A lecturer in Photonics from the Department of Physics for Imperial College London has described a new method for potentially encoding and storing up to one terabyte of data, or 472 hours of film, on one optical disk the size of a CD or DVD.

The Imperial researchers, working closely with colleagues at the Institute of Microtechnology, University of Neuchвtel, Switzerland, and in the Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Greece, estimate that MODS disks would cost approximately the same to manufacture as an ordinary DVD and that any system playing them would be backwards compatible with existing optical formats - meaning that CDs and DVDs could be played on a MODS (Multiplexed Optical Data Storage) system.

Under magnification the surface of CDs and DVDs appear as tiny grooves filled with pits and land regions. These pits and land regions represent information encoded into a digital format as a series of ones and noughts. When read back, CDs and DVDs carry one bit per pit, but the Imperial researchers have come up with a way to encode and retrieve up to ten times the amount of information from one pit.

Unlike existing optical disks, MODS disks have asymmetric pits, each containing a step sunk within at one of 332 different angles, which encode the information. The Imperial researchers developed a method that can be used to make a precise measurement of the pit orientation that reflects the light back. A different physical phenomenon is used to achieve the additional gain.

The 1TB disk would be double sided and dual layer, but even a single sided, single layer, MODS disk could hold the Lord of the Rings trilogy 13 times over, or all 238 episodes of Friends. MODS disks will not be the first to challenge DVDs domination of the audiovisual optical disk market. BluRay disks, which have five times the capacity of a DVD at 25GB per layer, are expected to be released towards the end of 2005 for the home market.

Dr Tцrцk believes that the first disks could be on the shelves between 2010 and 2015 if his team are able to secure funding for further development.