Optics 101

What is an Optical Amplifier?

Optical amplifiers are devices that amplify an optical signal without converting it into an electric signal. Optical amplifiers are of two kinds: laser amplifiers and feedback amplifiers. Laser amplifiers do not have an optical cavity, while the feedback amplifiers consist of a suppressed cavity.

Optical amplifiers are classified based on the mechanism that is incorporated for amplification of the signal. Optical amplifiers are useful in long distance communication that requires minimum attenuation loss. This datasheet will elaborate on the construction, working principle and the applications of the various types of optical amplifiers.

Working Principle

The working of the optical amplifiers varies with the mechanisms used for amplification. The working of each of the amplifier types is as below:

  • Laser/doped fiber amplifier – stimulated emission of the gain medium of the amplifier causes amplification of the input wavelength
  • Semiconductor optical amplifiers (SOAs) – the amplification is brought about by the recombination of the electron hole pairs
  • Raman amplifiers – elastic scattering of the incoming light with the phonons present in the lattice of the gain medium, results in the production of phonons that are coherent with the incoming light
  • Optical parametric amplifier – a weak input signal is amplified in a non-centrosymmetric non linear medium


The applications of the various types of optical amplifiers are given below:

  • Doped fiber amplifiers are used in wavelength division multiplexed communication and high power laser systems
  • Semiconductor optical amplifiers are used in optical signal processing, wavelength conversion, signal demultiplexing and pattern recognition
  • Optical parametric amplifier is used for expanding the tunability of ultrafast solid state lasers

Sources and Further Reading

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