Asymmetric Mach-Zehnder channel waveguide interferometers possessing a 1.1 ns delay in one of the arms were fabricated using flame hydrolysis deposition of silica glass on silicon. Two modules were combined to form a single time-division interferometer for optical pulses. The composite interferometer exhibited a high fringe contrast ratio of 1:200 making it eminently suitable for use in compact, low error-rate quantum cryptography systems.
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Bonfrate et al. (2001) studied this question.