Simple modeling approach for the temperature dependence of the gain of erbium-doped fiber amplifiers

In many practical wavelength-division multiplexed (WDM) systems, erbium-doped fiber amplifiers (EDFA) must maintain a flat gain spectrum over a broad bandwidth for a wide temperature range. When the flatness specification is tight, the temperature dependence of the erbium ion spectra is too great to allow flatness over a wide range of temperatures. To date, all observed temperature variation data has been for specific EDFA designs and no simple rule has been developed for extending the observations to a wide range of EDFAs. We show that the gain and absorption parameters of an erbium- doped fiber follow easily fit dependencies on temperature. Consequently, the change in an EDFA spectrum with temperature can be easily predicted by use of a computer model or sometimes by direct computations using the known dependencies. Physical insight into the meaning of the dependencies is presented and predictions for typical EDFAs are shown.