Digital Signal Processing for OFDM Synchronization

In high-speed coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems, wide range estimation of carrier frequency offset (CFO) and hardware-efficient symbol timing synchronization are essential. The CFO estimation using the Chinese Remainder Theorem (CRT) was recently proposed to provide wide range estimation. In this paper, the feasibility of the proposed CRT-based CFO estimation method is demonstrated in a real-time CO-OFDM system.

We also propose two-step symbol timing synchronization with simplified timing metric for CO-OFDM systems. The real-time experimental results show that the CRT-based CFO algorithm can estimate over a wide range corresponding to the sampling frequency and hardware-efficient, accurate symbol timing synchronization is achieved by the proposed synchronization method.