Nonlinear phase shifts in a two-core fiber

Abstract

We derive an exact analytical expression for the nonlinear phase shift of an optical pulse propagating in a two-core fiber (TCF) with single-input excitation. Applying our results to an input continuous-wave (CW) beam, we show that the nonlinear phase shift at the output is reduced and attains a saturation value when the joint effects of the linear and nonlinear couplings cause a periodic power transfer between the two fiber cores. To analyze this result, we define a critical coupling coefficient that determines the separation of the fiber cores at which the reduction in the nonlinear phase shift occurs.