Welcome to the Glass Age

78 can carry light over hundreds of kilometers before needing (optical) signal amplification. The Internet, namely the word-wide system of connected computers and other electronic devices, already offers fast personal and business communications and access to information databases. There is, however, a continuous search for faster and higher capacity data technologies, with 5G being one upcoming solution. 5G, in fact, is the fifth generation of cellular networks, and promises to be up to 10 times faster than the 4G technology currently used by most cellular phones. The development of internet and 5G will require a further expansion of the fiber optic lines that will remain the data-transport backbone of the overall network. Presently, over 500,000,000 kilometers of communications glass optical fiber are manufactured globally each year, a remarkable indication of the importance of glass and light [1]. The history of fiber optics, particularly from a glass-perspective, is as intriguing as it is timely. For a fuller treatment of this synergy, the reader is referred to Ref. [2]. Briefly, it had long been appreciated that the use of light as a medium onto which information could be encoded was far superior to electricity from the standpoint of capacity (bandwidth). Considerable efforts were already underway in the 1950s concerning free-space optical communications and gas-filled or mirrored pipes as microwave guides. The conceptualization and construction of the maser, and, subsequently, its shorter wavelength sibling, the laser, further accelerated research into communications using visible or near-visible optical carriers. With a collimated and coherent light source in the laser, studies into waveguiding materials were an obvious complement. The pioneering realization that glass could enable suitably high transparency (low loss) fibers was made by Charles Kao, in 1966, for which he was awarded the 2009 Nobel Prize in Physics. In 1970, Corning won the race to fabricate the first < 20 dB/km low loss fibers by implementing a chemical vapor deposition (CVD) process enabled by a flame hydrolysis method developed there in the 1930s. Soon thereafter, consistent pioneering achievements in silica glass-based optical fibers, both passive and active, were made by Corning, Bell Labs, NTT, and the University of Southampton, among others, into the late 1980s. This period, from 1966 through to, about, 1990, represents a critical first phase of glass development for fiber optics. By the early 1990s, optical fiber communication systems were beginning to be installed globally and materials efforts began to focus on glasses whose performance could exceed, at least in theory, that of silica. The most