Demonstration Of Symmetrical 50G-PON Transmission System Based On SOA

With the advent of the 5G era,various high-bandwidth new demands and new services continue to emerge,such as autonomous driving,4K/8K video streaming services,VR/AR and 3D video games,driving the explosive growth of Internet traffic.In order to meet the user's demand for network bandwidth,there is an urgent need to increase network capacity.50G-PON was selected as the evolution target of the next-generation PON network due to the obvious capacity increase and less wavelength resource occupation.Considering the system cost and the development status of high-bandwidth devices,this paper will use 25 G optical transceiver devices to complete the 50G-PON system transmission experiment.Then it will face the problem of insufficient bandwidth,and the dispersion tolerance gradually decreases with the increase of the single wavelength bit rate.How to overcome the problem of inter-symbol interference caused by insufficient device bandwidth and reduced dispersion tolerance,and reach a link budget of up to 33 d B is the focus of this paper.This paper verifies the feasibility of the experimental structure of a symmetrical 50G-PON system based on low-bandwidth optical transceivers.The downlink uses 25 G EML and 25 G APD to complete a single-wavelength 50 Gb/s signal transmission,the uplink uses 25 G EML and 35 G PIN to complete the same rate signal transmission.In order to compensate for the high fiber transmission loss in the O-band and achieve the high link budget requirements,a semiconductor optical amplifier(SOA)was introduced in the experiment.In order to reduce the system cost as much as possible,SOA is placed at the optical line terminal(OLT)in the uplink and downlink experiments.To maximize the link budget,this paper initially investigates the performances of SOA as a booster amplifier with different gain in the downstream.There is a trade-off between receiver sensitivity and launch power.As a result,when the input power of SOA is-2 d Bm,the system can reach the best optical receiving sensitivity of-25.78 d Bm.A maximum link budget of 36.74 d B can be obtained with an input power of 2 d Bm.In order to compensate the Intersymbol interference(ISI)caused by limited bandwidth and fiber dispersion,this paper studies the performance of NRZ and PAM-4 signals in the uplink and downlink under three electrical domain equalization techniques,including maximum likelihood sequence estimation(MLSE),feed-forward equalization(FFE)and decision-feedback equalization(DFE).Finally,by comparing the experimental results under different modulation formats and different equalizer structures,the optimal recommended schemes for modulation formats and equalizer structures in a 50G-PON system are given.The experimental results show that NRZ signal has better sensitivity performance than PAM-4 signal.When the transmission signal is in the NRZ format,the downlink using 7 taps FFE can reach a link budget of 34.97 d B,and the uplink using 3 taps FFE can reach a link budget of 33.76 dB.