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Proceedings Paper

Performance update of a terrestrial laser-communication link with quadrature amplitude modulation
Author(s): Penelope Polak-Dingels; Pierre R. Barbier; David W. Rush; David S. Glassner; Geoffrey L. Burdge
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Paper Abstract

In this paper we describe recent tests of a unidirectional laser communication link operating in strong atmospheric turbulence conditions, near ground level, over horizontal path distances up to 2.4 km. The source is a 1.3 micrometers Nd:YAG, diode-pumped laser which is fiber-coupled to an electro-optic modulator. The transmitter includes an active tip-tilt system which maintains rough link alignment and compensates for slow pointing drift. The transmitted light is collected by a 7 cm diameter receiver aperture and focused onto a InGaAs p-i-n photodetector. The receiver includes a CCD camera for coarse alignment of the link. The optical carrier is modulated by a 160 Mbps digital signal using quadrature amplitude modulation (QAM) at a subcarrier frequency of 140 MHz or by a 678 Mbps digital on-off keyed (OOK) signal. The link receiver includes an electronic automatic gain control circuit to compensate for atmospheric induced signal fading. The electronic test equipment at the transmitter and the receiver is connected through an RF ethernet link to enable automated measurements of symbol error rate as a function of optical power, modulation format, and energy-per-bit to noise-density ratio. We report on the measurement of bit error rates and demonstrate error- free operation of the communication link using 160 Mbps QAM over 0.9 km and 678 Mbps OOK modulation over 2.4 km under certain atmospheric conditions.

Paper Details

Date Published: 24 April 1997
PDF: 12 pages
Proc. SPIE 2990, Free-Space Laser Communication Technologies IX, (24 April 1997); doi: 10.1117/12.273712
Show Author Affiliations
Penelope Polak-Dingels, Univ. of Maryland/College Park (United States)
Pierre R. Barbier, Univ. of Maryland/College Park (United States)
David W. Rush, Univ. of Maryland/College Park (United States)
David S. Glassner, Univ. of Maryland/College Park (United States)
Geoffrey L. Burdge, Univ. of Maryland/College Park (United States)


Published in SPIE Proceedings Vol. 2990:
Free-Space Laser Communication Technologies IX
G. Stephen Mecherle, Editor(s)

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