Observation of new polarization dependence effect in long haul optically amplified system

A new polarization dependence effect, called active PDL, has been observed, which leads to there being a significantly higher gain in the polarization state orthogonal to a polarized signal in a long haul optically amplified transmission system. The gain differential was 4.8 dB in a 69 amplifier system. This causes the ASE to accumulate with length faster than expected which introduces additional noise on detection. It is shown that the problem is solved by modulation of the signal´s polarization state, which has the effect of eliminating the active PDL.<>