Hello Steemit!!
Today I am writing my post regarding the second part of Optical Fibre Communication lessons. Hope it will be beneficial to my readers.
So without any further delay, let's visit the post to start learning.
Single and Multimode Fibers:
- Light propagated in optical fiber in form of modes.
- Spatial distributions of EM fields do not change with time.
No of Modes?
- V number (normalized frequency) define number of
possible modes for a fiber:
V= (2πa*NA) / λ
where a is radius of fiber, and λ is wavelength of light.
For single mode propagation, V<2.405.
Uniformly and Non-uniformly doped fibers.
Single Mode Fibers:
- With the primary degrees of freedom of core cladding
diameter and the difference of refractive indices between
them they can be optimized for attenuation and dispersion. - Light propagation can be studied using geometrical optics.
Multi Mode Fibers:
- Different modes can exist simulatenously on the same wavelength.
- Depending upon profile shape they can be:
Multimode Step Index
Multimode Graded Index - The core index decreases like a parabolic-like law from the axis to the core cladding interface.
- Designed to minimize the intermodal dispersion effect (without significantly reducing the numerical aperature or the coupled power).
Electromagnetic Waves propagating in an optical fiber consist of :
- TE Modes.
- TM Modes.
- EH and HE Modes.
- Helical EH and HE modes contain both axial electric and magnetic fields.
- The mode can be EH or HE depending upon which component contribute more to the axial direction.
Starting from Maxwell equations:
- Wave equation in cylindrical coordinates is derived.
- The wave equation can be exactly solved for uniformly cored fibers.
- The classification of type of solutions lead to TE, EH, or EH and HE modes.
- For graded index non-uniform core profiles, approximate methods can be used.
Hope the post was satisfactory and you all like the information provided in the article. Any queries or opinions you want to share are heartily welcome!!
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