\-\-\-\--Original Message\-\-\-\--

From: Battaglia, Harold F \<Harold.Battaglia@SW.Boeing.com\>

To: \'Henning Leidecker\' \<hleideck@pop500.gsfc.nasa.gov\>;
EXT-Beverly, David

W \<david.w.beverly1@jsc.nasa.gov\>

Cc: Anna@seawire.traveller.com \<Anna@seawire.traveller.com\>;

bmitchell@BICCGeneral.com \<bmitchell@BICCGeneral.com\>;

carol.a.mcdonald@boeing.com \<carol.a.mcdonald@boeing.com\>;

Craig.T.Mueller@aero.org \<Craig.T.Mueller@aero.org\>; Gill, David J

\<DAVID.GILL@West.Boeing.com\>; DRothermel@BICCGeneral.com

\<DRothermel@BICCGeneral.com\>; elindholm@lucent.com
\<elindholm@lucent.com\>;

EXT-Bickel, Gary W \<Gary.Bickel@West.Boeing.com\>; Battaglia, Harold F

\<Harold.Battaglia@SW.Boeing.com\>; jplante@swales.com
\<jplante@swales.com\>;

jieli@lucent.com \<jieli@lucent.com\>; jcanham@mscmail.gsfc.nasa.gov

\<jcanham@mscmail.gsfc.nasa.gov\>; ray.prestridge@lmco.com

\<ray.prestridge@lmco.com\>

Date: Wednesday, June 07, 2000 5:30 PM

Subject: RE: My email re summarizing where we are on establishing the
root

cause.

\>Henning and everyone else: I agree with your summary as it is stated.
Some

\>advice on Root Cause determination. If there are some areas of the
Root

\>Cause investigation that cannot be definitively confirmed, it\'s
perfectly

\>acceptable to state what the experts believe is the \"Most Probable
Root

\>Cause\". This is the approach that is commonly used in PRACA\'s when
it\'s

\>determined that it is no longer value added to continue pursuing root

cause.

\>

\>

\>Harold Battaglia/Boeing Houston

\>Phone: 281-336-4581

\>Fax: 281-336-5353

\>

\>\> \-\-\-\--Original Message\-\-\-\--

\>\> From: Henning Leidecker \[SMTP:hleideck@pop500.gsfc.nasa.gov\]

\>\> Sent: Wednesday, June 07, 2000 1:30 PM

\>\> To: david.w.beverly1@jsc.nasa.gov

\>\> Cc: Anna@seawire.traveller.com; bmitchell@BICCGeneral.com;

\>\> carol.a.mcdonald@boeing.com; Craig.T.Mueller@aero.org;

\>\> DAVID.GILL@west.boeing.com; DRothermel@BICCGeneral.com;

\>\> elindholm@lucent.com; Gary.Bickel@west.boeing.com;

\>\> harold.battaglia@sw.boeing.com; hleideck@pop500.gsfc.nasa.gov;

\>\> jplante@swales.com; jieli@lucent.com;
jcanham@mscmail.gsfc.nasa.gov;

\>\> ray.prestridge@lmco.com

\>\> Subject: My email re summarizing where we are on establishing the

\>\> root cause.

\>\>

\>\> Gentles,

\>\>

\>\> I sent Dave Beverly and David Gill the following summary of where I
think

\>\> we are in our root cause investigation, and asking for some advice.

\>\>

\>\> During our telcon today, Dave Beverly suggested my summary could be
sent

\>\> to

\>\> parties interested in our progress. I am happy to do so. But I
would

\>\> like

\>\> to collect comments from all the team, and include these.

\>\>

\>\> I ask that you send these comments back to me by Fri afternoon, so
that I

\>\> can send my (possibly) revised summary to Dave Beverly by Fri COB.

\>\>

\>\> I plan to modify the text slightly, so that it is not asking for
advice,

\>\> but is stating where we now are. But I will leave it in its present
form

\>\> for now so you have a chance to give me advice.

\>\>

\>\> Thanks,

\>\> Henning Leidecker

\>\> ===================================

\>\> ===================================

\>\>

\>\> Executive summary:

\>\> =================

\>\> Point 1:

\>\> \-\-\-\-\-\--

\>\> Perhaps this is the time to publish the \"Root Cause Report\" that
Jeannette

\>\> Plante has almost finished revising, even though it does not
identify the

\>\> \"root cause of the root cause\" to the satisfaction of all
parties? Ray

\>\> Prestridge is clear with us: many people are knocking at his phone
for

\>\> news.

\>\>

\>\> (Ms Plante has emailed revised sections to the team as she has
finished

\>\> each. We can send you the whole thing in one email attachment if
you

\>\> would

\>\> like. Just ask. The last revisions are not quite done. But why wait
for

\>\> the last second to talk about this?)

\>\>

\>\> We have agreement re the root cause of the original problem:
excessive

\>\> insertion loss in links. These are the etch pits extending into the
core

\>\> of the fiber; these are caused by a corrosive agent attacking the
glass

\>\> through a (micron-scale) breach in the carbon coating. Everyone
agrees.

\>\>

\>\> We do not have agreement as to what is causing the breach in the
carbon

\>\> coating, or what is the source of the corrosive agent. We do not
have

\>\> agreement as to why the frequency of these etch pits was low (one
per

\>\> several kilometers) in 1996-vintage cable, and high (one per
several

\>\> meters) in 1997/1998-vintage fiber. We do not have agreement as to
what

\>\> is

\>\> to be done to keep etch pits away forever more in newly made cable.

\>\>

\>\> We have agreement re the existence of a new, previously unknown
problem:

\>\> excessive degradation of fiber breaking strength. The
fiber-breaking

\>\> factory at Boeing-HB has detailed the damage to the strength
distribution

\>\> curve associated with each step in the cabling activity. (The job
is not

\>\> quite complete. It will be complete when we have the curves for the

\>\> non-carbon coated stuff. Perhaps in a few more days?) We see
dramatic

\>\> variations between two lots, but we do not have any reliable
measure of

\>\> lot-to-lot variations. We do not have agreement as to what the
cause of

\>\> the damage is. We do not have agreement as to what is to be done to
keep

\>\> this kind of damage away forever more.

\>\>

\>\> So we have some things established, and some things left undone.
But

\>\> perhaps this is a good time to publish what we have established,
and NAME

\>\> what we have not yet done, rather than wait any longer.

\>\>

\>\> Point 2:

\>\> \-\-\-\-\-\--

\>\> What work shall we agree on, to try to wrap up this study? And what

\>\> time-scale what we try to do it on?

\>\>

\>\> And over what range of projects? I expect that NASA will continue
to be

\>\> interested in using fiber optic cables in space beyond ISS. Perhaps
NASA

\>\> HQ would be interested in participating in the future of this
study.

\>\>

\>\> I cannot estimate how much longer we will take to wrap up the
desired

\>\> \"root

\>\> cause of the root cause.\" Perhaps this nut will suddenly crack
apart

\>\> under

\>\> the stresses we have already applied. Perhaps we will have to
continue to

\>\> beat it with thunderingly big mallets for some time yet. I don\'t
know.

\>\>

\>\> But I do have confidence that we will get to the root cause of the
root

\>\> cause. Maybe another month will do it. Almost certainly, two or
three

\>\> will.

\>\>

\>\>

\>\> Long-winded version:

\>\> ===================

\>\> As you know, Jeannette Plante wrote a synthesis of all the emails
and

\>\> technical interchange meetings and telcons. Her intent was to
capture

\>\> Team

\>\> Two\'s findings & conclusions on the root cause of the fiber flaws.
She

\>\> circulated early drafts by email before the technical interchange
meeting

\>\> (TIM) in Huntington Beach in early May, and brought a mature draft
with

\>\> her

\>\> to this meeting where it was discussed in detail. Indeed, some
sections

\>\> were discussed line by line.

\>\>

\>\> The May TIM discussion demonstrated that there were substantial
areas of

\>\> agreement, as well as substantial areas of non-agreement.
BICCGeneral

\>\> sent

\>\> Ms Plante a three page memo detailing their objections.
Spectran/Lucent

\>\> sent a similar memo. Since her return, Ms Plante has been working

\>\> steadily

\>\> and for long hours re-writing the May report in the light of the
TIM and

\>\> these memos. She is nearly finished with what she is able to do
without

\>\> new experiments or substantiative new scholarship.

\>\>

\>\> The present (re-written) report does not identify \"the root cause
of the

\>\> root cause\" in a way that everyone will accept.

\>\>

\>\> That is, we know that the ROOT CAUSE of the insertion loss first
noticed

\>\> about a year ago is an etch pit made by a corrosive agent attacking
the

\>\> fiber through a localized breach in the carbon coating. These were
rare

\>\> in

\>\> 1996-era cable (we can say that since they were not noticed in
insertion

\>\> loss records of links made from this cable, and also since
Boeing-HB

\>\> inspected some 10 km of 1996-era cable and found precisely one etch
pit),

\>\> but commonplace in 1998/1999-era cable (many links were found to
have

\>\> excessive insertion losses, and many glows & OTDR echoes). Many
etch pits

\>\> have been imaged (using optical microscopes and SEM) and, in every
case

\>\> for

\>\> which the image permits examination, there is a feature within the

\>\> polyimide directly above the etch pit. In some cases, the polyimide

\>\> feature is a thinned zone. In others, the feature is a cavity of
some

\>\> kind. In both cases, external fluids (if any) have easy access to
the

\>\> glass, relative to an unfeatured polyimide coating. I think all
parties

\>\> agree with this.

\>\>

\>\> But not all parties agree that the corrosive agent is hydrogen
fluoride

\>\> created during the extrusion of the FEP buffer around the fiber.
Nor

\>\> agree

\>\> on the cause of the localized breaches in the carbon coating, or
the

\>\> associated features in the polyimide coating. It seems likely that

\>\> substantially more effort will be required to reach agreement on
these

\>\> points. So we do not have the \"root cause of the root cause\"
documented

\>\> satisfactorily.

\>\>

\>\> In addition, the fiber breaking factory created at Boeing-HB has

\>\> established that the great majority of low-strength breaks do not

\>\> originate

\>\> at etch pits, but rather at flaws at the surface of the fiber, at
the

\>\> interface between the glass cladding and the polyimide coating.
Some of

\>\> the photos made using optical microscopy seem to show a surface
feature

\>\> that resembles a crack sometimes as large as a few microns, and
sometimes

\>\> smaller, down to the limit of resolution of the optical system
used.

\>\> There

\>\> is the possibility that, if the images were made with better
resolution,

\>\> there would ALWAYS be such a surface feature, and I suspect this is
the

\>\> case. (SEM images could be definitive.) In every image that allows

\>\> inspection over the origin of the break, there is a feature within
the

\>\> polyimide coating directly above the site of origin of the fracture
in the

\>\> fiber. In some cases, this feature resembles a nearly spherical
cavity

\>\> whose diameter approaches the thickness of the polyimide coating,
with

\>\> small openings to the glass and to the outside. In other cases,
this

\>\> feature more nearly resembles a tube extending all the way through
the

\>\> polyimide coating. These flaws at the surface of the glass cladding
ARE

\>\> DISTINCT FROM THE ETCH PITS. We have discovered a second kind of
flaw.

\>\> This second kind is not responsible for excessive insertion loss in
links,

\>\> nor for glows induced by Visual Fault Finders, nor for echoes seen
by

\>\> OTDRs

\>\> (since they are present only at the surface of the cladding, and do
not

\>\> intrude into the core); however, they have a profound impact on the

\>\> distribution of breaking strengths. I think all parties would agree
to

\>\> this.

\>\>

\>\> We do not have a consensus on what causes these fracture-initiation
flaws

\>\> first seen in the Boeing fiber-breaking lab. So we have a distinct

\>\> \"second

\>\> kind of root cause\" (causing low-strength breaks, not the optical

\>\> anomalies

\>\> caused by the etch pits), and again no consensus on the \"cause of
the

\>\> second kind of root cause.\"

\>\>

\>\> Dave Gill has mentioned that he feels that the surface flaws are
produced

\>\> by the same mechanism as the etch pits. I agree. I suggest that an
ESD

\>\> event punches a hole through the polyimide, removes a patch of the
carbon

\>\> coating, and fractures the surface of the glass cladding layer.
(There is

\>\> probably a range in the size of the damage; it seems unlikely that
each

\>\> ESD

\>\> event would have the same size, and would create the same damage.)
If the

\>\> strength distribution is measured at this moment, one would find a
serious

\>\> reduction, caused by the surface cracks whose scale is 0.1 to 10
microns.

\>\>

\>\> In some cases, there is subsequent exposure to enough hydrogen
fluoride

\>\> and

\>\> water that the fracture is turned into an etch pit. This replaces a

\>\> sharp-tipped surface fracture by a smooth chemically-polished
hemisphere,

\>\> with a far smaller stress concentration factor: the strength
distribution

\>\> associated just with these flaws (smooth-walled etch pits) would be
close

\>\> to that of the original fiber. Thus, when one breaks many specimens
of

\>\> this sort of fiber, one would rarely find an etch pit at the break;

\>\> rather,

\>\> one would usually find a sharp-tipped (un-etched) crack there.

\>\>

\>\> The sharp-tipped cracks are expected to grow with time, when there
is

\>\> stress applied. Therefore, these features are especially dangerous
to a

\>\> long life expectancy. Conventional \"n theory\" should apply here.
But the

\>\> long-term behavior of the etch pits has not been established: we
can only

\>\> make some guesses. One guess is that the smooth,
chemically-polished etch

\>\> pit would retain it low-stress concentration factor for a
substantial

\>\> time,

\>\> but, eventually, water (entering through the hole in the polyimide)
would

\>\> corrode the walls, and begin to degrade the strength. We are in
unknown

\>\> territory here, and we can expect that we may stumble some number
of times

\>\> before we get this part of the puzzle worked out. Even if everyone
agreed

\>\> that these ideas were reasonable, we would have to agree that they
are as

\>\> yet untested and therefore probably wrong. (Most ideas, even the
plausible

\>\> ones, are wrong. There are many many ways to be wrong, and only one
way

\>\> to

\>\> be right.)

\>\>

\>\> We are in a position to go after these guesses, and construct
experiments

\>\> (including damaging fiber with controlled ESD events, and exposing
fiber

\>\> to

\>\> HF, and breaking many fiber specimens to establish distributions of

\>\> strengths). I think this is a good idea, and that we will locate

\>\> convincing evidence for the \"cause of both root causes\" \-\-- the
cause of

\>\> those flaws that cause etch pits, and the cause of those flaws that
cause

\>\> low-strength breaks. I welcome discussion of what we should do
next.