As can be seen from the name Amplified Spontaneous Emission (ASE), this is a process in which a spontaneously emitted radiation is amplified. This is also referred to as superluminescence. The ASE effect occurs wherever light signals are amplified, including in lasers, superluminescent diodes, fiber amplifiers, and other optical
amplifiers (OA). The ASE effect is an undesirable effect that can lead to parasitic reflections and natural oscillations of the laser and can also destroy it. It limits the possible gain from a single-stage optical amplifier to about 40 dB
to 50 dB. Higher gains are possible for light pulses and can be achieved by using optical amplifiers connected in series. In addition, the Amplified Spontaneous Emission goes directly into thenoise and thus into the optical signal-to-noise ratio
(OSNR). The higher the Amplified Spontaneous Emission, the higher the noise in the optical transmission systems and the lower the optical signal-to-noise ratio.