What exactly is Free Space Optics?

I decided to open this blog with information about free space optics because it really is a revolutionary technology that is highly under-used. I believe that it's underused because of the lack of knowledge and information available. I hope to help change that. I'll try to keep the discussions as colorful and un-boring as possible. If anyone wants to talk more technically then just feel free to leave a comment.



Free Space Optics: The Basics

Free space optics (FSO) is an optical communication technology that uses light propagating in free space to transmit data between two points. FSO is particularly useful where the physical connection, by use of fiber optic cable, is impractical due to high cost or other physical considerations. Fiber optic cables are often used for networking purposes such as connecting multiple buildings to one network. FSO eliminates the need for the physical cabling.



Free Space Optics are currently being used for communication between space craft by NASA. The optical links are implemented using infrared laser light; although short range communication is also possible by using LED's. The maximum range for terrestrial links is currently 10 km or a little over 6 mi. The stability and quality of the link however, is highly dependent on atmospheric factors such as rain, fog, dust, and heat. that is why it is important to make a good investment in a quality piece of equipment. In space the range is several thousand kilometers.

This is what the FSO hardware looks like. This one happens to be a great model that Canon makes called the Canobeam (it is hard to find good pictures of the hardware, so please forgive the name dropping).


A (very brief) History of Free Space Optics

Optical communication is not a new technology at all. The ancient Greeks polished their shields in order to use the light to send signals during battle. Several centuries later, a wireless solar telegraph called a heliograph was developed to send Morse code using flashes on sunlight which was widely used in the late 19th and early 20th centuries. Alexander Graham Bell developed a light based telephone is 1880 called a photophone that allowed the transmission of sound on a beam of light.

The invention of the laser in the early 1960's revolutionized Free Space optics. Military organizations in particular found use for this new technology and boosted research and development. The technology however began to lose market momentum with the wide use of fiber optic cables and the installation of optical fiber networks for wide-spread civilian use. I believe that this was due to the low initial cost outlay involved with fiber optics.

Applications of Free Space Optics

Free Space Optics has many practical applications, some of which I have listed here.

• LAN to LAN on campuses at fast Ethernet or gigabyte Ethernet speeds


• LAN to LAN connections in a city Ex: Metropolitan Area Network


• To cross a public road or other barriers which neither the sender or receiver own


• Speedy service delivery of high-bandwidth access to optical fiber networks


• Converged voice-data connection


• Temporary network installation (for events or other purposes)


• Reestablish a high speed connection quickly (disaster recovery)


• As an alternative or upgrade add-on to existing wireless technology


• As a safety add-on for important fiber connections (redundancy)


• For communications between spacecraft, including elements of a satellite constellation
  

The light beam can be very narrow, and therefore harder to intercept, improving security. In any case, it is comparatively easy to encrypt any data traveling across the FSO connection for even more heightened security. FSO is a vast improvement from EMI, or radio frequencies, behavior using light instead of microwaves; which is also significantly better for the environment. This keeps us with the green theme of the world we live in.

Advantages
This is a little technical but I did my best to give a brief translation.

• Ease of deployment


• License-free operation


• High bit errors (the number of bits that are conveyed per unit of time)


• Low bit error rates (the ratio of the number of bits received incorrectly to the total number sent)


• Immunity to electromagnetic interference (or EMI, the radio frequencies mentioned above)


• Full duplex operation (full communication in both directions)


• Protocol transparency (easy to see where the data comes from, what it is, who it is authenticated by, and any error detection)


• Very secure due to high directionality and the narrowness of the light beam


• No Fresnel Zone necessary (less signal interference)

Free implementation of FSO using high powered LED's





Extra Links

These are other links I thought would be helpful if you want more in depth information about this technology.

www.freespaceoptics1.com

http://www.esa.int/esaTE/SEMN6HQJNVE_index_0.html

http://www.seas.harvard.edu/hbbcl/fsoc.html

http://www.hqisec.army.mil/isec/publications/Analysis_of_Free_Space_Optics_as_a_Transmission_Technology_Mar05.pdf

http://www.hapcos.org/DOCS/wg2/wg2_home.php