Laser in Communications: Section Introduction

Optical fibre systems have revolutionized telecommunications. First proposed by Kao and Hockham [1] in 1966, the development of optical communication systems presented many challenges. First, low-loss fibres based on glass had to be produced. Second, optical communication systems differ from radio in that the photon energy is much larger and so receivers operate close to the quantum noise limit. The design of the total receiver (detector plus amplifier) is, therefore, critical. Finally, the development of the optical source has presented some of the greatest challenges. The original trial systems used light-emitting diodes, as these could be modulated at MHz frequencies. However, it was the development of room temperature semiconductors lasers that enabled the high-data rate, long-haul systems of today.