135 results about "Time-domain reflectometry" patented technology

The embodiment of the invention provides a soil nutrient spectrum detection and regulation method and system, and belongs to the technical field of soil nutrient spectrum detection and regulation. The method comprises the following steps: collecting soil multispectral original data and environmental data, generating a calibration matrix and a nonlinear correction parameter, executing optical reflectivity conversion, and synchronously fusing a time domain reflectometry dielectric constant and a spectral moisture index to obtain fused moisture content; selecting a nutrient diagnosis characteristic wave band pair to obtain a moisture inhibition type spectral index; and predicting the soil nutrient content by using a pre-trained transfer learning model to obtain a soil nutrient content prediction value, and performing fertilization regulation and control based on the fertilization decision risk coefficient. According to the invention, extreme soil moisture measurement deviation is solved through a soil type adaptive moisture fusion technology; through multi-source risk quantitative decision and PID self-adaptive regulation and control, the fertilization amount can be dynamically optimized, execution safety is guaranteed, and a detection-decision-execution precision agriculture closed loop is formed.

The invention discloses a DNAPLs pollutant diffusion migration path depicting method and system, and relates to the technical field of pollution monitoring, and the method comprises the steps: obtaining the soil conductivity of a target region through an improved TDR probe, obtaining the time sequence characteristics and spatial characteristics of a soil conductivity data set, obtaining the fusion spatial-temporal characteristics, calculating the spatial-temporal similarity of historical migration paths, and obtaining the DNAPLs pollutant diffusion migration path depicting result. Screening prior knowledge; constructing a space-time prediction model by using a graph neural network and priori knowledge, extracting deep space-time features from a space adjacent graph and a time-dependent heterogeneous graph corresponding to the target region, and obtaining a conductivity prediction value of a future time step; the diffusion direction of the pollutants is deduced by combining the relation between the resistivity and the DNAPLs concentration, migration frontal surface diagrams at different time points are drawn, and dynamic path visualization is achieved. According to the method, the improved TDR (time domain reflectometry) technology and the deep learning model are combined, so that high-precision monitoring and prediction of the dynamic migration process of the pollutants are realized.

The invention discloses a method capable of realizing wide-range positioning of a cable fault, a spread spectrum step frequency wave signal is obtained by performing binary phase shift keying (BPSK) and pseudorandom sequence modulation on a step frequency signal, and the method can overcome the problem that the cable fault detection range of a spread spectrum time domain reflectometry (SSTDR) is limited by code element duration. A cable fault detection device is installed at the head end of a cable, a detection signal is injected from the head end of the cable, a high-speed ADC is used for signal collection, cable fault information is obtained, and wide-range detection of cable faults is achieved.

The invention provides a BOTDR (Brillouin optical time domain reflectometry) system fusing Stokes-anti-Stokes light and a demodulation method, and belongs to the technical field of Brillouin distributed optical fiber sensing. The narrow linewidth laser is used for generating continuous optical signals; the input end of the coupler is connected with the laser, and the output end is connected with the pulse light branch and the local oscillator light branch. The pulsed light branch comprises a semiconductor optical amplifier, a random scrambler, a first erbium-doped optical fiber amplifier and a circulator which are connected in sequence; the local oscillator light branch comprises an electro-optical modulator, and the electro-optical modulator regulates and controls sideband frequency through a microwave module; the second erbium-doped optical fiber amplifier is used for extracting the Stokes light and the anti-Stokes light; the single-mode coupler mixes the double-sideband local oscillator light with the anti-Stokes light and the Stokes light; and the electrical beat frequency signals are acquired, filtered and enveloped and demodulated through an acquisition card. The detection capability of the Brillouin scattering signal is enhanced, the system structure is simplified, and the hardware cost and the maintenance difficulty are reduced.

There is provided a method of detecting a fault along a cable or transmission line. In the method, the following steps are performed: obtaining an echo response of the cable or transmission line using time domain reflectometry, TDR, identifying a plurality of reflections in the echo response, generating a representation of the plurality of reflections, normalising one of the representation or a threshold, and determining a fault condition based on the normalised representation. By doing this, the faults can be accurately determined in cables of different lengths.

The proposed full-coherent optical time domain reflectometry (FC-OTDR) solution extracts full optical phase and state of the polarization (SOP) information for fiber intrusion detection by constructing a continuous reflected SOP from each point of the fiber length. Intrusion location is then extracted from the resulting SOP change patterns.

A testing method for an optical fiber is provided. The method involves the use of a P-OTDR device to launch polarized light pulses from the P-OTDR device into the fiber extremity of an optical fiber and obtain a return light signal. Concurrently, a polarization state of light travelling in a distal fiber segment is varied, a polarization component of the return light signal is isolated, and a set of P-OTDR traces are acquired. The set of P-OTDR traces is processed to detect a change in polarization of the return light signal. Upon detecting such a change an information relative to the distal fiber segment and the fiber extremity can be reported. The method may for example be used as a fiber identification method or a geo-referencing method. A P-OTDR device is also provided.

The invention provides a power distribution network optical fiber fault positioning method and system based on time domain reflection, and relates to the technical field of power distribution networks, and the method comprises the steps: obtaining the basic parameter information of an optical fiber, generating and carrying out the phase modulation of an optical carrier signal, dividing the modulated signal into a chip sequence, and carrying out the orthogonal coding and time domain interleaving modulation; an enhanced detection signal with a space-time diversity characteristic is formed; signals are injected into the optical fiber, reflected signals are received, fault feature fingerprint information is extracted through multi-scale wavelet transform and adaptive threshold screening, fault type recognition and accurate position positioning are achieved, and fault detection accuracy and positioning precision are effectively improved.

The invention discloses a cable defect identification and positioning method and device based on time-varying matched filtering. Relates to the power equipment state detection technology and the application field thereof. The method comprises the following steps: connecting a measured cable to measuring equipment through a connecting line; disconnecting the measured cable and the connecting line, injecting a pulse signal by the measuring equipment, and measuring a reflected signal vos (t) generated when the tail end of the connecting line is short-circuited; the measured cable and the connecting line are connected, the measurement equipment keeps setting parameters unchanged, and a reflection signal in the measured cable is obtained; designing a time-varying matched filter based on a reflection signal generated when the tail end of the connecting line is short-circuited, filtering the reflection signal in the tested cable to obtain a filtered reflection signal curve, and determining reflection time through an extreme point on the filtered reflection signal curve; and calculating the position lf of the cable defect according to the reflection time. According to the invention, the detection capability of the time domain reflection technology on small defects in the cable and in a noise environment is improved, and the method has a wide application prospect.

The invention relates to the technical field of optical fiber sensing, in particular to a fusion type optical fiber disturbance detection system and method based on multi-mode scattering. The system comprises a light source module, an optical fiber sensing network, an optical signal demodulation module, a data processing unit and a self-adaptive disturbance identification module. By simultaneously extracting the feature information of Rayleigh scattering and Raman scattering, the detection sensitivity and precision of different types of disturbances can be improved. The system adopts a self-adaptive disturbance recognition algorithm and utilizes information entropy calculation to dynamically adjust the fusion weight of Rayleigh scattering and Raman scattering so as to adapt to disturbance detection requirements under different environmental conditions, the adaptability and reliability of the system are improved, and the false alarm rate is effectively reduced. Besides, the data processing unit is combined with the optical time domain reflection (OTDR) principle, and high-precision disturbance positioning is realized by calculating the time difference of the disturbance signal reaching the demodulation module.

The invention relates to the technical field of numerically-controlled machine tool monitoring, in particular to a numerically-controlled machine tool monitoring method and system, terminal equipment and a storage medium, and the numerically-controlled machine tool monitoring method comprises the following steps: based on key parts of a numerically-controlled machine tool, monitoring tiny wear or deformation by adopting a time domain reflection method and a frequency domain reflection method; and the collected ultrasonic signals are analyzed in combination with a convolutional neural network, phase changes and abnormal features in the signals are identified, data fusion processing is carried out, and wear identification indexes are generated. According to the method, the advanced monitoring and analysis technology is adopted, comprehensive optimization of the performance of the numerical control machine tool is achieved, the time domain reflection method and the frequency domain reflection method are combined with convolutional neural network analysis, the detection precision of tiny abrasion or deformation is improved, dynamic optimization is achieved on clamping force adjustment through fuzzy logic control, the method adapts to different machining conditions, and the machining precision of the numerical control machine tool is improved. Workpiece damage is reduced, the machining quality is improved, and the machining precision is improved through deep diagnosis and dynamic compensation strategies of multi-axis synchronous errors.

The invention discloses a cable fault detection method and system, and relates to the technical field of cable detection. Comprising the steps of obtaining a temperature signal and a stress signal of the surface of a to-be-detected cable, and obtaining a first fault point position when any signal exceeds a set threshold value; detecting the interior of the cable by adopting a spread spectrum time domain reflection method, and determining the position of a second fault point; obtaining a first fault type by comparing phases of the reflected signal and the incident signal at the position of the second fault point; respectively determining a second fault type and a third fault type according to electromagnetic field changes around the first fault point and the second fault point on the surface of the cable; and obtaining a fault detection result of the to-be-detected cable according to a judgment result whether the first fault point position and the second fault point position belong to the same fault point position or not and whether the first fault type, the second fault type and the third fault type belong to the same fault type or not. According to the invention, the accuracy and reliability of cable fault detection results can be improved.

The invention relates to the technical field of electric power, in particular to a cable nondestructive testing method which comprises the following steps: acquiring corresponding calibration parameters from a database according to the model of a to-be-tested cable, and calculating the total length and fault position of the to-be-tested cable at the near end of the to-be-tested cable by adopting a time domain reflection method; at the tail end of the cable to be detected, at the tail end, at least two core wires are short-circuited, a four-wire detection method is adopted to measure the direct-current resistance of a core wire loop at the near end, and standard temperature correction is conducted on the direct-current resistance of a single core wire; the resistivity to be measured is calculated by using the total length of the cable to be measured, the actual cross sectional area of the core wire and the direct current resistance of the single core wire at the standard temperature, and whether the actual core wire material of the cable to be measured is qualified is analyzed according to the resistivity to be measured and a resistivity threshold value set based on the calibrated core wire material. And early warning is carried out based on a core wire material analysis result and a fault position. According to the method, the cable length, the fault position and the core wire material qualification can be quickly, nondestructively and accurately detected on site.

A method of performing optical time domain reflectometry (OTDR) on a fiber under test (FUT) that comprises a portion of hollow core fiber (HCF) and a portion of solid core fiber (SCF) is described. The method comprises determining a position of a transition between the SCF and the HCF in the FUT; setting a time delay in switch control circuitry using the determined position of the transition; and generating an OTDR trace graph using light detected by a photodetector, wherein the time delay is used to control an optical switch to block light backscattered within the SCF from reaching the photodetector (e.g. by absorbing, attenuating or diverting the backscattered light).

The application discloses an optical time domain reflectometry (OTDR) method, system and OTDR equipment for avoiding event blind area, and relates to the technical field of OTDR. The OTDR method adds a second detector to the ground end of a first detector, and detects the optical signal emitted by a second light source by using the second detector. Then, when measuring the OTDR curve of a to-be-measured optical fiber, the second driver is controlled to drive the second light source to emit a compensation optical signal within a pre-determined saturation time interval, so that the photocurrent detected by the second detector offsets and compensates the photocurrent detected by the first detector, and the current input to the amplification circuit is lower than the saturation threshold, thereby eliminating the event blind area caused by saturation, enabling the blind area event to be detected, and without adding a selection switch, thereby avoiding introducing additional noise, improving the optical fiber OTDR test accuracy and having better noise performance.

The invention specifically relates to a cable defect identification and positioning method based on a broadband impedance spectrum, and belongs to the technical field of power distribution network equipment fault detection. According to the method, the advantages of the frequency domain reflection method and the reflection method are comprehensively considered, whether the parameters of the frequency domain reflection method and the time domain reflection method need to be corrected or not is judged by using the positioning deviation degree, the positioning deviation degree, the fluctuation width and the combined positioning ratio are used as indexes in the correction process, the respective defects of the frequency domain reflection method and the time domain reflection method are eliminated, and the correction accuracy is improved. The advantages are fused, and the corrected parameters are adopted for positioning, so that the accuracy of cable defect positioning and identification is greatly improved.

Systems, methods, and apparatus, including computer programs encoded on computer-readable media, for downhole fault detection in a well system are disclosed. A spread spectrum time domain reflectometry (SSTDR) apparatus of the well system may transmit an SSTDR signal downhole via a well electrical cable of the well system and receive a reflected SSTDR signal. The SSTDR apparatus may determine whether a downhole fault exists in the well electrical cable or in a well device based on a signal analysis of the reflected SSTDR signal and the transmitted SSTDR signal. The SSTDR apparatus may also use historical SSTDR data and a machine learning algorithm for downhole fault detection and analysis. When a downhole fault is detected, the SSTDR apparatus also may determine a type of the downhole fault and a location of the downhole fault, such as the depth downhole of the downhole fault.

The invention belongs to the field of ocean geophysical exploration, and particularly provides a device and a method for monitoring migration of CO2 in sediment based on a time domain reflectometry, the monitoring device comprises a reaction kettle, a vacuumizing and saturation system, a supercritical carbon dioxide preparation and injection system, a temperature control system, a dielectric constant test control system and a data acquisition and processing system; the dielectric constant test control system comprises a time domain reflection tester and a time domain reflection sensor assembly, wherein the time domain reflection sensor assembly comprises a plurality of axial time domain reflection sensors inserted from the bottom of the reaction kettle and a plurality of radial time domain reflection sensors inserted from the side surface of the reaction kettle. According to the device and the method, anisotropic dynamic monitoring of the continuous migration process of supercritical CO2 in the ocean sediment can be realized, and combined characterization of CO2 saturation and CO2 plume front migration dynamics in the sediment sample in the CO2 migration process can be realized, so that accurate evaluation of the storage efficiency and leakage risk of CO2 in the ocean sediment is realized, the monitoring effect is good, and the operation is simple.

The invention relates to a wafer test structure, a test wafer and a preparation method of the test wafer. The test structure comprises a test part located on the first side of the wafer and two test ports located at the two ends of the test part. Wherein the testing part comprises at least one characteristic line and at least two testing lines, and the testing lines are connected end to end through the characteristic lines; the width of the characteristic line is different from that of the test line; each test port is used for being connected with time domain reflection equipment, receiving a test signal transmitted by the time domain reflection equipment and receiving a reflection signal formed after the test signal is reflected by the characteristic line; wherein the test signal and the reflection signal are jointly used for determining electrical parameters of the characteristic line. Through the test structure, whether the wafer breaks and fails can be judged.

The invention provides an electronic wire harness anti-interference optimization method and system, and the method comprises the steps: S2, blocking a DC component and low-frequency interference through employing a band elimination filter according to the initial spectrum distribution, and extracting a core frequency band of high-frequency signal transmission from a filtered signal; s4, acquiring demand data of voltage grade separation from the signal output, designing an electrical isolation layer through a multi-layer shielding structure, and determining isolation boundaries among different voltage grades; s5, according to the isolation boundary, a space optimization algorithm is adopted to adjust wire harness arrangement in the compact layout, and structural parameters considering isolation and coupling balance are obtained; and S8, according to the final scheme, a time domain reflection method is adopted to detect the distortion rate in signal transmission, the actual effect of improving the anti-interference capability is judged from the detection result, and optimized operation parameters are obtained. The anti-interference capability and the signal transmission quality of the electronic wire harness in a complex electromagnetic environment are effectively improved.

The invention discloses an event identification method, device and equipment for COTDR data and a storage medium, and the method comprises the steps: obtaining coherent optical time domain reflectometry (COTDR) curve data, carrying out the smoothing of the COTDR curve data according to a preset moving average algorithm, and obtaining the smoothed COTDR curve data; dividing the smoothed COTDR curve data into an effective COTDR curve and noise, and obtaining abnormal point information of the effective COTDR curve; and analyzing the abnormal point information to obtain event point information corresponding to different events in different categories, so that the event information can be automatically obtained in real time, the personnel judgment difficulty is reduced, the operation and maintenance automation capability of the ocean communication system is improved, the arithmetic logic is simple, the code complexity is reduced, and the operation efficiency is improved. Unification of a COTDR monitoring system and a communication equipment management system is realized, and the event identification speed and efficiency of the COTDR data are improved.

This improves the degradation of the cross-correlation coefficient caused by the error between the set frequency and the actual frequency of the light source, and makes it possible to improve the degradation of the measurement accuracy of strain and temperature. [Solution] The light source unit has a frequency-stabilized wavelength-tunable laser that generates continuous light, and a first optical coupler splits the continuous light generated by the light source unit into two, sending one to a second optical coupler and the other to an optical frequency measurement unit. The optical frequency measurement unit measures the frequency of the continuous light generated by the light source unit, and the second optical coupler further splits the continuous light split by the first optical coupler into two, sending one as probe light to the optical pulse generation unit and the other as local light to a detection unit. The detection unit measures the frequency change Δf by means of coherent time domain reflectometry and a means for heterodyne detection of the Rayleigh scattered light and the local light resulting from Rayleigh scattering of pulsed light in the fiber under test. max and means for acquiring the

The invention discloses a device for detecting a pavement collapse position based on a time domain reflection method and a detection method, and belongs to the technical field of pavement collapse detection, and the device for detecting the pavement collapse position based on the time domain reflection method comprises a central processing unit, a timer, a driving circuit, a detection cable, a receiver and a data processing circuit. Meanwhile, the invention discloses a detection method of the device for detecting the collapse position of the road surface based on the time domain reflection method, pulse signals generated by the central processing unit are transmitted in the detection cable after being amplified by the driving circuit, and when the cable is broken due to collapse, the pulse signals are reflected back and received by the receiver, and after being processed, the pulse signals are transmitted to the detection cable. According to the device for detecting the road surface collapse position based on the time domain reflection method and the detection method, the data processing process is simple, the detection precision is high, real-time detection can be achieved, and the detection cost is greatly reduced.

The invention belongs to the technical field of optical fiber sensing, and relates to an optical time domain reflection monitoring method and device based on forward and reverse signal joint optimization, and the method comprises the steps: obtaining reverse and forward OTDR observation signals of a to-be-measured optical fiber; constructing a reverse OTDR linear signal reconstruction item based on a product of the orthogonal transformation matrix and a to-be-solved first sparse coefficient vector; constructing a forward OTDR linear signal reconstruction item based on the product of the orthogonal transformation matrix and a to-be-solved second sparse coefficient vector; constructing a data fidelity item based on the OTDR observation signal and the linear signal reconstruction item; constructing a joint sparse regular term based on the structural sparsity of the first sparse coefficient vector and the second sparse coefficient vector to be solved; and constructing a spatial constraint regular term based on the continuous smoothness of the reconstructed OTDR linear signal in the space, thereby constructing a joint optimization function and solving the joint optimization function to obtain a first sparse coefficient vector and a second sparse coefficient vector, and further reconstructing the OTDR linear signal to detect the optical fiber to be detected.

There is provided a method of detecting a shield-fault along a cable or transmission line. In the method, the following steps are performed: obtaining at least one echo response of the cable or transmission line using time domain reflectometry, TDR, identifying a plurality of reflections in the echo response, determining the presence of a shield-fault by comparing locations of reflections in the at least one echo response. By doing this, the shield-faults, and their location, can be accurately determined in cables of different lengths using time domain reflectometry.

A method for characterizing a cable or transmission line is provided, comprising: obtaining a first echo response using time-domain reflectometry; coupling a first end of the cable or transmission line to a time-domain reflectometer; Obtaining a second echo response using time domain reflectometry; determining a characteristic of the cable or transmission line by comparing the first echo response and the second echo response.

The invention discloses a method and a system for automatically analyzing OTDR (Optical Time Domain Reflectometry) test curves of a hollow-core optical fiber. The method comprises the following steps of: acquiring one OTDR test curve from each of two ends of the hollow-core optical fiber; respectively carrying out centralization processing on the two OTDR test curves, aligning the two OTDR test curves based on the position of the hollow-core optical fiber, calculating a difference value of backscattering power of the two OTDR test curves, and then calculating an average value to obtain a correction curve; performing filtering and noise reduction processing on the corrected curve to obtain a curve after noise reduction; extracting event information from the denoised curve by adopting a multi-scale analysis and dynamic threshold fusion algorithm; and exporting an event detection result according to the event information. According to the invention, automatic processing and analysis of the hollow-core optical fiber OTDR curve are realized while bump interference is avoided.

The present application relates to a method for performing optical time domain reflectometry (OTDR) on an optical fibre. The method comprises: a) setting (1010) a decision threshold of a photodetector; b) transmitting (1020) a first signal into an optical fibre, wherein the first signal comprises a sequence of optical radiation pulses based on a coded sequence; c) detecting (1030) optical radiation backscattered and / or reflected from the optical fibre using the photodetector; d) obtaining (1040) a measurement signal comprising bit sequences based on the detected optical radiation and the decision threshold of the photodetector; e) comparing (1050) the measurement signal with the first signal to obtain a correlation signal; f) adjusting (1060) the decision threshold of the photodetector; g) repeating (1070) steps (b)-(f) to obtain a plurality of correlation signals; and e) combining (1080) the plurality of correlation signals to obtain an OTDR trace of the optical fibre. The present application also relates to a computer program product, an apparatus for performing OTDR, an optical plug and a fibre optic system.

A computer-implemented method for performing an enhanced resolution time domain reflectometry is provided. Aspects include obtaining a plurality of waveforms by transmitting a first pulse on a transmission line, transmitting a second pulse on the transmission line, where the second pulse is transmitted after the first pulse by a delay, and capturing and measuring reflections of the transmitted pulses, where the delays corresponding to each of the plurality of waveforms are different. Aspects also include identifying a discontinuity of the transmission line based at least in part on the plurality of waveforms. Based on determining that the transmission line includes a discontinuity, the aspects include calculating a third derivative curve for each of the plurality of waveforms, and calculating a length of the discontinuity of the transmission line based on the third derivative curves. Aspects also include creating a notification indicative of the location and length of the discontinuity of the transmission line.

Detecting stress / strain in optical fibres using coherent optical time domain reflectometry (COTDR) where the apparatus operates in two modes and determines changes in optical path length. A first mode