Simultaneous measurement of temperature and strain based on a hollow core Bragg fiber

A novel, to the best of our knowledge, reflective sensor fabricated by simply sandwiching a homemade hollow core Bragg fiber (HCBF) between two single-mode fibers is proposed and demonstrated for the simultaneous measurement of the temperature and the strain. Different from traditional Fabry–Perot interferometer (FPI) sensors that can achieve only one-parameter sensing with inevitable cross-correspondence to other parameters, the proposed sensor based on the HCBF, which functions as an FPI-inducing FPI spectrum pattern and a weak waveguide confining light-inducing periodic envelope in reflection spectrum, ensures double-parameter sensing. For the HCBF-based reflective sensor, different sensing mechanisms lead to the various sensitivity values of temperature and strain (2.98 pm/^◦C, 19.4 pm/^◦C, 2.02 pm/µε, −0.36 pm/µε), resulting in a different shift of the confining spectrum envelope and the FPI spectrum fringe. Experimental results indicate that our proposed sensor can measure temperature and strain simultaneously by utilizing a 2 × 2 matrix. Taking advantage of the compact size, easy fabrication, and low cost, this sensor has an applicable value in harsh environment for simultaneous strain and temperature sensing.