Rate-4/5 4-ary modulation code for 4-level holographic data storage systems

This paper presents a 4/5 4-ary modulation code design for 4-level holographic data storage (HDS) systems. The multi-level HDS systems, capable of far greater storage densities than traditional storage technologies, are regarded as one of the most promising candidates for ultra-high-capacity optical storage devices. Significantly, the HDS systems promises to provide the best solutions for cloud storage services. Yet, the systems are significantly disturbed by many challenges, such as two-dimensional (2D) interference, blur effect, and misalignment. The proposed code is designed based on a 4-step procedure, where the codewords at the output of the encoder can avoid not only the effect of the worst 2D interference but also obtain a minimum distance between two arbitrary codewords of 0.47, which is larger than the minimum distance of a conventional 6/9 modulation code. Simulation results demonstrate that the proposal gains about 1 dB better than the traditional 6/9 modulation code at a 10(-9) bit error rate.