By Stephen Hardy
FTTH has made significant strides over the last several years – except in cable MSO networks.
Fiber to the home (FTTH) is catching on globally in networks of nearly every stripe: telco, municipality, utility, even country-wide efforts such as the National Broadband Network in Australia. But note the word “nearly,” as there is at least one domain where FTTH remains primarily an anomaly, and that’s within the networks of cable multiple systems operators (MSOs).
Sure, you can find examples of FTTH, usually either based on PON or RF over glass (RFoG), in some cable-operator networks. But most such service providers appear quite content to merely tweak their current hybrid fiber/coax (HFC) architectures. The ability of DOCSIS 3.0 to support 100-Mbps Internet offerings helps explain this comfort; a recently launched coax-friendly IEEE EPON standards effort should make HFC even more comfortable.
Yet as more MSOs seek to augment their residential services with others aimed at small and medium-sized businesses, they’re finding these desirable new customers beyond the reach of their existing HFC plant. Therefore, many cable MSOs have begun to investigate fiber-based technology to enable MEF-compatible services to match those of their telco competitors.
When EPON doesn’t mean fiber
To be fair, the rollout of DOCSIS 3.0 doesn’t mean that the “F” in “HFC” has fallen into neglect. Much as telcos find themselves pushing their nodes closer to the customer to enable VDSL2 deployments, cable MSOs have begun to embrace “fiber deep” architectures to support higher bandwidth while reducing the number of amplifiers between the node and customer. Meanwhile, the jury remains out regarding whether cable operators will require further changes to their optical arsenals as they adopt the proposed Converged Cable Access Platform (CCAP) specifications to enable more IP-friendly architectures.
But there appears little panic among cable operators in the face of competition from FTTH-based telco networks. Most major U.S. MSOs have their rollouts of DOCSIS 3.0 technology well underway, with 100-Mbps Internet offerings from Comcast and Charter Communications as examples of the results.
Some have suggested that cable MSOs’ burgeoning interest in EPON – and specifically 10G EPON – might lead to more fiber deployments. But if and when cable operators embrace EPON, a new standards initiative from the IEEE likely will make FTTH unnecessary in many cases. The IEEE 802.3 EPON Protocol over Coax (EPoC) Study Group, as its name implies, will investigate how cable operators can run EPON (or 10G EPON) over coax.
Needless to say, the advent of such a capability would prove popular. “This effort is an industry pull, not a technology push,” says David Law, chair, IEEE 802.3 Working Group, and distinguished engineer, HP Networking. “We are pleased with the enthusiastic reaction we’ve received from industry, who have turned to the IEEE specifically to investigate the potential for using the IEEE 802.3 EPON protocol on existing coaxial cable networks.”
EPoC capability would enable service providers – including telcos – to use EPON in multi-tenant and multiple-dwelling-unit (MDU) applications to provide services directly to individual units without first converting to a copper-based technology such as VDSL2 or running fiber within the building. But the proposed standards’ ability to enable EPON capabilities over existing HFC networks has drawn the most attention. EPoC was mentioned several times on the SCTE Cable-Tec exhibition floor last November as a potential successor or complement to DOCSIS 3.0 in cable MSO networks. Sources at some companies even expect to be able to show EPoC-friendly products this year.
The increasing strength of the tide toward coax-based DOCSIS 3.0 has created divergent eddies in the EPON supplier market. Hitachi Communication Technologies America has de-emphasized its EPON and RFoG offerings (none were visible in the company’s booth at SCTE Cable-Tec last November), while Aurora Networks has doubled down on the technology through its acquisition of the broadband access line of Enablence Technologies. Rather than using the acquisition to expand beyond its current focus on cable MSOs, Aurora made the deal with its current customers in mind, according to Dawn Emms, director of marketing at the company. The newly acquired Trident7 optical line terminal should have DOCSIS Provisioning of EPON (DPoE) capabilities this year as well as 10G EPON functionality in the near future.
Getting down to business
Speaking of DPoE, work on the next great cable MSO fiber hope (unless, of course, it gets paired with EPoC) continues to progress. All sources with whom Lightwave spoke see DPoE as a mechanism for business services support primarily if not exclusively; CableLabs, the group responsible for U.S. cable industry standards, has stated specifically that its goal is to enable the provisioning via DOCSIS of EPONs to support MEF-friendly business offerings (although the specification also supports IP high-speed data, which would include IP service delivery to residences).
The first version of the standard covers support of Ethernet private line services; the next version is expected to expand that charter to include other MEF services. However, there remains uncertainty regarding how quickly cable operators will adopt DPoE, if at all. At least one source in the vendor community says the first version of the DPoE specifications is complex to implement, and the second will likely be worse. Of the three cable operators behind the DPoE specification effort – Comcast, Time Warner Cable, and Bright House Networks – only Bright House has a significant EPON deployment it could leverage to deploy DPoE capabilities.
Meanwhile, for cable operators willing to run completely different business and residential networks, a solution to the business services problem already exists – basic Carrier Ethernet equipment. Comcast, for example, rolled out new metro Ethernet services last May based on Juniper Networks’ T Series core routers, MX Series edge routers, and EX Series Ethernet switches, with Ciena’s LE-311v Service Delivery Switch as the customer premises equipment. With this example in mind, several optical systems vendors have targeted the cable MSO space as a burgeoning market for their routers, switches, and WDM equipment.
While DOCSIS 3.0 certainly boosts HFC bandwidth to impressive levels, it doesn’t necessarily support MEF service requirements. Cable operators, therefore, must turn to alternatives such as Carrier Ethernet gear – or, eventually, DPoE – to meet the expectations of their customers as well as business-specific infrastructures. For this reason, it is the business realm that currently holds the most potential for customer connections via fiber.
STEPHEN HARDY is editorial director and associate publisher of Lightwave.
Past Lightwave Articles