Optical Wireless Solutions Based on Free Space Optical (FSO) Technology


Amid the pervasive talk about the promises of the information economy, it’s easy to overlook the logistical challenges of delivering the 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 the real challenge for fully realized networks is to create connections despite the very real physical and economic obstacles presented by today’s modern cities. The rewards for providing these connections are the likelihood of recouping previous investments in the fiber-optics network core/backbone—and establishing customer reliance on high-bandwidth networks for continued economic growth.

At one point,Guest Posting 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 prohibitivelyexpensive. Ongoing preservation and restoration of fiber-optic systems in the event of accidental disruptions or natural disasters is also time-consuming and technically challenging, as service providers must address the 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 the great quandaries of the 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 the most cost efficient and reliable solutions for addressing both primary connections and backhaul. For all-optical networks, fiber optics and optical wireless solutions are the 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 the 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 the term “optical” or “electro-optical” began with the introduction of the laser in 1960, which enabled the transmission of digital informationas pulses of light.


Recent developments in FSO technology target telecommunications improvements for Metropolitan Area Networks (MANs), but the technology has its roots in government applications dating backto 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 electronicsinnovations such as the transistor and integrated circuits enabled post-war telecommunications progress, the laser’s launching of electro-optical communication fueled research and development of advanced optical communications using the only medium for laser transmission availablethen to military and aerospace industry physicists: the atmosphere, or “free space,” hence the term free-space optics. Research and application of free-space optics continues to thrive in the aerospace industry to this day for applications beyond commercial and private telecommunications networks. Today’s commercially deployed optical wireless solutions are the result of a culmination of FSO technology advancements.


After 1970, the introduction of the fiber-optic cable as optical transmitter—along with the 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 the 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 the optical signals.
Given these advantages, fiber-optic cable held the promise of revolutionizing the telecommunicationssector, which was eager to build the initial fiber networks.2 The first practical fiber systems were deployed by the 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 the land. During the 1990s, the telecommunications network capacities grew nearly 10 times as much as the traffic itself, with most of the bandwidth concentrated in darkfibers along the network backbone often inaccessible to the end-user.5 The massive investment to put optical capacity in the 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 the United States’ 25 largest metropolitan areas to the nation’s long haul backbone networks. This network gap is often called the “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 the same areas, frequently near AT&T’s switches.

From there, they have runs to customers, data centers, Internet service providers and applicationservice providers.”5 While this network configuration sounds relatively simple, the logistics oflaying 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 the cost of building fiber routes for networks. Moreover, the convoluted processof 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 the permit process more complex to navigate than those insuburban 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 andtraffic disruption during construction projects to lay fiber.

Source 2: Just the Facts, Corning Incorporated, 1995Sorce 3: The Essential Guide to Telecommunications, Annabel Zodd, 2002Source 4 What Ever Happened to Broadband?, Erick Schonfeld, Business 2.0, October 2002Source 5: The Essential Guide to Telecommunications, Annabel Zodd, 2002Source 6: Can They Dig It?, Kate Gerwig, Teledotcom, March 2001

Today’s Emerging Synergistic OpticalWireless/Fiber Landscape

From rural farms to suburban hospital campuses to big city high-rise offices, high-speed network connections must be made available everywhere people live and work, if the information age is to reach full realization. Although rural, suburban and metropolitan connections each have their own sets of challenges; the metropolitan market is presenting the greatest difficulty for true highbandwidth connectivity. Complete, efficient, and profitable networks to meet emerging customer needs cannot exist without the creation of metro area connectivity using diverse medium and resources. While some may consider an all-fiber network the ideal connectivity solution, themedium’s high-bandwidth capacity comes at a high price that is not feasible everywhere.A number of compelling factors justify further integration of optical wireless solutions tocomplement fiber deployments to meet the growing connectivity demands. Service providers thathave invested significantly to build network fiber backbones now need communications traffic tofully utilize network upgrades and generate revenues to pay for such investments. Developingmetro optical network deployments (substantial bandwidth upgrades) extends the reach of metropolitan networks to the network edge. This is the same portion of the network whereregulation changes have encouraged telecommunications players to “race” to gain competitive advantage and deliver the best value to customers

EVOLVING INFRASTRUCTURESBecause metropolitan telecommunications network architectures—particularly those in theUnited States and Western Europe—have evolved as a patchwork of technologies, communications data is often slowed by protocols translations to manage and direct high-bandwidthinformation through metro networks. In growing economies such as China, India and Latin America, the growth in bandwidth demands presents a different challenge, due to relative lackof network infrastructure.

TECHNOLOGICAL ADVANTAGESOptical wireless solutions and fiber are the two optical technologies today that deliver high-speed optical bandwidth to meet market needs. Their integration offers several technological advantages. First, fiber optics and optical wireless solutions share several characteristics. Optical wireless solutions can use the same optical transmission wavelengths as fiber optics (850nm or 1550 nm).Second, optical wireless solutions and fiber can utilize the same system components such as lasers, receivers and amplifiers. Third, both fiber and optical wireless can transmit digital information using a range of protocols. Fourth—and critically important in meeting technologicaldemands—optical wireless delivers the bandwidth (up to 2.5Gbps) necessary to complement fiber networks.

STRONG BUSINESS MODELThe business advantages of optical wireless for network extensions include deployments at an average of one-fifth the cost of fiber-optic cable and in one-tenth the time. Optical wireless systems are a flexible investment that can be re-deployed to meet changing customer needs. Optical wireless and fiber also integrate seamlessly, and because optical wireless equipment is simple and easily installed, the technology can bridge optical network gaps effectively with reduced CAPEX risk. Installing optical wireless solutions to complement fiber enables serviceproviders to secure customers in a specific location first before installing the system to bridge to the fiber network, providing optimal alignment between capital expenditure and income.

Complementary FutureThe future of the information economy depends on profitability. Despite large debt loads and low cash flow, service providers cannot afford to forego investments necessary to grow their customer base—and that requires extending their networks to complete “last mile” connectivity.

Now that they are being more discriminating about the way they spend their money, service provider managers are demanding high-bandwidth technologies that will also lower OPEX. Flexible networks that can adjust to changing customer concentrations and metro environments are needed. Combining optical wireless and fiber to create optical networks offers the best solution to these problems. The reward for successfully combining these two optical technologies is attainable and economically viable.

Complementary deployment of optical wireless and fiber serves the needs of a variety of carrier types in metropolitan networks. Market growth for both last mile access and networkextension applications is predicted to experience a 219% growth rate in 2001 over 2000 and has the potential to extend metro last-mile networks.7Despite questions about economic growth, there is no reason to expect that customer demand for bandwidth will slow in the near future, and although carrier capital spending may have slowed to a crawl, prospects for growth remain strong.8 SG Cowen projects carrier spending on newequipment, after two years of decline, should hit $102 billion by 2003. Metro optical networks are expected to see $57.3 billion invested by 2005.

ConclusionThe most exciting possibilities for the future of the information economy will only be practical and profitable when network connectivity is expanded to reach a broad customer base. Telephone lines have this connectivity, but they don’t offer the capacity to enable true high-bandwidthcommunications. The network fiber backbone or “core” can carry the bandwidth, but has yet to be connected to the majority of potential users.A new paradigm for building optical networks offers an alternative to expensive and timeconsuming fiber-only metro networks. By combining optical wireless and fiber, networks can bebuilt quickly and provide affordable and scalable connections to end-users, who are expected to continue increasing demand for bandwidth.

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