Patent ID: 8488445

Claim:
A passive optical network (PON) system, comprising a plurality of ONTs (optical network terminals) each accommodating a telephone and an OLT (optical line terminal) including a gateway function and being connected to a telephone network, wherein the OLT is provided with a storage for storing telephone number information on the telephones connected to the plurality of ONTs; wherein the OLT acquires callee telephone number information included in voice data sent from a caller telephone connected to one of the plurality of ONTs to a telephone switch included in the telephone network, and, in a case where the callee telephone is also connected to the one of the plurality of ONTs, records information on a talk channel between the caller telephone and the telephone switch; wherein the OLT detects a call incoming from the telephone switch to the callee telephone and records information on a talk channel between the telephone switch and the callee telephone; and wherein the OLT, when a failure is detected in the telephone network, connects, based on the information on the two talk channels to which the caller telephone and the callee telephone are connected, respectively, the two talk channels and keeps the call active without involving the telephone network.