A fiber-optic twist sensor based on a pressure-induced birefringence singlemode fiber loop mirror is proposed. The
birefringer SMF is made by applying a transverse force against a short length of singlemode fiber. The sensitivity of the
twist angle measurement of 0.19 nm/o is achieved experimentally. The proposed sensor is more convenient and simple than that of standard polarization-maintaining fibers.
A relative humidity sensor based on polarization maintaining fiber (PMF) loop mirror is presented. The proposed sensors
are created through coating a thin layer of polyvinyl alcohol (PVA), whose refractive index varies as a function of
humidity level, onto a polarization maintaining fiber, from which a portion of the cladding is removed. The relative
humidity optical fiber sensor is tested with different surrounding humidity level, showing a linear response to parameter.
The sensitivity of the relative humidity measurement of 0.98 nm/%RH in the range from 20%-80% RH is experimentally achieved.