Which of the following best describes Four Wave Mixing (FWM)?
A . FWM is a linear impairment that produces crosstalk four adjacent wavelengths are used.
B . FWM is a non-linear impairment that produces crosstalk at the sum and difference of two wavelengths.
C . FWM is a non-linear impairment resulting from varying velocities at different frequencies.
D . FWM is a linear impairment resulting from pulses broadening over ultra-longdistances
Answer: A