International audienceThe Peregrine soliton is a localized nonlinear structure predicted to exist over 25 years ago, but not so far experimentally observed in any physical system. It is of fundamental significance because it is localized in both time and space, and because it defines the limit of a wide class of solutions to the nonlinear Schrödinger equation (NLSE). Here, we use an analytic description of NLSE breather propagation to implement experiments in optical fibre generating femtosecond pulses with strong temporal and spatial localization, and near-ideal temporal Peregrine soliton characteristics. In showing that Peregrine soliton characteristics appear with initial conditions that do not correspond to the mathematical ideal, our results may impact widely on studies of hydrodynamic wave instabilities where the Peregrine soliton is considered a freak-wave prototyp

Optical rogue waves are rare yet extreme fluctuations in the value of an optical field. The terminology was first used in the context of an analogy between pulse propagation in optical fibre and wave group propagation on deep water, but has since been generalized to describe many other processes in optics. This paper provides an overview of this field, concentrating primarily on propagation in optical fibre systems that exhibit nonlinear breather and soliton dynamics, but also discussing other optical systems where extreme events have been reported. Although statistical features such as long-tailed probability distributions are often considered the defining feature of rogue waves, we emphasise the underlying physical processes that drive the appearance of extreme optical structures.Many physical systems exhibit behaviour associated with the emergence of high amplitude events that occur with low probability but that have dramatic impact. Perhaps the most celebrated examples of such processes are the giant oceanic "rogue waves" that emerge unexpectedly from the sea with great destructive power [1]. There is general agreement that 2 the emergence of giant waves involves physics different from that generating the usual population of ocean waves, but equally there is a consensus that one unique causative mechanism is unlikely. Indeed, oceanic rogue waves have been shown to arise in many different ways: from linear effects such as directional focusing or random superposition of independent wave trains, to nonlinear effects associated with the growth of surface noise to form localized wave structures [1,2].The analogous physics of nonlinear wave propagation in optics and in hydrodynamics has been known for decades, and the focusing nonlinear Schrödinger equation (NLSE) applies to both systems in certain limits (Box 1). The description of instabilities in optics as "rogue waves" is recent, however, first used in 2007 when shot-to-shot measurements of fibre supercontinuum (SC) spectra by Solli et al. yielded long-tailed histograms for intensity fluctuations at long wavelengths [3]. An analogy between this optical instability and oceanic rogue waves was suggested for two reasons. Firstly, highly skewed distributions are often considered to define extreme processes, since they predict that high amplitude events far from the median are still observed with non-negligible probability [4]. And secondly, the particular regime of SC generation being studied developed from modulation instability (MI), a nonlinear process associated with exponential amplification of noise that had previously been proposed as an ocean rogue wave generating mechanism [2].These pioneering results enabled for the first time a quantitative analysis of the fluctuations at the spectral edge of a broadband supercontinuum, and motivated many subsequent studies into how large amplitude structures could emerge in optical systems.These studies attracted broad interest and have essentially opened up a new field of "optical rogue wave physics". Although most...

Numerical simulations of the onset phase of continuous wave supercontinuum generation from modulation instability show that the structure of the field as it develops can be interpreted in terms of the properties of Akhmediev Breathers. Numerical and analytical results are compared with experimental measurements of spectral broadening in photonic crystal fiber using nanosecond pulses.