The ONU improves cost and energy efficiency for the PON by entering {HEAD ~ a sleep mode} that disables {TAIL ~ communication} with the OLT to reduce energy consumption when the ONU is idle 
disables
The ONU improves cost and energy efficiency for the PON by entering { HEAD ~ a sleep mode } that disables { TAIL ~ communication } with the OLT to reduce energy consumption when the ONU is idle
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH