A semiconductor optical amplifier (SOA) is a compact, electrically pumped device that amplifies an optical signal directly. It works like a laser diode without end mirrors, using a semiconductor gain medium to boost passing light via stimulated emission. SOAs are prized for their small size and fast switching speeds, making them common in telecommunications and integrated photonics, though they suffer from higher noise figures and polarization sensitivity compared to fiber amplifiers.
We need to put an SOA in the circuit to boost the signal before the next splitter.
Because SOAs have very fast carrier dynamics, they are often used for nonlinear signal processing like wavelength conversion, not just raw amplification.
Related terms
EDFA
Erbium-Doped Fiber Amplifier: the optical amplifier that boosts signals near 1550 nm without converting them to electronics.
Gain medium
The material inside a laser or amplifier that amplifies light once it is pumped: a crystal, glass, gas, semiconductor or doped fiber.
Laser diode
A semiconductor laser driven by electric current, used as a light source in its own right and to pump other lasers.