In-fiber chirped Fabry-Perot cavity for temperature sensing

• Zhe Zhang, Min Zhou, Qingdian Lin, Yu Jun, Xiaoyang Guo, Cangtao Zhou, and Shuangchen Ruan
• received 04/03/2024; accepted 04/17/2024; posted 04/18/2024; Doc. ID 525506
• Abstract: Measurement resolution and dynamic range of conventional optical fiber sensors are often mutually restricted. In this work, an in-fiber chirped Fabry-Perot cavity (interferometer) is proposed for the first time to our knowledge, to resolve the conflict between the resolution and dynamic range. The chirped Fabry-Perot interferometer is constructed by two chirped fiber Bragg gratings inscribed in the opposite directions, resulting in a gradually varied (i. e. chirp) cavity length for different reflection wavelength. As such, the interference spectrum exhibits high Figure of Merit (FOM) and large Free Spectrum Range (FSR) at long and short wavelength regions, respectively, enabling high resolution and large dynamic range measurement simultaneously. Temperature tests are then carried out to confirm the validity of the solution. The proposed sensing schema may be developed further and find vital applications in biomedicine fields such as endosomatic temperature monitoring of living bodies. The proposed concept of chirped Fabry-Perot interferometer can provide breakout ideas for other sensing scenarios where high resolution and large dynamic range are both demanded and can be further generalized to other measurands or even free-space interference metrologies.