Low-transmission-loss prism for optical switches designed by means of optical-power-evaluation computer program

We have developed a low transmission loss prism for optical switches suitable for optical fiber systems which monitor and control factory equipment. We have realized the low transmission loss prism by using the geometrical property of ellipsoids and a newly developed optical power evaluation computer program which facilitates estimating the coupling efficiency between two optical fibers considering total reflection phenomena, numerical aperture and far field pattern of the optical fiber for an aspherical optical system. The transmission loss of the present ellipsoidal prism is 5 dB for the plastic fiber with the core diameter of 1 mm, and 5.8 dB for polymer clad fiber with core diameter of 0.2 mm. The present ellipsoidal prism improves transmission loss by 4 dB as compared with the conventional spherical prism for the optical fibers usually adopted to the optical fiber systems. The calculated loss and experimental loss agreed well. This agreement confirms the usefulness of our computer program.