What is Known as Fiber to the X

Fiber To The X (FTTx) is different from a traditional fiber optic network that would be used for a local area network (LAN) application. In most FTTX applications, only one optical fiber is used. That single optical fiber passes data in both directions. This is very different from a LAN application where the transmit optical fiber sends data in one direction and the receive optical fiber sends data in the other direction. In a LAN application, both optical fibers can have data passing through them at the same time.

In an FTTX single optical fiber application, full-duplex operation is typically not possible; Usually only half-duplex operation takes place. This means that part of the time the optical fiber is carrying a signal in one direction, and the rest of the time, it is carrying a signal in the other direction.

FTTx systems typically use multiple wavelengths. The downstream laser is always a different wavelength than the upstream laser. The downstream is typically the longer wavelength, such as 1480nm or 1550nm (or both), and the upstream laser is typically 1310nm.

FTTX is possible with optical fiber distances up to 20km because optical fiber is capable of transmitting information with a very low level of loss. The typical loss for an FTTX optical fiberat 1550nm is 0.25dB/km and 0.35dB/km at 1310nm.

Figure 1 A schematic illustrating how FTTX architectures vary — with regard to the distance between the optical fiber and the end-user

Fiber To the Home

A fiber-to-the-home (FTTH) PON uses optical fiber from the central office to the home; At the home, a converter box changes the optical signal from the optical fiber into electrical signals. Theconverter box interfaces with existing home cabling such as coaxial cabing for cable TV, twisted-pair cabling for telephone, and Category 5e or 6 cabling for Internet connectivity.

Fiber to the Building

A fiber-to-the-building (FTTB) PON is very similar to an FTTH PON. It uses optical fiber from the central office to the building and there are no electronics helping with transmission in between. The ptical signal from optical fiber is converter into electrical signals in a converter box at the building. The converter box interfaces with existing cabling such as coaxial cabling for cable TV, twisted-pair cabling for telephone, and Category 5e or 6 cabling for Internet connectivity.

Fiber optic setups enable higher speeds of delivery and greater bandwidth than some other kinds of infrastructure. Some of the fiber networks deploying signals to the most sophisticated equipment can benefit from a multimode fiber connection, where a specific kind of fiber optic cable may be used for optimal speed.

Fiber to the Curb

"Fiber to the curb" (FTTC) refers to the installation and use of Fiber Optical Cable directly to the curbs near homes or any business environment as a replacement for "plain old telephone service" (POTS). In a fiber-to-the-curb PON, optical fiber runs from the central office and stops at the curb. The "curb" may be right in front of the house or some distance down the block. The converter box is located where the optical fiber stops, and it changes the optical signal from the optical fiber into electrical signals. These electrical signals are usually brought into the home through the existing copper cabling. The electrical signal may need to be processed by another converter in interface with existing twisted pair cabling for phone, and cat 5e or 6 cabling for Internet connectivity.

Fiber to the Node

Fiber to the node (FTTN) is sometimes referred to as fiber to the neighborhood. A FTTN PON only has optical fiber from the central office to the node. The node is typically telecommunications cabinet that serves a neighborhood or section of a neighborhood. The optical signal from the optical fiber is converted into electrical signals inside the telecommunications cabinet. These electrical signals are distributed throughout the neighborhood through existing copper cables to the houses.

One of the main benefits of fiber to the node and similar systems is the ability to deliver data over more efficient fiber optic lines, rather than other lines with greater speed restrictions. The remaining area from the node to an individual destination, often called "last mile" service, can be achieved with copper or other types of wire. FTTN systems often use coaxial or twisted-pair cable in order to achieve delivery to multiple customers.

The Major Outside Plant Components for an FTTX PON

The outside plant components make up the PON infrastructure and are all designed for installation exterior to buildings. The cables connect different access points in the PON. Everything is initiated from the central office or central switching point.

* Cables

There are feeder, distribution, and drop cables are employed in an FTTX PON.

Feeder cables: Feeder cables run from the central switching point to the local convergence point. These cables typically contain multiple ribbons of 12 single mode optical fibers each. A common feeder cable will contain 18 ribbons for a total of 216 single mode optical fibers.

Distribution cable: Distribution cables run from the local convergence point to the network access point. A distribution cable can have as few as 12 optical fibers or as many as 144. A typical distribution cable has 72 optical fibers.

Drop Cables: A drop cable is a single optical fiber cable that is terminated at the factory, typically with SC connectors on both ends. The cable is environmentally sealed and the connectors are sealed when they are mated.

Figure 2 shows sc connector

* Local Convergence Point

The local convergence point (LCP) is the access point where the feeder cables are broken out into multiple distribution cables. Depending on the architecture of the PON, the local convergence point may or may not be the place where the optical signals are split. The optical signals may be split at the network access point with a Fiber Splitter like the one shown in Figure.

Figure 3 shows optical fiber field rated local convergence cabinet

Figure 4 shows optical splitter

* Network Access Point

The network access point (NAP) is located close to the homes or buildings it services. This is the point where a distribution cable is broken out into multiple drop cables. The NAP is a terminal that serves as a connection point for drop cables. The NAP is a terminal that serves as a connection point for drop cables. It may be installed in an aerial installation, in a pedestal, or in a hand hole.

* Network Interface Device

The drop cable runs from the NAP to the network interface device (NID). The NID is typically mounted to the outside of the house or building. It is an all-plastic enclosure designed to housethe electronics that support the network. The SC connector on the end of the drop cable mateswith the connector in the NID.