Microwave Generation Based on Optical Domain Microwave Frequency Octupling

A novel approach to achieving microwave frequency octupling in the optical domain is proposed and demonstrated. The proposed system consists of two cascaded Mach-Zehnder modulators (MZMs) that are both biased at the maximum transmission point, with a tunable optical phase shifter connected in between to introduce a phase shift. An input microwave signal is applied to the MZMs with its power adjusted to ensure the two MZMs having an identical phase modulation index. A theoretical analysis that leads to the conditions for achieving frequency octupling is provided. The approach is verified by experiments. The phase noise performance and the frequency tunability are also experimentally investigated.