Key Technology for Ultra Density Optical
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Key Technology for Ultra Density Optical Robert E. Somekh and Clare E. Davies Plasmon Data Systems Ltd., Whiting Way, Melbourn, Royston, Hertfordshire, SG8 6EN, UK. ABSTRACT Ultra Density Optical (UDO) has been designed as the Phase Change successor to 5¼-inch Magneto Optic data storage products, with a UDO road map spanning three product generations leading to 120GB capacity. First generation UDO will utilise 405nm wavelength, 0.7NA drive optics with 100 micron cover layer media construction in a robust, double-sided cartridged format with 30GB capacity. There will be two types of UDO, both aimed at the professional market: UDO Write Once for high density, high data rate, archival data storage applications, and high cyclability UDO Rewritable. The features of UDO and the underlying Media Engineering optimisation strategies are discussed. INTRODUCTION TO ULTRA DENSITY OPTICAL Since the 1980’s, the market for professional archival data storage applications (such as banking, the insurance industry and government) has been addressed by a range of optical data storage technologies, especially magneto optic (MO) media in a 5¼-inch form factor. The capacity of these discs has typically doubled approximately every two years. However, the technical requirements to increase the capacity have become increasingly difficult for MO: a witness to this is the fact that the most recent MO capacity increase has been from 8x to 14x rather than the 16x one might expect. By contrast, the development of new phase change technologies such as Blu-ray disc demonstrates the ability of phase change to meet the growing capacity and speed requirements during this decade. Whilst Blu-ray addresses the needs of the consumer market, Ultra Density Optical (UDO) has been developed as a permanent, professional, and cost effective product for the enterprise archival data storage market. The key features of UDO, with a roadmap extending at least three generations: 30GB, 60GB and 120GB, are summarized in Table 1.
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UDO Generation UDO Generation UDO Generation 1 2 3 Capacity Transfer Rate RPM Avg Seek Time Numerical Aperture Media Layers Encoding Sector Size SCSI Transfer Rate Load Time Unload Time MSBF (Mean Swaps between Failures)
30GB Up to 8 MB/s 2000 rpm 25 msec 0.7
60GB Up to 12 MB/s 3000 rpm 25 msec 0.7
120GB Up to 18 MB/s 3600 rpm 25 msec 0.85
1 1,7 RLL 8 kB 80 MB/s 5 seconds 3 seconds 750,000
2 1,7 RLL 8 kB 80 MB/s 5 seconds 3 seconds 750,000
2 ML 8 kB 80 MB/s 5 seconds 3 seconds 750,000
Table 1: UDO Specifications UDO FEATURES The core technology for UDO is essentially similar to Blu-ray although there are a number of key differences. The main features of UDO are: • •
• • •
UDO is based on blue laser recording using λ=405nm lasers from Nichia. The numerical aperture (NA) for the first two UDO generations will be 0.7. This design choice was made because it was considered that the technology for 0.85NA lenses would not be sufficiently mature to enable a product to be brought to market in 2003. The 0.7NA Opto-Mechanical
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