Optical computers, possibly using glass-fiber transmission lines and quantum-electronic storage elements, are now under consideration, according to L.C. Clapp of the Computer Development Laboratory, Sylvania Electric Products Inc. The Sylvania researcher discussed a number of approaches to optical computer design at the Western Joint Computer Conference in Los Angeles.
Mr. Clapp speculated that transmission lines in optical computers might be long glass fibers, which are extremely flexible and easy to use. "The low cost of these fibers," he said, "compares favorably with the expensive wave guides needed for microwave computers." The attenuation of light passing down such a fiber is due only to the absorption of the glass and is less than 1% of energy per inch, he added. Crosstalk between neighboring transmission lines would be eliminated by coating the optical fiber with a thin glass film of lower refractive index. To store information, quantum-level memory devices might be used. "Electrons can make transitions from one quantum level to another in very short times—on the order of 10−8 or 10−9 second at optical frequencies," Clapp explained. (Electronic Design, May 24, 1961, p. 10)
Although this brief article seems to report speculations more than actual developments, at least it shows the study of optical computing taking place in the early 1960s. Unfortunately, it doesn't mention the switching elements, but it does point to fiber optics as a digital transmission element. It should also be noted that these studies were proceeding despite the fact that the semiconductor laser wasn't announced until the following year.