Interleaver/deinterleavers causing little or no dispersion of optical signals

Abstract

Interleaver/deinterleavers for combining/separating optical channels. An interleaver/deinterleaver is “folded” when an optical signal follows an optical path that passes through a birefringent element multiple times. Double-pass refers to optical signals following a (folded) path through the birefringent element twice. Multi-pass refers to optical signals following a (folded) path through the birefringent element multiple times. When operating as a deinterleaver, the interleaver/deinterleaver separates an optical signal (e.g., WDM signal) into subsets of optical signals (e.g., even and odd ITU channels). When operating as an interleaver, the interleaver/deinterleaver mixes subsets of optical signals into a multiplexed optical signal. The interleaver/deinterleaver can be used to increase the bandwidth of an optical network. For example, the interleaver/deinterleaver can be used to interface components designed for a first channel spacing (e.g., 100 GHz) to components designed for a second channel spacing (e.g., 200 GHz). Folded interleaver/deinterleavers cause dispersion because the speed at which the ordinary beam of an optical signal passes through the birefringent element is different that the speed at which the extraordinary beam of the optical signal passes through the birefringent element. In order to reduce or eliminate dispersion, the polarization of the optical signal is reversed for alternating passes through the birefringent crystal. For example, if a signal is horizontally polarized for a first pass through the birefringent crystal, the signal is rotated to be vertically polarized for a second pass through the birefringent crystal. For a third pass through the birefringent element, the signal is rotated to be horizontally polarized.