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