\>\>From: \"BEVERLY, DAVID W. (JSC-NX)\"
\<<david.w.beverly1@jsc.nasa.gov>\>\
\>\>To: \"\'My Account\'\" \<<me@leidecker.gsfc.nasa.gov>\>\
\>\>Subject: RE: A resend of my \"report-lite\"\
\>\>Date: Thu, 22 Jun 2000 20:42:35 -0500\
\>\>X-Mailer: Internet Mail Service (5.5.2448.0)\
\>\>\
\>\>I did get your \"updated\" version yesterday but the JSC email has
been down\
\>\>from a virus until around 1pm today. Thanks Henning - I really
appreciate\
\>\>difference you make for NASA.\
\>\>\
\>\>David Beverly\
\>\>NX-EEE Parts\
\>\>(281) 483-0250 Mobile:(713) 825-5624\
\>\>Fax: (281) 244-2318\
\>\>E-mail: <david.w.beverly1@jsc.nasa.gov>\
\>\>\
\>\>\
\>\>\
\>\>\
\>\>\
\>\>\-\-\-\--Original Message\-\-\-\--\
\>\>From: My Account
\[[mailto:me@leidecker.gsfc.nasa.gov](mailto:me@leidecker.gsfc.nasa.gov)\]\
\>\>Sent: Monday, June 19, 2000 10:27 AM\
\>\>To: BEVERLY, DAVID W. (JSC-NX)\
\>\>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: A resend of my \"report-lite\"\
\>\>\
\>\>\
\>\>Dear Dave,\
\>\>\
\>\>I tried to send this last Monday, and my machine balked \-\-- we\
\>\>had had email problems all day long. But my machine eventually\
\>\>listed this email as having been sent. I just tried again a\
\>\>minute ago, and got \"cannot connect to mail server.\" So I am\
\>\>sending this from my UNIX machine, which connects to the\
\>\>internet through a different connection.\
\>\>\
\>\>Please drop a line when (IF!) this arrives.\
\>\>\
\>\>Thanks!\
\>\>Henning\
\>\>============old message follows==============\
\>\>\
\>\>\
\>\>Dear Dave,\
\>\>\
\>\>I\'ve gotten responses from Jeannette Plante, Harold Battaglia,\
\>\>Dave Rothermel, Ray Prestridge, and Dave Beverly.\
\>\>\
\>\>Dave Rothermel requests:\
\>\> Please forward a verbatim copy of anything you wish\
\>\> to publish to the end users of this product to\
\>\> Billie-Jo Mitchell\'s attention so that it can be\
\>\> reviewed by our legal department prior to issue.\
\>\>\
\>\>What I am sending to you today is my cut at the \"verbatium\
\>\>copy\". If you agree with my cut, let me know, and I\'ll send it\
\>\>to Billie-Jo (<bmitchell@BICCGeneral.com>). Or you could sent it\
\>\>\-\-- just let me know.\
\>\>\
\>\>Feel free to make changes.\
\>\>\
\>\>Best,\
\>\>Henning Leidecker\
\>\>===================================\
\>\>===================================\
\>\>\
\>\>Executive summary:\
\>\>=================\
\>\>Point 1:\
\>\>\-\-\-\-\-\--\
\>\>The \"Root Cause Team,\" also called \"Team Two\", was formed to\
\>\>find why an increasing number of links made by Boeing using\
\>\>fiber optic cable, vintage 1998/1999, had excessive insertion\
\>\>loss. We have agreement that the reason is the presence of etch\
\>\>pits extending into the core of the fiber, caused by a\
\>\>corrosive agent attacking the glass through a (micron-scale)\
\>\>breach in the carbon coating.\
\>\>\
\>\>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\
\>\>strength-testing facility at Boeing-HB has detailed the damage\
\>\>to the strength distribution curve associated with each step in\
\>\>the cabling activity. There are dramatic variations between two\
\>\>lots of carbon-coated fiber, and between two lots of a\
\>\>comparison fiber (OC1260: not carbon-coated, but with a\
\>\>polyimide plastic coating). 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.\
\>\>\
\>\>We are issuing this report to document what we have\
\>\>established, and what is so far unresolved.\
\>\>\
\>\>\
\>\>Discussion:\
\>\>==========\
\>\>Jeannette Plante has a synthesis of all the emails and\
\>\>technical interchange meetings and telcons relating to the work\
\>\>of Team Two (The \"Root Cause Team\"), and has added a summary of\
\>\>Team Two\'s findings and 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.\
\>\>This present document is a highly abreviated version of the one\
\>\>Ms Plante will release shortly.\
\>\>\
\>\>Ms Plante\'s re-written report does not presently 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. (This was directly confirmed in one experiment last\
\>\>Fall.) I think all parties agree with this.\
\>\>\
\>\>David DiGiovanni (and others too) have demonstrated that\
\>\>exposure of fiber, with localized breaches deliberately created\
\>\>in the polyimide and carbon coatings, to hydrogen fluoride acid\
\>\>creates etch pits that are identical in all respects with the\
\>\>etch pits seen in Boeing\'s damaged links. Further, it is\
\>\>well-known that hydrogen fluoride acid is created from FEP and\
\>\>water during a high temperature extrusion of FEP. But not all\
\>\>parties agree that the corrosive agent is hydrogen fluoride\
\>\>created during the extrusion of the FEP buffer around the fiber.\
\>\> Not all parties agree on the cause of the localized breaches\
\>\>in the carbon coating, or the associated features in the\
\>\>polyimide coating. (Various investigators have seen \"bubbles\"\
\>\>within the polyimide coating, but these would not, themselves,\
\>\>provide a breach in the carbon coating: something else is needed\
\>\>beside polyimide bubbles.) 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 strength-testing facility 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. These flaws are 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\
\>\>strength-testing facility. 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.\
\>\>\
\>\>