Receive Diversity-Based SNR Improvement in OPDM-OFDMA-PON Single-Wavelength Multiple Access

In order to accommodate the demands for the next-generation passive optical network (PON), it is necessary to maximize the transmission capacity and the multiple accesses (MAs) within a single wavelength. However, there is a serious problem that the optical beat interference (OBI) occurs in uplink MA. With optical pulse-division multiplexing (OPDM), the OBI can be reduced simply and effectively; thus, OPDM is a useful optical transmission technique for single-wavelength MA that offers various advantages. To increase the transmission capacity within the limited bandwidth of an optical modulator, we propose a signal-to-noise ratio (SNR) enhancement technique involving receive diversity achieved using the replica inevitably generated in OPDM. The SNR improvement was experimentally verified, via a 20-km optical transmission in OPDM-based single-wavelength MA. The enhanced SNR improves the modulation order and spectral efficiency, and relaxes the requirements of OPDM and the decoding complexity. The proposed replica-based receive diversity can increase the SNR of the uplink signal, reduce the OBI, and guarantees the advantages of OPDM; thus, it is a useful technique for effectively supporting the high data capacity and MA required for the next-generation PON.