For decades, global communications relied on radio frequency (RF) signals sent to and from Earth and satellites orbiting around 35,000 kilometres above. This slow and costly method was largely replaced in the late 1990s by an extensive optical fibre cable network running across oceans and continents, enabling the high speed communications many of us enjoy today. In fact, optical fibres were crucial for the deployment of the internet and, until recently, have been seen as a viable option for the future. However, a new approach shows promise to effectively bring the Earth’s global communications strategy full circle: free space optical communications, involving thousands of satellites linked to ground stations – and each other – by gossamer laser beams.
Laser-sharp comms
Laser-guided communication can carry significantly more information compared to RF transmissions, using less power and offering higher security, since the laser is highly focused and difficult to intercept. It also carries a lower risk of interference, as signal propagation is direct. This has the potential to deliver high speed internet to every corner of the world, and keep up with the ever-increasing transmission of data from a host of applications, from social media and streaming platforms to the ‘Internet of Things’ and personalised medicine. Faster communication is also crucial for deep space exploration, as it will be necessary to make mission-critical decisions across vast distances in planned future missions.
Good vibrations
This breakthrough approach doesn’t come without its challenges, and pointing solutions are required to keep the laser beam exactly on the target over large distances, especially in Earth-to-satellite communication, where atmospheric turbulence can shift the beam from its original path. Furthermore, a sophisticated stabilisation system is needed on the receiving end to account for the vibrations of the satellite. Piezoelectric or electromagnetic fast steering mirrors (FSMs) offer a means to compensate for these disturbances, and ensure the laser beam hits the target receiver precisely. To this end, Physik Instrumente (PI) has developed a fast piezo tip/tilt steering mirror platform, an instrument that has already been launched into space on the Solar Orbiter, where it functioned at extreme temperatures in a high vacuum. Piezo-driven FSMs are compact and effective at dealing with disturbances, providing angular resolution in the nanoradian range with excellent bandwidth.
PI’s FSM technologies have been widely used in both terrestrial and space-based testing, as well as in various bona fide applications. To discover PI’s laser beam stabilisation products, or to enquire about its confidential custom offerings, click here
