Step index and graded fibers pdf

Pdf effects of graded order on the characteristics of the. These fibers are available with acrylate coatings and also high performance polyimide, aluminum, and gold coatings that allow. The refractive index of core is nonuniform, the refractive index of core decreases parabolically from the axis of the fiber to its surface. Classification of optical fibers step index graded index. The step is the shift between the core and the cladding, which has a lower refractive index. The number of modes in the fiber is about half that of. As a result, graded index fibers have bandwidths which are significantly greater than step index fibers, but still much lower than singlemode fibers. Schematic diagram showing a multimode step index fiber, multimode graded index and single mode step index fiber, and the pulse broadening due to intermodal. A multimode fiber where the core is all the same index of refraction.

Step index fibers have a uniform core with one index of refraction, and a uniform cladding with a smaller index of refraction. Multimode optical fiber can be built with either graded index or step index. The advantage of the multimode graded index compared to the multimode step index is the considerable decrease in modal dispersion. Compare the numerical apertures na of a stepindex fiber with n11. Rp photonics encyclopedia v number, normalized frequency. Aluminum coatings not only enable the fiber to be used in applications of a wider temperature range, but also offers excellent protection at extended stress levels. The refractive index of the core is uniform and step or. This page describes single mode step index fiber and multimode graded index fiber. Structure, basics and types of optical fibers step index.

The refractive index of core is nonuniform, the refractive index of core decreases parabolically from the axis of the fibre to its surface. Pdf the properties of modes that propagate through the step index fiber were perfectly analyzed. Graded index fiber is of only of one type that is multi mode fiber. M u l t i m o d e s t e p i n d ex f i b r graded index fiber single mode step index fiber a b c 10 gm 125 gm. Modal dispersion can be further decreased by selecting a smaller core size less than 510. Graded index or step index multimode fiber fiber optic. These fibers are available with acrylate coatings and also high performance. A step index fiber is characterized by the core and cladding refractive indices n 1 and n 2 and the core and cladding radii a and b. The stepindex profile corresponds to a powerlaw index profile with the profile parameter approaching infinity. Step index fibers are used for the transmission of laser power in sensor technology, for industrial applications, and in medical technology. Types of optical fiber learning outcome epg pathshala.

In addition, multimode fibers are described using a system of classification determined by the iso 11801 standard om1, om2, and om3 which is based on the modal bandwidth of the multimode fiber. Within the multimode fiber choices, the degree of refraction change between the core and the cladding varies between graded index and step index. Jul 16, 2016 as a result, gradedindex fibers have bandwidths which are significantly greater than stepindex fibers, but still much lower than singlemode fibers. It remains constant throughout the cladding part of optical fiber. For linearly polarized waves in graded index fibers the scalar wave equation is effective. Optical fibers are classified into two types based on the refractive index profile of core and cladding. The relative gain of each stokes mode is calculated by considering the overlap the various pump and stokes modes of the fibers. Beam cleanup via stimulated raman scattering in multimode fibers is modeled by numerically considering the competition between the stokes modes of graded index and step index fibers. Here is the comparison between step index and graded index fibres on the basis of various parameters like basic structure, working principle, types, refractive index profile, propagation of light inside fibers, dispersion in optical fibers, advantages and disadvantages 1. Pdf design of mode scramblers for stepindex and gradedindex. Design of mode scramblers for stepindex and gradedindex plastic optical fibers article pdf available in journal of lightwave technology 233. We present numerically these issues in a gradedindex and stepindex multimode fibers and provide a first look at the complex spatiotemporal dynamics of similariton pulses. The fiber is used in applications requiring a wide bandwidth and low model dispersion. The parabolic graded index fibers were also analyzed.

The v number determines the fraction of the optical power in a certain mode which is confined to the fiber core. The most common refractive index profile for a graded index. Some popular fiber sizes the transition of the optical parameters from the core to the cladding can be discontinuous step index fiber or smooth graded index fiber. As a result, gradedindex fibers have bandwidths which are significantly greater than stepindex fibers, but still much lower than singlemode fibers. Pure fused silica step index multimode fibers simm, opti mised for applications in the uvvis and visir wavelengths.

Multimode stepindex fibers multimode gradedindex fibers. The main application for gradedindex fibers is in mediumrange communications, such as local area networks. From the example studied before, we have a 10km graded index fiber with a core. The stepindex profile is used in most singlemode fibers and some multimode fibers. Spatiotemporal evolutions of similariton pulses in. Step index multimode optical fibers newport corporation. It is maximum at the core axis and then it decreases generally parabolically with increasing distance from the core axis. Direct numerical integration of the wave equation is used to establish the validity of approximating the fundamental mode of gradedindex fibers by a gaussian function. Sep 19, 2015 there are two types of optical fibers depending on the refractive index of core and cladding are available. There are two types of optical fibers depending on the refractive index of core and cladding are available.

The v number is a dimensionless parameter which is often used in the context of stepindex fibers. An explanation of srs beam cleanup in gradedindex fibers. In a graded index fiber the velocity increases with distance from the core axis since the refractive index decreases. Some popular fiber sizes the transition of the optical parameters from the core to the cladding can be discontinuous stepindex fiber or smooth gradedindex fiber. The refractive index of the core is uniform and step or abrupt change in refractive index takes place at the interface of core and cladding in step index fibres. Suitable for light wave communication links and local area networks carrying voice, video and data. Sep 03, 2011 the refractive index of the core of the graded index fiber is maximum at the center of the core and then it decreases towards corecladding interface. A stepindex fiber is characterized by the core and cladding refractive indices n 1 and n 2 and the core and cladding radii a and b. Step index fiber is a fiber in which the core is of a uniform refractive index and there is a sharp decrease in the index of refraction at the cladding. Jul 16, 2016 as a result, graded index fibers have bandwidths which are significantly greater than step index fibers, but still much lower than singlemode fibers. For a stepindex fiber both single mode and multimode optical fibers, the refractive index of the core is uniform throughout the cladding region and undergoes an abrupt change at the corecladding boundary. Pdf design of mode scramblers for stepindex and graded.

The refractive index profile and ray transmission in a multimode graded index fiber. Step index and graded index fiber optical fiber refractive index. Geometry of an optical fiber, showing core, cladding, and jacket. Step index plastic optical fiber perfluorinated gradedindex polymer optical fibers gipofs combine high data transmission rates and low attenuation in the commercially desirable 8500nm range. Graded index fiber based on the number of modes of transmission, optical fibers are classified into two categories i. This indicates that in step index, core and cladding have their own constant index of refractions n1 and n2 respectively. Graded index or step index multimode fiber fiber optic solution. Stepindex fibers are used for the transmission of laser power in sensor technology, for industrial applications, and in medical technology.

For singlemode fibers, that fraction is low for low v values e. Graded index fiber is a type of fiber where the refractive index of the core is lower toward the outside of the fiber. Mode competition in a gradedindex fiber favors the lp01 stokes mode while. Step index means sharp step in the index of refraction between core and cladding interface. Jan 22, 2019 in this video, i have covered optical fibers with following outlines. Difference between step index fiber and graded index fiber. They get their name from the step shaped refractive index profile between the fiber core and fiber cladding. Gipofs offer a direct replacement and a low cost alternative to traditional glass. Graded index optical fiber in step index optical fiber. The refractive index of the core of the step index fiber is constant through out the core. Stepindex fibers have a uniform core with one index of refraction, and a uniform cladding with a smaller index of refraction. It is customary in the theory of optical fibers to make the weakly guiding approximation n. In this video, i have covered optical fibers with following outlines. Gradedindex multimode optical fibers, optimized for signal transmission at 850 and 0 nm, are available with 50125, 62.

The path followed by the light in a fiber is called the mode. The results showed that the similariton pulses can be generated in both multimode fibers. Spatiotemporal evolutions of similariton pulses in multimode. Fiber optics gradedindex polymer optical fiber gipof. A multimode or singlemode optical fiber with a uniform refractive index throughout the core. Mode competition in a graded index fiber favors the lp01 stokes mode while mode. It compares both step index and graded index fibers. Multimode fibers may be constructed with either graded or stepindex profile.

Gold coatings not only enable the fiber to perform in challenging applications, but also in a wider temperature range than conventional polymer coatings. Index of refraction is maximum at the center of the core. For a step index fiber both single mode and multimode optical fibers, the refractive index of the core is uniform throughout the cladding region and undergoes an abrupt change at the corecladding boundary. What is the difference between step index and graded index. It leads to the concept of linearly polarized modes. In fiber optics, a graded index is an optical fiber whose core has a refractive index that decreases with increasing radial distance from the optical axis of the fiber because parts of the core closer to the fiber axis have a higher refractive index than the parts near the cladding, light rays follow sinusoidal paths down the fiber. We present numerically these issues in a graded index and step index multimode fibers and provide a first look at the complex spatiotemporal dynamics of similariton pulses. Firstly an xdirection linearly polarized wave of the form is assumed. Step index fibers obtain their name from this abrupt change called the step. Optical fibers are therefore classified as stepindex or gradedindex, and multimode or singlemode, as illustrated in fig. While in case of graded index fibers, refractive index of the core is nonuniform. Step index and graded index fiber free download as powerpoint presentation.

Air serves as the cladding in the simple glass tube example. Multimode step index fibers multimode graded index fibers. Pdf equilibrium modal power distribution measurement of. The paper presents and compares the far field modal power distributions for i 2 km and 3 km stepindex multimode hard plastic cladding fibers, hpcf, simmf with 200 m silica core diameter, 0. The refractive index of the core of the graded index fiber is maximum at the center of the core and then it decreases towards corecladding interface. In a graded index fiber the velocity increases with distance from the core. An explanation of srs beam cleanup in gradedindex fibers and. Structure, basics and types of optical fibers step index and. Comparative investigation of graded index optical fiber. It bends the rays inward and also allows them to travel faster in the. They get their name from the stepshaped refractiveindex profile between the fiber core and fiber cladding.

Graded index fiber in step index fiber, core has the constant refractive index n2 as shown in figure 7a. As we have discussed in the earlier article about the light propagation through an optical fiber after total internal reflection. Beam cleanup via stimulated raman scattering in multimode fibers is modeled by numerically considering the competition between the stokes modes of gradedindex and stepindex fibers. Stepindex pmma fibers and their applications intechopen. We show that the fundamental modes of fibers, whose index profile can be expressed as a power law, are indeed very nearly gaussian in shape that is probably also true for gradedindex fibers with convex profiles other than a. Multi mode graded index n 1 n 2 the graded index reduces modal dispersing to 1nskm or less. Gaussian approximation of the fundamental modes of graded. A multimode graded index fiber with a parabolic index profile core is illustrated in figure 12. In a gradedindex fiber the velocity increases with distance from the core. When plotted on a graph as a function of distance from the center of the fiber, the index of refraction resembles a stepfunction. At the core cladding interface there is sudden decrease in the refractive index from n2 to n1. Stepindex fibers obtain their name from this abrupt change called the step.

The step index cable cross section is depicted in the figure2. Fiberguides agi fibers feature a graded index profile instead of a step index profile. Number of modes for step index fiber n v 2 2, where v is cut off frequency or normalized frequency or v number. Graded index fiber single mode step index fiber 125 micron. There are two methods to classify fiber optic cables. It simplifies the characteristic equation for the modes. When plotted on a graph as a function of distance from the center of the fiber, the index of refraction resembles a step function. Based on above, there are three types of fiber optic cable. In multimode step index fiber core refractive index is constant therefore all modes have same velocity but.