G&H, a leader in space photonics, takes immense pride announcing the groundbreaking research published in Optics Letters. This pioneering work, a collaborative effort between G&H, Thales Research and Technology Palaiseau, and Thales Alenia Space Toulouse, introduces “Optical Coherent Combination of High-Power Optical Amplifiers for Free-Space Optical Communications.”

Free Space Optical Communications

Feeder Free Space Optical Communication (FSOC) links serve as high-capacity channels for transmitting data within a network of space assets, often involving geostationary satellites positioned at significant distances from Earth. FSOC holds great potential for the future of satellite communication.

Given the exceptional data rates and vast distances between satellites, robust amplification of telecom signals is crucial. High power amplification is necessary due to the remarkably low probability to signal carrying photons successfully reaching their intended destination – the huge distances meaning as little as 1 in 100,000,000 sent photons are received.

FSOC links:

• Utilize laser light to transmit significantly more data than conventional radio frequencies allow
• Benefit from wide optical bands
• Are exempt from frequency regulation
• Seamlessly integrate with terrestrial networks

FSO links offer a promising solution for transmitting data between satellites and optical ground stations (OGS).

The Challenge: Optical Feeder Uplinks

A significant challenge arises when it comes to the optical feeder uplink – generating powerful enough optical carriers to transmit communication signals from OGS to geostationary satellites. Achieving high data rates, exceeding terabits per second, requires increasing the optical output power at OGS beyond currently available levels.

This study enables multi-gigabits per second data transfer at power levels within the 100W range in the C-band, with minimal performance penalties related to the generation of the very high powers utilized. The research employs two of G&H’s 50W C-band amplifiers, highlighting the potential of G&H’s technology for the next generation of high-power, high-throughput ground-to-space feeder FSOC links.

The research team used two methods to achieve very high optically powers. First, by directly leveraging G&H’s leading very high-power amplifier technology, and second, by harmonizing the outputs of two amplifiers through a process termed coherent combination. Coherent combination is where multiple sources/amplifiers are utilized in a manner that is akin to using a single source/amplifier, such that little beam quality degradation occurs. This is achieved via locking the relative phase of the sources/amplifier over time.

Summary

The paper demonstrates two world firsts - the highest power transmitted directly from an amplifier at a telecoms wavelength, whilst preserving a high data rate telecoms signal (25 Gb/s at 50W). Secondly the highest power output from a coherently combined source at telecom wavelengths whilst maintaining a high-speed telecom signal (25 Gb/s at 80W). The work introduces a state-of-the-art coherent beam combining (CBC) system with potential applications in long-range free space optical (FSO) communications, specifically ground-to-space feeder links.

Matthew Welch, Chief Engineer of Fiber Optic Systems for G&H stated, “Being part of this project has been truly rewarding. We have demonstrated that G&H’s amplifier technology is future ready, and that G&H is paving the way for transformative applications in long-range free space optical communications, including vital ground-to-space feeder links.”