WO2010103465A2

WO2010103465A2 - Optical crossbar switch technology

Info

Publication number: WO2010103465A2
Application number: PCT/IB2010/051026
Authority: WO
Inventors: Zeev Ganor; Rahav Cohen; Hai Pedut; Yossi Halfon
Original assignee: Fiberzone Networks Ltd.
Priority date: 2009-03-11
Filing date: 2010-03-10
Publication date: 2010-09-16
Also published as: WO2010103465A3

Abstract

A socket bank comprising a plurality of fiber-coupling sockets for optically coupling optic fibers, the socket bank comprising: a first gripping plate formed having gripping sockets, each gripping socket configured to receive and securely grip an optic fiber ferrule; and a second gripping plate formed having gripping sockets configured to receive and securely grip an optic fiber ferrule; wherein each gripping socket in the second plate is aligned with a gripping socket of the second plate to form a fiber-coupling socket.

Description

OPTICAL CROSSBAR SWITCH TECHNOLOGY

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application claims benefit under 35 U.S.C. §119(e) of US Provisional Application 61/159,109 filed March 11, 2009, the entire content of which is incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to crossbar switches and in particular to optical crossbar switches. BACKGROUND OF THE INVENTION

A crossbar switch generally operates to connect any one of a first plurality of signal ports to any one of a second plurality of signal ports. Generally, signal ports in the first and second pluralities of signal ports are bi-directional and any of the first or second ports in the crossbar switch can be used to both receive and transmit signals. The crossbar switch operates as a router that routes a signal received on any one of its ports in the first or second plurality of ports to a desired port of the other of the first and second plurality of ports from which the signal is transmitted. Crossbar switches are typically used, for example, for routing signals in communication networks such as LANs, WANs, and telecommunication networks and in routing data signals between processors comprised in parallel data processing systems. In many communication networks, signals are optical signals that are transmitted along optic fibers and routing is accomplished by optical crossbar switches. A first plurality of signal ports are ends of a first plurality of optic fibers and a second plurality of signal ports are ends of a second plurality of fibers. The crossbar switch operates to optically couple an end of a given fiber of the first plurality of optic fibers to an end of a given fiber of the second plurality of optic fibers, to provide a desired connection.

Optical crossbar switches are often required to accommodate very large numbers of optic fibers. As the number of fibers increases, the task of efficiently managing connecting and disconnecting large numbers of optic fiber ends without fibers becoming entangled becomes increasingly complex. Prior art crossbar switches for optically coupling and uncoupling large numbers of optic fibers tend to be complicated, unwieldy pieces of equipment that require relatively large volumes of operating space to accommodate the coupling and uncoupling operations. US 5,613,021 describes an optical crossbar switch in which a robot hand connects and disconnects ends of a plurality of first fibers to ends of a plurality of second fibers, which second fibers have their ends held stationary in a rectangular array in a coupling board. As an end of a fiber in the first plurality of fibers is connected or disconnected to an end of a fiber in the second plurality of fibers, length of the first fiber is respectively played out or "reeled in" by a fiber length adjusting unit which requires its own significant space volume. The robot hand "mimics" the way in which a human switchboard operator operates a telephone switch board, plugging and unplugging telephone cables from a switch board. During operation of the switch, first optic fibers cross each other as they are connected and unconnected from different second optic fibers. In an embodiment of the invention, the adjusting unit comprises a pair of rotatable reels on which surplus portions of the first fiber are wound. The reels are spring loaded to urge them apart and take up slack in the fiber wound between them.

US 6,307,983 describes an optical crossbar switch in which patch fibers are used to connect ends of a plurality of first fibers to ends of a plurality of second fibers. A first end of each of the patch fibers is connected to an end of a first fiber. The ends of the second fibers are mounted to a circular holding ring. The second ends of the patch fibers are mounted to a linear conveyor. The conveyor sequentially loads the second end of each patch fiber at a different desired loading location on the perimeter of a "loader ring", which is coaxial with the holding ring that holds the ends of the second fibers and has a same diameter as the holding ring. The second end of a patch fiber is loaded to the desired location on the loader ring by suitably rotating the loader ring about the axis of rotation and translating the linear conveyor so that the position of the second end of the patch fiber on the linear conveyor meets the desired location on the loader ring perimeter. After the loading ring is loaded with the second ends of the patch fibers, the loading ring is translated along the common axis it shares with the holding ring to "dock" the second ends of the patch fibers with the ends of the second fibers. A configuration of connections between the first and second pluralities of fibers is determined by the positions of the patch fiber second ends on the loader ring and an azimuth angle of the loader ring relative to the holding ring.

Japanese Patent Application 03-162441 entitled "Optic fiber Excessive-Length Processing Device"; Publication No. 04-361205; Patent Abstracts of Japan vol. 017, no. 235 (P-1533), 12 May 1993 describes a "take-up" reel spring-loaded with a coil spring for taking up slack in an optic fiber. The fiber seats in a groove formed in the perimeter of the reel and loops halfway around the reel. Tension in the coil spring moves the reel to maintain tension in the fiber and take up fiber slack as an end of the fiber is moved along a direction parallel to a direction along which the coil spring moves the reel.

European Patent Publication 0 567 143 Al entitled "Optical Matrix switch" describes partitions that isolate "a surplus length portion" of an optic fiber from other optic fibers in the switch to prevent their being entangled.

PCT publication WO 02/43432, the disclosure of which is incorporated herein by reference, describes an optical crossbar switch in which any given one of a plurality of first optic fibers is optically coupled to any given one of a plurality of second optic fibers by translating the ends of the given fibers along different linear trajectories.

PCT publication WO 2006/054300, the disclosure of which is incorporated herein by reference, describes an optical crossbar switch for optically coupling optic fibers in which a first optic fiber is coupled to two carriages that are movable along a same linear trajectory. A first, fiber-end carriage holds an end of the first fiber, and a second, slack-control carriage is coupled to the body of the first fiber. To optically couple the first fiber to a second fiber, a moving device moves the fiber-end carriage of the first fiber along its trajectory to a position at which the end of the first fiber is optically coupled to an end of the second fiber and moves the slack-control carriage to take up slack in the first fiber generated by movement of its fiber- end carriage.

SUMMARY OF THE INVENTION

An aspect of some embodiments of the present invention relates to providing an improved optical crossbar switch that provides for efficient management of the coupling and uncoupling of relatively large numbers of optic fibers in a relatively small volume of space. An aspect of some embodiments of the invention relates to providing an optical crossbar switch wherein large numbers of optic fibers may be coupled and uncoupled without the fibers becoming entangled.

An aspect of some embodiments of the invention relates to providing an optical crossbar switch for optically coupling and uncoupling optic fibers wherein substantially no or relatively little slack is generated in optic fibers during the process of optically coupling and uncoupling fibers.

In accordance with an embodiment of the invention, an optical crossbar switch comprises first and second pluralities of respectively first and second optic fibers. Each fiber is coupled to a different pair of moveable "fiber-end" and "slack-control" carriages. The fiber- end carriage of the pair comprises an optic fiber ferrule which projects from the fiber-end carriage and holds an optical end, hereinafter a "switch end", of the fiber at an end of the ferrule farthest from the carriage. The slack-control carriage is coupled to the body of the fiber. The end of the ferrule holding the switch end of the fiber is referred to as a "switch end" of the ferrule. The crossbar switch comprises at least one device, hereinafter "a mover", controllable to move the fiber-end carriage of each of the fibers so as to optically couple the switch end of any first fiber to the switch end of any second fiber by positioning the switch ends of their respective fiber ferrules, opposite to and facing each other. When moving the fiber-end carriage of a fiber, the at least one mover moves the slack-control carriage of the fiber to take up, or "reel in", slack in the fiber generated by motion of the fiber-end carriage or to "reel out" a length of fiber required to enable free motion of the fiber-end carriage.

In accordance with an embodiment of the invention, the at least one mover moves each of the fiber-end carriages of the first fibers along different, optionally straight-line, first trajectories. Optionally, the first trajectories are parallel and coplanar. Similarly, the at least one mover moves each of the fiber-end carriages of the second fibers along different, optionally straight-line, second trajectories. Optionally, the second trajectories are parallel and coplanar. Optionally, the planes of the first and second trajectories are parallel. A projection of each of the first trajectories on the plane of the second trajectories intersects each of the second trajectories. Optionally, the projection of a first fiber is perpendicular to the second trajectories. A point at which the projection of a first trajectory crosses over a second trajectory is referred to as a "crossover point" of the first and second trajectories, or alternatively, a crossover point of the first and second fibers associated with the trajectories. To optically couple any given first fiber to any given second fiber, the at least one mover moves the fiber-end carriage of each of the given fibers to position the switch ends of their respective fiber ferrules and thereby the switch ends of the fibers facing their common crossover point.

In some embodiments of the invention, the crossbar switch comprises a "socket bank" formed having a plurality of fiber-coupling sockets, wherein a different fiber-coupling socket is located in a neighborhood of each crossover point of first and second trajectories.

The fiber-coupling socket at a given crossover point is configured having a first and second openings for receiving the fiber ferrules of fiber-end carriages that can be moved along the first and second trajectories associated with the crossover point. To optically couple a given first fiber to a given second fiber, the at least one mover translates the switch ends of fiber ferrules holding the switch ends of the given fibers to their common crossover point and inserts the switch ends of the ferrules into the fiber-coupling socket at the cross over point.

In some embodiments of the invention, the fiber-coupling socket functions to aid alignment of the switch ends. In some embodiments of the invention, the socket alternatively or additionally provides mechanical support for the coupled switch ends. Optionally, the socket provides mechanical support for the fiber-end carriages to which the switch ends are mounted and mechanically supports the carriages in positions that maintain the switch ends optically coupled. In some embodiments of the invention, the fiber-coupling sockets are spring loaded to securely grip ferrules inserted into the socket.

Optic fibers are conventionally optically coupled using an "optic" sleeve typically formed from a ceramic or zirconium. Fibers to be coupled are inserted into an optic sleeve from opposite ends of the sleeve to a depth, typically between 4-6 mm, at which they make suitable optical contact. The sleeves are precision formed so that they firmly hold and align the fibers. Conventional procedures for producing optic sleeves typically involve a relatively complicated series of steps comprising different technologies, and generally require various precision grinding and polishing procedures.

An optic sleeve may, conventionally, be a split or a solid sleeve. Split sleeves comprise a precision formed cylinder having a slot formed in the cylinder wall parallel to the sleeve axis. The slot provides a measure of flexibility to the sleeve and a pathway for release of gas when fibers ferrules are introduced into the sleeve. Solid sleeves comprise a cylinder precision formed without a slot. Sleeves are often insert-molded into plastic housings for convenience of mounting the sleeve in optical systems.

A socket bank may be produced by press fitting conventional sleeves, or plastic housed sleeves, into a suitable support base to form sockets in the socket bank. However, producing a socket bank using conventional methods can be relatively complicated and expensive.

An aspect of some embodiments of the invention relates to providing a socket bank comprising fiber-coupling socket components that are integrally formed in a support plate of the socket bank. A socket bank in accordance with an embodiment of the invention comprises at least one support plate, referred to as an alignment plate, formed having an alignment socket for each fiber-coupling socket in the socket-bank. Optionally, an alignment socket comprises an optic sleeve integrally formed in the alignment plate. Optionally, the optic sleeve comprises a split sleeve. In some embodiments of the invention, the optic sleeve is defined by a through hole formed in the alignment plate. In an embodiment of the invention, features of the alignment socket are formed using lithographic production techniques conventionally used to produce integrated circuits and/or microelectromechanical systems (MEMS). And, the alignment plate comprises a material, such as silicon, suitable for production of features in the plate using the lithographic techniques. The inventors have determined that such lithographic techniques are suitable for relatively efficiently and inexpensively producing alignment sockets to tolerances that are satisfactory for optical coupling applications.

In some embodiments of the invention, the socket bank comprises a plate, referred to as "gripping plate", comprising sockets, referred to as "gripping sockets" that are configured to firmly hold ferrules inserted into the fiber-coupling sockets in the socket bank. Optionally, the gripping sockets are produced using lithographic techniques used to produce alignment sockets. Optionally, the gripping sockets are spring loaded for firmly holding ferrules. In an embodiment of the invention, each fiber-coupling socket in the socket bank comprises two gripping sockets. An aspect of some embodiments of the invention, relates to providing a socket bank comprising an indicator circuit that generates signals indicating which sockets are inserted with fiber ferrules. In an embodiment of the invention, the indicator circuit comprises a different first conductor for each first trajectory along which fiber-end carriages are moved and a different second conductor for each second trajectory along which fiber-end carriages are moved. Each conductor is electrically isolated form the other conductors. However, fiber- end carriages comprise a "contact conductor" for electrically connecting first and second conductors. When a ferrule of a fiber-end carriage is inserted into a fiber-coupling socket, the carriage's contact conductor connects first and second conductors associated with the socket. A suitable circuit determines which first and second conductors are electrically connected to determine which fiber-coupling sockets are occupied with ferrules.

In an embodiment of the invention, the at least one mover moves the slack-control carriage of each optic fiber along a same trajectory along which it moves the fiber's fiber-end carriage in order to take up slack in the fiber or reel out fiber length. Optionally, the slack- control carriage operates like a moveable pulley relative to the fiber-end carriage. The fiber is threaded into and out of the slack-control carriage looping through at least one, optionally "U" shaped channel formed in the slack-control carriage or around a configuration of at least one pulley wheel comprised in the slack-control carriage. The at least one channel or pulley wheel configures the fiber so that, optionally, at least two lengths of the fiber lie between the fiber- end and slack-control carriages. In accordance with an embodiment of the invention, the at least one mover moves the slack-control carriage about one half a distance that it moves the fiber-end carriage to increase or decrease the two lengths of the fiber in order to respectively take up or reel out fiber as needed. An aspect of some embodiments of the invention relates to providing a slack control system, hereinafter an "Apollonius" slack control system, for controlling slack in a optic fiber connected to a crossbar switch in accordance with an embodiment of the invention. The Apollonius slack control system comprises an Apollonius circle guide rail along which a sliding carriage, hereinafter a "slider", moves. The fiber is constrained to move through two stationary junction guides and the slider that moves along the Apollonius guide rail to control slack in the fiber as an end of the fiber is moved to couple to and uncouple from different fibers in the crossbar switch. .

An aspect of some embodiments of the invention relates to providing a slack control system for controlling slack in an optic fiber comprising a leaf spring formed having a groove in which the fiber seats. The spring, hereinafter referred to as a "C-spring" is curled into a shape resembling a letter C. The amount by which the C-spring is curled varies to take up slack in the fiber as an end of the fiber is moved to couple to or uncouple from other fibers in a crossbar switch.

In accordance with an embodiment of the invention, the crossbar switch is configured so that the first and second trajectories are arrayed with relatively small pitches and the dynamic coupling ranges and take-up ranges of the fiber-end and slack-control carriages are substantially equal to their respective minimum ranges. Optionally, to enable the relatively small pitches, the carriages are substantially planar structures having a relatively small thickness perpendicular to the trajectories along which they move. As a result, a relatively large number of first and second fibers can be accommodated by the crossbar switch and efficiently optically coupled and uncoupled in a relatively small volume. In addition, because the carriages associated with a given fiber move along a trajectory that is different from that of the other fibers, none of the first trajectories cross each other and none of the second trajectories cross each other and fibers don't tangle during operation of the switch. There is therefore provided in accordance with an embodiment of the invention, a socket bank comprising a plurality of fiber-coupling sockets for optically coupling optic fibers, the socket bank comprising: a first gripping plate formed having gripping sockets, each gripping socket configured to receive and securely grip an optic fiber ferrule; and a second gripping plate formed having gripping sockets configured to receive and securely grip an optic fiber ferrule; wherein each gripping socket in the second plate is aligned with a gripping socket of the second plate to form a fiber-coupling socket. Optionally, the gripping sockets are through holes formed in the gripping plate. Optionally, the gripping sockets are spring loaded to aid in gripping a fiber ferrule. Optionally, each of the gripping sockets comprises a split sleeve. Optionally, the split sleeve is integrally formed with the gripping plate.

In some embodiments of the invention, the gripping plates are spaced apart. In some embodiments of the invention, the gripping plates are contiguous. In some embodiments of the invention, the socket bank comprises an alignment plate located between the first and second gripping plates formed having alignment sockets, each configured to receive and align two optical ferrules and wherein each alignment socket is aligned with two gripping sockets to form a fiber-coupling socket. Optionally, the alignment sockets are through holes formed in the alignment plate. Optionally, each of the alignment sockets comprises a split sleeve. Optionally, the split sleeve is integrally formed with the alignment plate.

In some embodiments of the invention, the gripping plates and alignment plate are spaced apart. In some embodiments of the invention, the gripping and alignment plates are contiguous. In some embodiments of the invention, the alignment plate is formed from a material suitable for processing using a MEMS and/or photolithography manufacturing technique. In some embodiments of the invention, the alignment is formed from a material suitable for processing using a rapid manufacturing technique. In some embodiments of the invention, a gripping plate of the gripping plates is formed from a material suitable for processing using a MEMS and/or photolithography manufacturing technique. In some embodiments of the invention, a gripping plate of the gripping plates is formed from a material suitable for processing using a rapid manufacturing technique. In some embodiments of the invention, the material comprises a material chosen from the group of materials consisting of: silicon, glass, a polymer, a photopolymer, and a resin. In some embodiments of the invention, the fiber-coupling sockets have a pitch less than or equal to about 2.2 mm. In some embodiments of the invention, at least one of the plates has a thickness less than or equal to about 6 mm. Optionally, at least one of the plates has a thickness less than or equal to about 3 mm. Optionally, at least one of the plates has a thickness less than or equal to about 1.5 mm.

There is further provided in accordance with an embodiment of the invention, an optical crossbar switch for optically coupling optic fibers comprising: at least one first fiber and a plurality of second fibers; a socket bank according to an embodiment of te invention for coupling the first fiber to any of the plurality of second fibers; wherein to optically couple a first fiber of the at least one fiber to a second fiber, the first and second fibers are inserted into a same fiber-coupling socket.

There is further provided in accordance with an embodiment of the invention, a fiber- end carriage for optically coupling a fiber to another fiber, the fiber-end carriage comprising: a cylindrical body; a fiber ferrule for holding an end of a fiber, the ferrule mounted to the cylindrical body and configured for insertion into a fiber-coupling socket; and a fin extending from the cylindrical body and comprising a socket prong configured for insertion into the fiber-coupling socket. Optionally the fiber end carriage comprises a grabbing head to facilitate holding and moving the fiber-end carriage. Optionally, the grabbing head has a hexagonal cross section.

There is further provided in accordance with an embodiment of the invention, a fiber- end carriage for optically coupling a fiber to another fiber, the fiber-end carriage comprising: a body mounted with a fiber ferrule for holding an end of a fiber and configured for insertion into a fiber-coupling socket; and at least one socket prong configured for insertion into the fiber-coupling socket; and a resilient element that is inserted to the fiber-coupling socket with the socket prong to resiliently secure the socket prong in the socket. Optionally, the at least one socket prong comprises two socket prongs.

There is further provided in accordance with an embodiment of the invention, an optical crossbar switch for optically coupling optic fibers comprising: a plurality of fibers, each coupled to a fiber-end carriage according to an embodiment of the invention; a socket bank according comprising a plurality of fiber-coupling socket for coupling any two of the plurality of fibers; wherein to optically couple the two fibers each is inserted into a same fiber-coupling socket of the socket bank. There is further provided in accordance with an embodiment of the invention, a slack control system for controlling slack in an optic fiber having an end which is moved between different locations to optically couple the fiber to other fibers, the slack control system comprising: a first junction guide formed having a first junction through which the fiber moves freely; a second junction guide having a second junction at which the fiber is held stationary; a guide having a shape of an arc of a circle; a third junction that moves along the guide and is formed having a third junction through which the fiber moves freely; a device that urges the third junction guide towards one end of the guide; wherein, the first and second junctions are located substantially at Apollonius foci of the circle .

There is further provided in accordance with an embodiment of the invention, a slack control system for controlling slack in an optic fiber having an end which is moved between different locations to optically couple the fiber to other fibers, the slack control system comprising: a first junction guide formed having a first junction through which the fiber moves freely; a leaf spring curved along an arc having a center of curvature and formed having a channel in which the fiber seats and along which the fiber is free to move easily; a device that holds the fiber substantially fixed on a side of the leaf spring where the center of curvature is located; wherein the radius of curvature decreases or increases to take up or pay out slack when the fiber end is moved respectively towards or away from the leaf spring.

There is further provided in accordance with an embodiment of the invention, a slack control system for controlling slack in an optic fiber having an end which is moved between different locations to optically couple the fiber to other fibers, the slack control system comprising: a weight that hangs from the fiber; a guide along which the weight is substantially free to move with a component of motion along the direction of gravity; a device that holds the fiber substantially fixed on one side of the guide; wherein the weight moves down or up along the guide to take up or pay out slack in the fiber when the fiber end is moved respectively towards or away from the guide.

There is further provided in accordance with an embodiment of the invention, a slack control system for controlling slack in an optic fiber having an end which is moved between different locations to optically couple the fiber to other fibers, the slack control system comprising: an accordion extension arm having a first end fixed to a base; a fiber-end carriage attached to a second end of the extension arm; a disc attached to a point about midway along the length of the extension arm; and an optic fiber that passes through the fiber end carriage, loops around the disc and returns to the fiber-end carriage where an end of the optic fiber is held.

There is further provided in accordance with an embodiment of the invention, a slack control system for controlling slack in an optic fiber having an end which is moved between different locations to optically couple the fiber to other fibers, the slack control system comprising: a first pulley around which the fiber is looped; a guide along which the first pulley is constrained to move; second and third stationary pulleys; and a pulley belt that loops around the first second and third pulleys and has a first end fixed relative to the stationary pulleys and a second end that is connected to and moves with the fiber end.

There is further provided in accordance with an embodiment of the invention, a socket bank comprising a plurality of fiber-coupling sockets for optically coupling optic fibers, the socket bank comprising: a plate formed having rows and columns of holes; first and second sets of relatively narrow strips having long and short edges each formed having an array of holes extending along the length of the strip and a plurality of pins protruding from a same long edge of the strip; wherein the first set of strips are parallel to the rows of holes and have their pins inserted from a first side of the plate into alternate rows of the holes and the second set of strips are parallel to the columns of holes and have their pins inserted from a second side of the plate into alternate columns of the holes. Optionally, the strips are formed having holes configured to snap fit with prongs comprised in a fiber-end carriage.

There is further provided in accordance with an embodiment of the invention, a crossbar switch for optically coupling optic fibers, the cross bar switch comprising: a plate formed having through holes formed therein; a first set of optic fibers, each coupled to a male optic fiber ferrule configured to be inserted into the holes so that when inserted into a hole from a first side of the plate it protrudes to the second side of the plate; and a second set of fibers each coupled to a female optic fiber ferrule configured to receive and grasp an end of a male optic fiber when it protrudes through the plate.

There is further provided in accordance with an embodiment of the invention, a crossbar switch for optically coupling optic fibers, the cross bar switch comprising: a plate formed from a magnetic material and having through holes formed therein for receiving a fiber ferrule; and a fiber ferrule configured for insertion into the holes and comprising a magnetic material so that when the ferrule is inserted into a through hole, the magnetic materials of the ferrule and plate attract to provide a force that maintains the ferrule securely in the hole.

BRIEF DESCRIPTION OF FIGURES

A description of examples of embodiments of the present invention that references figures attached hereto is given below. In the figures, identical structures, elements or parts that appear in more than one figure are generally labeled with the same numeral in all the figures in which they appear. Dimensions of components and features shown in the figures are chosen for convenience and clarity of presentation and are not necessarily shown to scale. The figures are listed below. Fig. IA schematically shows an optical crossbar switch comprising a socket bank comprising fiber-coupling sockets, in accordance with an embodiment of the present invention;

Fig. IB schematically shows details of an optic fiber comprised in the optical crossbar switch shown in Fig. 1 coupled to a fiber-end carriage and a slack-control carriage, in accordance with an embodiment of the present invention;

Fig. 1C schematically shows an enlarged view of the socket bank comprised in the optical crossbar switch shown in Fig. IA, in accordance with an embodiment of the invention;

Fig. ID schematically shows fiber end carriages with their fiber-ferrules inserted into sockets in the socket bank shown in Figs. IA and 1C to couple two optic fibers, in accordance with an embodiment of the invention;

Fig. IE schematically shows an enlarged view of the mover shown in Fig. IA, in accordance with an embodiment of the invention;

Fig. IF schematically shows the crossbar switch shown in Fig. IA operating to couple optic fibers, in accordance with an embodiment of the invention; Fig. 2 schematically shows an indicator circuit for indicating which fiber-coupling sockets are inserted with fiber ferrules, in accordance with an embodiment of the present invention;

Figs. 3A-3C schematically show configurations of socket banks, in accordance with embodiments of the invention; Fig. 4 schematically shows a fiber-end carriage different from that shown in Fig. IB, in accordance with an embodiment of the invention;

Figs. 5 schematically shows a spring loaded socket prong and matching socket bank, in accordance with an embodiment of the invention;

Fig. 6A and 6B schematically shows side views of Apollonius slack-control systems, in accordance with an embodiment of the invention;

Fig. 7 schematically shows a side view of a leaf spring slack-control system, in accordance with an embodiment of the invention; Fig. 8 schematically shows an accordion arm slack-control system, in accordance with an embodiment of the invention;

Fig. 9 schematically shows a pulley slack-control system, in accordance with an embodiment of the invention; Fig. 10 schematically shows a side cross section view of a crossbar switch comprising a gravity feed slack control device, in accordance with an embodiment of the invention;

Fig. HA and HB schematically show exploded and assembled, perspective views of a crossbar switch comprising another socket bank in accordance with an embodiment of the invention; and Fig. 12 schematically shows a side cross section view of a crossbar switch comprising male and female fiber-end carriages, in accordance with an embodiment of the invention;

DETAILED DESCRIPTION OF EXAMPLES OF EMBODIMENTS

Fig. IA schematically shows an optical crossbar switch 20, in accordance with an embodiment of the present invention. Crossbar switch 20 comprises a first plurality of optic fibers 21, hereinafter referred to as "top optic fibers" 21, and a second plurality of optic fibers 22, hereinafter referred to as "bottom optic fibers" 22. Optionally, within switch 20, top fibers 21 are coplanar and perpendicular to bottom fibers 22, which are optionally coplanar. Each optic fiber 21 and 22 is mounted to a fiber-end carriage 41 and a slack-control carriage 42, and is shown in Fig. IA without obstruction by appurtenances that might be used to couple the fiber to the carriages in order to more clearly illustrate how the fiber is spatially configured, in accordance with an embodiment of the invention.

Optionally, crossbar switch 20 comprises a rectangular "socket bank" 100 (shown enlarged in Fig. 1C and discussed in detail below) having an array of columns 25 and rows 26 of optionally circular fiber-coupling sockets 28 located between the plane of top fibers 21 and the plane of bottom fibers 22. In an embodiment of the invention, each top fiber 21 extends along a different column 25 of fiber-coupling sockets 28 and each bottom fiber 22 extends along a different row 26 of the fiber-coupling sockets. A controller 29 controls crossbar switch 20 to optically couple any given one of top optic fibers 21 to any given one of bottom optic fibers 22 by inserting fiber-end carriages of the given top and bottom fibers into a same fiber-coupling socket 28. The fiber-coupling socket optionally aids in aligning the optic fibers and provides mechanical support for maintaining the fiber-end carriages in positions that provide optical contact of the fibers. In Fig. IA, none of top fibers 21 are connected to a bottom fiber 22 and all carriages

41 and 42 are in "parking positions" along the sides of socket bank 100. In parking positions, fiber-end and slack-control carriages 41 and 42 are optionally supported in parking sockets, optionally similar to fiber-coupling sockets 28 which, to prevent clutter, are not shown in Fig. IA.

For convenience of presentation, positions and orientations of components and elements of crossbar switch 20 are referenced with respect to a coordinate system 30. Rows 26 and columns 25 are parallel respectively to the x and y-axis of coordinate system 30. To prevent clutter, only some of identical features of crossbar switch 20 are labeled with reference numerals.

Fig. IB schematically shows details of a top fiber 21, its fiber-end and slack-control carriages 41 and 42 and the way the fiber is mounted to the carriages. Internal features of the carriages germane to the discussion, which would normally be hidden from view in the perspective of the figure, are generally shown in dashed lines. The fibers themselves are shown as solid lines, even when hidden from view, for clarity of presentation. Bottom fibers 22 are optionally mounted to their fiber-end and slack-control carriages 41 and 42 similarly to the way in which top fibers 21 are mounted to their carriages. The discussion of the way in which a top fiber 21 is mounted to its carriages applies equally well to the way in which a bottom fiber 22 is mounted to its carriages. Fiber-end carriage 41 optionally comprises a flat plate 50 having a protruding, fiber ferrule 44 a carrying handle 52 and optionally, two socket prongs 53. Optionally, carrying handle 52 comprises two "V" shaped gripping protrusions 55, each formed by beveled edges 56. Plate 50 is optionally formed having a "transfer" channel 58 and a "cross" channel 59 through which fiber 21 is threaded. Slack-control carriage 42 optionally comprises a flat plate 60 having two socket prongs 61 and a carrying handle 62. Optionally, carrying handle 62 comprises two V shaped gripping protrusions 63, each formed by beveled edges 64. Optionally, handles 52 and 62 are identical. Optionally, socket prongs 53 and 61 are identical. Optionally, slack-control carriage 60 is formed to have a single "U" shaped "return" channel 66 through which fiber 21 is threaded. Fiber 21 is threaded through transfer channel 58 in its fiber-end carriage 41 so that it passes through the fiber-end carriage and enters return channel 66 in slack-control carriage 42. Return channel 66 returns the fiber back to fiber-end carriage 41 where it is received by cross channel 59. Cross channel 59 optionally intersects transfer channel 58 and directs fiber 21 so that it crosses a portion of the fiber threaded through transfer channel 58 and continues on to a fiber ferrule 44 to which an end 45, i.e. a "switch end", of the fiber is anchored. Channels 58 and 59 in fiber-end carriage 41 and channel 66 in slack-control carriage 42 are formed using any of various methods and devices known in the art, so that fiber 21 is free to move easily along the channels.

Optionally, fiber ferrule 44 has a circular cross section and is rigidly connected to, or integrally formed with, plate 50 so that the position of switch end 45 of fiber 21 is fixed relative to the plate. Optionally, socket prongs 53 are rigidly connected to, or integrally formed with, plate 50. Similarly, socket prongs 61 are rigidly connected to, or integrally formed with, plate 60. Optionally, socket prongs 53 comprised in fiber-end carriage 41 and socket prongs 61 comprised in slack-control carriage 42 have circular cross sections of a same diameter as the circular cross section of fiber ferrule 44.

It is noted, it is possible to configure channels differently from the manner in which they are configured in Fig. IB. For example, transfer channel 58 in fiber-end carriage 41 could be positioned opposite the top end of U shaped return channel 66 in slack-control carriage 42 rather than opposite the bottom end of the return channel. In such a configuration, an optic fiber threaded through the transfer channel and return channel 66 back to fiber-end carriage 41 would, optionally, not be received by cross-channel 59, but by a channel that does not cross the transfer channel. The optic fiber would not cross itself in the fiber-end carriage. Socket bank 100, shown in Fig. IA is schematically shown in Fig. 1C in which a portion of the socket bank is shown enlarged and partially cutaway in an inset 107 of the figure, optionally comprises identical top and bottom gripping plates 101 and 103 and a middle alignment plate 102. Optionally, middle alignment plate 102 is similar or identical to gripping plates 101 and 103. The alignment and gripping plates are held in place by a suitable frame or spacers (not shown) that maintains the alignment and gripping plates aligned and alignment plate 102 spaced, optionally, a same distance from each gripping plate 101 and 103. Each fiber-coupling socket 28, one of which is indicated for clarity of exposition by a dashed line rectangle, in the socket bank comprises a spring loaded gripping socket 108 in each gripping plate 101 and 103 and an alignment socket 109 in middle alignment plate 102. The spring loading is such that when a fiber ferrule 44 or socket prong 53 is inserted into a gripping socket 108, the gripping socket securely holds the ferrule or socket prong in place.

In an embodiment of the invention, as shown in Fig. 1C, spring loading of a gripping socket 108 is provided by an elastic split sleeve 110 located inside the gripping socket and attached to the socket wall 111 by a short neck 112. Split sleeves 108 in a gripping plate 101 or 103 are integrally formed with the plate and have a slot 113 in a sleeve wall 114 that is spaced from socket wall 111.

Any of various suitable materials and processes may be used to form gripping and alignment plates 101 and 103. For example, in some embodiments of the invention, a gripping plate 101 or 103 is formed from a plate of suitable material, such as a metal or plastic, having a desired Young's modulus, by die stamping, hot embossing, and/or laser cutting gripping sockets 108 and their associated split sleeves 110. Optionally, the gripping plates are die cast. In some embodiments of the invention a gripping and/or alignment plate is formed using a rapid manufacturing technique, such as stereolithography or 3D printing, in which successive thin layers of the plate are fabricated one on top of the other from suitable materials, such as resins or photopolymers. In some embodiments of the invention, gripping plates 101 and 103 are formed using any of various MEMS techniques and/or lithographic techniques used in manufacturing semiconductor dies and technique compatible materials such as Silicon or glass.

An alignment socket 109 of a fiber-coupling socket 28 functions to align ferrules 44 of a top and a bottom fiber-end carriage 41 inserted into the fiber-coupling socket 28 so that switch ends 45 of their respective top and bottom fibers 21 and 22 are optically aligned. In some embodiments of the invention, socket 109 is defined by a hole formed in alignment plate 102 to tolerances advantageous for aligning ferrules inserted into the fiber-coupling socket 28. In some embodiments of the invention, as shown in Figs. IA and 1C socket 109 is similar to sockets 108 and comprises a split sleeve 110. Alignment plate 102 and its sockets may be formed using any of various suitable manufacturing techniques and material, such as those noted above in the discussion of the gripping plates. Distances between the alignment plate and the gripping plates, thickness of the plates, and length by which fiber ferrules 44 protrude from plates 50 of fiber-end carriages 41 are such that when ferrules 44 from a top fiber-end carriage 41 and a fiber ferrule from a bottom fiber-end carriage 41 are inserted into a same given fiber-coupling socket 28, the ferrules protrude into alignment socket 109 of the given socket. Dimensions and tolerances of features of fiber ferrules 44 and alignment sockets 109 are determined so that the ferrules protrude sufficiently into the alignment socket of the given fiber-coupling socket and are accurately aligned opposite each other in optical contact. By way of numerical example, to accommodate a standard ferrule having diameter of 1.25 mm and length of about 6 mm, optionally gripping plates 101 and 103 and alignment plate 102 have a same thickness equal to about 1.5 mm and each gripping plate is spaced by about 1.5 mm from the alignment plate. Lumens defined by sleeves 110 have a diameter about equal to 1.25 mm. In an embodiment of the invention, sleeves 110 have chamfered rims to facilitate insertion of a ferrule. Optionally, thickness of wall 114 of a sleeve 110 is equal to about 200 microns and slot 113 a width equal to about 200 microns. In an embodiment of the invention, wall 112 has a diameter of less than 2 mm and sockets 28 have a pitch less than 2.2 mm. It is noted that sockets in accordance with an embodiment of the invention characterized by the aforementioned dimensions are readily provided by conventional photolithographic processes characterized by feature size less 180 nm.

Fig. ID schematically shows an enlarged perspective view of a top fiber-end carriage indicated by alphanumeric 41 -T and a bottom fiber-end carriage 41 indicated by alphanumeric 41 -B having their respective fiber ferrules 44 inserted into a same given fiber-coupling socket 28. When fiber ferrule 44 of top carriage 41-T is inserted into the given fiber-coupling socket 28 its socket prongs 53 are inserted into fiber-coupling sockets 28, distinguished by labels 28- A and 28-B, on opposite sides of the given fiber-coupling socket 28 and in a same socket column 25 (Fig. IA) as that of the given fiber-coupling socket. Similarly, when fiber ferrule 44 of bottom carriage 41 -B is inserted into the given fiber-coupling socket 28, its socket prongs 53 are inserted into fiber-coupling sockets 28, distinguished by labels 28-C and 28-D, on opposite sides of the given fiber-coupling socket 28 and in a same row 26 (Fig. IA) as that of the given fiber-coupling socket.

Optionally, crossbar switch 20 comprises a top mover 70 as shown in Fig. IA, for moving and positioning fiber-end and slack-control carriages 41 and 42 of any given top fiber 21 along column 25 of fiber-coupling sockets 28 associated with the given top fiber. In Fig. IA, top mover 70 is shown in a parking position in which it is located along an edge of socket bank 100 and is not grasping any carriage 41 or 42.

Optionally, top mover 70 comprises a carrier beam 72, and identical fiber-end and slack-control carriage grabbers 73 and 74 respectively. A portion of carrier beam 72 and grabbers 73 and 74 are shown enlarged in Fig. IE. Each grabber 73 and 74 optionally comprises a pair of opposed tongs 75 shaped to receive a gripping protrusion 55 or 63 of carrying handle 52 or 62 respectively (Fig. IB) and having a groove 76 shaped to match the bevel shape of edges 56 or 64 of the gripping protrusion. Carrier beam 70 is supported by a suitable structure (not shown) that maintains the beam parallel to the x-axis and is controllable by controller 29 to move the carrier beam parallel to the y-axis so as to align the beam over and parallel to any column 25 (Fig. 1) of fiber-coupling sockets 28.

Each grabber 73 and 74 is controllable to be moved along beam 72, i.e. along the x- direction and up and down along the z-direction. Tongs 75 of the grabber are controllable to be spread apart and closed toward each other to grasp, hold and release a carrying handle 52 or

62 as required. Once top mover 70 is aligned over a column 25 of fiber-coupling sockets 28, each grabber 73 and 74 is therefore controllable to grasp a carriage 41 or 42 of top fiber 21 associated with the column by its handle, move the carriage along the column of fiber- coupling sockets, and insert the carriage's fiber ferrule 44 into any one of the fiber-coupling sockets in the column.

The bevel shape of edges 56 and 64 and matching grooves 76 of tongs 75 of a grabber 73 or 74 assure alignment of the tongs with V-protrusions 55 or 63 of a carriage carrier handle 52 or 62 when the grabber is used to grasp the carriage. The matching bevel edges 56 or 64 and grooves 76 also tend to promote stability of coupling between a grabber 73 or 74 and a carriage when carrying handle 52 or 62 is grasped by the grabber and tends to prevent the handle from slipping out from the grasp of the grabber.

Optionally, crossbar switch 20 comprises a bottom mover 80 (Fig. IA) for moving carriages 41 and 42 associated with bottom optic fibers 22. Optionally, bottom mover 80 comprises a beam 82 and grabbers 83 and 84, and is similar to and operates similarly to top mover 70 except that its beam 82 is parallel to the y-axis and moveable along the x-axis.

Controller 29 controls crossbar switch 20 to optically couple any given one of top fibers 21 to any given one of bottom fibers 22 by controlling top and bottom movers 70 and

80 to move the respective fiber-end carriages 41 of the given fibers to a fiber-coupling socket 28 at their common crossover point and to insert their respective fiber ferrules 44 into the fiber-coupling socket.

Fig. IF schematically shows crossbar switch 20 after controller 29 has controlled top and bottom movers 70 and 80 to optically couple a top fiber 21 labeled 21-1 to a bottom fiber

22 labeled 22-1. Fiber-end carriage 41 of top fiber 21-1, indicated by alphanumeric 41-1T, and fiber-end carriage 41 of bottom fiber 22-1, indicated by alphanumeric 41-1B, are inserted into a common fiber-coupling socket 28 labeled 28-1.

Fig. IF also schematically shows controller 29 controlling top and bottom movers 70 and 80 to optically couple top and bottom fibers 21 and 22 labeled respectively by alphanumerics 21-2 and 22-2. Top mover 70 is shown moving fiber-end and slack-control carriages of top fiber 21-2, which are labeled 41-2T and 42-2T respectively, so as to couple the fiber to bottom fiber 22-2. Carriages 41-2T and 42-2T are shown just prior to being inserted into appropriate fiber-coupling sockets 28. Portions of crossbar switch 20 are cutaway to show a portion of bottom mover 80 being controlled to couple bottom fiber 22-2 to top fiber 21-2. In the portion of mover 80 shown in Fig. IF, grabber 84 is shown grasping and moving slack-control carriage 42, labeled 42-2, of bottom fiber 22-2. Grabber 82 (Fig. IA), which is moving fiber-end carriage 41 of the fiber, is not seen in the figure.

In accordance with an embodiment of the invention, when controller 29 (Figs. IA and IF) moves a fiber-end carriage 41 of a top or bottom fiber 21 or 22, it controls the fiber's slack-control carriage 42 to move in concert and take up slack in the fiber or reel out fiber length as required by the fiber-end carriage motion. Whichever way along a column 25 of fiber-coupling sockets that the controller moves the fiber-end carriage, it simultaneously moves the slack-control carriage in the same direction along the column but at about half the velocity at which it moves the fiber-end carriage along the column.

The inventors have found that a crossbar switch in accordance with an embodiment of the invention, similar to crossbar switch 20 can be configured to accommodate and switch a relatively large number of optic fibers in a relatively small spatial volume. By way of a numerical example, in accordance with an embodiment of the invention, plates 50 and 60 of carriages 41 and 42 are optionally between about 0.5 mm to about 2.5 mm thick and have a width and height equal to or less than respectively about 20 mm and 50 mm respectively. (For top fiber-end carriages and top slack-control carriages, thickness is a dimension parallel to the y-axis in Fig. IA, width is a dimension parallel to the x-axis and height is a dimension parallel to the z-axis). Optionally, fiber ferrules 44 comprised in fiber-end carriages 41 and socket prongs 53 and 61 (Fig. IB) comprised in slack-control carriages 42 have diameters between about 1 mm and about 1.5 mm. Optionally, each fiber ferrule 44 protrudes from its respective fiber-end carriage 41 a distance between about 4 mm and about 6 mm.

In some embodiments of the invention, a socket bank, such as socket bank 100 comprises an indicator circuit that generates signals that indicate which fiber-coupling sockets 28 are occupied with a fiber ferrule 44.

Fig. 2 schematically illustrates an indicator circuit 120 formed on, by way of example, socket bank 119 similar to socket bank 100 shown for example in Figs. 1C and IF. Optionally, indicator circuit 120 comprises a top xy-grid 121 of conductors formed on a top surface 122 of socket bank 120 and optionally a mirror image bottom xy-grid, not shown in the perspective of figure 2, of conductors formed on a bottom surface 132 of the socket bank. The following description of top xy-grid 121 and its functioning to indicate which fiber- coupling socket 28 is occupied by a fiber ferrule 44 of a fiber-end carriage 41 applies, similarly, to the bottom xy-grid.

Optionally, top xy-grid 121 comprises an array of conductors 126, hereinafter referred to as "y-conductors", parallel to the y-axis of coordinate system 30, i.e. parallel to rows 26 of fiber-coupling sockets 28, and an array of conductors 125, hereinafter "x-conductors 125" parallel to the x-axis of the coordinate system, i.e. parallel to columns 25 of the fiber-coupling sockets. In an embodiment of the invention, there is a different y-conductor 126 for each row 25 of fiber-coupling sockets 28 and a different x-conductor 125 for each column of the fiber- coupling sockets. Optionally, each y-conductor 126 is formed as a straight strip of conductive material. Optionally, each x-conductor 125 comprises a straight strip 128 of conductive material parallel to the y-axis and conductive branches 129 extending parallel to the x-axis. Whereas x-conductors 125 are insulated from y-conductors 126, a given y-conductor

125 can be electrically connected to a given x-conductor 126 by pressing a conductor to the given y-conductor and a conductive branch 129 of the given x-conductor nearest the x- conductor. In accordance with an embodiment of the invention, each top fiber-end carriage 41 comprises a contact conductor which electrically connects a y-conductor 126 and a branch 129 of an x-conductor 125 associated with a column 25 and row 26 respectively of a fiber- coupling socket 28 into which fiber ferrule 44 of the fiber-end carriage is inserted. A suitable circuit (not shown) comprised in a crossbar switch comprising indicator circuit 120 determines which x and y conductors 126 and 125 are electrically connected to indicate which fiber-coupling sockets 28 are occupied by fiber ferrules. Fig. 2, by way of example, schematically shows a fiber-end carriage 41 shown in dashed lines having a contact conductor 130 on an underside edge surface 131 for establishing contact between an y-conductor 126 and a branch 129 of a x-conductor 125. Carriage 41 is shown having its fiber ferrule 44 inserted into a fiber-coupling socket 28 and contact conductor 130 contacting the y-conductor 126 and the x-conductor 125 (by contacting a branch 129 of the x-conductor) associated with the fiber-coupling socket.

In some embodiments of the invention, a crossbar switch comprises a socket bank that is different from that shown in Figs. IA and 1C. Figs. 3A-3C schematically show socket banks in accordance with embodiments of the invention that may be used in the practice of the invention and are different from socket bank 100.

Fig. 3A schematically shows a socket bank 200 having fiber-coupling sockets 202 and comprising gripping plates 203 that are contiguous and optionally bonded with an alignment plate 204. An inset 205 schematically shows a cross section of a fiber-coupling socket 202 into which fiber ferrules 44 of top and bottom fiber-end carriages 41 (Fig. IB) are inserted to optically couple fiber ends 45 of optic fibers mounted to the ferrules.

Fig. 3B schematically shows a socket bank 240 having fiber-coupling sockets 242 comprising spring loaded gripping sockets 246 formed in two optionally mirror image gripping plates 244, in accordance with an embodiment of the invention. The gripping sockets function as alignment sockets, in accordance with an embodiment of the invention. Each gripping socket 246 optionally comprises a split sleeve spring 247 for elastically gripping a ferrule inserted into the gripping socket. Each fiber-coupling socket 242 comprises a gripping socket 246 in one gripping plate and a mirror image gripping socket 246 in the other gripping plate 244.

An inset 248 schematically shows a cross section of a fiber-coupling socket 242 into which fiber ferrules, such as by way of example, fiber ferrules 44 of top and bottom fiber-end carriages 41 (Fig. IB) are inserted to optically couple fiber ends 45 of optic fibers mounted to the ferrules. Fig. 3C schematically shows a socket bank 250 comprising fiber-coupling sockets 252, in accordance with an embodiment of the invention. Socket bank 250 comprises two mirror image pairs 254 of gripping plates 255 formed with spring loaded gripping sockets 256. Optionally, each gripping socket 256 comprises an elastic split sleeve 257 for gripping a fiber ferrule inserted into the socket. Each fiber-coupling socket 252 comprises two gripping sockets 256 from one pair 254 of gripping plates 255 and the mirror image gripping sockets 256 in the other pair 254 of gripping plates 255. Two optic fibers are coupled by inserting a fiber ferrule of one of the fibers into the gripping sockets 256 in one of the pairs 254 of gripping plates 255 and the other fiber ferrule into the mirror image gripping sockets 256 of the other pair of gripping plates. Dimensions of elastic split sleeves 257, Young's modulus of material from which the split sleeves are formed and distance between gripping plates in each pair of gripping plates are determined to provide a stable and accurate angular attitude of a fiber ferrule inserted into the pair of gripping sockets 256. By way of example, each gripping plate 256 is about 0.8 mm thick and the plates are equally spaced apart a distance of 1.5 mm between plates.

An inset 258 schematically shows a cross section of a socket 256 into which, by way of example, fiber ferrules 44 of top and bottom fiber-end carriages 41 are inserted to optically couple fiber ends 45 of optic fibers mounted to the ferrules.

A crossbar switch in accordance with an embodiment of the invention optionally comprises a fiber-end carriage different from that shown and/or implied in Fig. 1C. By way of example, Fig. 4 schematically shows a barrel fiber-end carriage 260 comprising a cylindrical body 262 comprising a fiber ferrule 264 and a stabilizer fin 266 having a socket prong 268. The cylindrical body is formed or coupled to an optionally hexagonal grabbing head 270. A mover (not shown) for moving and positioning barrel fiber-end carriage 260 optionally comprises a grabbing socket matching grabbing head 270 for grabbing the barrel fiber-end carriage. In some embodiments of the invention, the grabbing socket comprises a magnet for holding grabbing head 270 in the socket. Optionally, grabbing head 270 also comprises a magnet (not shown). Optionally, the magnet in the grabbing head and/or the grabbing socket is selectably rotatable between different positions to effect holding and releasing grabbing head 270. Fiber-end carriage 260 is optionally configured having suitable dimensions for use with any of the socket banks discussed above.

It is noted that in the above description of embodiments of the invention, fiber- coupling sockets in socket banks comprise an elastic member, e.g. a split sleeve, for gripping a fiber ferrule inserted in to the socket. In some embodiments of the invention, a socket bank comprises fibber-coupling sockets that are not spring loaded. Instead, socket prongs used with the fiber-coupling sockets are spring loaded.

By way of example, Fig. 5 schematically shows a socket bank 280 comprising a socket plate 282 formed having fiber-coupling sockets 284 that are not spring loaded, and a fiber-end carriage 285 comprising a fiber ferrule 44 and spring loaded socket prongs 286 for use with the socket bank, in accordance with an embodiment of the invention

The fiber-coupling sockets are optionally constant radius through holes formed in a socket plate 282. Each socket prong 286 optionally comprises an inner core 287 mounted in a spring sleeve 288. Inner core 287 is optionally formed from a ceramic, and spring sleeve 288 optionally comprises elastic leaves 289. Inset 296 shows an enlarged image of a socket prong 286. Optionally, spring leaves 289 are seated in matching grooves 290 formed in inner core 287 so that when the ferule is inserted into a socket 284, the leaves deform and flatten into the grooves and exert an elastic force on walls of the socket. The diameter of inner core 287 is matched to the diameter of fiber-coupling sockets 284 so that when the ferrule is inserted into a socket 284, axes of the socket and ferrule are substantially coincident.

Whereas fiber-end carriage 285 is shown being used with a socket bank 280 comprising through holes formed in a single socket plate, fiber-end carriages comprising spring loaded socket prongs may of course be used with socket banks having configurations different from socket bank 240. For example, a fiber-end carriage 285 may be used with a socket bank, comprising a plurality parallel socket plates similar to socket bank 100 shown in Fig. 1C or socket bank 250 shown in Fig. 3C, but with sockets in the plates absent split sleeves.

It is also noted that whereas the various socket banks in accordance with embodiments of the invention are shown being used with fiber-end and slack-control carriages, the socket banks can of course be used for coupling fiber ferrules that are not mounted to fiber-end carriages and for crossbar switches that do not have slack-control carriages. It is further noted that whereas ferrule 286 is shown comprised in a fiber end carriage 285 the ferrule can of course be used without a fiber-end carriage and with fiber end carriages different from fiber end carriage 285.

In some embodiments of the invention, a crossbar switch is configured having a slack- control system different from that shown in Fig. IA and Fig. IF. Fig. 6A schematically shows a side view of an "Apollonius" circle slack-control system 300, in accordance with an embodiment of the invention.

Slack-control system 300 comprises a semicircular guide, optionally a guide rail 301, and a carriage 302, i.e. a "slider 302", which is attached to, and moveable along, the guide. An optic fiber 320 coupled to a fiber-end carriage 321 moveable, for example, along the x-axis of coordinate system 30 indicated in the figure passes through the slider 302 and through first and second junction guides 303 and 304. Fiber 320 is free to move relatively easily through junction guide 304 and through slider 302 and is optionally clamped at junction 303. Any of various methods and materials may be used to provide relatively free motion of fiber 320 through junction guide 304 and slider 302. For example, the guide and/or slide are optionally provided with a relatively low friction hole or channel through which the fiber slides or an arrangement comprising at least one wheel that contacts the fiber and which rotates to allow the fiber to move through the junction guide or slider. Slider 302 is optionally resiliently urged clockwise towards a clockwise end 306 of guide rail 301, optionally by an elastic member, such as a spring or elastic band (not shown) that extends along the guide rail. Optionally, slider 302 is attached to a "draw" cable anchored to a reel (not shown) located at clockwise end 306 of the guide rail. The reel is configured, optionally by a spring, to reel in the draw cable and pull slider 302 to end 306 of guide rail 301. As a result if fiber-end carriage 321 moves to the right along the x-axis slider 302 moves clockwise towards clockwise end 306 of guide rail 301. If the fiber-end carriage is pulled to the left along the x-axis, slider 302 moves counterclockwise away from end 306 and towards a counterclockwise end 308 of the guide rail.

In some embodiments of the invention slider 302 is not connected to an elastic member for biasing the position of the slider towards end 306 but is moved and along guide rail 301 by a suitable mover that grabs the slider and positions it appropriately along the guide rail to control slack.

In accordance with an embodiment of the invention, guide rail 301 and junction guides 303 and 304 are positioned to satisfy conditions of an Apollonius circle and maintain a constant ratio between a length 310 of fiber 320 between location of slider 302 along guide rail 301 and junction guide 304, and a length of fiber 312 between the slider and junction guide 303. Junction guides 303 and 304 are "foci" of guide rail 301 considered as an Apollonius circle. Let lengths 310 and 312 be represented by L310 and L312 respectively and β represent a ratio L312/L310 If junction guide 304 is located at an origin of the x-axis and if guide rail 301 has a radius RQ, then junction guide 303 is located along the x-axis at a point ^x303 ⁼ Rc(P^- l)/β ^and the center of guide rail 301 is located at a point XQ = βR^

As fiber-end carriage 321 moves in the positive and negative directions along the x- axis slider 302 moves along guide rail 301 between clockwise and counterclockwise ends 306 and 308 of the guide rail and maintains a constant ratio β = L3J2/L310- As a result, the fiber remains relatively taut and untangled for all positions of fiber-end carriage 321 for a maximum dynamic range of motion of the carriage equal to about R₍^(β+l)/β. By way of numerical example, if β = 2 and RQ = 20 cm, fiber-end carriage 321 has a maximum dynamic range of motion along the x-axis equal to about 30 cm. By way of another example if the dynamic range is to be limited to a quarter of the circumference of guide rail 301, and if a required dynamic range is equal to DR, then DR = %RQ/2. If DR is equal to 30 cm then R_C = 60 cm. Fig. 6B schematically shows an Apollonius circle slack-control system 330, in accordance with an embodiment of the invention that is a variation of Apollonius circle slack- control system 300.

Fig. 7 schematically shows another slack-control system 350, in accordance with an embodiment of the invention.

Slack-control system 350 comprises a leaf spring 352 optionally formed having an optic fiber groove 354 for receiving and channeling an optic fiber 356 coupled to a fiber-end carriage 358 in accordance with an embodiment of the invention. Fiber-end carriage 358 is optionally a fiber-end carriage similar to that shown in Fig. 4, and is by way of example, moveable by a mover, configured to grab the fiber-end carriage by its hexagonal grabbing head 360. An end 362 of leaf spring 352 is optionally mounted to an anchor block 364 that holds the end stably fixed. Fiber 356 lies at least partially in groove 354 and is free to slide in and along the groove. From leaf spring 352 fiber 356 passes through a junction 360 through which it moves freely and from there to fiber-end carriage 358. To the right of leaf spring 352 in Fig. 7, fiber 356 is held by a suitable device so that it substantially cannot move along its own length. Tension in the fiber is maintained by curling of the leaf spring. As fiber-end carriage 358 moves along the x-axis in the positive or negative direction, leaf spring 352 becomes respectively less or more curled to maintain tension in fiber 356 and prevent it from sagging and possibly entangling with other nearby fibers (not shown). Fig. 8 schematically shows another optic fiber slack control system 600 optionally for use in a crossbar switch (not shown), in accordance with an embodiment of the invention.

Slack control system 600 comprises a fiber-end carriage 641 for optically coupling an end of a fiber 621 to an end of another fiber (not shown) in the crossbar switch. Fiber-end carriage 641 is optionally similar to fiber-end carriage 41 comprised in crossbar switch 20 (Figs. IA, IB, IF). However, instead of slack control carriage 42 comprised in crossbar switch 20 slack control system 600 comprises an "accordion" extension arm 602 having a slack control disc 604 attached optionally substantially at a midpoint 606 of the extension arm. One end of the accordion arm is rotatably connected to fiber-end carriage 641 and the other end is optionally rotatably fixed to a suitable base 603. Fiber 621 passes through fiber-end carriage 641, loops around slack control disc 604 and returns to the fiber end carriage where it is coupled to ferrule 644. The fiber is free to move along the perimeter of slack control disc 604 either by sliding along the perimeter, or as a result of the disc being rotatable. For example, the fiber may be seated in a relatively frictionless groove in the disc along which the fiber is able to slide relatively freely.

When fiber-end carriage 641 is translated a given distance parallel to extension arm 602 to position fiber 621 to optically couple to another fiber, accordion extension arm 602 extends or retracts the given distance and disc 604 translates one half the given distance in a same direction that the fiber-end carriage translates to pay out or take up slack respectively.

Fig. 9 schematically shows another slack control system 650, optionally for use in a crossbar switch (not shown), in accordance with an embodiment of the invention.

As in Fig. 8, slack control system 600 is shown controlling slack generated by motion of a fiber-end carriage 641 for optically coupling an end of a fiber 621 to an end of another fiber (not shown) in the crossbar switch. Slack control system 650 comprises a moving slack control pulley 652 and two fixed pulleys 654 and 656 mounted to pulley supports 655 and 657 respectively. A slack control pulley guide 670 that supports slack pulley 652 and along which the pulley moves relatively freely. Optionally the slack control pulley guide is connected to and extends from pulley support 655. Optionally slack pulley guide 670 comprises a plate 671 formed having a slot 672 to which slack pulley 652 is mounted, optionally, using a wheel or bearing (on a side of the pulley not shown in the figure) that protrudes from the slack pulley and seats in the slot. A pulley belt 680 is optionally fixed to pulley support 655, loops around slack pulley 652 and fixed pulleys 654 and 656 and is connected to fiber-end carriage 641. When fiber-end carriage 641 is translated a given distance parallel to slot 672 to position fiber 621 to optically couple to another fiber, slack pulley 652 translates one half the given distance in a same direction that the fiber-end carriage translates to pay out or take up slack respectively.

Fig. 10 schematically shows a cross section of a portion of a crossbar switch 400 optionally comprising a socket bank 410 having fiber-coupling sockets, one of which is indicated by a dashed line 412 , fiber-end carriages 420, and gravity feed slack control devices 430 for controlling slack in fibers coupled to the crossbar switch. In the figure, a single optic fiber 402 is shown coupled to a fiber-end carriage 420 and a slack control device 430. Fiber end carriage 420 is shown inserted into a fiber-coupling socket 412. Socket bank 410 optionally comprises an alignment plate 414 similar to alignment plate 102 shown in Figs. 1C, ID and IF having alignment sockets 109 comprising split sleeves 110. The socket bank optionally comprises two mirror image gripping plates 416 each formed having through holes 417 that function as gripping sockets. Each fiber-coupling socket 412 comprises two gripping sockets 417 and an alignment socket 109.

Fiber end carriage 420 comprises a fiber ferrule 421 and two spring loaded socket prongs 422. Each socket prong 422 comprises an elastic arm 423 and a latch end 424. Fiber- end carriage 420 is inserted into fiber-coupling socket 412 by pressing the carriage into the socket with sufficient force and to a sufficient depth so that socket prongs 422 enter gripping sockets 417 adjacent the fiber-coupling socket and snap fit into the adjacent gripping sockets. The fiber-end carriage is extracted from fiber-coupling socket 412 by withdrawing the carriage from the socket with force sufficient to bend elastic arms 423 and unsnap latch ends 424 from gripping sockets 417.

To facilitate inserting and extracting fiber-end carriage 420 from a fiber-coupling socket 412, socket prongs 422 are provided with elastic arms 423 and latch ends 424 suitable for the snapping and unsnapping action of the socket prongs. Arms 423 are optionally provided with appropriate elasticity by forming them from a material having a suitable Young's modulus and having suitable dimensions. By way of example, in Fig. 10, the arms are shown relatively thin and latch ends 424 are shown having a semicircular shape.

Slack control device 430 comprises a "plumb bob" weight 432 mounted in a slide sleeve 434 so that the plumb bob is free to move up and down in directions indicated by double headed block arrow 436. Direction of gravity is in the "down" direction indicated by the lower arrowhead of block arrow 436. Slide sleeve 434 optionally comprises a frame 438 sandwiched between a back and a front panel of which only a back panel 439 is schematically indicted in Fig. 7. Frame 438 and the front and back panels constrain motion of plumb bob 432 substantially parallel to block arrow 436 and parallel to back panel 439.

Plumb bob 432 is formed having a fiber optic channel 440 through which optic fiber 402 is threaded and through which the fiber is able to slide relatively freely. The fiber optionally enters slack control device 430 along a receiving "lip" 441 of frame 438 and exits the slack control device along an exit lip 442 of the device on which the fiber also slides relatively easily. To provide for relatively free motion of fiber 402 in channel 440 and on lip 442, optionally, the channel and lip are coated with a suitable frictionless coating. Motion of plum bob 432 in slide sleeve 434 in accordance with an embodiment of the invention controls slack in fiber 402. As fiber-end carriage 420 is moved to the left or right in Fig. 10 to insert the carriage into a desired fiber-coupling socket 412 plum bob 432 moves respectively up or down in slide sleeve 434 to let out or take in fiber and control slack in the fiber. Optionally, to provide plum bob 432 with weight suitable for taking up slack, the plumb bob is "salted" with a relatively heavy material. For example, if the plumb bob is formed from a relatively light polymer the polymer might be mixed with metal pellets or formed around a metal insert. It is noted that whereas in crossbar switch 400 a fiber-end carriage 420 comprises elastic socket prongs 442 for securing the carriage in a fiber-coupling socket 412, other methods of securing a fiber-end carriage to a fiber-coupling socket, may used in the practice of the invention. For example, gripping plates 416 may be formed from a magnetic material, such as a magnetic metal, and a fiber end carriage, optionally similar to fiber-end carriage 420 may comprise a magnet in instead of socket prongs 422, in accordance with an embodiment of the invention. When the carriage is inserted into a fiber-coupling socket 412, magnetic force between the magnet in the carriage and the gripping plate secure the carriage in the socket.

Figs. HA and HB schematically show a socket bank 500 optionally for use with a spring loaded fiber-end carriage 520 similar to that shown in Fig. 10, in accordance with an embodiment of the invention. Fig. HA schematically shows an exploded perspective view of socket bank 500 and a fiber-end carriage 520 coupled to an optic fiber 522. Fig. HB schematically shows an assembled partially cutaway view of socket bank 500 and fiber end carriage 520 inserted into a fiber-coupling socket of the socket bank, in accordance with an embodiment of the invention. Optionally, socket bank 500 comprises a socket alignment plate 502 and first, "top" and second, "bottom" arrays 504 and 506 of top and bottom gripping strips 505 and 507 respectively. Alignment plate 502 is optionally formed having through holes 510, which function as alignment sockets and through holes 511 which function as assembly holes. For clarity of presentation, alignment sockets 510 are shown shaded. Optionally, the alignment sockets and assembly holes are identical. Optionally, alignment plate 502 is a printed circuit board (PCB). In some embodiments of the invention, alignment sockets 511 comprise an optic sleeve optionally mounted, e.g. by press fitting, in a through hole formed in the plate or integrally formed in the plate. For simplicity of presentation, except for shading, alignment plate 502 is shown having identical through holes that function as both alignment sockets 511 and as assembly holes 510.

Gripping strips 505 in top array 504 are optionally perpendicular to gripping strips 507 in bottom array 506. Each gripping strip 505 and 507 is produced from a relatively rigid material formed having gripping having holes, optionally in the shape of slots 508, and comprising assembly pins 509 that are configured to be received by assembly holes 510.

Socket bank 500 is assembled by inserting assembly pins 509 of top gripping bars 505 into rows of assembly holes 510 from a first, "top" side of alignment plate 502 and assembly pins 509 of bottom gripping bars 507 from an opposite, "bottom" side of the alignment plate. The assembly pins are securely fixed in holes 510 using any of various techniques and materials known in the art. For example, assembly pins 509 may be press fit, bonded with an appropriate adhesive, heat soldered, or ultrasonically welded in assembly holes 510.

Gripping slots 508 cooperate to snap fit with socket prongs 422 of fiber-end carriage 520 and secure a fiber-end carriage in an alignment socket into which the carriage is inserted. Fig. HB schematically shows fiber-end carriage 520 inserted into a fiber-coupling socket 511 and having its socket prongs 422 snap fit into gripping slots 508.

It is noted that whereas socket bank 500 is shown in use with a fiber-end carriage 520 the socket bank is not limited to use with a fiber-end carriage similar to 520. Any suitable spring loaded fiber-end carriage, for example a fiber-end carriage similar to that shown in PCT Publication WO/2008/104972, may be used with socket bank 500

Fig. 12 schematically shows a cross section view of another crossbar switch 550 comprising a socket bank 552 and male and female fiber-end carriages 561 and 562 respectively, in accordance with an embodiment of the invention. Male and female fiber-end carriages 561 and 562 are coupled to optic fibers 563 and 564 respectively. Male carriage 561, comprises a relatively long "male" fiber ferrule 565 optionally housed in a housing 567 having a groove 566 formed near its end. Female carriage 562 is formed having a "female" ferrule comprising a receptacle 570 for receiving the male ferrule and a pair of elastic "mandibles" 572 for grasping the male ferrule. A button tip 571 at the bottom of receptacle 570 holds an end of an optic fiber 564 for optical coupling to optic fiber 563 held by male ferrule 565 received by the female ferrule. As noted below, an "edge-on" cross section of male carriage 561 is shown when the male carriage is coupled to the female carriage and a "broadside" cross section of the male carriage is shown in an inset 580.

Fiber bank 550 comprises an alignment plate 582 formed having a plurality of through holes 584 that function as alignment sockets. Fibers 563 and 564 are coupled to each other by inserting male fiber-end carriage 561 into a socket 584 so that its fiber ferrule 565 protrudes through the socket. Female fiber-end socket 562 is then mounted onto the male fiber-end ferrule so that its mandibles 572 snap fit into groove 566. In Fig. 12 male fiber-end carriage 561 is shown mounted in socket 584 of socket bank 582 edge-on (rotated about its ferrule 565 by 90°) because the male and female fiber end carriages translate along orthogonal directions to couple to their respective optic fibers to other optic fibers.

In the description and claims of the present application, each of the verbs, "comprise" "include" and "have", and conjugates thereof, are used to indicate that the object or objects of the verb are not necessarily a complete listing of members, components, elements or parts of the subject or subjects of the verb.

The present invention has been described using detailed descriptions of embodiments thereof that are provided by way of example and are not intended to limit the scope of the invention. The described embodiments comprise different features, not all of which are required in all embodiments of the invention. Some embodiments of the present invention utilize only some of the features or possible combinations of the features. Variations of embodiments of the present invention that are described and embodiments of the present invention comprising different combinations of features noted in the described embodiments will occur to persons of the art. The scope of the invention is limited only by the following claims.

Claims

1. A socket bank comprising a plurality of fiber-coupling sockets for optically coupling optic fibers, the socket bank comprising: a first gripping plate formed having gripping sockets, each gripping socket configured to receive and securely grip an optic fiber ferrule; and a second gripping plate formed having gripping sockets configured to receive and securely grip an optic fiber ferrule; wherein each gripping socket in the second plate is aligned with a gripping socket of the second plate to form a fiber-coupling socket.

2. A socket bank according to claim 1 wherein the gripping sockets are through holes formed in the gripping plate.

3. A socket bank according to claim 1 wherein the gripping sockets are spring loaded to aid in gripping a fiber ferrule.

4. A socket bank according to claim 3 wherein each of the gripping sockets comprises a split sleeve.

5. A socket bank according to claim 4 wherein the split sleeve is integrally formed with the gripping plate.

6. A socket bank according to any of the preceding claims wherein the gripping plates are spaced apart.

7. A socket bank according to any of claims 1-5 wherein the gripping plates are contiguous.

8. A socket bank according to any of claims 1-6 and comprising an alignment plate located between the first and second gripping plates formed having alignment sockets, each configured to receive and align two optical ferrules and wherein each alignment socket is aligned with two gripping sockets to form a fiber-coupling socket.

9. A socket bank according to claim 8 wherein the alignment sockets are through holes formed in the alignment plate.

10. A socket bank according to claim 8 wherein each of the alignment sockets comprises a split sleeve.

11. A socket bank according to claim 10 wherein the split sleeve is integrally formed with the alignment plate.

12. A socket bank according to claim any of claims 8-11 wherein the gripping plates and alignment plate are spaced apart.

13. A socket bank according to any of claims 8-11 wherein the gripping and alignment plates are contiguous.

14. A socket bank according to any of claims 8-13 wherein the alignment plate is formed from a material suitable for processing using a MEMS and/or photolithography manufacturing technique.

15. A socket bank according to any of claims 8-14 wherein the alignment is formed from a material suitable for processing using a rapid manufacturing technique.

16. A socket bank according to any of the preceding claims wherein a gripping plate of the gripping plates is formed from a material suitable for processing using a MEMS and/or photolithography manufacturing technique.

17. A socket bank according to any of the preceding claims wherein a gripping plate of the gripping plates is formed from a material suitable for processing using a rapid manufacturing technique.

18. A socket bank according to any of claims 14-17 wherein the material comprises a material chosen from the group of materials consisting of: silicon, glass, a polymer, a photopolymer, and a resin.

19. A socket bank according to any of the preceding claims wherein the fiber-coupling sockets have a pitch less than or equal to about 2.2 mm.

20. A socket bank according to any of the preceding claims wherein at least one of the plates has a thickness less than or equal to about 6 mm.

21. A socket bank according to claim 20 wherein at least one of the plates has a thickness less than or equal to about 3 mm.

22. A socket bank according to claim 21 wherein at least one of the plates has a thickness less than or equal to about 1.5 mm.

23. An optical crossbar switch for optically coupling optic fibers comprising: at least one first fiber and a plurality of second fibers; a socket bank according to any of claims 1-22 for coupling the first fiber to any of the plurality of second fibers; wherein to optically couple a first fiber of the at least one fiber to a second fiber, the first and second fibers are inserted into a same fiber-coupling socket.

24. A fiber-end carriage for optically coupling a fiber to another fiber, the fiber-end carriage comprising: a cylindrical body; a fiber ferrule for holding an end of a fiber, the ferrule mounted to the cylindrical body and configured for insertion into a fiber-coupling socket; and a fin extending from the cylindrical body and comprising a socket prong configured for insertion into the fiber-coupling socket.

25. A fiber-end carriage according to claim 24 and comprising a grabbing head to facilitate holding and moving the fiber-end carriage.

26. A fiber-end carriage according to claim 25 wherein the grabbing head has a hexagonal cross section.

27. A fiber-end carriage for optically coupling a fiber to another fiber, the fiber-end carriage comprising: a body mounted with a fiber ferrule for holding an end of a fiber and configured for insertion into a fiber-coupling socket; and at least one socket prong configured for insertion into the fiber-coupling socket; and a resilient element that is inserted to the fiber-coupling socket with the socket prong to resiliently secure the socket prong in the socket.

28. A fiber-end carriage according to claim 27 wherein the at least one socket prong comprises two socket prongs.

29. An optical crossbar switch for optically coupling optic fibers comprising: a plurality of fibers, each coupled to a fiber-end carriage according to any of claims 24-28; a socket bank according comprising a plurality of fiber-coupling socket for coupling any two of the plurality of fibers; wherein to optically couple the two fibers each is inserted into a same fiber-coupling socket of the socket bank.

30. A slack control system for controlling slack in an optic fiber having an end which is moved between different locations to optically couple the fiber to other fibers, the slack control system comprising: a first junction guide formed having a first junction through which the fiber moves freely; a second junction guide having a second junction at which the fiber is held stationary; a guide having a shape of an arc of a circle; a third junction that moves along the guide and is formed having a third junction through which the fiber moves freely; a device that urges the third junction guide towards one end of the guide; wherein, the first and second junctions are located substantially at Apollonius foci of the circle .

31. A slack control system for controlling slack in an optic fiber having an end which is moved between different locations to optically couple the fiber to other fibers, the slack control system comprising: a first junction guide formed having a first junction through which the fiber moves freely; a leaf spring curved along an arc having a center of curvature and formed having a channel in which the fiber seats and along which the fiber is free to move easily; a device that holds the fiber substantially fixed on a side of the leaf spring where the center of curvature is located; wherein the radius of curvature decreases or increases to take up or pay out slack when the fiber end is moved respectively towards or away from the leaf spring.

32. A slack control system for controlling slack in an optic fiber having an end which is moved between different locations to optically couple the fiber to other fibers, the slack control system comprising: a weight that hangs from the fiber; a guide along which the weight is substantially free to move with a component of motion along the direction of gravity; a device that holds the fiber substantially fixed on one side of the guide; wherein the weight moves down or up along the guide to take up or pay out slack in the fiber when the fiber end is moved respectively towards or away from the guide.

33. A slack control system for controlling slack in an optic fiber having an end which is moved between different locations to optically couple the fiber to other fibers, the slack control system comprising: an accordion extension arm having a first end fixed to a base; a fiber-end carriage attached to a second end of the extension arm; a disc attached to a point about midway along the length of the extension arm; and an optic fiber that passes through the fiber end carriage, loops around the disc and returns to the fiber-end carriage where an end of the optic fiber is held.

34. A slack control system for controlling slack in an optic fiber having an end which is moved between different locations to optically couple the fiber to other fibers, the slack control system comprising: a first pulley around which the fiber is looped; a guide along which the first pulley is constrained to move; second and third stationary pulleys; and a pulley belt that loops around the first second and third pulleys and has a first end fixed relative to the stationary pulleys and a second end that is connected to and moves with the fiber end.

35. A socket bank comprising a plurality of fiber-coupling sockets for optically coupling optic fibers, the socket bank comprising: a plate formed having rows and columns of holes; first and second sets of relatively narrow strips having long and short edges each formed having an array of holes extending along the length of the strip and a plurality of pins protruding from a same long edge of the strip; wherein the first set of strips are parallel to the rows of holes and have their pins inserted from a first side of the plate into alternate rows of the holes and the second set of strips are parallel to the columns of holes and have their pins inserted from a second side of the plate into alternate columns of the holes.

36. A socket bank according to claim 35 wherein the strips are formed having holes configured to snap fit with prongs comprised in a fiber-end carriage.

37. A crossbar switch for optically coupling optic fibers, the cross bar switch comprising: a plate formed having through holes formed therein; a first set of optic fibers, each coupled to a male optic fiber ferrule configured to be inserted into the holes so that when inserted into a hole from a first side of the plate it protrudes to the second side of the plate; and a second set of fibers each coupled to a female optic fiber ferrule configured to receive and grasp an end of a male optic fiber when it protrudes through the plate.

38. A crossbar switch for optically coupling optic fibers, the cross bar switch comprising: a plate formed from a magnetic material and having through holes formed therein for receiving a fiber ferrule; and a fiber ferrule configured for insertion into the holes and comprising a magnetic material so that when the ferrule is inserted into a through hole, the magnetic materials of the ferrule and plate attract to provide a force that maintains the ferrule securely in the hole.