Multiplier-Free Carrier Phase Estimation for Optical Coherent Systems

A multiplier-free carrier phase estimation (CPE) algorithm is investigated in this letter. The Viterbi and Viterbi (V&V) algorithm is widely used in CPE, because the V&V algorithm is less complex than many other feed-forward CPE algorithms, including the blind phase search algorithm. In the V&V algorithm, an M th power operation is used to remove the modulated data phase. However, one disadvantage of the $M$ th power operation is its large computational complexity. In this letter, we extend our prior simplified M th power method from frequency offset estimation to CPE and propose an improved V&V algorithm, adopting the absolute operation as an approximation and making the V&V algorithm a multiplier-free CPE algorithm. Using simulations, the improved V&V algorithm is compared with the traditional V&V algorithm in the 32-GBd quadrature phase-shift keying, 8PSK, star-8QAM, and square-16QAM systems for CPE. The results show that the improved V&V algorithm outperforms the traditional V&V algorithm. In addition, the complexity is reduced effectively and no multiplier is required.