Dr. Umesh TiwariScientist

V-4 (PHOTONICS)

E.mail: umeshtiwari@csio.res.in

CSIR-CSIO, SECTOR 30, CHANDIGARH - 160 030

Fiber Optic Sensing: Principle & Developments

OUTLINE

FIBER OPTIC SENSOR BASICS

MODULATION MECHANISMS

TYPICAL FO SENSOR SYSTEMS

FOS TECHNOLOGY AT CSIO

CURRENT TRENDS AND FUTURE SCENARIO

Optical Fiber Sensor

Optical fiber sensor: A sensor that measures a physical quantity based on its modulation on the intensity, spectrum, phase, or polarization of light traveling through an optical fiber.

Compact size Multi-functional Remote accessibleMultiplexingResistant to harsh environmentImmunity to electro-magnetic interference

Advantages of optical fiber sensors

PresenterPresentation NotesTwo types of optical fibers (single mode for long haul transmission and multimode for short-distance transmission)Fiber configuration:Core: made of Ge-doped silica. 8um core diameter for single mode, 50/100um core diameter for multimodeCladding: pure silica. 125um in diameterBuffer/coating: polymer. 250um in diameterJacket: plastic for protection

Transmit light by total internal reflection

Optical transmission (light source, focus lens, optical fiber, photodetector)

Light can be characterized by: intensity (how bright the light is), wavelength (the color of the light), pulse width (for pulsed light)

OPTICAL SENSORS (CONVENTIONAL)

BULK OPTICAL COMPONENTS AND LIGHT SOURCES (GAS LASERS, HALOGEN LAMP ETC.)

PROBLEMS:

PORTABILITYREMOTE MONITORING COST RUGGEDNESSEFFICIENCY

SOLUTION EMERGED THROUGH OPTICAL FIBERS & OE OMPONENTS FOR SENSING e.g. FO SENSORS

LIMITED USE

FIBER OPTIC SENSORS: WHY?LARGE BANDWIDTH

EFFICIENT TRANSMISSION (LOW LOSS)

IMMUNITY TO EMI/ RFI/ EMP

SECURITY OF INFORMATION

GEOMETRIC VERSATILITY

SMALL SIZE AND LIGHTWEIGHT

FLEXIBILITY

RESISTANT TO HOSTILE ENVIRONMNT

FREEDOM FROM CROSS-TALKS

NO SPARKING AND FIRE HAZARDS

SINGLE FIBER SERVES BOTH AS SENSOR AND DATA TRANSMITTING CHANNEL

MULTIPLEXING & SPATIALLY DISTRIBUTED SENSING

HIGH PERFORMANCE

CLASSIFICATION

EXTRINSIC SENSORS

INTRINSIC SENSORS

EXTRINSIC SENSORS

Where the light leaves the transmitting fiber to be changed before it continues to the detector by means of the return or receiving fiber.

INTRINSIC SENSORS

Intrinsic sensors are different in that the light beam does not leave the optical fiber but is changed whilst still contained within it.

Optical Fiber Sensor TypesOptical Fiber Sensor Types

Point sensor: detect measurand variation only in the vicinity of the sensor

Multiplexed sensor:Multiple localized sensors are placed at intervals along the fiber length.

Distributed sensor:Sensing is distributed along the length of the fiber

Opto- electronics

Output, M(t, Zi )

Opto- electronics

Output, M(t,z)

Opto- electronics Sensing

elementOutput, M(t)

LIGHT WAVE PARAMETERS

1. Amplitude / Intensity

2. Phase

3. Wavelength

4. Polarisation

5. Time / Frequency

1. PHASEPhysical Mechanism

Interference between signal and reference fibers (Mach- Zehnder monomode system) or different propagation modes in multimode fiber

Detection CircuitryFringe counting, or fractional phase-shift detection

Main Limitations- Laser noise and stability- Measurement of small phase shifts- Elimination of unwanted spurious effects (other physical variables)

Typical Examples- Fiber Gyroscope and Hydrophone- Multimode Gage for Dynamic Pressure/Strain Measurement

OPTICAL MODULATION AND DETECTION TECHNIQUES

2. INTENSITYPhysical Mechanism

Modulation of transmitted light by absorption, emission or refractive index changes

Detection CircuitryAnalog (or digital for go/on-go transducers)

Main Limitations

Normalisation for source intensity variations and, variable line and connector losses (at long distances)

Typical Examples

- Strain/ Pressure Gage using Modulated Microbending Loss- Optical Encoders

OPTICAL MODULATION AND DETECTION TECHNIQUES

3. WAVELENGTHPhysical Mechanism

Spectral-dependant Variations of Absorption, Emission and Refractive Index

Detection CircuitryAmplitude Comparison at two Fixed Wavelengths, or Analogue Signal for Scanned Wavelength

Main Limitations- Suitable Scanned Wavelength Sources - Wavelength Dependant Line Loss

Typical ExamplesTemperature Measurement By:

- Variable Fabry-Perot Cavity- Birefringent Crystal- Semiconductor Band Gap Shift

OPTICAL MODULATION AND DETECTION TECHNIQUES

INTENSITY MODULATED SENSORS

Quasi-Distributed Sensing

• Fiber Bragg Grating (FBG)• Strain, Temperature, Pressure, Load

OTDR

Measurand field M(z,t)

M(zj ,t)

z

M(t) Fiber

Sensitized regions

FO INTERFEROMETRIC SENSORS

SENSORS FOR SMART STRUCTURES AND SKINS (BASIC SENSORS)

Extrinsic Fabry Perot Interferometer (EFPI)

Fiber Bragg Gratings (FBGs)

Long Period Gratings (LPGs)

EXTRINSIC FABRY PEROT INTERFEROMETRIC (EFPI) SENSOR

Variation of Output Intensity (in Arbitrary Units) with Change in Gap Separation `S’ (µm)

Schematic of EFPI Sensor

HIGH RESOLUTION WELL-LOCALISED SENSING REGIONABSOLUTE MEASUREMENTLINEAR OUTPUTINSENSITIVE TO OPTICAL SYSTEM INTENSITY FLUCTUATIONSCAPABILITY TO MULTIPLEX SEVERAL SENSORS ALONG ONE FIBERCOST-EFFECTIVE

FIBER GRATING SENSORS : ADVANTAGES

λB = 2neff Λ

(Bragg Condition)

λB :Bragg wavelength, neff. :Effective RI of the core ,

Λ:Grating pitch

Fiber Bragg Grating (FBG)

( ) ( ) TpeB

B Δ++Δ−=Δ αξελλ 1

Effective Photo-elastic coeffep =ε = Deformation ( )με

ξ = Thermo-optic coeffα = Thermal expansion coeff

Fiber Bragg Gratings

• The grating parameters – Length of grating – Strength of grating– Refractive index.manipulated to produce desired grating characteristics

• The different types of FBGs are – Chirped FBGS– Blazed/Tilted FBGs– Phase shifted FBGs– Long-Period In-Fiber FBGs

FBG SensorsWith more details, if the period of refraction changes due to an external strain ε

and/or a temperature

variation ΔT, the Bragg wavelength changes according to the law:

April 19th 2013

Normalize strain response at 

constant temperature

Normalize thermal response at 

constant strain

Sensing Principle of FBG

23

2. Tuneable laser interrogation unit 

illuminates fiber and measures reflected 

Bragg wavelengths

1. Numerous sensors recorded on a single fiber, mm or km apart. 

Sensors can measure strain, pressure, temperature etc

3. Processing Unit converts 

wavelengths to measurands

of 

interest, which are displayed real time 

or logged for future analysis

Fiber

Data

FBG Sensors

A Fiber Bragg Grating Sensing System

FBGs - FEATURES

LENGTH: 5 - 50 mm, PITCH (Λ) : 0.5 - 1 µm (TYPICAL)

STRONGEST INTERACTION or MODE COUPLING OCCURS AT BRAGG WAVELENGTH (λB )

WAVELENGTH CODED INFORMATION – SELF REFERENCING FEATURE (e.g ABSOLUTE SENSORS)

BASIC SENSING IS THROUGH GENERATION OF STRAIN – GENRIC SENSORS

SENSITIVITY TO STRAIN, TEMPERATURE AS GOOD AS OF FIBER INTERFEROMETERS

EASE OF MULTIPLEXING & DISTRIBUTED SENSING

Long Period Grating (LPG)

λi = [n01 - n(i)clad ] Λ

λi : Loss resonance wavelength coupled to the ith cladding mode

n01: : Effective index of core mode, n(i)clad : Effective index of the ith

cladding mode

(Phase Matching Condition)

A M Vengsarkar & V Bhatia 1995

COUPLES LIGHT FROM THE GUIDED CORE MODE INTO CLADDING MODES IN BANDS CENTRED AT λіLength: 10 - 50 mm, Pitch: 100 – 600 μm (TYPICAL)

FUNCTION AS WAVELENGTH DEPENDENT LOSS ELEMENTS

ANY VARIATION IN STRAIN, TEMPERATURE OR EXTERNAL R.I. CAN CAUSE LARGE WAVELENGTH SHIFTS IN LOSS RESONANCES

CONCENTRATION MEASUREMENT OF ANALYTES, LIQUIDS AND BIO ORGANISMS (PROCESS CONTROL and BIOTECH INDUSTRY)

SIMULTANEOUS MEASUREMENT OF MULTIPLE PARAMETERS

LPGs: FEATURES

FBG/LPG WRITING SYSTEM LAYOUT

Integrated Vehicle Health Monitoring (IVHM) for Aerospace Vehicles

X-33 is a half scale sub-orbital experimental flight test vehicle- a collaborative effort between NASA & Lockheed Martin

X-33 Vehicle Sensor Suite Involves:

Objectives: To provide an automated collection and paperless health decisions, maintenance and logistics systems

Greater need to reduce excessive cost associated with access to space

Focus on providing easy repair access for simplified servicing of infrastructures and expedited decision making from detected faults and anomalies

X-33 Advanced Technology Demonstrator

Distributed strain sensor (FBGs)Distributed Hydrogen Sensing (FBGs)Distributed Temperature Sensing (Raman OTDR)

FOS Technology Developments at CSIO

FBGFBG--LPG Writing SystemLPG Writing System

FBG Sensor applications: Force, pressure, strain/stress, displacement, temperature, acceleration, vibration, acoustics, Chemical and biological sensing, Electrical and magnetic measurements

Grating Writing Modes

1. Phase Mask (Static & Scanning)

2. Interferometric

3. Point-by-Point

• KrF Excimer Laser (248 nm) with LN module• UV beam conditioning and manipulating optics • Automated mask and fiber holder• Proximity phase mask • Optical diagnostic and feedback unit with all operation through computer

• Fiber and phase mask positioning and alignment systems• CCD camera based viewing system for monitoring and controlling mask to fiber relative position

• Fiber tension monitoring assembly • Provision for monitoring and display of the writing beam • OSA on-line monitoring of the grating inscription process• Computer control and software for the writing system

FBG/LPG Writing SystemFeatures:

FBG BASED PETROL LEAK SENSOR

1549.35

1549.4

1549.45

1549.5

1549.55

1549.6

1549.65

0 5 10 15 20Time (min)

Bra

gg w

avel

engt

h (n

m)

Dipping Drying Ph

cCurrent Science, 90(2), p 219-221, 2006

Design, development and Packaging of FBG sensors for structural Health Monitoring

0

50

100

150

200

250

300

350

-500-400-300-200-1000

Micro Strain

Load

in k

N

Strain Gage (Average)FBG (Average)

0 5 10 15 20 25 30-100

0

100

200

300

400

500

600

700

800

Com

pres

sive

Stra

in (μ

ε)Applied Load (Tonne)

FBG1 SG1 FBG2 SG2 FBG3 SG3

0 500 1000 1500 2000

0

100

200

300

400

500

600

700

Tens

ile S

train

(με)

Applied Load (Kg)

CSIO FBG ESG1 Micronoptics FBG ESG2

Current Sciences, 97, pp. 1539-42, 2009

MS Specimen

Concrete Specimen

Strain Guage

Interrogator Unit

Weldable Packaged FBG

1544.5 1545.0 1545.5 1546.0 1546.5

-70

-60

-50

-40

-30

Ref

lect

ed P

ower

(dB

m)

Wavelength (nm)

Precured FBG Sensor Postcured packaged FBG Sensor

Pre-cured and post-cured reflection spectrum of packaged FBG sensor

λB = 1545.54 nm and a grating length of 10 mm FWHM of the FBG was 0.141 nm

Comparison of the strain response of Comparison of the strain response of packaged and unpackaged FBGpackaged and unpackaged FBG

Presented at ICC-CFT, IISc Bangalore-2011

Weldable Packaged FBGs for Structures

Mild Steel Specimen

Hysterisis Plot

Temperature response of Packaged FBG

Embeddable Packaged FBGs for Structures

0

50

100

150

200

250

300

-500-450-400-350-300-250-200-150-100-500

Micro strain

Load

in k

N

FBGSG

Concrete Specimen

Comparison between Packaged FBG Sensors with ESGs under

Compressive Loading

Field Study of Metallic Bridge in Himachal Pradesh with NIT Hamirpur & HPPWD

3D design and photograph of fabricated FBG packaging fixture

Result of the FE Analysis for FBG packaging fixture

FBG Packaging

Photograph of the packaged FBG sensor for cementitious mounting

0 20 40 60 80 1000

20

40

60

80

100

120 Calibration Factor 1.3 pm/με

Shift

in W

avel

engt

h (p

m)

Measured Strain (με)

0100200300400500600700800900

25 35 45 55 65

Applied Temperature  ˚C

FBG W

avelen

gth Shift in

 pm 

Strain and temperature calibration plot

Results

BEAM TESTING IN THE LAB USING PACKAGED FBG SENSORS

FBG4 (λ4 )FBG2

(λ2 )FBG3 (λ3 )FBG1 (λ1 )

Roller end Rocker end

BeamLoad

A View of FBG sensors installed on the RC beam in Lab

Comparison of response of FBG sensor and ESG sensor on RC

beam

0

0.05

0.1

0.15

0.2

0.25

0.3

0 20 40 60 80 100 120 140 160

Applied load (KN)

Wavelen

gth shift (n

m) Δʎ1 (nm)

Δʎ2 (nm)Δʎ3 (nm)Δʎ4 (nm)

Response of FBG sensors at different locations on RC beam

Results

FIELD STUDIES OF FBG SENSORS

FBG=1544nm FBG=1541nm (with Tag)

FBG=1548 nm

FBG=1556nm

RAILWAY LINE

DELHIBridge Layout with FBG

sensors installed

0.0 0.5 1.0 1.5 2.0 2.5 3.0-3-2-10123456789

1011 Response of packaged FBG (1548 nm) near the pillar

Δλ

(pm

)

Time (Sec.)

MBIU+ Loaded truck 1 MBIU+ Light vehicle MBIU+ Loaded truck 2 MBIU only MBIU static

Various Sensors with FBG sensor on the Girder of the bridge and response of FBG sensor for different loading under bridge running condition

(19.03.14 – 21.03.14)

FBG1-1539.967 FBG2-1545.644 FBG3-1542.122

FBG7- 1555.223 FBG8-1558.712

FBG9-1559.012

FBG10-1537.985

TO DELHI TO HAPUR

FBG4-1548.751 FBG5-1538.791 FBG6-1545.046

RAILWAY LINE

FIELD STUDIES OF FBG SENSORS (23.04.14 – 25.04.14)

1454 1444

TO DELHI TO HAPUR

1090 1440 x

RAILWAY LINE

1462

Photograph of the close view of the mounted FBG and other

conventional sensors

Photograph of the test site of Girder Bridge near Hapur

Test Site

FBG 8‐1558.712Strain during a vehicle movement

‐2.000

0.000

2.000

4.000

6.000

8.000

10.000

12.000

0 20 40 60 80 100 120

Samples Recorded

Strain (µ

ε)

Results

FBG3‐1542.122Strain during a vehicle movement

‐10

0

10

20

30

40

50

0 20 40 60 80 100 120 140 160 180

Samples Recorded

Strain (µ

ε)

FBG5‐1538.791Strain during a vehicle movement

‐5.000

0.000

5.000

10.000

15.000

20.000

0 20 40 60 80 100 120 140 160 180

Samples Recorded

Strain (µ

ε)

FBG Sensors Technology for Energy SectorHot Spot Detection and Location in Transformer

Presented at ICOP -2009

FBG installed in 25 kVA Live Transformer at Vadodara since Sep.,2009

In Collaboration with ERDA, M/s Alstom, Vadodara and M/s Ardison, Mohali

DIT Sponsored Project

Wdg temp. using FBG

Top oil temp. using FBG Top oil temp. using TC

% Loading of Transformer

Ambient Temp. using TC

FBG Based Technique for Monitoring Demineralization of Bone (Bio-Mechanics Application)

0 2 4 6 8 10

0.0 0.5 1.0 1.5 2.0 2.5 3.0

0

200

400

600

800

1000

1200

1400

Stra

in G

radi

entB

1 (μ

ε/kg

)Cumulative Ca Loss (gm)

Decalcified Bone Untreated Bone

0

20

40

60

80

100

120

140

Strain Gradient B

2 (με/kg)

Time (Days)

Comparison of strain response of normal and decalcified bone

Experimental Setup

Results and Discussion

•Same load produced almost double strain in the demineralized sample as compared to that in untreated sample •Calcium loss of even 0.3906 gm (treatment 1) resulted in 1.3 times/ 24% more strain for same load and a calcium loss of 1 gm resulted in 50% increase in strain. As the calcium loss was more than 2 gm the strain increase was close to 300%

Orthopaedics and Traumatology: Surgery and Research (Accepted)

Presented at ISMOT - 2009

In consultation with Orthopedic Experts from PGIMER, Chandigarh

Impact absorption capability of a mouth guard using FBG sensors

Experimental Setup

Cricket ball impact on mouthguard and Jaw model using FBG Sensor

Impact absorption capability of custom-made mouthguard investigated utilizing FBG sensors in distributed manner

The impact absorption capability was found to be more than 90% for the center impact

This study will be useful for better designing of custom-made mouthguards

Ref: Tiwari et al. Dental Traumatology (2011)

1551.0 1551.5 1552.0 1552.5-55-50-45-40-35-30-25

Reference for 30 degree Impact for 30 degree Reference for 45 degree Impact for 45 degree Reference for 60 degree Impact for 60 degree

Ref

lect

ed P

ower

(dB

m)

Wavelength (nm)

1553.6 1554.4 1555.2 1556.0-55-50-45-40-35-30-25-20

Ref

lect

ed P

ower

(dB

m)

Wavelength (nm)

Reference for 30 degree Impact for 30 degree Reference for 45 degree Impact for 45 degree Reference for 60 degree Impact for 60 degree

Long Period Grating Based Humidity Sensor

LPFG Based Humidity Sensing

COBALT CHLORIDE/GELATINE 

BASED 

HYGROSCOPIC COATING

Sensing Probe Fabrication and Characterization

FE-SEM NSOM

RI=1.34146 nsur

Results

1510 1520 1530 1540 1550 1560-77

-76

-75

-74

-73

-72

-71

-70

Tran

smitt

ed P

ower

(dB

m)

Resonant wavelength (nm)

Air (Reference) 35% RH 45% RH 55% RH 65% RH 75% RH 85% RH 90% RH

The spectral signature of coated LPFG at different levels of known RH

Results

Hysteresis plot of coated LPFG w. r. t. various levels of RH

Hysteresis 

calculation wrt increasing RH  values 

± 0.2%

Hysteresis

Results

Response at 70% RH level for 300 

minutesStability 

error   0.06%

Stability plot

LPG based Biosensor

1350 1400 1450 1500 1550 1600 1650-80-78-76-74-72-70-68-66-64-62

Tran

smitt

ed P

ower

(dB

m)

Wavelength (nm)

STRUCTURE OF A BIO-SENSOR

• BIORECOGNITION ELEMENT : Biomolecules

(enzymes, micro-

organisms, strand of DNA) produced by interaction of an analyte

with an interface.

• INTERFACE : Surface of transducer with immobilized bioelements.

• TRANSDUCING ELEMENTS : Electrochemical,acoustic,piezo- electrical, optical etc.

Biosensor

= biorecognation molecule/bioreceptor

+ Transducer

EnzymeAntibodyMembranesOrganellesCellsTissuesCofactorsDNAPeptideMicroorganism

• Electrochemical – Amperometric– Potentiometric– Conductiometric• Piezo-electric• Calorimetric• Acoustic• Optical

ReceptorsTransducers

PhysicalChemical

•Transformation•Coupling

Preliminary Investigation on Long Period Grating based bio-sensor

Reference Protein

GlucaldihideAB

SilanizationGlutaraldehydetreatment

Protein A treatmentAntibody immobilization

SEM images of LPG surface after chemical processing

Shift in wavelength for different bio-agent binding

Presented at ISMOT - 2009

1520 1540 1560 1580 1600 1620 1640 1660-77

-76

-75

-74

-73

-72

-71

-70

Tx (d

Bm

)

Wavelength (nm)

H2So4 APTES GOx 10mg/3ml Glu15 mg/10ml

1520 1540 1560 1580 1600 1620 1640 1660

-76

-75

-74

-73

-72

-71

-70

-69

Tran

smitt

ance

(dB

m)

Wavelength (nm)

H2So4 APTES GOx 10 mg/3ml Glu 20 mg/10ml

Effective Wavelength Shift = 2.52nm Effective Wavelength Shift = 2.68nm

1520 1540 1560 1580 1600 1620 1640 1660-77

-76

-75

-74

-73

-72

-71

-70

Tran

smitt

ance

(dB

m)

Wavelength (nm)

H2So4 APTES GOx 15 mg/3ml Glu 30 mg/10ml

Effective Wavelength Shift = 2.88nm

LPG Sensor based on CoLPG Sensor based on Co--valentvalent Binding Binding Technique for Glucose DetectionTechnique for Glucose Detection

Ref: Deep

A. and

U. Tiwari

et al. Biosensors

and

Bioelectronics

(2012)

Long Period Grating based Sensor for Urea Detection

Sodium Bicarbonate

Pure Milk

Urea(toxic)

Glucose

starch

Vegetable oil

Salts

Milk Adulteration• Parameters affected are FAT and SNF content in MILK• Minimum content of FAT – 3.5%• Minimum content of SNF – 9%

COATING OF APTES/ENZYME ON LPFG

HF acid treatment Piranha

solution treatment

OH

OH

APTES

O

O

Si (CH2)3 NH2

COOH

Ureaseenzyme

Optical Fiber

LPFG Based Urea Sensing

Bare Fiber APTES treated Fiber Urease treated Fiber

FESEM image of the treated and untreated optical fiber

Normal Fiber

Normal Fiber

Urease treated Fiber

CLSM Image of Urease treated fiber and untreated Fiber

APTES treated Fiber

Urease treated Fiber

Fluorescence Comparison between APTES treated and UREASE treated

Fiber

Experimental Setup

Results

1580 1600 1620 1640 1660

-76

-75

-74

-73

-72

-71

-70

Tra

nsm

itted

Pow

er (d

Bm

)

Wavelength (nm)

10 mg/ml 20 mg/ml 30 mg/ml 40 mg/ml

1580 1600 1620 1640 1660

-77

-76

-75

-74

-73

-72

-71

-70

Tran

smitt

ed P

ower

(dB

m)

Wavelength (nm)

Pure Milk 10mg/ml Urea 20mg/ml Urea 30mg/ml Urea 40mg/ml Urea

Measured transmission spectrum

Untreated LPG for Pure Milk with different concentration of Urea

Treated LPG for Pure Milk with different concentration of Urea

Results

0 10 20 30 401619

1620

1621

1622

1623

1624

1625

1626W

avel

engt

h (n

m)

Concentration of Urea (mg)

Uncoated LPG Coated (Enzyme Immoblized) LPG

The comparison of wavelength variation of Pure Milk with different concentration of Urea in coated and uncoated LPG

• CONFIGURING OF EXISTING OPTICAL SENSORS WITH FIBER OPTICS

• EVOLUTION OF COST-EFFECTIVE AND EFFICIENT DESIGNS

• APPLICABILITY TO NEWER AREAS

• SENSOR DESENSITIZATION AND PACKAGING

• INTEGRATION WITH MICROMACHINED ELEMENTS

• MULTIPLEXING & DISTRIBUTED SENSING

TRENDS

Remarkable possibilitiesAn interesting & promising futureThe technology behind the fabrication, packaging and installation of FBG sensors has been presented for use in the structures.

Laboratory testing has been demonstrated involving the embedment of FBG sensors in the concrete beam and their performance have been presented under variable loading conditions. Field trials using packaged FBG sensor in distributed configuration on the concrete bridge on NH24 near Hapur have also been demonstratedBio-sensing based on LPG sensor for different applications have been experimentally demonstrated.

Summary

References1. Fundamentals of Fiber Optics in Telecommunication

and Sensors Systems, Edited by Bishu P Pal; Wiley Eastern Limted, New Delhi, Bangalore, Pune

2. Optical Fibre Sensors, Components & Subsystems, Vol. 1,2,3 & 4, Edited by Brian Culshaw & John Dakin; Artech House, Boston/London

3. Optical Fiber Sensor Technology – Fundamentals, Edited by K.T.V. Graltan & B.T. Meggitt; Kluwer Academic Publishers; Boston/ London

4. Fiber Optic Smart Structures, Edited by Eric Udd; John Wiley & Sons, Inc; New York/Tronto/Singalore

5. Optical Fiber Sensor Technology, Edited by K.T.V.Grattan & B.T. Megitt; Chapman and Hall; London/Glasgow/New York/Madras

Slide Number 1Slide Number 2Optical Fiber SensorSlide Number 4Slide Number 5Slide Number 6Slide Number 7Slide Number 8Optical Fiber Sensor TypesSlide Number 10Slide Number 11Slide Number 12Slide Number 13Slide Number 14Slide Number 15Slide Number 16Slide Number 17Slide Number 18Slide Number 19Slide Number 20Fiber Bragg GratingsFBG SensorsSlide Number 23Slide Number 24Slide Number 25Slide Number 26Slide Number 27Slide Number 28Slide Number 29Slide Number 30Slide Number 31Slide Number 32Slide Number 33Slide Number 34Slide Number 35Slide Number 36Slide Number 37Slide Number 38Slide Number 39Slide Number 40Slide Number 41Slide Number 42Slide Number 43Slide Number 44Slide Number 45Slide Number 46Slide Number 47Slide Number 48Slide Number 49Slide Number 50Slide Number 51Slide Number 52Slide Number 53Slide Number 54Slide Number 55Slide Number 56Slide Number 57Slide Number 58Slide Number 59Slide Number 60Slide Number 61STRUCTURE OF A BIO-SENSORSlide Number 63Slide Number 64Slide Number 65Slide Number 66Slide Number 67COATING OF APTES/ENZYME ON LPFGSlide Number 69Slide Number 70Slide Number 71Slide Number 72Slide Number 73Slide Number 74Slide Number 75Slide Number 76Slide Number 77Slide Number 78