Optical networks as described in previous chapters of this book have progressed steadily since the mid-1980s from point-to-point transmission systems to broadcast stars to ring networks to fully reconfigurable multiwavelength mesh networks utilizing a wide range of optical layer equipment: reconfigurable add/drop multiplexers, optical cross-connects, optical amplifiers, and optical access subnets. The next frontier in optical networking is the optical packet-switched network.

The present generation of multiwavelength optical networks are circuit-switched in their core, meaning that they are connection oriented. In these networks, regardless of the specific scheme used to set up an optical connection, a significant delay (typically of the order of milliseconds or more) is always incurred during the setup period, during which the intermediate switches between source and destination are configured to support data transport. This means that circuit switching is efficient only when the average duration of the connections is much longer than the setup time; i.e., seconds or more.

In current applications, exemplified by Internet browsing, a typical source will transmit data in short bursts (on microsecond timescales), possibly changing destinations with each burst. This is completely incompatible with the circuit-switched approach, where a source-destination pair holds a dedicated connection for an extended period of time. Of course, the currently accepted solution to this problem is to maintain the circuit-switched optical infrastructure and provide a packet-switched logical layer (e.g., a network of electronic IP routers) over the optical layer to deal with the bursty traffic.