Fiber Optic Sensor Based on Vernier Microwave Frequency Comb

We demonstrate a proposed fiber optic sensor based on detecting the envelope of a Vernier microwave frequency comb (VMFC). A mode-locked fiber laser was employed as a microwave frequency comb source. A fiber ring, functioning as a sensor head as well as a microwave photonic filter, tailored the amplitude of each harmonic of the microwave frequency comb. By carefully designing the fiber ring length and the frequency separation of the microwave frequency comb, the Vernier effect is generated on the photodiode recovered microwave frequency comb after the laser pulses pass through the fiber ring. The sensing information can be deduced by tracking the envelope of the VMFC. The experimental results of a temperature sensing test show that the frequency shifts of the envelope peak have a good linear relationship with temperature variation. Furthermore, the sensitivity of the proposed sensor system is controllable.