Free Space Optics

Optical Fibers have revolutionised the way we communicate. All Optical communication till recent times was focussed only on wired solutions. Now, wireless optics is coming up as a very viable solution to the so called "Last-Mile Problem". The issue is that though Optical Fibers provide high bandwidth backbones for ISP netwoks, the end user are unable to make use of the high data rates simply because they are connected through copper cables and laying optical fibers upto the office/homes is not economically viable. Hence, people started looking at alternative means and came up with the idea of providing connectivity through wireless optical links mounted on the tops of buildings.

Various issues like eye-safety (due to the high LASER powers used) and atmospheric interference came up. Eye-Safety norms have been laid down and a lot of research is currently going on into selecting the appropriate wavelength of light which is least harmful to the eye at high LASER powers. Atmospheric effects play a major role and visibility conditions determine the data rate available on the link at that instant of time. Factors like fog, rain, smog greatly influence the link availability and are being researched thoroughly by researchers all over the world.

Wireless Optical Links are also being established for intra-building communication. Standards like IR-LAN have come up. A major disadvantage of wireless optical links is that they are usually Line of Sight (LoS) i.e. the transmitter and receiver should be perfectly aligned in order for the communication to take place. This makes mobility impossible. Hence, all wireless optical links are immobile though recently research has started on diffused optical links wherein the strict LoS requirements are being loosened.

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