Designing long reach optical access networks

Abstract

The long reach optical access concept promises to reduce the cost of a future BT network through simplification. This is achieved by extending the reach and split of today’s passive optical network systems (PONs) to 100 km and 1024 respectively, thus eliminating the need for separate backhaul equipment. Compact, low-power optical amplifiers are used at exchange locations requiring very low electrical power consumption. Ultimately this could effectively eliminate local exchange buildings and consolidate BT’s network to around a hundred metro nodes, drastically reducing operational costs. In this paper we describe research to date on the techniques to overcome physical layer impairments at costs appropriate for residential access. We also highlight from an operator’s point of view the protocol requirements of the LR-PON concept, point out the necessary changes to the GPON protocol, and describe an experiment to show its suitability to work over 100 km distances at 10 Gbit/s.