Patent ID: 7130503

Claim:
An optical multiplexer/demultiplexer comprising: a plurality of cores optically interconnected for propagating light; and a filter element disposed at a place in which the cores are optically interconnected, for passing or reflecting light of a specific wavelength, the optical multiplexer/demultiplexer separating light of a desired wavelength from single-mode light of a plurality of different wavelengths being propagated in one core by the filter element so that the light of the desired wavelength is propagated in another core, or combining light of different wavelengths being propagated in the different cores by the filter element so that the light of the different wavelengths is propagated in another core, wherein a sectional area of a core, which is adapted for propagating light of a longest wavelength of a plurality of wavelengths among the cores, propagates the light of the longest wavelength in a single-mode and propagates light of another wavelength in a multiple-mode where the light of the other wavelength enters the core.