Underwater Full Duplex Optical Communication System Based On OOK Modulation And LED Array

With the increasing demand for Marine development,underwater wireless communication technology arises at the right moment.Visible light communication technology,as one of the underwater wireless communication technologies,has attracted extensive attention in recent years.The technology uses light of visible light band as information carrier to communicate in water through transmission of optical signals,overcoming the need to lay optical fiber and other transmission media restrictions,but also has the advantages of strong information carrying capacity,fast transmission rate and strong anti-electromagnetic interference ability.Underwater wireless optical communication technology can build short distance communication network in the underwater,in the military field of underwater unmanned combat cluster system,has a broad application prospect.This paper based on underwater wireless optical communication technology system design.In terms of scheme selection,this paper firstly simulates the effects of seawater on light scattering and absorption,and verifies the conclusion that blue-green light with a wavelength of 450 nm to 530 nm is the best underwater optical communication carrier.After comparing and comprehensively considering the transmission power,bandwidth,transmission capacity and other parameter performances of OOK(On-Off Keying),PPM(Pulse Position Modulation),DPPM(Differential Pulse Position Modulation)and DPIM(Digital Pulse Interval Modulation),OOK modulation is selected as the modulation mode of this system by virtue of its advantages such as minimum required bandwidth and maximum transmission capacity.This paper designs a hardware circuit platform of underwater wireless optical communication based on STM32F1 microcontroller.The whole hardware circuit platform includes Single chip microcomputer minimum system,power supply module,transmitting module and receiving module.In order to realize full-duplex communication,the transmitting and receiving processing systems are integrated together.Three high-power LED(Light Emitting Diode)s form the transmitting array to increase the reliability of the system information transmission.The receiving and processing module is composed of mutual impedance amplifier circuit,first-order filter circuit,automatic gain circuit,level conversion circuit and comparison circuit,which is used to realize the photoelectric signal conversion and the function of processing electrical signals.Then,based on the design rules of high-speed signal processing circuit board,PCB(Printed Circuit Board)design is carried out for the hardware circuit platform of this system.This paper completes the program design of underwater wireless optical communication system based on OOK modulation.Firstly,the communication frame format used by the system is designed and defined,and the system initialization program flow of the microprocessor is discussed.Then,the flow of transmitting data,transmitting and receiving synchronization flow and receiving data flow are introduced.Finally,the program realizes the functions of modulating and demodulating,sending and receiving text messages.Finally,experiments are carried out on the designed optical communication system.Firstly,the hardware part of the system was debutted,and then watertight equipment was added to the underwater wireless optical communication system to carry out field underwater text transmission experiment and bit error rate test.The experimental results show that the established wireless optical communication system achieves the design goal,and the system realizes full-duplex communication mode,underwater communication distance reaches 13 m,and the maximum communication rate is 2 Mbps.