9.1 Introduction

Optical fibre access network technology has become more complex over the last few years with bit rates steadily increasing. PON systems are available with bit rates in the range 155 Mbit/s to, currently, 622 Mbit/s. Newer systems, both PON and point-to-point, will allow this trend to continue with 2.5 Gbit/s systems becoming practicable in the near future. With this increase in technology has come an increase in the opportunities for fibre system to cost-reduce more of the network, including the metro space a fact that increases the appeal of the technology. Some of the newer PON systems are being designed using Ethernet as the underlying technology with a promise of reducing the price of the technology still further. How this will occur in practice, however, is still unclear. What is certain is that optical access technologies are expanding and are sure to find an opening in real networks in the foreseeable future.

Developing equipment for the access network has always been a risk for the equipment manufacturers. The size of the network means that equipment volumes can be huge but the equipment is extremely cost sensitive. Furthermore, the sheer cost of equipment rollout means that network operators do not attempt such a major upgrade of their networks lightly. Indeed, to date there have been no ubiquitous upgrades of the UK access network, rather there have been many small, ad hoc changes. Things are now beginning to change with the introduction of ADSL, although...