EE 566 EE 566 Optical CommunicationOptical Communication

Ming LiMing Li

minglimingli@buffalo.@buffalo.eduedu

Free Space Optic (FSO)

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Why still choose this topic?

September 11, 2001, New York

Every thing was destroyed Every thing was destroyed including normal fiber linkincluding normal fiber link

Wall street stock market was closed because the communication was destroyed

Two of these units were used Two of these units were used between building to re-establish a between building to re-establish a high speed communication link.high speed communication link.

FSO communication between Merrill Lynch FSO communication between Merrill Lynch Brokerage and Wall Street in New York Brokerage and Wall Street in New York following the terrorist attack that destroyed following the terrorist attack that destroyed normal fiber optic linknormal fiber optic link

History of Free Space OpticsHistory of Free Space Optics

The transmission of information using The transmission of information using light is actually not a new idea.light is actually not a new idea.

Great Wall

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

In the mid-1960's In the mid-1960's NASA initiated NASA initiated experiments to experiments to utilize the laser as a utilize the laser as a means of means of communication communication between the ground between the ground and space.and space.

Gemini-7

Birth of Laser FSO Communications

Space-to-Ground Lasercom LinkSpace-to-Ground Lasercom Link 2000 km Link Distance2000 km Link Distance 1 Gbps Transmission Rate1 Gbps Transmission Rate

Satellite Laser Communication

Chinese First Maned Spaceship

Air ForceAir Force Its potential for low Its potential for low

electromagnetic electromagnetic emanation when emanation when transferring sensitive transferring sensitive datadata

NavyNavy Secure Secure

communication communication with submerged with submerged submarines. submarines.

Military Application of FSO

Technology from Space Lasercom

Advantage of FSOAdvantage of FSO

Wireless communicate from A to BWireless communicate from A to B Low costs ($10K to $20K)Low costs ($10K to $20K) High bit rate (10 Mbps to 2.5 Gbps)High bit rate (10 Mbps to 2.5 Gbps) Set up a link in a few daysSet up a link in a few days The lasers used are eye safe, so The lasers used are eye safe, so

even a butterfly can fly unscathed even a butterfly can fly unscathed through a beamthrough a beam

Application of FSOApplication of FSO

Connectivity Solutions Connectivity Solutions 'Last-Mile' Network Solutions'Last-Mile' Network Solutions Temporary Network ProvisionTemporary Network Provision Cable Free Connectivity in the Finance Cable Free Connectivity in the Finance

SectorSector CCTV Security ApplicationsCCTV Security Applications GSM Microcell ConnectivityGSM Microcell Connectivity

Industrial estates, Science parks and university Industrial estates, Science parks and university campus environments typically exhibit a common campus environments typically exhibit a common

problem – a number of separate buildings, separated problem – a number of separate buildings, separated by roads or other obstacles, between which by roads or other obstacles, between which

communications links are frequently in demandcommunications links are frequently in demand..

Cable digging, increasingly unpopular in cities, is Cable digging, increasingly unpopular in cities, is regulated by the local authority who may restrict re-regulated by the local authority who may restrict re-digging frequency of roads - and the cost may be digging frequency of roads - and the cost may be

prohibitive in any case, especially if a river or railway is in prohibitive in any case, especially if a river or railway is in the way.the way.

FSO vs RFFSO 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 FSOChallenge of FSO

Challenge #1—hitting the Challenge #1—hitting the targettarget

Challenge #2—interrupted Challenge #2—interrupted signals signals

Hitting the targetHitting the target

Getting a laser beam to hit the mark in Getting a laser beam to hit the mark in a laboratory setting is easy, but in the a laboratory setting is easy, but in the real world it is much harder. real world it is much harder.

1)Atmospheric turbulence1)Atmospheric turbulence 2)Fog2)Fog 3)Building movement3)Building movement

Atmospheric Atmospheric attenuation and attenuation and scatterscatter

6.5 dB/km 150 dB/km 225 dB/km

300m distance to tall building

Solution Solution

Active beam steering (sometimes Active beam steering (sometimes involving MEMS), involving MEMS),

Multiple laser beams, Multiple laser beams, Automated power control, and Automated power control, and

calculated laser beam divergence. calculated laser beam divergence. Pulsed laser beams start out just Pulsed laser beams start out just centimeters wide and can diverge to 1 centimeters wide and can diverge to 1 meter or more over typical link meter or more over typical link distances—like using a really big bullet distances—like using a really big bullet to hit a small target. to hit a small target.

Challenge #2—Challenge #2—interrupted signalsinterrupted signals

An email is beaming across the An email is beaming across the FSO connection just as a bird flies FSO connection just as a bird flies through, blocking the signal. through, blocking the signal.

Solution #2—no lost Solution #2—no lost datadata No fear. FSO linkheads essentially "talk" to No fear. FSO linkheads essentially "talk" to

one another, and just as people repeat words one another, and just as people repeat words in conversation, data can be retransmitted in in conversation, data can be retransmitted in the event of a temporary beam blockage. the event of a temporary beam blockage.

Several companies even have redundant Several companies even have redundant radio-frequency links that simultaneously radio-frequency links that simultaneously transmit the FSO signal. When the radio or transmit the FSO signal. When the radio or the FSO signal is blocked, the counterpart is the FSO signal is blocked, the counterpart is automatically used—no loss of data, and no automatically used—no loss of data, and no delay. delay.

Companies and rapidly Companies and rapidly advancing FSO technology advancing FSO technology

AirFiberAirFiber Hybrid Free- space optic/RadioHybrid Free- space optic/Radio

LightPointeLightPointe Multi-beam sending processMulti-beam sending process

TerabeamTerabeam carrier-grade FSO equipment and servicescarrier-grade FSO equipment and services

AirFiber AirFiber www.www.airfiberairfiber.com.com San Diego, California, was founded in 1998San Diego, California, was founded in 1998

AirFiber's products AirFiber's products combine FSO with combine FSO with 60 GHz millimeter-60 GHz millimeter-wave radio, makes wave radio, makes wireless wireless communication communication possible in any possible in any weather.weather.

LightPointe LightPointe www.www.lightpointelightpointe.com.com San Diego, California, was foundedSan Diego, California, was founded

LightPointe's FSO LightPointe's FSO products utilize a products utilize a multi-beam sending multi-beam sending process, which process, which overcomes overcomes atmospheric atmospheric degradations and degradations and temporary beam temporary beam obstructions by obstructions by overlapping overlapping redundant infrared redundant infrared beams.beams.

Terabeam Terabeam www.www.terabeamterabeam.com.com

Kirkland, Washington, was founded in 1997Kirkland, Washington, was founded in 1997

Terabeam's Terabeam's FSO products FSO products have have advanced advanced beam-steering beam-steering features that features that update beam update beam direction up to direction up to 300 times per 300 times per second.second.

ConlusionConlusion

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

ReferenceReference

http://www.lightpointe.com/http://www.lightpointe.com/

http://www.freespaceoptic.com/http://www.freespaceoptic.com/

http://www.fsonews.com/http://www.fsonews.com/

http://www.cablefreesolutions.com/http://www.cablefreesolutions.com/

http://www.thefoa.org/http://www.thefoa.org/

http://www.free-space-optics.org/http://www.free-space-optics.org/

http://www.freespaceoptics.com/http://www.freespaceoptics.com/

http://www.opticsreport.com/http://www.opticsreport.com/