Excitation and spectral dependence of the rise and decay time responses of Eu2+- and Dy3+-doped strontium aluminates

Journal of Materials Science: Materials in Electronics - In this paper, we study the phosphorescence rise and decay time responses of Eu2+- and Dy3+-doped strontium aluminates prepared by different...     

A Müller-Stokes Description of Polarization-mode Transformation in Uniformly Perturbed Optical Fibres

Abstract

On the basis of coupled-mode equations Müller matrices describing the polarization-mode transformation of twofold and fourfold degenerate LP-modes in the quasi-monochromatic case have been derived. Single-mode, two-mode and multimode regimes of operation have been studied. Improved polarization holding in W-type elliptical-core multimode optical fibres has been observed. It has been shown that the LP₁₁ mode cut-off wavelength λ_C can be determined by measuring the wavelength dependence of the relative cross-coupled power.     

State of Polarization in Open- and Closed-loop Helices of Single-mode Fibres

Abstract

The state of polarization in helically wound single-mode fibres is described in terms of coupled-mode equations and the Mueller matrix for an elliptically birefringent single-mode fibre in the quasi-monochromatic case. Possible depolarization has been accounted for by means of the mutual correlation function |γ| between eigenpolarization modes. The polarization state in closed-loop fibre-optic helices has been studied experimentally under single- and dual-mode operation. It has been shown that the closed-loop set-up can be used for the development of compact fibre-optic sensors.     

A photonic crystal fiber sensor for pressure measurements

The pressure sensitivity of two photonic crystal fibers (PCFs) was measured. A PCF pressure sensor was then successfully developed with PCF PM-1550-01. The measurement results of the pressure sensor at three different temperatures are presented, and in the working region the maximum deviation is within 1% of the dynamic range of the sensor.     

Polarization analysis of LP01 and LP11intermodal interference in highly birefringent bow-tie optical fibers

A polarization analysis of bimodal highly birefringent fibers in which LP₀₁, LP₁₁, interference takes place is performed. The polarization state of the interference pattern is theoretically described in terms of recently proposed spatial Stokes parameters on the basis of coupled-mode equations and Jones matrix formalism. The general quasimonochromatic case is considered and depolarization as well as interference fading are accounted for. Special attention is paid to application of the results to fiber-optic sensors, and the basic schemes for the detection of the interference beat signal are discussed. The theoretical conclusions are supported by experiments in which the modal polarization and intermodal interferometric response to elongation of a bow-tie bimodal fiber is investigated. Measurements are carried out on both a separate fiber and on a multifiber assembly at various input conditions     

Interactions of Meibum and Tears with Mucomimetic Polymers: A Hint towards the Interplay between the Layers of the Tear Film

Recent clinical findings suggest that mucomimetic polymers (MMP) can alter not only the texture of the aqueous tear but also the spreading and structure of the tear film (TF) lipid layer, thereby allowing for their synchronized performance in vivo. Thus, we aimed to evaluate in vitro (i) the capability of pharmaceutically applicable MMP to ensure the formation of post-evaporative ferning patterns (a characteristic feature of the “healthy” tear colloid) and (ii) the MMP interactions with human meibum films accessed in the course of blink-like deformations via Langmuir surface balance and Brewster angle microscopy (BAM). Four MMP were used- hyaluronic acid (HA), cross-linked hyaluronic acid (CHA), carboxymethyl cellulose (CMC) and gellan gum (GG)- at the concentrations of 0.0001%, 0.001%, 0.01%, 0.05% and 0.1%. Significant differences were observed in the MMP fern formation capability: CHA (≥0.001%) > HA (≥0.01%) = CMC (≥0.01%) > GG (≥0.05%). All MMP affected the spreading of meibum, with BAM micrographs revealing thickening of the films. CHA was particularly efficient, showing concentration-dependent enhancement of tear ferning and of meibomian layer structure, surfactant properties and viscoelasticity. Thus, endogenous and exogenous MMP may play key roles for the concerted action of the TF layers at the ocular surface, revealing novel routes for TF-oriented therapeutic applications.     

A differential fiber-optic transducer for hydrostatic pressure measurement

A fiber-optic linear displacement sensor is developed to measure radial deformations in a free active element bulk-modulus transducer under high hydrostatic pressure. The response of the sensor was found to be practically linear within the range of 1000 bar and a 1.5% accuracy has been confirmed.     

Analysis of the polarization behavior of hybrid modes in highlybirefringent fibers

The polarization properties of hybrid waveguide modes in highly birefringent fibers are theoretically and experimentally investigated. The Jones spatial polarization matrix of the fiber for a hybrid mode is derived. Both monochromatic and quasimonochromatic cases are considered. The case of stress nonuniformities and its consequences to polarization preservation is addressed. The problems related to the polarization preservation along single- and two-mode fibers are discussed     

Low-noise bimodal all-fibre sensor using depolarized light

Abstract

A low-noise scheme for an all-fibre bimodal sensor is presented. Depolarized excitation of the sensor from a lower coherency source is used to eliminate polarimetric noises which inevitably arise due to polarizer/analyser and fibre-to-fibre misalignments. The sensor features simplicity and simultaneous detection of the X- and Y-polarized interference signals. Overall noise level as low as 0.8% is achieved.