Retro-reflective fiber optic filter with triple-fiber ferrule

A retro-reflective multi-port fiber optic device (100) includes a triple-fiber ferrule (10) with a GRIN rod lens (12). The ferrule (10) with three fibers (18,20,22) and the WDM filter (14) are attached to the opposite sides of the lens (12). A reflective mirror (16) is attached to the other side of the WDM filter (14). The coupled-in light from the common input pigtail fiber (18) is collimated and transmitted onto the WDM filter (14) wherein the in-pass-band part of the light is transmitted through the WDM filter (14), and is then successively retro-reflected back by the mirror (16), transmitted through the filter (14) again, and then coupled into one retro-reflective transmission output fiber/port (22) of the triple-fiber ferrule (10) as a demultiplexed channel. The out-pass-band light is not transmitted through the filter (14) but instead directly reflected back by the filter (14) and coupled into a reflection output fiber/port (20) of the triple-fiber ferrule (10).