Simulation Study On Techniques Of Underwater Visible Light Communication Based On LED

With the rapid development of world economic,the short of resource is becoming the main reason which restrict the development of the society.There are huge resources in the ocean which make up seventy percent of the world and the ocean is becoming more and more important in human life.The communicaton and data transmission is the guarantee for the exploitation of ocean resource. So,more and more attention is paid for the underwater communication.Underwater sound communication and underwater light communication are the main ways of underwater communication.They both have advantages and disadvantages.There are many advantages of underwater communication such as high speed data transmission n huge bandwidth?safe transmission?less consumption and tiny delay.With the development of information technology and better performance optics device,underwater light communication is becoming more and more important in many field such as the detection of ocean environment?the exploitation of ocean resource even the guarantee of country safety.Unerwater wireless light communication system is made up of emittion unit?underwater channel and reception unit. Filter is essential in emittion unit.The foundation of underwater channel model is based on the confirment of the impression of sea water to light.And the selection of modulation is also a very important job. So,this paper made researches on the above aspects.Firstly, This paper introduced common ways of underwater communication and the development of underwater communication domestic and abroad. We introduced constitution of underwater communication?laser light source and LED light source.Secondly, we deduce the formula of received light power and geometry loss of light.Then we compute and formulate the geometry loss of light. Based on the research of the characteristics, the system analyzed the impression of each component of the seawater to the scattering and absortion of light and analyzed the result.Thirdly, to realize the underwater communication and extract the useful signals from the bacdground light, this paper design five types of filter by using photonic crystal: single channel narrow band filter?wide bandgap single channel narrow band filter?single channel broadband filter?omnibearing single channel filter and omnibearing double channel filter.Then we analyzed and simulated the performance of the filter by using transmission matrix and analyzed the result.Finally, we compared different modulation systems. First, we introduced the formation of OOK?PPM?DPPM?DPIM?DHPIM?DAPIM?FDPIM. Then we compared the performance of the seven modulation systems by simulaton and computation. The result provide a reference for the selection of underwater light communication.