If You Could Lift Fiber Into the Sky

There's no question fiber is a technological marvel providing the foundation of our modern communications system. It provides the capacity, speed and availability needed for our increasingly bandwidth-hungry digital lives.

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By Chandrasekhar Pusarla

There's no question fiber is a technological marvel providing the foundation of our modern communications system. It provides the capacity, speed and availability needed for our increasingly bandwidth-hungry digital lives. It's used in core networks to carry large amounts of data across continents and across oceans; it connects cell towers to the network to provide 3G / 4G mobile communications; and it provides broadband connections to homes, buildings and businesses, among other uses.

There are times, however, when fiber isn't practical or feasible. The main drawback of fiber is the need to place it in the ground, which can be disruptive and time-consuming. In some cases, obtaining permits or the right-of-way for trenching fiber can be problematic or impossible. As a consequence, there's also a need for wireless communications technologies that can deliver some of fiber's performance for certain situations or applications.

What are the alternatives for those situations where fiber isn't practical?

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Emergence of Wireless Fiber

Microwave and millimeter wave have been the two primary wireless alternatives. Both have significant drawbacks, however, including reduced performance because of interference from weather-and neither deliver the combination of availability, range and bandwidth of fiber. While these technologies have sufficed for specific needs or applications, continued rapid growth of data traffic across global networks is rendering these technologies obsolete. New approaches are needed.

An emerging technology category referred to as wireless fiber combines the benefits of wireless networking technology with fiber-like performance. To be considered true wireless fiber, four requirements must be met:

1. Scalable, multi-gigabit capacity
2. Consistent data rate in all weather conditions
3. Unlimited or long range
4. Carrier-grade availability

These performance requirements are being met by blending technologies together-namely, adaptive optics and millimeter wave-to achieve the desired performance profile. Adaptive optics are lenses that can change shape at high speeds. These lenses help astronomers see farther into space by correcting for atmospheric scintillation.

This same technology can be used to send large amounts of data long distances over a narrow beam of light without loss of image quality. The technology has been successfully demonstrated under contract for the US Department of Defense, enabling aircraft flying at high altitudes to transmit 10-80 Gbps of data error-free over hundreds of miles to air or ground platforms. This technology, however, is also affected by one weather phenomenon-fog. But augmented with a parallel beam of an advanced form of millimeter wave signal carrying the same exact data, tuned with other innovations, and you have a system that will exceed the requirements of wireless fiber. This approach is referred to as Advanced Wavelength Diversity (AWD).

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Wireless Fiber Applications

Wireless fiber is useful for certain applications where fiber isn't a viable option. There are hundreds of thousands of offices in the US, for example, that don't have fiber connectivity for various reasons. Similarly, while the majority of cell sites in the US are connected to the core network with fiber, there are still a large number that aren't or can't be. In such instances, wireless fiber would help alleviate network congestion at those sites caused by the dramatic increase in mobile data use.

Remote site connectivity or temporary connectivity can also benefit from wireless fiber. Running fiber under the sea to an oil and gas platform is an extraordinary undertaking, but wireless fiber can simply be attached to existing structures-no undersea wiring required. Or, there are times when this level of high bandwidth, high availability connectivity is needed quickly and for only a limited time period-such as disaster relief, major events and military operations, to name a few. In these situations, wireless fiber can be installed quickly-even on existing structures-delivering high bandwidth and high availability as long as it is needed, then taken down.

There are also situations where organizations or government entities require redundant, diverse networks for security reasons. In these situations, fiber combined with wireless fiber provides a powerful solution.

Organizations considering adding wireless fiber to their portfolio need to understand some key technologies and innovations, in addition to adaptive optics, radio frequency (RF) and AWD that make wireless fiber work:

• Active Beam Steering (ABS) is one of those technologies. It allows automated steering of the optical and RF beams. It enables real time link alignment and compensates for tower twist and sway caused by conditions such as heavy wind, sun, and ice and snow build up. Real time steering means wireless fiber can be deployed on any type of tower or other structures without the stringent structural stability requirements typical of wireless solutions. This opens up more deployment opportunities and enables the shortest link paths possible-particularly relevant for ultra-low latency applications.

• Point Acquire and Track (PAT) technology is another-it automates link alignment. PAT simplifies installation and alignment with precision accuracy, repeatable results and verified performance, significantly reducing the cost of deployment.

While fiber will remain the workhorse of our communications infrastructure long into the future, there are situations where fiber-like performance is needed but fiber, for one reason or another, won't be an option. In those situations, RF technologies have filled the gap as best they can, but they have had significant drawbacks. In contrast, this new category of wireless fiber solves many of those drawbacks and provides the first true alternative when bandwidth, distance, availability and flexibility are needed.

About the author: Chandrasekhar Pusarla is VP and general manager for Communications at AOptix.

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