Abstract: An optical sensing system uses light scattered from a sensing fibre to sense conditions along the fibre, and has a receiver with a frequency to amplitude converter to obtain a frequency of a Brillouin component of the received scattered light, to deduce the conditions. This converter can avoid time consuming scanning of frequencies to obtain the Brillouin frequency spectrum, and avoids the heavy processing load of deducing a peak or average frequency from the spectrum. The converter can be implemented in the optical domain using a grating or interferometer, or in the electrical domain using a diplexer or electrical interferometer. It can generate complementary signals, having opposite signs, a ratio of these signals representing the frequency. This can avoid sensitivity to amplitude changes in the received scattered signals and provide common mode rejection of noise.

Abstract: Described herein is an electromagnetic locking device which integrates mechanical lock components in a hollow metal door frame with electronic access components. The physical and mechanical modifications comprise a magnetic field generating device, an appropriately shaped metal housing and a cam retaining locking bar. The method for integrating a magnetic field generating device and cam retaining locking bar with previously installed mechanical lock components minimizes service costs and replacement of doorframes.