What is a simple way to troubleshoot a toslink (optical) cable?  Or how can you tell it has gone bad (minus the fact that no sound goes through)?
Setup:
Digital Audio OUT from TV
Digital Audio IN to AVR
The problem occured after I turned my receiver to attach a new device to my AVR.  The toslink cable got accidentally pulled.  Anyway, I re-attached the cable and now no sound.  I checked the connectors and did not see any damage.  However, I did notice that the connector on the AVR-end is now emitting a red light.  The connector on the TV-end does not.  Is that an indication that the cable has gone bad?
Any help is appreciated.  Thanks!!
~Jay