WDM

cwdm

https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-G.694.2-200312-I!!PDF-F&type=items

dwdm

https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-G.694.1-201202-I!!PDF-E&type=items