HIGH-RESOLUTION ENCODING PROCESS FOR AN INTEGRATED OPTICAL ANALOG-TO-DIGITAL CONVERTER

A technique is described for extending the resolution of an integrated optical multi-interferometer guided-wave analog-to-digital converter. The optical output waveform for each interferometer is symmetrically folded at twice a proper modulus. A small comparator ladder mid-level quantizes each interferometer's detected output to encode the analog signal in a symmetrical number system (SNS) format. By incorporating the SNS encoding, resolution greater than 1 bit per interferometer can be provided. Analog signal levels that can cause possible encoding errors are examined and their impact on the overall amplitude analyzing function is discussed. The maximum laser pulse width and maximum fluctuation in the sampling interval that can be tolerated is also discussed. Results indicate that 11-bit resolution can be provided with three interferometers and 39 comparators.