Optical coupling device

TLDR: In this paper, an optical system for coupling an output light of a semiconductor laser element to the tip part of the optical fiber through a lens was proposed. But the optical system was not designed to suppress a noise, and to transmit a good optical output signal by providing an optical fiber which has welded thermally a transparent medium whose refractive index difference to the optical fibre is <=20%, to the point of view of the lens.

Abstract: PURPOSE:To suppress a noise, and to transmit a good optical output signal by providing an optical fiber which has welded thermally a transparent medium whose refractive index difference to the optical fiber is <=20%, to the tip part of the optical fiber, and an optical system for coupling an output light of a semiconductor laser element to the tip part of the optical fiber through a lens. CONSTITUTION:An output light from a semiconductor laser 1 is brought to optical coupling through a lens system 2 to a rod 6 consisting of a transparent medium which has a refractive index of the same degree as that of an optical fiber on the end face and whose diameter is the same as or above the diameter of the optical fiber, for instance, that which has welded thermally a quartz rod step index fiber to optical fibers 3, 4. In this case, even if the rod end face is vertical against an incident optical axis, a waist after a reflected light has transmitted the lens is in a more distant position than the semiconductor laser, and a semiconductor laser light emitting part, a beam size is large. Accordingly, a light energy density is also extremely low, and a variatio of a semiconductor laser output caused by a reflected return light from the optical fiber end in an optical coupling device, an increase of a noise, and deterioration of a modulated pulse waveform can be eliminated.