Module 15 : ERBIUM DOPED FIBER AMPLIFIERS (EDFA)
Lecture : ERBIUM DOPED FIBER AMPLIFIERS (EDFA)
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  In the absence of any radiation, the ions are in their ground states $ g$. If a beam of light of appropriate frequency is incident on the system, the ions will be excited to the higher levels. This radiation, called pump radiation , if chosen at 980 nm, will excite the ions to the level $ u$. The lifetime of the ions in the level $ u$is approximately $ 1 \mu s$. The ions readily decay to the metastable level $ m$by non-radiative transition, i.e. by releasing heat.
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