Definitions for "Optical Digital Output"
For digital data transmission without loss to other HiFi components with optical digital input, e.g. MD
An optical digital output sends audio signals in the form of light rather than electrical currents, thus eliminating one possible means of noise pickup in the cable. (Requires a special optical cable)
This allows you to connect the portable to a digital surround sound processor so that you can take advantage of a movie with a Dolby Digital 5.1 or DTS 5.1 soundtrack. A thin fibre optic cable is needed to connect the two.