"MODS" Discs

Each step in the evolution of the optical disc has been astounding. With its 750-megabyte storage capacity, the Compact Disc revolutionized the way music was recorded and played back. The DVD's 4.7 gigabyte capacity—twice that for a dual-layered disc—made possible the archiving of high-quality feature films on a durable, affordable medium. DVD is the first format that made building a film library a reality for ordinary movie fans. It's not a vast overstatement to say that DVD revived the film industry, creating unanticipated revenue streams.

Due sometime in the coming year, next-generation Blu-ray and HD-DVD discs promise to deliver both high density and high definition via the same 5" optical disc. Blu-ray backers claim that their format is capable of 25GB of storage per layer, enough to contain four or five feature films at DVD level of resolution. Promoters of Blu-ray and HD-DVD expect that the formats will fill the needs of movie lovers eager for high-definition home entertainment. It's reasonable to expect that high-def discs will get the same welcome from consumers that CDs and DVDs have received.

But what's over the horizon? How about a 1000GB (one terabyte) optical disc? That's enough to contain 236 feature films averaging two hours each. Such is the potential capacity of a 5" optical disc, according to physicist Dr. Peter Török.

In late September, at the Asia-Pacific Data Storage Conference 2004 in Taiwan, Dr. Török presented research done by him and his colleagues at London's Imperial College supporting the potentially vast storage inherent in a single disc. At the heart of their argument is the discovery that the space devoted to a single pit in an optical disc's surface could be encoded for as many as ten different data streams. Instead of "one bit per pit," the equivalent area could contain ten times more by precisely varying the angle of incoming and reflected light off "steps" etched into the sides of the pits, and by an interleaving technique he calls "Multiplexed Optical Data Storage" or MODS.

Should they become a commercial reality, MODS disc players could be backwards compatible with CD and DVD (and presumably, Blu-ray and HD DVD) players. The discs should ultimately cost no more to manufacture than ordinary discs do today. Török doesn't expect MODS discs to appear on the market until sometime in 2010 at the earliest, he stated. His group's ongoing work has been done in cooperation with researchers at the Institute of Microtechnology, University of Neuchâtel, Switzerland, and in the Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Greece, according to a September 27 report in Design Engineering.