237 results about "Fiber loop" patented technology

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 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 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 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 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 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.

This application provides an optical fiber sensing system, its calibration method, and a storage medium, relating to the field of optical fiber sensing technology, to improve the dynamic range of the optical fiber sensing system. The optical fiber sensing system includes a signal generator, an optical fiber circulator, a reference optical fiber, a single-photon detector, a processor, and a sensing optical fiber. The signal generator, reference optical fiber, and single-photon detector are respectively connected to the optical fiber circulator. The sensing optical fiber is connected to the reference optical fiber. The single-photon detector is used to acquire a first reference measurement signal and a second reference measurement signal. The first reference measurement signal has attenuation compared to the second reference measurement signal. The processor is used to determine a dead time based on the first reference measurement signal, the second reference measurement signal, and the attenuation coefficient corresponding to the attenuation. The single-photon detector is also used to acquire sensing measurement signals. The processor is also used to calibrate the sensing measurement signals based on the dead time. This optical fiber sensing system is used to detect the state of a target.

The application provides a distributed optical fiber acoustic wave sensing system and a pattern recognition method. The application relates to the fields of optical fiber sensing and pattern recognition, and the system comprises the following steps: continuous coherent light emitted by a narrow-line-width laser is split into two paths by a beam splitting fiber coupler, one path is used as local reference light, and the other path is used as probe light; the probe light is modulated into optical pulses in an acousto-optic modulator driven by a waveform generator, and the optical pulses are injected into a measured sensing optical fiber through a fiber loop; Rayleigh backscattering light returned through the measured sensing optical fiber is mixed with the local reference light through the fiber loop, and the mixed light is decomposed into two orthogonal polarized light beams in a polarization beam splitter and is transmitted to a first balanced photodetector and a second balanced photodetector respectively to be converted into electrical signals; and the two orthogonal interference electrical signals are synchronously collected by a data acquisition card and are sent to a host computer for demodulation. The application provides a new distributed acoustic wave monitoring method with high reliability and high generalization ability, and has extremely high engineering popularization value.

The invention discloses a photon neural network based on a time synthesis dimension and a training method thereof, and the photon neural network comprises a light input module which is used for generating a square wave light pulse; the light processing module is connected with the output end of the light input module and is used for regulating and controlling the amplitude and the phase of the square wave light pulse; the optical processing module is arranged based on a coupling optical fiber loop architecture, and an optical path is split into long and short optical fiber loops which are coupled with each other through a variable beam splitter, so that propagation paths of square wave optical pulses in the long and short optical fiber loops equivalently form time synthesis photonic crystals; and the light output module is connected with the output end of the light processing module and is used for detecting the light intensity of the square wave light pulse when the square wave light pulse is propagated in the light processing module. Wherein the optical processing module can be replaced by an integrated photonic chip architecture arrangement, and the optical processing module enables propagation paths of square wave optical pulses in long and short waveguide loops to equivalently form time synthesis photonic crystals through the long and short waveguide loops which are mutually coupled by a 50: 50 beam splitter.

The invention discloses a coherent optical frequency signal regeneration amplification system based on optical fiber transmission. The coherent optical frequency signal regeneration amplification system comprises a local narrow linewidth laser which outputs narrow linewidth laser; the first optical fiber coupler couples the narrow linewidth laser to the first acoustic optical modulator and the second acoustic optical modulator respectively; the output of the first acousto-optic modulator and superior transmission light are jointly coupled into a photoelectric detector by a second optical fiber coupler to generate a beat frequency signal; the signal processing module samples the beat frequency signal after conditioning the beat frequency signal, performs phase discrimination on the sampled signal and the digital reference signal to generate an error signal, and generates a first feedback signal and a second feedback signal according to the error signal to be respectively used by the local narrow linewidth laser and the first acousto-optic modulator; performing real-time cycle slip detection on the error signal and repairing a phase abnormal point to generate a third feedback signal to be used by a second acousto-optic modulator; and the second acousto-optic modulator outputs amplified regenerated laser. According to the invention, high-precision optical frequency signal transmission can be realized in a complex and changeable optical fiber environment with large noise.

The invention discloses an optical tomography system and method based on a long light needle metasurface lens. The system comprises a bandwidth near-infrared light source, an optical fiber circulator, an optical fiber beam splitter, a first optical fiber collimator, a plane mirror, a second optical fiber collimator, a two-dimensional scanning galvanometer, a long-light-needle metasurface lens, a collimator and a spectrograph, the bandwidth near-infrared light source emits near-infrared light, the near-infrared light is divided into two light beams by the optical fiber beam splitter after passing through the optical fiber circulator, and the two light beams are transmitted to the spectrograph. One beam of light reaches a first optical fiber collimator and then is transmitted to a plane mirror to form a reference arm signal; after the other beam of light reaches the second optical fiber collimator, the light passes through the two-dimensional scanning galvanometer and is transmitted to the long-light-needle metasurface lens, the long-light-needle metasurface lens achieves focusing through the diffraction effect of the light, high-precision three-dimensional tomography is completed, obtained sample scattering information interferes with a reference arm signal, generated interference information is returned to a collection position, and the high-precision three-dimensional tomography is achieved. And after passing through the collimator, the light enters the spectrograph to obtain corresponding interference spectrum data.

The invention provides a multi-state on-line monitoring system and method for molding sand in a sand casting process, and belongs to the technical field of manual molding of sand casting. The system comprises a high-speed spectrometer, an optical fiber circulator, a wide-spectrum light source, a hardness sensor control circuit board, a computer and a sensor for simultaneously detecting the temperature, the humidity and the hardness of sand in the sand casting process. During data acquisition, probe light emitted by a wide-spectrum light source is transmitted to each sensor node through an optical fiber circulator, a high-speed spectrometer analyzes the central wavelength offset of an interference spectrum in real time, hardness electric signals are synchronously acquired, and a multi-physical field database containing spatial and temporal distribution characteristics is constructed. A neural network model is adopted for quality correlation analysis, and a parameter-defect mapping relation is established by training multiple sets of process data. According to the invention, in-situ synchronous measurement of three parameters of temperature, humidity and hardness is realized in sand casting for the first time, and the industrial problem that a molding sand state cannot be comprehensively reflected by traditional single parameter detection is solved.

The invention provides a differential photoacoustic gas sensing system and method based on cross-correlation demodulation, and is suitable for the fields of trace gas monitoring, industrial process fine control and environment detection. The system comprises a gas excitation light source, a symmetrical double-probe gas sensor, an optical fiber circulator, a wide-spectrum light source, a 1 * 2 optical fiber coupler, two pieces of plain glass, a photoelectric detection array and a computer, acoustic wave signals excited by the photoacoustic effect generate difference superposition cavity length changes on the symmetrically-arranged double cantilever beams, and environment noise triggers cavity length responses which are counteracted in the same direction. The system adopts an optical cross-correlation demodulation algorithm to track peak displacement of a cross-correlation function in real time, dynamically demodulates cavity length change information, and inverts the gas concentration according to the information. According to the design scheme, effective photoacoustic signals are remarkably enhanced, meanwhile, effective suppression of environment vibration noise is achieved, and finally the trace gas detection system integrating the advantages of miniaturization, high sensitivity and low cost is constructed.

The application discloses a hydropower station network reconstruction method based on a redundancy technology, which comprises the following steps: upgrading an internal control network of a hydropower station into a hundred-megabit redundant fiber ring network and configuring an MRP sub-ring redundancy protocol; establishing a Hiper-Ring gigabit redundant fiber ring network between watersheds of cascade hydropower stations and starting three-layer routing function and VRRP function; using Hesmann three-layer switches for data transmission between a remote control center and the hydropower station; adopting a link aggregation technology to add a two-layer aggregation device between a dam LCU switch and a watershed switch RSPE30; and performing function test. The hydropower station network reconstruction method based on the redundancy technology provided by the application adheres to the principles of openness, expansibility, reliability and investment saving, eliminates existing problems based on the existing network, does not affect the operation of the network that has been put into use during later network access reconstruction, combines industrial control technology with IT technology, and provides a redundant, reliable and efficient automatic control communication network for a computer monitoring system of the hydropower station.

An optical fiber loopback assembly includes a fiber optic connector and a loopback shell coupled to a boot of the fiber optic connector. The fiber optic connector can be a known connector, thereby avoiding the need for specialized components or modifications. The loopback shell includes a portion behind the boot of the connector, but can have a compact design that is still configured to store excess length of loopback optical fibers.

The present invention discloses a high-precision liquid level measurement device and method based on frequency sweeping interferometry, belonging to the field of optomechanical and electrical integration measurement technology, and is used for high-precision liquid level measurement. The optical path consists of two parts: a frequency sweeping correction optical path and a measurement calibration optical path; the components include a frequency sweeping light source, an optical fiber splitter, a high-speed acquisition card, a computer, an optical fiber circulator, an optical fiber reflector, a Fabry-Perot (FP) etalon, a balanced photodetector (BPD), and a liquid level measurement probe. The FP etalon implements the frequency sweeping correction function, and the measurement calibration optical path switches channels through a one-to-two photoelectric switch, and high-speed signal acquisition is performed through the BPD and a high-speed acquisition card. The measurement process of the present invention does not involve mechanical movement and has the advantage of being maintenance-free. The introduction of the FP etalon for nonlinear frequency sweeping calibration improves measurement accuracy, and under relatively favorable experimental conditions, micron-level measurement accuracy can be achieved. This non-contact measurement method can meet the needs of high-precision liquid level measurement in fields such as chemistry and chemical engineering.