What is Free Space Optical Communication Used For?

By Owais AliReviewed by Lexie CornerMar 3 2025

Free-space optical (FSO) communication is transforming wireless networks by enabling high-speed, secure data transmission across both terrestrial and non-terrestrial systems.

Unlike traditional radio-based communication, FSO is resistant to electromagnetic interference and supports high-bandwidth applications, making it a key technology for next-generation networks.

Image Credit: Andrei Armiagov/Shutterstock.com

How FSO Communication Works

FSO transmits data using infrared or visible light through the atmosphere, eliminating the need for physical cables. A typical FSO system consists of three main components: a transmitter, an atmospheric channel, and a receiver.

The transmitter encodes data using specific modulation schemes and converts it into an optical signal with a driver circuit and a light source, such as an LED or laser. This optical beam is then sent through the atmosphere toward the receiver. At the receiving end, a lens captures the transmitted beam, and a photodetector converts it back into an electrical signal. A preamplifier circuit strengthens the signal before demodulation restores the original transmitted data.

Since FSO requires a clear line of sight (LOS) between the transmitter and receiver, precise alignment is crucial for maintaining signal integrity. While atmospheric conditions can affect performance, FSO remains a promising solution for high-speed, wireless communication in both terrestrial and space-based applications.¹

Applications of FSO Communication

Optical Wireless Backhaul for Network Densification

As mobile networks grow, the increasing deployment of small cells demands cost-effective, high-capacity backhaul solutions. Traditional wired options, such as copper and optical fiber, can be expensive and difficult to deploy in remote or densely populated areas. Wireless alternatives, like microwave radio links, offer flexibility but are often limited by interference and data rate constraints.

FSO provides a strong alternative by using infrared or visible light to establish high-bandwidth, low-latency connections between base stations, small cells, and network cores. It can achieve data rates of up to 1.72 terabits per second over distances exceeding 10 km.

In 5G and future networks, networked flying platforms (NFPs), including unmanned aerial vehicles (UAVs) and high-altitude balloons, integrate FSO to create dynamic relay networks. These airborne platforms help extend coverage in both urban and remote areas, using FSO links to connect small cells to the mobile core network. This reduces congestion in high-traffic locations such as stadiums and transportation hubs, enhancing overall network capacity and efficiency.²

FSO systems offer cost-effective deployment, especially in areas where traditional infrastructure is challenging to install. They reduce operational expenses and maintenance compared to physical infrastructure, making them an attractive option for network operators.

However, FSO also has challenges. Atmospheric conditions such as fog, rain, and turbulence can disrupt signal transmission. To mitigate this, FSO links greater than 125 m should be backed up by lower-data-rate microwave links, as microwave transmission is more affected by rain, while laser transmission is more affected by fog.

Precise alignment between transmitters and receivers is also essential, necessitating advanced tracking mechanisms and redundancy strategies to ensure reliable connectivity in dynamic environments.^3,4

Transceiver capacity and power constraints further limit performance, especially in mobile or energy-restricted environments. When integrated with NFPs, FSO systems must adapt to network reconfigurations to maintain stable connections.

Secure and Interference-Free Military Communications

Military communication is undergoing a major shift as strategic and tactical networks evolve. Traditionally, these systems have relied on the radio frequency (RF) spectrum, which is increasingly congested, vulnerable to interference, and subject to regulatory constraints.

To overcome these challenges, the military is adopting FSO as an alternative communication method. By using the infrared spectrum, FSO establishes high-speed, wireless optical links, reducing reliance on RF-based systems.

Recent demonstrations by the U.S. Army in Europe successfully integrated FSO and LiFi to create secure, resilient communication links across tactical operations centers.

These optical systems improved survivability in contested environments by minimizing RF emissions, making them harder to detect, jam, or intercept. This enables low-probability-of-interception (LPI) and low-probability-of-detection (LPD) communications, strengthening operational security and autonomy in the field.⁵

Additionally, FSO is not subject to host nation regulatory restrictions, allowing for rapid deployment without the need for spectrum allocation or authorization.

However, FSO relies on a clear line of sight, making it vulnerable to obstacles such as terrain, buildings, debris, and adverse weather conditions. Unlike RF signals, it cannot penetrate solid objects, limiting its effectiveness in urban or forested environments. To address this, hybrid RF-FSO links may be integrated for redundancy in hostile environments, combining the security of FSO with the penetrating capabilities of RF.

Ultra- High Bandwidth Satellite Communication

The growing demand for global bandwidth has accelerated the use of FSO-based inter-satellite networks. The European Data Relay System (EDRS), a collaboration between Airbus and the European Space Agency (ESA), was the first to achieve gigabit-speed laser satellite communication.

By linking low-Earth-orbit (LEO) satellites to geostationary satellites using FSO technology, EDRS ensured continuous ground station connectivity while reducing latency. This system enabled real-time transmission of terabytes of Earth observation data, supporting environmental monitoring, security, and disaster response.

Several LEO constellations, including Telesat Lightspeed (188 satellites), Rivada Space Networks (600 satellites), and Amazon's Project Kuiper (3,236 satellites), are being developed to enhance global connectivity.

Unlike terrestrial fiber-optic networks, FSO-enabled LEO constellations can be rapidly repositioned to restore communication in crises. This was demonstrated in early 2022 when Starlink terminals helped reestablish communication infrastructure in Ukraine.⁶

FSO communication in satellite networks enables ultra-high bandwidth data transfer with lower latency than RF and microwave links, allowing real-time transmission for Earth observation and global broadband. Its highly directional laser beams enhance security by resisting interception and electromagnetic interference.

Additionally, FSO systems consume less power, improving satellite efficiency and lifespan.

However, FSO technology faces challenges in the space environment. Satellites are exposed to mechanical, thermal, and radiation-induced stresses, necessitating robust designs for long-term performance. Maintaining stable inter-satellite links requires high-performance optical amplifiers and high-speed electronics, which increase system complexity and cost.

One of the most significant challenges in FSO satellite communication is the implementation of precise pointing, acquisition, and tracking (PAT) algorithms. These are essential for maintaining beam alignment between rapidly moving satellites. PAT systems require high-precision actuators, adaptive optics, and real-time error correction to compensate for satellite motion and environmental disturbances.^6,7

Indoor Networking

Indoor FSO enables short-range wireless data transmission using the optical wavelength spectrum (350–1550 nm), providing a license-free alternative to radio frequency systems. It relies on cost-effective components such as LEDs or laser diodes as transmitters and PN/PIN photodetectors as receivers. Existing lighting infrastructure can also be used for signal propagation, reducing the need for additional hardware.

FSO systems operate in either line-of-sight (LOS) or non-LOS configurations, depending on transmitter and receiver alignment. A highly directional LOS link ensures efficient communication, while wider beam angles in non-directed LOS links offer greater mobility but are more susceptible to shadowing.

For mobile receivers, a diffused link topology improves reliability by directing the transmitter beam toward the ceiling. Reflected signals then establish a connection within the receiver’s field of view, reducing shadowing effects and ensuring stable communication in dynamic environments.

Indoor FSO provides high-speed, interference-free data transmission without the need for cables or spectrum licensing. It can work with existing lighting, making it a cost-effective option for secure and flexible communication. Its ability to function without a direct line of sight improves mobility, making it useful for temporary setups, emergency response, and secure environments.

However, indoor FSO has limitations. Signals can weaken when they reflect off multiple surfaces, causing interference that slows down data transmission.

Eye safety regulations also limit transmitted power in the infrared spectrum, restricting overall system performance. Furthermore, high ambient noise levels, such as interference from sunlight or artificial lighting, can distort signal reception, reducing communication reliability and increasing the risk of data loss.⁸

The Future of FSO Communications

The increasing demand for high-speed, high-capacity communication is driving the growth of FSO, particularly as the Internet of Things expands to billions of connected devices. Its low latency, fast deployment, and resistance to interference make it well-suited for terrestrial, satellite, and secure indoor networks.

As 6G networks develop, rising bandwidth needs will push further advancements in FSO, reinforcing its role in next-generation communication systems.

For more on optical communication, satellite laser links, and space-based data transmission, explore these resources:

• The Future of Advanced Optical Filters in Satellite Communication Technologies
• Lunar Laser Communications and Atmospheric Discoveries: The LADEE Mission
• Optical Amplification in Quantum Communication Systems
• Optical Solitons in Optical Communication: Principles and Applications
• How is Laser Communication Used in Space?

References and Further Reading

1. Anbarasi, K., Hemanth, C., Sangeetha, R. G. (2017). A review on channel models in free space optical communication systems. Optics & Laser Technology. https://doi.org/10.1016/j.optlastec.2017.06.018
2. Dahrouj, H., Douik, A., Rayal, F., Al-Naffouri, T. Y., & Alouini, M. S. (2015). Cost-effective hybrid RF/FSO backhaul solution for next generation wireless systems. IEEE Wireless Communications. https://doi.org/10.1109/MWC.2015.7306543
3. Gu, Z., Zhang, J., Ji, Y., Bai, L., Sun, X. (2018). Network topology reconfiguration for FSO-based fronthaul/backhaul in 5G+ wireless networks. IEEE Access. https://doi.org/10.1109/ACCESS.2018.2880880
4. Elamassie, M., Uysal, M. (2023). Free Space Optical Communication: An Enabling Backhaul Technology for 6G Non-Terrestrial Networks. Photonics. https://doi.org/10.3390/photonics10111210
5. Foreman, A. (2024). Free Space Optics (FSO) and Light Fidelity (LiFi) Communications A Modern Day Transitional Crossroads by. [Online]. Available at: https://www.europeafrica.army.mil/Portals/19/documents/Eisenhower/2020/2nd%20Foreman.pdf?ver=15ea3Z0Z8zaa6J9W11YaUg%3D%3D
6. MARIE FREEBODY. (2023). Free-Space Optical Communications Soar with the Satellite Sector. [Online]. Available at: https://www.photonics.com/Articles/Free-Space_Optical_Communications_Soar_with_the/a68666
7. Yao, C. K., Lin, H. P., Cheng, C. L., Li, Y. L., Du, L. Y., Peng, P. C. (2024). Satellite communication and free space optics for open radio access network. Journal of Lightwave Technology, 42(10), 3546-3553. https://doi.org/10.1109/JLT.2024.3362696
8. Sharma, R., Aggarwal, M., Ahuja, S. (2016). Performance analysis of indoor FSO communication systems under receiver mobility. 2016 International Conference on Micro-Electronics and Telecommunication Engineering (ICMETE) (pp. 652-657). IEEE. https://doi.org/10.1109/ICMETE.2016.61

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