Analysis of a long-period grating inscribed in the core of a fibre with inverse parabolic-index cladding

The operation of a long-period grating inscribed into the core of a single-mode fibre with the cladding having an inverse parabolic-index profile is theoretically investigated. Two-dimensional bidirectional mode expansion and propagation method is used to simulate mutual interaction of rotationally symmetric LP modes in the fibre. Numerical analysis has shown that the inverse parabolic-index profile of the cladding helps increase the sensitivity of a fibre as a refractometric sensor.