Research On Channel Adaptive Control Technology Of Underwater Blue-green Optical Communication

Underwater wireless optical communication realizes high-speed transmission by using low attenuation window of blue-green light band of sea water.It is the key technology to realize close-range high-speed underwater wireless communication,and has the advantages of high speed and low power consumption.However,in practical applications,the dynamic changes of the underwater environment and channel differences have an impact on the stability and reliability of underwater wireless optical communication with specific modulation formats and rates,which puts forward an urgent need for channel adaptive regulation of underwater wireless optical communication.In this paper,the adaptive control problem of underwater wireless optical communication system is studied.The flexible modulation technology,time division duplex communication and control protocol and channel adaptive communication system are proposed,designed and implemented.The main work of this paper includes:Firstly,the modulation format and communication rate switching and bidirectional control protocol of underwater wireless optical communication based on time division duplex mode are designed and implemented.The underwater wireless optical communication system can perform real-time switching between OOK(On-off Keying)and PPM(Pulse-position Modulation)modulation formats and 5Mbps,6.25Mbps,12.5Mbps,25Mbps pulse modulation rates.Secondly,a channel adaptive communication system with automatic switching of transmission mode is designed and implemented.The communication system can complete the best signal reception according to the current channel environment,automatically switch to the best transmission mode,and establish a two-way stable communication.Compared with the communication system with 25Mbps OOK transmission mode,the farthest communication distance of the channel adaptive communication system increases by 7.6 attenuation lengths.Compared with the communication system with 5Mbps PPM transmission mode,the maximum service rate of the channel adaptive communication system is increased by 20.34Mbps.Thirdly,the underwater wireless optical communication system based on channel adaptive control technology is built,the channel adaptive control function is verified,the Ethernet service transmission function of the communication system and the communication performance of each transmission mode are tested.There are five transmission modes that the communication system can switch:5Mbps PPM,12.5Mbps PPM,25Mbps PPM,12.5Mbps OOK,25Mbps OOK.The corresponding maximum service rates are:1.06Mbps,2.67Mbps,5.35Mbps,10.7Mbps,21.4Mbps.When the packet loss rate is 0,the minimum received optical power is:55.72dBm,-54.86dBm,-53.71dBm,-51.07dBm,-48.12dBm.