Noise suppression of erbium-ytterbium co-doped fiber amplifier through annealing effects.

In the past few years, although annealing effects have been widely used to restore the power features of fiber amplifiers, their noise feature has not yet been sufficiently investigated. Thanks to the recovery of partial color centers (especially the ${{\rm Yb}^{2 + }}$Yb2+ center) through photobleaching, the absorption of seed signal light due to the presence of color centers is weakened, and the sensitized path of the irradiated erbium-ytterbium co-doped fiber amplifier (EYDFA) is partially restored, which helps to suppress amplified spontaneous emission as well as increases the gain of the EYDFA. The thermal annealing process is performed by the first amplification stage of the EYDFA, and the increase in the optical signal-to-noise ratio of the signal light indicates that our proposed scheme could be also exploited to further improve the output performance of the EYDFA. This work is anticipated to open up new prospects for future optical communications systems based on pre-amplification technology.