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

Fiber F-P sensor cavity length wavelet phase extraction demodulation method

The invention provides a rapid high-precision signal demodulation method of a fiber F-P sensor. With a wavelet threshold denoising method, denoising processing is carried out on obtained spectral data; on the basis of a Fourier transform demodulation algorithm, a cavity length of a fiber F-P sensor is calculated and is used as rough measurement cavity length value, and a hill-climbing searching starting point of the cavity length is determined; according to a variable-step-length hill-climbing searching algorithm, discrete cavity length coefficients of the cavity length and a previous cavity length under each step length are compared until a previous coefficient is larger than a next coefficient, a peak value under the step length is searched and is used as a next hill-climbing searching starting point, the step length set for each searching is less than the step length of the last time until preset target precision is reached, and the set step length searched at the last time is a demodulation resolution ratio and a cavity length corresponding to a discrete cavity length coefficient maximum value obtained at the last step is the need result. According to the invention, with the novel variable-step-length hill-climbing searching algorithm, the calculation load of the discrete cavity length coefficient demodulation algorithm is reduced, so that rapid high-precision signal demodulation is realized.

Rapid high-precision signal demodulation method of fiber F-P sensor

The invention discloses an LED modulating method and system based on visible light communication. The method comprises the steps that light intensity signals collected by an LED illuminating circuit are compared with backup emitting signals matched with the collected light intensity signals to obtain a signal difference result; according to the signal difference result, filter parameters are adjusted so as to achieve self-adaptive compensation, and therefore influences caused by LED device negative factors on visible light communication are overcome. According to the scheme, complex equalization processing does not need to be carried out on a channel, so that the complexity of signal processing in the visible light communication process is greatly lowered.

LED modulating method and system based on visible light communication

The invention provides an optical fiber pressure sensor of an inaction contact angle measurement error. The sensor adopts a high-sensitivity optical fiber F-P chamber to combine a spherical pressure conduction sealing structure so as to realize accurate pressure measurement of a non-contact angle measurement error. Measurement precision is not influenced by a sensing head contact angle change. Extraneous pressure is acted on a pressure sensitive terminal of the optical fiber F-P chamber through the spherical pressure conduction structure so that a chamber length is changed and an interference signal spectrum characteristic is changed. Through optical fiber F-P chamber reflection interference spectrum characteristic data analysis, pressure is accurately measured. Simultaneously, a temperature compensating fiber bragg grating is made on a reflected spectrum signal output optical fiber, cross sensitivity of the temperature and the pressure is eliminated and high precision measurement of a non-contact pressure angle error is realized. The apparatus of the invention possesses characteristics that high sensitivity is possessed; anti-electromagnetic interference is achieved; and there is no temperature crosstalk and the like and especially the pressure measurement precision is not influenced by the sensing head contact angle change.

Optical fiber pressure sensor of inaction contact angle measurement error

The invention provides a simplified device and method for measuring the bonding strength of a chip. The simplified device for measuring the bonding strength of the chip comprises a to-be-detected chip, a glass capillary tube, a transmission fiber, a pressure joint, a pressure inlet, a base, a sealing ring, a housing and a sealant. The method for measuring the bonding strength of the chip comprises the following steps of (1) applying proper initial pressure to the device for measuring the bonding strength of the chip by using a pressure source and recording spectral information at the moment; (2) selecting a proper pressurization step length, improving a pressure value applied to the device for measuring the bonding strength of the chip by the pressure source; and (3) reducing the pressure value applied by the pressure source, observing whether an interference signal is still displayed in a spectrograph or not, if so, repeating the step (2) until the interference signal of the spectrograph disappears after the pressure is reduced, if not, judging the pressure value applied in the previous step to be the affordable maximum pressure value of the to-be-detected chip after bonding, and directly reflecting the bonding strength of the chip.

Simplified device and method for measuring bonding strength of chip

The invention discloses a signal demodulation system for an optical fiber F-P acoustic emission sensor. The signal demodulation system comprises an optical self-calibration laser light source module, an optical circulator, an optical fiber F-P acoustic emission sensor, a weak signal photoelectric conversion module, a weak signal conditioning module, a high-speed signal acquisition module and a signal processing module; the optical circulator is provided with three ports, and the first port of the optical circulator is connected with the optical self-calibration laser light source module; the second port of the optical circulator is connected with the optical fiber F-P acoustic emission sensor; the signal reflected by the optical fiber F-P acoustic emission sensor is connected with the weak signal photoelectric conversion module through the third port of the optical circulator; the weak signal photoelectric conversion module, the weak signal conditioning module, the high-speed signal acquisition module and the signal processing module are connected in sequence, and the signal processing module finishes processing and analyzing the signal. The signal demodulation system solves the problems on light source self-calibration and weak signal processing in the continuous online working process of the optical fiber F-P sensor, so that the measurement accuracy is improved, the system preparation technique is simplified, and the cost is reduced.

Signal demodulation system for optical fiber F-P (Fabry-Perot) acoustic emission sensor

The invention provides an all-fiber F-P hydrogen sensor and a preparation method of a hydrogen sensitive film of the all-fiber F-P hydrogen sensor. The sensor is structurally composed of an all-fiber F-P resonant cavity, a sensitive film orientated expansion limiting piece, a fixing part, a sensor packaging part and the like; a Pd-Ag alloy sensitive film with certain thickness can be directly deposited on the outer layer of an all-fiber F-P resonant cavity sensitive glass sheet at low temperature by adopting a pulse laser depositing process; one surface of the sensitive film orientated expansion limiting piece is only in contact with the sensitive film through the fixing part and a limiting expansion block is made of a porous ceramic material, so that hydrogen can be absorbed; when the sensitive film absorbs hydrogen to have orientated expansion, the cavity length of F-P is compressed and reduced; and the cavity length of the all-fiber F-P resonant cavity is demodulated so that the change of the hydrogen concentration is measured. By adopting the preparation method, the low-temperature film plating of fibers is guaranteed; and the sensor is simple in structure and convenient to prepare, and industrialized production is easy to realize.

All-fiber F-P hydrogen sensor and preparation method of hydrogen sensitive film of all-fiber F-P hydrogen sensor

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Signal demodulation system for optical fiber F-P (Fabry-Perot) acoustic emission sensor

All-fiber F-P hydrogen sensor and preparation method of hydrogen sensitive film of all-fiber F-P hydrogen sensor