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width of PML

Posted 2012年6月15日 GMT-4 01:15 6 Replies

Md. Samiul Habib
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What will be the width of the PML( circular) to determine the confinement loss in hexagonal pcf.

Regards
Md. Samiul Habib
6 Replies Last Post 2013年2月5日 GMT-5 04:59
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 2012年6月15日 GMT-4 04:51
Hi

I would say a few (<10) wavelength of air, then 2-3 for the PML distance. but I havent modelled optics and fibre for some time, others out here might have better rule of thumbs

--
Good luck
Ivar
Hi I would say a few (
Alexander Kuznetsov
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Posted: 1 decade ago 2012年6月15日 GMT-4 12:40
First, make PML very large. Then gradually decrease its thickness until your solution starts changing significantly. This way you can find an optimum that's right for you.

If you plan to solve for range of different wavelength, optimize PML for the largest wavelength
First, make PML very large. Then gradually decrease its thickness until your solution starts changing significantly. This way you can find an optimum that's right for you. If you plan to solve for range of different wavelength, optimize PML for the largest wavelength
Md. Samiul Habib
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Posted: 1 decade ago 2012年6月16日 GMT-4 10:52
Thanx Ivar.
Thanx Ivar.
Farhan Hanaffi
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Posted: 1 decade ago 2013年2月4日 GMT-5 09:27
how about number of layer ?
how about number of layer ?
Alexander Kuznetsov
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Posted: 1 decade ago 2013年2月4日 GMT-5 19:52
I always use sweep mesh in PML with 3-5 layers. Again, you can increase the number of layers until you get the desired accuracy.
I always use sweep mesh in PML with 3-5 layers. Again, you can increase the number of layers until you get the desired accuracy.
RVN
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Posted: 1 decade ago 2013年2月5日 GMT-5 04:59
According to Comsol Support answer I got, it does not matter. The PML will always be "one-wavelength" thick per default, you should just take care how you mesh it. They suggested using mapped-quadratic elements and make sure you have between 1-10 elements across the thickness of the PML. In my experience 4-6 usually is more than enough and I have never had any real need of 10 elements, the marginal computational accuracy vs. the time it takes to compute is not worth it.


Hope this helps
--
/RVN
According to Comsol Support answer I got, it does not matter. The PML will always be "one-wavelength" thick per default, you should just take care how you mesh it. They suggested using mapped-quadratic elements and make sure you have between 1-10 elements across the thickness of the PML. In my experience 4-6 usually is more than enough and I have never had any real need of 10 elements, the marginal computational accuracy vs. the time it takes to compute is not worth it. Hope this helps -- /RVN

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