A Microwave Frequency Measurement System Based on Si3N4 Ring-Assisted Mach-Zehnder Interferometer

A microwave frequency measurement system based on a ring assisted Mach-Zehnder interferometer (RAMZI) with a large measurement range and high accuracy is proposed and experimentally demonstrated. By using single-sideband modulation, the microwave signal with unknown frequency is converted to an optical sideband signal, which is used to probe the two complementary output optical powers of the ring-assisted Mach-Zehnder interferometer, then a fixed frequency-to-power mapping is established by obtaining a highly linear amplitude comparison function (ACF). High-precision frequency measurement with a root mean square error (RMSE) of less than 30 MHz was achieved in a frequency range of 5.2 GHz, and relative low-precision frequency measurement with a RMSE of less than 102 MHz was achieved in a frequency range of 11 GHz. Besides, in order to break the trade-off between measurement range and measurement accuracy, a multi-band measurement method was implemented and frequency measurement range of 5~39 GHz with RMSE lower than 37 MHz was achieved.