IntroductionAmid
pervasive talk about promises of information economy, it’s easy to overlook logistical challenges of delivering necessary infrastructure to ensure everyone who wants connectivity is connected—regardless of where they live. Projected growth in customer demand for bandwidth will go wanting without connectivity, and real challenge for fully realized networks is to create connections despite very real physical and economic obstacles presented by today’s modern cities. The rewards for providing these connections are likelihood of recouping previous investments in fiber-optics network core/backbone—and establishing customer reliance on high-bandwidth networks for continued economic growth.
At one point, many telecommunications industry leaders and technology observers dreamed of all-fiber networks. But this vision is impractical for several reasons. The process of laying fiber in cities is time-consuming and often prohibitively expensive. Ongoing preservation and restoration of fiber-optic systems in event of accidental disruptions or natural disasters is also time-consuming and technically challenging, as service providers must address concerns of bandwidth dependent customers frustrated with every hour of lost network access.
That having been said, all-optical fiber-optic networks—with their high-bandwidth capacities—are promising. Still, a world complete with fiber connections for all is decades from reality.
Deciding how best to complete high-bandwidth connections across networks is one of great quandaries of information age, and choosing which technologies to deploy to complete network connections will depend on costs and reliability(1) A combination of high-capacity access technologies provides most cost efficient and reliable solutions for addressing both primary connections and backhaul. For all-optical networks, fiber optics and optical wireless solutions are only two technology choices.
(1) Source: Free Space Optics, Merrill Lynch Global Securities and Economics Group, 15 May 2001
Parallel Histories
It may seem to telecommunications carriers and industry analysts that FSO technology only recently appeared, like a beam of light, to optical communications landscape. But FSO is only new in one respect: as a market proven technology for optical wireless solutions that provide customer connectivity in private and public networks spanning more than 60 countries.
FSO technology itself is older than fiber optics. Technically, optical communications includes all forms of communications using light, including mirror signals and lighthouses, offering a rich and storied history.
The electrically powered optical technologies referred to by term “optical” or “electro-optical” began with introduction of laser in 1960, which enabled transmission of digital information as pulses of light.
FREE-SPACE OPTICS
Recent developments in FSO technology target telecommunications improvements for Metropolitan Area Networks (MANs), but technology has its roots in government applications dating back to World War I when military units and covert agencies needed secure communication systems that did not require cable and could withstand intentional interference, also known as “radio jamming”. Portability of these early FSO devices was a hallmark and made them particularly valuable to military personnel who needed secure communications equipment that was simple to set up, transmit information and move from location to location. Additional optical communications developments occurred during World War II, and post-war economic restructuring led to further telecommunications technology progress. While electronics innovations such as transistor and integrated circuits enabled post-war telecommunications progress, laser’s launching of electro-optical communication fueled research and development of advanced optical communications using only medium for laser transmission available then to military and aerospace industry physicists: atmosphere, or “free space,” hence term free-space optics. Research and application of free-space optics continues to thrive in aerospace industry to this day for applications beyond commercial and private telecommunications networks. Today’s commercially deployed optical wireless solutions are result of a culmination of FSO technology advancements.
FIBER OPTICS
After 1970, introduction of fiber-optic cable as optical transmitter—along with establishment of digital technology—combined to usher in a worldwide telecommunications revolution. Key among fiber’s attributes is its immunity to electrical interference (no electricity is run through fibers, so fiber signals do not interfere with each other); therefore, fiber can be run in areas without regard to interference from electrical equipment. Other benefits of fiber are:
• Security. It is resistant to taps and doesn’t emit electromagnetic signals.
• Compact size. Less duct space is required for these hair-strand sized fibers.
• High-bandwidth capabilities and low attenuation. Less fading or weakening of signals occur over long distances, which means fewer amplifiers are needed to boost optical signals.
Given these advantages, fiber-optic cable held promise of revolutionizing telecommunications sector, which was eager to build initial fiber networks.2 The first practical fiber systems were deployed by telephone industry in 1977 and consisted of multimode fiber. Single-mode fiber, a more recent development, was first installed by MCI in a long-haul network system that went into service in 1983.3 The result of fiber-optic cable deployment is an extensive network of fiber crisscrossing land. During 1990s, telecommunications network capacities grew nearly 10 times as much as traffic itself, with most of bandwidth concentrated in dark fibers along network backbone often inaccessible to end-user.5 The massive investment to put optical capacity in long-haul telecommunications network backbone looks relatively simple compared with today’s metropolitan network challenges.
Beginning in 2000, carriers intensified their focus to building fiber-optic cable connections between United States’ 25 largest metropolitan areas to nation’s long haul backbone networks. This network gap is often called “last mile,” where only 7 percent to 10 percent of end-users have access to fiber. “Routes in cities typically run to incumbent telephone company central offices and carrier hotels, which often are clustered together in same areas, frequently near AT&T’s switches.
From there, they have runs to customers, data centers, Internet service providers and application service providers.”5 While this network configuration sounds relatively simple, logistics of laying fiber connections in metropolitan areas are quite complicated and time-consuming. The expense of construction and right-of-way permits for laying fiber often amounts to 20 percent of cost of building fiber routes for networks. Moreover, convoluted process of obtaining permits can delay projects for 12 months to 16 months or longer. Metropolitan landscapes, with their busy streets, politically powerful neighborhoods, historic districts, and public works bureaucracies make permit process more complex to navigate than those in suburban and rural long-haul network routes.6 Time delays can be created by municipal public works departments whose staff members feel a responsibility to protect public investments in road surfaces, water mains and gas lines, plus quality of life concerns regarding noise, dust and traffic disruption during construction projects to lay fiber.
