56 results about "Rayleigh backscattering" patented technology

The invention relates to a phase-sensitive optical time domain reflectometer based on multi-frequency reference switching. Continuous laser generated by a continuous laser is divided into a local path and a detection path through an optical coupler; the local path is input to the polarization coherent receiving module, the detection path is incident to a light intensity modulator driven by the signal generation circuit module, and the light intensity modulator is converted into a multi-frequency pulse laser sequence with intensity modulation; the multi-frequency pulse laser sequence enters the sensing optical fiber to be measured through the optical circulator; generated Rayleigh backscattered light and local continuous laser are subjected to beat frequency coherent receiving in a polarization coherent receiving module through a circulator; and the signal acquisition circuit adopts a demodulation algorithm to compensate phase drift and sensitivity difference of detection pulse demodulation signals with different frequencies so as to realize dynamic strain sensing. Compared with the prior art, the phase drift and the sensitivity difference between the frequencies are extracted to realize the compensation of the interleaved signals, and the method does not depend on the fixed reference frequency, so that the robustness and the adaptability of the system in a complex environment are remarkably enhanced.

The invention provides a distributed optical fiber sensing system based on AOM frequency shift and a vibration positioning method, and relates to the technical field of optical fiber sensing, probe light emitted by a light source is divided into two branch light beams, one branch light beam is input into a first interferometer structure after frequency shift, and the other branch light beam is input into a second interferometer structure. The two split light beams are coupled in the interferometer structure to obtain sensing light and reference light, and the sensing light is coupled with the reference light in the light demodulation element after passing through the sensing optical fiber to obtain interference light. The two paths of interference light are converted into electric signals, then the signal processing assembly is used for eliminating Rayleigh backscattering noise signals, and the vibration position in the sensing optical fiber is determined according to the phase delay inequality between the two electric signals. According to the invention, the interference of Rayleigh backscattering is avoided, the sensing distance is increased, the signal-to-noise ratio of the system is improved, an additional light source is not needed, only a single optical fiber is used for transmission, and the cost is reduced.

The invention relates to a phase-sensitive optical time domain reflectometer based on a parallel frequency division multiplexing sequence. Continuous laser is divided into a local path and a detection path through an optical coupler; the local path is input to the polarization coherent receiving module, the detection path is converted into a pulse laser sequence with intensity modulation through a light intensity modulator driven by a radio frequency signal provided by the signal generation circuit module, and the radio frequency signal is composed of two frequency division multiplexing sequences with difference; the pulse laser sequence enters the sensing link to be measured to generate Rayleigh backscattered light, and the Rayleigh backscattered light and local continuous laser are subjected to beat frequency coherent receiving through a circulator; and the signal acquisition circuit is used for sampling and analyzing the interference signal, and performing frequency domain comparison on an interleaving result of the two frequency division multiplexing pulse sequences to eliminate a harmonic frequency and retain a real strain signal frequency. Compared with the prior art, the non-harmonic strain signal measurement is realized, the high-frequency response performance and the high-precision strain measurement capability are excellent, and meanwhile, the long-distance coverage capability is also realized.

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.

Earthquake detection via fiber sensing is provided using using a supervisory path of submarine cables wherein the supervisory system / path of a submarine optical cable conveys portion(s) of an optical signal back to an origin location periodically—i.e., at every repeater location. Advantageously, since it is known where a returning signal is coming from, a resolution equivalent to an undersea span length may be determined—which is sufficient for wide area disturbances such as earthquakes. The returned signal is sufficiently strong such that the signal-to-noise ratio of a returned / received signal is not limited by the ASE noise of the amplifiers. The returned signal is much larger as compared to a normal distributed acoustic sensing (DAS) return signal since the return signal according to aspects of the present disclosure is directed backward via an optical coupler / reflector / circulator having a much larger coupling ratio as compared to normal Rayleigh back scattering utilized in DAS.

The invention belongs to the technical field of optical fiber sensing, and discloses a distributed optical fiber sensing system and method. A narrow linewidth laser is used for emitting continuous laser, a coupler is used for dividing the continuous laser into two paths, one path serves as a local oscillator signal to be input into a receiving unit, and the other path serves as a detection signal to be input into a second modulation unit; the first modulation unit is used for generating an electric modulation signal, and the second modulation unit introduces random phase coding under the action of the electric modulation signal, modulates the amplitude and phase of a detection signal and outputs pulsed light; the amplified pulsed light is output to an optical fiber through a circulator, and a Rayleigh backscattering signal generated by the optical fiber is output to a receiving unit; performing beat frequency on the local oscillator signal and the Rayleigh backscattering signal by using a receiving unit to generate an electric signal; and the data acquisition unit is used for acquiring sensing information. The system has the capability of measuring the power and phase distribution of Rayleigh backscattering signals at the same time, and functions which can be completed by two sets of systems originally can be completed by one set of system.

The invention discloses a system for eliminating fading noise in a distributed optical fiber sound wave sensing system. The system comprises a light source, an optical frequency shift modulator, an optical amplifier, an optical circulator, a photoelectric detector, a data acquisition card and a data demodulator, laser emitted by the light source is modulated into double-pulse light with frequency difference through the light frequency shift modulator, the double-pulse light is injected into the optical fiber through the optical circulator after being amplified by the optical amplifier, Rayleigh backscattered light generated in the optical fiber is emitted back to the optical circulator, light emitted by the optical circulator is detected and converted into an electric signal through the photoelectric detector, and the electric signal is transmitted to the optical fiber through the optical circulator. The electric signals are collected and converted into digital signals through the data collection card, and the data demodulator demodulates the digital signals through a fading noise elimination method to obtain signals with fading noise eliminated. Therefore, fading noise in the distributed optical fiber acoustic wave sensing system can be effectively eliminated, the signal quality is improved, and error signal interference is eliminated.

The invention discloses a carbon dioxide formation leakage monitoring device and method based on distributed optical fiber sensing. The device comprises a simulated formation, an injection system and a DTS system. A thermal insulation device, a thermometer and a production well system are mounted on the simulated stratum; the injection system is used for injecting carbon dioxide and liquid into the simulated stratum; the DTS system comprises a light source assembly, an optical fiber group, a detection assembly and a data acquisition and processing unit which are connected in sequence; a plurality of monitoring points of the optical fiber group are arranged, and the plurality of monitoring points are arranged in the simulated stratum at intervals; the detection assembly is used for detecting Rayleigh scattering frequency shift and Rayleigh backscattering light intensity and phase in the optical fiber group, and the data acquisition and processing unit is used for acquiring signals output by the detection assembly and performing data processing and analysis. According to the invention, fine monitoring and continuous monitoring of carbon dioxide stratum leakage can be realized, the environmental interference resistance is high, and the installation and maintenance cost is low.

The long-distance frequency-broadening distributed optical fiber sensing system comprises a narrow linewidth laser, an optical fiber isolator, a dense wavelength division multiplexer, an optical fiber coupler, a continuous optical amplifier, a narrow-band filter, an acoustic optical modulator, an optical fiber circulator, a balance detector, an acquisition card and an upper computer, a segment of mode division multiplexing pulse sequence is obtained by selecting a narrow linewidth laser and controlling an arbitrary waveform generator. After the pulse sequence enters the to-be-measured optical fiber, a section of Rayleigh backscattered light is returned, and system original data is obtained after frequency beating with local light. And then signals are demodulated by using a compensation method, and undesired signals are suppressed successively, so that the problem of limited spurious-free dynamic range caused by phase mismatching of different modes is solved.

A fiber optic sensing cable located along a side of a paved road and runs parallel to a driving direction is monitored by distributed fiber optic sensing (DFOS) using Rayleigh backscattering generated along the length of the optical sensor fiber cable under dynamic vehicle loads. The interaction of vehicles with roadway locations exhibiting distressed pavement generates unique patterns of localized signals that are identified / distinguished from signals resulting from vehicles operating on roadway exhibiting a smooth pavement surface. Machine learning methods are employed to estimate an overall road surface quality as well as localizing pavement damage. Power spectral density estimation, principal component analysis, support vector machine (SVM) combined with principal component analysis (PCA), local binary pattern (LBP), and convolutional neural network (CNN) are applied to develop the machine learning models.

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.

The present invention relates to a distributed vibration sensing method based on Pearson correlation coefficient optical frequency domain reflection, comprising the following steps: a first step of measuring a reference signal and a measurement signal; a second step of compensating for nonlinear phase noise and calculating a Rayleigh backscattering spectrum; a third step of obtaining a local RBS in the optical frequency domain; a fourth step of calculating a distributed Pearson correlation coefficient (PCC); based on the principle that vibration will cause a step-like jump in the distributed Pearson correlation coefficient (PCC), and that the size of the jump is proportional to the vibration amplitude within a certain range, the PCC of the local reference RBS and the local measurement RBS in each window is calculated to obtain the distributed PCC of the reference signal and the measurement signal at various positions of the optical fiber to be measured; a fifth step of detecting a change point in the PCC using a pruned exact linear time (PELT) algorithm based on dynamic programming to determine a possible vibration position; a sixth step of determining the vibration position; and a seventh step of determining the vibration amplitude based on the differential PCC.

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 present application discloses a method and device for partial discharge localization based on optical fiber sensing to measure ultrasonic signals. The solution provided by the present application is based on the ultrasonic signals obtained by an optical fiber sensing measurement system. By performing a Hilbert transform on the output signal of the optical fiber sensing measurement system, that is, the amplitude of the Rayleigh backscattering spectrum curve group, and extracting its envelope, the modulation information of the ultrasonic signals is obtained. Then, through differential processing, the modulation effect on the disturbance signals is revealed. Based on the time interval when the peaks appear in the signal curve group after differential processing, combined with the speed of light and the equivalent group velocity in the optical fiber, and the triggering time of the pulse signal, the specific location of the disturbance is determined, realizing partial discharge localization based on optical fiber sensing to measure ultrasonic signals.

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.

It is disclosed a system (1000) for Rayleigh-based distributed acoustic sensing. A laser source (3) injects in an optical fiber (100) a probe light signal (a(t)) periodically modulated with a modulation frequency fm ; the probe light signal and the response light signal (b(t)) emitted by the optical fiber in response to the probe light signal undergoing Rayleigh backscattering are subjected to coherent detection, thereby providing respective probe and response electrical signals; these are sampled with a sampling frequency fs = M fm , M being a positive integer, thereby providing probe and response sampled signals; in these sampled signal, respective arrays of N consecutive probe and response samples are identified, with N = G · M, G being a positive integer; a Rayleigh response of the optical fiber is provided based on the arrays of probe and response samples; and information indicative of the acoustic event are obtained by processing the Rayleigh response of the optical fiber.

A long-distance frequency-expanded distributed optical fiber sensing system and sensing method, comprising: a narrow-linewidth laser, an optical fiber isolator, a dense wavelength division multiplexer, an optical fiber coupler, a continuous optical amplifier, a narrowband filter, an acousto-optic modulator, an optical fiber circulator, a balanced detector, an acquisition card, and a host computer. By selecting the narrow-linewidth laser and controlling an arbitrary waveform generator, a mode-division multiplexed pulse sequence is obtained. After the pulse sequence enters the optical fiber to be measured, a Rayleigh backscattered light will be returned. After beating with the local light, the original data of the system is obtained. Subsequently, a compensation method is used to demodulate the signal, and the unwanted signals are suppressed successively, solving the problem of limited spurious-free dynamic range caused by phase mismatch of different modes.

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.