26 km-long polarisation-maintaining optical fibre

The letter describes the development of a long-length and large-diameter preform for polarisation-maintaining optical fibres. The preform was 470 mm in length and 48 mm in diameter. As a result, a 26 km-long PANDA fibre is developed. This fibre achieves crosstalk of ?22 dB, corresponding to h = 2.4 × 10-7m-1 and a transmission loss of 0.3 dB/km at a wavelength of 1.56 ?m. These fibres will be useful for future high-speed and medium-span coherent optical communications.     

Deposition mechanism of fine glass particles and high-rate production of fibre preforms in the VAD process

In order to achieve the high-rate production of fibre preforms, the deposition mechanism in the VAD process has been investigated. The particle deposition rate was found to depend on the Reynolds number of the flame stream. The high-rate preform production of 4.5 g/min was attained by applying this result to the preform fabrication technique.     

Low-OH-content optical fibre fabricated by vapour-phase axial-deposition method

A low-OH-content and long-length optical fibre has been made by the v.a.d. method. The OH content in the rod preform was reduced to about 0.4 p.p.m. utilising the chemical reactions of SOCl2 or CCl4 with OH ions and H2O molecules In the porous glass rod. The minimum loss of the fibre, 20km long, was 1.0±0.1 dB/km at 1.2?m.     

Transmission loss characteristics of fluoride glass single-mode fibre

The transmission loss spectrum of a fluoride glass single-mode fibre as obtained with a new preform fabrication technique is shown. It is clearly confirmed on the loss spectrum that the obtained fibre is a single-mode waveguide in the minimum loss wavelength range (2?4 ?m). The minimum loss of this fibre is 8.5 dB/km at 2.2 ?m and the OH excess loss is 15dB/km at 2.85 ?m. This fabrication technique is effective in eliminating OH contamination.     

Transmission properties of lightguide fibres coated at a line speed of 10 m/s

We report the transmission characteristics of high-speed-coated lightguide fibres; the evaluation is based on a total length of 90 km of single-mode fibre. For this experiment the line speed was varied from 2 to 10 m/s, and each sample length obtained from a preform was ~ 10 km. We found that the average losses of the fibres coated at three different speeds (2, 5 and 10 m/s) are all ~ 0.4 dB/km at 1.32 ?m.     

Modified VAD method for optical-fibre fabrication

New techniques for protecting the burner flame and controlling gas pressure in a reaction vessel have been developed for the vapour-phase axial-deposition (VAD) method of soot preform. The growth of soot preform became more stable. It is found that there is a close correlation between the bottom shape of the soot preform and the refractive-index profile of a fibre preform. Optical fibres thus produced indicate improved reproducibility in the bandwidth above 800 MHz km at a wavelength of 0.85 ?m.     

Extruded singlemode, high-nonlinearity, tellurite glass holey fibre

The fabrication of the first singlemode tellurite glass holey fibre produced from an extruded preform is reported. Robust singlemode guidance was observed at 1047 nm in the fabricated small core holey fibre. An effective mode area of 2.6 /spl mu/m/sup 2/ and high effective nonlinearity of 580 W/sup -1/ km/sup -1/ at 1047 nm were predicted. The fibre loss was measured to be 3.5 dB/m at 1050 nm, and 5.8 dB/m at 1550 nm.     

0.27-dB/km attenuation achieved by MSP preform process [opticalfibers]

Mechanically shaped preforms (MSP) have been demonstrated to combine economic non-CVD (chemical vapor deposition) processing and low loss, with a published value of 0.63 dB/km and a size of 30 fkm/preform. Improved processing is proposed which results in a minimum loss of 0.27 dB/km at 1550 nm. Preforms capable of yielding 150 fkm have been produced. Reboiling during preform stretching and fiber pulling is identified as the last remaining problem of the process     

Hydroxyl concentration profile in low-loss graded-index fibres

Low OH-contamination in graded-index fibres was achieved by thin barrier layers of fluorine-doped silica and by chlorine drying in the preform collapse phase. A maximum of OH-concentration was found in the fibre core centre. Attenuation values of about 0.30 dB/km were measured between 1550 nm and 1600 nm.     

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.     

Bottom shape control of optical fiber soot preform by modified VADmethod

Control of the bottom shape of an optical fiber soot preform fabricated by a modified vapor-phase axial deposition (VAD) method is proposed as a way to realize indirect control of the refractive index profile exponent during soot deposition. The technique is based on the close correlation between the profile and the bottom shape. Diameter and refractive index profile fluctuations of the preform with and without control are analyzed. In the case of no control, the fluctuations are larger, and unstable growth of the preform is observed. By controlling the bottom shape, axial fluctuations in the refractive index profile of a transparent preform are reduced to half the magnitude for preforms with no control, and axial diameter fluctuations of the soot and transparent preform are reduced to below ±0.5%. As a result, fibers with a bandwidth of about 1 GHz km at a wavelength of 0.85 μm can be stably fabricated     

Transmission properties of 30.4 km v.a.d. fibre

A 30.4 km graded-index fibre has been fabricated by the vapour-phase axial deposition (v.a.d.) method. Optical-time-domain reflectometry was used to characterise the loss uniformity along the longitudinal direction of this fibre. Measured transmission loss and 6 dB bandwidth with good uniformity along this long fibre were 0.54 dB/km and 1200 MHzkm at the 1.3 ?m wavelength, respectively.     

The Outside Vapor Deposition Method of Fabricating Optical Waveguide Fibers

The outside vapor deposition (OVD) process for fabricating high performance glass optical waveguide fibers is reviewed. Starting metal halide chemicals, porous soot preform fabrication, sintering steps, and fiber drawing are discussed. Preform target size and its effect in obtaining deposition rates to 4 g/min is presented. Data comparisons of OVD fiber performance with other vapor deposited techniques are presented for attenuation, hydroxyl content, and strength (0.7 GPa / M/sup 2/ for 49.5 km of fiber). Single-mode fiber results including excellent geometric concentricity are also discussed.     

基于液相掺杂的低损耗近等厚芯层掺稀土光纤

过高的纤芯损耗和纤芯折射率非均匀性严重制约了掺稀土光纤在高功率光纤激光器中的应用,提出一种基于液相掺杂的低损耗近等厚芯层掺稀土光纤的工艺方法.结合改良的化学气相沉积(MCVD)溶液掺杂法制备了含有多层疏松层的掺稀土光纤预制棒,理论分析了光纤预制棒缩棒前、后芯层差的变化原理,采用流量递减沉积工艺降低了缩棒后不同芯层之间的...     

基于3D定位的光纤棒内部缺陷检测方法

为检测和定位光纤预制棒的内部缺陷并提高精度,提出一种光线追踪实现3D精确定位的线激光旋转扫描检测方法。利用光散射原理和暗场成像技术,成像设备采集光纤棒每个旋转角纵截面上缺陷的散射光;原始图像经过图像预处理和图像分割获取缺陷的二维信息;基于折射定律和光线追踪建立缺陷的精确定位模型,消除光纤棒表面折射带来的成像位置偏差;最后经过坐标转换、三维建模和三维连通域提取实现缺陷在光纤棒内部的3D定位。实验结果表明:120 W像素的工业相机在旋转角步长为0.9°的条件下,对大尺寸的光纤棒内部缺陷检测轴向定位精度为0.28 mm,径向定位精度为1.05 mm,可实现准确、自动化地检测和定位光纤棒的内部缺陷,为光纤棒的质检和指导光纤拉丝提供重要依据。     

Germanium-oxide glass optical fibre prepared by VAD method

Germanium-oxide glass optical fibre doped with antimony for transmission of the 2 to 3 ?m band has been prepared by the vapour-phase axial deposition (VAD) method. An attenuation loss of 13 dB/km at 2.05 ?m and 70 dB/km at 2.4 ?m has been achieved.     

High-rate fabrication of wholly synthesised fibre preforms by the multiflame VAD method using SiHCI3 raw materials

High-rate fabrication techniques for wholly synthesised graded-index fibre preforms were developed. An overall deposition rate of 5.6 g/min was attained using a multiflame VAD burner and using SiHCl3. A low loss of 0.25 dB/km at 1.59 ?m and a small eccentricity of less than 0.4% were obtained.     

Double-flame VAD process for high-rate optical preform fabrication

High-rate deposition techniques for the VAD process have been developed by increasing the size of synthesised fine glass particles by means of a new `double-flame burner?. VAD core preforms have been increased to 2500 g in size, from which a 580 km-length fibre with 50 ?m core diameter can be drawn. A deposition rate of 4.5 g/min from one burner has been attained. Fibres from high-rate deposited preforms exhibit transmission losses of 0.62 dB/km at 1.3 ?m and 0.44 dB/km at 1.55 ?m.     

光纤预制棒(MCVD法)的工艺理论研究

本文对光纤预制棒(MCVD)的工艺机理进行了理论分析,建立了沉积过程中的微粒沉降模型,该模型的基本原理与实验观察一致。对渐变型折射率分布多模光纤的结构分析表明,MCVD法能精确地控制a参数和数值孔径,为提高沉积速率和生产效率开辟了应用途径。     

Measurement of refractive-index profile of optical-fibre preform

An experimental system for nondestructive measurement of the refractive-index profile of an optical fibre preform is reported. The result shows that the profile does not significantly change from the preform stage to fibre stage.