Saurabh Bhalerao Sensor

8/7/2019 Saurabh Bhalerao Sensor

http://slidepdf.com/reader/full/saurabh-bhalerao-sensor 1/23

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



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




Slide-3

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.



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.


Slide-4




Slide-5

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/



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.


Slide-6



Overview - Extrinsic


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



Overview - Intrinsic


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



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



Major Advantages� Small

� Lightweight

� Passive

� Low power

� Wide bandwidth

� Rugged

� Resistant to EM interference� High sensitivity


Slide-10



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.


Slide-11



Principle ± Simple Extrinsic


Slide-12

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




Principle ±Extrinsic#2


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



Principle ± Angular Position


Slide-14


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.



Principle ± Intrinsic #1


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.


Courtesy: Andrew Moss optic fibersensors



Principle ± Intrinsic #2


Slide-16


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



Principle ± Spectrally Based


Slide-17

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.



Principle ± Interferometer Based


Slide-18


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.




Slide-19

Major Specifications� Accuracy

� Designed measurement parameters

� Dynamic range

� External sensors required (if any)

� Operating wavelengths

� Response time



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.


Slide-20



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.


Slide-21



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

Slide-22



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


Slide-23

Date post:	08-Apr-2018
Category:	Documents
Upload:	shrikant-bagrodia
View:	220 times
Download:	0 times

Saurabh Bhalerao Sensor

Documents