{HEAD ~ A coupler} includes input, output and {TAIL ~ interface points} for routing the optical signal 
includes
{ HEAD ~ A coupler } includes input , output and { TAIL ~ interface points } for routing the optical signal
HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH