Patent ID: 8023822

Claim:
An optical device for splitting/combining a first and second optical wavelength band, the optical device comprising: a first and a second optical splitting/combining element, each comprising a first, a second and a third optical path, the first optical path being optically coupled to the second optical path and the second optical path being optically coupled to the third optical path; and a differential optical delay device comprising a first, a second and a third optical path respectively interposed between and optically coupled to the first, second and third optical path of the first and second optical splitting/combining element, wherein: each of the first and second optical 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 with respect to optical radiation propagating through the second optical path and to optical radiation propagating through the second optical path with respect to optical radiation propagating through the third optical path, wherein m is a integer other than zero.