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.

Measurement of the Refractive Index of Glass Fibers by the Christiansen-Shelyubskii Method

Abstract: The Christiansen principle was employed to measure the refractive index of borosilicate glass fibers (13–41 μm diameter) over the visible range. The refractive index for glass fibers at 589.3 nm was measured by temperature and wavelength scan and values obtained were in close agreement. The refractive index for glass fibers as a function of wavelength was measured to an accuracy of < 10−4. The uniformity of the refractive index for a bundle of fibers of slightly different diameter was calculated using the modified Shelyubskii method and compared to experimental values. Theoretical calculations of the transmission by the present work suggest that, for high optical clarity and transmission of Christiansen cell (or transparent composite consisting of glass fiber and polymer), the refractive index must be controlled to the fifth decimal place. For example, the maximum transmission of a fiber/liquid mixture cell at 25°C can increase from 89 to 97% when the standard deviation is reduced from 13 × 10−5 to 9 × 10−5.

Multimode fiber having a refractive index profile

Abstract: The present invention relates to a multimode fiber having a refractive index profile, wherein the area surrounding the center of the fiber has a refractive index profile such that the responses of a DMD (Differential Mode Delay) measurement carried out on a fiber having a length of at least 300 m are obtained without any pulse splitting occurring in the center of the fiber.

Design of a Wavelength Selective Medium by Graded Index Photonic Crystals

Abstract: In this paper, a novel technique for spatial wavelength division using graded index photonic crystals (GRIN PCs) is proposed. The designed GRIN PC structure with hyperbolic-secant refractive index profile at a fixed frequency generates spatial shifts in the longitudinal direction with respect to different incident wavelengths so that distinct path trajectories are followed by propagating beams through the graded medium. Due to gradual variation of the refractive index profile (incremental decrease), an incident beam with an appropriately selected wavelength undergoes continuing refraction and finally, total internal reflection (TIR) occurs at the turning point. Due to the wavelength-dependency characteristic of GRIN PCs, TIR takes place at different positions for different wavelengths and thus, light wave emanates from the GRIN medium at different locations with different exit angles. It is revealed that the designed structure can work in three distinct frequency regimes and is able to separate a certain number of incident beams with different wavelengths, viz. from three to seven different wavelengths. This condition enables the deployment of the GRIN PC configuration for the design of wavelength selective media.

Pseudo slant fiber bragg grating, multiple series fiber bragg grating, optical fiber type coupler and optical connector

Abstract: An optical fiber (4) having a clad diameter of 125 µm is made by adding Ge to a core (41) having a core diameter of 8 µm and a relative index difference of 0.3% and two refractive index grating parts (41a, 41b) having a slant angle of 2~ are formed in series in the optical fiber (4) by a phase mask method using KrF excimer laser (.lambda.=248 nm). The central period (2.LAMBDA.) of the phase mask of a chirped grating is 1140 nm, the chirp rate (C) of the period is 1.2 nm/mm, the length (G) of the first and second index grating parts (41a, 41b) is 8 mm, the effective refractive index of the first and second index grating parts (41a, 41b) is 1.447, the refractive index modulation is 3×10-3, and the gap between the first and second index grating parts (41a, 41b) is 1 mm.