PIGTAIL MODULE, OPTICAL FUNCTION HEAD MODULE, AND FIBER LASER MODULE

PROBLEM TO BE SOLVED: To provide a pigtail fiber module having a configuration for retaining a cross-sectional shape of an emission beam to a state further close to a circular shape.SOLUTION: A pigtail fiber module 100A includes a pigtail fiber 120, a ferrule 110, an end cap 140, and an adhesive 150. The tip end portion of the pigtail fiber 120 having the end cap 140 attached to an end face 120a is inserted into a through hole 111 of the ferrule 110, and the ferrule 110 and the pigtail fiber 120 are fixed with the adhesive, with an end face 140a of the end cap 140 and a first end face 110a of the ferrule 110 according with each other. The through hole 111 includes an inner diameter whose mean clearance ((the inner diameter of the through hole-the diameter of the clad)/2) between a portion fixed with the adhesive and the clad is 1 μm or less.