Novel Torsion Sensor Based on the Interaction Between Modal Interference and Polarization Interference

A novel torsion sensor based on modal interference and the Lyot filter by utilizing the exciting mode in the single eccentric hole-assisted dual-core fiber (SEHADCF). Based on the interaction between the polarization functional modes and the mode of the suspended core, the phenomena of the interference resonance enhancement and the enhanced Vernier are realized by only adjusting the polarization of the incident light. The sensitivity of the proposed sensor reaches 171.97 dB/rad and 58.87 nm/rad, respectively. Furthermore, the vector property of the polarization state makes it possible to identify both the direction and the degree of the twist applied on the structure. Due to the selective amplification only applied on the parameter of the vector, the crosstalk from other mechanical parameters, including curvature and strain, is decreased significantly. The crosstalk of the strain is low to $7.474 \times {10}^{ - 7}\text{rad}/{\rm{\mu \varepsilon }}$. The proposed scheme of the sensor provides a new perspective of regulating both the polarization state and the fiber mode in the sensing field.