Long period grating filters fabricated with electric arc in dual concentric core fibers

Long period grating filters have been written using electric-arc technique in two dual concentric core fibers. The gratings have induced coupling between the fundamental modes of the two cores. We have obtained filters with rejected band around 1550 nm, characterized by insertion loss lower than 0.5 dB. Despite the high Ge-doping of the used fibers, thermal characterizations have shown a temperature sensitivity similar to that of the same gratings written in a standard single-mode fiber, by the same technique. We also have investigated the interest of using this fiber to implement a Mach-Zehnder modal interferometer with a higher spectral selectivity than the one realized in SMF. (C) 2003 Elsevier B.V. All rights reserved.