Plz solve both i and ii

(i) Explain concisely what is meant by the term "four-wave mixing" (FWM) and how it influences the operation of a dense wavelength division multiplexing (DWDM) system and how to reduce its influence. (ii) In a (DWDM) system, there are three channels 1 = 1535.00 nm, A, =1535.80 nm and 13 =1536.50 nm. Due to the FWM within the fibre, 12 possible wavelengths are generated. List all the 12 possible wavelengths and explain why there is no interference between the input DWDM channels