Design Of Underwater Wireless Optical Communication System Based On Blue-green Light

With the constant consumption of resources,the social development is restricted by the shortage of resources.Marine resources are rich in mineral resources and biological resources,and the exploration and development of Marine resources are inseparable from the support of communication technology.The types of underwater information transmission are mainly divided into wired communication and wireless communication.Wired communications require cables to connect,and flexibility is limited by the complex undersea environment Wireless communication has high flexibility,mainly including underwater acoustic communication and Underwater Wireless Optical Communication(UWOC).The most mature is underwater acoustic communication,which has long transmission distance but slow communication speed.UWOC has fast transmission speed,but the attenuation of light in seawater is large,so UWOC is suitable for underwater high-speed communication scenes at close range.Under this background,this paper designs an underwater wireless optical communication systemThis paper studies the influence of seawater on light and the modulation mode of light.The influence of seawater on light mainly includes the absorption effect and scattering effect of seawater on light,and the influencing factors are mainly water molecules,yellow substances,chlorophyll and non-pigment suspended particles in seawater.It is verified that the attenuation coefficient of light with wavelength of 450-550nm in seawater is the minimum.In this paper,OOK,SIR,PPM and DPIM modulation modes in UWOC are analyzed,and DPIM with high bandwidth utilization and energy utilization is selected as the modulation mode of the system.This paper designs the hardware and program of UWOC system.The hardware system is based on STM32F4 microprocessor,and the basic circuit and optical communication circuit are designed.The basic circuit consists of a power supply circuit,a human-computer interaction device circuit and a storage device circuit.The optical communication circuit consists of transmitter circuit and receiver circuit,in which the transimpedance circuit and automatic gain circuit are used to realize signal conversion and amplification.In order to increase the transmission distance,an optical system based on Fresnel lens is designed.This paper wrote the underlying driver based on FreeRTOS operating system,transplanted the FATFS file management system,designed the cache program,and realized the man-machine interaction and data storage function.This paper focuses on the design of optical communication protocol program,the implementation of optical communication DPIM modulation and demodulation,data frame packaging and unsealing,data transmission and receiving management mechanism,so as to achieve text transmission and voice transmission functions.In a word,this paper designs a UWOC system based on the actual application environment.The transmission and reception are integrated into the same system through duplex communication,and the experimental verification is carried out to effectively realize the functions of voice communication and text communication.