Research On Short Distance And High Speed Underwater Communication Technology Based On Optics

Compared with radio frequency and acoustics,UWOC has a higher transmission band-width and therefore possesses a higher data rate.Owing to the advantage of high-speed transmission,underwater wireless optical communication has drawn considerable attention in recent years.Underwater wireless optical communication system has many potential applications in environ-mental monitoring,offshore exploration,disaster prevention,and military operations.At the same time,key technologies like semiconductor light source devices and Visible Light Communication(VLC)make breakthroughs constantly.Coupled with the advantage that seawater features "transparent window" characteristic towards blue and green light,the research and application of Underwater Wireless Optical Communication(UWOC)will provide a new technical means for the high-speed wireless exchange of underwater data information.This article mainly studies underwater visible light communication channel modeling as well as high-speed transmission technology and designs a UWOC transmission test system based on Light Emitting Diodes(LEDs).The main research contents are as follows:1.In view of the limitations of the existing underwater optical channel model,the optical channel model under the corresponding water quality conditions is established by simulating the photon transmission process under water based on Monte Carlo method.The traditional Monte Carlo process has been improved in this thesis according to the characteristics of the underwater optical channel.The Russian roulette design for photons with weights less than the threshold is designed to reduce the time required by the Monte Carlo simulation method.The results show that Monte Carlo method has better adaptability than simple Beer's law in complex seawater conditions by simulation.2.In light of the low transmission efficiency interfered with high inter-symbol of existing multi-carrier underwater wireless optical communication;this thesis proposes a DC-based Optical Filter Bank Multi-Carrier technology(DCO-FBMC).In improved the FBMC technology,performed Hermitian symmetry on the modulated signal,and finally added a DC offset to make it suitable for IM/DD(Intensity-Modulation Direct Detection)channels.The Extended Gaussian Function(EGF)is used as a prototype function to improve its overall transmission efficiency.The feasibility of using FBMC in underwater wireless optical communication has not been verified.This thesis solved the problem that FBMC technology is not suitable for IM/DD channels,and proved that FBMC technology is better than other multi-carrier technology.3.Aiming at the main application scenarios of underwater visible light communication,a high-speed underwater visible light communication system is designed and implemented and this system is tested in water.This thesis provides detailed modules and functions of Under-water Wireless Optical Communication System and a multi-carrier technology of optical filter bank based on DC bias is proposed to show that this system has a higher transmission rate at a short distance.