We present a new approach for the development of a highly stable optical fiber refractometer based on a path-matching differential interferometer. Exploiting a single-channel phase tracker and new synthetic heterodyne demodulations, one can eliminate the thermal drift on a piezoelectric transducer stack as a phase modulator by subtraction. A transducer in a differential Fabry–Perot refractometer is designed to compensate for the thermal effects not only from thermal expansion but also from the thermo-optic effect. The experimental data show that the refractive-index change in the sensing system can be kept at a level of approximately 5 × 10<sup>−4</sup> without serious variations for a 1-h period of long-term monitoring associated with a temperature variation of from 25 to 50 °C. Accordingly, the proposed new system can be easily implemented and used as a long-term monitoring system for medical care applications such as monitoring patients during drug injection.
© 2001 Optical Society of America
(060.2370) Fiber optics and optical communications : Fiber optics sensors
(120.3180) Instrumentation, measurement, and metrology : Interferometry
(120.5710) Instrumentation, measurement, and metrology : Refraction
Yu-Lung Lo and Chin-Ho Chuang, "Differential Optical Fiber Refractometer Based on a Path-Matching Differential Interferometer with Temperature Compensation," Appl. Opt. 40, 3518-3524 (2001)