The Fluorescent Multilayer Disc (FMD) is an optical disc format developed by 3D Constellation that uses fluorescent materials instead of reflective materials for data storage. Disc formats based on reflective materials (such as CD and DVD) are in practice limited to two layers, mainly due to interference, scattering and crosstalk between layers. However, the use of fluorescent materials allows the FMD to use up to 100 layers. These extra layers allow the FMD to store capacities of up to one terabyte, maintaining the traditional size of optical disks. Operating Principles
The disadvantage of FMD is the infiltration of fluorescent materials. When light from a laser destroys some of the bright material, it emits light of different wavelengths. As FMD discs are transparent light can travel through layers without hindrance. The transparency of the discs, combined with the ability to filter the laser light, provides a signal-to-noise ratio far superior to that of reflective media. This allows the FMD to have many layers. The main limitation on the number of layers is the thickness of the disk. Development A 50GB prototype disk was exhibited at the COMDEX industry demonstration in November 2000. The first generation of FMD used 650nm red laser, delivering 140GB per disc. The second and third generations of FMD employ 405 nm blue laser, giving capacities of up to one terabyte. After Constellation 3D broke down due to a scandal (essentially the scandal was that the prototype shown in COMDEX 2000 was a fraud) a new company called D Data Inc. acquired the Constellation 3D patent in 2003. This company intends to bring to market multi-layer optical discs, reintroducing the technology under the new name of Digital Multilayer Disk (DMD).
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