Wireless Optical Systems
Another entry into the optical technology is a multichannel optical wireless system from [BELL99]. Figure 19 shows a system that operates at 10 Gbit/s using four wavelengths. It can transmit over 2.7 miles of free space. Each wavelength operates at 2.5 Gbit/s. It requires a line-of-sight topology. Other vendors are offering this system, including Nortel Networks.
Figure 19 Wireless optical systems.
The systems uses WDM with custom-built telescopes, and standard optical transmitters and receivers. Light signals are sent from a transmitting telescope to a receiving telescope and are focused onto the core of an optical fiber using coupling optics within the second telescope.
The system is attractive in situations where the deployment of fiber cable is not feasible, for example, across restricted-access terrain, or bodies of water. It can be deployed much more quickly than fiber cable systems. It can also offer a cost-effective solution to line-of-sight channels in conference and convention centers.
In most countries, optical wireless requires no governmental licensing or frequency allocation schemes.