Modulation codes of multilayer disk

Basing on the structure of multi-layer parallel-accessed disc, current modulation code is optimized to achieve higher density storage. Two problems, which may be serious after the optimization, are discussed: acceptable jitter and synchronization process of PLL. A novel method for procuring combined signal of channel bit clock for multi-layer disc is proposed, which satisfies the requirements of PLL. The novel method is at last proved by probabilistic theory. At the end of this paper, parameters of RLL for multi-layer disc are presented: d=4, k=10~15. These new parameters improve the track-density by 15% ~ 20%.