FEATURE CABLE NETWORKS
DOCSIS over EPON could be an interesting
alternative for cable operators, she says. CableLabs has defined the DOCSIS Provisioning of EPON (DPoE) standard, and provides interoperability testing and certification for EPON equipment to guarantee that it will work with DOCSIS back office systems. Tis allows cable operators to provision services across their network regardless of whether that specific customer resides within the cable or the fibre section of their network. ‘DOCSIS provisioning of EPON makes it
Dan Rice is vice president, access network technologies at CableLabs
operators are also having a very hard look at becoming fibre providers – and skipping some of the steps of going through a DOCSIS world.’
Fibre scenarios Optical fibre is the more obvious choice in Greenfield deployments, when cable operators expand into territories where they have no existing infrastructure. Tere are several technologies that can combine optical fibre with DOCSIS, which are aimed at operators that have both HFC and pure fibre networks. One approach is RF over glass (RFOG), which allows cable operators to provide traditional DOCSIS-based services using DOCSIS hardware over a generic passive optical network (PON). However, RFOG on its own doesn’t provide any
bandwidth enhancements compared to a standard HFC network. ‘Unless you are splitting up optical nodes with RFOG or you are upgrading to DOCSIS 3.1 then you are basically giving the customer the same bandwidth,’ said Els Baert, fixed networks product manager at Alcatel- Lucent. ‘You are just extending the fibre to the home; it increases a little the reliability and the quality of service but not really the bandwidth.’ A better way forward, she suggests, is FTTH
combined with standards-based PON technologies because of the extra bandwidth that it brings. ‘With GPON you can have 2.5 Gb/s download speeds, with 10G EPON you can have 10 Gb/s, now with TWDM PON coming you can have even 40 Gb/s and there are more evolutions coming on the fibre to increase that bandwidth even more.’
18 FIBRE SYSTEMS Issue 7 • Spring 2015
easier to integrate and operate the OSS/BSS [operations and billing] systems that cable operators are using,’ Baerts explained. ‘DPoE is just a management system; if you look at it from a soſtware perspective the EPON ONTs [optical network terminals] appear the same as cable modems in terms of provisioning and setting up services.’ Baert points out that the higher speeds enabled
by fibre networks will allow cable operators to serve not only residential customers but also supply business services. ‘We see that a lot of cable operators don’t typically address business customers so that is a potential growth area for them,’ she commented. Ovum is starting to see more cable operators
focus on the largely untapped business services market. ‘We see some very different approaches by different cable operators,’ said Ovum’s Julie Kunstler. ‘For example, [US cable operator] Bright House Networks began to deploy EPON back in 2006 for business services including
The cable industry has several paths to gigabit broadband
mobile backhaul. Now they are in a position to expand their fibre network to begin to support residential services.’ Tis move into the residential market was only possible because Bright House Networks started on the business side, where the return on investment is faster. Tis income stream then helped to support the investment on the residential side. Geoff Burke, senior director of corporate
marketing at Calix, is a fan of using one network to deliver any kind of service. ‘Tere has been a little bit of an epiphany for service providers over the course of the last decade, which is the idea that one [physical] network running separate customer networks is capable of delivering these
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services overall. Once they embrace this idea then it really causes them to look carefully at their infrastructure,’ he said. ‘Tey don’t want to be in a position where they are offering business services over fibre and then relying on the DOCSIS infrastructure for residential customers.’ Calix has given cable operators another option
with its DOCSIS provisioning over GPON (DPoG) system, which allows cable operators to blend GPON hardware with DOCSIS. Te product was unveiled last summer when the company announced that Grande Communications was using it to provide gigabit services to customers in Austin, Texas. Te key component of the system is the vendor’s Open Link Cable soſtware, which ‘translates DOCSIS commands into GPON commands’ so that GPON hardware appears to back office systems as if they were a cable modem termination system (CMTS) and cable modem. Calix says its product was designed to be
compliant with the new CableLabs DPoG specification, which was in draſt form at the time, but has since been issued. Meanwhile, CableLabs has also launched the OnePON initiative, which aims to simplify the options by bringing both EPON and GPON under one single standard for use in cable networks.
Reality check CableLabs’ Dan Rice thinks it makes a lot of sense for cable operators to stick with DOCSIS upgrades. ‘DOCSIS technology has had very economical cost trajectories as prior versions have been deployed at scale and we expect similar if not faster adoption of DOCSIS 3.1 than previous versions, resulting in similar absolute costs and much reduced euro per megabit cost,’ he said. He added: ‘In most deployments with existing
HFC networks, the economics to evolve to the 10G/1G capacities of DOCSIS 3.1 will make more sense than FTTH. But if, for example, 10G/10G- type performance is required then a PON solution would provide the capability. Tese speeds – whether DOCSIS 3.1 over HFC or PON – are very far ahead of current typical consumer market demand and should both be effective long-term network evolution paths.’ Ovum’s Julie Kunstler believes the limited
upload speed is more likely to constrain service offerings and cause consumer dissatisfaction in the future. ‘What I am starting to hear more and more is that if you really want to use the cloud, even for residential users, it requires a lot of upstream bandwidth,’ she said. She expects to see some adoption of fibre technology by cable operators this year, but
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