10 results about "Rayleigh backscattering" patented technology

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.

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 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.

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.

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 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.

This invention provides a method for extending the measurement distance of distributed sensing based on an optical frequency domain reflectometer. The method addresses the problem in distributed sensing technology based on an optical frequency domain reflectometer where the measurement distance is affected by tests of the reference state before signal generation and the measurement state after signal generation. The slight difference in the scanning range of the light source wavelength during these two tests causes a slight difference in spatial resolution. This difference gradually accumulates over long distances, leading to a mismatch between the positions of the sensing fiber in the reference and measurement states, or a change in the size of the sensing fiber after signal generation, resulting in a mismatch in the sensing fiber's position and causing measurement failure or decreased sensing resolution. This invention utilizes the invariance of local Rayleigh backscattering in the sensing fiber to calculate the mismatch between the corresponding positions of the sensing fiber in the reference and measurement states, and then performs correction, thereby overcoming the problems of measurement failure or decreased sensing resolution caused by mismatched sensing fiber positions.