TelephonyOnline in ETHERNET GETS ACTIVE IN ITS PITCH AGAINST PON reviews a consequence of this issue as it effects hardware choices: the choice between PON and active, ethernet fiber architectures. BellSouth, Verizon, and SBC, have issued a request for proposal centered on PON architectures. But is PON the best, or merely the cheapest way to go in the short term? Here's the chunk that raises the question:
“The more subscribers you put on a passive network, the less bandwidth you're delivering to the user,” said Kantner. “This is kind of the dirty little secret of passive optical networks. To be the most cost effective, you have to have the maximum number of users, which is the worst case from a bandwidth perspective. At some point you have so many subscribers, you can't throw any more bandwidth at it.”BellSouth is committing, again—as it has done with DSL and its flavors—to an incremental, limited, architecture that will require costly field upgrades to make available the full capacity of fiber optic networks. Given the demands of their ownership and the burden of a legacy system that choice may make sense for BellSouth. (Or not... it certainly does not acknowledge the impending bandwidth demands of HDTV which argue that those costly field upgrades will have to come sooner rather than later if they are to stand against Cox locally.)
Indeed, much of the argument for PON rests largely on economics. In an effort to keep down civil engineering costs (the digging of the trench and actual construction elements), PON shares the most expensive network elements among all users. In areas where telcos want to minimize the amount of fiber deployed, PON architectures call for one fiber to be brought to a neighborhood node or optical line terminal where the signal is split up to 32 ways and sent to each home over another fiber.
In an active Ethernet network, carriers deploy significantly more fiber to neighborhood nodes, run all services over an Ethernet protocol and do an optical-to-electrical-to-optical conversion and include other active elements in the access network. By nature, active Ethernet architectures are point-to-point.In an active Ethernet network, carriers deploy significantly more fiber to neighborhood nodes, run all services over an Ethernet protocol and do an optical-to-electrical-to-optical conversion and include other active elements in the access network. By nature, active Ethernet architectures are point-to-point.
We could do better for ourselves; and we should.