Strain Sensor Realized by Using Low-Birefringence Photonic-Crystal-Fiber-Based Sagnac Loop

An optical fiber strain sensor by using a low-birefringence photonic crystal fiber (PCF)-based Sagnac loop is demonstrated. A fiber Sagnac loop is formed by the low-birefringence PCF of about 40 cm, and a section of about 140-mm PCF is used as the strain sensing element. The output spectra of Sagnac loop under different strain levels are measured and analyzed. The sensitivity of the strain measurement of -0.457 pm/με is achieved within the range of 0-2520 με. The temperature effect is also analyzed.