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
Received: 27 August 2012
Published online: 4 July 2013
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) = a2ebz and γ(z) = a3ebz 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|.
Key words: Nonlinear Dynamics
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag 2013