Generalized study of microwave frequency multiplication based on two cascaded MZMs

A comprehensive analysis of photonically assisted microwave frequency multiplication based on two cascaded Mach–Zehnder modulators (MZMs) is presented. The expressions, including all harmonics, are entirely general in terms of the extinction ratio (EXT) of MZM. A theoretical derivation that induces operating conditions is developed to achieve frequency quadrupling, sextupling, and octupling. The impact of an imperfect EXT of MZM on optical sideband suppression ratio and RF spurious suppression ratio is investigated. The improvement of system performance through MZM modulation index optimization is also analyzed. Simulation verifications are provided for the microwave frequency multiplication schemes.