Potential niches for a power-over-fiber (PoF) technique can be found in hazardous areas that require controlling unauthorized access to risk areas and integration of multiple sensors, in scenarios ...avoiding electromagnetic interference, and the presence of ignition factors. This paper develops a PoF system that provides galvanic isolation between two ends of a fiber for remotely powering a proximity sensor as a proof of concept of the proposed technology. We analyze scalability issues for remotely powering multiple sensors in a specific application for the hazardous environment. The maximum number of remote sensors that can be optically powered and the limiting factors are also studied; considering different types of multimode optical fibers, span lengths, and wavelengths. We finally address the fiber mode field diameter effect as a factor that limits the maximum power to be injected into the fiber. This analysis shows the advantages of using step-index versus graded-index fibers.
Highly aligned intermingled fibre composites are produced from reclaimed and virgin carbon fibres using the High Performance Discontinuous Fibre (HiPerDiF) method. The stiffness and strength ...characteristics of these materials are studied as a function of the reclaimed to virgin fibres ratio. Interlaminated hybrid composites with discontinuous carbon fibre preforms sandwiched between continuous glass fibres are designed to demonstrate pseudo-ductility and allow investigation of the effect of the mixing ratio of reclaimed and virgin carbon fibres on the nonlinear stress-strain curve shape. The pseudo-ductile behaviour is explained by adapting the Damage Mode Map to describe the failure process of interlaminated hybrid specimens with different low elongation material strength. It is concluded that the HiPerDiF method is a valuable platform to remanufacture reclaimed carbon fibres into a high performance and potentially economical value recycled composite material. The Damage Mode Maps can be used to optimise the pseudo-ductile response of the interlaminated hybrid material.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Dual-wavelength mode-locked fiber lasers are considered as ideal solutions for fast, precise, and sensitive dual-comb spectroscopy. In this study, we present a self-started dual-wavelength fiber ...laser by combining a nonlinear amplifying loop mirror and a Lyot filter. Nonlinear phase accumulation, dual-wavelength competition, and crosstalk between the mode-locking mechanism and filtering effect are well addressed to realize the self-started dual-wavelength mode-locking. Furthermore, by temperature controlling the specific polarization-maintaining fiber, our dual-wavelength laser can be continuously tuned in a wavelength range of ∼6 nm, corresponding to a well-controlled repetition rates change of 80 Hz and their difference change of 30 Hz. Mutual coherence of the dual-wavelength pulses is demonstrated by detecting the multi-heterodyne beat notes and measuring the fluctuation of the repetition rate difference. Within 10 hours of measurement, the dual-wavelength repetition rates difference remains stable at 1180 Hz with an Allan deviation of ∼9 × 10 −3 Hz @ 1s. By virtue of the all polarization-maintaining structure, our dual-wavelength laser shows improved long-term stability and repeatability, which will facilitate the turn-key, robust, and reproducible dual-comb spectroscopy for high-power or field applications.
Stimulated Brillouin scattering and the longitudinal strain performance based on Brillouin Optical Time Domain Analysis (BOTDA) in a 50 cm long nonuniform As<inline-formula><tex-math ...notation="LaTeX">_{2}</tex-math></inline-formula>Se<inline-formula><tex-math notation="LaTeX">_{3}</tex-math></inline-formula>-PMMA tapered fiber is theoretically and experimentally investigated. In the BOTDA measurement a 20 ns pump pulse is used, of which the pulse-width equivalent length is longer than the fiber under test (FUT) of 50 cm nonuniform As<inline-formula><tex-math notation="LaTeX">_{2}</tex-math></inline-formula>Se<inline-formula><tex-math notation="LaTeX">_{3}</tex-math></inline-formula>-PMMA tapered fiber. The evolution of Brillouin gain spectrum (BGS) corresponding to different fiber sections is analyzed showing the strain performance of the shift of the BGS frequency and the change of BGS linewidth under the imposed longitudinal strain. A strain-insensitive BGS linewidth is achieved by selecting the fiber gain section under the combined effects of the longitudinal acoustic velocity <inline-formula><tex-math notation="LaTeX">V_{A}</tex-math></inline-formula>, strain dependence of refractive index <inline-formula><tex-math notation="LaTeX">n</tex-math></inline-formula>, the effective fiber length <inline-formula><tex-math notation="LaTeX">L_{eff}</tex-math></inline-formula> and also the pump intensity <inline-formula><tex-math notation="LaTeX">I</tex-math></inline-formula> along the nonuniform As<inline-formula><tex-math notation="LaTeX">_{2}</tex-math></inline-formula>Se<inline-formula><tex-math notation="LaTeX">_{3}</tex-math></inline-formula>-PMMA tapered fiber. The proposed method has the potential for many novel applications such as strain-insensitive sensing device, multiple-parameter sensors and the distributed sensing measurement along the nonuniform As<inline-formula><tex-math notation="LaTeX">_{2}</tex-math></inline-formula>Se<inline-formula><tex-math notation="LaTeX">_{3}</tex-math></inline-formula>-PMMA tapered fibers.
A liquid-crystal-filled photonic crystal fiber (PCF) is proposed for electro-optical modulation. The E7 liquid crystal is precisely filled in one of the innermost air holes of the PCF and forms an ...in-fiber optical coupler, and the resonance wavelength can be tuned with a sensitivity of 5.594 nm/Vrms when an external voltage is applied. The device can operate as an electro-optical switch/modulator and exhibits response and recovery times of approximately 47 and 24 ms, respectively from 1414 nm to more than 1700 nm. The proposed structure is expected to have potential applications in electric field sensing and wavelength-tunable electro-optical devices.
AbstractA theoretical method, termed the mesoscale fiber-matrix discrete model (MFDM), has been developed that can be used for estimating the shear contribution of steel fibers and calculating shear ...strength of ultrahigh-performance fiber-reinforced concrete (UHPFRC) beams. In the proposed model, an effective fiber distributed region (EDR) along the critical diagonal shear crack, where fibers are efficient at providing shear resistance, is defined. The total quantity of fibers within EDR is calculated by the EDR volume proportion of the beam based on a uniform distribution of steel fibers. Two concepts to determine the width of EDR are proposed: (1) probability theory and (2) the basis of the pullout load slip relationship. The bond strength between a single fiber and the matrix is determined by the probability method based on a uniform distribution of fibers. Combining the number of efficient fibers and the bond strength of a single fiber, the shear contribution of fibers is derived. The shear contribution of concrete is obtained using Rankine’s failure criteria and strain and stress distribution of compression zone while the shear contribution of stirrups is determined by the truss model. To evaluate the accuracy and reliability of the proposed model, an experimental program on ten simply supported UHPFRC beams was executed. Through comparison with test results, the proposed model shows good agreement with testing results.
Département d'Education Physique et de Réadaptation, Faculté de Médecine, Université Catholique de Louvain, Louvain-la-Neuve, Belgium
Submitted 23 August 2005
; accepted in final form 24 November ...2005
Functional performance of lower limb muscles and contractile properties of chemically skinned single muscle fibers were evaluated before and after 8 wk of maximal effort stretch-shortening cycle (SSC) exercise training. Muscle biopsies were obtained from the vastus lateralis of eight men before and after the training period. Fibers were evaluated regarding their mechanical properties and subsequently classified according to their myosin heavy chain content (SDS-PAGE). After training, maximal leg extensor muscle force and vertical jump performance were improved 12% ( P < 0.01) and 13% ( P < 0.001), respectively. Single-fiber cross-sectional area increased 23% in type I ( P < 0.01), 22% in type IIa ( P < 0.001), and 30% in type IIa/IIx fibers ( P < 0.001). Peak force increased 19% in type I ( P < 0.01), 15% in type IIa ( P < 0.001), and 16% in type IIa/IIx fibers ( P < 0.001). When peak force was normalized with cross-sectional area, no changes were found for any fiber type. Maximal shortening velocity was increased 18, 29, and 22% in type I, IIa, and hybrid IIa/IIx fibers, respectively ( P < 0.001). Peak power was enhanced in all fiber types, and normalized peak power improved 9% in type IIa fibers ( P < 0.05). Fiber tension on passive stretch increased in IIa/IIx fibers only ( P < 0.05). In conclusion, short-term SSC exercise training enhanced single-fiber contraction performance via force and contraction velocity in type I, IIa, and IIa/IIx fibers. These results suggest that SSC exercises are an effective training approach to improve fiber force, contraction velocity, and therefore power.
skinned fibers; fiber hypertrophy; plyometry; passive stretch
Address for reprint requests and other correspondence: D. Theisen, 1 Place P. de Coubertin, B-1348 Louvain-La-Neuve, Belgium (e-mail: daniel.theisen{at}edph.ucl.ac.be )
We investigate taper tapping in three types of single-mode fibers using simulations and experiments: Standard single-mode fiber (SMF), bend-resistant single-mode fiber (BR-SMF) with a shallow index ...trench, and bend-insensitive single-mode fiber (BI-SMF) with a deep index trench. Both trench-assisted fibers demonstrate a larger mode field expansion than the standard single-mode fiber, making them more susceptible to taper-tapping than standard single-mode fibers. Tapering both SSMF and BR-SMF fibers to as little as 25μm diameter results in a high information extraction efficiency for an eavesdropper (≥−20 dB) while maintaining low loss for the legitimate channel (≤1 dB), underlining the vulnerability of all fiber types to taper tapping. We also use optical time-domain reflectometry (OTDR) to identify changes in the fiber before and after tapering. Changes in the back reflected power of ≤0.5 dB and ≤0.25 dB are observed in 25μm tapers in SMF and BR-SMF respectively.
Space division multiplexing (SDM) is mainly seen as a means to increase data throughput and handle exponential traffic growth in future optical networks. But its role is certainly more diverse. ...Research on SDM encourages device integration, brings newfunctionality to network elements, and helps optical networks to evolve. As a result, the number of individual components in future networks will decrease, which in turn will improve overall network reliability and reduce power consumption as well as operational expenditure. After reviewing the state-of-the-art in SDMfiber research and development with a particular focus on weakly coupled single-mode multi-core fibers, we take a look beyond the capabilities of SDM as a means of boosting transmission capacity and discuss ideas and concepts on howto exploit the spatial dimension for improved efficiency and resource sharing in optical networks.
We propose and demonstrate 1, 1.5, and 2 μm passively Q-switched fiber lasers by exploiting a few-layer Molybdenum sulfide (MoS 2 ) polymer composite as broadband saturable absorber (SA), ...respectively. The few-layer MoS 2 nanosheets are prepared by the liquid-phase exfoliation method, and are composited with polyvinyl alcohol (PVA). The PVA-MoS 2 film is sandwiched between two fiber ferrules to form the fiber-compatible SA. The few-layer MoS 2 not only shows good transparency from ultraviolet to mid-infrared spectral region, but also possesses the nonlinear saturable absorption. The modulation depth and saturation optical intensity of the PVA-MoS 2 film are measured to be 1.6% and 13 MW/cm 2 at 1566 nm by the balanced twin-detector technique, respectively. By further inserting the filmy PVA-MoS 2 SA into the cavities of Yb-, Er- and Tm-doped fiber lasers, we achieve stable Q-switching operations at 1.06, 1.56, and 2.03 μm, respectively. The output characteristics of the Q-switched pulses at the three wavelengths have been investigated, respectively. The MoS 2 -based Q-switching enables the large pulse energy of ~1 μJ with a pulse width of 1.76 μs. This is, to the best of our knowledge, the first demonstration of MoS 2 -based Q-switched fiber lasers in a wide wavelength range (from 1 to 2 μm). Our results experimentally confirm that the new-type 2-D material, few-layer MoS 2 , is a promising broadband SA to Q-switch fiber lasers covering all major wavelengths from near- to mid-infrared region.
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