Design and Performance Analysis of Passively Extended XG-PON With CWDM Upstream

In this paper, we evaluate the design and performance of an entirely passive extended 10-gigabit-capable PON (XG-PON) using eight channels of coarse wavelength-division multiplexing (CWDM) in upstream transmission, which is called the Cu-XG-PON, with a first demonstration of the upstream physical layer specification for the extended class in ITU-T G.987 series of recommendations. In the new scheme, a single burst-mode receiver (BMRx) within an optical line terminal (OLT) receives arbitrary upstream data from the optical network terminals (ONTs) divided into eight groups, each group sharing a CWDM wavelength, through a CWDM filter and a power splitter as cascaded remote nodes (RNs) for the upstream link bridge. The downstream link is designed such that a high power OLT transmitter compensates for link loss using two power splitters as cascaded RNs. Based on the proposed architecture, we first analyze the overall system performance in the upstream and downstream links, and then evaluate the practical extension capabilities in terms of fiber distance and split ratio by conducting experiments to probe the upstream performance using a developed BMRx. We demonstrate that the BMRx is capable to -34.5 dBm sensitivity, which is feasible for a 36 dB optical path loss and a 0.5 dB optical path penalty with a 2 dBm ONT transmitter power. Based on the numerical analysis and experimental results, we confirm that the proposed Cu-XG-PON is capable of reaching 28 km for 256 ONTs, or 42 km for 64 ONTs, and furthermore, for ONT groups at long wavelength channels, maximum 40 km for 256 ONTs, or 60 km for 64 ONTs.