Performance analysis of AO‐OFDM‐CDMA with advanced 2D‐hybrid coding for amplifier‐free LR‐PONs
Résumé
All-optical orthogonal frequency division multiplexing (AO-OFDM) and optical code-division multiple-access system (OCDMA) are combined in the first analytical model, which considers subcarrier hopping by means of advanced two-dimensional (2D) hybrid-coded (2D-HC) signature. The model incorporates probabilistic subcarrier overlapping, multiple-access interferences and is tested, for the first time, over amplifier-free long-reach passive optical networks (LR-PONs) using cost-effective intensity modulations and direct detection. For the upstream direction at 40 Gb/s, AO-OFDM-OCDMA outperforms a ‘classical’ multi-channel OCDMA system for low received powers and any number of simultaneous users. In comparison to conventional 1D Walsh–Hadamard, 1D prime code and 2D prime hop system, coding with 2D-HC can improve the performance of AO-OFDM-CDMA, thus allowing a higher number of simultaneous users in LR-PON without optical amplification. From numerical simulations, the authors show that 16-quadrature amplitude modulation (16-QAM) AO-OFDM-CDMA with 45 users has comparable performance to conventional multi-channel 16-QAM coherent optical OFDM in the downstream direction and up to 58 km with 1:45 split ratio, without employing complex coherent technology. Similarly, based on the feasibility of physical implementation configuration, a budget power calculation is performed showing 108 km as maximum reachability distance for 40 Gb/s QAM signal, 1:64 split ratio when considering standard forward-error-correction.
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