RMS Roughness on a lens - POP/Sequential Mode

  • 3 June 2021
  • 1 reply

Dear Support,

I’m simulating, through POP/sequential mode, a system composed mainly by a DFB laser, as the source, and a microlens/mirror and evaluating its coupling to a standard SMF-28 fiber.

For my subsequent step, I need to take into account the surface roughness/imperfections of the microlens/mirror caused by the fabrication process.

The only parameter that I receive from my manufacturer is the rms of the surface, and I don’t know how I could properly implement it. I hope you could help me.

Thank you and looking forward to your answer.

Best regards,



Best answer by Sandrine Auriol 7 June 2021, 11:22

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Hi Andrea 

When tolerancing surfaces, we have an operand called TEZI that changes the surface into a Zernike Standard Surface. The TEZI operand specifies a RMS sag error. The coefficients of the Zernike are set so that they give the right RMS.

So I think you could use the same method in your case. If you want to have a look at how the software is doing it, you can run a tolerancing with TEZI and check a Monte Carlo file, or a sensitivity file by adding a SAVE operand in the tolerance data editor.

I have also copied a link that may help: How to use TEZI to tolerance for manufacturing-related surface sag error

Do not hesitate if you have any further questions.