High performance bandpass filters based on electric arc-induced π-shifted long-period fibre gratings

The inscription of π-shifted long-period fibre gratings with the electric-arc technique is presented. By exploiting the flexibility of this technique, the first bandpass filters having lateral rejected bands with isolation ≥20 dB have been realised. Also fabricated are high performance bandpass filters with larger bandwidths, this being achieved by introducing two π-phase-shifts into the grating.