76 results about "Chirp pulse" patented technology

Some non-limiting embodiments of the present disclosure relate to transmitting and / or receiving of sensing. A waveform of a hyperbolic frequency modulated (HFM) chirp pulse in a frequency range is obtained. A first signal including a plurality of HFM chirp pulses is transmitted. A second signal is received, wherein the second signal is a signal resulting from reflection of the first signal by at least one target. A subsampled first signal is obtained by sampling the first signal at a sampling frequency fS below a Nyquist rate fnyq. A subsampled second signal is obtained by sampling the second signal at the sampling frequency fS. A range of the at least one target and / or a Doppler frequency is determined by processing of the subsampled first signal and the subsampled second signal.

Techniques for detecting an impedance-based fault on a wire carrying power in a power delivery system. The techniques involve applying power to a wire of a power delivery system and applying onto the wire a chirp pulse comprising a sequence of waveforms of a plurality of frequencies. A signal is obtained from the wire. An impedance of the signal is analyzed at two or more frequencies of the plurality of frequencies with respect to a reference impedance to determine whether there is an indication of an impedance-based fault associated on the wire, such as a human touching the wire. The power to the wire is disconnected in response to determining an indication of the impedance-based fault.

The invention discloses an SSVEP (Steady-State Visual Evoked Potential) recognition system and method based on linear frequency modulation visual evoked potential migration. The visual stimulation generation and presentation module generates and presents a visual stimulation signal; the electroencephalogram signal acquisition module is used for acquiring Chirp-VEP and SSVEP electroencephalogram signals; the electroencephalogram signal preprocessing module is used for preprocessing the collected electroencephalogram signals; the Chirp pulse matrix construction module is used for converting a Chirp signal to obtain a Chirp pulse matrix, the Chirp-VEP decomposition module is used for constructing a least square optimization problem to solve common model parameters of Chirp-VEP, and the common model parameters are migrated to SSVEP through the SSVEP identification module to carry out feature extraction and classification. According to the method, the system overhead is reduced, the calibration time is shortened, the training cost is minimized while the optimal performance is kept, and the practicability of the brain-computer interface based on SSVEP is improved.

The invention discloses an ultrafast coherent modulation imaging device based on chirped pulse illumination, which can collect evolution information of intensity and phase along with time change in an ultrafast dynamic scene under the condition of single exposure. The device encodes an ultrafast scene by using the spectrum-time mapping characteristic of chirped pulses, realizes phase encoding through random phase modulation, then acquires an encoded diffraction pattern through a snapshot hyperspectral camera, and finally recovers space-time complex amplitude information of the ultrafast dynamic scene through a phase retrieval algorithm. The invention provides an imaging device capable of obtaining dozens of ultrafast time resolution complex amplitude images in single exposure, and the imaging dimension and the time resolution capability are remarkably improved. The device and method provided by the invention provide a new technical path for researching the ultrafast dynamic process, and have certain scientific research application potential and engineering popularization value.

The invention provides a mid-infrared optical frequency comb. The mid-infrared optical frequency comb comprises a near-infrared optical frequency comb seed source of a polarization-maintaining all-fiber structure; the all-fiber nonlinear amplification and pulse compression module is connected with the near-infrared optical frequency comb seed source through a polarization maintaining fiber and is used for amplifying the power of the seed light and compressing the pulse width after generating a linear chirped pulse; the all-fiber nonlinear spectrum broadening module is connected with the all-fiber nonlinear amplification and pulse compression module through a polarization maintaining fiber and is used for broadening a laser spectrum; the difference frequency module is used for receiving the laser pulse processed by the all-fiber nonlinear spectrum broadening module and generating an intermediate infrared laser pulse through intra-pulse self-difference frequency; wherein the seed source, the all-fiber nonlinear amplification and pulse compression module and the all-fiber nonlinear spectrum broadening module are connected through a polarization maintaining fiber to form an all-fiber integrated structure. By adopting the scheme, the anti-interference capability of the system can be enhanced, miniaturization and high operation reliability are realized, the debugging process is simplified, and the difference frequency efficiency is improved.

The invention relates to the technical field of digital-to-analog conversion, in particular to a large-dispersion compact chirped pulse time domain compression method, which comprises the following steps of: projecting a broadened chirped pulse to a first grating in an inclined incidence mode, and moving adjacent back and forth diffraction spots point by point in a direction parallel to a grating scribed line; the first grating and the second grating are oppositely arranged in parallel to form a double-grating group; controlling the chirped pulse to perform multiple back-and-forth diffraction between the first grating and the second grating to obtain a preset large dispersion amount; an angular dispersion steering module is arranged on a back-and-forth diffraction light path of the chirped pulse, and vertical angular dispersion introduced due to oblique incidence is turned into horizontal angular dispersion. An angular dispersion compensation module is arranged on a light path before the chirped pulse is output, and the angular dispersion accumulated by multiple back-and-forth diffraction is offset and compensated. According to the method, on one hand, the dispersion amount several times that of a traditional pulse time domain compressor can be obtained, on the other hand, the compact design of the structure of the compressor can be achieved, and the method has important engineering application value.

The invention discloses a chirped pulse Fourier transform microwave spectrometer and a detection method, and belongs to the technical field of microwave spectrums.The chirped pulse Fourier transform microwave spectrometer comprises a pulse sample introduction and reactant in-situ generation system, a segmented chirped pulse generation and radiation system, a signal detection and high-speed acquisition system, a synchronous time sequence control system and a signal processing and automatic acquisition assembly. According to the chirped pulse Fourier transform microwave spectrometer and the detection method, 18-40 GHz continuous broadband coverage is realized through a segmented chirped pulse sequence, and a pulse discharge sampling system is integrated, so that high-reaction-activity intermediates and molecular clusters thereof can be generated and directly detected in situ; the technical blank of a broadband high-sensitivity microwave spectrometer with the frequency band of 18-40 GHz is filled, and a powerful tool is provided for research on structures and reaction kinetics of key transient species in atmospheric chemistry, combustion chemistry and celestial chemistry.

A system and method for distributed temperature and strain sensing using Chirp-Pulse Coherent Optical Time-Domain Reflectometry (CP-COTDR) utilizes optical flow processing. The method involves constructing a two-dimensional (2-D) waterfall data array from collected CP-COTDR frames. Optical flow processing is applied directly to the 2-D data to estimate the local shift of features caused by external perturbations. The optical flow is preferably calculated using a weighted least squares method with an adaptive analysis window based on the local flatness of signal derivatives. This approach provides versatile and high spatial resolution, reduces accumulative errors, and enables efficient data processing compared to conventional cross-correlation techniques.

The application provides an X-ray ultrafast imaging system and method based on radiation conversion and spectral filtering, which solves the problems of poor universality, low time resolution or limited number of frames in existing X-ray ultrafast imaging technology. The system comprises an X-ray coupling module for coupling target X-ray signals to image on a semiconductor chip module, a semiconductor chip module for converting the X-ray intensity space-time distribution into the chip refractive index space-time distribution, a chirped pulse light generation module, a chirped pulse light coupling module for irradiating linear chirped pulse light generated by the chirped pulse light generation module to the semiconductor chip module and coupling the pulse light reflected by the semiconductor chip module into a phase extraction module, the phase extraction module, a spectral filtering frame reading module for imaging the linear chirped light intensity space-time distribution signal output by the phase extraction module into the data acquisition module, the data acquisition module and an image processing module for processing the image output by the data acquisition module.

Described are techniques for interleaving range and Doppler radar processing. A data cube is memory accessed differently, from one look period to the next, which allows Doppler processing for a current look period to happen in parallel with range processing for a next look period. Range processing for a first look period writes to rows of the data cube; Doppler processing reads from and empties its columns. But before Doppler processing can finish, a second look period begins. Rather than re-writing to the rows, range processing in the second look period writes to the columns just emptied by the ongoing Doppler processing. Doppler processing for the first look period is allowed to finish by executing during processing idle times in the second period, e.g., in-between chirps. With better processor utilization, Doppler processing is afforded more time to do its complex operations, while keeping look periods as short as possible.

An off-axis single-grating multi-pass pulse compressor disclosed by the present invention comprises a compression module and at least one group of mirror groups, the mirror groups are used for increasing dispersion compensation of the compression module, and the compression module comprises a D-shaped reflector, a grating, a plane reflector, a first horizontal mirror and a first high-low mirror. Each group of mirror group comprises two mirrors, one mirror of each group of mirror group is located at the laser output end of the compression module, and the other mirror of each group of mirror group is located above the first high-low mirror, or the other mirror of each group of mirror group is located above the second high-low mirror. And the other mirror of each mirror group is positioned on one side of the first high-low mirror and has the same height with the horizontal plane. According to the off-axis single-grating multi-pass pulse compressor, a multi-pass single-grating compressor can be achieved, the total dispersion compensation amount is greatly increased, the advantages of low cost and small size of a transmission-type single-grating compressor can be reserved, and the compression requirement of ultra-large chirped pulses can be met.

The application discloses a kind of mid-infrared discrete time stretching spectrum method, its characteristics are as follows:1) prepare the double-color pulse light source with slightly different repetition frequency;2) the pulse of pulse light source 1 is output wavelength broadening and time stretching for the signal light of nonlinear difference frequency, and the pulse of pulse light source 2 is output power amplification, for the pump light of nonlinear difference frequency;3) the time-domain broadening spectrum optical sampling of signal light by pump light pulse, obtain the pulse sequence of mid-infrared discrete time stretching;4) mid-infrared discrete chirp pulse is measured through low bandwidth mid-infrared detector after passing through the sample to be measured, and absorption spectrum information is obtained.The application has the advantages of wide band, high speed and high resolution compared with prior art, and the measurement of mid-infrared spectrum is completed by means of low bandwidth single-point detector, without dispersion spectrometer element and mechanical scanning device, which solves the problem of lack of time and high dispersion time-domain stretching medium in mid-infrared band, and expands the application of time stretching technology in mid-infrared band.

The embodiment of the present application relates to the technical field of ultra-high-speed imaging, and discloses a framing imaging device, which comprises a chirp spreading element, a diffraction element, a first Fourier lens, a framing element and a second Fourier lens, wherein the chirp spreading element is used for spreading incident light and emitting chirp pulse light; the diffraction element is used for splitting the chirp pulse light into diffraction beams propagating in different directions; the first Fourier lens is used for emitting the incident diffraction beams into central-symmetrical array beams; the framing element is used for framing the array beams into delay beams; and the second Fourier lens is used for converging the delay beams to the same illumination area. The present application also discloses a framing imaging system. The present application solves the technical problem of how to simplify the structure of a conventional framing imaging device under the premise of the same time resolution.

The present invention provides an optical time domain reflectometry system and demodulation method based on gas absorption spectrum frequency compensation. The optical time domain reflectometry system includes: a φ-OTDR system light source, a chirped pulse signal modulation module, a first amplifier, a coupler, a gas chamber, a first detector, a circulator, an optical fiber to be tested, a second amplifier, a filter, and a second detector. The continuous laser signal of the φ-OTDR system light source is converted into a chirped modulated pulse signal by the chirped pulse signal modulation module. One signal of the chirped modulated pulse signal enters the gas chamber, and the first detector obtains the gas absorption spectrum based on the transmission signal of the gas chamber. The other signal enters the second port through the first port and enters the optical fiber to be tested. The optical fiber Rayleigh scattering signal enters the third port through the second port and is amplified by the second amplifier. The scattered signal amplified by the second amplifier is filtered by the filter and then obtained by the second detector. The present invention can solve the technical problem that the existing frequency-sweeping φ-OTDR system is affected by the frequency drift of the light source, resulting in insufficient measurement accuracy.

The invention belongs to the technical field of lasers, and particularly relates to a dynamic dispersion compensation system and method for an intermediate infrared tunable fiber laser, and the system comprises an intermediate infrared ultrashort pulse light source mechanism which is used for outputting negative chirped pulse laser with the wave band of 2.8-4.5 microns; the pulse compression module comprises a transmission grating I and a transmission grating II which are arranged in parallel, an aberration removal structure positioned between the transmission grating I and the transmission grating II, and a roof prism; the negative chirped pulse laser sequentially passes through the first transmission grating, the aberration removing structure and the second transmission grating and then enters the ridge prism, and the negative chirped pulse laser is reflected by the ridge prism to enable the light to sequentially pass through the second transmission grating, the aberration removing structure and the first transmission grating and then outputs near Fourier transform limit pulsed light. The distance between the plane where the first transmission grating is located and the plane where the second transmission grating is located is the grating distance. And the grating distance is adjusted through the distance adjusting part. According to the invention, dynamic dispersion compensation of the mid-infrared band can be realized.

The invention provides a broadband response distributed sound wave sensing method and device, and relates to the technical field of optical fiber sensing. Single-frequency continuous light beams are split, double-sideband frequency sweep modulation is performed on a first path to generate double-sideband frequency sweep light, short-pulse-width chirped pulse light and long-pulse-width chirped pulse light are obtained through frequency band selection and pulse interception, and the short-pulse-width chirped pulse light and the long-pulse-width chirped pulse light are synthesized and injected into a sensing optical fiber; backward Rayleigh scattering light signals are collected, long-pulse-width and short-pulse-width Rayleigh scattering light signals are separated through optical filtering, and spontaneous emission noise is suppressed and amplified; coherent beat frequency detection and phase demodulation are carried out on the long-pulse-width Rayleigh scattering light signal, spectrum correlation processing is carried out on the short-pulse-width Rayleigh scattering light signal to obtain time offset, disturbance information recovery is achieved, and a sound wave measurement result distributed along the sensing optical fiber is output.

The invention relates to the technical field of femtosecond pulse measurement, in particular to a dispersion scanning pulse self-measurement method based on a chirped pulse amplification laser, which comprises the following steps of: jointly using a stretcher and a compressor which are arranged in the laser as a dispersion scanning system, and adopting a dispersion scanning coordination strategy; continuously adjusting the dispersion amount of the stretcher and the dispersion amount of the compressor, synchronously collecting second harmonic spectrum signals under different dispersion distribution combinations, and constructing a second harmonic spectrum track diagram; according to the method, an adaptive dispersion coupling phase reconstruction algorithm is adopted, iteration processing is conducted on a second harmonic frequency spectrum track diagram, a high-order dispersion compensation item is introduced for optimization, the time domain intensity and phase information of laser pulses are reconstructed, the optimal dispersion compensation amount is determined, and the narrowest pulse width value is output. Therefore, the precision of pulse phase and width measurement and the convergence speed of the algorithm are improved.

The present invention belongs to the field of laser ranging, and specifically relates to an absolute distance measurement method and device based on optical frequency comb chirped pulse interferometry. The method comprises: using an optical frequency comb to generate and split pulsed lasers; using one of the beams as signal light to generate reference light and measurement light, with a time delay between the two corresponding to the absolute distance to be measured; widening the other beam as local oscillator light, which interferes with the reference light and measurement light, respectively, to generate two interference pulses; widening the two interference pulses, and using a high-speed photodetector and a high-speed oscilloscope to collect information about the widened two interference pulses in real time; wherein the pulse width of the local oscillator light satisfies that the reference light and measurement light can interfere with the local oscillator light at any position; and subtracting the spectral phases of the two sets of chirped pulse interference fringe information to calculate the absolute distance to be measured. The present invention can achieve rapid absolute distance measurement along the entire path without blind spots.

Techniques for detecting an impedance-based fault on a wire carrying power in a power delivery system. The techniques involve applying power to a wire of a power delivery system and applying onto the wire a chirp pulse comprising a sequence of waveforms of a plurality of frequencies. A signal is obtained from the wire. An impedance of the signal is analyzed at two or more frequencies of the plurality of frequencies with respect to a reference impedance to determine whether there is an indication of an impedance-based fault associated on the wire, such as a human touching the wire. The power to the wire is disconnected in response to determining an indication of the impedance-based fault.

Single-sided MRI scanners, systems, and methods are disclosed. A method can include applying a first sweeping frequency pulse defining an X axis; applying a second sweeping frequency pulse defining a Y axis; applying a third sweeping frequency pulse defining the Y axis; and applying a fourth sweeping frequency pulse defines a −X axis. The sweep rate of the fourth sweeping frequency pulse can be less than the sweep rate of the third and / or second sweeping frequency pulse. The sweeping frequency pulses can be chirp pulses. Frequency sweep DEFT pulse sequences can provide the benefits of a broader bandwidth and less sensitivity to the inhomogeneity of a single-sided MRI scanner.

The present application provides a downward-looking three-dimensional terrain imaging radar system, comprising: an array antenna, a radio frequency and beam control device, a signal processing device, and an integrated display and control device; the signal processing device generates a chirp pulse signal, the radio frequency and beam control device performs digital-to-analog conversion, filtering, phase shifting, and amplification on the signal, the array antenna performs beam synthesis on it, generates a radar signal and transmits it to the target scene; the array antenna is further used to receive the radar echo signal returned from the target scene, the radio frequency and beam control device performs filtering, amplification, phase shifting, and beam synthesis on the radar echo signal, the signal processing device performs analog-to-digital conversion, pulse compression, synthetic aperture, real aperture super-resolution, and interference processing on it, and generates a three-dimensional topographic map directly below the flight platform; the present application generates a three-dimensional topographic map directly below the radar through real aperture super-resolution processing of the radar echo signal.

Single-sided MRI apparatuses, systems, and methods are disclosed. A method can include transmitting a frequency sweep excitation pulse comprising a low-to-high frequency sweep; phase encoding during the frequency sweep excitation pulse; and tuning the amount of phase accumulated during the frequency sweep excitation pulse from adjacent slices in the slab. The frequency sweep excitation pulse can be a chirp pulse. Encoding in this way can prevent spin echoes from drifting and prevent k-space truncation in certain instances. Moreover, the resultant images can be combined more efficiently.

The utility model relates to four program femtosecond laser compressor, through the light of first time through the compressor output is injected into the compressor for many times, incident chirp pulse is along the compressor light path and is emitted four times, total transmission grating 8 times, finally through the output mirror output completes compression output, make the number of times of light beam through grating increase to 16 times, make the same grating aperture and grating spacing compressor dispersion quantity turn 4 times, adapt to bigger spread width or bigger bandwidth chirp pulse amplifier, many times repeat, expand the use number of times of compression grating, obtain bigger compression under the condition that the grating spacing of compressor is unchangeable, can be compatible with bigger spread width of chirp pulse amplifier, solve the problem of design limit of chirp pulse amplifier, promote femtosecond laser output single pulse energy.

According to the four-way femtosecond laser compressor and the method, light output through the compressor for the first time is injected into the compressor for multiple times, incident chirped pulses enter and exit for four times along the light path of the compressor, the incident chirped pulses pass through a transmission grating for eight times in total, and finally the incident chirped pulses are output through an output reflector to complete compression output; the number of times that a light beam passes through the grating is increased to 16, so that the dispersion amount of a compressor with the same grating caliber and grating spacing is increased by 4 times, and the chirped pulse amplifier with larger spreading amount or larger bandwidth is adapted; according to the femtosecond laser, the use frequency of the compression grating is expanded repeatedly, and a larger compression amount is obtained under the condition that the space between the compression grating is not changed, so that the larger broadening amount of the chirped pulse amplifier can be compatible, the problem of design limitation of the chirped pulse amplifier is solved, and the output monopulse energy of the femtosecond laser is improved.

The invention, which relates to the technical field of ultrafast laser, discloses a multi-disc multi-pass ultrafast laser amplification system comprising a first grating assembly, a first laser adjustment assembly, a multi-disc gain assembly, a second laser adjustment assembly and a second grating assembly which are arranged in sequence. A plurality of disc crystals of the multi-disc gain assembly are arranged at equal intervals to form a gain area; the first laser turn-back mirror and the second laser turn-back mirror are oppositely arranged on two sides of the multi-disc gain assembly and are used for reflecting the pulse laser distributed in the strip shape for multiple times to pass through a gain area of the multi-disc gain assembly; the first pump light coupling mirror and the second pump light coupling mirror are oppositely arranged on the two sides of the multi-disc gain assembly and used for coupling the input collimated rectangular pump light to a gain area of the multi-disc gain assembly. The first grating assembly and the second grating assembly form a chirped pulse compressor. According to the invention, the problem that the laser and the pump light are difficult to fully realize spatial overlapping in a gain region is solved, and the energy of the laser amplifier is effectively extracted.

This invention discloses an attosecond-level delay diagnosis method between electron beams and pulsed lasers, belonging to the technical field of delay diagnosis between electron beams and pulsed lasers. The method includes: adjusting the delay between a chirped pulsed laser a and a chirped electron beam b via a delay device; recording the positions of the delay devices corresponding to the appearance and end of the transverse modulation of the electron beam on an electron spectrometer to obtain the transverse modulation and energy spectrum of the chirped electron beam b; obtaining the chirped distribution of the chirped electron beam b using an electron beam chirped diagnostic reconstruction method based on laser transverse modulation of the electron beam; obtaining the angular distribution of the chirped electron beam b in the spatial domain based on [variable name missing]; determining the positive or negative value of the delay; performing a spatial domain Fourier transform on the angular distribution of the chirped electron beam b in the spatial domain; and further calculating the delay difference between the chirped electron beam b and the chirped pulsed laser a. This invention can diagnose attosecond-level delays between electron beams and pump pulses; the device is simple; and it has good scalability, extending to any wavelength band.

The invention relates to the technical field of ultrafast laser, and discloses a pumping intensity optimization method of a laser, equipment and a medium. The method comprises the following steps: carrying out graded pumping design, and pre-amplifying signal light output by a mode-locked fiber oscillator by adopting a single-mode laser diode; the method comprises the following steps: establishing a mathematical model of pumping power and gain fiber length, and when the pumping power is increased from low power to preset power, adjusting the chirp amount of a chirp fiber grating through a temperature tuning device, and performing pre-chirp management on signal light input into a multimode gain fiber; under high pumping intensity, the initial chirp amount of signal light is optimized, so that the signal light entering the multimode gain optical fiber is in a negative chirped pulse state, the self-phase modulation and dispersion effect of the signal light when the signal light is amplified in the multimode gain optical fiber is balanced, and the stimulated Raman scattering and self-focusing phenomena are avoided; and the compressed pulse width is used as a feedback signal to realize the optimal matching of the signal light energy and the pulse width.

Techniques for detecting an impedance-based fault on a wire carrying power in a power delivery system. The techniques involve applying power to a wire of a power delivery system and applying onto the wire a chirp pulse comprising a sequence of waveforms of a plurality of frequencies. A signal is obtained from the wire. An impedance of the signal is analyzed at two or more frequencies of the plurality of frequencies with respect to a reference impedance to determine whether there is an indication of an impedance-based fault associated on the wire, such as a human touching the wire. The power to the wire is disconnected in response to determining an indication of the impedance-based fault.

The application discloses a chirp pulse stretching and compressing device and an amplification system, and relates to the field of lasers. The chirp pulse stretching and compressing device comprises a first polarization beam splitter prism, a pulse stretching and compressing device and a dispersion regulator. The chirp pulse stretching and compressing device has a stretching port and a compressing port arranged oppositely, is divided into a stretching light path part and a compressing light path part, the two light path parts share one main stretching and compressing module, and the stretching light path part is additionally provided with a dispersion regulator to provide adjustable and additional dispersion compensation. The chirp pulse stretching and compressing device provided by the application can be flexibly adapted to different amplification systems, so that the output light pulse reaches near-zero chirp and ultra-short pulse width is realized.

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.