Effects of crosstalk in demultiplexed photonic analog-to-digital converters

Summary form only given.Development efforts are underway for a new generation of high-sampling-rate A/D converters that exploit the unique features provided by optical sampling of electrical signals. An attractive means for increasing the sampling rate of these A/D converters is to use a demultiplexer at the output of the electro-optic modulator to direct sequential optical pulses to a parallel array of M electrical A/D converters. Two types of demultiplexing schemes are being explored: time-division demultiplexing and wavelength division demultiplexing. Demultiplexing techniques require an extremely precise match of all of the M parallel A/D channels so that digital outputs from these A/D converters can be interleaved to yield a precise representation of the signal. In both time- and wavelength-demultiplexing schemes, the possibility exists that there will be incomplete isolation of the different outputs. This crosstalk will cause undesirable spurs in the spectrum obtained by digitally processing the interleaved data from the separate electronic A/D converters. This paper analyzes the level of such spurs.