A receiver of an optical communications system includes a set of two or more analog-to digital A/D converters, a respective transform block connected to an output of each A/D converter, and a summation block. Each A/D converter samples a respective low-bandwidth analog signal comprising a respective portion of a high-bandwidth data signal. Each transform block calculates a set of spectral components of the respective low-bandwidth analog signal. The summation block combines respective spectral components calculated by each transform block to construct spectral terms of a combined signal having a spectrum corresponding to that of the high-bandwidth data signal.