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TwoDOS Two-Dimensional Optical Storage |
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SummaryThe objectives The further growth of today’s information
society will require larger storage capacities and faster access to ever
growing data bases and digital content. The classical roadmap for optical
storage seems to come to an end, both in capacity and in data rate. We
propose to develop a new and challenging concept for optical storage, in
which the information written on the disc fundamentally has a
two-dimensional character. We call this new concept TwoDOS (Two-Dimensional
Optical Storage). The aim is to generate key technologies
that realize an increase over the 3rd generation of
optical storage with a factor of two in data density and a
factor of 10 in data rate for an optical read-only system,
based on innovative two-dimensional channel coding and advanced signal
processing, in combination with a read-channel consisting of a multi-spot
light path realizing a parallel read-out. TwoDOS will achieve a capacity
of at least 50 GB for a 12 cm disc, with a data rate of at least 300 Mb/s. Description of the work The format of a TwoDOS disc will be based on a broad spiral, in which the information is recorded in the form of 2D features. Parallel read-out is realized using a single laser beam which passes through a grating which produces an array of laser spots. The information is written as a honeycomb structure and is encoded with a 2D channel code, which facilitates bit-detection. The array of spots scans the full width of the broad spiral. The light from each laser spot is reflected by the 2D pattern on the disc, and is detected on a photo-detector IC, which generates a number of high-frequency signal waveforms. The set of signal waveforms is used as the input of the 2D signal processing .The main challenges are in the field of advanced signal processing, and comprise innovative solutions for 2D channel coding, 2D timing recovery, 2D adaptive equalization and bit-detection. Major physical challenges include the mastering of discs, and the design of a complete test-player with a multi-spot light-path with new lenses and gratings. Manufacturing of 2D optical discs will require a mastering technology that is capable of writing the information preferably in a single pass of the 2D broad spiral: this can only be achieved by an electron beam recorder since it allows for fast deflections of the recording beam. As part of the risk management, an alternative route using a traditional laser beam recorder for mastering will also be followed, using multiple passes to record the broad spiral. The signal processing algorithms of the TwoDOS receiver are first generated and evaluated in software; subsequently, they are implemented in efficient low-complexity hardware. The electronics are further integrated with the test-player. The final proof-of-concept will evaluate the system margins at the target capacity of 50 GB. A feasibility study will analyze the further improvement that may be expected from the combination of TwoDOS with the promising multi-level technology.
Milestones and expected results Major achievements to be expected are: |
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