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

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

To: EXT-Bickel, Gary W \<Gary.Bickel@West.Boeing.com\>; \'John S.
Canham,

Ph.D.\' \<John.S.Canham.1@gsfc.nasa.gov\>; Henning Leidecker

\<hleideck@pop500.gsfc.nasa.gov\>

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

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

Craig.T.Mueller@aero.org \<Craig.T.Mueller@aero.org\>;

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

elindholm@lucent.com \<elindholm@lucent.com\>; EXT-Beverly, David W

\<david.w.beverly1@jsc.nasa.gov\>; Gill, David J
\<DAVID.GILL@West.Boeing.com\>;

harold.f.battaglia \<harold.f.battaglia@boeing.com\>; Jie Li

\<JieLi@lucent.com\>; jplante@swales.com \<jplante@swales.com\>;
Mitchell,

Billie-Jo \<BMitchell@BICCGeneral.com\>; ray.prestridge@lmco.com

\<ray.prestridge@lmco.com\>

Date: Thursday, July 06, 2000 9:01 AM

Subject: RE: vibrating fiber on the tower

\>Is there any merit to asking Lucent if they can confirm by
observation,

\>test, analysis or instrumenting the draw tower whether or not
vibration is

\>causing the latent defects in the polyimide/carbon coating. The team
needs

\>to decide how to best resolve the vibration theory.

\>

\>Harold Battaglia /Boeing Houston

\>ISS Deputy Chief Engineer

\>Office Phone: (281) 336-4581

\>Fax: (281) 336-5353

\>

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

\>\> From: EXT-Bickel, Gary W \[SMTP:Gary.Bickel@West.Boeing.com\]

\>\> Sent: Wednesday, July 05, 2000 3:47 PM

\>\> To: \'John S. Canham, Ph.D.\'; Henning Leidecker; EXT-Bickel, Gary
W

\>\> Cc: Anna@seawire.traveller.com; carol.a.mcdonald@boeing.com;

\>\> Craig.T.Mueller@aero.org; DRothermel@BICCGeneral.com;

\>\> elindholm@lucent.com; EXT-Beverly, David W; Gill, David J;

\>\> harold.f.battaglia; Jie Li; jplante@swales.com; Mitchell,
Billie-Jo;

\>\> ray.prestridge@lmco.com

\>\> Subject: RE: vibrating fiber on the tower

\>\>

\>\> I have a number of observations which I believe can focus this
discussion

\>\> based on my prior experience with fiber drawing and coating.

\>\>

\>\> \* I have never observed an optical communication fiber \"vanish\"
due to

\>\> vibration during draw. I don\'t know the details of drawing
fiberglass,

\>\> but

\>\> I believe there are sufficient differences that make this unlikely.
For

\>\> example, an optical fiber is somewhat larger diameter than
\"fiberglass\"

\>\> fibers, and diameter control is not a major requirement on the
latter, nor

\>\> is strength. Both of these requirements on optical fiber puts it in
an

\>\> entirely different class.

\>\> \* There is no doubt that there is some degree of vibration on the

\>\> fiber; I have seen indications of it in the just barely visible

\>\> fluctuations

\>\> of a HENE laser concentricity monitor.

\>\> \* I believe that the draw speeds on the tower are on the order or
20

\>\> m/min or (possibly considerably) more; this is somewhat higher that
the

\>\> value of 20 cm/sec.

\>\> \* Although the draw tension at the capstan will be considerably
higher

\>\> due to viscous drag in the 4 coating cups, the tension at the
draw-down

\>\> zone

\>\> of the furnace will be much less than 4 lbs. My specific
recollection is

\>\> on

\>\> the order of 35 gms, but my memory isn\'t as strong on this as it
is on

\>\> some

\>\> other items. Note that draw tension affects both the strength of
the

\>\> fiber

\>\> as well as the diameter control; low tension leads to faster
\'healing\' in

\>\> the draw -down zone resulting in stronger fiber, but encourages
vibrations

\>\> which in turn severely impacts diameter control. The latter, of
course,

\>\> is

\>\> a critical parameter for control of losses in connectors.

\>\> \* I believe the tensions added at the coating cups may be
comparable

\>\> to that of the draw furnace or possibly even higher since we are
dealing

\>\> with very thin coatings. Thus there may be considerable differences
in

\>\> the

\>\> resonant frequencies of the various zones on the tower. Henning, I
will

\>\> try

\>\> to recover the article we talked about last week. I forgot to do it
this

\>\> weekend.

\>\> \* I also recall with John C. that there is a directed transverse
air

\>\> (or N2) flow intended to keep soot out of the coating cups.
Henning,

\>\> thank

\>\> you for the elucidation of \"Aeloian Tones\".

\>\>

\>\> These comments are of course based on prior experience that is over
10

\>\> years

\>\> old. Any additional information and/or corrections that LSFT can
provide

\>\> without revealing proprietary information is eagerly anticipated.

\>\>

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

\>\> \> From: John S. Canham, Ph.D.
\[SMTP:John.S.Canham.1@gsfc.nasa.gov\]

\>\> \> Sent: Wednesday, July 05, 2000 5:27 AM

\>\> \> To: Henning Leidecker; EXT-Bickel, Gary W

\>\> \> Cc: Anna@seawire.traveller.com; carol.a.mcdonald@boeing.com;

\>\> \> Craig.T.Mueller@aero.org; DRothermel@BICCGeneral.com;

\>\> \> elindholm@lucent.com; EXT-Beverly, David W; Gill, David;

\>\> \> harold.f.battaglia; Jie Li; John.S.Canham.1; jplante@swales.com;

\>\> Mitchell,

\>\> \> Billie-Jo; ray.prestridge@lmco.com

\>\> \> Subject: Re: vibrating fiber on the tower

\>\> \>

\>\> \> I would agree with Henning that this is certainly a distinct

\>\> probability.

\>\> \>

\>\> \> Based upon the observation that the fiber goes into an
oscillation and

\>\> \> \"vanishes\", we can set a lower frequency bound of about 60 Hz
as this is

\>\> \> near the upper frequency limit for ocular response. The eye does
not

\>\> \> readily resolve events much faster than 60 Hz, in the absence of
a

\>\> \> stroboscope.

\>\> \>

\>\> \> Aeolian vibration could be stimulated by the coating gas flow
and I

\>\> \> believe

\>\> \> that it was mentioned that there was a cross flow of air to
assure that

\>\> no

\>\> \> soot pick up occurs in the draw tower.

\>\> \>

\>\> \> Additionally, due to the high modulus of the cooled fiber,
mechanical

\>\> \> vibration from capstans, motors, external acoustical sources,
coating

\>\> pump

\>\> \> pulsations, etc. could also induce a vibration. I know of
several

\>\> \> significant mechanical oscillations that set up significant
harmonics in

\>\> \> various apparatus. The frequency of these oscillations need not
be

\>\> \> harmonic

\>\> \> to be of significance. An axial tension input into the end of
the fiber

\>\> \> from drive noise, floor traffic, etc. could be expected to
\"pluck\" the

\>\> \> fiber sufficiently to result in an oscillation.

\>\> \>

\>\> \> Oscillation of the fiber passing through the coating die (or
knife) cup

\>\> \> could result in near contact and contact of the fiber on one
side of the

\>\> \> die. This brittle/brittle interaction would result in the
generation of

\>\> \> microfractures at the point of impact. The greater the impact
force, the

\>\> \> greater the micro crack depth. Additionally, the generation of a
zero or

\>\> \> near zero coating thickness would result in a near infinite
shear field

\>\> at

\>\> \> the contact point. Such extreme shear force is known to often
result in

\>\> \> bubble formation (cavitation.) Collapse of the cavitation would
result

\>\> in

\>\> \> either a bubble formation or a depression. The depression or
bubble,

\>\> \> depending upon the viscosity, surface tension, and surface
energy

\>\> \> differences (between the air, coating, and the fiber surface,)
would

\>\> have

\>\> \> variable \"leveling\" rates and extents of \"leveling.\" This
would result

\>\> in

\>\> \> the variability of the depth within and between lots.

\>\> \>

\>\> \> The probability of latent defect and actual defect generation in
this

\>\> \> process, would depend greatly upon the coating die positioning.
There

\>\> \> would

\>\> \> be axial sensitivities (due to node and anti-node positioning,
assuming

\>\> a

\>\> \> standing wave.) There would also be significant positioning
factors

\>\> based

\>\> \> upon the positioning directions orthogonal to the main fiber
axis, as

\>\> well

\>\> \> as positioning errors in the parallelism (?) of the die and the
fiber.

\>\> \>

\>\> \> Depending upon the Q of the oscillation, which is expected to be
quite

\>\> \> high, with the exception of minor damping functions in the
furnace

\>\> region

\>\> \> and a displacement limited damping in the coating region, the
resonance/

\>\> \> nonresonance transition could be quite abrupt. It is possible
that an

\>\> \> axial/ radial coupling could occur wherein the axial oscillation
could

\>\> be

\>\> \> continuous, and the radial coupling could be due to harmonic,
random or

\>\> \> parametric events.

\>\> \>

\>\> \> This should be investigated further as the root cause of the
latent

\>\> \> aligned

\>\> \> coating defects from LSF.

\>\> \>

\>\> \>

\>\> \> At 07:32 PM 7/3/00 -0400, Henning Leidecker wrote:

\>\> \> \>Gentles,

\>\> \> \>

\>\> \> \>We are interested in imagining how latent defects (thinned
regions \-\--

\>\> \> \>sinkholes \-\-- in the polyimide, some with ten micron
diameter bubbles)

\>\> \> \>might get into FlightGuide fiber at Spectran/Lucent.

\>\> \> \>

\>\> \> \>I take it for granted that the answer will have to come from
someone at

\>\> \> \>Lucent who \"lives on the tower\".

\>\> \> \>

\>\> \> \>But I cannot help speculating while we are waiting \...

\>\> \> \>

\>\> \> \>The purpose of this email is to sketch the possibility that
the fiber

\>\> is

\>\> \> \>sometimes driven into forced vibration, and that this produces
the

\>\> \> periodic

\>\> \> \>string of latent defects. I\'ve checked with someone who is
familiar

\>\> with

\>\> \> \>fiberglass draw towers, and I\'ve been assured that this sort
of thing

\>\> \> \>actually happens \-\-- the fiber \"vanishes\" from sight as it
begins to

\>\> \> \>vibrate from side to side.

\>\> \> \>

\>\> \> \>First, I compute the relation between the observed spacial
frequencies

\>\> of

\>\> \> \>the latent defects (1 to 4 mm) and the vibrational frequencies
that the

\>\> \> \>fiber must have, to make these.

\>\> \> \>

\>\> \> \>Second, I sketch the allowed vibrational frequencies of a
length of

\>\> \> \>FlightGuide fiber under tension.

\>\> \> \>

\>\> \> \>Third, I sketch some ways that the fiber might get excited
into

\>\> \> vibration,

\>\> \> \>from time to time.

\>\> \> \>

\>\> \> \>Henning Leidecker

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

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

\>\> \> \>

\>\> \> \>1. What vibrational frequencies are implied by the observed
latent

\>\> \> defects

\>\> \> \>\....

\>\> \>

\>\>

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

\>\> \> ==

\>\> \> \>Call the fiber draw speed S_fib, and the spacial period (the
distance

\>\> \> \>between latent defects) L. Then these latent defects move past
a fixed

\>\> \> \>point with a temporal period T = L/S_fib ; the frequency is f
= 1/T =

\>\> \> \>S_fib/L .

\>\> \> \>

\>\> \> \>The typical fiber draw speed is S_fib = 20 cm/sec, so latent
defects

\>\> \> spaced

\>\> \> \>by 1.0 mm move past a fixed point at a frequency of f = (20

\>\> cm/sec)/(0.10

\>\> \> \>cm) = 200/sec = 200 Hz. And latent defects spaced by 4.0 mm
move past

\>\> a

\>\> \> \>fixed point at a frequency of 50 Hz. This sets the scale of
the

\>\> \> \>vibrational frequencies that interest us: they are expected to
range

\>\> \> \>between 50 and 200 Hz.

\>\> \> \>

\>\> \> \>

\>\> \> \>

\>\> \> \>2. What are the vibrational frequencies of the natural modes
of the

\>\> \> fiber

\>\> \> \>on the tower \...

\>\> \>

\>\>

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

\>\> \> ===

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

\>\> \> \>We have known for centuries that the natural modes of
vibration of the

\>\> \> \>stretched fiber are given by

\>\> \> \>

\>\> \> \> f_n = (n / 2\*L) \* sqrt\[T/mu\] ,

\>\> \> \>

\>\> \> \>where \"n\" = 1, 2, 3, is the number of loops in the fiber
between its

\>\> \> fixed

\>\> \> \>ends, spaced a distance \"L\" apart, \"T\" is the tension of
the fiber, and

\>\> \> \>\"mu\" is the mass per length of the fiber.

\>\> \> \>

\>\> \> \>The fiber is fixed, or pinned, against transverse motion at
several

\>\> \> places

\>\> \> \>along the draw tower. (I do not mean \"pinned in space\";
certainly, the

\>\> \> \>fiber is in motion along its z-axis. I only mean that the
sideways

\>\> \> motion

\>\> \> \>is pinned.) I will suppose these are the places, and distances
between

\>\> \> them:

\>\> \> \>

\>\> \> \> L1 = distance between the top oven (where the draw begins)

\>\> \> \> and the 1st polymer coating \"cup\".

\>\> \> \> L2 = distance between the 1st and 2nd polymer coating
\"cup\"s.

\>\> \> \> L3 = distance between the 2nd and 3rd polymer coating
\"cup\"s.

\>\> \> \> L4 = distance between the 3rd and 4th polymer coating
\"cup\"s.

\>\> \> \> L5 = distance between the 4th polymer coating \"cup\" and

\>\> \> \> the capstan at the bottom of the tower.

\>\> \> \>

\>\> \> \>These are might all be different lengths. I think that the
order of

\>\> these

\>\> \> \>five \"L\"\'s is between 2 and 10 meters. I will suppose 5
meters for the

\>\> \> \>following computations, until someone who actually knows the
tower will

\>\> \> \>take mercy on me, and contribute accurate values.

\>\> \> \>

\>\> \> \>The tension in the fiber is mainly set by the contest between
the

\>\> \> viscosity

\>\> \> \>of the hot glass in the drawing furnace and the speed of the
capstan at

\>\> \> the

\>\> \> \>bottom. But there is probably a contribution of the viscous
drag of

\>\> the

\>\> \> \>fiber as it passes through each polymer coating \"cup\". All I
know

\>\> about

\>\> \> it

\>\> \> \>is that it must be substantially less than the breaking
strength of the

\>\> \> \>glass fiber, about 10 pounds. The proof test value is about 5
pounds,

\>\> \> and

\>\> \> \>so I will suppose that the tension is 4 pounds (= 17.8
newtons); again,

\>\> I

\>\> \> \>hope someone who actually knows realistic values will
contribute here

\>\> \> too.

\>\> \> \>

\>\> \> \>The mass per length is 0.425 mg/cm = 42.6 kg/m (if I did my
arithmetic

\>\> \> \>correctly; I\'ll weigh some).

\>\> \> \>

\>\> \> \>Therefore

\>\> \> \>

\>\> \> \> f_n = n \* (65 Hz) = 65, 130, 195, 260, \... Hz.

\>\> \> \>

\>\> \> \>These are clearly in the right ball-park to create the
observed latent

\>\> \> \>defects. This suggests to me that it is well-worth using
better and

\>\> more

\>\> \> \>realistic values, to see if this plausible agreement is
maintained in

\>\> the

\>\> \> \>face of better arithmetic.

\>\> \> \>

\>\> \> \>

\>\> \> \>

\>\> \> \>3. How can these vibrational defects be excited \...

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

\>\> \> \>There is the possibility that an air current, or some other
excitation,

\>\> \> \>might get the fiber into a lateral (i.e., transverse)
vibration, so

\>\> that

\>\> \> it

\>\> \> \>would periodically press into the side of something (perhaps a
die at

\>\> the

\>\> \> \>top or bottom of a polymer coating cup?).

\>\> \> \>

\>\> \> \>From \"A Textbook of Sound: being an account of the physics of

\>\> vibrations

\>\> \> \>with special reference to recent theoretical and technical

\>\> developments\"

\>\> \> by

\>\> \> \>A. B. Wood (first published in 1930).

\>\> \> \>

\>\> \> \>Start of \"AELOIAN TONES\"

\>\> \> \>When a steady flow of fluid passes an obstacle with a large
enough

\>\> speed,

\>\> \> \>it is usually found that eddies are formed behind the
obstacle. Such

\>\> \> \>effects are familiar in the case of a stream of water
\"swirling\" past a

\>\> \> \>rock. Similar effects are also produced in a stream of air. A

\>\> \> \>cylindrical obstacle, such as a rod or wire, in a stream of
air sets up

\>\> a

\>\> \> \>double series of vortices (Mallock, Proc. Roy. Soc. vol 9,
page 262,

\>\> \> 1907).

\>\> \> \> The stream of air past the wire is thus set into transverse

\>\> vibrations,

\>\> \> as

\>\> \> \>alternate left- and right-handed eddies are formed and
detached. This

\>\> \> \>results in alternating pressure waves, which can be audible
under

\>\> certain

\>\> \> \>circumstances. An experimental investigation of these vortex

\>\> vibrations

\>\> \> \>was first undertaken by Strouhal (1878) and later by
Kohlrausch (1881).

\>\> \> \>The frequency \"f\" of the tone in the air was independent of
the length

\>\> of

\>\> \> \>the wire and also the tension of the wire, and varied only
with the

\>\> \> \>thickness \"d\" and the speed \"s\" of the wire through the
air:

\>\> \> \>

\>\> \> \> f = 0.185 (s/d)

\>\> \> \>

\>\> \> \>The detachment of the alternating vortices, and the wavering
of the

\>\> \> stream

\>\> \> \>of air, produces an alternating transverse force on the wire,
which set

\>\> \> it

\>\> \> \>into forced vibration at the frequency \"f\". We have a
pronounced

\>\> \> resonance

\>\> \> \>when this frequency coincides with one of the natural modes of

\>\> vibration

\>\> \> of

\>\> \> \>the stretched wire,

\>\> \> \>

\>\> \> \> f_n = (n / 2\*L) \* sqrt\[T/mu\] ,

\>\> \> \>

\>\> \> \>where \"n\" = 1, 2, 3, is the number of loops in the wire
between its

\>\> fixed

\>\> \> \>ends, spaced a distance \"L\" apart, \"T\" is the tension of
the wire, and

\>\> \> \"mu\"

\>\> \> \>is the mass per length of the wire. This resonance can result
in a

\>\> large

\>\> \> \>amplitude of displacement of the wire.

\>\> \> \>

\>\> \> \>The music of the Aeolian harp is produced this way. The harp
consists

\>\> of

\>\> \> a

\>\> \> \>number of wires of graduated thickness mounted on a sounding
board.

\>\> The

\>\> \> \>wires are all turned to the same low fundamental note, which

\>\> consequently

\>\> \> \>has a wide range of overtones in the audible region. When a
wind moves

\>\> \> \>past these wires, and \"plays\" it, one or more of these wires
will

\>\> \> resonate

\>\> \> \>and emit the note of the appropriate overtone. Other examples
include

\>\> \> the

\>\> \> \>\"singing\" of overhead wires, the \"sighing\" and \"roaring\"
of wind in

\>\> \> trees,

\>\> \> \>and the \"whistling\" of wind through tall grasses.

\>\> \> \>End of \"AELOIAN TONES\"

\>\> \> \>

\>\> \> \>We now ask what air speed might excite a transverse vibration
of 50 to

\>\> \> 200

\>\> \> \>Hz, in a fiber whose diameter is 140 microns (before the first
coating

\>\> \> cup)

\>\> \> \>to 170 microns (after the last coating cup).

\>\> \> \>

\>\> \> \> s = 5.40 \* f \* d = 5.40 \* (50 to 200 Hz) \* (140 to 170
microns)

\>\> \> \> = 3.8 to 18 cm/sec

\>\> \> \>

\>\> \> \>So we look for \"drafts\" having an air speed of this range.
Perhaps

\>\> there

\>\> \> \>is a flow of air sideways across the fiber as it moves down
the tower?

\>\>

\>\> \> \>

\>\> \> \>The resonance-amplification of the fiber\'s motion could be a
factor of

\>\> 50

\>\> \> \>or more! (This is the quality factor of this motion.) If the
tension

\>\> in

\>\> \> \>the fiber were to vary with time, then the fiber would go into
and then

\>\> \> out

\>\> \> \>of resonance, with a large change in the amplitude of the
sideways

\>\> \> motion.

\>\> \> \>This is the sort of thing we see.

\>\> \> \>

\>\> \> \>Such a fiber motion would be very easy to see! We just examine
the

\>\> \> fiber.

\>\> \> \>When we can clearly see it as it moves down the draw tower,
then it is

\>\> \> not

\>\> \> \>in sideways motion at 50 to 200 Hz! When it vanishes, then
such a

\>\> motion

\>\> \> \>has begun. We can instrument this for automatic detection very

\>\> cheaply.

\>\> \> \>

\>\> \> \>

\>\> \> \>

\>\> \> \>

\>\> \> John S. Canham