Coupling device for guiding a light beam

Abstract

The invention relates to a coupling device for guiding a light beam sent through an end portion of an optical waveguide to the light-sensitive surface of a photodiode of a measuring instrument, in particular, an optical power meter, comprising an absorbing aperture associated with the end face of the optical waveguide, and having an aperture which widens conically towards the light-sensitive face of a photodiode, the aperture plate facing the end face of the optical waveguide with its side where the diameter of said aperture is smallest but slightly larger than the diameter of said end face of the optical waveguide. A device of simple construction and having substantially no reflection is obtained in that the light beam is directed straight to the light-sensitive surface of the photodiode, and the angular aperture .beta. of the conical inner surface of the aperture plate is larger than 2 arc tan .alpha..sub.max, tan .alpha..sub.max being the maximum permissible numerical aperture (NA) of an optical waveguide to be connected in accordance with the specifications, of the measuring instrument.

Dependencies are inferred from the claim text.