Group index in fibers

[sudipkc]

Can I get group index in fiber for a single wavelength? I am using * step_index_fiber.lms. How to get rid of group index for this file?

[kjohnson]

Hello @sudipkc,

The group index is calculated automatically for each mode when the modes are found. You can see them in the Eigensolver Analysis window results:

If you are using an older version of our software you may have to update your software to see this column.

[sudipkc]

Hi @kjohnson

Thanks for your response. I wanted to know how this group index is being calculated at a single frequency as it requires more than one frequency value.
ng(w)=n(w)+wdn/dw.

[kjohnson]

Hello @sudipkc,

I’m not sure of the exact calculation used, but this is discussed in the topic New automated group index calculation in eigenmode solver of MODE Solutions . From this topic:

@jpond

The usual approach to calculate the group index is to calculate n(f) and then take the derivative, and this is the approach used in the FDE solver of MODE Solutions when you do a frequency sweep. This allows you go calculate ng(f) over some bandwidth and also calculate dispersion. However, there is enough information in the modes at a single wavelength to calculate the group index, and it is this calculation that we implemented here to enable this feature. The agreement between both approaches is excellent.

[sudipkc]

Thanks a lot @kjohnson

[kjohnson]

You’re welcome @sudipkc!