Study On Transmission Performance Of Fronthaul Networks Based On WDM-PON

With the coming of 5G era,many new application scenarios,massive data transmission and large-scale access appear.5G fronthaul network as access network is facing a huge challenge.In order to meet the needs of future communication development,it is necessary to choose a suitable scheme for 5G fronthaul network.The fronthaul network between 5G DU and AAU has the requirements of high speed,large transmission capacity and supporting a large number of AAU access,while WDM-PON can meet the needs of 5G fronthaul network.In this thesis,WDM-PON is used as the carrier scheme of 5G fronthaul network,and the transmission performance of the system is improved by combining high-order modulation technology and polarization multiplexing technology.First of all,the thesis introduces the development of 5G and fronthaul network,and lists four kinds of forward network bearing schemes: optical fiber direct drive scheme,active WDM/OTN scheme,passive WDM scheme and WDM-PON scheme.The four schemes are analyzed in detail,and the conclusion is that WDM-PON has the most advantages,such as large capacity,high speed,rich topology and so on.Then the ONU colorless technology in WDM-PON system is studied,the ONU colorless technology using FP-LD laser,the ONU colorless technology using broadband light source spectrum segmentation,and the colorless ONU using remodulation are analyzed in detail.Secondly,the WDM-PON fronthaul network based on high-order modulation technology is studied in detail,including the modulation and demodulation principle of PAM-4 signal,the characteristics of PAM-4 signal in time and frequency domain,the noise and linearity of PAM-4 signal,and the generation mode of PAM-4 signal.And then,PAM-4 signal is applied in WDM-PON fronthaul network.Based on the advantage of the high spectral efficiency of PAM-4 signals,a 50 Gb/s PAM-4 WDM-PON fronthaul system based on RSOA is proposed.The advantage of this system is that low-speed optical devices can be used to transmit high-speed signals.And described in detail the characteristics,working principle and working process of the system.Through the simulation software Optisystem,a WDM-PON simulation system with an asymmetric architecture with a single-wavelength 50Gb/s PAM-4 signal in the downlink and a single-wavelength 10Gb/s NRZ signal in the uplink is built.This asymmetric architecture WDM-PON fronthaul system can more reasonably meet the requirements of the fronthaul network.The system is tested and analyzed from the aspects of clock recovery of PAM-4 signal,the influence of dispersion on transmission signal energy,the influence of transmission distance on transmission signal energy,the influence of transmission power on transmission system and dispersion compensation method.Finally,it is concluded that both the uplink and downlink transmission systems can meet the bandwidth requirements of 5Gfront transmission network.It can be concluded that the 50 Gb/s PAM-4 WDM-PON system based on RSOA can be used as the bearer scheme of fronthaul network.Finally,based on the third chapter,the WDM-PON fronthaul network based on polarization multiplexing technology is studied.First,the polarization multiplexing technology,the characteristics of polarized light,the principle of polarization multiplexing and the related components of the polarization multiplexing system are introduced.Polarization multiplexing device is a passive device,which can be well applied in WDM-PON system.Combining polarization multiplexing technology with 50Gb/s PAM-4signal,a 100 Gb/s PDM-PAM4 signal is generated.In the WDM-PON simulation system based on polarization multiplexing technology,the 100 Gb/s PDM-PAM4 optical signal is selected as the downlink transmission signal of the system,and the 10Gb/s NRZ optical signal is selected as the uplink transmission signal of the system.Based on the theory,the transmission performance of the system is analyzed from the aspects of the influence of dispersion on transmission performance,the influence of optical power on transmission performance,and the influence of transmission distance on transmission performance.Finally,the experimental results show that the 100 Gb/s PDM-PAM4 WDM-PON system can bring more bandwidth to the fronthaul network,so improve the transmission performance of the fronthaul network.