The OLT restarts communication with the ONU over {TAIL ~ the optical line} upon receipt of {HEAD ~ data traffic} for the ONU 
The OLT restarts communication with the ONU over { TAIL ~ the optical line } upon receipt of { HEAD ~ data traffic } for the ONU
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH