Tunable chromatic dispersion compensation in 40-Gb/s systems using nonlinearly chirped fiber Bragg gratings

Chromatic dispersion management and tunable compensation are essential features of 40-Gb/s wavelength-division-multiplexed (WDM) systems. In this paper, we demonstrate both single and multi channel 40-Gb/s tunable dispersion compensation using nonlinearly chirped FBGs (NC-FBGs). For single channel compensation, we show that the NC-FBG can be tuned over a moderate range (∼400 ps/nm) with tolerable third-order dispersion (<200 ps/nm²) within the channel´s data bandwidth (intrachannel third-order dispersion). For multichannel systems, we demonstrate 4×40-Gb/s tunable dispersion compensation using sampled NC-FBGs in two configurations. First, we show that a single, sampled NC-FBG with fairly low intrachannel third-order dispersion induces negligible penalty on all four channels. This solution has a limited dispersion tuning range because of the deleterious intrachannel third-order dispersion. We show a moderate tuning range from -300 ps/nm to -700 ps/nm. Second, we demonstrate that two inverse, concatenated, sampled NC-FBGs can cancel the high deleterious intrachannel third-order dispersion, thus extending the dispersion tuning range. This solution provides both positive and negative dispersion values by stretching the two NC-FBGs separately. A tuning range of -300 ps/nm to +300 ps/nm with zero intrachannel third-order dispersion is shown.