Fixed point precision requirements of the CMA for digital coherent access

We investigate the bit precision required for the implementation of a fixed point constant modulus algorithm equalizer with least mean squares tap updating for coherent receivers. We demonstrate that for a 10Gbit/s PM-QPSK access system operating over 80km, with 7% and 20% FEC overheads, the benefit of increasing the resolution of the fixed point arithmetic saturates at 5 bits.