Patent ID: 6970618

Claim:
A wavelength division multiplexer comprising: a fiber pigtail further comprising a fiber bundle and a ferrule having a tilted, cross-sectional end surface; a lens; a cannular spacer interfacing with said tilted, cross-sectional end surface of said ferrule on one side and an end of said lens on the other side; a filter; a cap connecting the other end of said lens and an end of said filter; a reflection mirror; and a tilted, cannular spacer interfacing with the other end of said filter on one side and said reflection mirror on the other side; wherein said fiber bundle comprises at least a common input fiber, a reflection output fiber, and a transmission output fiber, all inserted and fixed in said ferrule and arranged in a way so that: a center point between said common input fiber core and said reflection output fiber core has identical distances to said common input fiber core and said transmission output fiber core; and a line drawn between said transmission output fiber core and said reflection output fiber core is perpendicular to a line drawn between a center point of said ferrule and a highest point of said ferrule's said tilted, cross-sectional end surface.