Photonics Dictionary

free-space optics

Free-space optics (FSO), also known as optical wireless communication or optical wireless networking, refers to the transmission of data using modulated beams of light through free space (air or a vacuum) rather than using physical cables or fiber optics. FSO systems leverage the principles of optical communication, similar to fiber optic communication, but they transmit signals through the atmosphere over relatively short distances.

Key features and aspects of free-space optics include:

Transmission medium: FSO systems use the atmosphere (free space) as the transmission medium. The communication links are typically established between two or more points with a clear line of sight, and they can operate in various weather conditions.

Laser technology: FSO systems typically use lasers or light-emitting diodes (LEDs) to generate optical signals that carry data. These signals are modulated to encode digital information, and they are transmitted as beams of light through the free space.

Line-of-sight communication: For optimal performance, FSO systems require a direct line of sight between the transmitter and receiver. Obstructions such as buildings, trees, or atmospheric conditions like heavy rain or fog can attenuate or block the optical signal.

High data rates: FSO systems are capable of providing high data rates, making them suitable for applications where a significant amount of data needs to be transmitted quickly. They are often used in urban areas for point-to-point communication links.

Security: FSO communication is generally considered secure because the optical signals are confined to a narrow beam and are challenging to intercept without direct line of sight.

FSO technology is commonly used in various applications, including:

Wireless backhaul: FSO can be used to establish high-capacity links between communication networks, such as connecting cell towers or data centers.

Last mile connectivity: FSO can provide high-speed data connectivity in the "last mile" to homes or businesses, especially in areas where laying traditional cables is challenging.

Temporary or emergency communication: FSO can be quickly deployed for temporary communication needs, such as during events or in emergency situations.


While FSO has advantages such as high data rates and quick deployment, its performance can be affected by atmospheric conditions. Technologies like adaptive optics are sometimes employed to mitigate the impact of atmospheric turbulence on the quality of the optical link.

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