Discrete amplified sensing of temperature and strain

Abstract

In this paper, a parallel connected optical fiber interferometer is proposed, aiming to improve the strain and temperature sensitivity by using the Vernier effect (VE). The sensor is fabricated by an optimized 3 × 2 step manufacturing process, and implements simple and cost-effective techniques such as cleaving, splicing and gluing. The sensor consists of two Fabry–Perot interferometers (FPIs) with different propagation media, one is air and the other is a SiO2 suspension core, named C1 and C2 respectively. Separate FPIs are used as sensing units in temperature and strain sensing, and another FPI is used as a reference unit. It is proved that when the fine fringe of FPI is redshifted, the envelope is blueshift when the FPI with a large free spectral range (FSR) is used as the sensing unit, the envelope is redshift when the FPI with a small FSR is used as the sensing unit. The results show that the temperature and strain sensitivities are 188.38pm/°C and 201.18pm/μɛ, with amplification factors of 21.2 and 19.6, respectively. In addition, the sensor has a very low cross-sensitivity because C1 is far from the temperature environment and the free end of C2 cannot be fixed for strain measurement.