PURPOSE: To reduce the titled device at its size and to prevent C/N from deterioration by passing light radiated from a semiconductor laser through a lens coated with a neutral density filter and arranging the end surface of a condensing point.

CONSTITUTION: Light irradiated from the semiconductor laser 10 is condensed by the lens 11 and the end surface 13 of the optical fiber 14 is arranged on the condensing point. An incident surface on the end surface 13 of the fiber 14 is obliquely ground so that reflected light is not returned to the original path. Consequently, the returned quantity of reflected return light from the fiber connector part 14 again to a laser active layer is reduced down to about -70dB. Thus, the device is reduced at its size to form an economical module and the C/N is prevented from deterioration.