Tutorial.pdf

It is immediately seen that optimal gain flatness of < 1 dB can be achieved using fiber lengths of
approximately 25 km.
The influence of fiber losses
In the case of nonlinear devices like that broadband Raman amplifier it is not always true that less
background fiber losses assure better performance. In order to determine quantitatively the
influence of this parameter on the gain flatness of the amplifier we can perform another
“sweeping” calculation. Let the values of attenuation vary in the range 0.2 –0.3 dB/km.
Figure 98 - “Sweeping” the fiber attenuation
After the calculation we get the following results, which show that the optimal flatness and
small positive gain correspond to attenuation coefficient of 0.22-0.23 dB/km.
Figure 99 - The results as a function of the parametrically swept fiber attenuation
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