Abstract
Dense Wavelength-division multiplexing (DWDM) technology offers tremendous transmission capacity
in optical fiber communications. However, switching and routing capacity lags behind the transmission
capacity, since most of today’s packet switches and routers are implemented using slower
electronic components. Optical packet switches are one of the potential candidates to improve switching
capacity to be comparable with optical transmission capacity. In this paper, we present an optically
transparent ATM (OPATM) switch that consists of a photonic front-end processor and a WDM switching
fabric. A WDM loop memory is deployed as a multi-ported shared-memory in the switching fabric. The
photonic front-end processor performs the cell delineation, VPI/VCI overwriting, and cell synchronization
functions in the optical domain under the control of electronic signals. The WDM switching fabric
stores and forwards aligned cells from each input port to the appropriate output ports under the control
of an electronic route controller. We have demonstrated with experiments the functions and capabilities
of the front-end processor and the switching fabric at the header-processing rate of 2.5Gb/s. Other
than ATM, the switching architecture can be easily modified to apply to other types of fixed-length
payload formats with different bit rates. Using this kind of photonic switches to route information, an
optical network has the advantages of bit rate, wavelength, and signal-format transparencies. Within
the transparency distance, the network is capable of handling a widely heterogeneous mix of traffic,
including even analog signals.

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