Research On RoF-WDM-PON System Based On Polarization Multiplexing And Coherent Detection Technology

With the rapid development of the information age,a great amount of new multimedia services are emerging.The demand for transmission bandwidth in communication networks is increasing,and it is urgent to improve the performance of wireless and wired.access networks.Radio over Fiber(RoF)technology,which takes the advantages of both optical fiber communications and wireless communications,is the mainstream trend in the development of wireless access networks.Wavelength Division Multiplexing Passive Optical Network(WDM-PON),as a kind of wired access network,has many advantages such as high bandwidth utilization efficiency,large network coverage,and low management costs,therefore it has great potential in the future development of wired access network.With the combination of RoF technology and WDM-PON technology,the wired and wireless access services can be integrated into an identical network system,which can improve the transmission performance of the access network and meet the diversified service requirements of users.This converged system has a good prospect in the future field of communication.This paper mainly studies the RoF-WDM-PON system to realize the mixed access of wired signal and wireless signal.Firstly,the basic principles and key technologies of RoF system and WDM-PON system are studied separately.The working principle of optical modulator and light millimeter wave based on external modulator is deduced theoretically.Several colorless Optical Network Unit(ONU)technologies are compared.The fusion theory of wired signal and wireless signal and the networking scheme of RoF and WDM-PON system is proposed.Secondly,we studied the polarization multiplexing technology,coherent detection technology and carrier reuse technology.A full-duplex RoF system based on polarization-dependent modulation characteristics of Mach-Zehnder modulator(MZM)is proposed.By adjusting the polarization state of the input optical carrier of the MZM,the two polarization directions modulate the radio frequency signal and the data signal respectively.In the base station,using the heterodyne detection technology to generate millimeter waves.Wavelength reuse technology for uplink transmission to simplifying the base station structure.The proposed RoF link is simulated and analyzed to verify its feasibility.Finally,a full-duplex RoF-WDM-PON system based on polarization multiplexing and coherent detection technology is proposed.An integrated modulation device is used for the downlink transmission:dual-polarization DPMZM.Polarization multiplexing can be performed inside the device to enable wired and wireless signals to be transmitted through a single fiber.Besides,the wired signal and the wireless signal are generated by different signal sources respectively,which can meet the personalized needs of different users.An optical filter is used at the ONU to extract the central optical carrier of the downlink radio signal for uplink wired and wireless signal transmission,which prevent from the interference of additional laser sources.In addition,the uplink and downlink signal are received using coherent detection,which improves the receiving performance.With the establishment of the simulation link of the system,the feasibility of the system scheme is verified,and the performance of the system is further analyzed.