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Broadband SoHo FTTx Tutorial

FTTH / FTTP (Fiber to the Home / Fiber to the Premise) is a fiber-optic broadband triple play service (Voice/Data/Video) currently in deployment throughout the U.S. by various RBOC's such as Verizon, AT&T, and individual city municipalities. The architecture of this deployment is called a PON (Passive Optical Network), this is a completely passive (the signal is transported by laser with no electronics) network consisting of fiber optic cabling, passive splitters, attenuators, and couplers. These listed components are also referred as the ODN  (Optical Distribution Network) elements that distribute an optical signal through a branched topology to an ONT (Optical Network Terminal). This architecture is a point-to-multipoint system that allows a maximum of 32 ONT's to be serviced, with a OSP topology of 1x32 Home Run Split, 1x4 to 1x8 Distributed Split, or 1x8 to 1x4 Distributed Splitter configuration.

 FTTx Tutorial          Verizon FTTP Tutorial          FTTx MDU Services

**This entire FTTx section was updated 10/1/08

Note:  This tutorial was created to give a basic overview to a new field technician or client of this technology, and describe various deployment components that form this next-generation network. Please be aware that we are only describing some key points that customers have commonly questioned that pertain to the recent RBOC's deployment. Please refer to some of the links below for a complete PON overview. To all that have viewed, and promoted this tutorial ... Thank You !


Various FTTx PON Deployments

(Tellabs) Architecture Example - Click Here

FTTx ~ Fiber to the x , is the deployment of fiber (optical) cable to a specific location (proximity) in regards to the customer premise. The “X” is used to describe the specific application of the service. As you will read in magazines and various articles you will see these following terms below and used loosely, as some relate to each other, or just acronyms.

FTTc ~ Fiber to the Curb , is the deployment of fiber close to the customer but not fully to the customers residence. In this deployment the existing copper plant is still used to deliver service to the actual customer.  FTTN (Fiber to the Neighborhood) & FTTC (Fiber to the Cabinet) generally fall under the FTTC category. Both services are in deployment and in use, a perfect example is a DLC/NGDLC (Digital Loop Carrier) which some of us get our phone service from. A direct fiber from the CO (Central Office) is terminated at the DLC/NGDLC and then service is delivered to the customers residence via the copper plant.

FTTn ~ Fiber to the Node  (AT&T U-verse)

U-verse (ATT) is an example of a widely deployed FTTn system. This architecture was chosen by them to extend the fiber link as close to the neighborhood existing SAI terminal (distributes individual cable pairs to each customers residence) for triple-play service. The fiber link is extended with the help of the Alcatel 7330 ISAM (Intelligent Services Access Manager) which resides in an outdoor cabinet commonly called a VRAD, the ISAM converts the service to VDSL-2, which is then cross-connected to the customers existing copper POTS line.

(Alcatel  Lucent) - FTTN Architecture


The Economics of FTTN vs. FTTP  - (ADC) White Paper

FTTb ~ Fiber to the Building , is the deployment of fiber (optical) cable to a specific location within a building, then connected to the buildings existing copper, cable facilities. This deployment is also referred to as FTTB (Fiber to the Basement) & FTTB (Fiber to the Business). This deployment will be the typical for MDU’s & MTU’s also known as **  FTT mdu ~ Fiber to the MDU **

FTTh ~ Fiber to the Home , is the complete deployment of fiber to the customers home, with replacement of there existing NID (Network Interface Device). This replacement device is called an ONT (Optical Network Terminator).

FTTp ~ Fiber to the Premise , is a loosely used term. It can be the definition of FTTB or FTTH, it depends on how the context is used and specific location of where the fiber terminates. In general it falls under the FTTB definition.


Passive Optical Network Components

Below are the primary components that create a passive-optical network. As they are explained please read the following associated documents so you can see the physical component and achieve a better understanding of its role in the network. We recommend that you view the Verizon FTTP Tutorial to see their chosen network component brands. As you will notice you may come across various FTTx vendor equipment as a field technician, but they are generally the same, and perform the same function.


(ADC) - FTTP Infrastructure


OLT ~  Optical Line Terminal , is the networks control processor. This unit resides in the local CO (Central Office) cross connected to the video and data networks that will be delivered to your home, it consists of a special DFB (Distributed Feedback) calibrated laser that is always on. The OLT control card acts as a traffic signal to the remote ONT's for complete data / video throughput upstream and downstream. (Tellabs) OLT - Click Here     (Tellabs) OLT OSP Cabinet - Click Here

ODN ~  Optical Distribution Network , is part of the OSP architecture components. The actual fiber-optic cabling, passive splitters, FDH, attenuators and couplers.


(ADC) - FTTx Architecture


FDH ~  Fiber Distribution Hub , is the cross connection splice-point for the Central Office Fiber and Distribution Fiber to the FDT's servicing the customers community. This hub can come in various configurations (Aerial Pole mount / Ground Pedestal), the providers configuration will typically be the 144 / 216 user count, designed to be a plug and play system for the FDT / Drop Cable connections.  (ADC) FDH Picture - Click Here     (ADC) FDH Open - Click Here     (ADC) FDH Rear Panel - Click Here

FDT ~  Fiber Distribution Terminal , is the cross connection splice-point between the community serving FDH Distributing Cable, and the Drop Cable to the customers ONT.  Tech Note - The FDT is aka "Access Terminal", this term is used loosely.

DROP CABLE ~ This cable is the final connection to the customers ONT. This cable can be spliced from an aerial / underground FDT. Most providers have moved to a pre-terminated drop cable system, this saves cost and installation time. ADC - MST System

ONT ~  Optical Network Terminal , this is the CPE (Customer Premise Equipment) endpoint of the ODN. The ONT  is an Optical to Electrical to Optical device, that delivers your triple play services. It will replace your existing copper NID (Network Interface Device) , and coax connections. The existing POTS / Coax inside wiring will be cross connected to the SFU (Single-Family Unit) ONT. Since we understand that a PON is completely passive the endpoint must contain an AC voltage connection to perform the Optical to Electrical conversions for your services. Ex.1 (Siemens) ONT Picture - Click Here     Ex.2 ONT Picture - Click Here


MDU - Passive Optical Network Components

Above we listed the primary components that create a passive-optical network, and they are the same for an MDU deployment. Within the last year the FTTx MDU market has produced a vast amount of products. The only differences in the MDU deployment are the FDT's, Drop Cables, and ONT's.


(ADC) - FTTx MDU Architecture


iFDH ~  Indoor Fiber Distribution Hub , same as FDH, just an indoor unit.

iFDT ~  Indoor Fiber Distribution Terminal , same as FDT, just an indoor unit.

Drop Cable ~ This cable will enter the customers apartment from the FDT that's usually located in a closet, or stairwell in a high-rise building. In a small garden-style MDU deployment your drop cable may come from an FDT located on the outside of your building, and routed through the roof breezeway into your apartments designated closet.

ONU ~  Optical Network Unit , this is similar to the SFU-ONT but for a MDU / MTU, or small business. It contains 12 - 24 POTS Lines, multiple "Ethernet" or "VDSL" connections, and one / two high-powered RG video outputs. These ONT's come in two forms, a wall mountable or rack-mountable unit, they are typically installed in a stairwell area, or basement next to the existing SAI for that floor. Ex.1 (Siemens) ONU Picture - Click Here


ADC - RealFlex Drop Cable System

* The video below is from ADC, and contains a very detailed description of how important the Drop Cable is in the MDU network.


PON Transport Operation

FTTx is not a new technology, it has been around for sometime within the RBOC's (Bell South was one of the first to experiment with FITL and implement this service back in the late 80's)  but as years have passed the technology has advanced along with the reduction cost of fiber, creating what is the broadband craze of today. With this sudden craze and endless possibility of bandwidth , you should keep in mind a few several things. Fiber has the ability of offering a huge bandwidth , but within a  PON there are several formats with limitations. These formats are APON (ATM-PON) , EPON (Ethernet-PON), and GPON (Gigabit-PON) each has a unique set of features and transport process. At this time there is still a huge debate as to which format is the best and what should be the standard, but at this time most deployments are currently BPON, future deployments by the first of next year will generally be GPON if within the providers budget.


  • Fiber Cable Span no more than 20Km (12Miles) of Single-mode fiber

  • Asymmetrical 622 (OC-12) / 155 (OC-3) Mbs bandwidth per OLT path of 32 ONT's

  • OLT - WDM (Wave Division Multiplexing)

  • 1550nm (1480-1580) for downstream

  • 1310nm (1260-1360) for upstream

  • TDM (Time Division Multiplexing) of ATM packets

  • 1:32 Passive Splitter OSP Topology


  • ** Same as BPON standard except with the following differences

  • Asymmetrical 1.2 Gbps or 2.4 Gbps / 155 or 622 Mbs bandwidth per OLT path of 32 ONT's

** Note: These services can also be configured symmetrical also but the most common deployments will be asymmetrical.

  • FTTx Tutorial Links

Listed below are some recommended industry links to help in your further knowledge of this growing technology. As time permits I will update these links, for more examples of the passive optical network components please visit the Verizon tutorial.


Fiber Optic / FTTx Tutorials

Field Technician Training / News


Basic Principles of Fiber Optics

Fiber Optic Technology

FTTH Council

FTTH Explained

FTTH Interactive Tutorial

FTTH Video Overview


Telephonyonline FTTx News

Fiber / FTTx Training - The Light Brigade

Fiber / FTTx Training - Fiber Optic Association

Fusion Splicing Education

Fiber / FTTx Training - VDV Academy

Exfo FTTx / PON Network Testing


Legal Note:  Below are registered trademark logos for the following companies. This tutorial was created with the use of their unique company logos, and documents that discuss products, such as data sheets, white papers and spec sheets, and on product advertisements. With respect to this and the tutorial created, do not republish or use any part of this out of its context. To obtain further information on the products discussed in this tutorial, please click on the companies logo for that desired product.