Mixed-polar-amplitude-modulation pilot-based blind phase estimation for coherent optical OFDM system

In this paper, we propose an improved pilot-based blind (PBB) phase estimation method named mixed-polar-amplitude-modulation (MPAM-PBB) method for coherent optical orthogonal frequency-division multiplexing (CO-OFDM). In the previous PBB methods, all the selected so-called pilot subcarriers (PSs) are loaded with bipolar amplitude modulation (AM) format signal. In MPAM-PBB method, half of the selected so-called pilot subcarriers (PSs) are changed to be loaded with bipolar AM format signal, which will improve the SE. The performance of 3 phase noise estimation methods including the conventional pilot-aided-based (PAB) estimation method, PBB method and MPAM-PBB method are compared in a CO-OFDM transmission simulation. The results show that the proposed MPAM-PBB method can achieve comparable performance with PAB method and get higher SE of the system than PBB method without increasing the computational complexity.