The ONU is connected with {HEAD ~ an aggregating ONU} in {TAIL ~ the PON} through an alternate connection separate from the PON 
in
The ONU is connected with { HEAD ~ an aggregating ONU } in { TAIL ~ the PON } through an alternate connection separate from the PON
OTH OTH 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