Re: How much singlemode fiber is high-PMD?
Hi Vipul
There is also marketing and practical aspect to Equalization which the
group need
to consider. Fundamentally the fiber bandwidth is limited by the
dispersion and DMD.
Here are some base line assumption one can make:
- Equalization group can partially impact the SW specification by
requesting
ROFL or Vortex launch for all SW variant.
- Equalization specification will lag SW and LW spec.
- With current partition module power dissipation is already very
critical
and in red. As stand a Sw module PD is 4-5 W. Equalizer should not
add
more than 1W to be practical. Dissipating 5 watt's is very high for an
optical
module as many of these box will operate 55-70 deg. C with ambient of
40-45 degree.
- Product with IEEE compliant equalizer will be ~ 1 year after standard
products. What do you think the customers are going to do?
- If we can use a special path cord and avoid DMD and reduce power
dissipation
significantly then it should be considered. Path cord would be more
attractive
and lower cost than sophisticated cooling.
- Equalization will impact all variants later by improving margin for
the link
assuming it does not more than double an standard postAMP power.
Does anyone knows what is the maximum power dissipation for XGP module?
Thanks,
Ali Ghiasi
Vipul Bhatt wrote:
>
> Dear colleagues,
>
> Let's conceptually put all the singlemode fiber in two bins - old
> and new. We define new fiber as the one that conforms to the new IEC
> guideline of 0.5 ps/sqrt(km) max. We define old fiber as the one
> that doesn't.
>
> (The new fiber can be understood and dealt with. In fact, in
> parallel to this thread, I will soon resume discussion of estimating
> PMD and the outage probability for new fiber links. Our goal will be
> to go to 802.3ae with a description of the problem and some
> recommendations affecting the design of 1550 nm links.)
>
> The unknown, which makes me more uncomfortable, is the old fiber. We
> need to answer three questions.
>
> 1. What is the magic year when production of old fiber stopped and
> production of new fiber began?
>
> This is best answered by fiber manufacturers. A good source of data
> may be when the patents for processes that control PMD were filed by
> fiber manufacturers. Another source may be to look at IEC and ITU
> activities and identify the year when PMD specifications became
> topics of discussion.
>
> 2. How much of the old fiber is in the ground today?
>
> We are only interested in terrestrial metro routes, not long
> distance routes. We are more likely to find new fiber in metro
> routes - true?
>
> 3. What can we do to identify these old fibers? (I am assuming a
> worst case scenario where 802.3ae members insist on answering this
> question, regardless of the answer to question 2.)
>
> My initial thought was that we could just read the date code on a
> cable, but a colleague reminded me that often the markings fade or
> get scraped off...also, in a manhole, one may have just a few feet
> of cable to work with, so date code may not be accessible. Well,
> then, what instruments can we use? Surely, the Jones Matrix method
> is an overkill and impractical!! How about Interferometric test
> sets? They are portable, though not hand-held (or inexpensive).
> Perhaps the potential market size will encourage test instruments
> vendors to come up with a good solution. Any thoughts?
>
> It's important to answer these three questions, even partially, by
> November 5.
>
> Thanks,
> Vipul
>
> vipul.bhatt@xxxxxxxxxxx
> (408)542-4113