Abstract: Local birefringence is determined from a scatter signature of a birefringent waveguide. Four copies of a Rayleigh scatter time delay domain signature of the fiber are collected from two orthogonal polarization received states and from two orthogonal polarization launched states to form a Jones transfer matrix. Obtaining the Jones transfer matrix for the waveguide eliminates the need to align the instrument polarization launch state to the birefringence axes. Birefringence is determined from an autocorrelation of a polarization state averaged function calculated from the transfer matrix terms. Alternatively, the transfer matrix is rotated until fast and slow eigenvectors are separated, fast and slow amplitude functions are generated, and a cross-correlation is performed on the fast and slow amplitude functions in order to determine the birefringence.

Abstract: A normally closed electrical switch includes a first circuit board having a first switch contact thereon and an aperture therethrough near the first switch contact. A second, flexible circuit board has a second switch contact aligned with the first switch contact of the first circuit board. A spacer sheet separates the first and second circuit boards and has an aperture in registry with the aperture in the first circuit board. The switch contacts extend toward each other through the aperture in the spacer sheet such that they are in normally closed condition. A movable cover is provided on the first circuit board at least over the aperture therein. An actuator is operatively associated with the cover and extends through the aperture in the first circuit board, through the aperture in the spacer sheet and engageable with the second, flexible circuit board for flexing the second circuit board and opening the switch contacts in response to movement of the cover.