FLCS-PON—an opportunistic 100 Gbit/s flexible PON prototype with probabilistic shaping and soft-input FEC: operator trial and ODN case studies

Abstract

FLCS-PON is a concept of a flexible passive optical network (PON), where the modulation and coding parameters of the downstream signal, consisting of modulation order, code rate, and probabilistic shaping entropy, can be adjusted on a timeslot basis to opportunistically achieve mean net bitrate increase. The system harnesses unused margins of transceivers and optical distribution networks. In this work we describe the architecture of FLCS-PON, which is designed to leverage the 50G-PON ecosystem. We provide updated and accurate performance metrics for FLCS-PON low-density parity check (LDPC) forward error correction (FEC) codes. We then report on the operator trial of a FLCS-PON system prototype carried out jointly with Vodafone and demonstrate maximum achievable net bitrates as a function of the optical path loss for five different transmitter configurations (non-return-to-zero, PAM-4, and probabilistically shaped PAM-4 with three different entropy values). On the receiver side we test four different configurations: F F E 23 + D F E 5 or F F E 16 + D F E 1 equalizers, each followed by either a hard- or a soft-input LDPC decoder. Finally, we consider two study cases on mean bitrates achievable with FLCS-PON over deployed optical distribution networks (ODNs). We map net bitrates obtained during the operator trial to Vodafone’s actual ODN optical path loss probability distribution or an ensemble of simulated ODNs. We show that in the majority of cases, FLCS-PON can provide a significant improvement of mean net bitrate. Further, FLCS-PON also enables extension of nominal power budget classes, beyond guaranteed conventional ODN loss, making it possible to provision links that might otherwise be unsupported by conventional PON.