Fibre-optic smoke sensor

Abstract

Optical methods for remote smoke sensing have several advantages over conventional methods, especially in the presence of e.m.i. or explosive substances. In this work the study and a first realization of a fibre-optic smoke sensor based on light scattering from particles, which exploits the triangulation principle, are proposed. Sensor response is theoretically evaluated by varying both the smoke characteristics and the geometry of the system. These results are then compared with the results of experimental tests. The sensor realized is innovative with respect to similar ones. In fact, it makes possible not only the detection of smoke, but also the control of possible failures, such as failure in the illuminating system or presence of opaque deposits over the faces of the lenses. Particles with a radius greater than or equal to 0.02 μm and having a density of 108 part/cm3 were detected by the sensor. Smoke constituted of smaller particles is detectable only if present in a higher concentration. © 1992.