We propose a scheme for all-optical amplification based on a nonlinear-optical coupler in which one core is amplifying while another is attenuating. In this scheme the input signal is fed into the amplifying core, from where the output is also obtained. A weak input easily couples to the lossy core and gets dissipated in it, whereas a stronger signal stays and undergoes a nearly linear amplification in the active core. When it is used for reshaping pulses in a long transmission line, this scheme should allow the pulses to be amplified while simultaneously suppressing the noises between them. Simulating equations for the cw signal in this model, we are able to find a regime that provides for a strong contrast between the suppression of weak signals and amplification of strong ones as well as a steep transition from suppression to amplification at a certain threshold.
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