By Harj Ghuman, COX Communications
As the Cable industry investigates solutions for 10 Gigabits per second (Gbps) subscriber bandwidths and beyond, the convergence of the two main Multiple System Operator (MSO) network topologies in use today, Hybrid Fiber Coax (HFC) and Passive Optical Network (PON), becomes highly desirable. COX’s current access platform, the Optical Communications Module Link Extender (OCML), supports protected bi-directional transport of 10G Dense Wavelength Division Multiplexing (DWDM) optics over dual 5 to 60 km fiber links for Remote PHY Devices (RPDs), remote Optical Line Terminal (OLT) uplinks and business services. This paper describes COX’s next generation converged access platform, the ROCML (Raman OCML), that is targeted for 10 Gbps subscriber bandwidth utilizing Data over Cable Service Interface Specification (DOCSIS 4.0) and/or long distance (60+ km) multi-wavelength 10 Gbps Next-Generation Passive Optical Network 2 (NGPON2). Extended Spectrum DOCSIS 4.0 (ESD) usage of a full 1.8GHz Radio Frequency (RF) spectrum requires 25 Gbps optical interfaces at the Remote PHY Device/Remote MAC-PHY Device (RPD/RMD). The ROCML’s innovative combination of Raman, semiconductor and erbium doped fiber amplification (EDFA) transports both multi-wavelength NGPON2 and 25G DWDM optics over 60+ km optical links from the same integrated platform. It provides scalability to meet future bandwidth requirements such as multiwavelength 25G PON and Distributed Access Architectures (DAA) requiring >25G optical signals to RPDs/RMDs. The solution stays in line with COX’s preferred methodology of keeping the outside plant passive. Hitherto, deploying PON over optical links >20 km has been a challenge requiring COX to deploy outside plant remote OLTs, either in cabinets or in clamshell enclosures.
The ROCML’s long distance NGPON2 capability allows OLTs to remain in centralized indoor hub locations, creating a truly passive long distance PON, vastly improving reliability while reducing Op Ex and capital equipment costs. The ROCML’s scalability to multi-wavelength 25G PON ensures a path to a future all Fiber to the home (FTTH network); it also allows for the transport of high capacity Coherent 100G - 400G optical signals, providing a powerful multi-purpose optical access platform for today’s networks and tomorrow’s requirements.