CA2091466A1 - Optical fiber switch - Google Patents

Abstract

An optical fiber switch (10) in which the switching force is applied directly to the fiber (12). A biasing force, generated by a bending of the fiber (12), is exerted on the fiber (12) in a direction tending to urge the same toward the bottom (20 B) of a first groove (20). The switching force is applied transversely to the direction of the biasing force, and moves the fiber (12) out of the first groove (20) and into the second, adjacent groove. When in the second groove (22), the biasing force on the fiber urges the same toward the bottom (22 B) of the second groove (22).

Description

~)9~4~6 ~3 WO 92/0~460 ~ PCr/VS91/0674 OPTICAL FIBER SWITCH

~GRO~ID OF ~HE INVENTION

Field of the Invention This invention relates to a switch for switching an optical fiber from a first to a secand groove in response to a switching force and, in 10 particular, to a switch in which the switching force is imposed directly on the fiber.

~ iptjon, ~,f the Prior Art Fiber optic communication systems now use either single mode or 15 multimode optical fiber cables to transmit information within a local area network. Switches permit optical paths within the network to be changed to allow for the information to be directed to a particolar unit or units or even to bypass a particular unit. Switches for such uses 20 must exhibit a high degree of reliability over many switch cycles, low insertion loss, low crosstalk, and short switch times, Several forms of optical fiber switches are known.

2 5 In some switch arrangements the switching function is accomplished by placing an optical device within the optical path. Copending application Serial Number 07/462t 47, (ED-0385), filed December 18, 1989 and assigned to the assignee of the present invention, , 30 discloses the use of a movable blocking element to switch light from one fiber to another or to an off positi,on.
United States Patent 4,790,621 (Calaby et al.) shows the use of a movable prism to switch light from one fiber to another. United States Patent 4,261,638 (Wagner) SUB5T1~ E SHE:ET

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2091 4~6 wo 92/oj460 2 PC~IJS91/06749 discloses the use of a reflecting member to switch light along different optical paths.

- Mechanical switching arrangements are also known.
5 In such devices the optical fiber is fixedly mounted to a movable member and the member is physically displac~d from a first to a second position to switch the optical path. United States Patent 4,911,520 (Lee), also assigned to the assignee of the present invention, utilizes a ;
10 cantilevered glass tongue to which a fiber is edgewise mounted. A first and a second fiber are similarly mounted along edges of a fixed block. Moving the glass member from a first to a second position removes the fiber thereon from a first optical path that includes the first fixed fiber and places the fiber into a second optical path ~ `~
that includes the other fixed fiber. ~
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In United States Patent 4,407,562 (Young) optical fibers are secured in grooves disposed on the exterior 20 surface of a movable housing. Displacement of the housing brings the faces of the fibers into and out of alignment with other arrays of fibers thereby to cause the s~vitchin~
action. Alignment of the movable housing with the casing in which it is disposed is effected using alignment 25 grooves. United States Patent 4,896,937 ~Kraetsch et al.) provides two V-grooves, one in the cover and another in the base of a housing. The switching action is accomplished by moving a ferromagnetic strip to which a fiber is attached into position in one of the V-grooves.
United States Patent 4,759,597 (Lemonde) rnounts an optical fiber to a magnetic rocker arm. The pivotal motion of the rocker arm moves the fiber between correspondin~ ' fibers secured in grooves respectively provided in an 35 upper and a lower support slab.

5UBSTlTUrF SHE~T

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æ~ wo 92/0:~460 PCr/lJS91/0674 In the above discussed mechanical switches the switching action is accomplished by moving, in addition to the mass of an actuating element, a member to which the fiber is attached. That member is relatively large and massive as compared to the size and weight of the optical fiber. These devices would thus appear to be iimited in - their switching speed.

United States Patent 4,946,236 (Dautartas et al.) discloses a switch in which the displacing force is applied to the fiber itself. The switch includes fibers that are surrounded by a magnetic sleeve. The fibers are disposed within grooves defined by the corners of an elongated, - 15 diamond shaped, internal channel extending through a block. A magnetic field is applied to effect the displacement of the fibers from one corner of the groove to another.

In view of the foregoing it is believed advantageous to provide an optical,fiber switch having a repeatabiy low insertion loss, a relatively short switching time in which the switching action is accomplished by moving (in addition to the mass of the actuating element) only the 2 5 relatively minimal mass of the fiber.

SUMMARY OF THE INVENTION

The present invention relates to an optical fiber switch comprising a base having a block portion thereon.
The block has a surface in which at least a first and a second groove are formed. An optical fiber has a first predetermined portion of its length adjacent to its end face received in one of the grooves. The axis of the fiber 3 5 in this first predetermined portion thereof defines a SU~3STITIJTE SHl~T
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'~3'~1466 WO 92/0~460 4 PCT/US91/0674'J

predetermined positive an~le with respect to the axis of the groove. The fiber is biased by a biasing force acting on the optical fiber in a direction which urges the first predetermined portion of the fiber toward the bottom of 5 the groove. A second predetermined portion of the fiber spaced behind the first portion is mounted over an inclined ramp, thereby bending the portion of the fiber forwardly thereof. The biasing force is generated by the bending of the fiber. Preferably the surface of the ramp defines an 1 û angle with respect to the base that lies in a range from five (5) to fifteen (15) degrees. The ramp may be grooved, ~ -if dasired.
:, A switching member is reciprocally movable with 1~ respect to tha base from a first to a second position. The motion of the switching membar is generally transverse to the direction of the biasing force. During its movernent the switching member engages operatively against the fiber thereby to move the first predetermined portion 20 thereof against the biasing force out of the one groove and into the other groove. As the fiber is displaced the biasing force acts thereupon to urge the first predetermined portion of the fiber toward the bottom of that other groove. In the pref0rred instance the switching 25 member takes the form of a yoke connected via a rocker arrangement to an actuating solenoid. The yok~ engages operatively against an intermediate portion of the fiber disposed between the ramp and grooved block.

A switch embodying the teachings of the present invention may be used in any one of several switchin~
environments, such as a one-by-two switch, a two-by-two switch, or a crossover switch.

3 5 BRIEF DESCRIPTION OF THE ~RAW~NG$

SUBSTITUTE SHEET

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WC~ 92/~ 460 PCr/l,'S91/Ofi749 The invention may be more fully understood from the followin~ detailed description thereof, taken in connection with the accompanying drawings, which form a part of this application, and in which:

Figure 1A is a stylized p~rspective view of the elements of an optical fiber switch in accordance with the present invention from which the principles of operation thereof may be understood, the switching member baing illustrated in a first position and the fiber being `
illustrated as resident in a first groove;

Figure 1B is a view similar to Figure 1A with the switching member being illustrated in a second position and the fiber being illustrated as resident in a second groove; :

Figure 1C is a plan view of the switch shown in 20 Figures 1A and 1B, with the fiber being removed therefrom for clarity of illustration;

Figure lD is a side elevation view of the switch shown in Figure 1A with a portion thereof broken away, 25 while Figure 1E is an enlarged view of a portion Figure 1D;

Figure 1F is an elevation view taken along lines 1F-1 F in Figure 1 A;

Figure 2A is a view generally similar to Figure 1A of - a portion of the switch there shown illustrating the extension of the principles of the switch in accordance with the present invention to an environment for switching multiple optical fibers, the switch being shown with the switching member in a first position and the SUBSTITIJT SH~ET
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~)9 1 ~6 WO 92/0~460 , 6 PCI/US91/0674 movable fibers shown as each occupying a first groove, while Figure 2E~ is a view similar to Figure 2A with the switching member in a second position and the movable fibers each being switched into a second groove; -Figures 3A and 3B are views r~spectively similar to Figures 2A and 2B that illustrate the further extension of the principles of the switch in accordancs with the prssent invention to a crossover switch arrangement for 10 switching multiple optical fibers;

Figures 4A through 4C are diagrammatic views that illustrate the minimum spacin~ required between the arms of the yok~ of the switching member for a hNo fiber 1~ switch as illustrated in Figure 2; and Figures 5A through 5C are, respectively, a perspective, plan and side sectional views of the structure of a practical implementation of a switch in 2 0 accordance with this invention DETAILED DESCRIPTION OF THE INVENTION

Throughout the following detailed description, 25 similar reference numerals refer to similar elements in all Figures of the drawings. -. .
The various subparts of Fi~ure 1 (viz., Figures 1A
through 1 F) are highly stylized diagrammatic views of the 30 basic elements of a switch 10 in accordance with the present invention. Although more detailed drawings of the structure of the switch 10 are presented hereinafter, the various views comprising Figure 1 are useful in clearly indicating the basic structure and operation of the switch 35 10.
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The switch 10 is operative to switch at least one optical fiber 12 from a first position to at least a second position. In one and/or both positions, the fiber 12 may be 5 arran~ed to optically communicate with a fixed optical fiber F1 or F2, as will be developed.

The movable fiber 12 may be either a singie or a multimode optical fiber and is ~ypically fabricated of 10 fused siJica or plastic. The fiber 12 has a predetermined diameter D. The fiber 12 is illustrated in Figures 1A, 1B, ~ D, 1 E and 1 F with the jacket thereof removsd.
Accordingly the diameter D represents the diameter of the fiber core plus its surrounding claddin~. This diameter D, 15 for a single mods fiber, is typically on the order of one hundred hventy five ~125) micrometers.

The switch 10 includes a base 14 and a corresponding cover 16. The cover 16, illustrated only 20 schematically in Figure 1D is arranged in any convenient fashion for conjointure with the base 14. When joined to the base 14 the cover serves to enclose and thereby protect the elements of the switch 10.

The base 14 includes a block portion 18 located at a forward portion thereof. The ~lock 18 may be mounted on and secured to the base 14, or may be formed integrally therewith, as shown. The block 18 has a top surface 18T, a front surface 18F, and a rear surface 18R. The a~tial length of the block 18 is indicated by the reference character 18L (Figure 1D).

The top surface 18T has at least a respective first and a second open groove 20, 22, respectively, formed th~rein. The grooves 20, 22 interrupt at least the rcar TIJ~; S~E

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WO 92~0~460 8 PCr/US91/0674 surface 18R of the block 18 and extend axially along the block 18 for some predetermined axial distance. In most instances the grooves 20, 22 extend across the entire axial length 18L of the block 18 and thus also interrupt the front surface 18F thereof. A planar median 18M may be defined between the adjacent ~rooves 20, 22, if desired.

In the preferred instance the grooves 20, 22 are each generally V-shaped, with the sidewalls 20W1, 20W2 and 22W1, 22W2, as the case may be, of each ~roove tapering toward a pointed bottom 20B, 22B, respectively. The grooves 20, 22 each have an a~is 20A, 22A, respectiveiy, extending therethrough. The respective axis 20A, 22A of each groove 20, 22 is collinear with the bottom thereof.

As is apparent from the Fi~ures one sidewall of the groove adjacent each lateral extremity of the switch 10 extends a greater distance above the sidewalls of the grooves defined intermediate therebetween. Thus, in the context of the embodiment of Figure 1 the sidewall 20W1 -and the sidewall 22W2 extend above the intermediate sidewalls 20W2 and 22W1.

As will become more apparent herein, in accordance with the present invention, the precise location of the fiber 12 when the same is in each respective groove thereof is accomplished by the interac~ion of the fiber with the groove. With a V-shaped groove at least two point contact must be definsd betwcon the sidewalls of the grooves and the fiber for precise alignment of the fiber.

The bottoms 20B, 22B of the grooves 20, 22 each extend at least a predetermined depth into the block 18.

SUBSTITUTE SHEET

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W~ 92/~460 9 PCl/lJS9~/067 Generally speaking, the grooves 20, 22 must extend to a depth so that the fiber is precisely aligned as a result of at least two point contact with the sidewalls of the grooves. Thus, in practice, for a multiple movable fiber switch using ninety degree V-~rooves, the grooves should extend into the block for a distance approximately equal to the radius of the fiber 12. In the case of a single movable fiber, as illustrated in Figure 1, the depth 30 (Figure 1F) may be on the order of the fiber diameter D.
10 Although it is not required, in practice, the depth dimension should be the same for all the grooves.

In ths preferred case, best seen in Figure 1C, the axes 20A, 22A of the grooves 20, 22 are parallel and are 15 separated from each other by a distance 32 which is at least slightly larger than the diameter D of the fiber 12, thereby to prevent their touching as they rep~se in the grooves. Although a more precise definition of the spacing 32 of the grooves is set out hereinafter (Figure 4), it 20 should be noted that in the case of a single movable fiber (Figure 1) the magnitude of the separation distance 32 is not as critical as in the case of plural movable fibers. It lies within the contemplation of the present invention to arrange the axes 20A, 22A of the grooves 20, 22 such that 25 they subtend a predetermined angle (on the order of one degree) therebetween.

The fiber 12 has an end face 12E (Figure 1E), preferably defined by cleaving the fiber 12. In practice, a 3 0 suitable anti-reflection coating, such as a one-quarter wavelength thick layer of magnesium flouride, is provided on the end face 12E.

The fiber 12 has a first predetermined portion 12F
35 (perhaps best seen in Figures 1D and 1E) defined adjacent Sl~13StlTUTE SHEET

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'~091~6 WO 92/0~460 t O PCT/US91/06749 to the end face 12E thereof whil~ a second pred~termined portion 12R (perhaps best s~en in Figure 1D) is dcfined a predetQrmined distance rearwardly from the first portion 12F. The first portion 12F of the fiber 12 may be viewed 5 as that portion of the fiber 12 extending between the rear surface 18R of the block 18 and the end face t2E. The first portion 12F of the fiber 12 has a central axis 12A
(Figure 1 E) extendin~ thsrethrou~h.

In the embodiment shown in Figure 1, h~o stationary optical fibers F1, F2 are fixed in a manner such that they romain in place in a respective V-grooves 20, 22. For example, the stationary fibers F1, F2 may be secured to another block 30 (indicated in dot-dash lines in 15 Figure 1D) using a ultraviolet light curable resin such as that sold by Dymax Corporation, Torrington Connecticut as Dymax 305. Another suitable adhesive is that sold by Electro-Lite Corporation, Danbury, Connecticut under the product number 82001-ELC-4480. The portion of the fixed 20 fibers extending into the grooves 20, 22 is also secured into the block 18, with care being exarcised to prevent the adhesive from reaching the region of the grooves into which the movable fibers are disposed. The block 30 may be mounted on or formed integrally with the base 14. The 25 cleaved end faces of the fibers F1, F2 may be provided with anti-reflection coatings, such as that discussed above. Of course, it should be understood that if a simpler on-off switch arrangement is desired, one of the fixed fibers F1 or F2 may be omitted.
In a first switch position (Fisure 1 A) the first predetermined portion 1 2F of the fiber 12 is received within a first one of the grooves 20, 22, as the case may -be. Although not completely visible from Fi~ure lB, in the 3 5 second switch position the same predetermined portion ~ -.
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W092/0~460 1 t ~9~6 PCr/US91~0674~

12F of the fiber 12 is received within the other of the grooves 20, 22. When in each switched position the and face 12E of the movable fiber 12 lies within a predetermined close distance 34 (Figure 1E) of the end 5 face of the fixad fiber F1, F2 (as the case may be3 disposed in that groove.

In the embodiments of the invention shown herein the first portion 12F of each movable fiber 12 has an axial 10 dimension such that, when the fiber is in any switch position, the end face 12E of the fiber lies within a groove, intermediate the surfaces 18F and 18R of the block 18. The first portion 12F of the fiber 12 has an axial length typically between 0.25 millimeters and 0.40 15 millimeters when the axial length 18L of the block is on the order of 1.5 millimeters The gap 34 is on the order of approximately sixty-five (65) micrometers.

It should be understood, however, that the first 20 portion 12F of the fiber 12 may have an axial length such that, when the fiber is in either switch position, the end face 12E of the fiber 12 and some region of the first portion 12F projects from the groove in which it is disposed beyond ~he face 18F of the block 18. The 25 projecting end 12E of the fiber 12 may be placed in optical communication with either another fiber or with any active or passive opto-electronic device. The hypothetical fiber or the hypothetical opto-electronic device is suitably supported by any convenient expedient. The 30 support arrangement for the fiber or the device may be attached to or made integral with the base 14. As a yet further alternative, it should be understood that the first portion 12F of the fiber 12 may have an axial length such that, when the fibar is in either switch position, the end 35 face 12E of the fiber lies coplanar with the surface 18F of S~BS~ 5~EE~

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the block 18. In such an arrangement either the hypothetical optical fiber or the hypothetical opto-electronic device may be secured to the surface 18F of the block 18, eithsr directly or by a suitable mounting 5 arrangement.

Secured to the base 14 a predetermined distance 36 (Figure 1D) from the block 18 is a support pedestal 38.
The support pedestal 38 may be mounted on and secured to ~ -10 the base 14 or may be formed integraliy therewith, as is illustrated. The support pedestal 38 has a generally inclined ramp surface 40R and a frontal surface 40F
thereon. As will be discussed the ramp surface 40R
serves to develop a biasing force in the fiber 12. This 15 function is best served if the ramp surface 40S is inclined at a predetermined angle 42, measured as shown in Figure 1D. In practice the angle 42 IjBS in the range from five (~) to fifteen (15~ degrees.

The second prsdeterrnined portion 12R of the movable fiber 12 extends over the ramp surface 40S. The ramp surface 40S may be provided with a Qroove 44 in which the second portion 12R of the fiber 12 is received.
In either event the contact point at which the fiber 12 last touches the frontal surface 40F of the pedestal 38 is indicated by the reference character 46. The portion of the fiber 12 extending past the contact point 46 to the end face 12E is termed the ~free length" of the fiber.

The fiber 12 is secured in the groove 44 (or on the ramp surface 40S of the pedestal) at least in the vicinity of the contact point 46. Any suitable expedient, such as one of the adhesives mentioned earlier, may be used. The adhesive is indicated by the referenca character 48 (Figures 1A and 1B).

SaJBSTlTUTE SHE~:~

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W042/0~460 1 3 PCI~tUS91/0674') As is bost illustratod in Fi~ure lD the contact point 46 lies a predetermined offset distance 50 above the bottom of the grooves 20, 22. The axis 12A of ths portion 5 12F of the fiber 12 defines a predetermin~d angle 52 (Figure 1E) with respect to the axis 20A, 2?A (as appropriate) of the groove 20, 22. The angle 52 must be positive (i.e., above a reference plane P that is disposed parallel to the surface of the base 14 and includes the 10 axis of the groove) and is related to the clearance distance 36, the offset distance 50 and the pedestal angle 42 in accordance with the small angle approximation (in radians):

A = B- 1.5 (B- HJL), with A representin~ the angle 52, B representing the angle 42, H representing the offset distance 50, and L representing the clearance distance 36.

In practice, the angle 52 is on the order of onP (1) degree.

As seen from Figure lD, the axes of the fixed fib~rs 25 F1, F2 are arranged parallel to the axis of the groove in which they are disposed. However, it should be understood that the axes of the fixed fibsrs F1, F2 may also be inclined with respect to the axis of the grooves, similar to the inclination of the movable fiber 12. This condition 30 is suggested in Figure 1E. To this end, it may be desirable to slightly incline the block 30 (Figure 1D) in order to cause a bending in the fibers and thereby to obtain a biasing force thereon similar to the biasing force 56 imposed on the movable fibers, as will be discussed. This 3 5 alternative arrangement eliminates the adhesive Sl~E~STlTVT~ S~EET

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attachment of the fixed fibers in the grooves of the block 1 8.

Owing to the disposition of the first portion 12F in the groove 20, 22 and the second portion 12R on the ramp surface 40S (including bein~ disposed in the gr~ve 44 therein) the fiber 12 bends throughout its free length with the curvature being largest closer to tha pedestal 38.
This bending of the fiber 12 serves to impose a biasing force acting on the first portion 12F ther~of. The biasin~
force acts in a direction 56 urging the first portion 12F of the fiber 12 toward the bottom of the respective groove in which it is disposed. The biasing force thus acts in a direction 56 that is orientad generally perpendicularly to the top surface 18T of the block 18.

A switching member, diagrammatically indicated by the reference character 62, is operatively connected (Figure 1B) to an actuator 64 for reciprocating movement with respect to the base 14 in opposed directions 66A, 66B. The reciprocating motion of the switching member 62 in the directions 66A, 66B is in a direction generally transverse to the direction 56 of the biasing force and to the axis of the grooves 20, 22. The switching member 62 - 25 is disposed in the clearance space 36 provided between the block 18 and the pedestal 38, preferably as close to the rear surface 18R of the block 18 as possible.
Structural details of the preferred form of the switching member 62 and the actuator 64 are set forth hereinafter.
In general, the switching member 62 takes the form of a yoke having a crossbar 70 and a first and a second arm 72A, 72B thereon. The arms 72A, 72B are spaced apar~ a distance 74 sufficient to accept and to act against 35 a portion of the intermediate region 121 of the fiber 12, SUBSTITUTE SH~T

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wos2/0;46n 1 5 Pcr/uss that is, the region of the fiber intermediate the pedestal 38 and the block 18. The spacin~ 74 is such that the arms 72A, 72B do not contactthe fiber, other than when imparting a switching force thereto. A more precise definition of the spacing 74 bstween the arms 72A, 72B as well as a discussion of the the distance of travel of the switching yoke 62 is ~iven hereinafter.

The motion of the switching yoke 62 is limited by a 1 û suitable abutm~nt arran~sment, also to be described, diagrammatically illustrated in Fi~ure 1 B by the reference character 76. As will be discussed the abutment arrangem~nt 76 nceds to be only coarsely aligned inasmuch as it is not responsible for precise alignment of 15 the optical fiber. As noted, precise alignment of the fiber is accomplished by the V-grooves.

Wi$h reference to Figures 1A, 1B and 1F, the switching action of the switch 10 of the present invention 20 may be more fully understood. With the first portion 12F
of the fiber 12 disposed in the first groove 20, the switching rnember 62 is displaced by the actuator 64 in an initial direction 66A. The arm 72A is thus brought into engagement with the portion of the intermediate region 25 121 of the fiber 12 Iying close to the block 18. The switching force is thus transferred by the arm 72A to the fiber 1 2.

As may be better appreciate~ from Figure 1F the 30 camming reaction betwesn the sidewall 20W2 of the groove 20 and the first portion 12F of the fiber 12 causes the same to be lifted out of the first groove 20. The lifting motion is indicated by the character 78 and occurs against the action of the biasing force 56. Continued 35 motion of the switching membsr 62 in the direction 66A
SU8S'r1TllT SH~ET

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~V092/0~460 1 6 PCT/US91/0674'J ~1 causes the fiber 12 to transverse th~ median 18M (if provided) and brings the first portion 12F of the fiber 12 into the mouth of the other groove 22. The biasing force acting in the direction 58 urges the portion 12F of the 5 fiber 12 toward ttle bottom 22B of the other groove 22.
This motion is indicated by the character 80.

As may be appreciated ~rom the fore~oing the end ~?E of the fiber 12 thereby travels along a generally 10 semicircular path from its position of repose in the first groove 20 (Figure 1A) to its position of repose in the second groove 22 (Figure ~B). The ratcheting motion caused by the re-seatin~ of the blased fiber 12 into the bottom of the adjacent groove as the fiber 12 is traversed 15 across the block 18 provides a detent action that positively places the fiber into a succeeding groove. The alignment of the fiber 12 when in either the first or the second (and any subsequent) positions is, as noted, imparted by the sidewalls acting against the fiber 12. Of 20 course, the motion of the switching member 62 in the reverse direction 66B reverses the switching of the fiber 12 from the groove 22 to the groove 20 in an analagous manner. In each case the abutment arrangement 76 limits the range of motion of the switching member 62.
It is apparent from the foregoing that, in accordance with this invention, the switching force is transmitted by the switching member 62 directly to the fiber 12. This circumstance is to be distinguished from the mechanical 30 switch arrangements of the prior art in which the switching force is applied to the member on which the fiber is attached. Since only the mass of the actuator and the relatively less massive fiber is being displaced, the switching action in accordance with the present invention SU8~;TITVTE SHEET

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W092/0~460 ` .1 7 PCl/US91/06749 may be effected with relatively high switching spe~d, on the order of about two milliseconds.

To facilltate the motions of th~ discussed in Fi~ure 5 1F the free length of the fiber, the angle 42 of the ramp surface 40S, and the offsst distance 50 must be sized to provide sufficient force to overcome friction between the fused silica optical fiber and the material of the block 18 without breaking or cracking the optical fiber under 10 bending stress. In the preferrsd embodiment it has been found that if the free length is about 1.4 centimeters, the offset distance 50 should be about 0.0~6 centimeters above the V-groove when the angle 42 of the ramp is about ten ~10) degrees.

It should be rcadily appreciated from the foregoing that more than two grooves may be disposed in the block 18 and that the fiber 12 may be switched to any selected one of the grooves depending upon the magnitude of the 20 displacement of the switching member 62. Moreover, it should also be understood that the principles of the prssent invention may be extended to switch arrangements having more than one movable fiber therein. Accordingly, attention is now invited to the switch arrangements 25 -shown in Figures 2 and 3.

In th~ embodiment of Figures 2A and 2E~ the block 18 has three V-shaped grooves 20, 22, and 24 provided therein. Tha axes of the grooves 20, 22 and 22 aro each 30 spaced apart a distance 32 that is on the order of the diameter D of the movable fibers 12, 12'. Two stationary optical fibsrs F1, F2 are again fixsd so as to remain in place in two of the V-grooves 20, 22. Two movable optical fibers 12, 12' are mounted on the ramp surface 35 40S of the support pedestal 38 (not shown in Figure 2B) in SUBSTITUTE SHEET

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respactive grooves 44, 44' thereon. The fibers 12, 12' are thus each bent and, in the manner discuss~d in connection with Figure 1, a biasing force 56, 56' is thereby ~enerated ur~ing the first portion 12F, 12F of each of the fibers 12, 5 12' into the respective first V-grooves 20, 22.

The end faces 12E, 12E' of the fibers 12, 12' lie aligned with each other and are also positioned in confrontational relationship with the cleaved ends of the 10 fixed fibers F1, F2.

To switch the fibers 12, 12', the actuator 64 is asserted, and the arm 72A of the switching member 62 engages the fiber 12. Since the grooves are spaced apart a 1~ distance substantially equal to the diameter D of the movable fibers 12, 12', as the fiber 12 begins a semicircular movement (Figure 1F, Figure 4) similar to that discussed above the first portion 12F of the first fiber 12 abuts against the second fiber 12' tsee, Figure 2 0 4A, 4B). This abutting action transmits the switching force to the second fiber 12' and causes the same to begins its semicircular motion. In this manner each fiber 12, 12' is moved into an adjacent groove. The displacement of the switching member 62 is again limited 25 by the abutment arrangement 76 (Figure 2B). Again it is noted that the abutment arrangement 76 needs to be only coarsely aligned inasmuch as precise alignment of the resp~ctive movable and fixed fibers is accomplished by the V-grooves.
Figures 3A and 3B illustrate a yet further modification to the embodiment of Figures 1A and 1B. In the arrangemont of FiglJre 3A and 3B, the block 18 has four grooves 20, 22, 24, and 26. An additional crossover fiber 3~ 90 is disposed in a crossover switch configuration. A
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.. . . . ~ ~ , , ~9~6 W092t1)5460 ~ 9 PCl/l~'S91/0674 crossover switch configuration is useful to bypass an inoperative node in a network. One end 90E1 of the fi~er 90 is secured into the groove 26, as by mounting the same to the block 30, such that the cleaved end face 90E1 5 thereof is in alignment with the snd faces of the other stationary fibers Ft, F2. The cleaved end face 90E1 may have an anti-reflection coating thereon.

The fiber 90 is looped and inclines over the ramp 10 surface 40S, thereby imparting a bend thereto and generating a biasing force imposed on the end 90E2 thereof. A groove 44~ may b~ provided on the ramp surface 40S to rsceive the fiber 90. The portion nf the fiber 90 near to the end 90E2 thereof, the fiber 12, and the fiber 15 12' move as a group from groove to groove, in a manner directiy analagous to that plural movable fiber embodiment already discussed in connection with Figure 2.
The disposition of the group of fibers when moved to a switched state is illustrated in Figure 3B.
With reference now to Figures 4A through 4C, shown are diagrammatic illustrations of the considerations attendent upon the spacing 74 between the arms 72A, 72B
of the yoke 62 and the distance of travel thereof.
25 Consider two movable fibers 12, 12', each having a diameter D, arranged in a two fiber switching arrangement (Figures 2A and 2B). The distance 32 (Figure 1C) between the axes of adjacent grooves is the distance D + d, where d is a smali offset distance between the fibars 12, 12'.
Tln practice the fiber 12 must be pushed past the top of the adjacent groove by an amount E so that it will slide down the incline of the sidewall of the adjacent groove against ~riction. Adding all the length segments, it SUBSTITVTE S~

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WO 92/0~460 2 0 PCltUS91/Ofi74~ ~J

is clear that the minimum practical spacing 74 of the yoke 62 is given by the relationship:

Spacing 74 = 2.5 D + dl2 - E + 2e.
The character "e~ represents an additional increment since it is desired that the arms 72A, 72B not touch the fiber after the switching action is complete. However, it is aooarent that if precise control of the yoke motion can be 10 attained, the absolute minimum spacing for the gap 74 is given by the relationship:

Absolute Minimum Spacing 74 = 2D ~ d + 2e.

15 It is readily apparrent that these teachin~s as to the minimum spacing dsitance 74 may be extended to switches employing more than two fibers.

The displacement distance of the yoke is indicated 20 in Figure 4. The starting and ending positions of the yoke are selected for reliable switchin~ operation.

From the foregoing it is seen that Figure 1 illustrates the manner in which a switch 10 in accordance 25 herewith may be implemented in an on-off configuration or in a 1 x2 configuration. Similarly the implementation of the switch of the presen~ invention in a 2x2 configuration may be readily understood from Figure 2. Figure 3, as noted, illustrates a crossover bypass switch 3 0 configuration. Extensions to other switch configurations should be readily apparent to those skilled in the art.

With reference now to Fi~ures 5A, 5B and 5C, shown are perspective, plan and side sectional views of a SUBSTITIITE ~HE~T

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WO 92/0~460 ~ 1 3 ~ PCT/US91/0674 practical implementation of a switch in accordance with the invention.

The above-discussed elements of the switch 10 ars 5 molded integrally within a housing ~enerally indicated by the character 11 0 from a po!yester engineering thermoplastic resin material such as that manufactured and sold by E. I. Du Pont de Nemours and sold under the trademark "Rynite~. The housin~ 1tO has an upstanding 10 sidewall 112 that surrounds and encloses the base 14.
The top of the sidewall 112 has a ~roove 114 that en~ages a bead provided in the undersurface of a cover (not shown).
The cover 16 (not shown) is configured to close all open areas of the switch housing 110 shown in Fi~ure 5A, and 15 thereby protects the interior of the switch. Tha cover is glued in place, using any suitable adhesive, such as the adhesive sold by Loctite Corporation, sold as product number 404. The blocks 18 and 30, the pedestal 38 and the other of the elements above described are integrally 20 formed with the base 14.

The sidewall 112 is interrupted at opposed ends thereof by a first and a second fiber support shelf 116, 118, respectively. Each shelf is grooved, as at 116G, 25 118G, and respectively defines a support plafform whereby the movable fibers 12, 12' and the fixed fibers F1, F2 may enter the switch housing 110. The fibers are glued to the shelves 116, 118 (e. g., using the last-mentioned adhesive~ and a strain relief heat shrink tubing 30 used thereover.

Since the movable fibers 12, 12' enter the housing 110 with their jackets in place a transition pedestal 120 is disposed adjacent to the padestal 38. The transition 35 ped6stal 120 is grooved, as at 122G, with the grooves ~J~35~1~UT~ SH~

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~VO9~/0~460 `~ 314~6 22 PCI/US91/0674 bending toward th~ inl~ts of the ~rooves 44 on ths ramp surface 40S. The purpose of the transition pedestal 120 is to provide a space within the body of the switch 10 wherein the stripped fibers 12, 12' may be arranged prior 5 to their introduction onto the ramp surface 40S. Since the fixed fibers F1, F2 also en~er the housin~ with their jackets in place, a transition pedestal 122 adjacent to the support plate 118 serves a similar function ~or these fibers .

A gap 124 is defined between the block 30 and the block 18. This gap 124 prevents epoxy adhesive from flooding the grooved surface of the block 18.

1~ A pocket 130 is formed on the interior of the housing 110. The actuator 64 (Figures 5B, 5C) is received in the pocket 130. The actuator 64 is preferably implemented using a solonoid actuator such as that manu~actured by Aromat Corporation, New Providence, 20 New Jersey and sold as model TN2E-5V. Power is applied to the actuator 64 via leads 64L extending through openings formed in the base 14 (Figure 5C). With particular reference to Fi~ures 5B and 5C, the actuator 64 includes a bar 132 that is pivotally mounted on a r~d 134.
25 Fnergization of the coils of the actuator causes mction of the bar 132 in the opposed directions 134A, 134B.

Attached to the bar 132 is a generally L-shaped bracket 136. The long side 136L of the bracket 136 is 30 attached to the bar 132 by any suitable means of attachment. The short leg 136S of the bracket 136 has a cutout that serves to define the yoke shaped switching member 62 illustrated in the other drawing Figures. The opposed reciprocating motions 134A, 134B of the bar 132, 35 when transmitted to the bracket 136, impart the generally - SU8STITVTE S~E~T

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~9~6 W O 92/0~460 2 3 P ~ /US91/0674') transverse switching motions 66A, 66B of the switching member 62.

In the preferred instance the abutment arran~ement 76 limiting the motion of the switching member 62 is dcfined by a pair of locating screws 140A, 140B. The screws 140A, 140B are threaded through the sidewall 112 of the housing 110, and act against the surface of the long arm 136L of the bracket 136. It should be understood that 10 the adjustable screws 14ûA, 140B are provided to accommodate tolerances introduced during the manufacture of the switch. With tighter manufacturing control it may be possible to use fixed surfaces on theinterior ofthe housing as the abutments sur~aces.

Those skilled in the art, having the benefit of the teachings of the present invention as hereinabove set forth may effect numerous modifications thereto. It should be understood that such modifications are to be 2 0 construed to lie within the contemplation of the present invention, as defined by the appended claims.

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Claims (16)

WHAT IS CLAIMED IS:

1. An optical fiber switch comprising:

a block having a first and a second groove, each groove having a bottom therein;

an inclined ramp disposed a predetermined distance from the block;

an optical fiber having an end face, a first portion of the fiber adjacent to the end face being disposed within a groove in the block, a second portion of the fiber being disposed on the inclined ramp such that the fiber undergoes a bending intermediate the block and the ramp, the bending of the fiber imparting a biasing force thereto, the biasing force acting on the optical fiber in a direction such that the first portion of the fiber is urged toward the bottom of the groove in which it is disposed;
a switching member; and means for displacing the switching member in a direction generally transverse to the biasing direction thereby to move the first portion of the fiber out of the one groove in which it is disposed and into the other groove, the biasing force acting upon the first portion of the fiber to urge that portion of the fiber toward the bottom of the other groove.

2. The optical fiber switch of claim 1 wherein the inclined ramp is disposed a predetermined distance L from the grooved member.

the ramp is inclined at a predetermined angle B, and the point whereat the fiber last contacts the inclined ramp lies a predetermined distance H above the bottom of the groove, the first portion of the fiber thereby defining a predetermined positive angle A with respect to the bottom of the groove.

3. The optical fiber switch of claim 2 wherein the magnitude of the angle A is related to the angle B, the distance H and the distance L in accordance with the relationship:
A = B - 1.5 ( B - H/L).

4. The optical fiber switch of claim 1 wherein each groove has an axis therethrough, the grooves being disposed in side-by-side relationship with the axes thereof being substantially parallel.

5. The optical fiber switch of claim 4 wherein the fiber has a predetermined diameter, and wherein the axes of the grooves are spaced by a distance at least equal to the diameter of the fiber.

6. The optical fiber switch of claim 1 wherein the fiber has a predetermined diameter, and wherein the grooves have a depth dimension equal to at least one-half the the diameter of the fiber.

7. The optical fiber switch of claim 1 further comprising a fixed optical fiber disposed in one of the grooves.

8. The optical fiber switch of claim 11 further comprising a second fixed optical fiber disposed in the other of the grooves.

9 . An optical fiber switch comprising:

a block having a first, a second groove and a third groove, each groove having a bottom therein;

a first and a second output optical fiber, each output fiber having a face thereon and an axis therethrough, each output optical fiber being disposed in one of the grooves;

an inclined ramp disposed a predetermined distance from the block;

a first and a second input optical fiber, each input optical fiber having an end face, a first portion adjacent to the end face being disposed within a groove in the block and a second portion of the fiber being disposed on the inclined ramp such that each fiber undergoes a bending intermediate the block and the ramp, the bending of each fiber imparting a biasing force thereto, the biasing force acting on each input optical fiber in a direction such that the first portion of each input optical fiber is urged toward the bottom of the groove in which it is disposed;
a switching member; and means for displacing the switching member in a direction generally transverse to the biasing direction thereby to move the first portion of the first input optical fiber out of the one groove in which it is disposed and into abutting contact with the second input optical fiber, thereby to move the first portion of the second input optical fiber out of the groove in which it is disposed, the biasing force acting upon the first portion of each input optical fiber to urge that portion of each input optical fiber toward the bottom of another groove.

10. The optical fiber switch of claim 9 wherein the inclined ramp is disposed a predetermined distance L from the grooved member, the ramp is inclined at a predetermined angle B, and the point whereat each fiber last contacts the inclined ramp lies a predetermined distance H above the bottom of the grooves, the first portion of each fiber thereby defining a predetermined positive angle A with respect to the bottom of the groove.

11. The optical fiber switch of claim 10 wherein the magnitude of the angle A is related to the angle B, the distance H and the distance L in accordance with the relationship:
A = B - 1.5 ( B - H/L).

12. The optical fiber switch of claim 9 wherein each groove has an axis therethrough, the grooves being disposed in side-by-side relationship with the axes thereof being substantially parallel.

13. The optical fiber switch of claim 12 wherein the fiber has a predetermined diameter, and wherein the axes of the grooves are spaced by a distance at least equal to the diameter of the fiber.

14. The optical fiber switch of claim 9 wherein the fiber has a predetermined diameter, and wherein the grooves have a depth dimension equal to at least one-half the the diameter of the fiber.

15. An optical fiber switch comprising:

a block having a first, a second groove, a third groove and a fourth groove, each groove having a bottom therein;

a crossover fiber having a first end and a second end thereon, the first end of the crossover fiber being disposed in the one of the grooves, a first and a second output optical fiber, each output fiber having a face thereon and an axis therethrough, each output optical fiber being disposed in adjacent ones of the grooves;

an inclined ramp disposed a predetermined distance from the block;

a first and a second input optical fiber, each input optical fiber having an end face, a first portion adjacent to the end face being disposed within a groove in the block and a second portion of the fiber being disposed on the inclined ramp such that each fiber undergoes a bending intermediate the block and the ramp, the bending of each fiber imparting a biasing force thereto, the second end of the crossover fiber being disposed in a groove in the block different from the groove in which the first end of the crossover fiber is disposed, a portion of the crossover fiber also being disposed on the inclined ramp such that each fiber undergoes a bending intermediate the block and the ramp, the bending of each fiber imparting a biasing force thereto, the biasing force acting on each input optical fiber and on the second end of the crossover fiber in a direction such that the first portion of each input optical fiber and the second end of the crossover fiber is urged toward the bottom of the groove in which it is disposed;
a switching member; and means for displacing the switching member in a direction generally transverse to the biasing direction thereby moving the second end of the crossover fiber out of the one groove in which it is disposed and into abutting contact with the first input optical fiber and moving the first portion of the first input optical fiber out of the one groove in which it is disposed and into abutting contact with the second input optical fiber thereby to move the first portion of the second input optical fiber out of the groove in which it is disposed, the biasing force acting upon the second end of the crossover fiber and on the first portion of each input optical fiber to urge that portion of each input optical fiber and the second end of the crossover fiber toward the bottom of another groove.

16. The optical fiber switch of claim 15 wherein the inclined ramp is disposed a predetermined distance L from the grooved member, the ramp is inclined at a predetermined angle B, and the point whereat each fiber last contacts the