Optical antenna is used to transmit or collect optical signals in free space optical communication system, and the structure of optical antenna determines the detection performance of the system. This paper introduces the basic structures of optical antenna, the research progress of Cassegrain optical antenna, pointing, acquisition and tracking(PAT) system without independent beacon and the point-to-multipoint optical antenna in detail, the future research direction of optical antenna is prospected.

In order to improve the performance of free space optical communication system with multiple apertures transmitting, based on the "Research and verification of key technologies of marine high speed communication network" project, an analytical expression of bit error rate(BER) is proposed. The communication system uses intensity-modulation with direct-detection (IMDD) and works in a turbulent environment described by exponentiated Weibull(EW) distribution model. The aperture averaging effect under different channel parameters and the impacts on the average BER with different transmitting aperture numbers and communication rates are analyzed. The simulation results show that the multiple apertures transmitting system has good turbulence suppression ability at low communication rate. The difference of arrival time caused by different transmitting apertures will increase the bit error probability of the communication system at high communication rate.

The inter-satellite laser communication terminal has the advantages of small size, high communication rate and strong confidentiality, which is the first choice for large-scale constellation networking in the future. In order to further improve the communication rate and practicability of laser communication terminals, two types of laser communication terminals based on the swing mirror architecture are developed by using incoherent laser communication technology, beacon-free capture technology, prelight amplification and single-mode fiber coupling technology, and 3D printing thermal conductivity integration technology. Dynamic capture and tracking, high-speed communication test and environmental adaptability test are completed. The weight of the two models is 12 kg and 14 kg respectively, the average capture time is 12.4 s in 1 mrad uncertain region, the communication rate can reach 10 Gb/s@4000 km, and the bit error rate is less than 10-7 after forward error correction coding.

In order to minimize additional overhead and find the optimal transmission path, combined with the characteristics of line of sight transmission and long-distance transmission of laser communication, a deep space optical communication network routing algorithm(RA-ACA) based on ant colony algorithm is proposed. Firstly, the unidirectional link problem and node energy consumption problem in deep space optical communication are studied, and then RA-ACA is optimized based on the traditional routing algorithm. Finally, the simulation and comparison experiments are carried out. The simulation results show that the total remaining energy on the convergence path of RA-ACA is about 5 kW·h higher than that of TACA, and the convergence speed of RA-ACA is increased by 50% when it retains the node pheromone.

In order to further improve the speed and reliability of atmospheric optical communication systems, a back-propagation(BP) neural network assisted signal detection method is proposed to improve the bit error rate for pulse position modulation(PPM) and quadrature phase shift keying(QPSK) hybrid modulated faster-than-Nyquist(FTN) atmospheric optical communications system. BP neural network is utilized to extract the channel characteristics, which improves the bit error performance of the system in time-varying atmospheric channels. The simulation results show that compared with the maximum likelihood detection, the system bit error performance can be improved by 2.0 dB and 1.5 dB when the acceleration factor is 0.8, the bit error ratio is 10-3, and the roll off factor is 0.6 and 0.7, respectively. When the acceleration factor is 0.8, the bit error ratio is 10-4, and the roll off factor is 0.8 and 1, the system bit error performance can be improved by 2.0 dB and 1.8 dB, respectively.

In view of the characteristics of satellite link in space laser backbone network using advanced orbiting systems(AOS) frame for data transmission, limited on-board resources and long data transmission delay, in order to realize label switching and traffic engineering in satellite optical networks, the standard route based restricted label distribution protocol(CR-LDP) is impro-ved, including setting a fixed length for the size of protocol messages, designing a connectionless transport layer protocol, reducing protocol overhead and improving the establishment process of bidirectional label switching path(LSP), and then the software simulation and hardware test are carried out. The results show that the improved CR-LDP protocol has less resource consumption, supports bidirectional LSP establishment, and the process is simple and effective.

Coherent detection has the advantages of fast response, high detection sensitivity, and good filtering performance, compared with direct detection. It is a key to improve the receiving sensitivity of optical wireless communication system. This paper summarizes the research progress in the field of coherent detection of optical wireless communication system, and introduces the research work of Xi'an University of Technology in the field of coherent detection technology, including the influences on the performance of wireless optical communication due to atmospheric turbulence suppression, angle of arrival fluctuations, amplitude fluctuations, channel noise, optical signal polarization, local oscillator optical power and light source linewidth, and the performance analysis of subcarrier modulated non-optical heterodyne detection system in ideal and non-ideal channels. Finally, the development direction of wireless optical coherent communication technology is prospected.称号。

In order to further analyze the feasibility of Airy beam in optical communication, taking Airy beam as the carrier, the average bit error rate, outage probability and average channel capacity of free space optical(FSO) communication system based on lognormal distribution turbulent channel model under weak turbulence are studied, and the performance of FSO communication system with Gaussian beam as the carrier under the same turbulence conditions and transmission distance is compared. At the same time, the effects of beam width, exponential truncation factor and propagation distance of Airy beam on system performance are discussed. The simulation results show that under the same turbulence conditions and transmission distance, the performance of FSO communication system based on Airy beam is significantly better than that based on Gaussian beam, and with the increase of average signal-to-noise ratio, the link performance advantage of Airy beam as carrier is more significant.

Aiming at the problem that the short-term high temperature of optical fiber composite low-voltage cable(OPLC) in operation affects the transmission performance of optical fiber in the cable, a heat-resistant OPLC structure optimization scheme is proposed. Firstly, the OPLC structure is optimized and improved, and the OPLC material selection is studied. Then, the COMSOL multi-physics field simulation software is used to realize the simulation modeling of the heat-resistant OPLC three-dimensional model, and the simulation model is modified according to the current thermal effect and the reaction principle of temperature on the resistance, so as to explore the three-dimensional thermal field distribution of the cable in the simulation state under the optimized structure. Finally, combined with the current OPLC heat resistance test requirements, the test scheme of heat resistance and overload test suitable for heat-resistant OPLC is studied. The test results show that the fiber attenuation loss of OPLC is less than 0.15dB/km when the temperature is 10% higher than the maximum standard temperature for 15 min.

The new generation of submarine optical cable communication network will not only have the communication function of the traditional submarine optical cable communication network, but also provide plug and play, stable and reliable information transmission and power supply for submarine users. It can be used as a common information infrastructure for application systems such as submarine observation, navigation and positioning, and submarine communication. Focusing on the construction of a new generation of submarine optical cable communication network, this paper carries out preliminary basic research for the underwater internet of things required to serve various submarine prefabricated systems and unmanned autonomous systems in the future, introduces the latest development of the latest submarine optical cable information transmission network and its related equipment, as well as the development trend in this field, and finally points out the difficulties faced by the current submarine optical cable network.

In order to realize high-efficiency coupling between grating couplers and optical fibers, a low-loss, small-size silicon nitride grating coupler compatible with complementary metal oxide semiconductor(CMOS) process has been successfully designed and developedbased on the ultra-low loss Silicon nitride platform of United Microelectronics Center(CUMEC). Firstly, the key parameters of grating are simulated and the optimal parameters are selected to design the grating coupler. Then, the gratingis preparedbased on CUMEC ultra-low loss silicon nitride platform with good line-width structures.Since the focused grating structure is adopted, the size is reduced. An optical test system was built to characterize the performance of the focusing grating. The test results showed that the optimal loss was 4.48 dB at 1548 nm, and 1 dB bandwidth was greater than 45 nm.

In wireless channel system, co-site interferencewill cause the receiver's reception sensitivity to decline. Based on microwave photonics technology, according to the nonlinear characteristics of intensity modulated direct detection(IMDD) optical link, a radio frequency co-site interference suppression method is proposed. Firstly, the mathematical model of the output power of IMDD optical link is established, and the output power of interference signal and useful signal is described by mathematical equation. By making the output of interference signal zero, the solution of the equation is obtained, and the conditions of interference suppression are obtained. Then, through Matlab quantitative calculation, the curve of the output power of interference signals and useful signals in the link changing with the input interference signal power is obtained, the power output point of interference suppression is obtained, and the influence of half wave voltage on interference suppression is analyzed. The experimental results show that the suppression ratio of this method can reach -64.5 dB, and the output power of the useful signal is only lost by 6.4 dBm, which has excellent interference signal suppression ability.

In order to realize rapid opening and efficient maintenance of services, this paper designs an intelligent optical fiber dispatching system, which uses electronic labels to identify optical fibers, and provides clear guidance through optical port light-emitting diode(LED) real-time status indicator and network management information, completes the detectability, percep-tion and visualization of the optical path. The two-way optical path scheduling experimental results show that compared with traditional optical fiber dispatching system, using intelligent optical fiber dispatching system can effectively shorten the service opening time.

Aiming at the problem of inter-cell interference in indoor visible light communication(VLC) systems, a resource allocation algorithm for multi-cell coordinated multiple-input multiple-output(MIMO) orthogonal frequency division multiple access (OFDMA) VLC system with joint light source layout is proposed. First, without affecting the lighting, by optimizing the light source layout, the cell interference is limited to the coverage of two LEDs. Then, cooperative MIMO technology is introduced to take user fairness as the optimization goal. Finally, the resource allocation performance of MIMO OFDMA VLC system for two cooperative modes(SMP) and repetition coding(RC) is simulated. The simulation results show that the performance of the MIMO OFDMA VLC system of the two cooperative modes is better than that of the single-input single-output(SISO) OFDMA VLC system. The VLC system based on RC mode is robust to channel correlation, and its transmission rate is about 1.2 times that of the SISO OFDMA VLC system. When the channel matrix condition number is lower than six, the VLC system based on the SMP mode has better performance because of the larger multiplexing gain. When the channel matrix condition number is equal to two, the data transmission rate of the VLC system is approximately that of the SISO OFDMA VLC system 1.32 times.

In order to solve the problems of high energy consumption of imaging positioning and complex of non-imaging positioning equipment in indoor visible light positioning, an indoor visible light location method based on mobile phone ambient light sensor is proposed in this paper. Firstly, the original frequency of the signal sent by the light source are solved by using the frequency folding effect and the light source label recognition algorithm. Then through the light source frequency coordinate database established in advance to obtain the light source position, so as to obtain the equipment position. The experiment result shows that this method can realize the light source identification and equipment positioning in the light source coverage area on the premise of low power consumption and low calculation, the positioning accuracy depends on the light source density.

Aiming at the problems of static working point instability and signal distortion when using Mach-Zehnder(M-Z) interference structure in low frequency signal demodulation, a low frequency signal demodulation method based on M-Z interference structure is proposed. Phase compensation is carried out while phase modulation of interferometric detection system, and the traditional phase generation carrier method is improved by introducing direct-current filter. The optimal modulation depth is determined by software simulation, and the demodulation system is built to test the frequency and amplitude of low-frequency acoustic signals. The experimental results show that this method can successfully demodulate the low frequency signal with amplitude of 2.5 rad and frequency of 0.1 Hz, and the linearity of the signal frequency of 20 Hz is as high as 0.9995.

With ultra-high invulnerability of the requirements of the network, how to use incremental deployment of resources in order to enhance their business planning configuration way dynamic recoverability, a combined network growth planning algorithm for dual link faults(CA-DF strategy) is proposed, integer linear programming(ILP) model is established, and a simula-tion calculation was carried out. The simulation results show that CA-DF strategy can effectively improve the dynamic recovery rate under dual-link failure while adding as few network resources as possible.

In order to improve the efficiency of path calculation and the dissimilar of planning paths of K-short path(KSP) algorithm. First, this paper introduces the graph theory description of optical network, definition of path similarity and parallel edges theory. Then it describes the KSP problem and the traditional Yen algorithm briefly, and analyzes the research status of KSP algorithm. Finally, the paper proposes an Yen improved algorithm, and expounds the calculation strategy of dissimilar paths and the implementation steps of the improved algorithm emphatically. By constructing a topology map similar to the actual production environment, the Yen improved algorithm is verified, and the path proximity and calculation speed are compared with other algorithms to prove its effectiveness.

Since the time and date(ZDA) interface of the domestic core switching chip is generally the mobile ZDA standard interface, which is inconsistent with the Beidou standard ZDA interface of the Beidou satellite navigation system, the transmission of Beidou time cannot be realized in the backbone network with the domestic chip as the core processing unit. A conversion scheme between Beidou ZDA interface standard protocol and mobile ZDA interface protocol is designed. By comparing the similarities and differences of the two time-of-day(TOD) data frames between them in detail, the Unix timestamp is used as an intermediate medium to realize the conversion of different time expression between them. The experimental results show that under the built network environment, the ZDA output from Beidou satellite receiver can be stably converted into mobile standard ZDA, and the converted mobile time data can be parsed by domestic chips and transmitted to the core backbone network normally and stably.