Long period copper-coated grating as an electrically tunable wavelength-selective filter

For the first time, the behaviour of long period gratings with a metal coating has been investigated. It is shown that, in the case of a copper coating, couplings become slightly shifted and attenuated. By applying a DC current to the coating, a shift similar to 4nm is obtained for a resistive power close to 0.5W. This result suggests that long period gratings are more attractive than Bragg gratings for realising tunable wavelength-selective filters based on the electrical heating of a fibre through a metal coating.