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