Real time measurements of ultrafast spontaneous modulation instability and rogue waves in optical fibre

Abstract

Modulation instability (MI) is one of the most fundamental processes of nonlinear science, and develops in fibre optics when a weak perturbation on a continuous wave field experiences gain and evolves into strongly-localized “breather” structures. Although MI has been studied for decades, there continues to be intense interest in understanding its dynamics because, when triggered from noise, it generates high amplitude and statistically-rare “rogue waves” of importance in hydrodynamics and optics [1]. Due to experimental limitations, however, directly observing the ultrafast instability dynamics of noise-driven spontaneous MI in optics is extremely challenging and represents a major limitation in our ability to characterize this essential process. In this paper, we use an ultrafast time-lens magnifier system to perform direct measurements of real time temporal structures in MI. Our results show an extended series of transient high intensity breather pulses emerging from noise, and our statistical analysis allows the presence of long tails (rare events) to be readily seen.