Rigorous assessment of intersymbol interference impact on the performance of optically preamplified receivers

Intersymbol interference (ISI) may be a major impairment of optical fiber communication systems. In this contribution we extend the formulation presented previously, taking into account the different shape of each pulse in the received signal. This leads to a significant difference of ISI magnitude in comparison with the previous method. We conclude that methods of computing the BER using the same pulse shape for all bits are only accurate when the pulse superposition principle is valid. In most optical communication systems this principle is not valid and leads to significant discrepancies of BER and receiver sensitivity.