Patent ID: 8433196

Claim:
An optical device for splitting/combining first and second optical wavelength bands, the optical device comprising: first and second optical splitting/combining elements, each comprising first, second and third optical paths; and a differential optical delay device comprising first, second and third optical paths respectively interposed between and optically coupled to the first and second optical splitting/combining elements, wherein: each of the splitting/combining elements is of the (25-50-25%)λx/(0-0-100%)λy type, wherein λx is a wavelength within the first optical band and λy is a wavelength within the second optical band, and the first, second and third optical paths of the differential optical delay device are configured to introduce, at a wavelength λz within the first optical band, a phase delay Δφ of 2πm to optical radiation propagating through the first optical path, wherein m is an integer other than zero.