UDO (Ultra Density Optical)
UDO was designed to meet the demands of archival storage applications by offering higher media capacity than traditional optical storage. Capacity of DVD technology maxes out at 9.4G bytes, whereas the first generation of UDO drives and media can store 30G bytes. 60G- and 120G-byte versions are planned.
The limiting factor in optical capacity is the size of the "spot" produced by the recording laser. Traditional optical storage devices, including CD, DVD and magneto optical, utilize red or infrared laser technology.
But UDO drives use blue lasers, which feature a shorter wavelength (405 nanometers) than red lasers (780 nanometers for CDs and 650 nanometers in DVDs). The combination of the shorter wavelength and new optics let blue lasers focus on a smaller spot. And more spots in a given area means more data in that area.
UDO drives record data using an 8K-byte sector size to maximize media capacity and performance. In a process known as phase change recording, the drives write data by heating a spot on the media recording layer with a blue laser and changing it from a crystalline to an amorphous state, recording a data mark. The same laser, set at a lower intensity, is used to read the media.
Just like other types of optical media, UDO is available in rewritable and write once formats. Because both media types are non-contact, non-magnetic, data recorded on UDO does not degrade with use, is not sensitive to exposure to magnetic fields, and accommodates a wider range of environmental temperature and humidity conditions than do current optical drive technology. In tests, UDO media was shown to have a life expectancy of more than 50 years when stored in a typical office environment.
The International Organization for Standardization and International Electrotechnical Committee ratified the ISO/IEC 17345 standard for 30G-byte UDO media in December, 2003.
From UDO boosts storage capacity, Network World Tech Update, 09/27/04.
Additional resources
UDO Technology Forum
Vendor group.
UDO Technology Overview
Paper from Plasmon. Requires free registration.
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