Fiber Optic Probe Research Articles

Detection of Alcohol Content in Food Products by Lossy Mode Resonance Technique

The study deliberates the detection of ethanol/methanol concentration utilizing the phenomenon of lossy mode resonances on the multimode optical fiber by coating ZnO nanorods and bulk layers of TiO2 to serve as a lossy mode exciting layer. These layers have been characterized by FESEM, and their composition has been confirmed by EDS spectroscopy. Sensitivity of the ZnO nanorod coated optical fiber probe was found to be 28898.46 nm RIU−1, which is four times the sensitivity of the ZnO nanowire grown gas sensor for 1000 ppm of ethanol. Further, it is 4.5 times the sensitivity of TiO2 coated fiber probe. The sensitivity of TiO2 coated fiber optic probe comes about 7962.88 nm RIU−1, for methanol detection. The study reveals that the ZnO nanorod grown probe is highly recommended owning to the high figure of Merit i.e., 171.64 along with high sensitivity and detection accuracy values. The selectivity test also confirms the selectivity of this probe towards ethanol with ZnO NRs. Therefore, the development of an easy, durable, low-cost, and highly sensitive optical fiber sensing probe for the detection of ethanol and methanol has been achieved that may find ample considerations by the researchers in this field.

Highly Sensitive Imaging Spectrometer System Based on Areal Array to Linear Array Optical Fiber Probe for Biological Spectral Detection

Noninvasive bio-molecular spectral sensing method for scattered tissue can be utilized to accurately obtain and analyze bio-molecular information. Propagation of light in biological tissues will gradually present diffusive feature and results in severe attenuation of detection light intensity and deteriorating the signal-to-noise ratio of detection system. In our work, we built a three-channel imaging spectrometer system and designed a compatible special fiber bundle probe for diffusive spectral detection. The system can synchronously collect the spectral signals from 270 fibers in the fiber bundles then convert them into electrical signal. Aiming at the aberration in the system, we also designed a corresponding data processing method to effectively realize the wavelength calibration of spectral signals. Finally, the system was applied to the nondestructive detection of human tissues and mouse with the <inline-formula> <tex-math notation="LaTeX">$15 ~ \mu \text{W}$ </tex-math></inline-formula> white light and 4.05 mw 405 nm laser. For the above extremely weak excitation light source, our system can still obtain the high signal-to-noise ratio diffusive spectra with less than 1 s integration time. Experiments were conducted to obtain spectra of back-scattering and autofluorescence of biological tissue. Experimental results show that the system has certain advantages in biological tissue scattering spectroscopy detection and autofluorescence detection.

Ultrasensitive detection of Cr(VI) using a novel SERS optical fiber probe modified by dual-functional methimazole

Ultrasensitive detection of highly toxic Cr(VI) is of paramount importance as trace amount of Cr(VI) will result in inevitable deterioration to human health and the environment. In this work, a novel methimazole-functionalized SERS optical fiber probe was used for the first time for Cr(VI) determination with ultrahigh sensitivity. A special functionalization process of methimazole was designed after successful fabrication of silver coated fiber probe via a SnCl 2 -sensitized solvothermal method. Dual functional methimazole guaranteed ultrahigh sensitivity and good stability of the SERS fiber probe for Cr(VI) detection. On one hand, methimazole functions as a Raman reporter which exhibits SERS peak intensity decline in the presence of Cr(VI). On the other hand, methimazole acts as an oxidation inhibitor via coordinating with silver atoms through the lone pair of nitrogen and sulfur atoms. The optimized SERS fiber probe not only presents good stability and excellent reproducibility, but also exhibits ultrahigh sensitivity (10 −11 M) which exceeds SERS or other techniques for Cr(VI) determination reported so far. • Methimazole-functionalized SERS fiber probe was synthesized for the first time. • Methimazole acts as Raman reporter with ultrahigh sensitivity of 10 −11 M for Cr(VI). • Methimazole also functions as oxidation inhibitor of silver with good stability.

Eight-year follow-up of excimer laser trabeculostomy alone and combined with phacoemulsification in patients with open-angle glaucoma.

To describe the 8-year results of excimer laser trabeculostomy (ELT) alone and ELT in conjunction with phacoemulsification (phaco). University hospital. Retrospective review. 308 nm excimer laser energy delivered through an intraocular fiber-optic probe created channels through the inner wall of Schlemm canal. 2 groups were studied: ELT alone and ELT + phaco. Inclusion criteria were adult patients with open-angle glaucoma or ocular hypertension on 1 or more intraocular pressure (IOP)-lowering medications and, in the ELT + phaco group, presence of visually significant cataract. Primary outcome measures were change of IOP from baseline and number of IOP-lowering medications. 164 eyes in 2 groups, ELT alone (n = 90) and ELT + phaco (n = 74), were followed up for 8 years. Baseline IOP was 22.17 ± 7.0 mm Hg and 21.9 ± 6.44 mm Hg in the ELT alone and the ELT + phaco groups, respectively. IOP in the ELT alone group decreased to 16.84 ± 5.2 mm Hg at 1 year (n = 69) and remained at 15.9 ± 3.5 (n = 19) at 8 years. IOP in the ELT + phaco group was 14.04 ± 4.1 mm Hg at 1 year (n = 63) and 13.7 ± 2.8 mm Hg at 8 years (n = 13). The number of IOP-lowering medications at baseline in the ELT alone group was 1.85 ± 0.8 and decreased to 1.19 ± 1.10 at 1 year and 1.4 ± 1.4 at 8 years. In the ELT + phaco group, it was 1.58 ± 0.8 at baseline and decreased to 0.97 ± 0.95 at 1 year and 1.85 ± 0.7 at 8 years. ELT demonstrated long-term IOP lowering and decrease in the number of IOP-lowering medications. Benefits of this laser-based implant-free microinvasive glaucoma surgery procedure included a high safety profile and long-term efficacy.

A Handheld Fiber-Optic Probe to Enable Optical Coherence Tomography of Oral Soft Tissue.

This study presents a highly miniaturized, handheld probe developed for rapid assessment of soft tissue using optical coherencetomography (OCT). OCT is a non-invasive optical technology capable of visualizing the sub-surface structural changes that occur in soft tissue disease such as oral lichen planus. However, usage of OCT in the oral cavity has been limited, as the requirements for high-quality optical scanning have often resulted in probes that are heavy, unwieldy and clinically impractical. In this paper, we present a novel probe that combines an all-fiber optical design with a light-weight magnetic scanning mechanism to provide easy access to the oral cavity. The resulting probe is approximately the size of a pen (10 mm × 140 mm) and weighs only 10 grams. To demonstrate the feasibility and high image quality achieved with the probe, imaging was performed on the buccal mucosa and alveolar mucosa during routine clinical assessment of six patients diagnosed with oral lichen planus. Results show the loss of normal tissue structure within the lesion, and contrast this with the clear delineation of tissue layers in adjacent inconspicuous regions. The results also demonstrate the ability of the probe to acquire a three-dimensional data volume by manually sweeping across the surface of the mucosa. The findings of this study show the feasibility of using a small, lightweight probe to identify pathological features in oral soft tissue.

Autofluorescence detection and co-axial projection for intraoperative localization of parathyroid gland

BackgroundNear-infrared (NIR) autofluorescence detection is an effective method for identifying parathyroid glands (PGs) in thyroidectomy or parathyroidectomy. Fiber optical probes provide quantitative autofluorescence measurements for PG detection owing to its high sensitivity and high excitation light cut-off efficiency at a fixed detection distance. However, an optical fiber probe lacks the imaging capability and cannot map the autofluorescence distribution on top of normal tissue background. Therefore, there is a need for intraoperative mapping of PGs with high sensitivity and imaging resolution.MethodsWe have developed a fluorescence scanning and projection (FSP) system that combines a scanning probe and a co-axial projector for intraoperative localization and in situ display of PGs. Some of the key performance characteristics, including spatial resolution and sensitivity for detection, spatial resolution for imaging, dynamic time latency, and PG localization capability, are characterized and verified by benchtop experiments. Clinical utility of the system is simulated by a fluorescence-guided PG localization surgery on a tissue-simulating phantom and validated in an ex vivo experiment.ResultsThe system is able to detect indocyanine green (ICG) solution of 5 pM at a high signal-to-noise ratio (SNR). Additionally, it has a maximal projection error of 0.92 mm, an averaged projection error of 0.5 ± 0.23 mm, and an imaging resolution of 748 μm at a working distance ranging from 35 to 55 cm. The dynamic testing yields a short latency of 153 ± 54 ms, allowing for intraoperative scanning on target tissue during a surgical intervention. The simulated fluorescence-guided PG localization surgery has validated the system’s capability to locate PG phantom with operating room ambient light interference. The simulation experiment on the PG phantom yields a position detection bias of 0.36 ± 0.17 mm, and an area intersection over unit (IoU) of 76.6% ± 6.4%. Fluorescence intensity attenuates exponentially with the thickness of covered tissue over the PG phantom, indicating the need to remove surrounding tissue in order to reveal the weak autofluorescence signal from PGs. The ex vivo experiment demonstrates the technical feasibility of the FSP system for intraoperative PG localization with accuracy.ConclusionWe have developed a novel probe-based imaging and navigation system with high sensitivity for fluorescence detection, capability for fluorescence image reconstruction, multimodal image fusion and in situ PG display function. Our studies have demonstrated its clinical potential for intraoperative localization and in situ display of PGs in thyroidectomy or parathyroidectomy.

Rapid and sensitive magnetic field sensor based on photonic crystal fiber with magnetic fluid infiltrated nanoholes

A fast response time (0.1 s) magnetic field sensor has been demonstrated utilizing a photonic crystal fiber with nano-size air holes infiltrated with polyethylene glycol based magnetic fluid. The effect of magnetic nanoparticles concentration in the fluid on the magneto-optical sensor performance and its dependence under varying magnetic-field loads was investigated in detail. In particular, the sensor response was analytically modelled with a Langevin function with a good fit (Rge 0.996). A threshold sensing point as low as 20 gauss was recorded and a detection range of 0–350 gauss was demonstrated by means of optical transmission measurements. The experimental results were validated by theory using a waveguide light transmission model fed by finite-element method simulations of the principal guided modes in the infiltrated fiber sensor. The simple interrogation scheme, high sensitivity and quick response time makes the proposed hybrid fiber-optic magneto-fluidic probe a promising platform for novel biochemical sensing applications.

A Raman immunosensor based on SERS and microfluidic chip for all-fiber detection of brain natriuretic peptide

Early diagnosis of chronic heart failure (CHF) relies on the ultra-sensitive detection assay of its main biomarker, Brain natriuretic peptide (BNP). To meet such demand, we designed a near-infrared immunoassay biosensor, utilizing a fiber-embedded microfluidic chip for surface-enhanced Raman scattering (SERS) detection. A SERS probe, consisting of metal–organic framework and Au-HEPES coupling nanoparticles (AuHPs), was used to enhance the Raman signal of the toluidine blue (TB) dye. The probe anchored with TB is used as a SERS tag, which is linked to BNP through sandwich method. To enhance the Raman signal further, we embedded a SERS substrate at the bottom of the microfluidic channel, which serves an enhancer when the SERS tagged BNP passes through the microfluidic chip. The amplified Raman signal was collected by an optical fiber probe of a simple and portable Raman detection system with an all-fiber connected configuration. Such design resulted in the lowest detection limit of pg/mL, indicating that the proposed platform can be used for rapid and highly sensitive detection of BNP. In addition, our platform also has the advantages of low sample consumption and high throughput rate, providing an effective scheme for the early diagnosis of CHF.

Effects of Varying Laser Parameters During Laser Stapedotomy on Intracochlear Pressures.

Sensorineural hearing loss is a known complication of stapes surgery. We previously showed that laser stapedotomy can result in intracochlear pressures that are comparable to high sound pressure levels. Optimizing laser settings to those that correspond with the lowest pressure changes may mitigate risk for postoperative hearing loss. Here we quantify the effects of various laser parameters on intracochlear pressures and test the hypothesis that intracochlear pressure changes are proportional to the laser energy delivered. Basic and translational science. Cadaveric dissection and basic science laboratory. Cadaveric human heads underwent mastoidectomies. Intracochlear pressures were measured via fiber-optic pressure probes placed in scala vestibuli and tympani. Pulses of varied stimulus power and duration from a 980-nm diode laser were applied to the stapes footplate. Sustained high-intensity pressures were observed in the cochlea during all laser applications. Observed pressure magnitudes increased monotonically with laser energy and rose linearly for lower stimulus durations and powers, but there was increased variability for laser applications of longer duration (200-300 ms) and/or higher power (8 W). Results confirm that significant pressure changes occur during laser stapedotomy, which we hypothesize may cause injury. Overall energy delivered depends predictably on duration and power, but surgeons should use caution at the highest stimulus levels and longest pulse durations due to the increasing variability in intracochlear pressure under these stimulus conditions. While the risk to hearing from increased intracochlear pressures from laser stapedotomy remains unclear, these results affirm the need to optimize laser settings to avoid unintended injury.

Multipoint gas-liquid phase detection method based on a thin-film optical waveguide.

Gas-liquid phase detection is an important technique applied in a wide range of industries. In this study, we developed a phase detection method using a film-based optical waveguide. The optical waveguide is a thin and flexible film with multi-light paths that uses multi-microsensors for gas-liquid phase detection. The intensity of the reflected light generated by different refractive indices between gas and liquid aids in distinguishing the phase. Additionally, the sensing principle is identical to that of the typical optical fiber probing technique. In this study, we investigated the detection process considering the impact of a single droplet on waveguide sensors. Furthermore, we analyzed a droplet evaporation phenomenon and a thin-film liquid flow accompanied by a high-speed airflow on the sensors. Based on the obtained results, we determined that the proposed method can effectively measure the simultaneous local multipoint and high temporal resolution phase detection on a smooth surface. Therefore, we believe that our original sensor can diagnose such a dispersed two-phase flow near the wall inside of machines or curved tubes where the high-speed visualization is hard to be applied.

The hydrodynamics of low-density particles and optimization of the EMMS calculation process

Different reaction technology determines different catalytic materials and solid density affects the hydrodynamics behavior in a fluidized bed. An efficient hydrodynamics study is, therefore, highly desirable, even for evaluating the assumptions through pilot-scale investigation. To develop new fluidized bed technology that requires low-density particles (e.g., the vapor-phase Beckman rearrangement to produce ε-caprolactam), the authors thoroughly studied the hydrodynamics of low-density particles (true density 750 kg/m3, packing density 450 kg/m3) in a turbulent fluidized bed. Pilot-scale cold experiments were conducted in an ∅800 mm column with optical fiber probes. The TFM was adopted, where the Wen&Yu model, EMMS model, and six filtered models were coupled, respectively. The solution of the EMMS model is often challenging because of the iterative solution of nonlinear equations. In this work, the calculation process of the EMMS model was optimized, saving one global search for every possible state solution, and a set of nonlinear equations can be linearized. Comparisons between experiment and simulation results revealed that the EMMS models gave the best prediction. This work can provide a research model and guidance for the design of industrial fluidized bed reactors using low-density particles.

Rapid determination of urea formaldehyde resin content in wood fiber mat using near-infrared spectroscopy

Monitoring the process is crucial for ensuring high quality in wood-based panel production. Interest in the distribution of resin in fibers and particles has increased during the last couple of decades. This study considered the potential to determine urea formaldehyde (UF) resin content in fiber mat using near-infrared (NIR) spectroscopy. Fiber mats with various resin contents were investigated with NIR combined with the partial least squares (PLS) regression and root mean square error of calibration and validation (RMSECV). The external factors, such as the distance between the fiber optic probe and the sample surface and light sources, were also evaluated. The results showed that this technique can sufficiently determine the resin content in the resinous fiber mat with accuracy of up to 95%. The light sources and the distances from the probe to the surface did not significantly influence the discrimination and prediction of resin content.

D-shape optical fiber probe dimension optimization for LSPR based bio-sensor

The evanescent wave absorption based photonic sensing platform has been developed using D-shaped fiber optic probes for refractive index (RI) mediated bio-sensors. The RI sensitivity of this bare probe was established using different sucrose solutions by optimizing the active de-cladded surface area of the fiber. A linear correlation between probe sensing area and RI sensitivity was observed for different probe lengths. Further, these bare probes have been functionalized using amine (–NH2) functional groups on the air-exposed core using the standard silane treatment process. This probe was demonstrated as a localized surface plasmon resonance (LSPR) monitoring platform by immobilizing the spherical gold nanoparticles (AuNPs). The effect of D-shaped length/area on absorption sensitivity was compared with bare and LSPR probes. The biosensing property of this LSPR probe was tested using Immunoglobulin antibody (HIgG). An exponential bimolecular binding kinetic has been observed during this antigen–antibody conjugation and the limit of detection was measured (0.6 µg/mL) by varying concentrations of antigen (GaHIgG). These fiber optic LSPR probes can be integrated into an optical system to develop an evanescent wave absorption-based biosensor.

Efficacy and Safety of Micropulse Transscleral Laser Therapy in Silicone Oil-induced Glaucoma.

The purpose of this study was to assess the efficiency and safety of micropulse transscleral laser therapy (MP-TLT) in the management of silicone oil-induced glaucoma (SOG). A prospective case series of 33 eyes with uncontrolled SOG was enrolled at the Department of Ophthalmology of Mohamed Taher Maamouri Hospital, Nabeul, Tunisia. Patients were treated with MP-TLT using the IRIDEX Cyclo G6 Glaucoma Laser System with the MicroPulse P3 fiberoptic handheld probe. Patients underwent complete ophthalmologic examination during the 12-month follow-up period. The study included 33 eyes of 33 patients. The mean age was 50.39 years old. We included patients with SOG. Silicone oil tamponade was indicated for complicated rhegmatogenous retinal detachment in 22 cases, diabetic tractional retinal detachment in 10 cases, and posttraumatic retinal detachment in 1 case. Silicone oil was already removed before the procedure in 23 eyes. Silicone oil tamponade duration varied between 3 and 26 months. Intraocular pressure (IOP) measurements at enrollment; days 1, 7, and 15; and months 1, 3, 6, and 12 was respectively 37.94±13.61, 19.03±10.98, 16.5±6.17, 19.45±9.73, 19.27±8.33, 19.39±9.52, 19.97±10.03, and 19.7±9.58 mm Hg. The percentage of IOP lowering was 45.38% at 6 months and 45% at 12 months. The success rate was 93.93% at 6 months, remaining stable at 12 months. No major side effects were observed, in particular, no phthisis bulbi nor prolonged inflammation. There was no difference in IOP lowering between patients with silicone oil or those after silicone oil removal ( P =0.99). MP-TLT was safe and effectively lowered IOP in uncontrolled SOG.

Optimization of a flexible fiber-optic probe for epi-mode quantitative phase imaging.

Quantitative oblique back-illumination microscopy (qOBM) is an emerging label-free optical imaging technology that enables 3D, tomographic quantitative phase imaging (QPI) with epi-illumination in thick scattering samples. In this work, we present a robust optimization of a flexible, fiber-optic-based qOBM system. Our approach enables in silico optimization of the phase signal-to-noise-ratio over a wide parameter space and obviates the need for tedious experimental optimization which could easily miss optimal conditions. Experimental validations of the simulations are also presented and sensitivity limits for the probe are assessed. The optimized probe is light-weight (∼40g) and compact (8mm in diameter) and achieves a 2µm lateral resolution, 6µm axial resolution, and a 300µm field of view, with near video-rate operation (10Hz, limited by the camera). The phase sensitivity is <20nm for a single qOBM acquisition (at 10Hz) and a lower limit of ∼3 nm via multi-frame averaging. Finally, to demonstrate the utility of the optimized probe, we image (1) thick, fixed rat brain samples from a 9L gliosarcoma tumor model and (2) freshly excised human brain tissues from neurosurgery. Acquired qOBM images using the flexible fiber-optic probe are in excellent agreement with those from a free-space qOBM system (both in-situ), as well as with gold-standard histopathology slices (after tissue processing).

Experimental methods in chemical engineering: Optical fibre probes in multiphase systems

AbstractAs much as 75% of the raw materials in the chemical industry and 50% of consumer products are in the form of powders or granular solids. Gasification, pyrolysis, coating, granulation, drying, and mixing are examples of processes in which particles contact fluids. Researchers examine the hydrodynamics of these fluid–solid systems with pressure signals, acoustics, tomography, radioactive particle tracking, optical fibre measurements, and spectroscopy. Among these techniques, fibre optic probes are simple, inexpensive, and sensitive (spatial resolution of 100 μm) and have sampling frequencies of Hz. Optical probes measure local hydrodynamic properties, including particle velocity, solids fraction, and voids, which are difficult to measure in heterogeneous systems like spouted beds, risers, and turbulent fluidized beds. Light from a fibre optic bundle illuminates a specific volume, and fibres from the same or separate bundle return the reflected or transmitted photons to a detector (visible, near‐infrared spectroscopy, or Raman). Sample MATLAB codes included herein together with sample experimental data demonstrate how to process raw signals for gas/solids/and bubble holdup, particle and bubble velocity, bubble size, and solids flux.

Model-Based Optimization of Laser Excitation and Detection Improves Spectral Contrast in Noninvasive Diffuse Raman Spectroscopy.

Spatially offset Raman spectroscopy (SORS) is a powerful technique for subsurface molecular analysis of optically turbid samples. Numerical modeling of light propagation has been used to investigate opportunities for improving spectral contrast and signal to noise ratio when imaging regions of interest located 0-4.5mm below the surface in polymer bulk material. Two- and three-dimensional modeling results demonstrate that when analyzing a certain region of interest (ROI) of finite lateral dimensions below the sample surface, offsetting both the laser source and detector in opposite directions from the central point of the ROI can increase the spectral contrast as compared to conventional SORS approach where the detector or the laser source is maintained at the central point (centered SORS). The outlined modeling results have been validated experimentally using a bulk polymer sample with a trans-stilbene ROI (cylinder) below the sample surface. The results show that modeling of the spatial configurations of laser excitation and detection points can be used to optimize the instrument configuration to achieve significant improvements (up to 2.25-fold) in performance over the conventional centered SORS. Such optimal solutions can then be implemented, for example, using robust fiber optic probes, moveable optics, or flexible spatial light modulator instruments for specific applications.

Spectral Reflectance as a Unique Tissue Identifier in Healthy Humans and Inhalation Injury Subjects.

Tracheal intubation is the preferred method of airway management, a common emergency trauma medicine problem. Currently, methods for confirming tracheal tube placement are lacking, and we propose a novel technology, spectral reflectance, which may be incorporated into the tracheal tube for verification of placement. Previous work demonstrated a unique spectral profile in the trachea, which allowed differentiation from esophageal tissue in ex vivo swine, in vivo swine, and human cadavers. The goal of this study is to determine if spectral reflectance can differentiate between trachea and other airway tissues in living humans and whether the unique tracheal spectral profile persists in the presence of an inhalation injury. Reflectance spectra were captured using a custom fiber-optic probe from the buccal mucosa, posterior oropharynx, and trachea of healthy humans intubated for third molar extraction and from the trachea of patients admitted to a burn intensive care unit with and without inhalation injury. Using ratio comparisons, we found that the tracheal spectral profile was significantly different from buccal mucosa or posterior oropharynx, but the area under the curve values are not high enough to be used clinically. In addition, inhalation injury did not significantly alter the spectral reflectance of the trachea. Further studies are needed to determine the utility of this technology in a clinical setting and to develop an algorithm for tissue differentiation.

Flexible minimally invasive coherent anti-Stokes Raman spectroscopy (CARS) measurement method with tapered optical fiber probe for single-cell application

We proposed and demonstrated a flexible, endoscopic, and minimally invasive coherent anti-Raman Stokes scattering (CARS) measurement method for single-cell application, employing a tapered optical fiber probe. A few-mode fiber (FMF), whose generated four-wave mixing band is out of CARS signals, was selected to fabricate tapered optical fiber probes, deliver CARS excitation pulses, and collect CARS signals. The adiabatic tapered fiber probe with a diameter of 11.61 μm can focus CARS excitation lights without mismatch at the focal point. The measurements for proof-of-concept were made with methanol, ethanol, cyclohexane, and acetone injected into simulated cells. The experimental results show that the tapered optical fiber probe can detect carbon-hydrogen (C–H) bond-rich substances and their concentration. To our best knowledge, this optical fiber probe provides the minimum size among probes for detecting CARS signals. These results pave the way for minimally invasive live-cell detection in the future.

Comparison of the radial profiles of particles velocity between invasive and non-invasive measurement techniques

In this work, the radial profiles of the particles velocity in gas-solid fluidized beds were measured using two techniques: (1) an advanced optical fiber probe, an invasive technique, and (2) radioactive particle tracking (RPT), a noninvasive technique. Two gas-solid fluidized bed columns of 0.14 and 0.44 m inside diameters were used to estimate the radial profile of the particles velocity. The particle velocity was measured at different operating conditions and axial heights. It was found that the implementation of the noninvasive radioisotope particle tracking (RPT) technique was able to successfully guide the measurement of the radial profile of the particle velocity using the optical fiber probe technique. The average inversion point of the radial particle velocity, from positive to negative, was identified from the measurements using both techniques for different operating conditions and axial heights.