Tunable Ultrafast Effective Nonlinearity Using a Nonlinear Amplifying Loop Mirror

In this paper, the NALM as a device with tunable, ultrafast effective nonlinear phase response of either positive or negative sign with respect to the influence of the principal NALM parameters on the nonlinearity strength, the total amount of nonlinear phase shift and the linearity of the power transfer function is investigated. A NALM is a kind of nonlinear Sagnac interferometer which contains a bidirectional amplifier and a highly nonlinear fibre connected to a fibre loop by an asymmetric coupler. Additionally, a directional phase bias can be inserted into the fibre loop for compensating XPM effects and for fine tuning the transmission properties. In a dispersion-less model the transmission functions for power and phase can be derived analytically.