{TAIL ~ The egress module} is configured to transmit {HEAD ~ data} to the ONU over the optical line 
{ TAIL ~ The egress module } is configured to transmit { HEAD ~ data } to the ONU over the optical line
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH