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This paper presents a method for writing a Fabry-Perot (F-P) cavity in the tapered fiber. General idea for writing the F-P cavity in tapered fiber is based on utilization of chirped tapered fiber Bragg gratings (CTFBG) in counter-directional configuration. In such approach, the chirp resulting from tapered fiber and linearly increasing periods of the grating, cancel each other out. Presented numerical results consists of qualitative model, that provides the general design approach, as well as quantitative analysis, that allows for more detailed studies on presented structure. For this purpose Coupled Mode Theory (CMT) together with Transfer Matrix Method (TMM) were utilized.

In this work, a multilayer nanocomposite based fiber optic SPR sensor is considered and especially designed for CO2 gas detection. This proposed fiber sensor consists of fiber core, gold-silver alloy and the absorber layers. The investigation is based on the evaluation of the transmitted-power derived under the transfer matrix method and the multiple-reflection in the sensing area. In terms of sensitivity, the sensor performance is studied theoretically under various conditions related to the metal layer and its gold and silver nanoparticles to form a single alloy film. Effect of additional parameters such as the ratio of the alloy composition and the thickness of the alloy film on the performance of the SPR sensor is studied, as well. Finally, a four-layer structure is introduced to detect carbon dioxide gas. It contains core fiber, gold-silver alloy layer, an absorbent layer of carbon dioxide gas (KOH) and measurement environment. Lower price and size are the main advantages of using such a sensor in compare with commercial (NDIR) gas sensor. Theoretical results show by increasing the metal layer thickness the sensitivity of sensor is increased, and by increasing the ratio of the gold in alloy the sensitivity is decreased.

A high-precision test method based on infinity optical transformation system was investigated to detect the focusing performance of a small fiber lens. Consider the ultra-small gradient-index (GRIN) fiber probe as an example of the small fiber lens, its characters of focusing performances are analyzed. The infinity optical transformation system was employed to amplify and capture the exit beam from the probe in the non-contact mode. Then the curve fitting method is used to deal with the experimental data. The result shows that with the given small fiber lens the obtained working distance and waist diameter in the experiment system are 0.72 mm and 35 μm, respectively, while the calculated working distance and waist diameter based on the theory are 0.75 mm and 33 μm accordingly. The experimental results are in good agreement with the theoretical results. Therefore, the proposed test method based on infinity optical transformation system is applicable to detect the focusing performance of the small fiber lens.

Mode-division multiplexing (MDM), which allows different guided modes of a few-mode fiber to carry different signals, is a new technology being actively pursued worldwide to increase the signal-carrying capacity of a fiber. For the development of the MDM technology, many mode-controlling devices are needed, such as mode converters, mode (de)multiplexers, mode filters, and mode-selective switches. Among the various technologies available for the implementation of such devices, the polymer waveguide technology offers many distinct advantages. This paper presents a review of polymer waveguide devices for MDM applications, which include grating-based mode converters, 3D mode (de)multiplexers, graphene-based mode filters, and thermo-optic mode-selective switches.

Two dimensional code marks are often used for the production management. In particular, in the production lines of liquid-crystal-display panels and others, data on fabrication processes such as production number and process conditions are written on each substrate or device in detail, and they are used for quality managements. For this reason, lithography system specialized in code mark printing is developed. However, conventional systems using lamp projection exposure or laser scan exposure are very expensive. Therefore, development of a low-cost exposure system using light emitting diodes (LEDs) and optical fibers with squared ends arrayed in a matrix is strongly expected. In the past research, feasibility of such a new exposure system was demonstrated using a handmade system equipped with 100 LEDs with a central wavelength of 405 nm, a 10×10 matrix of optical fibers with 1 mm square ends, and a 10X projection lens. Based on these progresses, a new method for fabricating large-scale arrays of finer fibers with squared ends was developed in this paper. At most 40 plastic optical fibers were arranged in a linear gap of an arraying instrument, and simultaneously squared by heating them on a hotplate at 120°C for 7 min. Fiber sizes were homogeneous within 496±4 μm. In addition, average light leak was improved from 34.4 to 21.3% by adopting the new method in place of conventional one by one squaring method. Square matrix arrays necessary for printing code marks will be obtained by piling the newly fabricated linear arrays up.

International audience; ecause of the advantages in terms of reproducibility for optical resonators on chip which are designed of various topologies and integration with optical devices. To increase the Q-factor from the lower rang [104 - 106 ] to higher one [108 -1010] [1-4] one use crystalline resonators. It is much complicated to couple an optical signal from a tapered fiber to crystalline resonator than from a defined ridge to a resonator designed on a chip. In this work, we will focus on the optimization of the crystalline resonators under straight wave guide (based on COMSOL multi-physic software) [5- 7] and subject also to technological constraints of manufacturing. The coupling problem at the Nano scale makes our optimizations problem more dynamics in term of design space.© (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

The generation and amplification at wavelengths longer than 1100 nm is not straightforward when using Yb-doped optical fibers, since light emission of ytterbium occurs preferentially in the region of 1020 nm - 1100 nm with a maximum at 1030 nm. One well known approach is to heat the Yb-doped fiber up to temperatures above 100 °C. This increases the re-absorption in the lower emission band and also enhances at the same time the emission at longer wavelengths. Consequently, heating allows to extend the spectral gain-region of Yb-doped fibers by at least 60 nm up to 1160 nm. However, the drawback of this method is that it results in a shorter durability of the fiber, since heating damages the polymer-coating. Moreover, such a laser has a reduced overall efficiency, due to heating, isolation and heat removal issues. It has been reported, that at the presence of an aluminosilca host (silica doped with Al) efficient laser activity at around 1150 nm can be achieved by heating the Yb-doped fiber to only 60 °C. In this work we investigate the spectroscopy of a heated Yb-doped fiber with a high aluminum concentration. The fiber is drawn in our in-house fiber drawing tower. The preforms are produced by the sol-gel-based granulated silica method which allows us to vary the aluminum as well as the ytterbium concentrations within a large range. The fiber is investigated with respect to their spectroscopic data as well as their lasing performance.

In this work, improvements in the photosensitivity of undoped POFs, where there was a welldefined pre-annealing of both preforms in two-step process, were reported. We have noticed that when the primary and secondary preforms are annealed, the fiber photosensitivity is higher; otherwise, if any preform (primary or secondary) is not annealed, the fiber photosensitivity is lower. Two PMMA mPOFs are used where the primary and secondary preforms, during the two-step drawing process, have a different thermal treatment. The PMMA POFs drawn where the primary or secondary preform is not specifically pre-treat need longer inscription time than the fibres drawn where both preforms have been pre-annealed at 80°C for 2 weeks. Using two different UV lasers, for the latter fibre much less inscription time is needed compared to another homemade POF. The properties of a POF fabricated where there are both preform process with thermal treatment is different from those where just one preform step process is thermal treated, as previously shown in the literature, where these POFs are much less sensitive to thermal treatment. Some important parameters were considered such as drawing tension and water content, where using fibers drawn in different tensions give us a similar FBG inscription time.

In this paper we present a study aimed at investigating an optical resiliency of polymers that could be applied in 3D femtosecond laser lithography. These include popular in lithography SU8 and OrmoClear as well as hybrid organic-inorganic zirconium containing SZ2080. We show that latter material in its pure (non-photosensitized) form has the best optical resiliency out of all tested materials. Furthermore, its 3D structurability is investigated. Despite threshold-like quality degradation outside fabrication window, we show that this material is suitable for creating complex 3D structures on the tips of optical fibers. Overall it is demonstrated, that unique capability of 3DLL to structure pure materials can lead to very compact functional fiber-based devices that could withstand high (GW/cm 2 ) light intensities.

In this paper, limitation factor of high power narrow linewidth fiber laser is analyzed. The influence of Stimulated Brillouin Scattering and its suppressing theory are discussed. Influences of frequency number and frequency spacing to Stimulated Brillouin Scattering are analyzed respectively by simulation. The results indicate that increasing frequency number and controlling frequency spacing can reduce the power spectrum density in fiber. Then the Stimulated Brillouin Scattering threshold is increased. Finally, the fiber laser output power is increased a lot.

A multiscale approach is used to analyze the oxidation ablation of parallel carbon fiber (the fibers are parallel to the material surface) reinforced polymer composites(CFRP). The matrix and fiber will be eroded at extreme temperatures. Because the ablation rate of matrix is bigger than fiber, the fiber will be exposed in a certain depth from surface. In the microscale, a model is developed for analyzing the number of exposed fibers and the fiber geometry at low air flow and different temperatures. The model shows that the exposed number increases with the growth of ratio of ablation rate of matrix and fiber, and the ratio doesn’t monotonously increase with the rise of temperature. Surface ablation gradually turns to volume ablation with the increase of the number of exposed fibers. In the macroscale, the effective reactivity of the material is equal to the integral over the ablation zone. Compared with perpendicular carbon fiber reinforced polymer composites, both of them reach maximum number or length of exposed fibers during the transition temperature region where "reactivity limit" turns to "diffusion limit". When the fibers are perpendicular to the surface, the macro ablation behavior agrees with “weakest link law”, in other words the matrix recession rate is the most determining parameter for the effective behavior, but it may be not reasonable for parallel fibers.

We present an experimental study on low-threshold supercontinuum generation mainly based on cascaded stimulated Raman scattering (SRS) effect in a four-stage fiber master oscillator power amplifier (MOPA) system. The cascaded SRS is achieved by using a long passive fiber pumped by a pulsed fiber laser centered at 1064 nm wavelength. The cascaded SRS seed is amplified in a double-clad ytterbium-doped fiber amplifier, generating supercontinuum ranging from 960 nm to 1700 nm with 13.6 W maximum average output power and approximately 17.7 mW/nm average spectral power density.

We describe a versatile mid-infrared (Mid-IR) spectroscopy system developed to measure the concentration of a wide range of gases with an ultra-low sample size. The system combines a rapidly-swept external cavity quantum cascade laser (ECQCL) with a hollow fiber gas cell. The ECQCL has sufficient spectral resolution and reproducibility to measure gases with narrow features (e.g., water, methane, ammonia, etc.), and also the spectral tuning range needed to measure volatile organic compounds (VOCs), (e.g., aldehydes, ketones, hydrocarbons), sulfur compounds, chlorine compounds, etc. The hollow fiber is a capillary tube having an internal reflective coating optimized for transmitting the Mid-IR laser beam to a detector. Sample gas introduced into the fiber (e.g., internal volume = 0.6 ml) interacts strongly with the laser beam, and despite relatively modest path lengths (e.g., L ~ 3 m), the requisite quantity of sample needed for sensitive measurements can be significantly less than what is required using conventional IR laser spectroscopy systems. Example measurements are presented including quantification of VOCs relevant for human breath analysis with a sensitivity of ~2 picomoles at a 1 Hz data rate.

High performance in combination with small size, low weight and low power consumption are among the main drivers in modern defense and commercial applications of laser systems. Consequently, designers of such systems strive for innovative solutions in the field of laser technology. Ten years ago Safran Vectronix AG (hereafter Vectronix) pioneered these activities with the fielding of the first fiber laser for hand-held rangefinders. This paper will deal with the latest evolution of an eye-safe fiber laser source which can emit two wavelengths for an extended range of applications. In order to comply with high performance requirements the laser on one side has to produce high enough pulse energy and on the other side – especially due to the ever increasing requirement for compactness – to use so called single-stage amplification in combination with bending insensitive fiber solutions. Also, the ASE (Amplified Spontaneous Emission) has to be reduced as much as possible as this light enters the eye safety equation but does not contribute in terms of range performance. All of this has to meet severe environmental requirements typical for most demanding defense applications. Additionally, the laser in its rangefinding mode has to produce a sequence of high frequency pulses in such a way that no substantial temperature effects would arise and thus impair either the pulse energy or the boresight alignment. Additionally, in this paper, a compact dual-stage dual-wavelength version of the above laser will be described, which has been developed to generate much stronger pulses for very long rangefinding applications.

We report detailed theoretical analysis on the influence of the fused depth, launch mode and taper ratio on the performance of side-pumping combiner. The theoretical analysis indicates that the coupling efficiency and loss mechanism of the combiner is closely related to the fused depth, tapering ratio and the launch mode. Experimentally, we fabricate combiners consisting of two pump fibers (220/242 μm, NA=0.22) and a signal fiber (20/400 μm, NA=0.46). The combined pump coupling efficiency of two pump port is 97.2% with the maximum power handling of 1.8 kW and the insertion signal loss is less than 3%.

The superior thermal and optical properties of transparent polycrystalline ceramics make them attractive alternatives to glass-based materials for laser gain media. Fibers have other advantages of compactness, vibration-resistance, and reduced cooling requirements. Recently it was found that surface roughness caused by grain boundary grooving dominated optical scattering even though there were other scattering sources in the fiber. Therefore, a lot of effort went to fabrication of fibers with smooth surfaces. A mechanical polishing method for polycrystalline YAG fibers was developed. The fiber surface roughness was reduced, while maintaining a circular cross-section. Surface-polished 1.5% Ho-doped polycrystalline YAG fiber, 62 mm long with 31 μm diameter, was fabricated, and lasing was demonstrated from this fiber. Effects of surface-polishing on the surface roughness and scattering coefficient are presented, and lasing characteristics are discussed.

In this study, a numerical model based on finite element method was proposed to evaluate the thermo-mechanical behavior of a composite structure material. The composite structure consisted of substrate, thermal spray coating, and an embedded optical fiber. The stress level of the composite structure especially the embedded fiber at the end of elaboration process was analyzed. The variations of refractive index of the embedded fiber due to the thermo-optic effect and the elasto-optic effect were investigated. The results showed that the the variation of stress and refractive index during the elaboration process had an insignificant effect on the embedding quality of the optical fiber under the presented optimized experimental conditions.

Fiber gratings have been used to measure strain fields in pressure vessels made of composite materials and aircraft adhesive joints1 . Measuring transverse loads have traditionally been performed by inducing a differential strain across the optical core of a fiber. Small changes in load cause the birefringence in the fiber to increase and capturing the spectral shifts using this method necessitates extremely accurate readout systems and careful analysis. This paper suggests a new approach for measuring transverse load by converting it to longitudinal strain and covers a very high-speed system used for measuring velocity, position, and pressure events that are on the order of a few microseconds.

Brillouin distributed optical fiber strain sensors are often limited to static events because of the long acquisition time due to the classic frequency sweep technique. Recently, BOTDA sensor based on slope-assisted (SA) method has been proposed for fast strain measurement along the sensing fiber. In this paper, we present a novel dynamic SA-BOTDR for single-ended truly distributed strain measurement. Geometrical displacement and damping time of a 10.4 m instrumented pipe with a 3 glued fibers system. A 7.6 Hz acquisition rate was achieved with a strain error of 40 μe and a 1m spatial resolution. From integration of longitudinal strains, local pipe displacement is calculated with a 12 mm precision.

We report a quartz-enhanced photoacoustic sensor (QEPAS) for nitric oxide (NO) detection using a mid-infrared fibercoupled quantum cascade laser (QCL) near 5.2 μm. The QCL radiation was coupled into an InF 3 fiber (100 μm core diameter) for light delivery to the quartz tuning fork, a tiny piezoelectric element converting the acoustic wave induced mechanical vibration to the gas-absorption associated electrical signal. This mid-infrared fiber can achieve nearly single-mode light delivery for the target wavelength. The off-beam configuration was adopted for the fiber-coupled detection considering its simpler installation, optical alignment and comparative sensitivity to the traditional on-beam setup.

In this paper, an egg-shaped microbubble is proposed and analyzed firstly, which is fabricated by the pressure-assisted arc discharge technique. By tailoring the arc parameters and the position of glass tube during the fabrication process, the thinnest wall of the fabricated microbubble could reach to the level of 873nm. Then, the fiber Fabry-Perot interference technique is used to analyze the deformation of microbubble that under different filling pressures. It is found that the endface of micro-bubble occurs compression when the inner pressure increasing from 4Kpa to 1400KPa. And the pressure sensitivity of such egg-shaped microbubble sample is14.3pm/Kpa. Results of this study could be good reference for developing new pressure sensors, etc.

This work presents the proof of concept of the detection of global and surface optical index variations by surface plasmon resonance (SPR) thanks to optical fiber bundles. This work is the first necessary step for the future design of a lab-on-fiber tool dedicated to molecular analysis for endoscopic diagnosis. Our approach is based on nanostructured optical fiber bundles comprising several thousands of individual optical fibers. These nanostructures were coated by a thin gold layer in order to gain interesting optical properties such like SPR. The sensitivity and resolution of the bundle to global optical index changes were measured in retro-reflection. We performed numerical simulations in order to optimize the fiber tip geometry, gold coating thickness and finally enhance their analytical performances. We achieved a resolution of 10−4 refractive index unit, which is fully compatible with the detection of biological interactions involving large proteins or bacteria. Finally, we proved that our sensor was sensitive to surface optical index variations and able to detect the adsorption of a thin self-assembled molecular layer.

We present a technique to overcome the random transfer function of fiber-optic direct detection coherent optical time-domain reflectometry (C-OTDR). For this purpose, a standard optical fiber was treated by UV light in order to introduce local strongly scattering segments of definite size and distance to each other. Dynamic strain measurements were performed to demonstrate the sensory benefit in comparison to a non-manipulated fiber section. Our results show, that the modified fiber section exhibits a significant boost in strain sensitivity and in addition reduces the sensor dead time in a temperature-unstable environment as compared to a standard fiber.

We describe the fabrication and performance of a continuously grated twisted multicore fiber sensor array. The grated fiber sensor comprises nearly continuous Bragg gratings along its entire length. The gratings are inscribed over lengths in excess of 10m in fibers with UV transparent coating using a flexible and scalable reel to reel processing system. The arrays are tested using optical frequency domain reflectometry (OFDR). We report on automated analysis routines applied to these OFDR measurements that allow for characterization of 100s of individual grating exposures that make up a continuously grated fiber length. We also report on the spectral loss of the continuously grated fiber, showing that it is suitable for applications with sensors in excess of 100m. Finally, we report on the fiber sensing characteristics by performing measurements of fiber bend using a fiber shape reconstruction algorithm on OFDR traces obtained from four of the fiber cores.

A Graphene Oxide (GO) modified surface plasmon resonance (SPR) sensor based on the silver-coated side-polished fiber was demostrated. Stable GO aqueous dispersion was prepared through sonication, confirmed by UV-vis absorption spectrum and Tyndall effect. GO nanosheets were decorated on the Octadecanethiol (ODT)-silver sensor surface, where ODT act as a link between the silver and GO nano-films. The GO decoration process was in-situ monitored by SPR wavelength interrogation method. The proposed SPR fiber sensor show a refractive index sensitivity up to 2252.0 nm/RIU in the range of 1.30 ∼ 1.40 RIU and can be used as promising candidate in biosensing.

A novel liquid-level sensing system based on differential pulse-width pair Brillouin optical time domain analysis technology with a self-heated high attenuation fiber (HAF) is proposed and demonstrated in this paper, where the principle is to measure the temperature abruption position at the interface between liquid and air caused by the different thermal diffusion rates of the two kinds of mediums. The sensing optical fiber was glued to a 1-m HAF with an absorption coefficient of 20 dB/m, so that heat can be transmitted from the HAF to the sensing fiber through physical contact, which will cause temperature increase of the latter. The Brillouin frequency shift (BFS) profiles of the sensing fiber when the HAF was heated by different heating optical powers were characterized to find out the optimized heating power. The BFS distributions were measured for different water levels, with the result indicating that liquid-level sensing with a range of 20 cm and a resolution of 1 cm is realized.

A magnetic field fiber optic sensor based on Nano-magnetic fluid and Hi-Bi non-adiabatic tapered optical fiber in fiber loop mirror (HB-TFLM) is proposed and theoretically explained. As compared to the reported magnetic fluid (MF) based sensors, the achieved sensitivity of the proposed sensor is 255 pm/mT, which is enhanced by 3.6 times of magnitude relative to in line non-adiabatic tapered optical fiber sensor, used only 0.1% of the volume concentration of MF nanoparticles. Detection limit of the HB-TFLM to external magnetic field in range from 0 to 21 mT and 22 to 50 mT was 7.8 μT and 39.2 μT, respectively.

Sensitivity of two commercial perfluorinated (PF) polymer optical fibers (POFs) to gamma radiation was measured, compared and exploited for dosimetry purposes. Fiber radiation induced attenuation (RIA) was found to be highly wavelength dependent and pronounced towards the UV part of the spectrum. PF-POFs were shown to be highly radiation sensitive and RIA-based on-line radiation monitoring with sensitivity as high as 135 dBm−1/kGy was demonstrated at 460 nm with co-extruded PF-POF. In addition, thanks to low inherent attenuation in the near-infrared region, possibility of distributed radiation detection with PF-POFs was demonstrated for the first time, utilizing optical time domain reflectometry.

We propose and demonstrate a distributed fiber sensor based on cascaded microfiber Fabry-Perot interferometers (MFPI) for simultaneous refractive index (SRI) and temperature measurement. By employing MFPI which is fabricated by taper-drawing the center of a uniform fiber Bragg grating (FBG) on standard fiber into a section of microfiber, dual parameters including SRI and temperature can be detected through demodulating the reflection spectrum of the MFPI. Further, wavelength-division-multiplexing (WDM) is applied to realize distributed dual-parameter fiber sensor by using cascaded MFPIs with different Bragg wavelengths. A prototype sensor system with 5 cascaded MFPIs is constructed to experimentally demonstrate the sensing performance.

This work describes a method for producing a nano structured fiber optic device for sensing of pesticides in water environment. The device consists of a long period grating with a coating of gold nanoparticles functionalized with cysteamine. The LPG shows attenuation bands near the phase matching turning point at the visible spectral range. A bottom-up production route was used to deposit gold nanoparticles on the fiber surface. Sensitivity to the refractive index of the external medium was measured before and after the layer deposition. Cysteamine was used as a ligand for glyphosate present in water at a concentration of 100 μM.

We propose and demonstrate a miniature Fabry-Perot (F-P) interferometric sensor based on a hollow glass microsphere (HGM) for highly sensitive temperature measurement. The sensor head is fabricated by sticking a HGM on the end face of a single-mode fiber, and it consists of a short air F-P cavity between the front and the rear surfaces of the HGM. A sensor with 135.7280-μm cavity length was tested for temperature measurement from −5 °C to 50 °C. The obtained sensitivity reached up to 24.5 pm/°C and the variation rate of the HGM-F-P's cavity length was2.1 nm/°C. The advantages of compact size, easy fabrication and low cost make the sensor suitable for highly sensitive temperature sensing.

A 3D FEM model of an FBG in a PANDA fiber with an extended fiber length of 25.4 mm is presented. Simulating long fiber lengths with limited computer power is achieved by using an iterative solver and by optimizing the FEM mesh. For verification purposes, the model is adapted to a configuration with transversal loads on the fiber. The 3D FEM model results correspond with experimental data and with the results of an additional 2D FEM plain strain model. In further studies, this 3D model shall be applied to more sophisticated situations, for example to study the temperature dependence of surface-glued or embedded FBGs in PANDA fibers that are used for strain-temperature decoupling.

An all-fiber graphene oxide (GO) based ‘FRET on Fiber’ concept is proposed and applied in biochemical detections. This method is of both good selectivity and high sensitivity, with detection limits of 1.2 nM, 1.3 μM and 1 pM, for metal ion, dopamine and single-stranded DNA (ssDNA), respectively.

The subject of this work is the strain characteristic of fiber-optic flexural disk accelerometer. In the presented investigation, the strain distribution of flexural disk is studied and the result shows that the position of fiber coil has a significant effect on the strain of fiber coil. We simulated the strain distribution of fiber-optic flexural disk accelerometer that based on multilayer fiber coils and on the optimized position. In experiment, corresponding sample accelerometer is fabricated and tested in the Brillouin Optical Time-Domain Analysis. The experimental result is in good agreement with the simulated result, provides this theoretical approach is effective in designing the fiber-optic flexural disk accelerometer.

We report the efficient coupling of optical whispering gallery modes (WGMs) in liquid crystal microdroplets suspended in immiscible aqueous environment. Individual nematic liquid crystal (NLC) microdroplet is confined at the tip of a microcapillary used to generate the microdroplets and coupled through a tapered optical fiber waveguide positioned in the vicinity of the microdroplets. Efficient coupling of WGMs is observed in the NLC microdroplets with a diameter of 50–150 μm. In addition, the wavelengths of the WGMs can be tuned by temperature, making such NLC microdroplets suitable for thermal sensors. A temperature sensitivity of 0.244 nm/°C is achieved in a 75-μm-diameter microdroplet. The estimated thermal resolution of the microdroplet sensor is 8.2 × 10−2 °C.

New approach in simultaneous measurement of dynamic strain and temperature has been done by using a high birefringence PANDA fiber Bragg grating sensor. By this technique, we have succeeded in discriminating dynamic strain and temperature distribution at the sampling rate of 800 Hz and the spatial resolution of 1 mm. The dynamic distribution of strain and temperature were measured with the deviation of 5 mm spatially. In addition, we have designed an experimental setup by which we can apply quantitative dynamic strain and temperature distribution to the fiber under testing without bounding it to a specimen.

Radiation effects on the performances of TW-COTDR (Tunable Wavelength — Coherent Optical Time Domain Reflectometry) optical fiber sensors based on Rayleigh scattering have been studied online for Ge-doped and F-doped fibers. We confirm that the Rayleigh response is not affected by low radiation (dose ∼55 kGy). However we observed using the TW-COTDR technology, a radiation induced frequency shift increasing at higher radiation (dose ∼ 10MGy): up to 96 GHz for Ge-doped fiber and up to 25.5 GHz for F-doped fiber.

25th International Conference on Optical Fiber Sensors, 24/04/2017-28/04/2017, Jeju, Corea del Sur., European Commission, Ministerio de Economía y Competitividad

A mechanically robust and compact optical fibre sensor system is described to monitor the bending of the lower back bone in both sagittal and frontal plane. Both bending modes are monitored through the change of the coupled optical intensity ratio between three output fibers aligned to one input fiber. This provides real time feedback when different postures are sustained. The output ratio is calibrated to bending angles using an optical setup that utilized a precise rotational stage. An operation range between −12° to 12° is demonstrated. It is also demonstrated that sensor is suitable for use in a clinical diagnosis system with the additional benefits of being non-invasive, robust, straightforward to use and low cost.

An inline intermodal no core fiber (NCF) sensor based on direct ligand immobilization for detection of nickel ions (Ni2+) is proposed. Covalently immobilized nickel specific ligand, Meso-Tetra(4-carboxyphenyl)porphine, on the NCF surface serves as adsorption site for Ni2+ and can induce ambient refractive index (RI) change around the NCF on occurrence of binding events. The change in RI results in spectrum wavelength shifts, which was measured for continuous monitoring of Ni2+ concentration. The proposed sensor was observed to exhibit a sensitivity of 121.03 nm/mM towards Ni2+ ions. Published version

A Mach-Zehnder and Michelson Hybrid (M2) interferometer is promoted to measure backreflection of modes at the hollow-core photonic bandgap fiber (HC-PBF) terminations. The results show that compared to the incident light intensity into the HC-PBF, the modes reflectivity is less than −80 dB at the flat termination, and it is about −90 dB for the fundamental modes.

An optical fiber tactile sensor based on specklegram analysis is demonstrated. The system consists of microbending transducers attached to semi-rigid plates and distributed in form of array. The specklegrams produced by the multimode fibers are recorded and them the variations on fiber status, related to force magnitude, are assessed by specklegrams correlation. Finally, the spatial information was obtained by using a data fusion approach based on Bayesian inference. The sensor presented ∼0.08 N sensitivity and ∼1 mm resolution. Moreover, the data fusion technique provided the estimation of force distribution over a 30 × 30 mm2 area using only 3 fibers.

A new fiber-type Li-ion battery that consists of carbon nanotube fibers deposited with active materials has been developed and tested. The active materials, LiMn2O4 and Li4Ti5O12, were deposited on the surface of carbon nanotube fibers in order to use as electrodes. Tensile strength of the CNT fibers with active material was measured by tensile tests to investigate the mechanical characteristics. Electrochemical property is also measured by a battery tester during charging and discharging. The results show that current discharge capacity is about 25 mAh/g between 3.0 V and 4.2 V. That means the fiber with active materials is good for an anode electrode. Mathematical material models considering the lithium concentration and the length of Li-C bond have been established in order to predict the effective elastic modulus of electrode composite materials.

In fiber reinforced composite materials, the modes of damage accumulation, ranging from microlevel to macro-level (matrix cracks development, fiber breakage, fiber-matrix de-bonding, delamination, etc.), are complex and hard to be detected through conventional non-destructive evaluation methods. Therefore, in order to assure the outstanding structural performance and high durability of the composites, there has been an urgent need for the design and fabrication smart composites with self-damage sensing capabilities. In recent years, the macroscopic forms of carbon nanotube materials have been maturely investigated, which provides the opportunity for structural health monitoring based on the carbon nanotubes that are integrated in the inter-laminar areas of advanced fiber composites. Here in this research, advanced fiber composites embedded with laminated carbon nanotube layers are manufactured for damage detection due to the relevant spatial electrical property changes once damage occurs. The mechanical-electrical coupling response is recorded and analyzed during impact test. The design and manufacturing of integrating the carbon nanotubes intensely affect the detecting sensitivity and repeatability of the integrated multifunctional sensors. The ultimate goal of the reported work is to develop a novel structural health monitoring method with the capability of reporting information on the damage state in a real-time way.

We investigated the optical binding between dielectric microparticles in the evanescent fields of the first group of higher order microfiber modes. Particle groups consisting of up to five particles were propelled along the fiber and neighboring interactions were experimentally investigated and supported by numerical simulation.

Twist and Coiled soft Actuator (TCA) is simply fabricated by twisting a polymer fiber. In the previous researches, TCA was mainly fabricated with Nylon 6,6 fiber, and Nylon-TCA (NTCA) showed strong force outputs. However, the strain from NTCA was not much enough for practical application. This paper introduces SPX-TCA (STCA) which is fabricated with Spandex fibers. NTCA and STCA were fabricated, and their performances were compared by using the performance evaluation device. STCA showed larger strain, and it was actuated lower temperature than NTCA.

Fiber reinforcement increases many properties of the concretes, such as toughness, strength, abrasion, and resistance to corrosion. Use of recycled carbon fibers from industrial waste offers many advantages because it will reduce the waste, contribute the economy, protect natural resources and improve the property of structural units. The City of Wichita, KS is known to be “Air Capital of the World” where many aircraft companies have been producing aircraft, parts and components. Due to the superior properties of composites (e.g., light weight, low density, high impact resistance), they have been highly used by aircraft industry. Prepreg is the most preferred combination of the fiber and resin due to the easy application, but it has a limited shelf life (e.g., three months to one year at most) and scrap has no use after all in the same industry. Every year tons of un-used prepreg or after use scrap are being collected in Wichita, KS. Recycling prepreg from the post-consumer waste offers great advantages of waste reduction and resource conservation in the city. Reusing the carbon fibers obtained from outdated prepreg composites for concrete reinforcement will offer double advantages for our environment and concrete structures. In this study, recycled carbon fibers of the outdated prepreg composites were collected, and then incorporated with concretes at different ratios prior to the molding and mechanical testing. An undergraduate student was involved in the project and observed all the process during the laboratory studies, as well as data collection, analysis and presentation. We believe that experience based learning will enhance the students’ skills and interest into the scientific and engineering studies.

3D printing technology has been used for rapid prototyping since 1980’s and is still developing in a way that can be used for customized products with complex design and miniature features. Among all the available 3D printing techniques, Fused Deposition Modeling (FDM) is one of the most widely used technologies because of its capability to build different structures by employing various materials. However, complexity of parts made by FDM is greatly limited by restriction of using support materials. Support materials are often used in FDM for several complex geometries such as fully suspended shapes, overhanging surfaces and hollow features. This paper describes an approach to 3D print a structure using silicone elastomer and polylactide fiber (PLA) by employing a novel support material that is soluble in water. This support material is melted sugar which can easily be prepared at a low cost. Sugar is a carbohydrate, which is found naturally in plants such as sugarcane and sugar beets; therefore, it is completely organic and eco-friendly. As another advantage, the time for removing this material from the part is considerably less than other commercially available support materials and it can be removed easily by warm water without leaving any trace. Experiments were done using an inexpensive desktop 3D printer to fabricate complex structures for use in soft robots. The results envision that further development of this system would contribute to a method of fabrication of complex parts with lower cost yet high quality.

In this paper, we demonstrate a polymeric humidity sensor made of a cellulose based composite nanofiber. The device measures humidity via a humidity induced electrical impedance change. The compact, efficient design of the fiber makes it ideal to incorporate into textiles for biometrics applications such as body fluid monitoring. Initial test results show that the sensor can measure between 20 to 80% relative humidity with a sensitivity of about 2%. The impedance of the sensor material changes relatively linearly with relative humidity. The sensor also shows a relatively fast response (~4s) compared to current commercial sensors.

The optical fiber taper coupled with CMOS has advantages of high sensitivity, compact structure and low distortion in the imaging platform. So it is widely used in low light, high speed and X-ray imaging systems. In the meanwhile, the peculiarity of the coupled structure can meet the needs of the demand in microscopy imaging. Toward this end, we developed a microscopic imaging platform based on the coupling of cellphone camera module and fiber optic taper for the measurement of the human blood samples and ascaris lumbricoides. The platform, weighing 70 grams, is based on the existing camera module of the smartphone and a fiber-optic array which providing a magnification factor of ~6x.The top facet of the taper, on which samples are placed, serves as an irregular sampling grid for contact imaging. The magnified images of the sample, located on the bottom facet of the fiber, are then projected onto the CMOS sensor. This paper introduces the portable medical imaging system based on the optical fiber coupling with CMOS, and theoretically analyzes the feasibility of the system. The image data and process results either can be stored on the memory or transmitted to the remote medical institutions for the telemedicine. We validate the performance of this cell-phone based microscopy platform using human blood samples and test target, achieving comparable results to a standard bench-top microscope.