Photo coupling device

TL;DR: In this article, the photo coupling device of less laser noise is obtained by parting the photo detecting end face of the optical fiber forward and backward by the specified distance from the imaging position of semiconductor laser light.

Abstract: PURPOSE:To obtain the photo coupling device of less laser noise in which the reflected light of the optical fiber end does not return to semiconductor laser by parting the photo detecting end face of the optical fiber forward and backward by the specified distance from the imaging position of semiconductor laser light. CONSTITUTION:Exit light of a semiconductor laser 1 passes through a lens-form medium 2 and enters the optical fiber 4 in a plug 3. Thence, the end face B of the optical fiber 4 is so installed as to come to the position away backward by the distance at which the reflected luminous flux returning to the semiconductor laser 1 becomes 10% or less of the exit luminous flux with respect to the imaging position of the laser light by the medium 2. Then, the amount that the reflected light from the end face B of the optical fiber 4 and the end face A of the medium 2 is returned to the semiconductor laser 1 is considerably reduced. Thereby, the semiconductor laser noise may be considerably reduced, the SN ratio of optical transmission improved and the light signal output maintained stably.