A WDM coupler includes an optical collimating module disposed in an outer tube unit. The optical collimating module includes adhesive bonds made from UV-curing epoxy for bonding together an optical filter component and a first collimating lens, the optical filter component and a second collimating lens, the first collimating lens and a first fiber pigtail, and the second collimating lens and a second fiber pigtail. A method for making the WDM coupler is also disclosed.