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s We present a study of micro air vehicles (MAVs) with wingspans of 7.4 to 15 cm. Potential applications for MAVs, both military and civilian, are numerous. For most military applications, MAVs would be controlled by local users, operating covertly, to supply real-time data. This article focuses on a military surveillance application that uses either… (More)
—Optimal joint detection for interfering (nonorthog-onal) users in a multiple access communication system has, in general, a computational complexity that is exponential in the number of users. For this reason, optimal joint detection has been thought to be impractical for large numbers of users. A number of suboptimal low-complexity joint detectors have… (More)
We report the first demonstration of a near quantum-limited optical homodyne PSK receiver combined with powerful forward-error-correction coding, achieving 1.5 photons/bit sensitivity, within 4.5 dB of the Shannon limit. Phase-locking was achieved at 1.55 microm using an analog dither-based optical phase-locked loop with an external phase modulator.… (More)
In this paper we present a design for a photoncounting optical receiver—based on superconducting NbN nanowire detector arrays—that will be employed in the ground terminal for the NASA Lunar Laser Communications Demonstration. The ground receiver is designed with four, 40 cm apertures, each coupled to a novel multi-mode polarization-maintaining… (More)
We propose and demonstrate a scalable high-sensitivity approach for achieving multi-rate DPSK using a single transmitter and fixed-interferometer-receiver design. Near-theoretical real-time performance is demonstrated over static and fading channels at rates from 2.4Mbps to 2.5Gbps.
We describe a simple 4-PPM demodulator that uses analog delay lines and simple 1-bit comparators to determine the least-significant bit and most-significant bit of the 4-PPM encoded data without additional digital signal processing. We show that with good optical filtering the comparator-based demodulator can theoretically operate with sensitivity only 0.23… (More)
Frequency shift keyed (FSK) modulation formats are well-suited to deep space links and other high loss links. FSK's advantage comes from its use of bandwidth expansion. I.e., FSK counteracts power losses in the link by using an optical bandwidth that is greater than the data rate, just as pulse position modulation (PPM) does. Unlike PPM, increasing FSK's… (More)
We designed and successfully demonstrated a multimode fiber-coupled photon-counting optical receiver at 1550 nm for the Lunar Laser Communications Demonstration that achieves low coupling loss through atmospheric turbulence without requiring adaptive optics.