Free Space Optics
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Free Space Optics (FSO) uses visible light communication or infrared light to transmit data wirelessly over short to medium distances. It provides high-speed connectivity as an alternative to fiber for the "last mile" between buildings. FSO has advantages of high data rates up to 2.5 Gbps, easy installation without wiring, and high security. However, it also faces challenges of signal attenuation from factors like sunlight, fog, clouds, and building sway requiring techniques like automatic tracking and large beam divergence to maintain alignment. FSO is best suited for short-distance last mile connections between buildings where fiber may be difficult to install.
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Free Space Optics
- 1. Free Space Optics FSO Mohamed Fahmy and Mohamed Seif
- 2. Introduction
- 3. Why FSO? Only about 5% of commercial buildings are lit with fiber Wide Area Networks between major cities are extremely fast •Fiber based Local Area Networks in buildings are also fast The connections in between are typically a lot slower The “Last Mile” Bottleneck Problem
- 4. Overview of FSO Transmitter Channel Receiver Lens Lens/Mirror
- 6. Advantages of FSO No interference High Security
- 7. Advantages of FSO • High data rates • Up to 2.5 Gb/s
- 8. Advantages of FSO • Spectrum is too large
- 9. Advantages of FSO Easy to install • Rapid installations without trenching and permitting through the window • Direct connection to the end user • Bypasses the building owner • No roof rights • No riser rights
- 10. Challenges of FSO Sunlght Building Sway Alignment Window Attenuation Fog Each of these factors can “attenuate” (reduce) the signal. However, there are ways to mitigate each environmental factor. Scintillation Obstructions Low Clouds
- 11. Challenges of FSO • Building Sway -misalignment
- 12. Challenges of FSO • Compensating for Building Sway – 2 Methods • Automatic Pointing and Tracking using MEMS technology 0.2 – 1 mrad divergence = 0.2 to 1 meter spread at 1 km
- 13. Challenges of FSO • Compensating for Building Motion • Large Divergence and Field of View 2 – 10 mrad divergence =2 to 10 meter spread at 1 km
- 14. Challenges of FSO • Scintillation
- 15. Challenges of FSO • Atmospheric Attenuation
- 16. Challenges of FSO • Experiment • Line of sight =2.4 km
- 17. Challenges of FSO • Safety Considerations • Strict international standards have been set for safety and performance.
- 18. Applications
- 19. FSO technology roadmap • Enhance the performance of data rate • Highest speed 2.5 Gb/s • 10 Gb/s in the future • Fiber-like data rates
- 20. FSO technology rodmap • Future Application • FSO on HAPs
- 21. Comparison Criteria FSO Optical Fiber RF Installation Easy Difficult Easy Cost Moderate High Moderate Maintenance time Short Large Short Most common uses Last Mile solution (short distance) Long distance Short/Long distance Security Moderate High Moderate
- 23. References [1]LINCOLIN laboratory, MASSACHUSETS INSTITUTE OF TECHNOLOGY [2] http://www.fsona.com/technology.php?sec=fso_guide [3] http://www.laseroptronics.com/index.cfm/id/57-66.htm [4] LightPointe_White_Paper_What_is_Free_Space_Optics [5] http://spectrum.ieee.org/semiconductors/optoelectronics/fiber- optics-without-fiber
- 24. THANK YOU …
Editor's Notes
- Very Narrow and Directional Beams
- Flying birds can temporarily block a single beam, but this tends to cause only short interruptions, and transmissions are easily and automatically resumed.
- The movement of buildings can upset receiver and transmitter alignment.
- -Heated air rising from the earth or man-made devices such as heating ducts creates temperature variations among different air pockets. This can cause fluctuations in signal amplitude which leads to image fluctuations at the FSO receiver end. -Beam spreading and wandering due to propagation through air pockets of varying temperature, density, and index of refraction.
- -: The major challenge to FSO communications is fog. The primary way to counter fog when deploying FSO is through a network design that shortens FSO link distances and adds network redundancies. FSO installations in foggy cities such as San Francisco have successfully achieved carrier-class reliability
- To those unfamiliar with FSO, safety is often a concern because the technology uses lasers for transmission. Mitigation of power Wavelength=1550 nm
- Stratospheric Conditions. Low attenuation, no cloud interference, low tempreture…etc. Cost Effective (Compared to Satellites Estimated Range: more than 600km.