Optical Communication system On Matlab

shaiderrn

I have an Optical fiber communication system MATLAB code , in which a system has been designed to find out the Bit error rate of the system, i want to find out the Gain of that system, what will be the easiest way to find out the gain of that system ?
another question if i want to Imply Erbium Doped Fiber Amplifier in that system and find out gain after the inclusion of that amplifier how will i have to start with such cases ?