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Coherent optical array receiver for PPM signals under atmospheric turbulence

Citation

Munoz Fernandez, Michela (2006) Coherent optical array receiver for PPM signals under atmospheric turbulence. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-05252006-221314

Abstract

The performance of a coherent free-space optical communications system operating in the presence of turbulence is investigated. Maximum Likelihood Detection techniques are employed to optimally detect Pulse Position Modulated signals with a focal-plane detector array and to reconstruct the turbulence-degraded signals. Laboratory equipment and experimental setup used to carry out these experiments at the Jet Propulsion Laboratory are described. The key components include two lasers operating at 1064 nm wavelength for use with coherent detection, a 16 element (4 X 4) InGaAs focal-plane detector array, and a data-acquisition and signal-processing assembly needed to sample and collect the data and analyze the results. The detected signals are combined using the least-mean-square (LMS) algorithm. In the first part of the experimental results we show convergence of the algorithm for experimentally obtained signal tones in the presence of atmospheric turbulence. The second part of the experimental results shows adaptive combining of experimentally obtained heterodyned pulse position modulated (PPM) signals with pulse-to-pulse coherence in the presence of simulated spatial distortions resembling atmospheric turbulence. The adaptively combined PPM signals are phased up via an LMS algorithm suitably optimized to operate with PPM in the presence of additive shot noise. A convergence analysis of the algorithm is presented, and results with both computer-simulated and experimentally obtained PPM signals are analyzed. The third part of the experimental results, in which the main goal of this thesis is achieved, includes an investigation of the performance of the Coherent Optical Receiver Experiment (CORE) at JPL. Bit Error Rate (BER) results are presented for single and multichannel optical receivers where quasi shot noise-limited performance is achieved under simulated turbulence conditions using noncoherent postdetection processing techniques. Theoretical BER expressions are compared with experimentally obtained BER results, and array combining gains are presented. BER results are shown as a function of signal-to-noise ratio (SNR), photons per symbol, and photons per bit (PPB).

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:adaptive algorithms; coherent array receiver; deep space laser communications; shot noise
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Electrical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Hassibi, Babak
Thesis Committee:
  • Hassibi, Babak (chair)
  • Yang, Changhuei
  • Elachi, Charles
  • Mabuchi, Hideo
  • Mukai, Ryan
  • Vilnrotter, Victor
  • Psaltis, Demetri
Defense Date:19 December 2005
Author Email:michelamz (AT) gmail.com
Record Number:CaltechETD:etd-05252006-221314
Persistent URL:http://resolver.caltech.edu/CaltechETD:etd-05252006-221314
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2061
Collection:CaltechTHESIS
Deposited By: Imported from ETD-db
Deposited On:31 May 2006
Last Modified:10 Dec 2014 20:15

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