The very first Single-Mode optical fibres exhibited such high loss through absorption and scattering, that it was not possible to determine whether bends or the mechanical tolerances would make long distance propagation impossible. George Hockham used his microwave expertise and experience, to simulate the various mechanical properties and imperfections of an optical dielectric waveguide (fibre) at microwave frequencies. The large scaling factor between optical frequencies and microwave frequencies enabled him to investigate phenomena such as diameter variations, at manageable physical scales. He used finned brass rods and varied the diameter along the length to simulate microscopic diameter variations. This enabled him to verify that the tolerances achievable by drawing a glass fibre (from a larger diameter glass preform) would be acceptable.
