Re: PMD Compromise
Dear reflector members
It is interesting to see the discussion of 1300 nm versus 1550 nm over 40
km. At the Ottawa meeting two things happened.
1. I made a presentation were I pointed out that one should specify the
receivers for both 1300 nm and 1550 nm and that this should be at a very
small cost (The receivers must be tested at both wavelengths). This would
allow operation of both 1300 and 1550 nm lasers and hence keep the standard
open for both solution. This would be a single PMD with wavelength dependent
parameters. There was however no interest in this.Please explain to me why
this is a stupid proposal!
2. People were ask to raise their hand if they belived in1300 nm over 40 km.
I could hardly see anyone raising their hands. This discussion on the
reflector make me somewhat confused as there was so little support at the
meeting.
Personal I think that 1300 nm over 40 km is a possible solution that could
be of lower cost and easier design. This is especially true if OMA or a low
ER is specified in the standard.
However I also want to point out some things in favour of 1550 nm.
1. There is an eye safety issue with 1300 nm. Probably you need at least 4
dBm output and if I understand the FDA standard this could be a problem.
However, the eye safety standard might change or the calculations might be
wrong.
2. You cannot cover all 40 km links with the current attenuation
budget.There is really no upper limit on the attenuation. However, it would
be expensive to specify the standard to cover all cases but for 1550 nm you
could use an Er-amplifier to improve the power budget.
3. Today one typical only measure the attenuation at 1550 nm.
4. The receiver must be able to handle the higher power for 1300 nm (higher
dynamic range is needed).
/Krister Frojdh
>
> Vipul,
>
> In conversations that I have had with "carrier" people (more than just my
company) the perceptions were that 1500nm lasers would be
> tight tolerance and on the ITU grid. I do not believe that standardizing
on a high power, tight tolerance lasers at one of the ITU
> grid frequencies is what the P802.3ae TF had in mind.
>
> There was also the perception that the data switches would replace the LTE
network elements. This is a mistake that we (the service
> providers) made with POS. I was part of that at the time and will readily
admit that I, and many others were wrong. A normal,
> customer data switch is not, can never be, and should never be perceived
as an active carrier network element. There are carrier
> network element systems that are in the works that will have 802.3
switching functionality in them, that are designed specifically
> to be network elements, using full SONET (EoS). One vendor already has
one on the market. The P802.3ae TF has not assumed the
> charter to standardize on this type of equipment.
>
> True, 1300nm does not lend itself to EDFA amplifiers. By the time that
someone is paying for amplifiers, they are operating at a
> cost factor way out of the range of what I believe the TF invisions. As
such, amplifiers will be owned by the service or fiber
> providers not the enterprise customer. The service provider will want a
transducer between the customer and his fiber plant in
> order to support any SLAs that are in place. The transducer will move the
1300nm Ethernet WAN signal to the 1500nm, ITU grid space.
> 1500nm lasers are not necessary for the Ethernet WAN PHY to operate in the
very long reach systems. This is true of a lot of legacy
> OC48 transmission equipment today. The transducer/amplifier scenario is
exactly what happens today in the case of the older
> transmission network elements that have 1300nm lasers.
>
> The miss-perception on the part of service providers is natural when you
consider that 1500nm lasers are more in the domain of
> "carrier" space than anywhere else. By not having 1500nm in the
specification, the perception would be that the systems defined by
> the P802.3ae specification are not carrier type network elements. If a
vendor wants to enter the carrier network element market
> space with an P802.3ae data switch, that vendor would then fall under T1X1
specifications, not IEEE.
>
> I think that we need to make a clear distinction between the T1X1 based
EoS proposed standard and the P802.3ae proposed standard.
> One of the simplest ways to do that is by making the 40km specification at
1300nm, not 1500nm. If system vendors want to provide
> 1500nm lasers at power specifications beyond 40km, then they are free to
do that outside of the standard, just as several vendors do
> today with GbE.
>
> Thank you,
> Roy Bynum
>
>
>
> ----- Original Message -----
> From: "Vipul Bhatt" <vipul.bhatt@xxxxxxxxxxx>
> To: "P802.3ae Task Force Reflector" <stds-802-3-hssg@xxxxxxxx>
> Sent: Thursday, June 08, 2000 7:52 PM
> Subject: RE: PMD Compromise
>
>
> >
> > Jay,
> >
> > Jay Hoge wrote:
> > > Upon reflection, I agree with you on the 1.3u vs.
> > > 1.55u smf issue. If people want to go truly long
> > > haul in native Ethernet, there needs are
> > > outside the scope of this standard.
> >
> > No, I think that would be a mistake! This standard can't afford to
> > ignore a sizeable market need - how useful is a standard that fails
> > to specify a version many people want? Please allow me to argue in
> > favor of keeping 1550 nm link on the table.
> >
> > Ethernet backbone over dark fiber is appealing. It is a fast and
> > affordable alternative to SONET, enabling cost-effective high
> > bandwidth connectivity to data centers and Internet. Market is
> > changing; so should change the scope of a new standard. Metro links
> > are increasingly in demand, and we can't be sure that >40 kms will
> > be an insignificant piece of that market. If anything, we are
> > getting the opposite message from the market - sales of 80-km GBICs
> > are increasing at a rapid rate. We can't afford to ignore these
> > trends when drafting a new standard.
> >
> > The 1550 nm PMD will be expensive by LAN standards, but it will be a
> > bargain compared to SONET monthly rates. As volumes build up, prices
> > will drop further.
> >
> > In the near future, when we consider 40G operation, a 4:1 WDM of 10G
> > Serial links will be one of the major options. Compatibility with
> > 1550 nm WDM devices and amplifiers will be required then. I know we
> > are not obliged to take this future event into account, but why not
> > think about it?
> >
> > By refusing to standardize a significant market need, we will be
> > depriving the market of some key lubricants - interoperability,
> > competition and lower cost. The market will prevail despite us, but
> > magazine articles for years to come will keep reminding us of what a
> > poor decision we made.
> >
> > Regards,
> > Vipul
> >
> > vipul.bhatt@xxxxxxxxxxx
> > (408)542-4113
> >
> > =====================
> >
>
>