Difference Between Step Index And Graded Index Optical Fiber Pdf

difference between step index and graded index optical fiber pdf

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In optical fiber, a step index fiber is a fiber characterized by a uniform refractive index within the core and a sharp decrease in refractive index at the core-cladding interface so that the cladding is of a lower refractive index. In a step index fiber, the light rays propagate in zig-zag manner inside the core. The rays travel in the fiber as meridional rays and they cross the fiber axis for every reflection.

The refractive index of the core is uniform and step or abrupt change selection from engineering. Ray paths are different so that rays arrive at different times. 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.

In its simplest form an optical fiber consists of a cylindrical core of silica glass surrounded by a cladding whose refractive index is lower than that of the core. Because of an abrupt index change at the core-cladding interface, such fibers are called step-index fibers. In a different type of fiber, known as graded-index fiber, the refractive index decreases gradually inside the core. This figure shows schematically the index profile and the cross section for the two kinds of fibers.

Geometrical-Optics Description of Step-Index and Graded-Index Optical Fibers

Definition : Graded Index fiber is another type of optical fiber in which the refractive index of the core is non-uniform. This non-uniformity is present because the refractive index is higher at the axis of the core and continuously reduces with the radial movement away from the axis. However, the refractive index of the cladding is constant in the case of graded index fiber. Hence the nature of the refractive index of the core is somewhat parabolic. Unlike graded index optical fiber, the step index fiber has a constant refractive index at the core as well as cladding. In this type of fiber, the light ray experiences refraction thus gets bent towards the core.

Step-Index Multimode Fiber vs Graded-Index Multimode Fiber

Difference between Step Index fiber and Graded Index fiber. The refractive index of the core is uniform throughout and undergoes on abrupt change at the core cladding boundary. The path of light propagation is zig- zag in manner. Attenuation is more for multimode step index fiber but for single mode it is very less. When a ray travels through the longer distances there will be some difference in reflected angles. Hence high angle rays arrive later than low angle rays causing dispersion resulting in distorted output. This fiber has lower bandwidth.

Multimode fiber can be divided into step-index fiber and graded-index fiber according to the fiber refractive index distribution. Since the two types of multimode fibers differ in working principles, they are used in different scenarios. Read through this post to get the details of the two in working principles and applications as well as their differences. In optical fibers , a step-index fiber is a fiber where a uniform refractive index exists within the core and a sharply decreased refractive index exists in the core-cladding interface because of the lower refractive index in cladding. Light entering the fiber at different angles of incidence will go through different paths. Although the incident lights propagate at the same speed simultaneously at the input, the time to reach the output of the fiber is different, resulting in a temporal dispersion called modal dispersion.

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Measurement of Differential Mode Attenuation in Graded-Index Fiber Optical Waveguides

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. The most common refractive index profile for a graded-index fiber is very nearly parabolic. The parabolic profile results in continual refocusing of the rays in the core, and minimizes modal dispersion. Multi-mode optical fiber can be built with either graded index or step index.

Modal dispersion speed of guided light changes with fiber cores refractive index. Farther the light goes from the centre of the fiber, the faster it is. Speed difference compensate for the longer paths followed by the light rays that go farthest from the centre of the fiber. This equalizing of transit times of different modes greatly reduces modal dispersion.

Difference Between Step Index Fiber And Graded Index Fiber (With Comparison Chart)

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STEP INDEX FIBER: The refractive index of the core is uniform throughout and undergoes on abrupt change at Chapter: Physics - Photonics and fibre Optics Difference between Step Index fiber and Graded Index fiber.

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