Optical fiber temperature sensor based on phase shift by aluminum thermal expansion

Abstract

A method of using aluminum tube wounded by single-mode fiber as a temperature sensor is proposed in this paper. The optical source of this temperature sensing system is a 2-frequency He-Ne laser. When the temperature of fiber on aluminum is changed, a phase shift in optical signal appears. By using electronic circuits, this phase shift can be detected and compared with a reference signal obtained directly from the laser source. Then one will be able to get the information on temperature according to the difference of phases between these two signals. Two experiments have been performed in the laboratory. In the first experiment the aluminum tube is 12 cm in diameter, 8 cm in height, and 2 mm in thickness, with a fiber length about 60 m wounded 155 turns. The sensitivity is 2.1 X 10-2 rad/ degree(s)C-m. In the second experiment, the tube is 7.5 cm in diameter and height, and 2 mm in thickness, with a fiber about 10 m length wounded in 21 turns. The sensitivity is 4.9 X 10-2 rad/ degree(s)C-m. The temperature from 5 degree(s)C to 80 degree(s)C are measured with this design.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.