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13 February 2008 Direct-detection free-space laser transceiver test-bed
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NASA Goddard Space Flight Center is developing a direct-detection free-space laser communications transceiver test bed. The laser transmitter is a master-oscillator power amplifier (MOPA) configuration using a 1060 nm wavelength laser-diode with a two-stage multi-watt Ytterbium fiber amplifier. Dual Mach-Zehnder electro-optic modulators provide an extinction ratio greater than 40 dB. The MOPA design delivered 10-W average power with low-duty-cycle PPM waveforms and achieved 1.7 kW peak power. We use pulse-position modulation format with a pseudo-noise code header to assist clock recovery and frame boundary identification. We are examining the use of low-density-parity-check (LDPC) codes for forward error correction. Our receiver uses an InGaAsP 1 mm diameter photocathode hybrid photomultiplier tube (HPMT) cooled with a thermo-electric cooler. The HPMT has 25% single-photon detection efficiency at 1064 nm wavelength with a dark count rate of 60,000/s at -22 degrees Celsius and a single-photon impulse response of 0.9 ns. We report on progress toward demonstrating a combined laser communications and ranging field experiment.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Michael A. Krainak, Jeffrey R. Chen, Philip W. Dabney, Jeffrey F. Ferrara, Wai H. Fong, Anthony J. Martino, Jan F. McGarry, Stephen M. Merkowitz, Caleb M. Principe, Xiaoli Sun, and Thomas W. Zagwodzki "Direct-detection free-space laser transceiver test-bed", Proc. SPIE 6877, Free-Space Laser Communication Technologies XX, 687703 (13 February 2008);


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