absorbers 60a 60c are orthogonal to the bottom surface 50a of the substrate 50 any stray light that does not intersect the absorbers with a near normal incidence will intersect the bottom surface 50a of the substrate so it may also be advantageous to coat the bottom surface with a light absorbent material it is preferred for the light absorbers to have a relatively thin cross section so that the tops of the absorbers do not present a large surface from which stray light may reflect to minimize this effect by providing minimum width top surfaces the absorbers may have a triangular upright cross section i e the absorbers are wedge shaped or a trapezoidal upright cross section for example an embodiment of the invention incorporating upright triangular wedge shaped absorbers is shown in fig5 alternatively such wedge shaped absorbers can be inverted thereby directing reflected light toward the bottom of the substrate although providing a relatively wide top surface to the absorber in fig5 elements corresponding to similar elements in the embodiment of fig4 are illustrated with the same reference designations the embodiment of fig5 is also advantageous because the inclined input face of the absorbers causes stray light from fiber 100 to strike the absorbers with an angle that is even closer to perpendicular than is achieved by the absorbers in fig4 thus even further attenuating the stray light fig6 illustrates the effect of components of stray light reflected off of the absorbers of fig4 by way of example a stray light ray 70 strikes the absorber 60b at near normal incidence thus generating a weak reflected component 72 the component 72 then strikes the bottom surface 50a which.