Soliton dragging in discrete and distributed amplifiers

The authors introduce erbium-doped fibre amplifiers (EDFA) into soliton-dragging logic gates (SDLG) to improve their performance in terms of switching energy, fan-out and tolerance to timing jitter. In particular, they experimentally and numerically examine the frequency shifts associated with soliton dragging for orthogonally polarized pulses interacting in discrete and distributed amplifiers. The authors show that EDFA asymmetrize the interaction between pulses, leading to a frequency shift even when pulses completely walk through each other. The gain can increase the fan-out and/or reduce the switching energy, while proper positioning of the amplifier can loosen the timing restrictions for SDLG. We find reasonable agreement between calculations and measurements in the discrete amplifier case. However, discrepancies for the distributed amplifier case may result from non-uniform gain profiles along the length of the amplifier.