Design strategy for controlling four-wave mixing-induced crosstalk between channels in a fibre optical parametric amplifier

The four-wave mixing-induced crosstalk has been investigated in fibre parametric amplifiers. The required gain (and conversion efficiency) can be obtained by increasing fibre nonlinearity, fibre length or pump power. In each case, crosstalk is generated, however new results are presented that demonstrate that crosstalk in a fibre parametric amplifier is minimised by using a design with the highest possible pump power and a short fibre with low nonlinearity. For the parameters considered, the crosstalk in an amplifier with 20 dB of gain can be reduced by as much as 18 dB. Conversely, results are presented that demonstrate that crosstalk can be maximised, as is desirable when using parametric processes for signal reshaping, optical limiting or dispersion monitoring applications. For increasing channel counts the crosstalk is found to initially increase and then tends towards saturation. (C) 2004 Elsevier B.V. All rights reserved.