Distributed fiber optic chemical sensor with a temperature compensation mechanism

A distributed fiber optic chemical sensor with a temperature compensation mechanism is revealed using optical frequency domain reflectometry (OFDR). Distributed chemical sensing has already been achieved through chemical sensitive films deposited on the multimode fiber. However, chemical sensing signal interfered by the temperature where the fiber under test locates. In this paper, a new configuration of the fiber sensing is developed using a double cladding fiber. The sensor is feasible for multi-parameter sensing including temperature and another chemical of interest (pH value in this paper) at the same location. In this way, a temperature compensated distributed sensing algorithm can be developed and have both fundamental mode and multimode propagation in the same measure and field. The possibility to adjust the specifications of the fiber and OFDR configuration provides ample opportunity to satisfy requirements of temperature compensation from different chemical sensing applications.