DC-Free Coding of Run-Length-Limited Codes for Multi-Level Optical Recording Systems

Optical storage systems require the channel data sequence having DC-free characteristic. DC-free coding schemes for binary sequence are difficult to apply directly for high-rate multi-level optical recording systems. Thus, we present an effective coding scheme that DC-content is sufficiently controlled by inserting redundancy bits less than 1.25% for multi-level optical recording systems. This method is very simple and can be used for all multi-level run-length-limited codes.