A plug that is engaged with a receptacle for light emission of a light source unit that emits a light beam having a flat-shaped cross section and an optical fiber having a burr defect in a part of an outer peripheral portion of an incidence end surface on which the light beam is incident are included. The plug is attached to an incidence end portion of the optical fiber in an arrangement in which the burr defect is located in a short axis direction of a cross section on the incidence end surface of the light beam incident on the incidence end surface in a state in which the plug is engaged with the receptacle.
