“…This focus was due to the fact that microoptics is the natural solution for multimode fiberbased systems, which were dominant in the early eighties as explained in the introduction. Although some demultiplexer designs employ dichroic or interference filters, such as those made by NTT [88] and OCA, most microoptical WDM designs use collimating optics and a reflecting grating, such as those made by Jobin-Yvon [89], STC [94], NEC [84], AT&T [86], [93], BTRL [85], and Physical Optics Corporation [87]. The designs of OCA and Jobin-Yvon are illustrated in Fig.…”