Instantaneous Microwave Frequency Measurement Using a Special Fiber Bragg Grating

A photonic approach to realizing instantaneous microwave frequency measurement based on frequency to optical power ratio mapping using a special fiber Bragg grating (FBG) is proposed and demonstrated. The special FBG is designed to have a spectral response with two slopes that are inversely proportional to optical frequency, which enables the realization of a linear power ratio function, leading to an increased measurement range and improved measurement accuracy. The FBG is fabricated and the incorporation of the FBG in a system for frequency measurement is experimented. Instantaneous microwave frequency measurement with a measurement range of 1-10 GHz and a measurement accuracy of ±0.2 GHz under different input microwave power levels is realized.