What are laser inter-satellite links?

How it works

Each satellite in a laser-linked network carries an optical communications terminal that sends and receives laser signals in place of a radio crosslink. NASA explains that an optical signal is a tight beam aimed straight at its receiver, whereas radio can be spread across a wide area. The agency lists higher data rates and smaller, lighter, lower-power terminals among the benefits.

Aiming is a central difficulty. NASA notes that an error of even a fraction of a degree can make the beam miss.

Standards and early systems

The U.S. Space Development Agency (SDA) publishes an Optical Communications Terminal Standard meant to let terminals from different vendors work together. Version 4.0.0, dated June 28, 2024, says the document was first published in early 2020 as an optical intersatellite link (OISL) standard. It says it was renamed because it also covers links to aircraft, ships and the ground. The standard defines a common pointing, acquisition and tracking procedure for aligning two terminals. It limits channels to the optical C-band between 1,530 and 1,565 nanometers. It specifies continuous two-way Ethernet at up to 2.5 gigabits per second (Gbps).

The European Space Agency says its European Data Relay System collects data from low-orbiting satellites through two geostationary nodes. It says its optical links reach up to 1,800 megabits per second. Its first node, EDRS-A, launched on January 29, 2016. NASA lists its Laser Communications Relay Demonstration, launched on December 7, 2021, as a 1.244 Gbps optical relay.

Where things stand in 2026

SDA says its Transport Layer, envisioned at 300 to more than 500 satellites, will be interconnected by optical links. On July 16, 2026, it announced the launch of 21 Tranche 1 satellites. The on-orbit total at that point reached 63 of a planned 154.

Kepler Communications said on August 24, 2026 that its optical data relay network, launched in January 2026, was delivering commercial service. It said its expanded constellation would carry terminals supporting up to 100 Gbps.

TechCrunch reported in February 2026 that the fastest off-the-shelf laser links reach about 100 Gbps. Google researchers wrote in November 2025 that orbital AI clusters would need links of tens of terabits per second. They reported a bench test that reached 800 Gbps each way. Google said its design would keep satellites kilometers or less apart. It said two prototype satellites were slated to launch by early 2027.