Eur. Phys. J. D (2013) 67: 131
https://doi.org/10.1140/epjd/e2013-30530-y

Regular Article

All-optical soliton switching for the asymmetric fiber couplers

State Key Laboratory of Information Photonics and Optical Communications, and School of Science, Beijing University of Posts and Telecommunications, Beijing 100876, China

^a e-mail: tianbupt@163.com

Received: 27 August 2012
Published online: 4 July 2013

Abstract

Coupled nonlinear Schrödinger (CNLS) equations for the fiber couplers with asymmetric self-phase modulation (SPM) and cross-phase modulation (XPM) are studied. With symbolic computation, one- and two-soliton solutions are obtained for the constant- and variable-coefficient CNLS equations. Switching dynamics of the solitons is discussed, and effects of the second-order group-velocity dispersion β₂, SPM coefficient σ₁, XPM coefficient σ₂ and Kerr nonlinear intensity γ on the all-optical switching properties are studied, while other coefficients in those equations are seen not to affect the all-optical switching properties. For the constant-coefficient CNLS equations, we find that |β₂| is proportional to the optical switching speed, and the optical extinction ratios increase with the decrease of σ₁/σ₂ and increase of |β₂| and γ. A numerical simulation by the split-step Fourier and Runge-Kutta methods is presented on the constant-coefficient CNLS equations to analyse the stability of the one- and two-solitons with the random initial perturbations. For the variable-coefficient CNLS equations, effects of σ₁/σ₂, β₂(z) = a₂e^bz and γ(z) = a₃e^bz on the optical switching are analyzed (where a₂, a₃ and b are all constants, and z gives the direction of propagation in the fiber couplers): optical switching speed increases with the increase of |a₂| and decrease of |b|, and optical extinction ratios increase with the increase of |a₂| and decrease of σ₁/σ₂ and |a₃|.