LAUSR

Instantaneous frequency measurement (IFM) with single branch detection based on the birefringence effect is proposed and experimentally demonstrated. The unknown microwave frequencies are modulated to pump a length of polarization maintaining fiber. Due to the fiber birefringence effect, the input light signal is decomposed into two orthogonal-polarization signals with a relative time delay. After detection, an amplitude comparison function (ACF) is obtained by comparing the alternating-current and direct-current powers. Therefore, no multipath detection is needed so that the electrical variations in the photonic link can be cancelled out in ACF. A theoretical analysis is given to illustrate the mechanism of the proposed IFM system. The disturbances are investigated and discussed in simulation. A proof-of-concept experiment is carried out for verification with a result of ±0.2GHz over 2.2-5.2 GHz.