A DH surface emitter which has an emission area diameter of 50 m is butt jointed to an 80 m core step index fiber with

A DH surface emitter which has an emission area diameter of 50 μm is butt jointed to an 80 μm core step index fiber with a numerical aperture of 0.175. The device has a radiance of 35 W sr−1 cm−2 at a constant operating drive current. Estimate the optical power coupled into the fiber if it is assumed that the Fresnel reflection coefficient at the index matched fiber surface is 0.01.