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

It is shown, for the first time, how the amplitude of the group delay ripple, due to a pair of quasi-identical chirped fiber Bragg gratings, can be affected by a small change in the physical length of one of the gratings. It is theoretical and experimentally demonstrated that the dispersion of the gratings can be smoothened by a slight difference in length between them. The pair of gratings is arranged in a 4-port optical circulator, in a cascaded configuration. System simulations indicate that apodisation may be improved using such a scheme. This has implications for dispersion compensation in high bit-rate transmission systems.