Reviewed by Lexie CornerSep 9 2024
Researchers at Optica have utilized plasmonic modulators, which employ unique light waves called surface plasmon polaritons to control and manipulate optical signals, to achieve data rates of up to 424 Gbit/s over a 53-km turbulent free-space optical link. This new study lays the foundation for high-speed optical communication links that transmit data across open spaces or through the air.
Experimental setup of the FSO outdoor experiments. Tunable laser source (TLS), driving amplifier (DA), arbitrary waveform generator (AWG), transmitter digital signal processing (Tx-DSP), erbium-doped fiber amplifier (EDFA), bandpass filter (BPF), optical spectrum analyzer (OSA), polarization division multiplexing emulator (PDM), high power optical amplifier (HPOA), real-time controller (RTC), deformable mirror (DFM), wafefront sensor (WFS), optical power meter (OPM), local oscillator (LO), balanced photodetector (BPD), digital storage oscilloscope (DSO), receiver digital signal processing (Rx-DSP). Image Credit: Laurenz Kulmer, ETH Zurich
Free-space optical communication networks have the potential to enhance space exploration. They can transmit data at high speeds and large capacities with lower latency and interference compared to traditional radio frequency systems. This could lead to better connectivity, more efficient data transfer, and improved capabilities for space missions.
Laurenz Kulmer of the Leuthold group will present the study at ETH Zurich during the Frontiers in Optics + Laser Science (FiO LS) conference, which will be held at the Colorado Convention Center in Denver from September 23 to 26, 2024.
High-speed free-space transmission is an option to connect the world, or it may serve as a backup if underwater cables break. Nevertheless, it is also a step towards a new cheap high-speed internet that may connect all locations across the world. This way it may contribute towards a stable, high-speed internet for millions of people who are currently unconnected.
Laurenz Kulmer, Leuthold Group, ETH Zurich
With their compact design, ability to operate at high speeds across a wide temperature range, and low energy consumption, plasmonic modulators are ideal for space communication links.
In outdoor free-space optical experiments, the researchers achieved data rates of up to 424 Gbit/s below a 25 % soft-decision forward error correction (SD FEC) threshold—the level at which errors in transmitted data can still be corrected despite noise or interference. In experiments using a plasmonic IQ modulator in a standard fiber system, an even higher throughput of up to 774 Gbit/s per polarization (pol) was achieved while maintaining the same 25 % SD FEC threshold.
Based on these results, the researchers suggest that combining coherent free-space optical communication with plasmonic modulators could significantly boost overall throughput, potentially reaching peak speeds of 1.4 Tbit/s. Their findings also show that operating free-space optical links at maximum speeds, as opposed to lower speeds and higher-order modulation formats, provides significant advantages.
The researchers further state that, with continued advancements in device design and photonic integration, it should be possible to achieve polarization multiplexing data rates exceeding 1 Tbit/s per polarization channel.
Kulmer concluded, “In a next step, we are going to test the long-term reliability of our devices. High-speed performance has been shown, but we have to make sure they can operate for years to come in the harshest of environments, space.”