Optical Networks Seek Reconfigurable Add/Drop Options

Hector E. Escobar, Fujitsu Ltd.

The ability to add and drop wavelengths from dense wavelength division multiplexing systems is a key function. Accomplishing this task optically, rather than electrically, is an exciting challenge for photonics lightwave system developers.
Optical add/drop multiplexers, in the simplest of terms, add and drop wavelengths at intermediate points in a communications network. Ideally, these multiplexers would be capable of dynamic reconfiguration, which means operators could remotely add or drop any number of wavelengths, or change the network through software commands. This added flexibility would save operating and maintenance costs and improves network providersi response time.
Unfortunately, most optical add/drop multiplexers are not dynamically reconfigurable because the filters that perform the adding and dropping are hard-wired for specific wavelengths; changing wavelengths requires a hardware change. Two relatively new tunable filter technologies could change all that. One of them, acousto-optic technology, is ready for implementation.