Research On Dynamic Control Technology In Underwater High-Speed Blue-Green Laser Communication

The collection and development of marine resources are almost inseparable from underwater communication.Underwater blue-green laser communication,as a new underwater communication method that transmits information by optical waves,has a higher transmission bit rate and wider communication bandwidth than traditional underwater acoustic communication and underwater radio frequency communication.At the same time,the blue-green laser communication system has the advantages of small volume,low cost and high flexibility,which has broad application prospects in underwater environmental monitoring,offshore exploration,underwater networking and military operations.However,due to the complex marine environment,the received signal power of the laser communication system changes dynamically according to the change of communication distance,channel attenuation,platform jitter,underwater turbulence,and air bubbles.These effects reduce the performance of the communication system.This paper focuses on the dynamic fluctuation of the underwater received signal power,and studies the dynamic control technology applied in underwater high-speed blue-green laser communication.Then,an adaptive control system based on liquid crystal light valve(LCLV)and gain of photomultiplier tube(PMT)controlled technology is proposed,which realizes large dynamic range signal reception.The main work and innovation of this paper include:Firstly,an underwater blue-green light communication darkroom experimental environment based on high sensitivity PMT receiver is built,and the effects of different signal optical power,detector gain,bandwidth and other parameters on the UWOC system receiving performance is experimentally studied,then the optimal signal receiving relation of the system is established.Secondly,aiming at the limited receiving range and easily to be affected by the fluctuation of signal power in underwater blue-green optical communication system,the characteristics of various control methods are analyzed and compared,and the variable transmittance characteristics of electronic control LCLV and variable gain characteristics of electronic control PMT are studied experimentally,and the dynamic control method to achieve the best signal receiving based on the joint control of LCLV and gain of PMT is obtained,which provides an effective basis for the parameter selection and design of dynamic control system.Thirdly,a j oint dynamic control system based on LCLV and gain of PMT is designed and verified by experiments.The results show that dynamic receiving range of the system can be extended to 68dB(-63dBm?5dBm)at 100Mbps signal transmission rate modulated by OOK,and the bidirectional real-time data transmission with the transmission rate of 12.5mbps is realized in a 50m long pool.