Can OptiFiber calculate the cladding mode of singlemode fiber or multimode fiber

[Lizzie LiParticipant]

Hi,

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.

[Tech SupportParticipant]

Yes, OptiFiber can calculate the modal index of cladding modes.

[Lizzie LiParticipant]

Thanks 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.

[Steve DodsParticipant]

This 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.

[Lizzie LiParticipant]

Thanks 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.

[Steve DodsParticipant]

You 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.

[Lizzie LiParticipant]

Thanks Steve Dods very much.

[Jian FangParticipant]

Hi 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

[umer ashraf waniParticipant]

Real Fiber Sample

Dispersion Shifted Fiber

[Rajguru M. MohanParticipant]

Hi,
I suggest you to visit these links:

Single Mode Fiber

Fiber Propagation Modes

Thanks,

+3