Adaptive Transceivers for Mobile Free-space
Optical Communications
July 2006
Jeffrey R. Minch, The MITRE Corporation
David R. Gervais, The MITRE Corporation
Daniel J. Townsend, The MITRE Corporation
ABSTRACT
Free-space optical (FSO) communication links
are susceptible to a tremendous amount of variability
and offer a real challenge for efficient, robust system design.
Whether changes in link margin are predictable
(i.e. weather conditions or mission profiles) or truly random
(i.e. atmospheric turbulence induced scintillation or
boundary layer induced tracking errors), FSO communication
systems will experience a large dynamic range of
performance through most mission scenarios. Recent system
designs within commercial, academic, and military organizations
have focused on leveraging COTS technology
from the fiber optic telecommunications industry. These
systems are typically based on fixed designs that use set
data rates and modulation formats. Utilizing such modalities
in a mobile free-space environment can lead to systems
that are either overly conservative or have a high rate
of failure. To maximize overall system efficiency, we propose
a transceiver architecture with rate and modulation
agility. The presented transceiver is built with COTS components,
supports data rate adjustability, and can switch
modulation formats between Differential Phase-Shift Keying
(DPSK), Binary Pulse-Position Modulation (BPPM),
and On-off-Keying (OOK). A prototype system illustrating
adaptive operation is presented and experimental results
are shown.
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