Article New Methods of Enhancing the Thermal Durability of Silica Optical Fibers (original) (raw)

New Methods of Enhancing the Thermal Durability of Silica Optical Fibers

Materials, 2014

Microstructured optical fibers can be precisely tailored for many different applications, out of which sensing has been found to be particularly interesting. However, placing silica optical fiber sensors in harsh environments results in their quick destruction as a result of the hydrolysis process. In this paper, the degradation mechanism of bare and metal-coated optical fibers at high temperatures under longitudinal strain has been determined by detailed analysis of the thermal behavior of silica and metals, like copper and nickel. We furthermore propose a novel method of enhancing the lifetime of optical fibers by the deposition of electroless nickel-phosphorous alloy in a low-temperature chemical process. The best results were obtained for a coating comprising an inner layer of copper and outer layer of low phosphorous nickel. Lifetime values obtained during the annealing experiments were extrapolated to other temperatures by a dedicated model

Hot water aging performance of silica optical fiber with single coating characteristics

Wire journal international, 2004

Silica optical fiber is widely used in long-haul telecommunication systems. In these applications the fibers are frequently exposed to corrosive environments that can cause strength loss. However, optical fiber can be corroded chemically due to moisture attack, which is known as “zero-stress aging” and makes unreliable prediction of expected lifetime. 1 Optical fiber consists of two coating namely inner and outer coating. The inner coating, which is softer, protects the glass for improved bend sensitivity. The outer coating, which is harder, helps in reduce the handling damage on the fiber. Another function of this protective dual polymer coating applied to the fiber during the drawing process should be to protect against such corrosion. Zero stress aging, in terms of strength degradation and appearance of delamination at glass/coating interface in dual coated fiber, is caused by surface dissolution of silica , low degree of curing of coating and a change in other coating performanc...

New method for strength improvement of silica optical fibers

Optics and Lasers in Engineering, 2008

Besides signal transmission for telecommunications, fibers are used in an increasing number of devices. A number of applications relate to devices exposed to severe wet environment (hot water, chemical attacks…). It is the case for the sensors used in nuclear plants, high energy physics or plasmas devices. However, reliability issues must be addressed for optical fiber sensors operating under severe conditions such as harsh chemical solutions. The purpose of this work is to study the mechanical behavior and aging of fibers exposed to hot water action, to hydrofluoric acid vapours (HF) and to tetramethoxysilane (TMOS) for different durations. Dynamic fatigue tests were implemented using a two-point bending testing device or tensile test set-up. Standard fibers tested immediately after exposure show a broader distribution of fiber strength accompanied by the drastic decrease of the failure stress. In some particular cases, the gain compared to as received fibers can be positive. Polymer reacts with different wet environments, which induces viscosity changes. This is consistent with SEM observations.

Aging and strength improvement of silica optical fibers

Photonics North 2008, 2008

The reliability and the expected lifetime of optical fibers used in telecommunication technologies are closely related to the chemical environment action on the silica network. To ensure the long-term mechanical strength of the optical fibers, a polymer coating was applied onto the fiber surface during fiber fabrication. This external coating is vital to ensure a long fiber lifetime. Its protective action includes several functions, such as to protect glass fiber from any external damage, to limit chemical attack, in particular that of water, and finally to ensure fatigue protection and bending insensitivity. Since the mechanical strength of the fiber is controlled by its surface characteristics, we propose a new method for increasing fiber strength. Submitted to a mechanical stretching, fibers were plunged into hot water and aged for several days. Then, the fibers were removed from the water and various weights were suspended on the fiber ends. Just before the fiber rupture, the fibers were unloaded and subjected to dynamic tensile tests at different velocities. Result analysis proved that the aging in hot water increased the fiber strength. The Weibull's diagram study shows a bimodal dispersion of defects on the fiber surface and the important role of polymer coating.

Effect of metal coating on the optical losses in heated optical fibers

Technical Physics Letters, 2009

The effect of heating in air on the optical losses in metal-coated fibers has been studied. Two fibers were drawn from the same silica preform and coated by different metals (copper and aluminum). Dependences of a change in the optical losses on the temperature were measured in a 20-400 ° C range at a 50 ° C step. The optical losses of metal-coated fibers heated to temperatures below 300 ° C change mostly due to the microbending contribution. At temperatures above 300 ° C, the main contribution to increasing optical losses is due to the absorption on OH groups. It is established for the first time that the contribution to optical losses due to the OH groups is much more pronounced in Al-coated fibers than in Cu-coated ones. In addition, the Al-coated fibers exhibit growth in the optical losses above 300 ° C due the absorption on molecular hydrogen.

The strength and failure of silica optical fibers

Physica Scripta, 2010

The mechanical strength and failure behavior of conventional and microstructured silica optical fibers was investigated using a tensile test and fracture mechanics and numerical analyses. The effect of polymer coating on failure behavior was also studied. The results indicate that all these fibers fail in a brittle manner and failure normally starts from fiber surfaces. The failure loads observed in coated fibers are higher than those in bare fibers. The introduction of air holes reduces fiber strength and their geometrical arrangements have a remarkable effect on stress distribution in the longitudinal direction. These results are potentially useful for the design, fabrication and evaluation of optical fibers for a wide range of applications.

AGING AND RELIABILITY OF SINGLE-MODE SILICA OPTICAL FIBERS in Optical Fibers Research Advances

The optical fiber reliability in telecommunication networks has been still an issue, that's why the question of how long an optical fibers might been used without a significant probability of failure isn't out of interest. Much work was developed around this issue, but the optical fiber fatigue and aging process has not been yet fully understood. The reliability of the optical fibers depends on various parameters that have been identified: time, temperature, applied stress, initial fiber strength and environmental corrosion. The major and usually unique corrosion reagent is water, either in the liquid state or as atmospheric moisture. Glass surface contains numerous defects, either intrinsic, the so-called " Griffith's flaws and extrinsic, in relation to fabrication process. Under permanent or transient stress, microcracks grow from these defects, and growth kinetics depend on temperature and humidity. Although polymeric coating efficiently protects glass surface fr...

Strength measurements of silica optical fibers under severe environment

Optics & Laser Technology, 2007

Optical fibers are key components in telecommunication technologies. Apart from optical specifications, optical fibers are expected to keep most of their physical properties for 10-20 years in current operating conditions. The reliability and the expected lifetime of optical links are closely related to action of the chemical environment on the silica network. However, the coating also contributes largely to the mechanical properties of the fibers.

Stress corrosion in silica optical fibers: Review of fatigue testing procedures

AIP Conference Proceedings, 2018

The expected lifetime of optical fibers used either in telecommunication technologies or smart applications are closely related to the chemical reaction on the silica network. Due to the manufacturing processes or the handling procedures, the flaws spread on the fiber surface are inherently present. The aging mechanism is assumed to enlarge or to extend these flaws. Based on systematic experiments one may notice that water may induce a certain curing effect. Silica optical fibers have been aged in water; series of samples have been subjected to overlapped stretching or bending. Other series have been subjected to overlapped aging effect of microwaves and hot water. Finally, samples were submitted to dynamic tensile testing. The Weibull's diagram analysis shows mono or bimodal dispersions of flaws on the fiber surface, but the polymer coating appears vital for fiber lifetime. While humidity usually affects the fiber strength, the series of testing has revealed that in controlled conditions of chemical environment and controlled applied stress, fiber strength may be increased. A similar effect may be obtained by external factors such as microwaves or previous elongation, too.

Mechanical and chemical characteristics of hermetically coated silica optical fibre

Surface and Coatings Technology, 2008

The mechanical strength of carbon hermetically coated fibres, compared to standard single mode silica optical fibre, has been investigated through chemical exposure to fluorinated vapour reagents, known as the harshest reagents for silica. Two reagents were used: ammonium hydrogenofluoride and hydrofluoric acid.