Fiber Optic Technique Research Articles

A comparative evaluation of strain measurement techniques in reinforced concrete structures–A discussion of assembly, application, and accuracy

AbstractThe measurement of strain in structural elements is a necessary means of investigating the condition of a structure, both in research and in practice. The measurement methods for recording strain considered in this work represent both well‐established techniques (strain gauges), as well as techniques that are part of rather current research streams (fiber optic sensors, digital image correlation). This work's contribution lies in providing an overarching comparison of these approaches, thereby informing practitioners and researchers as to parameters concerning their assembly, application, and their accuracy. To such ends, two test series were carried out, one on RC tension rods and another on a RC beam in a four‐point bending test. From the latter scenario, for example, certain generalizations were to be deduced for varying load levels: low strains are measured well using the fiber optic technique. Conversely, digital image correlation was discovered to be an adequate choice when assessing higher strain levels and concomitant concrete cracking, as this non‐contact technique avoids imprecisions caused by adhesives. Findings are to assist the future user by contrasting the three techniques in terms of assembly, handling, application and resilience of sensors, external influences as well as measurement resolution and accuracy. Such practice‐oriented remarks should simplify a selection of the suitable measurement techniques catering to the respective, context‐dependent testing scenario.

Study Reviews Advances in Downhole Fiber-Optic Modeling and Analytics

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 200826, “Recent Advances in Downhole Fiber-Optics Modeling and Analytics: Case Studies,” by Derek S. Bale, SPE, Rajani P. Satti, SPE, and Roberto Failla, SPE, Baker Hughes, et al., prepared for the 2020 SPE Western Regional Meeting, originally scheduled to be held in Bakersfield, California, 27 April–1 May. The paper has not been peer reviewed. The upstream industry has witnessed significant breakthroughs in developing and deploying permanent, on-demand, and distributed temperature and acoustic fiber-optic monitoring systems to optimize well completions and enhance production. Beyond steady advances in hardware, challenges associated with the analysis of distributed optical data are being addressed to enable delivery of value-driven solutions and services. The complete paper discusses a methodology for integrating intelligent completion and production systems with a modeling and analytics framework for efficient development of fiber-optic-based data-interpretation services for complex downhole environments. Introduction During the last 30 years, the industry has found novel ways to apply fiber-optic technology to monitor in-well events, operations, and critical parameters. Recently, applications including the need to maximize hydrocarbon recovery, remotely manage assets for improved cost-efficiency and safety, and reduce carbon footprint have accelerated the adoption of fiber-optic-based systems. Specific to wellbore completions, the confluence of increased durability and reliability of downhole fiber-optic systems, computer processing speed, and the ability to couple fiber sensors to completion and production equipment has led to significant growth in several applications. Fiber-optic techniques such as distributed temperature sensing (DTS) and distributed acoustic sensing (DAS) have proved particularly successful for applications such as injection and production profiling, well-integrity monitoring, leak detection, perforation cluster efficiency, and fracture monitoring. For all the benefits delivered by downhole fiber-optic technology, challenges specific to data transmission and storage remain, in particular with regard to data analysis and interpretation, that must be understood to fully enable delivery of value-generating solutions. These challenges are illustrated in Fig. 1 of the complete paper. Philosophy and Description of Solutions The solutions to the challenges described previously need to be downhole-tool-centric, cost-effective, and time-efficient. The complete paper is focused on presenting a methodology that follows a scientific and pragmatic work flow and demonstrating successful applications using a combination of intelligent downhole hardware and advanced modeling and analytics. The methodology begins with designing and developing intelligent downhole tools capable of providing the necessary data to enhance or optimize production, mitigate risk, and improve operational efficiency. Intelligent downhole tools can include interval control valves, downhole pressure and temperature gauges, connectors, control units, and cables, and are deployed into a complex downhole environment. As these smart tools are run downhole, fiber-optic cables are deployed in tandem to acquire continuous, spatially distributed data (i.e., strain, temperature, or acoustic) along the completion.

Fiber optic sensor designs and luminescence-based methods for the detection of oxygen and pH measurement

Optical, and especially fiber optic techniques for chemical sensing have become very attractive in recent decades for a wide variety of biomedical and industrial processes and considerable progress in research in this field has been seen, evidenced by the significant number of papers published over several decades, commercial products developed and marketed and which continuing to be produced. This work extends the body of knowledge in the field and focuses on two industrially-important ‘chemical’ measurands: the determination of pH level and oxygen concentration (O2) - both are critically important for a broad range of applications globally, in fields as diverse at the life sciences, environmental monitoring, biomedical research and thus widely across industry.The many different optical platform designs and fabrication methods that have been developed are considered, including those for commercial applications, recognizing the wide range of industrial and scientific uses, and their performance compared. Further, the effect of specific fiber structures on sensor performance, e.g. on sensitivity, response time and long-term stability, and possible applications also has been analyzed. Applications are seen in difficult and ‘niche’ measurement environments to which conventional sensors are often not well suited, taking advantage of their lightweight nature, ease of miniaturization, potential to be multiplexed and low cost. Through a discussion of representative techniques that have reached commercial development, a comprehensive and state-of-the-art view of this exciting and important field is possible.

Correlation technique using of-the-shelf CW DFB laser for interrogation of fiber optic sensors

The paper presents a simple fiber-optic sensor technique based on methods of correlation optical time domain reflectometry. A correlation reflectometry technique can measure distribution of reflection coefficient along the optical fiber by calculating the correlation function between a probe optical signal (reference) and the signal returned back due to reflections or/and back-scattering from the fiber under the test. To obtain the best sensor performance, the probe signal power should be a truly random function of time. As an optical source we use a free-running DFB laser diode operating in a continuous wave regime without any external modulation. To generate the probe test signal, laser light is passed through an interferometer with an optical path difference much longer than the coherence length of the laser light. The light intensity at the interferometer output has a truly random fluctuations and its auto correlation function is suitable for correlation optical reflectometry. We present results of experimental verification of the techniques in different sensor configurations. Multipoint sensor using very low reflective fiber Bragg gratings with reflectivity of 0.01% printed in a long SMF-28 optical fiber was demonstrated.

Can optical fiber compete with profile analysis tensiometry in critical micelle concentration measurement?

Abstract Critical micelle concentration (CMC) is one of the important nominal characteristics of the surfactants which can be measured using various methods. In this study, to detect the CMC of two ionic surfactants, cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS), two methods were utilized: (a) optical fiber and (b) drop profile analysis tensiometry (PAT) techniques. The spectrum width center and surface tension of the solutions at different concentrations of the surfactant were measured. The preliminary outcomes showed a compliance between optical fiber method and PAT technique. However, there were differences in the behavior of two surfactants in optical fiber measurement. In this method, when the solid surface of fiber is put in the system, the interactions between surfactant molecules and the fiber surface must be carefully considered.

Mitigation of thermal curling of concrete slab using phase change material: A feasibility study

In this study, the effects of phase change material (PCM) on the thermo-mechanical behaviors of concrete pavement slabs are investigated so as to test the feasibility of utilizing PCM for mitigation of thermal curling of pavement. The PCM is elaborately stabilized in porous lightweight aggregate then loaded into concrete, without compromising strength associated with PCM incorporation. Thermal analysis indicates that the PCM introduces a latent heat capacity of about 21 J/g to the pavement slab. Two emerging fiber-optic monitoring techniques, i.e., truly distributed strain/temperature sensors and a high-resolution inclinometer, are employed to continuously monitor distributions of the temperature, strain, and tilting angle of the slabs subjected to heating and cooling, respectively. Validated by the obtained experimental results, a finite element simulation framework is established to further investigate the temperature gradient distributions, slab deformations/curvatures, and thermal strain and stress inside the slabs. The results suggest that the PCM-incorporated slab has a higher top surface temperature, a larger top-vs-bottom surface temperature difference, and thereof a larger curvature. However, the temeprature gradient reveals that heat accumulates at the upper layer before PCM melts completely, thus accounting for most of the temerpature difference. Moreover, regardless of the larger top-vs-bottom strain difference and stress nonlinearity, the linear strain of the PCM slab is smaller due to its lower coefficient of thermal expansion, and the later stage stress at the middle of the PCM slab center is smaller. Based on the findings, strategies of using PCM to control thermal curling of pavement slabs are proposed.

Safety of percutaneous dilatational tracheotomy (PDT) with the rigid tracheotomy endoscope (TED): a 6-month follow-up multicenter investigation

BackgroundThe rigid tracheotomy endoscope (TED) was recently introduced to improve the fiberoptic technique during percutaneous dilatational tracheotomy (PDT) in critically ill patients. The aim was to evaluate the long-term complications of PDT using TED equipment in a prospective multicenter investigation.MethodsOne hundred eighty adult patients underwent PDT using TED in four German hospitals. Patients who were alive or their guardians were contacted via telephone and interviewed using a structured questionnaire 6 months following the tracheostomy procedure. Patients with airway complaints were invited for outpatient clinical ENT examination. The incidence of adverse events related to PDT was registered.ResultsOf 180 patients who received tracheostomy, 137 (76.1%) were alive at the time of follow-up. None of the 43 lethal events was related to the PDT. Fifty-three (38.7%) patients were available for follow-up examination, whereas 14 (10.2%) were able to visit ENT physicians. Two (3.8%) out of 53 patients developed tracheocutaneous fistula with required surgical closure of tracheostoma. Dyspnea (7.5%), hoarseness (5.7%), stridor and swallowing difficulties (both with 3.8%) were the most common complaints. Tracheal stenosis was confirmed in 1 patient (1.88% [95% CI: 0.33; 9.93]).ConclusionThe use of TED for PDT in the clinical setting is safe regarding adverse events at 6-month follow-up. The incidence of tracheal stenosis after PDT with TED is comparable with that of flexible bronchoscopy; however, its role for PDT at the intensive care unit should be clarified in further investigations.

Laboratory Studies Using Electrical Resistivity Tomography and Fiber Optic Techniques to Detect Seepage Zones in River Embankments

We present the results of laboratory experiments on a down-scaled river levee constructed with clayey material collected from a river embankment where a permanent resistivity instrument has operated since 2015. To create potential seepages through the levee, two zones (5 × 4 cm and 10 × 2 cm) were filled with sand during the levee construction. Electrical resistivity tomography (ERT) technique and Fiber Bragg Grating (FBG) technology were used to study time-lapse variations due to seepage. The ERT profile was spread on the levee crest and the Wenner array with unit electrode spacing a = 3 cm was used. Six organic modified ceramics (ORMOCER) coated 250 μm-diameter fibers were deployed in different parts of the levee. Time-lapse measurements were performed for both techniques from the beginning of each experiment when water was added to the river side until the water was continuously exiting from the seepage zones. The results showed that ERT images could detect seepages from the early stages. Although with a short delay compared to ERT, fiber optic sensors also showed their ability to detect water infiltrations by measuring temperature changes. Both technologies being successful, a discussion about respective peculiarities and pros and cons is proposed to suggest some criteria in choosing the proper technique according to the specific needs.

Fiber optic quench detection for large-scale HTS magnets demonstrated on VIPER cable during high-fidelity testing at the SULTAN facility

Fiber-optic thermometry has the potential to provide rapid and reliable quench detection for emerging large-scale, high-field superconducting magnets fabricated with high-temperature-superconductor (HTS) cables. Developing non-voltage-based quench detection schemes, such as fiber Bragg grating (FBG) technology, are particularly important for applications such as magnetic fusion devices where a high degree of induced electromagnetic noise impose significant challenges on traditional voltage-based quench detection methods. To this end, two fiber optic quench detection techniques—FBG and ultra-long FBG (ULFBG)—were incorporated into two vacuum pressure impregnated, insulated, partially transposed, extruded, and roll-formed (VIPER) high-current HTS cables and tested in the SULTAN facility, which provides high-fidelity operating conditions to large-scale superconducting magnets. During surface heater induced quench-like events under a variety of operating conditions, FBG and ULFBG demonstrated strong signal-to-noise ratios (SNRs) ranging from 4 to 32 and measured single-digit temperature excursions; both the SNR and temperature sensitivity increase with temperature. Fiber thermal response times ranged between effectively instantaneous to a few seconds depending on the operating temperature. Strain sensitivity dominates the thermal sensitivity in the conditions achievable at SULTAN; however, measurements at higher quench evolution temperatures, coupled to future work to increase the thermal-to-strain signal, show promise for quench detection capability in full-scale magnets where temperature and strain may occur simultaneously. Overall, FBG and ULFBG were proven capable to quickly and reliably detect small temperature disturbances which induced quench initiation events for high current VIPER HTS conductors in realistic operating conditions, motivating further work to develop FBG and ULFGB quench detection systems for full-scale HTS magnets.

Comparison of Heating Strategies on Soil Water Measurement Using Actively Heated Fiber Optics on Contrasting Textured Soils

The actively heated fiber optics (AHFO) technique has the potential to measure soil water at high spatial and temporal resolutions, and thus it can bridge the measurement gap from point to large scales. However, the availability of power might restrict its use, since high power is required to heat long fiber optic cables under field conditions; this can be a challenge for long-term soil water monitoring under field conditions. This study investigated the performance of different heating strategies (power intensity and heating duration) on soil water measurement by the AHFO technique on three different textured soils. Different heating strategies: high power–short pulses (20 Wm−1–3 min), low power–short pulses (10 Wm−1–3 min, 5 Wm−1–3 min, 2.5 Wm−1–3 min) and low power–long pulses (10 Wm−1–5 min, 5 Wm−1–10 min, 2.5 Wm−1–15 min) were tested using laboratory soil columns. The study compared the sensitivity of the thermal response, NTcum to volumetric water content (VWC) and the predictive error of different heating strategies and soils. Results of this study showed that the sensitivity of NTcum increased and the predictive error decreased with increasing power intensity, irrespective of the soil type. Low power–short heat pulses such as 5 Wm−1–3 min and 2.5 Wm−1–3 min produced high predictive errors, RMSE of 5–6% and 6–7%, respectively. However, extending the heating duration was effective in reducing the error for both 10 and 5 Wm−1 power intensities, but not for the 2.5 Wm−1. The improvement was particularly noticeable in 5 Wm−1 –10 min; it reduced the RMSE by 1.5% (sand and clay loam) and 2.73% (sandy loam). Overall, the results of this study suggested that extending the heating duration of 10 and 5 Wm−1 power intensities can improve the sensitivity of the thermal response and predictive accuracy of the estimated soil water content (SWC). The results are particularly important for field applications of the AHFO technique, which can be limited by the availability of high power, which restricts the use of 20 Wm−1. For example, 5 Wm−1–10 min improved the predictive accuracy to 3–4%, which has the potential to be used for validating soil water estimations at satellite footprint scales. However, the effects of diurnal temperature variations should also be considered, particularly when using low power intensity such as 5 Wm−1 in surface soils under field conditions.

Label-Free Follow-Up Surveying of Post-Treatment Efficacy and Recurrence in Nasopharyngeal Carcinoma Patients with Fiberoptic Raman Endoscopy.

Recurrent nasopharyngeal carcinoma (NPC) is the main cause of poor prognosis for NPC patients after chemo- and radiotherapies. Subsequent long-term follow-ups of post-treatment patients are crucial for the early discovery of tumor recurrence with timely intervention. Current clinical imaging methods based on tissue morphology encounter difficulties in differentiating recurrent tumors from post-treatment inflammation and fibrosis. In this work, we apply a unique fiberoptic Raman endoscopy technique to address the challenges for label-free follow-up surveying of post-treatment NPC patients and accurate detection of tumor recurrence. Significant Raman spectral differences can be observed among normal, NPC, and nonrecurring post-treatment patients. Raman endoscopy provides diagnostic accuracy of 100% for detecting recurrent NPC from early post-treatment inflammation and diagnostic accuracy of 98.21% for separating recurrent NPC from long-term post-treatment fibrosis. Further quantitative Raman modeling on in vivo nasopharyngeal tissue Raman data acquired unveils the changes of major tissue biochemicals (e.g., triolein, elastin, keratin, fibrillar collagen, and type IV collagen) associated with primary NPC and post-treatment recurrent NPC tissue compared to normal nasopharyngeal tissue. This work demonstrates that fiberoptic Raman endoscopy can be a clinically powerful diagnostic tool for rapid, label-free post-treatment surveying and recurrent tumor detection in NPC patients at the molecular level.

Anesthesia for robotic thoracic surgery.

The management of the robotic thoracic surgical patient requires the knowledge of minimally invasive surgery techniques involving the chest. Over the past decade, robotic-assisted thoracic surgery has grown, and, in the future, it will take an important place in the treatment of complex thoracic pathologies. The enhanced dexterity and three-dimensional visualization make it possible to do this in the small space of the thoracic cavity. Familiarity with the robotic surgical system by the anesthesiologists is mandatory. Management of a long period of one-lung ventilation with a left-sided double-lumen endotracheal tube or an independent bronchial blocker is required, along with flexible fiberoptic bronchoscopy techniques (best continuous monitoring). Correct patient positioning and prevention of complications such as eye or nerve or crashing injuries while the robotic system is used is mandatory. Recognition of the hemodynamic effects of carbon dioxide during insufflation in the chest is required. Cost is higher and outcome is not yet demonstrated to be better as compared to video-assisted thoracic surgery. The possibility for conversion to open thoracotomy should also be kept in mind. Teamwork is mandatory, as well as good communication between all the actors of the operating theatre.

The Effect of Fiberoptic Bronchoscopy-guided Technique for Placement of a Left-sided Double-lumen Tube on the Intubation Performance Compared with the Conventional Method Using a Macintosh Laryngoscope

Background: The accurate placement of the double-lumen endotracheal tube is imperative for effective one-lung ventilation in thoracic surgery. Malpositioning and repositioning of a misplaced tube may cause excessive trauma. Objective: We hypothesized that the fiberoptic bronchoscope-guided method for double-lumen endotracheal tube placement would reduce the incidence of malpositioning as compared to the conventional method using the Macintosh laryngoscope. Methods: Fifty patients scheduled to undergo elective thoracic surgery were recruited and randomly assigned to the fiberoptic bronchoscope-guided [n=25; Group F] and conventional [n=25; Group C] method groups, according to the method of double-lumen endotracheal tube placement. The primary outcome was the incidence of double-lumen endotracheal tube malpositioning observed under the fiberoptic bronchoscope after initial placement. Secondary outcomes included the times for placement, confirmation, and total procedure of double-lumen endotracheal tube intubation. Results: The incidence of malpositioning after initial double-lumen endotracheal tube placement was significantly lower in Group F than in Group C (20.0% vs 68.0%). In addition, the time for placement was significantly higher in Group F than in Group C, and that for confirmation was significantly lower in Group F than in Group C. Conclusion: The fiberoptic bronchoscope-guided method for double-lumen endotracheal tube placement can reduce the incidence of malpositioning after initial placement and expedite the intubation process with a double-lumen endotracheal tube in thoracic surgery.

The refractive index of human blood measured at the visible spectral region by single-fiber reflectance spectroscopy

The refractive index is an essential biophysical parameter used in many diagnostic and therapeutic biomedical applications. In the present study, the refractive index of control and anemic blood was measured using the total internal reflection fiber optics technique. For control, the refractive index measured by the indicated method was significantly higher than anemic blood over the wavelengths in the visible spectral region used in this study. Strong linear correlations between refractive index and hemoglobin concentration were obtained for control and anemic blood. These findings could enhance the use of the refractive index in many applications of blood analysis and hematology.

In-Situ Monitoring of Solidification Process of PVA Solution by Fiber Optic Sensor Technique

In this research, we monitored the solidification process of PVA solution using a fiber optic refractive index sensor. During the monitoring process in this paper, two Fabry-Perot cavities were used to monitor the temperature and the refractive index of the PVA sample. The advantage of this method is that the related refractive index change is obvious, and the status of materials can be directly observed during the testing process. Furthermore, this method can be more cost-effective compared with its heat flow-based counterpart. Differential scanning calorimetry (DSC) tests were performed with the same material and the heating rate. Compared with the result given by DSC, the detected temperature range when the phase of PVA solution changes is much narrower. The method suggested in this paper is potentially useful to monitor the solidification process of transparent materials in an easier and cost-effective way.

Flexible gauge length intrinsic fiber-optic strain sensor using broadband interferometry [Invited

Monitoring strain is important in precision engineering applications that require maintaining the precise alignments of structures over time, such as those found in machine tools and metrology frames. We present a fiber-optic strain measurement technique based upon broadband interferometry that is variously configurable in terms of gauge length and sensitivity. This is achieved by the use of an unbalanced interrogation interferometer configuration that alleviates the cavity length limit imposed by the temporal coherence of the system. We also demonstrate that dispersion in fiber sensors based on intrinsic Fabry-Perot interferometers must be considered to optimize performance. The possibility of multisensor interrogation using the same optical system is also reported.

Multiscaling analysis of Soil Water Content during irrigation events. Comparison between surface and subsurface drip irrigation

A detailed knowledge of the spatial variability and temporal evolution of soil water content (SWC) is a key element for maximizing the irrigation efficiency. This paper presents a novel approach that uses Multifractal analysis (MFA) to characterize the scaling properties of SWC evolution during irrigation events through the Generalized Structure Function (GSF). A set of experimental runs were performed in two irrigated plots with either surface or subsurface drip irrigation. SWC was estimated through the cumulative temperature (Tcum) from a Distributed Temperature Sensor (DTS) recordings aided by the Active Heated Fiber Optic (AHFO) technique. The fiber optic cable was deployed at 5 and 25 cm underneath the soil in both plots.Results showed that SWC evolution during the experiments in subsurface irrigation was purely random and more homogeneous than in surface irrigation. The spatial and temporal variability of data from experiments in the surface irrigated plot is higher than that of the subsurface irrigated one, and clearly distant of a pure Brownian motion. The data revealed a persistent character at the upper layer of the surface irrigated plot caused by the unequal distribution of ponded water around certain emitters and a subsequent anti-persistent character at the bottom as a result of the heterogeneous infiltration. From an agronomic point of view, the paper provides an insight into the required adaptation of both irrigation water depths and frequency to avoid water loss in either surface or subsurface irrigation systems.

Revisiting wind speed measurements using actively heated fiber optics: a wind tunnel study

Abstract. Near-surface wind speed is typically only measured by point observations. The actively heated fiber-optic (AHFO) technique, however, has the potential to provide high-resolution distributed observations of wind speeds, allowing for better spatial characterization of fine-scale processes. Before AHFO can be widely used, its performance needs to be tested in a range of settings. In this work, experimental results on this novel observational wind-probing technique are presented. We utilized a controlled wind tunnel setup to assess both the accuracy and the precision of AHFO under a range of operational conditions (wind speed, angles of attack and temperature difference). The technique allows for wind speed characterization with a spatial resolution of 0.3 m on a 1 s timescale. The flow in the wind tunnel was varied in a controlled manner such that the mean wind ranged between 1 and 17 m s−1. The AHFO measurements are compared to sonic anemometer measurements and show a high coefficient of determination (0.92–0.96) for all individual angles, after correcting the AHFO measurements for the angle of attack. Both the precision and accuracy of the AHFO measurements were also greater than 95 % for all conditions. We conclude that AHFO has the potential to measure wind speed, and we present a method to help choose the heating settings of AHFO. AHFO allows for the characterization of spatially varying fields of mean wind. In the future, the technique could potentially be combined with conventional distributed temperature sensing (DTS) for sensible heat flux estimation in micrometeorological and hydrological applications.

Synthesis of MoO3 long microsheets and fiber optic gas sensing properties

This communication reports hydrothermal synthesis of molybdenum trioxide (MoO3) with long microsheets morphology and their gas sensing characteristics through clad-modified fiber optic gas sensor technique. Synthesized material is subjected to characterization analysis including XRD, SEM and Raman Spectra. Spectral analysis on the gas sensing characteristics reveal that MoO3 microsheets exhibit good gas response to methanol at room temperature. Gas sensing mechanism is also discussed.

Dual-wavelength fiber-optic technique to assist needle cricothyroidotomy

The traditional needle cricothyroidotomy procedure is performed blindly without any medical equipment. Complications including posterior tracheal wall perforation, accidental vessel puncture, and missed tracheal puncture are reported. Therefore, we proposed a dual-wavelength fiber-optic technique based on the technique of near-infrared spectroscopy to assist operators performing needle cricothyroidotomy in a swine model. We embedded optical fibers in a 16-gauge intravenous needle catheter. Real-time data were displayed on an oscilloscope, and we used the program to analyze the data immediately. The change of optical density corresponding to 690-nm and 850-nm wavelengths and hemoglobin parameters (HbO2 and Hb concentrations) was analyzed immediately using the program in the laptop. Unique and significant optical differences were presented in this experiment. We could easily identify every different tissue by the change of optical density corresponding to 690-nm and 850-nm wavelengths and hemoglobin parameters (HbO2 and Hb concentrations). Statistical method (Kruskal-Wallis H test) was used to compare differences in tissues at each time-point, respectively. The p values in every tissue in optical density change corresponding to 690 nm and 850 nm were all < 0.001. Furthermore, the p values in every tissue in Hb and HbO2 were also all < 0.001. The results were statistically significant. This is the first and novel study to introduce a dual-wavelength embedded fibers into a standard cricothyroidotomy needle. This proposed system might be helpful to provide us real-time information of the advanced needle tip to decrease possible complications.