Key Decision Points for FTTH Implementation
Fiber-to-the-home presents great promise along with myriad critical decisions as service providers seek to satisfy an exploding market demand for high speed communications
By Thomas Bludau, Manager, Strategic Planning and Analysis
3M Communication Markets Division
Austin, TX
The copper telephone network spread across the U.S. slowly and inexorably during the early 20th century, with an impact on American culture and the economy that may have equaled the sweeping changes brought by Henry Ford’s horseless carriage. After a number of decades even the most remote areas of the nation were connected to the network, and telephone service gradually became an essential component of daily life, even in the most remote areas.
Today we have become an electronic society, deeply dependent on voice, video and data content for both work and entertainment. Simple twisted pair wiring no longer meets our needs, and even accelerated copper plant services such as DSL cannot satisfy today’s exploding demand for high speed data and video.
At data transfer rates of up to 622 megabits per second, fiber optic technology blows past all other network options, and is clearly the telco pipeline for the future. The eventual predominance of fiber-to-the-home is assured, as providers respond to competitive pressure from cable TV services and seek to supply the ever growing needs of consumer, municipal and business markets for voice, video and data.
Beside its vastly improved bandwidth capacity, fiber optic transmission offers the advantage of reduced maintenance cost and more compact dimensions, which increases conduit and duct capacities. Electrical immunity gives this signal carrying pipeline less vulnerability to environmental challenges, particularly lightning damage, radio frequency interference, voltage surges and corrosion caused by moisture.
The North American fiber-to-the-home (FTTH) snowball is just beginning to form. Only about 1.5 million U.S. residences out of a base of 100 million presently enjoy fiber service. However, key players are fully committed to this evolution and it is likely that the new infrastructure will reach consumers far more quickly than did copper service.
For example, in a December 2003 announcement, Verizon reported that in the first half of 2004 it expected to deploy the new technology in more than 100 central offices across nine states and provide fiber accessible to about 1 million homes by the end of 2004. Their installation numbers for 2005 were expected to double. Verizon services approximately 62 million subscriber lines out of a total of 180 million across the U.S., and reportedly intends to achieve an FTTH penetration of at least 50% within five years. This commitment is having a substantial impact on the national communication infrastructure.
While FTTH implementation is inevitable, the process will not be simple. It presents providers with many variables and alternatives, and careful planning is necessary if companies are to meet today’s needs at the most efficient price and be prepared for future demands. Key decision points are encountered at every step from planning and design to implementation, testing, maintenance and upgrades. Following are some of the details to be considered in the last-mile FTTH installation process.
Customer Premise
Power at the house will be an issue. FTTH requires an electronic box on the exterior of subscriber premises, and this circuitry demands AC power. Cat 5E jack and cable will be needed inside the residence to handle broadband services, and this will require specialized tools and installer skills.
Drop Connectivity
The connection to each residence from the neighborhood terminal in the street or at the back of the lot will require an optical drop cable, which may be an off-the-shelf, pre-terminated cable in one of several standard lengths, an un-terminated length of cable that will need connectors on both ends, or a pigtail lead with pre-installed connector at the subscriber end and an added connector or splice at the terminal side.
Pre-terminated drop cables are tested in the factory and offer the benefit of fast installation with a minimum of tools and craft skills. However, a pre-terminated cable will likely have a slack section that must be coiled, stored and protected at the customer end. An inventory of various lengths of drop cable will be required for field installs.
A drop cable without pre-terminated connectors can be cut to length from a bulk reel of fiber drop cable to eliminate slack, and the cable cost per drop will be less than for pre-terminated lengths. However a skilled fiber optic technician with tools will have to terminate and test the drop during installation. Pigtail drops, used for fusion splicing at the terminal, fall between pre-terminated and un-terminated drop segments in terms of cable cost and labor requirements.
In the case of buried plant, a pre-terminated drop cable connector will need to be protected from the dirt as it is pushed into the pedestal from below. Connectors must be kept absolutely clean and free of contamination because even a tiny speck of dirt will foil the system.
Neighborhood Terminal Connectivity
Drop and feeder cables can be connected in the neighborhood distribution terminal by means of splice connectors or by fusion splicing. The former method requires connectors and labor but can be disconnected for bi-directional testing at the terminal. Fusion splicing is more dependable because it is effectively protected from dust and contamination and also reduces the potential for attenuation and reflectivity issues.
The terminal connection decision will impact the way the network is to be tested. Fusion splicing at the terminal limits testing to the fiber distribution hub and the subscriber premise. Dependable fusion splicing requires an experienced operator and well-calibrated, spotless fusion splicing equipment.
Neighborhood Terminal Selection
Local practice and neighborhood standards will determine whether a provider uses above-ground terminals or flush-grade distribution terminals to make local connections. Flush grade terminals are compact, low profile, and fit the standards of many newer municipalities. However, they require digging, offer limited work space and may be subject to infiltration by pests, overgrowth, flooding, snow cover and winter freezing. Above-ground pedestals make it easier to maintain, test and upgrade service but are unsightly, vulnerable to dust, vehicle damage or vandalism, and can also present insect problems.
In the case of above-ground pedestals, units are available that isolate the splicing area from the connector section, restricting unskilled crew access to the connector side for handling drop cables only. Installation and maintenance people have exclusive access to splice and test facilities in the other half of the cabinet.
Cable Selection
Users may opt for all-dielectric fiber distribution cable, which has no metal component and is thus isolated from damage caused by corrosion and lightning surges. However, this cable is difficult to trace and requires the use of either an adjacent tracer wire or buried markers along the route. In locations with high underground moisture content such as Florida and other regions of the south, tracer wires corrode quickly and, therefore, have reduced practicality.
The newest buried marker technology incorporates active circuitry in markers that not only pinpoints the underground location of a buried component or cable path also reveals critical details such as the owning utility, placement date, the exact nature of the buried element and its precise depth. This marker information can be recovered without exploratory digging.
Armor sheathed optical cables have greater physical strength and resistance to damage than all-dielectric products but require ground bonds and are vulnerable to the same challenges as traditional copper cables.
A second cable selection category is the choice between ribbon versus loose buffer tube products. Loose tube cables are composed of multiple fibers in a small plastic tube with a central strength member to form a small, high-fiber-count cable. This cable can be gel or powder filled for water production and is suited to outside plant including aerial, conduit and buried applications. Ribbon cable provides the highest packing density because fibers are laid in rows that can be stacked in parallel. It is also filled for water protection. There are key differences in splicing methodology and handling between these two cable types. Fiber optic distribution cables are vulnerable to the same accidental damage that threatens copper cables. However, once a break is located, the damage can usually be repaired much more quickly.
Cable Placement
New FTTH fiber distribution cables may be mounted on poles, direct buried, or placed in existing conduit. Aerial placement is potentially faster and simpler, but entails pole attachment fees. Conduit placement is also relatively easy compared to direct buried but is dependent on existing capacity in the serving area. Buried plant trenching is generally objectionable in developed neighborhoods, and direct boring may be required for distribution cables.
Cable Capacity
Yet another decision has to do with service capacity. Should the FTTH provider invest in spare capacity in anticipation of future requirements or install only what is required for the immediate future? Obviously, the decision will depend on the maturity of the service area and its potential for future growth. With careful planning, long-term cost can be controlled, but each decision must be tempered by the financial realities of the moment.
Training and Implementation
The switch to FTTH generally begins with conceptual training on fiber network and layout architecture and basic fiber plant characteristics including concepts such as single and multimode cables, insertion losses, splicing options and tools.
Once craft and maintenance employees are familiar with fiber technology, they will require secondary instruction on the specific products to be used, covering installation, maintenance and trouble-shooting details. Training support is commonly available from industry suppliers on request. The switch to fiber optic technology requires a shift in attitude and general assent to deployment and program timing. Resistance to fiber implementation at any organizational level will compromise results.
First Steps
Those providers who are in the beginning or early phase of FTTH implementation can take advantage of ample industry support for the process. Organizations such as the Fiber-to- Home-Council, the First Service Access Network, the International Telecommunications Union (ITU) and the IEEE have developed cooperative standards for every critical aspect of fiber optic technology to guide manufacturers and users and ensure materials compatibility and predictable performance.
In past years it was feasible to increase network capacity and meet service growth requirements by expanding the copper network. As the pricing of fiber and associated electronics drops and the demand for greatly expanded bandwidth rises, the cost/performance balance has shifted in favor of fiber optics. Additionally, the technological advantages of fiber (immense information capacity and greater resistance to electrical interference and lightning damage) give it the potential to deliver FTTH service that is exponentially superior to copper.
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Author:
Thomas Bludau is Manager of Strategic Planning and Analysis for the 3M Communication Markets Division in Austin, Texas.
3M develops and supports a range of fiber optic network products including cable assemblies, connectors, couplings, termination kits, splicing systems, closures, splice trays, test systems, fiber optic accessories and underground marking and locating systems. These products meet industry standards, and are marketed and used internationally.
3M Communication Markets Division
3M Telecommunications
6801 River Place Blvd.
Austin, TX 78726-9000
800/426 8688
Fax 800/626 0329
www.3MTelecommunications.com
Photos courtesy of 3M
(Fiber optic product application photos showing FTTH installation activities using 3M connectors, cables, terminals and tools. Captions to include 3M trade names.)
