MODS, media and misinterpretations

First published Dec 9th 2004

The new MODS – Multiplexed Optical Data Storage – discs could potentially store up to one terabyte of data each. Although not yet mastered, the team have ‘demonstrated what can be done’. To achieve the maximum storage capacity, the MODS discs will be double sided and dual layered, and instead of storing one bit per pit like conventional CDs and DVDs, MODS discs can store eight bits due to the asymmetrical nature of the pits.

Dr Peter Török will be attending a meeting later on this year to find out if the discs are viable for mass manufacture, and is confident that their fabrication will be easy and cheap. Research and funding permitting, Dr Török estimates that the discs will be available on the market within five to ten years. Although he emphasised that “there have been a lot of misinterpretations and misunderstandings” surrounding the new discs, and this timescale is “largely affected by political and financial factors as well as technological factors”, a fact missed out by a large majority of articles covering this technology.

The BluRay disc, although technically sound, has had its date of release pushed back due to these reasons. Before a new data disc comes into the market, a universal standard must be agreed by the companies which will produce it, which can take a great deal of time. The BluRay consortium was set up for this very purpose, to establish a universal standard for the BluRay media. The other factor is that the companies will want to make as much money as they can out of previous technologies before they render them obsolete and embrace new ones. This can be seen by the fact that only now is VHS being withdrawn from sale, and DVDs are being given greater emphasis. BluRay can only come out once the companies have made enough money from the sale of DVDs, or they are forced to market their product by the competition, and consequently MODS discs will most likely be able to come on to the market once the companies have milked all they can from BluRay.

Once it has been established whether it is technologically and financially possible to mass-produce MODS discs and share data, the team hope to further research whether a writing/rewriting facility can be made available. Dr Török mentioned that they do have the capacity to reach that status, but again it is heavily dependent on further funding.

30-year data storage pioneer Michael Thomas, owner of Colossal Storage, believes that the concept will fail because the design is prone to complex errors, and that it may just be better to continue to store large amounts of data on a hard drive, but Dr Török believes that this is only partially true. Any data system relying on fitting a large amount of data in a smaller space will always be prone to error for a number of reasons, even when comparing DVD and CD discs. The same thickness of scratch on a DVD takes out many more bits of data than on a CD, and this effect is even greater for MODS discs, especially as the wavelength of light involved is significantly smaller (around 405nm). This does not mean, however, that the whole technology can be dismissed and in actual fact the BluRay disc is likely to be similarly scratch sensitive. Hard drives are in fact far more delicate than discs, hence having to keep them contained. The advantage of MODS discs when it comes to data protection is that a large number of discs can be produced for low cost, so duplicate copies will be easy to produce.

Dr Török emphasised that whilst you could fit a large amount of data on one disc, for example a few series of The Simpsons, it may not necessarily reduce the cost of the MODS on the market. Whilst they are still cheap to produce, movies and music will still be subject to additional charges. “You don’t buy the disc [in that case], you support the large number of people behind the production”, so all episodes of a TV series on one MODS disc will cost no less than a box set of DVDs, but there will be the added convenience of having everything on one disc and saving valuable space on the shelf.

He also stressed that the project is very much collaborative, with a number of people significantly involved, including his PhD student, Mr Peter Munro. The other members of the team are Dr Martin Salt, Professor Hans Peter Herzig and Mr Carsten Rockstuhl from the University of Neuchatel in Switzerland and Emmanouil Kriezis from Aristotle University of Thessaloniki in Greece.

The team have applied for funding to EPSRC and are currently in the process of writing a European grant application to fund their research further. The latter is a collaboration between the Imperial physics and electrical engineering (led by Dr Eric Yeatman) departments, the Technical University of Delft, the University of Neuchatel and Aristotle University. Dr Török has also set up a website to reveal the facts behind popular claims, as well as further details behind the new technology. This can be found at www.imperial.ac.uk/research/photonics/pt_group/peter_torok_research.htm.