Intensity-Modulated Sagnac Loop Temperature Sensor Setup

In this article, the novel low-cost and simple intensity-modulated Sagnac loop based temperature sensor setup is presented. The sensor head consists of a short length of polarization-maintaining fiber (PMF), which is spliced to a single-mode fiber optic coupler. Due to the short section of PMF, the spectrum has wide separation between adjacent interferometer dips. This idea ensures that transmission of a broadband light source has different losses after propagation through Sagnac loop whether temperature changes and causes shift of interferometer dips. Therefore, tracking of wavelength shift of interferometer dip is not required in this setup as it relies on direct optical power measurement. Instead of using spectral analysis instruments, we present the novel intensity-modulated optical fiber temperature sensor based on Sagnac loop created of short section of PMF. This particular sensor was experimentally investigated for a temperature range of 25-50.5 degrees C and exhibited the sensitivity of 0.066mW/1 degrees C with resolution of 0.34 degrees C. The setup could be easily applied in order to create fiber optic sensor network for temperature monitoring.