Optical Filter-Based Mitigation of Group Delay Ripple- and PMD-Related Penalties for High-Capacity Metro Networks

In high-capacity metro networks, fiber Bragg gratings (FBGs) offer a potentially cost-effective solution for compensation of chromatic dispersion (CD). However, FBGs suffer from stochastic variations of their group delay, the so-called group delay ripple (GDR). We propose a novel statistical model to describe the effects of stochastic variations of GDR. The statistical properties of our model are verified by comparison to measurement data and Monte Carlo simulations as well as Multicanonical Monte Carlo (MMC) simulations. Results indicate that without further measures to counteract the GDR distortions, very large penalties (>; 10 dB) for the optical signal-to-noise ratio (OSNR) occur frequently at a bitrate of 112 Gbit/s. Thus, we investigated the performance of short and cost-effective optical finite and infinite impulse response equalizer structures to mitigate the GDR distortions and to enhance the signal quality. With the use of optical equalizers (which can be realized as planar lightwave circuits) we were able to reduce the mean OSNR penalty due to the GDR to less than 0.1 dB. We also demonstrate that the same filter structures can efficiently be used to mitigate all-order PMD distortions as well.