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Re: Estimating the magnitude of PMD




Vipul,

I'm not sure, but I believe you may still have an error in your
argument.  The spectral width of typical long haul sources at 1550 is
extremely small.  I don't believe the PMD response of this small band of
wavelengths is really independent.  So there will be no multiwavelength
averaging.

Gair



Vipul Bhatt wrote:
> 
> Dave and Jonathan,
> 
> Thanks for your responses.
> 
> About integrating the PDF tail to get the 10^-12 probability, duhh...of
> course. Thanks for catching it, Dave.
> 
> About using Gaussian approximation for vertical eye closure, and how to
> model horizontal eye closure, I will let others comment. Collectively, it
> seems like a big enough topic that we may have to kind of break it down
> into modules and tackle one at a time.
> 
> About why I chose 10^-12 as my target number: I think this question will
> expose a probable fallacy in my logic. I reasoned like this...at a given
> wavelength, the DGD value is randomly varying in time, obeying the
> Maxwell PDF. Therefore, at any instant, there is a 10^-12 probability
> that this value will exceed about 5 times the mean.
> 
> Now (what I think was) the fallacy in my logic. The total energy of a
> signal is divided among many wavelengths, and I assumed that all
> wavelengths have the same DGD value at the same time, but of course they
> don't. At every instant, every wavelength has its own probability density
> function of DGD. And this integral over a two-dimensional (time,
> wavelength) PDF should yield a much lower value of pulse broadening.
> 
> If I hear Jonathan, we should compute and agree on this value - soon!!
> Folks, if you think you can help, please don't hesitate to contribute.
> 
> Regards,
> Vipul
> 
> ====================

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