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Confinement losses in soft glass step-index fibers. Comparison with published results

Posted 25 nov. 2014, 04:04 UTC−5 Version 4.4 3 Replies

Bernd Mueller
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Dear community,

I am currently looking into the confinement losses with respect to wavelength for different fiber types: SIF, PCF, ... . To check my models for the simplest type (SIF) I found a publication from Kubat et al., "Mid-infrared supercontinuum generation to 4.5 um in uniform and tapered ZBLAN step-index fibers by direct pumping at 1064 or 1550 nm ," J. Opt. Soc. Am. B (2013) who showed the confinement losses for a ZBLAN fiber accross a wavelength range from 1 to 5 micron for different core diameters. I attached an adapted graph from the paper as Confinement losses.png below.
I took the Sellmeier coefficients from another paper and used a cylindrical PML to account for confinement losses. The simulation runs fine, the dispersion curve determined from the effective refractive index is the same as determined from the eigenvalue equation, but the confinement losses in z-direction (emw.dampzdB) does not correspond to the one in the paper. My confinement loss (in the model for 4 micron diameter) sets in roughly one micron later than in the publication. As they also used COMSOL and have more experience with the software I guess I have the suspicion that I did something wrong. My first thought that sth. went wrong with the PML [does the width actually haven an influence?], but I am not sure. Does someone have an idea? As the model was too large (even without mesh) I uploaded it here: www.dropbox.com/s/yn815et2wpw04qz/SIF-ZBLAN1.mph?dl=0

Thank you very much in advance,
Bernd

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3 Replies Last Post 8 juin 2016, 16:00 UTC−4
Charles Farley
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Posted: 10 years ago 25 nov. 2014, 05:44 UTC−5
Dear Bernd,

I think I had a similar problem recently and might have a fix for you. Unfortunately, I can't download your file.
You can easily compress the file size by pressing Main Menu Bar > Study and then "Delete all Solutions".
Feel free to send this compressed version here and I'll have a look.

Best regards
Charly
Dear Bernd, I think I had a similar problem recently and might have a fix for you. Unfortunately, I can't download your file. You can easily compress the file size by pressing Main Menu Bar > Study and then "Delete all Solutions". Feel free to send this compressed version here and I'll have a look. Best regards Charly
Bernd Müller
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Posted: 10 years ago 26 nov. 2014, 10:46 UTC−5
Hi Charly,

thank you very much for your reply. I am travelling and something is wrong with my VPN and cannot access the COMSOL software. I will post the mph-file as soon as I am back. Just out of curiosity if it is easy to explain: what had to be fixed in your case?

All the best,
Bernd
Hi Charly, thank you very much for your reply. I am travelling and something is wrong with my VPN and cannot access the COMSOL software. I will post the mph-file as soon as I am back. Just out of curiosity if it is easy to explain: what had to be fixed in your case? All the best, Bernd
Steffen Wittek
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Posted: 8 years ago 8 juin 2016, 16:00 UTC−4
That sounds like an interesting question. I tried it as well, but also got results that were off by quite a lot from the publication. The losses are way higher and also follow a different shape for higher wavelengths. The attached plot is for a core diameter of 3 um. If you are still around Charles, would you mind having a look at the attached mph-file?

I ran a parametric sweep between 1 and 5 um in steps of 0.5 um and then derived the confinement loss via 20*log10(exp(1))*real(-lambda). To implement the losses I included a PML after the cladding.

Thank you very much in advance,
Steffen
That sounds like an interesting question. I tried it as well, but also got results that were off by quite a lot from the publication. The losses are way higher and also follow a different shape for higher wavelengths. The attached plot is for a core diameter of 3 um. If you are still around Charles, would you mind having a look at the attached mph-file? I ran a parametric sweep between 1 and 5 um in steps of 0.5 um and then derived the confinement loss via 20*log10(exp(1))*real(-lambda). To implement the losses I included a PML after the cladding. Thank you very much in advance, Steffen

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