The Raman Wavelength Division Multiplexer (Raman WDM) Module is manufactured by using thin-film filter technology, it used to separate and combine different signal wavelengths at 1450nm, 1550nm, and 1660nm (or 1650nm). 695 standard and widely used in Raman DTS systems. They offer very low insertion loss, low polarization dependent loss, high isolation and excellent environmental stability. Raman Filter WDM Designed by Idealphotonics,inc Vancouver Branch with low.