what does a SMPTE cable look like?

A SMPTE cable? That's a new one.
SMPTE code is normally recorded on an empty track in the analog world. This track is read by the synchronizer and used to control the transport(s) of 'slave' reoorders in order to keep them in time with a 'master'. In a professional studio, SMPTE is sent from a master clock to the synchronizer via normal video cable. The synchronizer compares the master clock pulses with the code from all connected tape machines and varies their speeds in order to keep them in synch (all 'slaves' must be in vari-speed mode.)
In the digital world, SMPTE code is part of the 'control' track information, which all digital machines (and video tape) need to operate. A digital recorder would need to have 'external synch' selected to act as a slave. SMPTE is usually part of the digital signal, and is carried along with the audio and control information.
Word clock and MIDI synch require a separate cable, not SMPTE code.

there are no special smpte cables. smpte-generators or sync-interfaces like the zeta or the midi timepiece use a standard xlr or jack in/out for the smpte. it's an audible signal so you can use any symetric instrument cable.