Free Space Optic FSO EE 566 Optical Communication

Free Space Optic (FSO) EE 566 Optical Communication Ming Li mingli@buffalo. edu

Why choose this topic? Why still choose this topic?

September 11, 2001, New York

n Every thing was destroyed including normal fiber link Wall street stock market was closed because the communication was destroyed

n Two of these units were used between building to re-establish a high speed communication link. n. FSO communication between Merrill Lynch Brokerage and Wall Street in New York following the terrorist attack that destroyed normal fiber optic link

History of Free Space Optics n The transmission of information using light is actually not a new idea. Great Wall

In the late nineteenth century, Alexander Bell expanded his "phone-phone" communication which modulated by sunlight.

Birth of Laser FSO Communications Gemini-7 In the mid-1960's NASA initiated experiments to utilize the laser as a means of communication between the ground and space.

Satellite Laser Communication n Space-to-Ground Lasercom Link 2000 km Link Distance 1 Gbps Transmission Rate

Chinese First Maned Spaceship

Military Application of FSO n n Air Force Its potential for low electromagnetic emanation when transferring sensitive data n n Navy Secure communication with submerged submarines.

Technology from Space Lasercom

Advantage of FSO Wireless communicate from A to B n Low costs ($10 K to $20 K) n High bit rate (10 Mbps to 2. 5 Gbps) n Set up a link in a few days n The lasers used are eye safe, so even a butterfly can fly unscathed through a beam n

Application of FSO Connectivity Solutions n 'Last-Mile' Network Solutions n Temporary Network Provision n Cable Free Connectivity in the Finance Sector n CCTV Security Applications n GSM Microcell Connectivity n

Industrial estates, Science parks and university campus environments typically exhibit a common problem – a number of separate buildings, separated by roads or other obstacles, between which communications links are frequently in demand.

Cable digging, increasingly unpopular in cities, is regulated by the local authority who may restrict redigging frequency of roads - and the cost may be prohibitive in any case, especially if a river or railway is in the way.

FSO vs RF RF 2. 4 GHz systems were typically running at 2 -4 Mbps due to interference issues in the unlicensed frequency ranges FSO provided 10 Mbps of throughput for less than unlicensed RF FSO was less cost, more secure, and seemed simpler

Challenge of FSO n Challenge #1—hitting the target Challenge #2—interrupted signals n

Hitting the target n n Getting a laser beam to hit the mark in a laboratory setting is easy, but in the real world it is much harder. 1)Atmospheric turbulence 2)Fog 3)Building movement

Atmospheric attenuation and scatter 6. 5 d. B/km 150 d. B/km 225 d. B/km 300 m distance to tall building

Solution n Active beam steering (sometimes involving MEMS), Multiple laser beams, Automated power control, and calculated laser beam divergence. Pulsed laser beams start out just centimeters wide and can diverge to 1 meter or more over typical link distances—like using a really big bullet to hit a small target.

Challenge #2— interrupted signals n An email is beaming across the FSO connection just as a bird flies through, blocking the signal.

Solution #2—no lost data n n No fear. FSO linkheads essentially "talk" to one another, and just as people repeat words in conversation, data can be retransmitted in the event of a temporary beam blockage. Several companies even have redundant radio-frequency links that simultaneously transmit the FSO signal. When the radio or the FSO signal is blocked, the counterpart is automatically used—no loss of data, and no delay.

Companies and rapidly advancing FSO technology n Air. Fiber Hybrid Free- space optic/Radio n. Light. Pointe Multi-beam sending process n. Terabeam carrier-grade FSO equipment and services

Air. Fiber www. airfiber. com San Diego, California, was founded in 1998 n Air. Fiber's products combine FSO with 60 GHz millimeterwave radio, makes wireless communication possible in any weather.

Light. Pointe www. lightpointe. com San Diego, California, was founded n Light. Pointe's FSO products utilize a multi-beam sending process, which overcomes atmospheric degradations and temporary beam obstructions by overlapping redundant infrared beams.

Terabeam www. terabeam. com Kirkland, Washington, was founded in 1997 n Terabeam's FSO products have advanced beam-steering features that update beam direction up to 300 times per second.

Conlusion n FSO is just starting to be applied to solve the Internet “last-mile” interconnectivity problem. Some believe that it may be the unlimited bandwidth solution for the metro urban core of downtown building-tobuilding communication, as well as the optimal technology for home-to-home and office-to-office connectivity.

Reference http: //www. lightpointe. com/ http: //www. freespaceoptic. com/ http: //www. fsonews. com/ http: //www. cablefreesolutions. com/ http: //www. thefoa. org/ http: //www. free-space-optics. org/ http: //www. freespaceoptics. com/ http: //www. opticsreport. com/