Research Of Underwater High Speed Blue-green Laser Communication System And Networking Technology

With the increasing scarcity of land resources,human will change the development direction to the oceans which is occupied 71% of the earth's surface area,and oceans' s great value will promote the development of marine exploration technology.The wireless communication is mainly composed of infrared communication,radio communication and RF communication.However,these methods are not suitable for underwater environment.The main way of underwater communication is acoustic communication,but it has the disadvantages of large volume,high power consumption,low rate of communication and low bandwidth.Underwater optical communication technology has the characteristics of high speed,low cost,low power consumption and so on,so optical communication can make up for the defects of acoustic communication partly.Firstly,this paper summarizes the research of underwater optical communication technology in recent decades,and proposes a high-speed underwater blue-green laser communication system and network technology.The design index of the system is 1Mbps rate,and 50 meters distance in the case of end to end communication.Then,this paper presents the overall design of the system,,chooses laser diode and detector according to underwater optical transmission characteristic,and introduces the key technologies of underwater optical communication such as light source,photoelectric detection,modulation and networking.This paper introduces the hardware and software design of each module of the system: the system chooses STM32F407 micro controller and Ethernet circuit chip driver as control unit,chooses AD9660 laser driver chip for realizing an auto power control transmitter,chooses photoelectric detector,signal conditioning circuit,automatic gain control circuit and demodulation circuit for for realizing an auto distance control receiver.The control unit,transmitter and receiver constitute a full duplex communication system.Based on hardware design,this paper designs laser driver code,demodulation code,transplants the embedded Lw IP protocol stack for 10/100 M Ethernet,and designs a network protocol for underwater observation network which is proposed in this paper.This underwater observation network saves the sensors layout cost,time and difficulty,enhances the efficiency.Finally,the system has realized the communication test of 50 m distance and 1Mbps rate in the land environment and underwater environment.Because of this laser communication system characteristics of high speed,low power consumption and low cost,it has a certain practical value.