RF vs FSO | Difference between RF and FSO

This page compares RF vs FSO and mentions difference between RF and FSO (Free Space Optics)

Introduction: Both RF (radio frequency) and FSO (Free Space Optics) are used in un-guided systems for wireless communication.

What is RF ?

The term RF refers to Radio Frequency. It ranges from 3 KHz to 300 GHz. It finds applications in various domains other than wireless communication such as in medical domain for skin tightening, cancer treatment, vision correction and so on. It is also used for mobile, radio and television broadcasting.

wireless communication using RF

The figure depicts use of RF in satellite communication, microwave, cellular system and wifi system (based on IEEE 802.11 WLAN standard). As shown RF requires antenna for transmission and reception of EM (Electromagnetic) waves.

What is FSO ?

It is a wireless technology which transmits data via laser beams. It uses light waves to transmit data between buildings which have clear LOS (line of sight).

The difference between OFC and FSO is that OFC (Optical Fiber Communication) sends data via light through "fiber" where as FSO (Free Space Optic) communication sends data via light through "air".

FSO Block Diagram

Following points summarize working of FSO system as per block diagram.
• Information or data traffic is converted into pulses of invisible light which represent binary 1's and 0's.
• Transmitter transmits light pulses into the air. It uses LED or Laser Diode (LD).
• Receiver at the other end collects the light using lenses and/or mirrors. It uses photo-detector.
• Received signal is processed and converted back into transmitted information.

Difference between RF vs FSO

Following table compares RF versus FSO and mentions difference between RF and FSO.

Specifications RF FSO
• Frequency range 3 KHz to 300 GHz > 300 GHz
• Bandwidth Lower as frequency spectrum in the air is scarse resource. Much higher, Tb/s throughput can be achieved in single FSO channel
• Spectrum RF spectrum is scarse resource and regulated for allocation as per need. It is large and license free.
• Installation Difficult Moderate
• Data Rate Mbps to Gbps Gbps to Tbps
• Connectivity P2P short reach (Example Microwave radio) P2P, P2MP short and long Reach
• Multi-path fading Affected Not affected
• Security Poor, It is less secured as RF waves are susceptible to eavesdropping. Good, It is very difficult to intercept and hence it is highly secured.
• Components Larger in size Smaller in size
• Atmospheric loss Affected by rain Affected by rain, moreover RF signal gets attenuated due to signal absorption by gases such as O2 and H2O.
• Interference from EM waves Affected Immune
• Side lobes Present Not present

Conclusion : In order to leverage benefits of both RF (Radio Frequency) and FSO (Free Space Optics), combined hybrid RF/FSO based communication technologies have been developed. RF links complement FSO links to achieve carrier class availability 99.999%.

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