FreeSpaceOptics

Free-space optics (FSO) refers to the wireless transmission of data using light traveling through free space, such as air or vacuum, rather than through an optical fiber. The system typically uses infrared or visible wavelengths and establishes a line-of-sight link between a transmitter and a receiver, often over urban or campus distances.

How it works: A transmitter converts electrical signals into a modulated light beam emitted by a laser diode or LED. The beam is directed through the atmosphere to a sensitive photodetector at the receiver, which converts the light back into an electrical signal. Modern FSO links employ pointing, acquisition, and tracking systems to maintain alignment, especially in mobile or windy environments. Common modulation schemes include simple on-off keying and more advanced formats with forward error correction to improve reliability. Data rates span from Mbps to several Gbps depending on optics, distance, and weather conditions.

Advantages and limitations: FSO offers high bandwidth with unlicensed optical spectrum, low latency, and minimal radio frequency interference. The narrow beam provides security advantages and straightforward deployment for building-to-building, campus, and backhaul links. However, performance is sensitive to weather (fog, rain, snow), atmospheric turbulence, and daylight noise. The requirement for line-of-sight and precise alignment, plus practical range limitations, can impact reliability compared with fiber or RF systems.

Applications and standards: FSO is used for urban backhaul, last-mile connectivity, disaster recovery, temporary networks, and airline or space-relayed links in some cases. Eye-safety considerations govern equipment design, with compliance to relevant safety standards. International guidance often covers optical wireless performance, safety, and certification, depending on the application and jurisdiction.

Future directions: Ongoing work includes improving link reliability with adaptive optics, multi-channel WDM approaches, advanced modulation and coding, and integration with wireless networks to form hybrid RF/FSO solutions.