Impact of finite intermediate frequency on the performance of heterodyne ASK lightwave receivers

The impact of finite intermediate frequency (IF) on the sensitivity of heterodyne ASK lightwave receivers is examined and quantified. It is shown that certain choices of IF (f_IF=0.5 R_b, R_b, 1.5 R_b, etc.) yield ideal envelope detection results. For proper heterodyne detection, the worst-case sensitivity penalty is 1.72 dB which occurs when f_IF=0.75 R_b.