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