Step-index profile

About: Step-index profile is a research topic. Over the lifetime, 3104 publications have been published within this topic receiving 53199 citations.

A reflective optical fiber refractometer based on multimode interference

Abstract: A reflective multimode interference based-fiber optic sensor is described, aimed at measuring refractive index variations by means of intensity variation based on the fiber tip-interaction concept. The sensing head is a section of a multimode fiber, spliced to a single-mode fiber at the input end; its characteristics are studied when two multimode fibers, with distinct core diameters (viz. 50 and 105 μm), are considered. The multimode fiber end face is placed in contact with the liquid sample, so as to provide a refractive index measurement via variation in amplitude of the interference spectral peaks – which is essentially insensitive to temperature changes. Therefore, the proposed configuration permits measurement of refractive index variations free from system temperature cross-sensitivity effects. Resolutions of 2.2 × 10 −4 RIU and 3.8 × 10 −4 RIU, for multimode fiber tips with core diameters of 50 μm and 105 μm, respectively, could be achieved.

Microstructured optical fiber refractive index sensor.

Abstract: We describe a dual-core microstructured optical fiber designed for refractive index sensing of fluids. We show that by using the exponential dependence of intercore coupling on analyte refractive index, both large range and high sensitivity can be achieved in the one device. We also show that selective filling of the microstructure with analyte can increase the device sensitivity by approximately 1 order of magnitude.

On the determination of the refractive index of a fibre. II. Graded index fibre

Abstract: Two- and multiple-beam interference fringes are used to measure the refractive index of graded index fibres. A general expression considering the refraction of the beam by the graded index fibre has been derived, from which expressions for homogeneous and skin-core fibres can be obtained. Comparison between the results with the method used when neglecting refraction is dealt with using Philips, LDF (TM) optical fibres and drawn polypropylene. Considering the derived expressions in the refractive index determination gives a correction even when a matching liquid is used, this suggests that the refraction method should be used especially for graded index fibre.

Measurement of refractive-index profile and transmission characteristics of a single-mode optical fiber from its exit-radiation pattern

Abstract: A new exit-radiation pattern method for measuring the refractive-index profile of a single-mode fiber is proposed and used experimentally. In this method the profile is computed from the far-field exit-radiation pattern of the HE11 mode at the end of the single-mode fiber. This method can be applied to a cabled fiber, and the propagation constant, field profile, and group delay of the HE11 mode, and the single-mode limit can be obtained as well as the index profile. The principle, computer simulations, experimental setup, and experimental results are first described. The profile obtained shows a good agreement with that obtained from the interference fringe pattern measured before drawing the fiber. Computations of the group delay of the HE11 mode and the single-mode limit from the measured exit-radiation pattern are discussed.

Nondestructive refractive‐index profile measurements of clad optical fibers

Abstract: An interferometric method in conjunction with Abel inversion is used to precisely measure the index of refraction profile of clad optical fibers without perturbing them. The sample is immersed in index‐matching fluid, so that fiber index variations cause only small phase shifts for rays propagating perpendicular to the axis, making interferometric methods applicable.