The Next Step In 3-D Storage

Computerworld - As the demand from businesses and consumers for data storage explodes, developers of optical storage technologies are scrambling to condense more and more bytes into a smaller space. Until the long-awaited promise of holography as a storage medium is realized, fluorescent multilayer discs (FMD) may do quite nicely.

Constellation 3D Inc. (C3D) in New York has come up with a method of using red lasers and fluorescent dye to increase to 10 the number of information layers that can be put on each side of a disc, while matching the density and transfer speeds of DVD. In the future, the discs could have as many as 100 layers, according to John Ellis, director of marketing at C3D.

CD-ROMs use one information layer that reflects an infrared laser to supply 650MB of storage on a one-sided disc. DVDs use a red laser to supply up to 9GB of storage on a two-sided disc with two layers of storage per side.

In FMD technology, fluorescent dye replaces the reflective and semireflective coating in which information is stored in CD-ROMs and DVDs. This allows for more layers of information, because laser light isn't blocked from traveling deeper into the medium.

There's less noise and interference in the return signal as well, according to Ellis. That's because the fluorescent light that's emitted when a focused laser strikes a pit on one of the information layers has a different wavelength than the laser. The emitted fluorescent light carries the information, and the reflected laser is filtered out in the read device.

Both Philips Electronics NV and IBM have proposed the concept of multilayer reflective optical discs. The reflected coherent light of the probing laser, however, causes interference and cross talk among different information levels that drastically degrade the emitted signal.

The cost of a single FMD may be higher than that of other storage media, but its cost per gigabyte should be considerably lower, according to C3D. FMDs now in development will hold 140GB of data, as opposed to the 20GB predicted for next-generation DVDs.

C3D is banking on FMD technology becoming the standard in all kinds of small portable appliances and electronic devices. FMD will allow gigabytes of storage on a disc the size and shape of a credit card. Lev Zaidenberg, C3D's director of business development, says he expects the technology to revolutionize data storage within five years. It will replace CD and DVD technology and will be used in mobile phones, handheld computers, video recorders, PCs, digital cameras and high-definition TVs, he