52results about How to "Address cross-sensitivity issues" patented technology

The invention discloses a sensing device of optical fiber distribution type temperature and stress and mainly comprises a light source module (1), a frequency discriminator module (2), and a thermo tank module (3), which are all connected with one another by polarization-preserving fiber. The invention is a direct detection method which is based on optical fiber Raman scattering used as a carrier wave of temperature information, brillouin scattering used as a carrier wave of stress, rayleigh scattering used for measuring relative frequency of a outgoing laser beam to a frequency discriminator and Fabry-Perot etalon used for discriminating frequency and distributing sensing temperature and stress. The invention has the advantages of simple structure, fine stability, avoidance of outgoing power of the light source during coherent detection, outgoing frequency of the light source. Instability of acoustic modulation or electro-optic modulation frequency is directly referred to measure errors and the direct detection technology of the frequency discrimination is not sensitive to frequency drift of the light source and fluctuation of signal intensity.

The invention discloses a detection method suitable for a sensing device of optical fiber distribution type temperature and stress. The sensing device of the optical fiber distribution type temperature and stress mainly comprises a light source module (1), a frequency discriminator module (2), and a thermo tank module (3), which are all connected with one another by polarization-preserving fiber. The detection method of the invention is a direct detection method which is based on optical fiber Raman scattering used as a carrier wave of temperature information, brillouin scattering used as a carrier wave of stress, rayleigh scattering used for measuring the relative frequency of a outgoing laser beam to the frequency discriminator and Fabry-Perot etalon used for discriminating frequency and distributing sensing temperature and stress. The invention has the advantages of simple structure, fine stability, avoidance of outgoing power of the light source during coherent detection, and outgoing frequency of the light source. Instability of acoustic modulation or electro-optic modulation frequency is directly referred to measure errors and the direct detection technology of frequency discrimination is not sensitive to the frequency drift of the light source and the fluctuation of signal intensity.

The invention discloses a distributed strain and temperature optical fiber sensor based on brillouin scattering. The sensor comprises a light source, an electro-optical modulator, a pulse signal source, a first erbium-doped optical fiber amplifier, a second erbium-doped optical fiber amplifier, a circulator, a first optical coupler, a second optical coupler, double balance detectors, a signal processing system and a sensing optical fiber. The sensing optical fiber comprises a long period optical fiber grating and is an all-solid photonic crystal band gap optical fiber. Output light of the light source is divided into two paths, wherein one path of the output light is modulated to be detection pulse light by means of the electro-optical modulator, is amplified through the erbium-doped optical fiber amplifiers and is input into the sensing optical fiber through the circulator. The sensor can simultaneously obtain temperature and strain with high resolution through a single measurement, and can well solve the problem of cross sensitivity existing in measurement of a brillouin sensor.

The invention discloses a method for simultaneously measuring temperature and stress of fiber bragg gratings (obtained by corrosion) with different diameters. The method comprises a fiber bragg grating demodulation instrument or a device which has functions similar to those of the fiber bragg grating demodulation instrument, and the fiber bragg gratings (obtained by the corrosion) with the different diameters, wherein the fiber bragg grating demodulation instrument can be used for fast scanning lasers with different wavelengths; when the lasers with a certain length can meet reflection conditions of the central wavelengths of the fiber bragg gratings, the lasers with the certain wavelength can be sent back to the fiber bragg grating demodulation instrument and are recorded; and the fiber bragg gratings with the different diameters have different stress sensitivities and same temperature senstivity, so that two different fiber bragg gratings can generate different central wavelength drifts under a same environmental influence, two wavelength drift equations obtained by using the two fiber bragg gratings are simultaneous, namely the change conditions of the environment temperature and the stress can be respectively obtained by solving the simultaneous equations. According to the scheme, the characteristic that fiber bragg gratings with the different diameters have the different stress sensitivities is utilized, and the method is easy and feasible, is low in cost and can effectively overcome the cross sensitivity problem of the fiber bragg gratings.

The invention provides a polarization maintaining optical fiber interferometer capable of simultaneously measuring strain and temperature. The system comprises a narrow-band light source, a total polarization-maintaining Mach-Zehnder interferometer, an interference signal detection unit, a differential circuit and a demodulation system. A polarization-maintaining optical fiber device is adopted toconstruct a full-polarization-maintaining interferometer, and the optical signals are simultaneously transmitted in the fast axis and the slow axis of the polarization maintaining optical fiber, andtwo sensing systems are formed. The two sensing systems have different responses to the temperature and the strain respectively, so that simultaneous measurement of the two can be realized. The Mach-Zehnder interference structure does not have back-reflection transmission, and rayleigh scattering noise in the light transmission process is effectively inhibited. Light in the polarization maintaining optical fiber is separated from the fast and slow axes, the differential circuit is used for carrying out differential processing on the coaxial signals, the noise is reduced, and the measurement precision is improved. The polarization maintaining optical fiber interferometer is simple to manufacture, convenient to measure, high in precision and capable of effectively overcoming the problem of cross sensitivity. The polarization maintaining optical fiber interferometer can be applied to the fields of oil exploration, and seismic observation.

The invention discloses a fiber bragg grating (FBG) sensor based transformer fault gas monitoring system in the technical field of on-line monitoring system. The system comprises a gas sensor array, FGG demodulation equipment, a transformer fault monitoring center and the like. In the system, an FBG sensor is adopted, and the FBG sensor has strong anti-electromagnetic interference and is beneficial to application to environment with extremely severe electromagnetic environment; the sensor has high sensitivity and high resolution and can be used for simultaneously detecting all parts of the transformer on line, thereby the system maintenance cost is greatly reduced; and the system solves a series of problems of cross sensitivity among gases, slow oil-gas separation and balancing, short breathable film service life, and the like in the traditional fault monitoring method.

The invention provides a magnetic field and temperature simultaneous measurement method based on photonic crystal micro-cavities filled with magnetic fluid. Air holes in different regions of a photonic crystal waveguide flat plate are filled with two different types of magnetic fluid respectively so that the two cascaded photonic crystal micro-cavities can be formed, and therefore two resonance troughs corresponding to two resonant wavelengths can appear in an output spectrum of a photonic crystal waveguide, wherein the resonance troughs are independent of each other. According to the changes of the external magnetic field or the temperature, the refractive indexes of the two types of filling magnetic fluid can change to different degrees, and therefore the two resonant wavelengths in the output spectrum of the photonic crystal waveguide can move, and the sensitivity of the two resonant wavelengths to the changes of the refractive indexes of the magnetic fluid is inconsistent. Finally, the change amount of the external magnetic field and the change amount of the temperature can be obtained through reverse calculation according to the movement amount of the two resonant wavelengths by means of a double-wavelength matrix method, and the magnetic field and the temperature can be simultaneously measured. Calculation shows that the minimum detectable magnetic field change amount is 1.333Oe, and the minimum detectable temperature change amount is 0.301K.

The invention discloses an optical fiber temperature and strain sensing device based on a high spectral resolution technology. The optical fiber temperature and strain sensing device comprises an optical transmitting system, an optical fiber sensing system, a high spectral resolution scanning system, an optical filtering system, a data acquisition system and a control system. The invention further discloses an optical fiber temperature and strain sensing method based on a high spectral resolution technology. According to the invention, temperature and strain carriers based on optical fiber brillouin scattering are used for the distributed sensing of temperature and strain; a narrowband reflective tunable Bragg grating is used for filtering out optical fiber brillouin back scattering, a cavity length-tunable Fabry-Perot interferometer is used for the full spectrum scanning of optical fiber brillouin scattering spectrum, a single photon technology is used for detecting a back brillouin scattering signal in the optical fiber; the invention has the advantages that the structure is simple, s the stability is high, compared with coherent detection, the signal detection and processing difficulty and complexity are reduced, and the detection distance resolution and accuracy are improved.

The invention relates to a method for detecting micro photoelectrons, in particular to a method for detecting temperature and a magnetic field simultaneously based on a magnetofluid-filled crystal fiber loop mirror. According to the method, magnetofluid is selectively filled into air holes of a structurally-symmetrical photonic crystal fiber along the center line in the horizontal direction; the birefringence characteristic of the photonic crystal fiber is changed accordingly, and a temperature/magnetic field-adjustable birefringent photonic crystal fiber is formed; a traditional birefringent fiber in a Sagnac fiber loop mirror is replaced by the temperature/magnetic field-adjustable birefringent photonic crystal fiber, the distance between two adjacent resonance valleys and the drift distance of the resonance valleys are changed along with the changes of the temperature and the magnetic field with different change sensibilities, and accordingly the temperature and the magnetic field can be simultaneously detected through the two-parameter matrix method. The method improves the stability performance and measuring sensitivity of a sensor, solves the problem of cross sensitivity of the temperature and the magnetic field of the optical fiber sensor and achieves the purpose of measuring the temperature and the magnetic filed simultaneously through one optical fiber.

The invention belongs to the technical field of measurement, and particularly relates to a multimode fiber-based method and a multimode fiber-based system for simultaneously measuring temperature and strain. The system comprises a laser device, a first coupling device, a polarization controller, an electro-optical modulator, a pulse generator, a first optical amplifier, a first circulator, a first optical grating, a multimode circulator, a multimode optical fiber, a second optical amplifier, a second circulator, a second optical grating, a second coupler, a polarization scrambler, a photoelectric detector, a data application and processing module and a computer display module; by measuring two modes with different brillouin frequency shift-temperature coefficient and brillouin frequency shift-strain coefficient of the multimode optical fiber, a coefficient matrix is formed to realize the simultaneous measurement of the temperature and strain, the cross sensitivity problem in brillouin distribution type optical fiber sensing can be solved, the measurement precision is high, the positioning is accurate, and the cost is low.

The invention discloses a wind speed sensing device based on fiber bragg gratings, and a wind direction monitoring system. The device comprises a wind energy transmission mechanism, a constant strength cantilever beam, and a packaging housing. The wind energy transmission mechanism consists of a windward pressed plate and a connecting rod, wherein the connecting rod is perpendicular to the windward pressed plate. One end of the windward pressed plate is fixed at the center of the connecting rod, and the other end of the windward pressed plate is fixed at the top of the constant strength cantilever beam. The top of the packaging housing is provided with an opening, and a cantilever beam installation pedestal is fixed at the bottom of the interior of the packaging housing. The constant strength cantilever beam stretches into the opening at the top of the packaging housing, and is detachably fixed on the cantilever beam installation pedestal. The surface of the windward pressed plate is parallel to the surface of the constant strength cantilever beam. The axes of the front and back surface of the constant strength cantilever beam are respectively provided with one fiber bragg grating. The system comprises two wind speed sensing devices which are arranged in an orthogonal manner, and the measured data is transmitted to a remote terminal. The device is compact in structure, is small in size, and is resistant to electromagnetic interference.

The invention provides a rotating wheel vibration measurement method and a rotating wheel vibration measurement device based on fiber gratings. The rotating wheel vibration measurement method comprises the following steps of binding the fiber gratings with different central wavelengths with two sides of a rotating wheel; making the rotating wheel rotate in a constant speed, in rotation of the rotating wheel, transmitting a vibration signal which is generated by the rotating wheel to the fiber gratings, and generating strain signals by the fiber gratings; performing photoelectric conversion on the strain signals of the fiber gratings, and performing data acquisition; processing the acquired data and drawing a time-wavelength line chart in which the wavelength changes along with time, and obtaining a corresponding vibration characteristic of the rotating wheel; making the rotating wheel perform constant-speed rotation in different rotating speeds, performing data acquisition in different rotating speeds, drawing a rotating-speed-wavelength line chart in which the wavelength changes along with the rotating speed, and obtaining the corresponding vibration characteristic of the rotating wheel; making the rotating wheel perform constant-speed rotation in a certain rotating speed, performing data acquisition in different angles-of-attack, drawing an angle-of-attack-wavelength line chart in which the wavelength changes along with the angle-of-attack, and obtaining corresponding vibration characteristic of the rotating wheel.

The invention provides a device and a method for measuring a transient sliding friction coefficient based on fiber gratings. The device comprises a small wheel assembling mechanism, a large wheel assembling mechanism, a demodulator and an industrial personal computer; fiber gratings are respectively and symmetrically arranged on front and back surfaces of two supports on the two sides of a small wheel and front and rear sides of a steering wheel; an incidence angle regulator is further installed on a supporting plate; a central plane of a large wheel of the large wheel assembling mechanism and a central plate of the small wheel are on the plane, and wheel sides are tangent; a light source built in the demodulator is transmitted to each of the fiber gratings through a rotary connector, contact points between the large wheel and the small wheel produce a friction force with the rotation of the large wheel, the friction force is transmitted to each of the fiber gratings and the fiber gratings generate strain signals; the demodulator demodulates the strain signals of the fiber gratings and sends demodulated signals to the industrial personal computer; the industrial personal computer receives the demodulator signals, performs acquisition and analysis, calculates transient positive pressure and friction force of the small wheel according to the wavelength shift of the fiber gratings, and calculates a transient transverse friction coefficient at the contact points through a corresponding formula.

The invention discloses an optical frequency domain reflection system for simultaneously measuring temperature and strain, and particularly belongs to the technical field of distributed optical fiber sensing. The system is characterized in that sweep-frequency light emitted by a tunable laser device enters a circulator, detection light enters a to-be-measured optical fiber from an outlet at one end of a circulator through a wavelength division multiplexer, Raman scattering light and backward Rayleigh scattering light are generated, and temperature and strain measurement is completed; and a Rayleigh scattering signal, a Stokes signal and an anti-Stokes signal are respectively demultiplexed by the wavelength division multiplexer and are respectively demodulated, a backward Rayleigh scattering spectrum offset is calculated by adopting a related algorithm to realize temperature and strain detection, and a Raman double-path analysis pulse response method is adopted to carry out temperature compensation, so that the problem of cross sensitivity between the temperature and the strain is solved, and simultaneous measurement of the temperature and the strain is realized.

The invention provides a thermal stability sensing demodulation system and method using a narrowband dual phase shift fiber bragg grating. The system comprises a wavelength tunable laser, a polarization controller, a phase modulator, a three-port optical circulator, a dual-phase-shift fiber bragg grating, an optical fiber amplifier, a photoelectric detector, a microwave amplifier and a microwave coupler which are mutually connected. The first port of the optical circulator is connected to the output port of the phase modulator. The second port of the optical circulator is connected to the dual-phase-shift fiber bragg grating. The third port of the optical circulator is connected to the optical fiber amplifier. The input end of the microwave coupler is connected to the output end of the microwave amplifier. The first output end of the microwave coupler is connected to the radio frequency end of the phase modulator. The second output end of the microwave coupler is connected to an electric spectrometer.

The invention discloses a metasurface-based optical fiber humidity sensor and a manufacturing method thereof and belongs to the technical field of sensing and measurement application. The optical fiber sensor disclosed by the invention is mainly composed of an optical fiber, an adhesive, a metasurface and a sensitizing substance. The end face of the optical fiber and the metasurface are fixed together through the adhesive; the sensitizing substance coats the metasurface; and the metasurface is composed of nanopore arrays which have rectangular cross sections and have different sizes and different azimuth angles. According to the optical fiber sensor, a plurality of harmonic peaks with different refractive index sensitivities are generated by adopting metal micro-nano structures with different rotation angles, and measurement of a plurality of sensing parameters can be realized by monitoring changes of characteristic parameters of the harmonic peaks. According to the manufacturing method, the manufacturing cost and the manufacturing period of the fiber end optical fiber sensor can be reduced. The sensor has the advantages of small effective sensing area, multiple harmonic peaks and high robustness, and is applied to the fields of industry, agriculture, medical treatment, chemical biology and the like.