The possibility of using smectic liquid crystals in active waveguide devices is explored through the analysis of both an integrated electro-optic switch and a continuously tunable filter. The two devices are based on a Bragg grating in planar waveguide with a liquid crystal overlayer, which enables changing the spectral behavior of the device. The fast and bistable switching of smectic C* in the surface-stabilized liquid crystal structure is used to investigate the possibility of realizing an integrated electro-optical switch. The principal advantage of this device is its spectral signature, which enables us to overcome the problems of intensity dependent devices. The soft-mode of smectic A* liquid crystals, enabling a continuous modulation of extraordinary refractive index, is used to design an integrated wavelength filter in the wavelength range of interest for optical communications. The principal advantages of such device …