A coaxial to optical converter is a small device that interprets data coming in from a coaxial cable, and converts it to an optical, also known as TOSLINK® signal, that can be output and read by an optical jack in a receiver. These are used most commonly in home audio and home theater settings, where a source and receiver are not directly compatible. Higher end converters are able to work in both directions, converting an optical input to coaxial output as needed.
The vast majority of TOSLINK® applications are audio in nature, and so in most cases a coaxial to optical converter will be employed to convert coaxial audio from a source, such as a digital video disk (DVD) or compact disc (CD) player, to the optical jack of a home theater receiver. Physically, most coaxial to optical converter devices are small boxes with jacks on either end to accept one of the two types of plugs. Most converters must be plugged into an electrical outlet to operate, but draw little energy.
Optical audio has several advantages over older technology, such as coaxial, including the ability to retain sound quality over greater distances. Generally, with any distance greater than about ten ft (three m), coaxial cable begins to suffer from interference and degraded sound. Quality optical cable does not suffer from this limitation, and reliable maximum lengths can reach up to 33 ft (ten m). In addition, optical cabling is also not subject to radio frequency interference, which can hamper coaxial cables placed too close to power cords.
The technology needed to translate coaxial signals into optical is not cheap however, and a coaxial to optical converter, while it may seem like a small, simple device, can be quite expensive. Optical audio technology has also been superseded by high definition multimedia input (HDMI®) technology, which is relatively cheap, of better quality, and combines audio and visual data in the same cable. Nevertheless, some older home theater devices do not have HDMI®, and therefore TOSLINK® is the best available option for audio quality.
Though optical audio is a digital technology, some coaxial to optical converters cannot output in surround sound. Therefore, while a coaxial signal from a DVD player, for instance, may be in 5-1 channel surround, after running through the converter it will be reduced only to a two-channel stereo signal. Prospective buyers should be sure to check whether a given coaxial to optical converter meets their needs in this regard.