Planar waveguide optical filters and polarization transformers for compensating dispersive effects

Signal distortions in optical fibre systems arise from dispersive effects such as group velocity dispersion (GVD) and polarization mode dispersion (PMD). Dispersive optical filters offer the opportunity to completely compensate GVD. For PMD, adaptive polarization transformers in addition to 2×2 polarization-dependent filters are needed. Multi-stage 2×2 filters incorporating optical all pass filters are discussed that can compensate arbitrary polarization-dependent amplitude and phase responses across a desired bandwidth. To mitigate time-varying dispersion-induced impairments, adaptive filters are required, and control signals are needed to set the filter parameters to achieve the desired performance. Recent results are reviewed for planar waveguide device implementations with applications to tunable chromatic dispersion compensation, compensation of arbitrary phase responses, GVD and PMD monitoring, polarization transformers, and PMD compensation.