Fitted optical cable to Samsung d8000 TV which fitted and click into place
But now I can't remove it
Any suggestions as to what I'm doing wrong

If it's the one that uses the adapter (looks like a headphone jack on one end, the other end is where the optical cable plugs in), then just disconnect the adapter from the TV, as this might make it easier to disconnect.

If the fiber optic cable plugs directly into the TV, then pull firmly and pull straight away from the TV. Try not to bend it at all. It might be pretty snug.