We propose a novel add-drop multiplexer for dense wavelength division multiplexing optical communications ( DWDM) operating in C band (1530-1565 nm). The device has been designed for channel in-diffused glass waveguides. The device is switchable because a POLICRYPS (POlymer LIquid CRYstal Polymer Slices) based grating is deposited on top of the wider bimodal waveguide. At our knowledge this is the first example of switchable add-drop multiplexer.