4 TH IOS, SZCZYRK 2010 PL0471 A. Waz, P. Kaczmarek, A. Antończak, J. Sotor, G. Soboń, M....

44THTH IOS, SZCZYRK 2010 IOS, SZCZYRK 2010

PL0471

A. Waz, A. Waz, P. P. KKaczmarekaczmarek, A. Antończak, J. Sotor, , A. Antończak, J. Sotor, G. Soboń, M. Walczakowski, G. Soboń, M. Walczakowski, K. M. AbramskiK. M. Abramski

Laser & Fibre Electronics Group, Laser & Fibre Electronics Group, Institute of TelecommunicationInstitute of Telecommunication, Teleinformatics, Teleinformatics and Acoustic, and Acoustic,

Wroclaw University of TechnologyWroclaw University of TechnologyWybrzeze Wyspianskiego 27, 50-370 Wroclaw, PolandWybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland

WDM WDM Fiber VibrometryFiber Vibrometry


PL0471

• IntroductionIntroduction

• The idea of multipoint fibre vibrometerThe idea of multipoint fibre vibrometer

• Heterodyne signalsHeterodyne signals

• DemodulatorsDemodulators

• Experiment and signal processingExperiment and signal processing

• ConclusionsConclusions

OutlineOutline


PL0471IntroductionIntroduction

information information about velocityabout velocity

Fourier analysisFourier analysis spectrumspectrum

integrationintegration

differentiationdifferentiation

displacementdisplacement

accelerationacceleration

FFM M demodulatordemodulator

PC PC LabViewLabViewADCADC


PL0471Homodyne Homodyne vvs. heterodyne detections. heterodyne detection

The low frequency noise spectrumThe low frequency noise spectrum Advantages of using heterodyne techniqueAdvantages of using heterodyne technique


PL0471FeaturesFeatures

Advantages:Advantages:

1.1. Visible radiation, aVisible radiation, an analyzedn analyzed point can be easy localized point can be easy localized

2.2. High resolution, it depends on a source wavelengthHigh resolution, it depends on a source wavelength

Disadvantages:Disadvantages:

1. Low output power, less than 1mW1. Low output power, less than 1mW

2. Multipoint measurement in the same time is impossible2. Multipoint measurement in the same time is impossible


PL0471Motivation for 1550 nmMotivation for 1550 nm

1.1. Relatively low prices of fibre elements, such like: optical Relatively low prices of fibre elements, such like: optical isolators, couplers, photodetectors, fibre Bragg gratings isolators, couplers, photodetectors, fibre Bragg gratings etc.etc.

2. Narrow linewidth laser diodes (DFB, DBR) are available2. Narrow linewidth laser diodes (DFB, DBR) are available

3. ”Eye safe” 1550 nm radiation3. ”Eye safe” 1550 nm radiation

4. Unique possibility of weak optical signals amplification by 4. Unique possibility of weak optical signals amplification by very useful device: Erbium Doped Fibre Amplifier (EDFA)very useful device: Erbium Doped Fibre Amplifier (EDFA)

5. WDM technique allows to make a multichannel vibrometer5. WDM technique allows to make a multichannel vibrometer


PL0471Idea of laser-fiber vibrometerIdea of laser-fiber vibrometer


PL0471

Multipoint vibrometerMultipoint vibrometer


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Experimental set-upExperimental set-up


PL0471

Fibre – free space out couplingFibre – free space out coupling


PL0471

EDFA - spectral gain characteristicEDFA - spectral gain characteristic

The best The best area for area for

multipoint multipoint vibrometervibrometer

The best The best wavelength wavelength for single for single

point point vibrometervibrometer


PL0471

WDM characteristicsWDM characteristics


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Optical spectraOptical spectra


PL0471

Detection of heterodyne signalsDetection of heterodyne signals

)(

)(

)cos()sin(

)sin()cos(

)(

)(

2

1

2

1

fE

fE

lli

lile

fE

fE

i

ili

o

o

Balanced photodetectorBalanced photodetector


PL0471Demodulation of heterodyne signalsDemodulation of heterodyne signals

c

lV

f

c

f

lVc0

0001

1 1 – observed wavelength, – observed wavelength, 00 – source wavelength, c – light velocity, V – light source velocity, l – unit – source wavelength, c – light velocity, V – light source velocity, l – unit

vector in the direction of observation, fvector in the direction of observation, f00 – frequency of light source – frequency of light source

0101

ccfff

c

lVfcf 02

0

0lV

f

For 1550 nm we obtain carrier signal with frequency deviation:For 1550 nm we obtain carrier signal with frequency deviation:

sm

MHzlVD /

29,120

For For 632,8632,8 nm frequency deviation nm frequency deviation is is::

sm

MHzlVD /

16,320


PL0471Demodulation of heterodyne signalsDemodulation of heterodyne signals

V = 0V = 0÷÷8 cm/s8 cm/s

V = 0V = 0÷÷16 cm/s16 cm/s

V = 0,004V = 0,004÷÷5 m/s5 m/s


PL0471

Demodulation characteristicsDemodulation characteristics

Testing set-up for demodulatorsTesting set-up for demodulators

TDA7000TDA7000

MC13155MC13155 NE564NE564


PL0471

Demodulation characteristicsDemodulation characteristics


PL0471ExperimentExperiment

drivingdrivingsignalsignal

vibration vibration at first at first pointpoint

vibration vibration at second at second

pointpoint


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Signal processing and acquisitionSignal processing and acquisition


PL0471

ConclusionsConclusions

• WDM systems can be particularly useful for multichannel fibre vibrometry.WDM systems can be particularly useful for multichannel fibre vibrometry.

• We obtain heterodyne signals with SNR good enough for FM demodulation.We obtain heterodyne signals with SNR good enough for FM demodulation.

• Our experiment showed practical advantage of the system which can be Our experiment showed practical advantage of the system which can be adapted to many measurement application, particularly can be very flexible. adapted to many measurement application, particularly can be very flexible.

• The signal processing for speed – displacement – acceleration The signal processing for speed – displacement – acceleration measurement based on LabView environment is under development.measurement based on LabView environment is under development.


PL0471

AcknowledgmentsAcknowledgments

This work has been carried out in the frame of This work has been carried out in the frame of „The EEA Financial Mechanism & Norwegian Financial „The EEA Financial Mechanism & Norwegian Financial

Mechanism” (PL0471) entitled: Mechanism” (PL0471) entitled:

„„Developing novel laser-fiber monitoring technologies to prevent Developing novel laser-fiber monitoring technologies to prevent environmental hazards from vibrating objectsenvironmental hazards from vibrating objects””


PL0471

Thank YouThank You

4 TH IOS, SZCZYRK 2010 PL0471 A. Waz, P. Kaczmarek, A. Antończak, J. Sotor, G. Soboń, M....

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