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We have developed a new type of piezoelectric poly-/-lactic acid (PLLA) braided cord that can be embroidered (piezoelectric PLLA embroidery) as a motion-sensing material for a new type of wearable sensor. We then examined the motion-sensing function of the piezoelectric PLLA embroidery in response to different types of movement. On the basis of the experimental results, we produced e-textiles embroidered with the piezoelectric PLLA braided cord as materials for a new wearable sensor. These e-textiles with piezoelectric PLLA embroidery, which are flexible, feel soft and are similar to high-quality fabrics, can sense complex human motion without using a complex computer system. [ABSTRACT FROM AUTHOR]

In this article, we fabricated and tested a series of extrinsic fiber Fabry–Perot interferometric acoustic sensors based on the corrugated silver diaphragms. These diaphragms were fabricated through a simple and low-cost method. The corrugations were first etched on the silicon surface permanently and then transferred to the silver diaphragm with the help of photoresist as the sacrificial layer. The sensors with different corrugation depths were fabricated. The experimental results showed the same trend with the theoretical results on the mechanical sensitivities of the fabricated corrugated diaphragms, which first increased and then decreased with the increase in the corruption’s depth. Other characteristics of the fabricated optical acoustic sensors based on the corrugated silver diaphragms were also tested in detail. The proposed fabrication method of the corrugated diaphragm showed the advantages of simplicity and low cost, and the acoustic sensors showed high sensitivity, which was suitable for weak acoustic’s sensing. [ABSTRACT FROM AUTHOR]

A corrugated silver diaphragm-based optical fiber microphone (OFM), formed by extrinsic Fabry–Perot interferometric structure, was proposed. The sensor’s sensitivity was improved by releasing diaphragm’s initial stress with the help of corrugations. A simple “gray-scale exposure” method was proposed to fabricate the corrugation. Experimental results indicated that the mechanical sensitivity of the fabricated corrugated diaphragm (CD) was 52 nm/Pa, which was twice that of the planar diaphragm under the same parameters. Other characteristics of the fabricated microphone were also tested in detail. The proposed CD-based OFM showed the advantages of high sensitivity, simplicity and low cost, which was expected to be applied in the field of weak acoustic sensing. [ABSTRACT FROM AUTHOR]

A new piezoelectric sensor was developed in the shape of a traditional Japanese braided cord known as a Kumihimo by weaving piezoelectric poly-l-lactic acid (PLLA) fibers (piezoelectric PLLA braided cord). We found that the piezoelectric PLLA braided cord tied in various decorative knots, and worn as an accessory such as a choker or necklace, can detect pulse waves, swallowing, and coughing in a systematic way in one's daily life. To demonstrate this, we developed a system for measuring pulse waves with a Wi-Fi communication system using a piezoelectric PLLA braided cord with decorative knots. [ABSTRACT FROM AUTHOR]

Zylon fibers, which are made of high-strength polymer, are used at the National High Magnetic Field Laboratory for structural reinforcement of high field pulsed magnet coils. Most polymers are subject to chain scission, which is the result of aging degradation of the fibers in the absence of chemical agent. We studied chain scission of Zylon fibers stored with and without visible light. No mechanical strength degradation was found in Zylon stored without exposure to visible light for 8 years. Prolonged exposure to lab-lighting rendered formation of surface defects, resulting in reduction in mechanical strength. [ABSTRACT FROM AUTHOR]

This paper presents the investigation results on light absorption of silica optical fibers under effect of \gamma -quanta with the energy of 2.5 MeV. Exposure radiation doses were 100–300 R, \gamma -quanta had the energy of ~13.5 MeV with the exposure radiation dose of 20–40 kR. Influence of the electron beam having the energy of 2.5 MeV at absorbed dose up to ~200 krad at rise time up to \sim 10^13 rad/s, and pulselength \tau 1/2 –20 ns in the wavelength range from 0.53 to 1.30 \mu \textm was also studied. This paper describes investigation of the fibers with pure silica cores and the silica cores with different dopants. One could observe difference in behavior of the fibers absorption at exposure dose of 40 kR and absorbed dose of 200 krad. Increasing the light wavelength from 0.53 to 1.3 \mu \textm , we observed the decrease of the optical absorption that was caused by radiation exposure for all studied fiber samples. We also studied optical characteristics of a single-mode fiber (pure SiO2 core and F doped cladding) fabricated using low-birefringence technology. One can also see that radiation exposure did not cause depolarization of the linearly polarized light and did not result to polarization plane angle change for the specified fiber. This allows using of the specified fiber as the fiber-optical probe for current (tens of megamperes) and magnetic field (tens of megagauss) measurements in the conditions of high-power radiation exposure. The presented results allow selecting of the optimum light wavelength and composition of the dopants for the fibers in order to minimize the optical losses. [ABSTRACT FROM PUBLISHER]

We report on a quenching behavior of the 3.4~\mu \textm dual-wavelength pumped fiber laser that can be accounted by the adverse contribution from a new excited state absorption transition in Er3+:ZrF4 glasses. The transition occurs between levels 4F9/2 and 4F7/2 and partially overlaps with the 1976 nm pump wavelength. We show that this upconversion process causes strong quenching of the lasing power at 3.4~\mu \textm under insufficient 974 nm pumping. Intracavity fluorescence at 550 nm from levels (2H11/2, 4S3/2) is also monitored as a witness of this excited state absorption mechanism. Through numerical modeling, we estimate the cross section value of the process and show that it is essential to reproduce both power and fluorescence curves. This paper also emphasizes the critical role played by the pump wavelengths. [ABSTRACT FROM AUTHOR]

The performance of mid-infrared Er3+-doped fiber lasers has dramatically improved in the last few years. In this paper, we present a numerical model that provides valuable insight into the dynamics of a dual-wavelength pumped fiber laser that can operate on the 3.5- and 2.8- \mu \textm bands. This model is a much needed tool for optimizing and understanding the performance of these laser systems. Comparisons between simulation and experimental results for three different systems are presented. [ABSTRACT FROM PUBLISHER]

We report a fiber optic sensor for measuring the viscosity of Newtonian liquids. The sensing principle of the proposed sensor is based on sliding of liquid drop on an open air channel during which the liquid interacts with two decladded regions of an optical fiber. When liquid slides over the first decladded region, transmitted light intensity of the fiber undergoes an upward transition. As the liquid again slides over the second decladded region, another upward transition occurs. The time interval between the two transition events is known as transition time of the proposed sensor, and it is found to increase with increase in viscosity of the liquids when longitudinal displacement between the decladded regions and inclination of the flow channel are held constant. [ABSTRACT FROM AUTHOR]

The Water Cherenkov Detector Array (WCDA) is one of the key parts in the Large High Altitude Air Shower Observatory (LHAASO). In the WCDA, 3600 Photomultiplier Tubes (PMTs) and the Front End Electronics (FEEs) are scattered within a 90000~\m^2 area, while a time measurement resolution better than 0.5 ns is required in the readout electronics. To achieve such time measurement precision, high quality clock distribution and synchronization among the 400 FEEs (each FEE for 9 PMTs readout) is required. To simplify the electronics system architecture, data, commands, and clock are transmitted simultaneously through fibers over a 400-m distance between FEEs and the Clock and Data Transfer Modules (CDTMs). In this article, we propose a new method based on the White Rabbit (WR) to achieve completely automatic clock phase alignment between different FEEs. The original WR is enhanced to overcome the clock delay fluctuations due to ambient temperature variations. This paper presents the general scheme, the design of prototype electronics, and initial test results. These indicate that a clock synchronization precision better than 50 ps is achieved over 1 km fibers, which is well beyond the application requirement. [ABSTRACT FROM AUTHOR]

The assessment of disrupted myocardial fiber arrangement may help to understand and diagnose hypertrophic or ischemic cardiomyopathy. We hereby proposed and developed shear wave imaging (SWI), which is an echocardiography-based, noninvasive, real-time, and easy-to-use technique, to map myofiber orientation. Five in vitro porcine and three in vivo open-chest ovine hearts were studied. Known in physics, shear wave propagates faster along than across the fiber direction. SWI is a technique that can generate shear waves travelling in different directions with respect to each myocardial layer. SWI further analyzed the shear wave velocity across the entire left-ventricular (LV) myocardial thickness, ranging between 10 (diastole) and 25 mm (systole), with a resolution of 0.2 mm in the middle segment of the LV anterior wall region. The fiber angle at each myocardial layer was thus estimated by finding the maximum shear wave speed. In the in vitro porcine myocardium (n=5), the SWI-estimated fiber angles gradually changed from +80^\circ\pm 7^\circ (endocardium) to +30^\circ\pm 13^\circ (midwall) and -40^\circ\pm 10^\circ (epicardium) with 0^\circ aligning with the circumference of the heart. This transmural fiber orientation was well correlated with histology findings (r^2=0.91\pm 0.02, p<0.0001). SWI further succeeded in mapping the transmural fiber orientation in three beating ovine hearts in vivo. At midsystole, the average fiber orientation exhibited 71^\circ\pm 13^\circ (endocardium), 27^\circ\pm 8^\circ (midwall), and -26^\circ\pm 30^\circ (epicardium). We demonstrated the capability of SWI in mapping myocardial fiber orientation in vitro and in vivo. SWI may serve as a new tool for the noninvasive characterization of myocardial fiber structure. [ABSTRACT FROM PUBLISHER]

In the final objective of elaborating an optical sensor of dimensional change in a nuclear testing reactor, we present extreme high level irradiation tests, up to 1.3 1020 nfast/cm² and 16GGy, conducted on high purity silica and hollow core photonic bandgap (PBG) fibers. These tests are performed in the OSIRIS reactor at CEA Saclay. We measure continuously Radiation Induced Absorption (RIA), at 3 optical wavelengths: 980 nm, 1064 nm and 1310 nm. The evolution with the time of the spectral dependency over larger wavelength range is also reported. As well as reporting RIA up to higher dose than presented before, we demonstrate here the excellent superiority of hollow core PBG fibers over their conventional counterparts in term of radiation resistance up to over 1020 nfast /cm² and 10GGy. We also report some Optical Time Domain Reflectometry (OTDR) measurements that probe the irradiated parts of the fibers and show a back scattering peak which appears, widens spatially then duplicates. We provide an interpretation based on the change of silica when it turns to metamict phase. [ABSTRACT FROM AUTHOR]

Exposing optical silica fibers to radiative environments leads to an increase of fiber attenuation. This gamma-sensitivity of the fibers is strongly wavelength dependent. Many papers already mentioned the strong Radiation-Induced Attenuation (RIA) in the UV and Visible ranges, which is explained by radiation-induced defects absorbing in these spectral ranges. However, the origin of RIA at longer wavelengths (λ > 1000 nm) is less clear. An exception is phosphorous-doped fibers for which P1 defects absorbing around 1700 nm have already been highlighted. For fibers with no phosphorus, the RIA at Near-InfraRed (NIR) wavelengths is usually assumed to be small as it results from the UV-visible absorption tail, which decreases with increasing wavelength. In this paper, we study three prototype silica based optical fibers and show that the RIA does not monotically decrease with increasing wavelength, highlighting RIA-contributions having their origins at NIR-wavelengths. We show that these NIR-absorbing defects are generally the main contributor to RIA at telecommunication wavelengths (1310 nm and 1550 nm), the impact of UV-visible absorption tail being secondary only. The nature of defects involved in these NIR absorptions depends on fiber composition. For fibers with no phosphorous, we propose Self Trapped Hole defects (STH) as origin. [ABSTRACT FROM AUTHOR]

We evaluated the performances of the hydrogen-loading technique to reduce the radiation-induced absorption in optical fibers in the visible part of the spectrum. A reduction factor as large as one order of magnitude can be obtained in high dose-rate regime. Based on a spectral deconvolution method, we showed that hydrogen preferentially interacts with NBOHC defects while the number of POR defects is not affected. [ABSTRACT FROM AUTHOR]