FTTH (Fiber to the Home)
FTTH includes fiber-optic access solutions designed for residential deployments. In FTTH networks, fibers are directly connected to individual homes or multitenant buildings. FTTH includes various flavors of both PONs and PTP Ethernet-based solutions. Fiber-to-the-node (FTTN) solutions where fibers are not installed all the way to the residential premises are not included in the FTTH segment. FTTN solutions are instead tracked according to the technology used in the last mile (typically VDSL). With FTTH solutions, the “in-house” connectivity may be based on fiber, coaxial cable, copper or wireless technologies. FTTH covers only the electronics associated with the FTTH rollouts; it excludes associated cabling and civil works.
FTTH promises connection speeds of up to 100 megabits per second (Mbps). These speeds are 20 to 100 times as fast as a typical cable modem or DSL (Digital Subscriber Line) connections. Implementing FTTH on a large scale would be costly because it requires installation of new cable sets over the "last links" from existing optical fiber cables to individual users. Some communities currently have fiber to the curb (FTTC) service. FTTC 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.
The evolution of FTTH
FTTH has grown since the 1980s to accommodate the growing network demands of the modern world. Many fiber cables implemented in the 1980s are still in use today, which is a testament to their flexibility over time. Since the 1980s, fiber technology has become easier to install and cheaper than it was. Today, usage of FTTH and fiber optics continues to increase.
Why Is GPON Popular in FTTH Network?
GPON (Gigabit passive optical network) is defined by ITU-T recommendation series G.984.x. It can transport not only Ethernet, but also ATM and TDM (PSTN, ISDN, E1 and E3) traffic. It represents an increase in bandwidth compared with ATM PON (APON) and broadband PON (BPON). Supporting triple-play services, high bandwidth and long reach (up to 20 km), GPON can be applied in many scenarios especially in FTTx networks. Besides, GPON customers are typically homes or small businesses. Since the GPON technology can deliver data, voice, and IP video, it is suitable and popular for fiber to the home (FTTH) transmission. In FTTH application, the passive optical network (PON) based FTTH network is a point-to-multipoint, fiber to the premises network architecture where unpowered optical splitters are used to enable a single optical fiber to serve 32-128 premises. The following text will focus on components and architecture of GPON FTTH access network.
FTTH Components and General Architecture
The main
components and general architecture of the FTTH network at any telecom operators include the Optical Line Terminal (OLT),
Optical Distribution Frame (ODF), Passive Optical Splitter (POS), Fiber
Distribution Terminal (FDT), Fiber Access Terminal (FAT), Fiber Terminal Box
(FTB), Optical Distribution Box (ODB), Optical Splitter Box (OSB), Optical
Network Unit/Terminal (ONU/ONT). These all components are the main component to
built a FTTH networks.
The Access Node is located in the Central Office, wherein the OLT, the ODF and the first POS stage are housed. From the Access Node the Feeder Network is based in a number of Feeder routes and cables that interconnects the FDTs in a ring topology to provide network resiliency. The FDT is the aggregation element that performs the Remote Node functions. The FDT houses the second POS stage, although some fibers are reserved to pass-through it without splitting.
Ahead of the FDT, the Distribution Network approaches the network to the end users by means of a number of Distribution Cables. Along the path of each Distribution Cable, a number of FATs are connected. The FATs perform the Dispersion Node functions. From the FAT, the Drop Cables provide individual connectivity to each building in a star topology, either Single Dwelling Units (SDU) or Multi-Dwelling Units (MDU). Some buildings can have a dual homing connectivity to two separate FATs
ACCESS NODE FOR FTTH
The Access Node is the starting point of the optical access network in its fiber path up to the end user. The function of the Access Node is to house all active transmission equipment, manage all fiber terminations and facilitate the interconnection between the optical fibers and the active equipment. The size of the Access Node is determined by the size and capacity of the FTTH area to serve in terms of users and future upgrades.
OLT (Optical Line Terminal)
OLT is a device which serves as the service provider endpoint of a passive optical network. It is an active Ethernet aggregation device that is usually located in a data center or the main equipment room. It is the engine that drives the FTTH system. An OLT converts the optical signals to the electrical signals and presents them to a core Ethernet switch. The OLT replaces multiple layer 2 switches at distribution points. OLT distributing signal is connected with backbone cabling or horizontal cabling through optical splitters, which are connected to the optical network terminal at each work area outlet.
ODF AND OSF
The Optical Distribution Frame (ODF) is the network frame where the fibers from the outdoor cables are terminated and become available to interface with the active equipment or patching.
Typically, outdoor cables are terminated in the underground facility that provides the entrance to the Central Office. From there a fire retardant ISP transfer cable is spliced to the outdoor cable and transported up to the ODF. In some cases, the outdoor cable itself terminates at the ODF.
The ODF offers flexible patching between active equipment ports or splitters and the outdoor cable termination. Fibers are identified and stored in physically separated housings or shelves to simplify fiber maintenance and to protect or avoid accidental interference to fiber circuits.
Each fiber from the Feeder cables is spliced to a connectorized pigtail and terminated in an LC/APC adapter at the front of the ODF panel.
Adapter: A device mounted on the patch panel, used to mechanically align, couple and mate or join two plug-in optical connectors of patch cords and pigtails. This is intended to provide a readily available or separable connection between two optical fibers.
Connector LC/APC: A device for providing a readily separable plug-in connection between two optical fibers using a matching adapter. LC is a type of optical connector and APC (Angle Physical Contact) is a type of polish fiber end-face.
Patchcord: Single fiber cable pre-assembled with a connector at both ends, type LC/APC.
Pigtail: A short length of single fiber cable pre-assembled with a connector at one
end , and the other end being connected to the fiber cable by
fusion splicing.
Fiber distribution terminal (FDT)
The FDT (fiber distribution terminal) is used in FTTH networks to connect feeder cables and distribution cables. The device can be used to fixed and protect optical cables, terminate and splice fibers, distribute and dispatch fibers, and protect other parts.
Fiber access terminal (FAT)
The FAT adopts the FastConnect technology, which makes FTTH deployment and maintenance efficient and convenient. The FAT include the FAT-8 and FAT-16 for splicing, distribution, and optical splitting of distribution and drop cables. The FAT-8 and FAT-16 are outdoor devices that output 8 and 16 pre-connected drop cables respectively at the user access nodes. When the FAT-16 is equipped with 1:8 or 1:16 splitters, it can be deployed at an optical distribution node.
Optical
Splitter
The optical splitter splits the
power of the signal. That is to say, each fiber link entering the splitter may
be split into a given number of fibers leaving the splitter. Usually, three or
more levels of fibers correspond to two or more levels of splitters. This
enables sharing of each fiber by many users. The passive optical splitter has
the characteristics of broad operating wavelength range, low insertion loss and
uniformity, minimal dimensions, high reliability, and supporting network
survivability and protection policy.
Splitters are critical devices in PONs. Its quality has a relevant influence in the PON performance and optical reach. Splitters constructed with PLC technology are preferable for their insertion loss and loss uniformity figures and for their wider operation wavelengths.
Optical splitters
are provided pre-connectorized with an LC/APC connector at both ends.In FTTH
architecture, optical splitters may be placed in different locations:
- Central Office, besides the OLT (housed in the ODF rack).
- Fiber Distribution Terminal (FDT).
- Fiber Access Terminals (FAT). Only in exceptional cases.
- Optical Splice Box (OSB) housed in Multi Dwelling Units (MDU) buildings.
ONT
(Optical Network Terminal)
ONT is deployed at customer’s premises. It is connected to the OLT by means of optical fiber and no active elements are present in the link. In GPON, the transceiver in the ONT is the physical connection between the customer premises and the central office OLT.
Why is FTTH important?
With an increasing number of forward-thinking companies, people in many countries are already enjoying FTTH-enabled high-speed internet.
Looking ahead, FTTH networks will continue to expand rapidly to meet the needs of the next generation of technology. With the explosion of the IoT space and the influx of smart devices into homes, consumers will need more than copper to get the level of connectivity they want.
As a fibre network developer, understanding how to design, build and manage FTTH networks can be a major growth area in the future.
With Tente,
you have all the tools you need to maintain your network and ensure that your
consumers get the highest level of internet connectivity.
