Coupling Effects Among Degenerate Modes in Multimode Optical Fibers

Abstract

Multimode optical fibers have recently received revived attention in the framework of space-division multiplexed systems, where the spatial diversity of fiber modes is exploited to increase transmission capacity. The complexity of these systems strongly depends on the coupling characteristic of the fiber. Therefore, a better description of coupling effects may lead to the more accurate modeling of the system and to an optimized design of multimode fibers. In this paper, we analyze coupling among (quasi) degenerate modes as a consequence of different kinds of coupling sources.

Birefringence effects in multi-core fiber: coupled local-mode theory

“…In addition, the nonlinear MCCs are given by the expressions (in W −1 ·m −1 ): where Nax(z;t):= ∫∫Fax 2 (x,y;z,t)dS∞; S∞ is the infinite cross-sectional area of the MCF; and Sa(b) is the cross-sectional area of each core. It should be noted that, in coherence with [18], the longitudinal random perturbations of the fiber are included in the MCCs. Nevertheless, in our method we have considered not only longitudinal perturbations, but also temporal ones.…”

“…However, the fiber dispersion effects are omitted in this work in order to evaluate only the time dependence of the crosstalk induced by the temporal birefringence fluctuations of the MCF, as it was pointed out previously. Alternatively to the CLMT, the theoretical models reported in [14][15][16][17][18][19] can also be extended to describe the temporal perturbations of the optical media inducing a crosstalk time dependence in MMFs and MM-MCFs.…”

“…On the other hand, in [14][15][16][17] the Manakov equations have been extended to multi-mode fibers (MMFs) and multi-mode multi-core fibers (MM-MCFs) to analyze linear and nonlinear propagation in SDM systems modeling intra-and inter-core coupling effects. In addition, in [18,19] the mode coupling has also been theoretically investigated in MMFs and MM-MCFs considering both orthogonal polarizations and the longitudinal random perturbations of the fiber. In [18] the bending and twisting of the media were modeled in the coupling matrix (composed by the coupling coefficients of the coupled-mode theory proposed in [20] for anisotropic optical waveguides), and in [19] the spatial random perturbations were included in the propagation matrix of the optical media.…”

“…In [18] the bending and twisting of the media were modeled in the coupling matrix (composed by the coupling coefficients of the coupled-mode theory proposed in [20] for anisotropic optical waveguides), and in [19] the spatial random perturbations were included in the propagation matrix of the optical media. In all these previous works [8][9][10][11][12][13][14][15][16][17][18][19], the longitudinal perturbations of the fiber have been described assuming ideal modes but omitting the temporal fluctuations of the SDM fiber perturbations.…”

Multimode Nonlinear Fiber Optics: Massively Parallel Numerical Solver, Tutorial, and Outlook

“…[63], [99], to Ref. [100] for analytic expressions of disorder-induced mode-coupling coefficients for typical fiber manufacturing errors, and to Ref. [98] for propagation with the multimode Manakov and coupled Manakov equations.…”