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Proceedings Paper

Experimental comparison of 3-mode and single-mode coupling over a 1.6-km free-space link
Author(s): D. J. Geisler; T. M. Yarnall; G. Lund; C. M. Schieler; M. L. Stevens; N. K. Fontaine; B. S. Robinson; S. A. Hamilton
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Paper Abstract

Free-space optical communications links have the perpetual challenge of coupling light from free-space to a detector or fiber for subsequent detection. It is especially challenging to couple light from free-space into single-mode fiber (SMF) in the presence of atmospheric tilt due to its small acceptance angle; however, SMF coupling is desirable because of the availability of extremely sensitive digital coherent receivers developed by the fiber-telecom industry. In this work, we experimentally compare three-mode and single-mode coupling after propagating through 1.6 km of free-space with and without the use of a fast-steering mirror (FSM) control loop to mitigate atmospherically induced tilt. Here, the 3-mode fiber is a 3-mode photonic lantern multiplexer (PLM) that passively couples light into three SMF outputs. With the FSM control loop active, coupling into the PLM and the SMF yielded nearly identical coupling efficiencies, as expected. Experimental results with the FSM control loop off show that coupling from free-space to PLM increases the average power received, and mitigates the negative impacts of tilt-induced fading relative to coupling directly to SMF.

Paper Details

Date Published: 15 February 2018
PDF: 10 pages
Proc. SPIE 10524, Free-Space Laser Communication and Atmospheric Propagation XXX, 105240H (15 February 2018); doi: 10.1117/12.2294039
Show Author Affiliations
D. J. Geisler, MIT Lincoln Lab. (United States)
T. M. Yarnall, MIT Lincoln Lab. (United States)
G. Lund, MIT Lincoln Lab. (United States)
C. M. Schieler, MIT Lincoln Lab. (United States)
M. L. Stevens, MIT Lincoln Lab. (United States)
N. K. Fontaine, Nokia Bell Labs (United States)
B. S. Robinson, MIT Lincoln Lab. (United States)
S. A. Hamilton, MIT Lincoln Lab. (United States)

Published in SPIE Proceedings Vol. 10524:
Free-Space Laser Communication and Atmospheric Propagation XXX
Hamid Hemmati; Don M. Boroson, Editor(s)

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