Low-frequency suppression in RLL codes for optical recording

New demanding applications of write-once and erasable optical media for video and data storage, put high constraints on the signal-to-noise ratio in the servo loops and require channel codes with improved low-frequency characteristics. New run length limited (RLL) block codes for optical recording with higher suppression of the low-frequency components are presented. These result from new criteria and design features in the choice of the alphabet of the codewords, in the algorithms for the minimization of the low-frequency contents and in the merging procedure. Results of the spectra calculation according to the described design have shown very good improvements in the low-frequency contents of the EFM code. Other results of optimized d=2 codes, suitable for optical recording applications are reported