Thermal and mechanical properties of tapered single mode fiber measured by OFDR and its application for high-sensitivity force measurement.

We investigate the thermal and mechanical properties of optical fiber taper by using a high spatial resolution Optical Frequency-domain Reflectometry scheme. It was found that the spectral shifts induced by the temperature or strain changes in the fiber taper region are strongly related to the refractive index change of the fundamental mode. It is shown that residual stress induced by taper process results in the inhomogeneous thermal properties, which are eliminated by annealing treatment. The wavelength-force sensitivity is dramatically enhanced by the reduced waist diameter of the taper. It was demonstrated that a taper with a waist diameter of ~6 μm has a wavelength-force coefficient of 620.83 nm/N, ~500 times higher than that of the standard single mode fiber.