FW: modal noise, PMD power penalty
-----Original Message-----
From: Hanson, Thomas A [mailto:HansonTA@xxxxxxxxxxx]
Sent: Thursday, November 02, 2000 10:05 AM
To: 'Bhatt, Vipul'
Subject: RE: modal noise, PMD power penalty
I personally can't comment on Q1.
On Q2, consider that in Namihira's experiment both horizontal and
vertical eye closure contributed to BER - hence penalty.
I also believe that the reason Poole's original published penalty
formula needs to be multiplied by a factor of two is related not only
to the type of detector (PIN vs APD), but also (and probably related)
the horizontal eye aspects.
Poole's original formula would yield a penalty of 0.5 dB for DGD/T =
0.3. The Namihira result - and the updated formula - yield a penalty
of 1.0 dB for DGD/T = 0.3.
> ----------
> From: Vipul Bhatt[SMTP:vipul.bhatt@xxxxxxxxxxx]
> Sent: Thursday, November 02, 2000 12:57 PM
> To: Equalization Ad-Hoc Reflector
> Subject: modal noise, PMD power penalty
> Importance: High
>
>
> For those who won't be able to attend the Sunday meeting, but feel
> qualified to answer the following two questions... please attempt a
> reply before Saturday evening. These two questions are unrelated to
> each other.
>
> 1. I don't see any difference between the phrases "time variance of
a
> multimode fiber as a channel" and "modal noise". Do you agree? I am
> assuming that the effect of laser is implicitly accounted for. If
you
> agree, isn't the wheel already invented - don't we already know that
> modal noise is a slow variation phenomenon? [If there is no mode
> partition noise - and this is where the answer may be different for
> 10G VCSEL and DFB lasers - refractive index changes due to
mechanical
> stress and local temperature variations will occur on a time scale
> representative of the strain mechanisms, i.e., on the order of
> milliseconds or longer. Paraphrased from Lasky, Osterberg and
> Stigliani, Optoelectronics for Data Communication. ISBN
> 0-12-437160-4.]
>
> 2. Is it true that PMD Power Penalty, if accounted for in the link
> power budget, will make it unnecessary to account for horizontal eye
> closure? The converse may not be true - compared to a zero-PMD link,
a
> link with PMD will see the receiver eye suffer from both vertical
and
> horizontal eye closure. But if more power is thrown at the link, the
> eye will open up both vertically and horizontally. Do you agree? [I
> don't want to recommend something to P802.3ae that falsely includes
a
> double penalty.]
>
> Thanks,
> Vipul
>
> vipul.bhatt@xxxxxxxxxxx
> (408)542-4113
>
>