The long-awaited deployment of dense wavelength division multiplexing (DWDM) in long-haul networks is fast becoming a reality. In the access network DWDM becomes a serious option to accommodate increasing multimedia, broadband, and IP traffic.

Fueled by the need for rapidly increasing volumes of information transfer, and by new requirements that are far less predictable than they have been for telephony, the development of optical fiber communication moves ever forward. DWDM that corresponds to the superimposition of optical signals at different wavelengths closely spaced at 100 GHz or less on each fiber, becomes, as a matter of fact, the unavoidable solution, not only for a capacity increase at lower cost, but also for switching and routing in the optical domain.

The optical add/drop multiplexer (OADM) and optical cross-connect technology are seen as a viable option in the large network optical nodes, when the digital cross-connectors are unable to scale to higher port-density and higher speed interface requirements at affordable costs, or in general, when the optical/electrical/optical conversion would be unnecessary and questionable.

Today's telecommunications networks have benefited from research in symbiosis in the fields of materials, electromechanics, microelectronics, computing, and optics.

Nowadays, low nonlinearity fibers, dispersion management on fibers, lasers with high wavelength stability...