Modulational Instabilities in Passive Cavities: Theory and Experiment

Abstract

For both its fundamental and applied interests, modulational instability (MI) in fibers has attracted growing attention over the last two decades (see e.g., [1]). As regards applications, modulational instability provides a natural means of generating ultrashort pulses at ultra-high repetition rates and is thus potentially useful for the development of future high capacity optical communication systems. Modulational instability in an optical fiber leads to the spontaneous break-up of continuous wave (cw) excitation into a periodic train of ultrashort pulses, provided that the dispersion of the fiber is anomalous and the cw input power sufficiently high [2, 3]. Owing to the simplicity of this ultrashort pulse formation process, the exploitation of MI has been considered in many theoretical and experimental studies for the realization of laser sources adapted to ultrahigh bit-rate optical transmissions. However, despite its simplicity, the MI process in fibers is difficult to control and presents, in this respect, some important drawbacks. For instance: — The generated pulse train repetition rate depends on the incident power level and is therefore subject to fluctuations. — The required cw power level is relatively high and is, in general, much larger than the power threshold for Brillouin scattering so that, in practice, cw operation cannot be performed. — The pulses generated by MI are superimposed on a complex background field, which is detrimental to their subsequent propagation in fiber.