https://www.meisuoptics.com/application-of-collimator-array-in-oxc.html Developments of wss optical exchange technology In 2000, the emerging optical add/drop multiplexing (OADM) technology ushered era of optical exchange. However, it could only accomplish the one-way up and down wavelength of optical network nodes. Around 2008, the replaceable OADM (ROADM) technology appeared, enabling the optical layer to have the function of all-connected exchange. Its main structure is a multi-dimensional ROADM (MD-ROADM) based on multiple 1XN selective switching (WSS) units, according to the different implementation modes of optical switching nodes in local upper and lower wavelength. ROADM went through three generations, and it succesffully made the switching function more and more complete and the networking more and more flexible. The development history of all-optical exchange is shown in Figure 1 below.