The design, development, and demonstration of a 4-bit 1-Gsample/sec analog-to-digital converter (ADC) is reported. This 4-bit ADC consists of a comb-generator-driven GaAlAs diode laser, a LiNbO3 Ti-indiffused interferometric modulator array, Si avalanche photodiodes (APDs), wideband dc-coupled amplifiers, and special 1-GHz Si-integrated circuits consisting of comparators and 1–8 serial-to-parallel converters. A 2-bit 1-Gsample/sec ADC has been reported previously.1 Here we report on substantial improvements in LiNbO3 waveguide-bend/branch technology that allows the extension from 2 to 4 bits as well as experiments involving the reduction of the modulator phase drift caused by the photorefractive effect in LiNbO3 through material processing and an autocalibration circuit. A 498-MHz sinusoid has been analog-to-digital converted, and then a slowed version is reconstructed to demonstrate device performance. Efforts to fiber couple the various optical components will also be reported.
© 1984 Optical Society of AmericaPDF Article