Polarization-Maintaining Photonic-Crystal-Fiber-based Polarimetric Strain Sensor with a Short Sensing Head

In this paper we have implemented a temperature-insensitive polarimetric fiber strain sensor based on a Sagnac birefringence interferometer composed of a short polarization-maintaining photonic crystal fiber (PM-PCF), a 3-dB fiber coupler, and polarization controllers. The PM-PCF used as a sensor head was 2 cm long, which is the shortest length for a sensing element compared to other polarimetric fiber strain sensors using a PM-PCF. The proposed sensor showed a strain sensitivity of ~0.87 pm/με with a strain measurement range from 0 to 8 mε. The temperature sensitivity was also investigated and measured as approximately-12 pm/℃, when ambient temperature changed from 30 to 100℃. This temperature sensitivity is about 82 times smaller than that of conventional polarization-maintaining fiber (approximately-990 pm/℃). In particular, from a practical perspective we have experimentally and theoretically confirmed that the wavelength selected for the indicator dip location doe