Small-diameter Optical Fiber Research Articles

Development of a High-Function Fiber Stylus for Microstructure Measurement with Water-Repellent and Antistatic Coatings

The precise measurement of microstructures and other micron-sized materials has garnered considerable interest in recent years. We have developed a measurement system that uses an etched small diameter optical fiber as a stylus to measure microstructures with low contact force. However, when the diameter of the stylus tip is less than a few tens of micrometers, the surface forces between the measured surface and the stylus tip become larger than the gravity of the stylus tip, causing the stylus tip to stick to the measured surface. This adhesion leads to an increase in measurement time and a decrease in measurement accuracy. In this study, we fabricated a high-function stylus with water-repellent and antistatic coatings applied to the stylus tip to reduce the adhesion between the stylus tip and measured surface due to surface forces, and conducted performance evaluation tests. As a result, the average separation distance was 13.8 µm when a fluorinated resin coating with a contact angle of 105° was used, confirming that the influence of liquid bridge forces could be reduced by approximately 78%. Additionally, when static elimination experiments were conducted by scanning the charged surface at a pitch of 0.5 µm using an antistatic coating stylus with a gold on the stylus surface, the average adsorption distance was 3.6 µm, confirming that the effect of electrostatic force could be reduced by 71%.

Ultrahigh Fiber Count and High-Density Cables, Deployments, and Systems

Since the 1980s, the single-core optical fiber cable has been the essential data transmission wiring media, with ongoing increases in deployments. Its use case has broadened, with transmission distances ranging from meters to 10000s km, including intrabuilding, fiber-to-the-home (FTTH), terrestrial, and even submarine trunk lines. Currently, optical fiber cable deployment is strongly driven by cloud-based storage, X as a Service (XaaS), and worldwide data center (DC) functionality with the optical interconnection of massive servers on DC campuses. Hence, it is quite natural that the optical fiber cable industry has developed ultrahigh fiber count, high density, and small diameter optical fiber cable, e.g., 6912-fiber-count cable. With high-density cables, massive data capacity can be installed at one time while saving limited space in an underground duct. High-density cable designs have been developed not just by cable structure optimization but through the process of bundling fibers and the use of high-grade optical fibers. Moreover, many enabling technologies have been developed to support the deployment of ultrahigh fiber count cables, such as fiber identification, connectors, mass fusion splicing, and storage systems for fusion splicing points. In this article, state-of-the-art technologies and prospects for ultrahigh-count and ultrahigh-density optical fiber cables and enabling technologies are explained.

In vitro analysis of mechanism of pulsed-laser thrombolysis.

Thrombolytic therapy in the treatment of cardiogenic acute cerebral embolism caused by coagulated blood carries the risk of hemorrhagic complications, and there is a need to develop safer and more reliable treatment methods. Laser thrombolysis therapy, which utilizes the difference in energy absorption between the thrombus and the arterial wall, has shown promise as a new treatment method because it can selectively act only on the thrombus. It has not been applied clinically, however, and one of the main reasons for this is that its underlying mechanism has not been elucidated. We developed a pulse laser thrombolysis system for treating cerebral blood vessels that consists of a diode-pumped solid-state neodymium-yttrium aluminum garnet laser, which has excellent stability and maintainability and is suitable for clinical applications coupled to a small-diameter optical fiber. Moreover, we analyzed the mechanisms that occur during pulsed laser irradiation of transparent glass tubes and gelatin phantoms. We found that bubbles form as a thermal effect in addition to ablation of the pulsed laser irradiation. Furthermore, we detected no shock waves or water jets associated with the bubbles. We analyzed the bubbles’ dynamics and growth rate, and their effect on a rabbit blood clot phantom. We concluded that the bubbles generated by the laser irradiation physically cut the thrombus and thereby had a thrombectomy effect. We believe that this study will clarify the mechanism of laser thrombolysis therapy and contribute greatly to the realization of its clinical application.

Development of measurement system for microstructures using an optical fiber probe: improvement of measurable region and depth

The precise measurement of microstructures and other micron-sized materials has garnered considerable interest in recent years. However, a limited measurement region and the unavailability of miniaturized probes are the major issues in the realization of such systems. In this study, we have presented a system for microstructures based on a small-diameter optical fiber probe. In the improved measurement system, the prism was installed near the stylus shaft to expand the measurable region and depth. This means that there is no limitation on the width of the measurement object. The standard deviation of the repeatability of the point measurement in the X-, Y- and Z-directions was 31, 38 and 19 nm, respectively. A pin gauge with a diameter of 100 µm was measured ten times for assessing the repeatability of measurements in the X- and Y-directions. The standard deviation of the diameter in these measurements was 25 nm. A step height standard with a calibrated height of 189.6 nm was measured ten times for assessing the repeatability of measurement in the Z-direction. The average height in these measurements was obtained as 200.2 nm with an expanded uncertainty of 49.3 nm (coverage factor k = 2). We confirmed that this system enabled accurate measurement in the X-, Y- and Z-directions.

OS7-3 Study on the Loading Localization by Small-Diameter Optical Fiber Sensors(Stress and strain measurement I,OS7 Stress and strain measurement,MEASUREMENT METHODS)

OS7-3 Study on the Loading Localization by Small-Diameter Optical Fiber Sensors(Stress and strain measurement I,OS7 Stress and strain measurement,MEASUREMENT METHODS)

Small diameter fiber Bragg gratings and applications

Small diameter optical fibers are preferred in sensing systems as they have less influence on mechanical performance of smart composite. The static and dynamic monitoring capabilities of the small-diameter fiber Bragg gratings (FBG) are experimentally studied in this paper. Firstly, a small-diameter FBG is used as a strain sensor. Secondly, a temperature sensor is fabricated using a specific FBG. Thirdly, a simple sensing system is proposed in order to discriminate temperature at sensing point. Finally, utilization of these small diameter FBGs for vibration monitoring is discussed. The experiments revealed that the central wavelengths of the small-diameter fiber Bragg gratings shift linearly with strain or temperature. The FBG is more sensitive than a thermocouple inside the thermostat. Acquisition and analysis of the dynamic signal indicates that the designed FBG can be used for dynamic signal monitoring.

Absolute calibration method for nanosecond-resolved, time-streaked, fiber optic light collection, spectroscopy systems

This paper describes a convenient and accurate method to calibrate fast (<1 ns resolution) streaked, fiber optic light collection, spectroscopy systems. Such systems are inherently difficult to calibrate due to the lack of sufficiently intense, calibrated light sources. Such a system is used to collect spectral data on plasmas generated in electron beam diodes fielded on the RITS-6 accelerator (8-12MV, 140-200kA) at Sandia National Laboratories. On RITS, plasma light is collected through a small diameter (200 μm) optical fiber and recorded on a fast streak camera at the output of a 1 meter Czerny-Turner monochromator. For this paper, a 300 W xenon short arc lamp (Oriel Model 6258) was used as the calibration source. Since the radiance of the xenon arc varies from cathode to anode, just the area around the tip of the cathode ("hotspot") was imaged onto the fiber, to produce the highest intensity output. To compensate for chromatic aberrations, the signal was optimized at each wavelength measured. Output power was measured using 10 nm bandpass interference filters and a calibrated photodetector. These measurements give power at discrete wavelengths across the spectrum, and when linearly interpolated, provide a calibration curve for the lamp. The shape of the spectrum is determined by the collective response of the optics, monochromator, and streak tube across the spectral region of interest. The ratio of the spectral curve to the measured bandpass filter curve at each wavelength produces a correction factor (Q) curve. This curve is then applied to the experimental data and the resultant spectra are given in absolute intensity units (photons/sec/cm(2)/steradian/nm). Error analysis shows this method to be accurate to within +∕- 20%, which represents a high level of accuracy for this type of measurement.

Confined High-Pressure Chemical Deposition of Hydrogenated Amorphous Silicon

Hydrogenated amorphous silicon (a-Si:H) is one of the most technologically important semiconductors. The challenge in producing it from SiH(4) precursor is to overcome a significant kinetic barrier to decomposition at a low enough temperature to allow for hydrogen incorporation into a deposited film. The use of high precursor concentrations is one possible means to increase reaction rates at low enough temperatures, but in conventional reactors such an approach produces large numbers of homogeneously nucleated particles in the gas phase, rather than the desired heterogeneous deposition on a surface. We report that deposition in confined micro-/nanoreactors overcomes this difficulty, allowing for the use of silane concentrations many orders of magnitude higher than conventionally employed while still realizing well-developed films. a-Si:H micro-/nanowires can be deposited in this way in extreme aspect ratio, small-diameter optical fiber capillary templates. The semiconductor materials deposited have ~0.5 atom% hydrogen with passivated dangling bonds and good electronic properties. They should be suitable for a wide range of photonic and electronic applications such as nonlinear optical fibers and solar cells.

Simultaneous Force and Temperature Sensor Using Small-Diameter FBGs

In order to decrease the influence on mechanical performance of smart composite, small diameter optical fibers are usually preferred as strain sensors. Therefore, fiber Bragg gratings in small diameter were manufactured. In applications, the FBG measures both strain (or force, pressure, displacement) and thermal expansion. In order to overcome this inconvenience and to measure both parameters at the same time and location, a simple temperature insensitive force sensor was proposed. A pair of small-diameter FBG was attached on a uniform strength beam. One of the FBG was affixed on the upper surface of the cantilever, and the other one on the bottom. The central wavelength shifts of the two FBGs are proportional to load value F and –F respectively. Therefore, coefficient matrix is well conditioned. The force and temperature in sensing point could be discriminated. Experiments were carried out to study the force and temperature cross sensitivity. Experimental results match the theoretical ones well. The temperature and force were calculated and the errors were 2% and 7% respectively.

Multi-day pre-clinical demonstration of glucose/galactose binding protein-based fiber optic sensor

We report here the first pre-clinical demonstration of continuous glucose tracking by fluorophore-labeled and genetically engineered glucose/galactose binding protein (GGBP). Acrylodan-labeled GGBP was immobilized in a hydrogel matrix at the tip of a small diameter optical fiber contained in a stainless steel needle. The fiber optic biosensors were inserted subcutaneously into Yucatan and Yorkshire swine, and the sensor response to changing glucose levels was monitored at intervals over a 7-day period. Sensor mean percent error on day 7 was 16.4 ± 5.0% using a single daily reference blood glucose value to calibrate the sensor. The GGBP sensor's susceptibility to common interferents was tested in a well-plate system using human sera. No significant interference was observed from the tested interferents except for tetracycline at the drug's maximum plasma concentration. The robust performance of the GGBP-based fiber optic sensor in swine models and resistance to interferents indicates the potential of this technology for continuous glucose monitoring in humans.

Distributed strain measurements using fiber Bragg gratings in small-diameter optical fiber and low-coherence reflectometry

Optical low coherence reflectometry and fiber Bragg gratings written in small diameter (50 micrometer) optical fibers were used for measurements of non-homogenous internal strain fields inside an epoxy specimen with sub-grating length resolution. The results were compared with measurements using Fiber Bragg gratings in standard size (125 micrometer) single mode fibers and show that smaller fibers are less intrusive at stress heterogeneities.

Distributed Fiber Optic Strain Sensing with Embedded Small-Diameter Optical Fibers in CFRP Laminate

Although demand for composite structures rapidly increase due to the advantages in weight, there are few effective assessment techniques to enable the quality control and guarantee the durability. In particular, an invisible microscopic damage detection technology is highly required because damages such as transverse cracks, debondings, or delaminations can lead to the critical failure of the structures. Among many non-destructive evaluation (NDE) methods for composite structures, fiber optic sensors are especially attractive due to the high sensitivity, the lightweight, and the small size. In the current trend of the structural health monitoring technology, fiber Bragg gratings (FBG) sensors are frequently used as strain or temperature sensors, and Brillouin scattering sensors are also often used for a long distance distributed measurement. The Brillouin distributed sensors can measure strain over a distance of 10km while a spatial resolution was limited to 1m. Some novel sensing method is proposed to improve the spatial resolution. The pulse-prepump Brillouin optical time domain analysis (PPP-BOTDA) is one of the latest distributed sensing applications with a cm-order high spatial resolution. The PPP-BOTDA commercial product has the spatial resolution of 10cm, and can measure the strain with a precision of ±25og. This precision, however, can be achieved by using conventional single-mode optical fibers. In our research, small-diameter optical fibers with a cladding diameter of 40om were embedded in the CFRP laminate to avoid the deterioration of the CFRP mechanical properties. Thus, in order to verify the performance of PPP-BOTDA, the distributed strain measurement was conducted with the small-diameter optical fibers embedded in the CFRP laminate.

Feasibility studies on active damage detection for CFRP aircraft bonding structures

This paper presents a part of the feasibility study for employing a damage monitoring system using a PZT actuator/FBG sensor. The goal of this research is to improve the present safety level of aircrafts by ensuring structural integrity and reducing maintenance/operation costs of advanced composite materials that will be employed for the primary structures of the new generation aircraft. Our novel sensor system employing a PZT actuator and an FBG optical fiber sensor can detect several types of damage, such as delamination and debonding, which are expected to occur in the highly efficient bonding structures of an aircraft wing box when the main/tail wing section is designed using composite materials. In this system, elastic waves will be transmitted into the structure by PZT actuators and received by small-diameter FBG optical fiber sensors that are embedded in the critical section of the primary structure of an aircraft. The onset and growth of damage can be detected with a very high accuracy through the change in the received elastic waves. In this study, a conceptual design was implemented in order to employ the novel system. We also selected the optimum application candidate area in order to verify the effects of the system. Further, the investigation and experiment on the novel sensor system that uses a bonded PZT actuator and an FBG sensor was carried out, and the basic damage detection technique was established based on the experimental results of the received elastic wave. Furthermore, compressive tests were carried out using the coupon specimen with an embedded small-diameter or standard-diameter optical fiber sensor. It was verified that the coupon specimen with an embedded small-diameter optical fiber suffered no degradation of its material properties.

細径光ファイバを用いた高密度光バックプレーンの開発

Rapidly increasing broadband access has led to the requirement for much higher transmission throughput within a network equipment. The most promising solution is optical interconnection using an optical backplane. We have developed a high-density optical backplane using a small-diameter optical fiber to realize multi-tera bit/s throughput. To achieve this, we developed a new high-delta and small-diameter optical fiber (clad diameter=80μm, coating diameter=125μm), a high-den-sity optical fiberboard with small bending radius (r=5mm), a high-density MT ferrule, an easy assemble MT ferrule and compact optical right angle connector. Using these new devices, we fabricated a high-density optical backplane, which complies with the structure of an ATCA backplane. It has achieved a high throughput performance of 3 Tbit/s, which is five times that of an electric backplane.

Development of smart composite structures with small-diameter fiber Bragg grating sensors for damage detection: Quantitative evaluation of delamination length in CFRP laminates using Lamb wave sensing

The authors and Hitachi Cable, Ltd. have recently developed small-diameter optical fiber and its fiber Bragg grating (FBG) sensor for embedment inside a lamina of composite laminates without strength reduction. The outside diameters of the cladding and polyimide coating are 40 and 52 μm, respectively. First, a brief summary is presented for applications of small-diameter FBG sensors to damage monitoring in composite structures. Then, we propose a new damage detection system for quantitative evaluation of delamination length in CFRP laminates using Lamb wave sensing. In this system, a piezo-ceramic actuator generates Lamb waves in a CFRP laminate. After the waves propagate in the laminate, transmitted waves are received by an FBG sensor attached on or embedded in the laminate using a newly developed high-speed optical wavelength interrogation system. This system was applied to detect interlaminar delamination in CFRP cross-ply laminates. When the Lamb waves passed through the delamination, the amplitude decreased and a new wave mode appeared. These phenomena could be well simulated using a finite element analysis. From the changes in the amplitude ratio and the arrival time of the new mode depending on the delamination length, it was found that this system could evaluate the delamination length quantitatively. Furthermore, small-diameter FBG sensors were embedded in a double-lap type coupon specimen, and the debonding progress could be evaluated using the wavelet transform.

A MULTICHANNEL FIBER-OPTIC MAPPING SYSTEM FOR INTRAMURAL RECORDING OF CARDIAC ACTION POTENTIALS.

Measuring cardiac action potentials at many sites within the ventricular wall is important for understanding cardiac arrhythmias; however, recording in the depth of the heart wall presents many difficulties. We have developed a multichannel optical mapping system for recording cardiac action potentials transmurally. Each channel uses a single small-diameter optical fiber to transmit and collect light from the cardiac tissue. Excitation light is supplied by low-power green lasers. Wavelength separation is performed with a dichroic mirror, and fluorescence is detected with a photodiode. We have recorded action potentials with an unfiltered signal-to-noise ratio (SNR) as high as 60:1 and a temporally filtered SNR as high as 200:1. The collection of fluorescence is optimized so that low excitation light intensity can be used, which increases the available recording time. Channels are modular and compact, and the system can be easily expanded to include additional channels, ratiometry or dual-dye mapping. In addition, the system is highly flexible and can be used for virtually any experiment from single cell recording to surface and transmural mapping of the whole heart.

Recent advances in composite fuselage demonstration program for damage and health monitoring in Japan

The Japanese Smart Material/Structure System Project started in 1998 with four research groups: (1) structural health monitoring; (2) smart manufacturing; (3) active/adaptive structures; and (4) actuator material/device development. Based on the above research accomplishment, two demonstrators were fabricated and tested in late 2002. This paper presents a summary of test results obtained in the damage detection and suppression composite fuselage demonstrator program where novel developed monitoring techniques such as small-diameter optical fiber sensors were implemented in the composite structure. This damage detection and suppression composite fuselage demonstrator provided a solid foundation for more practical applications of structural health monitoring technology in advanced large-size composite structures. Copyright © 2005 John Wiley & Sons, Ltd.

1704 損傷検知・抑制能力を有する知的ハニカムサンドイッチパネル(J08-1 材料モニタリング,損傷検知・抑制,J08 知的材料・構造システム)

The authors developed a smart sandwich panel for aerospace structures that could detect impact damages and debonding in honeycomb sandwich structures caused by out-of-plane loadings by using small-diameter optical fiber sensors, such as fiber Bragg grating sensors, embedded in the adhesive layer between the facesheet and the core of the panel. Furthermore, the cell walls of the honeycomb core were made of shape memory alloy (SMA) foils for damage suppression. When the SMA honeycomb sandwich panel with impact damages was heated, the local backlings of the core walls and the deformation of the facesheet disappeared and the bending stiffness of the panel could be recovered.

Detection of impact damage of stiffened composite panels using embedded small-diameteroptical fibers

It is well known that barely visible damage is often induced in composite structuressubjected to out-of-plane impact, and the mechanical properties of the compositesdegrade markedly. The stiffened composite panels which are the representativestructural elements of airplanes are characterized by impact damage differentfrom that of coupon-level specimens. Therefore, the objective of this study is toapply small-diameter optical fiber sensors to stiffened composite panels for thedetection of impact damage. In this study, both multi-mode optical fibers andfiber Bragg grating (FBG) sensors are used for detecting impact load and impactdamage in stiffened composite panels. The fibers have polyimide coating with40 µm cladding diameter which has no serious effect on the mechanical properties of composites.Impact tests are performed using stiffened composite panels with embedded optical fibers.The characteristics of impact damage are investigated. The impact load, the strain and theoptical responses of the optical fibers are measured as a function of time. And we discussthe relationships among the optical responses, the impact load and the impact damage.

Neutron degradation of UV enhanced optical fibers for fusion installation plasma diagnostics

The remote diagnostics of plasmas in fusion installations requires adequate connection links to transfer the measured signals in media subjected to high electromagnetic disturbances. We evaluated the neutron irradiation induced optical absorption in several commercially available optical fibers, as they were assessed for their possible use in fusion installations. Optical fiber samples were subjected to subsequent irradiation with fluences from 6 × 10 11 to 6 × 10 13 n/cm 2. Significant radiation induced absorption was observed in the 220–260 nm spectral band, mainly for small core diameter optical fibers (200/220 μm), independent of the cladding material used.