A TOSLINK cable is a type of optical digital audio cable used to transmit sound between compatible audio equipment. Unlike conventional electrical cables, TOSLINK carries the digital audio signal using pulses of light.

TOSLINK was originally developed by Toshiba, with its name derived from Toshiba Link. The connection became widely adopted and can now be found on televisions, CD players, games consoles, DACs, amplifiers, soundbars and other audio equipment.

When audio is sent through a TOSLINK connection, the transmitting device converts the digital audio data into pulses of light. These pulses travel through the optical fibre inside the cable to the receiving device, where they are detected and converted back into an electrical digital signal.

The receiving equipment then processes the digital information. If the signal is being sent to a DAC or an amplifier containing a DAC, the digital-to-analogue converter converts the digital audio into an analogue signal that can subsequently be amplified and sent to loudspeakers.

One advantage of an optical connection is that there is no electrical connection between the two pieces of equipment. This means a TOSLINK cable cannot carry electrical interference or create a ground loop between the connected devices.

TOSLINK commonly carries two-channel PCM digital audio and can also support certain compressed multichannel surround-sound formats. Its capabilities are more limited than modern HDMI connections, so HDMI is generally preferred for newer high-bandwidth home cinema audio formats.

The optical fibre used in a TOSLINK cable should not be excessively bent or kinked because this can interfere with the transmission of light. The connectors should also be inserted correctly into the optical input and output sockets, which are often protected by small covers or doors when not in use.

For a hi-fi system, TOSLINK provides a straightforward way of transferring digital audio from a source to a separate DAC or digital amplifier. The cable itself does not carry analogue music; it transports digital information using light, with the receiving equipment responsible for converting that information into the analogue signal that ultimately becomes sound.