Automatic geometric dimension measurements of single-mode fiberpreforms using a novel shadow method

A method is described in which a test preform is immersed in an index-matching liquid so as to detect optical signals from the core/cladding and cladding/index-matching liquid interfaces simultaneously. A light-beam sweeper with a mirror is used to sweep a He-Ne laser beam across a fiber preform, and the time intervals during which the preform intercepts the beam and casts a composite shadow on a photodetector are measured. The method is simple and accurate and has sufficient spatial resolution (better than 10 μm) to obtain detailed measurements of core eccentricity, core and cladding diameters and their ratio, and ellipticity in a step-index single-mode fiber preform for a subscriber line. On the basis of this principle, an automated geometry measurement system has been developed. The system is attractive for quality control applications in mass-production lines of single-mode fibers     

半导体锗芯光纤拉丝过程中的芯-包层流速差异研究

半导体芯光纤因其特殊的光电特性而受到广泛关注。由于纤芯和包层材料之间的性质差异,制备高质量的半导体芯光纤比传统掺杂石英玻璃光纤更为困难。以锗芯光纤为研究对象,通过有限元法,模拟仿真了激光拉制锗芯光纤的动态过程,研究了拉制过程中芯层锗和包层石英玻璃材料的流速差异,以及不同拉丝速度对其流速差异的影响。仿真结果表明:在预制棒颈缩区,芯层锗和包层石英玻璃材料的流速差异最大,且不同拉丝速度对预制棒芯层锗和包层石英玻璃材料的流速影响不同。     

Fluoride glass preforms prepared by a rotational casting process

A new approach has been developed to fabricate fluoride-glass-cladded fibres from preforms having controlled core/clad ratios and uniform cladding thicknesses. In contrast to earlier casting methods, preform core/clad ratios remained unchanged over the entire length of all preforms. The new method also permits fabrication of much larger preforms.     

An Erbium Fiber Fabricated by the “Core-Suction” Technique

An erbium doped fiber preform having a lead germanate erbium glass core with silica cladding was fabricated by a newly developed technique named “Core-Suction”. This preform was then drawn into fiber and fiber cross-section, loss spectrum and refractive index profile measured. A 30 cm piece of the manufactured fiber was spliced to a standard silica fiber using a commercial available splicer. This spliced fiber was then used to setup an erbium doped fiber amplifier (EDFA) and gain spectrum of the amplifier measured. Distributed gain of the manufactured erbium fiber was measured using an optical frequency domain reflectometry (OFDR) based optical backscatter reflectometer (OBR). It is demonstrated that the “Core-Suction” technique can be used to make a high-gain amplifier that is compatible with conventional silica fibers.      

Fabrication of fluoride glass single-mode fibers

Single-mode optical fibers are obtained using ZrF4-based fluoride glasses. The fibers are drawn from a preform and jacketing tube. The preform with cladding/core ratio of 5.1 is made by using a built-in casting method. The cutoff wavelength of the fiber is experimentally determined to be 2.7 μm by bending loss measurement. Minimum transmission loss of the obtained fiber is 160 dB/km at a wavelength of 3.28 μm. TheV-value at this wavelength is estimated to be 2.03 from the core diameter and the refractive index difference.     

Laser‐Induced In‐Fiber Fluid Dynamical Instabilities for Precise and Scalable Fabrication of Spherical Particles

Scalable fabrication of spherical particles at both the micro‐ and nanoscales is of significant importance for applications spanning optical devices, electronics, targeted drug delivery, biodevices, sensors, and cosmetics. However, current top‐down and bottom‐up fabrication methods are unable to provide the full spectrum of uniformly sized, well‐ordered, and high‐quality spheres due to their inherent restrictions. Here, a generic, scalable, and precisely controllable fabrication method is demonstrated for generating spherical particles in a full range of diameters from microscale to nanoscale. This method begins with a macroscopic composite multimaterial solid‐state preform drawn into a fiber that defines precisely the initial conditions for the process. It is then followed by CO₂ laser heating to enable the transformation from a continuous fiber core into a series of homogeneous spheres via Plateau–Rayleigh capillary instability inside the fiber. This physical breakup method applies to a wide range of functional materials with different melting temperatures from 400 to 2400 K and 10 orders of difference in fiber core/cladding viscosity ratio. Furthermore, an ordered array of silicon‐based whispering‐gallery mode resonators with the Q factor as high as 7.1 × 10⁵ is achieved, owing to the process induced ultrasmooth surface and highly crystalline nature.     

Loss increase in deuterium-doped VAD fibres with heat treatment

The origin of the increase in the intensity of OH bands with heat treatment has been investigated using deuterium-containing VAD fibres. Remarkable loss increases only in the absorption peaks due to the OH ions have been observed after 200?500°C heat treatment applied to three kinds of fibre: drawn from a preform prepared by a D2-O2 flame, and OD-doped in the core and in the cladding. It was confirmed that the origin of the hydrogen causing the loss increase is not in the synthesised glass materials.     

A homogeneous heating technique in preform manufacturing

A new heating technique in preform manufacturing, which enables a faster collapse and a larger preform size, has been developed. On an ordinary MCVD preform station, the torch has been replaced by a microwave (dielectric) heater. With this equipment both deposition and collapse of thick-walled tubes have been performed. Preforms, of single-mode design and with an outer diameter of 35 mm, have been fabricated. This preform size corresponds to 40 km of fiber per half meter preform.     

An optical amplifier having 5 cm long silica-clad erbium doped phosphate glass fiber fabricated by “core-suction” technique

We have fabricated an erbium-doped phosphate glass fiber with a silica cladding and used 5 cm length of it to form an optical amplifier. A bulk erbium phosphate glass called MM2 was used as a core glass in a silica cladding tube to prepare a preform using “core-suction” technique. This MM2 glass preform was drawn to a fiber and the resultant fiber was of good optical quality, free from air bubbles and major defects. The fiber was mechanically strong enough to allow for ease of handling and could be spliced to conventional silica fiber using commercial fusion splicer. This fiber was then used to setup an EDFA. Our work demonstrates the potential to form silica clad optical fibers with phosphate cores doped with very high levels of rare-earth ions. It is demonstrated that the core suction technique can be used to make a high-gain erbium phosphate fiber amplifier that is compatible with conventional silica fibers.     

The Design and Fabrication of Monomode Optical Fiber

The design of monomode fibers is discussed in the context of optimizing fiber loss and dispersion simultaneously, with reference to the materials choices and limitations to preform and fiber fabrication by the MCVD technique. Two classes of monomode structure-matched cladding and depressed cladding-are considered. Ultralow attenuation has been achieved reproducibly in both classes of fiber. The control of fiber geometry and dispersion is also discussed. Matched cladding fiber suitable for systems operating at both 1.3 and 1.55 µm has been studied and mean losses of 0.45 dB/km at 1.3 µm and 0.28 dB/km at 1.55 µm have been achieved for a total of 130 km. The behavior of depressed cladding fiber is compared with predictions from the theory of propagation in W fibers. Depressed cladding fiber with stable guidance has been demonstrated with attenuation of 0.37 dB/km at 1.3 µm and 0.21 dB/km at 1.55 µm.     

Drawing glass fibers with complex cross section

Techniques are presented for fabrication of glass fibers with complex cross-sectional shapes by drawing from a composite preform. To prevent distortion of the fiber shape by surface tension during drawing, a soluble glass cladding is added to the preform complete its cross section to a circular shape. After the drawing process, the cladding is dissolved chemically. Fibers with zigzag and meander-like cross sections and minimum dimensions of 2 μm are demonstrated     

Mathematical Modeling as an Accurate Predictive Tool in Capillary and Microstructured Fiber Manufacture: The Effects of Preform Rotation

A method for modeling the fabrication of capillary tubes is developed that includes the effects of preform rotation, and is used to reduce or remove polarization mode dispersion and fiber birefringence. The model is solved numerically, making use of extensive experimental investigations into furnace temperature profiles and silica glass viscosities, without the use of fitting parameters. Accurate predictions of the geometry of spun capillary tubes are made and compared directly with experimental results, showing remarkable agreement and demonstrating that the mathematical modeling of fiber drawing promises to be an accurate predictive tool for experimenters. Finally, a discussion of how this model impacts on the rotation of more general microstructured optical fiber preforms is given.     

Propagation characteristics of radially inhomogeneous optical fibre

A numerical method for computing the propagation characteristics of a radially inhomogeneous fibre is presented. The method is quite general and can be applied to a fibre with any refractive-index profile. The fibre considered here consists of a core with a parabolic refractive-index profile and a thin homogeneous cladding. Dispersion curves for the seven lowest-order modes are computed with and without the infinite-cladding approximation. The results have been found to agree with those of other investigators. The effect of the finite cladding, however, has not been studied previously.     

Fabrication of Organized Porphyrin‐Nanotube‐Attached Heat‐Sensitive Polyelectrolyte Capsules

A facile method of connecting fluorescent meso‐tetrakis(4‐sulfonatophenyl)porphine tetranion nanotubes to polyelectrolyte capsules is developed. Heat‐sensitive robust polyelectrolyte capsules consisting of poly(diallyldimethylammonium chloride) and poly(styrene sulfonate) multilayers have been fabricated using the conventional layer‐by‐layer technique. Supramolecular aggregation of porphyrin monomers to nanotubes is induced in the microenvironment of the capsules by sequential addition of salt and acid. Scanning electron microscopy, transmission electron microscopy, and atomic force microscopy images reveal satellite‐like structures consisting of a central capsule core with porphyrin nanotubes emerging radially from the capsule walls. The growth and the distribution of the porphyrin units have been monitored by UV‐vis spectroscopy, fluorescence spectroscopy, and confocal laser scanning microscopy. Changing the temperature alters the dimensions and the arrangement of the nanotubes on the capsule walls. Such an attachment of porphyrin tubes onto robust functional capsules should help in developing an artificial light‐harvesting system.     

Influence of Ge concentration on UV-excited luminescence in agraded-index fibre preform

A germanosilicate glass graded-index fibre preform thin sample was submitted to a wide range of 266 nm excitation powers across its core. The resulting 400 nm luminescence signal was found to follow the index profile of the preform at low excitation power and to be bleached at higher power above a certain Ge-concentration threshold. This threshold changed to lower Ge-concentration values with higher excitation power     

Étude des propriétés des fibres unimodales à gaine interne déprimée

This paper presents some results of an experimental investigation of fibres with a depressed inner cladding (W type). It has been confirmed that fibers with low losses and weak dispersion in the 1.3 – 1.7 μm range can be achieved. The sensitivity to fabrication parameters is very important. Information is given on preform fabrication and index profile measurements.     

Forces between Surfactant‐Coated ZnS Nanoparticles in Dodecane: Effect of Water

The forces between mica surfaces confining solutions of spherical and rod‐shaped ZnS nanoparticles (diameter ca. 5 nm) coated with hexadecylamine or octadecylamine surfactant in dodecane have been measured in the absence and after the introduction of trace amounts of water. Initially, or at very low water content, the water molecules cause the nanoparticles to aggregate and adsorb on the hydrophilic mica surfaces, resulting in a long‐range exponentially decaying repulsive force between the surfaces. After longer times (> 20 h), water bridges nucleate and grow between the nanoparticles and mica surfaces, and attractive capillary forces then cause a long‐range attraction and a strong (short‐range) adhesion. It is found, as has previously been observed in nonaqueous bulk colloidal systems, that even trace amounts of water have a profound effect on the interactions and structure of nanoparticle assemblies in thin films, which in turn affect their physical properties. These effects should be considered in the design of thin‐film processing methodologies.     

浅析大尺寸光纤预制棒(OVD法)的制备工艺

光纤预制棒的大型化是降低光纤拉丝成本的必要手段,本文介绍了利用OVD法生产大尺寸光纤预制棒的工艺方法,主要包括大尺寸光纤预制棒在沉积、烧结、保温过程中的设备与工艺介绍.     

Single-Mode Perfluorinated Polymer Optical Fibers With Refractive Index of 1.34 for Biomedical Applications

We demonstrate a technique for the fabrication of single-mode perfluorinated polymer optical fiber (PPOF). The PPOF preform is composed of poly-methyl-methacrylate (PMMA)-based outer cladding and a graded-index multimode PPOF as the core. A photosensitive graded-index single-mode PPOF with a core diameter of about 6.6 $ mu{hbox {m}}$ and cladding diameter of 400 $ mu{hbox {m}}$ was fabricated. The fiber has a cutoff wavelength of 854 nm and exhibits single-mode characteristics at wavelengths of 1310 and 1550 nm. The transmission loss is less than 0.2 dB/m in the wavelength range of 1410–1540 nm and less than 0.5 dB/m for wavelengths up to 1610 nm, significantly less than the typical transmission loss of $sim$100 dB/m for PMMA fiber. Another important feature of the PPOF is its low refractive index of 1.34, close to aqueous solution of biomaterials, permitting strong optical coupling for biomedical applications.      

Solid‐State Approach for Fabrication of Photostable,Oxygen‐Doped Carbon Nanotubes

A novel procedure for effective fabrication of photostable oxygen‐doped single‐walled carbon nanotubes (SWCNTs) in solid‐state matrices has been developed. SWCNTs drop‐cast on various types of substrates are coated with oxide dielectric thin films by electron‐beam evaporation. Single tube photoluminescence spectroscopy studies performed at room and cryogenic temperatures reveal that such thin film‐coated tubes exhibit characteristic spectral features of oxygen‐doped SWCNTs, indicating the oxide thin film coating process leads to oxygen doping of the tubes. It is also found that the doping efficiency can be effectively controlled by the thin film deposition time and by the types of surfactants wrapping the SWCNTs. Moreover, aside from being the doping agent, the oxide thin film also serves as a passivation layer protecting the SWCNTs from the external environment. Comparing the thin film coated SWCNTs with oxygen‐doped tubes prepared via ozonolysis, the former exhibit significantly higher photostability and photoluminescence on‐time. Therefore, this one‐step deposition/oxygen‐doping procedure provides a possible route toward scalable, versatile incorporation of highly photostable oxygen‐doped SWCNTs in novel optical and optoelectronic devices.