1 / 28

Yair Antman , David Elooz , Avi Zadok

High Resolution Distributed Fiber-optic Sensors of Strain and Temperature for Aerospace and Civil Engineering Applications Optical Engineering , Feb. 26, 2014. Yair Antman , David Elooz , Avi Zadok Faculty of Engineering, Bar- Ilan University, Ramat- Gan 52900, Israel

kawena
Télécharger la présentation

Yair Antman , David Elooz , Avi Zadok

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. High Resolution Distributed Fiber-optic Sensors of Strain and Temperature for Aerospace and Civil Engineering ApplicationsOptical Engineering, Feb. 26, 2014 YairAntman, David Elooz, AviZadok Faculty of Engineering, Bar-Ilan University, Ramat-Gan 52900, Israel Avinoam.Zadok@biu.ac.il

  2. Outline What is distributed Brillouin sensing? Commercial equipment: specification, deployment examples New applications: improve resolution towards cm-scale Solution principle Experimental results Ongoing work: integration of high-resolution distributed measurements within composite materials. Dr. Avi Zadok, Bar-Ilan Univ., COST Technical Meeting, Oct. 2013

  3. Stimulated Brillouin scattering Image curtsy of Luc Thevenaz, EPFL Switzerland Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  4. Brillouin Fiber Sensing • Localization and measurement of strain variation Pump Probe Source: www.neubrex.com • Repeat for various positions, frequency offsets Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  5. Commercial Deployment Examples Omnisens, Switzerland. Focus on Energy Sector. Pipeline integrity monitoring: Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  6. Commercial Deployment Examples Omnisens, Switzerland. Undersea cables monitoring: Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  7. Commercial Deployment Examples Omnisens, Switzerland. Downhole monitoring: Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  8. Commercial Deployment Examples Omnisens, Switzerland. Power plants and cables Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  9. B-OTDA Y. Peled, A. Motil, and M. Tur, Opt. Express 20, 8584-8591 (2012) S. M. Foaleng, M. Tur, J.-C. Beugnot, and L. Thevenaz, JLT 28, 2993 (2010) CW probe amplified by counter-propagating, pulsed pump Most widely known and employed Brillouin analysis scheme Long range: towards 100 km! For a given frequency offset, one scan maps out the entire fiber That scan can be very fast (towards hundreds of Hz at 1 km) Resolution (of ‘classic’ scheme): on the order of 1 meter Many elaborate configurations for resolution enhancement: pre-excitation, multiple pulse widths, etc. Centimeter-scale resolution is challenging Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  10. Acoustic Field in Space and Time Probe (CW) Pump (pulsed) Output probe is ‘imprinted’ with SBS gain information that is accumulated over long section Intensity of stimulated acoustic field: where and when do the pump and probe waves interact effectively? The B-OTDA case (reference for following schemes): Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  11. Motivation • Provide distributed Brillouin sensing with: • Centimeter-scale resolution • Hundreds of meters range (tens of thousands of resolution points) • Reduced acquisition times: simultaneous interrogation of a large number of high-resolution points. Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  12. High Resolution: Correlation Domain • Analogous to the charging of a capacitor with a time constant . • Acoustic field: integrate over driving force cross correlation. • Localization of SBS interactions through manipulations of the cross-correlation between pump and probe envelopes • B-OCDA (Prof. Hotate, Univ. of Tokyo): Sync. FM of both waves • Inner product stable at few correlation peaks, oscillates elsewhere • Sub-cm resolution. Periodic peaks restrict the unambiguous measurement range to hundreds of resolution points K. Hotate and M. Tanaka, IEEE Photonics Tech. Lett. 14, 179-181 (2002). Driving force for the acoustic field buildup: inner product of pump and probe Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  13. PRBS Phase Coding Y. Antman, N. Primerov, J. Sancho, L. Thevenaz, and A. Zadok, Optics Express 20, 7807 (2013) Pump and probe co-modulated by a binary PRBS phase code Code length: . Bit duration: Narrow correlation peaks: (100 ps bits  1 cm resolution) Arbitrarily long separation between neighboring peaks (and range of unambiguous measurements): Resolution and range effectively decoupled Correlation peak can be scanned along the fiber under test, through timing of modulated waves. Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  14. PRBS Phase Coding: Acoustic Field Probe (fast PRBS phase code) Pump (fast PRBS phase code) SBS interaction is stationary and localized Output probe affected by SBS at a single location only Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  15. Difficulties with Phase Coding • Each noise contribution is weak, but there are 10,000 of them… • Large number of averages • SBS is built and interrogated one-point-at-a-time • (for each frequency offset): Number of scans equals the number of resolution points: long acquisition times High resolution and (in principle) long range, but… Off-peak acoustic fields are non-zero, and contribute parasitic SBS amplification (‘coding noise’). Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  16. Coding Noise Reduction Y. Antman, N. Levanon, and A. Zadok, Optics Letters 37, 5269-5271 (2012) Weaker coding noise with judicious choice of code. Simulations: Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  17. Coding Noise Reduction (Continued) Y. Antman, L. Yaron, T. Langer, N. Levanon, M. Tur, and A. Zadok, Opt. Letters 38, 4701(2013) Experimental results: Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  18. Solution Paths: Interrogation of Multiple Points Probe (fast and short PRBS phase code) Pump (fast and short PRBS phase code) Output probe is again amplified at numerous locations. Wasn’t that what we were trying to avoid? Use shortphase codes (~ 130 bits): multiple correlation peaks are introduced. Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  19. Short Phase Codes with Overlaying Pulsed Pump Pump (fast and short PRBS phase code, with amplitude pulses) Probe (fast and short PRBS phase code) Correlation peaks are introduced at different times. Probe amplification can be monitored in time domain, unambiguously. Use amplitude pulsed modulation of the pump wave on top of the phase codes Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  20. Experimental Results • Periodic, isolated peaks repeat every 26 ns (code period), corresponding to SBS gain of individual correlation locations. • Phase codes re-timed to move on to next 2 cm-long sections, and so on… 200 m-long fiber. 127 bits-long phase code. 2 cm resolution. Overlaying pump pulses: 26ns duration Example: output probe power as a function of time Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  21. Experimental Results: Continued A hot spot: one of the peaks is missing, and reappears at a different frequency offset. Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  22. Brillouin Gain Map This experiment: two spliced fibers, 400 m, 2 cm resolution. All 20,000 resolution points covered with only 130 scans. Acquisition time: 20 minutes, mostly saving of scope traces and equipment switching. Net acquisition time << 1 minute. Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  23. Brillouin Gain Map • Uncertainty in Brillouin shift : ±3 MHz (±3 C): rather large… D. Elooz, Y. Antman, N. Levanon, and A. Zadok, accepted for publication, Opt. Express 5 cm-long hot-spot towards the end of a 400 m-long fiber 128 averages used. Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  24. Latest Results: 1600m Range 5 cm-long hot-spot towards the end of a 1600 m-long fiber (“More than a mile, less than an inch”). 512 averages Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  25. Summary • Co-modulation of pump and probe by short, high-rate phase codes to obtain numerous, movable correlation peaks • Amplitude modulation of pump pulses to generate correlation peaks one after another. • Time-domain analysis of probe to separate between peaks • Demonstrated complete scan of 1,600 m fiber with 2 cm resolution, 80,000 points, with only 127 scans per frequency offset. • Number of scans pre frequency offset for M resolution points: • B-OTDA: 1 (low resolution) • Phase-coding: M ~ 10,000 – 100,000 • Proposed hybrid method: code length N ~ 130 << M Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  26. Next Phase • Implement distributed Brillouin measurements over fibers embedded in composite materials. • Much work has been done, by Tel-Aviv Univ. (Tur group) and IAI, and elsewhere world-wide: • Discrete, point sensors (fiber Bragg gratings), including measurements during flights! • Distributed monitoring based on Rayleigh scattering • Distributed Brillouin monitoring, including dynamic measurements, with lower resolution. • MAGNETON project: Xenom Ltd. and Bar-Ilan University. Demonstrate high-resolution Brillouin measurements within the products of the company. Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

  27. Xenom-BIU MAGNETON Project Early days… more to follow Dr. Avi Zadok, Bar-Ilan Univ., COST Technical Meeting, Oct. 2013

  28. Acknowledgements Chief Scientist Office, Israeli Ministry of Industry, Trade and Labor (MoITaL): KAMIN program European Union Cooperation on Science and Technology (COST) Action TD-1001, OFSESA. EPFL, Switzerland: Prof. Luc Thevenaz, NikolayPrimerov, AndreyDenisov Tel-Aviv University: Prof. Moshe Tur, Tomy Langer, LiorYaron Dr. Avi Zadok, Bar-Ilan Univ., Optical Engineering, Feb. 2014

More Related