Spie Wjthomes 7070 Vibration

8/14/2019 Spie Wjthomes 7070 Vibration

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Vibration performance comparison study on current fiber optic

connector technologies

William J. Thomes, Jr.a, Frank V. LaRoccaa, Robert C. Switzera, Melanie N. Ottb,

Rick F. Chskaa, Shawn L. Macmr!h"a

aM#$ Technolo%ies & N'S' (o))ar) S!ace Fli%ht Center, Lanham, M*, +S' --/bN'S' (o))ar) S!ace Fli%ht Center, (reenbelt, M*, +S' -0

ABSTRACT

Fiber o!tic cables are increasin%l" bein% se) in harsh en1ironments where the" are sb2ecte) to 1ibration.

+n)erstan)in% the )e%ra)ation in !er3ormance n)er these con)itions is essential 3or inte%ration o3 the 3ibers into the

%i1en a!!lication. S"stem constraints o3ten re4ire 3iber o!tic connectors so that sbs"stems can be remo1e) or

assemble) as nee)e). $n the !resent work, 1arios t"!es o3 3iber o!tic connectors were monitore) in5sit )rin%

1ibration testin% to e6amine the transient chan%e in o!tical transmission an) the stea)"5state 1ariation 3ollowin% the

e1ent. The 3iber en)3aces an) connectors were ins!ecte) at selecte) inter1als thro%hot the testin%.

Keywords:S!ace 3li%ht, 3iber o!tics, 3iber, 1ibration, 3iber connector, 3iber termination

1 !"TR#$%CT!#"

Fiber o!tic s"stems are bein% se) in an e1er5increasin% nmber o3 s"stems )e to their man" a)1anta%es o1er electrical

s"stems7 li%hter wei%ht, lower !ower, smaller size, immnit" to electrical inter3erence, an) hi%her )ata rate ca!abilit".

These are es!eciall" im!ortant consi)erations when bil)in% s"stems that mst be )e!lo"e), whether it is lanchin% the

s"stem into s!ace or carr"in% it aron) in the 3iel). 8t there are challen%es to o1ercome when consi)erin% re!lacin%electrical s"stems with o!tical ones. There has been a consi)erable amont o3 work )one in a))ressin% most o3 these

concerns, an) 3iber o!tic5base) s"stems ha1e been sccess3ll" se) in man" hi%h5conse4ence s"stems where

reliabilit" an) 3nctionalit" are crcial. To)a", most o3 the hesitation o1er im!lementin% 3iber5base) !lat3orms stems

3rom lack o3 knowle)%e abot the !ro!er )esi%n an) se o3 3iber o!tics rather than 3rom inherent !roblems with the

a1ailable technolo%ies.

$n this !a!er, we in1esti%ate) the !er3ormance o3 1arios 3iber o!tic connectors o1er sccessi1el" harsher 1ibration

testin% le1els. 'lmost all lar%er s"stems will re4ire that there be !oints at which the 3iber o!tic cables will nee) to be

connecte) an) )isconnecte). Varios %ro!s bil) )i33erent !arts o3 the o1erall !ro2ect, an) these !arts will ha1e to be

inte%rate) to%ether. Choosin% the correct 3iber connector will allow inte%ration with acce!table loss in transmission an)stable o!eration o1er mission en1ironments.905:; Vibration !er3ormance is 2st one consi)eration when choosin% the

correct 3iber o!tic cable )esi%n, an) other 3actors, sch as thermal, ra)iation, an) mechanical constraints, will nee) to be

incl)e). For the crrent st)", we e6amine) the !er3ormance o3 the 'V$M, FC, SM', MT>

with >?-@ termini.

& '()'R!*'"TA+ $'S!,"

&- V!BRAT!#" T'ST!", )R#.!+'S

Vibration testin% was !er3orme) at increasin% le1els in three mtall" !er!en)iclar a6es. Vibration testin% )ration

was : min&a6is in each orientation. The 1ibration !ro3iles chosen re!resent ran)om 1ibration at 0-.-, [email protected], -.-, an)

:@./ (rms. The 0-.- (rmsle1el is base) on the acce!tance le1el test criteria 3or small bo6 com!onents as s!eci3ie) in the

(eneral #n1ironmental Veri3ication Stan)ar) A(#VSB 3or N'S' (o))ar) S!ace Fli%ht Center A(SFCB. 9@; The (#VS

ran)om 1ibration re4irements ha1e a lower le1el workmanshi! test o3 /.= (rmsthat is a minimm test 3or all !arts se)

on (SFC s!ace 3li%ht s"stems.


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st)ie), so there3ore the 0-.- (rmsle1el was chosen as an initial test con)ition. (#VS testin% re4irements !ro1i)e a

%eneral %i)eline 3or an" !art bein% se) 3or a (SFC mission. The (#VS testin% le1els are mo)i3ie) base) on s!eci3ic

mission )esi%ns an) anal"sis, bt the" are se) as a re3erence !oint. The onl" mo)i3ication to the stan)ar) 3or the

crrent testin% was that the test )ration was increase) 3rom 0 min&a6is to : min&a6is. This chan%e was ma)e base) on

recent 3li%ht !ro2ect re4irements that )ictate) the lon%er test to simlate lanch con)itions 3or a satellite. Table 0%i1esthe 1ibration testin% le1els o1er the ran%e o3 3re4encies 3rom - to --- z. Fi%re 0 shows a %ra!hical re!resentation

o3 the 0-.- (rmstestin% !ro3ile.

Table 1: 1-- ,rms Vibration )rofile

FREQ(Hz) ASD(G2/Hz) dB OCT dB/OCT AREA Grms

20.00 0.0130 * * * * *

50.00 0.0800 7.89 1.32 5.97 1.25 1.12

800.00 0.0800 0.00 4.00 0.00 61.25 7.83

2000.00 0.0130 -7.89 1.32 -5.97 99.91 10.00

.igure 1: Vibration profile for 1-- ,rms testing based on ,'VS

The ne6t 1ibration le1el teste) was [email protected] (rms, as )eri1e) 3rom the (#VS re4irements 3or ran)om 1ibration

4ali3ication le1el testin% o3 3li%ht har)ware. This wol) also be consi)ere) the !roto3li%ht le1el 3or com!onents

wei%hin% ?- lbs or less. Table %i1es the 1ibration testin% le1els o1er the ran%e o3 3re4encies 3rom - to --- z.

Fi%re shows a %ra!hical re!resentation o3 the [email protected] (rmstestin% !ro3ile.

Table &: 1/1 ,rms Vibration )rofile

ASD(G2/Hz) dB OCT dB/OCT AREA Grms

0.0260 * * * * *

0.1600 7.89 1.32 5.97 2.51 1.58

0.1600 0.00 4.00 0.00 122.51 11.07

0.0260 -7.89 1.32 -5.97 199.82 14.14


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.igure &: Vibration profile for 1/1 ,rms testing based on ,'VS

The N'S' (SFC Co)e ?/


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.igure 0: Vibration profile for &-- ,rms testing based on )hotonics ,roup reuirements

Most s!ace 3li%ht !ro%rams wol) not re4ire testin% to 1ibration le1els hi%her than -.- ( rms, bt testin% was also

con)cte) to :@./ (rmsin an attem!t to e6!ose weaknesses o3 an" o3 the connectors in this st)". The :@./ ( rmsle1el

was chosen becase o3 mechanical limitations o3 the 1ibration s"stem bein% se). Vibration testin% at hi%her le1els

wol) reslt in the shaker )rm tra1elin% otsi)e o3 its )is!lacement limits. Table @ lists the 1ibration !ro3ile, an)Fi%re @ shows a %ra!hical re!resentation 3or the :@./ (rmstestin%.

Table /: 0/2 ,rms Vibration )rofile

FREQ(Hz) ASD(G2/Hz) dB OCT dB/OCT AREA Grms

20.00 0.1560 * * * * *

50.00 0.9600 7.89 1.32 5.97 15.04 3.88

800.00 0.9600 0.00 4.00 0.00 735.04 27.11

2000.00 0.1560 -7.89 1.32 -5.97 1198.89 34.63


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.igure /: Vibration profile for 0/2 ,rms testing based on euipment limitations

&& Vibration Test Setup

Vibration testin% was con)cte) sin% a sin%le a6is 1ibration )rm mo)el 8W50--C 3rom 8DW #n%ineerin% with a8W5


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'n accelerometer was se) as 3ee)back to the 1ibration control s"stem. The accelerometer also allowe) monitorin% o3

the 1ibration le1els o1er the 3re4enc" ran%e o3 interest bein% a!!lie) to the !arts. ' threa)e) montin% hole was

locate) on 1arios !oints o3 the 3i6tre sch that the accelerometer was in close !ro6imit" to the connection bein%

teste).

&0 .iber Terminations

Three t"!es o3 3iber cables were st)ie) with the 1arios connectors. These incl)e) a 0--&0@- ste! in)e6 3se) silica

3iber with a 3lat !olish, a @--&@@- ste! in)e6 3se) silica 3iber with a 3lat !olish, an) a 0--&0@- %ra)e) in)e6 3se) silica

3iber with a show re!resentati1e

insertion loss )ata )rin% 1ibration testin% o3 the )i33erent 3ibers in each a6is. 's can be seen 3rom the %ra!hs, the


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insertion loss chan%e was less than -.- )8. Fi%re =illstrates a small shi3t in the 3iber ali%nment imme)iatel" a3ter

the start o3 the 1ibration testin%, bt o!tical !er3ormance was stable 3ollowin% this sli%ht chan%e.

.igure 6: !nsertion loss of 1--71/- graded inde8 fiber in AV!* connector tested at 03 ,rms along connector a8is 49 a8is5

.igure : !nsertion loss of 1--71/- step inde8 fiber in AV!* connector tested at 03 ,rms perpendicular to ferrule endface

with ;ey in displacement direction 4( a8is5


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.igure ibration testing Top pictures show

entire metal ferrule ends? while bottom pictures show the fibers under higher magnification

'3ter 0-.- (rmsTestin% '3ter :@./ (rmsTestin%


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Table 3: !nsertion +oss of AV!* cables before and after >ibration testing

Cable !dentification

!nsertion +oss

)re@Vibration

Testing

!nsertion +oss

)ost@Vibration Testing

!nsertion +oss

Change 4dB5

'V$M5'V$M 0--&0@- Ste! $n)e6 SN H 0 -. -.?: 0.26

'V$M5'V$M 0--&0@- Ste! $n)e6 SN H -.- -.0 0.18

'V$M5'V$M 0--&0@- Ste! $n)e6 SN H : -.0@ -.-> -0.05

'V$M5'V$M 0--&0@- Ste! $n)e6 SN H @ -.0 -.0 0.04

'V$M5'V$M 0--&0@- (ra)e) $n)e6 SN H 0 -.-0 -.0@ 0.14

'V$M5'V$M 0--&0@- (ra)e) $n)e6 SN H -.-0 -.? 0.24

'V$M5'V$M 0--&0@- (ra)e) $n)e6 SN H : -.0 -.0@ -0.07

'V$M5'V$M 0--&0@- (ra)e) $n)e6 SN H @ -.-0 -.0/ 0.15

'V$M5'V$M @--&@@- SN H 0 -. -./= -0.04

'V$M5'V$M @--&@@- SN H -. -./: -0.09

'V$M5'V$M @--&@@- SN H : -./@ -.?> -0.05

'V$M5'V$M @--&@@- SN H @ -./> -./ -0.07

Table ? %i1es the insertion loss o3 the 'V$M cables be3ore an) a3ter 1ibration testin%. The ma6imm chan%e in

insertion loss 3ollowin% all 1ibration testin% on these cables was -./ )8. *e to the small ma%nit)e o3 these chan%esan) 1ariabilit" in the test set!, the cables are consi)ere) to ha1e shown no )e%ra)ation in !er3ormance )e to the

1ibration testin%.

0& The .C Connector

The FC connector has a 3errle nearl" i)entical to the 'V$M connector, as shown in Fi%re 00. The s!rin%5loa)e)

3errle is .? mm in )iameter. ' connector ke" an) matchin% slot on the a)a!ter !ro1i)e ali%nment an) anti5rotation

3eatres. The connector attaches to the a)a!ter with a lar%er oter nt. Secon)ar" 3astenin% is re4ire) 3or r%%e)

en1ironments to ensre the connector )oes not loosen.

.igure 11: The .C connector and adapter

Since the FC connector is similar to the 'V$M in terms o3 the loa)s !lace) on the 3iber 3errle, onl" the @--&@@- 3iberwas teste) as !art o3 this st)" to ensre similarit" o3 o!tical !er3ormance an) to monitor 3or mechanical chan%es, sch

as loosenin% o3 the connector 3astenin% nt. The a)a!ter ses a s!lit ceramic slee1e i)entical to the 'V$MIs to maintain

ali%nment between the mate) 3errles.

$nsertion loss )ata 3rom a re!resentati1e 1ibration test o3 the FC connectors are %i1en in Fi%re 0. #n)3ace ima%es are

shown in Fi%re 0:. 8oth reslts are similar to those 3on) )rin% e1alation o3 the 'V$M connector, in which the

insertion loss was essentiall" nchan%e) )rin% 1ibration testin% to :@./ ( rms, bt the oter e)%es o3 the metal 3errle

e6hibite) some !ittin% an) scratchin%.


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.igure 1&: !nsertion loss of /--7//- step inde8 fiber in a .C connector tested at 03 ,rms along the connector a8is 49 a8is5

.igure 10: 'ndface images of .C connector showing damage during subseuent >ibration testing

Table 2: !nsertion loss of .C cables before and after >ibration testing

Cable !dentification!nsertion +oss

)re@Vibration Testing

!nsertion +oss

)ost@Vibration Testing

!nsertion +oss

Change 4dB5

[email protected] /--7//- S" 1 -3 -30 @--3

[email protected] /--7//- S" & -2& -&< @-00

[email protected] /--7//- S" 0 -3& -3 --2

[email protected] /--7//- S" / -6& -0< @-00

'3ter 0-.- (rmsTestin% '3ter :@./ (rmsTestin%


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Table /shows the chan%e in insertion loss o3 the FC cables be3ore an) a3ter 1ibration testin%. The ma6imm chan%ewas an im!ro1ement o3 -.:: )8. '%ain, this is mainl" attribte) to the test set! se) to take these measrements.

00 The S*A Connector

The SM' connector has a 3i6e) :.0/ mm )iameter 3errle that is either ceramic or metal. There are two common

1arieties o3 SM' connectors, the SM'>-? an) SM'>-/. The SM'>-? has the same )iameter alon% the entire len%tho3 the 3errle, while the SM'>-/ )ro!s to a smaller )iameter near the connector en)3ace. The metal 3errle SM'>-?was se) 3or all testin% in this st)". Fi%re 0@shows the SM' connector an) a)a!ter. There is no ke"in% 3eatre with

this connector. The oter nt screws onto the a)a!ter to hol) the connector in !lace, so some t"!e o3 secon)ar" lockin%

Asall" e!o6" or wire tieB is nee)e) to ensre that the connector )oes not loosen )rin% harsh en1ironments. The

matin% a)a!ter 3or the SM' is a threa)e) barrel that has a smooth inner wall to ali%n the 3iber en)3aces.

.igure 1/: The S*A


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Fi%re 0shows re!resentati1e en)3ace !ictres o3 the SM' 3ibers taken 3ollowin% 1ibration testin% at the s!eci3ie)le1els. No )ama%e was 3on) on the %lass 3ibers themsel1es, bt the metal 3errle srron)in% the 3iber showe) si%ns

o3 scratchin% an) !ittin%. *e to the lack o3 a ke"in% 3eatre on the SM' connector, the 3errle can rotate insi)e o3 the

a)a!ter, casin% this t"!e o3 circlar )ama%e !attern. Table lists the insertion loss o3 the SM' cables be3ore an) a3ter

1ibration testin%. No !ermanent )e%ra)ation o3 o!tical transmission 3or the SM' cables was 3on) to ha1e been case)

b" the 1ibration testin%.

0/ The *!+@S)'C 0?-@ termini, as shown in Fi%re 0=. This

connector is se) in man" s!ace a!!lications, sch as the $nternational S!ace Station, an) in militar" s"stems.


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The MT< connector with mltimo)e 3iber showe) a chan%e in insertion loss o3 less than -.? )8 )rin% testin%, with

t"!ical reslts mch lower. For 3ibers e6hibite) e1i)ence o3 some mo1ement )rin% 1ibration, with minor

scratchin%&!ittin% o3 the 3iber en)3aces. Fi%re 0> shows the en)3ace !ictres 3ollowin% 1ibration testin% 3or these

connectors. These reslts are consistent with 1ibration testin% !re1iosl" !er3orme) b" this %ro! 3or other !ro%rams.9/;

.igure 1ibration testing at 1&6 ,rms

#n)3ace %eometr" will in3lence !er3ormance o3 the MT< connector in a mate) !air con3i%ration. Fi%re -shows

en)3aces taken on two )i33erent 3iber o!tic cables that were terminate) b" an otsi)e 1en)or an) sent to (SFC 3or

ins!ection. The )esire) %eometr" is 3or all o3 the 3ibers to be e4al in hei%ht an) sli%htl" !rotr)e) 3rom the com!osite

3errle, as in the ima%e on the le3t. owe1er, i3 not ti%htl" controlle) an) ins!ecte), the 3ibers can be !olishe) at

ne1en hei%hts, resltin% in the %eometr" shown in the ima%e on the ri%ht. The ne1en 3ibers will be s!rin%5loa)e) into

the matin% 3ibers an) the 3orces will be carrie) b" the !rotr)in% 3ibers. This will likel" reslt in !er3ormance3lctations an) 3iber )ama%e.

.igure &-: *T) fiber geometry on cables manufactured by an outside >endor and sent to ,S.C for inspection %ne>en

polishing of connector on right will result in une>en loading of fibers? resulting in higher insertion loss fluctuations

and possible damage

02 The ST Connector

The ST connector has a .? mm )iameter 3errle that is ceramic, metal, or ceramic with a metal insert. The bo)" o3 the

connector is s!rin%5loa)e) a%ainst the oter ntK. ' ke" on the connector !ro1i)es ali%nment an) !re1ents rotation o3

the 3errle insi)e the a)a!ter. Two slots in the oter ntK sli)e o1er small tabs on the a)a!ter an) are locke) b"

twistin% to en%a%e the tabs into o33set in)entations in the slots. Fi%re 0shows the ST connector an) a matin% a)a!ter.

.igure &1: The ST connector and adapter )icture on right shows engagement of adapter tabs into connector slots

ST connectors are commonl" 3on) on testin% e4i!ment. The" !ro1i)e a 4ick metho) o3 connectin% 3iber o!tic

cables. owe1er, the" )o not !ro1i)e as hi%h a le1el o3 mechanical r%%e)ness as other a1ailable 3iber o!tic connectors

3or se in harsh en1ironments. ' small twist in the oter nt o3 the connector will )isen%a%e the lockin% mechanism,

casin% the two matin% connectors to s!rin% a!art 3rom each other. Likewise, 3ailre o3 the small metal tabs on the


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Spie Wjthomes 7070 Vibration