Optically linearized modulators: chirp control for low-distortion analog transmission

TitleOptically linearized modulators: chirp control for low-distortion analog transmission
Publication TypeJournal Article
Year of Publication1997
AuthorsJackson, M. K., V. M. Smith, W. J. Hallam, and J. C. Maycock
JournalLightwave Technology, Journal of
Pagination1538 -1545
Date Publishedaug.
Keywords300 km, 50 km, 80-channel North American frequency plan, analog transmission systems, cable television, chirp control, chirp modulation, composite-second-order distortion, CSO-limited range, first-principles model, increasing fiber length, linearity, low-distortion analog transmission, modulator chirp parameter, modulator design, optical fibre subscriber loops, optical fibre theory, optical modulation, optical noise, optically linearized Mach-Zehnder modulators, optically linearized modulators, optimized low-chirp modulator, standard single-mode fiber, system CSO calculations

We show that an increase of composite-second-order (CSO) distortion with increasing fiber length can occur in analog transmission systems using optically linearized Mach-Zehnder modulators and that the degradation is due to generation of chirp in the modulator. We extend a first-principles model to calculate the modulator chirp parameter and show that system CSO calculations using this model are in excellent agreement with measured results. Finally we propose and demonstrate a novel modulator design where chirp is greatly reduced while preserving excellent linearity. For an 80-channel North American frequency plan an optimized 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


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