Updated US data storage specialist C3D will today show off a technique for creating a CD-sized disc capable of holding up to 140GB of information. Current CD-ROMs can store 0.65GB of data. Double-sided DVD-ROMs can hold 6GB. C3D's system, dubbed FMD ROM, uses a multi-layer disc containing fluorescent materials as the active optical storage medium. Regular CD units operate by reflecting laser light off the surface of the disc to read. FMD (Fluorescent Multi-layer Disc) uses the laser simply to stimulate the fluorescent material to emit light. "This fluorescence property enables writing and reading of multi-layer structures with much greater storage capacity than offered by current optical memory products," says the company. One interesting side-effect of the use of fluorescent materials is that each disc is transparent -- to visual light, at any rate. And since the technique isn't based on reflection, a single laser can pass through the disc, activating the fluorescent material in each layer as near as damnit simultaneously, allowing multiple tracks to be read at the same time. That means data can be read much more quickly than before. But there's a snag: the system isn't compatible with current CD and DVD drives. However, C3D reckons existing equipment can be made to read FMD ROM discs with "minimal retooling". That's probably part of the reason why the technology won't see light of day before Q4 2000. As with current optical technologies, FMD will initially only be available in read-only formats -- write and re-write versions will come on-stream sometime later, though the company couldn't say when. C3D is also working on a compact version of the technology, aimed at the mobile market, that squeezes a sliver of FMD material plus reader/writer hardware into a PC Card case. ®