Optical wavelength multiplexer/demultiplexer and demultiplexer/remultiplexer

摘要

A multichannel wavelength demultiplexer has two or more cascaded birefringent filter stages (45 and 47) for dividing an input signal (20) consisting of a plurality of adjacent channels of optical signals among a number of outputs, each of said filter stages (45 and 47) having a transmission function (83, 84, 85) with even symmetry about optical frequencies at the centers of both the longest and the shortest wavelength channels. This symmetry, common to all transmission functions, permits all birefringent filter stages (45 and 47) to be con­structed from sequences of the same one size crystal element, thereby greatly lowering the cost of construction because solely one size crystal element is fabricated, tested and assembled. A multichannel multiplexer, identical to the above defined demultiplexer, but operated in reverse, is set forth. A combination multichannel wavelength demultiplexer/ remultiplexer consists of a single birefringent filter stage (45) for use in conjunc­tion with multichannel multiplexer/demultiplexer to divide a common set of adjacent wavelength channels on its primary input between its primary and secondary outputs (51, 52) in any combination, and simultaneously to accept at its secondary input (25) different optical signals within the same wavelength channels as those exiting its secondary output (52) and recombine them to exit at its primary output (51), wherein said single filter stage has a transmission function (83-89) with even symmetry about optical frequencies at the centers of both the longest and the shortest wavelength channels. This symmetry, common to its transmission function and to those of said multi­channel multiplexer/demultiplexer, permits all birefringent filter stages to be constructed also from sequences (54) of the same one size crystal element.