Design of an optical fiber sensor for linear thermal expansion measurement

Design and operation of an optical fiber device for temperature sensing and thermal expansion measurement are reported. The modulated intensity has been measured by using a pair of 450 mum core fiber, one acting as the source and the other one as receiving fiber. In this design, the light intensity modulation is based on the relative motion of the optical fibers and a reflective coated lens. By using displacement calibration data for this sensor, the linear thermal expansion of the aluminum rod is determined. This sensor shows an average sensitivity of about 11.3 mV/degreesC for temperature detection and 7 mum/degreesC for thermal expansion detection. Device resolution for a linear expansion measurement is about 3 mum for a dynamic range of 600 mum corresponding to a temperature change of 100degreesC. The measured linear expansion results are checked against the expected theoretical ones and an agreement within +/-2 mum is noticed. The operation of this sensor was also compared with other types and some advantages are observed, which verify the capability of this design for such precise measurements. (C) 2002 Elsevier Science Ltd. All rights reserved.