Optical fiber switch

Abstract: An optical fiber switch has a substrate (12) with a straight groove into which the free ends of two optical fibers are pushed into abutting relation to permit signals incoming on one of the fibers to be transmitted to the other. Preferably, the switch (10) is a 2 X 2 fiber array. In one 2 X 2 switch (22,26), a substrate has two mutually perpendicular surfaces, each formed with a pair of grooves, and all four optical fibers are simultaneously pushed into one set of grooves to connect the fibers in one way, or pushed into the other set of grooves to switch the alignment. In a different 2 x 2 switch (40), a substrate has a central, longitudinal passageway that is square in cross section, and the grooves are provided by the four corners of the passageway.

Description: Background of the Invention Field of the Invention The invention concerns devices for mechanically switching optical signal paths between optical fibers and is particularly concerned with a 2 X 2 switching array. Description of the Related Art Numerous devices have been proposed for switching an incoming optical signal path to different outgoing optical fibers. Some such switches physically move the optical fibers so that their ends can be in abutting relationship with different optical fibers as in U.S. Pats. 4,337,995 (Tanaka et al.); No. 4,189,206 (Terai et al.); No. 4,223,978 (Kummer et al.); and No. 4,407,562 (Young). The switch of U.S. Pat. No. 4,568,143 (Yamada et al.) has a stationary block holding two input optical fibers and a movable block holding four output fibers to permit contact between the ends of various of the input and output fibers. The switch of U.S. Pat. No. 4,441,785 (Petrozello) has a rotary drum containing short lengths of optical fibers by which incoming signals on one set of optical fibers can be channeled to different outgoing optical fibers. Some switches use a movable prism as in U.S. Pat. No. 4,790,621 (Calaby) and or combination of prisms as in U.S. Pat. No. 4,303,303 (Aoyama). GB-A-2200764 discloses an optical fiber switch in which three or four fibers are equally spaced around a stand-by fibre in a channel within a substrate. The width of the walls of the passageway is substantially wider than two diameters of the optical fibers. If any of the fixed fibers fails, the associated movable fiber is switched by pistons into the gap between the other three so that it becomes optically connected with the stand by fibre. Each of the above-cited switches and every other prior optical fiber switch known to the inventor is or would be expensive to manufacture and typically requires a large number of precision parts. Summary of the Invention According to this invention there is provided a 2 x 2 optical fiber switch as claimed in claim 1 or 7 herein. In one 2 X 2 switching array of the invention, a substrate is formed to have two mutually perpendicular surfaces, each formed with a pair of straight, parallel precision grooves. First and third optical fibers are mounted with their free ends normally in parallel juxtaposition to different grooves of each pair, and the second and fourth optical fibers are mounted with their free ends projecting parallel to the free ends of the first and third optical fibers and in the opposite direction, with all four free ends terminating substantially in a plane that is orthogonal to the grooves. The second and fourth optical fibers normally are out of alignment with the first and third fibers but likewise extend in parallel juxtaposition to different grooves of each pair. Typically, the jacket of each of the first and second optical fibers has been stripped back to expose their protective buffers which also have been stripped back to make said free ends bare. A proximal portion of the bare end is bonded to the substrate to leave a distal portion of the fiber projecting freely in substantially parallel juxtaposition to the groove, and the distal portion becomes seated in the groove when the pushing means is actuated. By "a bare end" is meant the portion of the optical fiber from which the buffer is stripped off, e.g., a core-cladding. When there is a non-strippable protective layer beneath the buffer, that protective layer is part of the bare end. For switching between optical fibers of different sizes, the groove of the mount of the novel connector can be formed with a step to permit the first and second optical fibers to be coaxial upon actuation of the pushing means. A 2 x 2 switch of the invention should preferably have at least two pushing means. When it has only two pushing means, one can push four optical fibers into a first pair of grooves and another can push the four into a second pair of grooves. When pushed into the first pair of grooves, the free ends of the first and third optical fibers are abutting the ends of the second and fourth fibers, respectively. When pushed into the second pair of grooves, the free ends of the first and third optical fibers abut those of the fourth and second, respectively. By equipping a 2 X 2 switching array with four pushing means, each of which simultaneously pushes two of the four fibers into one of the two pairs of grooves, any of six switching combinations can be achieved as illustrated in FIGS. 5B-G of the drawings, or the switch can be left in the off position of FIG. 5A. The pushing means can be electrically or mechanically energized and can be so controlled that all four fibers are always seated in one of the two pairs of grooves except when being switched. Brief Description of The Drawings The invention may be more easily understood in reference to the drawing, all figures of which are schematic. In the drawings: FIG. 1 is a fragmentary perspective view of a first 2 X 2 optical fiber switch of the invention; FIGS. 1A, 1B and 1C diagramatically illustrate the operation of the switch of FIG. 1; FIG. 2 is an perspective view of a second 2 X 2 optical fiber switch of the invention, partly broken away to reveal details; FIG. 2A is a cross section at line 2A---2A of FIG. 2 and, together with FIGS. 2B and 2C, diagramatically illustrates the operation of the switch of FIG. 2; FIG. 3 is an perspective view of a third 2 X 2 optical fiber switch of the invention; FIG. 4 is a fragmentary longitudinal cross section of the switch of FIG. 3; and FIGS. 5A-G diagramatically illustrate the operation of the switch of FIG. 3. Detailed Disclosure The optical fiber switch 10 of FIG. 1 has a substrate consisting of a base block 11, a meet block 12 mounted at the center of the base block, and a pair of anchor blocks 13 and 14 mounted at the extremities of the base block. Incoming signals are received through a pair of optical fibers, here called first fiber 16 and third fiber 17, and are transmitted through the switch to a pair of optical fibers, here called second fiber 18 and fourth fiber 19. The buffer 20 of each of the fibers has been stripped off, and a proximal portion of a bare end of each fiber has been bonded at 21 to one of the anchor blocks 13 and 14 such that a distal portion of each bare end of the first and third fibers 16 and 17 projects in opposition to the free ends of the second and fourth optical fibers 18 and 19. Formed in a first surface 22 of the meet block 12 are a first pair of straight, parallel precision V-grooves 23 and 24. Formed in a second surface 26 of the meet block which is perpendicular to the first surface 22 are a second pair of straight, parallel precision V-grooves 27 and 28. A plane bisecting each of the V-grooves is orthogonal to the surface at which the groove is formed. In the absence of any force, (a) the distal or free end of each of the four optical fibers projects in parallel juxtaposition to one groove of each pair of grooves as shown in FIG. 1A; (b) the free ends of first and third fibers 16 and 17 are out of alignment with the free ends of second and fourth fibers 18 and 19; and (c) the free ends of all four optical fibers terminate substantially in a plane that is orthogonal to the grooves. Mounted in the cover 30 of the switch 10 are a first pushing means 32, which pushes the free ends of the optical fibers in the vertical direction when the switch is oriented as in FIG. 1, and a second pushing means 34 which pushes the free ends horizontally. The first pushing means 32 seats the four fibers in the first pair of grooves 23 and 24 as shown in FIG. 1B, and the second pushing means 34 seats the four fibers in the second pair of grooves 27 and 28 as shown in FIG. 1C. When positioned as shown in FIG. 1B, incoming signals in first and third fibers 16 and 17 are transmitted through second and fourth fibers 18 and 19, respectively; when positioned as shown in FIG. 1C, incoming signals in first and third fibers 16 and 17 are transmitted through fourth and second fibers 19 and 18, respectively. By omitting the fourth optical fiber 19 from the switch 10, signals can be transmitted between the second optical fiber 18 and either the first or third optical fibers 16 and 17, and there is no need for two of the grooves 24 and 28. By also omitting the third optical fiber 17, the switch can be used to transmit optical signals between the first and second optical fibers 16 and 18 or to interrupt such transmission. The 2 X 2 switch 40 of FIG. 2 has an elongated base block 41 which is formed with a precision, central, longitudinal passageway 43 that is substantially square in cross section but may have filleted corners. A proximal portion of an end of each of first and third optical fibers 46 and 47 has been bonded to the walls of the passageway 43 at one extremity of the block 41 so that the distal end of each fiber projects to approximately the midpoint of the passageway. A proximal portion of an end of each of second and fourth optical fibers 48 and 49 has been similarly bonded into the passageway 43 so that its distal end projects in the opposite direction. Each wall of the passageway 43 is slightly wider than two diameters of the free end of each fiber. The projecting distal or free ends of the four fibers, when not subjected to any force, appear as illustrated in FIG. 2A and terminate substantially in a plane that is orthogonal to the corners of the passageway 43. Pivotably mounted on the block 41 are a first spring lever 52 and a second spring lever 54. The bent-back actuating end 52A and 54A, respectively, of each spring lever has a rounded profile as seen in FIGS. 2A-C. When the first spring lever 52 is depressed, its actuating end 52A pushes the four fibers downwardly and outwardly (obliquely) to the positions shown in FIG. 2B, thus seating each of the fibers in one of the two grooves provided by the two lower corners of the mutually perpendicular walls of the passageway 43. In this position, the optical fibers are precisely aligned, and incoming signals on the first and third optical fibers 46 and 47 are transmitted on the second and fourth optical fibers 48 and 49, respectively. When the second spring lever 54 is depressed, the four fibers are pushed obliquely into corners as shown in FIG. 2C, thus switching the transmission from the first and third optical fibers 46 and 47 to the fourth and second optical fibers 49 and 48, respectively. Because the second optical fiber 48 assumes the same position under the action of both levers, it could be permanently bonded into the corner into which it is pushed. The 2 X 2 switch 60 of FIG. 3 has an elongated base block 61 with a precision, central, longitudinal passageway 63 that is substantially square in cross section. Bonded to the walls of the passageway at one extremity of the block 61 are proximal portions of the ends of first and third optical fibers 66 and 67, and bonded at the opposite extremity of the block are proximal portions of the ends of second and fourth optical fibers 68 and 69. Each wall of the passageway 63 is slightly wider than two diameters of the bare fibers. The projecting distal or free ends of the four fibers, when not subjected to any force, are in the position illustrated in FIG. 5A and terminate substantially in a plane that is orthogonal to the corners of the passageway 63. Pivotably mounted on the block 61 are four spring levers 72, 73, 74 and 75, each of which acts against only two of the four optical fibers. As indicated in FIG. 4, when only the spring lever 72 is depressed, the first optical fiber 66 is pressed into a lower corner at which it is hidden by the third fiber 67 and approximately aligned with the second fiber 68 which is not subjected to any force, allowing optical signals to pass only between the first and second fibers. Depressing only one of the spring lever 73, 74 and 75 results in the approximate alignment of FIGS. 5C, 5D and 5E, respectively. When the spring levers 72 and 74 are depressed simultaneously, all four optical fibers are pushed obliquely into the lower corners as in FIG. 5F wherein both the first and second optical fibers 66 and 68 are precisely aligned in one corner and the third and fourth optical fibers 67 and 69 are precisely aligned in another corner of the passageway 63. When spring levers 73 and 75 are pressed simultaneously, the optical fibers are pushed obliquely into corners of the passageway as shown in FIG. 5G, again affording precise alignment of the optical fibers. Example The switch 40 of FIG. 2 can be made by drawing glass through an orifice and then using a laser to cut spring-lever openings. Key dimensions: block 41 2 mm square length 20 mm passageway 43 255 µm square diameter of optical fibers 125 µm spring levers 52,54 overall length 11 mm width 0.25 mm radius of end 52A 125-250 µm

Claims: A 2 x 2 optical fiber switch (10) comprising a substrate (11, 12) formed to have four straight, parallel precision grooves in two pairs (23, 24; 27, 28), the first pair formed in a first surface and the second pair formed in a second surface of the substrate, means (13, 14) for mounting on the substrate first and third optical fibers (16, 17), each having a free end that in the unactivated state projects from the mounting means in substantially parallel juxtaposition to one of said grooves of each pair, means (13, 14) for mounting on the substrate second and fourth optical fibers (18, 19), each having a free end that in the unactivated state projects from the mounting means in the opposite direction to and out of alignment with the free ends of the first and third fibers, and in substantially parallel juxtaposition to one of said grooves of each pair, the disposition of the fibre ends and the grooves being such that each of the four optical fibers is in juxtaposition with a unique two of said four grooves (23, 24; 27, 28), the free ends of all of said fibers terminating substantially in a plane that is orthogonal to the grooves, and means (32, 34) for pushing each of said free ends either into the one of the two grooves of the first pair with which it is in alignment or into one of the grooves of the second pair with which it is in alignment such that the fibers extending in opposite directions are in abutting relationship with one another. An optical fiber switch as defined in claim 1 wherein each of said free ends is a bare end and a proximal portion of each bare end is bonded (21) to the substrate to leave a distal portion free. An optical fiber switch as defined in claim 1 or 2 wherein the walls of each said groove (23,24; 27,28) are perpendicular to each other. An optical fiber switch as defined in any preceding claim wherein said pushing means (32,34) includes means for simultaneously pushing all four optical fibers into one pair of grooves and means for simultaneously pushing all four optical fibers into the other pair of grooves. An optical fiber switch as defined in any of claims 1 - 3 wherein said pushing means includes four separately actuable means, each for simultaneously pushing only two of said optical fibers into one pair of grooves. An optical fiber switch as defined in any preceding claim wherein the substrate comprises a base block (11), a pair of anchor blocks (13,14) mounted at the extremities of the base block, and a meet block (12) mounted at the center of the base block, which meet block is formed with two mutually perpendicular surfaces, and each of said pairs of grooves is formed in one of said surfaces. A 2 x 2 optical fiber switch (40) comprising a substrate (41) formed with a precision, central, longitudinal passageway (43) of substantially square cross-section, means for mounting on the substrate first and third optical fibers (46, 47), each having a free end that in the unactivated state projects in substantially parallel juxtaposition to one of a pair of diagonally opposing corners of the passageway, means for mounting on the substrate second and fourth optical fibers (48, 49), each having a free end that in the unactivated state projects from the mounting means in the opposite direction to and out of alignment with the free ends of the first and third fibers and in substantially parallel juxtaposition to one of the other pair of opposing corners of the passageway, the free ends of all of said fibers terminating substantially in a plane that is orthogonal to the passageway, the walls of the passageway being each slightly wider than twice the diameter of the free end of an optical fiber (46, 47, 48, 49), and means (52, 52A, 54, 54A) for pushing each of said free ends either into one of the corners of a first wall with which it is in alignment or into one of the corners of a second wall adjacent to said first wall with which it is in alignment, such that the fibers extending in opposite directions are in abutting relationship with one another.

Inventors: BLOMGREN JACK P, BLOMGREN, JACK P., BLOMGREN, JACK P. C/O MINNESOTA MINING AND
Applicants: MINNESOTA MINING & MFG, MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1990
Main classification: G02B26
IPC codes: G02B6, G02B26