Four-wave mixing crosstalk in optical fibre parametric amplifiers with orthogonal pumps

We experimentally investigated the generation of new unwanted frequencies generated by four-wave-mixing in fibre optical parametric amplifiers with two orthogonally polarised pumps and 17 dB of small signal gain. At these gain levels, we simultaneously observe two distinct types of mixing interactions and demonstrate that they vary with changing output power and gain at different rates. We also demonstrate that a combination of high pump power and low nonlinearity fibre results in less power in the unwanted peaks than a combination of low pump power and highly nonlinear fibre. Because these new unwanted four-wave mixing peaks result in crosstalk between wavelength division multiplexed channels, building parametric amplifiers with a combination of high pump power and fibre of low nonlinearity is desirable.