Expansion of bandwidth of tunable dispersion compensator based on ring resonators utilizing negative group delay

In this paper, a novel method to expand the compensation bandwidth of a tunable dispersion compensator (TDC) based on ring resonators utilizing a negative group-delay peak is presented. The operation conditions of the ring resonator, where the negative group-delay peak appeared, are theoretically analyzed and then experimentally verified. The ratio of the usable bandwidth to the channel spacing (25 GHz) was increased from 75% to 86%, employing the proposed scheme of the expansion method. The improved dispersion-compensation characteristic was confirmed in a 10-Gb/s experiment.