An optical sound card is a sound card that outputs sound to devices that have a digital optical input. Usually used for multi-channel sound feeds, a digital optical input uses an optical fiber cable to transport the data from the optical sound card to the optical-ready sound device. As optical fibers lend themselves well to multichannel sound, optical inputs are most frequently found on sound receivers for home theater setups. A computer equipped with an optical sound card can output multichannel sound from the computer to an optical input on a home theater receiver.
Essential to producing sound from a computer, a sound card is an internal or external device that processes sound information from a computer for play on an output device like a set of speakers, headphones, or an audio receiver. Internal sound cards are installed in a slot located inside the computer, while external sound cards usually connect to the computer using universal serial bus (USB) or FireWire. Generally, optical capabilities are found on sound cards that handle high-end, multichannel audio.
An optical cable can also be called a TOSlink cable. This type of cable is made up of a series of optical fibers, thin, light-carrying tubes constructed out of flexible transparent material like silica or fluoride glass. Inside the cable, an optical fiber moves data from one place to another by transmitting light waves down a refractory tube. Optical fiber is flexible, bendable, and has shown data transmission speeds significantly faster than those achieved on most types of metal cable. The field that studies the use of optical fibers is called fiber optics.
Optical fibers are advantageous for use with high definition audio signals because they experience less interference and less loss than the metal fibers used in wires. Less interference means that cables from an optical sound card can still transmit a clear signal when placed in closer proximity to other, potentially interfering electronic objects than metal-based sound card wires. This can help improve sound quality in locations with interference from many electronic devices.
Loss and interference are some of the most common audio quality issues experienced by sound card users. When discussing audio and data, loss indicates a degradation in the quality of the data or sound feed as the cable's length extends. A cable that loses less information would be considered to be less lossy. As they are less lossy than metal wires, an optical cable like those used in an optical sound card can transmit a faster, higher quality data feed over longer distances than sound transmitted over a metal wire.