289 results about "Fiber loop" patented technology

The invention belongs to the technical field of distributed optical fiber sensing, and particularly relates to an OFDR system phase noise compensation device and method based on an or equivalent optical fiber loop auxiliary interferometer. The optical fiber 2 * 2 coupler and the delay optical fiber form a loop and serve as a delay optical path of the auxiliary interferometer, the optical delay can be doubled every time laser passes through the loop, and therefore a plurality of beat frequency signals with different optical delays are obtained. And according to the to-be-measured optical fibers at different distances on the main interferometer, the beat frequency signal of the auxiliary interferometer with the closest optical delay is selected for compensation. And splicing the compensated reflected signals at different distances to obtain a distance domain reflected signal of the whole sensing optical fiber, thereby realizing phase noise compensation in the full range of the OFDR system. The OFDR full-range high-precision measurement is realized, and the OFDR full-range high-precision measurement device has the characteristics of simple structure, stable performance, low manufacturing cost and the like.

The invention discloses a high-resolution optical fiber integrated diamond color center sensor and a measuring method, the sensor comprises an optical fiber responsible for inputting exciting light and collecting fluorescence, the end face of the optical fiber is provided with a diamond color center, the diamond color center is excited by the output of the optical fiber, and a quartz capillary is arranged outside the optical fiber and the diamond color center. A microwave antenna is wound outside the quartz capillary tube, and a part of a bare wire of the microwave antenna is connected with the radio frequency line. The measuring method comprises the following steps: exciting a diamond color center; applying microwaves to the diamond color center; fluorescence generated by stimulated radiation of the NV color center is output by the optical fiber circulator and is input into the photoelectric detector through the filter; the upper computer controls the microwave generator to sweep frequency; the photoelectric detector performs photoelectric conversion, and the upper computer processes microwave frequency sweeping signals and electric signals. The magnetic field size and the temperature size of the sample to be measured in the micro space can be measured, and the device has the advantages of being high in spatial resolution, high in integration level, high in flexibility, high in controllability and the like.

The invention provides a device and a method for universally testing the performance of a silicon optical chip and a gyroscope. The device comprises a chip and gyroscope measurement and control module, an external light source module, an external phase modulator, an optical fiber loop and a light source module, wherein the chip and gyroscope measurement and control module comprises a driving and temperature control unit, a power supply control unit, an electric switch control unit, an optical switch control unit, a signal generation unit and an acquisition and control unit and is used for testing instruction processing and data processing, and the light source module is used for providing stable optical power input for a silicon optical chip without a light source. The analog electric switch controls the signal generation unit to output signals which are respectively applied to the phase modulator on the silicon optical chip or the external phase modulator, and the four optical switches form three test channels and are communicated with the external phase modulator and the optical fiber loop to form a gyroscope optical path. According to the invention, the universal test of the performance of different types of silicon optical chips and gyroscopes can be realized, and the accuracy and timeliness of the test are ensured.

The invention discloses a rotor and stator axial clearance online measuring device and method based on optical carrier microwave interference. The measuring device comprises a broadband light source, a first polarization maintaining optical fiber, an electro-optical modulator, a second polarization maintaining optical fiber, an optical fiber circulator, a first single-mode optical fiber and a coated optical fiber probe which are connected in sequence, and the coated optical fiber probe directly faces the axial end face to be measured; a first port of the optical fiber circulator is connected with the second polarization maintaining optical fiber, a second port of the optical fiber circulator is connected with the first single-mode optical fiber, and a third port of the optical fiber circulator is sequentially connected with the second single-mode optical fiber, the photoelectric detector, the signal conditioning unit, the signal acquisition unit and the digital processing unit; the signal acquisition unit is connected with the micro-control unit, the micro-control unit is connected with the microwave frequency sweep signal generation unit, and the microwave frequency sweep signal generation unit is connected with the electro-optical modulator. According to the invention, non-contact on-line high-precision measurement of the axial clearance of the rotor and the stator of the aero-engine under the conditions of limited measurement space and complex signal leading-out path can be realized.

The invention belongs to the technical field of optical fiber gas sensing, and discloses an optical fiber photoacoustic gas sensing system and method suitable for a low-pressure environment. The system comprises a programmable logic gate array circuit, a distributed feedback laser, a laser transmission optical fiber, an optical fiber photoacoustic sensing probe, a super-radiation light-emitting diode light source, an optical fiber circulator and a spectrograph. The air pressure is monitored according to the linear relation between the resonance frequency of the cantilever beam and the ambient air pressure, the characteristic that the acoustic sensitivity at the resonance position of the cantilever beam is enhanced under the low air pressure is utilized to make up for signal attenuation in the photoacoustic excitation process, and the sensitivity is corrected in combination with the air pressure measured by the cantilever beam. Therefore, high-precision and high-sensitivity detection of trace gas in a low-pressure environment is realized. The system only adopts a single cantilever beam and a single demodulator, has the functions of gas pressure and gas concentration detection, and can realize accurate detection of trace gas in a gas pressure change environment. And an all-fiber scheme is adopted, so that intrinsic safety is realized, and remote measurement and multi-point network group detection are easy.

The invention discloses a power cable monitoring system and method based on single-core optical fiber multi-parameter sensing. The monitoring system comprises a laser, a first optical fiber coupler, an acousto-optic modulation unit, an optical fiber circulator, a distributed sensing optical fiber, a power cable, a wavelength division multiplexer, a second optical fiber coupler and a data acquisition monitoring unit. When the power cable to be detected is subjected to temperature change and vibration change, the temperature value of the power cable can be obtained by demodulating Raman scattering light data in backscattering light of the distributed sensing optical fiber, and Rayleigh scattering light in the backscattering light and local laser are subjected to interference frequency mixing to obtain a beat frequency signal; and the beat frequency signal is demodulated to obtain a vibration signal of the power cable. Based on the Raman scattering effect and the Rayleigh scattering effect, the temperature and vibration signals of the power cable can be detected at the same time only through one single-core optical fiber, and the method has the advantages of being high in signal-to-noise ratio, low in cost, easy and convenient to operate and the like.

The invention relates to the technical field of quantum measurement, and provides a high-precision quantum distance measuring device and method based on a frequency entangled state, and the device comprises an entangled photon source, a polarization beam splitter, a single-mode optical fiber coupler group, an optical fiber circulator, and an optical receiving and transmitting antenna. The entangled photon source comprises a pump light source, a first lens, a nonlinear optical crystal, a temperature control furnace, a temperature control module, a second lens, a dichroscope and a long pass filter; a third port of the polarization beam splitter is connected with a reflector, the reflector is connected with a second single-mode optical fiber coupler, and the second single-mode optical fiber coupler is connected with a second single-photon detector; a second port of the polarization beam splitter is connected with a first single-mode optical fiber coupler, the first single-mode optical fiber coupler is connected with an optical fiber circulator, one end of the optical fiber circulator is connected with an optical transceiving antenna, and the other end of the optical fiber circulator is connected with a first single photon detector; the method has the advantages of wide range and high-precision distance measurement, and can better complete distance measurement.

The invention provides a distributed optical fiber sound wave sensing chip, system and method based on polarization state detection. The chip comprises an optical pulse source module, a first spot size converter, a second spot size converter and a high-speed polarization analysis module, the optical pulse source module generates pulse light and outputs the pulse light to the optical fiber circulator and the sensing optical fiber through the first spot size converter; the second spot size converter receives scattered light returned from the sensing optical fiber and the optical fiber circulator and inputs the scattered light into the high-speed polarization analysis module; the high-speed polarization analysis module comprises a polarization beam splitting rotator, four interference structures and six photoelectric sensors; the polarization beam splitting rotator divides the scattered light into a TE mode and a TM mode, rotates the TM mode to the corresponding TE mode and then outputs the scattered light through two output ports of the polarization beam splitting rotator; each output end of the polarization beam splitting rotator is connected to one photoelectric sensor and one input end of the four-way interference structure; the four-way interference structure is provided with four output ends which are respectively connected to the rest photoelectric sensors.

The invention relates to a self-coherence optical fiber interference device and method for simultaneously measuring morphology and thickness. The device comprises a light source module (1), a measurement light path (2), a compensation light path (3), a spectrograph (4), a mechanical motion module (6) and a data processing module (5), the measuring light path (2) comprises an optical fiber circulator (21), an optical fiber retroreflector (22) and an optical probe (23) and is used for realizing focusing measurement and enabling reflected light of the end face of the optical fiber retroreflector (22) and reflected light of a transparent object to be measured to return; reflected light of the end face of the optical fiber retroreflector (2) and reflected light of the transparent object to be measured form a measuring light beam, and the measuring light beam enters the compensation light path (3); the compensation light path (3) comprises an optical fiber splitter (31), an optical fiber delay line (32) and an optical fiber coupler (33), the measuring light beam is subjected to optical path compensation to generate a compensation light beam, and the compensation light beam and the measuring light beam are combined and input into the spectrograph (4) together.

The invention discloses a TGD-OFDR / OCC-BOTDR integrated multi-parameter sensing system and a working method thereof, and relates to the technical field of optical fiber sensors. The multi-parameter sensing system comprises a laser, an optical fiber coupler, an electro-optical modulator, an optical fiber circulator, an optical fiber Bragg grating, an acoustic optical modulator, an erbium-doped optical fiber amplifier, a random scrambler, a piezoelectric ceramic tube, a heating vessel, a delay optical fiber, a photoelectric balance detector, a filter and detector, a data acquisition card, a polarization controller, a direct-current power supply and a microwave source. An arbitrary waveform generator and the like. According to the invention, multiple parameters can be represented at the same time, the measuring speed is fast, and the sampling rate of the system can be effectively improved under the condition that sensing parameters are the same; the method has the advantage of high spatial resolution; the sensor has the advantages of high fusion and low cost, can realize simultaneous measurement of vibration and temperature / strain through single sensing, and is high in fusion and effective in cost control.

The utility model discloses a distributed sound wave sensing system for multi-frequency pulse modulation, and relates to the technical field of distributed sound wave sensing. The system comprises a narrow linewidth laser, an optical fiber coupler, a polarization-maintaining optical isolator, an acousto-optic modulator, a polarization-maintaining delay optical fiber, an erbium-doped optical fiber amplifier, a polarization-maintaining dense wavelength division multiplexer, an optical fiber circulator, an optical fiber Bragg grating, a piezoelectric transducer, a polarization controller, a photoelectric balance detector, a data acquisition card, an arbitrary waveform generator and the like. According to the utility model, the multi-frequency delay ring is utilized to carry out multi-frequency modulation, the frequency number of light waves is increased along with the circulation times of the light waves in the delay ring, and under the condition that the utilization of a large-bandwidth electro-optical modulator is not increased, the flexible modulation of the frequency is realized by utilizing a low-bandwidth acousto-optical modulator without being influenced by carrier frequency and sidebands of each order; the low-bandwidth acousto-optic modulator is used for frequency modulation in the multi-frequency delay ring, and compared with an electro-optical modulation or multi-acousto-optic / multi-light source modulation scheme, the modulation cost is effectively saved.

A system and method for locking laser frequency based on a hollow fiber FP resonant cavity are characterized in that the output end of a laser is connected with the first port of an optical fiber circulator, the second port of the optical fiber circulator is connected with the input end of an optical fiber coupler, and the first output end of the optical fiber coupler is connected with the input end of a polarization controller; a second output end of the optical fiber coupler is connected with an input end of the optical trap, an output end of the polarization controller is connected with an input end of the hollow-core optical fiber Fabry-Perot resonant cavity, and an output end of the hollow-core optical fiber Fabry-Perot resonant cavity is connected with a third port of the optical fiber circulator; the second output end of the optical fiber coupler is connected with the input end of the optical trap, the second output end of the optical fiber coupler is aligned with the input end of the optical trap, and optical signals output by the second output end of the optical fiber coupler directly enter the optical trap. The system is simple in structure, low in implementation cost, wide in locking range, high in anti-interference capability and high in integration degree.

The invention discloses an optical fiber winding defect real-time detection system based on an embedded development platform, which relates to the technical field of optical fiber winding and detection and comprises the embedded development platform, a motor module, a tension acquisition module, an image acquisition module, an optical fiber path auxiliary module and a pay-off and take-up module. According to the method, the YOLOv3-tiny algorithm based on deep learning is adopted, rapid classification and positioning of the optical fiber winding defects can be achieved, the detection time is within 200 ms, the high requirement of an optical fiber winding machine for real-time performance is met, hardware acceleration of the YOLOv3-tiny algorithm is achieved through optimized deployment on an embedded development platform, and compared with a CPU and a GPU, the method has the advantages that the hardware speed is high, and the cost is low. When the algorithm is operated by an embedded development platform, the energy efficiency can be improved by 5.2 times and 2.1 times. The calculation efficiency is improved, and the cost and power consumption are reduced.

The embodiment of the invention discloses an intrinsic frequency on-line adjusting system and method, a parameter adjusting method, equipment and a medium, and the device comprises at least one electromagnetic coil, an electromagnetic coil drive circuit, an optical fiber loop and a light beam processing module. The electromagnetic coil driving circuit is electrically connected with the electromagnetic coil and is used for providing target driving current for the electromagnetic coil so as to change the magnetic field of the electromagnetic coil through the target driving current; the electromagnetic coil is used for adjusting the refractive index of the optical fiber loop through a generated magnetic field; the optical fiber loop penetrates through the at least one electromagnetic coil, and the tail ends of extension branches at the two ends of the optical fiber loop are connected with the light beam processing module and used for maintaining the target eigenfrequency of the target equipment based on the current refractive index. According to the technical scheme provided by the embodiment of the invention, the on-line adjustment of the eigenfrequency of the optical fiber ring can be realized in a full-temperature range, so that the environmental adaptability of equipment is improved.

The invention discloses a high-order mode fiber laser based on a few-mode fiber grating, and belongs to the technical field of optical communication. The fiber laser is composed of a pumping source, a wavelength division multiplexer, a single-mode erbium-doped fiber, a first few-mode long-period fiber grating, a second few-mode long-period fiber grating, a few-mode fiber coupler, a few-mode fiber circulator, a few-mode fiber Bragg grating, a few-mode fiber circulator and a single-mode fiber coupler. Mode conversion is achieved through the few-mode long-period fiber bragg grating, mode reflection and mode separation are achieved through the few-mode fiber bragg grating, and simultaneous output of LP01 mode lasing, LP11 mode lasing and LP21 mode lasing is achieved under a single resonant cavity. The method for outputting the laser by taking the optical fiber as the medium is one of effective methods for realizing optical tweezers, and the high-order mode optical fiber laser based on the few-mode optical fiber grating can output a low-order mode light beam and a high-order mode light beam at the same time, realizes multi-dimensional control of particles, and has a better application prospect in the fields of material science and life science.

The invention discloses a GHz pulse train generation device and method, and relates to the technical field of laser, and the device comprises a seed light source, a first acousto-optic modulator, a 50: 50 coupler, an optical fiber loop, and a third acousto-optic modulator. Wherein the fiber loop comprises a second acousto-optic modulator, a first chirp long-period fiber grating, a polarization-maintaining double-clad fiber and a second chirp long-period fiber grating. By using the first chirp long-period fiber grating, the polarization-maintaining double-clad fiber and the second chirp long-period fiber grating, the dispersion effect in a fiber loop can be compensated, and the conversion rate of the chirp long-period fiber grating is relatively high, so that the transmission loss in the fiber loop can be reduced; group delay ripples of the chirp long-period fiber bragg grating and the optical fiber high-order LP0m mode are very low, the shape and the width of pulses in a GHz pulse string on a time domain can be controlled, and finally, the optical fiber of the chirp long-period fiber bragg grating is a polarization-maintaining double-clad optical fiber, so that the nonlinear effect can be effectively inhibited.

The invention discloses a parameter-adjustable 9-shaped cavity mode-locked fiber laser based on a liquid crystal phase retarder, and belongs to the technical field of mode-locked lasers. Comprising a reflector, a first polarization beam splitter prism, a first liquid crystal phase delay adjustable wave plate, a Faraday rotator, a second liquid crystal phase delay adjustable wave plate and a second polarization beam splitter prism which are sequentially distributed in the light path direction. An optical fiber loop is arranged on one side of the polarization beam splitter prism II and comprises an optical fiber collimator I, a gain optical fiber, a wavelength division multiplexing-light splitting mixer and an optical fiber collimator II which are connected in sequence; the tail fiber slow axis of the optical fiber collimator I is aligned with the horizontal direction of the polarization beam splitter prism II; a tail fiber slow axis of the second optical fiber collimator is aligned with the vertical direction of the second polarization beam splitter prism; the pumping input end of the wavelength division multiplexing-light splitting mixer is connected with a pumping semiconductor laser, and the signal output end of the wavelength division multiplexing-light splitting mixer is connected with an FCAPC jumper wire; therefore, continuous and rapid adjustment of laser parameters is realized.

The invention provides a gas saturation absorption optical path structure based on dual optical path enhancement, which belongs to the field of laser optical path design and comprises an optical fiber circulator, a gas absorption chamber and an optical fiber reflector. A first port of the optical fiber circulator is connected with a laser output optical fiber, a second port of the optical fiber circulator is connected with an input collimator of the gas absorption chamber, and a third port of the optical fiber circulator is connected with a detector and is used for providing frequency reference for gas absorption; and the optical fiber reflector is connected with the output end of the gas absorption chamber. According to the invention, the physical contradiction between the air chamber size and the optical path gain is broken through, and a compact frequency stabilization system with miniaturization and high stability is realized.

The long-distance frequency-broadening distributed optical fiber sensing system comprises a narrow linewidth laser, an optical fiber isolator, a dense wavelength division multiplexer, an optical fiber coupler, a continuous optical amplifier, a narrow-band filter, an acoustic optical modulator, an optical fiber circulator, a balance detector, an acquisition card and an upper computer, a segment of mode division multiplexing pulse sequence is obtained by selecting a narrow linewidth laser and controlling an arbitrary waveform generator. After the pulse sequence enters the to-be-measured optical fiber, a section of Rayleigh backscattered light is returned, and system original data is obtained after frequency beating with local light. And then signals are demodulated by using a compensation method, and undesired signals are suppressed successively, so that the problem of limited spurious-free dynamic range caused by phase mismatching of different modes is solved.

The invention relates to the technical field of fiber bragg gratings, and particularly provides a birefringent FBG-based fiber environment event identification method, which comprises the following steps: constructing a spectral pulse matrix according to fast axis spectrums and slow axis spectrums of a plurality of spectral pulses, the spectral pulses being echo spectral pulses transmitted by a birefringent FBG; solving a joint optimization problem, and separating a first matrix and a second matrix from the spectral pulse matrix; solving a first optimization problem of the first matrix based on a first dictionary learning algorithm to obtain a vibration event recognition matrix used for representing a vibration event signal; and solving a second optimization problem based on a second dictionary learning algorithm to obtain a temperature offset feature vector used for representing the temperature change signal, the second optimization problem being determined according to the merged vector of the second matrix. The problem of difficulty in signal decoupling of the FBG in a complex environment in which temperature change and vibration events exist at the same time in the prior art is solved.

The invention discloses an OCC-BOTDA / TGD-OFDR fusion system capable of simultaneously measuring multiple parameters and a working method of the OCC-BOTDA / TGD-OFDR fusion system, and relates to the technical field of optical fiber sensors. The system comprises a narrow linewidth laser, an optical fiber coupler, an electro-optical modulator, an optical fiber circulator, a polarization maintaining fiber bragg grating, a semiconductor optical amplifier, a random scrambler, a delay optical fiber, an erbium-doped optical fiber amplifier, an adjustable grating filter, an optical attenuator, a photoelectric balance detector, a photoelectric detector, a data acquisition card, an arbitrary waveform generator, a direct-current power supply and the like. According to the integrated OCC-BOTDA system and the TGD-OFDR system provided by the invention, simultaneous detection of vibration and temperature / strain along the line can be simultaneously realized through a single sensing optical fiber; the device has the advantages of high fusion degree and low cost, cross aliasing and power competition between pulse light are effectively avoided, and simultaneous measurement of multiple parameters is achieved; the system is high in fusion degree and low in cost.

The invention relates to the technical field of optical fiber fault detection, in particular to a health monitoring system and method for a water diversion engineering optical fiber network, and the system comprises a sensing module which is used for synchronously collecting optical fiber environment parameters through an edge calculation node and a multi-source sensor array; the transmission network construction module is used for carrying out short-distance networking and constructing a backbone transmission network by adopting an industrial grade PON (Passive Optical Network) optical fiber network; the cloud management platform is used for preprocessing the data acquired by the transmission network construction module; inputting the preprocessed data into a preset D-S evidence theory fusion model to obtain an early warning trigger signal; and the fault classification module is also used for carrying out fault positioning and classification through the trained fault classification model after the edge node detects an abnormal signal, and outputting a fault position and a fault type. According to the invention, the problems of insufficient real-time performance and incapability of dealing with sudden faults in the prior art can be solved; the positioning precision and the fault identification capability are limited; the long-distance deployment cost is high; and the management complexity is high.

A loop pigtail compensation method for a fiber-optic gyroscope, and a fiber length compensator. The fiber length compensator is fixed on a loop pigtail of the fiber-optic gyroscope, and the fiber length compensator includes a peripheral fiber loop and an expansion-and-contraction shaft core capable of realizing deformation of expanding and contracting; and upon detecting that there is a drift in an output of the fiber-optic gyroscope, a length of the peripheral fiber loop of the fiber length compensator is changed by adjusting a coefficient of linear expansion of the expansion-and-contraction shaft core of the fiber length compensator, so that the compensation for the loop pigtail of the fiber-optic gyroscope is realized, and the problem of low accuracy of online adjustment of the pigtail of the fiber-optic gyroscope is solved.

The invention belongs to the technical field of optical fiber sensing, and discloses a static ice pressure and temperature compensation sensor based on a double-optical-fiber annular ring-down cavity, which comprises a cavity substrate, an H-shaped base is arranged on the bottom surface of the cavity substrate, a first long groove and a second long groove are respectively formed in the upper surface and the lower surface of the H-shaped base, a first optical fiber is arranged in the first long groove, and a second optical fiber is arranged in the second long groove; the upper surface of the cavity substrate is provided with an elastic membrane used for sealing the cavity, the bottom of the elastic membrane is provided with a protrusion, the first optical fiber and the second optical fiber are provided with a first fiber bragg grating and a second fiber bragg grating respectively, the first fiber bragg grating is fixedly connected with the protrusion, and the second fiber bragg grating is fixedly connected with the protrusion. The second fiber bragg grating is fixedly connected with the second long groove; two ends of the first optical fiber and the second optical fiber are led out from two ends of the cavity substrate and then are respectively connected with an optical fiber annular ring-down cavity. According to the invention, the static ice pressure sensing precision can be improved.

The utility model provides a kind of optical fiber optical tweezers fluorescence lifetime detection equipment, by the light beam emitted by light source is divided into two ways, using the first optical fiber coupler to the two-way light signal received is coupled, and the light signal after coupling is transmitted to the optical fiber circulator connected, transmission to displacement control assembly by optical fiber circulator. Displacement control assembly utilizes one-way light signal to carry out target micro-particle capture, utilizes another light beam corresponding light signal to excite target micro-particle to generate excitation fluorescence signal, utilizes detection assembly to carry out photon number detection to excitation fluorescence signal, determines the fluorescence lifetime of target micro-particle. The utility model equipment can be realized in flexible control micro-particle, and the fluorescence lifetime of micro-particle is detected, and the utility model is more simple and efficient, applicable to precision large instrument to carry out ultrafast signal detection.

The application discloses a Stokes parameter encoder, which comprises a fiber optical circulator and an optical path round trip path; a polarization maintaining fiber Faraday rotator is arranged on the optical path round trip path to rotate the polarization of light by 45 degrees; the fiber optical circulator is a polarization maintaining fiber optical circulator; the fiber optical polarization beam splitter is a polarization maintaining fiber optical polarization beam splitter; the delay fiber is a polarization maintaining delay fiber; and the fiber optical phase modulator is a polarization maintaining fiber optical phase modulator. The application further discloses a parameter encoding method of the encoder. The above technical scheme can perfectly offset the rotation angle deviation problem caused by the device, can guarantee the stability of the rotation angle regardless of the angle deviation of the device, is easy to realize the driving circuit, is easy to integrate and small in size due to the pure fiber structure, and can realize the continuous variable quantum key distribution of the complete GG02 protocol based on the Stokes encoder.

The invention provides a self-calibration high-strength optical fiber hydrophone based on an end face reflection principle, and relates to the technical field of hydrophones. Comprising the steps that a laser light source emits a first laser beam, and an optical fiber isolator suppresses reflection and outputs a second laser beam. And the optical fiber variable optical attenuator adjusts the incident power and outputs a third laser beam. The 1 * 2 optical fiber coupler splits the laser beam into a fourth laser beam and a fifth laser beam, and the first photoelectric detector monitors power. The optical fiber circulator transmits the fifth laser beam to the optical fiber sensing module, generates reflected light and transmits the reflected light to the second photoelectric detector, and the second photoelectric detector converts the reflected light into a voltage signal. The data acquisition card acquires the signals, the signal demodulation processing unit calculates sound pressure sensitivity according to a mapping relation formula of the voltage signals and sound pressure, and the standard voltage module provides standard voltage for the data acquisition card. The problem that in the prior art, a high-strength hydrophone cannot be repeatedly used and cannot be self-calibrated after being damaged is solved.

The invention discloses a distributed feedback laser array line width narrowing device and method based on self-injection feedback, and the device is characterized in that a laser array is connected with an array waveguide grating, the array waveguide grating is connected with an optical fiber circulator, and the optical fiber circulator is connected with an optical fiber coupler; the output of the laser array is combined through the array waveguide grating and then input into the optical fiber circulator, part of laser entering the optical fiber coupler from the optical fiber circulator passes through the optical fiber circulator and the array waveguide grating again and is injected into the laser array in the form of optical feedback, and the working state of the laser array is influenced by the optical feedback. And the line width of the laser array is narrowed. Through the synergistic effect of the laser array, the array waveguide grating, the optical fiber circulator and the optical fiber coupler, a self-injection feedback loop is constructed, part of output laser is re-injected into the laser unit after wave combination and light splitting, and phase noise is suppressed through optical feedback, so that the linewidth is remarkably reduced.

This invention discloses a 9-cavity mode-locked fiber laser with adjustable parameters based on a liquid crystal phase delay device, belonging to the field of mode-locked laser technology. It includes, along the optical path, a mirror, a polarizing beam splitter prism, a liquid crystal phase delay adjustable waveplate, a Faraday rotator, a liquid crystal phase delay adjustable waveplate, and a polarizing beam splitter prism. A fiber optic loop is provided on one side of the polarizing beam splitter prism, comprising, in sequence, a fiber collimator, a gain fiber, a wavelength division multiplexing-splitter mixer, and a fiber collimator prism. The slow axis of the fiber collimator prism's pigtail is aligned horizontally with the polarizing beam splitter prism prism 2; the slow axis of the fiber collimator prism 2's pigtail is aligned vertically with the polarizing beam splitter prism prism 2. A pump semiconductor laser is connected to the pump input of the wavelength division multiplexing-splitter mixer, and an FCAPC jumper is connected to the signal output of the wavelength division multiplexing-splitter mixer. This enables continuous and rapid adjustment of the laser parameters.

The utility model relates to a central air-conditioning monitoring system for a high-speed rail station, which comprises a monitoring host and a cold and heat source host PLC master station connected with the monitoring host, and the cold and heat source host PLC master station is accessed to the monitoring host through network cable jump. The tail end sensor is arranged in an air conditioner fan box, is connected to the DDC control cabinet, and is in signal connection with the monitoring host through a BAS optical fiber ring network of a station; the environment monitoring sensor comprises an environment parameter integrated monitor installed in a waiting room and a fuel gas monitor installed in a heating and ventilation power machine room, and the environment monitoring sensor is in signal connection with the monitoring host through a BAS optical fiber ring network of a station. Compared with the prior art, the cold and heat source host, the terminal air-conditioning box of the waiting room and the monitoring sensor of the waiting room environment are connected to the monitoring host of the elimination control room through the station local area network, so that information such as the running state of the central air-conditioning system, the temperature and humidity of the outdoor environment, the heat and humidity state of the terminal air-conditioning box and the like can be obtained; management personnel can conveniently know the environment in the station and the running state of the central air conditioner.