Optimized eight-dimensional lattice modulation format for IM-DD 56 Gb/s optical interconnections using 850 nm VCSELs

In this paper a novel eight-dimensional lattice optimized modulation format, Block Based 8-dimensional/8-level (BB8), is proposed, taking into account the tradeoff between high performance and modulation simplicity. We provide an experimental performance comparison with its n-level pulse amplitude modulation counterparts in a 28 GBd 850-nm vertical-cavity surface-emitting laser based intensity-modulation direct-detection system. Successful data transmission over 100 m multimode fiber links of OM3 and OM4 types is demonstrated, with a power margin close to 2 dB at 100GBASE-SR4 forward error correction threshold. A simplified bit-to-symbol mapping and corresponding symbol-to-bit demapping algorithms, together with a hyperspace hard-decision, are designed specifically for applications of short-reach data links. These algorithms are expected to use affordable computational resources with relatively low latency.