Development and characterization of a direct detection fiber optic distributed acoustic sensor
Author
Uyar, Faruk
Advisor
Özbay, Ekmel
Date
2018-09Publisher
Bilkent University
Language
en_US
Type
ThesisItem Usage Stats
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Abstract
Phase-sensitive optical time domain re ectometer (ø-OTDR) based distributed
acoustic sensor (DAS) systems have attracted increasing attention in recent years
due to their remarkable advantages in a wide range of industrial and military applications
such as health monitoring and security of civil infrastructures, railways,
oil and gas pipelines, borders, and so on. They measure vibrations and detect
perturbations along a section of fiber. Different approaches have been adopted
to realize the ø-OTDR systems and process the data from these sensors.
In this thesis, a direct detection DAS based on ø-OTDR architecture with
long sensing range and high signal-to-noise ratio (SNR) is demonstrated. Testing
and characterization of critical system components is conducted before integrating
them into the system. The results of laboratory tests are presented, in which
the detected traces are successively analyzed in order to localize and investigate
the perturbation events along the test fibers. The field tests are demonstrated
with different external events such as digging, walking, and motor vibration.
Considering the random nature of Rayleigh backscattered light and fading effect
encountered in these tests, a new performance metric, which is Mean SNR, is
proposed for assessing and comparing the system performances. Besides, statistical
characteristics of the SNR of the vibration events in different distances for
both laboratory tests and field tests is experimentally measured. The photon
statistics of Rayleigh backscattered signal in a ø-OTDR based fiber sensor in
the presence of amplified spontaneous emission noise is theoretically modeled and
experimentally demonstrated, as well.
Keywords
Distributed Acoustic SensorOptical Time Domain Reflectometer
ø-OTDR
Rayleigh Scattering
Fading
Fiber Optics