Photonic quantization using dual-output Mach–Zehnder modulators and balanced photodetectors

Abstract A novel approach for photonic quantization using dual-output Mach–Zehnder modulators (DOMZMs) and balanced photodetectors (BPDs) is proposed and experimentally demonstrated. Based on the phase-shifting technique, all DOMZMs used in the scheme have identical half-wave voltages but are biased at different voltages. Due to the use of BPDs and DOMZMs with complementary outputs, the threshold voltages of comparators can be kept at zero, which eliminates the influence of power fluctuation of the input sampling pulses and improves the effective number of bits (ENOB) of the analog-to-digital conversion (ADC) system. After the comparators, a digital Gray code that represents the analog signal to be digitized is obtained. Proof-of-concept experiments with 8 and 16 quantization levels are implemented to verify the feasibility of the proposed approach. Bit resolution, ENOB degradation induced by bias voltage errors and potential for photonic integration are also discussed.