A photonic technique for instantaneous microwave frequency measurement utilizing a phase modulator

We propose a simple microwave frequency measurement approach utilizing a phase modulator. After properly adjusting the polarization controllers in the proposed system, two dispersion-induced power penalty functions with different variation trends are obtained. A distinct relationship between the power ratio and the microwave frequency can be constructed by comparing the two power penalty functions. Thus, the microwave frequency can be determined by the power ratio value. Since only a bias drift free phase modulator and a single laser source are needed, the measurement system is significantly simplified. In the experiment, a frequency measurement over the range of 1.6-24.6 GHz with measurement errors within ±0.3 GHz is achieved.