Spot detection technology plays an important role in modern scientific research and application. Due to its advantages of high detection sensitivity, simple signal processing, and strong anti-interference ability, four-quadrant detectors have been widely used in spot detection technology and are the key components in acquisition, tracking, and pointing systems. Firstly, the spot models commonly used in spot detection and the principle of four-quadrant detector spot detection were introduced. Then, the research results of four-quadrant detector spot detection at home and abroad, as well as the factors affecting the accuracy of four-quadrant detector spot detection and the commonly-used spot detection algorithms were analyzed. The four-quadrant detector spot detection system was introduced, including the beam alignment detection system, four-quadrant detector tracking communication composite system and micro-nano laser communication system. Finally, the development prospects of spot detection technology was prospected.

The main function of an adaptive optics correction system is to correct for wavefront distortion and compensate for wavefront distortion of incident light. In order to measure the wavefront error of the adaptive optics system, a wavefront detection device with a working wavelength of 1 030 nm was developed using non-spherical technology. The device could detect the wavefront of a large-size near-infrared rectangular beam with a clear aperture of 200 mm×80 mm, and the center field of view of the system had a PV value of 0.123 λ and an RMS value of 0.036 1 λ, which indicated the imaging quality was good. Based on the optical design, the structural design of the device was completed and the device was assembled and tested in the laboratory environment. The test results show that the optical and mechanical parameters of the device meet the design specifications and can complete the wavefront detection task of the adaptive optics system.

The off-axis reflection system has the characteristics of no chromatic aberration, no central obscuration and compact structure, but due to its asymmetric structure, its field of view is often a linear field of view. An off-axis three-mirror system with a large symmetric field of view was designed based on Zemax. The field of view is 13°×13°, the relative aperture is 1/5, the focal length is 800 mm, and the wavelength is 400 mm~1 000 mm. The primary mirror and the third mirror are free-form surfaces, and the secondary mirror is a quadratic surface. The design results show that the root mean square of spot diagram diameter of the proposed system is less than 5 μm, 80% of the energy is in the one pixel, the optical transfer function is close to the diffraction limit, and all the indicators meet the application requirements.

In the glass-plastic hybrid fixed-focus security lens, the material properties of the plastic lens, glass lens and frame are quite different. Under the complex temperature environment, the thermal deformation of the lens mechanical structure and the optical heat dissipation design will jointly affect the image quality. In order to ensure the stability of the lens imaging, according to the test temperature of ?40 ℃~80 ℃ of the security lens, the optical, mechanical and thermal integration analysis of the lens was carried out. A finite element model of the thermal structure of the lens was established in Ansys workbench to calculate the thermoelastic deformation of the lens. Zernike polynomial was used to fit the surface shape change of the mirror, and the fitting results were imported into Zemax to judge the influence of temperature load on image quality. The simulation results show that under the ultimate test temperature load, when the base material is polycarbonate mixed with 20% glass fiber, the thermal defocus amount of the simulated optical system itself in Zemax is effectively compensated. When the frame material is polycarbonate mixed with 30% glass fiber, the maximum extrusion strain of the plastic lens is 2.36×10?3 mm. When the frame material is polycarbonate mixed with 20% glass fiber, the maximum extrusion strain of the plastic lens is 0.53×10?3 mm, which can keep the image quality of the lens stable. Finally, through the high and low temperature flange focal length measurement test of lens, the temperature adaptability of the lens and the correctness of the optical-mechanical-thermal integration analysis were verified.

NaI (TI) detector is a typical scintillator radiation detector, and its detection process involves radiation energy deposition, generation and transport of visible light signal, photoelectric conversion, signal processing and other physical processes. Firstly, the process of ray particles converting into visible light signal output in crystals was simulated and analyzed by Monte Carlo method, Birks formula and ray tracing program. Combined with the index parameters of photomultiplier tube and signal processing circuit, the pulse voltage signal parameters for the final output of the detector were obtained. Then, the experiment was verified by using Φ50 mm×50 mm NaI (TI) crystal-coupled photomultiplier in 137Cs source radiation field. The experimental results show that the rise/fall time ratio of the output pulse signal of detector is 0.39, which is about 7.69% different than the simulated value of 0.36, indicating that the output results of the simulation calculation model are basically consistent with the measured data, which preliminarily proves the correctness of the simulation calculation model and calculation analysis process. The proposed method is of certain reference significance for deeply understanding transmission law of fluorescent visible light excited by radiation particles in crystal scintillator and optimization design of scintillator radiation detector system.

In order to reduce the volume and energy consumption of the laser communication terminal, and to ensure the aperture and magnification, an improved Dall-Kirkham receiving telescope was designed according to the Gaussian optics and Seidel aberration theory of catadioptric telescopes. The lens consisted of two mirrors and five lenses, the wavelengths of the received signal light were 974 nm and 1 550 nm, the aperture diameter was 60 mm, the relative aperture was 1/3.38, the exit pupil distance was 50 mm, the field of view angle was 6 mrad, the total length was 111.04 mm, and the working temperature was 20 ℃±10 ℃. The wave aberration of the optimized lens in the 0.5 mrad field of view was better than (l/40) λ, and that in the 6 mrad field of view was better than (l/20) λ, with the energy was concentrated. In order to realize the athermalization design, the selection and design of structural materials were given, and the wave aberration of optical system under ±10 ℃ was analyzed. The results show that the lens imaging quality is good and meets the application requirements.

Because of the complexity of space light environment, suppressing stray light is particularly important to ensure the imaging performance of space cameras. The stray light analysis and suppression optimization design were carried out for the optical system of the space probe camera for wide-band imaging. The optomechanical model was established through the lossless data interaction between SOLIDWORKS and TracePro, and the stray light model was optimized from the surface characteristics, mechanical structure, lens transmittance and other aspects of the optomechanical material. Then, the forward and reverse directions were traced by the Lambert body light source, and the key surfaces of the system were sampled and analyzed in combination with the half-section diagram of the optomechanical model. The analysis results show that the point source transmittance of the optimized optomechanical system at the off-axis angle of 10.3°~15.4° decreases by 66%~99.4% compared with that of the original system. The point source transmittance at the off-axis angle of more than 14.2° is close to the order of 10-4, and the point source transmittance of stray light at the off-axis angle of 18.4° is about 10-4. The ghost image experiment further proves that the optimized design of optomechanical system has good stray light suppression effect.

The chromatic confocal displacement sensor has good applicability in the measurement of the scratch depth of the locomotive wheel axle, and the dispersive objective is the key device that determines the detection range and resolution of the sensor. According to the detection requirements, combined with the chromatic confocal principle and linear dispersion conditions, an appropriate initial structure was selected. The Zemax optical design software optimized and analyzed the initial structure, and designed a high-linearity and short-conjugate dispersion lens. The measurement range is 1 mm, the operating spectral range is 400 nm~700 nm, and the spherical aberration of the lens is less than 1.7 μm. The axial displacement resolution of the system is 0.615 μm, the dispersion linearity determination coefficient R2 is 0.997 5, and the conjugate distance is 104 mm, which makes the lens miniaturized and has the advantages of high resolution and high linearity.

Primary and secondary mirror support technology is one of the key technologies of common optical path system. For the airborne optical system operating within the temperature change range of ±60 ℃, the pairing of invar steel and ULE, titanium alloy and K9 were selected as the materials of primary and secondary mirrors as well as supporting structures according to the matching principle of thermal expansion coefficient, and the athermalization flexible support structure with high stiffness was designed. Finally, the imaging quality of the primary and secondary mirror types as well as the whole optical system was analyzed by using a self-developed opto-mechanical co-simulation program. The results show that when invar steel and ULE are paired, under uniform temperature difference of ±60 ℃ and 10 ℃ axial and radial temperature gradient, the surface shape is better than (1/100) λ after the primary and secondary mirror removing defocus, and the root-mean-square (RMS) radius of spot diagram of the whole optical system is smaller than Airy spot radius. The central wavefront of the phase surface is better than (1/50) λ, the MTF@63 lp/mm is better than 0.45, and the first-order natural frequency with athermalization flexible support is up to 263 Hz. When titanium alloy and K9 are paired, the imaging index of the system under uniform temperature difference of 60 ℃ meets the requirements, and the imaging quality at 10 ℃ axial and radial temperature cannot meet the requirements. The resolution of invar steel and ULE paired opto-mechanical system was tested at low temperature, and there is no obvious change in resolution, which indicates that the design and analysis are feasible.

Oriented object detection is a crucial task in remote sensing image processing. The large-scale variations and arbitrary orientations of objects bring challenges to automatic object detection. An improved RoI Transformer detection framework was proposed to address above-mentioned problems. Firstly, RoI Transformer detection framework was used to obtain rotated region of interest (RRoI) for extraction of robust geometric features. Secondly, high-resolution network (HRNet) was introduced in the detector to extract multi-resolution feature maps, which could maintain high-resolution features while adapting to multi-scale changes of the target. Finally, Kullback-Leibler divergence (KLD) loss was introduced to solve angle periodicity problem caused by the standard representation of oriented object, and improve the adaptability of RoI Transformer to targets in arbitrary directions. The object localization accuracy was also improved through the joint optimization of bounding box parameters of oriented object. The proposed method, called HRD-ROI Transformer (HRNet+KLD ROI Transformer), was compared with the typical oriented object detection method on two public datasets, namely DOTAv1.0 and DIOR-R. The results show that the mean-average-precision (mAP) of detection results on DOTAv1.0 and DIOR-R datasets is improved by 3.7% and 4%, respectively.

Characterization and measurement of monocrystalline-silicon dislocation density are the important parameters for detecting the crystal growth quality and studying the dislocation formation mechanism. Based on atypical characteristics of dislocation corrosion pits such as large differences in morphology and complex background, as well as low accuracy and efficiency of traditional artificial optical microscopy detection, an improved YOLOv5 algorithm was proposed to detect the density distribution of dislocation corrosion pits of monocrystalline silicon. The attention mechanism was introduced based on the original YOLOv5 algorithm to optimize the network structure and strengthen the calculation ability of the model. The network detection accuracy was further improved by strengthening the feature fusion, and the loss function was optimized to enhance the accuracy of positioning and improve the training speed. The experimental results show that the improved algorithm can detect monocrystalline-silicon dislocation pits of different corrosive fluids with accuracy of 93.52% and 98.82%, respectively, the mean average precision (mAP) can reach 96.17%, and the frame rate can reach 47 frame/s, which satisfies the requirements of real-time detection.

The sintering flame image has fine-grained local flame state feature information and complex global flame state feature information. However, the traditional convolutional neural network is often more sensitive to local features, and it is difficult to extract the global feature information of the flame state, which restricts the expression ability of sintering flame features, resulting in low accuracy in the classification and recognition of the sintering flame state. In response to such problems, a dual-stream network feature fusion classification method based on CNN-Transformer was proposed, which includes two modules: convolutional neural networks (CNN) flow and Transformer flow. Firstly, the CNN block and the Transformer block were designed in parallel. The CNN stream extracts the local feature information of the RGB image of the sintering flame, and the Transformer stream extracts the global feature information of the GRAY image of the sintering flame. Then, the local feature information and the global feature information of the sintering flame state extracted by the dual-stream network was fused using the cascade interactive feature fusion method. Finally, the softmax classifier was used to achieve the classification of sintering flame states. The experimental results show that the flame classification accuracy can reach 96.20%, which is 6%~8% higher than that of the traditional convolutional neural network.

In order to enhance the quality of nighttime low-light image, improve the accuracy of the object detection model under the nighttime low-light condition and reduce the calculation cost of the model, a multi-task model for nighttime low-light image enhancement and object detection based on knowledge distillation and data enhancement was proposed. Knowledge distillation was performed based on the high-quality image model, and the feature information of the high-quality image was used to guide the model training, so that the model could extract the feature information similar to that of the high-quality image in the nighttime low-light images. These feature information could be used to achieve enhancement of image contrast, denoising and objects detection. The experimental results show that the proposed distillation method can improve the object detection accuracy of nighttime low-light by 16.58%, and the image enhanced by this method can achieve the effect of mainstream image enhancement based on deep learning.

Aiming at the problems of ghosts, shadows, and false detections occur when traditional ViBe algorithm detects moving targets in complex backgrounds, an improved ViBe moving target detection algorithm was proposed, which was called GS-ViBe algorithm. In the initialization stage of GS-ViBe background model, the maximum posteriori estimation method was used to determine the optimal number of Gaussian distributions of each pixel to form a multi-frame fusion background instead of single-frame background initialization method of ViBe, so that the ghosts were eliminated. In the GS-ViBe foreground detection stage, the multi-feature fusion shadow detection process was added, and the detection results were fused with ViBe foreground targets to obtain the foreground targets after eliminating shadows. Finally, in the GS-ViBe background model update stage, a dynamic update factor was introduced instead of a fixed update factor, so that the background could be updated adaptively, thereby reducing the false detection rate of targets. In comparison with traditional ViBe algorithm in a variety of complex backgrounds, it is found that the recall rate of GS-ViBe algorithm is increased by 37.74% on average, the accuracy rate is increased by 19.83% on average and the false detection rate is reduced by 52.57% on average. It shows that the GS-ViBe algorithm can effectively eliminate the interference from ghosts, shadows and false detections, which obtains the complete foreground targets.

Infrared ship target detection and recognition technology is the key technology of infrared imaging guidance for anti-ship missile, which is of great significance to the guidance performance of weapon equipment. For the accuracy and speed in complex environment, an infrared ship target detection algorithm based on YOLOX-S was proposed. Firstly, the depthwise separable convolution (DSC) was introduced to replace the traditional convolution in the feature pyramid network (FPN) and YOLOHead residual structures, which could reduce the amount of parameters of the model. Secondly, the ECANet channel attention mechanism was introduced to improve the attention of network, which could reduce the false detection rate and missed detection rate of ship targets. Finally, the CIoU loss function was used to further improve the detection accuracy of the network. The experimental results show that the average precision (AP) of the optimized algorithm reaches 98% and the detection speed is 56 frame/s. Compared with the previous YOLOX-S algorithm, the detection speed and the average precision are improved by 6 frame/s and 3%, respectively, and the model is more lightweight. The experimental results fully prove that the proposed algorithm can effectively complete the infrared ship target detection task.

A digital, high-precision and portable real-time interferometric measurement system for liquid refractive index based on Fourier transform spectrum analysis technology was proposed. Based on the equal-thickness interferometry optical path composed of a split-tip liquid container, the common-path interferometric measurement system was built recorded by a charge coupled device (CCD) camera. Taking the Raspberry Pi hardware system as platform and the Python language as programming basis, the accurate extraction of the number of interference fringes from the CCD plane was realized through Fourier transform spectrum analysis and cubic spline interpolation. Moreover, a graphical user interface (GUI) was designed to realize the dynamic visualization for the measurement process. The measurement process only needed to determine the initial fringe number before injecting any liquids, then the real-time measurement of the refractive index of flowing liquid could be realized without additional preset parameters. In the experiment, the refractive indices of three liquids were determined and the time stability of the measurement system was verified. The results show that the measurement system can achieve better time stability as the initial fringe number is greater than 180, and the measured relative errors of the refractive indices are all within 0.754%.

Spectral range and signal-to-noise ratio (SNR) are important parameters to evaluate the performance of terahertz time-domain spectrometer (TDS). To solve the calibration problems of spectral range and SNR for TDS, the composition and principle of TDS were introduced. The advantages and disadvantages of the commonly-used calibration methods were compared, and one of the methods was selected to design the parameter calibration method of terahertz time-domain frequency-domain SNR. The frequency range corresponding to 1/M of the maximum amplitude of signal in the frequency domain was taken as the spectral range, and the influence of M value on spectral range was studied. The larger the M value, the wider the spectral range. When M value was greater than or equal to 50, the spectral range changed little. The signal and noise of the time-domain signal were defined, and the time-domain SNR was calculated. Using the frequency-domain power spectrum of air as the signal, the frequency-domain power spectrum in the light path covered by matal plate was taken as the noise, and the frequency-domain SNR was calculated. The calibration experiments of spectral range and SNR were carried out, and the influence of humidity variation on spectral range and SNR parameters of TDS was studied by contrast method. When the relative humidity was less than or equal to 50%, the influence on spectral range and time-domain SNR was not obvious. When the relative humidity was greater than 50%, because the absorption of water vapor increased sharply, the spectral range and SNR decreased sharply.

To achieve high-precision 3D measurement of surface profile of the object, a telecentric optical path measurement system with large field of view (FOV), object distance and measuring range was proposed. The composition of the system and the principle of optical triangulation were introduced, the construction of the optical path with the angle of 45 ° between the projection and double optical path and the normal line of the measured surface could reduce the requirement of depth of field of the imaging objective lens for large depth measurement range. The theoretical model of system depth calibration was established, and the theoretical value of CCD unit pixel depth was 0.554 4 μm. The magnification, numerical apertures and other optical parameters were calculated and the optical path was constructed. The resolution, measuring range, minimum width of light stripe and edge quality of the system were analyzed by experiments. The experimental results show that the longest projection stripe is 2 mm, the minimum line width is 8.96 μm, and the stripe edge is clear and smooth. The imaging distortion of the system is small, and the optical resolution of 1.62 μm and the depth pixel resolution of 0.54 μm can be achieved. The object distance is 65 mm, the depth measurement range is no less than 140 μm. The system has good measurement performances.

Phase-shifting interferometry is a highly sensitive non-contact optical measurement method that has been widely used in the field of precision measurement. The spatiotemporal phase-shifting method (ST-PSM) is a phase-shifting algorithm known for its high accuracy, which can avoid periodic errors that are typical of traditional phase-shifting algorithms. This makes it suitable for use in the presence of uneven background light intensity, modulation fluctuations and phase-shifting errors, as well as for measuring distorted interferometric fringe images. However, the interpolation fitting step of this method requires the interferogram to be in a rectangular region, which makes it difficult to measure the complete surface shape of optical elements with non-rectangular apertures. To address this limitation, a novel approach that combined the interferogram spreading technology with the ST-PSM method was proposed. This involved spreading the interferogram into a rectangle, which enabled the ST-PSM method to extract the phase and obtain the complete surface shape information. Numerical simulations and experimental results show that for interferograms with the same shape, the peak-valley values and root mean square values of the wave surface measured by the ST-PSM method with spreading are more accurate than those obtained by using the ST-PSM method without spreading. Taking the circle as an example, the peak-valley value decreases from 0.123 6 λ to 0.044 6 λ after extension, and the root mean square value decreases from 0.011 7 λ to 0.010 9 λ (where λ is 633 nm). The above results demonstrate that the proposed method can be used for accurate measurement of non-rectangular optical elements.

When the size of the detection target is small and is in the far distance, due to the small field of view of the photoelectric system, the effective pre-stage target guidance is the premise for the photoelectric system to track and point the target. The essence of target guidance is converting the target point under the geodetic coordinate system into the local coordinate system of the photoelectric system. Since a series of rotational and translational parameters will be introduced in this conversion process, the accuracy of these parameters will determine the ultimate target guidance accuracy. A guidance error correction method was proposed for the photoelectric system, namely acquisition-tracking-pointing (ATP) system, based on unmanned aerial vehicle (UAV) track, which used the track data around ATP system to solve optimal parameters for coordinate conversion in the process of computing target guidance data, thereby to improve the target guidance accuracy. Experimental device built for this project achieves the following results: the azimuth guidance standard variance is better than 0.052°, the elevation guidance standard variance is better than 0.04°, and the maximum error does not exceed 0.7°. The results also show that the higher the accuracy of pre-stage guidance, the faster the target acquisition speed of ATP system, which is of great significance for improving the corresponding speed of the target disposal.

A trajectory monitoring method and system of rotation shaft center based on swept-source optical coherence multi-point vibrometer (SSOCMV) were proposed by the combination of frequency-division multiplexing technique and swept-source optical coherence vibrometer, which have advantages of non-contact, non-invasive, high accuracy and simultaneous muti-point vibration measurement. Firstly, the system composition and measurement principle of SSOCMV were introduced and analyzed. Then, the experimental comparison system was set up to verify the measurement accuracy of the SSOCMV system, and the eddy current sensor was installed in a symmetrical position of the probe of the SSOCMV system to synchronously monitor the trajectory of rotation shaft center, so as to compare the measurement results of these two systems. The experimental results show that the trajectory monitoring system of rotation shaft center based on SSOCMV has a higher displacement resolution and a better signal to noise ratio (SNR) than eddy current sensor. Therefore, the SSOCMV has a good application prospect in the rotating mechanical condition monitoring, parameter identification and fault diagnosis.

A theoretical model of passively mode-locked fiber laser was constructed, and the influences of high-order dispersion on output pulse characteristics were studied by numerical simulation in both time domain and frequency domain. In terms of time domain, the third-order dispersion resulted in distortion of pulse shape, asymmetry of pulse time-domain profile and temporal shift. In terms of frequency domain, the third-order dispersion caused changes in position and intensity of sidebands. At the same time, it was found that the fourth-order dispersion could broaden the pulse and change sidebands intensity of the pulse. The results are instructive for the practical applications of the passively mode-locked ytterbium-doped fiber lasers.

An all-fiber coherent laser windfinding radar system was developed, which used a fiber laser to synchronously trigger and transmit the 1.5 μm laser signals that were safe for human eyes. Through the design of all-fiber circular link, high image quality transceiver lens and optical wedge could scan the space cone 45° range vertically, the dual-channel high-reliable double-pass data acquisition and module processing were adopted to achieve the processing and inversion of three-dimensional vector wind field at medium and low altitude. To meet the adaptability of laser radar working in outdoor high and low temperature environment (?25 ℃~40 ℃), the heat source module of laser radar system was simulated. Through the design and development of thermal control module and refrigeration module, the feasibility of working in high and low temperature environment was realized. Finally, the indoor experiment and outdoor wind field calibration experiment of laser radar were carried out. The laser radar can measure the highest wind field height of 3 km, the wind speed accuracy is better than 0.36 m/s, and the wind direction accuracy is better than ±5°.

A zoom beam expansion system for OPO(optical parametric oscillation) laser rangefinder transmitter was designed. The system adopted two-stage laser beam expansion, which compressed the divergence angle of OPO laser beam for the twice. The primary laser beam expansion was variable magnification beam expansion, and the secondary laser beam expansion was constant magnification beam expansion, so that the divergence angle of the output beam could be continuously adjusted to realize the wide range ranging of the laser rangefinder and improve the human-eye safety in the laser ranging process. The divergence angle of the output beam of OPO laser is 6 mrad, the diameter of the output beam is ?7 mm, and the beam expansion rate is 6 to 12 times, among which the variable magnification beam expansion rate of the primary laser is 2 to 4 times, and the beam expansion rate of the secondary laser is 3 times. The designed optical system meets the requirements of large-aperture beam incidence, and has the function of variable magnification beam expansion, which break through the limitation that the existing variable magnification beam expansion system can only achieve small-aperture beam incidence. The total length of the finally designed optical system is 285 mm, which is simple in structure and conducive to engineering.

In order to monitor the working condition of the power system more accurately, a discrete multi-point detection scheme applied to partial discharge (PD) detection of power transformers was proposed. Based on the heterodyne interference principle of optical fiber, the sensing system was composed of four sensing heads to realize multi-point detection and partial discharge source localization. The sensitivity of the sensor was improved by optimizing the structure of the sensor head. At the same time, the compact package of the sensor enabled it to be installed in the power transformer, which improved the accuracy of the detection results. The experimental results show that the single-channel resolution of the proposed sensing scheme can reach 4 mrad. The constructed three-phase power transformer model is experimentally demonstrated and analyzed, and the resolution of sound source localization can be 1 cm when the 150 kHz PD ultrasonic multi-channel measurement is carried out. Because of its compact structure, high resolution and low cost, the proposed scheme has great application potential in security detection of power system.

Underwater visible light communication (UVLC) system with light emitting diode (LED) as transmitter has a low transmission rate due to the limited device bandwidth and it is greatly affected by water environment quality that makes the communication comprehensive performance poor. In order to improve the channel capacity and communication quality, the channel multiplexing technology into the LED-UVLC system was applied. The FPGA was used as the data processing core, LED blue and green light emission array and avalanche photodiode (APD) receiving array were built, and a 4×4 multichannel UVLC system was designed. We placed the system in an underwater environment with a length of 20 m and achieved bidirectional transmission with a bit error rate (BER) of approximately 10?7 at a communication rate of 26.7 Mbit/s. The experimental results show that when transmitting data files of different sizes, compared with the traditional single input single output (SISO)-UVLC system, the communication time is saved about 4 times and the channel capacity gain is consistent with the simulation. In addition, with the same water quality and communication distance, the system can achieve better BER performance.

The UAV free space optical (FSO)/radio frequency (RF) hybrid relay-link transmission rate optimization method was proposed for the mismatch of communication rate between the FSO link and the RF link, and the problem of communication service state change caused by ground multi-user movement. Taking user fairness, minimum quality of service and total UAV power as constraints, a free space optical communication/radio frequency (FSO/RF) hybrid communication downlink model through UAV relay was established, and a joint optimization algorithm based on UAV dynamic trajectory and transmitting power was proposed. Using successive convex approximation and Lagrange dual function method, the original nonconvex model was transformed into a convex optimization problem for solving. Analysis of the link transmission rates at different visibility levels shows that both the FSO link and the RF link reach full-speed transmission when the visibility is 1.7 km. The proposed algorithm has a 447.5% improvement over fixed relay and a 32.5% improvement over non-power optimization algorithm link in average communication rate.

The increase of working temperature of fiber-optic gyroscope (FOG) is mainly limited by the optical path system, which can be improved by optimizing the control scheme. Through the theoretical analysis of FOG optical system, the FOG control scheme based on dynamic temperature control was proposed. The improved effect of the was verified by experiments. On the one hand, the dynamic temperature control scheme of FOG can reduce the power consumption at high temperature and improve the high-temperature working temperature. On the other hand, it can reduce the change of FOG scale factor caused by the temperature fluctuations.