Abstract

Polarimetric optical-fiber sensors have been reported (e.g., Ref. 1) and the same principle is discussed here with regard to compensating for the effect of contamination on the surface of the sensor. In polarization-maintaining waveguides the input light may be split into two mutually orthogonally polarized modes that exhibit different propagation velocities. The out-coupled modes of the fiber interfere, and hence using a polarizer with its axes at 45° to both polarization directions causes an intensity variation as a function of the relative phase difference to be produced. The birefringence of the overcoated D-fiber sensor structure with no contaminants on the surface, as shown in Fig. 1, is calculated to be 1.268×10⁻³ for a sol–gel overlay with a thickness of 0.165 μm. This level of birefringence is caused by the asymmetric shape of the D-fiber enhanced by the overlay.²

© 1995 Optical Society of America