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