An apparatus is provided that is capable of achieving bidirectional, full-duplex communication with an optical transceiver. In some instances, the communication is achieved over a single electrical connection of the transceiver and via the use of a duplexing circuit on the transceiver and a complementary duplexing circuit on a distal circuit coupled to the transceiver via the single electrical connection. The techniques described may be used to modify existing optical transceivers to provide diagnostic or health information without interrupting normal transceiver operation.