A comparison among various PMD mitigation approaches

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The proposed methods of Polarization Mode Dispersion (PMD) mitigation can be divided into three main approaches: (i) electrical PMD compensation, (ii) optical PMD compensation, and (iii) mitigation by use of robust modulation formats, increased power margin etc. In this paper, we discussed each of these sententiously, with less emphasis on comparing the first and the second, but with more emphasis on the third. We quantify the benefits of using different techniques for compensation of PMD in fiber-optic communication systems by means of numerical simulations. This is done both with respect to PMD-induced pulse broadening and in terms of system outage probability for different data formats [nonreturn-to-zero (NRZ) and return-to-zero (RZ)]. With our experimental results, we find that RZ performs better than NRZ, furthermore, it is comparable with 2-3 DOF PMD compensator, and can be expected to be a practical alternative in particular if used in combination with error correcting codes. We also study the trade-off between power margin and acceptable PMD. Moreover, it is generally believed that a PMD compensator with a polarization controller and a variable delay line can only compensate the PMD to the first order. Our experimental results show that, the counterintuitive fact that this scheme can also partially compensate for higher order PMD. We also investigate the benefit of using a polarizer as compensation element where the optical average power can be used as a feedback signal.