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The interception of optical wireless systems operating with narrow beams in infrared spectral wavelength range is far more difficult. In fact, military organizations or government entities that rely heavily on extremely secure transmission technologies were among earliest users of optical wireless communication systems as a way to avoid signal interception. Therefore, it is understandable why study of FSO technology in military labs and security agencies dates back several decades. In early days of FSO development, ability to transmit information at high data rates was actually a less important factor than fact that FSO technologies offered one of easiest and most secure ways to exchange information between remote locations. The small diameter of beam of typically only a few meters in diameter at target location is one of reasons why it is extremely difficult to intercept communication path of an FSO-based optical wireless system: The intruder must know exact origination or target location of (invisible) infrared beam and can only intercept beam within very narrow angle of beam propagation. Even more difficult, intruder must have free and undisturbed access to installation location of optical wireless transceiver and be able to install electronic equipment without being observed. In majority of cases, installation location does not allow free access to a potential intruder because installation location is part of customer premise such as roof or an office (when optical wireless equipment is installed behind windows).
The direct interception of an optical wireless beam between two remote networking locations is basically impossible because beam typically passes through air at an elevation well above ground level. Due to fact that transmission beam is invisible and that any attempts to block beam would occur near optical wireless equipment terminus points, transmission process imposes another obstacle. Picking up signal from a location that is not directly located within light path by using light photons scattered from aerosol, fog, or rain particles that might be present in atmosphere is virtually impossible because of extremely low infrared power levels used during optical wireless transmission process. The main reason for excluding this possibility of intrusion is fact that light is scattered isotropically and statistically in different directions from original propagation path. This specific scattering mechanism keeps total number of photons or amount of radiation that can potentially be collected onto a detector that is not directly placed into beam path well beyond detector noise level
Summary Optical wireless communication systems are among most secure networking transmission technologies. Unlike microwave systems, it is extremely difficult to intercept optical wireless light beam carrying networking data because information is not spread out in space but rather kept in a very narrow cone of light. To intercept this invisible light beam, intruder must be able to obtain direct access to light beam. Due to very narrow beam diameter, interception of beam can virtually only be accomplished at customer premise where system is installed. At that point, it would be certainly easier for an intruder to plug directly into network by using existing copper-based infrastructure (e.g. unplug a CAT 5 networking cable and plug it into a laptop). Scattered light can not be used as a method of interception. Moreover, higher protocol layers can be used in conjunction with layer one optical wireless physical transport technology to encrypt sensitive network information and provide additional.
Lightpointe are a pioneer in the development of Optical Wireless products based on free-space optics (FSO) technology. Lightpointe's wireless solutions are installed and supported in the UK by WAN Partnership Ltd. For more information and discussion about Wireless technologies please visit http://www.wanpartnership.co.uk