US Patent 7106508 Hybrid cell

The present invention is a hybrid cell that utilizes a PBS pair in conjunction with a wedge tuner and a crystal to achieve a more stable interleaver. A first PBS splits an incoming optical signal into two orthogonally polarized beams which follow different optical paths through the cell. The length of the wedge tuner and crystal are selected such that the periodicity of the cell is approximately inversely proportional to the free spectral range at a target frequency. The length of the wedge tuner and crystal are also selected such that there is no change in an optical path difference between the two optical paths with respect to a change in temperature over an operating temperature range.