Subsurface multi-physical characterization of mountain excavation and city construction in loess plateau with a fiber-optic sensing system

Mountain excavation and city construction(MECC)projects being launched in the Loess Plateau in China involve the creation of large-scale artificial land.Understanding the subsurface evolution characteristics of the artificial land is essential,yet challenging.Here,we use an improved fiber-optic monitoring system for its subsurface multi-physical characterization.The system enables us to gather spatiotemporal distribution of various parameters,including strata deformation,temperature,and moisture.Yan’an New District was selected as a case study to conduct refined in-situ monitoring through a 77 m-deep borehole and a 30 m-long trench.Findings reveal that the ground settlement involves both the deformation of the filling loess and the underlying intact loess.Notably,the filling loess exhibits a stronger creep capability compared to underlying intact loess.The deformation along the profile is unevenly distributed,with a positive correlation with soil moisture.Water accumulation has been observed at the interface between the filling loess and the underlying intact loess,leading to a significant deformation.Moreover,the temperature and moisture in the filling loess have reached a new equilibrium state,with their depths influenced by atmospheric conditions measuring at 31 m and 26 m,respectively.The refined investigation allows us to identify critical layers that matter the sustainable development of newly created urban areas,and provide improved insights into the evolution mechanisms of land creation.

Fiber-Optic Sensors and Their Practical Research in the Internet of Things

With the rapid development of the Internet of Things(IoT)technology,fiber-optic sensors,as a kind of high-precision and high-sensitivity measurement tool,are increasingly widely used in the field of IoT.This paper outlines the advantages of fiber-optic sensors over traditional sensors,such as high precision,strong resistance to electromagnetic interference,and long transmission distance.On this basis,the paper discusses the application scenarios of fiber-optic sensors in the Internet of Things,including environmental monitoring,intelligent industry,medical and health care,intelligent transportation,and other fields.It is hoped that this study can provide theoretical support and practical guidance for the further development of fiber-optic sensors in the field of the Internet of Things,as well as promote the innovation and application of IoT.

Thermal integrity profiling of cast-in-situ piles in sand using fiber-optic distributed temperature sensing

Defects in cast-in-situ piles have an adverse impact on load transfer at the pile‒soil interface and pile bearing capacity. In recent years, thermal integrity profiling (TIP) has been developed to measure temperature profiles of cast-in-situ piles, enabling the detection of structural defects or anomalies at the early stage of construction. However, using this integrity testing method to evaluate potential defects in cast-in-situ piles requires a comprehensive understanding of the mechanism of hydration heat transfer from piles to surrounding soils. In this study, small-scale model tests were conducted in laboratory to investigate the performance of TIP in detecting pile integrity. Fiber-optic distributed temperature sensing (DTS) technology was used to monitor detailed temperature variations along model piles in sand. Additionally, sensors were installed in sand to measure water content and matric suction. An interpretation method against available DTS-based thermal profiles was proposed to reveal the potential defective regions. It shows that the temperature difference between normal and defective piles is more obvious in wet sand. In addition, there is a critical zone of water migration in sand due to the water absorption behavior of cement and temperature transfer-induced water migration in the early-age concrete setting. These findings could provide important insight into the improvement of the TIP testing method for field applications.

Dual-channel fiber-optic surface plasmon resonance sensor with cascaded coaxial dual-waveguide D-type structure and microsphere structure

To address the restriction of fiber-optic surface plasmon resonance(SPR) sensors in the field of multi-sample detection, a novel dual-channel fiber-optic SPR sensor based on the cascade of coaxial dual-waveguide D-type structure and microsphere structure is proposed in this paper. The fiber sidepolishing technique converts the coaxial dual-waveguide fiber into a D-type one, and the evanescent wave in the ring core leaks, generating a D-type sensing region;the fiber optic fused ball push technology converts the coaxial dual waveguides into microspheres, and the stimulated cladding mode evanescent wave leaks, producing the microsphere sensing region. By injecting light into the coaxial dual-waveguide middle core alone, the sensor can realize single-stage sensing in the microsphere sensing area;it can also realize dual-channel sensing in the D-type sensing area and microsphere sensing area by injecting light into the ring core. The refractive index measurement ranges for the two channels are 1.333–1.365 and 1.375–1.405, respectively, with detection sensitivities of 981.56 nm/RIU and 4138 nm/RIU. The sensor combines wavelength division multiplexing and space division multiplexing technologies, presenting a novel research concept for multi-channel fiber SPR sensors.

Ultrasonic sensitivity-improved fiber-optic Fabry-Perot interferometer using a beam collimator and its application for ultrasonic imaging of seismic physical models

An ultrasonic sensitivity-improved fiber-optic Fabry-Perot interferometer （FPI） is proposed and employed for ultra- sonic imaging of seismic physical models （SPMs）. The FPI comprises a flexible ultra-thin gold film and the end face of a graded-index multimode fiber （MMF）, both of which are enclosed in a ceramic tube. The MMF in a specified length can collimate the diverged light beam and compensate for the light loss inside the air cavity, leading to an increased spectral fringe visibility and thus a steeper spectral slope. By using the spectral sideband filtering technique, the collimated FP1 shows an improved ultrasonic response. Moreover, two-dimensional images of two SPMs are achieved in air by recon- structing the pulse-echo signals through using the time-of-flight approach. The proposed sensor with easy fabrication and compact size can be a good candidate for high-sensitivity and high-precision nondestructive testing of SPMs.

Monitoring the hydrolyzation of aspirin during the dissolution testing for aspirin delayed-release tablets with a fiber-optic dissolution system

The purpose of this study was to investigate the hydrolyzation of aspirin during the process of dissolution testing for aspirin delayed-release tablets. Hydrolysis product of salicylic acid can result in adverse effects and affect the determination of dissolution rate assaying. In this study, the technique of differential spectra was employed, which made it possible to monitor the dissolution testing in situ. The results showed that the hydrolyzation of aspirin made the percentage of salicylic acid exceed the limit of free salicylic acid （4.0）, and the hydrolyzation may affect the quality detection of aspirin delayed-release tablets.

Design of fiber-optic collector for spectrometer based on curved mirror

To enlarge the detection range of traditional fiber-optic spectrometer,two rotating parabolic mirrors were first used in the design of fiber-optic collector for spectrometer,which can extend the detection range of spectrometer from centimeter-scale to50m,as a super-low altitude remote sensing detector under passive lighting conditions.According to the performance requirements of fiber-spectrometer for optical collector,this study deduced the calculation formulae of design size of parabolic optical collector applied to different sensitivity spectrometers,different detection targets,different detection ranges and different weathers.Based on the calculation results,the model of fiber-optic collector with a diameter of16mm and a height of7.8mm was designed by ZEMAX.And then,TracePro,a light simulation software,was applied to ray tracing.The simulation results of optical radiation magnification agrees well with theoretical value,and the relative error is less than0.78%.This optical collector can effectively extend the detection range of spectrometer and expand its application fields and scopes.Compared with traditional refractive optical collector,it has several advantages of compact structure,low weight and low cost.

A Design of High-precision High-Voltage Fiber-Optic Analog Signal Isolation Converter

This paper introduces a design of high-precision high-voltage fiber-optic analog sig-nal isolation converter based on the technology of Voltage-to-Frequency (V/F) and Frequency-to-Voltage (F/V) conversion. It describes the principle, system configuration and hardware design.

Using Brillouin fiber-optic ring laser to provide base station with uplink optical carrier in a 10 GHz radio over fiber system

In this paper, a 10 GHz radio over fiber system is analyzed. The Brillouin fiber-optic ring laser is used in the center station （CS） to suppress the optical carrier for the modulation depth enhancement. Simultaneously, the Stockes wave induced by the Brillouin amplification injects and locks the Fabry-Perot （FP） laser to output a signal-mode optical source, which works as the uplink optical carrier.

Experimental Measurements of the Sensitivity of Fiber-optic Bragg Grating Sensors with a Soft Polymeric Coating under Mechanical Loading,Thermal and Magnetic under Cryogenic Conditions

The strain and temperature sensing performance of fiber-optic Bragg gratings （FBGs） with soft polymeric coating, which can be used to sense internal strain in superconducting coils, are evaluated under variable cryogenic field and magnetic field. The response to a temperature and strain change of coated-soft polymeric FBGs is tested by comparing with those of coated-metal FBGs. The results indicate that the coated-soft polymeric FBGs can freely detect temperature and thermal strain, their At variable magnetic field, the tested results indicate accuracy and repeatability are also discussed in detail. that the cross-coupling effects of FBGs with different matrixes are not negligible to measure electromagnetic strain during fast excitation. The present results are expected to be able to provide basis measurements on the strain of pulsed superconducting magnet/cable （cable- around-conduit conductors, cable-in-conduit conductors）, independently or utilized together with other strain measurement methods.

Improving effect of sputum aspiration combined with bronchoalveolar lavage by fiber bronchoscope on the condition and inflammation in lung cancer patients with postoperative pulmonary infection

Objective:To study the improving effect of sputum aspiration combined with bronchoalveolar lavage by fiber bronchoscope on the condition and inflammation in lung cancer patients with postoperative pulmonary infection.Methods:A total of 78 patients with lung cancer who received surgical treatment in our hospital between August 2013 and January 2015 and were with postoperative infection were selected as the research subjects and randomly divided into two groups, control group received mechanical ventilation therapy, observation group received bronchoalveolar lavage by bronchoscope combined with mechanical ventilation, and the inflammatory factor levels, RAAS system activity and respiratory mechanics indexes of two groups were determined after treatment.Results:3 d after treatment, serum hs-CRP, TNF-α, IL-8, PCT, renin, angiotensin II and aldosterone levels of observation group were lower than those of control group, and PIP, Raw and WOB values were lower than those of control group while Cdyn value was higher than that of control group.Conclusion:For lung cancer patients with postoperative pulmonary infection, bronchoalveolar lavage by bronchoscope combined with mechanical ventilation can optimize patients' condition, relieve systemic inflammatory response and improve respiratory function, and it has positive clinical significance.

Effect of lung lavage via fiber bronchoscope combined with non-invasive positive pressure ventilation on the blood gas results and systemic state of patients with COPD complicated by severe pneumonia

Objective: To discuss the effect of lung lavage via fiber bronchoscope combined with non-invasive positive pressure ventilation on the blood gas results and systemic state of patients with COPD complicated by severe pneumonia. Methods: A total of 68 patients with COPD complicated by severe pneumonia who were treated in the hospital between November 2015 and April 2017 were collected, retrospectively analyzed and then divided into the group A (n=35) who received noninvasive positive pressure ventilation and the group B (n=33) who received lung lavage via fiber bronchoscope combined with non-invasive positive pressure ventilation. The differences in arterial blood gas and serum index levels were compared between the two groups before and after treatment. Results: Before treatment, there was no statistically significant difference in arterial blood gas index levels as well as serum contents of inflammatory mediators, stress hormones and myocardial enzyme spectrum indexes between the two groups. After treatment, arterial blood gas indexes PH and PaO2 levels of group B were higher than those of group A;serum inflammatory mediators HMGB1, PCT and hs-CRP contents were lower than those of group A;serum stress hormones Cor, AngⅠ and AngⅡcontents were lower than those of group A;serum myocardial enzyme spectrum indexesα-HBDH and cTn-Ⅰ contents were lower than those of group A. Conclusion: Lung lavage via fiber bronchoscope combined with non-invasive positive pressure ventilation can effectively optimize the arterial blood gas levels, reduce systemic inflammatory stress state and protect the myocardial function of patients with COPD complicated by severe pneumonia.

Review of Fiber-optic Distributed Acoustic Sensing Technology

A distributed optical-fiber acoustic sensor is an acoustic sensor that uses the optical fiber itself as a photosensitive medium,and is based on Rayleigh backscattering in an optical fiber.The sensor is widely used in the safety monitoring of oil and gas pipelines,the classification of weak acoustic signals,defense,seismic prospecting,and other fields.In the field of seismic prospecting,distributed optical-fiber acoustic sensing(DAS)will gradually replace the use of the traditional geophone.The present paper mainly expounds the recent application of DAS,and summarizes recent research achievements of DAS in resource exploration,intrusion monitoring,pattern recognition,and other fields and various DAS system structures.It is found that the high-sensitivity and long-distance sensing capabilities of DAS play a role in the extensive monitoring applications of DAS in engineering.The future application and development of DAS technology are examined,with the hope of promoting the wider application of the DAS technology,which benefits engineering and society.

Laboratory investigations of the thermal strain of frozen soils,using fiber-optic strain gauges based on Bragg gratings

Measurements of the thermal deformations of frozen soil samples were performed in the cold laboratory in temperature range from 0°C to-12°C.Fiber Bragg Gratings strain and temperature sensors were used to measure the deformation and temperature inside the samples.A number of tests with the samples prepared from Kaolin and Cambrian clay saturated with fresh water,and prepared from fine and silt sand saturated with fresh or saline water,are performed.Thermal deformations of the samples are analyzed depending on the cyclic changes of their temperature.

Cryorecanalization after cryosurgery for immediate treatment on central airway obstruction via flexible bronchoscope

Objective In order to achieve immediate relief of central airway obstruction caused by malignant tumor after interventional therapy, we observed the efficacy and safety of cryorecanalization after cryosurgery via flexible bronchoscope.

Removal of metallic stents using flexible bronchoscope:report of 29 cases

Objective:Placement of self expanding metallic stents(SEMS) is invariably associated with complications and often necessitates their removal usually by rigid bronchoscope.There have been few reports published on use of flexible bronchoscope(FB) for the removal.This article summarizes the indications,methods and complications of SEMS removal by FB.Methods:We reviewed our experience with removal of SEMS using FB retrospectively.The clinical data on 29 patients with average age of(39.0±13.2) years was analyzed who underwent removal of SEMS using FB between April 2002 and August 2008.Results:Thirty-seven procedures were performed in 29 consecutive patients to remove 37 stents.The average duration of stent placement was(55± 94.7) d(0-472 d).Twenty-two procedures(59.4%) were performed under local anesthesia.The percentage of procedures under general anesthesia was 13%(3/24),67%(4/6) and 100%(7/7) for the short-term(≤30 d),medium-term(31-90 d) and long-term(>90 d) of stents placement,respectively.Indications for stents removal included migration in 15(40.6%),scar restenosis in 11(29.7%),airway shaping in 5(13.5%),stent fracture in 2(5.4%),stent incomplete expansion in 2(5.4%),improper size in 1(2.7%),mucus plugging with chest pain in 1(2.7%).And 85.7% of long-term stents were removed due to scar restenosis.The total success rate was 92%.There was no significant difference in success rate between the uncovered and covered group(82.3% and 100%,P>0.05).Complications were encountered in 13 patients,bleeding being the most common(53.8%).Conclusion:Operation by FB may be an alternative method to remove SEMS effectively and safely based on the proper anesthesia chosen.

Reflective Ladder Topology Network Based on White Light Fiber-Optic Mach-Zehnder Interferometer

In order to improve the multiplexing capability of the optical sensors based on the lower interferential optic fiber sensing technology and the white light fiber-optic Mach-Zehnder interferometer,reflective ladder topology network ( RLT) with tailored formula was proposed. The topology network consists of 6 rungs sensing elements linked by 5 couplers. Two cases with different choices of couplers were contrasted: one is equal coupling ratio,and the other is tailored coupling ratio. Through the simulation of these two cases,the detailed multiplexing capability was analyzed,and accordingly the experiments were also carried out. The simulation results showed that,the tailored formula enhances the multiplexing capability of the structure. In the first case, the maximum number of sensors which can be multiplexed is 8,and in the other case is 12 fiber optic sensors. The experimental results have a good agreement with numerical simulation results. Thus,it is considered expedient to incorporate RLT into large-scale building,grounds,bridges,dams,tunnels,highways and perimeter security.

Fluorescence Referencing for Fiber-optic Sensor Using Visible Wavelengths

A kind of fluorescence optic-fiber thermometer is devised based on the ruby and absorbing glass sample. The optic- fiber temperature measurement probe based on ruby is developed. This system is particularly adaptable to the temperature measurement in the range of 0℃ to 130℃. A considerably improved performance is seen in this new device. The drive current to the LED can be easily kept within the required defined bounds through the control circuitry.

Recent advances in fiber-optic DNA biosensors

Fiber-optic DNA biosensors are a kind of ana-lytic setups, which convert the Waston-Crick base pairs matching duplex or Hoogsteen’s tri-plex (T/A-T, C/G-C) formation into a readable analytical signals when functionalized single- strands DNA (ssDNA) or double-strands DNA (dsDNA) of interest are immobilized on the sur-face of fiber-optic hybrids with target DNA or interacts with ligands. This review will provide the information about the fiber-optic DNA bio-sensors classified into two categories depend-ing on the end fiber and side fiber with or with-out the labels—label-free fiber-optic DNA bio-sensors and labeled fiber-optic DNA biosensor in recent years. Both are dissertated, and em-phasis is on the label-free fiber-optic DNA bio-sensors. Fiber-optic DNA biosensors had got great progresses because fiber-optic has more advantages over the other transducers and are easily processed by nanotechnology. So fiber- optic DNA biosensors have increasingly at-tracted more attention to research and develop the new fiber-optic DNA biosensors that inte-grated with the “nano-bio-info” technology for in vivo test, single molecular detection and on-line medical diagnosis. Finally, future pros-pects to the fiber-optic DNA biosensors are predicted.

Effects of pulse energy ratios on plasma characteristics of dual-pulse fiber-optic laser-induced breakdown spectroscopy

Laser-induced plasmas of dual-pulse fiber-optic laser-induced breakdown spectroscopy with different pulse energy ratios are studied by using the optical emission spectroscopy(OES)and fast imaging.The energy of the two laser pulses is independently adjusted within 0–30 m J with the total energy fixed at 30 m J.The inter-pulse delay remains 450 ns constantly.As the energy share of the first pulse increases,a similar bimodal variation trend of line intensities is observed.The two peaks are obtained at the point where the first pulse is half or twice of the second one,and the maximum spectral enhancement is at the first peak.The bimodal variation trend is induced by the change in the dominated mechanism of dual-pulse excitation with the trough between the two peaks caused by the weak coupling between the two mechanisms.By increasing the first pulse energy,there is a transition from the ablation enhancement dominance near the first peak to the plasma reheating dominance near the second peak.The calculations of plasma temperature and electron number density are consistent with the bimodal trend,which have the values of 17024.47 K,2.75×10^(17)cm;and 12215.93 K,1.17×10^(17)cm;at a time delay of 550 ns.In addition,the difference between the two peaks decreases with time delay.With the increase in the first pulse energy share,the plasma morphology undergoes a transformation from hemispherical to shiny-dot and to oblate-cylinder structure during the second laser irradiation from the recorded images by using an intensified charge-coupled device(ICCD)camera.Correspondingly,the peak expansion distance of the plasma front first decreases significantly from 1.99 mm in the single-pulse case to 1.34 mm at 12/18(dominated by ablation enhancement)and then increases slightly with increasing the plasma reheating effect.The variations in plasma dynamics verify that the change of pulse energy ratios leads to a transformation in the dual-pulse excitation mechanism.