Showing papers on "Hard-clad silica optical fiber published in 2008"

Subwavelength-diameter silica wires for low-loss optical waveguiding

Abstract: The present invention provides nanometer-sized diameter silica fibers that exhibit high diameter uniformity and surface smoothness. The silica fibers can have diameters in a range of a about 20 nm to about 1000 nm. An exemplary method according to one embodiment of the invention for generating such fibers utilizes a two-step process in which in an initial step a micrometer sized diameter silica preform fiber is generated, and in a second step, the silica preform is drawn while coupled to a support element to form a nanometer sized diameter silica fiber. The portion of the support element to which the preform is coupled is maintained at a temperature suitable for drawing the nansized fiber, and is preferably controlled to exhibit a temporally stable temperature profile.

High temperature fiber sensor with high sensitivity based on core diameter mismatch

Abstract: We report a simple fiber sensor for measurement of high temperature with high sensitivity. The sensing head is a multimode-single mode-multimode (MM-SM-MM) fiber configuration formed by splicing a section of uncoated single mode fiber (SMF) with two short sections of multimode fibers (MMF) whose core is composed of pure silica. Because of the mode-field mismatch at the splicing points of the SMF with 2 sections of MMFs, as well as index matching between the core of the MMF and the cladding of the SMF, optical power from the lead-in fiber can be partly coupled to the cladding modes of the SMF through the MMF. The cladding modes of the SMF then re-coupled to the lead-out fiber, in the same fashion. Due to the effective index difference between the core and cladding modes, an interference pattern in the transmission spectrum of the proposed device was obtained. The interference pattern was found to shift to the longer wavelength region with respect to temperature variation. The temperature sensor can measure temperature stably up to more than 900 °C with sensitivity of 0.088 nm/°C.

Bend resistant multimode optical fiber

Abstract: Bend resistant multimode optical fibers are disclosed herein. Multimode optical fibers disclosed herein comprise a core region and a cladding region surrounding and directly adjacent to the core region, the cladding region comprising a depressed-index annular portion comprising a depressed relative refractive index.

Silicon optical fiber.

Abstract: Described herein are initial experimental details and properties of a silicon core, silica glass-clad optical fiber fabricated using conventional optical fiber draw methods. Such semiconductor core fibers have potential to greatly influence the fields of nonlinear fiber optics, infrared and THz power delivery. More specifically, x-ray diffraction and Raman spectroscopy showed the core to be highly crystalline silicon. The measured propagation losses were 4.3 dB/m at 2.936 µm, which likely are caused by either microcracks in the core arising from the large thermal expansion mismatch with the cladding or to SiO2 precipitates formed from oxygen dissolved in the silicon melt. Suggestions for enhancing the performance of these semiconductor core fibers are provided. Here we show that lengths of an optical fiber containing a highly crystalline semiconducting core can be produced using scalable fiber fabrication techniques.

Fiber optic position and/or shape sensing based on rayleigh scatter

Abstract: A fiber optic position and/or shape sensing device includes an optical fiber with either two or more single core optical fibers or a multi-core optical fiber having two or more fiber cores. In either case, the fiber cores are spaced apart so that mode coupling between the fiber cores is reduced, and preferably, minimized. The optical fiber is physically associated with an object. Strain on at least a portion of the optical fiber where it is associated with the object is determined by an OFDR using one or more Rayleigh scatter patterns for that portion of the optical fiber. The determined strain is used to determine a position and/or a shape of the object.

Active optical fiber and method for fabricating an active optical fiber

Abstract: A section ofactive optical fiber (11) which comprises an active core (1),an inner cladding layer (2) andan outer cladding layer (3).The diameter of said core (1) and the thickness of said inner cladding (2) change gradually along the length of said section of active optical fiber (11). This formsa tapered longitudinal profile enabling a continuous mode conversion process alongthe length of the section of fiber (11). The method for fabricating a section of tapered active optical fibercomprises the steps of fabricating a preform for drawing active optical fiber from said preform,installing said preform into a drawing tower, drawing optical fiber in said drawing tower and altering at least one of the two parameters including the take-off preform speed and the take-up fiber speed during drawing of the optical fiber.

Multi-cladding fiber

Abstract: Multi-cladding optical fibers to be used in the context of fiber amplifiers and fiber lasers are described herein. Embodiments of optical fibers include a rare-earth doped core into which the signal field is to be amplified. The doped core is surrounded by multiple claddings that guide the pump field to be absorbed by the reactive core material. The first cladding has a depressed refractive index to improve high-order mode bending losses without incurring significant fundamental mode bending losses.

Microstructured optical fibers and methods

Abstract: Method of making a microstructured optical fiber. Silica glass based soot is deposited on a substrate to form at least a portion of an optical fiber preform by traversing a soot deposition burner with respect to said substrate at a burner traverse rate greater than 3 cm/sec, thereby depositing a layer of soot having a thickness less than 20 microns for each of a plurality of burner passes. At least a portion of the soot preform is then consolidated inside a furnace to remove greater than 50 percent of the air trapped in said soot preform, said consolidating taking place in a gaseous atmosphere containing krypton, nitrogen, or mixtures thereof under conditions which are effective to trap a portion of said gaseous atmosphere in said preform during said consolidation step, thereby forming a consolidated preform which when viewed in cross section will exhibit at least 50 voids therein.

Photodarkening rate in Yb-doped silica fibers.

Abstract: Yb-doped fibers are widely used in laser applications requiring high average output powers and high-peak-power pulse amplification. Photodarkening (PD) is recognized as one limiting factor in these fibers when pumped with high-intensity radiation. We describe an approach for performing quantitative PD studies of fibers, and we present measurements of the rate of PD in Yb-doped single-mode fibers with varying inversion levels. The method is applicable to large-mode-area fibers. We observed a seventh-order dependence of the PD rate on the excited-state Yb concentration for two different fibers; this result implies that PD of a Yb-doped fiber source fabricated using a particular fiber will be strongly dependent on the configuration of the device.

Coupling Composition for Optical Fiber Cables

Abstract: The present invention relates to a novel coupling composition that is used within optical fiber cables to protect optical fibers and to couple the optical fibers and the surrounding buffer tube casing. The present invention also relates to optical fiber cables that use the novel coupling composition.

Optical fiber, optical fiber ribbon, and optical interconnection system

Abstract: An optical fiber includes a core and a cladding which are made from silica glass, allows single mode transmission at a wavelength of 1100 nm, and has a mode field diameter of not less than 4 μm at a wavelength of 1100 nm, and a bending loss of not more than 1 dB per turn with a curvature radius of 1 mm at a wavelength of 1100 nm.

Transmission optical fiber having large effective area

Abstract: The present invention relates to a transmission optical fiber. The optical fiber includes, from its center to its periphery a central core, an intermediate cladding, and a depressed cladding. The optical fiber has an effective area (S eff ) of at least about 120 μm 2 at a wavelength of 1550 nm and an effective cutoff wavelength (λ Ceff ) of less than 1600 nm. The optical fiber has an effective area of more than 120 μm 2 with a cutoff wavelength limited to less than about 1600 nm without degradation of other optical parameters (e.g., attenuation losses and dispersion).

Amplifying optical fiber and method of manufacturing.

Abstract: Disclosed is an amplifying optical fiber having a central core and an optical cladding surrounding the central core. The central core is based on a silica matrix that includes nanoparticles, which are composed of a matrix material that includes doping ions of at least one rare earth element. The amplifying optical fiber can be employed, for example, in an optical amplifier and an optical laser.

Fiber optic evanescent field sensor for detection of explosives and CO2 dissolved in water

Abstract: A fiber optic approach for the determination of the carbon dioxide concentration in the gas or fluid phase during sequestration, as well as for the sensing of the explosive TNT is described. The sensor consists of a quartz glass multimode fiber with core diameter of 200 μm and is based on the evanescent field principle. Cladding and jacket of the fiber are removed in the sensing portion, therefore interaction between light within the fiber and the surrounding medium is possible. A single-mode distributed feedback (DFB) laser diode with an emission wavelength around λ= 1.57 μm and a frequency doubled passively Q-switched Cr4+:Nd3+:YAG microchip laser (λ= 1064 nm)are used as light sources. The experimental setup and the sensitivity of the evanescent field sensor are characterized.

Fiber Optic Sensing Systems and Methods

Abstract: Fiber optic sensing systems and methods. In a described embodiment, a fiber optic sensing system includes an optical fiber transmitting energy to a chemical vapor deposited diamond material proximate a substance in a well. The diamond material is deposited as a coating on a substrate. The substrate and coating are heated when the energy is transmitted by the optical fiber. This heats the substance in the well, which is detected to determine a property of the substance. In another embodiment, light energy is transmitted through the diamond material.

Highly nonlinear silica suspended core fibers

Abstract: Suspended-core fibers are systematically studied. We show that confinement loss in suspended-core fibers can be effectively reduced by an increase of air-cladding width for even sub-micron core diameters and, therefore, provides a considerable simpler solution than equivalent photonic crystal fibers with a large number of air holes for a wide range of nonlinear applications. We have further demonstrated a suspended-core silica fiber with core diameters of 1.27µm and sub-dB splice loss to Hi1060. Loss at 1.55µm was measured in this fiber to be 0.078dB/m, a record for this small core diameter, limited mainly by scattering loss at the glass and air interface. The combination of high nonlinearity, low splice loss and low transmission loss of the suspended core silica fibers will enable a new class of low loss all-fiber nonlinear devices.

Detailed investigation of self-imaging in largecore multimode optical fibers for application in fiber lasers and amplifiers

Abstract: Properties of the self-imaging effect based on multimode interference (MMI) in large-core passive optical fibers are investigated and analyzed in detail, with the purpose of using multimode active fibers for high power single-transverse-mode emission. Although perfect self-imaging of the input field from a standard single-mode fiber (SMF-28) in a multimode fiber becomes practically impossible as its core diameter is larger than 50 microm, a quasi-reproduction of the input field occurs when the phase difference between the excited modes and the peak mode inside the multimode fiber is very small. Our simulation and experimental results indicate that, if the length of the multimode fiber segment can be controlled accurately, reproduction of the input field with a self-imaging quality factor larger than 0.9 can be obtained. In this case, a low-loss hybrid fiber cavity composed of a SMF-28 segment and a very-large-core active multimode fiber segment can be built. It is also found that for the hybrid fiber cavity, increasing the mode-field diameter of the single-mode fiber improves both the self-imaging quality and the tolerance on the required length accuracy of the multimode fiber segment. Moreover, in this paper key parameters for the design of MMI-based fiber devices are defined and their corresponding values are provided for multimode fibers with core diameters of 50 microm and 105 microm.

Antiresonant reflection and inhibited coupling in hollow-core square lattice optical fibres

Abstract: We propose a guidance mechanism in hollow-core optical fibres dominated by antiresonant reflection from struts of solid material in the cladding. Resonances with these struts determine the high loss bands of the fibres, and vector effects become important in determining the width of these bands through the non-degeneracy of the TE and TM polarised strut modes near cut-off. Away from resonances the light is confined through the inhibited coupling mechanism. This is demonstrated in a square lattice hollow-core microstructured polymer optical fibre.

A new material for high-power laser fibers

Abstract: We have developed a new technique to produce a Yb-doped fused silica bulk glass which is very well suited for fiber laser applications. The starting point is a liquid suspension of SiO2 particles which is doped by a solution of rare earth ions. After dehydration, purification and vitrification we achieve a bubble-free homogeneous Yb-doped fused bulk silica, which is further processed by the plasma outside deposition (POD) technique into preforms for active laser fibers with a large active fiber core. The laser function of our Yb-doped silica was successfully proved in a side-pumped fiber laser setup. We present the results of the laser experiments.

Fiber optic sensor for detecting multiple parameters in a harsh environment

Abstract: A fiber optic sensor is provided. The fiber optic sensor includes a fiber core having a plurality of Bragg grating elements wherein, the grating elements comprise a periodic or a quasiperiodic modulated microcrystalline and rigid silicon dioxide tetrahedral structure and a cladding disposed about the fiber core.

Fluoride glass microstructured optical fiber with large mode area and mid-infrared transmission.

Abstract: We demonstrate the first fluorozirconate microstructured fiber for use in the mid-infrared. The fiber preform was manufactured via extrusion of a 200 g billet through a complex graphite die. The fiber exhibits large mode area of 6,600 microm(2), loss of 3 dB/m at 4 microm and only marginal excess loss relative to a corresponding unstructured fiber.

Square-lattice large-pitch hollow-core photonic crystal fiber.

Abstract: We report on the design, fabrication and characterization of silica square-lattice hollow core photonic crystal fibers optimized for low loss guidance over an extended frequency range in the mid-IR region of the optical spectrum. The fiber’s linear optical properties include an ultra-low group velocity dispersion and a polarization cross-coupling as low as -13.4dB over 10m of fiber.

New Developments in Elastic Fibers

Abstract: This paper reviews the developments of essential elastic fibers. The elastic fibers include extensible polymer fibers with low or high elasticity and reversibility which consists of the polyurethane elastic fiber, polyester‐ether elastic fiber, polyester elastic fiber, olefin based elastic fiber like XLA, hard elastic fiber, bio‐component fiber, and the shape memory fibers. The emphasis of the review is on the development and research process of polymer synthesis, production, characteristics, microstructure, and end‐use in industry. It also draws some conclusions about the current problems and future directions.

Highly Birefringent Index-Guiding Photonic Crystal Fiber with Squeezed Differently Sized Air-Holes in Cladding

Abstract: We propose a novel high-birefringence index-guiding photonic crystal fiber (PCF). This PCF is composed of a solid silica core and a cladding with two differently sized squeezed elliptical air-holes. The mode birefringence of a fundamental mode in such PCFs is analyzed numerically by the finite-element method. Numerical results reveal that an extraordinarily high modal birefringence at the excitation wavelength of λ=1550 nm, 2.6×10-2, is acquired. The contributions of the cladding with two different sizes of air-hole ellipticity, the center-to-center distance between the air-holes, and the the number of cladding rings as well as the confinement loss to the birefringence are systematically evaluated. The evolution of birefringence with the structural variations shows that our highly birefringent fiber can be designed in a controlled manner.

Special optical fiber for temperature sensing based on cladding-mode resonance.

Abstract: A fiber-optic temperature sensor by using a multi-cladding special fiber is presented. It works on the basis of leaky mode resonance from fiber core to outer cladding. With the thin-thickness inner cladding, the cladding mode is strongly excited and the resonant spectrum is very sensitive to the refractive index variation of coating material. By coating the special fiber with temperature-sensitive silicone, the temperature response was investigated experimentally from -20 degrees C to 80 degrees C. The results show high temperature sensitivity (240 pm/degrees C at 20 degrees C) and good repeatability.

Capillary optical fiber - design, fabrication, characterization and application

Abstract: The paper presents a modification of capillary optical fibers fabrication method from an assembled glass preform. A change of dimensional proportions in the capillary optical fiber drawn from a single preform is allowed on-line via the control of overpressure and thermal conditions in the outflow meniscus which essentially lowers the manufacturing costs. These conditions are among the solutions (velocity fields) of the Navier-Stokes equations adapted to the capillary optical fiber pulling geometry and temperature distribution in the oven. The velocity fields give solutions to other quantities of interest such as flow rate, pulling force and fiber geometry. The calculation and experimental results for capillary optical fibers were shown in the following dimensional range: internal diameters 2-200 μm, external diameters 30–350 μm, within the assumed dimensional stability (including ellipticity) better than 1%. The parameters of fabricated capillary optical fibers of high-quality low-loss optical multicomponent glasses were: lossesi100 dB/km, mechanical strength above 1GPa with Weibull coefficient in the range 3–7, internal numerical aperture 0.1–0.3, external numerical aperture 0.1–0.3, core index 1.5–1.8, transparency 0.4–2 μm, thermally and/or chemically conditioned internal surface, double polyimide protection layer, soft or hard jacketed, connectorized. The capillary optical fibers were applied in our own and several external laboratories in spectroscopy, refractometry, micro-fluidics and functional microoptic components. The paper summarizes a design, technological and application work on capillary optical fibers performed during a recent national research program devoted to optoelectronic components and modules.

Optical fiber containing alkali metal oxide

Abstract: Disclosed is an optical fiber having a silica-based core comprising an alkali metal oxide a silica-based core, said core comprising an alkali metal oxide selected from the group consisting of K2O, Na2O, LiO2, Rb2O, Cs2O and mixtures thereof in an average concentration in said core between about 50 and 1000 ppm by weight, and a silica-based cladding surrounding and directly adjacent the core, said fiber comprising a cable cutoff less than 1400nm chromatic dispersion at 1550nm between about 13 and 19 ps/nm/km and a zero dispersion wavelength less than about 1324nm. By appropriately selecting the concentration of alkali metal oxide dopant in the core and the cladding, a low loss optical fiber may be obtained.

Fabrication and experimental observation of monolithic multi-air-core fiber array for image transmission

Abstract: Two kinds of multi-air-core optical fibers were designed and fabricated by extruding optical grade PMMA pellets and drawing to fiber. The imaging function of the fibers was investigated with home-made specialized microscopy. This new type of fiber provides strong potential for applications in endoscopy, chemical sensing, biosensors, fiber-optical faceplates.

Acoustic modal analysis and control in w-shaped triple-layer optical fibers with highly-germanium-doped core and F-doped inner cladding

Abstract: The numerical study of acoustic modal properties in w-shaped optical fibers with high-delta germanium-doped core and F-doped inner cladding (F-HDF) is demonstrated The cutoff conditions of acoustic modes in the F-HDF show opposite behaviors in contrast with those of optical ones because F-doped inner cladding contributes differently to acoustic and optical waveguides The acoustic dispersion characteristics vary to a great extent with respect to the location of the acoustic modes in the fiber’s core or in the fiber’s inner cladding The resonance frequency spacing between neighboring acoustic modes is theoretically and experimentally found to have a quadratic relation to the core’s germanium concentration We also investigate the critical conditions to move high-order acoustic modes into the F-doped inner cladding and validate the optimal feasibility of employing L01 and L03 acoustic modes to fiber-optic Brillouin-based discriminative sensing of strain and temperature

High power fiber laser system with cladding light stripper

Abstract: A powerful fiber laser system is configured with at least one gain block. The gain block includes an input fiber guiding a pump light, a multiclad active fiber receiving the pump light so that a major portion is absorbed in the core of the active fiber while a minor portion of the pump light propagates in the inner cladding of the active fiber, and a multiclad output fiber. The multiclad output fiber is configured with a core, guiding a signal lased by the core of the active fiber upon absorption of the major portion of the pump light, an inner cladding receiving the minor portion of the pump light and an outer cladding. The inner and outer claddings of the multiclad output fiber have respective refractive indexes which are selected so that the refractive index of the outer cladding is higher than that one of the inner cladding. The configuration of the output fiber allows for the removal of substantially the entire light from the inner cladding of the output fiber before the signal is emitted through the downstream end of the output fiber.