Research On The Technical Method Of Pulse Position And Amplitude Modulation In Optical Space

Compared with the traditional airwave communication methods,wireless optical communication has the advantages of high bandwidth,good confidentiality,and large information capacity.With the development requirement of high speed and high efficiency in the future,wireless optical communication technology is facing great innovation.In the process of optical signal transmission in atmospheric,absorption,scattering,background light,bad weather and other reasons will affect the quality of beam transmission,which may reduce communication performance.Therefore,For purpose of achieving the demand of high spectrum efficiency and low error rate,It is crucial to make full use of communication spectrum resources using superior performance modulation,coding and technology fusion methods.Combined with the high spectral characteristics of pulse amplitude modulation and the high energy utilization characteristics of pulse position modulation,this paper proposed a joint modulation method using both pulse amplitude modulation and pulse position modulation on the basis of the traditional modulation,and do research about the signal modulation coding and technology realization.Compared with the traditional single modulation methods,through the coordination of the two modulation methods,the joint modulation technology transmits information using the amplitude of the pulse and the time slot where it is located,which not only reduces the average transmit power of optical equipment in terms of power consumption,but also makes use of spectrum resources effectively to improve transmission performance.This paper completed the theoretical analysis of the relationship between spatial modulation and layered mapping,and simulated the performance and data of different modulation methods.Besides,it designed a joint optical space modulation system based on laser diode array and photoelectric detectors,and constructed a hardware system with FPGA as the core for experimental testing.According to experimental data,the system finished the data encoding joint modulation of space mapping(SM)and layered transmission effectively in the atmospheric environment of a certain distance range.In this system,the transmission rate can reach 5Mb/s,and the error rate is better than 10^-4.The experimental results provide a new technical method for the subsequent application research.