Signals weaken as they travel. An amplifier is a device that increases the strength of a signal. It takes a weak input and produces a stronger output. In telecom, amplifiers boost radio signals, optical signals, and electrical signals. Without them, long-distance communication would be impossible.

Amplifiers come in many types. Electronic amplifiers use transistors to increase voltage or current. Optical amplifiers boost light directly without converting it to electricity. Erbium-doped fiber amplifiers are used in undersea cables and long-haul fiber routes. They can amplify many wavelengths at once.

Key specs

• Gain: how much the signal is amplified
• Bandwidth: range of frequencies it handles
• Noise figure: how much noise it adds
• Output power: maximum strength it can produce
• Linearity: how faithfully it reproduces the signal

Amplifiers add noise. They also distort if pushed too hard. Engineers balance gain against noise and distortion. In fiber networks, amplifiers are spaced every 50 to 100 kilometers. In radio networks, they are built into base stations and repeaters. The amplifier is the booster of the telecom world.