Phlux Technology, a producer of avalanche photodiode (APD) infrared sensors, has partnered with Airbus Defence and Space and The University of Sheffield on a €500,000 initiative to develop more efficient free space optical communications (FSOC) satellite terminals. This project, funded by the European Space Agency (ESA), aims to achieve reliable 2.5 Gbps communication with Low Earth Orbit (LEO) satellites at a wavelength of 1550 nm. These satellites orbit the Earth at altitudes of up to 2000 km. The long-term goal is to create links capable of operating at 10 Gbps.
Central to this project are Phlux’s Noiseless InGaAs avalanche photodiodes (APDs), which serve as infrared sensors in FSOC receivers. These APDs are anticipated to provide 6 dBm greater sensitivity than conventional InGaAs APDs operating at 1550 nm. This enhanced sensitivity enables the detection of much lower signal levels, facilitating the development of faster, higher bandwidth links with low latency. Additionally, they maintain performance for extended periods as the link integrity remains stable over a wider angle during the satellite’s overhead passage.
A technical challenge in FSOC is the diffraction of infrared signals as they pass through the troposphere, the Earth’s closest atmospheric layer. Variations in air temperature, humidity, and turbulence in the atmosphere cause fluctuations in the infrared signal’s intensity and angle of incidence. This results in the beam wandering over the signal detector area, limiting performance. The project addresses this by developing a large-area, high-sensitivity APD to create a wider receptor.
The radiation-hard detector module being developed also has potential applications in space debris monitoring, greenhouse gas detection, and space navigation.
Ben White, Phlux Technology CEO, said: “This project is an endorsement of the value of our patented APD technology developed at The University of Sheffield. With more than an order-of-magnitude improvement in sensitivity over traditional devices, we offer the enabling component that makes other technology breakthroughs possible. Higher performance FSOC links are a perfect example and it’s exciting to be working with such prestigious organisations as ESA and Airbus Defence and Space.”
Ludovic Blarre, leading Airbus Space Systems optical communication roadmap said: “The availability of APD products at 1550 nm for optical communication with sensitivities close to those of fibered low noise optical amplifiers could be a game changer for the development of cost-effective laser terminals and optical ground stations. This will be an enabler for the rapid development of optical communication in satellites for direct-to-earth applications and inter-satellite links with data rates below 10Gbps. Our team is delighted to work with Phlux Technology and the University of Sheffield towards this goal and to carry out irradiation tests on their patented APD technology.”
Professor Chee Hing Tan from the University of Sheffield added, “This is a very challenging and exciting project that will provide opportunities for our team to extend our patented technology to an exciting new application in FSOC. Working with ESA we hope to provide a disruptive technology that will accelerate the adoption of satellite to ground FSOC.”
As the demand for bandwidth exceeds the capabilities of radio frequency systems, the FSOC market is projected to reach $4.8 billion by 2031, with a compound annual growth rate (CAGR) of 31.3%, according to Allied Market Research.
The first phase of the project will run until the end of September 2025.
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