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We discuss an optical ground terminal receiver architecture based on multi-aperture digital coherent combining. Experimental results using four receivers demonstrate lossless coherent combining in the laboratory at power levels below 0.1 photons/bit/receiver, and mitigation of scintillation through a 3.2-km free-space link due to spatial diversity.
We report a demonstration of narrow-beam laser communication through the waters of Narragansett Bay in Rhode Island, USA. The transmitter and receiver were mounted on an aluminum truss and placed in the water alongside a pier operated by the Naval Undersea Warfare Center. The transmitter consisted of a real-time modulator and encoder, a 515 nm wavelength commercial laser, collimating optics, and a...
Undersea laser communications represent a promising area of research with a large set of applications. Wide dynamic range receivers are necessary to operate through a range of possible water qualities and link distances. In the signal-starved regime, photon-counting photomultiplier tubes (PMTs) are a key technology for high-sensitivity communications. When more signal is available, linear avalanche...
Robust clock recovery is essential for optical receivers that can operate over a wide range of data rates. The multi-rate burst-mode DPSK format that is finding applications in NASA’s Laser Communications Relay Demonstration (LCRD) leverages a single optically-preamplified receiver that can maintain nearly theoretical performance for data rates spanning more than two orders of magnitude. Clock recovery...
We demonstrate an average-power-based technique for aligning data and clock signals in consolidated tri-state multi-rate burst-mode DPSK transmitters with a simple and low-SWaP implementation.
Optical communications provides an attractive means of achieving wideband data transfer over long distances. We review perceived challenges and enabling technology developments that promise to facilitate a new era of free-space laser communications.
We demonstrate phase modulation, pulse carving, and burst-mode windowing in a single Mach-Zehnder modulator, significantly reducing size, weight, power, and complexity of prior three-modulator designs with only 0.6-dB additional performance penalty.
We demonstrate the potential for 1.85 Mbit/s secure key rates over 101 km of fiber, >100 times faster than previously demonstrated, using the differential phase shift quantum key distribution protocol and superconducting nanowire single-photon detectors.
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