30-07-2013, 03:16 PM
Acousto-Ultrasonic Optical Fiber Sensors
[attachment=56832]
INTRODUCTION
This seminar gives a review of acoustic and ultrasonic
optical fiber sensors (OFSs). The review covers optical fiber sensing
methods for detecting dynamic strain signals, including general
sound and acoustic signals, high-frequency signals, i.e., ultrasonic/
ultrasound, and other signals such as acoustic emissions, and impact
induced dynamic strain. Several optical fiber sensing methods
are included, The OFS include single fiber sensors and optical fiber devices, fiber-optic interferometers, and fiber Bragg gratings (FBGs).
The single fiber and fiber device
sensors include optical fiber couplers, microbend sensors, refraction-
based sensors, and other extrinsic intensity sensors. The
optical fiber interferometers include Michelson, Mach–Zehnder,
Fabry–Perot, Sagnac interferometers, as well as polarization and
model interference
Theory
Acoustic emissions (AEs) are elastic waves generated by a
sudden release of energy within a solid . For example, energy
dissipated by the growth of a crack can be in the form of an
elastic wave. An elastic wave describes a stress or strain wave,
propagating through an elastic medium, typically a solid. In general,
the amount of energy released as an elastic wave as apposed
to other forms of energy, depends on the initial conditions of the
source. Specifically, the initial conditions are how localized the
release was, and the time period over which it takes place. That
is, rapid localized releases of energy generated elastic waves,
with frequencies in the ultrasonic range.
Applications
Electrical power can be measured in a fiber by using a structured bulk fiber ampere sensor coupled with proper signal processing in a po
larimetric detection scheme.
Fiber-optic sensors are used in electrical switchgear to transmit light from an electrical arc flash to a digital protective relay to enable fast tripping of a breaker to reduce the energy in the arc blast.
[attachment=56832]
INTRODUCTION
This seminar gives a review of acoustic and ultrasonic
optical fiber sensors (OFSs). The review covers optical fiber sensing
methods for detecting dynamic strain signals, including general
sound and acoustic signals, high-frequency signals, i.e., ultrasonic/
ultrasound, and other signals such as acoustic emissions, and impact
induced dynamic strain. Several optical fiber sensing methods
are included, The OFS include single fiber sensors and optical fiber devices, fiber-optic interferometers, and fiber Bragg gratings (FBGs).
The single fiber and fiber device
sensors include optical fiber couplers, microbend sensors, refraction-
based sensors, and other extrinsic intensity sensors. The
optical fiber interferometers include Michelson, Mach–Zehnder,
Fabry–Perot, Sagnac interferometers, as well as polarization and
model interference
Theory
Acoustic emissions (AEs) are elastic waves generated by a
sudden release of energy within a solid . For example, energy
dissipated by the growth of a crack can be in the form of an
elastic wave. An elastic wave describes a stress or strain wave,
propagating through an elastic medium, typically a solid. In general,
the amount of energy released as an elastic wave as apposed
to other forms of energy, depends on the initial conditions of the
source. Specifically, the initial conditions are how localized the
release was, and the time period over which it takes place. That
is, rapid localized releases of energy generated elastic waves,
with frequencies in the ultrasonic range.
Applications
Electrical power can be measured in a fiber by using a structured bulk fiber ampere sensor coupled with proper signal processing in a po
larimetric detection scheme.
Fiber-optic sensors are used in electrical switchgear to transmit light from an electrical arc flash to a digital protective relay to enable fast tripping of a breaker to reduce the energy in the arc blast.