Design And Implementation Of Optical Links For Digital And Analog Hybrid Signal Transmission

With the rapid development of technology,Radio-over-fiber technology has been applied to RFID,Internet of things,satellite communications,ect.The trend of the future network must be high mobility,high flexibility,large capacity,high speed,seamless connection,intelligent mangement and ubiquitous service.But there are also many technical problems.Because of the intelligent ROF network,there's a problem about the hybrid transmission of the digital control data and the radio frequency signal.It can solve the signals transmission flexibility by using Subcarrier multiplexing technology.So we solve the hybrid signals transmission of the intelligent ROF system by using subcarrier multiplexing technology.The achivements are as follows,The intelligent ROF network contains the optical transmission medium,the remote antenna,remote network monitoring module and the center.the The optical fiber is used as the transmission link between the center and the remote antenna.The optical fiber is used as the transmission medium,which has the characteristics of long transmission distance,large transmission capacity,low loss,ect.Remote network monitoring module can detect the optical power and other information of the remote optical module which is the part of the remote antenna.The detected information is transmitted to the center.The center of the system which contains the control station,the information processing part and the exchange station can centralized the management of the ROF system.The center will process the detected information and adjust the parameters of the remote optical module.While weakening the function of the remote antenna unit can reduce the cost and power consumption.In the whole communication system,threre are two kinds of signal,the digital signals include the optical power data which the remote network monitoring module detected and the control data from the center to adjust the the parameters of the remote optical module.The radio frequency signal is a useful information which is in a certain frequency range.According to the principle of sub carrier multiplexing,the digital signal is converted into 433M analog signal by frequency shift keying.The converted signal is coupled with the radio frequency signal.And then the coupled signal transmits through optical fiber.The process of the reception is the opposite.By designing the hybrid ROF transmission link which transmits the digital control data and radio frequency signal,It ensures that the center can receive the correct data from the remote module and send the correct control signal to adjust the the parameters of the remote optical module without affecting the normal transmission of the radio frequency signal.At the same time,the digital signal is as small as possible in the transmission process.