The effect of strong inline filtering on the amplitude jitter in long optical systems

The accumulation of amplitude jitter in ultralong-haul (ULH) systems deploying strong optical filters is studied. It is shown that in such systems that operate with nonsoliton waveforms, the selective inclusion of filters may lead to the enhancement or suppression of amplitude noise accumulation, depending on the filter's positioning. This paper explains the improvement in performance that was demonstrated experimentally in a 60-span 12.5-Gb/s system with 12 periodically positioned bandlimited dynamic gain equalizers (DGE) (Optical Fiber Communication Conf., 2005). It is also shown that the same noise suppression as in (Optical Fiber Communication Conf., 2005) achieved by such a system can be achieved with as few as two strong filters if their positioning is properly optimized