In this paper, we propose a novel super-receiver architecture for Nyquist-wavelength-division-multiplexing (WDM) superchannel optical coherent systems. As opposed to a conventional coherent receiver, where each subchannel is demodulated independently, the proposed super-receiver jointly detects and demodulates multiple subchannels simultaneously. By taking advantage of information from side channels that use joint DSP to cancel interchannel interference (ICI), the proposed super-receiver performs much better than a conventional receiver. This architecture also has the potential to compensate for cross-channel impairments caused by linear and nonlinear effects. We examine the proposed architecture through experiment and simulation. OSNR is improved by more than 5 dB after 1280 km fiber transmission with narrow channel spacing.