With the continuous development of laser communication technology, UAV-based laser communication ATP system is gradually developing towards lightweight and miniaturization. This paper presents a multiplex system based on fourquadrant detector, which integrates tracking and communication. By using a four quadrant detector, the precision tracking detector and communication detector in conventional laser communication systems are combined into one. This can reduce the weight, size and power consumption of the fiber optic terminal. The receiving unit uses the diversity receiving and merging function of the four quadrant detector to improve the signal-to-noise ratio and improve the communication performance.
Due to the diversity of underwater environments, it is difficult to test the underwater optical communication systems in actual seawater. This letter uses the Monte Carlo model to study channel capacity of underwater optical communications. Matlab is used to analyze the transmission of laser of various wavelengths in different water and the influence of changes in water quality. Furthermore, the influences of seawater type, divergence Angle, transmission distance and beam type on the power received by the receiver are analyzed when blue-green laser is used as the light source. The experiment shows that in the same water quality, with the increase of divergence Angle and transmission distance, the light intensity received by the receiver becomes smaller and smaller and the photon distribution becomes more and more dispersed. Compared with the Gaussian beam, when the attenuation coefficient is small, the energy of the receiving end is more concentrated when flat-top beam is used as the light source.
Due to increasing demand for high-speed and large capacity of data transmission, seamless connection between space network and Internet becomes one of the current trends of space communication. Under this background, this paper proposes an IPv6 over AOS gateway system based on FPGA to integrate the Internet and the space network. The system achieves protocol conversion to transmit IPv6 packets through the packet service in the AOS spatial data link protocol, and also has the function of address resolution and label switching. The main contents of this paper are as follows: 1. The IPv6 protocol, NDP protocol, MPLS technology and the conversion mechanism of IP over AOS protocol are studied. 2. The system test environment was set up to simulate the datagram transmission of spatial link between different node, the system performance and link stability were carried out by using logic analyzer and network packet capture tools. 3. The results of the function verification and performance test were analyzed and summarized according to packet loss rate and bandwidth availability ratio. The system achieves a variety of data types and large capacity information data transmission, it can also reduce networking costs while improving the transmission efficiency.
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