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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 18, Iss. 9 — Apr. 26, 2010
  • pp: 8948–8962

Synergy of adaptive thresholds and multiple transmitters in free-space optical communication

James A. Louthain and Jason D. Schmidt  »View Author Affiliations

Optics Express, Vol. 18, Issue 9, pp. 8948-8962 (2010)

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Laser propagation through extended turbulence causes severe beam spread and scintillation. Airborne laser communication systems require special considerations in size, complexity, power, and weight. Rather than using bulky, costly, adaptive optics systems, we reduce the variability of the received signal by integrating a two-transmitter system with an adaptive threshold receiver to average out the deleterious effects of turbulence. In contrast to adaptive optics approaches, systems employing multiple transmitters and adaptive thresholds exhibit performance improvements that are unaffected by turbulence strength. Simulations of this system with on-off-keying (OOK) showed that reducing the scintillation variations with multiple transmitters improves the performance of low-frequency adaptive threshold estimators by 1-3 dB. The combination of multiple transmitters and adaptive thresholding provided at least a 10 dB gain over implementing only transmitter pointing and receiver tilt correction for all three high-Rytov number scenarios. The scenario with a spherical-wave Rytov number = 0.20 enjoyed a 13 dB reduction in the required SNR for BER’s between 10−5 to 10−3, consistent with the code gain metric. All five scenarios between 0.06 and 0.20 Rytov number improved to within 3 dB of the SNR of the lowest Rytov number scenario.

© 2010 OSA

OCIS Codes
(010.1290) Atmospheric and oceanic optics : Atmospheric optics
(010.1330) Atmospheric and oceanic optics : Atmospheric turbulence
(060.4510) Fiber optics and optical communications : Optical communications
(060.2605) Fiber optics and optical communications : Free-space optical communication
(070.7345) Fourier optics and signal processing : Wave propagation

ToC Category:
Atmospheric and Oceanic Optics

Original Manuscript: February 18, 2010
Revised Manuscript: March 29, 2010
Manuscript Accepted: April 7, 2010
Published: April 14, 2010

James A. Louthain and Jason D. Schmidt, "Synergy of adaptive thresholds and multiple transmitters in free-space optical communication," Opt. Express 18, 8948-8962 (2010)

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