Interferometric analog-to-digital conversion scheme

A novel interferometric analog-to-digital converter (ADC) scheme for real-time conversion at multiple-gigahertz bandwidth is presented and theoretically analyzed. The input analog signal is applied as an optical phase modulation in one of the arms of a Mach-Zehnder interferometer and the digital output is obtained in encoded form as a set of optical intensities in the interference pattern. Particular benefits of the proposed device are its simple design which facilitates integration, the extremely high bandwidth, and the inherent 2π-periodicity that in comparison with conventional flash ADCs relaxes the demands on the comparators and allows unwrapping of the output for higher resolution.