A passive optical network (PON) is a system that brings optical fiber cabling and signals all or most of the way to the end user. Depending on where the PON terminates, the system can be described as fiber-to-the-curb (FTTC), fiber-to-the-building (FTTB), or fiber-to-the-home (FTTH). All PON systems have essentially the same theoretical capacity at the optical level. The limits on upstream and downstream bandwidth are set by the electrical overlay, the protocol used to allocate the capacity and manage the connection. The first PON systems that achieved significant commercial deployment had an electrical layer built on Asynchronous Transfer Mode (ATM, or "cell switching") and were called "APON." These are still being used today, although the term "broadband PON" or BPON is now applied. APON/BPON systems typically have downstream capacity of 155 Mbps or 622 Mbps, with the latter now the most common. Upstream transmission is in the form of cell bursts at 155 Mbps.
Fiber to the curb (FTTC) refers to the installation and use of optical fiber cable directly to the curbs near homes or any business environment as a replacement for plain old telephone service (POTS). Think of removing all the telephone lines you see in your neighborhood and replacing them with optical fiber lines. Such wiring would give us extremely high bandwidth and make possible movies-on-demand and online multimedia presentations arriving without noticeable delay. Fiber to the curb implies that coaxial cable or another medium might carry the signals the very short distance between the curb and the user inside the home or business.
Fiber to the building (FTTB) refers to installing optical fiber from the telephone company central office to a specific building such as a business or apartment house. Fiber to the neighborhood (FTTN) refers to installing it generally to all curbs or buildings in a neighborhood. Hybrid Fiber Coax (HFC) is an example of a distribution concept in which optical fiber is used as the backbone medium in a given environment and coaxial cable is used between the backbone and individual users such as those in a small corporation or a college environment.
Fiber to the home (FTTH), also called fiber to the premises (FTTP), is the installation and use of optical fiber from a central point directly to individual buildings such as residences, apartment buildings and businesses to provide unprecedented high-speed Internet access. FTTH dramatically increases the connection speeds available to computer users compared with technologies now used in most places. While FTTH promises connection speeds of up to 100 megabits per second (Mbps) -- 20 to 100 times as fast as a typical cable modem or DSL (Digital Subscriber Line) connection -- implementing FTTH on a large scale will be costly because it will require installation of new cable sets over the "last links" from existing optical fiber cables to individual users. Some communities currently enjoy "fiber to the curb" (FTTC) service, which refers to the installation and use of optical fiber cable to the curbs near homes or businesses, with a "copper" medium carrying the signals between the curb and the end users.