Wider Use of Satellite Laser Links Expected
Optical inter-satellite links are on the cusp of widespread use in low earth orbit satellite constellations, with adoption by SpaceX (see 2101270048) and with Telesat a part of a growing wave of use, satellite industry players and observers told us. One selling point is the lack of regulation and regulatory issues, they said.
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OISL use by Telesat's planned Lightspeed constellation (see 2102090015) "will be a competitive differentiator," said Telesat Vice President-LEO Erwin Hudson. "we expect future LEO constellations to follow Telesat’s lead and incorporate OISLs in their future generation satellites."
Inter-satellite laser links command "real technological benefits over RF," said Sven Meyer-Brunswick, chief operating officer of German laser communications company Mynaric. He said satellite operators such as Viasat also are discussing OISL. He said it's difficult to see how other broadband mega constellations could forgo laser for backhaul if SpaceX and Telesat offer higher bandwidths and lower latencies. The Space Development Agency and Defense Advanced Research Projects Agency are moving toward deployment of LEO networks for DOD that will use laser communication, he said.
Citing the proliferation of announced LEO constellations, California State University-Dominguez Hills information systems professor Larry Press said companies "that survive will all have them" because they reduce latency and hugely reduce ground infrastructure. He said geostationary satellite operators might also employ OISLs to communicate with LEOs in mesh networks.
Supporters consider OISL tech mature. German laser communications company Tesat has 10 laser communication terminals in space and performs 20 OISL operations a day, said Matthias Motzigemba, head of sales-laser communication.
Telesat's Hudson said it looked at optical and microwaved inter-satellite link technologies early in Lightspeed's design and development and opted for optical because of physical size, mass, power consumption, performance and cost. Even for 1 Gbps, he said, a microwave inter-satellite link needs an antenna close to a meter in diameter, which is "much too big and heavy for a LEO satellite."
Lightspeed's OISL use will let it "connect any point on earth to any other point on earth without transiting other networks and without intermediate hops to the ground and back, a level of security that ground systems cannot provide," Hudson said. "We can provide aircraft and ships at sea with continuous uninterrupted service anywhere in the skies and across the oceans without building earth stations in remote or hostile locations."
Hudson said Telesat has worked with Thales Alenia Space for more than four years to develop the Lightspeed OISL terminals. "The design is quite mature at this point, and the Thales ... team is ready for final design reviews, followed by the start of manufacturing," he said.
Tesat's Motzigemba said routing data traffic between satellites and keeping it in space is more economical than high numbers of ground stations for constellations of more than 10 satellites. He said that unlike RF communications, OISLs are jam resistant, have giga- or terabit bandwidth and lower footprints in size, weight and power.
Mynaric's Meyer-Brunswick said the physics of lasers enables higher bandwidths than RF while being "nearly impossible to jam or tap." The record for millimeter-wave technology is 40 Gbps, but it's more than 13,000 Gbps for laser communication, he said. The first OISL dates back to 2001 and European Space Agency experiments, but widespread deployment has been slow due to "a historic approach of one-off highly expensive units to prove technology." He said Mynaric focused on serial production, and the company is moving from initial preproduction "into fuller production capabilities to start to address this need."
OISLs don't need satellite licensing, Telesat's Hudson said. "We do not anticipate regulatory issues associated with our use of OISLs," he said. "Optical terminals have very narrow beams that minimize interference. With a constellation of LEO satellites, orbital dynamics and satellite-to-satellite pointing are such that possible interference between Lightspeed OISLs and other constellations is negligible." Tesat's Motzigemba agreed OISLs aren't regulated "due the very narrow beam-diameter with no harmful interference."
"As a general matter, the FCC doesn’t have any rules specific to these laser communications -- though many applicants do provide that info in their applications," an FCC spokesperson said.