Reproducibility of splicer-based long-period fiber gratings for gain equalization.

We fabricated long-period fiber gratings (LPFGs) using electric arc discharges. We observed that the fiber becomes slightly tapered due to longitudinal tension during the arc: this effect depends on the arc current and time length. We experimentally investigated how these characteristics can influence grating’s performances, especially in view of employing the LPFG as gain equalizer for an erbium-doped optical amplifier. As expected, we found that the spectral response of the grating depends on the period ›, the intensity of the perturbation, the grating length and the type of mode-coupling induced. Since this last parameter cannot be estimated directly from the transmission spectra, we propose a method to determine the mode-coupling occurring in the device and to assess the index modulation induced by the electric arcs. This method combines both experimental and simulated data, and can be used to characterize LPFGs made-up by any method.