Temperature-Insensitive and Sensitivity-Enhanced FBG Strain Sensor by Using Parallel MPF

A temperature-insensitive and sensitivity-enhanced FBG strain sensor with the Vernier effect is proposed and demonstrated. The FBG sensor consists of two FBGs with different Bragg wavelengths as the sensing heads and two parallel-installed fiber ring resonator (FRR)-based microwave photonic filters (MPF) as the interrogation devices. The measurements can be read from the frequency shift in the notch of the envelope signal. Thanks to the Vernier effect produced by the parallel-FRR-based MPF, the sensitivity of the proposed sensor to strain is improved about 23 times compared with the single FRR-based strain sensor, which is experimentally demonstrated to be −33.862 kHz/
$\mu \varepsilon $
. And the sensitivity of the sensor to temperature was drastically decreased from 325.583 kHz/°C to 1.031 kHz/°C. The unique merits of the proposed sensor, such as high sensitivity, high resolution, and stability against random disturbances, give the sensor great potential for sensing applications in complex environments.