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Fluorescent Multi-Layer Disc (FMD)

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Fluorescent Multi-Layer Discs (FMDs) are a new technology being developed by Constellation 3D Inc. They store digital data in three dimensions (in layers, like DVDs) and, at the time of writing, are being touted as a more advanced successor to DVD.

An FMD can hold up to 140 gigabytes of data (23 times more than a DVD, 215 times greater than a CD, 99555 times the capacity of a floppy disk, 1195 times greater than an LS-120 drive - you get the message, it is big!).

Because of its high capacity it is likely to be used for high quality video and large pictures. For example, it can be used to store an archive of maps in very high detail, and even when uncompressed it will be able to store a large amount of files. It could also store the whole of a series of a TV programme (eg, 20 episodes, each an hour long) and still have room to spare. Other examples of uses include digital cinema film, HDTV (high definition television) players, Internet content streaming and data backup storage.

The initial size of the first FMDs will be between 25 and 140GB - still much higher capacity than DVD. Eventually over a terabyte (approximately a thousand gigabytes) of data could potentially be stored on a single FMD.

As well as FMD reading drives, in the future of FMD there will probably be another drive released for writing to FMDs. It will be a WORM drive (Write Once Read Many)1. Alongside FMD, a miniaturised version of FMD is being developed, called ClearCard. It will be a credit card-sized drive with a 50mm FMD disk and with a capacity hundreds of times higher than current 'flash' type memory (used in cameras, handheld computers, etc) and at only a fraction of the cost.

The Technology Behind FMD

The technology involved is unlike DVD in that it doesn't rely on coherent light reflection; coherent light produces a lot of noise and distortion. Instead it uses fluorescent materials and can therefore have more layers per disk than DVD (which is currently limited to two layers) - over ten. When the writing laser hits the materials, they are stimulated to produced coherent and incoherent light. The data is stored in the incoherent light. When reading the data, the laser light is filtered so that interference and stray light is minimised.

Backwards Compatibility

Existing CD and DVD player designs could easily be re-tooled to work with FMD. FMD drives are also backwards compatible with CDs and DVDs. As the drives are based on the same technology as CD and DVD the construction costs will be at similar level to current DVD players.

Durability and Higher Capacity

FMDs can withstand more extreme conditions (temperature, vibration, etc) during manufacture than that of CDs and DVDs.

Several layers can be read at once, unlike DVD where reflections limit that ability. This will allow increased retrieval rates, maybe of over a gigabit per second.

1A WORM device, a CD-R for example, can only be written to once. They are mainly used as archives or backups.

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