36 results about "Rayleigh backscattering" patented technology

An optical frequency domain reflectometer with environmental disturbance resistance and large strain measurement capability belongs to the field of distributed optical fiber sensing and comprises an opposite sweep frequency light frequency modulation continuous wave signal generation module, a light splitting device, a modulation device, a circulator, a polarization controller, an optical coupling device, a photoelectric conversion module and a data acquisition and processing module. An optical signal generated by an opposite sweep frequency light frequency modulation continuous wave signal generation module is divided into probe light and local oscillation light through a light splitting device, the probe light is modulated through a modulation device and sent to an optical fiber through a circulator, and a Rayleigh back scattering light signal generated by the optical fiber and the local oscillation light interfere in an optical coupling device to obtain interference light; the photoelectric conversion module mixes beat frequency signals of interference light, and the data acquisition and processing module analyzes and processes the beat frequency signals. According to the invention, the position information of the Rayleigh backscattering point is marked by using the modulated probe light, the Rayleigh scattering signal at the corresponding position is restored, crosstalk between channels is inhibited, and high-precision measurement in a large dynamic range and resistant to environmental disturbance is realized.

The invention discloses a multidimensional communication sensing system integrating an optical transmission network and BOTDR / DAS distributed sensing, and relates to the technical field of optical fiber communication and optical fiber sensing. The system comprises an OTN transmission subsystem, an optical fiber link and a BOTDR / DAS fusion sensing subsystem. Wherein the OTN transmission subsystem is used for realizing high-capacity data transmission through an optical fiber link; and the BOTDR / DAS fusion sensing subsystem is used for realizing strain, temperature and vibration distributed measurement of an optical fiber link through a Brillouin scattering and Rayleigh backscattering mechanism. According to the system, a double-self-heterodyne demodulation architecture and a reverse wavelength division multiplexing mechanism are adopted, cooperative demodulation and high-isolation transmission of BOTDR and DAS signals are achieved under the common-fiber condition, and high-speed communication and distributed temperature, strain and vibration synchronous monitoring within the 100 km range can be achieved. According to the method, a technical foundation can be laid for realizing physical layer intelligentization of the in-service power OTN.

The invention provides a distributed phase detection device and method with a large dynamic measurement range. The device comprises a first laser, a second laser, a first pulse modulation and frequency shift module, a second frequency shift module and a receiving module, wherein the first laser is used for generating a signal with the frequency of 0; the second laser is used for generating a signal with frequency; the first pulse modulation and frequency shift module is used for generating a detection light pulse containing two frequencies based on the signal with the frequency of 0 and the signal with the frequency of 0; the detection light pulse is used for being injected into a to-be-detected optical fiber to generate Rayleigh backscattered light with two frequencies; the second frequency shift module is used for generating a signal containing the frequency Y. based on the signal containing the frequency Y. The receiving module is used for receiving Rayleigh backscattered light with two frequencies, a signal with the frequency of 1, and a beat frequency signal of the signal with the frequency of 1; the beat frequency signal is used for phase detection; the receiving module comprises a coherent receiver and a data acquisition module. According to the device provided by the embodiment of the invention, two sets of coherent receivers and acquisition modules required in a traditional dual-wavelength scheme are simplified into one set, and the hardware complexity and equipment cost of the system are remarkably reduced while an equivalent measurement function is maintained.

The application provides a distributed optical fiber acoustic wave sensing system and a pattern recognition method. The application relates to the fields of optical fiber sensing and pattern recognition, and the system comprises the following steps: continuous coherent light emitted by a narrow-line-width laser is split into two paths by a beam splitting fiber coupler, one path is used as local reference light, and the other path is used as probe light; the probe light is modulated into optical pulses in an acousto-optic modulator driven by a waveform generator, and the optical pulses are injected into a measured sensing optical fiber through a fiber loop; Rayleigh backscattering light returned through the measured sensing optical fiber is mixed with the local reference light through the fiber loop, and the mixed light is decomposed into two orthogonal polarized light beams in a polarization beam splitter and is transmitted to a first balanced photodetector and a second balanced photodetector respectively to be converted into electrical signals; and the two orthogonal interference electrical signals are synchronously collected by a data acquisition card and are sent to a host computer for demodulation. The application provides a new distributed acoustic wave monitoring method with high reliability and high generalization ability, and has extremely high engineering popularization value.

This application provides a self-injection-locked narrow-linewidth laser with a quasi-continuous locking region, comprising: a semiconductor laser source for generating an initial linewidth laser and outputting it via end-face coupling; a photonic integrated microcavity chip including a bus waveguide and a microring resonator coupled to it via an evanescent wave, for receiving the initial linewidth laser and providing feedback light to the semiconductor laser through Rayleigh backscattering of the microring resonator to excite a self-injection-locking effect; the microring resonator is a compact folded waveguide microcavity with an ultra-low free spectral range, the free spectral range of which is less than a preset threshold, so that when the driving current of the semiconductor laser is changed for wavelength tuning, the self-injection-locking regions of adjacent resonant modes in the cavity physically overlap or are closely spliced ​​in the current tuning parameter space, so that the semiconductor laser can continuously transition between adjacent modes without experiencing permanent unlocking during continuous current tuning, forming a quasi-continuous locking region.

Methods for a DFOS / DAS system that uses a Rayleigh backscattering optical signal, employs a transmitter / interrogator that generates optical signals with multiple frequencies and directs the generated optical signals into a optical fiber sensor, receives, by a receiver, backscattered signals, processes each frequency received and combines and interleaves frequency bands for improved signal-to-noise and a faster sampling rate. The receiver uses a correlation method for polarization and band combining / interleaving, that rotates the polarization and band diversities into a direction of one with highest averaged power, by aligning a same location along the length of the optical fiber sensor from different bands to a same clock cycle, apply correlation methods to the band diversities, to rotate the same location from the different bands to the same direction, and combines sub-bands allocated for SNR improvement, and delays resulting bands and interleaves them.

This invention discloses a bidirectional continuous-variable quantum key distribution method and system based on frequency division duplexing in a single-transceiver ring network. The method is based on a monolithically integrated silicon photonics transceiver chip. By pre-setting optical carrier frequency offsets for the forward and reverse links, it isolates the quantum signal from Rayleigh backscattering noise in the fiber in the frequency domain. The transmitting end generates a broadband waveform containing quantum signals and pilot signals, which is transmitted bidirectionally through a single optical fiber. The receiving end uses a laser source from the same chip as the local oscillator for coherent heterodyne detection. A digital signal processing module performs orthogonalization correction, phase recovery, and matched filtering to suppress noise and extract the quantum signal to generate a secure key. This invention solves the problems of inflexible networking, low fiber utilization, and severe scattering noise interference in bidirectional transmission over a single fiber caused by the separation of the transmitting and receiving ends in integrated continuous-variable quantum key distribution systems. It provides a low-cost and highly flexible solution for metropolitan quantum ring networks.

The invention provides a multi-order sideband-based multi-resolution distributed optical fiber acoustic wave sensing method, which comprises the following steps of: generating a detection light pulse comprising a plurality of linear frequency modulation sidebands with different sweep bandwidths, and injecting the detection light pulse into a sensing optical fiber; receiving a Rayleigh backscattering signal generated in the sensing optical fiber to obtain an electric signal containing vibration information distributed along the sensing optical fiber; matching filter banks corresponding to a plurality of linear frequency modulation sidebands with different frequency sweeping bandwidths are adopted, parallel matching filtering processing is carried out on the electric signals, a plurality of distributed sound wave sensing signals with different spatial resolutions are decoupled from the electric signals, and the spatial resolutions are determined by the frequency sweeping bandwidths corresponding to the linear frequency modulation sidebands; based on a plurality of distributed sound wave sensing signals with different spatial resolutions, multi-resolution sound wave vibration monitoring along a sensing optical fiber is realized.

The application discloses a distributed acoustic sensing data processing method, device and computer program product, wherein the method comprises: performing time-frequency transformation on Rayleigh backscattering original time domain signals collected by a distributed acoustic sensing system to obtain a frequency spectrum; extracting a main lobe part with concentrated energy from the frequency spectrum to obtain a main lobe frequency spectrum; quantizing conjugate representation components of each frequency spectrum coefficient in the main lobe frequency spectrum to form a binary symbol sequence; performing entropy coding on the binary symbol sequence to generate a compressed code stream; in response to a reconstruction requirement, performing entropy decoding on the compressed code stream to recover the binary symbol sequence and performing inverse quantization to reconstruct a main lobe frequency spectrum estimation; and performing inverse time-frequency transformation on the main lobe frequency spectrum estimation to reconstruct Rayleigh backscattering time domain signals. Through the synergistic effect of main lobe extraction, extreme quantization and entropy coding, the application realizes efficient compression and high-fidelity reconstruction of massive DAS data under the premise of retaining key phase information, significantly reduces storage and transmission overheads, and is suitable for hardware deployment.

The application discloses a kind of intelligent substation secondary circuit fault arc online monitoring method and device, pulse optical signal is sent to the redundant optical fiber in the substation secondary circuit optical cable by optical time domain reflectometer, and Rayleigh backscattering signal is collected;Wavelet packet transform is carried out on scattering signal, the energy characteristics and entropy characteristics of each frequency band are calculated, and multidimensional feature vector is obtained;Non-dominated solution set is filtered by applying Pareto Front Optimization algorithm, and the Pareto optimal solution set of arc characteristics is obtained;The directed graph model of optical fiber sensing network is constructed, the arc candidate position is determined by applying directed minimum cut algorithm, and positioning is carried out by tree filling algorithm;Feature and position information are constructed into time sequence feature matrix, input into the CNN-LSTM hybrid network of Bayes online resource allocation optimization for classification identification;Locking decision strategy is generated based on fault diagnosis result, encapsulated as MMS message and sent to station control layer, and protection linkage is realized.

The application discloses a kind of fiber communication sensing integration system based on frequency-sweeping laser, including frequency-sweeping optical carrier generation and intensity modulation transmitting part, same optical fiber transmission part, remote direct detection communication receiving part and coherent Rayleigh backscattering sensing receiving part;The whole system is composed of frequency-sweeping laser, low-speed arbitrary function generator, polarization maintaining fiber coupler, Mach-Zehnder modulator, arbitrary waveform generator, electric amplifier, erbium-doped fiber amplifier, fiber optic circulator, fiber to be measured, adjustable optical attenuator, photodetector, data acquisition equipment one, coherent receiver, data acquisition equipment two.The system of the application is simple in structure, high in system integration degree, simple in communication receiving end structure, improved in communication transmission performance, and flexible optimization in sensing performance, suitable for different communication transmission distance and distributed sensing application scenarios.

The application belongs to the technical field of optical fiber distributed sensing, and particularly relates to a DAS system based on a linear frequency modulation pulse and a phase demodulation method thereof. Laser emitted by a narrow linewidth laser in the device is divided into two parts through a polarization maintaining coupler. A part of light divided through the polarization maintaining coupler is modulated into LFM optical pulses through a double-parallel Mach-Zehnder modulator driven by an LFM signal generator, and the LFM optical pulses are output to a sensing optical fiber through an optical circulator after being filtered through an optical filter. Rayleigh backscattering light generated in the sensing optical fiber is output through the optical circulator and then is incident on an interference coupler. The other part of light divided through the polarization maintaining coupler is incident on the interference coupler as reference light. An interference signal output by the interference coupler is detected by a balanced photodetector and is subjected to phase demodulation by a computer to obtain a vibration signal. The application realizes rapid positioning and high-fidelity demodulation of the vibration signal.

This invention relates to a phase-sensitive optical time-domain reflectometer based on orthogonal frequency division multiplexing (OFDM) pulse coding. A continuous laser beam is split into a local path and a probe path via an optical coupler. The probe path, driven by a radio frequency signal, generates multiple frequency-orthogonal intensity-coded pulse sequences through an optical intensity modulator. These sequences are arranged sequentially in time, possessing the same symbol information but different chip sequences. The Rayleigh backscattered light generated by the pulse sequences entering the sensing fiber under test undergoes coherent interference with the local light in an optical bridge and polarization diversity module. The signal acquisition circuit utilizes an unmatched filter to achieve pulse compression and Rayleigh scattering signal separation, and synthesizes the results of the pulse coding sequences at each frequency to obtain the strain signal. Compared with existing technologies, this invention achieves pulse compression by designing an unmatched filter, improving the signal-to-noise ratio while maintaining spatial resolution. Furthermore, by synthesizing the results of orthogonal frequency pulse sequences, coherent fading is eliminated, achieving fading-free, high signal-to-noise ratio strain measurement.

A kind of data analysis method for distributed vibration sensing system, using distributed optical fiber sensing system to constitute front-end system output detection signal, using circulator to inject detection signal into the optical fiber to be measured and using detector to directly detect backscattering signal, realize the receiving and analysis of the signal to be measured;The detection signal collected by the detector is composed of a series of backscattering / reflection curves, and each detection pulse obtains a backscattering / reflection curve;The length of each backscattering / reflection curve is proportional to the length of the distributed vibration sensing optical fiber;The record curve matrix is redrawn to provide two-dimensional matrix data of backscattering / reflection curve, and the output of specific position is determined as a function of time;The two-dimensional matrix data of Rayleigh backscattering / backreflection curve is Fourier transformed along the distance direction row by row, and the disturbance information of the optical fiber sensing along the line is obtained.

The application discloses a kind of very low frequency disturbance perception positioning and large-capacity optical fiber communication fusion device, and the perception positioning detection signal is fused with digital subcarrier multiplexing (DSM) communication signal by frequency division multiplexing, to improve the spectral efficiency of optical fiber communication system;Compatible with space division multiplexing and wavelength division multiplexing and other expansion mechanisms, large-capacity optical fiber communication can be realized;Based on the direct detection distributed acoustic sensing (DAS) technology of chirped pulse, very low frequency disturbance perception positioning is realized;It is suitable for all communication optical fibers, including but not limited to single-mode optical fiber, multi-core optical fiber and multi-core few-mode optical fiber;While maintaining the performance advantages of traditional DAS system, different fiber core / mode Rayleigh backscattering intensity is received by diversity using multi-dimensional multiplexing, so as to improve the signal-to-noise ratio and sensitivity of disturbance perception positioning signal.

Methods for a DFOS / DAS system that uses a Rayleigh backscattering optical signal, employs a transmitter / interrogator that generates optical signals with multiple frequencies and directs the generated optical signals into a optical fiber sensor, receives, by a receiver, backscattered signals, processes each frequency received and combines and interleaves frequency bands for improved signal-to-noise and a faster sampling rate. The receiver uses a correlation method for polarization and band combining / interleaving, that rotates the polarization and band diversities into a direction of one with highest averaged power, by aligning a same location along the length of the optical fiber sensor from different bands to a same clock cycle, apply correlation methods to the band diversities, to rotate the same location from the different bands to the same direction, and combines sub-bands allocated for SNR improvement, and delays resulting bands and interleaves them.

The application discloses a system for eliminating fading noise in a distributed optical fiber acoustic wave sensing system, which comprises a light source, a light frequency shift modulator, a light amplifier, an optical circulator, a photoelectric detector, a data acquisition card and a data demodulator; the laser emitted by the light source is modulated into double-pulse light with a frequency difference by the light frequency shift modulator, the double-pulse light is amplified by the light amplifier and then injected into an optical fiber through the optical circulator, the Rayleigh backscattering light generated in the optical fiber is emitted back to the optical circulator, the light emitted from the optical circulator is detected by the photoelectric detector and converted into an electric signal, the electric signal is collected by the data acquisition card and converted into a digital signal, and the data demodulator demodulates the digital signal by using a fading noise elimination method to obtain a signal in which the fading noise is eliminated. Therefore, the application can effectively eliminate the fading noise in the distributed optical fiber acoustic wave sensing system, improve the quality of the signal and eliminate the interference of the error signal.

The application belongs to the technical field of optical fiber distributed sensing, and discloses a distributed optical fiber acoustic sensing device and method based on a linear frequency modulation pulse sequence, which comprises a narrow linewidth laser, double-parallel Mach-Zehnder modulators and an arbitrary waveform generator; the arbitrary waveform generator is connected with the double-parallel Mach-Zehnder modulators and used for generating a linear frequency modulation pulse sequence including multiple pulses with sequentially increasing or decreasing center frequencies to drive the double-parallel Mach-Zehnder modulators; laser emitted by the narrow linewidth laser is divided into two parts, one part of which is used as reference light, and the other part is used as signal light, which is modulated into a linear frequency modulation pulse sequence by the double-parallel Mach-Zehnder modulators and then output to a sensing optical fiber; Rayleigh backscattering light generated in the sensing optical fiber interferes with the reference light, and an interference signal is detected by a balanced photodetector and then collected by a collection card. The application can realize dynamic strain measurement with high resolution and large measurement range.

The invention discloses a vibration sensing method based on a distributed optical fiber sound wave sensing system, which comprises the following steps of: injecting continuous light waves into a sensing optical fiber, and applying dynamic polarization disturbance to obtain a polarization state evolution sequence of Rayleigh backscattered light; performing differential processing on the polarization state sequence to extract polarization state variation caused by vibration; and inputting the signal subjected to differential processing into a pre-trained deep neural network model, and directly outputting vibration distribution information along the sensing optical fiber by the model, including vibration position, frequency and amplitude. The system comprises a narrow linewidth laser source module, a polarization modulation and disturbance module, a circulator, a sensing optical fiber, a polarization detection module and an intelligent signal processing module. According to the method, the problem of fading noise in traditional phase-sensitive distributed optical fiber sensing is solved by utilizing polarization state difference and deep learning.

The application discloses an optical frequency domain reflectometer with environmental disturbance resistance and large strain measurement capability, and belongs to the field of distributed optical fiber sensing.The optical frequency domain reflectometer comprises a frequency-modulated continuous wave signal generation module, a light splitting device, a modulation device, a circulator, a polarization controller, an optical coupling device, an optoelectronic conversion module and a data acquisition and processing module.The frequency-modulated continuous wave signal generation module generates an optical signal, which is split into probe light and local oscillator light by the light splitting device.The probe light is modulated by the modulation device and is sent to an optical fiber by the circulator.The Rayleigh backscattering light signal generated by the optical fiber and the local oscillator light interfere with each other in the optical coupling device to obtain interference light.The optoelectronic conversion module mixes beat signals of the interference light, and the data acquisition and processing module analyzes and processes the beat signals.The probe light is modulated to mark the position information of the Rayleigh backscattering point, and the Rayleigh scattering signal corresponding to the position is restored, so that the crosstalk between channels is suppressed, and high-precision measurement with large dynamic range and environmental disturbance resistance is realized.

The application discloses a kind of based on GPU acceleration's pulse compression DAS frequency domain matching filter method and system, it is related to optical fiber sensing technical field, including: the initial receiving signal after Rayleigh backscattering signal and local light interference of pulse compression DAS system are carried out band-pass filter processing, obtain the receiving signal after pre-processing;Based on GPU parallel and the transmitting linear chirp pulse signal of pulse compression DAS system are carried out frequency domain matching filter to the receiving signal after pre-processing, obtain compressed time-domain signal;Compressed time-domain signal is carried out vector rotation average processing, obtain the time-domain signal of suppression coherent fading;Phase demodulation is carried out to the time-domain signal of suppression coherent fading, obtain the disturbance information of measured optical fiber.The application has alleviated the technical problems of low signal demodulation efficiency, difficult to meet the real-time monitoring needs of prior art.

The invention relates to the technical field of geotechnical engineering and oil and gas drilling, and provides a system and method for detecting the crushing degree of fractured stratum rock mass, and the system comprises a load applying device, a laser, a coupler, a measuring optical fiber and an optical fiber demodulation device; the load applying equipment is used for applying pressure to the fractured core column, and a measuring optical fiber is arranged on the fractured core column; laser emitted by the laser is divided into first signal light and second signal light through the coupler, the first signal light enters the measuring optical fiber, the second signal light enters the optical fiber demodulation equipment, and backward Rayleigh scattering light generated by the first signal light in the measuring optical fiber enters the optical fiber demodulation equipment through the coupler; and the optical fiber demodulation equipment obtains optical fiber strain data by demodulating a beat frequency signal formed by Rayleigh backscattered light of the first signal light and the second signal light, wherein the optical fiber strain data is used for determining a breakage index. According to the method, subjective errors of manual identification can be avoided, micro cracks can be identified, and the identification efficiency and precision of the crushing degree can be improved.

An optical fiber temperature measurement device (10) comprises: a COTDR measurement unit (1) that measures Rayleigh backscattered light from an optical fiber to be measured, the COTDR measurement unit (1) causing light emitted from a first light source to be incident on the optical fiber to be measured, the first light source performing temperature control by changing the frequency by hopping and being capable of changing the line width of the emitted light; a BOTDR measurement unit (2) that measures Brillouin backscattered light from the optical fiber to be measured, the BOTDR measurement unit (2) causing light emitted from a second light source to be incident on the optical fiber to be measured, the second light source being capable of changing the line width of the emitted light and sweeping the emitted light by changing the frequency by triangular chirp pulses; a calibration optical fiber (8) that calibrates temperature and the like; and an LPR analysis unit (5) that calculates the intensity of the Rayleigh backscattered light and the intensity of the Brillouin backscattered light on the basis of the outputs of the COTDR measurement unit (1) and the BOTDR measurement unit (2), and measures the temperature of the optical fiber to be measured at a prescribed position using a Landau-Placzek ratio obtained on the basis of the outputs of the COTDR measurement unit (1) and the BOTDR measurement unit (2).

A device includes a narrow linewidth laser, a dual-parallel Mach-Zehnder modulator and an arbitrary waveform generator. The arbitrary waveform generator is connected to the dual-parallel Mach-Zehnder modulator, and is configured to generate the linear frequency modulation pulse sequence including a plurality of pulses with sequentially increased or decreased central frequencies, so as to drive the dual-parallel Mach-Zehnder modulator. A laser transmitted by the narrow linewidth laser is divided into two parts, one part serves as reference light, and the other part, as signal light, is modulated into the linear frequency modulation pulse sequence by the dual-parallel Mach-Zehnder modulator and then output to a sensing optical fiber. Rayleigh backscattered light generated in the sensing optical fiber interferes with the reference light. An interference signal is detected by a balanced photodetector and subsequently acquired by an acquisition card.

The present application relates to a kind of temperature pressure acoustic multi-parameter synchronous measurement with optical fiber sensing system and measurement method, optical fiber sensing system includes light output component, circulator, optical fiber component and demodulation component;Light output component is connected with the first port of circulator, optical fiber component is connected with the second port of circulator, demodulation component is connected with the third port of circulator;Multiple bragg gratings are engraved on optical fiber component;Measurement method is: laser injection is obtained in optical fiber-distributed acoustic signal, temperature value and pressure value by demodulation;Compared with traditional sensing system, by setting optical fiber component, the tail end of optical fiber component realizes the measurement of pressure;Bragg grating realizes the quasi-distributed measurement of temperature;Rayleigh backscattering light is used to realize the distributed measurement of acoustic wave, thereby, reduce construction difficulty;At the same time, when monitoring in situ to natural gas hydrate production well, reduce installation difficulty, improve installation efficiency.

This invention provides a distributed optical fiber sensing system and vibration localization method based on AOM frequency shifting, belonging to the field of optical fiber sensing technology. The system splits the probe light emitted from a light source into two beams. One beam is frequency-shifted and input into a first interferometer structure, while the other beam is input into a second interferometer structure. Both beams are coupled in the interferometer structures to obtain a sensing light and a reference light. The sensing light passes through the sensing fiber and is coupled with the reference light in an optical demodulation element to obtain interference light. The two interference lights are converted into electrical signals, and Rayleigh backscattering noise is eliminated using signal processing components. The vibration location in the sensing fiber is determined based on the phase delay difference between the two electrical signals. This invention avoids Rayleigh backscattering interference, increases the sensing distance, improves the system's signal-to-noise ratio, eliminates the need for an additional light source, and uses only a single optical fiber for transmission, thus reducing costs.

The application discloses a kind of Φ-OTDR data real-time processing system and method based on unscented Kalman filter.The system includes modulated signal generation module, data acquisition module, data combination reading module, phase calculation module, data transmission module, phase unpacking module and communication module.The method is: three adjacent pulsed light produces Rayleigh backscattering into unbalanced Michelson interferometer, and modulation voltage is applied to PZT piezoelectric ceramic, so that three-way interference RBS has additional phase;signal acquisition module acquires three-way light intensity signal and stores into data combination reading module, and reads the light intensity signal of corresponding detection sequence;Phase calculation module calculates the corresponding wrapped phase, and inputs data to unscented Kalman filter module for phase unpacking;Communication module sends the phase information unpacked to host computer.The application realizes the data real-time processing of Φ-OTDR system, and improves the accuracy and noise immunity of phase unpacking.

The application discloses a low-frequency optical fiber sensing signal enhancement method, device, equipment and medium, and belongs to the technical field of optical fiber sensing. The low-frequency optical fiber sensing signal enhancement method comprises the following steps: obtaining Rayleigh backscattering signals, and performing fading suppression on the Rayleigh backscattering signals to obtain complex signals; performing inverse tangent demodulation and phase unwrapping on the complex signals to obtain an initial two-dimensional phase image; performing discrete cosine transform-non-local mean algorithm on the initial two-dimensional phase image to obtain a noise-suppressed phase image; and performing a low-frequency-oriented adaptive phase correction algorithm on the noise-suppressed phase image to obtain a corrected waveform. The application adopts a four-step full-process processing architecture for low-frequency optical fiber sensing signal enhancement, so that the reconstructed corrected waveform is highly matched with the real low-frequency vibration signal, the signal-to-noise ratio and waveform fidelity of the low-frequency signal are improved, and reliable basic data is provided for accurate identification and positioning of vibration events in a landslide monitoring scene.

The application discloses an OFDR scattering spectrum distortion recovery method based on dynamic time warping. In view of the correlation degradation and demodulation failure problems caused by the nonlinear scale distortion of Rayleigh backscattering spectrum of an optical fiber under large strain conditions and the position deviation accumulation, the method uses a dynamic time warping algorithm to establish an adaptive and point-by-point nonlinear mapping relationship between a reference spectrum and a sensing spectrum. The method can simultaneously compensate for the scale compression / stretching distortion in a local demodulation window and the position drift between global windows, realize accurate position matching between scattering points, effectively recover the distorted scattering spectrum, and thus improve the correlation. Experiments show that while maintaining high spatial resolution, the application significantly improves the strain measurement range of the OFDR system to 20000 mu epsilon, and solves the problem of high-precision distributed sensing under a large strain deformation environment.

An apparatus receives a radio frequency (“RF”) signal. The apparatus includes a first modulator encoding the RF signal on an optical carrier. The optical carrier includes a plurality of sidebands. The apparatus includes a filter operably coupled to the first modulator and passing therethrough an isolated sideband of the plurality of sidebands. The apparatus includes a Rayleigh-backscattering (“RBS”) speckle spectrometer. The RBS speckle spectrometer includes a second modulator receiving the isolated sideband and modulating the isolated sideband into alternating short and long, interrogation pulses. The RF speckle spectrometer generates a first collected signal based on Raleigh backscattered light in a first polarization and a second collected signal based on Raleigh backscattered light in a second polarization. The apparatus includes a processor receiving the first collected signal and the second collected signal, and recovering therefrom the RF spectrum of the RF signal.