Search results for "Instability"
showing 10 items of 724 documents
Experimental evidence of the real multimode nature of geometric parametric instability
2020
We show experimentally that geometric parametric instability in graded-index multimode fibers is composed by several multimode spectral components. The experimental observation is obtained by using a new 3D technique of high-resolution spatial and spectral analysis.
Higher-order modulation instability in optical fibers
2012
International audience; We report on theoretical, numerical and experimental study of a new form of instability in a nonlinear fiber. This process of higher-order modulation instability arises from the nonlinear superposition of elementary instability dynamics.
Universal spectral dynamics of modulation instability : theory, simulation, experiment
2011
A central process of nonlinear fibre optics is modulation instability (MI), where weak perturbations on a continuous wave are amplified to generate a parametric cascade of spectral sidebands. Although studied for many years, it has only been recently appreciated that MI dynamics can be described analytically by Akhmediev breather (AB) solutions to the nonlinear Schrodinger equation (NLSE) [1]. This has led to important results, including the first observation of the Peregrine Soliton [2]. AB theory has also shown that the spectral amplitudes at the peak of the MI gain curve yield a characteristic log-triangular spectrum, providing new insight into the initial phase of supercontinuum generat…
Real-time measurements of spontaneous breathers and rogue wave events in optical fibre modulation instability
2016
Modulation instability is a fundamental process of nonlinear science, leading to the unstable breakup of a constant amplitude solution of a physical system. There has been particular interest in studying modulation instability in the cubic nonlinear Schrödinger equation, a generic model for a host of nonlinear systems including superfluids, fibre optics, plasmas and Bose–Einstein condensates. Modulation instability is also a significant area of study in the context of understanding the emergence of high amplitude events that satisfy rogue wave statistical criteria. Here, exploiting advances in ultrafast optical metrology, we perform real-time measurements in an optical fibre system of the u…
Active reduction of fluctuations in fourth-order modulation instability
2012
International audience; We experimentally study the fluctuation properties of a scalar fourth-order modulation instability process obtained by pumping a photonic crystal fiber in the normal dispersion region. We observe large wavelength-dependant pulse-to-pulse fluctuations which cannot be significantly reduced by stimulating the process with a single seed. Their reduction requires two seeds slightly detuned from the maximum gain frequency in order to also stimulate the second-order modulation instability process cascaded from the fourth-order one. This concept is validated by experiments and numerical simulations.
Temporal dynamics of incoherent waves in noninstantaneous response nonlinear Kerr media
2012
International audience; We consider the temporal evolution of an incoherent optical wave that propagates in a noninstantaneous response nonlinear medium, such as single mode optical fibers. In contrast with the expected Raman-like spectral redshift due to a delayed nonlinear response, we show that a highly noninstantaneous response leads to a genuine modulational instability of the incoherent optical wave. We derive a Vlasov-like kinetic equation that provides a detailed description of this process of incoherent modulational instability in the temporal domain.
Seeded and spontaneous higher-order modulation instability
2012
International audience; We report on the dynamics of the higher-order modulation instability in optical fibers and show that it is the very same phenomenon that underpins the emergence of rogue waves in the early stage of supercontinuum generation.
Effects of structural irregularities on modulational instability phase matching in photonic crystal fibers
2004
International audience; The effect of structural irregularities in photonic crystal fibers on scalar and vector modulational instability (MI) processes is studied by numerical simulations and experiments. For an anomalous-dispersion regime pump, variations in core ellipticity as small as 0.5% over length scales of the order of several meters are shown to have a negligible effect on scalar MI, yet they completely suppress vector MI. In contrast, for a normal-dispersion regime pump, vector MI is shown to be robust against such fluctuations.
Experimental Study of Modulational Instability and Vector Solitons in Optical Fibers
2003
This chapter brings forth the experimental study of modulational instability and vector solitons in optical fibers.
Extreme events in fiber based amplifiers
2009
International audience; We present experimental and theoretical results showing the emergence of rogue wave-like extreme intensity spikes during fiber-based amplification processes such as Raman effect or induced-modulational instability that rely on quasi-instantaneous gain. We outline that under certain circumstances, a partially incoherent pumping can induce large fluctuations of the amplified signal, and we propose various means to spectrally select the most extreme structures.