Research On Modulated Retro-Reflective Free Space Optical Communication System

As one of the key technologies of optical communication,the free-space optical(FSO)communications is used to construct the high-speed wireless communication links.The FSO technology has the advantages of ultrahigh data rate,anti-electromagnetic interference,high security,small size and light weight.The technology utilizes narrow laser beam for the signal transmission in free space channel.To establish a stable bidirectional communication link,it is difficult to achieve alignment between two communication nodes in a long free space channel transmission.The traditional FSO communication link establishes a bidirectional communication link by configuring a high-precision acquisition,pointing and tracking(APT)systems at both terminals of the communication system.However,APT system not only increase the size,weight and power consumption of the communication link terminal to a certain extent but also reduce the payload of the terminal.For the above issue,this paper proposes a modulating retro-reflector free-space optical(MRR FSO)communication system,which is an asymmetric FSO system based on a MRR.The MRR FSO system dispense with a terminal's transmitter and ATP system by replacing another one terminal of traditional FSO system communication link with MRR terminal,thus reducing the size,weight and power consumption of the terminal.The research work and related results of this paper mainly focus on the principle and design scheme of the MRR FSO communication system,which details are as follows:Firstly,this paper discusses in detail the basic principles and system construction of MRR FSO technology.The technical points and precautions of each part of the system are presented,and the matching conditions of each part of the MRR FSO system are given;the modulation principle of the optical modulator commonly used in the MRR terminal is introduced,and the modulation characteristics are experimentally studied.Then,paper analyze the influence of atmospheric turbulence on laser signal transmission,the channel model of laser signal transmission in the atmospheric channel is established.The theoretical research and performance analysis of full-duplex modulation and demodulation scheme of the MRR FSO system is deeply studied.Finally,based on the current experimental conditions and the actual problems in the device matching process,designed optical transceiver and MRR scheme in MRR FSO system.Produce the high-speed uplink based on fiber-optic communication devices and the downlink based on acousto-optic modulators(AOM).The preliminary function verification of the short distance MRR FSO system was carried out on the atmospheric turbulence simulation chamber.And the long-distance MRR FSO experimental system was built in the real atmospheric turbulent environment to test the performance indicators of the system.