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ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and ActuatorsAssignment#01: Literature Survey on Sensors and Actuators
Topic: Optical Fiber Sensors
Prepared by: Saurabh Bhalerao
Dept. of Electrical and Computer Engineering
Utah State UniversityE: [email protected]
3/1/2009
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4/20/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-2
Outline ± Reference list
± Overview
± Major applications
± Basic working principle illustrated ± Major specifications
± Limitations
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Reference list� Proceedings of the NATO Advanced Study Institute on Optical
Fiber Sensors, Erice, Italy, May 2-10, 1986
� Blue Road Research, µOverview of Fiber Optic Sensors¶,
www.bluerr.com/papers/Overview_of_FOS2.pdf
� K.T.V Grattan and B.T. Meggit, µOptical Fiber Sensor
Technology, Advanced Applications ± Bragg Gratings and
Distributed Sensors¶ Kluwer Academic Publishers, 2000
� 1. E. Udd, Editor, µ Fiber Optic Sensors: An Introduction for
Engineers and Scientists¶,Wiley, New York, 1991.
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Reference list continued� Ghosh, S.K.; Sarkar, S.K.; Chakraborty, S. (2002). "Design
and development of a fiber optic intrinsic voltage sensor".
P roceedings of the 12th IMEKO TC4 international
symposium P art 2 (Zagreb, Croatia): 415± 41
� Sensornet. "Upstream oil & gas case study" (pdf).
http://www.sensornet.co.uk/download.cfm?casestudy_id=41
&type=casestudy.
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To explore further
(survival pointers of web references etc)� http://www.bluerr.com/
± Blue Road Research, good information in the Applications and
Publications section.
� http://www.boulder.nist.gov/div815/81503_pubs/ofs.htm
- List of NIST publications
� http://en.wikipedia.org/wiki/Optical_fiber#Fiber_optic_sensors
- Basic Definitons
� http://www.opticalfibersenors.org
� http://www.osa.org/meetings/topicalmeetings/ofs/
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Overview� Two major types of fiber optic sensor:
± Extrinsic or Hybrid
± Intrinsic or All Fiber
� Light in optical fibers can be modulated by
amplitude, frequency, phase or polarization to
carry signals.
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Overview - Extrinsic
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Slide-7
An optical fiber leads up
to a "black box" which
impresses information
onto the
light beam in response to
an environmental effect.
The information could be
impressed in
terms of intensity, phase,
frequency, polarization,
spectral content or other methods.Diagram from:
http://www.bluerr.com/images/Overview _of_FOS2.pdf
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Overview - Intrinsic
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Slide-8
An optical fiber to
carry the light beam and
the environmental effect
impresses information
onto the light beam whileit is in the fiber.
Diagram from:Fiber Optic Sensor Workbook, Eric Udd
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Major Applications� Measure:
± Acceleration
± Acoustics
± Chemical measurements
± Electric and magnetic field strengths ± Linear and angular position
± Humidity
± Pressure
± Rotations
± Strain
± Temperature
± Vibrations
± Viscosity
± And more«4/20/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
Slide-9
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Major Advantages� Small
� Lightweight
� Passive
� Low power
� Wide bandwidth
� Rugged
� Resistant to EM interference� High sensitivity
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Slide-10
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Major Advantages� Multiplexing
± Optical fiber sensors can be multiplexed in a variety of ways
allowing multiple sensors to be attached to a single fiber. This
allows for large, distributed sensor networks.
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Principle ± Simple Extrinsic
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Light is injected into one of
the optical fibers and when it
exits the light expands into a
cone of light whose angle
depends on the difference
between the index of refraction of the core
and cladding of the optical
fiber. The amount of light
captured by the second
optical fiber
depends on its acceptance
angle and the distance d
between the optical fibers
Diagram from:Fiber Optic Sensor Workbook, Eric Udd
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Principle ±Extrinsic#2
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Slide-13
� Here a mirror is used that is flexibly mounted to respond to an
external effect such as pressure. As the mirror position shifts the
effective separation between the optical fibers shift with a resultant
intensity modulation.
Diagram from:Fiber Optic SensorWorkbook, Eric Udd
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Principle ± Angular Position
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Slide-14
Diagram from:Fiber Optic Sensor Workbook, Eric Udd
A rotary position sensor that consists of a code plate with
variable reflectance patches placed so that each position hasa unique code. A series of optical fibers are used to
determine the presence or absence of a patch.
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Principle ± Intrinsic #1
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Slide-15
An optical fiber ends
with a right angle as
shown which reflects all
of the light back throughtotal internal reflection.
When the probe is placed
in a medium other than
the reference, the index
of refraction changes andsome of the light escapes
the probe, decreasing the
amplitude.
Diagram from:Fiber Optic Sensor Workbook, Eric Udd
Courtesy: Andrew Moss optic fibersensors
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Principle ± Intrinsic #2
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Diagram from:Fiber Optic Sensor Workbook, Eric Udd
Two simple optical fibers
are placed in close
proximity. Some of the
light leaks from one to
the other, ie cross
coupling occurs. The
amount of evanescence
caused depends onseveral factors which can
be sensed through the
measured coupling.
Courtesy: Andrew Mossoptic fibersensors
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Principle ± Spectrally Based
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Diagram from:
Fiber Optic Sensor Workbook, Eric Udd
When the blackbody¶s temperature increases it begins to glow, acting as a lightsource. This is transmitted to detectors where the blackbody is measured and
used to determine the temperature. A blackbody cavity is placed at the end of an
optical fiber. When the cavity rises in temperature it starts to glow and act as a
light source.
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Principle ± Interferometer Based
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Diagram from:Fiber Optic Sensor Workbook, Eric Udd
Fiber optic gyroscope.
Light is injected into a
fiber coil from both
directions. The phasedifference of the two
signals is then detected.
If the coil is stationary
the phase difference is 0,
but if it is rotating the phase difference is
proportional to the
rotation rate.
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Major Specifications� Accuracy
� Designed measurement parameters
� Dynamic range
� External sensors required (if any)
� Operating wavelengths
� Response time
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Limitations� Generally have to be tuned to a specific
wavelength to function properly.
± This can be used to limit noise susceptibility but limits
the general application of any given sensor.
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Limitations� Multiple potential error sources (connectors,
splices, microbending, misalignment, etc)
± May be circumvented by using two wavelengths in the
sensor, one of which is used to calibrate out the noise.
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Other Considerations� Research area
± Optical fiber sensors are relatively new for most
applications because the cost of lasers and optical
fibers has only recently become practical for mostthings. This means that new research is still being
conducted to find new ways to apply optical sensors.
It is a changing area at this time.
� Robustness ± The robustness of optical fibers makes them usable in
many conditions(high temperature, EM interference,
etc) which exclude other sensors.4/20/2011 ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators
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Other Considerations� Generally Optical fiber sensors are found at most
major suppliers of electronic sensors.
� They are classified specifically by the parameter
they are designed to sense and not as Optical fi
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