Many homes today likely have multiple TVs and PCs, as well as traditional phones, cell phones, numerous portable audio devices such as MP3 players and an insatiable appetite for connectivity. Most homes have CATV, and many are soon going to have an option for Internet protocol TV (IPTV) or digital TV streamed over the Internet (if they have not already discovered YouTube.com or similar sites). Home theaters are becoming popular in big homes. Almost 10 million homes use Voice over Internet Protocol (VoIP) phone service. Security systems may include intrusion alarms and video monitoring, and they probably connect to a monitoring service. You can also get systems that remotely control heating and AC, lighting or other electrical devices.
Use of these devices is limited, however, since much of this new technology requires high speed connections to the outside world over digital subscriber loop (DSL), cable modem, wireless or fiber to the home. In addition, they need connections to each other for sharing broadband, playing games, music, sharing files, etc., as well as mass data storage for ripped or downloaded music and video for shared viewing and listening.
The utilization issue is partly hardware and partly software, and that goes for both inside and outside the home. Development of appropriate technologies is focusing on how to format content (music and video) so that it is compressed enough to be transmitted easily over communications networks while not materially affecting its quality and protecting copyrights. Transmission technologies are being developed to more efficiently distribute content.
Right now, we are going to concentrate on the connection between the home and the outside world, examining the options and solutions for providing high-bandwidth service.
Connecting the home
There are four options available for broadband connections to the home today: cable modem, DSL, wireless and fiber to the premises (FTTP), with more on the horizon. Availability of each option often is localized, depending on geography, economics and politics. The first broadband connection for the home, cable modem service from CATV operators, continues to have the largest number of subscribers. Of the 70 million homes that have cable TV, almost half also have high-speed Internet access over their cable connection. CATV uses a standard cable modem over a hybrid fiber-coax network, which offers reasonable bandwidth and, of course, easy video connections and large selections of programming, which has helped it become the broadband leader.
In response, the phone companies offered first ISDN and then DSL service. ISDN was too little, too late. At 64 kb/s, it was little faster than analog modems of the era but much more expensive. DSL offers speeds over phone wires comparable to cable modems, but connection speed is affected by the length and the quality of the phone wires. For many phone companies, their copper infrastructure was too old and too long to support DSL. Most DSL service is offered in newer suburban areas, leaving older urban or rural areas without service.
Wireless seems too good to be true (and often it is). Wireless allows connections without cabling for those who have the right hardware or subscribe to the right service. Wireless includes Wi-Fi, what most users have available in their laptop, Internet over cell phones, satellite, WiMax, Bluetooth, Zigbee and more.
Wi-Fi (IEEE 802.11) is the most popular, available in coffee shops and from municipal networks in many cities. At the current time, the standards for Wi-Fi are at the “n” revision, as the manufacturers keep rolling out new technologies to make it faster. Since not all Wi-Fi versions are compatible with earlier versions, using the latest, fastest version requires new hardware purchases. Wi-Fi is very limited in distance, perfect for coffee shop or inside a small home, but municipal networks require antennas, called access points, spaced closely around city streets. Security is a problem with Wi-Fi; unless properly set up, anyone can access any Wi-Fi network. And finally, limited bandwidth means limited download speeds, number of users or both.
Most of the other options are small players or works in progress. Cell phone networks offer Internet connections also, but the limitations of these voice networks makes access very slow, practically limiting them to e-mail use. They also tend to be expensive. Satellite connections offer Internet along with video, but mostly require a phone line for uplinks, limiting speed. WiMax is a long-distance wireless network still under development for municipal and suburban connections, while broadband over power lines has been around a long time but appears to have both technical and economic issues.
That leaves FTTP. Since the phone companies began deploying fiber more than 20 years ago, they have completely rebuilt their long-distance and municipal networks using fiber. However, that covers only about 20 percent of their network distance. The final 80 percent, the connection to the home, remains copper. Fiber to the home is the only current option that is either a stable technology or offers virtually unlimited bandwidth and distance reach for future expansion, so it is the only option for connecting every home that can carry all the proposed services for the foreseeable future.
But, market conditions are changing. Telcos are losing landlines to cell phones and VoIP phones. Old copper lines that will not support DSL also are expensive to maintain. Users want all the new entertainment options becoming available online, and telcos want to provide them. Finally, the economics of FTTP are changing. After the dot-com era went bust, the prices of fiber optic components dropped as much as 70 percent. New architectures for FTTP allow sharing expensive components to reduce the cost of connecting a single subscriber to not much more than copper. The telcos are adopting two fiber architectures, FTTP and fiber to the curb (FTTC).
Besides the telcos, others are seeing the advantages of FTTP, as municipalities and private investors are getting into the market, taking advantage of the declining cost of fiber hardware and the desire of local governments to provide a benefit their constituency wants. With all the activity, it is not surprising that fiber connects to more than 1 million homes, a number expected to double annually for the next few years.
Let’s see how the technology works.
Fiber to the premises architecture
There are several ways to implement FTTP, with different architectures having different applications and advantages/disadvantages:
Home run—A fiber is run from central office (CO) directly to every home. Each connection is a full duplex optical link, making this option generally more expensive from the standpoint of fiber and electronics requirements. It is used in some small systems, such as gated communities, sometimes with two fibers, one for digital services such as Internet and VoIP, the other for analog CATV. Some people refer to this as a P2P or point-to-point network.
Active star—An active star network uses fiber from the CO to a local active node (switch) carrying multiplexed signals to be distributed on another fiber link to every customer. At the active node, (electronic) switching selects each customer and connects to a dedicated optical link to the premises. This may be a more expensive network due to the electronics and local powering required, since the node requires uninterruptible local power to support services like 911, or it may be cheaper for small networks that do not need the size or capability of a PON network. Each system needs to be considered carefully in light of all options.
Passive optical network (PON)—Most FTTP systems are based on PON architectures. The PON uses a passive optical splitter near the subscribers to share a single fiber connecting a group of up to 32 subscribers to the CO. Not only does a PON share fiber, it shares electronics, using one transmitter at the CO split at the coupler to connect all 32 homes, greatly reducing connection costs. Basic PON architectures are widely used because they usually are the least expensive way of implementing FTTP. The coupler used near the subscriber is passive, so no power is required except at the CO and subscriber.
A PON system uses wavelength-division multiplexing (WDM), which sends multiple signals over a single fiber, each using a different wavelength of light, to send multiple services over a single fiber. Usually a PON network sends voice and data downstream on 1,490 nm and video downstream at 1,550 nm. The upstream signal uses inexpensive 1,310 nm lasers at each subscriber location. Upstream data from multiple subscribers is time-division multiplexed, so each subscriber has a time slot to send data back to the system.
Fiber to the curb
An alternative to FTTP is FTTC, which brings fiber to the neighborhood and installs a local switch, usually in or near a current pedestal. The fiber replaces the copper from the pedestal to the CO, using only the short copper run from the pedestal to the customer premises to make the final connection. These short lengths of copper allow higher DSL speeds than a direct CO connection and, therefore, more flexibility in services offered. Telcos are using FTTC in newer subdivisions where the copper cabling is new enough or short enough to support faster DSL services.
A new standard for Ethernet in the first mile (802.3ah) is possible with higher capability than current DSL. Also, if sufficient fibers are installed from the CO to the pedestal at the time of a FTTC upgrade, the system can be converted to a FTTP PON system later by running fiber optic drop cables to each customer.
No broadband connection offers either the current performance of FTTP or the future options for even higher speed upgrades. As a result, FTTP is the focus of many telcos and municipalities. More than 1 million homes were connected on fiber in 2006. This is creating new opportunities for contractors and installers, although job skills are not just traditional fiber skills (see Fiber Optics, February 2007), but include traditional telephone and CATV installation plus PC networking. For those with appropriate skills, training and certification, the opportunity is practically unlimited.
For more information on FTTP, see the FTTP section of The Fiber Optic Association Web site: www.thefoa.org/FTTX/. EC
HAYES is a VDV writer and trainer and the president of The Fiber Optic Association. Find him at www.jimhayes.com.