Patent ID: 6144783
Filing Date: 2000-11-07
Classification: G02B

Abstract:
An optical multiplexer/demultiplexer for the multiplexing/demultiplexing of optical signal channels at a substantially uniform optical frequency spacing, which multiplexer/demultiplexer includes a set of input/output ports optically coupled with an output/input port via a tandem arrangement of first and second diffraction gratings that provide multiple optical paths from each member of the set of input-output ports to the output/input port via different grating elements of the gratings,wherein the difference in optical path length occasioned by paths via adjacent elements of the first grating is greater than that occasioned by paths via adjacent elements of the second grating,wherein said difference in optical path length defines for its associated grating a frequency range, the Free Spectral Range, being the frequency range over which said optical path length difference produces a phase difference whose value ranges over 2.pi.,wherein the Free Spectral Range of the first diffraction grating is matched with the optical frequency spacing of the optical signal channels,wherein the Free Spectral Range of the second diffraction grating is at least as great as the sum formed by the addition of the difference in frequency between adjacent frequency channels of the multiplexer/demultiplexer to the difference in frequency between the highest and lowest frequency channels of the multiplexer/demultiplexer,and wherein the portion of the optical coupling between the set of input/output ports and the output/input port that extends between the first and second diffraction gratings couples spatial information between the two gratings in addition to intensity information.