BY:Mujeeb ur Rehman, B.E-VIIElectrcial Engineering Department, SUKKUR IBAMujeeb.soomro@iba-suk.edu.pk

IntroductionIntroduction

HistoryHistory

Why Free Space Optics?Why Free Space Optics?

How FSO works?How FSO works?

ChallengesChallenges

SafetySafety

Applications of Free Space OpticsApplications of Free Space Optics

What is Free-Space Optics (FSO)?• FSO is a wireless technology that transmits data via

laser beams.

FSO uses light to transmit data between buildings that have clear a line of sight (LOS).

FSO TRANSMITTER FSO RECIEVER

1. Originally developed by the

U.S military and NASA.

2. The invention of lasers in the 1960s

revolutionized free space optics.

3. In 1880 Alexander Graham Bell created the photophone .

FSO can send large amounts of data (around 2.5 Gbps of data).

Can transmit at distances around 4 km (almost 2 and one half miles).

No need to get a license, the spectrum used is an unlicensed worldwide.

The cost is often less than that of using fiber optic cables.

FSO systems can be installed quickly (in days). because it uses light there is no RF interference.

With FSO, especially through With FSO, especially through the window, no permits, no the window, no permits, no

digging, no fees digging, no fees

1 Network traffic converted into pulses of invisible light representing 1’s and 0’s

2 Transmitter projects the carefully aimed light pulses into the air

5 Reverse direction data transported the same way.

• Full duplex

3 A receiver at the other end of the link collects the light using lenses and/or mirrors

4 Received signal converted back into fiber or copper and connected to the network

Anything that can be done in fiber can be done with FSO

FSO systems use optical wireless link each having:

a transceiver with a laser or LED transmittera lens or telescope (can have more that one)

shaping overcomes building movementa receiver usually a semiconductor (photodiode)

May also employ servo motors, and mirrors.

FSO operates in the infrared (IR) range around 850 and 1550 nm (frequencies around 200 THz).

Rapid installations without trenching and permitting.

Direct connection to the end user.

Bypasses the building owner.

License-free operation

High bit rates

Low bit error rates

Immunity to electromagnetic interference

Full duplex operation

Very secure due to the high directionality and narrowness of the beams

RONJA , a free implemantation of FSO utilizingHigh intensity LEDs

Sunlight

Alignment

Fog

Each of these factors can “attenuate” (reduce) the signal. However, there are ways to mitigate each environmental factor.

Scintillation

RangeObstructions

Low Clouds

Absorption or scattering of optical signals due to airborne particles

High availability deployments require short links that can operate in the fog.

Low Clouds Very similar to fog

Rain Extremely heavy rain (can’t see through

it) can take a link down

Heavy Snow May cause ice build-up on windows

Sand Storms Likely only in desert areas; rare in the

urban core

Beam spreading and wandering due to propagation through air pockets of varying temperature.

This atmospheric turbulence can deteriorate the quality ofthe image formed at the receiver, and can cause fluctuations inboth the intensity and the phase of the received signal .These intensity fluctuations, often referred to as scintillationSolution: Large receiver diameter to cope with image dancing

Challenges:

Scintillation

The two major concerns involve eye exposure to light beams and high voltages within the light systems and their power supplies.

Strict international standards have been set for safety and performance.

Choice of the wavelength 1550 nm yields better eye safety than for the common 850 nm for FSO wavelength

APPLICATIONS OF FSO1.MILITARY AND GOVERNMENT

Secure and undetectable FSO system can connect large areas safely with minimal planning and deployment time.

2. Wireless Service Provider

Unlike microwave or fiber, deployment of FSO does not require spectrum licensing, physical disruption to a location, or government zoning approvals. Carriers are free to grow their business.

3. Enterprise connectivity

To cross a public road or other barriers which the sender and receiver do not own.

Companies, airports, hospitals and schools can use safe, secure Free space optical wireless links to connect buildings within their campus environments.

4.Temporary network installation (for events or other purposes)

5.Reestablish high-speed connection quickly (disaster recovery).

6.FSO on High-Altitude Platforms (Future Application)

•HAPs are aircraft or airships situated well above the clouds at typical heights of 17 to 25 km.•Where the atmospheric impact on a laser beam is less severe than directly above ground•1.25 Gbps for Downlink•10 Gbps for Upwnlink