In dual-polarization coherent optical fibre transmission, adaptive blind equalizers based on constant modulus algorithm (CMA) have been proposed for polarization demultiplexing and inter-symbol interference compensation since it allows good convergence at low computational complexity. While CMA is known to be hampered by singularities induced by correlations between the equalizer’s output signals, it has been shown that their occurrences can be avoided by modifying the CMA scheme o penalize these correlations. However, the dependence of the singularity avoidance according to both the parameters of the CMAs and the channel has not been exhaustively studied. Hence, considering optical access networks with the objective to avoid CMA singularity in a wide range of polarization mode dispersion (PMD) situations, we study this dependence by computer simulations over deterministic realizations of the channel. We introduce a refined CMA scheme and exhibit proper sets of parameters for singularity-free operation up to 5 ps/√km PMD realization (22.36 ps DGD) in a 32 GBaud dual-polarization QPSK system. Solutions for covering extended PMD ranges are suggested also.