Method and system for synchronous high speed Ethernet GFP mapping over an optical transport network

An interworking device, method and system distribute reference timing between at least two communication networks. The interworking device includes a first communication interface operable to communicate with a first communication network operating using a first communication protocol and a second communication interface operable to communicate with a second communication network operating using a second communication protocol. The interworking device also includes a client generic framing procedure/optical transport network ("GFP/OTN") mapping block in communication with the first communication interface and the second communication interface. The client GFP/OTN mapping block recovers a first reference timing signal from data received from the first communication network. At least one hybrid synchronous equipment timing source transforms the first reference timing signal into a second reference timing signal that is phase and frequency locked to the first reference timing signal, and supplies the second reference timing signal to the client GFP/OTN mapping block to clock the second communication network.