Development Of Fiber Optic Sensor Research Articles

Development of a Novel Fiber Optic Sensor Combined with a Fluorescence Turn-on Probe for Cu (II) Detection

Existing staining-based methodology for the detection of metal ions is not well suited for real-time or in situ use. This is a significant problem, given that these ions can have a considerable impact on both human health and the environment. Thus, there is growing interest and need for simple, rapid and in-situ monitoring techniques for the purpose of detecting various target analytes (e.g. heavy metals), which is of a significant importance in many fields ranging from environmental monitoring to the study of intracellular processes. Among various sensors developed, optical fiber-optic sensors (FOS), based on fluorescence, are one class of sensors that address this goal (1). Optical fibers are ideal for environmental sensing applications because of their ability to transmit optical signals to and from the sensing region without the use of free-space optics. In this work, we present, for the first time, a simple FOS incorporating novel fluorescence mechanism (2) that could detect Cu (II) as low as 10 -4 M. Traditionally, fluorescence quenching or turn-off was used to detect Cu (II) (3). In recent years, fluorescence turn-on emerges as a preferable tool. The developed fiber-optic sensor has two fiber leads and one probe head. One fiber lead includes 6 fibers for He-Ne laser excitation light delivery (e-fibers). Another fiber lead has one receiving fiber (r-fiber) connected to an Ocean Optics QE65000 scientific grade spectrometer, which is interrogated by a computer via USB connection. The SpectroSuite software is used to observe and to record all spectra. The probe head combines all fibers together to form a coaxial structure with the r-fiber placed in the center. The key component in the proposed fluorescent sensing system is a probe prepared by binding a receptor containing a zwitterionic chromophore (M1), through noncovalent interactions, to the fluorescent polymer (P1) resulting in quenching its emission. The sensing mechanism involves the release of P1 (a fluorescent indicator) from its non-fluorescent indicator/receptor (P1/M1) pair upon exposure to Cu (II). The zwitterionic chromophore (M1) was found to show high selectivity and sensitivity to Cu (II), making it an ideal receptor for the recognition of Cu (II) (4). The optimum operating conditions and performance characteristics for the new sensor will be discussed.

Radiation hard humidity sensors for high energy physics applications using polyimide-coated fiber Bragg gratings sensors

This work is devoted to a feasibility analysis for the development of fiber optic humidity sensors to be applied in high-energy physics (HEP) applications and in particular in experiments actually running at the European Organization for Nuclear Research (CERN). Due to the stringent sensors requirements concerning radiation hardness capability and low temperature operation, we focus our attention on the investigation of fiber optic humidity sensors based on polyimide-coated fiber Bragg gratings (FBG). Data here reported, obtained during a wide experimental campaign carried out in the laboratories of CERN, demonstrate that the selected technological platform is able to perform relative humidity (RH) measurements with percent resolution in the temperature range −15 to 20 °C as well as in presence of ionizing radiations up to 10 kGy, largely outperforming conventional humidity sensors, currently employed within CERN environment.

Development of Fiber Optic Acoustic Emission Sensors for Applications in Civil Infrastructures

Recent developments of fiber optic acoustic emission sensors (FOAESs) have provided an excellent choice for nondestructive evaluation (NDE) of structures in civil engineering. FOAESs have the advantages of small dimensions, good embeddability within structures, as well as immunity to electric and electromagnetic fields. They can be serially multiplexed along a single fiber to make distributed measurements. Besides, acoustic emission (AE) is an excellent indication signal for real-time long-term damage detection systems. These advantages make FOAESs a better method than other traditional monitoring methods and devices to some extent. This paper provides a review of recent developments in FOAESs as well as some practical and laboratory applications of FOAESs to the heath condition monitoring of civil infrastructures. Existing problems of FOAESs with their applications to heath condition monitoring of civil infrastructures are also discussed.

Fiber Surface Modification Technology for Fiber-Optic Localized Surface Plasmon Resonance Biosensors

Considerable studies have been performed on the development of optical fiber sensors modified by gold nanoparticles based on the localized surface plasmon resonance (LSPR) technique. The current paper presents a new approach in fiber surface modification technology for biosensors. Star-shaped gold nanoparticles obtained through the seed-mediated solution growth method were found to self-assemble on the surface of tapered optical fibers via amino- and mercapto-silane coupling agents. Transmitted power spectra of 3-aminopropyltrimethoxy silane (APTMS)-modified fiber were obtained, which can verify that the silane coupling agent surface modification method is successful. Transmission spectra are characterized in different concentrations of ethanol and gentian violet solutions to validate the sensitivity of the modified fiber. Assembly using star-shaped gold nanoparticles and amino/mercapto silane coupling agent are analyzed and compared. The transmission spectra of the gold nanoparticles show that the nanoparticles are sensitive to the dielectric properties of the surrounding medium. After the fibers are treated in t-dodecylmercaptan to obtain their transmission spectra, APTMS-modified fiber becomes less sensitive to different media, except that modified by 3-mercaptopropyltrimethoxy silane (MPTMS). Experimental results of the transmission spectra show that the surface modified by the gold nanoparticles using MPTMS is firmer compared to that obtained using APTMS.

Thin film based sensors for a continuous monitoring of hydrogen concentrations

The transition toward a more sustainable energy infrastructure is inextricably connected to the development of reliable hydrogen sensors. One of the most promising configurations for such a device is a thin film based fiber optic detector. We demonstrate that with such a device not only the detection of a specific threshold concentration is possible, but also a quantitative determination of the hydrogen concentration. A varying hydrogen concentration can be measured optically using Pd–Ta alloy sensing materials. The optical properties of a Pd–Ta sensing layer change in a one-to-one relation with the applied partial hydrogen pressure. Thus, in a thin film optic fiber configuration, the hydrogen concentration can be quantitatively determined up to 300mbar at room temperature in reflection mode. This Pd–Ta sensor remains optically and mechanically stable up to at least 60 hydrogenation cycles without any indication of degradation. The response time during absorption and desorption is fast (typical<50s) as compared to Pd based detectors. Furthermore, pressure composition isotherm measurements indicate that the hysteresis between hydrogen absorption and desorption becomes very small for Pd–Ta alloys containing more than 5at.% Ta, which results in an almost one-to-one relation between the applied hydrogen pressure and the optical response. However, due to the loss of optical response in reflection at higher Ta concentrations, the most optimal composition range between 5.0 and 6at.% Ta. Furthermore, we find that optical transmission measurements are more sensitive and allow to use higher Ta concentrations of up to 7at.% and enables the measurement of pressures up to 1000mbar H2. The presented research is a first step toward the development of a quantitative fiber optic hydrogen sensor for the measurements of hydrogen concentrations in processes involving the production, transportation, storage and use of hydrogen.

基于光子晶体光纤环镜的光纤传感器的研究及进展

基于光子晶体光纤环镜的光纤传感器的研究及进展

Fiber optic humidity sensors for high-energy physics applications at CERN

This work is devoted to a feasibility analysis for the development of novel fiber optic humidity sensors to be applied in high-energy physics (HEP) applications and in particular in experiments actually running at the European Organization for Nuclear Research (CERN). On this line of argument and due to the wide investigations carried out in the last years aimed to assess the radiation hardness capability of fiber optic technology in high energy physics environments, our multidisciplinary research group has been recently engaged in the development of near-field fiber optic sensors based on particle layers of tin dioxide to perform the monitoring of low values of relative humidity RH even at low temperatures. While this sensor type has been successfully employed for ppm and sub-ppm chemical detection in air and water environments, it is the first reported use for relative humidity measurements. The RH sensing performance of fabricated probes was analyzed during a deep experimental campaign carried out in the laboratories of CERN, in Genève. A very good agreement was observed between humidity measurements provided by the optical fiber sensors and commercial polymer-based hygrometers at 20 °C and 0 °C, with limits of detection for low RH regimes below 0.1%.

Development of a Novel Fiber Optic Sensor for On-Line Monitoring of Soymilk Coagulation

Mechanical evolution of soymilk coagulation was investigated using a novel fiber optic sensor in order to solve the problem of instability in Chinese traditional tofu quality. The sensor signal was measured, and studied the effects of temperature, soymilk concentration, and calcium chloride solution concentrations on tofu making parameters. The scattering light ratio followed a sigmoid increase during soymilk coagulation. Tofu firmness, tofu moisture content, and tofu yield were predicted from the time to the maximum slope of the first derivative of scattering light ratio. The proposed mathematical model shows potential for on-line monitoring of soymilk coagulation.

Development of silver nanorod array based fiber optic probes for SERS detection

The development of intrinsic SERS fiber optic sensors, i.e., fiber optical sensors that also serve as SERS active platforms, is challenging in that an easy, robust method that integrates the SERS active platform with fiber optics is still largely missing. There is a trade-off between implementing optimal morphology of SERS active nanostructures for best enhancement effect and preserving optical transparency that allows maximum transmission of the excitation radiation and the detected signals. In the present work, highly sensitive and reproducible silver nanorod arrays (AgNRs) have been integrated to a fiber optic probe for SERS detection. The films underlying the AgNR coating have been tailored to allow maximum light transmission while maintaining optimal SERS activity. The intense spectral background from the probe fiber core is largely eliminated by using a GRIN lens to produce a tight focus of the incident radiation at the AgNR coating. The performance of the AgNR fiber optic probes has been evaluated in a forward scattering optical configuration using BPE and adenine. The low detection limit of BPE and adenine is 10 −7 M. Reproducibility and sampling methods are also discussed.

A novel temperature self-compensation FBG vibration sensor

There has been considerable interest recently in the development of fiber optic sensors based on Fiber Bragg gratings(FBGs)and FBGs are being used in various applications. In the measuring of the FBG, temperature compensation is one of the most important aspects. This paper describes a new FBG sensors use two FBGs and packaged them with novel structure, and then they can achieve self-compensating of temperature. Two FBGs with 0.2nm different wavelengths are made in one optic fiber, and they are fixed on symmetrical position of a cantilever girder's surface. Wavelength shift of two FBG caused by the temperature is equal and can be eliminated. To inspect and verify the FBG vibration sensor, we fixed it on the standard vibration system, and set the vibration frequency from 5Hz to 30Hz, record the wavelengths of two FBGs over time. The experimental value caught by this novel sensor and setting value is agreement. This sensor have a good frequency response characteristic, it can measure vibration frequency accurately.

Fabrication and characterization of fiber loop ringdown evanescent field sensors

The evanescent field (EF) sensing mechanism has been widely implemented in the development of fiber optic sensors (FOSs). Challenges in the development of EF-FOSs include the enhancement of the sensor's sensitivity and implementing high precision control in the fabrication of a sensor head to allow the desired strength of the EF to be excited in the interface. We combine the EF sensing mechanism with the fiber loop ringdown (FLRD) sensing scheme to create FLRD-EF sensors. The multi-pass nature of the ringdown technique enables the detection sensitivity of the FLRD-EF sensors to be enhanced by more than ten-fold. The EF sensor heads are fabricated by etching the cladding of the single-mode fiber, and the process is monitored by the FLRD technique in real-time, on-line, and with a control precision of 0.1 µs in terms of ringdown time, which corresponds to a 0.5 µm precision in etched fiber diameters. Multiple evanescent field sensor heads consisting of various etched fiber diameters and fiber lengths are fabricated to form different FLRD-EF sensor units. The effect of the sensor head dimensions on the sensors' response time and detection sensitivity are investigated. New FLRD-EF scattering sensors based on index difference are demonstrated for the detection of water at 1515.25 nm.

Fiber-optic sensors for high-temperature applications

Fiber-optic sensors enable measurements of a variety of parameters in conditions where other sensor technologies fail or simply cannot operate. This type of sensing device has intrinsic advantages, including resistance to electromagnetic interference, non-electrical conductivity, passive measurements, small size and low weight, and the option of multipoint measurements. Development of fiber-optic sensors for operation in harsh environments (such as for temperatures of up to 1000C) is becoming an increasingly important field. Fiber-Bragg gratings (FBGs) are widely used for structuralhealth monitoring and ambient sensing. Their main advantages compared with other optical-sensing techniques are their measurement of reflected light, wavelength-encoded sensing, and multiplexing capability.1 FBGs are constructed by exposing optical fibers to an intense UV interference pattern that creates a periodic refractive-indexmodulation. However, this modulation is not permanent. Depending on fiber type, for high-temperature sensing applications, the modulation decays until it is completely depleted around 600–700iC.2, 3 Several techniques have recently been developed to increase FBG temperature stability. One of the most promising methods involves the use of chemical-composition gratings (CCGs).4–6 CCGs are fabricated from hydrogen-loaded optical fibers that are subjected to a subsequent annealing treatment at high temperature. This process replaces the FBG’s refractive-index modulation by a more temperature-stable chemical structure. During annealing, the original FBG is completely wiped out, and a new refractive-index modulation is generated in the zones that were previously exposed to UV radiation. These gratings are, therefore, also known as regenerated fiber-Bragg gratings. We successfully made CCGs using two different types of fibers, including standard telecommunications germanium (Ge)-doped and photosensitive Ge/boron (B) co-doped fibers. We analyzed the regeneration process, sensing properties, Figure 1. Chemical-composition-grating (CCG) regeneration process for two fiber-Bragg gratings (FBGs) with different initial amplitudes using germanium (Ge)-doped fibers. The blue and green curves correspond to the CCG-amplitude axis, while the red curve represents the temperature variation.

Fiber Loop Ringdown — a Time-Domain Sensing Technique for Multi-Function Fiber Optic Sensor Platforms: Current Status and Design Perspectives

Fiber loop ringdown (FLRD) utilizes an inexpensive telecommunications light source, a photodiode, and a section of single-mode fiber to form a uniform fiber optic sensor platform for sensing various quantities, such as pressure, temperature, strain, refractive index, chemical species, biological cells, and small volume of fluids. In FLRD, optical losses of a light pulse in a fiber loop induced by changes in a quantity are measured by the light decay time constants. FLRD measures time to detect a quantity; thus, FLRD is referred to as a time-domain sensing technique. FLRD sensors have near real-time response, multi-pass enhanced high-sensitivity, and relatively low cost (i.e., without using an optical spectral analyzer). During the last eight years since the introduction of the original form of fiber ringdown spectroscopy, there has been increasing interest in the FLRD technique in fiber optic sensor developments, and new application potential is being explored. This paper first discusses the challenging issues in development of multi-function, fiber optic sensors or sensor networks using current fiber optic sensor sensing schemes, and then gives a review on current fiber optic sensor development using FLRD technique. Finally, design perspectives on new generation, multi-function, fiber optic sensor platforms using FLRD technique are particularly presented.

Optical oxygen sensors based on Pt(II) porphyrin dye immobilized on S-layer protein matrices

This paper describes the development of planar and fiber optic oxygen sensors utilizing surface layer (S-layer) proteins as immobilization matrix for oxygen sensitive dyes. S-layer proteins have the intrinsic capability to reassemble into two-dimensional arrays in suspension and at interfaces. Due to their crystalline character the distribution of functional groups, such as carboxylic groups, is repeated with the periodicity of the lattice and thus allows the reproducible and geometrically distinct binding of functional molecules. For the development of oxygen sensors an oxygen sensitive Pt(II) porphyrin dye was covalently bound to the S-layer matrix. Measurement of the oxygen concentration was performed by phase modulation fluorimetry. Setups comprising low cost optoelectronic components like LEDs and silicon photodiodes were constructed. For both sensor setups (planar and fiber optic) variations in the oxygen concentrations resulted in distinct and reproducible changes in luminescence lifetime and intensity. The luminescence quenching efficiency of these sensors was found to be 1.5–1.9 (expressed as the ratio of signal under nitrogen and air) which compares well to other sensor systems using luminophores embedded in polymer matrices. These results demonstrated the application potential of S-layers as immobilization matrices in the development of (bio-)sensors.

A critical comparison between two different ratiometric techniques for optical luminescence sensing

Luminescence has become an invaluable analytical tool for development of robust fiber optical sensors for many industrial, biomedical and environmental applications. Direct intensity measurements of the luminescent emission are, due to their simplicity, a very common measuring principle. Consequently, many optical fiber sensors are based on the intensity measurement of the luminescence emission. Unfortunately, direct luminescent intensity measurements suffer from a series of analyte-independent fluctuations, which make them inappropriate for the development of reliable instrumentation for chemical sensing applications.A possibility for solving this trouble is to measure the lifetime of the luminescence emission. The drawbacks of such approach are an increase in the complexity of the system measurement, particularly for measurement of low lifetimes (e.g. nanoseconds), but also the limited number of available chemical sensors that suffer from a change in the luminescence lifetimes after interaction with the analyte.The ratiometric measurement can solve many of the trouble previously exposed. As it is well know, ratiometric measurements are an alternative to classical intensity or lifetime measurements due to their proved insensitivity to background light and instrumental fluctuations. Thus, they can be applied to the development of robust luminescence optical sensors.In this paper two measurement systems based on ratiometric techniques are compared. One of them is a ratiometric method in the frequency domain and the other one is a wavelength ratiometric method.The analytical performance of the dynamic ratiometric method has been assessed using a phosphorescent oxygen sensor, which is a good example of a sensor that suffers a dynamic luminescence deactivation after interaction with the analyte.The potential of the proposed ratiometric systems to overcome the problems of accuracy in luminescent sensing is evaluated by constructing two respective optical fiber instruments. The interest in designing an instrumental prototype specially adapted to a particular chemical sensor is also analyzed.

Studies of the Development of Optical Fiber Sensors for Biochemical Analysis

An optical fiber sensor utilizing Thymol blue and an ion-exchange resin complex in a cellulose acetate membrane was developed. By monitoring several different chromophores of Thymol blue, the sensor could measure the pH of the solution from 1.0 to 12.0 with good reproducibility. An optical fiber glucose sensor utilizing a cellulose acetate membrane containing glucose oxidase, 2,7-diaminofluorene dihydrochloride, and sodium N-(3-sulfopropyl)-3,3',5,5'-tetramethylbenzidine was developed. Reflectance changes at 580 nm were large enough to trace changes in glucose concentration in physiological saline solution.

Integrated Development of Chemoptical Fiber Nanosensors

The development of fiber optic chemical sensors based on the integrated design of novel sensitive nanocoatings combined with advanced sensing configurations is reported in the present study. Different sensitive coating materials have been exploited togheter with their deposition techniques, i.e nano-porous polymers deposited by using dip coating, carbon nanotubes deposited by Langmuir-Blodgett method and metal oxides, prepared by electrostatic spray pyrolysis. In accordance to the chemo-optical properties of these materials novel sensing schemes based on nano-coated Long Period Fiber Gratings, modified Fabry-Perot interferometers involving near field effect and photonic bandgap modification in Hollow-core Optical Fibers, have been proposed, respectively, to provide the best sensing performance. Experimental results reveal the potentiality of the integated approach that simultaneously accounts for the selection of the coating materials and of the fiber optic sensing scheme in developing optical devices for a wide range of applications related to the environmental monitoring either in air and water environments.

Rapid Constructions of Microstructures for Optical Fiber Sensors Using a Commercial CO2 Laser System

Exposing an optical fiber core to the measurand surrounding the fiber is often used to enhance the sensitivity of an optical fiber sensor. This paper reports on the rapid fabrication of microstructures in an optical fiber using a CO2 laser system which help exposing the optical fiber core to the measurand. The direct-write CO2 laser system used is originally designed for engraving the polymeric material. Fabrications of microstructures such as in-fiber microhole, D-shaped fiber, in-fiber microchannel, side-sliced fiber and tapered fiber were attempted. The microstructures in the fibers were examined using a SEM and an optical microscope. Quality of microstructures shown by the SEM images and promising results from fluorescence sensor tests using in-fiber microchannels of 100μm width, 210μm depth and 10mm length show the prospect of this method for use in optical fiber sensor development. The direct-write CO2 laser system is a flexible and fast machining tool for fabricating microstructures in an optical fiber, and can possibly be a replacement of the time consuming chemical etching and polishing methods used for microstructure fabrications of optical the fiber sensors reported in other literatures.

Development of fiber optic fluorescence oxygen sensor in both in vitro and in vivo systems

The accurate measurement of arterial blood oxygen partial pressure often plays an important role in the clinical assessment of patients with respiratory conditions such as an acute exacerbation of chronic obstructive pulmonary disease and acute lung injury/adult respiratory distress syndrome. An oxygen-sensitive fluorescence indicator with high biocompatibility was synthesized and then fabricated to the end of an optical fiber. The properties and accuracy of this oxygen sensor were investigated in vitro using physiologic solutions under varying conditions or human blood, and in vivo by obtaining measurements after inserting this optical sensor into the collateral circulation system of rabbits. The sensitivity of the oxygen sensor was relatively stable during altered conditions of pH, P(CO2), osmolality, and protein concentration in solutions and during alterations of oxygen and nitrogen content in human blood. There was a linear correlation between the reciprocal value of the fluorescence intensity and Pa(O2) in both in vivo and in vitro experiments (animal arterial circulation and human blood). Our results suggest that this oxygen-sensitive fluorescence indicator, which has a high biocompatibility, may have the potential for use in real-time monitoring of blood oxygen partial pressure in various clinical settings.

Indicator immobilization on Fabry-Perot nanocavities towards development of fiber optic sensors

Two fabrications processes based on the Electrostatic Self Assembly method have been studied in order to develop a potential fibre optic sensor for detection volatile organic compounds (VOCs). A nano Fabry-Perot is constructed onto a cleaved ended fibre optic pigtail, and is doped with a vapochromic complex of formula [Au2Ag2(C6F5)4(C6H5N)2]. This material is presented in form of red powders, shows fluorescence at 585 nm when illuminated with a light at 380 nm, and suffers changes in its color and refractive index when is exposed to VOCs. Both different possibilities of doping the nano Fabry-Perot studied keep the optical properties of the sensing material. To verify the sensing ability of the final devices, they have been exposed to ethanol vapors, taking measures of their absorbance spectra and the intensity modulated reflected signal at 850 nm, employing a reflection scheme.