Microwave photonic IFM receiver with adjustable measurement range based on a dual-output Sagnac loop

A photonic-assisted approach for instantaneous frequency measurement (IFM) based on two Phase Modulator (PM) in a Sagnac interferometer with a tunable measurement range is proposed. The structure provides two double sideband (DSB) modulations in the output ports of the Sagnac interferometer, resulting in two frequency-dependent DC power after photo-detection. Using an amplitude comparison function (ACF), the frequency information converted to the RF phase shift can be measured. The tunability of the system is investigated using a tunable optical delay line (TODL). The simulation demonstrated RF frequency measurement from 0 to 14 GHz with a measurement error of less than 75 MHz.