CA2245917A1 - Alignment assembly for multifiber or single fiber optical cable connector - Google Patents

Abstract

The present invention provides a precise optical fiber cable connector (10) for aligning and connecting ends of a pair of cables. The connector (10) has a fiber alignment block (12) having a fiber receiving surface (14) and a connector engagement surface (18). First and second openings (44, 46) are provided in the connector engagement surface (18). An alignment ball (62) is provided and is retained in the first opening (44). The alignment ball (62) is for aligning the connector (10) with another like connector, and specifically, for aligning optical fibers carried on the connector alignment assemblies.

Description

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W O 97/34179 PCT~US96/160S2 . .

AIIIGNMENT ASSE~MBLY FOR MULTIFIBER OR
SINGLE I~lBElR OPTICAI, CABLE CONNECTOR
F~F~ n OF I~F INVENTION
The present invention relates generally to co~ e~,lcl~ for optical fibers. In p~Lc~llar, the present invention relates to an ~ nm~nt assesnbly for an optical fiber cable co.~l-eelor having ~li~m~nt balls retained on a face of a fiber ~1ig.~ block for ~ u-l~oses.
BACKGROUN~ OF T~F rNVENTION
Fiber optic cables are well known for the ~ .. ;c.~;o,. of optical signals. Use of optical cable has generally been limited to long haul - trunlcing inct~ tionc where the illlyloved ll~ c~ s~;on char~ct~ricfics of the optica1 fibers justify the greater eyI~ence and ~lifl~c~llties associated with their m~n11f~*1sing and in~t~ tion As the d~m~n~s on co~ ;c~tion media contin11e to in~ ,ase, the advantages of using optical cable for tr~n~.niC- ol~ of signals across shorter dict~nces or, for interconnecti~ local devices, continues to grow. Much development work has been devoted to the provision of practiC~1 low loss glass 2U sn~t~.ri~lc and prc!d1-~ion techni~ c for producing glass fiber cable, such as optical fiber ribbon cables. Obviously, if fiber optic cables are to be used in practical signal l~ ;S~on and p-oce~ Sy~h.llS, practical comlcclo,~ for the co~ e ;tion and disco~ ecl;~n of fiber optic cables must be provided.
Of conc;tl~rable relevance to the problem of developing practical fiber optic co~ e~ilors is the question of optical l-~.sreL ~ffic;en~y at the cn~ e~,lor. Various factors affect the optical ~l~rel efficiency at a connPctor in~ ing gap sep~lion at the point of ~t-,"~ .l and lateral separation due to axial mi~1ig...,.~
Nu,.~c.~us optical co~ o,s have been developed to aid in the colme-,lion of fiber optic ribbon cables. FY~mrles of pin-type connectors - W O 97/34179 PCT~US96/16052 are shown and described in U.S. Patent No. 5,315,678 issued to Maekawa, et al., and U.S. Patent No. 5,430,819, issued to Sizer, II, et a .
Both the '819 and the '678 patents describe metho~s for using ~liP~
pins for ~li~i~ co~ clor portions. There are several problems encuu-llered when using Ali~ pins which can be allt:vi~Led by using ~ti~nmPnt spheres. First, precise, tight tolerance ~lignmPnt pins are tiffic~llt to f~hnc~te and thus e,.~ensi~r_. In cGnL~ well understood ball bearing m~m-f~ctl~rin~ techniqlles can produce precise, tight tolerance spheres at ~ fir~ntty lower cost. ~econ~f smal ~lignm~nt pins are neither robust nor durable, regardless of composition; brittle pins tend to break while ductile pins tend to bend. Spheres, by virtue of their symmetricaf shape, tend neither to break nor to bend. Third, ~lig~ing parts - using two or more pins mPch~ni~Ally ovelcollsll~ins the ~fi~nm~nt and re.luiles that the angular orient~ti~n~ location, and çYtPn~fecf. cross-se~;ol-A1 rfi~mPt~r of each pin socket, as well as the ~f~ e~ and str~ightnp~ss of each pin, be tightly controlled to avoid co~ oullding errors which degrade the a~ip~ 1 In contrast, ~li nmP!nt using spheres depends only on the .lifi~ t~?~ of the spheres and the accurate location of the sockets which retain them, thus r.~ î;..g ov~.con~L,~i"l and the potential for compounding errors.
U.S. Patent No. 4,087,155 issued to Deacon discloses a method for ~tigning a pair of single fibers that does not use ~tignment pins.
Spe~ific~lly~ the Deacon '155 patent ~ti.~ ses a co~ e~;lor for coupling a pair of single optical fibers ~tili~in~ three equal fti~meter spheres to define a tricuspid inle,~Lil;al space ~I,e~ n into which an individual fiber is inserted. The spheres surround the ch-iulllr~el-ce of the fiber to keep the fiber ceQL~,ed in the co~neilQr, which has a circular race to hold the spheres. When a second like conl-ei~or is mated in an axial abutting relationship, the spheres in the cQ~ r-i!c,l~ nest with respect to each other to align the individual fibers. In order to properly align single fibers in thismanner, it is imperative that the equal ~ ..t,t~ r spheres sull~Julld the entire , .,i.~;u.l~er~..ce of the sing}e fiber. Unfortunately, the technique described in the Deacon 'l~S patent is not applicable to mllltifih~r cables such as O ribbon cables.
While there are co~ c~lo. ~ ~esi~ned for both single-and multi-fiber optical cables, there is a contin-led need for durable, precise, inrYrçn~ive and easy to m~nllf~lre optical connr,~,lo.~ that will ac~;ul~Lely align multiple optical fibers in two adjoining cc~ e.ilG. ~.
SIJMMARY OF THE INV~TION
The present invention provides a precise ~lignmrnt assellll/l~ for an optical fiber cable colin~clc-r for ~ligni~ and conne~ ends of a pair of mlTltifiher or single fiber optical cables. The ~li nm~.nt assembly would be comhin~d with ~d-1iti-)n~l coluleclor components, such as fiber strain relief - - m~.mhers and colule-i~or l~tçhinf~ members, to form a complete fiber optic colule~ lor. The ~li nm~nt assembly has a fiber ~tignm~nt block having a fiber ,t;ceivil~ surface and a connector ç~gem~ont surface. First and second op~ are provided in the conl~ ~Qr en~ nnent surface. An P.ti nm~nt ball is provided and is t}ghtly retained in the first opening for ~ti~i~ the co"ne~lor with another like connector, and specifically, for ~tignin~ optical fibers carried in the connectors.
The present invention also provides an optical cable connectQr sllig~ assembly ha-ving a sec~lrin~ member for se~ g individual fibers from a cable on~o the ~li~)....~..l assembly. The ~li~....~.ll assellll,ly has a fiber ~li~m~nt block that has a fiber receiving surface and a conne~lor ~gem~nt surface. The fiber receivill~ surface has a channel formed in it with at least one ~li nm~nt groove formed in the rh~nnPl A
se~ulh,~ member is provided that is sized to fit into the channel to retain individual fibers in the ~lignm~nt grooves. First and second openings are . provided in the colule-;~or en~ ment surface. An ~ nmPnt ball is provided and is tightly l~,~h.cd in the first opening for ~ ning the col~nçclor ~ emhly ~,-vith another like connector ~lignmrnt wo 97/34179 PCT/USg6/16052 assembly, and spe~-ifi~lly, for ~li ning optical fibers carried in the col-l-P.,lu- ~.
Also disclosed is a method for assembling such colnP,ctQr ~ligrmPnt assemblies to a fiber optic ribbon cable. A pair of ~li nmPnt assemblies are provided and are placed in a face to face arr~n~-PmP-nt The ~li nm~Pnt assemblies are app-opl;ately spaced apart by a spacing member.
A length of cable, optionally prepaled for insertion in the ~li nmPnt assemblies by removing some or all of the cabling and fiber coating m~tPri~l from a section of the fibers, is then provided on top of the ~lignm~Pnt ~ FS A sec~ring mPm~r is then in~t~ltP,d to retain the individual fibers from the cable in the ~li nm~nt grooves,of the z~li~mPnt assel..l)liF,s. The length of cable is then sawed or cleaved between the - ~lignmPnt assemblies. Finally, any necesc~ly end finichin~ or poli~hin~ iS
done.
BRIEF DESCJ~IPTION OF TE~ DR AWrNGS
Figure 1 is a pel~ye~Liv-e view of an optical cable comle~i~or s~lignmP.nt assembly according to the present invention.
Figure 2 is a front plan view ofthe Sllip~ F..~ assembly of Figure 1.
Figure 3a is a perspective view of a pair of ~lignm~nt assemblies acco,~ling to the present invention about to be connecte~l Figure 3b is a pt~:~ye~lliv~; view of the ~lignm~nt assemblies in Figure 3a co~ s.;Led Figures 4a-d illustrate an assembly process for assell,bli"g a plurality of 5l1igtlment ~c.~r.,~l,l;o,c in accG~ ce with the present invention vitha ,-l~ ir~ optical cable.
Figures 5a-c illu~ e an ~s~ ly process for applying an ~lignmPnt assembly in accordal ce with the present invention to an end of an optical cable.
Figure 6 is a pel~peclive view of an ~lignn~Pnt assembly of an ~hPrn~tive embodiment ofthe present invention.
Figure 7 is a cross section~l view taken along line 7--7 of Figure 6.

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Figure 8 is a cross secti()n~l view taken along line 8--8 of Figure 6.
DETAIL~D DESCRIPTION QF I~IE INVENIION
Figure 1 illustrates an optical cable co--neclQr ~lignm~nt assembly 10 accorlil,~ to one embodiment of the present i~ ion. ~li nment &ss_.llt~ly 10 has a fiber ~lignm~nt block 12 having a front edge 13, a rear edge 15, an optical fiber leCt;iv~llg surface 14 which tonp;~ges an optical cable 16, a co~ e~ilQr Fng5~g~...P...I surface 18 which abuts a CO~ ;lor engagement surface on another like connectQr ~li nm~nt assembly, a rear face 19 (illustrated in Figure 3a), a first side surface 21 and a second side surface 23 (not seen). Cable 16 is col"~lised of one or more individual optical fibers 17, and in the pr~rt;;-led embodiment the individual optical fibers are positioned ~dj~cçnt one another in a .sllbst~nti~lly planar - ori~nt~ti- n to form a ribbon cable.
Fiber receiving surface 14 cont~in~ a channel 20 formed out of fiber ~lignm~nt block 12. The channel co.~ c first and second channel g lips 22, 24 re~e.;liv~ly, and a charmel floor 26. Ret~inin~ lips 22, 24 are angled ou~v~,c,rd from front edge 13 to rear edge 15 to form a trapezoidal shaped çh~nnel Specifically, as ~ .;.lg lip 24 extends from front edge 13 to rear edge 15, it angles towards first side surface 21. As lel~ ;"~ lip 22 extends from front edge 13 to rear edge 15, it angles toward side surface 23. Also, IG~ g lips 22, 24 are slanted from top to bottom to form a locking mec.l~ni~... Preferably, ret~inin~ lips 22, 24 are formed from upper lip edges 22a, 24a and lower lip edges 22b, 24b, respectively. P~t~ini~ lips 22, 24 slant in at al~plux;...~t~ly a 30 degree angle such that lower lip edges 22b, 24b are doser to side edges 23, 21, ,t;;spe.;~i~rely than are upper lip edges 22a, 24a. It should be noted that greater or lesser angles of slant could be used without departing from the spirit or scope ofthe Llv~llLiol~.
One or more ali~nm~snt grooves 28 are formed in channel floor 26 to retain individual fibers 17 from fiber optic cable 16. ~li~mPnt grooves 28 ofthe plt;rt:lled embodiment are i~ sLlaled as being V shaped grooves, but grooves of other cross sectional shapes, such as rect~n~ r, U shaped or semi-circular shaped grooves could also be used without departing from the spirit or scope of the invention. Also formed in channel floor 26 is a cable jacket receiving channel 30. In normal operation, fiber optic cable 16 will be partially ~ ed to expose individual fibers 17 for pl~cPmPnt into ~ grooves 28. The cable jacket and optionally any fiber coating surrounding individual fibers 17 will be stripped back a ~l;s~ re at least equal to the length of ~lignm~nt grooves 28. By providing cable jacket receiving channel 30, individual fibers 17 may ~ .in a subst~nti~lly planar path throughout the entire width of fiber ~lignmPnt block 12.
Co,~..ç.;lor engagement surface 18 and fiber receiving surface 14 in - the pl~rel,ed embodiment are planar sllrf~cPc that lie perpen~ r to each other. It is also possible, and in some cases bçnPfi~ to have the plane of connector çn~gPmPnt surface 18 a few degrees ~preferably 6~-9~) from being perpçn~licul~r with fiber receiving surface 14, in order to reduce back rPflection of light within the fibers. The fiber rece;~ing sur~ace could be either 6~-9~ up or down from ho.i~ al without dep~i"g from the spirit or scope of the invention. ln other words, the angle between fiber lt;cei~/il,g surface 14 and cQnnectQr ~gPmPnt sur~ace may be in the range of 81~-99~
The optical fibers of the present invention may be single or mllhimode, glass or plastic fibers. l~llltimt~e glass fibers typically have a core di~mPtpr ranging from 50-100 micrometers. Single mode fibers have smaller core ~ mPtPrs. Because the mllltimo~le fibers have larger core di~ , they offer relaxed ~li nm~nt tolerances co",paled to single mode fibers.
A dove tail ~ .;..p. l"elY~ber 32 having a front edge 34, a rear edge 36 and side m~mhers 38, 40, is provided to secure cable 16 in channel 20, and in particular each of individual fibers 17 in ~lignmPnt grooves 28. An ~ccP.mhly detent 42 is provided on ret~inin~ m~mher 32 to W O 97/34179 PCT~US96/16052 assist in in~t~lling the rc~ .,.e "l~er. LTI the present embodiment dove tail mPmher 32 is ll~e20idal in shape with front edge 34 being shorter than rear edge 36. Side .Y~ c;~ 38 and 40 are s~ y the same size. Dove tail member 32 ~.ll,s~ lly COI~llllS to the size and shape of channel 20 and is sized to çng~ginf~ly slide under channel ret~inin~ lips 22 and 24. }?t;(~ C~ 32 has a width at front edge 34 greater than the ce between upper lip edges 22a, 24a and lesser than the ~ t~nce bc;lw~ lower lip edges 22b, 24b at front edge 13, and has a width at rear edge 36 greater than the t~ re between upper lip edges 22a, 24a and lesser than the ~ nce between lower lip edges 22b, 24b at rear edge 15.
member 32 has a height less than the vertical ~ t~nce from channel floor 26 to upper lip edges 22a, 24a. The height of ret~ininP
member 32 is appr-x;...~lPly 2 rnm, but greater or lesser heights can be used without dep~li"~ from the spirit or scope of the invention. l?çt~inin~
member 32 is sized such that front edge 34 is wider than channel 20 is at front edge 13, to ensures that when ret~inirl~ member 32 is inct~lled in channel 20, front edge 34 does not extend past front edge 13 and prohibit tight engagement with opl)osi,lg col-nec~
Fiber ~li~mPnt block 12 and ~ p member 32 are molded out of ceramic in the plerell~d embodiment. It would also be possible to make fiber ~ nmP,nt block 12 out of plastic, glass, metal, or any other known cc l~n~ , block materiat. By using a moldable m~ter;~l in the ~ rt:lled embod~m~nt, fiber ~ ""~," block 12 may be quickly and easily m~m-~ctllred as a one piece unit. For PY~mplP~ instead of having to carve out channel 20, and ~li nmPnt grooves 28, in the plerelled embodiment they can simply be created by the molrlin~ process.
Col.l.P-ilQr Png~PmPnt surface 18 colll~ns a first and a second opening 44, 46 respectively. Ca~tPll~ted projections 48, 49 are provided ~ and project ~om fiber ~ nmPnt block 12 sllbst~nti~lly parallel to each other and optionally ~ul~s~ lly perpenflic~ r to connector çng~g~mPnt surface 18. Projections 48, 49 are positioned ~rli~cpnt openings 44, 46, - W O 97134179 PCT~US96/16052 lt;~ec~ ely, and are integrally molded as part of fiber ~li nm~nt block 12 In the p.~ir~llt;d embodiment, c~lP~ ed projection~ 48, 49 extend from ~n~ement surfiace 18 appl~x;~ (ely 1/2 the di~m~tPr of an ali nmPnt ball 62, which will be d~s~..lJed in greater detail below. As can be seen in Figure 1, proje.,PQI~ 48, 49 have rounded inner 50, 51 and outer 52, 53 ~Irf~CP~ respectively. l?-lmded inner s~r~ces 50, 51 are adapted to receive the ~ ball, while outer surface 52, 53 are ~d~rted to clea~ ce fit into openings 44, 46 as will be described in detail below.
Openings 44, 46 can be seen in greater detail in Figure 2. As can be seen, openings 44, 46 are ~.lb~ iiy similar in shape, but opening 46 is rotated 90 degrees from opening 44. The purpose of this will be readily ap~ l after reading the description below. Opening 44 comprises a - main ~iylilldli~,al receiving cavity 54 and a pair of cleA,~ulce cavities 56.
Opening 46 comrr ~es a main ~;yLIl~;cal receiving cavity 58 and a pair of clea~ce cavities 60. Main cylin~ c~1 cavities 54, 58 have t1i~metçrs dl, d2, re~e~ tely~ in-iirated by arrows 57, 59, resl)e.;lively. Diallle~e,~ dl, d2 col.e~ond to the ~ t~nr~e bc;~ween cA~Ie~ ed projections 48, 49, re~e-;lively. In the l)lere-led embodiment of the present invention, ~i~mPtPr d2 of cylindrical cavity 58 is slightly larger than ~;;A~ r dl of cy1in~1rir,~l cavity 54, and acccldi.~ ly the tli~t~nre beLw~ell projections 49 is slightly greater than the ~lict~nce between projections 48. In the ~rert; I~;d embo-lim~nt the difference in ~ mPt~rs dl, d2 is on the order of a few microns. The precise ~limpn~ions will depend upon the type of fiber and comle~i~or materials sPlectecl :25 As can be seen in Figure 2, dearance cavities 56 and c~tPll~ted projections 48 subst~nti~lly ~ullou~d main cylindrical cavity 54. Likewise, c~tPll~ted projections 49 and clearance cavities 60 s~ lly ~u~Jùnd main cylindrical cavity 58. Cle~lce cavities 56, 60 are shaped ~ulJ~ ly similar to c~QtPIl~ted projectionR 48, 49 respectively, and are deep enough to completely receive the projections It is important that clea ance cavities 56, 60 be at least as deep as the c~t~ ted pr~e~,Lions W O 97/34179 PCT~US961160~2 48, 49 so that when two connectQrs are joined, their engagement surfaces 18 can contact each other, thus allowing the ends of the optical fibers carried by each col-ne~iLor to be in close ~l.J~mlLy.
Precision ~li~m~nt ball 62 is provided for insertion into opening 44 b~;Lw~en c~ct~ ted pro~ectionC 48. r~ci~;on ~li nm~nt ball 62 is provided to prccisel)~ align fibers 17 in ~ nm~nt grooves 28 for ~ nmPnt with fibers in another like conn~ or~ as will be ~lescrihed below. Ball 62 is a highly precise stee1 ball bearing but could also be formed from other materials having the precision of a ball bearing such as tlln~.ct~n carbide, ceramic, other metals, or plastics, such as liquid crystal polymers, without departing from the spirit or scope of the invention. In the ~rerel,ed embodiment, ball 62 has a (li~met~r of app~ Iy 2mln and a f~
- tolerance of applu~;.. ~t~ly :tO.S microns. It is hl~olL~IL to note that tolerances will vary depending upon the material used for the ali~nm~n ball. While the tolerance ranges are illl~o~ to the proper operation of the present invention, it will be recognized that greater or lesser ~ met~r may be used, without dep&-L I~ from the spirit or scope ofthe invention.
As stated above, dl of main cylin-lric~l cavity 54, and therefor the rlict~n~e between proje.ilion~ 48, is slightly smaller than d2 of cavity 58.
This is to tightly retain ball 62 in cavity 54. C~te11~ted projections 49 are dçci~ned such that the ~ ce b~:Lweell them (d2) allows them to releasably slide about ball 62 If ball 62 was inserted into opening 46, it would not be tightly retained and could fall out. The tolerances for the t~nees between projectirnc 48, 49 once again depend upon the m~eri~l used. IntheplefelIcdembodiment, ceramicisusedforthefiber~ nment block, inr~ in~ the projections. In this case, the toleramce for the ~lict~nce bc~ween projections 48 (which form an illL~lrerence fit with the ali~nm~nt ball) is approx;.n~e1y +7-3 microns, and the tolerance for the tli~t~nce ~ between projections 49 (which form a clearance fit with the ~ nm~?nt ball) is approx;~ le1y iO-2 microns. If plastic is used for the projections, the tolerance for the ~lict~ e between projectionc 48 is appl.,~lnately iS0 microns and for projections 49 is a~)plox;~ ely +50 microns.
It is important to note that in the present embodiment, ball 62 need not be at any specific depth or position in cavity 54, beLween projection 48. Ball 62 may be retained belween projection~ 48 entirely outside of cavity 54, it may be half inside of cavity 54 and half o~tei~le~ or it may be entirely inside of the cavity, or anywhere in bclwec~, without altering the capabilities ofthe present invention. It should also be noted that ball 62 could be bonded belwcen projection.~ 48, if desired, without departing from the spirit or scope of the invention. Furthermore, it should be noted that it would be possible to have cylindrical cavit;es 54, 58 the same size, such that both cavities slidingly receive ~lipnmPnt ~all 62.
While such an embodiment would not prevent ball 62 from falling out of a cavity when conl-P~ilo.~ are not molmted together, it would give ~rltlition~l freedom in de~;dinf~ which cavity to insert the ball into.
Figures 3a and 3b illustrate two connectQr ~ nm~nt assemblies made accoldi.l~ to the present invention being plecisely fitted together.
Conn~ctQr ~lignmPnt ~ lies 10 are illustrated having fiber optic ribbon cables 16 retained in ~li~m~nt grooves 28 by l.;Lni~ g member 32. As can be seen, balls 62 have been inserted into receiving cavities 54 of both conl~e.ilor ~li~mPnt asse ..l~lies 10. Ca~t~ ted projections 48 provide a tight fit to retain ball 62 in cavity 54. As the connector ~lignment ~semhti~s are brought together, c~ct~ ted projections 48 fit into cleal~lce cavities 60 and projections 49 fit into clearance cavities 56.
R m-led inner surfaces 51 of projections 49 slidingly engage ball 62 as they are inserted into clearance cavities 56. When co~ e-;le~l as in Figure 3b, individual fibers 17 of ribbon cables 16 are plccisely aligned with each other, and the conn~ctor ~ nm~nt assemblies are consll~ined from moving in ~ ;ple directions.
The present invention also provides a method of alltom~ting the assembly of connector ~lignm~nt ass_.lll)lies 10 with a ribbon cable. This W O 97/34179 PCT~US96/16052 m~tho~is illustrated sc~ y in Figures 4a-d. As can be seen, a pair of CO~ e~il(!t s~li~mPnt s~.e.eP.mhlieS 10 are provided and are positionPd in a face to face ~uln~ .l In the p~ert;lled embodiment, a spacing member 71 is provided to space connectQr AlignmPnt assemblies 10 an a~lop-;aLe ~lic~nce apart. Spacing Inrn~b~r 71 of the present invention is a disposable spacer that spaces the ~li~mPnt assemblies apploxi~ çly 0.015 inch (0.038 cm) apart, but greater or lesser rliet~ncP~s may be chosen without dep~~ g from the spirit or scope of the L./e..lion. Spacer 71 is ~l~;r~ bly made of plastic, but any other suitable spacing m~tçri~l may also be used. Connsctor ~tignm~nt assemblies 10 may also be secured in place by some sort of ~ l~",p;l~g .. ecl~Al~icm without departing from the spirit or scope ofthe invention.
- Once the connPctor ~ nmPnt assemblies are applul ,iaLely spaced apart, a length of fiber optic ribbon cable 72 is provided from a continuous roll or similar contimlolle supply. The ribbon cable is poeitioned over connector ~ligll...~,.,l ae~e~ e 10 such that individual fibers are positioned in each of Ali nmPnt grooves 28. A r~ g mPmhPr 32 is then installed on both ~AlignmP.nt assemblies 10 to tightly retain the ribbon cable on the co~ P~;lor ~lignmPnt ~eeemhliPe At this point, ribbon cable 72 is then sawed or cleaved at the location of spacer 71. Finally, any neCP~ee~ry fini.ehin~ or polishing of the fiber ends is done. The above method is also equally applicable to Aeeçmhlin~ a single connectQr to the end of a length of ribbon cable.
The co~ e~iLQr ~ eePmhlies of the present invention are also very well suited for easy field connP.iLo. ;,~ion. This type of m~ml~l fie~d connectQri7~tion process is illustrated in Figures 5a-c. In the field, a te~.hn~ n first locates a desired lor,~tir~n for conl-e~lQr 10 along a length of ribbon cable 75. The cable is then cut at that point. The ine~ tion ~ coating about the fibers is then stripped to expose individual fibers 76.
The individual fibers are then placed directly above ~ nmPnt grooves 28 of the ~ nm~nt assembly. Next, ~ . member 32 is slid into channel W 097/34179 PCT~US96/16052 20 of the ali~nmPnt assembly to tightly retain fibers 76 in ~ nmPn grooves 28. The portion of the fibers c~ beyond connPctor Pngape~.~e~.~ surface 18 is then cut off, and any np~cess~y fini~hinf~ or polishing is then l~c~ ed.
A first alle~llalive embodiment of the present invention is illustrated in Figure 6. Figure 6 ill~lDL-~L~,s a pair of like ~lignmPnt ~cs~ hlip~s 80 about to be joined together. ~Ati~mPnt assembly 80 comprises a fiber ~ nm~Pnt block 82 that has an optical fiber ~ecc.~ surface 84 and a Cnl~ ;LQr engagement surface 86, which abuts a connP,ctQr en~ PmPnt surface of another like co~ e~;lor. In this embodiment, fiber ~lignmPnt block 82 is molded out of ceramic or glass. A plurality of ~li~mPnt grooves 88 are formed in fiber receiving surface 84 to retain individual - fibers from a fiber optic cable. The fibers are retained in ~li nment grooves 88 by any known securing means, such as with adhesive tape or a bonding agent.
Co~ e~ilor er~Ag~ surface 86 co~ .e a first and second opening 90, 92, lc~lJeclivcly. O"e~ g~ 90, 92 are co~ led to bores 90a, 92a, Ic~e~ ,ly, that co~tim~e though the length of ~lip,.,,~.~..l assembly 80 and tr~ Je at rear openings 90b, 92b, respectively. Bores 90a, 92a 2û and rear openings 90b, 92b can be seen in greater detail in Figures 7 and 8. Opening 90 is sized to recesve a subsLal.l;al portion of an ~ nm~nt ball 94, as will be des~"il ed in detail below. Opening 92 colll~.-ises a ~l~h~ r 93 which is sized to receive and have secured inside a portion of ~li nm~nt ball 94.
Chamfer 93 can be seen in greater detail in Figure 7. As can be seen, e~ 93 is formed to retain less than 1/2 of ~ nmPnt ball 94.
SPe~;fiC~11Y~ A~r~ 93 has a depth d3 inrlic~ted at 95 which is less than the radius R, jn~ic~ted at 97, of ~li~mPnt ball 94. In the plere.led alternate embo~lim~nt ali~nmPnt ball 94 has a ~ eleJ d4, in~ic~ted at 99, of al,plu~ cly 2 mm, Ih~-t;rore it has a radius of applu~lalely 1 mm.
Thus, d3 95 is less than applv~illlalcly 1 mm and is in range of about 0.5-CA 022459l7 l998-08-l3 W O 97/34179 PCTrUS96/16052 0.7 mm deep. Once ball 94 has been seated in ~h~ r~ 93, a bonding agent is introduced through rear ope~ 92b, to secure ball 94 in opening 92. It should be noted that it would also be possible to have an ~li nm~n assembly without bores 90a, 92a throughout the length of the ali~nm~nt ~ 5 assembly. A bonding agent could be applied directly to G~ 93 and then ball 94 could be inserted therei4 as long as the bonding agent is irol..~ly applied so that ~lig"".~ ball 94 accu-~ely seats in c~ r~l 93.
P~ef.olTinp now to Figure 8, OpG~ g 90 is illusl~Led in greater detail. Opening 90 is sized slightly larger than ~i~m~tPr d4, as inrlie~ted at 99. This allows ~ nmpnt ball 94 to slidingly fit into opening 90. As can be seen in Figure 8, rear openlllg 90b and bore 90a are larger than openillg 90. This is to reduce the area needed to be m~r.hin~tl Precision is the key - to ~li n;n~ optical fibers, thus openillg 90 is m~.. hined to very tight tolerances, on the order of 4 or 5 microns. By having bore 90a and rear opening 90b larger than opening 90, a m~hinin~ tool only has to m~hine a small surface area.
Precision ~lignm~nt ball 94 is provided for insertion into opening 92. Ball 94 is provided to precisely align a pair of connector ~lignment assemblies 80 which in turn precisely align individual fibers of the fiber optic cable secured to the ~lig~.,.,~.,l asse--l~lies. Ball 94 is a highly precise steel ball bearing having tolerances in the range of ~0.5 microns for applications using single mode fibers and in the range of +~ microns for applications using ml~ltimode fibers. Ball 94 could also be formed from other m~teri~le having the precision of a ball bearing such as tlmp;eten carbide, ceramic, other metals or plastics, such as liquid crystal polymers, without dep&lling from the spirit or scope of the invention. As stated above, ball 94 is bonded into opellillg 92. The bonding can be achieved by an adhesive or a low melting tGIl~e-~lule ceramic seal glass, which would ~ flow at moderately high telll~GlalulGs, and then bond to both the ceramic or glass fiber ~lignm~nt block 80 and the ~lignm~nt ball 94 upon cooling.

W O 97/34179 PCTrUS96/16052 Other bonding agents may also be used without departing from the spirit or scope of the present invention.

Claims (18)

1. An optical fiber cable connector alignment assembly (80) comprising:
- a fiber alignment block (82) having a top-loading fiber receiving surface (84) for receiving at least one optical fiber from an optical fiber cable (16) and a connector engagement surface (86), - first and second openings (92,90) formed in the connector engagement surface (86), wherein the first opening has a depth d1 and the second opening is generally cylindrical and has a diameter d2, and - an alignment ball (94) having a radius R retained in the first opening, wherein R > d1 and 2R < d2.

2. The connector alignment assembly as in claim 1 wherein the fiber receiving surface comprises at least one alignment groove (28) for retaining at least one fiber from the optical fiber cable.

3. The connector alignment assembly as in claim 1 wherein the connector engagement surface forms an angle in the range of 81° to 99°, with the fiber receiving surface.

4. The connector alignment assembly as in claim 1 wherein the second opening is sized to slidably receive an alignment ball retained in a corresponding connector alignment assembly to which the optical fiber cable connector will be mated.

5. The connector alignment assembly as in claim 1 further comprising a first pair of projections (48) adjacent the first opening and a second pair of projections (49) adjacent the second opening wherein the projections project from the connector engagement surface.

6. The connector alignment assembly as in claim 5 wherein the alignment ball is retained between the first pair of projections.

7. The connector alignment assembly as in claim 5 wherein the alignment ball is slidably engageable with the second pair of projections.

8. The connector alignment assembly as in claim 5 wherein the first opening is sized to receive the second pair of projections and wherein the second opening is sized to receive the first pair of projections.

9. The connector alignment assembly as in claim 1 wherein the alignment ball is fixedly secured into the first opening.

10. The connector alignment assembly as in claim 1 wherein the alignment ball is bonded in the first opening.

11. The connector alignment assembly as in claim 1 wherein the first and second openings connect to first and second bores respectively, and wherein the first and second bores extend throughout the width of the fiber alignment block.

12. An optical fiber cable connector alignment assembly (10) as in claim 1, further comprising:
- a channel (20) formed in the fiber receiving surface, - at least one alignment groove (28) formed in the channel (20), and - a securing member (32) sized to fit in the channel (20) to secure the at least one optical fiber in the at least one alignment groove (28).

13. The connector alignment assembly as in claim 12 wherein the channel has a channel surface (26) and first and second channel lips (22,24) and wherein the channel lips (22,24) comprise upper and lower lip edges (22a,24a,22b,24b) wherein the upper lip edges are a first distance apart and the lower lip edges are a second distance apart and the upper lip edges are a third distance from the channel surface (26) and wherein the channel lips slant inward from the upper lip edge to the lower lip edge such that the first distance between the upper lip edges is less than the second distance between the lower lip edges.

14. The connector alignment assembly as in claims 12 and 13 wherein the securing member has a thickness less than the third distance between the upper lip edges and the channel surface.

15. The connector alignment assembly as in claim 14 wherein when the securing member is inserted into the channel the securing member is retained in the channel by the first and second channel lips.

16. The connector alignment assembly as in claim 12 wherein the alignment ball (62) is retained in the first opening.

17. A method of assembling at least a pair of optical connector alignment assemblies (10) on a continuous optical fiber cable (72) wherein the connector alignment assemblies (10) have a fiber alignment block (12) having a fiber receiving surface (14) for receiving at least one optical fiber from the cable (72) and a connector engagement surface (18), a channel (20) formed in the fiber receiving surface (14), at least one alignment groove (28) formed in the channel (20), and a securing member (32) sized to fit in the channel (20), the method including the steps of:
- positioning the at least one pair of connector alignment assemblies (10) in a face to face arrangement, - positioning a spacing member (71) between the connector engagement surfaces (18) of the at least one pair of connector alignment assemblies (10), - laying the continuous optical cable (72) over the connector alignment assemblies (10) such that individual uncoated fibers of the cable (72) are positioned in each groove of the alignment grooves (28), - installing the securing member (32) to retain the cable in the alignment grooves (28), and - cutting the cable (72) between the connector alignment assemblies (10).

18. A method of assembling an optical fiber cable (16) with at least one pair of connector alignment assemblies (10) wherein the alignment assemblies (10) have a fiber alignment block (12) having a fiber receiving surface (14) for receiving at least one optical fiber (17) from the cable (16) and a connector engagement surface (18), a channel (20) formed in the fiber receiving surface (14), at least one alignment groove (28) formed in the channel (20), a securing member (32) sized to fit in the channel (20), first and second openings (44,46) formed in the connector engagement surface (18), and an alignment ball (62) retained in the first opening (44), the method including the steps of:
- positioning the at least one pair of connector alignment assemblies (10) in a face to face arrangement, - positioning a spacing member (71) between the connector engagement surfaces (18) of the at least one pair of connector alignment assemblies (10), - laying the optical cable (16) over the connector alignment assemblies (10) such that individual fibers of the cable (16) are positioned in each groove of the alignment grooves (28), - installing the securing member (32) to retain the cable (16) in the alignment grooves (28), and - cutting the cable (16) between the connector alignment assemblies (10).