One of the next big upgrades in telecom will involve satellites firing lasers at each other—to beam data, not blow stuff up.
The upside of replacing traditional radio-frequency communication with lasers, that encode data as pulses of light, can be much like that of deploying fiber-optic cable for terrestrial broadband: much faster speeds and much lower latency.
“Laser links in orbit can reduce long-distance latency by as much as 50%, due to higher speed of light in vacuum & shorter path than undersea fiber,” SpaceX founder Elon Musk tweeted in July about the upgrade now beginning for that firm’s Starlink satellite constellation.
The first batch of laser-equipped Starlink satellites went up to polar orbits in January, Musk confirmed January 24. Its most recent launch in early September featured version 1.5 spacecraft with the latest laser technology.
In a report posted April 5, the market-research firm MoffettNathanson called lasers essential to Starlink’s ambition of providing worldwide connectivity from its more than 1,500 satellites, even over oceans and the poles.
“The importance of linking satellites together cannot be overstated,” the note read. “Not only do interlinks enable sharing of capacity more efficiently by making use of otherwise wasted satellite capacity over regions without ground stations, they also enable the provision of service to areas where it is impossible to put a ground station.”
SpaceX may be getting the most attention for its use of optical communication, but multiple companies are developing laser systems to deploy on satellites and even in applications closer to Earth.
“Creating that ubiquitous mesh network connectivity is becoming more and more important right now,” said Tina Ghataore, chief commercial officer at Mynaric. That firm, with offices in Gilching, Germany, and Hawthorne, California, builds laser-optical terminals for use in satellites as well as in the air. “The commercial sector is seeing the value of incorporating this tech.”
Lasers can also provide immense bandwidth, thanks to advances in technology that allow more precise control of a beam.
“We routinely do 100 gigabits per second,” said Barry Matsumori, CEO of the Denver optical-communications firm BridgeComm. “We’re heading toward being able to do a terabit.”
Traditional radio-frequency links, he said, can’t keep up.
“If you really really need speed, like more than 10 gigs per second, RF starts falling apart,” Matsumori said. He added that we’re running out of frequencies to free up for broadband use: “RF spectrum, the usable part, is basically all allocated.”
Plus, lasers can be aimed precisely at a receiver, while radio broadcasts indiscriminately, making eavesdropping a much bigger risk.
MoffettNathanson’s early-April report also noted that laser links can require their own tradeoffs of weight, power consumption, and cost—”interlinking satellites with lasers is hard”—and noted that SpaceX had only launched 10 laser-equipped Starlink satellites at that point.
SpaceX did not answer an emailed request for the number of laser-equipped Starlinks in service, but if every launch to polar orbits so far featured them, the total would be 64 of the 1,428 in service.
In late August, SpaceX chief operating officer Gwynne Shotwell allowed that the need to add laser hardware to Starlink satellites had led to a slowdown in launches. Speaking at the Space Symposium conference in Colorado Springs, Colorado, according to a recap in the trade journal Via Satellite, Shotwell also called the laser terminals “expensive” but said its in-house hardware was much less so than terminals from outside vendors.
Ghataore says that Mynaric is out to quash the idea “that laser comm is this boutique product.” The company aims to bring its per-satellite cost below $1 million when its terminals are purchased in bulk for a constellation of hundreds of spacecraft.
DARPA is also running a separate program to advance laser datalinks called Space-Based Adaptive Communications Node . . . and yes, that Arlington, Virginia, agency abbreviates it to “Space-BACN.”
Meanwhile, back on Planet Earth
Ghataore and Matsumori both advise against expecting too much out of laser communication at ground level—as Matsumori puts it, “The nemesis of optical communications with laser is atmospherics”—but a project from X, Alphabet’s research arm focused on “moonshots,” recently reported success on that front. Project Taara, building on lessons learned from X’s Project Loon attempt at broadband via high-tech balloons, set up a laser link between the African cities of Brazzaville and Kinshasa, on opposite sides of the Congo River, that previously were connected only via fiber that took a 400-kilometer detour around that wide and deep river.
In a September 16 post, Taara engineering director Baris Erkmen wrote that in 20 days, this optical link had delivered nearly 700 terabytes of data at speeds of up to 20 Gbps over 4.8 kilometers “with 99.9% availability.”
Erkman credited such advances as more precise, pointing and tracking, and smarter automatic adjustment of transmission power for allowing the system to ride out such complications as weather, birds, and, “monkeys jostling Taara’s terminals” during earlier tests.
Sending lasers into Low Earth orbit may be much harder than deploying them in one of Africa’s largest cities, but it also allows them to avoid Earthbound hazards, such as curious monkeys. So watch that (ahem) space.