Effect of a Waist Diameter of a Microtapered Polarization-Maintaining Fiber on Temperature and Ambient Index Sensitivities

The effect of a waist diameter of a microtapered polarization-maintaining fiber (PMF) on the temperature and the ambient index sensitivities is investigated theoretically and experimentally. Stress-induced and geometrical birefringences strongly depend on the waist diameter of the microtapered PMF, which plays a key role in temperature and ambient index sensitivities of the Sagnac interferometer. By reducing the waist diameter to ~5 μm, we successfully control the ambient index and the temperature sensitivities of the Sagnac interferometer to be -98.7 nm/RIU and -0.16 nm/°C, respectively, which are ~23 times higher and 1.7 times lower than those with a waist diameter of 25 μm.