Topic
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.
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01 Jun 1980
TL;DR: In this paper, the authors discuss methods for measuring the refractive index distribution in optical fibers and for predicting their impulse response and signal bandwidth from the measured profiles, and some attention is also given to preform and single-mode fiber profiling.
Abstract: The refractive index distribution in the core of a multimode optical-fiber waveguide plays an important role in determining the transmission properties of the guide. The closer the index profile is to the required ideal distribution, the greater the resulting information carrying capacity of the fiber. This review paper discusses methods for measuring the refractive index distribution in optical fibers and for predicting their impulse response and signal bandwidth from the measured profiles. Some attention is also given to preform and single-mode fiber profiling.
32 citations
TL;DR: In this paper, two routes can be considered for the elaboration of a single mode fiber: the first method consists in preparing a classical step index fiber (SIF) with a core-clad configuration.
Abstract: Chalcogenide glasses are known for their large transparency in the mid infrared, which includes the two atmospheric windows lying from 3–5 μm and 8–12 μm. Chalcogenide single mode fibers present numerous potential applications in the IR field, such as military countermeasures, LIDAR spectroscopy and spatial interferometry. Two routes can be considered for the elaboration of a single mode fiber. The first method consists in preparing a classical step index fiber (SIF) with a core-clad configuration. This procedure is based on two glass compositions (core and clad) with compatible thermal and optical properties and having a refractive index difference allowing the single mode propagation. The second route is based on the design of a microstructured optical fiber (MOF) in which the guiding function is ensured by the refractive index contrast between the core glass and the air contained in the capillaries surrounding the core. Two kinds of fibers exhibiting single mode propagation were fabricated; the first one is a SIF with a 22 μm core diameter and the second one is a three rings of holes MOF. The geometry of the MOF shows a d/Λ around 0.35 and a 40 μm core diameter. In both cases the optical losses in the 2 to 12 μm region were measured and compared.
32 citations
TL;DR: In this article, a method for determining the refractive index and thickness of a transparent film from measurements of transmittance at normal incidence is presented, which has been applied successfully to films of Ta2O5.
Abstract: A method in which the refractive index and thickness of a transparent film are determined simultaneously from measurements of transmittance at normal incidence is presented. This has been applied successfully to films of Ta2O5.
32 citations
TL;DR: In this paper, a photonic quasi-crystal fiber-based refractive index biosensor (PQF-RIBS) was proposed, which works based on the surface plasmon polariton.
Abstract: Using finite-element method, we propose a photonic quasi-crystal fiber-based refractive index biosensor (PQF-RIBS), which works based on the surface plasmon polariton. We determine the loss spectra for two different variations of the refractive index of analyte, $n_{a}$ . From the detailed numerical analysis, we find that the PQF-RIBS exhibits a maximum refractive index sensitivity of 6000 nm/RIU and a resolution of $1.6\,\, \times \,\,10^{-6}$ RIU when $n_{a}$ is increased from 1.45 to 1.46. Besides, this sensor does exhibit the negative refractive index sensitivity of −4000 nm/RIU and a resolution of $2.5\,\, \times \,\,10^{-6}$ RIU for a sensing range from 1.52 to 1.53. Furthermore, we carry out selective filling of liquid in the selective holes of the proposed biosensor for a sensing wavelength range from 900 to 1200 nm. Finally, we also study the influence of the structural parameters, namely, diameter of the core and diameter of the air holes in the cladding over the loss spectra of a fundamental mode for a particular $n_{a}$ of 1.47.
32 citations
TL;DR: When expected material dispersion effects were deconvolved from the output pulse spreading, the resultant pulse width was approximately 75 times less than the result expected for a comparable step-index fiber, which is the largest pulse width reduction reported yet.
Abstract: Dispersive differences between B2O3 and SiO2 constituents make nonparabolic profiles optimal equalizers of intermodal group delays in fibers with graded B2O3–SiO2 cores and uniform B2O3–SiO2 cladding. Pulse dispersion measurements were correlated with profile shapes in a systematic study of multimode fibers with near power law gradients. Far field spatial ray filters were used to diagnose impulse response shapes so that new fibers could be fabricated with closer-to-optimal profile gradients. One of the fibers had an α ≈ 1.77 power law exponent that was nearly optimal for λ = 907.5-nm wavelength and caused 2σ = 0.26-nsec/km full rms output pulse spreading. When expected material dispersion effects were deconvolved from the output pulse spreading, the resultant pulse width was approximately 75 times less than the result expected for a comparable step-index fiber. This is the largest pulse width reduction reported yet.
32 citations