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  • Print publication year: 2016
  • Online publication date: August 2018

Appendix C - Wireless Optics

Summary

The wireless optics holds great potential for fixed wireless communications as well as for other wireless applications. In spite of all other technology developments, wireless optics has promised an economical alternative to last mile connection solution in the wireless domain. The concept of wireless optics was originally developed over few decades ago by the military. An optical wireless technology, also known as free space optics (FSO) technology, provides broadband data communication links between line-of-sight (point-to-point) locations.

Wireless optics (sometimes called fibreless optics) is an optical, wireless, line-of-sight, point-to-point, broadband technology. It basically uses infrared transmission instead of RF in the unlicensed higher frequency spectrum above 300 GHz. FSO signals are transmitted using low-power infrared beams (invisible) through free space, thereby limiting the coverage range. Another constraint on its usage is that the radiated power under any circumstances must not cross the specified limits in order to avoid any visual impairment to the human eye.

Wireless optics transceivers are generally installed in the middle or upper floors, or on an open roof of the building so that a clear line-of-sight transmission path between two stations is available. However, in some applications, these transceivers can be mounted behind a window in an existing office/home building.

In short, we can say that wireless optics is a matured technology based on line-of-sight propagation which uses optical light for transmission of user information such as voice, data, image, or video in open space. It allows optical connectivity without the use of optical fiber cables. Wireless optics system requires a light source such as LED or a LASER at the transmitter end which is capable of emitting a highly-focused light beam. The LASER beams are preferred in wireless optics because of its advantages as offered in optical fiber communications. Obviously, the only difference is the transmission medium – free space (unguided) as compared to optical fiber (guided). We know that the light travels all the way through air only at a much faster speed than through the optical fiber cable. Wireless optics, also referred to as open-air photonics or optical wireless or free-space photonics (FSP), deals with propagation of modulated optical beams in visible infrared (IR) range over air to provide broadband wireless communications.