Showing papers on "Bend radius published in 2007"

Fiber optic cables that kink with small bend radii

Abstract: Fiber optic cables are disclosed that allow a relatively small bend radius and/or may kink while still preserving optical performance. In one embodiment, the fiber optic cable includes at least one optical fiber, a first strength member, a second strength member, a core material, and a cable jacket. The core material generally surrounds the optical fiber, the first strength member, and the second strength member and the core material is deformable for cushioning the optical fiber. The cable jacket generally surrounds the core material and allows a bending radius of about 10 millimeters or less while maintaining a suitable level of optical performance.

Modeling and measurement of losses in silicon-on-insulator resonators and bends.

Abstract: We present an analytical model to quantify losses in resonators and bends without uncertain contributions from fiber coupling in/out or waveguide cleavage facets. With resonators in add-drop configuration, intrinsic losses are calculated from the free spectral range, through-port extinction and drop-port bandwidth. We fabricated and characterized silicon-on-insulator resonator for loss analysis. At 1.55 µm, racetrack resonators with a bending radius of 4.5 µm show intrinsic losses as small as 0.14±0.014 dB/round-trip. Meanwhile, intrinsic losses increase up to 1.23 dB/round-trip in the racetrack resonator that has a bending radius of 2.25 µm. Losses in a 180o bend are estimated as a half of the intrinsic losses in these racetrack resonators, i.e., 0.07±0.007 dB/turn for a bending radius of 4.5 µm and 0.62 dB/turn for a bending radius of 2.25 µm. Loss in a 90° bend with a radius of 4.5 µm is determined to be 0.06±0.006 dB/turn at 1.55 µm. The losses in 180° or 90° bends are found to be mainly due to the transition loss between waveguide bends and straight waveguides.

Mode scalability in bent optical fibers

Abstract: This paper introduces a simple, analytical method for generalizing the behavior of bent, weakly-guided fibers and waveguides. It begins with a comprehensive study of the modes of the bent step-index fiber, which is later extended to encompass a wide range of more complicated waveguide geometries. The analysis is based on the introduction of a scaling parameter, analogous to the V-number for straight step-index fibers, for the bend radius. When this parameter remains constant, waveguides of different bend radii, numerical apertures and wavelengths will all propagate identical mode field distributions, except scaled in size. This allows the behavior of individual waveguides to be broadly extended, and is especially useful for generalizing the results of numerical simulations. The technique is applied to the bent step-index fiber in this paper to arrive at simple analytical formulae for the propagation constant and mode area, which are valid well beyond the transition to whispering-gallery modes. Animations illustrating mode deformation with respect to bending and curves describing polarization decoupling are also presented, which encompass the entire family of weakly-guided, step-index fibers.

Transition, radiation and propagation loss in polymer multimode waveguide bends.

Abstract: Design curves for insertion loss of multimode polymer waveguide 90 bends are reported as a function of bend radius for several waveguide widths. For the first time, to our knowledge, in multimode rectangular waveguides the insertion loss is resolved into its components of transition, radiation and propagation loss, in order of decreasing strength, separating them from input and output coupling loss by calibration and comparison of experimentally measured and beam propagation method ( BPM) modeled curves. We used the method of nested bends for the first time in multimode polymer waveguides to calculate the propagation loss on a small substrate without using destructive cut-back. The lowest loss of 0.74 dB occurred for a 50 mu m square cross section, Delta n=0.0296, 13.5 mm radius waveguide bend. (c) 2007 Optical Society of America.

InP photonic wire waveguide using InAlAs oxide cladding layer

Abstract: We proposed a novel InP based photonic wire waveguide with an InAlAs oxide cladding. The InGaAsP/InAlAs-oxide structure in the vertical direction provides an ultrahigh index contrast waveguide, and it allows a bend radius of a few μm with no vertical leakage loss. The InP photonic wire waveguide with a 500×300-nm rectangular channel core (refractive index n ~ 3.36) and an InAlAs oxide cladding (n ~ 2.4) was numerically analyzed using the three-dimensional time-domain beam propagation method (3D TD-BPM). We predicted that the U-bend waveguide with a 3-μm bend radius can be realized with the propagation loss of < 0.5 dB.

Telecommunications housing with optical fiber management

Abstract: A telecommunications housing includes a plurality of outer walls defining a housing interior volume and an exit. A plurality of adapters is disposed on an interior panel for connection to connectors of fiber optic cables. At least one radius guide is mounted in the interior volume and has a cable guide portion configured to receive portions of the fiber optic cables and guide the fiber optic cables toward the exit without violating a predetermined minimum fiber optic bend radius. An external guide member may also be located on the outside the housing adjacent the exit. The external guide member has a cable guide portion configured to receive portions of the fiber optic cables and guide the fiber optic cables away from the exit without violating a predetermined minimum fiber optic bend radius.

Fundamental-mode operation in polarization-maintaining ytterbium-doped fiber with an effective area of 1400 micro m2.

Abstract: We report, for the first time to our knowledge, fundamental-mode operation in polarization-maintaining ytterbium-doped fiber with an effective area of ∼1400 μm2 and birefringence of 2.1×10−4. The measured critical bending radius, Rc, defined as the radius at which the loss is equal to 3 dB for 1 m of fiber, is ∼4 cm. Lasing with slope efficiency exceeding 60% and M2 of 1.2 has also been demonstrated.

Periodic dielectric waveguide beam splitter based on co-directional coupling

Abstract: A compact beam splitter consisting of three branches of periodic dielectric waveguides (PDW) is designed and analyzed theoretically. Both the symmetrical and asymmetrical configurations of the beam splitter are studied. The band structure for the guided modes is calculated by using finite-difference time-domain (FDTD) method with Bloch-type boundary conditions applying in an appropriate supercell. The field patterns for the whole structure and the transmissions for the output ports are calculated using the multiple scattering method. By utilizing the co-directional coupling mechanism, the light injected into the input branch can be efficiently transferred into the two output branches if the phase matching conditions are satisfied. The coupling length is short and the broad-band requirement can be achieved. Bending loss is small and high transmission (above 95%) can be preserved for arbitrarily bent PDW if the bend radius of each bend exceeds five wavelengths. This feature indicates that the periodic dielectric waveguide beam splitter (PDWBS) is a high efficiency device for power redistribution while avoiding the lattice orientation restriction of the photonic crystal waveguides (PCW).

Numerical analysis of silicon-on-insulator ridge nanowires by using a full-vectorial finite-difference method mode solver

Abstract: The characteristics of silicon-on-insulator (SOI) ridge waveguides are analyzed by using a cylindrical full-vectorial finite-difference method mode solver with a perfectly-matched layer treatment. First, the single-mode condition for an SOI ridge nanowire with different Si core thicknesses is obtained. The obtained single-mode condition is different from that for the conventional micrometrical SOI ridge waveguides with a large cross section. By adjusting the cross section (the core width and the etching depth), one can have a nonbirefringent SOI ridge nanowire. The analysis on the bending loss of SOI ridge nanowires shows that one can have a relatively small bending radius even with a shallow etching (i.e., a small ratio γ between the etching depth and the total thickness). For example, even when one chooses a small ratio γ=0.4, one still has a low bending loss with a small bending radius of 15 μm for an SOI nanowire with a thin core hco=250 nm, which is very different from a conventional large SOI ridge waveguide.

Low loss, high contrast optical waveguides based on CMOS compatible LPCVD processing

Abstract: A new class of integrated optical waveguide structures is presented, based on low cost CMOS compatible LPCVD processing. This technology allows for medium and high index contrast waveguides with very low channel attenuation. The geometry is basically formed by a rectangular cross-section silicon nitride $(Si_{3}N_{4})$ filled with and encapsulated by silicon dioxide $(SiO_{2})$. The birefringence and minimal bend radius of the waveguide is completely controlled by the geometry of the waveguide layer structures. Experiments on typical geometries will be presented, showing excellent characteristics (channel attenuation ≤0.06 dB/cm, IL ≤0.6 dB, PDL ≤0.2 dB, Bg «1 x $10^{-3}$, bend radius ≤500 μm).

Macrobending fibre loss filter, ratiometric wavelength measurement and application

Abstract: A macrobending standard single-mode fibre (SMF28) is optimized as an edge filter, with the optimal bending radius and length determined according to the bend loss and polarization sensitivity of the bending fibre. An all-fibre ratiometric wavelength system is built and calibrated. The system's accuracy and resolution is discussed with the influence of noise of input signal and photodetectors. Finally, the ratiometric system is employed for the demodulation of FBG strain sensing.

Single-Facet Folded-Cavity Diode Laser With Ultrasmall Bend Radius High-Index-Contrast Oxidized AlGaAs Ridge Waveguide

Abstract: AlGaAs heterostructure high-index-contrast (HIC) ridge waveguide (RWG) diode lasers incorporating a folded-cavity single-facet resonator with a folding bend radius as small as r=10 mum are demonstrated. Fabricated by a self-aligned deep dry etch (through the active region) plus nonselective O2-enhanced wet thermal oxidization process, the low-index, insulating, and interface-passivating wet thermal oxide grown directly on the etch-exposed AlGaAs waveguide sidewalls yields a high lateral refractive index contrast of Deltan~1.7 and provides strong optical mode confinement. The HIC RWG device geometry also completely eliminates lateral current spreading, which results in an excellent overlap between the optical field and the gain region of the single InAlGaAs quantum-well graded-index separate confinement heterostructure. A threshold current of Ith=65mA is obtained for the r=10 mum device (a half-racetrack ring resonator), giving a threshold current density of Jth=1503 A/cm2, 3.34 times higher than that of same-length straight lasers. At a bend radius of r=150 mum, Ith=16.6 mA, and Jth is comparable to straight cavity values, indicating that at this curvature there is negligible bending and scattering loss for the lowest-order waveguide mode

Warm Hemming of Magnesium Sheet

Abstract: Magnesium sheet has received increasing interest for automotive body and closure applications. However, implementation of these applications faces many challenges involving room temperature formability. Hemming a closure panel with a magnesium outer panel will be difficult because of the sharp bend radius. Bending behavior of AZ31B-O at elevated temperatures was investigated to approximate the hemming of closure panels with acceptable surface appearance. Surface quality from small-radius bending was quantified as a function of temperature between 180 and 300 °C. Flanging with a 1.5 mm die radius yielded an acceptable surface quality at 210 °C and higher. Hemming required a minimum temperature of 270 °C for an acceptable surface condition with a 2 mm outer radius. The complex pattern of grain size and morphology of the deformed microstructure was documented with respect to the elevated temperature deformation behavior of Mg alloys. These results suggest that Mg can be hemmed at elevated temperatures with a small radius (∼1½ times the sheet thickness) and therefore could be used for vehicle closures.

Volume reflection of high-energy protons in short bent crystals

Abstract: Characteristics of volume reflection for high-energy protons in short bent crystals are considered by simulation. The deflection efficiency and angle depend on the bend radius of the crystal. The concurrent process of volume capture of particles into channeling states limits the reflection efficiency. The optimal parameters of a crystal for using it as a beam reflector were determined. It was shown that the deflection efficiency of high-energy proton beams by the sequence of reflections in short bent crystals is high for small deflection angles. This allows considering possible applications of crystal reflectors for the beam collimation of hadrons colliders and for high-energy physics experiments.

Flexible plastic optical fiber cable

Abstract: A plastic optical fiber cable that is strong in repeated flexure, ensuring low light loss at bending with a bend radius of 2 mm. The plastic optical fiber cable is one composed of a multicore plastic optical fiber strand including 7 to 10,000 cores of transparent resin, island portions each consisting of at least one core-surrounding sheath layer of transparent resin with a refractive index lower than that of the transparent resin constituting the cores and sea portion of resin surrounding the island portions and, enclosing the multicore plastic optical fiber strand, a coating layer, characterized in that the resin constituting at least either the sheath layer or sea layer is one of 25 to 55 Shore D hardness while the resin constituting the coating layer consists of a thermoplastic resin of 500 to 2000 MP flexural modulus.

Right-angle optical fiber connector assembly

Abstract: A right-angle optical-fiber connector assembly for providing an optical connection to an external device such as a circuit board. The connector assembly includes a rigid ferrule having at least one right-angle bend and that defines an interior region and first and second ferrule ends, and a maximum optical fiber bending radius RMAX. One or more bend-performance optical fibers traverse the interior region. Each optical fiber has an associated minimum bending radius RMIN and includes a bending radius RF such that RMIN≦RF≦RMAX, wherein at least one of the one or more optical fibers has RF=RMIN. The first and second connector ends are respectively located at or near the first and second ferrule ends and operably support the first and second optical fiber ends. The connector ends are each adapted to provide an external optical interconnection to an external device such as a circuit board.

Effect of die corner radius on the formability and dimensional accuracy of tube shear bending.

Abstract: Tube shear bending is a beneficial technique to realize considerable small bending radii. The authors have investigated the tube shear bending process of circular tubes experimentally. Moreover, an elastoplastic 3D finite element simulation has been conducted, aimed at clarifying the forming mechanism. Both the experiment and simulation results indicate that, in order to perform successful forming, the value of the applied pushing force on the tube must be appropriate. In this paper, the mechanism of defect generation was clarified. Two failure criteria were introduced and employed to recognize the occurrence of defects in the simulation. The effects of the die corner radius, as the main parameter, on the defect generation of circular A1050 aluminum tubes were investigated both by experiments and numerical simulation. From the results, the formability of tube on dies with different corner radii applying various pushing pressures was clarified. Moreover, the influence of the die radius on the dimensional accuracy of the deformed tube regarding cross-section ovality and thickness changes of the deformed tube was evaluated. The results of this study indicate that, whilst a small bending radius results in high cross-section ovality, increasing the die corner radius raises the wrinkling tendency of the tube. However, the die radius has a small effect on the suitable values of pushing pressure required for a successful shear bending deformation. Moreover, the effect of the die corner radius on the thickness strain of the deformed tube is insignificant.

Flexible-paper-base friction material

Abstract: The invention discloses a soft paper based friction material that contains 3-7wt% flexibility reinforcement fiber, 5-20wt% carbon fiber, 4-25wt% other fiber, 2-20wt% flexibility adhesive, 20-44wt% friability adhesive, 10-25wt% frictional properties regulator, and 15-30wt% filling material. The invention has good flexibility, and improved frictional wear ability of the paper base friction material. The minimum bending radius of curvature is 6.0-6.8cm, and good mechanical strength and thermal endurance.

Reduction of bend loss in large-mode-area Bragg fibres

Abstract: The delivery or generation of high power in optical fibre requires the increase of the core size to increase the threshold of nonlinear effects and the damage threshold. However the bend loss strongly limits the increase of the effective area (A eff ). All-solid photonic bandgap fibres are attractive for the delivery of power since they can be made singlemode whatever the core diameter is. Moreover the silica core can be doped with rare-earth ions. A Bragg fibre is a bandgap fibre composed of a low index core surrounded by N concentric layers of high and low index. We have fabricated Large Mode Area Bragg fibres by the MCVD process. These Bragg fibres present a ratio A eff /λ 2 close to 500. A first Bragg fibre, defined by N = 3 and an index contrast between the cladding layers Δn = 0.01, exhibits a measured critical bend radius R c close to 16 cm (bend loss equal to 3 dB/m). Increasing the index contrast Δn leads to a tighter field confinement. The field distribution of the guided mode strongly decays in the periodic cladding and is thus less sensitive to bending. We propose here the design of an improved Bragg fibre with a very large index contrast Δn = 0.035 which leads to a dramatic reduction of the bend loss. The critical bend radius was measured to be lower than 3 cm. This fibre is less bend sensitive than an equivalent solid core fibre, either a step-index fibre or a photonic crystal fibre.

Modeling Flexforming (Fluid Cell Forming) Process with Finite Element Method

Abstract: In this paper, the flexforming process is modeled by finite element method in order to investigate the operation window of the problem. Various models are established using explicit approach for the forming operation and implicit approach for the unloading one. In all analyses the rubber diaphragm has been modeled revealing that the modeling of this diaphragm is essential. Using the material Aluminum 2024 T3 alclad sheet alloy, three basic experiments are conducted: Bending of a straight flange specimen, bending of a contoured flange specimen and bulging of a circular specimen. By these experiments the effects of blank thickness, die bend radius, flange length and orientation of the rolling direction of the part have been investigated. Experimental results are compared with finite element results to verify the computational models.

A Study on the Bending Process for Precision Pipe Forming

Abstract: The arbitrarily-bended pipe is widely used in a heat exchanger system. Thus, the pipe bending process has important role in performance and productivity of heat exchanger system. The purpose of this study is to investigate the bending process for manufacturing of sound pipe. And, the spring-back effect and the variation of pipe thickness should be controlled effectively. The change of spring-back ratio and the thickness variation of pipe according to the change of bending radius, bending angle and pipe thickness are analyzed by FEM analysis. The analytic results are compared with the experimental data, accordingly the results show good agreement. The method of the analysis can be applied for manufacturing of precision bended pipe.

Experimental assessment of cold-bent glass panels

Abstract: Curved glass is traditionally formed in a prefabricated mould at elevated temperatures. More recently, also cold-bending processes have been developed, in which flat glass panes can be bent at the building site. The main advantages of cold-bending processes are the reduced material costs, the ease of transportation and the production speed. “Freeform glass” is a patented coldbending system in which laminated panes are first bent on a cylindrical frame and then fixated in their curved form with a clamping system. For a given glass configuration, it was considered to apply this system for a canopy with a bending radius of only 3 meters. By means of an experimental testing program, different combinations of PVB have been investigated in order to evaluate the possibilities of each composition with respect to at the one hand the required bending energy and at the other hand the ability to carry loads according to the Dutch building codes for roofs. It was possible to bend panes to the desired curvature. According to experimental results, however, design loads were very difficult to meet. Furthermore, the experiments showed that the load-carrying capacity was highly dependent on the specific PVB interlayer (stiffness and thickness) that was used.

Apparatus and method of press-bending tubular material

Abstract: PROBLEM TO BE SOLVED: To provide a new apparatus and method of bending a tubular material by which the compatibility of three properties of the bending work of a large bend radius without requiring large-scale equipment and die, a bending work by which wrinkles and buckling can not be generated inside the bending and a bending work having high productivity is made possible SOLUTION: This apparatus is a press-bending apparatus for performing the three-point bending of the tubular material with a punch 12 and a set of rolls 13, 13, the punch 12 has a groove 12a having width larger than the width of a round tube 11 and the set of the rolls 13, 13 are supported with stands 14 The rolls 13, 13 are freely movable on the stands 14 in the direction away from each other in the state where they are brought into contact with the punch 12 The stands 14 have a void 14a for making the punch 12 which is lowered during the bending work of the round tube 11 and the round tube 11 which is bent with the lowering freely movable COPYRIGHT: (C)2008,JPO&INPIT

Fiber Optic Enclosure Internal Cable Management

Abstract: A fiber access terminal assembly includes a front housing piece with an exterior side and an interior side having a slack storage area and a rear housing piece mounted to the interior side of the front housing piece. A bend radius limiter having a retention portion with a first end and an oppositely disposed second end, a radius limiting portion disposed at the first end, and a side portion disposed at the second end is mounted in the slack storage area. The retention portion, the radius limiting portion, and the side portion cooperatively define a passageway for optical fiber routing. A method of routing cable in the fiber access terminal includes providing a fiber access terminal assembly, inserting cable through a cable entry in the housing, routing optical fibers of the cable loosely through the passageway, and connecting ends of the optical fiber to fiber optic adapters.

Fabrication Tolerance Analysis of Bent Single-Mode Rib Waveguides on SOI

Abstract: The influence of fabrication tolerances on the minimum bending radius of both rectangular and trapezoidal single-mode rib waveguides on silicon on insulator (SOI) is analyzed. In order to reduce the number of simulations, we present a semi-analytical procedure which yields an estimation of the bending radius, and facilitates the interpolation of the obtained data. We conclude that the tolerances of today’s fabrication processes hinders the miniaturization of integrated circuits if single-mode behavior is required. Besides, the sidewall angle tapering in 90° turns of wet etched waveguides is analyzed in a worst case approach.