Opto-Mechanical Interactions in Multi-Core Optical Fibers and Their Applications

Abstract

Optical fibers containing multiple cores are being developed towards capacity enhancement in space-division multiplexed optical communication networks. In many cases, the fibers are designed for negligible direct coupling of optical power among the cores. The cores remain, however, embedded in a single, mechanically-unified cladding. Elastic (or acoustic) modes supported by the fiber cladding geometry are in overlap with multiple cores. Acoustic waves may be stimulated by light in any core through electrostriction. Once excited, the acoustic waves may induce photo-elastic perturbations to optical waves in other cores as well. Such opto-mechanical coupling gives rise to inter-core cross-phase modulation effects, even when direct optical crosstalk is very weak. The cross-phase modulation spectrum reaches hundreds of megahertz frequencies. It may consist of discrete and narrow peaks, or may become quasi-continuous, depending on the geometric layout. The magnitude of the effect at the resonance frequencies is comparable with that of intra-core cross-phase modulation due to Kerr nonlinearity. Two potential applications are demonstrated: single-frequency opto-electronic oscillators that do not require radio-frequency electrical filters, and point-sensing of liquids outside the cladding of multi-core fibers, where light cannot reach.

Forward stimulated Brillouin scattering and opto-mechanical non-reciprocity in standard polarization maintaining fibres

“…Emit–receive processes with two separate waveguides are unaffected by Kerr nonlinearity. Similar separation may be achieved in multi-core PM fibres 57 , 60 . The present study was carried out for a specific class of PM fibres, known as panda type.…”

Forward Stimulated Brillouin Scattering Analysis of Optical Fibers Coatings

“…Forward stimulated Brillouin scattering (F-SBS) is a nonlinear optical effect that couples between two copropagating optical fields and an acoustic wave that are guided in a common medium [6][7][8][9][10][11][12][13][14][15][16][17][18]. F-SBS has been studied in standard optical fibers since 1985 [6].…”

“…F-SBS has been studied in standard optical fibers since 1985 [6]. Unlike the more widely employed effect of backwards SBS, the acoustic modes that mediate forward Brillouin scattering in fibers are predominantly transverse [6][7][8][9][10][11][12][13][14][15][16][17][18]. These modes are guided by the whole fiber cross-section, and their transverse profiles span the entire cladding and reach its outer boundary [6][7][8].…”

Brillouin mirror with an inverted acoustic profile in the presence of strong acoustic dispersion

“…Nevertheless, a kind of 'renaissance in Brillouin scattering research' could recently be heralded [16], with a remarkable extension of the realm of Brillouin lasers in numerous and varied new kinds of waveguides, including microstructured fibers, silica [17] or chalcogenide [18], but also multicore fibers [19], micro-and nano-fibers [20,21], hollow core PCFs [22,23] as well as silicon [24] and silicon nitride [25,26] waveguides, optomechanical waveguides [27] and even on-chip SBS laser devices [28].…”

“…Recent advances in cavity optomechanics also allowed to design tight confinement structures with acoustic dispersion values that deviate substantially from the usual linear dispersion relation of bulk materials or traditional SMFs [33], or even nontrivial topological acoustic band structures at interfaces [34]. A direct corollary is that some tightly confined acoustic modes may present a finite cutoff frequency, yielding a flat, Raman-like acoustic dispersion relation ( ) [19,25,29], that is, a strong acoustic group velocity dispersion near cutoff.…”