Optical storage

Method to store and retrieve computer data using optics

Optical storage refers to a class of data storage systems that use light to read or write data to an underlying optical media. Although a number of optical formats have been used over time, the most common examples are optical disks like the compact disc (CD) and DVD. Reading and writing methods have also varied over time, but most modern systems use lasers as the light source and use it both for reading and writing to the discs. Britannica notes that it "uses low power laser beams to record and retrieve digital (binary) data."

Optical storage is the storage of data on an optically readable medium. Data is recorded by making marks in a pattern that can be read back with the aid of light, usually a beam of laser light precisely focused on a spinning optical disc. An older example of optical storage that does not require the use of computers, is microform. There are other means of optically storing data and new methods are in development. An optical disc drive is a device in a computer that can read CD ROMs or other optical discs, such as DVDs and Blu ray discs. Optical storage differs from other data storage techniques that make use of other technologies such as magnetism, such as floppy disks and hard disks, or semiconductors, such as flash memory. Optical storage in the form of discs grants the ability to record onto a compact disc in real time. Compact discs held many advantages over audio tape players, such as higher sound quality and the ability to play back digital sound. Optical storage also gained importance for its green qualities and its efficiency with high energies. Optical storage can range from a single drive reading a single CD ROM to multiple drives reading multiple discs such as an optical jukebox. Single CDs (compact discs) can hold around 700 MB (megabytes) and optical jukeboxes can hold much more. Single layer DVDs can hold 4.7 GB, while dual layered can hold 8.5 GB. This can be doubled to 9.4 GB and 17 GB by making the DVDs double sided, with readable surfaces on both sides of the disc. HD DVDs were able to store 15 GB with a single layer and 30 GB with a dual layer. Blu ray discs, which won the HDTV optical format war by defeating HD DVDs, can hold 25 GB for single layer, 50 GB for dual layer and up to 128 GB for quad layer discs. Optical storage includes CDs and DVDs.