CA1230381A - Piezoelectric apparatus for positioning optical fibers - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A communication exchange comprising a first plurality of electromagnetic transmitting units each of which provides a beam of information bearing electromagnetic radiation trans-mitters; and means for causing a second plurality of electromagnetic radiation receiving units arranged in radiation receiving relationship with said first plurality, each receiving unit being arranged to receive radiation from said first plurality of electromagnetic radiation transmitters; and means for causing the radiation from any selectable one of said transmitting units to be received by any select-able one of said receiving units for establishment of communications therebetween. In a preferred embodiment said communications exchange is comprised of apparatus for select-ably positioning an optical fiber end along a range of posi-tions comprising a bender assembly including at least one piezoelectric bender element and having a first end thereof arranged for association with one or more optical fiber ends and a second end thereof located at a reference position.
Suitable application of electrical energy to the piezoelectric bender element causes it to assume a selected position along the range of positions. Various embodiments of bender assemblies and applications thereof in communications are also described.

Description

1 This applic~tion is a division of co-pending application serial number 36~,08~ filed on January 22, 1981.
The present invention rela-tes to optical fiber commun-ication~ and more particularly to optical fiber switching and interconnections.

E~ACKGROUND OF THE INVENTION
In recent yèars optical fibers have come into widespread use in a wide variety of applications and particularly in commun-ications. The efficient ~tilization of optical fibers in many applications is depen~ent on the ability of associated apparatus to accurately and repeatably position optical fiber ends. Pre-sently various mechanical devices such as x-y-z translators, concentric tubing and V - groove assemblies are employed for positioning of the optical ~iber ends.
It has been proposed to employ a single piezoelectric bender element as a t~o position sw~tch for an optical fiher.
See Y~ Ohmori and H. Ogiwara, Applied Qptics, Vol. 17 No. 22 P.3531. ~his reference does not contaln any sugyestion of usincJ
such a bender element for selectable positionin~ alor,g a ranc3e of positions~
Swi-tching employing directable light ~eams has also been proposed in U.S. Patents 3,985,975 and 4,065,644, using holograms and CRT tubes for directin~J
the ligh-t beam.
The mecnanical apparatus presently used for positioning of optical fibers involves significant disadvantages in terms of cost, cleslgn limltations and reliability. The inadec~uacies of presently known optical fiber positioni.ng apparatus are believecl to limit the introduction of optical fiber technology into many other possible applications.
SU~ARY OF THE :[NVENTION
The present invention seeks to overcome the disadvantages of the prior art apparatus for positioning optical fibers and to provide apparatus for positioning optical fibers which is characterized by yreatly improved perEormance characterlstics, design flexibility and eeonomy and significantly smaller size.
There is thus provided in accordance with the present invention apparatus for selectably positioning an optical. fiber end along a range of positions com~rising a bender assembly comprising at least one piezoelectric bender element and having a first end thereof arranged for association with one or more optical fiber ends and a second end thereof located at a reference position. Suitable application of electrical energ~ to the piezoelectric bender elemen-t causes it to assume a selectecl position cl.-~OnCJ the range of positions.

Further in accordance ~Ji th an embodiment of the present invention there is provided apparatus ~or selec~abl~
positioning an optical fiber end comprising a bender assembly comprising a plurality of piezoelectric bender elements arranged - in serles and such that the motion of the bender elements have mutually perpendicular components.
~ e present invention also seeks to provide a switch-ing exchange for telephone or o-ther communications apparatus which is simple and which is easy to construc-t, economical and modular in the sense that it can be accommodated changeably to the growing needs of a customer.
There is thus provided according to the invention a communications exchange comprising a Eirst plurality of electromagnetic radiation transmitting units each of which provides a beam of information bearing electromagnetic radiation;
and a second plurality of electromagnetic radiation receiving units arranged in radiation receiving relationship with said first plurality, each receiving unit being arranged to receive radiation from said firs-t plurality of electromagnetic radiation transmitters; and means for causing the radia-tion from any selectable one of saio. transmitting units to be received by any selectable one of said receivi}lg units for establishment of communications therebetween.
There is further provided in accordance with a preferred ; ernbodiment o-f the invention a communications exchange comprising a first array of transmitters employin~ piezoelectric bender elements, each o-f which provides a beam of information bearing electromagnetic radiation in a selectable direction;
a second array of electrornagnetic radiation receivers arranged in radiation receiving relationship with the first array whereby the radiation output o:E any of the transmitters may be directed for receipt thereof by any selected one of the receivers. In accordance with the invention, instrucfiorls are provided to the transmitters for establishing communications between subscribers connec-ted to respective transmitters and subsc-ibers connected to respective receivers impinged upon by -~diation from respective transmitters.

~ urther in accordance with an embodiment of the invention each subscriber is connected to one -3a-~æ~r3~3~

transmitt~r and to orle recei.ve~ 5ucn that t'~O--~7rl~
communica~i.on is establlshed by -the ~a~l of modulated radia-tion beams. Preferahly, every transmitter can communicate with every receiver.
Additionally in accordance wlth an embodiment of the present invention there is provided a communications exchange comprising a first array o~
transmitters, each of which provides a beam of information beariny electromagnetic radiation and at 1~ least one directable electromagnetic radiation receiver arranged for selectable radiation receiving relationship with one or more transmitters of the first array.
It is a particular fea-ture of the present invention that substantially no cross talk is encountered since the intersection of electromagnetlc radiation produces substan-tially no interference.
BRIEF DESCRIPTION OF THE D~WLNG~
The present invention will be more fully understood and appreciated from the following detailed description taken in conjunction with the drawings in which~
Fig. 1 illustrates a one-dimensional optical fi.ber end positioning device constructed and operative in accordance with an embodi.ment of the present invention;
Fig.s. 2 and 3 illustrate respective two- and three-dllnensional counterparts of the device illustrated in Fig. 1, ~ig. 4 is a schematic illustration of a ~irectable transmit-ter;

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E'ig. 5 is a schematic illustratiori OL a transmitter constructed and operati~e in accordanc~
with an alternative embodiment of the invention;
Fig. 6 illustra-tes display apparatus employing positioning devices of the present invention;
Fig. 7 illustra-tes cletecting apparatus employiny positioning devices of the present inven-tion;
F,ig. ~ illustrates a one-dlmensional optical fiber end positioning device associated ~Jith a single array of optical fibers;
Fig. 9 illustrates a one-dimensional optical fiber end positioning device associated with a plurality of arrays of optical fibers;
E'ig, 1~ illustrates optical fiber positioning apparatus employing rod lenses;
Fig. 11A illustrates a multi-position selector for coupling one op-tical fiber to a selected one of a plurality of optical fibers;
Fig. llB is a sectlonal view taken along lines

2~ A ~ A of Fig. llA;
Fig. 12 illustrates coupling of an optical fiber to a radiation transmitter;
Fig. 13A illustrates coupling of an optical fiber to a selected one of a plurality of radiation transmitters;
Fig. ~3B is a sectional view taken along lines A - A of Fig. 13A;
Fig. 14 is a schematic illustration of a portion of a communications exchange cons-tructed and operative in accordance with an embodiment of the preserlt inv~ntion;

Fig. 15 is a scllematlc illustratiGrl of transmitter and receiver arrays use,ul in the exchange of Fig. 14i FigO 16 shows alternative arrangements of - transmitter and receiver arrays useful in the exchange of Fig. 14;
Fig. 17 is a schematic illustra-tion of a s~itching exchange comprising a pair of faclng arrays each having in-terspersed receivers and transrnitters;
Fig. 18 is a schematic illustration of a switching exchange comprising an array of inter-spersed receivers and transmilters and a reflecting element;
Fig. 19 is a block diagram illustration of transmission and receiving apparatus associated with a single subscriber in the exchange of Fig. 14;
Fiy. 20 illustrates, in blo_k diagram form, apparatus for calibrating the transmission apparatus i]lus-trated in Fig. 19;
Fig. 21 is a schematic il~ustration of a swltching exchange useful for cable television and similar transmissions;
Fig. 22 is a block diagram lllustration of apparatus for high accuracy feedbac}c co~trol of a direc-tional transmitter;
Figs. 23 and 2~ are pic-torial illustr~tions of arrangements of opticaL Eihers associated with piezoelectric bender assemblies in accordance with the present invention.

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.i D~L;,Ir~1LEI) D~.~C~IP'11IOi`1 OF. T~1E INVE~IT~ J
The preferred ernbodi.rnent of the invention will now be describeA with reference to Flgs. 1 - 24 which illustrate a varie-ty of constructions thereof suitable for different applications.
Re:Eerring now to Fiy. 1 there is seen apparatus for positioning an optical fiber end constructed and operative in accordance wi.th a pre:Eerred embodiment of the present invention and comprising a generally elongate piezoelectric bender elemen-t 20 which is mounted at a first end thereof onto a base 22.
The piezoelectric bender element 20 may be of conventional cons-truction and manufacture such as a G-1278 head Zinconate-Titanate Thin Sheet piezoceramic manufactured by Gulton Industries of Metuchen, New Jersey, U.S.A. Leads 24 associated with the piezoelectric bender element may be connecte~
to any suitable source of electrical voltage for controlling the position oE the free end 26 of the bender element.
In accordance with the present inven-tion, the free end 28 of an optical fiber 18 is attached as by glueing, clamping or by any o-ther suitable means onto the ree end 26 of the bender element ~0 or adjacent thereto or motion together therewith.
Fig. 1 illustrates bender element 20 in a straight orientation at rest when the bender element is de-energized and curved to one side when a voltage o a firs-t polarity is applied to leads 24 by means of a selectable vol-tage source 16. It may be appreci.at~cl that nc),~rn<ll.1y L:he ~ nder elel,lcr~L-. may al.so ~ ~3~3~ -be bent in an opposi-te direction by application oi a voltclge of an opposite polari-ty to leads 24.
Furthermore any desired position intermediate tne two extreme bent positions may be realized by tne application of a suitable volta~e to the leads ~4.
It is a particular feature of the present inven-tion that piezoelectric bender elements 20 of the type employed herein display a generally linear and repeatable position in response to voltage inputs within part of their operative range. ~he position-voltage characteristics can be calibrated and an open loop control may thus be employed.
P~elatively complex control circuitry employi.ng microprocessor technology may be employed to ~ake into account the hysteresis behaviour of the posi.tion voltage curve of the bencler elements~
~onventional technology is available for th.is purpose.
Referx.~ng now to Fig. 2, there is seen apparatus for positioning an optical fi~er end along two dimensions. The apparatus comprises the apparatus of Fig. 1 to which is at~.ached at the free end of bender element 20 a second bender element ~0 which is oriented such that it`s plane of bending lies perpendicular to the plane of bendlng of bender e:Lement 20. In the illustration, t.he apparatus Ol Fig. 1 is shown rotated 90 degrees from the illustrati.on of Fig. 1 and bender element 30 is attached to the free end of bender element 20 by means of a mounting element 32 formed of metal or any o~her suitab.le m.ll,eri.,~l. Bender elelllent 30 is ~l~3~)3~ ~
provi~ed ~ tll leadc; ~t~ hich a~e coupled to position control ci,rcultry (not sho~,m). The free end 28 of the optical fiber is mounted on the free end of bender element 30.
Fig. ~ shows appara~us for posltioniny an optical fib~r en~ along three dimensions and comprises the apparatus of Fig. 2 to ~7hich is attached ~y means of a second mounting element 36 a third bender element 38 a-t the free end of second l() bender element 30. Leads 40 are associated with the third bender element 38 and are coupled to position control circui-try (not shown). In practice third bender element 38 is oriented such that its bendincJ plane,is perpendicular to the bending planes of bender elemen-ts 20 and 3n and serves to position the free end 2~ of the optical fiber which is attached to its free end for focussing purposes.
Bencler elements 20 and 30 may be movea through their position ranges to provlde a scanning function.
It is apprecia-ted that the bender elements forming a multi-element bender assembly need not neces.sarily be arranyed in perpendicuLar planes.
Instead it may be sufficient that their directions of motion have respecti,ve perpendicular components, Fig. 4 shows a simp:Lified version of a transmitter useful in t~1e present invention and comprising a selectable position modulatable light source 42 which is substantially similar to those lllustrated in Figs, l, 2 and ~. The free end 28 of the op'ical fiber 2rovides a beam of electromagnetic radi~ i Gii ~ A~ i .i. Ci-l i. m ~ J ~'S ~ tl ~ ~16 i,t.lict~ u~
the beam at a location which iS se~ected to correspolld

3~ ~
1 to a receiver ~. 1he l~ositic,r~ of tlle opt-ifal ~7r,er ''.d ~8 determines the locat:ion of tne irlpinginy~ ~oc~sed 'r,ea Reference is now rnadc to Fig. 5 ~7hich illustra-tes a transmitter substantially similar to that lllustrated in Fi~s. 1, 2 and ~ with the difference being that here the lens 50 is mounted on the free end of the bender element 52 in front of the end of th~- fiberopt:ic conduit 54 and thus moves together with the free end of the bencler element. Beam directing is achieve~ by changing the dlrection of the free end of the bender element.
A rod lens may be used instead of the lens 50.
~ lternatively, the elements described in Figs. 4 and 5 may be utilized as directable radiation detec-tors.
Fig. 6 illustrates one of the applications of the positioning apparatus illustrated in Figs. 1, and 3. In Fig. 6 r two dimensional positloning apparatus 56, such as that illustrated in Fig. 2, is associated with a lens 58 which images light emerging from the free end 60 o~ the optica7 flber onto a screen 62. A liyh-t source 6~ which communicates with the opposite end of the optical fiber 68 supplies desired radiation which may be positioned on the screen or scanned thereover as desired, simllar to the rastex scan of a televlsion but slower.
I'he apparatus of Flg. 6 is particularly suitable for use in 510w scan applications in which cathode ray tubes are presently employed such as :in I:lfctrocarc1:iogr!phs.

~303~
1 A r~diation de-~ector may ~e constructed using the positioner of the present invention as illustrated in Fig. 7. ~ lens 70 provides an image 7~ of an ob]ect 7~. Positionlng app~ratus 7 such as that lllustrated in any of Fi~s. 1, 2 and 3 positi.ons the end 77 o~ -the optical flber 78 to the i.rnage location so as to enable light from the image to be transmitted along the optical fiber 7 t:o a de-tec-tor 76.

In accordance with a preferred embodiment of the present invention, a plurality o:E images of radiation sources may be provided by lens 70. The positioning apparatus 75 is then operative to selectably and changeably position the optical fiber end at a selectable image, thus providing a direc-table receiver.
A multi-fibcr end one dimensional scanner is illustrated ln Fig. ~ and comprlses a relatively wide piezoelectxic bender element 80 mounted on a base 82 and having associated with the free end ~4 thcreof a one-dimensional array of optical fiber ends 86. Oscillation of bender element 80 along one dimension provides a raster scan of a scene imaged by a lens 88. A rela-tively fast scan may be provided in this manner. The optical fibers may be connected at their opposite ends 89 to a linear detector array 87-~ s seen in Fig. 9, a plurality of arraysof op-tical fiber ends may be associated with a s.ingle bender elernent 80. In such a way a color televi.sion type~ c.l~ner-l may be con~tructe~l b-y employlng detectors ~1 havinc3 diEferent spec'-ral ~3(3~
J responses. Similarly a color television t~pe camera may be constructecl on the hasis of L~e apparatus illustrated in Yig. ~ by employincJ
optical fiber ends transmit-tinc3 spectrally different lic3ht or de-tectors of dif~erent spectral response in array 87.
It may be appreciated that by replacing the detectors in the apparatus of Flgs. 8 and 9 with li~ht sources, a raster scanned display rnay be provicled.
Referriny now to Fi~. 10 which illustra-tes selectable swit~hln~ and couplin~ apparatus employing optical fiber ends, rod lenses 90 and 92 are connected to the free ends 94 and 9~ of respec-tive optical flbers 98 and 100. Rod lenses 90 and 92 are mounted on the free ends of respective piezoelec-tric bender elements 102 and 10~ which are arranged to have perpendicular bending planes and are mounted onto a frame 106. It is no~ecl that the bender elements are employed to selectably vary -the direction of the rod lenses. In the illustrated embodiment, when the rod lenses are directed parallel, radiation -transmission there-be-tween is permi-tted and when t:hey are directed in dif~erent directions, lit-tle or no such transmission occurs.
It is noted with respect to the embodiments illustrated in Fig. 10 that a plurality o~ bender elements arranged in series in the sense of Figs. 1, 2 and 3 may be employed. Also a plurality of o,t:ical Eit~c~3^ encls may be Inoul-l-'-ecl on each b~nd~
element.

1 Reference is now made to Figs. llA and 11~
which illustrate an optical fib~-?r switch 110 which is operative to selectably place an opticai fiber end 111 in a desired alignment with a selectable - one of an array 11~ of optlcal fiber ends. In the illustr~ted construc-tion a one-dimensional positioning device similar to tha-t illustrated in Fig. 1 ls employec1 for positioning of optical fiber end 111 ancl the array 112 of optical fibel ends are arranged in the bending pl~ne of fiber end 111 in a rac~ial orientation. It may be appreciated that control apparatus 11~ may be provided for applying a desired voltage to the bender element 116 of the positioning device to effect alignment of fiber end 111 with a desired fiber end in array 112 for radiation t,ransmission therewith.
All optical fiber ends ll.L and 112 lie on flat surface 1~6 of the base 1~8 which produces the needed alignment of fibers in the plane parallel to surface 126. Agai.n, two dimenslonal benders can be utiliæed to eliminate the need for surface 126 and a third bender element may be used to adjust the fiber end-to~end distances. T~e surface 126 may he grooved in order to define discreet positions for the fiber ends 112 for precise alignrnent thereof with fiber end 111.
Some of the fiber ends 112 may be use~l for calibration purposes. Suppose that fibers 118, 120, - 1~2 and 124 are connected t:o a light source 125 having differen-~ light charactteris~ics which can be d:i.st,inc3uished frc~r.l .I.igllt eln~.?r~Ji.ng from t~ t)tllt?:

r~3~ , fiber endc; 112, and having part of the light enterin~3 fiber end 111 detected by detector 1~3.
By scanning the fiber end 111 from a po~ition facing fiber 118 to a position faciny the end Or fiber 120, the cli~ferent voltages applied to the piezoelectric c~lemen-t 11~ may be recorded wnile the light of source 125 is reachin~ peak value on detector 123. By extrapolation, the voltage needed to reach a position facing any of the fiber ends 112 may be calclllated. Fibers 122 and 124 may serve to increa~e the aceuracy of extrapolation.
The hysteresis behavior of the position-voltage characteristics o~ the piezoelectric element 116 will be covercome by ]etting the element travel a sufficient distance to have element 116 reach its llnear characteristics before fiber end 111 comes to a pOSitiOIl facing fiber 118.
Similar calibration can be achieved by replaeing detector 12~ with a light source and light source 125 with a detector.
Control circuitry 114 may conveniently comprise a microprocessor of conventional construction which is progra~ned to carry out the desired func-tlons.
Reference is now made to Fig. 12 which illustrates the selectable coupling of an optical fi~er end 130 to a ligh-t source 1~2 such as a laser diode. The optical flber end 130 may be conveniently mounted at the free end of a positioning device 134, typieally a three dimensional positioning clevice ~0 of the type illustrated in I'ig. 3 and is positioned to facc tll~ Jht ~;ource 13~ at a desirecl ~,o.,ition relative there-to.

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further refinement of the apparatus of Fig. 12 is illustrated in F'lgs. 13~ an~l 13B
wllich illus-trate apparatus for selectable coupling an optical fiber end ]40 to a selected one of a plurality of llght sources 144. Such an arranyement is particularly useful with laser diodes ~hich are known to have limi-ted li~etimes which are sometimes shorter than a desired serviclng cycle. In such applications the opera-tion of a bender element 142 of the type illustrated in any of Figs. 1, ~ and 3 can be controlled to shift the fiber end to a new light source when the brightness of the old light source falls below a predetermined threshold.
Control oE elemen-t 142 may be simply achieved ~y adjusting for maximum light to enter the fiber.
Platform 146 is used toc~ether with a curved arrangement of lasers 144 to establish a minimum distance between the output area of the lasers and the center o~ the fiber end. The need for platform 146 and the arrangement of lasers 144 can be eliminated by having a two or three ~imenslonal positioner instead of one dlmensional positioner 1~2.
The laser array 144 and plat~orm 146 may be constructed from a unitary plece of material for production cost savings.
Reference is now made to Fig. 14 which illustrates a portion of a communications exchanc;e constructed and operative in accordance with an embodiment of the present invention. ~he exchange is suitable for use in telephorle, telegraph, radio or any ot'rier mode o~ co-,ln1nnica~:ion :in which inFormClti~
can be transmltted vla elec-tromagn~-tic radiatir~--lS-~31~

.L The app~ratus of r'iy. 14 cor,lprises an arra~
of transmitters 150 disposed in spaced facing relationshlp to an array of receivers 152. ~ach subscriber, indicated ~y reference numeral 1~4, is interconnected with a sinyle transmitter 1~0 and a single receiver 152 via circuitry 156, an e~emplary embodiment of whieh will be described hereinafter in detail.~ In the illustrated embodiment, three subseribers U, V and W are shown eonr.ected to respective transmitters and receivers. Two way eomnunication between subscribers U and W is illustrated, with a radiated beam of eleetromagnetic radiation being beamed by the transmitter of subseriber U so as to implnge on the reeeiver of subseriber W, and a radiated beam oE eleetromagne~ic~
radiation being beamed by the transmitter of Subseriber W to impinye on the reeeiver of subseriber U.
It is appreeiated -that there may be cases in which eaeh subseriber may be associated with more than one transmitter and more than one receiver, as in eonferenee call faei.lities, ~or example.
Any suitable form of electromagnetic r~diation may be employed. In accordance with a preferrecl embodiment of the inven-tion infra--red radiation is preferred.
Referring now to Fig. 15 tllere is seen~ in .schemcltie illustration, an array arrangement for a eommunications exchanye constrwc-ted and operative ~ in aecordance ~Jith a preferrec1 embodiment o~ the inv(?lltiorl. There i.s pro-vided a firc;t arrcly :l6n o^

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trarlsmitters 162, disposed in selectable radiation communication rela-tiollship with a second array 164 of receivers 166. As seen in the illustrated example, arrays lS0 and 164 are generally flat arrays disposed in spaced facing orientation such that a beam of radiation provided by any one of the transmitters 162 rnay selectively impinge on any individual one of the receivers 166 for the establishment: of communica-tion therebetween.
Each transmitter 162 is associated with a given subscriber and coupled thereto by appaxatus prividing a modulated racliation beam containing information to be con~unicated. 1'his modulation may take any suitable form depending on the communication requirements of the sys-tem.
Each transmitter 162 may be constructed similarly to tlle direc-table transmi-t-ter described in Fig. 4, and the optlcal fi~er may be coupLed to a light emitting diode or laser diode.
Since modulation oE light beams for communications applications is widely known in the li-terature it will not be described here, and reference will only be made here to the employment of such modula-ted light information transmission.
A general descri.ption of ]ight communication is provided in:
Optical Communication Research and Technology;
Fiber Optics, by T . G. Giallorenzi, Proc. of the IEEE, Vol. 66, No. 7, July, 1978, p. 744.
The receiving elements may typically comprise ~hoto cletec-tclrs e~acll of ~ ;.ch is coupled via s;li.tahle amplification meanr. to a qiven subscriber.

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,, Fig. 16 illustrates an alternative ~orm. of arrangement of transmitters an~ receivers e~ploying a reflectiny element for communication. Here arrays 170 and 172, comprising transmltters 174 and receivers 176 respectively, are disposed in adjacen-t angled rela-tionship facing a reflecting element 178 and arranged so that beams of radlation from any of the transmitters 174 can selectably impinge on any of the receivers 176.
.o ~ccording to an alternative embodlment o~ the invention illustrated in Fig. 17 first and second arrays 1.80 and ~82 are provided in respectlve facing arrangement. ~ach`of the ar,rays comprises an inter.spersed arrangement o~ transmitters and receivers 184 and 186. It i.s appreciated that the transmitters an~l r~ceivers 184 and 186 on the same .
array cannot communicate. Nevertheless, such a construc-tion would be suitable for use with a submarine cable, where such local communication 2(J would not ~e requ.ired.
Fig. 1~ shQws an alternative embodiment of the invention in which a single array 192 is arranged facing a reflecting element 1~4. Array 192 comprises an interspersed arrangement of transmitters 196 and receivers 198. It is appreci.a-ted that in thi.s arran~ement any of the transmitters 1'~6 can communicate with any of the receivers lg8.
Reference is now made to Fiy. 1~ t~hich illustrates transmission and receiving apparatus a!-.s~cia~ed with a si.n~T1~ -;u~scri,ber in the e~cha~ge of Piy. 14. A su.!.~-~ri,be.r, 236 wh1ch may 1 represent any deslred t~pe of cor~lunicatiorls terminal is coupled to transmitter and receiver circuits 2~0 and 2~2, respectlvely. Transmltter circuit 240 comprises a line receiver 2~4 which separates the dialing information ~in the case of a tc-lep~lone link) or alterna-tively the address instr~ctions from -the voice or data information.
' The di.aling information passes to a dialing i.nformation decoder 246 while the voice or data information passes to a modulator 248.
The voice or data information causes the modulator 248 to operate a source of radiation, for example a LED with a selectable modulation representative of the voice or data signal, received thereby. This radiation is transmitted along an optical fiber link 2~0 and from an end thereof through a lens 252 which beams the radiation at a desired receiver.
The dialing or acldress instxuctions are emplo~ed to determine the angular orientation of the radiation beam, typically by suitable energiæation of a piezoelectric bender element, as shown in Fig. 2.
The dialing decoder 246 employs a conventional microprocessor 254, such as an Intel 8080 and memori.es 256 for decoding received adclress or clialing inputs into X and Y positi.on co-ordinates.
Decoder 24~ provides X and Y position ou-tputs along a data bus to first and second latches 257 and 258, each of which is coupled to a respective Dlgita.~ to ~naloy converter 260 and 262. Digital to ~n~locJ converte~ 260 .is co~pled to the electrodes of a pi.ezoel.ectric bender element 261 ~19~

31~ , arranged to bend alony a~ axis and converter 262 is coupled to the electrodes of a piezoelectric bender element 26~ arranyed to bend along a '~-axis.
T]le receiver cixcui-t 2~ comprlses a wlde fi,eld of View detector 264 which is arrange~ to receive an incidellt beam of light from a transmitter and which provi.des an output to an amplifier 26~.
Amplifier 266 provldes an output to a call detector 268 whi.ch may be of conventional constructlon and whlch interfaces with the dialing information decoder 246 for producing dialing or address information on the basis of information`given by the incoming beam.
Amplifier ~6 also provides an output to a demodulator 270 which provides a decoded voice or data output to a line transmi~ter ~72 which also receives an address or dialing input from call detector 268 and which is coupled to the subscriber terminal.
Signalling can be accomplished using a common electrical bus shared among all of the subscribers ancl a ti.me ordered usage o.~ this bus by subscribers.
An alternative control arrangement may be utilized using a central processor unit shared among several subscribers.
Accordiny to a preferred embodiment of the invention, a swi,tchiny exchange may be cons-tructed having a 10,000 subscriber capaci-ty and comprising transmitter and receiver arrays arranged in a 100 x 100 grid. In such an exam~le, each array w-JI~ld ihave to be o:E a:rea l.m , each trans~litter and receiver being separa-ted by 10 mm from each :~3~
adjacent transmitter and receiver in their respecti-~,e arrays. ~ssuminy -that the arrays are arranged in facing relationship as shown schematlcally ln F:ig. 15, the separation between the arrays ~ould be approximately 5 me~ers.
If a transmi-tter of the general type illustrated in ~i'ig. 2 were employed, the diameter of the fiber optic core would be 5 microns and the focal length of the lens 5 mm. The diameter of the spot of radiation impinging on the opposite array would be 8 mm. The f number of the lens would be between 1 and 2. The field of mo-tion of the free end of the fiber optic would be :L x 1 mm.
The preEerred piezoelectric bender elemen~
is catalog number G-1~18 manufactured by Gulton Industries, Inc., of New ~ersey and is made of Zirconate Titanate. It has a piezoelectric ~12m constant as follows: d = -270 ~ 10 v .
The thickness of the piezoelectric bender element is selected -to be 0,125 mm and its length is selected to be 25 mm. Its voltage requirement is ~0 volts for producing a 1 mm rnovement. The light source is preferably a LED and the detector is P.I.N. Silicon.
Fig. 20 illustra-tes calibration appara-tus for a beam directing system such as that employed for directing the transmitter beams in accordance with dialing or address informatlon. A plurality of decectors 210 are arranged faclng a transmitter 212. The detectors 210 rnay conveniently be arranyed in cl grid 200 and are :~ndividuall~
connected to a selector circuit ~14. The selector ~3(;~

1 is coupl.ed to an analog to di~ital conv~rte~ 21~
which in -turn is coup~e~ to a Ir,icro)roc~essor 2J~, which may be of conventional construction and in-terfaces with one or more EPRO~I memories ~20.
- Tile mic.roprocessor 2l.~ ~rovides direction signals to the transmitte~r 212 and selection signals to selector 214.
. Calibration i.s effecte~ as folLows:
A beam is transmitted in sequence to the individual de-tectors 210 disposed on grid 200, which defines the detection surface. ~he signal receive~ by each detector will be maximi.zed by adjustl~,ent of the beam direction, The instructlons producing the hes-~ direction for each detector are written on the EPROM and this data may be used to interpolate for any other detectors intermediately positioned between detectors 210. The microprocessor 218 may be employed as microprocessor 154 (Fig. l9).
ReEerence is now made to Fig. 21 ~Jhich illustrates another type of switching exchange.
Here, as opposed to -the configurations described hereinabove, a plurality of transmitters 222 provi.des a wide heam that impinges on substantially all of the recei.vers ~24 arranged in a fac:;.ng grid 226. Each rece.iver 22~ is coupled to a subscriber and is selectab.Ly directable so as to receive the radi.ation from only a single transmitter 222 at any c~iven time. It is noted that this type of exchange is par-ticular:Ly useful in cable te~.evision sys-tems.

1 It may be ap~reciated that the s~,Jitrhing e~changc operates hy provi,cling to each selectably clirectable receiver 2~1 control inputs ~Jhich causes it to aim its detector a-t a desired sinyle transmitter, thus coupling a subscriber associated with that receiver to the information channel associated with that transmitter. In a cable television system, each television receiver rcceives a broadcast channel by controlling the directable recei.ver 22~. The optical fiber that emerges from receiver 224 may be extended towards the television receiver and carry T.V. channel information directly to the receiver.
- Reference is now made to Fig. 22 which is a block diagram illustration of ap~aratus for high accuracy feedback control of a directional transmitter. The transmitter 280, which may be a transmitter of the type illustrated in any of Fic3s. l, 2 and 3, receives a signal input from a data source 282 and from a control signal source 284.

A detector 286 receives the combined data and control signals which may be differentiated from each other by conventional frequen,cy filters or equivalent techniques. The data outputs from detector 286 are supplied to a data destination 2~8 and the control outputs from detector 286 are supplied to a contro~. signal utilization c.ircuit 290~ ~ microprocessor control 292 senses the received control signal at circuit 290 and aims the transmitter accordingly.

-~3-)3~ , :l Fig. 23 illustrates an arrangernent ~ a pair of optical fibers 293 and 294 arranye(l on the free end of bender element 296. Preferably one of the optical fibers is a data carryiny fiber while the other carries control information for assisting in accurate aiming.
Fi.g. 24 shows a plurality of optical fibers arranged on the free end oE bender element 298. A
center fiber 300 carries clata while the remaining fibers 302 carry control signals for providing a very high level of aiming accuracy.
Bender assemblies having a plurality of optical fibers associ.ated therewith an including both data and controL information carrying fibers may be incorporated in any of the switching exchanges i.llustrated in Figs.
It will be appreciated by persons skilled in the art that the invention is not limited to the particular examples illustra~ed and di.scussed herein. Rather the scope of the present invention is defined only by t~e claims which follow.

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Claims (22)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A communications exchange comprising:
a first plurality of electromagnetic radiation transmitting units each of which provides a beam of information bearing electromagnetic radiation;
a second plurality of electromagnetic radiation receiving units arranged in radiation receiving relation-ship with said first plurality, each receiving unit being arranged to receive radiation from said first plurality of electromagnetic radiation transmitters;
means for causing the radiation from any selectable one of said transmitting units to be received by any selectable one of said receiving units for estab-lishment of communications therebetween.

2. A communications exchange according to claim 1 and wherein said means for causing comprises at least one device for selectably orienting an end of an information bearing optical fiber.

3. A communications exchange according to claim 2 and wherein said device for selectably orienting comprises:
a bender assembly including at least two piezoelectric bender elements arranged for bending motion in different directions, said bender assembly having a

Claim 3 continued...
free end and a mounting end, the free end being arranged for association with at least one optical fiber end and the mounting end being located at a reference position.

4. A communications exchange according to claim 3 and also comprising at least one second optical fiber end arranged for selectable radiation communication with said at least one optical fiber end by means of suitable positioning of said at least one optical fiber end.

5. A communications exchange according to claim 4 and wherein said bender assembly comprises at least two piezoelectric bender elements arranged for bending motion in two perpendicular planes.

6. A communications exchange according to claim 1 and also comprising means for measuring the intensity of the information bearing electromagnetic radiation.

7. A communications exchange according to claim 1 and also comprising feedback means responsive to the intensity of said beam of information bearing electromag-netic radiation for governing the positioning of said at least one optical fiber end.

8. A communications exchange according to claim 1 and wherein said information bearing optical fiber carries video telephone communication signals.

9. A communications exchange according to claim 1 and wherein said transmitting units and said receiving units comprise apparatus for selectably positioning an optical fiber end including:
a bender assembly including at least two piezoelectric bender elements arranged for bending motion in different directions, said bender assembly having a free end and a mounting end, the free end being arranged for association with at least one optical fiber end and the mounting end being located at a reference position;
and beam forming means for association with said at least one optical fiber end.

10. A communications exchange according to claim 1 and wherein said first plurality comprises a multiplicity of transmitting units and said second plurality comprises a multiplicity of receiving units and wherein said means for causing is operative to establish simultaneous individual communications between a plurality of said transmitting units and a plurality of said receiving units.

11. A communications exchange according to claim 1 and wherein said means for causing is operative to selectably direct said transmitting unit to a desired receiving unit.

12. A communications exchange according to claim 1 and wherein said means for causing is operative to selectably direct said receiving unit to a desired transmitting unit.

13. A communications exchange according to claim 1 and wherein a communications subscriber is connected to a single transmitting unit and to a single receiving unit, such that two way communication is effected by passage of a pair of beams.

14. A communications exchange according to claim l and wherein said means for causing is operative to enable every one of said transmitting units to communicate by means of an electromagnetic radiation beam with any one of said receiving units.

15. A communications exchange according to claim 1 and wherein said electromagnetic radiation is infra-red radiation.

16. A communications exchange according to claim 1 and also comprising beam detection and feedback means for monitoring the accuracy of beam direction.

17. A communications exchange according to claim 1 and wherein said first and second pluralities are flat arrays arranged in generally parallel, spaced orientation across a gap and in direct electromagnetic radiation beam

Claim 17 continued...
line of sight.

18. A communications exchange according to claim 17 and wherein said flat arrays comprise arrays of inter-spersed transmitting units and receiving units.

19. A communications exchange according to claim 1 and also comprising selecting means disposed intermediate said first and second pluralities of electromagnetic radiation units for reflecting said beams of information bearing electromagnetic radiation, thereby providing radiation communication between said first and second pluralities.

20. A communications exchange according to claim 19 and wherein said first and second pluralities are arranged in generally coplanar coextensive and inter-spersed relationship to each other in respective first and second arrays.

21. A communications exchange according to claim 1 and also comprising microprocessor means for providing control instructions to said transmitting units.

22. A communications exchange according to claim 21 and also comprising memory means which are used to memorize calibration data to enable accurate directing of said radiation beam for corresponding receiving units locations.