An alternative to using oxide glass is to use fluorozirconate (ZrF) glass. commonly known as ZBLAN glass. Though its glassy structure is not fully understood, it provides a good host for rare earth ions. The major glass forming components of ZBLAN glass are Al (which along with Zr, acts as a glass former), La (intermediate), Ba and Na (network modifiers). The La atoms are easily substituted by rare earths such as Er.
The figure above shows a typical configuration of EDFA based communication system. The optical output is first passed through an optical isolator which prevents reflection, i.e. allows light to move from left to right. The coupler allows the pump input to be fed into the fiber with minimum loss.
3.
Principle of EDFA:
Energy levels of Er doped system is shown in the figure. It may be noted that the energy levels form three groups of energy levels marked with their specroscopic notations. For simplicity, we will model these three groups of energy levels by three sharp levels of energy denoted by and , representing respectively the upper, the metastable and the ground states.
) glass. commonly known as ZBLAN glass. Though its glassy structure is not fully understood, it provides a good host for rare earth ions. The major glass forming components of ZBLAN glass are Al (which along with Zr, acts as a glass former), La (intermediate), Ba and Na (network modifiers). The La atoms are easily substituted by rare earths such as Er. 
doped system is shown in the figure. It may be noted that the energy levels form three groups of energy levels marked with their specroscopic notations. For simplicity, we will model these three groups of energy levels by three sharp levels of energy denoted by 
and 
, representing respectively the upper, the metastable and the ground states. 
