Electrical modulation of an etched long-period fiber grating with a liquid-crystal cladding

The development of optical fiber communication systems has required passive devices of flexible characteristics. Recently, controllable long-period fiber gratings (LPFGs) devices have been demonstrated using liquid crystals (LCs), where the nematic director of the LC is electrically controlled. The LC material can be placed either in a core or cladding region. The optical characteristics of the LC depend on the orientation of the director because the director, i.e., the optic-axis direction of the LC, determines the effective index for the light transmission. These can be utilized as dynamic-gain-flattening filters in broadband amplifier modules and as controllable polarization-dependent loss (PDL) compensators. In this paper, we present the electrical modulation of an etched LPFG with a liquid-crystal cladding, in which the controllability and the stability of the LC-cladding LPFG are improved by reducing the diameter of the optical fiber to 50 μm by means of chemical etching