1M. Atmospheric and fog attenuation, which are exponential in nature, limit practical range of FSO devices to several kilometres. However, free-space optics based on 1550 nm wavelength, have considerably lower optical loss than free-space optics using 830 nm wavelength, in dense fog conditions. FSO using wavelength 1550 nm system are capable of transmitting several times higher power than systems with 850 nm and are safe to the human eye (1M class). Additionally, some free-space optics, such as EC SYSTEM, ensure higher connection reliability in bad weather conditions by constantly monitoring link quality to regulate laser diode transmission power with built-in automatic gain control. See also Atomic line filter#Laser tracking and communication Extremely high frequency KORUZA Laser safety Mie scattering Modulating retro-reflector N-slit interferometer Optical window Radio window Rayleigh scattering Free-space path loss References Further reading Master's Thesis External links Free Space Optics on COST297 for HAPs Explanation of Fresnel zones in microwave and optical links International Space Station to Beam Video Via Laser Back to Earth, March 2014 NASA's Optical Payload for Lasercomm Science demonstration mission to the ISS Wireless Optical Link Budget (with python examples). Laser communication in space Optical communications Telecommunications equipment Wireless communication systems Optical wireless interfaces