An optical switching apparatus is designed to implement a serial switching architecture for wavelength division multiplexed (WDM) optical communication systems. The design allows for add/drop switching of a selected wavelength channel without switching a non-selected wavelength channel, thereby avoiding potential data loss on the non-selected channel during the add/drop switching interval. Exemplary implementations utilize fiber-optics and free-optics based approaches. The serial architecture readily accommodates new wavelength plans and/or the addition of new wavelength channels.
