The PMDWDM series are designed and manufactured to Telcordia standard and ITU standard, they can preserve the polarization of optical signals. The devices use environmentally stable Thin Film Filters and advanced packaging technology to achieve wide passband, low insertion loss, high channel isolation, excellent environmental stability and high extinction ratio. They can be used individually to perform single channel add or drop function or can be used in DWDM systems and sensor systems, etc.