TO ALL: Did anyone read my previous post? Any ideas? OK, next "hint" read this post lifted from GBLX thread this morning. JDN
To: X-JOE-O (4000 )
From: Kent Rattey Sunday, Jan 16 2000 6:48AM ET
Reply # of 4001
MPLS
telecoms-mag.com
Free-Space Photonics:Lighting the Way to the Future
Technical Update
James J. Auborn and Stuart J. Waldman
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There?s a communications revolution in progress and service providers are reaping the rewards. Innovative technologies are allowing providers to develop a host of revenue-generating services and opportunities to strengthen customer relationships. A key factor driving this revolution is dense wavelength division multiplexing (DWDM), which delivers the bandwidth necessary to generate the vast array of voice, video and data services that end users expect from their service providers. DWDM is about to go where it has never gone before--directly through the air.
It?s estimated that Internet traffic will double in the next three to four months, with Internet users driving demand for bandwidth to the enterprise, the desktop and the home. In the next 15 to 20 years, 700 million phone lines will be installed. Today, DWDM is one of the most effective ways to accommodate these colossal increases in network traffic. In fact, optical networking is the key to providing the unconstrained bandwidth service providers must have to manage the exponential increase in network traffic.
Using light to transmit huge amounts of information is not just for long distance anymore. Optical networking is rapidly spreading to the local service provider and enterprise markets as technology advances make DWDM systems more cost effective for these short-haul networks. According to Pioneer Consulting, the metro DWDM market is expected to grow from about $200 million in 1998 to $1 billion by 2003 and will represent 23 percent of the projected $4.4 billion DWDM market.
When multigigabit signals come off a long-haul route or an urban ring, they often lose speed as they reach equipment on the edge of the network--whether it?s an enterprise server or cramped loop facility that slows down the bit stream. But with recent metro DWDM systems offering ring-based and point-to-point solutions, optical signals soon will race freely all the way to the business desktop--and eventually to people?s homes.
Extending Fiber?s Reach
Despite the options now available with conventional DWDM systems, there are many carriers and enterprise customers facing congested urban streets and conduits that severely limit fiber?s reach. To address these types of challenges, beams of light are now being used to transmit information directly through the air. Using breakthrough open-air optical networking technology--also known as free-space optics--high-capacity fiber optic systems are being extended to local networks, bringing increased bandwidth closer to the end user. New free-space DWDM systems will be able to boost the capacity of local data networks by a factor of up to 65 over fixed wireless solutions.
In cases where cost, geography or other constraints make fiber connections impractical (it?s estimated that only 5 percent of office buildings in the United States are equipped with fiber), free-space optics can provide another opportunity for service providers to dramatically increase bandwidth in their local networks. As an extension of fiber?s reach, free-space optics can be the link in a series of networking segments that take a step closer to providing higher bandwidth right to the desktop.
Here?s how the technology works: Each open-air photonics system uses innovative high-power optical amplifiers plus a telescope that transmits multiple wavelengths of light through the atmosphere to another telescope that receives the information. At that point, the receiving telescope connects to a high-sensitivity receiver through an optical fiber and a DWDM demultiplexer. The system is bidirectional, meaning each telescope can simultaneously transmit and receive information.
Open-air photonics systems can be placed on rooftops or in office windows. They are smaller than most satellite or microwave systems and easy to install, making it a quick, easy and cost-effective way to transmit voice, data or video traffic from point to point through the air.
Unlike radio frequencies, the technology requires no spectrum licenses. It is easily upgradeable, and its open interfaces support equipment from a variety of vendors, which helps carriers protect the investment in their embedded infrastructures.
Open-air DWDM systems enable photons carrying data, video and voice communications to travel through space reliably and safely. When engineered to accommodate local weather conditions, these photons can transmit signals error-free. On a clear day, an open-air DWDM system can transmit information 5 km or more. In fact, based on visibility data collected from major cities around the world, these systems should be able to achieve better than 99.9-percent availability at varying distances in most environments.
The expanded nature of state-of-the-art, free-space optics signals makes them safe for unaided vision. In fact, looking into a beam is no more dangerous than looking at a dim light bulb. Additionally, the system will not be affected if a bird, kite or similar size object flies through its path. If a large object strays into the beam?s path for more than a few seconds, the system will stop transmitting until the object is out of the way and then resume transmission immediately. Moreover, airborne photonic signals are extremely secure--making the technology potentially useful for government organizations as well as for the world?s growing e-commerce industry.
Service providers and enterprise customers already are exploring the many potential applications of this new technology. For example, service providers will be able to use this technology to bring fiber optics to areas where laying fiber is impractical, giving them another avenue to provide customers with high-capacity local data networks.
Open-air photonics also can make instant market entry possible for new service providers by helping them avoid the huge capital outlay associated with deploying new fiber-based networks. Other applications may include companies occupying multiple floors of high-rise buildings that might use free-space optics to beam information between floors, saving the cost of running cable through various crawl spaces. These same companies might use the technology to connect buildings separated by a river. Additionally, ships will be able to use this technology to transmit information to the mainland while anchored off shore.
For special events such as an international soccer match or a pay-per-view music festival, a high-capacity data link can be set up between the stadium or arena hosting the event and a studio across town. As the 21st century unfolds, customers? demands for more and more bandwidth will continue to grow, and open-air optics will enable service providers to meet that need--with or without fiber.
James J. Auborn (auborn@lucent.com) is director of communications technology for the government solutions R&D organization of Lucent?s Bell Labs. Stuart J. Waldman (swaldman@lucent.com) is the WaveStar OpticAir OLS market development manager for Lucent Technologies. Global Crossing is scheduled to begin trials of WaveStar OpticAir this fall.
RSNo. 317
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