AW: [EFM] AW: [EFM-P2P] RE: Single wavelength, single fibre PMD f or P2P

[Thomas.Murphy@xxxxxxxxxxxx]

Jack,

Thanks for the reply. Do not agree that my discussion was technically
inaccurate, and like yourself, I also pointed out that it
is possible to have DFBs operating over an extended temperature range.
In the discussion at the meeting, if I am not mistaken, you also highlighted some
possible temperature limitations of VSCELs/DFBs and as a result rated these sources equally with 
FPs. I rated FPs marginally better so I think that we are both coming from the
same stand point.

Regards

Tom



-----Ursprüngliche Nachricht-----
Von: Jack Jewell [mailto:Jack.Jewell@xxxxxxxxxxxxx]
Gesendet am: Montag, 18. Februar 2002 16:56
An: 'Thomas.Murphy@xxxxxxxxxxxx'; Jack Jewell; mdudek@xxxxxxxxxxxx;
Hans.Mickelsson@xxxxxxxxxxxxxxx
Cc: stds-802-3-efm@ieee.org; stds-802-3-efm-p2p@majordomo.ieee.org;
bob.barret@xxxxxxxxxxxxxxxxxx; david@xxxxxxxxxxxxxx; doravv@xxxxxxxxxx;
FEffenberger@xxxxxxxxxxxxxxxxx; jradcliffe@xxxxxxxxxxxxxxxxxxxx;
jstiscia@xxxxxxxxxx; mark.sankey@xxxxxxxxx; meir@xxxxxxxx;
n.kleiner@xxxxxxxxxxxx; PengL@xxxxxxxxxxx; raanan@xxxxxxxxxxxxxxx;
rbrand@xxxxxxxxxxxxxxxxxx; sasaki144@xxxxxxx;
schelto.vandoorn@xxxxxxxxx; Tonyshouse@xxxxxxx; wdiab@xxxxxxxxx;
Vipul_Bhatt@xxxxxxxx
Betreff: RE: [EFM] AW: [EFM-P2P] RE: Single wavelength, single fibre PMD
f or P2P

Tom,

The real situation is as follows.  In a VCSEL or DFB, the gain curve tunes
faster with temperature than does the cavity (lasing) wavelength.
Appropriately designed VCSELs have the gain and cavity peaks detuned at low
temperatures, with the gain peak at a shorter wavelength than the cavity
peak, hence the term "gain offset."  Thus, as the temperature increases, the
gain peak moves TOWARD the cavity peak and compensates for the inherent
broadening of the gain peak and decrease of its peak value.  At a given
current, the optical power can actually increase with temperature.  In a FP,
the lasing wavelength tracks the gain peak.  The inherent degradation of the
gain peak with temperature has no compensating mechanism in a FP; thus the
threshold increases and the power drops monotonically with temperature.  Of
course, this does NOT prevent FPs from being used over extended
temperatures.  If we're going to have a laser discussion in this thread,
let's keep it technically accurate.

Jack

 -----Original Message-----
From: 	Thomas.Murphy@xxxxxxxxxxxx [mailto:Thomas.Murphy@xxxxxxxxxxxx] 
Sent:	Monday, February 18, 2002 8:36 AM
To:	Jack.Jewell@xxxxxxxxxxxxx; Thomas.Murphy@xxxxxxxxxxxx;
mdudek@xxxxxxxxxxxx; Hans.Mickelsson@xxxxxxxxxxxxxxx
Cc:	stds-802-3-efm@ieee.org; stds-802-3-efm-p2p@majordomo.ieee.org;
bob.barret@xxxxxxxxxxxxxxxxxx; david@xxxxxxxxxxxxxx; doravv@xxxxxxxxxx;
FEffenberger@xxxxxxxxxxxxxxxxx; jradcliffe@xxxxxxxxxxxxxxxxxxxx;
jstiscia@xxxxxxxxxx; mark.sankey@xxxxxxxxx; meir@xxxxxxxx;
n.kleiner@xxxxxxxxxxxx; PengL@xxxxxxxxxxx; raanan@xxxxxxxxxxxxxxx;
rbrand@xxxxxxxxxxxxxxxxxx; sasaki144@xxxxxxx; schelto.vandoorn@xxxxxxxxx;
Tonyshouse@xxxxxxx; wdiab@xxxxxxxxx; Vipul_Bhatt@xxxxxxxx
Subject:	AW: [EFM] AW: [EFM-P2P] RE: Single wavelength, single fibre
PMD f or P2P

What I meant is that with changes in temperature, the VCSEL/DFB grating
wavelength position
shows small shifts (arising from changes in the refractive index), however,
what 
happens is that the gain curve moves away from this fixed grating position
and
hence the intensity drops. With an FP,
the gain curve and centre wavelength show the same temperature dependence,
hence the
intensity variations are smaller.  This is why fewer (not none) DFBs are
specified over 
an extended temperature range.

Tom

 

-----Ursprüngliche Nachricht-----
Von: Jack Jewell [mailto:Jack.Jewell@xxxxxxxxxxxxx]
Gesendet am: Montag, 18. Februar 2002 16:22
An: 'Thomas.Murphy@xxxxxxxxxxxx'; mdudek@xxxxxxxxxxxx;
Hans.Mickelsson@xxxxxxxxxxxxxxx
Cc: stds-802-3-efm@ieee.org; stds-802-3-efm-p2p@majordomo.ieee.org;
bob.barret@xxxxxxxxxxxxxxxxxx; david@xxxxxxxxxxxxxx; doravv@xxxxxxxxxx;
FEffenberger@xxxxxxxxxxxxxxxxx; jradcliffe@xxxxxxxxxxxxxxxxxxxx;
jstiscia@xxxxxxxxxx; mark.sankey@xxxxxxxxx; meir@xxxxxxxx;
n.kleiner@xxxxxxxxxxxx; PengL@xxxxxxxxxxx; raanan@xxxxxxxxxxxxxxx;
rbrand@xxxxxxxxxxxxxxxxxx; sasaki144@xxxxxxx;
schelto.vandoorn@xxxxxxxxx; Tonyshouse@xxxxxxx; wdiab@xxxxxxxxx;
Vipul_Bhatt@xxxxxxxx
Betreff: RE: [EFM] AW: [EFM-P2P] RE: Single wavelength, single fibre PMD
f or P2P

This is incorrect.  The grating (or cavity) structure of a VCSEL or DFB is
exactly what allows VCSELs (and to some extent DFBs) to display little
variation in threshold and/or power over large temperature ranges.

Jack

 -----Original Message-----
From: 	Thomas.Murphy@xxxxxxxxxxxx [mailto:Thomas.Murphy@xxxxxxxxxxxx] 
Sent:	Saturday, February 16, 2002 10:39 AM
To:	mdudek@xxxxxxxxxxxx; Hans.Mickelsson@xxxxxxxxxxxxxxx
Cc:	Thomas.Murphy@infineon.com; stds-802-3-efm@ieee.org;
stds-802-3-efm-p2p@xxxxxxxxxxxxxxxxxx; bob.barret@xxxxxxxxxxxxxxxxxx;
david@xxxxxxxxxxxxxx; doravv@xxxxxxxxxx; FEffenberger@xxxxxxxxxxxxxxxxx;
jradcliffe@xxxxxxxxxxxxxxxxxxxx; jstiscia@xxxxxxxxxx; mark.sankey@xxxxxxxxx;
meir@xxxxxxxx; n.kleiner@xxxxxxxxxxxx; PengL@xxxxxxxxxxx;
raanan@xxxxxxxxxxxxxxx; rbrand@xxxxxxxxxxxxxxxxxx; sasaki144@xxxxxxx;
schelto.vandoorn@xxxxxxxxx; Tonyshouse@xxxxxxx; wdiab@xxxxxxxxx;
Vipul_Bhatt@xxxxxxxx
Subject:	[EFM] AW: [EFM-P2P] RE: Single wavelength, single fibre PMD
for P2P


In the analysis of the temperature response of a VCSEL (and DFB) I 
as refering to intensity variations and not shifts in wavelength.
The grating structure of both implies a larger sensitivity in
output power to temperature shift.

Tom



-----Ursprüngliche Nachricht-----
Von: Mike Dudek [mailto:mdudek@xxxxxxxxxxxx]
Gesendet am: Freitag, 15. Februar 2002 19:35
An: Hans Mickelsson (ERA)
Cc: 'Thomas.Murphy@infineon.com'; stds-802-3-efm@ieee.org;
stds-802-3-efm-p2p@xxxxxxxxxxxxxxxxxx; bob.barret@xxxxxxxxxxxxxxxxxx;
david@xxxxxxxxxxxxxx; doravv@xxxxxxxxxx; FEffenberger@xxxxxxxxxxxxxxxxx;
jradcliffe@xxxxxxxxxxxxxxxxxxxx; jstiscia@xxxxxxxxxx;
mark.sankey@xxxxxxxxx; meir@xxxxxxxx; n.kleiner@xxxxxxxxxxxx;
PengL@xxxxxxxxxxx; raanan@xxxxxxxxxxxxxxx; rbrand@xxxxxxxxxxxxxxxxxx;
sasaki144@xxxxxxx; schelto.vandoorn@xxxxxxxxx; Tonyshouse@xxxxxxx;
wdiab@xxxxxxxxx; Vipul_Bhatt@xxxxxxxx
Betreff: Re: [EFM-P2P] RE: Single wavelength, single fibre PMD for P2P

VCSEL change in wavelength as a function of temperature is similar/slightly
better than the quoted number for the DFB.

"Hans Mickelsson (ERA)" wrote:

> Tom,
>
> Good work, see below for some comments.
>
> "Fewest variations of PMD to track in field". I agree that it will be less
PMDs to track however if this is a real problem is not clear. Assume that
you decide to use a certain lamda for downstream then it it ijust to follow
this approach in all your switches and the problem will be non-existing.
>
> Can you explain "Use of inexpensive TOSA a bit further"?
>
> "Temperature performance". An un-cooled DFB (0.01 nm/K) is less temp
dependent than a FP (0.03 nm/K). Can anyone give some figures for a VCSEL?
>
> "Leverage of 1310 nm....", True, but you raise an interesting question
here. The use of parallel optics will be very difficult with any single
fiber solution.
>
> Some othe options to consider are;
>
> The need for angled polished connectors for controlling refelctions in the
network. Not necessary for dual but probably necessary for single.
>
> Will the be any difference between the two options in an up-grade scenario
to higher bit-rates?
>
>         Brgds//HANS MICKELSSON
>
> > -----Original Message-----
> > From: Thomas.Murphy@xxxxxxxxxxxx [mailto:Thomas.Murphy@xxxxxxxxxxxx]
> > Sent: den 14 februari 2002 17:25
> > To: stds-802-3-efm@ieee.org; stds-802-3-efm-p2p@majordomo.ieee.org;
> > bob.barret@xxxxxxxxxxxxxxxxxx; david@xxxxxxxxxxxxxx;
> > doravv@xxxxxxxxxx;
> > FEffenberger@xxxxxxxxxxxxxxxxx; hans.mickelsson@xxxxxxxxxxxxxxx;
> > jradcliffe@xxxxxxxxxxxxxxxxxxxx; jstiscia@xxxxxxxxxx;
> > mark.sankey@xxxxxxxxx; meir@xxxxxxxx; Thomas.Murphy@xxxxxxxxxxxx;
> > n.kleiner@xxxxxxxxxxxx; PengL@xxxxxxxxxxx; raanan@xxxxxxxxxxxxxxx;
> > rbrand@xxxxxxxxxxxxxxxxxx; sasaki144@xxxxxxx;
> > schelto.vandoorn@xxxxxxxxx; Tonyshouse@xxxxxxx; wdiab@xxxxxxxxx
> > Cc: Vipul_Bhatt@xxxxxxxx
> > Subject: Single wavelength, single fibre PMD for P2P
> >
> >
> > Hello All,
> >
> > First off I apologise for a blanket bomb approach with
> > sending out this e-mail but
> > I have my reasons, as will become clear below.
> >
> > As most of you will know, I am currently co-ordinating the development
> > of a single fibre, single wavelength PMD proposal for P2P links.
> > During a recent discussion of this work, it became clear that
> > a number of people
> > were unaware of what was happening or still unclear of some
> > of the technical issues involved. Several questions arose
> > which had already been answered in the course of dedicated
> > telephone conferences and
> > some new issues were also raised.
> >
> > Of course this discussion is very good for the quality of the
> > standard. However,
> > in the interest of progress and completion of a baseline
> > proposal for March, it
> > is essential that people allay any concerns they may have in
> > the interim and go
> > into the meeting feeling ready to make an informed decision.
> >
> > I would therefore ask people who have an opinion (or concern)
> > in this direction
> > to speak up, raise the issues and avoid further surprises in St Louis.
> >
> > Arising from the aforementioned discussions was the idea that
> > a 2 wavelength
> > PMD may be an alternative approach. In order to facilitate
> > comparison of the
> > two ideas, a matrix was proposed which I have included here
> > in a somewhat modified
> > form. I divided the table into Today and Future, the former
> > represent current laser sources (FP and DFB)
> > and the later assuming the use of VCSELs, be that at 1310,
> > 1490 or 1550 nm. I dislike the 1-10
> > approach of comparing as this is too subjective, rather a
> > binary 0 or 1 representing the better solution
> > for a particular criteria. In some cases there are no
> > differences and both receive 0. The 'points'
> > are added and a comparison may be made.  NOTE, this will not
> > be the basis of the decision, rather an aid
> > to objective comparison. I have included comments behind each
> > issue cells detailing my evaluation.
> >
> > So, speak up, play with the table, add issues if necessary,
> > send it back to me,
> > get on the telephone conferences.
> >
> > Best regards and looking forward to further progress.
> >
> > Tom and the P2P group
> >
> >  <<Comparison matrix for 1 and 2 wavelength PMDs.xls>>
> >