{TAIL ~ The method} 5, wherein the grant specifies {HEAD ~ a transmission window} on the optical line during which only the ONU can transmit data to the OLT 
{ TAIL ~ The method } 5 , wherein the grant specifies { HEAD ~ a transmission window } on the optical line during which only the ONU can transmit data to the OLT
TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH