The present disclosure provides systems and methods for extending a deterministic network over a wide geographical area. According to one embodiment, an IED may transmit data frames using a deterministic frame-based communication protocol, such as EtherCAT, via a local deterministic fieldbus. A first transceiver may encapsulate the data frames for transmission over a multiplexing synchronized optical network, such as a SONET network. A second transceiver may de-encapsulate the encapsulated data frames and transmit them via a remote deterministic fieldbus, such that communication between the local and remote deterministic fieldbuses is deterministic. Accordingly, an IED may communicate with a high level of determinism and/or in real-time with various components in a power delivery system across a wide geographical area including multiple deterministic fieldbuses.