Effect of modulator chirp and sinusoidal group delay ripple on the performance of systems using dispersion compensating gratings

The implications that the nonideal characteristics of a dispersion compensating grating have on system performance are determined, for the most part, by the group delay ripple (GDR) of the grating response over the modulated signal bandwidth. Since the GDR typically exhibits an irregular variation with wavelength that has periodic features, it is convenient to use a sinusoidal variation to assess the implications on system performance. The portion of the grating bandwidth occupied by the modulated optical signal is determined by the carrier signal wavelength, bit rate, modulation format, and modulator chirp. The implications of modulator chirp on the performance of 10-Gb/s dispersion compensated systems are considered. Using a LiNbO3 Mach-Zehnder modulator, an electroabsorption modulator, and a multiple quantum-well Mach-Zehnder modulator with distinct chirp properties, the results demonstrate that to accurately assess the implications of GDR, the properties of the modulator chirp must be considered. In particular, results for chirp-free optical signals underestimate the implications of the GDR on system performance.