Contents Introduction
A wavelength selective switch (WSS) based on free space optics and a liquid-crystal spatial light modulator (LC-SLM) [1] offers flexible applications as optical add drop multiplexers (OADM) [2]–[3], with the benefits of a broad flat top passband profile and continuous filter function between adjacent channels. A WSS switch in general can be configured with 1 × 1 or 2 × 2 port arrangements. For example, a 2×2 WSS can be independently configured either for the ‘bar’ state or for the ‘cross’ state on individual channel basis. When the adjacent channels are in the same state, the filter function shows a nearly continuous spectrum between the two channel passbands.
