angle piece wt1 a leaf spring fe1 is likewise provided both leaf springs support at their end support plates ap1 and ap2 with which they rest under spring pressure on the exterior surface of the coated optical waveguide lf1c in order to keep these optical waveguides in their position in the v shaped grooves of the guide prisms fp and fn a hold down device nh illustrated in broken lines can be provided which exerts a sufficiently large pressure on the optical waveguide but simultaneously permits the latter to still execute a rotational movement it is also possible to provide additional hold down devices in the region of the guide prisms fp1 and fn which however must likewise be selected so that the rotational movement of the respective optical waveguide piece lf1 and lf1c is guaranteed the support plates ap1 and ap2 preferably are comprised of plastic with a sufficiently great friction resistance in the case of a rotational movement on the adjustment knob ek in such a manner that the angle piece wt1 is shifted to the left the lower support plate ap1 moves to the left whereas due to rotation of the rocker arm kh1 the upper support plate ap2 is moved to the right thus the longitudinal movement of both support plates which proceeds tangentially to the surface of the optical waveguide piece lf1c run in opposite directions and thus exert a torque on the optical waveguide lf1c this rotational movement is continued until corresponding to the examples according to fig2 and fig4 the.