It wasn’t long after the laser was invented in the early ’60s that many began speculating about the use of coherent light in communications. That would eventually come to fruition with the emergence of the first fiber optic telecommunication networks in the closing years of the 20th century. But developing a comparable space-based optical communications network capable of transmitting terabits of data proved more challenging, and only recently have the technology, components and economies of scale converged for successful proof-of-concept demonstrations. Don Boroson of MIT Lincoln Laboratories has been a central figure in moving free-space laser communications from concept to reality, having worked on the architecture of the first space-to-ground laser communication system in 2001 and, more recently, on the NASA-sponsored Mars Laser Communications Demonstration study team. In “Free-Space Optical Communications Comes of Age” (read article), Boroson examines the evolution in transmitters and receivers, and highlights recent breakthroughs that include the European Data Relay System from the European Space Agency (ESA) and the Lunar Laser Communication Demonstration, a joint project between MIT’s Lincoln Laboratory and NASA. Elsewhere in the magazine: • Optical sensors for ophthalmic diagnostics, skin cancer detection and biometrics are smaller and more robust than ever. Don’t miss “Added Intelligence Transforms Medical Sensors Into Diagnostic Devices,” by Contributing Editor Marie Freebody (read article). • Superluminescent LEDs may be less well-known than their LED and laser diode cousins, but their short temporal coherence makes them well-suited for imaging applications and use within fiber optic pressure sensors. Be sure to read Christian Velez’s “Superluminescent LEDs Bridge the Gap” (read article). • In “A Breakthrough for Reference-Free Holography” (read article), KyeoReh Lee and YongKeun Park of the Korea Advanced Institute of Science and Technology discuss the use of a single-unit camera that incorporates an optical diffuser to capture holograms. Instead of using conventional optical lenses, diffusers such as frosted glass can extract light intensity and phase information from a single image, without a reference light. • For more than 40 years, the red “Danger” sign served as a strong warning that high-power lasers were in use. Guidance from the American National Standards Institute in 2014 called for the use of the word “Warning” as the signal word, replacing “Danger” in some instances. Ken Barat examines the change in “Laser Safety Sign Changes Cause Confusion,” (read article). • This month’s special section examines the fiber optics market, from telecommunications to seismic monitoring for the oil and gas industries. The “Fiber Optics Evolution” from Senior Editor Justine Murphy (read article). Enjoy the issue!