Highly Sensitive Strain Sensor Based on a Novel Mach-Zehnder Interferometer with TCF-PCF Structure.

A highly sensitive strain sensor based on a novel fiber in line Mach-Zehnder interferometer (MZI) was demonstrated experimentally. The MZI was realized by splicing a section of photonic crystal fiber (PCF) with the same length of thin core fiber (TCF) between two single mode fibers (SMFs). The fringe visibility of MZI can reach as high as 20 dB in air. In particular, the strain sensitivity of -1.95 pm/με was achieved within a range from 0 to 4000 με. Furthermore, the strain properties of different length of MZI was investigated. It was found that the sensitivity was weekly dependent on the length of MZI. The strain sensitivities corresponding to the MZI with 35 mm PCF, 40 mm PCF and 45 mm PCF at 1550 nm band were -1.78 pm/με, -1.73 pm/με and -1.63 pm/με, respectively. Additionally, the sensor has advantages of simple fabrication, compact size and high sensitivity as well as good fringe visibility.