FOA Guide


Fiber To The Home Network Design

   There is really no way to generalize on the design process for fiber to the home (FTTH) networks - or any fiber optic network for that matter - since every system is unique. If you are familiar with FOA's other design materials, you know we don't give you formulas or outlines to follow. Rather than telling you how to design a FTTH network, we will illustrate some of the different network architectures, construction methods, etc. possible, then offer options that may work for your network and stimulate your design processes.

    If you are new to fiber optic network design, we recommend you study the design pages on the FOA Guide, read the FOA textbook Reference Guide to Fiber Optic Network Design, and perhaps take the Fiber Optic Network Design self-study course on Fiber U to prepare yourself for designing your own network. That will help you understand how to design and install systems most efficiently before beginning your own project. And, of course this complete series on FTTH here on the FOA Guide.

    The best way to understand the options in FTTH network design is to consider several very different types of networks which differ by subscriber density, geography and technical issues which affect the design decisions that must be made.
  • Urban
  • Suburban
  • Multi-dwelling Units
  • Rural
   Within each of these we will discuss design options that have been proven successful in the real world. We will look at how to design the architecture of the system as well as the design of the cable plant itself, down to the component level. We will also look at cost implications and future upgrades. We'll try to illustrate the options to help you understand them.

We begin with some important background material.

Jargon

PON (Passive Optical Network)
  Most FTTH networks are based on passive optical network architectures, simply because that's usually the lowest cost way to design a FTTH network. There are other architectures that may be preferable in some circumstances and we'll discuss those too. This drawing shows the location of the hardware used in creating a typical PON network. This drawing also defines the network jargon for cables: a "feeder" cable extends from the OLT (optical line terminal) in the CO (central office) to a FDH (fiber distribution hub) where the PON (passive optical network) splitter is housed. It then connects to "distribution" cables that go out toward the subscriber location where "drop" cables will be used to connect the final link to the ONT (optical network terminal).

FTTH PON jargon

Active Star
    An alternate to a PON is an active star network, also called a point-to-point (P2P) or "home run" system where each subscriber has a dedicated fiber and Ethernet link to the head end or central office.  The main difference with a PON is the amount of fiber required for the network, especially if the service provider's switches are located at the head end. Switches can be remote, closer to the subscribers, but the switch requires power, a UPS and perhaps even heat/AC, making that option much more complex.

P2P

We will focus on PONs but mention P2P and even some options for wireless or wireline for drops.

Gig or 10Gig?
    Standards for PONs give you an option of gigabit or 10 gigabit networks. Technically what is called gigabit (G for short) is regular GPON which offers OLT ports at 2.5G downstream and 1.25G upstream, shared among 32 (normal) or 64 (rare) users. Provisioning is generally for 1G down and some lower value up on each OLT port. If you don't understand the stochastic nature of networks, you might assume that 32 users with 1Gb/s of bandwidth have only about 30Mb/s (1Gb/s = 1000Mb/s, divide by 32 = 31.25Mb/s). But that's not realistic. The full 1G of bandwidth is available to all users who only use it a fraction of the time, so their data is transferred at 1G speeds. Average usage for most FTTH networks averages only a few Mb/s, so 1G PONs are very effective.

    But 10G PONs are available and like all electronics, costs keep coming down, so they are being considered for many networks. It is doubtful that any FTTH
network aimed at consumer subscribers needs 10G, but some business customers might. The GPON designers were clever, however, making 10G use different wavelengths than 1G, so if you build a 1G GPON network, you can upgrade at any time - say to accommodate a network expansion aimed at businesses - and run both networks simultaneously over the same cable plant. Generally, we recommend building networks at 1G to take advantage of the lower cost electronics, but knowing that upgrades can be made simply and use the very same cable plant.

Network Architectures

    PONs have options on architectures that can affect cost and ease installation. One of the first decisions the designer needs to make is where to locate splitters as that will affect other hardware decisions like how many fibers should cables have and what types of hardware to use. To make that decision, one first needs to understand the distribution of subscribers as location and density are important for designing an efficient system. Here are some options on design:

    PONs work on the principle that splitters allow one central port to communicate with 32 or 64 users over a single fiber to the splitter and then a single fiber to each user. Typical PON architectures are shown like this:

FTTH

    In reality, there is a lot of flexibility in the location of splitters. For example, some dense urban or suburban networks move the splitter into the Central Office (CO - a traditional telecom term) or Head End (the CATV term) and run a fiber to every user like this:
FTTH
    While this option requires more fiber, large fiber count cables are readily available and fiber cost is low, so the incremental cost to use more fibers in a cable is reasonable. If the splitter is in the CO, the OLT can be utilized more efficiently since each port can support 32 or 64 users from any location in the service area. If splitters are moved closer to the users, some ports must be left open for future expansion, meaning that OLT port will support fewer than the maximum number of users - about 24 ports being used seems average, with 8 ports being open for future subscribers. With a central splitter and fiber to each user configuration, there is flexibility to use each OLT port more efficiently, adding new OLT ports only when needed, and when every customer has a dedicated fiber, the CO can even support several ISPs (Internet Service Providers) by simply patching the user to their chosen ISP.

    Where subscriber density is lower, it's common to cascade splitters where splitters with fewer splits are connected to other splitters in series like this:
FTTH
    Cascaded splitters are useful for areas like the suburbs or rural areas where subscribers are spread out but often in clusters. An example is to use a 4 or 8 port splitter to serve a street in the suburbs or a small cluster of homes in a rural area or to connect multiple users in a multi-dwelling unit (apartment or condo building - see the section on MDUs below.)

    PONs are standardized on splits of 32 or 64 per OLT port, and the economics of the electronics depends on the efficient use of the OLT port. But subscriber take rates are not 100%, so one needs to leave spare ports for drops to future subscribers. Some systems limit subscribers to 20-24 per port to allow new subscribers. Others have built networks around a fiber from the head end to every potential user and leaving the fibers to non subscribers dark. The central office houses all the splitters which can be fully populated, optimizing the electronic ports. New subscribers already have a dark fiber and just need plugging into a splitter at the head end. New OLT ports are added as subscribers fill up ports already in use.

    Much of the design time is likely to be spent deciding where to place splitters to optimize the cable plant. In dense urban areas, there may be locations where subscriber density is high enough to justify using a single 32 port splitter. In less dense areas, it will probably be more efficient to cascade splitters to equal the 32 splits. Splitters come in binary ratios (2, 4, 8, 16, 32) and can be cascaded in any sequence as log as the multiplied split ratios are no more than 32, e.g. 2+16, 4+8, 2+4+4, etc.

cascaded FTTH splitters

    Choosing splitter locations can be challenging, but generally it is done where one finds groups of subscribers in close proximity so the length of drop cables is shortest. In urban or suburban areas, one can look at the number of residents in a building or the number of homes on a street. In dense population areas, a pedestal or underground fiber distribution hub (FDH) containing splitters may be placed in a neighborhood and drops run from the FDH to buildings from there. If a building has many residents, a smaller FDU with splitters may be placed inside the building with individual fibers run to each subscriber. A large FDH is not needed for splitters. Splice closures often have provision for splitters, so a backbone or distribution cable can be split out to drop cables for subscribers in the closure. That closure can be in a manhole or handhole if the cable plant is underground or suspended with aerial cable.


PON Loss Budgets
    PONs are designed around a certain split ratio for OLTs and have a range of power at the receiver that must be met for the network to function. For example, GPON has a Power Budget range of 
13dB (min) to 28dB (max) w/32 split. When calculating the loss budget, one needs to ensure the loss is at least 13 dB but less than 28 dB, usually less the acceptable loss margin for the link. The minimum of 13 dB is usually not going to be a problem since splitters add large amounts of loss.
FTTH PON LOss Budget
PON network diagram with loss budget components noted.

    PON networks with splitters require calculating a loss budget like any other network. Besides the losses from fiber length, splices and connections, one must add in the loss of the splitters. Each split of a factor of 2 loses 3dB and in addition there are losses due to splitter inefficiency, so losses can be quite high. In the example above, the splitters are cascaded so one would have a 1X4 with 7 dB loss and a 1X8 with 11 dB loss to include in the loss budget for a total splitter loss of 18 dB. The the loss of the remaining components in the cable plant would be added.

Splitter Ratio 1:2 1:4 1:8 1:16 1:32
Ideal Loss / Port (dB) 3 6 9 12 15
Excess Loss (dB, max) 1 1 2 3 4
Typical Loss (dB) 4 7 11 15 19

    After calculating a loss budget, it needs to be compared to the power budget of the PON version or link (if using P2P architecture) chosen for the network.

Rural Architecture Options
    Rural areas are characterized by low subscriber density and long distances, not the conditions PONs were designed for. There is a "long reach" GPON version with a capability of 64 users and 60km that can work in some applications. Another option sometimes considered is not using splitters but taps, special splitters at drops that are not symmetrical - multiple equal outputs - but split off a small portion of the signal in the fiber, like 10% and pass 90% along to the next drop.

FTTH Rural - Taps
    The problem with the tap architecture is the inefficiency of tap splitters, The excess loss in taps can be as much as 1dB per tap. That excess loss adds up fast, rapidly cutting the length the network can reach (1dB = ~2.5km of fiber). FOA has done an analysis of the use of taps in rural FTTH which can be used as a model for analyzing the use of taps in any FTTH network.

    Another option which has been developed for low subscriber density like rural areas uses is a remote OLT with only a few ports. OLTs designed for CO use generally have options for many OLT ports because they are intended for applications with large numbers of users - hundreds of thousands in a dense city. But rural areas may only have a few subscribers in a small town or scattered along country roads. Large numbers of ports are not needed. What is needed is an architecture that allows a service provider to connect users spread out over large areas.

FTTH
    The remote OLT option allows creating a "head end" periodically along a rural road where users are grouped. The Remote OLTs can take advantage of the fibers already installed along many roads and since some allow "daisy-chaining," the use of two fibers along the route is all that's needed. They are in small enclosures similar to CATV amplifiers and can be mounted on poles or suspended from messenger wires.

    The long reach version of GPON is another option for rural areas. It can reach 60km with up to 64 users per port, but in countries like the US, 60km is short compared to the distances in rural areas. And it will use much more fiber than the remote OLT architecture.

FTTH Fiber Optic Cable Plant Design

    When FTTH using PONs first began being installed around 2005-7, it was considered a extension of regular telephone systems, where subscribers were being connected to a telephone system replacing copper wires. Cabinets or pedestals containing the PON couplers were placed near a group of subscribers. Cables were pulled between the cabinet and the central office containing the PON system electronics and spliced on each end by the usual outside plant (OSP) installation crews and were tested as was normally done with telecom fiber optic networks.

    On the subscriber end, drop cables were placed to the home and connected either by splicing or installing connectors (usually APC connectors to prevent reflectance problems). Drop cables could be installed aerially, underground or buried. Installing the cables through customer's yards created a problem as it is time consuming and disruptive to the customer. Simple trenching was sometimes dropped in favor of directional boring, an expensive process. Connectors were installed either by fusion splicing on pigtails or using splice-on connectors.

    After the cable plant was installed, the optical network terminal (ONT) was installed at the home. Some systems installed ONTs on the outside of the house, some inside garages, some inside the home. Some home builders built new homes with provision for the ONT inside the home and installed cabling and power to the same area to create a home prepared for broadband. See the examples below.

    After the ONT was installed and tested, it was necessary to complete the installation by connecting the customers phones, TVs and computers. In all, three or four groups of installers of different experience and skill levels were needed to install a FTTH customer.

Systems Evolving With Experience
    After some experience with the systems, methods were tried to simplify the process and cut costs. A big breakthrough came with the development of prefabricated cabling systems (sometimes call pre-terminated cabling) that eliminated the need for most of the splicing. Cables with weatherproof connectors were purchased already made to the lengths needed and pedestals were factory made with connectors for the drop to the home and a cable ready to splice onto the cable installed from the central office.

    The prefab drop cables could be run aerially, even lashed to current telephone wires. They were also small enough they could be pulled through small PVC conduit often installed to home in new construction. Most of the systems use multi-connector cables near the homes being connected so homes can be connected during the first install or later when more customers decide to take the service.

FTTH prefab
Aerial installation in Santa Monica, CA, using prefab cabling system.

FTTH prefab
Closeup of the six-port drop.


  If the cable is underground, it will usually be pulled through conduit from connection to the distribution cable or the splitter to the home. Here a preterminated system has two home drops connected to the distribution cable.


Prefab cable underground
Underground installation of prefab cable system in Long Beach, CA.

    Other systems used microduct installation which requires little or no digging to install underground or under a road. Microducts are designed to accommodate small microcables that are installed by "blowing in" the cables, a technique used in many systems.

Microduct install
Microduct installation using a saw on a paved street.

  The splitter can be housed in a central office, a pedestal or even a splice closure used for drops in the neighborhood near the homes served. The advantage of PONs is that the pedestal or splice closure is passive - it does not require any power as would a switch or node for fiber to the curb.

 FTTH pedestal   FTTH closure w splitter

On the left is a typical pedestal that has connections to the CO, splitters and fibers out to each home in a sealed enclosure. Pedestals like this can be specified and purchased ready to install; installation involves only splicing the distribution cable to a short cable provided as part of the pedestal. On the right, a tech is splicing drop cables in a closure that has provision for a splitter in the splice tray (red arrow.)

   A network interface device called an ONT (optical network terminal) containing a fiber optic transceiver will be installed at the house. Some are installed on the outside of the house, others are indoors. Some houses are now being built with cabinets in the house for connecting to the FTTH fiber and then distributing phone, TV and Internet connections throughout the house over state of the art cabling. The incoming cable needs to be terminated at the house, tested, connected to the interface and the service tested.

Basic Component Selections
    Two components of FTTH cable plants are almost universal. Every network should use standard singlemode fiber, G.652, or its bend-insensitive equivalent G.657, in all the cabling. This is regular SM fiber and is appropriate for current PONs as well as upgrades to 10G PONs in the future. Connectors are generally SC-APC, the SC connector with an angled physical contact ferrule to reduce reflectance problems in the short cables and splitters. Check equipment requirements to see if SC-APC connectors are specified or if SC-PC is required for the transceivers. Beyond these basic choices, cable designs and other hardware will be chosen for the environment of the cable plant.

New Cable Types And Hardware For Subscriber Drops
  Several new cable types were developed for use in FTTH. Until FTTH, most single fiber cables were complicated structures with tight buffered fibers and aramid fiber strength members inside plastic jackets, usually 3mm in diameter or sometimes smaller. While these cables were adequate for factory termination into prefabricated assemblies, they were not ideal for field termination or use inside buildings. With the advent of bend-insensitive fibers that required less protection, a new type of drop cable was developed that molded a bend-insensitive fiber inside a small plastic structure surrounded by metal or aramid fiber strength members. This design could also be made as a "figure 8" cable with a messenger for support in aerial installation. Here are some photos of this type of cable.

FTTH Drop Cable

FTTH Drop Cable, 1 fiber, showing steel strength member

FTTH Drop Cable

FTTH Drop Cable, 2 fiber

FTTH Drop Cable

FTTH Drop Cable, 1 fiber with messenger for aerial support

To work with these cables, special fiber closures were developed that are more convenient for field installation.

FTTH Drop Cable Closure

  This closure has entries for distribution cables, including one coming in and one going out  - continuing on to another closure for daisy-chained cables using midspan access. There are multiple outputs for drop cables which are terminated in connectors. Some closures like this one have provision for splicing on pigtails to terminate the distribution cables while others are designed for direct termination using prepolished-splice connectors. Patching with connectors in a re-enterable closure allows adding new drops when needed.

    Early ONTs being installed on the outside of the house looked like this. Most networks have moved to just installing a demarcation box on the outside of the house where the drop cable is connected to a fiber optic cable running into the house. This connection allows for a test point for techs where they do not have to enter the house to see if signal is being received at the house. Inside, the FTTH ONT is now a small box like a cable or DSL modem.

ONT


A house with premises cabling has this cabinet inside the home for distributing services from the FTTH connection. Some builders now include equipment boxes like this in new homes.

ONT inside the home

Design For Geography

    The best way to understand the options in FTTH network design is to consider several very different types of networks which differ by subscriber density, geography and technical issues which affect the design decisions that must be made.
  • Urban
  • Suburban
  • Multi-dwelling Units
  • Rural

Urban FTTH Networks
    Urban FTTH networks feature high subscriber density requiring less fiber because the distances are shorter and more splitters and head-end electronics because the subscribers are more numerous. In dense urban areas, many if not most users are going to be in MDUs, so the  OSP design and installation can be simpler - just getting fiber to the building - but inside the premises it may perhaps be more complicated - how to run fiber inside the building to each subscriber. See the section on MDUs below.

    Inside a city, the most complicated part of designing a network is accommodating the cables needed to get from the CO/Head End to the building where the users are located. Cities often have congested conduits with too many cables already, so running more cables can be a problem. Techniques exist to add cables to crowded ducts, sometimes removing fiber ducts that have only one fiber and replacing them with microducts with multiple microcables or using fabric ducts that can double or triple the number of cables a conduit can accommodate. Rather than digging up streets, systems can be built using microtrenching with minimal impact. Techniques also exist to remove the core of CATV hardline coax and use the jacket as a fiber duct and use robots to install cables in sewers. Fiber optic companies can be quite inventive.

    Most cities have the majority of cables underground, but many also have aerial cables in alleys. If possible, running FTTH cables in alleys behind buildings and using aerial drop closures will greatly reduce the cost of building an urban FTTH network.

    But before deciding how to install more cables, inventory what exists already. Many cities have fiber optic cable plants installed for city communications, security, traffic systems, citywide WiFi, etc. and may have spare fibers. If no spare fibers exist, it may be possible to use wavelength division multiplexing to get more links. Likewise, other service providers including electrical utilities may have fiber or spare conduits that can be used, and their interest may be higher if they can benefit from the new network.

    Another problem in cities is finding space for fiber hubs where drop cables connect to the distribution cables. They can take up lots of space and be a problem in cities where sidewalk space is at a premium and underground utilities crowd the areas under streets and sidewalks. Putting hubs inside buildings may be much easier that doing major construction outdoors.

FTTH In Multi-Dwelling Units (MDUs)
  Multi-dwelling units (MDUs in some suppliers jargon) are sometimes handled like FTTC, where fiber is brought into the building and individual units are connected over copper cables, either twisted pair from phones or computer networks or coax from CATV or satellite. A standard for Ethernet over CATV Coax (MOCA) is often used to make this connection if the telephone wires are inadequate, but be careful as those cables may not be owned by the building owner but the service provider.

MDU


But MDUs are ideal for FTTH (that is to each unit in the building) since there are many users in a very small space and fiber lengths are short. Besides using less fiber, MDUs generally require less time per drop to install. One issue is where to place PON splitters. If it is a small building, the splitter(s) can be installed at the entry facility and individual cables run to each unit. In larger buildings, splitters can be cascaded and a splitter placed on each floor (if space permits) and short cables run to each unit.

MDU    MDU

    Each building should have some space for the fiber to enter the building, have a rack or box for splitters and connecting to cables to run to each user. Since the PON network is passive, it is not necessary to have power at this location, just some space and room to work on the hardware connecting or moving users.

    A major problem in older buildings has been finding places to run cables to each subscriber, but new types of bend-insensitive fiber and the special small drop cables shown above make it easy to route fibers along walls or place in stick-on raceways on the walls. Here is an example from Corning on how bend-insensitive fiber can be treated without problems, but we offer a caution regarding stapling these fibers - it could be a long-term problem and should be avoided in our opinion.

Bend-insensitive fiber installed in older building (L - Corning) and hardware to stick cable on the wall (R-3M).
bend-insensitive fiber  cable

    Cables installed in buildings should be done neatly. Residents and owners are likely to complain if the cabling is done badly.

Suburban FTTH Networks
    Suburban networks are less dense and installing new cables can be much easier. Some areas have aerial infrastructure which makes installation much easier, since aerial installation is always easier and less expensive and special FTTH closures can allow placing fiber hubs with splitters on poles or suspended from messenger wires. Aerial drops are easier to individual homes or buildings also.  If the cables must be installed underground, which is becoming more common, and conduit space is not available, microtrenching along the curb can simplify the installation. Handholes will need to be located where splitters and drop closures are located.

    Underground drop cables to each home can be a problem since the cable or ducts needs to go from a curbside handhole through the customer's lawn. Running the cables alongside the driveway alleviates most of the problem in many drops. If the drop cable is buried in the lawn, there can be a problem in the future with the owner digging up the cable because they forgot where it was located or a landscaper or installer of invisible dog fences starts digging. As close to the driveway as possible is safer. Directional boring is also possible but can be extremely expensive and has the danger of hitting current utilities and causing damage. Not all - probably few - owners know where their underground utilities are located and using locating equipment is time consuming and expensive. Gas lines are especially dangerous and can cause fires and explosions.

    From the outdoor demarcation box, a fiber needs to be run to a location inside the home to the location of the FTTH ONT. In any indoor installation, it is important that the work be done neatly. A survey of the home to locate where other cables (telephone and CATV or satellite) enter the building and are run indoors can help locate the easiest path for the FTTH fiber cable. As with MDUs, the resident/owner will expect the cables to be installed in a neat and workmanlike manner.

Rural FTTH
    Rural FTTH is going to be more expensive no matter what you do. Service providers have used wireless drops to avoid running long fibers to each subscriber, but the limited bandwidth, cost of the equipment on a pole and at the subscriber (not to mention updates) and the lifetime of powering it may prove to be no bargain compared to running a fiber optic drop cable to the subscriber. Most rural networks are aerial which makes the cost much lower than underground. If the utility poles already have low voltage cables, generally aging telephone wires, the FTTH fiber distribution cable can probably be lashed to the same messenger, by far the least expensive way to install fiber.

    The big problem with rural FTTH is distance. That means longer cables and more cable and installation costs. It also means that many networks will exceed the length maximum of GPON while having fewer subscribers than the number allowed by splitting. The solution in many cases may be using the remote OLT architecture shown above. Cables can be run alongside rural roads and the remote OLTs installed in areas where there are multiple users within the reach of the OLT.

    Electrical utilities and coops have rights of way and transmission lines into rural areas that are ideal for FTTH. Many utilities already have fibers installed, often in optical power ground wire, but sometimes have only a few fibers available. WDM (wavelength division multiplexing can expand the fibers capacity if permitted. When you already have towers or poles, installing fiber is easy with several options. Cable can be lashed to messengers even overlashing to current fiber or copper cables. ADSS (all-dielectric self-supporting) fiber optic cable can be installed on poles or towers without a messenger for long spans. There are even methods that use lightweight cables that can be wrapped around current-carrying conductors.

    Rural telephone companies also have rights of way and cable infrastructure. Many already run fiber backbones. For them, the biggest obstacle is usually financing and fortunately there are programs to provide grants and loans for rural broadband.

    Cable cost is higher for the longer distances, but fiber optic cable is very inexpensive, especially when compared to installation cost. The cost of fiber itself is only part of the cable cost; the materials used in the cable predominate for cables with fewer than 24 fibers, so buying or installing cables with fewer than 24 fibers is generally not cost effective. And installing more fibers means that spare fibers can be leased to other carriers - municipal/county/state agencies, telecom companies, wireless service providers, electrical utilities, etc. to defray the cost.


Additional Reading on Rural FTTH
The August 2021 issue of the FOA Newsletter compares rural broadband today with rural electrification almost a century ago. The situations are quite similar and the solutions, including assisting rural electrical or telco coops, are  quite the same.
rural netowrks
From the 1940 USDA yearbook article on rural electrification.




Designing The FTTH Central Office or Head End

    Whether you call it a central office or head end depends on whether your background is telco or CATV. IT types might call it the equipment room or data center. But the location of the electronics for a FTTH network is another design decision that requires careful consideration and planning. The location should generally be as central as possible to simplify and perhaps minimize cable lengths. Space is not a big problem as FTTH PON OLTs are not large because each OLT port serves as many as 32 or 64 users. But the design must accommodate cables and electronics and allow for future expansion.

FTTH PON head end 
FTTH PON OLT head end for ~5,000 subscribers

     The head end is also an entrance facility, with incoming fiber optic cables from the outside Internet connection and outgoing cables from the OLT. Sufficient patch panel space is required for both incoming and outgoing cables. Hardware needed includes cable trays and management as well as rack space for the patch panels. There will have to be rack or wall space for the interface to the Internet service provider. This is essentially a router with incoming signals at high speeds. The router connects to the OLT to handle the Internet connections.

     The OLT connects the Internet to the users by converting signals to PON protocols and connecting users. The OLT does lots more also, including managing users and encrypting signals for subscriber privacy. The OLT requires a trained operator, at least part time, to manage subscriber connections and other regular service, so plan on having an operator attend training by the equipment provider.

   Since the subscribers require 24/7/365 operation, the entire electronics package needs conditioned power and an uninterruptible power supply (UPS) that can keep it going for at least 8 hours in a power outage. Many FTTH systems also provide – or at least recommend – a UPS at the subscriber’s site to also provide nonstop operation.


Before you Start, Things To Remember

Uniqueness:  Like most fiber optic networks, every FTTx installation is unique. It must be designed for the location it is to serve and choices on components and installation methods should be optimized for the system. Construction and installation methods may include every type of OSP installation. Suppliers familiar with FTTx can advise customers on what others  have done to make installations simpler, easier and less expensive. Most systems prefer to use as many factory-made components as possible as they are generally less expensive than doing the same work in the field. New installation methods should be considered as well to reduce costs.

Consultants:   Be wary of consultants. Consultants can be extremely valuable in designing a FTTH system, as long as they have relevant experience, are up to date on new components and techniques and are highly recommended by previous clients. Unfortunately we have seen problems with consultants, including over-designed networks with costs much higher than necessary, installation practices recommended that were unnecessary or ignore newer technology, systems designed around components that were higher performance (and price) than necessary, and in one case a consultant took the clients payment, went away for a year and came back with an admission that they could not design the network (but they kept the consulting fees.)

Contractors: As with any fiber optic project, the quality of the installation depends on the quality of the installer. Look for contractors with knowledge, experience and references. And preferably relevant certifications like the FOA CFOT. Be especially wary of subcontractors. Any subcontractors should have equal qualifications and be approved by the network owner. We have seen landscape contractors with no fiber training used as subcontractors for cable plant installation - one cut several cables to buildings that had been installed by a member of the FOA advisory board!

Call Before You Dig! Every day some major fiber optic cable is cut by a contractor. The jurisdiction issuing permits should help you with locating other buried utilities. There is a service that helps you locate underground utilities that may be in your construction path. See the FOA web page on Digging Safely. 

What Fiber Do You Already Have?     Before you design or install a new fiber optic cable plant, inventory the fiber you have already and/or negotiate to lease fiber where others have cables with dark (unused) fibers. Also talk to other organizations who may need communications to see if they want to share costs or lease dark fibers or communications links from you. Cities, counties and states need fiber. Utilities need fiber. Fire and life safety organizations need fiber. Traffic departments need fiber. Cellular companies really need a lot of fiber.

What Other Services Can Share The Fiber?   Consider what other services than FTTH you can carry on your fiber optic cable plant - cellular backhaul, traffic systems, security/surveillance systems, leased fiber, etc. to generate additional revenue. A few years ago a large American city sent out a RFP (request for proposal) for an urban FTTH network. The document dealt strictly with FTTH to connect the city's citizens with fiber and ignored all the other services the city had that already used or needed fiber - city communications, security/video surveillance, intelligent traffic management, public transportation communications, wireless networks(small cells and 5G), utility communications, etc., etc., etc.

Dig Smart -Dig Once:    This same document also covered the difficulty of urban installation - digging up streets already filled with underground utilities, limited space for pedestals, few options for aerial cable and  other issues that are typical problems for urban fiber installation. No mention of "Dig Once" to make future installations easier. Share fibers. Use spare fibers. Use additional wavelengths in current fiber. Consider all the alternatives. Plan ahead - future proof is a myth, but one can make certain decisions that will make the future easier.     If you are considering using FTTH design software, ask to talk to customers who have used it. Determine what you need to know first in order to use it, e.g. GIS data on every utility pole, manhole or handhole, subscriber location, etc. and how much training it takes to become proficient. Will you use your personnel or hire outsiders, and how do you evaluate them.

Cost Savings:   Fiber optic cable and components are not expensive, but labor is. Saving money on components may look good in first analysis, but more savings will come from optimized designs and efficient installation practices. More experienced contractors are more efficient and may save costs by their speed and efficiency.  And design for the future - if you dig a trench for anything, not just fiber but any underground utility, bury a number of fiber ducts for future use, install cables with more fibers than you need - lots more - fiber is cheap, installation is expensive. The program is called "Dig Once."

Take Rates Are Important:   "Take rates" for new FTTH networks vary from low to high, depending on the satisfaction with the current ISP (Internet service provider.) When Google Fiber started in Kansas City, the take rate was high because the current service was bad, but in later cities when the local ISPs knew they were coming and improved their service and/or lowered their prices, the take rate was lower. Competition tends to drive take rates and take rates determine the economics of the system, Know your competition. Offering gigabit services are often the top selling point of FTTH. Every GPON network is a gigabit network, but subscribers can opt for slower speeds at lower costs.

What Makes A Successful Fiber Optic Project?

    People call FOA for advice all the time. Most of the calls deal with technical questions about products, installation and testing. But in one call; a manager who was starting to plan a fiber optic project wanted advice on how to proceed. It was a long call! His basic question was “What does it take to have a successful fiber optic project?” We responded with 4 words: financing, commitment, expertise and patience. (This section is repeated from the introductory section on FTTH because it's important for the designer and managers of a FTTH project.)

Financing:     The story goes that someone asked Neil Armstrong what he was thinking about while sitting on top of the rocket ready to launch Apollo 11 to the moon. “Every part was made by the lowest bidder,” was supposedly his reply. (The same quote has been attributed to most early astronauts!)

    Fiber optics are not necessarily expensive; in fact, fiber has been used so widely because it is the least expensive communications medium in virtually all projects. But fiber optic projects may require a lot of construction which makes the project expensive. Like all other projects, it never pays to cut corners. Planning and running the project properly is what saves money, trying to cheapen the project. Not all jobs should go to the lowest bidder, unless they meet all the criteria for a qualified bidder. Likewise, one needs to ensure that when a project starts, there are funds available to complete the job properly, including some extra for unplanned changes or modifications.

Commitment:    Just like having sufficient finances to compete the project, one needs a commitment to finish the job once it is started. Changes of management or changes in governments often lead to confusion or even modifying a project in midstream. There is nothing wrong with making changes based on what learns as the project progresses; it may even involve greater efficiency or cost savings, but arbitrary changes may jeopardize the project's timetable, completion or even its usefulness.

    If the project is under the auspices of a government entity, changes in administration or management that causes changes in a project will invariably make it more expensive and may jeopardize the success of the entire project. Ideally, the personnel who propose, design and plan the network should see it to completion.

Expertise:     Fiber requires expertise and experience. It's obvious the installers need to know what they are doing, but in reality, so must the managers who work for the organization that is contracting for the work. There are many instances of projects where the managers signed off on the project when it was incomplete or improperly installed. The only way to properly manage a project is to understand every aspect of it well enough to know if it is being done properly and when it is actually complete.

    Planners, designers, contractors and installers should all be trained and certified as well as being experienced with good references. That holds doubly so for consultants. In many places, to be a consultant or cabling contractor means little other than registering as a business and advertising your services. Some of the problems we've seen with outside services, include consultants who took contracts, spent time on a project, then told the customer they could not help them with the project, but kept the money.

    We have seen contractors doing shoddy installations, ruining expensive fiber optic cable during pulling and leaving jobs half done but getting paid because the customer knew no better. One of the biggest problems is subcontractors. A contractor with good credentials gets the job but subcontracts some of the work to a contractor who will do the work at a lower price, but does not have the training or experience (or motivation) to do it right. In your contract with an installer, we recommend a clause giving the project manager responsibility for evaluating and approving all subcontractors.

    The manager must know better to prevent problems. FOA also has pages on what the manager needs to know.

Patience:     From concept to acceptance, a typical OSP fiber project can take 2-5 years and a premises project 1-2 years. It depends on the size of the project, the time to properly design it, create project paperwork, get permits, buy components, hire contractors and properly install it.  Proper workmanship takes time and is not easily rushed. Saving time generally means cutting corners and that is often the cause of the problems encountered. Take your time, plan, design, select, install, test and document your network properly.

    And by the way, "future proofing" is a myth! Who would have known in 1990 how ubiquitous the Internet would be today? How reliant we could be on smartphones other mobile devices? How many workers would be working remotely or using videoconferencing for meetings? Technology moves too fast and is too disruptive for anyone to make reliable predictions. The IBMer who developed MRP - the original company organizational software - used to tell everyone, "A forecast is wrong from the moment it is made." Plan for the future, but assume you will upgrade, change directions, etc. driven by new tech and changes in the world around us.


Technical Information on FTTX  From The FOA Online Guide
FTTH Introduction  
FTTH Architectures
FTTH in MDUs (Multiple Dwelling Units)  
FTTH PON Standards, Specifications and Protocols  
FTTH Design    
FTTH Installation 
FTTH Customer Premises Installation  
FTTH Network Testing  
FTTH Case Studies: Do-It-Yourself FTTH  
FTTH Project Management


The Fiber Optic Association Fiber To The Home Handbook: For Planners, Managers, Designers, Installers And Operators Of FTTH - Fiber To The Home - Networks
FOA FTTH Handbook
The Fiber Optic Association Fiber To The Home Handbook
Available in paperback or as an eBook on the Amazon Kindle  Available direct from Amazon.com, local booksellers and other distributors.

Training & Certification
Fiber U Online FTTx Self Study Program (free)

FOA Certification Overview
FOA FTTx Certification Requirements
FOA-Approved Training Programs


 Table of Contents: The FOA Reference Guide To Fiber Optics





 


(C)2021, The Fiber Optic Association, Inc.