ICT Role in 21st Century Education & its Challenges.pptx
Free Space Optics
1. BY TAMAL GHOSH ;Electronics & Communication ;AOT
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14. 1 ° ≈ 17 mrad -> 1 mrad ≈ 0.0573° 1 mrad 1 km 1 m Small angle approximation: Angle (in milliradians) * Range (km)= Spot Size (m) Divergence Range Spot Diameter 0.5 mrad 1.0 km ~0.5 m (~20 in) 2.0 mrad 1.0 km ~2.0 m (~6.5 ft) 4.0 mrad (~ ¼ deg) 1.0 km ~4.0 m (~13.0 ft)
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16. Sunlight Building Motion Alignment Window Attenuation Fog Each of these factors can “attenuate” (reduce) the signal. However, there are ways to mitigate each environmental factor. Scintillation Range Obstructions Low Clouds
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21. Type Cause(s) Magnitude Frequency Tip/tilt Thermal expansion High Once per day Sway Wind Medium Once every several seconds Vibration Equipment (e.g., HVAC), door slamming, etc. Low Many times per second
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