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 include fast tuning speed, wide tuning range, low power dissipation, and low cost.