Performance-Enhanced Optical Non-Orthogonal Multiple Access Enabled by Orthogonal Chirp Division Multiplexing

In this paper, we propose a novel optical non-orthogonal multiple access (NOMA) scheme based on orthogonal chirp division multiplexing (OCDM) in a low-cost intensity modulation and direct detection system for passive optical networks (PON). The proposed OCDM-NOMA scheme can effectively improve spectral efficiency and serve more users by multiplexing spectrally overlaid OCDM signals in power domain. Under the advantages of the chirp spread spectrum, the proposed OCDM-NOMA scheme can also enhance the bit error rate (BER) performance compared to NOMA scheme based on orthogonal frequency division multiplexing (OFDM). A 17.8 Gb/s OCDM-NOMA PON transmission over 25 km standard single-mode fiber is experimentally demonstrated. The results show that, when compared to OFDM-NOMA and precoding OFDM-NOMA, OCDM-NOMA can achieve receiver sensitivity gains of 1.3 dB and 0.5 dB for the high-power branch signal, and 1.4 dB and 0.6 dB for the low-power branch signal at a BER of 3.8x10(-3). Furthermore, we investigate the feasibility of using higher-order modulation in NOMA technology for the first time to further improve data throughput and spectral efficiency. In a 22.2 Gb/s transmission, the optimal power division ratio is determined, and the transmission performance is investigated. According to the experimental results, OCDM-NOMA with higher-order modulation can be a promising candidate for next-generation PONs.