AS SKIERS SCHUSSED AND SWERVED in a snow park outside Beijing during the 2022 Winter Olympics, a few may have noticed a string of towers along the way. Did they know that those towers were collecting wavelengths across the spectrum and scouring the data for signs of suspicious movement? Did they care that they were the involuntary subjects of an Internet of Things–based experiment in border surveillance?
This summer, at the Paris Olympic Games, security officials will perform a much bigger experiment in the heart of the City of Light, covering the events, the entire Olympic village, and the connecting roads and rails. It will proceed under a temporary law allowing automated surveillance systems to detect “predetermined events” of the sort that might lead to terrorist attacks.
Researchers at the University of Sydney have combined a photonic filter and modulator on a single chip in a way that allows them to precisely detect signals across a wide band of radiofrequency (RF) spectrum. The work brings photonic chips one step closer to one day potentially replacing bulkier and more complex electronic RF chips in fiber optic networks.
The Sydney team exploited stimulated Brillouin scattering, a technique which involves converting electrical fields into pressure waves in certain insulators, such as optical fibers. In 2011, the researchers reported that Brillouin scattering held potential for high-resolution filtering, and developed new manufacturing techniques to combine a chalcogenide Brillouin waveguide on a silicon chip. In 2023, they managed to combine a photonic filter and modulator on the same type of chip. The combination gives the experimental chip a spectral resolution of 37 megahertz and a wider bandwidth than preceding chips, the team reported in a paper published 20 November in Nature Communications.
VLEO refers to orbits between about 100 kilometers and 300 or 400 km (although the exact range depends on who you ask), in contrast to LEO, which starts around 300 or 400 km and extends up to 2,000 km. The first satellites in VLEO were short-lived US spy satellites in the 1960s and 1970s, which dropped their film payloads for mid-air capture by aircraft. It’s probable that their descendants are still dipping into VLEO.
Before architect César Martín Gómez could send his latest thermoelectric experiment to Antarctica in 2018, he had to make sure that soldiers from the Spanish Army could get it right on the first try. In the laboratory, he could always run the experiment—a scale model of a solid-state thermoelectric heater—a second time if it needed troubleshooting.
But at Spain’s Gabriel de Castilla base in the South Shetland Islands, soldiers would be too busy running other civilian experiments to troubleshoot Martín’s for him if it failed. And in a place like Antarctica, the goal of his experiment—providing efficient heat from direct current electricity—was both important and difficult. The experience “forced us to make a jump in quality,” recalls Martín, who is a professor at the University of Navarra in Pamplona, Spain.