System limitations due to four-wave mixing in single-mode optical fibres

The transmission of a multichannel coherent optical system is limited by four-wave mixing. In a 100-channel monomode fibre link, 5 GHz channel separation, -20 dB crosstalk level, the input power per channel should be lower than 0 to -5 dBm for a subscriber line (5 km), or -10 dBm for a trunk line (>100 km), employing low-loss dispersion-shifted fibre.