Method and apparatus for an optical multiplexer and demultiplexer with an optical processing loop

Abstract

An optical device that can be used in a range of telecommunications applications including optical multiplexers/demultiplexers and optical routers. The optical device includes an optical processing loop which allows multi-stage performance characteristics to be achieved with a single physical filtration stage. Optical processing on the first leg and second legs of the loop is asymmetrical thereby improving the integrity of the optical signals by effecting complementary chromatic dispersion on the first and second legs. In an embodiment of the invention the optical device includes a fundamental filter cell, a retro reflector and a splitter/combiner. The fundamental filter cell filters optical signals propagating on each of two legs of an optical loop which intersects the fundamental filter cell. The fundamental filter cell operates as a full waveplate to the odd set of channels and a half waveplate to the even set of channels on a selected one of the two legs and as a half waveplate to the odd set of channels and a full waveplate to the even set of channels on a remaining one of the two legs. The retro reflector optically couples with the fundamental filter cell to reflect the optical signals from one of the two legs to an other of the two legs to form the optical loop. The splitter/combiner optically couples between the fundamental filter cell and the retro reflector to split or combine the odd set of channels and the even set of channels depending on the propagation direction of the optical signals along the optical loop.