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