TV digital audio output cable can be optical or coaxial. It depends on what connection type have your TV. It can be equipped with only coaxial or only optical digital audio output, or both outputs. These types of connections use different modes of data communication. First transmits signal traditionally, in the form of electric current, second in the form of light.
Connection type, which should be selected to connect audio devices, depends on which input and output (out) is available on your TV and audio devices (AV Receiver, Speaker System).
Based on this, you should select the cable type: optical or coaxial.
It makes sense to buy quality digital cable only for connecting good stationary CD-player or DVD-A/SACD player with an amplifier or sufficient qualitative AV Receiver. For example, for CD-player of the middle class (for $300-500) it makes sense to buy a digital audio cable for $40-70. But to connect the TV, you can use inexpensive cables for $10-20.
You can order such cables in specialized on audio equipment online stores. As a rule this stores have a search Form at their sites, where you can introduce product name to find it. See examples: One and Two.