We show for the first time that signal processing schemes based on noncoherent signal addition will require signal transfer characteristics exhibiting high degrees of curvature. We quantify this by proposing a set of single-input, dual-output, power-conserving transfer functions and generating designs based on these characteristics. We then analyze the sensitivity of such a design scheme to nonidealities in the signal level and device behavior,and show that a sampling operation is only possible for transfer characteristics with residual"low"output of less than about 10% and low intensity reflectivity higher than 98%. For single device signal loss of up to 0.1 dB,we show that the best possible crosstalk-to-noise ratio in a packet forwarder (27 dB), is limited by the availibility of the sampling operation.
Erik Johnson and Edward H. Sargent, "Function and Sensitivity of Signal Processing Systems Based on Addition Followed by Limiting," J. Lightwave Technol. 20, 1388- (2002)