Theoretical Comparative Studies of Cross- Section Evaluation in Erbium-doped Optical Fibers

In this paper, we introduce a different approach of previously reported method to determine absorption and emission cross-sections (σa and σe), and dopant concentration in Erbium doped optical fibers (EDOFs) with low background loss (α). We call this new method as variant input single cutback method (VISCM). There is technical similarity between VISCM and conventional cutback method (CCM) for determination of cross-sections, but in former pump and signal powers are not used together. We numerically verify the effect of different parameters such as input power, background loss, and EDOF amplifier cutback length on the cross-sections using VISCM and CCM. We also present the simulation results of maximum gain and optimum length using obtained cross-sections by two methods. We show that the VISCM presents more accuracy than that of CCM in any conditions. In the presence of α, both CCM and VISCM give not actual but pseudo values for the σa and σe. Using pseudo parameters values obtained by VISCM for α < 10 dB/km, the error of maximum gain and optimum length of designed EDOF is shown negligible. Received 23 May 2010, Accepted 8 July 2010, Scheduled 21 July 2010 Corresponding author: F. E. Seraji ([email protected]). 148 Karimi and Seraji