George Hockham and Charles Kao, while engineers at Standard Telecommunications Laboratories, an ITT subsidiary, developed the first conceptual breakthrough in the development of fiber optic transmission systems. In 1966, Kao and Hockham determined that optical fibers of fused silica could satisfy signal attenuation requirements by overcoming issues of absorption, diffusion, and bending loss. At the time, an attenuation of 20 dB per kilometer was considered satisfactory for a commercially viable system. See also fiber optics.