11.2. MULTISTAGE APPROACHES TO OPS: NODE ARCHITECTURES FOR OPS
One of the best known, or at least quite impressive, optical switching technologies is MEMS using tiny mirrors to deflect light from a particular input to a particular output port. Both two-dimensional (2-D) (where mirrors are either tilted up or lie down and let light pass) and three-dimensional 3-D) variants (with mirrors tilting along two axes) have been demonstrated. While the characteristics in terms of optical signal quality distortion are quite good, this approach is not feasible in an OPS concept where very fast switching times (range of nanoseconds) are mandatory. Two widespread approaches are: one based on arrayed waveguide grating (AWG) with tunable wavelength converters (TWCs), and another based on a broadcast-and-select (B&S) concept using, for example, semiconductor optical amplifier (SOA) technology .
The AWG approach is also studied in the European research project STOLAS . An interesting feature of the AWG component is that when light is inserted via one of its input ports, which output port it will come out of depends on the wavelength used. Thus, by providing wavelength converters at the AWG's inputs, one can exploit the structure as a space switch. By a table lookup operation, what wavelength to use to reach a particular output from a given input can be found .
The B&S approach is deployed in the recent research project DAVID . The switch fabric's architecture comprises several subblocks. ...