Interferometry Analysis Research Articles

Insights into the dynamics of the 2010 Eyjafjallajökull eruption using seismic interferometry and network covariance matrix analyses

Applying seismic interferometry and network covariance matrix-based analyses to detect and locate the source of volcanic tremor during the 2010 Eyjafjallajökull effusive flank and explosive-effusive summit eruptions has provided new insights into this iconic event. The tremor source locations derived from the network covariance matrix approach were spatially distinct during the two eruptions. The tremor was radiated between the surface and 5–6 km depth during the effusive flank eruption, including an apparently progressive upward migration in early April 2010, but was strictly confined to the surface during the summit eruption. Each phase of the summit eruption left a distinct fingerprint in the seismic records. Effusive phases radiated continuous tremor between 0.6 and 5 Hz, whereas explosive phases produced tremor in a more pulsating fashion over a wider frequency band (0.2–10 Hz). A period of intermittent tremor bursts (called banded tremor) on 15 April, associated with formation of a new vent at the summit, was most likely generated by magma-gas-meltwater interaction within a subglacial enclosure. The banded tremor ceased following an abrupt draining of the newly formed subglacial cauldron, resulting in a large slurry glacial meltwater flood (jökulhlaup). This study highlights the importance of new data processing methodologies for future monitoring of volcanic tremor in real-time.

Improving VLBI analysis by tropospheric ties in GNSS and VLBI integrated processing

Tropospheric delay modeling is challenging in high-precision Very Long Baseline Interferometry (VLBI) analysis due to the rapid water vapor variation and imperfect observation geometry, where observations from Global Navigation Satellite Systems (GNSS) co-locations can enhance the VLBI analysis. We investigate the impact of tropospheric ties in the VLBI and GNSS integrated processing during the CONT05–CONT17 campaigns, and present a method that automatically handles the systematic tropospheric tie biases. Applying tropospheric ties at VLBI–GNSS co-locations enhances the observation geometry and improves the solution reliability. The VLBI network is stabilized, with station coordinate repeatability improved by 12% horizontally and by 28% vertically, and the network scale improved by 32%. The Earth Orientation Parameters (EOP) improve by up to 20%. Both zenith delay and gradient ties contribute to the improvement of EOP, whereas the gradient ties contribute mainly to the improvement of length of day and celestial pole offsets.

The impact of helical slide honing on surface microtexture compared to plateau honing process through relevant characterization methods.

The cylinder engine surface texture has a major influence on the functional performances of the ring-pack tribo-system. The cylinder engine surface microtexture manufactured by plateau honing (PH) and helical slide honing (HSH) processes have been analyzed using white light interferometry (WLI), and stereometric analysis. The approaches in three-dimensional (3-D) white light interferometer measurements and surface stereometric analysis are important for the correct interpretation of 3-D local surface texture features and can be applied in mathematical models for calculating the friction. The samples were divided into two groups: plateau honing (PH) samples and helical slide honing (HSH) samples to discuss the obtained results, according to the honing techniques obtained after several stages: the rough and finish honing and final stage. The obtained results demonstrated that the surface of group PH has the higher values of root mean square height (Sq=1.83 μm) and fractal dimension (Df=2.74 ± 0.01), while the lowest values of root mean square height (Sq=0.63 μm) and fractal dimension (Df=2.60 ± 0.01) were found for HSH samples. These values highlight that the PH samples are more irregular (both as surface and topography) in comparison with HSH samples. HIGHLIGHTS: We characterized the micromorphology of surface microtexture in plateau and helical slide honing. The nanostructure morphology was investigated using the white light interferometry, fractal and stereometric analyses. The surface topography during the HSH process has different characteristics than the PH process and can be used to obtain better friction and lubrication performances.

Increase in landslide activity after a low-magnitude earthquake as inferred from DInSAR interferometry

On August 16th, 2018, a Mw 5.1 earthquake struck the Molise region (central Italy), inducing 84 earthquake-triggered landslides that predominantly involved soil covers of clayey materials and flysch on gently dipping slopes. To quantify the spatiotemporal landslide activity in the months immediately after the earthquake, a differential SAR interferometry (DInSAR) analysis was performed for a time span from 2 years before to one year after the earthquake, recognising both first-time and reactivated landslides. The results showed a clear increase in landslide activity following the low-magnitude earthquake with respect to the activities recorded in the same months of the previous years. Several coherent landslides (earth slides and earth flows) were observed following seasonally recurrent rainfall events. Such increases were observed for both reactivated and first-time landslides, showing decreases in inactive periods and activity over longer periods. Furthermore, the spatial density distribution of the landslides was investigated in the postseismic time interval along transects perpendicular and parallel to the direction of the tectonic element responsible for the seismic event. An asymmetrical distribution was deduced parallel to the fault strike with a higher number of landslides located inside the compressional sector according to a strike-slip faulting mechanism.

Inferring subsidence characteristics in Wuhan (China) through multitemporal InSAR and hydrogeological analysis

Wuhan (China) is facing severe consolidation subsidence of soft soil and karst collapse hazards. To quantitatively explore the extent and causes of land subsidence in Wuhan, we performed multitemporal interferometry (MTI) analysis using synthetic aperture radar (SAR) data from the TerraSAR-X satellite from 2013 to 2017 and the Sentinel-1A satellite from 2015 to 2017. MTI results reveal four major subsidence zones in Wuhan, namely, Hankou (exceeding −6 cm/yr), Xudong-Qingshan (−3 cm/yr), Baishazhou-Jiangdi (−3 cm/yr), and Jianshe-Yangluo (−2 cm/yr). Accuracy assessment using 106 levelling benchmarks and cross-validation between the two InSAR-based results indicate an overall root-mean-square error (RMSE) of 2.5 and 3.1 mm/yr, respectively. Geophysical and geological analyses suggest that among the four major subsiding zones, Hankou, Xudong-Qingshan, and Jianshe-Yangluo are located in non-karstic soft soil areas, where shallow groundwater (< 30 m) declines driven by engineering dewatering and industrial water depletion contribute directly to soft soil compaction. Subsidence in the Baishazhou-Jiangdi zone develops in the karst terrain with abundant underground caves and fissures, which are major natural factors for gradual subsidence and karst collapse. Spatial variation analysis of the geological conditions indicates that the stage of karst development plays the most important role in influencing kart subsidence, followed by municipal construction, proximity to major rivers, and overlying soil structure. Moreover, land subsidence in this zone is affected more via coupling effects from multiple factors. Risk zoning analysis integrating subsidence horizontal gradient, InSAR deformation rates, and municipal construction density show that the high-risk areas in Wuhan are mainly distributed in the Tianxingzhou and Baishazhou-Jiangdi zone, and generally spread along the metro lines.

Integrated use of Sentinel-1 and Sentinel-2 data and open-source machine learning algorithms for land cover mapping in a Mediterranean region

ABSTRACT This paper aims to develop a supervised classification integrating synthetic aperture radar (SAR) Sentinel-1 (S1) and optical Sentinel-2 (S2) data for land use/land cover (LULC) mapping in a heterogeneous Mediterranean forest area. The time-series of each SAR and optical bands, three optical indices (normalized difference vegetation index, NDVI; normalized burn ratio, NBR; normalized difference red-edge index, NDRE), and two SAR indices (radar vegetation index, RVI; radar forest degradation index, RFDI), constituted the dataset. The coherence information from SAR interferometry (InSAR) analysis and three optical biophysical variables (leaf area index, LAI; fraction of green vegetation cover, fCOVER; fraction of absorbed photosynthetically active radiation, fAPAR) of the single final month of the time-series were added to exploit their correlation with the canopy structure and improve the classification. The random forests (RF) algorithm was used to train and classify the final dataset, and an exhaustive grid search analysis was applied to set the optimal hyperparameters. The overall accuracy reached an F-scoreM of 90.33% and the integration of SAR improved it by 2.53% compared to that obtained using only optical data. The whole process was performed using freely available data and open-source software and libraries (SNAP, Google Earth Engine, Scikit-Learn) executed in Python-script language.

Long-term noise interferometry analysis in the northeast Pacific Ocean.

Long-term noise interferometry analysis is conducted over six years of data using two hydrophones on the Ocean Observatories Initiative Cabled Array. The two hydrophones are separated by 3.2 km and are bottom-mounted at 1500 m. We demonstrate the ability of ambient noise interferometry to reliably detect multi-path arrivals in the deep ocean from bottom-mounted hydrophones. An analysis of the multi-path arrival peak emergence is presented, as well as long-term trends of the signal-to-noise ratio of the arrival peaks. Last, we show that long-term ambient noise interferometry provides the opportunity for monitoring directional, coherent ambient sound such as the fin whale chorus.

Uplift of the surface of the earth above abandoned coal mines. Part A: Analysis of satellite data related to the movement of the surface

After the closure of several coal fields in Europe at the end of the 20th century, a new phenomenon in the field of strata or ground control was observed above abandoned coal mines, i.e., the upward movement or uplift of the surface. This also was observed above the Eisden mine in the eastern part of the Belgian Campine coal basin. The uplift was measured above the area mined by the longwall method and its surroundings, and it is linked to the flooding of the underground infrastructure and the surrounding rock mass . A detailed analysis of Interferometry with Synthetic Aperture Radar data showed the complexity of this phenomenon. There was a large spatial variation of uplift values, but there also was a variation as a function of time. At the start of the observation (about four years after the mine was closed), the average uplift rates were characterized by a wide spread of values, e.g., in a sub-area of 1 km 2 . Afterwards, the range of the values narrowed somewhat, and the rate of uplift decreased during the 20-year period of the study. For the central area, the uplift averaged about 22 mm/year during the first half of the observation time, and it averaged about 10 mm/year for the second half. Along a north-south transect, the shape of the curve of the uplift values could be best approximated by an inverse trough. However, the curve was not fully symmetrical. The extent of the zone of influence was several times larger than the depth of the longwall panels.

Elucidation of the anti-inflammatory mechanism of Er Miao San by integrative approach of network pharmacology and experimental verification

Traditional Chinese medicine (TCM) has been long time used in China and gains ever-increasing worldwide acceptance. Er Miao San (EMS), a TCM formula, has been extensively used to treat inflammatory diseases, while its bioactive components and therapeutic mechanisms remain unclear. In this study, we conducted an integrative approach of network pharmacology and experimental study to elucidate the underlying mechanisms of EMS in treating human rheumatoid arthritis (RA) and other inflammatory conditions. Quercetin, wogonin and rutaecarpine were probably the main active compounds of EMS in RA treatment as they affected the most RA-related targets, and TNF-α, IL-6 and IL-1β were considered to be the core target proteins. The main compounds in EMS bound to these core proteins, which was further confirmed by molecular docking and bio-layer interferometry (BLI) analysis. Moreover, the potential molecular mechanisms of EMS predicted from network pharmacology analysis, were validated in vivo and in vitro experiments. EMS was found to inhibit the production of NO, TNF-α and IL-6 in lipopolysaccharide (LPS)-stimulated RAW264.7 cells; reduce xylene-induced mouse ear edema; and decrease the incidence of carrageenan-induced rat paw edema. The carrageenan-induced up-regulation of TNF-α, IL-6 and IL-1β mRNA expression in rat paws was down-regulated by EMS, consistent with the network pharmacology results. This study provides evidence that EMS plays a critical role in anti-inflammation via suppressing inflammatory cytokines, indicating that EMS is a candidate herbal drug for further investigation in treating inflammatory and arthritic conditions.

Investigation into the effect of substrate material on microstructure and optical properties of thin films deposited via magnetron sputtering technique

This study aims at investigating the effect of the substrate material on growth mechanism and also microstructure of Ta2O5 thin films. For this purpose, atomic force microscopy, scanning electron microscopy, and interferometry analyses were implemented to reveal the influence of silicon wafer and amorphous BK7 glass substrates on the nucleation and growth mechanisms of Ta2O5 thin films deposited via the radio frequency magnetron sputtering technique. Results indicated that those films with finer morphologies had relatively higher nucleation densities. Compared with BK7 glass substrate, crystals formed on the silicon wafer were shown to be finer and had lower mean areas in more nucleation sites. Moreover, optical properties and morphological characteristics of the films on the silicon substrates had much more endurance after the annealing treatment. It was observed that shift in the transmission spectra of the deposited films after the treatment was insignificant, implying high packing density of the films. However, a 6-nm shift in the transmission spectra indicated low density and high porosity of the films. Finally, atomic force microscopy analysis along with the light scattering measurements confirmed the formation of a low-roughness film on the silicon wafer substrates.

Characterization of Single-Chain Fv Fragments of Neutralizing Antibodies to Rabies Virus Glycoprotein

Rabies has almost a 100% case-fatality rate and kills more than 59,000 people annually around the world. There is no established treatment for rabies. The rabies virus (RABV) expresses only the glycoprotein (RABVG) at the viral surface, and it is the target for the neutralizing antibodies. We previously established mouse monoclonal antibodies, 15–13 and 12–22, which showed neutralizing activity against the RABV, targeting the sequential and conformational epitopes on the RABVG, respectively. However, the molecular basis for the neutralizing activity of these antibodies is not yet fully understood. In this study, we evaluated the binding characteristics of the Fab fragments of the 15–13 and 12–22 antibodies. The recombinant RABVG protein, in prefusion form for the binding analysis, was prepared by the silkworm–baculovirus expression system. Biolayer interferometry (BLI) analysis indicated that the 15–13 Fab interacts with the RABVG, with a KD value at the nM level, and that the 12–22 Fab has a weaker binding affinity (KD ~ μM) with the RABVG compared to the 15–13 Fab. Furthermore, we determined the amino acid sequences of both the antibodies and the designed single-chain Fv fragments (scFvs) of the 15–13 and 12–22 antibodies as another potential biopharmaceutical for targeting rabies. The 15–13 and 12–22 scFvs were successfully prepared by the refolding method and were shown to interact with the RABVG at the nM level and the μM level of the KD, respectively. These binding characteristics were similar to that of each Fab. On the other hand, differential scanning fluorometry (DSF) revealed that the thermal stability of these scFvs decreases compared to their Fabs. While the improvement of the stability of scFvs will still be required, these results provide insights into the neutralizing activity and the potential therapeutic use of antibody fragments for RABV infection.

Detection of sinkhole activity in West-Central Florida using InSAR time series observations

Sinkhole activity in Florida is a major hazard for people and property. Its increasing frequency is often related to an accelerated use of ground-water and land resources in the region. In this work, we use a combined approach of radar interferometry and spatial clustering analysis over three selected sites in West-Central Florida to identify localized deformation that may be caused by sinkhole activity. The region of West-Central Florida is a densely active sinkhole region, where sinkholes tend to be small and land cover is mixed resulting in variable interferometric coherence that complicates Interferometric Synthetic Aperture Radar (InSAR) surveys. In this work, we present a combined methodology implementing InSAR and a Density-Based Spatial Clustering Analysis (DBSCAN) algorithm to detect unknown sinkhole activity and to alert to possible precursors of sinkhole collapse. The data used for the study consist of acquisitions from three TerraSAR-X frames covering time spans of ~1.7 and 2.5 years with spatial resolutions ranging from 25 cm up to 1 m. We applied the Persistent Scatterer Interferometry (PSI) technique using the Stanford Method for Persistent Scatterers (StaMPS) and confirmed the observed deformation signals by also processing the data using the SAR PROcessing tool (SARPROZ). Results show several areas of localized subsidence, from which the cluster with highest rates for each site was selected for detailed inspection. Locations of selected clusters were found in buildings with sizes ranging from 300 m2 to nearly 2000 m2, with subsidence trends ranging from −3 to −6 mm/yr. Results were compared with in-situ observations such as ground penetrating radar (GPR), electrical resistivity tomography (ERT) surveys, visual structural inspection and public county archive documents to help as ground truthing; subsiding locations were found to be related to sinkhole presence or development.

The Potsdam Open Source Radio Interferometry Tool (PORT)

The Potsdam Open Source Radio Interferometry Tool (PORT) is the very long baseline interferometry (VLBI) analysis software developed and maintained at the GFZ German Research Centre for Geosciences. Chiefly, PORT is tasked with the timely processing of VLBI sessions and post-processing activities supporting the generation of celestial and terrestrial reference frames. In addition, it serves as a framework for research and development within the GFZ’s VLBI working group and is part of the tool set employed in educating young researchers. Starting out from VLBI group delays, PORT estimates station and radio sources positions, as well as Earth orientation parameters, tropospheric parameters, and station clock offsets and drifts. The estimation procedures take into account all the necessary data analysis models that were agreed on for contributing to the ITRF2020 processing activities. The PORT code base is implemented in the MATLAB ® and Python programming languages. It is licensed under the terms of the GNU General Public License and available for download at GFZ’s Git server https://git.gfz-potsdam.de/vlbi-data-analysis/port.

Ruscogenin alleviates LPS-triggered pulmonary endothelial barrier dysfunction through targeting NMMHC IIA to modulate TLR4 signaling

Pulmonary endothelial barrier dysfunction is a hallmark of clinical pulmonary edema and contributes to the development of acute lung injury (ALI). Here we reported that ruscogenin (RUS), an effective steroidal sapogenin of Radix Ophiopogon japonicus, attenuated lipopolysaccharides (LPS)-induced pulmonary endothelial barrier disruption through mediating non-muscle myosin heavy chain IIA (NMMHC IIA)‒Toll-like receptor 4 (TLR4) interactions. By in vivo and in vitro experiments, we observed that RUS administration significantly ameliorated LPS-triggered pulmonary endothelial barrier dysfunction and ALI. Moreover, we identified that RUS directly targeted NMMHC IIA on its N-terminal and head domain by serial affinity chromatography, molecular docking, biolayer interferometry, and microscale thermophoresis analyses. Downregulation of endothelial NMMHC IIA expression in vivo and in vitro abolished the protective effect of RUS. It was also observed that NMMHC IIA was dissociated from TLR4 and then activating TLR4 downstream Src/vascular endothelial cadherin (VE-cadherin) signaling in pulmonary vascular endothelial cells after LPS treatment, which could be restored by RUS. Collectively, these findings provide pharmacological evidence showing that RUS attenuates LPS-induced pulmonary endothelial barrier dysfunction by inhibiting TLR4/Src/VE-cadherin pathway through targeting NMMHC IIA and mediating NMMHC IIA‒TLR4 interactions.

Persistent Scatterer Interferometry and Statistical Analysis of Time-Series for Landslide Monitoring: Application to Santo Stefano d’Aveto (Liguria, NW Italy)

Landslides are a major threat for population and urban areas. Persistent Scatterer Interferometry (PSI) is a powerful tool for identifying landslides and monitoring their evolution over long periods and has proven to be very useful especially in urban areas, where a sufficient number of PS can be generated. In this study, we applied PS interferometry to investigate the landslide affecting Santo Stefano d’Aveto (Liguria, NW Italy) by integrating classic interferometric techniques with cross-correlation analysis of PS time-series and with geological and geotechnical field information. We used open-source software and packages to process Synthetic Aperture Radar (SAR) images from the Copernicus Sentinel-1A satellite for both ascending and descending orbits over the period 2015–2021 and calculate both the vertical motion and the E-W horizontal displacement. By computing the cross-correlation of the PS time-series, we identified three families of PS with a similarity greater than 0.70. The cross-correlation analysis allowed subdividing the landslide in different sectors, each of which is characterized by a specific type of movement. The geological meaning of this subdivision is still a matter of discussion but it is presumably driven by the geomorphological setting of the area and by the regional tectonics.

Theoretical analysis of Hanbury Brown and Twiss interferometry at soft-x-ray free-electron lasers

In this work we provide theoretical background for the analysis of second-order correlation functions in experiments performed at the soft x-ray free-electron lasers (XFELs). Typically, soft x-ray beamlines at XFELs are equipped by the variable line spacing (VLS) monochromators. We perform examination of the beam propagation through such VLS monochromator taking specially into account the interplay between the finite monochromator resolution and the exit slits width. We then provide general analysis of the second-order correlation intensities in spectral and spatial domains. Finally, we connect these functions with the statistical properties of the beam incoming to the monochromator unit in the limit of Gaussian Schell-model pulses.

Multi-sensor remote sensing analysis of coal fire induced land subsidence in Jharia Coalfields, Jharkhand, India

The subsidence in coal mines induced by surface and subsurface fires leading to roof collapse, infrastructure loss, and loss of lives is a prominent concern. In the study, satellite imagery from thermal and microwave remote sensing data is used to deduce the effect of coal fires on subsidence in the Jharia Coalfields, India. The Thermal Infrared data acquired from the Landsat-8 (band 10) is used to derive the temperature anomaly maps. Persistent Scatterer Interferometry analysis was performed on sixty Sentinel-1, C-band images, the results are corrected for atmospheric error using Generic Atmospheric Correction Online Service for InSAR (GACOS) atmospheric modelling data and decomposed into vertical displacement values to quantify subsidence. A zone-wise analysis of the hazard patterns in the coalfields was carried out. Coal fire maps, subsidence velocity maps, and land cover maps were integrated to investigate the impact of the hazards on the mines and their surroundings. Maximum subsidence of approximately 20 cm/yr. and temperature anomaly of up to 25 °C has been observed. The findings exhibit a strong positive correlation between the subsidence velocity and temperature anomaly in the study area. Kusunda, Keshalpur, and Bararee collieries are identified as the most critically affected zones. The subsidence phenomenon in some collieries is extending towards the settlements and transportation networks and needs urgent intervention.

Plumbagin can potently enhance the activity of xanthine oxidase: in vitro, in vivo and in silico studies

BackgroundAbnormally elevated xanthine oxidase (XO) activity has been verified to cause various pathological processes, such as gout, oxidative stress injury and metabolic syndrome. Thus, XO activators may exhibit above potential toxicological properties. Plumbagin (PLB) is an important active compound in traditional Chinese medicine (TCM), while its obvious toxic effects have been reported, including diarrhea, skin rashes and hepatic toxicity. However, the potential toxicity associated with enhancement of XO activity has not been fully illuminated so far.MethodsThe present study investigated the effect of PLB on XO activity by culturing mouse liver S9 (MLS9), human liver S9 (HLS9), XO monoenzyme system with PLB and xanthine. Then, the molecular docking and biolayer interferometry analysis were adopted to study the binding properties between PLB and XO. Finally, the in vivo acceleration effect also investigated by injected intraperitoneally PLB to KM mice for 3 days.ResultsPLB could obviously accelerate xanthine oxidation in the above three incubation systems. Both the Vmax values and intrinsic clearance values (CLint, Vmax/Km) of XO in the three incubation systems increased along with elevated PLB concentration. In addition, the molecular docking study and label-free biolayer interferometry assay displayed that PLB was well bound to XO. In addition, the in vivo results showed that PLB (2 and 10 mg/kg) significantly increased serum uric acid levels and enhanced serum XO activity in mice.ConclusionIn summary, this study outlines a potential source of toxicity for PLB due to the powerful enhancement of XO activity, which may provide the crucial reminding for the PLB-containing preparation development and clinical application.

Probing the tunneling electron wave packet using the counter-rotating bi-circular fields

We experimentally measure the photoelectron momentum distributions of Ar atoms using two-color 800 nm (ω) + 400 nm (2ω) counter-rotating circularly polarized fields. By employing a weak fundamental circularly polarized field at 800 nm, the atomic potential barrier formed by the strong second harmonic field at 400 nm can be modulated. This introduces a spatially rotating temporal two-slit interferometry between the photoelectron wave packets tunneling from the modified barriers in the consecutive cycles. The modulation of the barrier would leave its imprint on the photoelectron interference pattern. In analogy to the analysis of the traditional optical interferometry, we perform the Fourier transform on the photoelectron interference. The modulation on the amplitude and phase of the electron wave packets induced by the weak fundamental field is retrieved.

Lean Blowout Sensing and Processing via Optical Interferometry and Wavelet Analysis of Dynamic Pressure Data

This paper introduces a novel approach to monitor combustion instabilities in turbomachinery. This innovation is motivated by the need to better analyze flame health in a continuous flow machine, and more precisely in its hot core expressed by machine OEMs and end-users. This improved monitoring system will support an optimization of the machine performance, leading to a safer, cleaner, more flexible and more cost-efficient operation for the end-user. There have been several numerical studies that simulate the nonlinear dynamics of flame instabilities limit in simple combustors, they predict the pressure oscillations frequency is very low 5-25 Hz. Nowadays, in gas turbine monitoring, dynamic pressure measurement sensors are based on electrical working principle technologies such as piezoelectric, piezo-resistive and capacitive measurement. While exposed to high temperatures, due to pyro-electric effects and noise spectral density of charge amplifiers, piezo sensors signal to noise ratio (SNR) decreases sharply at low frequencies (about a factor 10 every 100°). Optical sensing systems provide much better stability, in the low frequency range when exposed to high temperature and, moreover, are intrinsically insensitive to vibration or EMI perturbation. This feature allows analyzing more accurately low frequency flame dynamics. Within the frame of a joint study between Meggitt, Combustion Bay One e.U. and FH Joanneum GmbH, the behavior of an optical measurement system was tested under different combustion instability conditions. By acting on system parameters (equivalent ratio, air speed) several tests have been conducted where combustion has been driven to different instability conditions such as premixed to diffusion flame transition, lean blow out, flashback. Data have been recorded and analysed from both the optical and the piezo sensors installed within the combustion chamber. The objective of the test campaign is twofold: compare optical to piezo system performances under flame combustion instabilities and, taking advantage of improved low frequency SNR of pressure data coming from optical sensors, to develop and validate an algorithmic strategy to detect/prognose phenomena such as Lean Blow Out and Flashback. The paper initially describes the principia of the used optical sensing technology, including some relevant hardware and software aspects of the measurement chain. After that, the experimental set-up and tests conditions are presented. About piezo to optical data comparison, SNR analysis of test data confirms the expectations of a lower noise at low frequency and the improved visibility of flame instabilities provided by optical sensor. Based on this, in order to analyze the transient behavior at low frequencies associated to flame instabilities two algorithmic strategies have been developed: wavelet analysis and chaos dimension analysis. Based on these methodologies several Lean Blow Out indicators have been implemented and tested. Details of their behavior in response to the variation of the equivalence ratio close to the flame blow out are presented and discussed. Three of the proposed indicators, under the investigated test conditions, proved to possess the capability to detect the blow out event. Depending on how the approach to the blow out event occurs, some indicators also shown prognostics capability. Results show some indicators start reacting as the flame approaches to extinction or as the equivalence ratio reduces. These indicators can be considered flame health meters. The test campaign results shown in the paper allow to conclude that optical sensing technologies provide advantages over piezoelectric sensing technologies such as: insensitivity to pyro-electric effects and inherent insensitivity to external perturbations, i.e. electromagnetic interferences and radio frequency interferences, vibrations. Particularly the improved accuracy at low frequencies of the sensor coupled with new signal processing techniques, as the ones presented, may support a flame health monitoring capability and the ability to sense blowout precursors. The replacement of piezo-electric with fiber optic sensors will therefore be desirable for many combustion monitoring applications, especially the ones requiring monitoring of low frequencies. This can, provide significant payoffs in engine reliability and operability, in enabling optimal performance over extended time periods as an engine ages, in reducing maintenance costs, and in increasing engine life.