Tolerance to amplitude and group-delay ripple for systems using chirped fiber Bragg grating

摘要

Chromatic dispersion compensation is an important and inevitable signal distortion in 10 Gbit/s systems transmitted over 80 km, and 40 Gbit/s systems transmitted over 5 km of single-mode fiber. Among the solutions introduced to compensate chromatic dispersion, chirped fiber Bragg gratings (FBG) are of special interest due to their compact size, negligible nonlinearities and low insertion loss. A novel technique to dynamically compensate dispersion using a tunable nonlinearly chirped grating (Feng et al, 1999) makes FBG even more attractive for future high-speed reconfigurable optical networks. However, the performance of chirped FBGs may be affected by nonideal group-delay (GD) and amplitude reflectivity ripple. In this paper, we investigate the tolerance of 10 and 40 Gbit/s NRZ and RZ systems to GD and amplitude ripple. For 10 Gbit/s systems and realistic ripple periods, amplitude and GD ripple should be less than 1.2 dB and 50 ps respectively to keep the system penalty below 0.5 dB. The constraints remain the same for 40 Gbit/s systems.