An improved multiplier-free feed-forward carrier phase estimation algorithm is proposed for dual-polarization quadrature- phase-shift-keying (DP-QPSK) with coherent detection. The bit error rate (BER) performance, block length effect and linewidth tolerance of the proposed algorithm are evaluated for a 112 Gbit/s DP-QPSK system. A linewidth symbol duration product of 2.9×10^-4is demonstrated for 1 dB optical signal-to-noise-ratio (OSNR) penalty at BER of 10^-3for the proposed algorithm. The hardware complexity of the proposed multiplier-free algorithm is demonstrated to be much lower than that of the 4th power algorithm.