How is graded index fiber made ?

[Aagno3]

TL;DR

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Hey everyone .
I was recently studying about fiber optics and it had a little to do with graded index fiber. And its given that the refractive index of the core changes from the axis to the cladding .
So , my question is , how is that fiber designed ? It must be quite complicated to carefully vary the refractive index . And if so, is it really the right choice ? Because it needs lots and lots of care, so wouldn't it be better to use some other mode , or maybe single index fiber instead ?

 

[Cryo]

https://www.fibercore.com/expertise/fiberpaedia/graded-index-mm-fiber
"In the fiber manufacturing process, this graded refractive index profile is usually achieved by doping the silica core with a graded level of germanium. "

Basically you add some atoms to the main glass material, which allows to very slightly change it's index. Specifics of how it is done is not my area of expertise.

 

[sophiecentaur]

Summary: ...

It must be quite complicated to carefully vary the refractive index

If you started by making a wide bar of the material - built up in layers to the required formula - and then draw it out (like a stick of seaside rock) you would get a thin enough fibre with the same gradient as the original bar. That's a pretty standard way of producing lengths of many kinds of thin fibres with ductile materials.

Summary: ...

so wouldn't it be better to use some other mode

What are the advantages of a single mode fibre (look it up)? Can you find another mode that performs as well over long distances?