Communication methods employing optical transmission means existed, albeit in a very primitive form, for millennia; well before the work of the abbot Claude Chappe. However, the amount of information thus transmitted remained low. Telecommunications, which at first were exclusively optical, really started only at the end of the 18 ^th century with the appearance of the optical telegraph. For fifty years, wireless optics enabled individuals to communicate over long distances. However, the quality of service (QoS) remained low due to the lack of reproducibility and reliability of both the transmitters and the receivers; of the men and the materials; and the changing nature of the air as a transmission medium.

Electricity (electric charges moving through copper) rapidly replaced optics (photons moving through the air). Information can be transferred along copper lines at relatively high flow rates. At the beginning of the third millennium, these copper-based links are still extensively exploited. Copper has served for decades as the basic material for very long distance links, and has been instrumental in establishing a network for the transmission of information across the whole globe.

The invention of the laser in 1960 paved the way to another solution, in the form of optical telecommunication based on optical fibers, which offers a quasi-unlimited line capacity. The almost simultaneous development in 1970 1971 of low-attenuation optical fibers, and semiconductor lasers emitting in continuous mode at room temperature, led to the explosion of wired optical telecommunications. Glass is the transmission medium for photons, and glass...