Single Mode Step Index Optical Fiber

In fiber optic communication a single mode optical fiber is an optical fiber designed to carry only a single mode of light the transverse mode.

Single mode step index optical fiber.

Multimode graded index fiber. Single mode step index fiber. The step index profile is used in most single mode fibers and some multimode fibers. Examples of standard core and cladding diameters 2a 2b are 8 125 50 125 62 5 125 85 125 or 100 140 units of µm.

The step index cable cross section is depicted in the figure 2. Single mode step index optical fiber structure and plot it is also a step index fibre but due to its small diameter of the core 2 10 micrometre it can support only single mode of light. In single mode step index fiber there is no distortion. There are several causes of attenuation in an optical fiber.

The diameter of the core is between 50 200µm in the case of multimode fiber and 10µm in the case of single mode fiber. Therefore this type of step index fiber is known as single mode step index fiber. This is the case in. These modes define the way the wave travels through space i e.

Typical values range from 10 db km for step index fibers at 850 nm to a few tenths of a db km for single mode fibers at 1550 nm. Waves can have the same mode but have different frequencies. In single mode light takes single path through the fiber core. Modes are the possible solutions of the helmholtz equation for waves which is obtained by combining maxwell s equations and the boundary conditions.

Rayleigh scattering microscopic scale variations in the index of refraction of the core material can cause considerable scatter in the beam leading to substantial losses of optical power. The bandwidth is about 50 mhz km for multimode step index fiber whereas it is more than 100 mhz km in case of single mode step index fiber. A step index fiber is characterized by the core and cladding refractive indices n1 and n2 and the core and cladding radii a and b. Step index means sharp step in the index of refraction between core and cladding interface.