(Ultra Density Optical) A 5.25" rewritable optical disc technology from Plasmon, Broomfield, CO (www.plasmon.com) that also supports write-once (WORM) media. Using blue laser optics and phase change recording, 30GB drives and cartridges were introduced in 2003, and second generation UDO2 with 60GB capacity came out in 2007. The future roadmap includes capacities of 120 and 240GB.

Although conceptually similar to the rewritable CD/DVD drives used by consumers, UDO was designed with more hardy engineering for commercial applications and long-term storage. For example, rewritable UDO uses eight layers in the disk compared to four, which is typical for rewritable consumer media.

Where Magneto-Optic Stopped
Designed to supersede magneto-optic (MO) disks in capacity, UDO's first blue laser 30GB drives offered a big storage jump over 9.1GB, the final format for 5.25" MO drives. UDO's phase change technology provides a stable recording layer that is expected to last 50+ years compared to 25 for MO. See blue laser, phase change disk, PDD and magneto-optic disk.