6.1 Introduction

Those building IP networks see two types of connection as key to them the access connections, the cables, fibres or wireless systems that connect their customers to the PoP, and the core connections, the fibres that connect the PoPs together. This chapter describes the latter aspect, looking at today's and tomorrow's transmission technology. Utilising cost effectively the capacity of the fibres buried in the ground and being able to reconfigure the transmission network in a timely manner to meet rapidly growing customer demand are of interest chiefly to ISPs and carriers that have their own transmission network. However, the cost of installing and managing the transmission network is a fundamental cost that is inherited by the IP networks.

The pace of change in telecommunications networks, driven by information technology, continues to accelerate, resulting in a whole new range of narrowband and broadband data services. This has placed new requirements on the underlying transport infrastructure (SDH, WDM, and fibre) in terms of capacity growth [1] and management, where BT spends some 1bn per annum on new equipment, operations and support. Whereas new operators purchase the latest technology 'off-the-shelf', rolling out 'green-field' networks, BT and the other established operators face the challenge of interworking with their existing network.

Using the development of the BT core transport network as a case in point, the chapter discusses long-haul and metropolitan networks, but excluding the last mile from the local exchange to the customer. An...