A fast optical switch can be fabricated/constructed, when vanadium dioxide (VO2) ultra thin-film or a cluster of vanadium dioxide particles (less than 0.5 microns in diameter) embedded in an ultra thin-film of a polymeric material or in a mesh of metal nanowires is activated by either an electrical pulse (a voltage pulse or a current pulse) or a light pulse just to induce rapid insulator-to-metal phase transition (IMT) in vanadium dioxide ultra thin-film or vanadium dioxide particles embedded in an ultra thin-film of a polymeric material or in a mesh of metal nanowires. The applications of such a fast optical switch for an on-Demand optical add-drop subsystem, integrating with or without a wavelength converter are also described.