Once predicted to take communications carriers by sudden storm, the all-optical network is instead unrolling piece by piece.

Under pressure to boost bit rates and cut the cost per bit of data communications, designers are transplanting as many optical elements as they cost-effectively can into long-haul and metropolitan transport systems. The result is a hybridization of today's circuit-switched Sonet and SDH architectures, originally designed for voice data, to handle the growing demands of Internet traffic that ends up on packet-switched networks, Ethernet in particular.

One element easing the transition is the electronic crossbar switch, as Herman Eiliya of Analog Devices Inc. notes in this week's InFocus. These switches are a foundation for routing very high-data-rate serial signals across optical backplanes.

For metropolitan transport networks, packet-switched transport technologies like carrier-class Ethernet and the resilient packet ring access control procedure are taking hold, as described by Ronnie Neil of Agilent Technologies. And next-generation Sonet/SDH devices are adding enhanced data services and lowering costs thanks to such data plane technologies as Generic Framing Procedure, virtual concatenation and link-capacity adjustment.

Further evidence of networks' pushing to an all-optical world is the drive toward optical add/drop multiplexers and optical cross-connects, described here by Reuven Duer of Lynx Photonic Networks. And Ciena Corp.'s Jeff Livas, Tad Hofmeister and Karl Horne discuss all-optical broadcast-and-select switch architectures built on passive splitters and reconfigurable wave blockers.

Olivier Jerphagnon of Calient Networks Inc. describes the key design aspects of 3-D MEMS switches which, along with tunable lasers, provide a key building block for the next-generation communications network infrastructure.

Finally, Anthony Kam of Sycamore Networks Inc. argues for a move away from conventional, ring-based architectures and toward an optically switched mesh-based topology for its appealing protection and restoration options.