Free Space Optics (FSO): Advantages and Disadvantages

This page explores the advantages and disadvantages of Free Space Optics (FSO) technology. It outlines the benefits and drawbacks associated with FSO systems.

What is FSO?

Introduction: Free Space Optics (FSO) is a wireless optical technology that transmits data via laser beams. It leverages light waves to transmit and receive data in a Line-of-Sight (LOS) path between buildings.

Unlike Optical Fiber Cable (OFC), FSO uses air as the medium for data transportation using light. In contrast, OFC employs a physical cable for data transport using light.

FSO Block Diagram

The figure above depicts a simplified block diagram of an FSO system. As shown, there are three primary components:

• Transmitter: This includes a data source encoder, a Light Emitting Diode (LED) or Laser Diode (LD), and a lens or mirror.
• Channel: This is the free space (air) through which the laser beam travels.
• Receiver: This consists of a photodetector, a signal processor, and a decoder.

Here are some key features and characteristics of FSO:

• Frequency: Greater than 300 GHz
• Bandwidth: Tens of GHz
• Transmission Power: Dozens of watts
• Receiver Noise Figure: Approximately 15 dB
• Receiver Sensitivity: Approximately -56 dBm

Benefits or Advantages of FSO

Here’s a rundown of the benefits and advantages of using FSO:

• License-Free Operation: Because FSO uses air as the transmission medium, no specific license is needed to transmit laser beams.
• Easy and Fast Installation: FSO systems are relatively straightforward to install, and maintenance time is typically short.
• Moderate Cost: The cost of deploying FSO is generally moderate compared to other technologies.
• High Power Operation: FSO is capable of operating at higher power levels.
• High Bit Rates and Low Bit Error Rates: FSO offers the potential for high data transmission speeds and low error rates (BERs).
• Immunity to Electromagnetic Interference: FSO systems are not susceptible to electromagnetic (EM) interference.

Drawbacks or Disadvantages of FSO

Now, let’s examine the drawbacks and disadvantages of FSO technology:

• Higher Spreading Loss and Atmospheric Loss: FSO signals experience higher spreading loss as they travel through the air. Additionally, atmospheric conditions, like water and carbon dioxide molecules, can contribute to signal loss.
• Higher Power Consumption: FSO systems tend to consume more power compared to other communication methods.
• Security Concerns: Due to its propagation through open air, FSO signals are potentially easier to intercept, making it less secure than OFC.
• Line-of-Sight Requirement: The transmitter and receiver must maintain a clear Line-of-Sight (LOS) for the system to operate correctly.
• Signal Blockage and Weather Dependence: The transmitted FSO signal can be blocked by various obstructions, including trees, animals, buildings, and atmospheric conditions like fog or heavy rain. Birds and scintillation (atmospheric turbulence) can also cause beam interruptions. Consequently, the availability of an FSO link is heavily dependent on weather conditions.