Are you holding a fistful of fiber? - Technology Information

Go ahead, make your day with optical wireless.

The need for higher bandwidth is growing to a point where some of today's products can not meet the demand. Two ways this bandwidth issue can be solved are by using fiber-optic cables and optical wireless. Once fiber is installed, however, it is permanent for that location.

With optical wireless, the installation can be completed in two to four hours by one person, and--if the need should arise in a year or two--where a system needs to be relocated, it is simply unbolted and reinstalled at the new location.

All optical wireless communication systems must meet certain conditions and be certified by the U.S. federal government for eye safety before being sold to the public. The designations that identify that a system has met the U.S. federal certifications for safety are CDRH and UL. The designations that identify that a system has met Canadian and European certifications are CSA and CE.

Other advantages, all based on the fact that optical wireless systems have a distance limitation, include:

* usually cost-effective, especially at distances of more than 300-500 feet;

* can transverse physical barriers;

* from purchase order to complete installation, the time spent is much less;

* no license is required;

* do not create nor are they affected by EMI or RFI;

* very high levels of bandwidth; and

* very private or very secure transmission.

Without a doubt, all optical wireless systems are limited in distance. This limitation is based on the ability of light to travel through the air to a distant point, especially in fog.

TRACKING VS. SENSITIVITY

Two important elements to consider in optical systems are, first, "alignment maintenance" or tracking, and second, the sensitivity of the system.

Tracking is necessary to maintain alignment throughout the temperature cycles in a day, and to compensate for building movement or sway. Without tracking, a system could easily move enough to be outside the active area of the beam of light coming to the unit, and communications would be lost.

Some manufacturers try to overcome this problem by opening up the divergence of the beam of light, reducing the system's sensitivity at a given distance. Systems with tracking can maintain alignment without opening up the beam, resulting in concentrated light, which allows for longer distances.

The term used to indicate sensitivity is fade margin, defined by how much interference or signal loss is acceptable before the system is no longer able to communicate. Systems with the highest fade margin usually go longer distances. In systems with tracking, the light coming to each end of the system provides a small amount of light that is received and split off to electronics that measure the increase or decrease of that light.

When a decrease occurs, the electronics automatically begin a series of movements to reposition the system to the most useful area of the beam of light. Both ends are equipped with this technology, allowing for consistent alignment and better fade margin. The signal used to achieve this tracking is independent of the customer's network information, a "protocol independent" connection to the network.

THE SYSTEM AT WORK

A typical installation mounts the system outdoors on any masonry material, overhanging the roof edge, where a clear line of site can be made to the position of the other side of the link. With the tracking built in, the installation is made simple. The connections on the laser system are all weatherproof, and the only task remaining--once installation is finished--is to install a weather shield on each end. Normally, no regular maintenance is required, other than to annually check the optical lenses for dirt and to check the fiber connection.

In one configuration, a number of buildings are in close proximity to each other, like a campus or industrial park. Instead of each building's tenants purchasing his own expensive server and/or switches, all tenants can be supplied access to a high-speed network by way of optical systems from a central source.

This same technique can be used when a company outgrows its facilities and obtains additional space in a building several blocks away. Here again, the cost saving-- which more than pays for the optical system--is in not having to purchase a server and/or switch. Whenever a need to move exists, the optical system can move.

Optical systems have the ability to move a lot of information from point to point. A T-1 line has the ability to handle 24 individual telephone conversations at the same time. Fast Ethernet handles 100 Mbps of network data. It is entirely possible to have 100 Mbps and four T-1s running at the same time on one optical wireless system. All this requires is the necessary peripherals that multiplex the different formats together. If a totally different need exists--for a full teleconferencing capability, for example

--with the proper selection of multiplexers, an optical wireless system can accommodate the required information transfer.

Walter is president of LaserWireless Inc., Lancaster, PA.

www.laserwireless.com

Circle 252 for more information from LaserWireless

COPYRIGHT 2001 Nelson Publishing
COPYRIGHT 2001 Gale Group