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 provides a photonic crystal fiber transverse stress sensor based on temperature compensation. Four super-large side holes in cross distribution are introduced in an optical fiber cladding layer; each side hole is internally coated with a gold nanofilm, and one side hole is filled with magnetic fluid; and small air holes are distributed in the cladding layer in an octagonal manner. The sensor realizes high-sensitivity transverse stress sensing in any direction. A measurement device thereof comprises a light source portion, a transverse stress sensor portion and a demodulation portion. The sensor combines the super-large side holes with surface plasma technology, thereby greatly improving the sensitivity of the transverse stress sensor. Magnetic fluid filling causes Y polarization fundamental mode loss peak to have double peaks, brings new degree of freedom and realizes temperature compensation. Through a multi-parameter demodulation and orthogonal decomposition method, measurement of transversal stress in any direction is realized. The result shows that, under the transversal stress, fundamental mode X polarization maximum sensitivity is 3.4 nm / N, and Y polarization maximum sensitivity is 4.6 nm / N. The sensor is simple in structure, high in sensitivity, small and compact, and is suitable for accurate measurement of transversal stress in multiple fields.

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 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 disclosed sensor includes fiber of sensing probe, an insulative fixed frame and two insulative moving frames. An F shaped moving frame and an L shaped moving frame arranged in interlacing are installed on the fixed frame. Optical fiber of sensing probe passing through the interlaced part of the two moving frames is installed on the fixed frame. Three segments of fiber gratings positioned in interlaced and separated part of the two moving frames are made on fiber of sensing probe. First segment of fiber is in use for measuring stress. Two other segments of fiber gratings having same peak wavelength in reflectance spectrum are in use for measuring stress and temperature. Using principle of differential amplification, the invention raises measuring sensitivity, solves crossed sensitivity so as to be able to apply in high voltage and high electromagnetism harsh environment.

The invention provides a rotary machine temperature measuring method and a rotary machine temperature measuring device based on fiber gratings, wherein the temperature measuring method comprises the following steps of binding the fiber gratings with different central wavelengths with one side of a large wheel, binding the fiber gratings with same central wavelengths at symmetrical positions at the other side of the large wheel and successively marking; connecting the fiber gratings with a demodulating instrument through a rotatable connector; connecting the rotating speed of a large-wheel variable-frequency motor, generating heat at a contact point between the large wheel and a small wheel through friction along with rotation of the large wheel, and transmitting the heat to the fiber gratings; performing transmission from a light source which is arranged in the demodulating instrument to the fiber gratings through the rotatable connector, realizing wavelength change of the fiber gratings along with temperature change, and generating a temperature signal; performing demodulation on the temperature signal of the fiber gratings and transmitting a demodulated signal to an industrial control computer by the demodulating instrument; receiving the demodulated signal by the industrial control computer and performing acquisition and analysis, and furthermore a wavelength-time change chart of each fiber grating according to an acquisition and analysis result.

The invention discloses a Brillouin Optical Time Domain Reflectometry (BOTDR) temperature and strain rapid separation method in the icing monitoring of a smart grid. The optical fiber composite overhead ground wire (OPGW) cable in the power grid is used for sensing and monitoring to obtain Brillouin Abyss scattering spectrum. Select points within 3dB of the maximum value of the Brillouin scattering spectrum along the fiber path to perform quadratic polynomial fitting based on the least squares method. After fitting, the polynomial equation is obtained. After calculating the peak power and center frequency according to the polynomial coefficients, the obtained Power and frequency shift curves. According to the frequency shift curve and power curve, select the fiber splicing point, and recalibrate the temperature coefficient and gauge coefficient of Brillouin power. After the coefficient is corrected, the temperature and strain can be accurately separated.

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 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 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.

The invention provides a device and method for detecting the humidity of the tail gas of a knitted fabric boarding machine, and the method comprises the steps of coating a grating region of an optical fiber Bragg grating with modified fluorine-containing polyimide to prepare a humidity sensor; calibrating the humidity sensor by using a saturated salt solution humidity calibration method, and enabling the central wavelength value of the optical fiber Bragg grating to correspond to the humidity value; performing temperature compensation on the fiber Bragg grating humidity sensor, obtaining a temperature compensation coefficient through a segmented calibration method, and obtaining a relation between the variation of the central wavelength of the sensor and the variation of the external environment temperature; obtaining the central wavelength drift distance of the optical fiber Bragg grating caused by temperature change through a linear interpolation method, compensating the central wavelength of the optical fiber Bragg grating, and carrying out inversion calculation on the humidity, so that the problems that in the prior art, a sensing probe based on zirconium dioxide needs to be replaced regularly, the maintenance difficulty is large, the cost is high, and a fiber Bragg grating humidity sensor is sensitive to temperature and humidity in a cross mode, are solved.

The invention discloses a vibration monitoring system and a vibration monitoring method for divided conductors. The vibration monitoring system comprises a divided conductor vibration monitoring device (25), optical fiber (26), an optical fiber composite overhead ground wire (29), a fiber bragg grating demodulator (30) and a computer system (31). According to the vibration monitoring system and the vibration monitoring method, vibrations of the divided conductors of a power transmission line in three directions, especially the integral torsional vibration and the sub-conductor torsional vibration of a divided conductor beam are monitored, and the multipoint real-time monitoring can be carried out on the torsional rigidity of the power transmission line; and various types of divided conductors can be monitored through simple transformation, and the influence on the inherent property of the line is less. The defects that a field power supply is needed, the anti-electromagnetic interference capability is poor and the like as the torsional vibration of the conductors cannot be monitored, especially a system which can be used for implementing vibration monitoring of the divided conductors is absent and the self property of the line is easily influenced by installation of the traditional sensing system in the prior art are overcome, and convenience is provided for operation and maintenance of the line.

The invention discloses a side surface polished open-loop PCF-SPR sensor. The side surface polished open-loop PCF-SPR sensor comprises a fiber core and a cladding covered outside the fiber core, wherein the fiber core is eccentric with the cladding, and the cladding is provided with air holes which are arranged in the axial direction of the fiber core; the air holes comprises a first air hole, a plurality of second air holes and a plurality of third air holes, the first air hole is arranged at the center of the cross section of the optical fiber, the second air holes surround the first air hole to form an annular N-angle structure with a layer number of K, and the third air holes are symmetrically arranged on two sides of the fiber core to substitute the positions of second air holes; theside surface of an optical fiber is provided with a polishing plane, and the polishing plane is provided with an open loop; and the open loop is covered with a sensing membrane, and the open ring is used as a sensing channel. By adopting a way of combining the side surface polished optical-fiber end surface and the open loop, the SPR sensing layer is most closest to the fiber core, so that substances with a refractive index less than 1.3 such as liquid oxygen, liquid CO2, fluorine-containing organic matters can be detected sensitively at a high amplitude or high wavelength and can be sensed byvirtue of multiple channels, so that the application range of the existing PCF-SPR sensor can be enlarged.

The invention relates to a temperature-self-reference photonic crystal fiber surface plasma resonance magnetic field sensor. The sensor comprises a D-type photonic crystal fiber body and a magnetic fluid layer; the top of the D-type photonic crystal fiber body is polished to form a polished plane, a gold film layer is plated on the polished plane, and the magnetic fluid layer is applied on the gold film layer; the D-type photonic crystal fiber body comprises a silicon dioxide cladding and 21 air holes positioned in the silicon dioxide cladding; four layers of air holes are formed upwards from the bottom of the D-type photonic crystal fiber body; the circle centers of the air holes in each layer are positioned on the same straight line; the inner wall of the third air hole in the third layer is plated with a gold film, and the third air hole is filled with polydimethylsiloxane. The D-type photonic crystal fiber is combined with the SPR technology to measure the magnetic field, and the problems that a magnetic field sensor is large in size, low in sensitivity and the like are solved; and a mode of plating the gold film in the D-type photonic crystal fiber and filling the D-type photonic crystal fiber with the magnetic fluid and PDMS is adopted, so that simultaneous measurement of the magnetic field and the temperature by the sensor is realized.

The invention proposes a method for simultaneously measuring the magnetic field and temperature based on the magnetic fluid filling the photonic crystal microcavity. Two cascaded photonic crystal microcavities are formed by filling two different types of magnetic fluids in the air holes in two different regions of a photonic crystal waveguide plate, so that the output spectrum of the photonic crystal waveguide will appear in two independent resonance valleys (corresponding to two resonance wavelengths). As the external magnetic field or temperature changes, the refractive index of the two filled magnetic fluids will change to varying degrees, so that the two resonance wavelengths in the output spectrum of the photonic crystal waveguide will move, and the two resonance wavelengths will refract the magnetic fluid. Sensitivity to rate changes is inconsistent. Finally, the dual-wavelength matrix method is used to deduce the change of the external magnetic field and temperature according to the movement of the two resonance wavelengths, so as to realize the simultaneous measurement of the magnetic field and temperature. It can be calculated that the minimum detectable magnetic field change is 1.333Oe, and the minimum detectable temperature change is 0.301K.

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 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.