162results about How to "Improve demodulation accuracy" patented technology

An automatic frequency controller includes a frequency offset estimating section that calculates phase distortion quantities and the average thereof from known signals contained in a received signal. The frequency offset estimating section obtains, from the average distortion quantity, signal powers corresponding to a plurality of candidate frequency offsets set at frequency offset estimation accuracy intervals in a frequency offset estimation range. The frequency offset estimating section looks at the signal powers through a frequency window with a frequency width corresponding to a transmission path state. This makes it possible to maximize the signal power of a frequency of a radio wave or radio waves corresponding to the transmission path state, and to place the radio wave or radio waves corresponding to the transmission path state as a frequency controlled object. This can improve demodulation accuracy. Fine adjustment of the candidate frequency offsets can improve the estimation accuracy of the frequency offset without changing the frequency offset estimation range.

The invention discloses a fiber laser static-state strain beat frequency demodulation system based on single-sideband frequency sweep modulation. The system comprises a pumped source, a coupler, a first wavelength division multiplexer, a second wavelength division multiplexer, a first polarization controller, a second polarization controller, a sensing fiber laser, a reference fiber laser, a first isolator, a second isolator, a first beam combiner, a second beam combiner, a first broadband photoelectric detector, a second broadband photoelectric detector, a control processor, a narrow linewidth laser light source, a third isolator, a third polarization controller, a third beam combiner, a suppressed carrier single-sideband modulator, a fourth beam combiner, a frequency sweep signal generator, a phase modulator, a radio frequency signal generator, a frequency stabilization source and a photoelectric detector. The system provided by the invention realizes high-precision static-state strain measurement of the fiber lasers and solves the problems of incapacity of realizing high-precision static-state strain measurement, influences exerted by tunable laser frequency sweep non-linearity on demodulation precision, and the like by use of a conventional fiber laser demodulation technology.

The invention discloses a laser beat frequency sensing technology-based high-precision inclinator and a measurement method, and is applied to the inclination change measurement of the crust. The high-precision inclinator comprises two communicated water tanks, floaters, optical fibers, sensing fiber Bragg gratings, reference fiber Bragg gratings, fixed side plates and sensing signal generation and demodulation devices. A principle for realizing inclination measurement is dual-ring cavity single longitudinal mode fiber laser-based laser beat frequency sensing demodulation technology, and two inclination measurement implementation schemes are provided for different base lengths of a water pipe inclinator. A laser beat frequency sensing technology is applied to the measurement of a crustal inclination signal through an ingenious structural design, and a corresponding fiber water pipe inclinator device is designed; and therefore, compared with the prior art, a system has the advantages of high demodulation precision, high reliability, simple structure, lower cost, high stability, automatic temperature compensation mechanism and the like.

The invention provides a fiber F-P sensor cavity length wavelet phase extraction demodulation method. At first, the interference spectrum is calculated by means of a fast fourier transform algorithm to obtain a cavity length value to be a cavity length rough measuring value; the searching scope of a scale factor is determined by taking the 2-3 times of the precision of the fast fourier transform algorithm as the radius, and the phase information corresponding to each point in the interference spectrum is solved by continuous complex wavelet transform; and the cavity length value of the fiber F-P sensor is calculated by the linear gradient obtained by the linear fitting phase and wavenumber to be the final cavity length value. The absolute measurement of the F-P sensor cavity length can be achieved, so that the high-precision and high-resolution measurement of physical quantity can be achieved.

The invention relates to an implementation method for processing an FBG (fiber bragg grating) sensing signal based on a three-point peek-seeking algorithm. The method comprises the steps of providing a peek-seeking processing flow, and giving three elements influencing the peek-seeking accuracy according to the flow, wherein reasonable selection of a window size is a key point for improving the peek-seeking accuracy, and the size of a spectral processing window is determined by adopting a derivation method; the spectrum in the window is resampled by arranging sampling intervals, and sparse spectrum data is acquired and subjected to polynomial fitting; a proper wavelength interval delta lambda is selected according to the fitting result, the coordinates of three points can be determined, the peak value of the FBG reflectance spectrum is detected, so that the central wavelength can be acquired, and external physical parameters can be demodulated.

The present invention discloses an F-P and FBG fiber sensor demodulation system, and aims to provide an F-P / FBG demodulation system which is high in wavelength resolution, and enables the demodulation precision to be improved. The F-P / FBG fiber sensor demodulation system of the present invention is realized by the following technical scheme that under the control of an operation control unit, a tunable laser emits out a beam of C-wave band laser of a constant wavelength, by an optical amplifier SOA and / or an optical isolator, and by being divided equally via a beam splitter, the incident light respectively irradiates to n F-P / FBG sensors in one-to-one correspondence, the light reflected by the F-P / FBG sensors is coupled to n phototriodes in one-to-one correspondence by n optical couplers, the optical power is converted into an optical current, the optical current is converted into an optical voltage entering an analog-digital converter by a logarithmic amplifier, the wavelength-reflection optical voltage digital quantity acquired in a time-sharing manner is stored in a memorizer of the operation control unit, the operation control unit carries out the fast Fourier transform on a sampled spectrum, the types of the F-P / FBG sensors are distinguished, and a peak searching demodulation algorithm is carried out to obtain a gradient value containing the cavity length information.

The invention discloses a frequency modulation and demodulation device based on a fiber bragg grating sensor array. The frequency modulation and demodulation device comprises a laser, a radio frequency signal source, an acoustic optical modulator, a delay optical fiber pair, a Mach-Zehnder modulator, an optical filter, an optical amplifier, an optical isolator, a circulator, the fiber bragg grating sensor array, a photoelectric detector and a data sampling card. Through cooperative use of the delayed light pair and the fiber bragg grating, reflected light pulses of the front grating and the rear grating are superposed in a time domain so as to form interference, and multi-point array type interference demodulation is realized. The device is simple in structure, a demodulation algorithm iseasy to realize, and the device has the characteristics of high demodulation precision, simple realization and the like.

The invention discloses a low coherent interference demodulation method based on a chromatic dispersion characteristic and an envelopment peak value. According to the method, an F-p sensor is chosen to serve as a sensing element, a double refraction optical wedge serves as an optical path difference space scanning element, an interference fringe is formed in a zero optical path difference local area, an F-P cavity length is demodulated according to the interference fringe, and therefore atmospheric pressure is felt. According to the method, firstly, Fourier filtering is carried out on an interference signal; then a low precision distance corresponding to a peak value position according to a peak value position obtained by the envelopment peak value method and a cluster refractive index of a low coherent interference system dispersion element is obtained; finally, a theoretical phase position is calculated by the utilization of the peak value position chromatic dispersion characteristic, and the distance error of the envelopment peak value method is determined according to the theoretical phase position and a measured phase position and high-precision demodulation is achieved. Under the condition that prior information is not needed, the system chromatic dispersion characteristic and the envelopment peak value are utilized to achieve wide-range high-precision measurement of low coherent interference. The low coherent interference demodulation method is applied to the optical fiber sensing filed, the three-dimensional shape detecting and optical chromatographic technique, and other distance measurement fields.

The invention discloses a method and device for demodulating a distributed optical fiber vibration sensing system. The method comprises that two continuous ultra-narrow linewidth lasers with the sameoptical power are subjected to acousto-optic modulation and electro-optic modulation to be converted into two pulsed light signals; the two pulsed light signals are input into a sensing fiber at an interval of set pulse width; the backward Rayleigh scattered light of the two pulsed light signals generate a set frequency difference such that the returned Rayleigh light signals exhibit sinusoidal interference fringes; when a disturbance signal has an effect on the sensing fiber, the phase difference of the returned Rayleigh light signals changes, and the vibration waveform and position sensed bythe sensing fiber are obtained according to the phase difference. When the disturbance signal appears, a detector can quickly obtain the position of the disturbance signal and the intensity of the disturbance signal, which solves the problem that the demodulation algorithm of a [phi]-OTDR system is complex and a laser frequency drifts, and guarantees that the positioning error of the system is within + / -1m.

The invention discloses a fiber laser sensor light-carried microwave signal digital demodulation system and the demodulation method thereof. The system is used to demodulate the light-carried microwave signal outputted from a fiber laser sensor and outputs a demodulation signal capable of restoring a wideband large dynamic sensing signal in real time. The system comprises a photoelectric conversion module, a radio frequency signal processing channel module, a high-speed analog-to-digital conversion module, and a real-time digital signal demodulation processing module. The radio frequency signal processing channel module performs automatic gain amplification and bandpass filtering on the heterodyne frequency modulation signals outputted by the photoelectric conversion module in sequence and converted into digitalized radio frequency signals by the high-speed analog-to-digital conversion module. The real-time digital signal demodulation processing module uses two channels of orthogonal local oscillator sequences to multiply the digitalized radio frequency signals respectively, and two orthogonal baseband signals are obtained from the downsampling after the low-pass filtering followed by the division, four-direction anti-tangent operation, and then the periodic expansion of the arctangent result so that the phase demodulation phase signal obtained from phase adjustment is subjected to digital differential processing.

The invention provides a signal demodulation method and device so as to reduce the influence of Doppler frequency shift on transmission speed. When received radio-frequency signals sent by a base station are demodulated, reference clock signals provided by a PMU are obtained, then the movement speed of a mobile terminal needs to be determined, a Doppler frequency offset value generated when the mobile terminal receives the radio-frequency signals transmitted by the base station is determined according to the movement speed, and then the received radio-frequency signals sent by the base station are demodulated according to the reference clock signals and the Doppler frequency offset value. Due to the fact that the influence of Doppler frequency offset is considered when the radio-frequency signals sent by the base station are demodulated, demodulation precision is high, and therefore the problem that the transmission speed is too low when the Doppler frequency offset exists is solved.

The invention discloses a cavity length demodulation algorithm of a short cavity optical fiber fabry-perot sensor, and belongs to the technical field f optical fiber sensing. The cavity length demodulation algorithm of the short cavity optical fiber fabry-perot sensor is characterized by comprising the following steps: irradiating the short cavity optical fiber fabry-perot sensor by broadband light emitted by a white light source, acquiring reflection spectrum of the short cavity optical fiber fabry-perot sensor, moving the original reflection spectrum signal by a certain distance, which is less than the cycle length of the reflection spectrum signal, in the x-coordinate direction of a power spectrum density map to obtain an additional reflection spectrum signal, evaluating phase difference of the original spectrum signal and the additional spectrum signal by utilizing an ellipse fitting method, and obtaining an actual absolute cavity length value according to a fabry-perot cavity length calculation formula. By the cavity length demodulation algorithm of the short cavity optical fiber fabry-perot sensor, the problem about cavity length demodulation when the short cavity optical fiber fabry-perot sensor demodulation system acquires incomplete spectrum is solved, and the requirement on the light source spectrum range by the system is reduced.

The invention discloses a digital converter of a magnetic encoder, comprising a magnetic encoder, a signal processor, a phase-sensitive detector, a feedforward signal generator and a state observer. The signal processor caries out amplitude conditioning and analog-to-digital conversion to the output signal of the magnetic encoder; the phase-sensitive detector can generate an error signal containing phase information according to the output signal of the magnetic encoder and an angle estimation value output by the state observer; the feedforward signal generator calculates a feedforward angular velocity value needed by the state observer according to the output signal of the signal processor; and the state observer demodulates the angle and the angular velocity of a tested rotating device according to the error signal and the feedforward angular velocity value. The invention can greatly reduce the phase lag of the demodulated signal when the rotating device continuously rotates and has high demodulation accuracy and strong anti-interference capability.

The invention discloses a low-coherence interferometric demodulation method based on spectrum nonlinear effect dispersion compensation. The method comprises the following steps: step 1, achieving discrete Fourier transform of interference fringe signals to obtain the magnitude spectrum and the phase spectrum under the discrete frequency domain; step 2, setting a threshold H, taking a region of which the amplitude is larger than H, except for the low-frequency part, as the selected discrete frequency band, calculating wave numbers corresponding to all points in the frequency band, and transforming the phase spectrum from the discrete frequency domain to the wave number domain; step 3, selecting the wave number corresponding to the maximum amplitude in the magnitude spectrum, within the wave number band in which the optical spectrum of a light source is distributed, as the specific wave number, carrying out phase unwrapping in the wave number band, calculating the interference level of the specific wave number, reconstructing the absolute phase of the specific wave number, which directly reflects the range information, according to the relative phase value and the interference level of the specific wave number. The low-coherence interferometric demodulation method realizes high-precision distance demodulation and is suitable for light sources with any wideband.

The invention provides a low-coherence interference demodulation method based on a monochrome frequency absolute phase, belonging to the field of optical fiber sensing. The low-coherence interference demodulation method based on the monochrome frequency absolute phase is widely applied to measurements of various static physical quantities, such as temperature, pressure, displacement and refractive index, and detection of object three-dimensional feature. According to the method, a Fabry-Perot sensor is selected as a sensing element for sensing external air pressure intensity variation, an optical wedge is used as an optical path difference space scanning element, and interference strips are formed in a partial area with an optical path difference of zero. The low-coherence interference demodulation method comprises the following steps of: firstly, carrying out Fourier conversion on an interference signal to obtain phase information which is aliased within a section of (-pi, pi); then selecting a phase with a standard frequency as a reference phase, carrying out phase unwrapping according to frequency-phase monotonous properties, and carrying out linear least-squares regression on the unwrapped phase so as to obtain a fitting straight intercept; and finally, dividing the intercept by an integer part of 2*pi, so as to obtain an interference order of a reference frequency; and finally, obtaining the absolute phase of the reference frequency by combining a relative phase obtained through the Fourier conversion. Therefore, the demodulation is realized.

The invention discloses a multi-channel high-precision fiber grating sensor demodulation device. The quantity of fiber grating sensor channels is increased and large-capacity multi-channel high-precision fiber grating demodulation is realized by combining an optical switch, a beam splitter and a beam combiner on the premise that the quantities of photoelectric detectors, signal amplifiers and AD acquisition channels are not increased and even reduced; the temperature of a tunable filter and an etalon is controlled via a TEC (Thermoelectric Cooler) temperature control module, thereby reducing the nonlinear influence of temperature on the output wavelength of the tunable filter and the influence of temperature on comb-like spectral line offset of the etalon, and improving the demodulation precision of the fiber grating demodulation device.

The invention discloses a self-mixing interference orthogonal detection vibration measuring device and method. A single-mode semiconductor laser diode adjustable in constant current source control outputs incidence laser, one part of the incidence laser is reflected to a second photoelectric diode, and optical signals are converted into current signals which are detected by a second photoelectricdetection module and fed back to a collecting module; the other part of the incidence laser is irradiated on the surface of a to-be-detected object and is reflected to a first photoelectric diode according to the original path, and the optical signals are converted into the current signals which are detected by a first photoelectric detection module and fed back to the collecting module. Comparedwith a traditional self-mixing measuring device, the self-mixing interference orthogonal detection vibration measuring device has the advantages that the orthogonal self-mixing signals can be acquired, inverse tangent demodulation of the vibration signals is completed, signal demodulation difficulty of the system is reduced, high displacement resolution is achieved, demodulation precision of the vibration signals of the system is improved, and real-time and online measuring can be realized.

The invention discloses a method and device for digitally demodulating a phase generated carrier by adopting analog front end. The device is characterized by consisting of analog demodulation, digital compensation and digital demodulation modules. The method comprises four steps of frequency mixing of an interference signal with a primary-frequency carrier signal and a doubled-frequency carrier signal respectively and carrying out of low-pass filtering, digital compensation, elimination of random phase fading, reduction of a detected signal, and the like. Compared with an existing digital demodulation method, the method can be used for obviously reducing a demodulation response time; a frequency mixing algorithm and a low-pass filtering algorithm in the existing digital demodulation are removed; the algorithm complexity is decreased; the demodulation precision is improved; the problem that a dynamic range is limited by the existing digital demodulation method is solved.

The invention discloses a phase generated carrier demodulation device and a method based on phase program control. The device and the method are based on a sampling clock as a baseline and comprise the following: synchronously completing the analog-to-digital conversion of an interference signal and a one-time frequency multiplier carrier signal; aligning the phases of the two signals; performing frequency mixing and lowpass filtering of the phase aligned interference signal with the one-time frequency multiplier carrier signal and the two-time frequency multiplier carrier signal; and after that, the transmitting the interference signal to the demodulation module for demodulations so as to realize the demodulation of a detected signal. According to the device and the method, the interference signal and the one-time frequency multiplier carrier signal are acquired in real time, and the phase difference of the second path of signal is tracked; in accordance to the acquisition point position corresponding to the peak point, the phase difference between the carrier signal and the one-time frequency multiplier signal and the two-time frequency multiplier signal is adjusted, which not only solves the un-synchronization problem of the interference signal and the frequency multiplier signals when they go through different optical paths and circuits, but also eliminates the unfavorable influence of the random change in phase caused by carrier frequency drifting on the demodulation result, therefore, increasing the demodulation precision.

The invention relates to a fiber Bragg raster sensing device based on a high-speed pulse laser. The fiber Bragg raster sensing device includes the high-speed pulse laser, a dispersion module, a fiber Bragg raster array, a data acquisition module, and a data processing module. Based on the high-speed pulse laser, the narrow pulse being broad in band and high in repetition rate is provided, and the demodulation rate and the dynamic range of a fiber Bragg raster sensing demodulation system is greatly improved. Through the adoption of a photon time stretching method, the measurement of the wavelength shift of the optical fiber Bragg raster in the frequency domain is converted to the measurement of the time shift in the time domain, and the signal processing precision of the time domain is higher. Therefore, the demodulation precision of fiber Bragg sensing system can be significantly improved, and the requirement on the sampling rate of the data acquisition and processing modules is also reduced.

The invention relates to a distance-measuring method and a device for an optical fiber, which comprises a wavelength-scanning light source (1), fiber-optical couplers (2, 2', 2''), fiber-optical gratings (3, 3'), a fiber-optical collimating device (4), a surface of an object for measuring (5), light-sensitive detectors ( 6, 6'), an A / D convertor (7) and a computer (8). Outlet light of the wavelength-scanning light source is separated to two paths through the fiber-optical couplers, one light path enters into the two fiber-optical gratings whose central wave length are different, reflected light of the fiber-optical gratings are detected by the light-sensitive detectors, the other path which enters into the fiber-optical collimating device is partially reflected by the end surface portion of the collimating device, the reflected light is partially reflected return to the fiber-optical collimating device by the surface of the object for measuring, two beams of the reflected light are detected by the light-sensitive detectors after being interfered. Output signal of the light-sensitive detectors is input into the computer through the A / D convertor, an distance between the end surface of the fiber-optical collimating device and the surface of an object for measuring is calculated through fourier transform white light interferometric phase demodulation method.

The invention relates to a recursion demodulation method for an electrical tomography system, which is characterized by comprising the following steps: (1) establishing an initial equation and a recursion equation according to an excitation frequency f and a sampling frequency f s of a system; (2) taking a zero phase moment of an excitation signal as an initial moment, and calculating initial values of a data matrix B and a state matrix P based on an initial equation in step (1) according to two sampling point data of a measurement signal immediately after the initial moment; (3) substituting the initial values of the data matrix B and the state matrix P as well as newly added sampling point data into the recursion equation in step (1) so as to update B and P; and (4) judging whether a demodulation result meets the accuracy requirement of the system or not, if not, returning to step (3), and if so, finishing demodulation and outputting the amplitude and phase data of the measurement signal. The recursion demodulation method only needs at least two sampling point data, and can improve demodulation accuracy and anti-noise ability by adding sampling points.

The invention discloses a grating sensing device based on a Brillouin filter. The grating sensing device comprises a broadband light source, a first circulator, a sensing optical fiber grating, the Brillouin filter, a synchronization signal module, a photoelectric detector and a signal acquisition and processing module. The Brillouin filter comprises an optical fiber section generating the stimulated Brillouin scattering SBS effect, a second circulator and a narrow linewidth tunable light source. Broad spectrum continuous signal light outputted by the broadband light source is outputted to the sensing optical fiber grating through the first circulator, and the reflected light meeting the Bragg's condition of reflection is generated and outputted to the optical fiber section through the first circulator. The narrow linewidth tunable light source outputs frequency sweep light to be outputted to the optical fiber section through the second circulator. The reflected light and the frequency sweep light are reversely transmitted in the optical fiber section to generate the SBS effect, and the amplified reflected light is outputted to demodulate the central reflection wavelength of the sensing optical fiber grating. The invention also discloses a method of the grating sensing device based on the Brillouin filter. The device is simple in structure and high in measurement precision.

The invention relates to an optical fiber temperature and pressure composite sensor, in particular to an optical fiber temperature and pressure composite sensor which can be used for simultaneous measurement of the temperature, absolute pressure or relative pressure of liquid and gas, and belongs to the field of optical fiber sensing technology. The sensor realizes simultaneous measurement of thetemperature and pressure through a simple two-layer structure, a transmission optical fiber with collimated microlenses on its end faces is used to enhance the signal quality of the sensor, two spectral analysis modules containing optical wedges with different thicknesses are used to demodulate a pressure sensing cavity length and a temperature sensing cavity length respectively, interference signals of the two cavities are separated through the one-to-one correspondence between the wedge thicknesses and the cavity lengths, in this way, the data processing steps are simplified, the demodulation speed is increased, and the measurement of dynamic pressure and temperature signals facilitated.

The invention relates to a PDH multi-sensor strain measuring device using pseudo-random code division multiplexing, and belongs to the technical field of photoelectric detection. A high-stability light source and modulation module in the invention is connected with a single-mode optical fibre loop, a polarization state controller and an integrated multi-channel fibre grating resonator in sequence;and the other end of the single-mode optical fibre loop is connected with a random code modulation and demodulation module, a photoelectric detector, an orthogonal demodulation module, a data acquisition card, a PID controller and the high-stability light source and modulation module in sequence. According to the PDH multi-sensor strain measuring device using pseudo-random code division multiplexing in the invention, multiplexing of multiple fibre gratings can be realized; the device is easy to realize; furthermore, the improvement cost can be reduced; noise can be reduced through a code division multiplexing technology; furthermore, any fibre grating can be measured continuously for a long time; noise is eliminated; the signal demodulation precision is improved; an all-fibre optical pathis adopted; the device has the characteristics of being small in volume, high in measurement precision, good in temperature stability and anti-vibration stability and the like; a demodulation algorithm can be in digital hardware implementation; after being acquired, a signal also can be sent into a computer to demodulate; and the design is flexible.

The present invention relates to an optical fiber pressure sensor based on a micro ellipsoidal air cavity and a manufacturing method of an optical fiber pressure sensor based on a micro ellipsoidal air cavity, belonging to the technical field of optical fiber pressure sensors. The optical fiber pressure sensor comprises a single-mode optical fiber and a pressure-sensitive film; the upper end of the single-mode optical fiber is fixedly connected with the lower end of the pressure-sensitive film; and the single-mode optical fiber and the pressure-sensitive film are connected with an air Fabry-Perot cavity. The materials of the optical fiber pressure sensor are silicon dioxide, so that the thermal expansion coefficients of the optical fiber pressure sensor are the same, thereby avoiding structural failure due to high temperature mismatch of different materials and achieving small temperature crosstalk and low cost. The manufacturing process of the sensor head only needs welding, cutting and grinding, and the process is simple; the confocal Fabry-Perot cavity in the device has the advantages of small interference cavity loss and high interference fringe contrast ratio and high demodulation precision compared with the Fabry-Perot cavity made by the etching process or the femtosecond laser in the prior art.

A demodulator includes a reference signal generator for generating a reference signal, an FM demodulation circuit for demodulating a modulated signal, and a control circuit for controlling demodulation sensitivity of the FM demodulation circuit. The control circuit controls the demodulation sensitivity of the FM demodulation circuit so that an output signal, obtained when the reference signal from the reference signal generator is inputted to the FM demodulation circuit, becomes a specified value. This structure can stabilize the demodulation sensitivity of the demodulation circuit while restraining increases in circuit scale and current consumption, and can adjust dispersions in the demodulation sensitivities of the respective ICs due to relative errors of a resistance value of a resistor and a capacity value of a condenser in an IC, the resistor and the condenser constituting the demodulator.

The invention discloses a method used for array waveguide optical grating demodulating system temperature compensation in smart clothes. The central wavelength lambda i of all channel output spectrums of an array waveguide optical grating has a temperature drift phenomenon, when human body temperature measurement is carried out through an array waveguide optical grating demodulating system in the smart clothes, due to the fact that the temperature difference among the left chest, the right chest, the left axilla, the right axilla and the back in the human body is within the range of 1.7 DEG C, the temperature variation value delta T of the array waveguide optical grating and a fiber bragg grating is considered to be integrated, the central wavelength is replaced with a relational expression containing the delta T, and an array waveguide optical grating temperature demodulating formula with the temperature compensation is derived. According to the method, the result of temperature demodulating shows that a kind of stable linear relation exists between a temperature value and a light intensity comparison value, temperature sensitivity is 0.25733 dB / DEG C, and demodulating precision of the array waveguide optical grating demodulating system used for the human body temperature measurement in the smart clothes can be effectively improved.

The invention relates to a non-scanning demodulation system based on an optical fiber Fabry-Perot sensor, whichbelongs to the technical field of optical fiber sensing. The system comprises a positivelens, a first free-form surface reflector, a second free-form surface reflector, an optical wedge, a plano-convex cylindrical lens, a linear array CCD and a data processor. The positive lens is used for receiving light with cavity length information obtained from the optical fiber Fabry-Perot sensor, and the light is emitted to the positive lens through the optical fiber and is diffused into parallel light; the first free-form surface reflector is used for receiving the parallel light diverged by the positive lens and converting the parallel light into flat-topped light; the second free-form surface reflector is used for collimating the emergent direction of the flat-topped light to ensure that the signal light incident to the optical wedge is perpendicular to the surface of the second free-form surface reflector; the plano-convex cylindrical lens is used for converting the rectangular light spot transmitted by the optical wedge into one-dimensional linear light; and the linear array CCD is used for detecting the one-dimensional linear light passing through the plano-convex cylindrical lens and outputting a voltage signal. The signal contrast can be effectively demodulated, and thedemodulation precision of a demodulation system can be improved.

The invention relates to a multi-frequency recursive demodulation method for electrical tomographic systems. The method is characterized by comprising the following steps: (1) establishing an original equation and a recursive equation according to m component frequencies of an excitation signal and the sampling frequency of a system; (2) with a zero-phase time of the excitation signal as a starting time, according to data of 2m sampling points a measuring signal, which are closely following the starting time, calculating the initial values of a data matrix B and a state matrix P according to the original equation in the step (1); (3) substituting the initial values and the new sample point data into the recursive equation in the step (1) so as to update B and P; and (4) judging whether a demodulation result meets the accuracy requirements of the system, if so, completing the demodulation operation, and outputting the amplitude values and phase data of m frequency components of the measuring signal; otherwise, returning to the step (3). By using the recursive demodulation method disclosed by the invention, data of at least 2m sampling points is required, and due to the increase of the number of sampling points, the demodulation accuracy and the anti-noise capacity can be improved.