Lim Jun Long & Co.

Abstract

Non-local mean (NLM) can significantly improve the signal-to-noise ratio (SNR), but it inevitably reduces the spatial resolution of distributed optical fiber sensors (DFOS), which hinders its practical application and the improvement of DFOS performance. In this paper, the quantitative relationship between the signal broadening of a phase-sensitive optical time-domain reflectometer (𝜑 -OTDR) and the NLM parameters is analyzed to identify the cause and extent of the spatial resolution degradation. The denoising results for the mimic periodic and 𝜑 -OTDR vibration signals indicate that the signal broadening is mainly due to the similarity window size of NLM, and the signal amplitude reduction is caused by the Gaussian smoothing parameter. Compared with the reference signals, the signal broadening of the mimic and 𝜑 -OTDR signals after denoising are 2.56% and 2.74%, respectively, which is much less than the previous results. The signal amplitude is reduced by 9.25% and 13.62%, respectively. This work promotes the application of NLM and improves the performance of DFOS.

Abstract

A high-sensitivity axial force sensor with a large measurement range based on a dual-peak long-period fiber grating (LPFG) is proposed and experimentally demonstrated. Previously, the relationship between the grating period and the dual-peak wavelengths has been investigated based on the coupled-mode theory. In our experiment, the LPFG was fabricated in our laboratory by illuminating the fiber core with the aid of a 213 nm UV laser. The sensitivity of the proposed axial force sensor can reach −14.047 nm/N in the force range from 0.490 N to 4.508 N. Taking the advantages of a compact size, low cost, and large measurement range, our force sensor has more applicable abilities in harsh environments.

Abstract

The combined effects of temperature (from −80 °C to +80 °C) and 100 kV X-ray exposure (up to 108 kGy(SiO2)) on the physical properties of Brillouin scattering and losses in three differently doped silica-based optical fibers, with varying dopant type and concentration (4 wt%(Ge), 10 wt%(Ge) and 1 wt%(F)), are experimentally studied in this work. The dependencies of Brillouin Frequency Shifts (BFS), Radiation-Induced Attenuation (RIA) levels, Brillouin gain attenuation, Brillouin frequency temperature (CT) and strain (Cε) sensitivity coefficients are studied under X-rays in a wide temperature range [−80 °C; +80 °C]. Brillouin sensing capabilities are investigated using a Brillouin Optical Time Domain Analyzer (BOTDA), and several properties are reported: (i) similar behavior of the Brillouin gain amplitude decrease with the increase in the RIA; (ii) the F-doped and heavily Ge-doped fibers do not exhibit a temperature dependence under radiation for their responses in Brillouin gain losses. Increasing Ge dopant concentration also reduces the irradiation temperature effect on RIA. In addition, Radiation-Induced Brillouin Frequency Shift (RI-BFS) manifests a slightly different behavior for lower temperatures than RIA, presenting an opportunity for a comprehensive understanding of RI-BFS origins. Related temperature and strain sensors are designed for harsh environments over an extended irradiation temperature range, which is useful for a wide range of applications.

Abstract 

Magnetic field sensing has the potential to become necessary as a critical tool for long-term subsurface geophysical monitoring. The success of distributed fiber optic sensing for geophysical characterization provides a template for the development of next generation downhole magnetic sensors. In this study, Sentek Instrument’s picoDAS is coupled with a multi-material single mode optical fiber with Metglas® 2605SC cladding wire inclusions for magnetic field detection. The response of acoustic sensing fibers with one and two Metglas® 2605SC cladding wires was evaluated upon exposure to lateral AC magnetic fields. An improved response was demonstrated for a sensing fiber with in-cladding wire following thermal magnetic annealing (~400 °C) under a constant static transverse magnetic field (~200 μT). A minimal detectable magnetic field of ~500 nT was confirmed for a sensing fiber with two 10 μm cladding wires. The successful demonstration of a magnetic field sensing fiber with Metglas® cladding wires fabricated via traditional draw processes sets the stage for distributed measurements and joint inversion as a compliment to distributed fiber optic acoustic sensors.

Abstract 

The plastic scintillation optical fiber (PSOF) detector, characterized by its large contact area with measurement targets, effectively detects and quantifies radiation in diverse radiation-contaminated areas and liquid environments. While it is extensively utilized for measuring alpha, beta, gamma, and neutron radiations, comprehensive documentation on the spectrum measurement and energy calibration methods for gamma nuclides has not been reported. Accurate energy calibration is crucial for the precise quantification of radiation doses from various sources. The pulse-height spectrum produced by the PSOF detector does not display a Compton maximum because of the significant Gaussian energy broadening. Additionally, this spectrum compresses as the distance increases between the radiation source and the light measurement device. In this study, the energy spectrum of a PSOF for gamma nuclides was characterized by energy calibrations using Compton edge (CE). The CE channel in the measurement spectrum of the PSOF detector for three gamma nuclides was identified using the first-order differentiation method. This technique was successfully applied to spectra measured at various radiation source positions to determine the attenuation coefficients. The proposed energy calibration method allows for the conversion of pulse-height spectra obtained from alpha, beta, and neutron radiation measured with PSOF detectors into energy spectra.

Abstract 

We discuss how the dual-wavelength differential detection (DWDD) of fiber Bragg grating sensors can be used to build standardized high-resolution, high-accuracy, large-measurement-range, multichannel instruments and associated sensors. We analyze the system resolution and experimentally show that the high signal-to-noise ratio can allow the design of sensors with a ratio of range to resolution superior to 14 bits, and temperature measurement ranges of more than 180 °C. We propose a scheme for real-time signal correction to cancel the drift of the instrument using two internal reference sensors, and a calibration method using centralized golden sensors that allows traceability to international standards for all instruments and sensors, allowing the creation of a global sensor/instrument ecosystem.

Abstract 

Optical fiber sensors consist of multiple Mach–Zehnder (MZ) interferometers and are common in the protection of different compounds. These sensors are very sensitive to any intrusion or threat. However, the spatial resolution is proportional to the number of MZ interferometers along the sensor. Consequently, a long sensor with a high resolution can be costly. In this paper, we suggest replacing the cascaded MZ interferometers with a couple of adjacent fibers, each of which have a harmonically varying refractive index. In this theoretical study, it is shown that two fibers with varying refractive indices demonstrate a sensitivity equivalent to that of multiple MZ interferometers. Furthermore, when the coupling coefficient between the fibers is weak, an analytical expression can be derived for the transmission between the fibers. This transmission reveals a quantization rule for which the light coupling between the two fibers vanishes.

Abstract

In the ever-evolving landscape of modern technology, integrating communication and sensing systems has become increasingly essential for a wide range of applications, from military and defense to autonomous vehicles and beyond. The integration offers a convergence of capabilities that enhances operational efficiency and provides adaptability in complex environments. In this paper, we develop, in simulation and experiment, an integrated communication and sensing system, exploring the cutting-edge utilization of spread spectrum and radio-over-fiber (RoF) photonic technologies. RoF technology inherits the benefits of optical fibers, which include low attenuation and longer reach distance compared to other media. First, we consider the integration of communication and sensing functions using a spread spectrum–binary phase-shift keying waveform. In this integrated system, the sensing function is performed using a radar system. The performance of the proposed system is evaluated in terms of the peak-to-sidelobe ratio of the radar correlator output and the bit error rate for the communication system. The results are obtained through extensive MATLAB simulations. Next, we consider the realization of the proposed integrated communication and sensing system using photonics technology. This phase commences with the utilization of specialized photonics-based software for extensive simulations at different fiber lengths, which is an essential foundational step toward the practical implementation of the proposed system using photonics. Lab experiments are also presented to validate the simulation results.

Abstract

Dosimetry is crucial in radiotherapy to warrant safe and correct treatment. In FLASH radiotherapy, where ultra-high dose rates (UHDRs) are used, the dosimetric demands are more stringent, requiring the development and investigation of new dosemeters. In this study, three prototype fiber-optic dosemeters (FODs)—an inorganic, an organic–inorganic hybrid metal halide, and an organic (plastic) scintillator are optimized and investigated for UHDR electron irradiations. The plastic FOD is developed by Medscint, whereas the others are in-house made. The stem signal is minimized by spectral decomposition for the plastic scintillator, and by band-pass wavelength filters for the inorganic and organic–inorganic hybrid metal halide FOD. All prototypes are tested for the dose rate defining parameters. The optimal band-pass wavelength filters are found to be centered around 500 nm and 425 nm for the inorganic and organic–inorganic hybrid metal halide FODs, respectively. A sampling frequency of 1000 Hz is chosen for the inorganic and organic–inorganic hybrid metal halide FODs. The plastic FOD shows to be the least dose rate dependent with maximum deviations of 3% from the reference for the relevant beam settings. The inorganic and organic–inorganic hybrid metal halide FODs, in contrast, show large deviations of >10% from the reference and require more investigation. The current FOD prototypes are insufficient for application in UHDR electron beams, and require further development and investigation.

Total number of publications in top 10% = 4 of 24 (16.67 % overall)

Total number of publications in 1st quartile = 8 of 24 (33.33 % overall)

Published in these selected highly influential journals (top 10% or 1st quartile):

• 1. Optics Letters (CiteScore top 10% in 2015) - 2X articles

     • Rank = 10 / 159, CiteScore = 7.0, 94th percentile

     • Rank 3 in Citation 2012-2015 

     • Rank 3 in Documents 2012-2015

     • Rank 7 in % Cited

  2. Optics Express (CiteScore top 10% in 2015) - 1X article

     • Rank = 9 / 159, CiteScore = 7.1, 94th percentile

     • Rank 1 in Citation 2012-2015

     • Rank 1 in Documents 2012-2015

  3. IEEE Journal of Selected Topic in Quantum Electronics (CiteScore top 10% in 2015) - 1X article

     • Rank = 13 / 159, CiteScore = 6.1, 92nd percentile

  4. IEEE Photonics Technology Letters (CiteScore 1st quartile in 2015) - 1X article

     • Rank = 21 / 159, CiteScore = 5.2, 87th percentile

     • Rank 10 in Citation 2012-2015

  5. IEEE Photonics Journal (CiteScore 1st quartile in 2019) - 3X articles

     • Rank = 33 / 159, CiteScore = 4.2, 79th percentile

Total number of publications in 1st quartile = 8 of 28 (28.57 % overall)

Published in these selected highly influential journals (1st quartile):

• IEEE Journal of Selected Topic in Quantum Electronics (CiteScore 1st quartile in 2019) - 1X

  1. Rank = 21 / 183, CiteScore = 7.4, 88th percentile

• Optics Letters (CiteSscore 1st quartile in 2019) - 2X

  1. Rank = 22 / 183, CiteScore = 7.2, 88th percentile

  2. Rank 5 in Citation 2016-2019

  3. Rank 9 in Documents 2016-2019

• Optics Express (CiteScore 1st quartile in 2019) - 2X

  1. Rank = 26 / 183, CiteScore = 6.7, 86th percentile

  2. Rank 1 in Citation 2016-2019

  3. Rank 2 in Documents 2016-2019

• IEEE Photonics Technology Letters (CiteScore 1st quartile in 2019) - 1X

  1. Rank = 38 / 183, CiteScore = 5.5, 79th percentile

• IEEE Photonics Journal (CiteScore 1st quartile in 2019) - 3X

  1. Rank = 45 / 183, CiteScore = 5.0, 78th percentile

• 1. CiteScore™ Percentile 2020, CiteScore™ Rank 2020, CiteScore™ Quartile  2020. Calculated by Scopus on 05 May 2021.

  2. CiteScore™ Percentile 2019, CiteScore™ Rank 2019, CiteScore™ Quartile  2019. Calculated by Scopus on 31 May 2020.

1. CiteScore™ Percentile 20XX. Calculated by Scopus on 31 May 20XX for Atomic and Molecular Physics, and Optics. Available from www.scopus.com/sourceid
2. CiteScore™ Rank 20XX. Calculated by Scopus on 31 May 20XX for Atomic and Molecular Physics, and Optics. Available from www.scopus.com/sourceid 
3. CiteScore™ Quartile 20XX. Calculated by Scopus on 31 May 20XX for Atomic and Molecular Physics, and Optics. Available from www.scopus.com/sourceid