Index profile is the refractive index distribution across the core and the cladding of a fiber. Click the fiber profile icon in the navigator pane. Some optical fiber has a stepindex profile, in which the core has one uniformlydistributed index and the cladding has a lower uniformlydistributed index. For simpler cases, the rp fiber calculator software is sufficient definition. Optical fibers are classified into two types based on the refractive index profile of core and cladding. Osa singlemodefiber refractiveindex profile measurement. The induced refractive index profile variation of the bent optical fiber, for parallel and perpendicular components of the light beam, is calculated considering the refraction of the light beam traversing the fiber. When the core radius of a test fiber is only a few times larger than the laser beam spot size, the reflected power distribution does not indicate the refractive index correctly. In this approach the fiber is divided into layers and slabs, simultaneously. Refractive index dispersion and related properties in. Bent induced refractive index profile variation and mode.
In the case that the refractive index changes in a step between the core and the cladding. For this refractive index profile structure, the sum of the material and waveguide dispersions is zero near 0nm. Refractive index profile an overview sciencedirect topics. These fibers are more difficult to make because of the complex refractive index profile in the core. Sokkar and others published bent induced refractive index profile variation and mode field distribution of stepindex multimode optical fiber find, read and. Optical fibers are classified into two types based on the refractive index profile of core. Sep 21, 2017 therefore this type of step index fiber is known as single mode step index fiber. 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. Fiber geometry parameters and mode field diameter at userspecified wavelengths can be calculated from the s14 index profile data. The refractive index profile may be defined as, nr n r aug 17, 2018 in particular. In a graded index fiber the velocity increases with distance from the core. Pdf measuring the refractiveindex profile of optical fibers by the. It is a measure of the decay of signal strength, or loss of light power, that occurs as light pulses propagate through the length of the fiber.
Profiling enables the spatial variations of the refractive index to be measured and hence provides information such as core and cladding diameter, concentricity and numerical aperture na. The refractive index of the core of step index fiber is constant throughout the core. The refractive index profile of an optical fiber is characterized by a radially. Fused silica optical fibers with graded index nanostructured core. The variations in the core refractive index are due to the introductions of dopants such as geo 2 and f, which increase and decrease the refractive index, respectively. For all considered fiber designs, the refractive index outside. Novdec 2008 numerical aperture of fiber is given by na n1. Fimmwave allows you to define the radial refractive index profile and calculate the modes of a step index fibre extremely easily. A graded index fiber has a core with a parabolic refractive index profile which has a.
The optical fiber with a core of constant refractive index n1, and a cladding of a slightly lower refractive index n2 is known as step index fiber. Step index fibers have a uniform core with one index of refraction, and a uniform cladding with a smaller index of refraction. Determination of optical fiber refractive index profiles by a nearfield scanning technique article pdf available in applied physics letters 285. Some optical fiber has a step index profile, in which the core has one uniformlydistributed index and the cladding has a lower uniformlydistributed index. Pdf a new measurement system has been developed that simply determines the refractiveindex profile of any optical fiber by analyzing the propagation. Types of optical fiber learning outcome epg pathshala. The spatial resolution is high, and the accuracy is good when the fiber diameter and the refractive index variation are.
The fiber profile dialog box helps you design the refractive index profile of the fiber. Refractive index a property of optical materials that relates to the velocity of light in the material. Estimate the numerical aperture for the fiber when the core index is 1. When plotted on a graph as a function of distance from the center of the fiber, the index of refraction resembles a step function. They get their name from the step shaped refractive index profile between the fiber core and fiber cladding. Guide modes of stepindex and other fibers can be calculated and optimized with the rp fiber power software. Please specify the following parameters when ordering. Further in the refractive index tab you can enter the index range, i. Rp photonics encyclopedia stepindex fibers, optical fiber. Graded index fiber is of only one type,that is multi mode fiber. Step index fibres have a very simple refractive index profile see fig.
Expired lifetime application number ep19840104408 other languages german. The s14 refractive index profiler provides accurate, precise characterization of the refractive index profile of singlemode, multimode, and specialty fibers using the rnf refracted near field technique. In this paper, observation of mode profiles and calculation of modal power of different. Pdf determination of optical fiber refractive index. Pdf refractiveindexprofile determination of singlemode optical. Measuring the refractiveindex profile of optical fibers by the claddingmode nearfield technique article pdf available in optics letters 129. The refractive index profile of an optical fiber is characterized by a radially varying refractive index n r that is normalized to the cladding index nc by.
Optical fiber tutorial optic fiber communication fiber. Having a basic understanding of the guiding properties of optical fibers and recognizing their. The step index profile is used in most singlemode fibers and some multimode fibers. Although the step index profile is mathematically very simple, it can be somewhat problematic in numerical simulations of beam propagation.
T his bec ause th er f c tive po ile or ype of i er makes s nge core cladding interface. A multimode step index fiber with a core diameter of 80. A refractive index profile is the distribution of refractive indices of materials within an optical fiber. The refractive index profile and ray transmission in a multimode graded index fiber. A multimode graded index fiber with a parabolic index profile core is illustrated in figure 12. A matchedclad single mode step index fiber has a core of radius a and a constant refractive index n 1. The refractive indices in the core and cladding are constant.
In a gradedindex fiber the velocity increases with distance from the core. The step index profile corresponds to a powerlaw index profile with the profile parameter approaching infinity. Importing a refractive index profile from a profiler. The proposed method is applicable to an arbitrary profile and is nondestructive. Mode analysis of different step index optical fibers at.
The optical properties of the fiber material which is usually fused silica. Bc0614504 ofs quad fiber cable, stepindex, heavy duty. For example, for a simple stepindex fiber, take a single core segment and choose a step profile. Some optical fiber has a step index profile, in which the core has one uniformly distributed index and the cladding has a lower uniformly distributed index.
Measurement of refractive index profile of optical fibres ufe. Stepindex fibres have a very simple refractiveindex profile see fig. Graded index fibers will have a larger bandwidth compared to the step index multimode fibers up to mhz. The waveguide effect comes from the fact that the core is surrounded by a region with lower refractive index. The waveguide dispersion can be influenced to a great extent by changing the refractive index profile structure. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed. Geometry, refractiveindex profile, and typical rays in. Ep0126304b1 a single mode lightguide fiber having a. In a gradedindex fiber the velocity increases with distance from the core axis since the refractive index decreases. Pdf a new technique is presented for determining the refractiveindex profile of a singlemode optical fiber. For all considered fiber designs, the refractive index outside the core equals n2. Pdf measuring the refractiveindex profile of optical. The refractive index of the core of the graded index fiber is maximum at center,core and then it decreases towards corecladding interface. Graded index fiber in step index fiber, core has the constant refractive index n2 as shown in figure 7a.
This paper describes a new method the scatteringpattern method for determining the refractive index profile in an optical fiber from its scattering pattern for a normally incident laser beam. Bc0359710bl ofs simplex fiber cable, stepindex, plenum rated, polyethyleyne jacket ofs simplex fiber cable, 200230 m stepindex plenum rated, 2. Although rays of greater inclination to the fiber axis must travel farther, they travel faster, so that the travel times of the different rays are equalized. Since it is a type of step index fiber, therefore the refractive index of this optical fiber makes step sudden change at the core cladding interface. Air serves as the cladding in the simple glass tube example.
Modal dispersion can be reduced by grading the refractive index of the fiber core. In multimode step index fiber core refractive index is constant therefore all modes have same velocity but travel different length this causes dispersion. Jul 16, 2016 for step index 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 fibers. Bc0359710bl ofs simplex fiber cable, stepindex, plenum. Attenuation loss is a logarithmic relationship between the optical output power and the optical input power in a fiber optical system. These graded index multimode fibers are mainly used in lans local area networks. When the profile type is refractive index the dialog. Other optical fiber has a gradedindex profile, in which the refractive index varies gradually as a function of radial distance from. Optical fibers are therefore classified as stepindex or gradedindex, and multimode or singlemode, as illustrated in fig. You can conveniently define the fibre profile via the thickness and the refractive indices of the concentric shells. You can see the image shown above, how a single mode of light is propagating through the core of the optical fiber. The waveguide effect comes from the fact that the core is surrounded by a region with lower refractiveindex.
The properties of both single and multimode fibres are determined by the refractive index profile of the fibre. In multimode step index fiber core refractive index is constant therefore all modes have same velocity but. The core and the cladding regions feature homogenous materials with a constant refractive index each. Rp photonics encyclopedia stepindex fibers, optical. A new technique for measuring the refractive index profile of singlemode fibers based on the reflection method is described, and experimental results are demonstrated. Step index fibers are used for the transmission of laser power in sensor technology, for industrial applications, and in medical technology. A cladding of slightly lower refractive index surrounds the core. Modes of optical fibers singlemode and multimode fiber. The refractive index of a typical single mode fiber is a step index profile with a refractive index difference delta. Fiber laser, effective refractive index, evanescent field. The ability to shape the index profile of optical fibers holds the key to fully flexible engineering of their optical properties and future applications.
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