Coexistence of collapse and stable spatiotemporal solitons in multimode fibers

Abstract

We analyze spatiotemporal solitons in multimode optical fibers and demonstrate the existence of stable solitons, in a sharp contrast to earlier predictions of collapse of multidimensional solitons in three-dimensional media. We discuss the coexistence of blow-up solutions and collapse stabilization by a low-dimensional external potential in graded-index media, and also predict the existence of stable higher-order nonlinear waves such as dipole-mode spatiotemporal solitons. To support the main conclusions of our numerical studies we employ a variational approach and derive analytically the stability criterion for input powers for the collapse stabilization. [3,4]. Wave collapse (also known as blow-up or selffocusing) occurs in a range of physical systems including nonlinear optics, plasmas, fluid dynamics, physics of atmosphere and ocean, and solid state physics [5]. Typically, wave collapse is associated with multidimensional physical problems [3][4][5][6][7][8][9][10][11][12][13]. From a broader perspective, wave collapse is the process of the singularity formation in a finite time (or at a finite distance), which is typically arrested by higher-order effects not accounted for in the original model. Effect of wave collapse can be exploited for compression of optical pulses [8][9][10][11] and optical pulse fusion [11,12]. An arrest of wave collapse and emergence of stable coherent structures in higher-dimensional systems have been studied in various physical contexts (see, e.g. the review paper [14] and references therein). Solitons localized in time and one transverse spatial dimension have been observed in quadratic media [15], and such solitons suffer from modulation instability which breaks elliptical beams into filaments. Three-dimensional spatiotemporal solitons were demonstrated in arrays of weakly coupled optical waveguides [16,17], but such solitons are largely controlled by the lattice discreteness being stable for a weak coupling.For long time, the use of single-mode optical fibers was the solution of choice for long-haul communication systems, allowing to avoid spatial scattering of light for delivering optical signals without spatial-mode dispersion over thousands of kilometers. However, a fast-growing demands on capacity of fiber systems and challenges imposed by nonlinear signal interaction attracted the recent attention to the technology of spatial-division multiplexing (SDM) for future high-capacity optical communications (see, e.g. Refs. [18,19] and references therein). A solution based on the use of multiple systems over parallel fibres while always possible, is not attractive due to linearly scaled (with growing capacity) transmission costs and power consumption. Potentially, the SDM technology might offer a cost-per-bit reduction and improved energy efficiency. One of the considered possibilities for implementing the SDM technology is the use of multimode fibers (MMFs) for parallel communication channels. In MMFs optical pathways are defined by different spatial modes, and spatial signal pr...

Wave condensation with weak disorder versus beam self-cleaning in multimode fibers

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Frontiers in multidimensional self-trapping of nonlinear fields and matter

“…Standard optical fibers used in telecommunications and other applications are usually designed to be single-mode, thus they may be considered as 1D media in the context of self-trapping [103]. Graded-index multimode fibers feature a large transverse area where nonlinearity can couple multiple modes, resulting in potential complex spatiotemporal field dynamics [104][105][106][107][108][109][110]. In particular, nonlinearityinduced locking of duration and location of relatively long pulses in different modes resulting in the formation of spatio-temporal localized states was experimentally observed in graded-index multimode optical fibers [106].…”

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