Compact wavelength multiplexer-demultiplexer providing low polarization sensitivity

Abstract

An optical multiplexing and demultiplexing device includes: a fiber mounting means for securing a plurality of optical fibers each terminating in a fiber end, at least one of the fiber ends radiating a corresponding input beam having a polarization state defined by a polarization plane that may vary as a function of time, and at least one of the fiber ends for receiving an output beam; collimating and focusing means having a focal length, and providing collimation of the input beams, and focusing of the output beams; diffraction means including at least one diffractive element providing for dispersion of optical beams passing therethrough, each diffractive element having an associated diffraction efficiency that varies as a function of the polarization state of light beams passing therethrough; and a polarization rotating means for rotating the plane of polarization of a beam passing therethrough by a specified number of degrees. The device provides for a particular input beam having a first polarization state to be diffracted by the diffractive elements in accordance with a first diffraction efficiency based on the first polarization state. The beam is then passed through the polarization rotating means at least once and thereby rotated into a second polarization state. The rotated beam is then diffracted by at least one of the diffractive elements in accordance with a second diffraction efficiency based on the second polarization state, whereby the device provides a spectral resolution that is substantially insensitive to variations in the polarization state of the input beam.