A TWDM-PON with Advanced Modulation Techniques and a Multi-Pump Raman Amplifier for Cost-Effective Migration to Future UDWDM-PONs

Dense wavelength-division multiplexing passive optical networks and ultra-dense wavelength-division multiplexing passive optical networks are strong candidates to future nextgeneration passive optical network stage 3 access networks in order to satisfy increasing bandwidth demand, but their deployment is still a great challenge for telecommunication operators. Time and wavelength division multiplexed PON (TWDM-PON) has already been chosen by ITU-T as one of the best architectures in brownfield contexts to allow the reuse of the optical distribution network. Our proposal exploits the advantages of TWDM in order to reach a balance between coexistence with legacy systems and gradual and cost-effective migration towards pure wavelength division multiplexed PON (WDM-PON). In order to fulfill this aim, with reference to downstream traffic enhancement, two main novelties are presented: 1) the use of a multi-pump Raman amplifier (MRA) to satisfy the future necessity of large gain bandwidth; 2) the introduction of advanced modulation techniques to increase spectral efficiency and the future number of user channels (a less than 7 GHz-wide channel bandwidth providing 10 Gb/s bitrate has been demonstrated). A coherent system has been also proposed and its main impairments have been evaluated. The MRA has been accurately optimized to minimize power consumption without compromising performances. In the upstream direction, a semiconductor optical amplifier has been considered. The performances of the proposed TWDM-PON have been predicted through numerical simulations based on a system-level commercial CAD software.