Few Mode Fiber

[Abdallah Ismail]

Dear all,
I designed Few Mode fiber through Optifiber and i calculated the resulting modes and they were 4 modes LP01,LP02,LP11 and LP21
then i generated “.dat” to use it in optisystem But when i tested the designed fiber in optisystem using (spatial CW laser , Measured index multimode fiber and spatial visualizer),The spatial visualizer is given only two modes LP01 and LP02.
Can anyone help me to know where the problem?
Also the LP11 is two modes LP11a and LP11b can i use the two generated modes?
Best Regards,

[Damian Marek]

Hi Abdallah,

The problem here could be that the spatial CW laser is not exciting the higher order modes because it not have the right generated modes. Try playing with these settings to excite the fiber modes.

From my understanding the LP11a and LP11b modes are just different polarizations of the same mode. If you inject light that is both x and y polarized you should detect these different modes at the output.

Regards

[Abdallah Ismail]

Thanks Damian,
I didn’t get that point,please add more details. I tried to change the setting (Spatial effects).Please check the attached file.
the generated modes is LP01,LP02,LP11 but still LP21 is not generated.
can you help me to generate all modes and how i control that.
Best Regards,

[Damian Marek]

Hi Abdallah,

Thanks for the project file. Just from looking at the output of the Parabolic fiber though I can see that you are indeed generating many modes, however I do not see a clear LP21 mode at the output of the parabolic fiber.

Here’s what I suggest:

1) In the LED change the mode type to Laguerre-Gaussian.

2) Change the Mode X (m,n) index array to include 2,1, so for example write “0 1, 0 2, 1 1, 2 1”. This should generate LP01, LP02, LP11 and LP21.

Hope this helps, if it doesn’t please also include your fiber data file, so I can look at it!

[Abdallah Ismail]

The attached file

[Abdallah Ismail]

It’s working well.
Thank you very much.

[Aadil Raza]

In the project discussed above. I have one query.

I have used the same FMF design made by Abdallah mentioned above.

Why I am not getting the good power of each mode (LP01, and two LP11 degenerated modes) after Power splitter using mode selector. I mean if you compare powers at laser output and at fiber output and finally after mode selector. why the power substantially reduces specially after fiber and mode selectors ? please see attached files for detail.

[Author]

Posts