Digital audio can be transmitted via three different connection methods: AES/EBU (Audio Engineering Society/European Broadcasting Union), S/PDIF (Sony/Philips Digital Interface), and Toslink. Toslink is a standardized connection that uses optical cable to transmit digital audio. It is often used in home theater applications, where the professional style AES/EBU is overkill and the short length of the cable runs ensures that accuracy won't be lost.
TOSLINK was developed by Toshiba and is a fiber optic connection that transmits the signal via red light. The name is a short for "Toshiba-link." It was used to connect Toshiba CD players to receivers. It is easy to see if the signal is passing through the cable by looking at one end; you should see a red light coming out of the connector.
TOSLINK connectors are available in both standard and mini sizes. The mini TOSLINK connectors are often found on computers. The mini TOSLINK looks like a mini-headphone plug, while the standard connector is a hexagonal shape. TOSLINK is the least-secure connector of the three types of digital audio cables.
TOSLINK cables are limited to runs of 5 meters. Theoretically, they can be made up to 10 meters, but these runs aren't common. Any cable over 10 meters would require the use of a signal booster.
TOSLINK cables can use either a basic plastic fiber optic material or very high quality strands.
How It Works
Because it is transmitting digital information, TOSLINK works by sending on/off pulses of red light along the cable. Early generations were not favored in the audio community because they didn't seem to sound as good as S/PDIF. This may have been due to the effects of jitter (the signal is out of phase or has deviations from the original), which causes the signal to sound limited or harsh. With improvements in the quality of the connectors and the quality of the cable, TOSLINK has evolved to be comparable to S/PDIF connections.