Refractive index profile changes caused by arc discharge in long-period fiber gratings fabricated by a point-by-point method.

Long-period fiber gratings were inscribed in a commercial silica fiber by a point-by-point arc discharge technique with different discharge conditions. The refractive index (RI) profile change induced by arc discharge was measured using the quantitative phase microscopy for the first time to our knowledge. The causes of the transmission variations induced by different arc discharges and the mechanisms of the RI profile change were investigated based on the measured phase profiles.

Transfer-matrix method based on a discrete coupling model for analyzing uniform and nonuniform codirectional fiber grating couplers.

A simple and efficient transfer-matrix method based on a discrete coupling model is presented to analyze uniform and nonuniform fiber grating couplers between copropagating core and cladding modes. Uniform and piecewise-uniform long-period gratings were fabricated by a point-by-point arc discharge technique. Their measured transmission spectra were compared with the transmission spectra calculated by the presented method.

Analysis of solving multimode-coupled equations and its improvement for modulated fiber Bragg gratings.

An efficient numerical method to solve multimode-coupled equations with two point boundary conditions is improved. Our method [Abrishamian et al., Opt.