25 GB read-only disk system using the two-dimensional equalizer

In order to achieve a higher density disk system, we applied a two-dimensio nal equalizer along with a limit equalizer to an optical disk drive system which has an objective lens with a numerical aperture of 0.85 and a thin tr ansparent cover layer of 0.1 mm thickness. Consequently we realized the 25G B read-only disk system with sufficient margins against disk tilt and defoc us. The two-dimensional equalizer is composed of a cross-talk cancel system and a tangential adaptive equalizer, and could prevent deterioration due t o inter-symbol interference and cross-talk from adjacent tracks. Using the limit equalizer could prevent deterioration due to disk noise. By measuring the jitter with the limit equalizer, which has an ability to expand the sy stem margin almost equivalent to that of the Viterbi decoder. we could eval uate the disk quality for standardization and verification.