Performance of 4-ary ASK in Nonlinear, Multi-Channel Environments

This effort focuses on the comparison of On Off Keying (OOK) to incoherent 4-ary Amplitude Shift Keying (ASK). We show that a 0.4 bits/s/Hz improvement in spectral efficiency is obtained by utilising 4-ary ASK. We determined the filter steepness required to achieve this maximum obtainable spectral efficiency. The comparison of OOK and 4-ary ASK in terms of dispersion tolerance for Non-Return-to-Zero and Return-to-Zero is performed. We also prove that cross phase modulation, on its own, should not affect the maximum obtainable spectral efficiency of 4-ary ASK. Finally, we present simulation work showing that 4-ary ASK can potentially increase the capacity of Kerr effect limited DWDM systems. For the first time, comparison of 4-ary ASK and OOK is performed in the nonlinear regime.