Performance Investigation of OFDR Sensing System With a Wide Strain Measurement Range

Gao

et al. 2020

Sensors

The distributed high temperature measurement of an optical fiber subjected to electric arc discharges based on optical frequency-domain reflectometry is experimentally demonstrated. The distributed temperature profile is attained in an open glow regime of a few milliamps with maximum detectable temperature up to 2100 ± 20 °C. The discharge arc-induced softened length of the fiber and mechanical stress are measured and statistically analyzed in terms of the correlation of the Rayleigh spectra. The large wavelength scanning range of OFDR enables much higher accuracy for the delay time measurement with a minimum measured delay of 40 fs. The delay shift over the entire heating range for a single discharge duration is statistically calculated by using a temporal correlation method. The reliability of the thermal sensitivity coefficient as 10 pm/°C for telecom single mode fiber (SMF, @1550 nm) is quantitatively analyzed and evaluated by the correlation coefficient. Lastly, a spectral mapping method is employed in spectrum monitoring for discharge dynamic impact on the optical path length (OPL) and local Rayleigh scatter.

Section: Experimental Results and Data Analysismentioning

confidence: 99%

Section: Experimental Results and Data Analysismentioning

confidence: 99%

Distributed High Temperature Monitoring of SMF under Electrical Arc Discharges Based on OFDR

Gao

et al. 2020

Sensors

“…Although varying the reference will not help resolve large spatial variations in temperature or strain, several other techniques have been proposed to this end. For example, summing the upstream strains and shifting the gauge position downstream by the cumulative calculated upstream strain has been demonstrated to improve OFDR measurements [ 29 , 44 ]. The gauge length could also be decreased to reduce the variation in temperature or strain over the gauge at the expense of temperature or strain resolution [ 45 ].…”

Section: Discussionmentioning

confidence: 99%

Graphical Optimization of Spectral Shift Reconstructions for Optical Backscatter Reflectometry

Sweeney

Petrie

2021

Sensors

Optical backscatter reflectometry (OBR) is an interferometric technique that can be used to measure local changes in temperature and mechanical strain based on spectral analyses of backscattered light from a singlemode optical fiber. The technique uses Fourier analyses to resolve spectra resulting from reflections occurring over a discrete region along the fiber. These spectra are cross-correlated with reference spectra to calculate the relative spectral shifts between measurements. The maximum of the cross-correlated spectra—termed quality—is a metric that quantifies the degree of correlation between the two measurements. Recently, this quality metric was incorporated into an adaptive algorithm to (1) selectively vary the reference measurement until the quality exceeds a predefined threshold and (2) calculate incremental spectral shifts that can be summed to determine the spectral shift relative to the initial reference. Using a graphical (network) framework, this effort demonstrated the optimal reconstruction of distributed OBR measurements for all sensing locations using a maximum spanning tree (MST). By allowing the reference to vary as a function of both time and sensing location, the MST and other adaptive algorithms could resolve spectral shifts at some locations, even if others can no longer be resolved.

“…The maximum detectable dynamic strain is limited by the positiondependent Rayleigh scattering pattern correlation in OFDR traces, i.e., backscattered traces depend on the spatial distribution of the inhomogeneity in the sensing fiber [65]. To overcome this limit, the position calibration is for spectrum registration was proposed to reduce the deterioration induced by the position segment mismatch in the spatial domain; this allowed the 7000 με range [66].…”

Section: Optical Frequency Domain Reflectometry (Ofdr)mentioning

confidence: 99%

Recent Advancements in Rayleigh Scattering-Based Distributed Fiber Sensors

Bao

Wang

2021

Adv Devices Instrum

Recently, Rayleigh scattering-based distributed fiber sensors have been widely used for measurement of static and dynamic phenomena such as temperature change, dynamic strain, and sound waves. In this review paper, several sensing systems including traditional Rayleigh optical time domain reflectometry (OTDR), Φ-OTDR, chirped pulse Φ-OTDR, and optical frequency domain reflectometry (OFDR) are introduced for their working principles and recent progress with different instrumentations for various applications. Beyond the sensing technology and instrumentation, we also discuss new types of fiber sensors, such as ultraweak fiber Bragg gratings and random fiber gratings for distributed sensing and their interrogators. Ultimately, the limitations of Rayleigh-based distributed sensing systems are discussed.