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Multiple effective indices for a supposedly single mode step index fiber
Posted 2 ago 2010, 04:00 GMT-4 3 Replies
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Hi all,
I have recently started using Comsol for the modeling of light in waveguides. I started off with the modeling of light in a single mode, step index fiber using Rf module>>2D>Perpendicular wave>Hybrid mode waves>mode analysis to solve for the effective refractive index of the fundamental mode. However, the solver returns several values of which only one is the right one. Why did the solver return so many values and how do i pick the right one if i do not know how the fundamental mode looks like?
Thanks in advance.
I have recently started using Comsol for the modeling of light in waveguides. I started off with the modeling of light in a single mode, step index fiber using Rf module>>2D>Perpendicular wave>Hybrid mode waves>mode analysis to solve for the effective refractive index of the fundamental mode. However, the solver returns several values of which only one is the right one. Why did the solver return so many values and how do i pick the right one if i do not know how the fundamental mode looks like?
Thanks in advance.
3 Replies Last Post 13 lug 2011, 18:32 GMT-4
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Posted:
1 decade ago
This is how I attempt to pre-specify the eigenmode in 3.5a:
Solve->Solver parameters-> (select eigvalue solver) -> Number of effective mode indices (set how many you want) -> search for effective mode indices around: (set the search point)
The closer your search point to the index of the mode you are looking for, the higher the probability of finding that mode.
At the end of the day, there is just probability for us that Comsol will find exactly the mode we are looking for.
Solve->Solver parameters-> (select eigvalue solver) -> Number of effective mode indices (set how many you want) -> search for effective mode indices around: (set the search point)
The closer your search point to the index of the mode you are looking for, the higher the probability of finding that mode.
At the end of the day, there is just probability for us that Comsol will find exactly the mode we are looking for.
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Posted:
1 decade ago
By the way, if you are sure that theoretically there can't be more than one mode, then it is probably numerical junk.
Set the number of modes searched for to one, as I described earlier, and then if it still occasionally gives you junk then you probably need to increase mesh density.
Set the number of modes searched for to one, as I described earlier, and then if it still occasionally gives you junk then you probably need to increase mesh density.
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Posted:
1 decade ago
Hi there,
Can you please explain to me how to model the spatial modes & dispersion values in a
step index fiber with a simple construction? Thanks in advance.
Please feel free to contact me directly at my email address: ediskander@hotmail.com
Cheers,
-Ed
Can you please explain to me how to model the spatial modes & dispersion values in a
step index fiber with a simple construction? Thanks in advance.
Please feel free to contact me directly at my email address: ediskander@hotmail.com
Cheers,
-Ed