72results about How to "Avoid nonlinear effects" patented technology

A method for determining the time-of-flight of a device under test, wherein a return signal returning from the device under test in response to the probing signal comprising a sequence of pulses according to a first code sequence is detected and a second code sequence from the detected return signal is derived, and a correlation function is determined by correlating the first code sequence and the second code sequence, a main peak is identified, a time position of the main peak is determined and the time-of-flight is derived from the time position.

The invention discloses a servo system position IP controller model-free self-correcting method based on fractional order. The method includes: setting a reference model, exciting a system to obtain an offline database, initiating the related parameters of the system, updating the database according to input and output data newly collected at a current moment, selecting similar data queues according to a similarity criterion function, selecting the order of a fractional order controller, and using particle swarm optimization algorithm to perform self-correcting on fractional-order IP controller parameters. The method has the advantages that the fractional order feature of the system is considered, performance such as overshoot, rising time, error convergence speed and controller parameter variation is appraised comprehensively, the instantaneity of the system is guaranteed by using the similarity criterion function, the method is unaffected by unmodeled dynamics, and the robustness, disturbance rejection ability and control precision of the system are increased.

The present invention provides a double-frequency interference-based THz radar target three-dimensional imaging method, wherein the coordinates of a target in three dimensions of distance, azimuth and pitch can be obtained. Meanwhile, the azimuth-pitch 2D image of the target, including the 2D coordinates of the target and the 2D scattering intensity distribution of the target, is obtained through the azimuth-pitch imaging process. The distance-dimension coordinates of the target are obtained through the interference treatment on two azimuth-pitch images of two adjacent frequency points. During the double-frequency interference-based azimuth-pitch imaging process, the small-angle two-dimensional rotation of a target is utilized to obtain the high resolution in the dimensions of both azimuth and pitch. Meanwhile, the double-frequency imaging mode avoids the usage of wideband signals during the 3D imaging process and the non-linear influence of signals. The above method is simple in imaging process and high in efficiency, which realizes the 3D imaging of a radar target.

The invention provides a femtosecond laser fiber spectroscopic device based on dispersion pre-compensation, which comprises a femtosecond light source, a dispersion pre-compensator, a fiber coupling device and a fiber spectroscope. The femtosecond light source is used for generating seed laser with the pulse width in the magnitude of femtosecond, the dispersion pre-compensator is used for providing negative dispersion for the femtosecond laser generated by the femtosecond light source so as to compensate positive dispersion introduced into fiber transmission, the fiber coupling device is used for coupling the femtosecond laser which is outputted from the dispersion pre-compensator and carries the negative dispersion, and the fiber spectroscope is used for dividing laser coupled by the fiber coupling device into a plurality of channels of laser pulses to be outputted. The femtosecond laser fiber spectroscopic device has the advantages that the femtosecond pulses with the pulse width close to that of the seed laser can be obtained at a fiber output end, the spectrum and the waveform of the pulses can be kept beneficially after the pulses are transmitted in an optical fiber, the provided negative dispersion can be changed, and accordingly the pulse width of laser outputted after optical fiber transmission is adjusted.

A high-power, tunable and narrow linewidth external cavity semiconductor laser belongs to the technical field of a semiconductor laser and aims to solve the problem that the comprehensive requirements such as mode characteristic, beam quality, linewidth, coherence and tunability of a single laser are difficult to be met. The high-power, tunable and narrow linewidth external cavity semiconductor laser is formed by directly coupling a gain chip, a tunable external cavity and an inclined power amplifier with a curved waveguide through an end surface, wherein the gain chip is used for achieving laser output of single-mode wide spectrum; the tunable external cavity adopts a silicon on insulator (SOI) material; the linewidth is narrowed by increasing cavity length and a quality factor Q of a laser resonant cavity; the tunability is achieved by the adoption of refractive index of a thermal modulation material; and by the arrangement of the inclined power amplifier with curved waveguide, laser output with high power and high beam quality is achieved under ensuring the stability of the gain chip and the tunable external cavity. By the high-power, tunable and narrow linewidth external cavity semiconductor laser, a novel semiconductor laser integrating a single mode, high power, high beam quality, narrow linewidth, high coherence, tunable wavelength and the like is achieved, and the high-power, tunable and narrow linewidth external cavity semiconductor laser has important application prospect in the fields such as space laser communication and laser radar.

The invention provides an adjustable gap nonlinear research test bed which comprises a cantilever beam, a gap size adjusting assembly, a gap rigidity adjusting assembly, a gap position adjusting assembly, a cantilever beam supporting assembly and a base. Gaps of different positions, different sizes, different rigidities and different numbers can be obtained through a gap adjusting device and the good test bed is provided for research on influence on cantilever beam vibration by the different gaps and identification of a system with the gaps. The principle of the adjustable gap nonlinear research test bed is that gap positions can be adjusted through the method that a gap position adjusting frame moves along a guiding groove; the bending rigidity of a gap rigidity beam is equivalent to the gap rigidity and the gap rigidity is adjusted through the change of materials of the gap rigidity beam and the change of the thickness of the gap rigidity beam; different gap values are obtained through replacement of pads of different thicknesses; the number of gap adjusting devices is increased so that research on the gaps can be achieved. According to the adjustable gap nonlinear research test bed, the structure is novel, functions are multiple, operation is simple, manufacturing is easy, and the structure is compact.

The invention relates to a coherent beam combination system for an optical feedback ring cavity of a pulsed fiber amplifier array, which comprises a seed source and is characterized in that the ring cavity is formed by a beam combiner, a chopper, an optical fiber preamplifier, a beam splitter, two or more than two amplifying links, a lens and a feedback optical fiber entering the beam combiner along the direction of a laser outputted by the seed source; the input end of the feedback optical fiber is positioned on a back focus of the lens; the output ends of a plurality of amplifying links in each amplifying link ensure that light beams are outputted in a collimating manner and are not overlapped, and the directions of the light beams and an axis of the lens are coupled into the input end of the feedback optical fiber through the lens in parallel; and the seed source is a continuous laser. The coherent beam combination system has the advantages of simple principle and easiness in adjustment, overcomes the defect that a traditional passive beam combination method can not realize the multi-path high-repetition rate frequency and the phase lock output of a pulse laser with narrow pulse width and improves the brightness outputted by the pulsed fiber amplifier array with narrow pulse width and high peak power.

The invention relates to the fields of optical fiber sensing and underwater acoustic signal measurement, in particular to an anti-polarization-induced-fading interference type optical fiber hydrophone system comprising a light source modulation unit (1), a multi-wavelength single-frequency laser emitting unit (2), a wavelength multiplexing unit (3), a pulse modulation unit (4), a first amplifier (5), a fiber circulator (6), a sensing array (7), a matched interference unit (8), a second amplifier (9), a wavelength demultiplexing unit (10), A photoelectric conversion and demodulation unit (11), and a display and control unit (12). Therefore, under the circumstance that the hydrophone array is processed into a fine array less than or equal to 30mm, a polarization induced-fading phenomenon is avoided.

The invention relates to a Brillouin optical time domain analysis system and a Brillouin optical time domain analysis method. The system obtains dual-frequency optical carriers through modulating continuous light by an electro-optic modulation link, four different frequencies of detection light and dual-frequency pulse light are generated through a detection light generation link and a dual-frequency pulse light generation link, and the optical signal power for each frequency is below the nonlinear threshold; the dual-frequency pulse light is controlled to generate time delay through a first Bragg grating module to eliminate crosstalk of the dual-frequency pulse light, two ways of pump light are thus formed and are injected to an optical fiber, time delay compensation is carried out on Brillouin signal light formed due to interaction between the detection light and the pump light injected to the optical fiber through a second Bragg grating module, and finally, after signal processing, Brillouin frequency shift data of the optical fiber are acquired. Thus, nonlinear effects caused by single-frequency pulse light and over high signal optical power can be avoided, power demands of the pulse light are reduced, the signal-to-noise ratio of the system is improved, and non local effects caused by pump depletion can be reduced.

The invention discloses a millimeter wave adjustable filter. A millimeter wave filter structure can comprehensively consider low loss, rapid debugging, high Q values and miniaturization of the filter,sensitivity and the dynamic range of a system can be remarkably improved, and millimeter wave transceiving system performance is greatly improved. The millimeter wave filter structure comprises an upper substrate, a lower substrate and a metal carrier, a millimeter wave filter inverted micro-strip circuit is arranged on the upper substrate, a liquid crystal cavity is formed in the center of the lower substrate and filled with liquid crystal, feed lines electrically connected with the liquid crystal are arranged on two sides of the liquid crystal cavity, the upper substrate, the lower substrate and the metal carrier are sequentially arranged from top to bottom, a micro-strip metal wire in the millimeter wave filter inverted micro-strip circuit and the liquid crystal are closely combined, and a liquid crystal injection hole communicated with the liquid crystal cavity is formed in the upper substrate. The millimeter wave filter structure has good frequency reconfigurable characteristics.

The invention relates to a modulation method and a modulation device by which optical continuous phase frequency shift keying (CPFSK) with any modulation index can be realized. The device comprises a modulation part and a demodulation part, wherein the modulation part is implemented by using a two-arm structure of a mach zehnder interferometer (MZM), and a phase continuity mode is implemented by controlling the time delay of an input waveform. The invention can provide a modulation-index variable optical CPFSK method and a modulation-index variable optical CPFSK device, by which an optical CPFSK signal with constant envelope, continuous phases and any modulation index can be generated, thereby overcoming a nonlinear effect in an optical transmission process, and improving the dispersion tolerance and the PMD (polarization mode dispersion) tolerance.

The invention discloses an alternating current servo system model distinguishing method and a control system based on frequency data, and belongs to the field of alternating current servo system control. The method comprises the following steps that: establishing an alternating current servo system model to be distinguished, obtaining the frequency response data of the system by an excitation system so as to construct a model distinguishing target criterion function, and according to an amplitude value and phase position equal condition, utilizing a set residual error to finish the optimization distinguishing of an optimal model parameter in an iteration domain. By use of the weighting iteration model distinguishing method and the control system based on the frequency data, the determination of a system model structure and the distinguishing of the model parameter under distributed frequency data are realized, in addition, a time delay link in a practical system is simultaneously considered, and a following residual error kurtosis coefficient and a weighting iteration algorithm are used for guaranteeing model parameter update optimization.

The invention discloses a subtend compression chirped pulse amplification laser system, comprising a seed source, a stretcher, a subtend compressor and a focusing mirror; the subtend compressor consists of a raster compressor, two polarizing beam-splitter plates, two polarization converters, one delayer and five reflectors. The subtend compression chirped pulse amplification laser system realizes the two-way time-sharing secondary utilization of the raster compressor, breaks through the limitation of the bearing capacity of the taster compressor, avoids the non-linear effect, has the identical dispersion compression amount and realizes multiplication of the output capability of the chirped pulse amplification laser system.

The invention discloses a BOTDR system based on Bark sequences and a long-distance detection method thereof. The method comprises the steps that continuous light is divided into two paths; a set of bipolar Bark sequences is generated, and the bipolar Bark sequences is divided into two sets of unipolar Bark sequences; the two sets of unipolar Bark sequences are utilized for controlling the electric field to modulate probe light, and light pulse signals of the two sets of unipolar Bark sequences are obtained; the two sets of signals are amplified, optical fibers are injected, and two sets of backward Brillouin scattering light signals are obtained; vibration light signals are in coupling coherence with the two sets of backward Brillouin scattering light signals respectively, and two sets of Brillouin scattering electric signals are collected through photovoltaic conversion, frequency sweeping and filter and amplification; the two sets of Brillouin scattering electric signals are in coherence, Brillouin frequency shift of each point distributed along the optical fiber is obtained, and changes of the temperature or strain around the optical fiber are obtained. An electro-optic modulation module in the system comprises an electro-optic intensity modulation module and a Bark sequence generating module. The self-correlation characteristics of the Bark sequences are utilized for improving the signal to noise ratio and improving the distance detecting distance under the condition that the system space resolution ratio is not reduced.

The invention discloses a photoacoustic probe and an optical system provided with the photoacoustic probe and applied to photoacoustic imaging. The optical system comprises a laser, a light spot adjusting device, a light guide arm and the photoacoustic probe. The light guide arm ensures that the system has high light energy transmission efficiency and is conveniently operated by doctors. The photoacoustic probe comprises a casing, a light processing device and an ultrasonic probe, wherein the casing is provided with a light inlet, a first light outlet and a second light outlet; the light processing device is positioned in the casing, and is used for receiving incident light and performing light shape adjustment, and finally transmitting light to the first light outlet and the second outletand emitting the light to irradiate a tested sample; the ultrasonic probe is positioned in the casing, and is used for receiving photoacoustc signals from the tested sample and converting the photoacoustc signals into electric signals, so as to output the electric signals. As an engineering effuser is mounted in the light processing device, a laser beam can more uniformly irradiate the tested sample, the light energy emitted into the texture of the tested sample can be maximized, and the imaging depth is improved.

The method realizes outputting laser from fiber laser finally through following means: using femtosecond level pulsed laser with specific parameters to carry out slant punching on side of doubly coated fiber; next, embedding coupled apparatus of semiconductor laser diode; then, adding front and back cavity mirrors on two end faces of doubly coated fiber to form resonance; finally, realizes outputting laser from fiber laser. The invention possesses advantages: (1) not influence on transmission of optical waveguides, no additional dislocation or defect on slant hole so as to avoid non-linear effect and heat melting; (2) raising quality in light mode of pump source, being in favor of maintaining, and eliminating heat so as to prolong service life; (3) cumulating pumped power unlimitedly in order to implement outputting large power of fiber laser; (4) convenient operation.

The invention discloses a screw operator-based fingerprint detail point characteristic obtaining method, and relates to the technologies of fingerprint preprocessing and the like. The method comprises three steps of fingerprint preprocessing, phase field demodulation and detail point characteristic obtaining; a fingerprint image is regarded as a two-dimensional variable-cycle stripe graph signal; detail points in the fingerprint image are expressed as screw singular points in a phase field; and a fingerprint detail point detection problem is converted into a function solving problem, wherein phase demodulation is obtained by solving a single base signal through an analysis function, and the screw singular points are obtained by calculating extremum points obtained by Poincare index integral of the phase field. According to the method, the problem of information loss in operations of binarization, detailing and the like is avoided; very good noise resistance is achieved; the post-processing of removing fake detail points does not need to be carried out; the system time cost is effectively reduced; meanwhile, the influence caused by a fingerprint pressure, translation, rotation and a dry-wet environment during fingerprint image collection is avoided; and the method has the advantages of low complexity, high processing speed, high comparison precision and the like.

The invention provides a high-power narrow-linewidth optical fiber laser based on an annular cavity oscillator seed source. The high-power narrow-linewidth optical fiber laser comprises the annular cavity oscillator seed source, a main laser amplifier and a main output end, and the annular cavity oscillator seed source, the main laser amplifier and the main output end are connected in sequence; and the annular cavity oscillator seed source comprises a filter device, a laser output module and a pre-laser amplifier, the filter device, the laser output module and the pre-laser amplifier are sequentially connected to form an annular structure, and the annular cavity oscillator seed source is connected with the main laser amplifier through one output end of the laser output module. The laser provided by the invention only needs one-stage amplification, is simple in structure and reliable in performance, can reduce the complexity of a high-power narrow-linewidth fiber laser system, enables the power to be further amplified without being inhibited by a nonlinear effect, is more stable in output laser time sequence, and can improve the inhibition capability of stimulated Raman scattering in the power amplification process.

The invention discloses a high-performance distributed optical fiber sensing system and method. The system comprises a multi-wavelength narrow linewidth light source, a modulation unit, a splitter, a wavelength division multiplexer, a wavelength division demultiplexer, a circulator, a sensing optical fiber, a demodulation module and an upper computer. The continuous light emitted by the multi-wavelength narrow-linewidth laser is modulated by using the sweep-frequency filter or the multi-path signal generator, asynchronous modulation among wavelengths is realized by controlling the sweep-frequency rate of the sweep-frequency filter or the multi-path signal generator to trigger the modulator in a parallel time delay manner, and the pulse interval, the pulse width and the pulse repetition frequency are flexible and adjustable. And the demultiplexer and the wavelength division multiplexer are utilized to realize multi-channel synchronous sensing, so that the measurement efficiency is improved. Pulse light with multiple wavelengths is used as detection light to enter a sensing optical fiber, information carried by Rayleigh scattering signals under each wavelength is demodulated, and the signals are comprehensively processed. According to the invention, system complexity is reduced, and system performance is improved.

The invention discloses a frequency modulation laser signal generation device based on a phase modulator. The frequency modulation laser signal generation device comprises a laser light source, the phase modulator, a frequency modulation signal generator, a base frequency signal generator, a frequency mixer, a radio-frequency amplifier and an optical filter. According to the device, frequency mixing signals of frequency modulation signals generated by the frequency modulation signal generator and base frequency signals generated by the base frequency signal generator serve as driving signals of the phase modulator, the driving signals drive the phase modulator to generate frequency modulation laser signals, and the optical filter restrains harmonic waves to reserve frequency modulation laser signals of needed orders. According to the device, the frequency of the base frequency signals is controlled, frequency overlapping of various orders of frequency modulation laser signals can be avoided, high-order double-frequency signals can be acquired, and broadband adjustment is achieved. According to the device, filtering is achieved by the aid of the optical filter, and the obtained frequency modulation laser signals have a high sideband suppression ratio.

The invention provides a streamline analog-to-digital converter and a streamline analog-to-digital converting method based on sampling capacitor randomization. A sampling capacitor is marked to different working states through a sampling capacitor selector. Furthermore before a sampling phase, random selection of a group is performed on the capacitors which are not in working currently as the sampling capacitors for the phase in next sampling so that sampling holding and margin signal amplification of each streamline structure unit are synchronously performed, thereby realizing coarse quantification and margin amplification output on an input signal by an n-th grade streamline structure unit. According to the streamline analog-to-digital converter and the streamline analog-to-digital converting method, each streamline structure unit performs coarse quantification and margin amplification output on the input signal. The capacitors which are used at a sampling phase and an amplification phase for one sampling point by each streamline are in the same capacitor set; but the capacitors for performing a sampling process and an amplification process on different sampling points at the same time are independent from one another. The streamline analog-to-digital converter and the streamline analog-to-digital converting method realize independent and synchronous execution of a sampling keeping process and a margin signal amplification process of each streamline, and furthermore greatly improve conversion speed of the analog-to-digital converter.

The invention discloses a single-ended dual-wavelength high-precision distributed optical fiber temperature sensor, and belongs to the technical field of optical fiber sensing. In the single-ended dual-wavelength high-precision distributed optical fiber temperature sensor, two light sources with different wavelengths are connected to a pulse driver to ensure that the required precision of spatial resolution is achieved while the required pulse light energy is provided by utilizing the pulse widths of the two light sources. Therefore, the problem that the spatial resolution cannot meet the required precision in the prior art is solved, and the single-ended dual-wavelength high-precision distributed optical fiber temperature sensor is suitable for places with high precision requirement, such as petrochemical pipelines, electric high-voltage switches and the like.

The polarization controller, wavelength division multiplexer in the back end of oscillator, pumping source in the back end of oscillator are set at first row in broad ways on the mounted panel. The optical isolator relating the polarization, wavelength division multiplexer at front end of oscillator, pumping source in front end of oscillator, pumping source of amplifier are set on the second row in broad ways on the mounted board. The back end polarization controller, osc out coupler, osc check and out coupler, optical isolator not relating to polarization, wavelength division multiplexer of amplifier, collimated grating, and lifting mirror are set at the third row in broad ways on mounted board. The check out and output coupler of amplifier, collimation coupling lens, and diffraction grating are set at the fourth row in broad ways on the mounted board. The convergence coupling les is set at fifth row in broad ways on mounted board.

The invention relates to a high-power narrow-linewidth fiber laser based on rayleigh scattering and a working method thereof. The laser comprises a pump laser, a wavelength division multiplexer, a YAG-SiO2 doped fiber, a first fiber circulator, a polarization controller, a second fiber circulator, a YAG-SiO2 fiber, a variable optical attenuator and a faraday rotation mirror which are arranged along the light path. The first fiber circulator is also connected with high-reflectivity fiber Bragg gratings. The output end of the first fiber circulator is also connected with a fiber coupler. One output end of the fiber coupler is connected with the wavelength division multiplexer. The other output end of the fiber coupler is the output end of the whole laser. The wavelength division multiplexer,the YAG-SiO2 doped fiber, the first fiber circulator, the polarization controller, the second fiber circulator and the fiber coupler form a ring cavity together.

The invention discloses a method for checking parameters of an activated sludge mathematical model. The method mainly includes the first step of constructing the activated sludge mathematical model and determining basic data for model parameter checking, the second step of screening the parameters, needing to be checked, of the activated sludge mathematical model, the third step of conducting identification and ranking analysis on parameter sets, needing to be checked, of the activated sludge mathematical model through the calculation methods of sensibility, a colinearity index gamma k and an identifiable degree rho k, the fourth step of solving the parameter sets by adopting the weighted error quadratic sum of four indexes of COD, NH4<+>-N, TN and TP of discharged water as an objective function according to the model so that checked model parameter sets can be obtained, and the fifth step of substituting the checked model parameter sets into the activated sludge mathematical model to carry out dynamic examination and examining whether parameter checking meets requirements or not. According to the method, the needed workload is small, calculation precision is high, the problem that the parameters influence one another is reduced or solved, and the method can be widely applied to checking parameters of various activated sludge treatment process mathematical models.

The invention relates to a high-power, high-repetition-frequency and pulse-width-adjustable ultrafast laser system. Laser pulses with the repetition frequency of GHz or above are generated through a laser seed source. A broadening and amplifying module is used for amplifying and broadening the laser pulse. A pulse modulation module modulates the amplified and broadened laser pulses to generate a plurality of laser pulse strings with different frequencies and different duty ratios, and the laser pulse strings are amplified step by step by adopting a multi-stage amplification module. A nonlinearcompression amplification module adjusts the spectrum broadening by controlling the pumping power or the nonlinear quantity; and the broadening degree of the laser pulse and the frequency and duty ratio of the pulse modulation module are continuously adjusted by combining the broadening amplification module, so that different nonlinear compression pulse widths can be obtained, and the pulse widthcan be continuously adjusted from picosecond to femtosecond. The pulse compression module compresses and outputs the laser pulse with continuously adjustable pulse width, so that the laser pulse withhigh power, high repetition frequency and adjustable pulse width is output.

The invention discloses a noise measurement and stability control method and system of an ultra-short optical pulse amplification compression system CEP, and the implementation principle is as follows: seed light passes through the ultra-short optical pulse amplification compression system, and then passes through an acousto-optic frequency shifter to generate optical frequency shift; the frequency shift amount of the optical frequency shift comes from a stable radio frequency signal applied externally, so that signal light with additional bias frequency relative to the bias frequency of the seed light is generated; carrying out beat frequency on the signal light carrying the additional bias frequency and the seed light to obtain a beat frequency signal; the noise spectrum of the CEP noise signal generated by the ultra-short optical pulse amplification and compression system can be obtained by measuring the power spectrum density of the beat frequency signal; performing phase comparison detection on the beat frequency signal and the radio frequency signal to obtain a phase detection signal; and a phase detection signal is fed back to the photoelectric dispersion modulator through phase-locked amplification so as to realize full-band bandwidth stable control of the CEP. The method is simple and practical in implementation process, and is suitable for various forms of ultra-short light pulse amplification and compression systems.