By Hang Jin & John T Chapman, Cisco Systems
Full duplex (FDX) DOCSIS is one of the latest innovations in Cable industry. It allows the downstream and upstream to use the same spectrum at the same time, leading to ~100% increase on spectrum efficiency, and drastic increase on US capacity without scarifying DS capacity. FDX DOCSIS has been adopted into Cablelabs DOCSIS 3.1 specification release I12 on Oct 2017, and MSOs/vendors have conducted numerous successful lab and field trials since. FDX DOCSIS is one of the key technologies that enable HFC to deliver 10Gbps symmetric services.
Current FDX D3.1 standard specifies FDX operation for N+0 coaxial network. Today’s networks are mainly N+M (M>0) network; migrating from N+M (M>0) network to N+0 network requires substantial network re-planning effort and CAPEX. There is a strong interest in cable industry to remove this N+0 network deployment constraint and allow FDX technology to be deployed in N+M (M>0) network.
Deploying FDX in N+M (M>0) network requires FDX amplifier. This paper explains the working principle of FDX amplifier, the design considerations and challenges, as well as its impacts on the field deployment and the overall FDX system operation.