A data transmission system with optical fiber interface to ethernet interface is designed in order to meet the needs of high-speed and reliable data transmission such as synthetic aperture radar real-time imaging and data playback, and to solve the problems that traditional data transmission systems are not suitable for field tests due to high interface requirements, large volume and power consumption, and inflexible network configuration. This paper mainly introduces the realization method of data transmission, and puts forward an optimization strategy of three-stage ping-pong and instruction parallel to ensure the correct data and improve the transmission speed. The network configuration can be flexibly modified by means of embedded Linux system. Compared with traditional systems, the system has obvious advantages in volume, power consumption and flexibility. Experimental results show that the data transmission speed can reach 770 Mb/s.

In an outdoor visible light communication (VLC) system, a photodetector is vulnerable to strong sunlight, bright elec-tronic billboards, and numerous artificial light sources, which leads to its saturation or nonlinear behavior. To solve this problem, this paper first overviews the research progress on VLC for outdoor intelligent transportation. Then, it introduces the transceiver techniques of interference mitigation, including Fountain codes for optical channel fluctuation and occlusion, reception techniques by attenuation diversity to mitigate strong ambient light interference and detector saturation, and the auto-alignment and tracking methods under multiple light source interference. Finally, the future improvement and research direction of these interference mitigation transceiver technologies are pointed out.

For the problem that unmanned underwater vehicle(UUV) is easy to be interfered by the complex environment, which results in relative light source attitude deflection and affects positioning and communication, an underwater positioning communication scheme based on curved surface array is propseed, and a set of underwater positioning communication system based on field programmable gate array(FPGA) is designed and tested. The test results show that the system can accurately estimate the attitude of the receiver relative to the light source and adjust it. After adjusting the attitude, the communication performance of the system is improved obviously.

In view of the problem that the visible light signal is easily blocked by obstacles in the transmission, the author proposed a solution that the direct link and the diffuse link alternately transmit the optical signal. Based on this scheme, this paper uses function calculation method and experimental simulation method to analyze the response characteristics of order reflection pulse in the diffuse channel of indoor optical communication. On this basis, the response characteristics of the order reflection pulse and the influence factors of the average receiving power are discussed, and they are simulated by experiments. The experiment results show that the position of the emitting light source, the angle of the emitting light θimg and the angle of the beam diffusion θmax are the influencing factors of the average receiving power.

Fiber is one of the important ways to transmit clock signal over a long distance. The vibration of fiber will change the polarization mode dispersion of fiber, which will affect the transmission performance of clock signal. In order to reduce the impact of fiber vibration on clock transmission, the reasons of clock signal transmission degradation caused by fiber vibration are analyzed in detail, and a new anti fiber vibration transmission technology scheme is proposed. The experimental results show that the phase noise can be improved by 10~15 dB.

In view of the problems of nonuniformity of forward error correction coding(FEC) technical standards for 100G optical transmission network(OTN) equipment and difficulties in interconnection of line side interfaces, this paper first introduces the principle and defects of 100G interconnection technology for single manufacturer's equipment, and then proposes a device technology compatible with line side coherent interfaces of several manufacturers' 100G OTN equipment. The module of analog / digital, digital / analog and data pre-processing is introduced between the analog coherent optical(ACO) functional unit and the digital signal processing(DSP) chip to complete the high-speed analog / digital, digital / analog conversion function. Through the data pre-processing function, the manufacturer's category information of the signal is analyzed and the back-end DSP chip is selected and switched. The experimental results show that the equipment scheme can be compatible with 100G OTN equipment of several manufacturers.

Aiming at the problems of high pilot overhead of traditional channel estimation algorithm and low frequency utilization of the underwater direct current optical orthogonal frequency division multiplexing (DCO-OFDM) system, an underwater optical channel estimation method based on compressed sensing depth-first multi-path matching pursuit (MMP-DF) is proposed. Based on the frequency domain response at the pilot frequency of DCO-OFDM system, this method constructs a compressed sensing model applies the MMP-DF algorithm to underwater optical channel estimation, and then estimates the channel time-domain impulse response. Simulation results show that in the DCO-OFDM system, compared with the traditional channel estimation algorithm, this method requires less pilot overhead and high estimation accuracy. When the number of pilots is small, the estimation accuracy of MMP-DF algorithm is better than orthogonal matching pursuit (OMP) algorithm.

In order to solve the problem of service conflict in space division multiplexing elastic optical network nodes, full range spectrum converter(FRSC) and space selection switch(SSS) are configured in the dynamic function node structure to convert the spectrum of conflicting services. Based on this node structure, a spectrum conflict resolution algorithm based on spectrum concentration(SCRASC) is proposed. This algorithm comprehensively considers the used spectrum block ratio and the distance between the free frequency block spectrum and the largest spectrum block to optimize the frequency of the spectrum concentration. Simulation results show that the algorithm achieves better performance in terms of bandwidth blocking rate.

Aiming at the crosstalk and noise problems of wireless optical signal transmission in space laser communication, combined with constant modulus algorithm (CMA) and least mean square (LMS) algorithm, a two-stage cascade variable step size adaptive equalization algorithm——CMA-LMS equalization algorithm is proposed, the size of the step factor has a nonlinear relationship with the theory in a certain range. The product of the theoretical data and the step factor is used to update the algorithm variables to achieve the nonlinear adaptive equalization of the channel. The experimental results show that the CMA-LMS equalization algorithm can improve the performance of the system, and under 16 quadracture amplitude modulation (16QAM), CMA-LMS equalization algorithm can effectively suppress the noise and crosstalk of the system.

In order to solve the problems of large delay and low channel utilization of existing dynamic bandwidth allocation (DBA) algorithms in fiber-wireless(FiWi) networks, a low latency distributed DBA(LLD-DBA) algorithm is proposed. Each polling cycle of LLD-DBA consists of two sub-cycles of wireless reporting and upstream data transmission, which can be carried out in parallel on the wireless channel and the upstream channel, respectively. The bidirectional polling is adopted in the sub-cycle of wireless reporting, and each node can transmit the Gate frame to its neighbor node and upload its data in parallel. Extensive simulation results show that compared with the existing algorithms, the proposed algorithm can reduce the average packet delay, average queue length of nodes, and improve the utilization of upstream channel.

In order to solve the problem of excessive spectrum fragmentation in elastic optical networks, this paper proposes an odd-even partition spectrum assignment algorithm based on holding time. The algorithm considers the factors such as the mixed line rate services and the holding time for services, according to the different types of services in the link, the special area is divided into two types: odd and even, which makes the adjacent odd and even areas form a shared area and improves the success rate of service transmission. Combined with the holding time of the services, a partition-time combine strategy is adopted to effectively reduce the spectrum fragmentation in the time domain. The simulation results show that the algorithm can effectively reduce the bandwidth blocking probability and improve the spectrum utilization ratio.

Optical fiber embedding technology is the key to realize distributed optical fiber sensing of transformer winding. In the winding process of transformer, the copper flat wire needs to be stretched, bent and twisted to a certain extent. In this process, the optical fiber is often stretched and broken. In order to optimize the process of embedding optical fiber into the winding line of transformer, 200 m optical fiber is embedded into the winding line in the experiment, and the strain of the whole processing process of the winding line is monitored by using fiber Bragg grating(FBG), and the strain values of different links in the process of copper flat wire winding are obtained. The test results show that the maximum strain of the optical fiber in the process of copper wire winding is in the position of the take-up machine, about 4800 με, which is within the tolerable range of the optical fiber. The optical fiber is not broken and the FBG does not chirp in the whole process.

Aiming to the problems of slow modulation speed, high loss, and large package size of traditional electro-optic modulators, an electro-optic modulator based on oscillating microring is proposed by using high electro-optic coefficient polymer materials and the theory of slit waveguide. The key performance of the modulator is analyzed by using COMSOL Multiphysics and Lumerical FDTD solutions simulation software. The analysis results show that the electro-optic modulator has excellent photoelectric performance under the condition of small package size and is compatible with complementary metal oxide semiconductor(CMOS) standard manufacturing process.

Plastic optical fiber(POF) is widely used in the detection of high-energy physical cosmic rays. The quality of the optical fiber end face determines the performance of the detector largely, thus affecting the accuracy of cosmic ray spectrum and composition measurement. In this paper, the BCF-92 POF used in the electromagnetic particle detector of the high altitude cosmic ray project is taken as the research object. The image of the optical fiber end face is preprocessed by the way of Matlab image processing. The geometric parameters of the end face of the core cladding are determined by the iterative least square ellipse fitting method, and the end face out of roundness is calculated. The experimental results show that 95.4% of the sample optical fiber is qualified, and the average non circularity of the end face is about 0.75%. This method can meet the detection requirements of high altitude cosmic ray project.