Effect of bending and orientation on the fiber modal mach–zehnder interferometer

By introducing two notches along the fiber axis in a normal single‐mode fiber through CO 2 laser exposure, a vector curvature sensor based on a modal Mach–Zehnder interferometer has been proposed and experimentally demonstrated.Transmission spectral response regarding the spectrum shift and transmission loss variation of the proposed sensor has been characterized and the experimental results show that due to the nonperfect circular geometry of the fiber cladding, the peak wavelength and the transmission loss of its spectrum are sensitive to applied bending orientation. Our proposed sensor has many advantages such as low cost, easy fabrication and good stability under harsh environment.