White LED Is Some Key Technologies Of Optical Communication Research

With the "smart" proposed,visible light communication has become the theme of today's society.Many people are thinking: How to pass the time on the plane? How to deal with the urgent business on the plane? How can the surgery be operated without electromagnetic interference in the hospital? How can the communication be carried out without the use of electromagnetic signals in the mine? In order to solve these problems,people think a lot of ways,visible light communication arises at the historic moment.In optical communication,People do not have to worry that the electromagnetic interference will affect the normal operation of the aircraft;there is no need to worry about the effect of electromagnetic on surgery in hospital;also there is no need to worry about because of the role of magnetic sparks,make people suffer mine disaster.Due to various reasons,the advantages of visible light communication can be more prominent,so the visible light communication has become a hot spot of communication research.There are a variety of modulation modes in the visible light,such as: Frequency shift keying modulation,Amplitude shift keying modulation,phase shift keying modulation,orthogonal frequency division multiplexing(OFDM)modulation and so on.The proposed OFDM modulation technique solves many problems which can not be solved by modulation.For example: Because of its orthogonality,the bandwidth is saved;after the cyclic prefix is added in OFDM,the problem of inter symbol interference is solved.On the basis of previous studies,this paper makes further research on the communication.Through further study,this paper chooses to OFDM modulation method to carry out the modulation and demodulation.In visible light communication,based on the OFDM modulation in the presence of inter symbol interference(ISI),in order to remove the inter symbol interference signal,in the OFDM system joined the cyclic prefix(CP),in cyclic prefix using synchronization algorithm,and carries on the further analysis and research.The algorithm of this paper is the maximum likelihood estimation algorithm,and then the time domain equalization algorithm based on decision feedback is studied.Coupled with the time domain equalization of cyclic prefix due to the nonlinear equalizer,and the nonlinear error rate is smaller than the linear error rate.And the application of decision feedback equalizer in cyclic prefix can reduce the inter symbol interference caused by multipath fading and the instability of the channel.In this paper using MATLAB as simulation tools,setting up the module in Simulink,The simulation results show that the OFDM modulation and demodulation simulation graphics.Through the simulation analysis,it is found that,when the signal to noise ratio is lower,the addition of Gauss white noise will seriously affect the transmission of the signal;When the SNR is relatively large,the interference between the channels will seriously affect the transmission of the signal.