A photonic approach for instantaneous microwave frequency measurement based on simultaneous phase modulation and intensity modulation using Mach-Zehnder interferometers

A novel photonic configuration for instantaneous microwave frequency measurement is proposed and demonstrated experimentally. A polarizer is used in one output branch of a phase modulator to implement the simultaneous phase modulation (PM) and intensity modulation (IM). The transmission responses related with the unknown microwave frequency are then obtained by sending the phase and intensity modulated optical signals to the Mach-Zehnder interferometers (MZIs). Thanks to the MZIs, the response speed of the measurement system is greatly enhanced compared to the previous works using long dispersive medium. Furthermore, the proposed scheme provides improved measurement range and resolution in virtue of the complementary nature of the transmission responses. The measurement errors as shown in experimental results can be kept in 0.2GHz over a frequency range of 0.1GHz-5.3GHz.