Fiber-To-The-Home

Fiber-To-The-Home

Fiber optics (to be discussed in "Physical Media") can offer considerably higher transmission rates than twisted-pair copper wire or coaxial cable. Some local telcos (in many different countries), having recently laid optical fiber from their COs to homes, now provide high-speed Internet access along with traditional phone and  television services over the optical fibers. In the United States, Verizon has been specifically aggressive with FITH with its FIOS service [Verizon FIOS 2009].

There are many competing technologies for optical distribution from the CO to the homes. The simplest optical distribution network is called direct fiber, for which there is one fiber leaving the CO for each home. Such distribution can provide high bandwidth, since each customer gets its own dedicated fiber all the way to the central office. More commonly, each fiber leaving the central office is in fact shared by many homes; it is not until the fiber gets comparatively close to the homes that it is split into individual customer-specific fibers. There are two competing optical-distribution network architectures that carry out this splitting: active optical networks (AONs) and passive optical networks (PONs). AON is basically switched Ethernet, which is discussed in "The Link Layer and Local Area Networks". Here we briefly talk about PON, which is used in Verizon's FIOS service. The following figure shows FTTH using the PON distribution architecture. Each home has an optical network terminator (ONT), which is attached by dedicated optical fibter to a neighborhood splitter, The splitter combines a number of homes (typically less than 100) onto a single, shared optical fiber, which  connects to an optical line terminator (OLT) in the telco's CO. The OLT, providing conversion between optical and electrical signals, connects to the Internet using a telco router. In the home, users connect a home router (normally a wireless router) to the ONT and access the Internet via this home router. In the PON architecture, all packets sent from OLT to the splitter are replicated at the splitter (similar to a cable head end).

FTTH can potentially provide Internet access rates in the gigabits per second range. However, most FTTH ISPs provide different rate offerings, with the higher rates naturally costing more money. Most FTTH customers today enjoy download rates in the 10 to 20 Mbps range and upload rates in the 2 to 10 Mbps range. In addition to Internet access, the optical fibers carry broadcast television services and traditional phone service.

FTTH Internet access


Tags

transmission rate, distribution network, telco

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