Distributed Fiber Optic Threshold Temperature Sensor

Based on the OTDR and SMA (shape memory alloy) techniques, a novel distributed fiber optic threshold temperature sensing system has been proposed and demonstrated. The advantage of this sensing system includes the sensitive to the designed temperature threshold along the all fiber line and the ability of location for the possibility of the events. As a fire alarm system, it could be wildly used in civil structures and big buildings for the potentials of fire events monitoring.The distribution fiber optic temperature threshold sensor is consisting of a twist fiber and SMA wire. If the ambient temperature is over the threshold of the SMA wire in somewhere, the loss of the fiber there will increased, then the position of the event can be located by the OTDR. Theoretically, the deformation of the fiber macro-bends forced by the shape memory alloy wire has been analyzed as the temperature over the acting threshold value of the SMA. Experimentally, a series results are obtained under the condition of the temperature changed from 60 to 89 . It is shown that the distributed fiber optic threshold temperature sensing system could be realized by using the combination of OTDR and the SMA techniques.