If you've confused some of the recent TV commercials from Verizon, AT&T and the cable companies with ads from Metamucil, that's to be understood. Both, after all, extol the virtues of fiber. But while the former claims it can help you lead a longer life, the latter promises to make it a happier one. That's because as consumers clamor for an ever-vaster assortment of high-def programs and new interactive services, fiber-optic systems, which send data as pulses of light, have the capacity to deliver it.

Given the recent ads, fiber-optic networks have become talking points for many TV service providers. The reality is that while many cable companies and AT&T employ fiber in parts of their distribution network, Verizon is actually the only one running fiber all the way from the head end to the customers home in all its installations (AT&T's U-verse does run fiber all the way in some new-home construction).

Although the emphasis on fiber is new, the technology isn't; fiber-optic cables have been used since the mid-1990s, when cost-effective lasers, capable of sending signals down long lengths of fiber-optic pipes, were developed and deployed in cable systems. But it never really seemed sexy enough to talk about until Verizon launched its FiOS TV and Internet service in 2005, making it the relative new kid on the TV service block. But TV has long been on the company's radar; in fact, Verizon conducted a test-run of a copper-based TV service in Tom's River, New Jersey, back in 1993.

Given its come-from-behind status in the TV service race, it's not surprising that Verizon has been aggressively promoting and rolling out its fiber-optic FiOS services. At times slow going due to the market-by-market franchise approval process, FiOS TV has been helped by several states passing statewide franchising legislation. By the time you're reading this, the company should have close to 1.5 million FiOS TV subscribers, having passed the 1-million subscriber mark back in January and adding about a quarter-million new takers per quarter. By comparison, AT&T had 230,000-plus U-verse subscribers at the end of 2007, and it predicts it'll have 1 million subscribers by the end of 2008. Thanks to existing distribution agreements, both companies also resell satellite-TV services in a number of markets, so each company actually has a greater total number of video users.

Why is everyone so stoked about fiber-optics? Clearly in this world of more HD, capacity is its biggest calling card. High-speed Internet and high-definition video are pushing bandwidth requirements to 20-25 Mbps for each user, and it's anticipated that it could increase to 50-60 Mbps per user by 2010. Although more efficient compression schemes, such as MPEG-4 and VC-1, and new technologies, such as switched digital (which treats all programming like video-on-demand) are helping cable deal with the bandwidth required for more HDTV content, many cable networks are currently strained to capacity, unable to offer more HD without cutting back on other services, such as analog channels. That's why the theoretically nearly limitless bandwidth of fiber-to-the-home (FTTH) networks, such as that employed by Verizon, is so appealing. Although FTTH is much more expensive to deploy than systems that use fiber in only parts of the distribution system, it currently provides about four times more bandwidth of those other systems, with unshared data streams up to 100 megabits per second (Mbps).

"In the last 20 years in data communication, there's been one axiom: the amount of bandwidth people are consuming today will be materially less than what they'll want tomorrow," says Brian Whitton, executive director of technology for Verizon's Access Network Design and Integration Group. And because fiber-optic pipes can carry so much data, he says, when Verizon wants to mine more bandwidth from its network, all they need to do is change the lasers on the end points of that fiber cable. "That's important because of simple economics: Labor will be more expensive tomorrow than it is today, and a laser will be cheaper. When we need to increase the productivity of that fiber, we can simply upgrade the network on both ends without using labor."

Still, the cost of building a completely fiber network can be staggering. For example, Verizon anticipates spending $23 billion on its network through 2010. But because the system is passive — more on that later — there are no active or powered elements between the main office and the customer. Result: Operational costs, including maintenance, are dramatically lower than copper-based systems, which require multiple RF amplifiers along the line. The active elements can not only add noise and distortion to the signal, they're also subject to mechanical failure.

In addition, according to Whitton, many of the elements in Verizon's fiber-optic system are self-diagnostic, enabling the company to proactively monitor the network, thereby boosting reliability. "The devices in our networks have processors in them, and they've been designed from day one to sound an alarm if something goes wrong so the customer isn't impacted," he says. Often, he says, issues can be resolved remotely, without a service technician being called in, whereas "cable companies find out there's a problem when their customers call in and tell them." That type of efficiency can also yield financial benefits: Verizon expects to recoup $5 billion of its investment in lower operating costs through the end of the decade.

There are several other advantages to fiber. For one, unlike electrical signals sent over copper wire, light pulses aren't susceptible to the same kinds of electrical interference or crosstalk between channels, which can impair video quality. There's also less signal loss, particularly when traveling over long distances, and since electricity doesn't pass through the wires, fires are less of a concern. And fiber optic cables are smaller, lighter and more flexible than copper-based cables, making them more efficient to pull and distribute.

To understand why many analysts believe that Verizon's approach of running fiber to the home (FTTH, or FTTP, for fiber-to-the-premises) is a better, longer-term solution than either cable's hybrid fiber coaxial (HFC) or AT&T's fiber-to-the-node (FTTN) systems, it's helpful to first understand how it works.

At the heart of any fiber-optic distribution system is the actual fiber-optic "cable" itself, which consists of a bundle of single optical fiber strands, each barely the size of a human hair. At the center of each of these strands is the core, made of glass silica. A laser, which encodes data as pulses of light, sends the pulses through the fiber-optic cable's core. Surrounding the core is a mirror-like optical material, called the cladding, which reflects the light back into the core. Because the cladding doesn't absorb light, the light pulses are able to travel long distances. Surrounding the cladding is the buffer — sometimes both a primary and secondary buffer — which is a hard plastic coating applied to the core and the cladding for protection against damage and moisture. To give the cable added strength, especially for pulling runs, the buffer is generally surrounded by a sheath of aramid fibers (such as Kevlar). The cable is then finally wrapped in a flame resistant protective jacket, typically made of PVC.

Both transmission lasers and LEDs can be used as the light source, but lasers, which are more powerful, are more commonly employed. To understand how the system works, think of the laser as an extremely powerful flashlight that blinks billions of time each second. When the laser is turned on, the equivalent of a digital "1" is transmitted, and when it's off, a digital "0" is represented. The high level of internal reflectivity of the cladding allows the light to be transmitted down the length of the cable, even through the twists and turns of its run. Sometimes a pumping laser and "doped" fibers — which act to amplify the light — are used in the system to increase the maximum distance the light pulses can travel.

Both Verizon and AT&T employ passive optical networks (PONs), which allow multiple homes to share a single fiber. Rather than running individual fibers for each user (as would be the case in a point-to-point network), a PON uses point-to-multi-point architecture where splitters placed at junctions within the fiber loop divide the signal, so a single optical fiber can serve 32 customers. At the customer's home, the light pulses enter a receiver, called an optical network terminal (ONT), where they're converted back into common electrical signals. Video is typically sent to a Verizon set-top box (or DVR) via standard RG6 coax cable, while Internet connectivity is generally provided via Cat5e (Ethernet) cables and a supplied router. Verizon's set-top boxes have the capability of receiving both RF and IP (Internet Protocol) video.

Unlike Verizon's FTTH network, which runs fiber directly to the customer's home, AT&T's U-verse service is largely "fiber to the node" (FTTN), where programming is delivered via fiber from the head end only to neighborhood nodes — usually within 3,000 feet of customers' homes — then sent the rest of the way using existing copper wiring. Cable's HFC works similarly, but uses coax cable between the neighborhood nodes and homes. Running fiber all the way to the home can provide up to four times the bandwidth of FTTN networks, but there are other advantages to Verizon's FiOS service.

In all fiber-based networks, lasers can produce different wavelengths of light to transmit data. For example, remember the Verizon ad where a precocious kid explains to his dad that Verizon brings fiber-optics on three different frequencies of light ("You got your 1310, your 1490, and your 1550...")? He's right! In the FiOS system, downstream voice and data (such as Internet downloads and interactive services) are sent from the central office's optical line terminal (OLT) using the 1490 nanometer (nm) wavelength, while upstream data sent from the customer travels along the 1310 nm wavelength. The 1550 nm wavelength is reserved for optional overlay services — in FiOS TV's case, video.

That makes Verizon's approach different from AT&T's. In the latter's U-Verse service, everything, including video, is delivered via Internet Protocol. Verizon uses a hybrid approach where broadcast channels are sent as RF (QAM) video, while IP is used to deliver interactive services such as video on demand, the interactive program guide, and the widgets you can create that deliver local news and weather onscreen. As a result, AT&T has to reserve a portion of its IP bandwidth for video, limiting Internet access speeds to 10Mbps. Verizon doesn't, enabling it to offer Internet customers up to 50Mbps speeds. Verizon modulates the RF video onto the 1550 nm wavelength, then combines it with the 1490 IP wavelength (via optical couplers and a process called wave division multiplexing, or WDM), and sends it out through the PON. By using the optical splitters, 32 customers are served by a single fiber. WDM is also used to direct the returning 1310 nm traffic back from the customer's ONT to the head-end OLT.

Both Verizon and AT&T currently use what are called broadband PONs (BPONs), which are capable of 622-Mbps downstream, and 155Mbps upstream, data rates. However, Verizon has already started deploying an even faster network, called GPON (gigabit passive optical network) that offers a fourfold increase — to 2.4 Gbps — in downstream speeds, while upstream speeds jump from 155 Mbps to 1.2Gbps, and eightfold increase in upstream bandwidth back to the network. The latter will likely become important, given the growing amount of user-generated content being uploaded to the Internet. Verizon is already rolling out GPON in parts of California, Maryland, Massachusetts, New Jersey, New York, Rhode Island, Pennsylvania, Virginia, and Texas.

But Verizon is also looking beyond GPON; in its labs, it's testing an even more robust technology called wavelength-division multiplexing networks (WDM-PON), which could give each customer his or her own 1-Gbps (or more) wavelength into the home. However, the company believes that GPON will serve its — and its customers' — needs well into the future. But the extensibility of its network is another Verizon advantage.

Given the greater capacity of Verizon's FTTH network, it's ironic that when it comes to HD content, the company has so far been lagging not only the satellite TV service providers, but many of the capacity constrained cable companies. As this article goes to press, Verizon's offering of about 30 HD channels, and only limited amounts of HD video-on-demand in certain markets, is dwarfed by DirecTV's 90-odd full-time HD channels.

The company blames the content-provider negotiation process for the delay, and promises an upcoming HD deluge: 150 HD channels by the end of 2008, and an ever-growing assortment of HD VOD in all its markets. Verizon also anticipates adding a variety of new interactive features along with more HD. For example, the company envisions sports fans being able to call up scores of other game while local teams are battling, or being able to download a printable recipe during a cooking show. The company already allows viewers to add widgets to their screen that show local weather and traffic information.

For many of us looking at the TV service providers, the game gets really interesting once all of them are able to offer 150 HD channels. Then, the differentiators won't necessarily be who has more, but who has the best: video quality, support, reliability, and customer service.

Here again, Verizon may have the edge. In a recent Consumer Reports survey of their readers who subscribe to cable, satellite and telco-delivered TV service, Verizon was the top-rated provider — and the only company to earn the highest scores possible in every category.