SMOKE DETECTION BY LIGHT EXTINCTION OVER A SHORT-DISTANCE

Smoke is detected by the measurement of light extinction. Extremely hi gh sensitivity is realised by the use of an integrated optical circuit . Four wave guides or light paths 50 mu m wide and 20 mu m deep are em bedded in a glass chip; one path is interrupted by a 25 mm air path th at allows for the measurement of light extinction. Light emitters and receivers are attached at positions at the end ports of the light path s where maximum optical throughput occurs. The sensitivity of the devi ce is demonstrated experimentally and is compared to other optical mea surement devices. (C) 1997 Elsevier Science Ltd.