Patent ID: 6847786
Filing Date: 2005-01-25
Classification: G02B,G02F,H04J,H04Q

Abstract:
1. An optical wavelength filter separating an input signal into a first output signal having a first spectral band and a second output signal having a second spectral band, wherein the first and second spectral bands are substantially complementary, said optical wavelength filter comprising: a polarizer converting an input signal to a predetermined polarization; a series of birefringent waveplates providing a polarization-dependent optical transmission function such that the polarized input signal is decomposed into a first beam component carrying the first spectral band at a first polarization and a second beam component carrying the second spectral band at a second polarization that is orthogonal to the first polarization; a beam displacer spatially separating the beam components exiting the waveplates into a pair of orthogonally-polarized beams; a reflector reflecting the beams from the beam displacer back along optical paths through the beam displacer and waveplates; a polarization rotating element rotating the polarization of the beams such that the reflected beams are rotated by 90 degrees with respect to the polarization of the orthogonally polarized beams exiting the beam displacer; wherein the beam displacer routes the reflected beams along optical paths through the waveplates that are offset, but parallel to the optical path of the polarized input signal; wherein the waveplates further purify the spectral characteristics of the reflected beams and maintain the polarization of one of the reflected beams, while rotating the polarization of the other reflected beam so that both reflected beams have substantially the same polarization; a first routing element operable to further offset the reflected beams from the polarized input signal; and a second routing element routing one of the reflected beams exiting the waveplates to a first output port and the other reflected beam to a second output port.