Fibre Amplifiers & WDM
Erbium-doped fibre amplifiers (1987) boost light inside the glass, so one device amplifies many wavelengths at once; with wavelength multiplexing one fibre carries many channels.
Open in the interactive tree →Gain in erbium-doped fibre was shown in 1986-87 by two groups, David Payne's at Southampton and Emmanuel Desurvire's at Bell Labs. Pumped by laser diodes, the amplifier works in the 1550 nm band where silica glass is most transparent, so signals no longer have to be converted to electricity and back at every repeater. Ciena released the first dense wavelength-division multiplexing system in June 1996, and TAT-12/13 (1996) was the first transatlantic cable system with these amplifiers, carrying 2 x 5 Gbit/s. Payne and Desurvire received the 1998 Benjamin Franklin Medal.
Prerequisites
- Semiconductor Laser Diode1962Semiconductor laser diodes at 980 or 1480 nm pump it.
- Optical Fiber1970The amplifier is a length of doped optical fibre inside the cable.
Unlocks
- Fibre Submarine Cables1988Optical amplifiers replaced electronic repeaters in cables from TAT-12/13 (1996).