Digital optical cables transmit sound signals by using fibre-optic technology, or strands of glass that transmit digital information to receivers. Digital optical ports are found on some music players, but are more common in comprehensive systems used for entertainment or gaming. Digital optical connections are generally considered the best, since the pulses of light that travel through the cables refract faster and more clearly than any other type of available communication technology. As a result, digital optical cables are also the most expensive cables, and will cost more per foot than other options.
Digital optical cables should not be confused with either coaxial digital cables or HDMI cables. Coaxial digital cables are an alternative choice that use normal copper wire to transmit audio signals. They resemble RCA cables and are set up in a similar manner, but focus solely on sound and are capable of carrying more information. Instead of sending light pulses, they send pulses of electricity that are then decoded in a similar fashion. Because of their lower price, coaxial digital cables are the most common type of audio signal cable used in entertainment systems. HDMI cables, on the other hand, carry a compact sound signal, too, but also transmit video signals. Like the optical cables, HDMI cables can be used between any devices that have the proper ports and are used for very high-quality signals, but they, too, are equipped with copper wire and do not use fibre optics.
The goal of digital optic cables is to carry precisely the same signal from the start of the cable to the end. When dealing with electricity and copper wire, the signal is almost always degraded a little as it passes through the cable, slight amounts of information slipping away before it can be received. Because of light's strange properties, it can be refracted through carefully designed glass threads without changing or losing any part of the signal, so optical cables can transmit a "pure" signal. This is not the same as an analogue attachment, since the digital pulses still need to be decoded, but all of the information is preserved from the source to the receiver, resulting in purer sound.
Digital optical cables are also smaller and lighter than the alternative choices, since the glass/fibreglass strands used to transmit the light are smaller. The connection-ends are known as Toslink connectors-- specific types of connectors that will not work with any other type of cable and that are specifically designed to read the light pulses generated by the other Toslink port. There is only one different type of digital optical cable: the mini-optical, which requires a smaller Toslink connector on one end of the cable. These mini-optical cables are found mostly on portable devices, such as media players.