A New Data Detection Method for 35 Gbit/inch2 Multilevel Recording Using a Blue Laser and 0.85 Numerical Aperture Optics

概要

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In this study, a commercial Blu-ray disc was used for multilevel recording. The goal is to make its present capacity 2 times larger and data transfer rate 2 times faster. This technology is a promising candidate for improving extending the standard of the Blu-ray disc. To achieve this specification corresponding to an areal density of 36 Gbit/in.2, the bit length is reduced to 56 nm. The features of technology for 36 Gbit/in.2 are as follows: First, eight-level recording is adopted. Second, a new detection method named cell boundary data detection (CBDD) is developed to overcome severe intersymbol interference (ISI) from outer cells at a small cell length. Finally, we use the same optical pickup as that of the Blu-ray disc for doubling areal density. CBDD utilizes data sampled at the cell boundary, which is almost free of the influence of ISI without an equalizer. In addition, the popular error correction code of Bose–Chaudhuri–Hocquenghem (BCH) is applied to the part of the least-significant bit (LSB). As a result, CBDD with the BCH code achieved a bER of $1 \times 10^{-5}$ at the effective bit length of 57.6 nm, which indicates an areal density of 35 Gbit/in.2 by computer simulation. Moreover, we experimentally obtained a bER of less than $1 \times 10^{-5}$ using CBDD with the BCH code at a cell length of 200 nm.
2006-02-15