set step size, laying a solid foundation for high spatial resolution and fast response. The optical transmission and amplification module can isolate the backlight to protect the laser, complete C-band signal amplification, and realize unidirectional loop transmission of optical signals, effectively extending the sensing distance and ensuring stable system operation. The non-isolated weak fiber grating array adopts an N-partition architecture. Within the same partition, wavelength division multiplexing is used to improve resolution and isolate channel crosstalk. Time division multiplexing is used between different partitions to greatly expand the measurement point capacity, combined with low reflection... The high emissivity and narrow bandwidth characteristics result in a superior signal-to-noise ratio. The photoelectric conversion and data acquisition module efficiently converts optical signals to electrical signals and performs synchronous A / D sampling, accurately capturing reflected signals and ensuring acquisition synchronization. The control and processing module coordinates global signal synchronization, simplifying control logic and improving demodulation speed through time-domain filtering, spectral sliding filtering, and peak-finding demodulation, accurately retrieving wavelength information for each grating. The overall system balances high resolution, large capacity, high response speed, and high signal-to-noise ratio, making it adaptable to quasi-distributed fiber optic sensing in various scenarios such as temperature, strain, and vibration, thus enhancing its practicality and scalability. This solves the problems of high transmission loss and low reliability in existing technologies.

[0019] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0020] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the structure of a high-resolution, high-capacity fiber optic quasi-distributed sensing system according to an embodiment of this application; Figure 2 This is a schematic diagram of the system hardware architecture and signal transmission logic provided according to an embodiment of this application; Figure 3 This is a schematic diagram of a wavelength demodulation and signal processing flow according to an embodiment of this application; Figure 4 This is a flowchart illustrating a demodulation method for a high-resolution, high-capacity fiber optic quasi-distributed sensing system according to an embodiment of this application. Figure 5 This is a schematic diagram of a demodulation method for a high-resolution, high-capacity fiber optic quasi-distributed sensing system according to an embodiment of this application. Detailed Implementation

[0021] The technical systems of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] The following description, with reference to the accompanying drawings, illustrates a high-resolution, high-capacity fiber optic quasi-distributed sensing system and demodulation method according to embodiments of this application. Addressing the low reliability issue mentioned in the background section, this application provides a high-resolution, high-capacity fiber optic quasi-distributed sensing system. In this system, the optical emission and pulse modulation module can rapidly emit narrowband lasers at set step sizes and output nanosecond-level optical pulses, laying a solid foundation for high spatial resolution and fast response. The optical transmission and amplification module can isolate the backlight to protect the laser, amplify C-band signals, and achieve unidirectional loop transmission of optical signals, effectively extending the sensing distance and ensuring stable system operation. The non-identical weak fiber grating array adopts an N-partition architecture, using wavelength division multiplexing within the same partition to improve resolution and isolate channel crosstalk. Different intervals utilize time-division multiplexing to greatly expand the measurement point capacity, while low reflectivity and narrow bandwidth characteristics result in a superior signal-to-noise ratio. The photoelectric conversion and data acquisition module efficiently converts optical signals to electrical signals and performs synchronous A / D sampling, accurately capturing reflected signals and ensuring acquisition synchronization. The control and processing module coordinates global signal synchronization, simplifying control logic and improving demodulation speed through time-domain filtering, spectral sliding filtering, and peak-finding demodulation, accurately retrieving wavelength information for each grating. The overall system balances high resolution, large capacity, high response speed, and high signal-to-noise ratio, making it adaptable to quasi-distributed fiber optic sensing in various scenarios such as temperature, strain, and vibration, thus enhancing its practicality and scalability. This solves the problems of high transmission loss and low reliability in existing technologies.

[0023] Figure 1 This is a schematic diagram of the structure of a high-resolution, high-capacity fiber optic quasi-distributed sensing system provided in an embodiment of this application.

[0024] This application provides a high-resolution, high-capacity fiber optic quasi-distributed sensing system, the system 10 comprising:

[0025] The system includes an optical emission and pulse modulation module 100, an optical transmission and amplification module 200, a non-identical weak fiber grating array 300, a photoelectric conversion and data acquisition module 400, and a control and processing module 500.

[0026] The optical emission and pulse modulation module 100 is used to emit narrowband laser light at a set step size, and to perform pulse chopping and optical amplification on the narrowband laser light to output optical pulses. The optical transmission and amplification module 200 is used to isolate the return light, amplify the optical pulses in the C-band, and perform unidirectional loop transmission of the optical signal, guiding the amplified optical pulses into a non-identical weak fiber grating array, while simultaneously exporting the signal light reflected from the array. The non-identical weak fiber grating array 300 is divided into N partitions, each partition containing M weak fiber gratings with different center wavelengths. Within the same partition... Wavelength division multiplexing is used to transmit signals, while time division multiplexing is used to transmit signals between different partitions. The photoelectric conversion and data acquisition module 400 is used to convert the reflected light signal into an electrical signal and to perform A / D sampling and synchronous acquisition on the electrical signal. The control processing module 500 is used to send synchronous control signals to the light emission and pulse modulation module and the photoelectric conversion and data acquisition module to synchronize light emission, pulse chopping and data acquisition, and to perform time-domain signal filtering, spectral sliding filtering and peak finding demodulation on the acquired signal to invert the wavelength information of each weak fiber grating.

[0027] It is understood that in this embodiment, the optical emission and pulse modulation module can rapidly emit narrowband lasers and output nanosecond-level optical pulses according to a set step size, laying a solid foundation for high spatial resolution and fast response; the optical transmission and amplification module can isolate the backlight to protect the laser, complete C-band signal amplification, and realize unidirectional loop transmission of optical signals, effectively extending the sensing distance and ensuring stable system operation; the non-identical weak fiber grating array adopts an N-partition architecture, with wavelength division multiplexing used within the same partition to improve resolution and isolate channel crosstalk, and time division multiplexing used between different partitions to greatly expand the measurement point capacity. The combination of low reflectivity and narrow bandwidth results in a superior signal-to-noise ratio. The photoelectric conversion and data acquisition module efficiently converts optical signals to electrical signals and performs synchronous A / D sampling, accurately capturing reflected signals and ensuring acquisition synchronization. The control and processing module coordinates global signal synchronization, simplifying control logic and improving demodulation speed through time-domain filtering, spectral sliding filtering, and peak-finding demodulation, accurately retrieving wavelength information for each grating. The overall system balances high resolution, large capacity, high response speed, and high signal-to-noise ratio, making it adaptable to quasi-distributed fiber optic sensing in various scenarios such as temperature, strain, and vibration, thus enhancing its practicality and scalability. This solves the problems of high transmission loss and low reliability in existing technologies.

[0028] In this embodiment, the optical emission and pulse modulation module 100 includes a tunable laser unit and an optical pulse modulation unit.

[0029] The tunable laser unit emits narrowband lasers in a set step size using an electrically tuned method, enabling continuous scanning and rapid switching of wavelengths. The optical pulse modulation unit is used to pulse chop and pre-amplify the narrowband laser, outputting optical pulses whose pulse width can be adaptively adjusted according to the sensing distance and spatial resolution requirements.

[0030] It is understood that the laser unit in this embodiment achieves narrowband laser emission with set step size, continuous wavelength scanning and rapid switching through electrical tuning. Combined with C-band coverage and flexibly configurable tuning parameters, it improves the system's sensing adaptability. The pulse modulation unit completes pulse chopping and pre-amplification, and the pulse width can be adaptively adjusted according to the sensing distance and resolution, balancing detection capability and resolution, ensuring the stability of the optical pulse, ensuring the accuracy of the sensing signal from the source, and helping the system achieve high-resolution, high-capacity sensing detection.

[0031] In this embodiment, the optical transmission and amplification module 200 includes: an optical isolator, a C-band optical amplifier, and a three-port optical circulator.

[0032] The optical isolator is used to completely isolate the reflected light returning from the sensing link, preventing the reflected light from interfering with the stable operation of the laser or even causing damage to the device; the C-band optical amplifier is used to amplify the power of the optical pulses passing through the isolator, compensate for the loss during optical transmission, and extend the sensing distance; the three-port optical circulator receives the amplified optical pulses at the first port and outputs them to the non-identical weak fiber grating array from the second port, while simultaneously exporting the reflected signal returned from the second port unidirectionally to the photoelectric conversion and data acquisition module from the third port, performing unidirectional loop transmission and transceiver separation of optical signals.

[0033] It is understood that the optical isolator in this application embodiment can completely isolate the backlight returned from the sensing link, effectively preventing the backlight from interfering with the stable operation of the laser and damaging the device, and ensuring the safety and stability of the core components of the light source; the C-band optical amplifier can amplify the power of the optical pulses passing through the isolator, compensate for the loss in the optical transmission process, and significantly extend the system sensing distance; the three-port optical circulator realizes the unidirectional loop transmission and transmission-reception separation of the optical signal, accurately outputs the amplified optical pulses to the non-identical weak fiber optic grating array, and unidirectionally exports the array reflection signal to the photoelectric conversion and data acquisition module, ensuring the unidirectionality and accuracy of the optical signal transmission.

[0034] In this embodiment, the non-identical weak fiber Bragg grating array 300 includes: a partitioned time division multiplexing unit, a co-partitioned wavelength division multiplexing unit, and a wavelength-sensitive sensing unit.

[0035] The partitioned time-division multiplexing unit divides the entire sensing fiber into N independent sensing partitions, and uses time-division multiplexing to separate the signals of different partitions spatially. The co-partition wavelength-division multiplexing unit deploys M weak fiber gratings with different center wavelengths in each sensing partition, and uses wavelength-division multiplexing to distinguish the signals of multiple measurement points in the same partition. The wavelength-sensitive sensing unit uses weak fiber gratings as the basic sensing element, uses its wavelength-sensitive characteristics to sense changes in external physical quantities and reflect the corresponding wavelength signal light, and adopts a low reflectivity design to reduce channel crosstalk between gratings.

[0036] It is understood that the partitioned time-division multiplexing unit in this application divides the sensing fiber into N independent sensing partitions. Time-division multiplexing achieves spatial separation of signals from different partitions, effectively avoiding signal interference between partitions, improving the system's spatial resolution and expanding the sensing coverage. The co-partition wavelength-division multiplexing unit deploys M weak fiber gratings with different center wavelengths in each partition. Wavelength-division multiplexing enables signal differentiation of multiple measurement points within the same partition, significantly increasing the number of system measurement points and improving sensing capacity. The wavelength-sensitive sensing unit uses weak fiber gratings as the basic sensing element. It utilizes the wavelength-sensitive characteristics to accurately sense changes in external physical quantities and reflect corresponding wavelength signal light. At the same time, the low reflectivity design effectively reduces crosstalk between gratings, ensuring the purity of signal transmission and sensing accuracy.

[0037] In this embodiment, the photoelectric conversion and data acquisition module 400 includes a C-band photoelectric conversion unit and a high-speed data acquisition unit.

[0038] The C-band photoelectric conversion unit linearly converts weak reflected light signals in the C-band range into analog electrical signals, ensuring the fidelity of the signal conversion; the high-speed data acquisition unit performs A / D sampling on the analog electrical signals, and the sampling rate can be flexibly adjusted according to the requirements of light pulse width and spatial resolution.

[0039] It is understood that the C-band photoelectric conversion unit in this application embodiment can linearly convert weak reflected light signals in the C-band range into analog electrical signals, effectively ensuring the fidelity of signal conversion, avoiding signal distortion, and providing a high-quality electrical signal foundation for subsequent signal demodulation and processing; the high-speed data acquisition unit performs A / D sampling on the analog electrical signals, and the sampling rate can be flexibly adjusted according to the requirements of light pulse width and spatial resolution, which can accurately adapt to the needs of different sensing scenarios, ensuring that the acquired electrical signals accurately correspond to the characteristics of the light signals, and ensuring the accuracy of subsequent signal processing.

[0040] In this embodiment of the application, the control processing module 500 includes: a signal synchronization control unit and a signal demodulation processing unit.

[0041] The signal synchronization control unit generates timing synchronization control signals, which are sent to the optical emission and pulse modulation module and the photoelectric conversion and data acquisition module, respectively, to perform timing matching of optical wavelength emission, pulse chopping and data acquisition. The signal demodulation processing unit processes the acquired raw electrical signals, removes baseline drift and random noise, performs time-domain signal filtering to separate the effective spectral information of weak fiber grating locations, performs multi-point sliding filtering on the effective spectrum to smooth the spectral curve and reduce the influence of occasional discrete acquisition points on the peak finding results, and uses a peak finding algorithm to fit the peak position of the spectral response curve to obtain the center wavelength information of each weak fiber grating.

[0042] It is understood that the signal synchronization control unit in this application generates a timing synchronization control signal and sends it to the optical emission and pulse modulation module and the photoelectric conversion and data acquisition module to achieve precise timing matching of optical wavelength emission, pulse chopping and data acquisition. This effectively avoids problems such as signal misalignment and acquisition distortion caused by timing deviations, ensuring the synchronization and reliability of signal acquisition and laying the foundation for subsequent signal processing. The signal demodulation processing unit performs a series of processes on the acquired raw electrical signal, removing baseline drift and random noise, filtering effective spectral information, smoothing the spectral curve through multi-point sliding filtering and reducing the influence of occasional discrete points, and then obtaining the center wavelength information of each weak fiber grating by fitting the peak position through a peak-finding algorithm. This not only improves the purity and integrity of the signal, but also improves the accuracy of wavelength detection, ensuring that changes in external physical quantities can be accurately sensed and inverted.

[0043] This application proposes a high-resolution, high-capacity fiber optic quasi-distributed sensing system. The optical emission and pulse modulation module can rapidly emit narrowband lasers and output nanosecond-level optical pulses at set step sizes, laying a solid foundation for high spatial resolution and fast response. The optical transmission and amplification module can isolate the backlight to protect the laser, amplify the C-band signal, and achieve unidirectional loop transmission of the optical signal, effectively extending the sensing distance and ensuring stable system operation. The non-identical weak fiber Bragg grating array adopts an N-partition architecture. Within the same partition, wavelength division multiplexing is used to improve resolution and isolate channel crosstalk, while time division multiplexing is used between different partitions. The system significantly expands the measurement point capacity, and its low reflectivity and narrow bandwidth characteristics result in a superior signal-to-noise ratio. The photoelectric conversion and data acquisition module efficiently converts optical signals to electrical signals and performs synchronous A / D sampling, accurately capturing reflected signals and ensuring acquisition synchronization. The control and processing module coordinates global signal synchronization, simplifying control logic and improving demodulation speed through time-domain filtering, spectral sliding filtering, and peak-finding demodulation, accurately retrieving wavelength information from each grating. The overall system balances high resolution, large capacity, high response speed, and high signal-to-noise ratio, making it adaptable to various fiber-optic quasi-distributed sensing scenarios such as temperature, strain, and vibration, thus enhancing its practicality and scalability. This solves the problems of high transmission loss and low reliability in existing technologies.

[0044] The following will illustrate a high-resolution, high-capacity fiber optic quasi-distributed sensing system through a specific embodiment, including:

[0045] This embodiment builds a complete sensing system based on a high-resolution, high-capacity fiber optic quasi-distributed sensing system. The system integrates wavelength division multiplexing and time division multiplexing technologies, and uses a non-identical weak fiber optic grating array to achieve accurate detection of physical quantities. The system hardware architecture and signal transmission logic are as follows: Figure 2 As shown, the wavelength demodulation and signal processing flow is as follows: Figure 3 As shown, all module components, operating parameters, and data processing rules strictly follow the system design standards, achieving synergistic optimization of high spatial resolution, ultra-large measurement point capacity, and fast signal demodulation.

[0046] like Figure 2 As shown, this sensing system consists of an optical emission module 1, an optical pulse module 2, an optical isolator 3, an optical amplification module 4, an optical circulator 5, a non-identical weak fiber optic grating array 6, a photoelectric conversion module 7, a data acquisition module 8, an optical pulse drive module 10, and a control and processing module 9. These ten modules each perform their specific functions and work together to complete the entire process of optical signal emission, pulse modulation, transmission amplification, sensing reflection, photoelectric conversion, data acquisition, and signal processing. The optical emission module 1 is the core of the system's light source, possessing the core function of rapidly emitting narrowband light in set steps. It internally houses a tunable laser, compatible with various types such as DBR scanning lasers, DFB array scanning lasers, and VCSEL scanning laser arrays. The wavelength scanning range fully covers the C-band from 1525nm to 1565nm. It uses current tuning to achieve rapid wavelength switching, with the tuning step strictly controlled within 5GHz to ensure the accuracy and continuity of narrowband laser emission, providing a stable light source foundation for subsequent pulse modulation and grating sensing.

[0047] The optical pulse module 2 and the optical pulse drive module 10 form a modulation drive combination. The optical pulse drive module 10 specifically provides pulse drive signals for the optical pulse module 2. Under the action of the drive signal, the optical pulse module 2 completes pulse chopping and optical amplification processing, and can stably output nanosecond-level optical pulses. In this embodiment, the pulse width is set to 10ns, which can meet the detection requirements of high spatial resolution and ensure the transmission power of the optical pulse, adapting to the signal transmission requirements of long-distance sensing links. The optical isolator 3 is deployed between the optical pulse module 2 and the optical amplification module 4. Its core function is to isolate the backlight generated by the sensing link, completely blocking the reverse-transmitted optical signal from entering the front-end emission and modulation modules, avoiding laser malfunction or device damage caused by backlight, and ensuring the long-term stable operation of the light source system and the modulation system.

[0048] Optical amplification module 4 focuses on power amplification of C-band signal light, compensating for the energy of the optical pulses passing through optical isolator 3, offsetting the power loss of the optical signal during optical fiber transmission and grating reflection, effectively extending the effective transmission distance of the sensing link, and meeting the deployment requirements of ultra-large capacity measurement point arrays. Optical circulator 5 adopts a three-port optical loop design and is the core device for optical signal transmission and reception separation in the system. The first port receives the amplified optical pulses from optical amplification module 4, the second port directs the optical pulses into the non-identical weak fiber grating array 6, and the third port unidirectionally receives the signal light reflected by the array and outputs it to photoelectric conversion module 7, realizing unidirectional loop transmission and transmission and reception isolation of optical signals, eliminating signal crosstalk and transmission disorder.

[0049] The non-isolated weak fiber grating array 6 is the core sensing unit of the system. It adopts a partitioned multiplexing architecture, dividing the entire array into N independent sensing partitions, with a maximum of 10,000 partitions. Each partition deploys M weak fiber gratings with different center wavelengths, and the number of gratings in a single partition does not exceed 20. Within the same partition, weak fiber gratings transmit signals using wavelength division multiplexing (WDM), relying on the difference in center wavelengths to achieve synchronous differentiation of signals from multiple measurement points, effectively reducing channel crosstalk. Different partitions transmit signals using time division multiplexing (TDM), utilizing the temporal difference of optical pulses to achieve spatial separation of signals from different partitions, maximizing the expansion of measurement point capacity while improving spatial resolution. The core parameters of the weak fiber gratings are precisely calibrated: reflectivity not exceeding 0.01%, half-maximum bandwidth maintained between 0.1nm and 0.3nm, and a minimum spacing between gratings of 5cm. The low reflectivity design reduces signal interference between gratings, the narrow bandwidth design improves wavelength detection sensitivity, the dense grating layout achieves centimeter-level spatial resolution, and the partitioned multiplexing design breaks through the limitations of the number of measurement points in traditional sensing systems.

[0050] The photoelectric conversion module 7 possesses C-band optical signal linear conversion capability, accurately converting the weak reflected light signal exported from the optical circulator 5 into an analog electrical signal, fully preserving the amplitude and wavelength characteristics of the signal, and ensuring the fidelity of the signal conversion. The data acquisition module 8 is equipped with a high-speed A / D sampling unit with a sampling rate set to 2GHz. The sampling period is uniformly synchronized by the control processing module 9, perfectly matching the timing of light emission and pulse modulation. It converts the analog electrical signal into a digital signal and stores it, completely capturing the time-domain and spectral information of the reflected light signal. The control processing module 9 is the central control unit of the system, responsible for generating a global synchronization signal, realizing the timing coordination of the optical emission module 1, optical pulse module 2, and data acquisition module 8. It also performs noise reduction, screening, filtering, and peak finding calculations on the raw data, ultimately inverting the center wavelength information of each weak fiber grating to complete the core calculations for physical quantity sensing.

[0051] During system operation, the control processing module 9 sends a global synchronization signal, and the optical transmission module 1 continuously transmits scanning wavelengths in fixed steps of 1 GHz, covering the wavelength sequence from λ1 to λi, where i ranges from 1 to 5000, completing a precise wavelength scan across the entire C-band. After each wavelength transmission stabilizes, the optical pulse module 2, driven by the optical pulse drive module 10, performs a chopping operation to generate a standard optical pulse with a width of 10 ns. The optical pulse passes sequentially through the optical isolator 3, the optical amplification module 4, and the optical circulator 5, entering the non-identical weak fiber Bragg grating array 6. When the wavelength of the incident optical pulse falls within the wavelength bandwidth of a certain weak fiber Bragg grating, the grating reflects the signal light of the corresponding wavelength. Unmatched optical pulses are directly transmitted to the next grating until the optical pulse completes the transmission and round trip of the entire array. After the reflected signal light is exported through the third port of the optical circulator 5, it is converted into an analog electrical signal by the photoelectric conversion module 7. The data acquisition module 8 completes A / D sampling and data storage under the trigger of the synchronization signal. After a complete scan cycle, the system generates a two-dimensional array Pij. The rows of the array correspond to the backlight signal of the entire grating array under a single wavelength pulse, reflecting the spatial position information of the measurement point. The columns of the array correspond to the response signal of a single spatial measurement point in the full scan wavelength range, reflecting the spectral characteristics of the grating, and completely recording all the original data of the sensing link.

[0052] like Figure 3 As shown, the system's wavelength demodulation process relies on the original acquired data. It achieves accurate inversion of the center wavelength of weak fiber gratings through four main steps: time-domain accumulation, threshold filtering, sliding filtering, and peak fitting. First, each column of the two-dimensional array Pij is accumulated to generate a new one-dimensional array Pj. This accumulation operation integrates the full-wavelength response signal of a single spatial location, enhancing the amplitude characteristics of the effective grating signal and reducing background noise interference. Then, a system noise floor threshold Pthre is set, and array Pj is judged against this threshold. When the value of Pj is greater than Pthre, a weak fiber grating is determined to exist at that spatial location; otherwise, it is determined to be a blank location without a grating. Threshold filtering quickly separates effective sensing points, eliminates invalid noise data, and significantly improves subsequent processing efficiency.

[0053] After filtering, the system records the spatial position index of the effective gratings. Based on the index, it extracts the data of the corresponding column from the original two-dimensional array Pij to generate a dedicated demodulation array Pink. This array retains only the spectral response information of the effective gratings, providing a clean data foundation for subsequent wavelength calculations. For the dedicated demodulation array Pink, the system uses sliding filtering at least three points to smooth the fluctuation characteristics of the spectral curve and eliminate the influence of occasional discrete sampling points on peak finding accuracy. The filtered spectral curve better matches the actual response law of the weak fiber grating. After filtering, the peak position of the spectrum is fitted by a peak finding algorithm to determine the sequence index of the grating center wavelength. Various peak finding algorithms can be used, such as Gaussian fitting algorithm, centroid algorithm, and polynomial fitting algorithm. This embodiment uses Gaussian fitting algorithm as the core peak finding method. By approximating the sampled signal waveform with a Gaussian function, the Gaussian function is converted into a quadratic function with a downward opening. The wavelength sequence corresponding to the peak position is calculated. Then, combined with the light source scanning step and the starting wavelength, the actual center wavelength of the weak fiber grating is accurately calculated.

[0054] This system, through the fusion design of wavelength division multiplexing (WDM) and time division multiplexing (TDM), completely solves the industry problem of the mutual constraint between spatial resolution and pulse width in traditional weak fiber optic grating array sensing. WDM technology within the same partition improves spatial resolution while effectively isolating channel crosstalk, eliminating the need to compress pulse width to increase resolution and avoiding the problem of shortened sensing distance caused by reduced pulse power. TDM technology across different partitions increases the measurement point capacity to the 200,000 level. A design with 20 gratings per partition and 10,000 partitions enables simultaneous sensing of 200,000 measurement points. A 5-centimeter grating spacing achieves centimeter-level spatial resolution, while a 10-nanosecond pulse width and a 2-GHz sampling rate ensure microsecond-level response speed, comprehensively breaking through the performance bottlenecks of traditional sensing systems.

[0055] The reflected signal intensity of a non-identical weak fiber Bragg grating array is significantly higher than that of a fully distributed sensor, resulting in a substantial improvement in the system's signal-to-noise ratio. This allows for stable signal output even in long-distance, weak-signal detection scenarios. Furthermore, the system employs time-domain peak-finding demodulation with a scanning light source, eliminating the need for energy integration and accumulation. This significantly improves demodulation efficiency compared to traditional coded demodulation systems, simplifies control logic, and eliminates the need for complex pulse coding and decoding processes, reducing the development difficulty of both hardware and software and making it more suitable for large-scale engineering deployments. The system can be widely applied to quasi-distributed detection scenarios for physical quantities such as temperature, strain, and vibration, demonstrating significant application value in areas such as large-scale structural health monitoring, long-distance pipeline inspection, and industrial equipment condition sensing.

[0056] Combining the system's core technological advantages of high resolution, large capacity, long distance, and high signal-to-noise ratio, it can be adapted to various mainstream distributed fiber optic sensing engineering scenarios, including the following specific application scenarios:

[0057] I. Monitoring of Slopes Along Mountain Expressways: The distribution of slopes and landslide hazard points along mountain expressways is scattered and the monitoring range is wide. Furthermore, the complex mountain environment and numerous interference factors place extremely high demands on the monitoring system's measurement point capacity, anti-interference capability, and spatial resolution. This system, relying on an ultra-large measurement point capacity of 200,000 points, can achieve full coverage of both slopes along the entire mountain expressway. Combined with centimeter-level spatial resolution, it can accurately capture minute strain, displacement, and vibration changes in the slope, and monitor the relaxation, cracking, and sliding trends of the slope's soil and rock in real time. Simultaneously, the system possesses advantages such as stable long-distance transmission, low crosstalk, and a high signal-to-noise ratio. It can adapt to the complex temperature, humidity, wind, frost, rain, and snow environments in mountainous areas, continuously collecting slope sensor data 24 hours a day. Through real-time demodulation and analysis of the data, it can predict potential geological hazards such as landslides and slope collapses in advance, providing accurate data support for traffic safety management and slope maintenance early warning in mountainous expressways, effectively avoiding road safety accidents.

[0058] II. Bridge Structural Health Monitoring: Highway and railway bridges are constantly affected by factors such as vehicle loads, environmental temperature changes, wind and rain erosion, and structural aging, making them prone to defects such as beam cracking, pier settlement, steel structure fatigue, and abnormal cable stress. Traditional point-based monitoring methods suffer from problems such as monitoring blind spots, insufficient measuring points, and data lag. This system can deploy non-identical weak fiber optic grating arrays on key stress-bearing components of the bridge, such as the main beam, piers, supports, and cables. Through quasi-distributed full-coverage monitoring of strain, temperature, and vibration physical quantities, it can collect real-time data on the deformation and stress changes of the entire bridge structure. Relying on the system's high-speed demodulation and synchronous data processing capabilities, it can accurately identify minor structural damage and abnormal vibrations in the bridge, track the evolution of bridge structural aging and fatigue damage over the long term, and achieve early detection and early warning of bridge defects. This provides comprehensive and accurate quantitative data for regular bridge inspections, structural assessments, and safe operation and maintenance, ensuring bridge traffic safety and extending the service life of bridges.

[0059] III. Tunnel Engineering Inspection and Monitoring: Underground engineering structures such as highway tunnels, railway tunnels, and mountain tunnels are enclosed, with damp and dark environments, making them prone to hidden dangers such as lining cracking, surrounding rock convergence, arch settlement, and water seepage voids. These hidden dangers are often difficult to detect due to their concealment. This system is adapted to the long-distance, comprehensive monitoring needs of tunnels. Fiber optic sensor arrays can be deployed along the circumferential and longitudinal directions of the tunnel lining, leveraging the advantage of a large number of measuring points to achieve comprehensive, blind-spot-free monitoring of the entire tunnel. The system can monitor tunnel lining strain, structural deformation, ambient temperature, and micro-vibration in real time, accurately capturing hidden defects such as minute cracks in the lining and minor displacements in the surrounding rock. Furthermore, thanks to its high signal-to-noise ratio, it can withstand the influence of complex working conditions such as humidity, dust, and interference from electromechanical equipment within the tunnel, providing stable monitoring data output. Through long-term continuous monitoring and iterative data analysis, the development trend of tunnel structural defects can be predicted, providing reliable technical support for daily tunnel operation and maintenance, defect remediation, and emergency rescue, ensuring the long-term stable operation of tunnel projects.

[0060] IV. Grain Storage Monitoring: During the storage of grain in large grain reserves and silos, the grain is susceptible to damage from factors such as uneven environmental temperature and humidity, grain accumulation and settling, localized heating and mold growth, insect infestation, and vibration. This can lead to grain spoilage and structural damage. Traditional manual inspections and fixed-point temperature measurements suffer from low efficiency, incomplete monitoring, and significant time lag. This system deploys fiber optic sensor arrays inside the grain silo, on the surface of the grain pile, and at key locations in the storage building structure. On one hand, it can monitor the temperature distribution and temperature gradient within the grain silo with high precision, accurately locate localized heating points in the grain, and provide early warnings of mold growth and potential heat accumulation. On the other hand, it can monitor the structural strain and settlement deformation of the silo walls, roof, and floor, identifying potential safety hazards such as cracks and deformation in the storage building. The system's microsecond-level response speed enables real-time data updates and 24 / 7 unattended monitoring, significantly improving the level of intelligent monitoring in grain storage, ensuring grain storage safety, and mitigating storage losses.

[0061] In summary, the embodiments of this application effectively solve the problem of the mutual constraint between spatial resolution and pulse width in traditional sensing by combining wavelength division multiplexing and time division multiplexing technologies with a non-identical weak fiber Bragg grating array. It achieves synergistic optimization of centimeter-level spatial resolution, 200,000-level measurement point capacity, and microsecond-level response speed. Its non-identical weak fiber Bragg grating array design significantly improves the system's signal-to-noise ratio, enabling stable output in long-distance, weak signal scenarios. The scanning light source's time-domain peak-finding demodulation method simplifies control logic, improves demodulation efficiency, reduces the difficulty of software and hardware development, and facilitates large-scale engineering deployment. At the same time, the system can accurately detect physical quantities such as temperature, strain, and vibration, and is widely used in fields such as large-scale structural health monitoring, long-distance pipeline inspection, and industrial equipment condition sensing, providing a stable, accurate, and efficient sensing solution system for various scenarios.

[0062] Next, referring to the accompanying drawings, a demodulation method for a high-resolution, high-capacity fiber optic quasi-distributed sensing system according to an embodiment of this application is described.

[0063] like Figure 4 As shown, the demodulation method for this high-resolution, high-capacity fiber optic quasi-distributed sensing system includes the following steps:

[0064] In step S101, the scanning wavelength signal and spatial position sequence are acquired.

[0065] It is understood that the embodiments of this application acquire scanning wavelength signals and spatial position sequences, which can accurately establish the data correspondence between the scanning wavelength dimension and the fiber optic deployment spatial position dimension. This provides a complete original data source for the subsequent construction of a regular wavelength spatial joint data array. It can comprehensively collect optical signal data corresponding to different spatial points during the full-domain scanning process, which not only meets the data acquisition and storage requirements of large-capacity weak grating arrays, but also achieves accurate matching between signal data and actual deployment positions. This facilitates the subsequent rapid identification of effective grating points and the removal of useless background noise data. It can also provide complete and logically corresponding basic data for subsequent data superposition operations, sliding filtering processing, and fitting to solve the actual center wavelength of the fiber optic grating. This effectively ensures the orderly progress of the entire demodulation process and simultaneously improves the spatial positioning accuracy and wavelength resolution of the sensor demodulation.

[0066] In step S102, a first array is determined based on the wavelength signal and the spatial position sequence. Each column of the first array is superimposed to obtain a second array. The second array is judged. If the second array exceeds the noise floor threshold, it is judged that there is a fiber grating at the corresponding spatial position; otherwise, it is judged that there is no fiber grating.

[0067] Among them, the noise floor threshold refers to the lowest noise level limit that can effectively identify a valid signal from background noise.

[0068] It is understood that the noise floor threshold set in this application embodiment can effectively distinguish the effective light signal reflected by the fiber grating from the useless noise signals generated by environmental stray light, circuit electrical noise, and optical path transmission loss. It can accurately eliminate interference data at locations without gratings, quickly identify the actual spatial locations where weak fiber gratings exist, avoid misjudgments and incorrect judgments of grating existence caused by noise signals, significantly reduce the redundant computation of subsequent data processing, simplify the effective data processing range, and eliminate the adverse effects of noise floor interference on subsequent array superposition, filtering, and Gaussian fitting peak finding processes. It can also stabilize the accuracy of sensor location identification and improve the overall computational efficiency and reliability of the wavelength demodulation results of the demodulation method.

[0069] In this embodiment of the application, before determining the first array based on the wavelength signal and spatial position sequence, the process includes: transmitting multiple consecutive scanning wavelengths according to a synchronization signal; after the current wavelength stabilizes, chopping it to form a light pulse with a preset pulse width; the light pulse enters a weak fiber grating array; if the incident wavelength is within the wavelength bandwidth of a certain fiber grating, the fiber grating reflects the signal light of the corresponding wavelength and performs data acquisition; if the incident wavelength is not within the wavelength bandwidth of any fiber grating, the signal light is directly transmitted to the next fiber grating until the light pulse signal completes a round trip transmission, and then the next wavelength is switched.

[0070] Chopper refers to a power electronic conversion technology that uses switching devices to intermittently cut DC voltage or current into pulse waveforms to achieve voltage or current regulation.

[0071] It is understood that the embodiments of this application chop the stabilized scanning wavelength beam to form a fixed pulse width optical pulse, which can accurately control the emission duration and transmission sequence of the incident light signal, achieve precise synchronization of wavelength switching and spatial position signal acquisition, effectively avoid signal superposition and aliasing and optical path crosstalk caused by continuous beam transmission, regulate the round-trip transmission order of the optical pulse in the weak fiber grating array, and reasonably control the output energy of the optical signal, reduce stray interference signals formed by diffuse reflection of the optical path, conform to the working logic of the grating's position-by-position transmission and reflection, and allow each wavelength pulse to complete the full-domain optical path traversal acquisition in sequence, so that the acquired reflected signal has clear timing and clear boundaries, further improving the purity of the original acquired signal, and laying a solid foundation for timing and signal quality for subsequent point discrimination, data integration and precise wavelength demodulation.

[0072] In this embodiment of the application, the first array is: ; in, The acquired light signal intensity / voltage amplitude value; The sequence number for the scanning wavelength; The sequence number is used to collect data at spatial locations;

[0073] The second array is: ; in, For the first The wavelength, the first The light signal intensity / voltage amplitude values ​​were collected at each location; For the same spatial location All scanning wavelengths signal The total signal value after column-by-column summation;

[0074] The third array is: ; in This is the index of the effective raster positions after filtering; The wavelength-spatial signal array is re-extracted to retain only the spatial locations of weak fiber Bragg gratings.

[0075] It is understood that in this application embodiment, the first array organizes and integrates all the original optical signal data corresponding to the scanning wavelength and spatial position, and builds a complete two-dimensional basic data framework, which facilitates subsequent unified calling and batch calculation; the second array gathers energy by superimposing the column signals at the same spatial position, amplifies the numerical difference between the effective signal reflected by the grating and the ambient noise, and quickly completes the initial screening of grating positions with the help of thresholds; the third array removes redundant position data without gratings and retains only the accurate data content corresponding to the effective gratings, which greatly simplifies the data volume and reduces the consumption of invalid calculations, so that the subsequent core demodulation steps such as sliding filtering and Gaussian fitting peak finding are only carried out on the effective data. This ensures that the original effective signal is completely preserved, simplifies the data processing flow step by step, effectively improves the demodulation operation speed, and at the same time ensures the accuracy and stability of the demodulation results of the high-resolution, high-capacity fiber optic sensing system.

[0076] In step S103, when it is determined that there is a fiber optic grating, the index of the spatial location information is obtained, and the data at the corresponding index position in the first array is extracted according to the index to obtain the third array.

[0077] It is understood that, by obtaining the spatial location index corresponding to the effective fiber optic grating and extracting the corresponding data from the first array based on the index to generate the third array, the embodiment of this application can accurately locate the target position of the actual grating deployment, quickly eliminate a large amount of invalid and redundant data without gratings, achieve accurate screening and efficient simplification of sensor data, significantly reduce the total amount of data processed by subsequent algorithms, reduce system computing pressure and resource consumption, and at the same time completely retain the original wavelength signal data of all dimensions under the effective grating position, ensuring that useful sensing information is not lost. This provides pure and reliable computational data for subsequent sliding filter noise reduction, Gaussian fitting peak finding, and accurate solution of the actual center wavelength, which not only speeds up the overall demodulation processing speed, but also eliminates the interference of invalid position clutter in the core demodulation process, further improving the demodulation efficiency and result accuracy of the high-capacity fiber optic sensing system.

[0078] In step S104, the third array is fitted using a Gaussian fitting algorithm to demodulate the center wavelength of the actual fiber optic grating.

[0079] Gaussian fitting algorithm is a curve fitting method that uses a Gaussian function model to estimate the parameters of data distribution. It is often used to extract features such as peak position, width and intensity.

[0080] The formula for the Gaussian fitting algorithm is: ; Where y is the sampling voltage amplitude, x is the pulse wavelength sequence, u is the actual center wavelength sequence, σ is the Gaussian standard deviation, and a is the amplitude.

[0081] Take the logarithm of the right side of the equation, denoted as . Simplified to: ; ; but ,but Given a quadratic function with its opening facing downwards, the location of its peak point is... Then the center wavelength ,in This is the wavelength scanning step size. The starting wavelength.

[0082] It is understood that the Gaussian fitting algorithm used in this application embodiment is used for peak finding, which can fit the Gaussian distribution waveform characteristics of the reflection spectrum of weak fiber gratings. It can effectively adapt to the grating reflection signal shape and offset the waveform distortion caused by optical path loss, environmental noise and signal transmission distortion. Compared with conventional peak finding methods, it has stronger anti-interference ability and can accurately lock the wavelength index corresponding to the peak of the reflection spectrum, greatly reducing the peak positioning error. Based on the accurate index and the light source current value, after conversion, the actual center wavelength of the grating with higher accuracy can be obtained. At the same time, the algorithm has strong computational adaptability, which meets the demodulation requirements of high-resolution and high-capacity fiber optic quasi-distributed sensing systems, effectively improving wavelength demodulation accuracy, measurement stability and overall sensing and detection reliability.

[0083] In this embodiment of the application, the center wavelength of the actual fiber optic grating is demodulated by fitting the third array with a Gaussian fitting algorithm. This includes: performing sliding filtering on each column of the third array, using a Gaussian fitting algorithm to find the peak, obtaining the index of the center wavelength, and calculating the center wavelength of the actual fiber optic grating based on the index of the center wavelength.

[0084] It is understood that the embodiments of this application smooth the third array data through sliding filtering, effectively filtering out clutter interference and environmental noise during the sensing acquisition process, and regularizing the grating reflection spectrum waveform. Then, the Gaussian fitting algorithm is used to accurately complete the spectral peak finding and determine the center wavelength index. Relying on the characteristic of Gaussian function to fit the actual reflection spectrum shape of weak fiber grating, it can effectively improve the identification deviation problem caused by the low amplitude of weak grating signal and the easy distortion of waveform. It can not only greatly improve the demodulation accuracy and wavelength resolution of the center wavelength of the fiber grating, avoid the influence of background noise to cause peak misjudgment, but also adapt to the working requirements of multi-grating parallel demodulation of high-resolution, large-capacity quasi-distributed sensing systems, ensuring that the demodulation results of all effective fiber grating wavelengths in the array are accurate and stable, and comprehensively improve the signal resolution reliability and actual sensing and detection performance of the entire fiber optic sensing system.

[0085] According to the demodulation method of a high-resolution, high-capacity fiber optic quasi-distributed sensing system proposed in this application, the optical emission and pulse modulation module can rapidly emit narrowband lasers and output nanosecond-level optical pulses according to a set step size, laying a solid foundation for high spatial resolution and fast response; the optical transmission and amplification module can isolate the backlight to protect the laser, complete C-band signal amplification, and realize unidirectional loop transmission of optical signals, effectively extending the sensing distance and ensuring stable system operation; the non-identical weak fiber Bragg grating array adopts an N-partition architecture, with wavelength division multiplexing used within the same partition to improve resolution and isolate channel crosstalk, and time division multiplexing used between different partitions. The system significantly expands the measurement point capacity through multiplexing, and its low reflectivity and narrow bandwidth characteristics result in a superior signal-to-noise ratio. The photoelectric conversion and data acquisition module efficiently converts optical signals to electrical signals and performs synchronous A / D sampling, accurately capturing reflected signals and ensuring synchronous acquisition. The control and processing module coordinates global signal synchronization, simplifying control logic and improving demodulation speed through time-domain filtering, spectral sliding filtering, and peak-finding demodulation, accurately retrieving wavelength information from each grating. The overall system balances high resolution, large capacity, high response speed, and high signal-to-noise ratio, making it adaptable to various fiber-optic quasi-distributed sensing scenarios such as temperature, strain, and vibration, thus enhancing its practicality and scalability. This solves the problems of high transmission loss and low reliability in existing technologies.

[0086] The following will illustrate a demodulation method for a high-resolution, high-capacity fiber optic quasi-distributed sensing system through a specific embodiment, such as... Figure 5 As shown, it includes:

[0087] The core demodulation objective of the fiber optic quasi-distributed sensing system is to extract the effective grating position from the scanning optical signal and the spatial echo signal, and to calculate the actual center wavelength of the fiber optic grating. The entire demodulation process is completed through seven major steps: optical signal transmission, pulse modulation, data acquisition, array construction, threshold judgment, data filtering, filtering, and Gaussian fitting for peak finding.

[0088] After demodulation is initiated, the system's optical transmission module transmits a continuous scanning wavelength according to the synchronization control signal, with the wavelength sequence covering... to The wavelength scanning step is strictly set to This step value is a fixed parameter of the system, ensuring the uniformity of wavelength scanning and demodulation accuracy. A stable wavelength is output from the optical emission module. Then, the optical pulse module immediately chops and modulates the continuous light to generate a pulse with a width of [value missing]. light pulses, The pulse width is set to the optimal value for the system, ensuring spatial resolution while avoiding laser power attenuation caused by excessively narrow pulses.

[0089] The pulsed light passes sequentially through an isolator, an optical amplifier module, and a circulator before being incident on a non-identical weak fiber Bragg grating array transmission link. When the incident wavelength... When an incident wavelength falls within the bandwidth of a fiber Bragg grating, the grating reflects the corresponding wavelength of light. The reflected signal is transmitted via a circulator to a photoelectric conversion module for photoelectric conversion, and then acquired by a data acquisition unit. If the incident wavelength does not match the grating bandwidth, the light signal is directly transmitted to the next fiber Bragg grating until a single pulse completes a round trip transmission. At this point, the system switches to the next wavelength to continue transmission. During this process, the system simultaneously records the scanning wavelength sequence. Spatial location acquisition sequence The acquisition of the scanning wavelength signal and spatial position sequence is the data input foundation for the entire demodulation method.

[0090] After completing the full-cycle wavelength scan and data acquisition, the system constructs the first array based on the acquired light intensity data. The row dimension of the first array represents the reflected light signal of the entire weak fiber grating array acquired under a single wavelength pulse, used to reflect the spatial location information of the measurement point. The row sequence corresponds to the scanning wavelength sequence. The range of values ​​is to The column dimension of the first array represents the response of a single measurement point in space to the full scan wavelength range, reflecting the spectral information of the weak fiber grating at the measurement point. The column sequence corresponds to the spatial location acquisition sequence. This array stores all valid light intensity data within the system's full scan cycle and serves as the core data source for subsequent demodulation operations. The system automatically generates the first array upon completion of the scan cycle. Proceed to the next step of data processing.

[0091] After the first array is constructed, the system performs a column-by-column superposition operation on each column of data in the first array. By superimposing the columns, random noise interference of single-wavelength signals is eliminated, and the signal characteristics of the effective grating positions are enhanced. The superposition results in the generation of the second array. Each element of the second array Represents the corresponding spatial location The total return signal intensity can directly reflect whether an effective fiber Bragg grating exists at that location. The system then processes each element of the second array... With preset noise threshold Perform numerical comparison and execute threshold judgment logic: If Determine the spatial location There is a weak fiber grating at that location; if Determine the spatial location In areas lacking weak fiber gratings, invalid data at grating locations is discarded and not included in subsequent calculations. The threshold judgment step is a crucial step in selecting valid grating locations, significantly reducing background noise interference and improving demodulation efficiency and accuracy. It is the core of the initial data screening in the demodulation method.

[0092] After confirming the spatial location of a weak fiber Bragg grating through threshold judgment, the system automatically records the array index corresponding to that valid location. This index is a unique identifier connecting the first array of raw data to the valid raster data. The system then uses the recorded index... Extract the first array in reverse The third array is generated by removing all invalid noise data and raster-free position data from the original data at the corresponding index position. The third array retains only the spectral response data for valid grating positions, significantly reducing data dimensionality and improving signal purity, thus providing a high-quality data foundation for subsequent filtering and peak finding operations. This step strictly follows the index extraction rules of the demodulation method, achieving accurate screening and reconstruction of valid data.

[0093] After the third array is generated, the system performs sliding filter processing on each column of data in the third array, with the number of filter points set to at least [number missing]. One point, Point-sliding filtering is the optimal filtering configuration for the system, which can smooth noise while preserving spectral peak characteristics and avoid signal distortion caused by over-filtering. After the filtering operation is completed, the system uses a Gaussian fitting algorithm to perform peak finding on the filtered data. The Gaussian fitting algorithm is the core peak finding method specified in this scheme, which can accurately locate the center wavelength position of the grating spectrum.

[0094] Gaussian fitting operation with sampled voltage amplitude as the dependent variable The pulse wavelength sequence is the independent variable. The sampled signal waveform is approximated by a Gaussian function, and its core formula is: To simplify the calculation, the system performs a logarithmic transformation on the right side of the formula, converting the Gaussian function into a quadratic function with its opening facing downwards. ,in , , These are the transformed fitting coefficients. The peak value is calculated using the quadratic function peak value formula. The sequence index corresponding to the center wavelength can be calculated. Finally, the scanning step size is combined with the light source wavelength. With the starting wavelength Through formula After completing the fitting calculation, the actual center wavelength of the weak fiber grating is finally obtained. The entire peak finding and wavelength calculation process does not require integration time accumulation, resulting in fast demodulation speed and high accuracy, perfectly matching the system's requirement for rapid demodulation, marking the completion of the entire demodulation method.

[0095] In summary, the embodiments of this application effectively eliminate background noise interference and simplify data dimensions through array construction, threshold judgment, and data filtering. Combined with Gaussian fitting for peak finding, it achieves accurate calculation of grating position and center wavelength without the need for integration time accumulation, thus balancing demodulation speed and accuracy. Its function is to clearly present the complete logic and practical process of demodulation work, and to concretely demonstrate the end-to-end implementation method from optical signal transmission and data acquisition to final wavelength calculation. It provides a referenceable and feasible practical example for the demodulation scheme design, parameter optimization, and practical engineering application of this type of sensing system, and also confirms the feasibility and efficiency of the demodulation method.

[0096] In the description of this specification, the references to the terms "an embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0097] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of those features. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0098] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0099] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware as in another embodiment, it can be implemented using any of the following techniques known in the art, or a combination thereof: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0100] Those skilled in the art will understand that all or part of the steps of the methods described in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0101] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A high-resolution, high-capacity fiber optic quasi-distributed sensing system, characterized in that, include: The system includes an optical emission and pulse modulation module, an optical transmission and amplification module, a non-identical weak fiber grating array, a photoelectric conversion and data acquisition module, and a control and processing module; among which... The optical emission and pulse modulation module is used to emit narrowband lasers at a set step size, and to perform pulse chopping and optical amplification on the narrowband lasers to output optical pulses; The optical transmission and amplification module is used to isolate the return light, amplify the optical pulse in the C-band, and perform unidirectional loop transmission of the optical signal. The amplified optical pulse is then introduced into the non-identical weak fiber grating array, while the signal light reflected from the array is exported. The non-identical weak fiber Bragg grating array is divided into N partitions, each partition containing M weak fiber Bragg gratings with different center wavelengths. Wavelength division multiplexing is used to transmit signals within the same partition, and time division multiplexing is used to transmit signals between different partitions. The photoelectric conversion and data acquisition module is used to convert the reflected light signal into an electrical signal, and to perform A / D sampling and synchronous acquisition of the electrical signal; The control processing module is used to send synchronization control signals to the optical emission and pulse modulation module and the photoelectric conversion and data acquisition module to synchronize optical emission, pulse chopping and data acquisition, and to perform time-domain signal filtering, spectral sliding filtering and peak finding demodulation on the acquired signals to obtain the wavelength information of each weak fiber grating.

2. The high-resolution, high-capacity fiber optic quasi-distributed sensing system according to claim 1, characterized in that, The optical emission and pulse modulation module includes a tunable laser unit and an optical pulse modulation unit. The tunable laser unit emits narrowband lasers in a set step size using an electrically tunable method, performing continuous wavelength scanning and rapid switching. The optical pulse modulation unit is used to pulse chop and pre-amplify the narrowband laser to output optical pulses. The pulse width can be adaptively adjusted according to the sensing distance and spatial resolution requirements.

3. The high-resolution, high-capacity fiber optic quasi-distributed sensing system according to claim 1, characterized in that, The optical transmission and amplification module includes an optical isolator, a C-band optical amplifier, and a three-port optical circulator. The optical isolator completely isolates the reflected light returning from the sensing link, preventing the reflected light from interfering with the stable operation of the laser or even causing damage to the device. The C-band optical amplifier amplifies the power of the optical pulses passing through the isolator, compensating for losses during optical transmission and extending the sensing distance. The three-port optical circulator receives the amplified optical pulses at its first port and outputs them to the non-identical weak fiber Bragg grating array from its second port. Simultaneously, it unidirectionally exports the reflected signal returned from the second port to the photoelectric conversion and data acquisition module from its third port, performing unidirectional loop transmission and transceiver separation of the optical signal.

4. The high-resolution, high-capacity fiber optic quasi-distributed sensing system according to claim 1, characterized in that, The non-identical weak fiber Bragg grating array includes a partitioned time-division multiplexing unit, a co-partitioned wavelength-division multiplexing unit, and a wavelength-sensitive sensing unit. The partitioned time-division multiplexing unit divides the entire sensing fiber into N independent sensing partitions, using time-division multiplexing to spatially separate signals from different partitions. The co-partitioned wavelength-division multiplexing unit deploys M weak fiber Bragg gratings with different center wavelengths within each sensing partition, using wavelength-division multiplexing to distinguish signals from multiple measurement points within the same partition. The wavelength-sensitive sensing unit uses weak fiber Bragg gratings as the basic sensing element, utilizing their wavelength-sensitive characteristics to sense changes in external physical quantities and reflect corresponding wavelength signal light. It also employs a low reflectivity design to reduce channel crosstalk between gratings.

5. A high-resolution, high-capacity fiber optic quasi-distributed sensing system according to claim 1, characterized in that, The photoelectric conversion and data acquisition module includes a C-band photoelectric conversion unit and a high-speed data acquisition unit. The C-band photoelectric conversion unit linearly converts weak reflected light signals in the C-band range into analog electrical signals, ensuring the fidelity of the signal conversion. The high-speed data acquisition unit performs A / D sampling on the analog electrical signals, and the sampling rate can be flexibly adjusted according to the requirements of light pulse width and spatial resolution.

6. The high-resolution, high-capacity fiber optic quasi-distributed sensing system according to claim 1, characterized in that, The control processing module includes a signal synchronization control unit and a signal demodulation processing unit. The signal synchronization control unit generates timing synchronization control signals, which are sent to the optical emission and pulse modulation module and the photoelectric conversion and data acquisition module, respectively, to perform timing matching of optical wavelength emission, pulse chopping, and data acquisition. The signal demodulation processing unit processes the acquired raw electrical signals, removes baseline drift and random noise, performs time-domain signal filtering to separate the effective spectral information of weak fiber grating locations, performs multi-point sliding filtering on the effective spectrum to smooth the spectral curve and reduce the influence of occasional discrete acquisition points on the peak finding results, and uses a peak finding algorithm to fit the peak position of the spectral response curve to obtain the center wavelength information of each weak fiber grating.

7. A demodulation method for a high-resolution, high-capacity fiber optic quasi-distributed sensing system according to any one of claims 1-6, characterized in that, The method includes: Acquire the scanning wavelength signal and spatial position sequence; A first array is determined based on the wavelength signal and spatial position sequence. A second array is obtained by superimposing each column of the first array. The second array is judged. If the second array exceeds the noise floor threshold, it is judged that there is a fiber grating at the corresponding spatial position; otherwise, it is judged that there is no fiber grating. When a fiber optic grating is detected, the index of the spatial location information is obtained, and the data at the corresponding index position in the first array is extracted according to the index to obtain the third array; The third array is fitted using a Gaussian fitting algorithm to demodulate the center wavelength of the actual fiber optic grating.

8. The demodulation method for a high-resolution, high-capacity fiber optic quasi-distributed sensing system according to claim 7, characterized in that, Before determining the first array based on the wavelength signal and spatial position sequence, the process includes: transmitting multiple consecutive scanning wavelengths according to a synchronization signal; chopping the current wavelength after it stabilizes to form a light pulse with a preset pulse width; the light pulse entering a weak fiber grating array; if the incident wavelength is within the wavelength bandwidth of a certain fiber grating, the fiber grating reflects the signal light of the corresponding wavelength and performs data acquisition; if the incident wavelength is not within the wavelength bandwidth of any fiber grating, the signal light is directly transmitted to the next fiber grating until the light pulse signal completes one round trip transmission, and then the next wavelength is switched.

9. The demodulation method for a high-resolution, high-capacity fiber optic quasi-distributed sensing system according to claim 7, characterized in that, The first array is: ； in, The acquired light signal intensity / voltage amplitude value; The sequence number for the scanning wavelength; The sequence number is used to collect data at spatial locations; The second array is: ； in, For the first The wavelength, the first The light signal intensity / voltage amplitude values ​​were collected at each location; For the same spatial location All scanning wavelengths signal The total signal value after column-by-column summation; The third array is: ； in This is the index of the effective raster positions after filtering; The wavelength-spatial signal array is re-extracted to retain only the spatial locations of weak fiber Bragg gratings.

10. The demodulation method for a high-resolution, high-capacity fiber optic quasi-distributed sensing system according to claim 7, characterized in that, The process of fitting the third array with a Gaussian fitting algorithm to demodulate the center wavelength of the actual fiber optic grating includes: performing sliding filtering on each column of the third array, using a Gaussian fitting algorithm to find the peak, obtaining the index of the center wavelength, and calculating the center wavelength of the actual fiber optic grating based on the index of the center wavelength.

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