OPTICALLY LINEARIZED MODULATORS - CHIRP CONTROL FOR LOW-DISTORTION ANALOG TRANSMISSION

We show that an increase of composite-second-order (CSO) distortion wi th increasing fiber length can occur in analog transmission systems us ing optically linearized Mach-Zehnder modulators and that the degradat ion is due to generation of chirp in the modulator, We extend a first- principles model to calculate the modulator chirp parameter and show t hat system CSO calculations using this model are in excellent agreemen t with measured results, Finally we propose and demonstrate a novel mo dulator design where chirp is greatly reduced while preserving excelle nt linearity, For an 80-channel North American frequency plan an optim ized low-chirp modulator is predicted to extend the CSO-limited range of the system over standard single-mode fiber from approximately 50 km to greater than 300 km.