Coherent Fiber Optics

The general principles of fiber optics imaging were already known in the mid-1920’s, but the transmission of a useful image with a fiber optic bundle remained an impractical dream until the winter of 1956-7 when Michigan physicists Professor Wilbur Peters and, notably, his undergraduate student Larry Curtiss working in the sub-basement of Randall Lab developed a way to surround an ultra-thin glass fiber with a coating of higher-index glass and thereby overcome the problem of light leakage from individual fibers that had crippled all previous attempts.

This enabled them to construct flexible, ordered bundles of these fibers that could transmit very clear images over distances of a meter or more.   Dr. Basil Hirschowitz, a young MD and research fellow at the Michigan Medical School, then used the Curtiss-Peters fiber bundles to make a gastroscope that could be easily used with minimal discomfort for the patient. The astonishing clinical success of that Michigan gastroscope in February of 1957 led in following years to the many fiber optic imaging instruments that are used today’s medicine for diagnostics and for arthroscopic surgery and also for many industrial imaging applications. [An informative reference is Jeff Hecht’s book City of Light, Oxford University Press, 1999]

Beyond their utility for imaging, low-loss coherent optical fibers are also sine qua non for communication systems in which digital messages are sent with unprecedented bandwidth over an optical fiber instead of a copper wire. Economics dictates that a communication cable should contain many fibers, and it is notable that the Michigan research originally directed at problems of imaging was also essential for making cables in which messages would not leak from one fiber to another. It would have been much to the Michigan’s advantage if this had been recognized in the University’s patent applications because the method of clad fibers is basic to the success of any large-scale fiber optic communication systems..

 Additional Coherent Optics Sculptures

Two rather different sculptures are proposed to commemorate Michigan’s achievements in coherent fiber optics. .

1. The first represents the formation of a layered, coaxial optical fiber being narrowed as it is pulled from a hot oven. A ray of light is shown as being trapped within the central region of the fiber by total internal reflection at the interface between inner core of low-index glass and the coating of higher-index glass.
2. The second  is more demonstrative in that it invites the viewer to put an object on one end of a convoluted pipe to see the image appear at the other end. The construction is that of an actual coherent fiber bundle but with 256 coated fibers (each perhaps 1 mm diameter) spaced out over the area of a pipe that might be much larger overall diameter (perhaps 20 cm) to provide a 16×16 mosaic as an actual example of the fiber optic. With appropriate construction and precautions a sculpture of this design could be relatively maintenance free, even for outdoor display.