scispace - formally typeset
Search or ask a question
Author

Simon Zaslawski

Bio: Simon Zaslawski is an academic researcher from École Polytechnique Fédérale de Lausanne. The author has contributed to research in topics: Brillouin zone & Brillouin scattering. The author has an hindex of 5, co-authored 14 publications receiving 61 citations.

Papers
More filters
Journal ArticleDOI
TL;DR: A technique is proposed, encoding the interrogating light signal by a single-sequence aperiodic code and spatially resolving the fibre information through a fast post-processing, enabling a performance enhancement using an unmodified conventional configuration for the sensor.
Abstract: Distributed optical fibre sensors deliver a map of a physical quantity along an optical fibre, providing a unique solution for health monitoring of targeted structures. Considerable developments over recent years have pushed conventional distributed sensors towards their ultimate performance, while any significant improvement demands a substantial hardware overhead. Here, a technique is proposed, encoding the interrogating light signal by a single-sequence aperiodic code and spatially resolving the fibre information through a fast post-processing. The code sequence is once forever computed by a specifically developed genetic algorithm, enabling a performance enhancement using an unmodified conventional configuration for the sensor. The proposed approach is experimentally demonstrated in Brillouin and Raman based sensors, both outperforming the state-of-the-art. This methodological breakthrough can be readily implemented in existing instruments by only modifying the software, offering a simple and cost-effective upgrade towards higher performance for distributed fibre sensing. Performance of distributed optical fiber sensing is partially limited by the need for hardware changes. Here, the authors introduce a coding algorithm that enables enhanced performance through faster processing using only software-based methods.

42 citations

Journal ArticleDOI
TL;DR: It turns out that the optimal SNR performance depends in inverse proportion on the value of maximum single-pulse Brillouin amplification, which is ultimately determined by the spatial resolution.
Abstract: The performance of unipolar unicolor coded Brillouin optical time-domain analysis (BOTDA) is evaluated based on both Simplex and Golay codes. Four major detrimental factors that limit the system performance, including decoded-gain trace distortion, coding pulse power non-uniformity, polarization pulling and higher-order non-local effects, are thoroughly investigated. Through theoretical analysis and an experimental validations, solutions and optimal design conditions for unipolar unicolor coded BOTDA are clearly established. First, a logarithmic normalization approach is proposed to resolve the linear accumulated Brillouin amplification without distortion. Then it is found out that Simplex codes are more robust to pulse power non-uniformity compared to Golay codes; whilst the use of a polarization scrambler must be preferred in comparison to a polarization switch to mitigate uncompensated fading induced by polarization pulling in the decoded traces. These optimal conditions enables the sensing performance only limited by higher-order non-local effects. To secure systematic errors below 1.3 MHz on the Brillouin frequency estimation, while simultaneously reaching the maximum signal-to-noise ratio (SNR), a mathematical model is established to trade-off the key parameters in the design, i.e., the single-pulse Brillouin amplification, code length and probe power. It turns out that the optimal SNR performance depends in inverse proportion on the value of maximum single-pulse Brillouin amplification, which is ultimately determined by the spatial resolution. The analysis here presented is expected to serve as a quantitative guideline to design a distortion-free coded BOTDA system operating at maximum SNR.

34 citations

Journal ArticleDOI
TL;DR: In this paper, the benefits and limitations inherent to 2D post-processing of measurements from Brillouin optical time-domain analyzers are investigated from a fundamental point of view.
Abstract: The benefits and limitations inherent to the 2D post-processing of measurements from Brillouin optical time-domain analyzers are investigated from a fundamental point of view. In a preliminary step, the impact of curve fitting on the precision of the estimated Brillouin frequency shift is analyzed, enabling a fair comparison between the representative noise-reduction algorithms studied in this article. The performances in terms of signal-to-noise ratio, experimental uncertainty $\sigma _B$ on the Brillouin frequency shift and spatial resolution delivered by advanced image processing methods—such as wavelet transform and non-local means algorithms—are then compared with the impact of a 2D Gaussian filter. The major discrepancies observed when comparing the gain in signal-to-noise ratio to the $\sigma _B$ reduction are then determined by exploiting the separability of the Gaussian filter, which reveals that noise reduction is only effective along 1-D of the 2D array of measurements and originates from a digital reduction of the system analog bandwidth. The signal-to-noise ratio improvement obtained from filtering in the spectral dimension is only illusory, since its action is redundant with the curve fitting procedure to estimate the Brillouin frequency shift. Finally, the maximum $\sigma _B$ reduction achievable by digital post-processing is theoretically given, hence setting a fundamental limit to the improvement brought by data processing.

23 citations

Journal ArticleDOI
20 Mar 2021
TL;DR: In this paper, the frequency shift of a short optical pulse subject to the phase chirp modulation caused by harmonic FSBS oscillation is probed by a standard Brillouin optical time-domain analyzer.
Abstract: Distributed measurement of forward stimulated Brillouin scattering (FSBS) attracted substantial attention for its ability to probe media surrounding optical fibers. Currently, all techniques extract the information from the FSBS-induced local energy transfer among distinct optical tones, this transfer being fundamentally sensitive to intensity perturbations imposed by nonlinear effects. Instead, here we propose to extract the local FSBS information by measuring the frequency shift of a short optical pulse subject to the phase chirp modulation caused by harmonic FSBS oscillation. In full contrast with existing techniques, the optical pulse is much shorter than the period of the acoustic oscillation, enabling ultrashort spatial resolutions, and its frequency shift is precisely probed by a standard Brillouin optical time-domain analyzer. The proposed technique is validated in both remote and integrally distributed sensing configurations, demonstrating spatial resolutions of 0.8 m and 2 m, respectively, substantially outperforming state-of-the-art techniques.

23 citations

Proceedings ArticleDOI
28 Aug 2019
TL;DR: In this paper, a broad pass-band filter was used to perform distributed forward stimulated Brillouin scattering (FSBS) measurements, which obtains the local peak gain when probing the FSBS resonance.
Abstract: Brillouin optical time-domain reflectometry is used to perform distributed forward stimulated Brillouin scattering (FSBS) measurements. This configuration suppresses the need for an additional frequency scanning to evaluate the local Brillouin peak gain when probing the FSBS resonance. The use of a broad pass-band filter makes the system insensitive to moderate temperature or strain fluctuations, but enables to accurately retrieve any change in intensity due to FSBS.

11 citations


Cited by
More filters
Journal ArticleDOI
TL;DR: A technique is proposed, encoding the interrogating light signal by a single-sequence aperiodic code and spatially resolving the fibre information through a fast post-processing, enabling a performance enhancement using an unmodified conventional configuration for the sensor.
Abstract: Distributed optical fibre sensors deliver a map of a physical quantity along an optical fibre, providing a unique solution for health monitoring of targeted structures. Considerable developments over recent years have pushed conventional distributed sensors towards their ultimate performance, while any significant improvement demands a substantial hardware overhead. Here, a technique is proposed, encoding the interrogating light signal by a single-sequence aperiodic code and spatially resolving the fibre information through a fast post-processing. The code sequence is once forever computed by a specifically developed genetic algorithm, enabling a performance enhancement using an unmodified conventional configuration for the sensor. The proposed approach is experimentally demonstrated in Brillouin and Raman based sensors, both outperforming the state-of-the-art. This methodological breakthrough can be readily implemented in existing instruments by only modifying the software, offering a simple and cost-effective upgrade towards higher performance for distributed fibre sensing. Performance of distributed optical fiber sensing is partially limited by the need for hardware changes. Here, the authors introduce a coding algorithm that enables enhanced performance through faster processing using only software-based methods.

42 citations

Journal ArticleDOI
TL;DR: Detailed methodologies of SNR enhancement post-processing algorithms ininline-formula-OTDR systems employed with pattern classification algorithms are described in this paper to provide a design pathway for improving the performance of these systems.
Abstract: Distributed optical vibration sensors (DOVS) have attracted much attention recently since it can be used to monitor mechanical vibrations or acoustic waves with long reach and high sensitivity. Phase-sensitive optical time domain reflectometry (Φ-OTDR) is one of the most commonly used DOVS schemes. For Φ-OTDR, the whole length of fiber under test (FUT) works as the sensing instrument and continuously generates sensing data during measurement. Researchers have made great efforts to try to extract external intrusions from the redundant data. High signal-to-noise ratio (SNR) is necessary in order to accurately locate and identify external intrusions in Φ-OTDR systems. Improvement in SNR is normally limited by the properties of light source, photodetector and FUT. But this limitation can also be overcome by post-processing of the received optical signals. In this context, detailed methodologies of SNR enhancement post-processing algorithms in Φ-OTDR systems have been described in this paper. Furthermore, after successfully locating the external vibrations, it is also important to identify the types of source of the vibrations. Pattern classification is a powerful tool in recognizing the intrusion types from the vibration signals in practical applications. Recent reports of Φ-OTDR systems employed with pattern classification algorithms are subsequently reviewed and discussed. This thorough review will provide a design pathway for improving the performance of Φ-OTDR while maintaining the cost of the system as no additional hardware is required.

41 citations

Journal ArticleDOI
TL;DR: In this paper, a review of the basic operating principles and measurement schemes of standalone and hybrid distributed optical fiber sensors based on Raman and Brillouin scattering phenomena is presented, and advanced techniques based on pulse coding used to overcome the tradeoff between sensing distance and spatial resolution affecting both types of sensors, thereby allowing measurements over tens of kilometers with meter-scale spatial resolution.
Abstract: We present a review of the basic operating principles and measurement schemes of standalone and hybrid distributed optical fiber sensors based on Raman and Brillouin scattering phenomena. Such sensors have been attracting a great deal of attention due to the wide industrial applications they offer, ranging from energy to oil & gas, from transportation to structural health monitoring. In distributed sensors, the optical fiber itself acts as a sensing element providing unique measurement capabilities in terms of sensing distance, spatial resolution and number of sensing points. The most common configuration exploits optical time domain reflectometry in which optical pulses are sent along the sensing fiber and the backscattered light is detected and processed to extract physical parameters affecting its intensity, frequency, phase, polarization or spectral content. Raman and Brillouin scattering effects allow the distributed measurement of temperature and strain over tens of kilometers with meter-scale spatial resolution. The measurement is immune to electromagnetic interference, suitable for harsh environments and highly attractive whenever large industrial plants and infrastructures have to be continuously monitored to prevent critical events such as leakages in pipelines, fire in tunnels, structural problems in large infrastructures like bridges and rail tracks. We discuss the basic sensing mechanisms based on Raman and Brillouin scattering effects used in distributed measurements, followed by configurations commonly used in optical fiber sensors. Hybrid configurations which combine Raman and Brillouin-based sensing for simultaneous strain and temperature measurements over the same fiber using shared resources will also be addressed. We will also discuss advanced techniques based on pulse coding used to overcome the tradeoff between sensing distance and spatial resolution affecting both types of sensors, thereby allowing measurements over tens of kilometers with meter-scale spatial resolution.

30 citations

Journal ArticleDOI
TL;DR: In this article, the authors review the recent advances on the high-performance distributed Brillouin optical fiber sensing, which include the conventional distributed optical fiber sensor, which includes backward stimulated BrillouIN scattering and two other novel distributed sensing mechanisms based on BrillOUin dynamic grating and forward stimulated Brillhouin scattering, respectively.
Abstract: This paper reviews the recent advances on the high-performance distributed Brillouin optical fiber sensing, which include the conventional distributed Brillouin optical fiber sensing based on backward stimulated Brillouin scattering and two other novel distributed sensing mechanisms based on Brillouin dynamic grating and forward stimulated Brillouin scattering, respectively. As for the conventional distributed Brillouin optical fiber sensing, the spatial resolution has been improved from meter to centimeter in the time-domain scheme and to millimeter in the correlation-domain scheme, respectively; the measurement time has been reduced from minute to millisecond and even to microsecond; the sensing range has reached more than 100 km. Brillouin dynamic grating can be used to measure the birefringence of a polarization-maintaining fiber, which has been explored to realize distributed measurement of temperature, strain, salinity, static pressure, and transverse pressure. More recently, forward stimulated Brillouin scattering has gained considerable interest because of its capacity to detect mechanical features of materials surrounding the optical fiber, and remarkable works using ingenious schemes have managed to realize distributed measurement, which opens a brand-new way to achieve position-resolved substance identification.

25 citations

Journal ArticleDOI
TL;DR: In this article , the authors reviewed advances in performance enhancements and typical applications of Raman distributed optical fiber sensing, and integration of this optical system technology with knowledge based, that is, demodulation technology etc.
Abstract: Abstract Raman distributed optical fiber sensing has been demonstrated to be a mature and versatile scheme that presents great flexibility and effectivity for the distributed temperature measurement of a wide range of engineering applications over other established techniques. The past decades have witnessed its rapid development and extensive applicability ranging from scientific researches to industrial manufacturing. However, there are four theoretical or technical bottlenecks in traditional Raman distributed optical fiber sensing: (i) The difference in the Raman optical attenuation, a low signal-to-noise ratio (SNR) of the system and the fixed error of the Raman demodulation equation restrict the temperature measurement accuracy of the system. {ii) The sensing distance and spatial resolution cannot be reconciled. (iii) There is a contradiction between the SNR and measurement time of the system. (iv) Raman distributed optical fiber sensing cannot perform dual-parameter detection. Based on the above theoretical and technical bottlenecks, advances in performance enhancements and typical applications of Raman distributed optical fiber sensing are reviewed in this paper. Integration of this optical system technology with knowledge based, that is, demodulation technology etc. can further the performance and accuracy of these systems.

24 citations