Using Mode Coupling Mechanism in Symmetrical Triple-Core Photonic Crystal Fiber for High Performance Strain Sensing

Basing on the mode coupling mechanism of symmetrical triple-core photonic crystal fiber (STCPCF), a highly sensitive strain sensor is proposed and experimentally demonstrated. Particularly, the triple-cores are arranged in an equilateral triangle on the pure silica host STCPCF. As a result, the coupling coefficient among the triple-cores of the STCPCF can increase as the fiber stretches. Moreover, the proposed sensor is designed by monitoring the wavelength shift of the coupling output spectrum. The experimental results show that the maximum strain sensitivity can be as high as -29.8 pm/με, which outperforms most of mode interference theory based fiber sensors. In addition, the strain sensitivity can be predicted by using mode-coupling mechanism in triple-core fiber. Theoretical results reveal that the sensitivity can be further improved up to -58.15 pm/με by optimizing the fiber structure parameters. Finally, the experimental results also show a high repeatability and stability, and a low temperature-strain cross-sensitivity of the proposed sensor.