The invention of the laser and its demonstration is dated 1960. It was suggested in 1966 that optical fibres might be the best choice for using laser light for optical communications, as they are capable of guiding the light in a manner similar to the guiding of electrons in copper wires. The main problem was the high losses of optical fibres: fibres available during the 1960s had losses in excess of 1 000 dB/km. A breakthrough occurred in 1970 when the losses could be reduced to below 20 dB/km in the wavelength region near 1 000 nm. At about the same time, GaAs semiconductor lasers, operating continuously at room temperature, were demonstrated. The simultaneous availability of compact sources and of low-loss optical fibres led to a worldwide effort for developing optical fibre communication systems.