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A

Seminar

On

FREE SPACE OPTICS TECHNOLOGY

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Presented

By

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SHRUTI GAJANAN SHINDE

(PRN NO. 2030331372019)

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Under Guidance of

Prof. S. S. Gaikwad

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CONTENT

1. Introduction

2. History of FSO

3. How FSO works

4. FSO Architecture

5. Why FSO

6. FSO Challenges

7. FSO Security

8. Applications

9. Advantages

10. Disadvantages

11. Conclusion

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1. INTRODUCTION

  • FSO is a wireless technology that transmits data via laser beams.

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  • FSO- Optical Communications technology that uses light propagating in Free space to transfer data.

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  • Line of sight technology.

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  • Bandwidth up to 1.25 Gbps.

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  • Uses LED or Laser as a light source.

Fig.1.1 Metro Area Network

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2. HISTORY OF FREE SPACE OPTICS

  • In 1880, Alexander Graham Bell and his assistant Charles Summer Tainter created the photophone.

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  • The first know use of Free Space Optics was when the ancient Greeks used polished shields during battle to send signals to troops on the battle field using the light from the sun.

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3. HOW FREE SPACE OPTICS WORKS

  • Modem laser system provide network connectivity at speed of 622 Mega bits/sec onwards.
  • Two beams are kept narrow.
  • The receiver detectors are either PIN diodes or Avalanche Photodiode.
  • FSO transmits invisible light beams between two beams.
  • It works in Tera Hertz (THz) spectrum.

Fig.3.1 FSO Working

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3. HOW FREE SPACE OPTICS WORKS

Fig.3.2 Subsystem of FSO

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4. FSO ARCHITECTURE

Three main FSO architectures have been used so far.

Fig.4.1 Point-to-point Architecture

  • Point-To-Point architecture is a dedicated connection that offers higher bandwidth but is less capable.
  • FSO can support speeds between 155Mbits/sec and 10Gbits/sec at a distance of 2 kilometers (km) to 4km.

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1. Point-To-Point Architecture:

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4. FSO ARCHITECTURE

Fig.4.2 Mesh architecture

  • Mesh architectures may offer redundancy and higher reliability with easy node addition but restrict distances more than the other options.
  • A meshed configuration can support 622Mbits/sec at a distance of 200meters (m) to 450m.

2. Mesh Architecture:

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4. FSO ARCHITECTURE

3. Point-To-Multipoint Architecture:

Fig.4.3 Point-to-multipoint architecture

  • This architecture offers cheaper connections and facilities node addition but at the expense of lower bandwidth than the point-to-point option.
  • FSO can support the same speeds as the point-to-point arrangement -155Mbits/sec to 10Gbits/sec at 1km to 2km.

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5. WHY FSO

There are several options to address "connectivity bottleneck," but most don't make economic sense.

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  • The first, most obvious choice is fiber-optic cable.

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  • Second Radio frequency (RF) technology.

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  • The third wire- and copper-based technologies, (i.e. cable modem, T1s or DSL).

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  • The fourth-and often most viable-alternative is FSO.

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  • Only about 5% of commercial buildings are connected with fiber.

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6. FSO CHALLENGES

1. Fog:

  • It affected on near infrared wavelength.
  • FSO wavelength and Fog droplets are close to equal in size – (Mie scattering)
  • Absorption or scattering of optical signals due to airbone particles.
  • Primarily FOG but can be rain, snow, smoke, dust, etc.

Fig.6.1 Fog

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6. FSO CHALLENGES

2. Physical Obstruction:

  • Flying birds can temporarily block a single beam, but this tends to cause only short interruptions and transmissions are easily and automatically re-assumed.

3. Scintillation:

  • Beam spreading and wandering due to propagation through air pockets of varying temperature, density, and index of refraction.

Fig.6.2 Scintillation

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6. FSO CHALLENGES

4. Solar Interference:

It can be combated by

  • Long pass optical fiber window
  • Optical Narrowband filtering

5. Building Sway / Seismic Activity:

  • Movement of building upsets transmitter-receiver alignment.
  • Solution: - Beam divergence

- Active tracking

Fig.6.3 Building Motion

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7. FREE SPACE OPTICS SECURITY

FSO is far more secure than RF or other wireless based transmission technologies for several reasons:

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  • Laser beams cannot be detected with spectrum analysers or RF meters.

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  • The laser beams are narrow and invisible, making them harder to find and even harder to interrupt and crack.

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  • Data can be transmitted over an encrypted connection adding to the degree of security available in FSO network transmissions.

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8. APPLICATIONS

  • Telecommunication and computer networking.
  • Point-to-point LOS links.
  • Temporary network installation
  • For communications between spacecraft, including elements of satellite constellation.
  • Security applications.
  • Military application
  • Metro Area Networks (MAN)
  • Enterprises connectivity
  • Fiber backup
  • Backhaul
  • Service acceleration
  • Last-Mile access

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9. ADVANTAGES

  • License – Free operation

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  • Installation is easier and fast

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  • The cost is moderate

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  • It has ability to operate at higher power levels

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  • High bit rates

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  • Low bit error rates

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  • Immunity to electromagnetic interference

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10. DISADVANTAGES

  • Spreading loss is higher and there is atmospheric loss due to water and carbon dioxide molecules.

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  • Power consumption is higher.

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  • Easy to intercept due to its propagation medium

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  • Transmitter and receiver should be in LOS (Line of Sight) to each other for its operation.

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  • FSO transmitted signal gets blocked due to trees, animals, buildings and other atmospheric conditions.

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  • Birds and scintillation cause beam interruptions.

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11. CONCLUSION

  • Free space optics (FSO) provides a low cost, rapidly deployable method of gaining access to the fiber optic backbone.

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  • FSO technology not only delivers fiber-quality connections, it provides the lowest cost transmission capacity in the broadband industry.

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  • As a truly protocol-independent broadband conduct, FSO systems complement legacy network investments and work in harmony with any protocol, saving substantial up-front capital investments.

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  • A FSO link can be procured and installed for as little as one-tenth of the cost of laying fiber cable, and about half as much as comparable microwave/RF wireless systems.

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REFERENCES

  • fSONA unveils 2-5-Gbps free-space optical systems. September 5, 2012.

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  • Heinz Willebrand, and Baksheeesh S. Ghuman. Free-Space Optics: Enabling Optical Connectivity in Today`s Networks. SAMS Publishing; 2002.

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  • Andy Emmerson,”Fiberless Optics”, Everyday practical electronics, April 2003 pp . 248 .

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  • Vikrant kaulgnd, “Free space optics Bridges the last mile”, Electronics for u, June 2003 pp. 30-40

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  • https://en.wikipedia.org/wiki/Freespace_optical_communication

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  • www.studymafia.com

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  • https://www.cablefree.net/wirelesstechnology/free-space-optics/fso-guide/

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THANK YOU