Suppression technique for fiber four-wave mixing using optical multi-/demultiplexers and a delay line

A technique is proposed for suppressing four-wave mixing (FWM) in optical fiber lines that have multistage optical amplifiers. The phase relationship of the FWM light components is randomized by combinations of optical multi-/demultiplexers and a delay line, so that the total FWM light power is reduced. A preliminary experiment confirming the suppression mechanism is carried out, and the effect of the new suppression technique in multichannel systems is evaluated. The calculations show that the technique reduces the FWM crosstalk in the zero-dispersion wavelength region.