Cable providers that want to build fiber networks to offer business services seem to have a preference for Ethernet Passive Optical Network (EPON). However, telcos steer toward Gigabit PON (GPON). Why the different preferences?
Geoff Burke, senior director of corporate marketing at Calix, says one reason is simply heritage.
"GPON is really an ITU standard, and EPON is an IEEE standard," he says. “They come from different sides of the technology world. There’s a little bit of a political aspect. I don’t think either industry wants to wholly adopt the other’s standards."
According to Burke, GPON was designed to emulate phone networks, and it is built for both business and residential services. Calix has won 20 new projects, totaling more than $225 million, stemming from broadband stimulus awards. And the majority of these projects are for telcos that are building GPON networks.
Aside from politics, there are relevant technical reasons for the different choices as well. "GPON is the only technology that can gracefully support RF over it for analog video," explains Burke. "Customers that have an existing cable headend are forced into selecting GPON."** See Ed. Note below.
They could potentially build an all-new EPON network in parallel with their existing infrastructures but, for small telcos, it’s more efficient to run all their services over one GPON network.
"We have hundreds of customers that use GPON as their RF carrier," says Burke. "They’ve been able to consolidate into one network that runs over GPON and rides over the top of new fiber."
Cable, on the other hand, is more inclined to EPON when deploying fiber. EPON has the advantage of providing symmetrical upstream and downstream bandwidth. CableLabs is creating DPoE (DOCSIS Provisioning over EPON) specifications. For that original announcement, click here. And for an in-depth examination, see "A Proposal for DOCSIS 4.0: The Best of DOCSIS and PON."
In A Perfect World
Burke sees both GPON and EPON as steps toward the ultimate goal: All-IP services over all fiber.
"Nearly 50 percent of the fiber business we win these days is actually point-to-point Ethernet, with no sharing involved," he notes.
Many of the telcos that scored stimulus money actually are "home-running" the fiber, he adds: "It runs contrary to the efficiencies of GPON, which is one of the most fiber-efficient of PON technologies. But these folks are thinking ‘as we look to the future, we see the importance of symmetrical. We won’t have to spend any money laying any more fiber.’ Nirvana is a point-to-point connection."
**Ed. Note: SCTE IPS910 (RFoG) was recently passed, and it supports EPON, GPON and other PONS.