Polymers beyond standard optical fibres – fabrication of microstructured polymer optical fibres

This paper reports the overall fabrication process of microstructured polymer optical fibres (mPOFs). mPOF fabrication involves a two‐step process: on the one hand, the design and creation of a preform containing a large‐scale version of the desired fibre and, on the other, the precise heating and drawing of the preform to the final fibre. The preforms are produced either by an improved drilling technique or by capillary stacking. For a correct and accurate drawing of the fibre, a controlled and precise heating unit has to be designed, an issue that will be explained in detail in this work. The quality and optical performance of the final mPOF depends strongly on key factors such as the preform annealing, the accuracy of the technique selected for the creation of the preform structure, the heating stage, as well as on the drawing parameters. All of them are analysed in detail and some drawn mPOFs of interest are reported as well. © 2018 Society of Chemical Industry     

Digital mathematical model of spinning of chemical optical fibres

A digital mathematical model of drawing of optical fibres was obtained. A first-order extrapolation gives a more accurate approximation than a zero-order extrapolation.     

Ultrafast modulation of optical transitions in monolayer and multilayer graphene

We study ultrafast modulations of absorption spectra for both monolayer and multilayer graphene, by performing time-resolved transmission measurements with tuning probe photon energy. While reduced absorptions by photo-excited carriers are observed in monolayer graphene irrespective of the probe energy, multilayer graphene shows increased absorption at around 0.6 eV, which is explained by the optical transitions between subband states. Intraband carrier relaxation and electron–hole recombination times are found to be as fast as 0.5 and 10 ps, respectively. Modifications of ultrafast carrier dynamics are also studied with changing temperature and excitation density.     

Temperature dependence of processes during oxidation of PAN fibres

The 3000-PAN-filament tows have been stretched by a constant axial load during heating in air at a constant rate of . The extension of the tow begins about the glass-transition temperature (70°C). Temperature dependence of the fibre diameter, width of X-ray reflection of the PAN, and endothermic effect occurring at low temperature (below 240°C), suggest that at 130°C begins a molecular rearrangement. IR spectra of the oxidized fibres and gas evolution suggest that near this temperature (at about 145°C) begins cyclization, but the cyclized fraction of the fibres remains very low up to over 220°C, unless a prolonged oxidation at this temperature is carried out. TGA and DTA results suggest that at about 240°C begins rapid cyclization, which is at about 320°C followed by partial degradation of the fibres. In these processes the fibres lose about 26% of their original weight. Final degradation of the fibres begins at about 400°C.     

Temperature dependence of water vapor diffusion into hydrocellulose fibres

Conclusions -- Coefficients of internal mass transfer in the sorption of water vapor by hydrocellulose high-modulus Siblon have been measured.-- The extremal dependence of the velocity of the process on the magnitude of water vapor sorption is explained by devitrification of the cellulose, cluster formation of the sorbate molecules, and hindrance to sorption in the ordered regions of supermolecular structure.Translated from Khimicheskie Volokna, No. 6, pp. 31–32, November–December, 1990.     

A nondestructive method of measuring losses in polymeric optical fibres

Conclusions A procedure has been described for nondestructive measurement of specific light losses in polymeric optical fibres, from lateral scattering. The procedure is applicable in the case of a nonuniform optical fibre in which the intensity of lateral scattering does not change exponentially along the fibre.To measure light losses in a specimen of lengthl, it is necessary to measure the intensity of the light scattering through the side surface of specimen sections of lengthl ₁ andl ₂ (l=l ₁+l ₂) twice: interchanging the places of the input and output ends of the fibre.Translated from Khimicheskie Volokna, No. 1, pp. 22–24, January–February, 1990.     

Determination of the whiteness of viscose fibres processed with optical bleaches

Conclusions The possibility has been shown of using a Zeiss leucometer for obtaining a comparative reproducible index of the whiteness of fibres processed with OB. The reflection factor of the light from the samples with a blue colour filter can serve as such an index.Klin Combine. All-Union Correspondence Institute of Textile and Light Industries (VZITLP). Translated from Khimicheskie Volokna, No. 6, pp. 64–65, November–December, 1969.     

Temperature field and residual stress analysis of multilayer pyroelectric thin film

The two-dimensional finite element model was built for the multilayer pyroelectric thin film. The temperature field and residual stress were simulated. The results show that porous silica film as a thermal-insulation layer and a reasonable model structure are effective for decreasing the heat loss. The silicon substrate and pyroelectric thin film that influence the temperature variation rate in pyroelectric thin film are also discussed. The annealing temperature and model structure have significant influence on residual stresses of pyroelectric thin film. The residual stresses increase rapidly with the increase of annealing temperature. The scanning electron microscopy (SEM) is employed to investigate the morphology of the pyroelectric thin film. The results show that the pyroelectric thin film annealed at 750 °C has a crack structure.     

Microstructure and optical properties of Ag/ITO/Ag multilayer films

Transflective and highly conductive Ag/ITO/Ag multilayer films were prepared by magnetron sputtering on glass substrates. The microstructure and optical properties of Ag/ITO/Ag multilayer films were systematically investigated by X-ray diffraction, scanning electron microscopy, and ultraviolet-visible spectroscopy. The optical properties of the multilayer films were significantly influenced by the thickness of the Ag surface layer from 3.0 to 12.6 nm. The multilayer film of Ag9.3nm/ITO142nm/Ag9.3nm shows the best comprehensive property. It could satisfy the requirement for transflective LCD.     

Temperature sensitivity of the reflectance coefficient of SbSI

The reflectance coefficient of SbSI has been studied under a small temperature modulation using null ellipsometry. The intent of this work was to determine the temperature sensitivity of the optical constants. The reflectance coefficient was found to be highly sensitive to small temperature changes at wavelengths around the absorption edge. It is feasible to detect temperature changes of OC by monitoring the reflectance coefficient.     

Effect of heat and mechanical effects on optical fibres with different coatings

The effect of different coatings on the sensitivity of an optical fibre to heat and mechanical effects was investigated. The thickness of the coatings at which the sensitivity of the fibres to external effects is not a function of random variations in its diameter was determined. The values of the coefficients of the sensitivity of the fibre to external effects for a determined coating thickness were found. Moscow State Textile University. Translated fromKhimicheskie Volokna, No. 6, pp. 52–53, November–December, 1999.     

Estimation of the optical and geometric parameters of polymer fibres with light-scattering diagrams

It was found that analysis of the interference pictures of scattering of laser radiation is a very informative method for evaluating the fine structure of organization of oriented systems, chemical fibres in particular. This method can be used in studying macro- and microstructural changes in the morphology of fibres in different stages of their fabrication. Translated from Khimicheskie Volokna, No. 2, pp. 39–43, March–April, 1998.     

Temperature sensitivity of Burning Rate of Ammonium Perchlorate Propellants

The temperature sensitivity of burning rate of ammonium perchlorate (AP) composite propellants was studied as a function of AP particle size and a burning rate catalyst. A simplified temperature sensitivity model was presented in order to discriminate the effect of the gas phase and solid phase reactions on the initial propellant temperature (T₀). The temperature sensitivity was decreased by the addition of small sized AP particles and/or 2,2-bis(ethylferrocenyl)propane (BEFP). This is caused by the insensitive burning surface temperature to T₀. Thus, the gas phase reaction rate becomes little dependent on T₀, and the temperature sensitivity decreases.     

Optimisation of tailored diamond coating conditions onto optical fibres through the Taguchi method

The characterization of different diamond coatings onto optical fibres is presented. The experimental conditions of each deposition were determined by the Taguchi method, considering five different parameters at four levels. With these experiences it was intended to find the suitable diamond deposition conditions for the optical fibres coating. The application of the Taguchi method demonstrated to be a fundamental tool in the targeting of the appropriate conditions to coating the fibre.     

Implementing optical fibres for the structural health monitoring of composite patch repaired structures

Abstract

Structural health monitoring is increasingly being implemented to improve the level of safety of structures and to reduce inspection and repair costs by allowing for correct planning of these actions, if needed. Composite patch repairing presents an appealing alternative to traditional repair methods as it enables the reduction of closedown time and the mitigation of complications associated with traditional repair methods. As reinforcement with the use of composite patches is predominantly performed at defected structures, the urge to monitor the performance of the repair becomes even greater. This work deals with the use of Fabry Perot optical fibres and strain gages at suitable positions in such a repair. To this end a patch repaired notched steel plate has been tested in tension, opting to gain insight on the mechanisms which govern the failure. In order to investigate how these mechanisms are reflected to the recorded strain measurements, finite element models have been generated. Results indicate that composite patch repairing drastically increased the load bearing capacity of the plates and that optical fibres constitute an appealing health monitoring system for such applications, being able to capture the initiation and evolution of damage.     

Effect of annealing on the optical and mechanical properties of cold drawn polypropylene fibres

Refractive indices and birefringence changes with strain produced by different stresses in annealed and unannealed polypropylene fibres (4 : 1 draw ratio, 515 tex polypropylene from Bolton, UK) were measured interferometrically. Calculations were carried out using multiple-beam Fizeau fringes in transmission to determine the Cauchy's constants, dispersive coefficient and the dielectric constant at infinity. The orientation factor and orientation angle of the fibre material were calculated for different strain values. Poisson's ratio and the strain optical coefficient were also determined. An empirical formula is suggested to correlate the orientation factor, orientation angle, area of cross-section and birefringence with the draw ratio, and the constants of this formula were determined. The effect of the draw ratio on the refractive index profile was studied. Microinterferograms and curves are given as illustrations.     

Temperature regime features in fabrication of optical fiber boules

Translated from Steklo i Keramika, No. 7, pp. 13–15, July, 1990.