Optical Disc Archive Optical Disc Archive Optical Disc Archive is a storage technology that was introduced by the Sony Corporation. It uses removable cartridges, where each cartridge holds 12 optical discs. Each of the internal optical discs is similar to, but not compatible with, a Blu-ray disc. The latest version of the cartridge, that has a total capacity of about 3.3TB, uses discs that hold about 300GB each. The technology was publicly announced on 16 April 2012 during the NAB Show with the first units shipping in February 2013. Generation 2 of the Optical Disc Archive technology is scheduled for mid-2016. Generation 2
Optical medium Optical medium An optical medium is material through which electromagnetic waves propagate. It is a form of transmission medium. The permittivity and permeability of the medium define how electromagnetic waves propagate in it. The medium has an "intrinsic impedance", given by where formula_2 and formula_3 are the electric field and magnetic field, respectively. In a region with no electrical conductivity, the expression simplifies to: For example, in free space the intrinsic impedance is called the characteristic impedance of vacuum, denoted "Z", and Waves propagate through a medium with velocity formula_6, where formula_7 is the frequency and formula_8 is the wavelength