Fiber-To-The-?
By David Pheteplace, Bishop & Associates Inc.

FTTx is the all-inclusive term that covers a number of possibilities for fiber optic networking. Fiber-To-The-Home, FTTH, is probably the first one that comes to most peoples’ minds. It is also called Fiber-To-The-Premises and Fiber-To-The-Building. Terms less often heard are FTTN and FTTC, and each are addressed separately below.

The entire FTTx system architecture is pictured below as shown on Commscope’s website, a major provider of FTTx solutions. It starts at the headend, which belongs to service providers such as Verizon’s FIOS, AT&T, or Comcast. Fiber is usually part of the service provider’s network, particularly in areas of newly constructed neighborhoods. In older cities, more of the backbone structure tends to have been done with coaxial cable, which is the preceding technology. Some service providers are actively replacing the backbone coax with fiber optic cable.

 

FTTH is the ideal situation, as it provides the greatest bandwidth and speed to the user. FTTH brings the fiber optic cable from the headend all the way to a network interface box on the side of a home, apartment complex, or office building. At this point, the signal is usually converted to a radio frequency electrical signal for distribution within the structure. This is accomplished with a micro-node. A typical installation from Commscope is pictured to the right. The connector interfaces are 75 ohm female F-type connectors and an SC/APC female fiber optic connector.

The distribution of the signal in a home or building can also be accomplished with fiber optics. ElectronicLinks International has a plastic optical cable system, which can distribute the fiber optic signal (pictured below). The system works using an active optical system over duplex fiber cable. The conversion of the signal from light to electrical is accomplished in the connectors that have a receiver and transmitter built into each side of the connector. The system (pictured) takes the RF signal from a cable modem, converts it to light, transmits it to the cable box on your TV, for example, and then converts it back to an RF signal. The system is capable of transmitting signals up to 100 meters in length at speeds up to 250 Mb/s. The connectors in the system are standard RJ45s on the electrical side and custom POF connectors on the optical side. The connectorization is simple. It just requires cutting and stripping the duplex cable and then inserting the fibers into the connector. The alignment of the fibers is accomplished through alignment features in the connector and the active LED components. No fiber polishing is required.

FTTH solutions can be direct fiber or shared fiber. Direct fiber is a single fiber running from the headend to the home. It has the best performance. Shared fiber is a single fiber running from the headend to a node located in a neighborhood, where it is then split and delivered to the individual customers. It is the most common system. The signals on the shared fiber are multiplexed and encrypted so each customer’s information is secured.

FTTH solutions can also be active or passive optical networks (PON). Active optical networks require passing the signal from the headend through electrically powered equipment that can amplify to signal, and also direct the signal using Internet Protocol (IP) switching/routing. A passive network is light only from the headend. The signal is physically divided off to individual customers by splitters and protected by encryption. A passive optical splitter from Omron (left, below) is capable of splitting the light signal into 64 separate signals. Termination of the individual fibers is accomplished through splicing. An ADC passive optical splitter module (right, below) is capable of splitting a light signal into 32 separate signals for each module installed in a rack or cabinet. These fibers are pre-terminated with connectors for easier installation.

FTTN (fiber-to-the-node) and FTTC (fiber-to-the-curb) both refer to optical cable being run into a neighborhood on fiber optic cable, where it is terminated in a cabinet on the street. In FTTH, the light signal will be passed on to the homes in the neighborhood. In many systems, particularly in older neighborhoods, the signal is converted to an RF signal over coax cable, or, with phone service, is converted to a DSL signal over twisted-pair wires, which is then connected to each home. The signal is then converted to Internet Protocol by the cable or DSL modem.

FTTH is still in its infancy. The Verizon FIOS system is currently available in selected areas—mostly metropolitan—in 16 states. Verizon plans to deploy their system in selected areas in another 12 states, for a total of 28 states. For those in rural areas, it is likely that the systems will never be deployed, due to the high cost per subscriber. Besides standard phone lines, most rural customers that want high speed Internet service will have to opt for the relatively lower-cost satellite services now being deployed.

David Pheteplace Bishop & Associates Inc., Managing Director - Cable Assembly Division David Pheteplace joined Bishop & Associates Inc. in 2008. As the managing director, he is establishing a new division for Bishop & Associates focused on the cable assembly industry. Pheteplace is also the market segment director for telecom. He has more than 20 years of experience in the interconnect industry, including managing divisions of Amphenol, Cinch, and Robinson Nugent. Pheteplace can be reached at dpheteplace@bishopinc.com.