4 TH IOS, SZCZYRK 2010 PL0471 A. Waz, P. Kaczmarek, A. Antończak, J. Sotor, G. Soboń, M. Walczakowski, K. M. Abramski Laser & Fibre Electronics Group, Institute of Telecommunication, Teleinformatics and Acoustic, Wroclaw University of Technology Wybrzeze Wyspianskiego 27, Wroclaw, Poland WDM Fiber Vibrometry

4 TH IOS, SZCZYRK 2010 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 Outline

4 TH IOS, SZCZYRK 2010 PL0471 Introduction information about velocity Fourier analysis spectrum integration differentiation displacement acceleration FM demodulator PC LabView ADC

4 TH IOS, SZCZYRK 2010 PL0471 Homodyne vs. heterodyne detection The low frequency noise spectrum Advantages of using heterodyne technique

4 TH IOS, SZCZYRK 2010 PL0471 Features Advantages: Advantages: 1.Visible radiation, an analyzed point can be easy localized 2.High resolution, it depends on a source wavelength  Disadvantages: 1. Low output power, less than 1mW 2. Multipoint measurement in the same time is impossible

4 TH IOS, SZCZYRK 2010 PL0471 Motivation for 1550 nm 1.Relatively low prices of fibre elements, such like: optical isolators, couplers, photodetectors, fibre Bragg gratings etc. 2. Narrow linewidth laser diodes (DFB, DBR) are available 3. ”Eye safe” 1550 nm radiation 4. Unique possibility of weak optical signals amplification by very useful device: Erbium Doped Fibre Amplifier (EDFA) 5. WDM technique allows to make a multichannel vibrometer

4 TH IOS, SZCZYRK 2010 PL0471 Idea of laser-fiber vibrometer

4 TH IOS, SZCZYRK 2010 PL0471 Multipoint vibrometer

4 TH IOS, SZCZYRK 2010 PL0471 Experimental set-up

4 TH IOS, SZCZYRK 2010 PL0471 Fibre – free space out coupling

4 TH IOS, SZCZYRK 2010 PL0471 EDFA - spectral gain characteristic The best area for multipoint vibrometer The best wavelength for single point vibrometer

4 TH IOS, SZCZYRK 2010 PL0471 WDM characteristics

4 TH IOS, SZCZYRK 2010 PL0471 Optical spectra

4 TH IOS, SZCZYRK 2010 PL0471 Detection of heterodyne signals Balanced photodetector

4 TH IOS, SZCZYRK 2010 PL0471 Demodulation of heterodyne signals 1 – observed wavelength, 0 – source wavelength, c – light velocity, V – light source velocity, l – unit vector in the direction of observation, f 0 – frequency of light source 1 – observed wavelength, 0 – source wavelength, c – light velocity, V – light source velocity, l – unit vector in the direction of observation, f 0 – frequency of light source For 1550 nm we obtain carrier signal with frequency deviation: For 632,8 nm frequency deviation is:

4 TH IOS, SZCZYRK 2010 PL0471 Demodulation of heterodyne signals V = 0÷8 cm/s V = 0÷16 cm/s V = 0,004÷5 m/s

4 TH IOS, SZCZYRK 2010 PL0471 Demodulation characteristics Testing set-up for demodulators TDA7000 MC13155 NE564

4 TH IOS, SZCZYRK 2010 PL0471 Demodulation characteristics

4 TH IOS, SZCZYRK 2010 PL0471 Experiment drivingsignal vibration at first point vibration at second point

4 TH IOS, SZCZYRK 2010 PL0471 Signal processing and acquisition

4 TH IOS, SZCZYRK 2010 PL0471Conclusions 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 adapted to many measurement application, particularly can be very flexible.Our experiment showed practical advantage of the system which can be adapted to many measurement application, particularly can be very flexible. The signal processing for speed – displacement – acceleration measurement based on LabView environment is under development.The signal processing for speed – displacement – acceleration measurement based on LabView environment is under development.

4 TH IOS, SZCZYRK 2010 PL0471 Acknowledgments This work has been carried out in the frame of „The EEA Financial Mechanism & Norwegian Financial Mechanism” (PL0471) entitled: „Developing novel laser-fiber monitoring technologies to prevent environmental hazards from vibrating objects”

4 TH IOS, SZCZYRK 2010 PL0471 Thank You