In this paper, primary technical challenges for emerging optical mobile backhaul (MBH) networks are discussed, with a focus on novel optical access and digital signal processing (DSP) architectures for future MBH. The first downstream/upstream Orthogonal Frequency Division Multiple Access and Time Division Multiple Access Passive Optical Network (OFDMA/TDMA-PON) achieving >100 Mb/s per-cell mobile backhaul and burst-mode operation using off-the-shelf avalanche photodiodes (APDs) is proposed and experimentally demonstrated for last-mile optical MBH with 200 cells per fiber. In the new approach, the use of OFDMA is motivated by the capability to establish low latency, virtual point-to-point links in the frequency-domain to serve high-density cell areas, while a judicious hybrid of DSP-enhanced digital radio-over-fiber (dRoF) and TDMA is proposed as an efficient way to meet <1 ms latency constraints subject to a 3 dB upstream burst-mode dynamic range tolerance. By thus enabling high speed, low latency, and low cost via simplified optics, the novel OFDMA/TDMA-PON is promising for future 4G and beyond optical backhaul networks.
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