Bringing Fiber Connectivity to Cable Broadband Power Supplies
By Chuck Chapman and Greg Laughlin
Cable operators are increasingly deploying passive optical networks (PONs) for greenfield expansion and rural broadband initiatives—and while fiber PONs differ in many ways from traditional DOCSIS®-based HFC networks, one common element between both architectures is the power supply. Optimizing the transition from DOCSIS-based HFC to PON, however, requires remote status monitoring into the power system over fiber instead of legacy DOCSIS scenarios. Fortunately, the cable broadband community can rely on standards around physical connection and provisioning to help with the transition to monitoring over fiber. However, without applying special configurations to your PON modem, your power supplies could be at risk.
Physical connections
Fiber connectivity to the power supply will pass through a standards-based SFP (small form-factor pluggable) interface which allows operators to communicate with the power supply using their chosen vendor solution. Small PON transceivers plug directly into the power supply’s SFP port which also provides the transceiver with the power it needs. The use of an SFP transceiver allows a single power supply model to support a wide range of optical standards, interfaces, and power levels by just switching to an inexpensive SFP designed to fit that specific optical network application.
DOCSIS Provisioning of EPON
CableLabs developed some tools to ease the transition to a non-RF world through the creation of DPoETM or DOCSIS Provisioning of EPON. DPoE provides a method where existing provisioning systems for DOCSIS modems can be leveraged over communication media like Ethernet or fiber optics. This provisioning method enables provisioning for a DOCSIS modem or PON device from the same system—meaning you don’t have to create an entirely new provisioning system for your fiber modems.
Security challenges
Plugging a power supply into a standard customer modem (DOCSIS or PON) by default brings the unit online through the customer or ‘public’ network, which is much less secure than the broadband operator’s management network. This can present significant vulnerability to security threats not only to the power supply, but also to the management network if the power supply element management system resides there.
For DOCSIS, the innovative solution to this dilemma was to develop specialty modems that could communicate power supply status and alarms through the secure management network instead of through the public network. Unlike plugging into a standard customer modem, the power supply will never register an IP address in the public network but will be fully accessible through the secure management network. This creative approach not only provides protection but also preserves public IP address space for paying customers. Unfortunately, this special inter-device communication does not exist for PON modems.
The good news is that these shortcomings can be circumvented by creative network and provisioning configurations that leverage DPoE to allow the essential services to reach this new edge device. Many items must be addressed to create the secure PON management connections including the definition of new edge network spaces, support of services used by the edge powering, the implementation of DPoE, and the configuration of firewalls to allow the essential services to reach this new edge device.
Summary
More and more broadband network buildouts are using fiber optical cables with remote outdoor PON OLTs replacing or coexisting with legacy HFC nodes. Power supplies built for powering DOCSIS-based HFC nodes work well for optical equipment, but remote monitoring must be configured and implemented correctly to provide secure reliable management communications. While not simple, network administrators have the tools necessary to help ensure your critical infrastructure elements are protected.
Chuck Chapman,
EnerSys
Chuck Chapman is a senior cable broadband technologist at EnerSys, with 30+ years in the cable broadband industry. As a senior systems engineer for several companies, Chuck gained deep knowledge of DOCSIS® and fiber optic networks, network powering, remote management, as well as emerging technologies for smart cities and advanced communications.
Greg Laughlin,
EnerSys
Greg Laughlin is a strategic marketing manager for broadband markets at Enersys. In his 15+ years at Enersys, formerly Alpha Technologies, Greg has served as a senior product manager for DOCSIS® power supply communication and gateway products.
