Temperature-independent strain sensor based on a Hi-Bi photonic crystal fiber loop mirror

This work presents an optical sensor based on a highly birefringent photonic crystal fiber (Hi-Bi PCF) loop mirror. The length of the sensing head is 380 mm and its corresponding wavelength spacing between two interferometer minima is 8 nm. The optical sensor was characterized in strain and in temperature with an uncoated Hi-Bi PCF and with an acrylate coated Hi-Bi PCF. Different results for strain and temperature sensitivity were obtained. Relatively to the strain measurement, the sensor with the uncoated Hi-Bi PCF presents slightly less sensitivity (1.11 pm/mu epsilon) when compared with coated Hi-Bi PCF (1.21 pm/mu epsilon). For the temperature measurement and with the uncoated Hi-Bi PCF, the optical sensor is insensitive to temperature (0.29 pm/K).