Home › Forums › FIBER › Can OptiFiber calculate the cladding mode of singlemode fiber or multimode fiber
- This topic has 9 replies, 6 voices, and was last updated 8 years, 10 months ago by
Rajguru M. Mohan.
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April 25, 2014 at 10:30 pm #11097
Lizzie Li
ParticipantHi,
I am really interesting in how to calculate the effective refractive index of cladding modes of single-mode fiber or multimode fiber. Of course, we can get these cladding modes by using matlab, but it is complicated.
I am wondering if OptiFiber can simulate or calculate the effective refractive index of cladding modes.
thanks.
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April 28, 2014 at 2:25 pm #11185
Tech Support
ParticipantYes, OptiFiber can calculate the modal index of cladding modes.
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April 28, 2014 at 8:45 pm #11199
Lizzie Li
ParticipantThanks for your attention.
But how can I do this calculation? Is there any example about this kind of simulation? I do not know how to set the parameters to calculate the modal index of cladding modes even though I have calculated the core modes index.
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April 29, 2014 at 10:53 am #11225
Steve Dods
ParticipantThis calculation is done the same way as any other mode. OptiFiber does not distinguish between cladding modes and core modes. It just finds modes. When you look at the mode field pattern, you may find the majority of power of some of them to be in the cladding, rather than the core. That’s a cladding mode.
In order for the cladding mode to appear, you need to make a layer in the simulation having the width of the cladding. You also need to include another layer outside the cladding, consisting of air or whatever material is found there. The refractive index of that outer layer is usually much smaller than glass, so a thin layer will suffice for the simulation.
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April 29, 2014 at 9:01 pm #11248
Lizzie Li
ParticipantThanks Steve Dods,
As you said, I have to look at the mode field pattern if I want to know whether a single mode is cladding mode or not. So if I want to calculate the refractive index of cladding modes of multimode optical fiber with hundreds of core modes, I should check out every single core mode to find the cladding modes, especially those modes which are close to cladding mode. Apparently this is not convenient.
I am thinking why OptiFiber does not add a new function which is capable of calculating and simulating the core modes and the cladding modes, respectively.
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April 30, 2014 at 9:05 am #11257
Steve Dods
ParticipantYou don’t need to observe the field pattern to determine if it is a cladding mode. There is another way to identify cladding modes. They are the ones whose modal index is smaller than the refractive index of the cladding layer. When the modal index is smaller than the cladding index, the mode number in the radial direction is a real number. Then the wavefunction follows harmonic Bessel functions and not exponential ones. That is why the field can persist to the cladding boundary. The modal field propagates out to the cladding boundary and it makes it a cladding mode.
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April 30, 2014 at 9:13 pm #11295
Lizzie Li
ParticipantThanks Steve Dods very much.
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May 5, 2015 at 6:38 am #20405
Jian Fang
ParticipantHi Lizzie:
You can add another circle with RI = 1.0 (air) outside the cladding.
Then you can see the calculated results of the cladding modes.
Cheers,
James Fang -
May 5, 2016 at 10:11 am #38889
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May 5, 2016 at 11:50 am #38894
Rajguru M. Mohan
Participant
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