In-line displacement sensor based on fiber-to-tapered planar waveguide coupler

A fiber-optic displacement sensor based on a side-polished single-mode (SM) fiber in contact with a tapered planar waveguide (PWG) is investigated theoretically and experimentally. The thickness variation of the tapered PWG in the side-polished region leads to a shift in the resonance wavelength, and the sensor revealed a highly linear relation between the variation of the resonance wavelength and the displacement of the tapered PWG. The design and fabrication technique are presented, and the spectral and polarization characteristics measured and explained.