13 elements - Erbium

Erbium
Rare earth element
Atomic number: 68
Used in: optical fibres
Criticality rating: not rated

Reading this article online? Or keeping half an eye on your email while you read? If so you are probably doing it with erbium.
Erbium is a crucial ingredient in the optical fibres used to transport light-encoded information around the world. These cables are remarkably good at keeping light bouncing along, easily outperforming a copper cable transporting an electrical signal. Even so, the light signal slowly fades as it racks up the kilometres, making amplification necessary.
Excitable ions of erbium are just the ticket. Embedded every so often within short sections of the optical fibre wall, they are pushed into a high-energy state by irradiating them with a laser. Light signals coming in along the fibre then stimulate the excited erbium ions to release their stored energy as more light of precisely the right wavelength, giving the signals a boost.
The good news is that while supplies of erbium are relatively tight, demand for optical fibres is not skyrocketing as it is for other technologies. On current trends, this is one element we will continue to be able to live with.