A photonic analog-to-digital conversion scheme using Mach-Zehnder modulators with identical half-wave voltages

A novel photonic analog-to-digital conversion scheme implemented using an array of Mach-Zehnder modulators (MZMs) with identical half-wave voltages is proposed and demonstrated. It is different from the scheme proposed by Taylor where the MZMs should have geometrically scaled half-wave voltages; the proposed scheme here uses MZMs with identical half-wave voltages, which eliminates the need for the MZMs to have very low half-wave voltages. By properly biasing the MZMs, the transfer functions of the MZMs are laterally shifted, which leads to the generation of a linear binary code to represent the analog input signal. The use of the MZMs with identical half-wave voltages simplifies greatly the design and implementation, which provides a high potential for integration. A proof-of-concept experiment for analog-to-digital conversion with a quantization level of 16 is demonstrated.