Power Sparse Code Division Non-Orthogonal Multiple Access Scheme for Next-Generation Flexible Optical Access

Abstract

In this paper, a power sparse code division non-orthogonal multiple access (PSCD-NOMA) scheme is proposed for next-generation flexible optical access, which is based on the multi-stack network. All the optical network units (ONUs) are allocated with different power levels according to path loss to achieve power multiplexing. Compared with sparse code multiple access (SCMA), the proposed sparse code considers users’ information as a whole, and a larger number of users can be implemented with relatively low complexity and similar or better performance. It can achieve 150% overload by sparse code. Moreover, an irregular-shaped 8 quadrature amplitude modulation (IS-8QAM) constellation diagram is devised that is more suitable for PSCD-NOMA. Orthogonal chirp division multiplexing (OCDM) is employed for its advantages of the stronger anti-dispersion ability. A 10.23 Gb/s PSCD-NOMA transmission over 25 km standard single-mode fiber is experimentally demonstrated. The results show that IS-8QAM can get at least 0.6 dB gain than the conventional 8QAM scheme. The difference in sensitivity between ONUs of different power levels is 2.8 dB, which corresponds to the loss between different paths. The sensitivity difference between different users at the same power level is only 0.3 dB, which indicates the proposed PSCD-NOMA has good fairness. PSCD-NOMA is a potential method for future optical access systems due to its great performance.