Instantaneous microwave frequency measurement with a uniform resolution and improved dynamic range

A photonic approach to realizing instantaneous measurement of microwave frequency using a pair of fiber Bragg grating (FBG)-based optical differentiators is proposed and experimentally demonstrated. In this approach, a first-order and a second-order FBG-based optical differentiators are used to achieve a linear power ratio function with a uniform measurement resolution and improved system dynamic range. A proof-of-concept experiment is performed. A frequency measurement range of 6.5-15 GHz with a measurement resolution of ±0.3 GHz at different input microwave power levels is realized. The dynamic range of the system is analyzed and an improvement of about 10 dB is obtained.