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What is PER?
(Polarization Extinction Ratio)
Amplified Spontaneous Emission (ASE) is unwanted broadband optical emission generated in a gain medium, such as a rare-earth doped fiber, when spontaneously emitted photons are amplified as they propagate through the medium.
ASE is an important characteristic of fiber amplifiers and fiber lasers because it consumes available gain and can reduce the signal-to-noise performance of an optical system.
HOW Polarization Extinction Ratio Works
ASE begins with spontaneous emission from excited ions and becomes amplified as the emitted photons propagate through the gain medium. Unlike a coherent signal, ASE is broadband and has a random phase.
Spontaneous emission
Excited ions in the gain medium spontaneously release photons at wavelengths within the material's emission band.
Optical amplification
Some of these photons travel through the gain medium and stimulate further emission, increasing their optical power.
Broadband noise
Because spontaneous emission occurs across a range of wavelengths and with random phase, the resulting ASE forms a broadband noise component that competes with the desired optical signal for available gain.
