Design aspects of long-reach optical access networks

To deliver future broadband services, network operators need to build optical fibre access networks and at the same time reduce the unit cost of bandwidth transport. Passive optical networks (PONs) are a promising optical access solution, and are now becoming commercially available. These systems have a reach of similar to20 km and so synchronous digital hierarchy (SDH) outer core (or metro) equipment would typically be needed to provide connectivity to the inner core network. Using optical amplifiers to extend the reach of PONs allows the SDH outer core to be bypassed and so reduces the overall cost. Optically amplified PONs have been reported previously but we believe are worthy of further study due to advances in technology (for example, forward error correction and 10 Gbit/s optoelectronics) and because the commercial deployment today of broadband services reinforces the need to develop the next step.