Abstract: A device in a fiber optic system for variably attenuating the signal between optical fibers consisting of two fixedly mounted optical fibers and a moveably mounted reflective surface disposed therebetween. Light emitted from the face of the first fiber strikes the reflective surface and is redirected toward the collecting face of the second fiber. That amount of redirected light which will fall incident upon the face of the second fiber, within a predetermined angle to the optical axis of the second fiber will be transmitted through the fiber and be measured by a light detector. By moving the reflective surface calibrated amounts with respect to the faces of the fixed fibers, the amount of light incident on the face of the second fiber, and thereby transmitted, can be varied, measured and controlled.