The embodiments of the invention relate to {HEAD ~ a system} for improving energy and cost efficiency in {TAIL ~ a passive optical network} 
The embodiments of the invention relate to { HEAD ~ a system } for improving energy and cost efficiency in { TAIL ~ a passive optical network }
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL