  We demonstrate an interferometric fiber-optic bending/micro-displacement
sensor based on a plastic dual-core fiber with one end coated with a silver
mirror. The two fiber cores are first excited with the same laser beam, the
light in each core is then back-reflected at the mirror-coated fiber-end, and,
finally, the light from the two cores is made to interfere at the coupling end.
Bending of the fiber leads to shifting interference fringes that can be
interrogated with a slit and a single photodetector. We find experimentally
that the resolution of our bending sensor is ~3x10-4 m-1 for sensing of bending
curvature, as well as ~70 nm for sensing of displacement of the fiber tip. We
demonstrate operation of our sensor using two examples. One is weighting of the
individual micro-crystals of salt, while the other one is monitoring dynamics
of isopropanol evaporation.
