Home Forums FIBER Few Mode Fiber

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    • #12282
      Abdallah Ismail
      Participant

      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,

    • #12287
      Damian Marek
      Participant

      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

    • #12294
      Abdallah Ismail
      Participant

      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,

      • #12304
        Damian Marek
        Participant

        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!

    • #12296
      Abdallah Ismail
      Participant

      The attached file

      Attachments:
    • #12353
      Abdallah Ismail
      Participant

      It’s working well.
      Thank you very much.

    • #29870
      Aadil Raza
      Participant

      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.

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