Short-reach And Large-capacity Photonic Interconnects Based On PAM-4 Signal

The global IP traffic is witnessed an exponential growth,due to the coming 5G commercialization and the emerging applications including Internet of Thing,enhanced virtual reality,cloud computing and cloud storage.Thus,there occurs an urgent request for short-reach photonic inter-datacenter interconnection(DCI),where large transmission capacity and cost-effective solution are ideally desired.In this thesis,based on wavelength division multiplexing(WDM)four-level pulse amplitude modulation(PAM-4)signal,we carry out comprehensive investigations for two potential solutions.One is direct detection system,while the other is the simplified coherent detection system.The main outcomes of my thesis includes:(1)as for the direct detection system used for the DCI,we numerically investigate the interaction between chromatic dispersion(CD)and fiber nonlinearity arising in short-reach photonic DCI.We propose a digital CD management technique at the transmitter side and a sparse Volterra equalizer at the receiver side,for the purpose of fiber nonlinearity mitigation,leading to obvious computational complexity reduction of digital signal processing(DSP).Finally,we have experimentally demonstrated single-lane112 Gb/s PAM-4 signal transmission over an 80 km standard single mode fiber(SSMF).(2)as for the PAM-4 signal,we propose a polarization-insensitive simplified coherent receiver without the use of DSP,which consists of three single-ended photodetectors(PDs),a 3×3 coupler and some analog devices to realize the demodulation.Then we theoretically optimize and experimentally verify its feasibility for WDM PAM-4 signal.(3)Based on the simplified coherent detection receiver and ultra-dense WDM passive optical network(UDWDM-PON)with a wavelength spacing of 6.25 GHz,we successfully realize 4×5Gb/s PAM-4 signal transmission over 20 km SSMF with-28 dBm sensitivity at the 7% hard-decision forward error correcting threshold(Hard-FEC),which avoids the modification of current optical distribution network(ODN).