What Are Optical Storage Devices?

An optical storage device is an electro-mechanical unit that can save and retrieve (write and read) information on a special disc medium using a laser light. Optical drives are designed to work with several types of media: CDs ("compact disc"), DVDs (digital versatile disc" or "digital video disc") and Blu-ray discs.

How They Work

An optical storage drive that is capable of writing data to a disc uses a laser beam to burn pits (or bumps) into a special material. This data stream is placed in a spiral path, as found on a vinyl record, but in this case the data begins at the innermost track and works its way out toward the edge of the disc. In industrial mass produced discs, such as those distributing music or movies, the data is placed on the disc by a stamping machine. Data is retrieved by a laser beam that reflects off the disc, detecting the pits. Optical drives come in various speeds, spinning between 200 and 4,000 RPMs.

CD-R, CD-RW, DVD-R, DVD-RW, Blu-ray

CD-R (or CD-ROM) is a read-only-memory optical disc which can be written to only once. CD-RW (or "re-writable") can be written to many times, similar to a VHS videotape. The same designation is used for read-only DVDs (DVD-R or DVD-ROM) and re-writable DVDs (DVD-RW). The next generation of optical discs includes a format known as Blu-ray discs, which can store more information in the same physical space. These are useful for storing such content as High Definition movies.

Storage Capacity

The standard storage capacity for CDs is about 700MB (megabytes). To put it in perspective, that's enough space to store over 300,000 pages of text or about 80 minutes of music. A full-length movie can be stored on a DVD, which holds about 4.7GB (gigabytes) of memory. The data on optical discs is conservatively estimated to be viable for five to 10 years, so discs storing valuable data should be checked occasionally, and fresh copies made after several years. Store them upright in "jewel" cases, and keep them in a dry, room temperature environment.

Applications

Optical discs are used to store audio, video and computer data (which can be information or computer programs). Music CDs are now the medium of choice for distribution of music albums. CD players are found in home stereo systems, car audio systems, and personal computers. Similarly, DVDs have become standard for movie distribution, containing both audio and video, which have replaced the popular VHS videotape medium. Video game consoles also use optical discs for game software. Both CD and DVD drives are available in computers that are capable of both reading and writing information. DVDs are especially useful for archiving computer data, due to their relatively large storage capacity. For making routine backup copies, however, they are losing popularity to other storage devices which have much faster data transfer rates, including USB flash drives and external hard drives.

Optical Media Are Susceptible to Damage

Unlike hard disks, which are in a sealed unit, and floppy disks, which are in a protective housing, optical discs have no protection once they are removed from their storage case. Similar to vinyl records, optical discs are vulnerable to scratches, dirt, breakage and fingerprints, although fingerprints can usually be removed by wiping with a soft, damp cloth. Do not touch the surface of optical discs, and hold them by the outer edges and the hole in the middle, as you would vinyl records. Unlike records, there is no wear from repeated playing of optical discs.