Single Subcarrier Gold Sequences Modulated Timing Synchronization for Upstream OFDMA-PON

In this paper, we propose a timing synchronization scheme based on Gold sequences modulated on a single subcarrier for the orthogonal frequency-division multiple access passive optical network (OFDMA-PON). The intensity-modulation and direct-detection real-time experimental demonstrations are carried out over 25-km standard SMF, the performance of the synchronization is investigated by using two optical network units (ONUs) and one optical line terminal based on field-programmable gate array. The results show that the accurate timing symbol synchronization can be achieved at received optical power as low as -21 dBm on the condition of sampling frequency offset range from 0 to 70 ppm between two ONUs. The measured bit error rate is below the forward error correction threshold for both ONUs at received optical power of -18 dBm.