System impact of the physical length of unapodized chirped fiber Bragg gratings on dispersion compensation

It is shown, for the first time, how the group-delay ripple, due to a pair of identical unapodized dispersion compensating gratings, can be affected by a small change in the physical length of one of the gratings. It is theoretically and experimentally demonstrated that the ripple can be smoothened by a slight difference in length between the gratings. The pair are arranged in a four-port optical circulator in a cascading configuration. System simulations indicate that the performance of the unapodized gratings may be improved by using such a scheme. This has implications for dispersion compensation in high-speed long-haul transmission systems.