Ultra-high sensitivity strain sensor based on Mach-Zehnder-Sagnac interferometer

A highly sensitive strain sensor is demonstrated experimentally. A segment of thin-core fiber (TCF) was fusion spliced with the polarization maintaining fiber (PMF) and then prepared TCF-PMF structure was fusion spliced with 3 dB optical fiber coupler to build a Sagnac loop. The Mach-Zehnder interferometer formed by TCF interacts with the Sagnac interferometer constructed by PMF and a coupler. The configuration of proposed sensor extremely enhances the axial strain sensitivity. The strain sensor with an excellent fringe contrast of 27.5 dB was observed. The interference spectra had a blue-shift with increasing strain and the strain sensitivity of -200 pm (mu epsilon)(-1) was obtained experimentally. Moreover, the temperature characteristics of the strain sensor were also investigated. The proposed sensor with a cost-efficient setup and simple fabrication could be used for strain measurement.