RE: How much single-mode fiber is high-PMD?
Ali,
I am glad to hear there are others interested in exploiting launch conditioning to extend multimode fiber bandwidth and link length capability. I will be more than glad to accept your assistance and would be glad to have you join TIA FO 2.2.1. (Please confirm your interest before I subscribe you to the task group's reflector.)
I would suggest to you and Vipul, however, that this IEEE ad hoc group remain focused on equalization. The TIA group has worked for more than 4 years on developing launch conditioning. The current conclusion is that launch conditioning worked well for the installed base of fiber where the patchcord specified in the 1 GbE standard ensures installed 1300 nm 62.5 um fiber performs with the rated bandwidth when combined with a single-mode laser. Also, FO-2.2.1 determined that when a) new 62.5 um fiber meeting an enhanced restricted mode launch (RML) bandwidth and b) transceivers producing a restricted launch (as measured by encircled flux) are combined, the 270 meter link length can be extended to 500 meters.
Equalization, however, has the potential of extending the capability of the installed base, just by swapping out the transceiver. This seems to me to be the key opportunity for equalization. It seems to me that a good starting point is to see how well it works on 1 GbE. Once this is proven, then the next step of moving to 10 Gb should be easier.
Mike Hackert
Chair, TIA FO 2.2.1
Task Group on the Modal Dependence of Multimode Fiber Bandwidth
> ----------
> From: Ali Ghiasi[SMTP:aghiasi@xxxxxxxxxxxxx]
> Sent: Monday, October 16, 2000 8:15 PM
> To: Vipul Bhatt
> Cc: Equalization Ad-Hoc Reflector; Ali Ghiasi
> Subject: 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
>