The ingress module is configured to receive {TAIL ~ data} from the ONU over {HEAD ~ the optical line} 
The ingress module is configured to receive { TAIL ~ data } from the ONU over { HEAD ~ the optical line }
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD