Brillouin optical time-domain fiber optic sensing is a continuously distributed fiber optic sensing technology that can be widely used to obtain the distribution of physical quantities such as temperature and strain along the sensing fiber. In order to meet the fast measurement requirements in engineering applications, improving the measurement and processing speed of Brillouin scattering signals is one of the main concerns of researchers in the field of Brillouin fiber sensing. By analyzing the time-consuming sources of traditional Brillouin optical time-domain optical fiber sensing systems, the research progress of fast measurement technology in Brillouin optical time-domain sensing based on frequency modulation, power spectrum measurement, image processing denoising and improvement of Brillouin spectrum fitting methods were reviewed.

Optical fiber shape sensing technology is an innovative technological solution for 3D morphological recovery such as flexible body morphological measurement, real-time morphological tracking of optical cables, and real-time tracking of medical interventional needle trajectories, and so on. Optical fiber shape sensor taking optical fiber as the sensing components. The sensor has many advantages such as simple structure, easy embedding and installation, measurement without visual contact, corrosion resistance, and anti-electromagnetic interference, etc. It is suitable for large-scale structure morphology measurement in complex environments such as underwater and underground. In recent years, fiber optic shape sensors have received increasing attention. In this paper, the latest research progress of optical fiber shape sensing technology was reviewed. Taking one demension optical fiber curvature sensor, omnidirectional optical curvature fiber sensor and spatial shape sensor as clues, the current research status of the sensors at each stage and the challenges faced by them were introduced.

Magnetic fluids (MF) feature various excellent magneto-optical properties, which provides a new way for the realization of optical fiber magnetic field sensors. After more than ten years of development, it has become an important research direction in the field of optical fiber magnetic sensing. A large number of MF based optical-fiber magnetic field sensors employing different structures and principles have been proposed so far, and in general they have experienced the development from scalar to vector magnetic field sensing. In this review, the magneto-optical properties of MF and realization methods of the MF-based magnetic sensors were sorted out and summarized. Finally, some problems that still exist at present were pointed out, and prospections were made about this field.

In view of the urgent need to improve the comprehensive performance of fiber optic gyroscopes in the fields of unmanned aerial vehicles, robots and automatic driving, the integrated fiber optic gyroscopes with technical advantages such as small size, high performance and low cost have become the current research hotspot. The latest research results and product technology trends of integrated fiber optic gyroscopes in the United States and Russia were sorted out. The technical and technological problems faced by the integrated fiber optic gyroscope were expounded from three aspects of the design and processing of integrated optical chip, the winding of miniature high-symmetry optical fiber coil, and the direct coupling between integrated optical chip and miniature optical fiber coil, and the solutions were analyzed. Finally, the future development trend and application of the integrated fiber optic gyroscope were prospected.

In order to improve the real-time performance of Brillouin optical-time domain analyzer (BOTDA), a method based on compressed sensing was proposed in this paper. It contained sparse representation, random sampling and signal reconstruction. Firstly, the sparse representation of Brillouin gain spectrum (BGS) was obtained by K-means singular value decomposition algorithm, and then BGS could be reconstructed with Gaussian random matrix and orthogonal matching tracking algorithm. To verify the performance of the proposed method, BGS at different SNR were generated and a 45km BOTDA was built for temperature experiments. Simulation and experiments show that the proposed algorithm improves the signal-to-noise ratio by 6.37dB at a cumulative average of 100 times, which is better than 10.13dB at a cumulative average of 3000 times, and the corresponding measurement time is reduced by 1/30. Besides, using 8MHz step data to reconstruct the Brillouin gain spectrum, the correlation coefficient of the reconstruction result of this method with the 4MHz step data is 0.9992, which makes the sweep time decrease by 1/2. The compressed sensing method not only ensures the measurement accuracy but also improves the real-time performance of BOTDA.

Based on the mode coupling theory of fiber grating, the transmission spectrum characteristics of cascaded long- and short-period fiber grating were analyzed by transmission matrix method. The transmission matrices of long-period fiber grating (LPFG), connected fiber and short-period fiber Bragg grating (FBG) were obtained by the coupling mode equation, and then the total transmission matrix of cascaded fiber gratings could be obtained by multiplying them. Finally, the transmission spectrum of long- and short-period cascaded fiber Bragg grating (CLBG) was obtained by combining boundary conditions. The transmission spectrum of CLBG was further simulated numerically and verified by experiment. The experimental results show that there are two resonant peaks formed by the coupling of core mode and cladding modes in the transmission spectrum of CLBG, which are consistent with the simulation results. It verifies the feasibility of the transmission matrix method to solve the transmission spectrum of CLBG, and provides theoretical support for the wide application of CLBG in the field of multi-parameter sensing and measurement.

When the storage tank is covered with soil, the tank body may be deformed and leak due to soil pressure. Therefore, it is particularly important to adopt reliable online monitoring technology for tank leakage to ensure the safety of storage tank production. To solve the problems of low positioning accuracy, slow response time, and small monitoring range in the current storage tank leakage safety monitoring, this paper adopted a new generation of weak reflection fiber Bragg gratings (FBGs) dual-wavelength wavelength division/time division hybrid multiplexing networking technology to achieve full time and full area online monitoring of the surface temperature of earth-covered storage tanks. The temperature measurement accuracy of the FBGs array was ±1℃, and the spatial resolution of the sensor was 1m. After two months of data monitoring and high-pressure water filling experiments on the earth-covered storage tanks, the long-term stability and reliability of the sensor in the earth-covered situation were verified. The results show that the application of FBGs to storage tank monitoring will effectively improve the production safety of storage tanks and has great value for promotion and application.

Interferometric fiber optic gyroscope (IFOG) is affected by various physical fields such as particle radiation and electromagnetic field in space environment, which deteriorates the angular velocity output error. In this paper, the magnetic field error model of fiber optic gyroscope was derived by analyzing the main sources of the magnetic field error of fiber optic gyroscope. Based on the magnetic field error model, the influence of radiation on the parameters of magnetic field error was investigated and the theoretical model of radiation-induced magnetic field error was established. Based on the model, by the influence mechanism analysis and experimental verification, it is determined that the radiation mainly affects the output zero bias of IFOG by changing the Verdet constant and stress-induced birefringence. Furthermore, by establishing a miniaturized IFOG prototype, the polarization maintaining fiber coil was radiated and the corresponding magnetic field error was measured. The experimental results show that the magnetic field error of IFOG varies with the total radiation dose, and its variation law conforms to the radiation-induced magnetic field error variation model.

To meet the needs of three-dimensional vibration signal measurement in vibration measurement, a fiber Bragg grating three-dimensional acceleration sensor was designed based on flexible hinge. The vibration model of the pickup mechanism of the sensor was constructed, the structural model and measurement principle of the sensor were introduced, the theoretical formulas for the resonant frequency and sensitivity of the sensor were deduced, the mathematical model of the pickup mechanism was established, and the key dimension parameters of the pickup mechanism of the sensor were optimized and designed by MATLAB. The sensor was fabricated according to the optimized dimension, and its performance was tested by vibration experiments. The experimental results show that the resonant frequencies of the sensor in the X-axis, Y-axis and Z-axis directions are 673, 667 and 1376Hz, respectively, the operating frequency ranges are 0~220Hz, 0~220Hz and 0~450Hz, respectively, and the sensitivities are 72.3, 70.2 and 83.1pm/g, respectively. The designed sensor has good lateral anti-interference degree and can meet the requirements of three-dimensional vibration signal measurement.

Sapphire is a crystal material with a melting point of 2045℃. It has excellent high-temperature physical and chemical properties such as high strength, high heat resistance, and high corrosion resistance. The single crystal sapphire fiber can transmit optical signals in the ultra-high temperature environment over 1000℃. Optical fiber Fabry-Perot(F-P) sensors based on sapphire fiber is resistant to ultra-high temperature and intrinsically safe, and can be used in dangerous and harsh environments. In recent years, many scholars have carried out related research and developed sapphire fiber sensors for the measurement of temperature, pressure and vibration in ultra-high temperature environments. In this paper, the research progress of sapphire fiber F-P sensor was reviewed, and the work done by the optical fiber sensing and measurement technology research team of the school of optics and photonics of Beijing institute of technology on sapphire fiber sensing technology was introduced. Finally, the author analyzeed and summarized the research of sapphire fiber F-P sensor and give an outlook on its development trend.

In recent years, the frequent occurrence of lithium-ion battery safety accidents has brought serious negative impact on the lithium-ion battery industry. In order to reduce the occurrence of such accidents, the battery management system can be used to safely manage the lithium-ion battery and ensure its normal operation. It is very necessary to use sensors to monitor battery parameters in the management process. Optical fiber sensors have the advantages of small size, strong anti-electromagnetic interference ability, and distributed measurement, which can realize accurate monitoring of lithium-ion batteries. Starting from the monitoring needs of lithium-ion batteries, this paper briefly introduced three mainstream optical fiber sensing principles, and summarized the latest research results of various optical fiber sensing for lithium-ion battery monitoring. Finally, the application of fiber optic sensing technology in monitoring lithium-ion battery parameters was prospected.

The extrinsic Fabry Perot interference scheme was used to design an acoustic wave sensor based on chromium gold composite metal thin film. At the same time, the phase demodulation method based on fast Fourier transform was used to demodulate the white light interference between the optical fiber end face and the energy conversion film, which improved the phase sensitivity. The experimental results show that the sensitivity of the sensor remains in the range of -119.98~-120.99dB re 1rad/μPa in the range of sound wave frequency of 5~1000Hz, and the sensitivity change is less than 1.01dB, with a wide response flat range. It works stably in frequency 150Hz and in the range of sound pressure 0.18~5.30Pa, and there is a good linear relationship between sound pressure and phase.

With the further extending of the transmission distance in remote optical fiber hydrophone system, the effects of various optical nonlinear effects are becoming prominent, and have become the bottleneck that limits the performance of the system. This paper reviewed the research progress on the optical nonlinear effects in remote optical fiber hydrophone system, analyzed the main nonlinear effects in remote fiber optic hydrophone system, and focused on the mechanism of stimulated Brillouin scattering and modulation instability. The effects of SBS and MI on the systems phase noise were presented. Finally, the methods to suppress the nonlinear effects were introduced.

The main error factors affecting the accuracy of interferometric fiber optic gyroscopes (I-FOGs) were firstly analyzed. Subsequently, the influence of test equipment, such as angular rate turntable, test fixture and time reference source, on the error of I-FOGs were researched. Finally, a suppression method based on the high-precision counter for the accuracy evaluation of the turntable combined with the long-period and fixed-cycle test method of the turntable was proposed.With this method, the experimental results demonstrate that the zero bias test error caused by the test fixture error is reduced by 66.7%, both the scale factor absolute error caused by angular rate turntable error and the scale factor repeatability error caused by time reference error are reduced by an order of magnitude. This research is of great significance to the experimental equipment improvement and accuracy improvement of I-FOGs.

Measurement technology is constantly developing in the direction of precision, intelligence and integration, and one of the most representative methods is chromatic confocal microscopy (CCM). CCM is developed on the basis of laser scanning confocal microscope, using the dispersion principle and spectrometer decoding analysis to achieve high-precision measurement. It can perform displacement measurement, 3D reconstruction, surface roughness inspection and thickness inspection, and has the advantages of contactless, high efficiency and online measurement, which are playing an important role in precision measurement and widely used in microelectronics, engineering materials, biomedical and aerospace fields. In recent years, significant developments have been made in various aspects of CCM systems, such as optical system structure, optical lens design, light source optimization and data processing algorithms. This paper reviewed the chromatic confocal microscopy based on extensive research, discussed the advantages of CCM compared with other measurement methods, reviewed the measurement principle, development history and application progress of chromatic confocal microscopy, and outlooked the development trend of CCM.

In order to improve the dynamic range of CMOS image sensor and apply it to day night compatible imaging, a new dynamic range expansion method is proposed in this paper. In this method, multiple reset barriers are set in the pixel to prolong the saturation time of photodiode in the exposure process. At the same time, by switching the pixel integral capacitance in different imaging environments, the response sensitivity of low light level imaging and the full well capacity of high light level imaging are improved, so as to realize day night compatible high dynamic imaging. MATLAB simulation shows that this method can expand the dynamic range of traditional CMOS image sensor from 61dB to 102dB.

In0.53Ga0.47As single photon avalanche diodes (SPAD) response wavelength of 950~1700nm. With the advantages of small size and high sensitivity, In0.53Ga0.47As SPADs are widely used in quantum communication, laser ranging and Lidar. Operating temperature is an important factor affecting the performance of In0.53Ga0.47As SPAD. The higher the temperature is, the greater the dark count rate will be, which leads to the greater noise of the device. So the study of temperature characteristics of device can provide important way to suppress dark count. This paper built a mathematical model to extract photoelectric parameters. By analyzing the influence of charge carriers in absorber layer and multiplication layer, optimized structure parameters were obtained. Finally, an In0.53Ga0.47As SPAD chip with a photosensitive surface diameter of 70μm was fabricated, packaged and tested.The results show that the detection efficiency reaches 14.2%, the dark counting 88.6kHz and the NEP 3.82×10-16W·Hz-1/2. The test results agree with the simulation.

The threshold voltage, gate internal resistance, and the gate capacitance are the key electrical parameters of silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs). However, the extraction process is complicated and prone to inaccuracies due to the limited factors such as the parasitic resistance, gate-dielectric interface state in the devices. Therefore, through device modeling and experimental testing, the nonlinear characteristics of gate capacitance of MOSFETs were revealed, and a capacitance-resistance series circuit test method was constructed. Then, the gate internal resistance and threshold voltage characteristics of SiC MOSFETs were studied. The variation law of gate impedance and gate-source voltage, gate capacitance and gate-source voltage were obtained separately in this paper, revealing that when at a gate voltage of -10V, the error between the gate internal resistance and the target value was less than 0.5Ω. Meanwhile, the voltage at the maximum variation of series capacitance with respect to the gate source voltage was approximated as the device threshold voltage. The results were compared with those attained by the constant current method, and verified in SiC planar-gate and trench-gate MOSFETs respectively. Therefore, this capacitance-resistance method provides a relatively convenient method for evaluating and predicting the characteristics of the threshold voltage drift and gate switching oscillations in SiC MOSFET.

In this paper, the handling capacity of sense node was designed based on CCDs full well charge capacity and the work voltage range of the on-chip amplifier, and the expressions for the optimizing design of the handling capacity of sense node was deduced. As can be seen from the expressions, besides matching the transferring of the full well charge for the CCD, the voltage change range of sense node inducted by the signal charge also must be in the linear region of the on-chip amplifier so that the CCDs output nonlinearity and full well charge capacity will not be affected. Therefore, the CCD designers must consider not only the sense nodes capacitance, but also the MOSFETs wide-length ratio, threshold voltage, work voltage etc. of the on-chip amplifier during the design of charge handling capacity of sense node.

The effects of various parameters on the effective refractive index of TE mode and TM mode of multiple quantum well materials were analyzed. The results show that when the number of wells increases, the effective refractive index of multiple quantum wells decreases. When the number of quantum wells is more than 3, the change of the effective refractive index is not obvious. As the barrier thickness increases, the effective refractive index decreases slightly. There is a suitable amount of tensile strain to make the peak wavelengths of effective refractive index of TE mode and TM mode close, meanwhile the difference between the refractive indices is the smallest as a whole, and the polarization dependence is the smallest. Based on the above analysis, a design method is proposed to realize low polarization dependence of effective refractive index of multiple quantum well and a multiple-quantum well InGaAs/InGaAsP with low polarization dependence of refractive index within C-band (1530~1565nm) is designed. The research result is helpful for designing practical quantum well materials with low polarization dependence of effective refractive index.

The length of semiconducting single-walled carbon nanotubes(s-SWCNTs) is shortened during dispersion and separation. The existence of many ultra-short tubes with length less than 100nm will increase the lap resistance between tubes and increase the scattering probability of carriers, which will lead to the degradation of device performance. It is not beneficial to the development and application of high-performance carbon nanotube devices. However, there is still a lack of research on the separation of s-SWCNTs length in organic system, especially the controllable removal of ultra-short tubes. In this paper, a silica gel adsorption technology in organic system was developed, which successfully achieved the efficient removal of ultra-short carbon nanotubes and effectively regulated the length distribution of semiconducting carbon nanotubes. Prepared by the CNTs with length sorting, the on-state current and maximum transconductance of the transistors were 8.9μA/μm and 0.5mS/μm, which were about 300% and 250% respectively, higher than those of the device without length sorting.

An improved scheme of optical pump terahertz probe (OPTP) technique was proposed. Using an ultrashort broadband terahertz (THz) pulse of air-induced plasma radiation ionized by a two-color femtosecond laser field as the probe pulse, the photo-excited dynamics in silicon was characterized with the improved OPTP, and the capability of the OPTP system based on the improved scheme of this paper was verified through a characterization process. The pump depth of silicon increase with higher pump power, so that the pump depth of 400nm pump pulse is greater than that of 800nm pump pulse. The pump depth of p-doped silicon is the largest, followed by intrinsic silicon, and the smallest for n-doped silicon while using 400nm pump pulse. However, the pump depth of p-doped silicon is the largest, followed by n-doped silicon, and the smallest for intrinsic silicon while using 800nm pump pulse. Furthermore, based on the ultrawide bandwidth and ultrashort pulse width of the probe pulse, the sub-picosecond phonon wavepacket oscillation in excited state is observed.

High-performance ZnSnO/AgNW bi-layer transparent electrode was prepared by the processes of spin coating and magnetron sputtering. The morphology and phase structure of ZnSnO/AgNW bi-layer electrode were characterized and analyzed by X-ray diffractometer and scanning electron microscope, and the electrical and optical properties of ZnSnO/AgNW bi-layer transparent electrode were characterized by UV-visible spectrophotometer and four-probe tester, respectively. The experimental results show that the ZnSnO/AgNW bi-layer transparent electrode displays excellent electrical and optical properties. Under the optimal conditions, the square resistance is 12.3Ω/□ at transmittance of 88.1%, while the quality factor is as high as 231. The ZnSnO/AgNW bi-layer transparent electrode is tested for 1000 bends at a curvature radius of 5.0mm, and its resistance increased by only 13%, demonstrating its excellent flexibility. In addition, the square resistance remained basically unchanged after 20 tape adhesion tests and high temperature and humidity tests, indicating its excellent adhesion and oxidation resistance.

In this paper, an on-orbit calibration method based on distortion gradient reconstruction distortion is proposed. It makes full use of the star spacing measurement technology with the measurement accuracy of micro arc seconds, thus it does not need to use star catalogue, and is not limited by the accuracy of stellar right longitude and declination. The calibration accuracy of optical distortion of the telescope can reach the order of micro arc seconds. The principles of distortion reconstruction based on distortion gradient are introduced, and the distortion calibration simulation experiment is carried out on the optical system derived from the optical design software. The results show that when the wave aberration of the optical system is controlled within 0.0733λ and the measurement error of star angle spacing is 0.3 micro arc seconds, the distortion calibration accuracy can reach 0.28 micro arc seconds, which meets the distortion calibration requirements of nearest neighbor habitable planet exploration.

Three-dimensional reconstruction of highly reflective surfaces has always been the focus and difficulty in structured light technology. Based on the multiple exposure method and the method of adjusting the projected fringe intensity, this paper proposed a selection method of exposure time sequence and fringe brightness sequence. Using the statistical histogram of the number of overexposed pixels on the surface of the tested objects under different projection conditions, combined with the non-overexposure ratio of the number of pixels in the image, the desired exposure time and fringe intensity sequence was calculated, and the high dynamic range technology for highly reflective surfaces was completed. The experimental results show that the proposed method can effectively improve the accuracy of 3D reconstruction of highly reflective surfaces, and the number of effective pixels in the point cloud can reach more than 96%.

Aiming at the problem of front-end drift error accumulation of the V-SLAM algorithm, a visual odometry method based on optical imaging simulation was proposed. This method used the dense 3D point cloud data to perform Poisson reconstruction of the target surface and correlation of the physical properties of materials, and then built a physically based rendering engine (PBRT) according to optical physical properties and ray-tracing principle to generate simulated images of the target characteristics under different observation conditions. The simulated images of the target characteristics and the image captured by the optical camera were registered and the motion deviation was recovered, and the extended Kalman filter (EKF) was designed to output the optimal estimation value of the pose state. The prototype system development and experimental evaluation show that this method effectively overcomes the problem of drift error accumulation in the traditional methods and improves the front-end positioning accuracy by 56% compared to the traditional ORB-SLAM2 algorithm, which provides a new technical idea for the design of visual odometry.

Traditional radar Doppler jamming signal generation based on DRFM is proven to be an effective method, which cheats radars by the method of storing radars signal in digital domain, and generating Doppler frequency shift through modulating. On the other hand, radar jamming signal generation based on photonic radio frequency storage is able to reserve radar signals fingerprint information, but is not able to generate desired Doppler modulation. This article suggests a technology of radar Doppler jamming signal generation based on microwave photonics time-stretch effect. Taking advantage of photonic radio frequency storage, through the effect of microwave photonics time-stretch, it added a certain Doppler frequency shift to the radar signal modulated into the optical domain, in order to cheat radars in velocity. Simulation was conducted to prove this methods feasibility and its effect.

Infrared images with complex background are usually characterized by low signal-to-noise ratio (SNR), insignificant grayscale changes of adjacent pixels, and easy interference by clutter signal and noise, which makes detection of small infrared targets difficult. In order to solve the above problems, an infrared small target detection algorithm based on feature saliency fusion was proposed. Firstly, in the spatial domain, the grayscale difference between the target and its local background was used to calculate the grayscale saliency map, and in the frequency domain, the background suppressed frequency domain saliency map was calculated by combining the spectral residuals. Secondly, the grayscale significance map and frequency domain significance map were normalized and fused with each other by Hadamard product. Finally, the target region was extracted by adaptive threshold segmentation and Unger filter to eliminate small noise points. Experimental results show that the proposed algorithm can improve the image SNR by tens of times, and has a significant effect on background suppression, and has the advantages of high detection rate and low false alarm rate, which is an effective small target detection algorithm.

A weighted optical coupling array-based photoelectric arbitrary waveform generation scheme was proposed. In this scheme, different wavelength weighting and parallel coupling method were used to realize the DAC transform of signal optical domain. Through the spectral analysis of the signal, the time domain waveform was interfered by beat noise which was concentrated in the high frequency region. After wavelength presetting and filtering process, the high frequency noise could be effectively filtered out. However, some peak interference would appear at the time of signal alternation. When further filtering and smoothing process matching the bandwidth of the transform signal, the peak interference could be suppressed to a certain extent. Finally, the triangle wave, sawtooth wave, Gaussian pulse and square wave sequence were realized by the optical digital-to-analog conversion with signal rate of 10Gb/s and quantization accuracy of 5bits.