Backbone tube array for slack management of internal fiber interconnects in robotic fiber cross-connects

Abstract

An optical switch element is disclosed, comprising a stacked arrangement of movable backbone tube assemblies designed to provide strain relief to optical fibers sliding within them. The tube assemblies facilitate fiber exit at large angles while ensuring a minimum fiber bend radius of 5 mm. Constructed from a combination of tubes and materials, the assemblies offer low fiber sliding friction, fatigue resistance under cyclic loading at large divergence angles, and reduced fiber coating wear. The supporting structure allows tube assemblies to shift in a direction normal to the stacking arrangement, ensuring substantial separation at fiber exit locations. This configuration enhances optical performance, durability, and reliability in high-strain environments.

Description

Backbone Tube Array for Slack Management of Internal Fiber Interconnects in Robotic Fiber Cross-Connects Copyright Statement

[0001] This patent document contains material subject to copyright protection. The copyright owner has no objection to the reproduction of this patent document or any related materials in the files of the United States Patent and Trademark Office, but otherwise reserves all copyrights whatsoever.CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of prior-filed provisional application No.63 / 752,828, filed on February 2, 2025, titled “Backbone Tube Array for Slack Management of Internal Fiber Interconnects in Robotic Fiber Cross-Connects,” the entire contents of which are hereby incorporated herein by reference, as though set forth herein, for all purposes.FIELD OF USE

[0003] This application relates to an optical fiber routing assembly for use in a robotic fiber cross-connect system and to slack management of internal fiber interconnects in robotic fiber cross-connects.Background

[0004] Large-scale robotic fiber optic cross-connect switches enable data center and telecom networks to be automated by replacing manual patch panels. Current fiber optic cross-connect technologies, such as crossbar switches, scale as N2, where N is the number of ports, significantly limiting their utility. A type of cross-connect for very large port counts is based on a robotic system comprised of braided fiber optic strands and the application of the mathematics of topology (Theory of Knots and Braids) to drive a pick-and-place robot such that fiber entanglement during reconfiguration is prevented. This Knots and Braids Switching (KBS) approach scales linearly as N and thereby achieves significant scalability advantages over crossbar switches.1© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patent

[0005] A fiber that loses tension and does not follow the requisite straight-line path as dictated by the KBS algorithm. For example, in a system with an array of twelve front connector columns, those fibers plugged into ports in column 1 and in column 12 experience the greatest congestion because of the relatively small angular deviation of fibers on either side of column 1 (i.e., in column 2) and column 12 (i.e., in column 11). Fiber congestion is relatively rare, but if a fiber loses tension due to excessive friction and does not retract, subsequent reconfiguration by the robot is paused until the problem is resolved to prevent subsequent fiber entanglement.

[0006] FIG. 1A is a drawing of the prior art cross-connect system implementing the KBS algorithm and linearly scaling as N, the number of ports, as disclosed by current inventors in US Patent No. 8,068,715, US Patent No. 8,463,091, US Patent No. 8,488,938, and US Patent No. 10,042,122. These modular, expandable systems are configured to minimize reconfiguration time and to operate with high reliability and high fiber-optic port density. This cross-connect system has multiple unique attributes to facilitate large-scale, arbitrary robotic reconfiguration of a multiplicity (i.e., hundreds or thousands) of internal fibers without damaging, tangling, or otherwise overstressing the fibers, and they are physically re-routed within the system. The gaps between vertical columns in the two-dimensional matrix are sized to permit the transport of a gripper mechanism attached to a robotic actuator therebetween. The robotic actuator can move the gripper parallel to the columns and parallel to the stacked array of backbone tubes. The rows of input terminals in the two-dimensional matrix are shiftable in either direction transverse to the columns by a clearance increment adequate to permit passage of the transport mechanism and a selected strand therebetween.

[0007] A multiplicity of fiber-optic strands is disposed in a spatially coherent configuration, with interconnections having potentially different path lengths between a fixed configuration of strand guides parallel to one axis at one plane and interconnected to variable positions along a second two-dimensional plane. A modular, expandable system of rotatable reels and / or a spring-loaded pulley arrangement comprising the fiber modules enables the interconnections at the plane of the two-dimensional matrix to be varied while maintaining tension and preserving more than a minimum radius of curvature on the optical fiber strands.

[0008] This fiber optic cross-connect system establishes arbitrary, low-loss optical links between a multiplicity of input connections and a multiplicity of output connections, joined by continuous lengths of low-loss, flexible optical waveguides defining vectors2© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patenttherebetween. Robotic manipulation of an affected optical fiber surrounded by a multiplicity of unaffected optical fibers is performed by traversing the unaffected optical fibers. The robotic manipulation trajectory passes individually through one or more of the sub-braids, defining a column by programmed splitting of the sub-braid into two partial sub-braids. The splitting is adequate to enable non-interfering passage of the affected fiber through the split in the sub-braid. The two partial sub-braids are then merged after the passage by affected fiber is complete by reshuffling the rows as determined by the KBS algorithm for the next column in the sequence. Additional horizontal exchange rows are provided to allow for the transfer of a connector and its fiber being reconfigured under the columns of other connectors and their fibers.

[0009] In these prior art implementations, the fiber optic bundles pass through a linear assembly of non-shiftable backbone tubes, as illustrated in FIG. 2, at a mid-span portion along the strands (located internal to the system and identified as the one-dimensional backbone). Each of these tubes is fixed at a central location by a rigid support structure. In FIG. 2, the tubes are illustrated in their free configuration before insertion of optical fibers. When the internal optical fibers pass through and exit at different angles, the backbone tubes are free to independently deflect with an angle of about + / - 45 degrees in the horizontal and + / - 70 degrees in the vertical direction, such that the backbone tubes bend to follow the fiber tension vector while providing strain relief so that the optical fibers do not bend excessively sharp at the exit location of the rigid support structure. The front ends of the tubes fan out under the influence of the tensioned fiber in potentially arbitrary directions dictated by the potentially arbitrary directions (FIG. 3) to the unique endpoint locations at the front two-dimensional array of connectors.

[0010] Fully automated patch-panel systems (FIG. 1A) implementing the KBS algorithm use a three-axis pick-and-place actuator with a single gripper at one end of a telescopic robotic arm that moves along a gantry system. The robotic arm is narrow in width and shallow in depth to allow it to descend into the fiber-optic interconnect volume without mechanical interference or contact with the surrounding optical fibers. The system typically includes fibers in the lower half of the enclosure and a robot in the upper half (FIG. IB). During a fiber reconfiguration process, the gripper travels above topmost row of fibers with sufficient clearance above the interconnect volume, then crosses and travels down column(s) in a column-by-column, serial fashion. To enable the robot to move horizontally in this position, the top half of the system does not contain front-panel receptacles or internal fiber3© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentstrands that would otherwise limit the robot's ability to move horizontally. This provides a region for the robotic arm to retract and move to any column within the array of front panel receptacles.

[0011] Internal fiber strands move dynamically when transported by the robot and must be under slight tension to avoid slack and entanglement. Tensioned fibers emanate from an array of intermediate backbone tubes that are stacked vertically. This array of bendable tubes is clamped / bonded at one end to maintain a fixed endpoint for each tube. With fibers in an arbitrary or random state, this one-dimensional backbone with fixed tubes (FIG. 2) will be bent in arbitrary and changing directions based on the dynamic direction of the fiber tensile force. Under certain conditions dependent on the direction of each fiber tension vector, the backbone tube may experience bending and buckling, and the fiber passing therein may experience drag upon contact with other fibers or the outside of other backbone tubes (FIG. 3). This is called “fiber congestion” or “backbone tube congestion,” in which the vertical displacement of fibers and tubes at the backbone is forced into horizontal displacement from the ideal one-dimensional backbone due to the spatial congestion of tubes and fibers exiting the backbone location.

[0012] For optical fiber(s) with an outer diameter (outer diameter) of 0.016 inch (0.406 mm), these tubes are typically extruded, semi-crystalline or amorphous PEEK (Polyether Ether Ketone) or PEEK-PTFE blended tubes (PEEK with PTFE, Polytetrafluoroethylene) with an outer diameter of 0.036 inch (0.914 mm), inner diameter (inner diameter) of 0.022 inch (0.559 mm), and length of 3 inches (76.2 mm). The tubes are mounted such that about 1 inch (25.4 mm) of free length is provided to give a sufficiently gradual bend under the influence of any potential off-axis fiber tension. For high-utilization cross-connect systems with reconfigurations greater than about 1,000 flexural cycles per fiber interconnect, the cyclic stresses on the PEEK backbone tubes can potentially exceed their fatigue strength, leading to buckling, pinching of the internal fiber, cracking, and ultimately tube failure. For this reason, it is important to design a new backbone tube design in which a fiber or fiber bundle can dynamically and cyclically pass through the tubes while experiencing low static and dynamic friction, low buckling, and low fatigue to allow greater than 100,000 flexural cycles per fiber interconnect.SUMMARY

[0013] The present invention is specified in the claims as well as in the description.4© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patent

[0014] These features, along with additional details of the invention, are described further in the examples herein, which are intended further to illustrate the invention but are not intended to limit its scope in any way.

[0015] In some aspects, a backbone routing architecture is described in which a plurality of backbone tube assemblies are arranged in a vertically stacked array and supported by a structure that constrains relative vertical position while permitting independent lateral translation of individual backbone tube assemblies. Each backbone tube assembly is free to laterally displace in response to tensile forces applied by an optical fiber passing through it, so that adjacent backbone tube assemblies passively separate at fiber exit regions as the fiber routing geometry changes.

[0016] In some cases, each backbone tube assembly comprises a rigid tubular segment configured to provide structural stiffness and at least one flexible strain-relief segment coupled to the rigid tubular segment to control fiber bending during reorientation. Optional low-friction liners may be provided within the rigid tubular segment to facilitate the sliding of optical fibers or optical fiber assemblies. Support structures for maintaining vertical separation while permitting lateral translation may include stacked divider plates, wire-based comb structures, or other mechanical arrangements providing equivalent constraint behavior.

[0017] The disclosed backbone routing architecture enables passive accommodation of changing fiber exit angles under nominal operating tension while maintaining controlled bend radius and reducing mechanical interference between adjacent backbone tube assemblies.

[0018] In one general aspect, a backbone tube assembly may include a rigid tubular segment extending along a longitudinal axis. The backbone tube assembly may also include a low-friction liner disposed within the rigid tubular segment along substantially the full length thereof. The backbone tube may furthermore include first and second flexible strain-relief segments coupled to opposite ends of the rigid tubular segment. The backbone tube may, in addition, include a configuration in which the backbone tube assembly is configured to receive at least one optical fiber therethrough, to slide laterally when supported in a vertically stacked backbone structure, and to reorient under tensile forces applied by the optical fiber while limiting a minimum bend radius of the optical fiber to not less than 5 mm.

[0019] Implementations may include one or more of the following features, alone or in combination(s):5© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patent• The backbone tube assembly, where the low-friction liner may include a PTFE sleeve. The backbone tube assembly, where the PTFE sleeve is surface-etched.• The backbone tube assembly, where the PTFE sleeve is bonded to the rigid tubular segment or to an adjacent strain-relief segment using an adhesive.• The backbone tube assembly, where the adhesive may include a UV-curable adhesive, cyanoacrylate adhesive, acrylate adhesive, or epoxy adhesive.• The backbone tube assembly, where the flexible strain-relief segment may include a polymer tube bonded to an end of the rigid tubular segment.• The backbone tube assembly, where the polymer tube may include a Pebax material. • The backbone tube assembly, where the backbone tube assembly is dimensioned to receive an optical fiber assembly having one or two optical fibers, and where: the rigid tubular segment has an inner diameter of approximately 0.58 mm and an outer diameter of approximately 0.71 mm; the low-friction liner has an inner diameter of approximately 0.51 mm and an outer diameter of approximately 0.56 mm; and each flexible strain-relief segment has an inner diameter of approximately 0.74 mm and an outer diameter of approximately 1.02 mm.• The backbone tube assembly, where the backbone tube assembly is dimensioned to receive a bundled optical fiber assembly having eight or more optical fibers, and where: the rigid tubular segment has an inner diameter of approximately 0.74 mm and an outer diameter of approximately 0.83 mm; the low-friction liner has an inner diameter of approximately 0.66 mm and an outer diameter of approximately 0.71 mm; and each flexible strain-relief segment has an inner diameter of approximately 0.84 mm and an outer diameter of approximately 1.09 mm.

[0020] In another general aspect, an optical fiber routing assembly may include a plurality of backbone tube assemblies arranged in a vertically stacked array. The optical fiber routing assembly may also include each backbone tube assembly defining an internal passage configured to receive and guide at least one optical fiber extending between a rear slackmanagement region and a front connector region. The optical fiber routing assembly may furthermore include a support structure that constrains the relative vertical position of the backbone tube assemblies while permitting each backbone tube assembly to translate laterally in a direction normal to the stacking direction. The optical fiber routing assembly may, in addition, include each backbone tube assembly being free to laterally displace independently 6© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentof adjacent backbone tube assemblies in response to tension vectors applied by the optical fiber passing therethrough, such that adjacent backbone tube assemblies separate from one another at locations proximate to fiber exit regions. The optical fiber routing assembly may moreover include where each backbone tube assembly includes a rigid tubular segment and at least one flexible strain-relief segment configured to limit bending of the optical fiber as the backbone tube assembly reorients under tension.

[0021] Implementations may include one or more of the following features, alone or in combination(s):• The optical fiber routing assembly, where lateral displacement of each backbone tube assembly occurs passively under fiber tension without active actuation.• The optical fiber routing assembly, where the backbone tube assemblies are configured to accommodate fiber exit divergence angles of at least 45 degrees in a horizontal plane. • The optical fiber routing assembly, where adjacent backbone tube assemblies are separated laterally by at least 2 mm at fiber exit regions under nominal operating tension.• The optical fiber routing assembly, where the flexible strain-relief segment limits a minimum bend radius of the optical fiber to not less than 5 mm during reorientation. • The optical fiber routing assembly, where each backbone tube assembly may include a thin-walled metal tube forming the rigid tubular segment.• The optical fiber routing assembly, where the thin-walled metal tube is stainless steel, has a wall thickness not exceeding 0.075 mm.• The optical fiber routing assembly, where each backbone tube assembly includes a low- friction liner disposed along at least a portion of the internal passage.• The optical fiber routing assembly, where the low-friction liner may include a PTFE sleeve extending substantially the full length of the rigid tubular segment.• The optical fiber routing assembly, where the PTFE sleeve is surface-etched to modify surface chemistry before assembly within the rigid tubular segment.• The optical fiber routing assembly, where the surface etching may include chemical or plasma etching of the PTFE sleeve.• The optical fiber routing assembly, where the PTFE sleeve is bonded to the rigid tubular segment or to an adjacent strain-relief segment using an adhesive.7© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patent• The optical fiber routing assembly, where the adhesive may include an a-curable adhesive, cyanoacrylate adhesive, acrylate adhesive, or epoxy adhesive.• The optical fiber routing assembly, where the flexible strain-relief segment may include a polymer tube bonded to an end of the rigid tubular segment.• The optical fiber routing assembly, in which the polymer tube may include Pebax.• The optical fiber routing assembly, where the support structure may include a plurality of rigid divider plates stacked in parallel and defining laterally open slots for receiving respective backbone tube assemblies.• The optical fiber routing assembly, where the divider plates have a thickness in a range of 0.13 mm to 0.25 mm.• The optical fiber routing assembly, where the divider plates are spaced to define a stacking pitch of approximately 1.02 mm.• The optical fiber routing assembly, where the support structure may include a comb of elongated wire elements arranged to laterally constrain and vertically separate the backbone tube assemblies while permitting lateral translation.• The optical fiber routing assembly, where the elongated wire elements may include piano wire having a diameter of approximately 0.25 mm.• The optical fiber routing assembly, where each backbone tube assembly is configured to rotate about its longitudinal axis as the optical fiber is displaced vertically.• The optical fiber routing assembly, where the optical fiber is maintained under static tension in a range of 28 g to 57 g during operation.• The optical fiber routing assembly, where the backbone tube assemblies are configured to withstand at least 10,000 reorientation cycles under nominal operating tension without mechanical failure.• The optical fiber routing assembly, where an axial sliding coefficient of friction between the optical fiber and each backbone tube assembly is less than 0.2 under nominal operating conditions.• The optical fiber routing assembly, where the backbone tube assemblies are located at an intermediate span of the optical fibers between a rear slack-management pulley system and a front two-dimensional connector array.8© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patent• The optical fiber routing assembly, where each backbone tube assembly may include: a rigid tubular segment having a first inner diameter; a low-friction liner disposed within the rigid tubular segment along substantially its entire length; and first and second flexible strain-relief segments coupled to opposite ends of the rigid tubular segment, where the rigid tubular segment, the low-friction liner, and the flexible strain-relief segments are fixed relative to one another to form an unitary backbone tube assembly configured to slide and reorient as a single body.• The optical fiber routing assembly, where the backbone tube assembly is dimensioned to receive an optical fiber assembly having one or two optical fibers, and where: the rigid tubular segment has an inner diameter of approximately 0.58 mm and an outer diameter of approximately 0.71 mm; the low-friction liner has an inner diameter of approximately 0.51 mm and an outer diameter of approximately 0.56 mm; and each flexible strain-relief segment has an inner diameter of approximately 0.74 mm and an outer diameter of approximately 1.02 mm.• The optical fiber routing assembly, where the backbone tube assembly is dimensioned to receive a bundled optical fiber assembly having eight or more optical fibers, and where: the rigid tubular segment has an inner diameter of approximately 0.74 mm and an outer diameter of approximately 0.83 mm; the low-friction liner has an inner diameter of approximately 0.66 mm and an outer diameter of approximately 0.71 mm; and each flexible strain-relief segment has an inner diameter of approximately 0.84 mm and an outer diameter of approximately 1.09 mm.

[0022] In another general aspect, a robotic optical fiber cross-connect system may include an enclosure defining an internal three-dimensional fiber routing volume. The robotic optical fiber cross-connect system may also include a plurality of optical fibers extending between a rear slack-management subsystem and a front connector array disposed in a two-dimensional arrangement. The robotic optical fiber cross-connect system may furthermore include a robotic actuator disposed within an upper region of the enclosure and configured to reposition selected optical fibers among the front connector array while traversing between adjacent optical fibers. The robotic optical fiber cross-connect system may, in addition, include a backbone assembly located at an intermediate span of the optical fibers between the rear slack-management subsystem and the front connector array, the backbone assembly having: a plurality of backbone tube assemblies arranged in a vertically stacked array, each backbone tube assembly defining an internal passage through which at least one optical fiber 9© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentpasses; and a support structure that constrains relative vertical position of the backbone tube assemblies while permitting each backbone tube assembly to translate laterally in a direction normal to the stacking direction. Each backbone tube assembly may be configured to reorient and laterally displace independently in response to tension vectors applied by the optical fiber passing therethrough, such that adjacent backbone tube assemblies passively separate from one another at fiber exit locations as optical fibers are repositioned by the robotic actuator. The robotic optical fiber cross-connect system may, in addition, include where each backbone tube assembly may include a rigid tubular segment and at least one flexible strain-relief segment coupled to the rigid tubular segment and dimensioned to limit a minimum bend radius of the optical fiber to not less than 5 mm.

[0023] In yet another general aspect, a robotic optical fiber cross-connect system may include an enclosure defining an internal fiber routing volume. The robotic optical fiber cross-connect system may also include a plurality of optical fibers extending between a rear slack-management subsystem and a front connector array. The robotic optical fiber crossconnect system may furthermore include a robotic actuator configured to transport selected optical fibers across and between other optical fibers to effect reconfiguration of connections at the front connector array. The robotic optical fiber cross-connect system may, in addition, include a backbone assembly located at an intermediate span of the optical fibers. The robotic optical fiber cross-connect system may moreover include where the backbone assembly that includes a plurality of backbone tube assemblies arranged in a vertically stacked array and supported by a structure that constrains the relative vertical position of the backbone tube assemblies while permitting each backbone tube assembly to translate laterally in a direction normal to the stacking direction. The robotic optical fiber cross-connect system may, in addition, include mechanically preventing fixation of the backbone tube assemblies in the horizontal direction. The robotic optical fiber cross-connect system may moreover include such that, during robotic reconfiguration, backbone tube assemblies associated with optical fibers experiencing differing tension vectors laterally displace and separate from one another at fiber exit regions. The robotic optical fiber cross-connect system may also include where each backbone tube assembly that includes a rigid tubular segment and at least one flexible strain-relief segment configured to limit bending of the optical fiber to a minimum bend radius of not less than 5 mm during lateral displacement.

[0024] In another general aspect, an optical fiber routing system may include a slackmanagement subsystem including a plurality of fiber storage elements configured to apply10© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentcontrolled tensile force to optical fibers. The optical fiber routing system may also include a plurality of optical fibers extending forward from the slack-management subsystem toward a connector region. The optical fiber routing system may furthermore include a backbone assembly positioned along the optical fibers between the slack-management subsystem and the connector region, the backbone assembly having a plurality of backbone tube assemblies arranged in a vertically stacked array. The optical fiber routing system may, in addition, include where each backbone tube assembly defines an internal passage through which at least one optical fiber passes and is supported by a structure that permits lateral translation of the backbone tube assembly in response to tensile forces applied by the optical fiber while maintaining vertical separation from adjacent backbone tube assemblies. The optical fiber routing system may moreover include where the slack-management subsystem maintains the optical fibers under static tension in a range of 28 g to 57 g. The system may also include where variations in fiber length introduced by robotic reconfiguration at the connector region cause corresponding passive lateral displacement of the backbone tube assemblies, thereby maintaining straight-line fiber paths forward of the backbone assembly and preventing loss of fiber tension.

[0025] In another general aspect, an optical fiber routing assembly may include a plurality of backbone tube assemblies in a vertically stacked array, each defining a passage for at least one optical fiber support structure that constrains vertical position while permitting lateral translation, where each backbone tube assembly is independently laterally displaceable in response to tension applied by an optical fiber passing therethrough.

[0026] In another general aspect, a backbone tube assembly may include a tubular segment defining a longitudinal passage configured to laterally translate when supported in a vertically stacked arrangement that reorients under tensile forces applied by an optical fiber.

[0027] In another general aspect, an optical fiber routing assembly may include a plurality of backbone tube assemblies arranged in a vertically stacked array. The optical fiber routing assembly may also include each backbone tube assembly defining an internal passage for at least one optical fiber. The optical fiber routing assembly may furthermore include a support structure that constrains the relative vertical position of the backbone tube assemblies while permitting each backbone tube assembly to translate laterally. The optical fiber routing assembly may, in addition, include where each backbone tube assembly laterally displaces independently in response to tension applied by the optical fiber passing therethrough.11© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patent

[0028] In another general aspect, an optical fiber routing assembly may include a vertically stacked array of backbone tube assemblies. The optical fiber routing assembly may also include where each backbone tube assembly passively translates laterally without active actuation in response to tension vectors applied by optical fibers.

[0029] In another general aspect, the method may include arranging a plurality of backbone tube assemblies in a vertically stacked array. The method may also include supporting the backbone tube assemblies such that vertical positions are constrained. The method may further include permitting lateral translation and allowing the backbone tube assemblies to independently displace laterally in response to tension applied by optical fibers passing therethrough. The method may, in addition, include maintaining straight-line fiber paths and preventing tension loss.

[0030] In another general aspect, an optical fiber routing system may include backbone tube assemblies that are laterally displaced in response to varying fiber tension vectors while maintaining vertical separation between adjacent backbone tube assemblies.

[0031] In one general aspect, an optical switch element may include a stacked arrangement of movable backbone tube assemblies providing strain relief to the optical fibers sliding therein and exiting at large angles, where the tube assemblies are selected of a combination of tubes and materials to provide low fiber sliding friction, fatigue resistance during cyclic loading at large fiber divergence angles, minimum optical fiber bend radius of 5 mm, and low wear of fiber coating, and wherein the structure supporting tube assemblies allows tubes to shift in a direction normal to stacking direction so that tube assemblies are substantially separated at locations in which optical fibers exit the tube assemblies

[0032] Implementations may include one or more of the following features, alone or in combination(s):• The optical switch element, where the backbone tube assembly may include a thinwalled, stiff stainless-steel tube with Pebax strain relief tube tips at ends thereof and lined along its entirety by an etched PTFE sleeve, where the stainless-steel tube, Pebax 7233 strain relief tips, and PTFE sleeve are permanently attached to one another with UV-cured adhesive.• The optical switch element, where the tube dimensions are selected to allow a 0.016- inch outer diameter optical fiber assembly comprised of one or two optical fibers to slide therein.12© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patent• The optical switch element, where the stainless-steel tube dimensions are about 1 inch long, 0.023-inch inner diameter, 0.028-inch outer diameter, Pebax strain relief is 8 mm long, 0.029-inch inner diameter, 0.040-inch outer diameter, and the etched PTFE sleeve is 0.020-inch inner diameter, 0.022-inch outer diameter.• The optical switch element, where the tube dimensions are selected to allow a 0.024- inch outer diameter optical fiber assembly, which may include 8 or more fibers to slide therein.• The optical switch element, where the stainless-steel tube dimensions are 0.026-inch inner diameter, 0.028-inch outer diameter, PTFE sleeve, 0.029-inch inner diameter, 0.032-inch outer diameter, SS tube, and 0.033-inch inner diameter, 0.043-inch outer diameter, Pebax 7233 tube.• The optical switch element, where the tubes are separated by rigid divider plates that are uniformly spaced apart in the stacked arrangement.• The optical switch element, where the rigid divider plates are 0.005 inch to 0.010- inch-thick stainless steel and stacked to produce a 0.040-inch pitch.

[0033] In another general aspect, an optical switch element is located between an array of optical fiber slack tensioning pulleys on the rear side and an array of moveable fiber connectors on the front side, where the rear and front sides spanned by contiguous optical fibers that follow straight-line paths in the volume between the front size and the optical switch element, wherein each optical fiber passes through an intermediate tube comprised of a rigid element, one or more flexible elements, and a low friction element.

[0034] Implementations may include one or more of the following features, alone or in combination(s):• The optical switch element where the flexible elements are selected to limit the bend radius experienced by the tensioned optical fiber to be greater than or equal to 5 mm.• The optical switch element, where static tension on the optical fibers is in the range of approximately 1 to 2 ounces.

[0035] In yet another general aspect, an optical switch element may include a stacked arrangement of movable backbone tube assemblies that provide strain relief to the optical fibers sliding therein and exiting at large divergence angles exceeding 45 degrees, where the tube assemblies selected of a combination of tubes and materials to provide low fiber sliding13© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentfriction with a coefficient of friction less than 0.2, fatigue resistance during cyclic loading of 10,000 or more cycles at large fiber divergence angles, minimum optical fiber bend radius of 5 mm, and low wear of fiber coating, and wherein the structure supporting tube assemblies allows tubes to shift in a direction normal to the stacking direction so that tube assemblies are substantially separated by more than 2 mm at the locations in which optical fibers exit the tube assemblies

[0036] Implementations may include one or more of the following features, alone or in combination(s):• The optical switch element where the backbone tube assembly may include a thinwalled (< 0.003 inch or 0.075 mm) thick, stiff stainless-steel tube with Pebax strain relief tube tips at the ends thereof and lined along its entirety by an etched PTFE sleeve, where the stainless-steel tube, Pebax 7233 strain relief tips, and PTFE sleeve are permanently attached to one another with UV-cured adhesive.• The optical switch element, where the tube dimensions are selected to allow a 0.016 inch (0.41 mm) outer diameter.• The optical fiber assembly may include of one or two optical fibers to slide therein, and the stainless-steel tube dimensions are about 25.4 mm long, 0.023 inch (0.58 mm) inner diameter, 0.028 inch (0.71 mm) outer diameter, Pebax strain relief is 8 mm long, 0.029 inch (0.74 mm) inner diameter, 0.040 inch (1.02 mm) outer diameter, and etched PTFE sleeve is 0.020 inch (0.51 mm) inner diameter, 0.022 inch (0.56 mm) outer diameter.• The optical switch element, where the tube dimensions are selected to allow a 0.024 inch (0.61 mm) outer diameter optical fiber assembly, may include 8 or more fibers to slide therein.• The optical switch element where the stainless-steel tube dimensions are 0.026 inch (0.66 mm) inner diameter, 0.028 inch (0.71 mm) outer diameter PTFE sleeve, 0.029 inch (0.74 mm) inner diameter, 0.032 inch (0.83 mm) outer diameter SS tube and 0.033 inch (0.84 mm) inner diameter, 0.043 inch (1.09 mm) outer diameter Pebax 7233 tube.• The optical switch element, where the tubes are separated by rigid divider plates that are uniformly spaced apart in the stacked arrangement.14© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patent• The optical switch element, where the rigid divider plates are 0.005-inch (0.13 mm) to 0.010-inch (0.25 mm) thick stainless steel and stacked to produce a 0.040-inch (1.02 mm) pitch.

[0037] In another general aspect, the optical switch element may include an optical switch element located between an array of optical fiber slack-tensioning pulleys on the rear side and an array of movable fiber connectors on the front side, the rear and front side spanned by contiguous optical fibers that follow straight-line paths in the volume between the front size and the optical switch element, wherein each optical fiber passes through an intermediate tube comprised of a rigid element, one or more flexible elements, and a low friction element.

[0038] Implementations may include one or more of the following features, alone or in combination(s):• The optical switch element where the flexible elements are selected to limit the bend radius experienced by the tensioned optical fiber to be greater than or equal to 5 mm.• The optical switch element, where static tension on the optical fibers is approximately 28 to 57 grams (1 to 2 ounces).Numbered Examples

[0039] A set of numbered examples is given in the following example clauses A to AT:Example Clause A . A backbone tube assembly for routing an optical fiber in a robotic fiber cross-connect system, may include: a rigid tubular segment extending along a longitudinal axis; a low-friction liner disposed within the rigid tubular segment along substantially the full length thereof; and first and second flexible strain-relief segments coupled to opposite ends of the rigid tubular segment, where the backbone tube assembly is configured to receive at least one optical fiber therethrough, to slide laterally when supported in a vertically stacked backbone structure, and to reorient under tensile forces applied by the optical fiber while limiting a minimum bend radius of the optical fiber to not less than 5 mm. Example Clause B. The backbone tube assembly of Example Clause A, where the low- friction liner may include a PTFE sleeve.15© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentExample Clause C. The backbone tube assembly of Example Clause A or Example Clause B, where the PTFE sleeve is surface-etched.Example Clause D. The backbone tube assembly of any one of Example Clauses A-C,where the PTFE sleeve is bonded to the rigid tubular segment or to an adjacent strain-relief segment using an adhesive.Example Clause E: The backbone tube assembly of any one of Example Clauses A-D,where the adhesive may include a UV-curable adhesive, cyanoacrylate adhesive, acrylate adhesive, or epoxy adhesive.Example Clause F: The backbone tube assembly of any one of Example Clauses A-E, where the flexible strain-relief segment may include a polymer tube bonded to an end of the rigid tubular segment.Example Clause G. The backbone tube assembly of any one of Example Clauses A-F,where the polymer tube may include a Pebax material.Example Clause H. The backbone tube assembly of any one of Example Clauses A-G, where the backbone tube assembly is dimensioned to receive an optical fiber assembly may include one or two optical fibers, and where: the rigid tubular segment has an inner diameter of approximately 0.58 mm and an outer diameter of approximately 0.71 mm; the low-friction liner has an inner diameter of approximately 0.51 mm and an outer diameter of approximately 0.56 mm; and each flexible strain-relief segment has an inner diameter of approximately 0.74 mm and an outer diameter of approximately 1.02 mm.Example Clause I. The backbone tube assembly of any one of Example Clauses A-H. where the backbone tube assembly is dimensioned to receive a bundled optical fiber assembly may include eight or more optical fibers, and where: the rigid tubular segment has an inner diameter of approximately 0.74 mm and an outer diameter of approximately 0.83 mm; the low-friction liner has an inner diameter of approximately 0.66 mm and an outer diameter of approximately 0.71 mm; and each flexible strain-relief segment has an inner diameter of approximately 0.84 mm and an outer diameter of approximately 1.09 mm.Example Clause J. An optical fiber routing assembly for a robotic fiber cross-connect system, may include: a plurality of backbone tube assemblies arranged in a vertically stacked array; each backbone tube assembly defining an internal passage configured to receive and guide at least one optical fiber extending between a rear 16© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentslack-management region and a front connector region; a support structure that constrains relative vertical position of the backbone tube assemblies while permitting each backbone tube assembly to translate laterally in a direction normal to the stacking direction; where each backbone tube assembly is free to laterally displace independently of adjacent backbone tube assemblies in response to tension vectors applied by the optical fiber passing therethrough, such that adjacent backbone tube assemblies separate from one another at locations proximate fiber exit regions; and where each backbone tube assembly includes a rigid tubular segment and at least one flexible strain-relief segment configured to limit bending of the optical fiber as the backbone tube assembly reorients under tension.Example Clause K. The optical fiber routing assembly of Example Clause J, where lateral displacement of each backbone tube assembly occurs passively under fiber tension without active actuation.Example Clause L . The optical fiber routing assembly of Example Clause J or Example Clause K, where the backbone tube assemblies are configured to accommodate fiber exit divergence angles of at least 45 degrees in a horizontal plane.Example Clause M: The optical fiber routing assembly of any one of Example Clauses J-L,where adjacent backbone tube assemblies separate laterally by at least 2 mm at fiber exit regions under nominal operating tension.Example Clause N: The optical fiber routing assembly of any one of Example Clauses -M.where the flexible strain-relief segment limits a minimum bend radius of the optical fiber to not less than 5 mm during reorientation.Example Clause O. The optical fiber routing assembly of any one of Example Clauses J-N,where each backbone tube assembly may include a thin-walled metal tube forming the rigid tubular segment.Example Clause P. The optical fiber routing assembly of any one of Example Clauses J-O,where the thin-walled metal tube is stainless steel having a wall thickness not exceeding 0.075 mm.Example Clause Q. The optical fiber routing assembly of any one of Example Clauses J-P,where each backbone tube assembly includes a low-friction liner disposed along at least a portion of the internal passage.17© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentExample Clause R The optical fiber routing assembly of any one of Example Clauses J-Q, where the low-friction liner may include a PTFE sleeve extending substantially the full length of the rigid tubular segment.Example Clause S. The optical fiber routing assembly of any one of Example Clauses J-R,where the PTFE sleeve is surface-etched to modify surface chemistry before assembly within the rigid tubular segment.Example Clause T. The optical fiber routing assembly of any one of Example Clauses J-S,where the surface etching may include chemical or plasma etching of the PTFE sleeve.Example Clause U: The optical fiber routing assembly of any one of Example Clauses J-I.where the PTFE sleeve is bonded to the rigid tubular segment or to an adjacent strain-relief segment using an adhesive.Example Clause V'. The optical fiber routing assembly of any one of Example Clauses J-U,where the adhesive may include a UV-curable adhesive, cyanoacrylate adhesive, acrylate adhesive, or epoxy adhesive.Example Clause W. The optical fiber routing assembly of any one of Example Clauses J-V,where the flexible strain-relief segment may include a polymer tube bonded to an end of the rigid tubular segment.Example Clause X. The optical fiber routing assembly of any one of Example Clauses J-W,where the polymer tube may include a Pebax material.Example Clause Y The optical fiber routing assembly of any one of Example Clauses J-X,where the support structure may include a plurality of rigid divider plates stacked in parallel and defining laterally open slots for receiving respective backbone tube assemblies.Example Clause Z. The optical fiber routing assembly of any one of Example Clauses J-Y,where the divider plates have a thickness in a range of 0.13 mm to 0.25 mm.Example Clause AA . The optical fiber routing assembly of any one of Example Clauses J-Z,where the divider plates are spaced to define a stacking pitch of approximately 1.02 mm.Example Clause AB . The optical fiber routing assembly of any one of Example Clauses J- AA, where the support structure may include a comb of elongated wire elements18© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentarranged to laterally constrain and vertically separate the backbone tube assemblies while permitting lateral translation.Example Clause AC : The optical fiber routing assembly of any one of Example Clauses J- AB, where the elongated wire elements may include piano wire having a diameter of approximately 0.25 mm.Example Clause AD . The optical fiber routing assembly of any one of Example Clauses J- AC, where each backbone tube assembly is configured to rotate about its longitudinal axis as the optical fiber is displaced vertically.Example Clause AE. The optical fiber routing assembly of any one of Example Clauses J- AD, where the optical fiber is maintained under static tension in a range of 28 g to 57 g during operation.Example Clause AF: The optical fiber routing assembly of any one of Example Clauses J- AE, where the backbone tube assemblies are configured to withstand at least 10,000 reorientation cycles under nominal operating tension without mechanical failure.Example Clause AG . The optical fiber routing assembly of any one of Example Clauses J- AF, where an axial sliding coefficient of friction between the optical fiber and each backbone tube assembly is less than 0.2 under nominal operating conditions.Example Clause AH. The optical fiber routing assembly of any one of Example Clauses J- AG, where the backbone tube assemblies are located at an intermediate span of the optical fibers between a rear slack-management pulley system and a front two- dimensional connector array.Example Clause Al The optical fiber routing assembly of any one of Example Clauses J- AH, where each backbone tube assembly may include: a rigid tubular segment having a first inner diameter; a low-friction liner disposed within the rigid tubular segment along substantially its entire length; and first and second flexible strainrelief segments coupled to opposite ends of the rigid tubular segment, where the rigid tubular segment, the low-friction liner, and the flexible strain-relief segments are fixed relative to one another to form a unitary backbone tube assembly configured to slide and reorient as a single body.Example Clause AJ . The optical fiber routing assembly of any one of Example Clauses J- AI, where the backbone tube assembly is dimensioned to receive an optical fiber assembly may include one or two optical fibers, and where: the rigid tubular19© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentsegment has an inner diameter of approximately 0.58 mm and an outer diameter of approximately 0.71 mm; the low-friction liner has an inner diameter of approximately 0.51 mm and an outer diameter of approximately 0.56 mm; and each flexible strain-relief segment has an inner diameter of approximately 0.74 mm and an outer diameter of approximately 1.02 mm.Example Clause AK. The optical fiber routing assembly of any one of Example Clauses J- AJ, where the backbone tube assembly is dimensioned to receive a bundled optical fiber assembly may include eight or more optical fibers, and where: the rigid tubular segment has an inner diameter of approximately 0.74 mm and an outer diameter of approximately 0.83 mm; the low-friction liner has an inner diameter of approximately 0.66 mm and an outer diameter of approximately 0.71 mm; and each flexible strain-relief segment has an inner diameter of approximately 0.84 mm and an outer diameter of approximately 1.09 mm.Example Clause AL. A robotic optical fiber cross-connect system, may include: an enclosure defining an internal three-dimensional fiber routing volume; a plurality of optical fibers extending between a rear slack-management subsystem and a front connector array disposed in a two-dimensional arrangement; a robotic actuator disposed within an upper region of the enclosure and configured to reposition selected optical fibers among the front connector array while traversing between adjacent optical fibers; a backbone assembly located at an intermediate span of the optical fibers between the rear slack-management subsystem and the front connector array, the backbone assembly may include: a plurality of backbone tube assemblies arranged in a vertically stacked array, each backbone tube assembly defining an internal passage through which at least one optical fiber passes; and a support structure that constrains relative vertical position of the backbone tube assemblies while permitting each backbone tube assembly to translate laterally in a direction normal to the stacking direction; where each backbone tube assembly is configured to reorient and laterally displace independently in response to tension vectors applied by the optical fiber passing therethrough, such that adjacent backbone tube assemblies passively separate from one another at fiber exit locations as optical fibers are repositioned by the robotic actuator; and where each backbone tube assembly may include a rigid tubular segment and at least one flexible strain-relief20© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentsegment coupled to the rigid tubular segment and dimensioned to limit a minimum bend radius of the optical fiber to not less than 5 mm.Example Clause AM A robotic optical fiber cross-connect system, may include: an enclosure defining an internal fiber routing volume; a plurality of optical fibers extending between a rear slack-management subsystem and a front connector array; a robotic actuator configured to transport selected optical fibers across and between other optical fibers to effect reconfiguration of connections at the front connector array; and a backbone assembly located at an intermediate span of the optical fibers, where the backbone assembly may include a plurality of backbone tube assemblies arranged in a vertically stacked array and supported by a structure that: mechanically constrains relative vertical positions of the backbone tube assemblies; mechanically permits independent lateral translation of each backbone tube assembly in a horizontal direction normal to the stacking direction; and mechanically prevents fixation of the backbone tube assemblies in the horizontal direction, such that, during robotic reconfiguration, backbone tube assemblies associated with optical fibers experiencing differing tension vectors laterally displace and separate from one another at fiber exit regions, and where each backbone tube assembly includes a rigid tubular segment and at least one flexible strain-relief segment configured to limit bending of the optical fiber to a minimum bend radius of not less than 5 mm during lateral displacement.Example Clause AN An optical fiber routing system for a robotic fiber cross-connect, may include: a slack-management subsystem including a plurality of fiber storage elements configured to apply controlled tensile force to optical fibers; a plurality of optical fibers extending forward from the slack-management subsystem toward a connector region; a backbone assembly positioned along the optical fibers between the slack-management subsystem and the connector region, the backbone assembly may include a plurality of backbone tube assemblies arranged in a vertically stacked array; where each backbone tube assembly defines an internal passage through which at least one optical fiber passes and is supported by a structure that permits lateral translation of the backbone tube assembly in response to tensile forces applied by the optical fiber while maintaining vertical separation from adjacent backbone tube assemblies; where the slack-management subsystem maintains the optical fibers under static tension in a range of 28 g to 57 g; and where variations in21© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentfiber length introduced by robotic reconfiguration at the connector region cause corresponding passive lateral displacement of the backbone tube assemblies, thereby maintaining straight-line fiber paths forward of the backbone assembly and preventing loss of fiber tension.Example Clause AO. An optical fiber routing assembly may include: a plurality of backbone tube assemblies in a vertically stacked array, each defining a passage for at least one optical fiber support structure constraining vertical position while permitting lateral translation, where each backbone tube assembly is independently laterally displaceable in response to tension applied by optical fiber passing therethrough. Example Clause AP: A backbone tube assembly may include: a tubular segment defining longitudinal passage configured to laterally translate when supported in a vertically stacked arrangement that reorients under tensile forces applied by optical fiber. Example Clause AQ An optical fiber routing assembly for a robotic fiber cross-connect system, may include: a plurality of backbone tube assemblies arranged in a vertically stacked array; each backbone tube assembly defining an internal passage for at least one optical fiber; and a support structure that constrains relative vertical position of the backbone tube assemblies while permitting each backbone tube assembly to translate laterally, where each backbone tube assembly laterally displaces independently in response to tension applied by the optical fiber passing therethrough.Example Clause AR. An optical fiber routing assembly may include: a vertically stacked array of backbone tube assemblies, where each backbone tube assembly passively translates laterally without active actuation in response to tension vectors applied by optical fibers.Example Clause AS: A method of preventing fiber congestion in a robotic optical fiber cross-connect system, may include: arranging a plurality of backbone tube assemblies in a vertically stacked array; and supporting the backbone tube assemblies such that vertical positions are constrained while permitting lateral translation; and allowing the backbone tube assemblies to independently displace laterally in response to tension applied by optical fibers passing therethrough, where straight-line fiber paths are maintained and tension loss is prevented.Example Clause AT An optical fiber routing system that prevents fiber congestion by independently displacing backbone tube assemblies laterally in response to varying 22© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentfiber tension vectors while maintaining vertical separation between adjacent backbone tube assemblies.

[0040] A second set of examples is given in the numbered paragraphs 1 to 18.Paragraph 1 : An optical switch element may include of a stacked arrangement of movable backbone tube assemblies providing strain relief to optical fibers sliding therein and exiting at large angles, the tube assemblies selected of a combination of tubes and materials to provide low fiber sliding friction, fatigue resistance during cyclic loading at large fiber divergence angles, minimum optical fiber bend radius of 5 mm, and low wear of fiber coating, and where the structure supporting tube assemblies allows tubes to shift in a direction normal to stacking direction so that tube assemblies are substantially separated at locations in which optical fibers exit the tube assemblies.Paragraph 2 An optical switch element in accordance with as described in Paragraph 1, where the backbone tube assembly may include a thin-walled, stiff stainless- steel tube with Pebax strain relief tube tips at ends thereof and lined along its entirety by an etched PTFE sleeve, where the stainless-steel tube, Pebax 7233 strain relief tips, and PTFE sleeve are permanently attached to one another with UV-cured adhesive.Paragraph 3. An optical switch element in accordance with as described in either of Paragraphs 1 or 2, where the tube dimensions are selected to allow a 0.016 inch outer diameter optical fiber assembly may include of one or two optical fibers to slide therein, and the stainless steel tube dimensions are about 1 inch long, 0.023 inch inner diameter, 0.028 inch outer diameter, Pebax strain relief is 8 mm long, 0.029 inch inner diameter, 0.040 inch outer diameter, and etched PTFE sleeve is 0.020 inch inner diameter, 0.022 inch outer diameter.Paragraph 4. An optical switch element in accordance with as described in any of Paragraphs 1 to 3, where the tube dimensions are selected to allow a 0.024- inch outer diameter optical fiber assembly may include of 8 or more fibers to slide therein, and the dimensions are 0.026-inch inner diameter, 0.028-inch outer diameter PTFE sleeve, 0.029-inch inner diameter, 0.0325-inch outer diameter SS tube and 0.033-inch inner diameter, 0.043-inch outer diameter Pebax 7233 tube.23© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentParagraph 5 An optical switch element in accordance with as described in any of Paragraphs 1 to 4, where the tubes are separated by rigid divider plates that are uniformly spaced apart in the stacked arrangement.Paragraph 6 An optical switch element in accordance with as described in any of Paragraphs 1 to 5, where the rigid divider plates are 0.005 inch to 0.010-inch- thick stainless steel and stacked to produce a 0.040-inch pitch. Paragraph 7: An optical switch element located between an array of optical fiber slack tensioning pulleys on the rear side and an array of moveable fiber connectors on the front side, the rear and front side spanned by contiguous optical fibers under slight tension so that they follow straight-line paths in the volume between the front size and the optical switch element, where each optical fiber passes through an intermediate tube may include of a rigid element, one or more flexible elements and a low friction element.Paragraph 8. An optical switch element in accordance with as described in Paragraph 7, where the flexible elements are selected to limit the bend radius experienced by the tensioned optical fiber to be greater than or equal to 5 mm. Paragraph 9. An optical switch element in accordance with as described in either of Paragraphs 7 or 8, where static tension on the optical fibers is in the range of approximately 1 to 2 ounces.Paragraph 10. An optical switch element may include of a stacked arrangement of movable backbone tube assemblies providing strain relief to optical fibers sliding therein and exiting at large divergence angles in excess of 45 degrees, the tube assemblies selected of a combination of tubes and materials to provide low fiber sliding friction with a coefficient of friction less than 0.2, fatigue resistance during cyclic loading of 10,000 or more cycles at large fiber divergence angles, minimum optical fiber bend radius of 5 mm, and low wear of fiber coating, and where the structure supporting tube assemblies allows tubes to shift in a direction normal to the stacking direction so that tube assemblies are substantially separated by more than 2 mm at the locations in which optical fibers exit the tube assemblies.Paragraph 11 : An optical switch element in accordance with as described in Paragraph 10,where the backbone tube assembly may include a thin-walled ( < 0.003 inch of 0.075-inch mm) thick, stiff stainless-steel tube with Pebax strain relief tube 24© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patenttips at the ends thereof and lined along its entirety by an etched PTFE sleeve, where the stainless-steel tube, Pebax 7233 strain relief tips, and PTFE sleeve are permanently attached to one another with UV-cured adhesive. Paragraph 12. An optical switch element in accordance with as described in either of Paragraphs 10 or 11, where the tube dimensions are selected to allow a 0.016 inch (0.41 mm) outer diameter optical fiber assembly may include of one or two optical fibers to slide therein, and the stainless-steel tube dimensions are about 25.4 mm long, 0.023 inch (0.58 mm) inner diameter, 0.028 inch (0.71 mm) outer diameter, Pebax strain relief is 8 mm long, 0.029 inch (0.74 mm) inner diameter, 0.040 inch (1.02 mm) outer diameter, and etched PTFE sleeve is 0.020 inch (0.51 mm) inner diameter, 0.022 inch (0.56 mm) outer diameter.Paragraph 13. An optical switch element in accordance with as described in any of Paragraphs 10 to 12, where the tube dimensions are selected to allow a 0.024 inch (0.61 mm) outer diameter optical fiber assembly may include of 8 or more fibers to slide therein, and the dimensions are 0.026 inch (0.66 mm) inner diameter, 0.028 inch (0.71 mm) outer diameter PTFE sleeve, 0.029 inch (0.74 mm) inner diameter, 0.032 inch (0.83 mm) outer diameter SS tube and 0.033 inch (0.84 mm) inner diameter, 0.043 inch (1.09 mm) outer diameter Pebax 7233 tube.Paragraph 14. An optical switch element in accordance with as described in any of Paragraphs 10 to 13, where the tubes are separated by rigid divider plates that are uniformly spaced apart in the stacked arrangement.Paragraph 15. An optical switch element in accordance with as described in any of Paragraphs 10 to 14, where the rigid divider plates are 0.005-inch (0.13 mm) to 0.010-inch (0.25 mm) thick stainless steel and stacked to produce a 0.040- inch (1.02 mm) pitch.Paragraph 16. An optical switch element located between an array of optical fiber slack tensioning pulleys on the rear side and an array of moveable fiber connectors on the front side, the rear and front side spanned by contiguous optical fibers that follow straight-line paths in the volume between the front size and the optical switch element, where each optical fiber passes through an intermediate tube may include of a rigid element, one or more flexible elements, and a low friction element.25© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentParagraph 17: An optical switch element in accordance with as described in Paragraph 16, where the flexible elements are selected to limit the bend radius experienced by the tensioned optical fiber to be greater than or equal to 5 mm. Paragraph 18. An optical switch element in accordance with as described in either of Paragraphs 16 or 17, where static tension on the optical fibers is in the range of approximately 28 to 57 grams (1 to 2 ounces).Brief Description of the Drawings

[0041] Other objects, features, and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification. None of the drawings is to scale unless specifically stated otherwise.

[0042] FIGS. 1A-1B show prior art cross-connect systems implementing the KBS algorithm;

[0043] FIG. 2 illustrates aspects of the prior art one-dimensional static arrangement of intermediate backbone tubes with tensioned fibers passing therein for the entire system;

[0044] FIG. 3 illustrates aspects of the prior art one-dimensional static arrangement of intermediate backbone tubes with tensioned fibers passing therein;

[0045] FIG. 4 shows different configurations or types of single and multi-fiber bundles that must slide with low friction and bend stress through a backbone tube;

[0046] FIG. 5 illustrates aspects of the one-dimensional dynamic arrangement of shifting intermediate backbone tubes for tensioned fibers to slide therein with low friction, according to embodiments hereof;

[0047] FIGS. 6A to 6C show aspects of a tube element according to exemplary embodiments hereof;

[0048] FIG. 6D shows a backbone tube subassembly built up from several tube elements to maintain low sliding friction of optical fibers and bundles;

[0049] FIGS. 7A-7H illustrate aspects of an example of a fiber optic cross-connect system with shifting backbone tubes stacked in a layered support structure.26© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patent

[0050] FIGS. 8A-8D illustrate aspects of a slack fiber management unit including shifting backbone tube subassemblies including a comb of piano wire dividers.Detailed Description

[0051] In the following, exemplary embodiments are described, referring to the figures. These examples are provided to further illustrate the invention without limiting its scope.

[0052] The following detailed description is made with reference to the accompanying drawings, which illustrate example embodiments and are not necessarily to scale. Like reference numerals refer to like elements throughout. The embodiments are illustrative, not limiting, and are not restricted to the particular arrangements shown.

[0053] Reference numerals have been referred to for quicker understanding and are not intended to limit the scope of the present invention in any manner.Glossary and Abbreviations

[0054] As used herein, unless used otherwise, the following terms or abbreviations have the following meanings:

[0055] ID means inner diameter.

[0056] OD means outer diameter.

[0057] PEEK means Polyether Ether Ketone.

[0058] PTFE means Polytetrafluoroethylene.

[0059] PEEK-PTFE means PEEK combined or blended with PTFE.Description

[0060] Devices and methods to enable the backbone tubes to individually shift, fan out, or separate horizontally under the influence of the changing fiber tension vectors so that fiber backbone congestion and fiber wear are significantly reduced are disclosed. Examples of multi-element backbone tubes comprised of rigid, low-friction, and low-fatigue elements are presented.

[0061] In a first example, the tensioned optical fibers passing through their associated backbone tubes redirect the nominally straight, rigid tubes with flexible tips in the horizontal 27© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentplane. At the flexible tips, the fiber radius is limited by virtue of the compliance of the fatigue-resistant tube elements, thereby preventing abrupt, sharp deflections of the fiber up or down (vertically). Because each individual fiber passing through a tube is tensioned, the resulting force experienced by the tube is adequate to redirect it to be essentially parallel to the horizontal component of the fiber tension vector. This separation in the horizontal direction significantly reduces the spatial congestion of tubes and fibers before they potentially bend in the vertical direction while maintaining freedom for the fiber to slide within and transfer the tension from behind the backbone tube to in front of the backbone tube. This ensures that all fibers retain straight-line paths in front of the backbone tubes, as required for the robotic KBS algorithm to operate without fiber entanglement.

[0062] The system disclosed herein further utilizes a combination of unique design elements, including the fiber and / or fiber bundles, fiber backbone tubes, and tube support structures. The multiplicity of fibers or multi-fiber, sleeved bundles extends from slack management pulleys to the rear of backbone tubes, passes through the fiber backbone tubes with low friction, wear, and stress, and are directed forward to changeable connector terminals disposed in a two-dimensional planar or curved matrix of terminals. The fiber bundles are generally contiguous and have a length of about 3 meters (3000 mm). These fibers / fiber bundles internal to the system come in a wide range, examples of which are illustrated in FIG. 4. The number of optical fibers in these examples ranges from 1 to 16 per interconnect bundle, potentially increasing to 32 or more per bundle. The fibers lie within a flexible sleeve, e.g., made of nylon, HDPE, LDPE, PVC, PBT, or Pebax. For constituent fiber with an acrylate outer coating diameter of 0.125 mm to 0.135 mm, the corresponding bundle diameters range up to 0.024 inch (0.61 mm) for eight fibers, up to about 0.034 inch (0.86 mm) for sixteen fibers. One or more optical fibers enclosed within a common sleeve or coating and presenting a single effective outer diameter are also referred to herein as an optical fiber assembly.

[0063] With reference now to FIG. 5, each fiber optic bundle passes from the slack management system 502 in the rear, through a shiftable backbone tube 504 arrayed vertically into an assembly 506, and to the front connector row 508, as depicted schematically in FIG. 5. The backbone tubes (individually and collectively 504) are located at a mid-span portion along the strands (internal to the system and identified as the one-dimensional backbone). In a particular example, each of these tubes 504 is free to independently shift, rotate azimuthally, and spread horizontally at an angle of about + / - 45 degrees in the28© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patenthorizontal plane, as well as rotate and / or bend with an angle of about + / - 60 degrees in the vertical direction. The front ends of the rigid backbone tube assemblies with flexible tips fan out under the influence of the tensioned fiber extended to unique endpoint locations within the front two-dimensional array of connectors.

[0064] The fiber / fiber bundles provide suspended optical fiber interconnects, which span a ID array of backbone tube guides internal to the system and an externally facing 2D array of ports. The fiber interconnects comprising the switch fabric are included in fiber modules, each module including, for example, blocks of 48 or 96 fibers.

[0065] The fiber interconnect modules and robot are housed within a rigid frame and enclosure that houses and supports a robotic actuation system. A robotic gripper can rearrange the suspended fiber interconnects arbitrarily among the 2D array of termination points or, equivalently connector ports. The gripper is attached to a long robotic arm that descends into the interconnect region. The gripper may include a motor, solenoid, sensors, and potentially one or more built-in cameras and light sources. The reconfiguration process utilizes a robotic arm to transport a fiber along a multi-segment path between and over the front connector ports. These movements of the tensioned fiber / fiber bundles in front of the backbone tubes result in the changing orientation of their corresponding backbone tubes. The movements generated by the KBS algorithm to cross any particular column can be considered in isolation from other columns. As the fiber is transported between these different front panel locations, the backbone tubes at an intermediate location along the fiber must be free to reorient such that they are substantially parallel to the fiber bundle tension vector.

[0066] For a particular example, FIGS. 6A to 6C illustrate a backbone tube subassembly 604 (corresponding to tube 504 in FIG. 5) made of various constituent tube segments. In this particular example, a stainless-steel hypo tube 606 is lined with PTFE tube 608, and both ends of the stainless-steel hypo tube 606 are tipped with 8 mm long Pebax strain relief tubes 610-1, 610-2 (collectively 610) that each extend 4 mm beyond the end of the stainless-steel hypo tube 606. The PTFE tube 608 is glued to the Pebax strain relief tube 610-1 at the rightmost location (612), and the Pebax strain relief tubes / tips (610) are glued to the stainless-steel hypo tube 606 at both ends (614, 616). Suitable adhesives include cyanoacrylate, acrylate, UV epoxy, or thermal cure epoxy.

[0067] In a particular example, the individual backbone tube element is lined along its entire length with a thin-walled, etched PTFE sleeve to reduce friction. Fatigue-resistant29© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentPebax 7233 strain relief tips are bonded to the ends of a central, rigid stainless-steel hypo tube that can slide and reorient freely between the divider sheets or wire. The round construction allows the tube to reorient or rotate 180 degrees about its longitudinal axis as the fiber is pulled up or down, thereby reducing the effects of cyclic fatigue on the Pebax strain relief tips. FIG. 6B identifies the location of adhesive to attach the tubes to the stainless-steel hypo tube while allowing the front Pebax tip to bend while maintaining a sufficiently large inner clearance of 0.002 inch (0.051 mm) to 0.004 inch (0.102 mm) to prevent pinching and excessive friction of the optical fiber / bundle sliding therein.

[0068] FIG. 6D illustrates the stack 620 of twelve of the same tubes 604 (604-1, 604-2, ... 604-12) in close vertical relation to one another, yet able to pass by one another in the horizontal plane.

[0069] In a further example, FIGS. 7A-7H illustrate the mechanical relationships between the front fiber optic connector array, slack management tray for 12 fibers, each passing through their intermediate, shiftable backbone tube, the slack management pulleys, back fiber optic connectors, and the overall chassis, which houses a robot (not visible) in the upper portion of the system in FIG. 7A.

[0070] FIGS. 7A-7H illustrate aspects of an example of a fiber optic cross-connect system with shifting backbone tubes stacked in a layered support structure.

[0071] FIG. 7A depicts a fiber slack management module 702 within a robotic system 700 with capacity for over 1000 ports / backbone tubes and capacity for 10 or more fiber modules.

[0072] FIGS. 7B and 7C illustrate the insides of an individual slack fiber module with a capacity of 96 ports / backbone tubes. These drawings show the relationship among the shiftable backbone 702, the row of front connectors 704, the intermediate fiber interconnect volume 706, the spring-loaded slack management spools 708, and the row of back connectors 710

[0073] FIG. 7D illustrates an individual tray 708 of 12 ports / backbone tubes 702. Eight of these trays are stacked within a fiber module.

[0074] FIGS. 7E and 7F detail aspects of the backbone assembly 702 of a tray of 12 fibers passing through an intermediate backbone.30© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patent

[0075] FIG. 7G is an exploded view of backbone assembly 702, comprised of dividers 714, spacers 716, tubes 718, and brackets. The tubes 718 in FIG. 7G correspond to the tubes 604 described above.

[0076] In some cases, the dividers 714 may be uniformly spaced and rigid divider plates 0.005-to-0.010-inch (approximately 0.13 mm to 0.25 mm) thick stainless steel, stacked to produce a 0.040-inch (approximately 1.02 mm) pitch.

[0077] FIG. 7H illustrates the eight stacked slack management trays with backbone tube assemblies assembled into a single 96-port fiber slack module.

[0078] In this system, the array's reconfigurable input terminals are located near the front of the enclosure. Variations in the lengths of the suspended portion of the fiber optic strands in front of the backbone tube result from the changeable and arbitrary interconnection state at the front connector array. These length variations, or “slack fiber,” are retained on a stacked, low-elevation pulley subsystem mounted within shallow-height slack management modules. A subset of pulleys, around which a fiber bundle is repeatedly wrapped, themselves are part of a carriage that is slidable and attached to an elongated power or retractor spring. The system allows a variable length of a fiber optic bundle to be withdrawn to the length necessary to reach the front connector port while maintaining tension to maintain a straight, slack-free orientation. In addition, a subset of pulleys is fixed, one of which incorporates a rotational encoder in the form of regular incremental reflection variations circumferential about its central axis. The top-most tray of the slack fiber management module is illustrated in FIGS. 7B and 7C. An individual tray is detailed in FIG. 7D, along with the backbone stack shown in FIGS. 7E and 7F. FIG. 7G is an exploded view of an individual backbone assembly for 12 tubes comprised of dividers, spacers, tubes, and brackets.

[0079] The system illustrated in FIGS. 7A-7H provides a multiplicity of fiber-optic strands that extend outward into a three-dimensional module volume, enabling reconfiguration by a gripper and positioning system. The spring element and optical fiber may be coextensively disposed within a flexible or compliant housing (i.e., extruded plastic tube). A spring of appropriate compliance is all that is required for maintaining the optical fiber bundle under a controlled tension for withdrawal of about 28 to 57 grams (1 to 2 oz), and for subsequent return of a portion of the fiber bundle length into the pulley slack storage arrangement. FIG. 7H illustrates eight tray subunits stacked to form a 96-channel slack fiber management module.31© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentExamples

[0080] FIGS. 8A and 8B illustrate shifting backbone tubes in straight paths and angularly deflected paths. FIG. 8C is a detailed view of the shiftable backbone tubes, interposed so they can slide between fixed piano-wire supports 802. FIG. 8D illustrates a one-dimensional, stacked dynamic arrangement of horizontally passively shiftable backbone tubes.Example 1: 16-fiber Backbone Tube with Stacked, Flat Divider Plates

[0081] In a particular example illustrated in FIG. 8A, each fiber bundle is comprised of eight fibers within a tube of 0.024 inch (0.61 mm) outer diameter and 3 m length. The fibers are protected by a 0.021 x 0.024-inch (0.53 x 0.61 mm) outer-diameter Pebax 7233 sleeve. The fiber bundle passes through a backbone tube, the backbone tube comprised of a coaxial assembly of 0.026 inch (0.66 mm) inner diameter, 0.028 inch (0.71 mm) outer diameter PTFE liner or sleeve, a 0.029 inch (0.74 mm) inner diameter, 0.0325 inch (0.83 mm) outer diameter stainless-steel tube and 0.033 inch (0.84 mm) inner diameter, 0.043 inch (1.09 mm) outer diameter Pebax 7233 tube segments at opposite ends of the stainless-steel tube. The tubes are arranged in independent slots formed by stacked 0.005-inch (0.13 mm) thick photoetched stainless-steel dividers separated by 0.035-inch (0.89 mm) spacers, as illustrated, e.g., in FIG. 7G.Example 2: 1 or 2 Fiber Backbone Tube with Stacked, Flat Divider Plates

[0082] In a further example, each fiber bundle comprises one or two fibers within a tube with an outer diameter of 0.016 inch (0.41 mm) and a length of 3 m. The fiber passes through a backbone tube, the backbone tube comprised of a coaxial assembly of 0.020 inch (0.51 mm) inner diameter, 0.022 inch (0.56 mm) outer diameter PTFE liner or sleeve, a 0.023 inch (0.58 mm) inner diameter, 0.028 inch (0.71 mm) outer diameter stainless steel tube and 0.029 inch (0.74 mm) inner diameter, 0.040 inch (1.02 mm) outer diameter Pebax 7233 tube segments at opposite ends of the stainless-steel tube. The tubes are arranged in independent slots formed by stacked 0.005-inch (0.13 mm) thick photoetched stainless-steel dividers, separated by 0.035-inch (0.89 mm) thick spacers.32© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentExample 3: 1 or 2 Fiber Backbone Tube with Piano Wire Divider Comb

[0083] In this example, FIGS. 8A, 8B, and 8C illustrate an individual backbone tube subassembly with tensioned fiber in (a) a straight path and (b) an angularly deflected path, and passively shiftable backbone tubes with tensioned fibers passing therein and interposed with thin and fixed piano wire supports. Each fiber bundle is comprised of one or two fibers within a tube of 0.016 inch (0.41 mm) outer diameter and 3 meters in length. The fiber passes through a backbone tube the backbone tube comprised of a coaxial assembly of 0.020 inch (0.51 mm) inner diameter, 0.022 inch (0.56 mm) outer diameter PTFE liner or sleeve, a 0.023 inch (0.58 mm) inner diameter, 0.028 inch (0.71 mm) outer diameter stainless-steel tube and 0.029 inch (0.74 mm) inner diameter, 0.040 inch (1.02 mm) outer diameter Pebax 7233 tube segments at opposite ends of the stainless-steel tube. The tubes are arranged in independent slots formed between 0.010-inch (0.25 mm) diameter piano wire dividers forming a comb with 0.040-inch (1.02 mm) center-to-center spacing. FIGS. 8A-8C illustrate various views of the comb of piano wire dividers for the 12-fiber tray subunit. FIG. 8D illustrates a one-dimensional, stacked dynamic arrangement of horizontally, passively shiftable backbone tubes with tensioned fibers passing therein and interposed with a comb of piano wire supports. This illustrates a front view of the fiber slack management module, comprised of 8 stacked tray subunits corresponding to 96 backbone tubes.Discussion

[0084] The foregoing description sets forth specific embodiments of backbone tube assemblies, backbone routing assemblies, and robotic optical fiber cross-connect systems that address congestion, fatigue, and friction issues arising in high-density, reconfigurable optical fiber routing environments. In particular, disclosed embodiments describe a backbone architecture in which a plurality of backbone tube assemblies are arranged in a vertically stacked array and supported to constrain relative vertical position while permitting independent lateral translation of individual backbone tube assemblies in response to tensile forces applied by optical fibers passing therethrough.

[0085] As described, this mechanical allocation of degrees of freedom allows backbone tube assemblies to passively separate laterally at fiber exit regions as fiber routing geometry changes, thereby reducing tube-to-tube interference, maintaining controlled fiber tension, and preserving minimum bend radius constraints during robotic reconfiguration.33© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patent

[0086] The disclosure further describes unitary backbone tube assemblies comprising rigid tubular segments, optional low-friction liners, and flexible strain-relief segments, as well as dimensional examples suitable for guiding optical fiber assemblies comprising one or more optical fibers or bundled optical fiber assemblies comprising multiple optical fibers.

[0087] The embodiments described herein are illustrative of the principles of the invention and are not intended to be limiting. Variations in materials, dimensions, support structures, and configurations may be employed while maintaining the described mechanical behavior of constrained vertical stacking combined with permitted lateral translation under fiber tension. For example, support structures may include stacked divider plates, wire-based comb structures, or other mechanical arrangements that achieve the same functional constraint of vertical position while allowing lateral displacement. Likewise, rigid tubular segments, liners, and strain-relief segments may be formed from different materials or combinations of materials appropriate to the operating environment.

[0088] Unless otherwise indicated, numerical values, ranges, and dimensional relationships described herein are intended to include reasonable manufacturing tolerances and variations consistent with the disclosed functionality. References to specific dimensions or materials are provided to illustrate representative embodiments and do not exclude alternative implementations that achieve the same mechanical and functional results.Conclusion

[0089] As used herein, including in the claims, the phrase “at least some” means “one or more” and includes the case of only one. Thus, e.g., the phrase “at least some ABCs” means “one or more ABCs” and includes the case of only one ABC.

[0090] As used herein, including in the claims, the term “at least one” should be understood as meaning “one or more,” and therefore includes both embodiments that include one or multiple components. Furthermore, dependent claims that refer to independent claims that describe features with “at least one” have the same meaning, both when the feature is referred to as “the” and “the at least one.”

[0091] As used herein, including in the claims, the term “portion” means some or all. So, for example, “A portion of X” may include some of “X” or all of “X .” In the context of a thing, the term “portion” means some or all of the thing (e.g., a portion of a tube means some or all of the tube).34© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patent

[0092] In general, as used herein, including in the claims, unless the word “only” is specifically used in a phrase, it should not be read into that phrase. Where only one item is intended, the phrase “only one” or similar language is used.

[0093] As used herein, including in the claims, the phrase “distinct” means “at least partially distinct.” Unless expressly stated, distinct does not mean fully, wholly, or entirely distinct. Thus, e.g., the phrase, “X is distinct from Y” means that “X is at least partially distinct from Y,” and does not mean that “X is fully distinct from Y.” Thus, as used herein, including in the claims, the phrase “X is distinct from Y” means that X differs from Y in at least some way.

[0094] As used herein, including in the claims, the terms “multiple” and “plurality” mean “two or more” and include the case of “two.” Thus, e.g., the phrase “multiple ABCs” means “two or more ABCs” and includes “two ABCs.” Similarly, e.g., the phrase “multiple PQRs” means “two or more PQRs” and includes “two PQRs.”

[0095] As used herein, including in the claims, the term “automatic,” with respect to an action, generally means that the action occurs with little or no human control or interaction. The term “automatic” also includes cases with no human control or interaction. Thus, e.g., the term “triggered automatically” means “triggered with little or no human control or interaction” and includes the case “triggered with no human control or interaction.”

[0096] As used herein, including in the claims, singular forms of terms are to be construed as also including the plural form and vice versa unless the context indicates otherwise. Thus, it should be noted that as used herein, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.

[0097] Throughout the description and claims, the terms “comprise,” “including,” “having,” and “contain” and their variations should be understood as meaning “including but not limited to” and are not intended to exclude other components unless expressly so stated.

[0098] Although particular combinations of features are recited in the claims and / or disclosed in the specification, these combinations are not intended to limit the disclosure of various implementations. Many of these features may be combined in ways not explicitly recited in the claims and / or disclosed in the specification.

[0099] Although each dependent claim listed below may directly depend on only one claim, the disclosure of various implementations includes each dependent claim in combination with every other claim in the claim set.35© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patent

[0100] No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such.

[0101] As used herein, the term “or” is intended to be inclusive when used in a series and may be used interchangeably with “and / or,” unless explicitly stated otherwise (e.g., if used in combination with “either” or “only one of’).

[0102] As used herein, the terms “has,” “have,” “having,” or the like are intended to be open-ended terms.

[0103] It will be appreciated that variations to the embodiments of the invention can be made while still falling within the scope of the invention. Alternative features serving the same, equivalent, or similar purpose can replace features disclosed in the specification, unless otherwise stated. Thus, unless stated otherwise, each feature disclosed represents one example of a generic series of equivalent or similar features.

[0104] The present invention also covers the exact terms, features, values, and ranges, etc., in case these terms, features, values, and ranges, etc. are used in conjunction with terms such as about, around, generally, substantially, essentially, at least, etc. (i.e., “about 3” shall also cover exactly 3 or “substantially constant” shall also cover exactly constant).

[0105] Use of exemplary language, such as “for instance,” “such as,” “for example” (“e.g.,”), and the like, is merely intended to illustrate the invention better and does not indicate a limitation on the scope of the invention unless specifically so claimed.

[0106] The words “first” and “second” in the description and claims are used to distinguish or identify and not to show a serial or numerical limitation. Similarly, letter or numerical labels (such as “(a),” “(b),” and the like) are used to help distinguish and / or identify, and not to show any serial or numerical limitation or ordering.

[0107] While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiment but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0108] Although certain presently preferred embodiments of the invention have been described herein, it will be apparent to those skilled in the art to which the invention pertains36© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentthat variations and modifications of the described embodiments may be made without departing from the spirit and scope of the invention.37© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patent

Claims

Claims:We claim:

1. A backbone tube assembly for routing an optical fiber in a robotic fiber crossconnect system, comprising:a rigid tubular segment extending along a longitudinal axis;a low-friction liner disposed within the rigid tubular segment along substantially the full length thereof; andfirst and second flexible strain-relief segments coupled to opposite ends of the rigid tubular segment,wherein the backbone tube assembly is configured to receive at least one optical fiber therethrough, to slide laterally when supported in a vertically stacked backbone structure, and to reorient under tensile forces applied by the optical fiber while limiting a minimum bend radius of the optical fiber to not less than 5 mm.

2. The backbone tube assembly of claim 1, wherein the low-friction liner comprises a PTFE sleeve.

3. The backbone tube assembly of claim 2, wherein the PTFE sleeve is surface-etched.

4. The backbone tube assembly of claim 2, wherein the PTFE sleeve is bonded to the rigid tubular segment or to an adjacent strain-relief segment using an adhesive.

5. The backbone tube assembly of claim 4, wherein the adhesive comprises a UV-curable adhesive, cyanoacrylate adhesive, acrylate adhesive, or epoxy adhesive.

6. The backbone tube assembly of claim 1, wherein the flexible strain-relief segment comprises a polymer tube bonded to an end of the rigid tubular segment.

7. The backbone tube assembly of claim 6, wherein the polymer tube comprises a Pebax material.

8. The backbone tube assembly of claim 1, wherein the backbone tube assembly is dimensioned to receive an optical fiber assembly comprising one or two optical fibers, and wherein:the rigid tubular segment has an inner diameter of approximately 0.58 mm (0.023 inch) and an outer diameter of approximately 0.71 mm (0.28 inches);the low-friction liner has an inner diameter of approximately 0.51 mm (0.020 inches) and an outer diameter of approximately 0.56 mm (0.022 inches); and38© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patenteach flexible strain-relief segment is about 8 mm long, has an inner diameter of approximately 0.74 mm (0.029 inch), and an outer diameter of approximately 1.02 mm (0.040 inch).

9. The backbone tube assembly of claim 1, wherein the backbone tube assembly is dimensioned to receive a bundled optical fiber assembly comprising eight or more optical fibers, and wherein:the rigid tubular segment has an inner diameter of approximately 0.74 mm and an outer diameter of approximately 0.83 mm;the low-friction liner has an inner diameter of approximately 0.66 mm and an outer diameter of approximately 0.71 mm; andeach flexible strain-relief segment has an inner diameter of approximately 0.84 mm and an outer diameter of approximately 1.09 mm.

10. An optical fiber routing assembly for a robotic fiber cross-connect system, comprising:a plurality of backbone tube assemblies arranged in a vertically stacked array; each backbone tube assembly defining an internal passage configured to receive and guide at least one optical fiber extending between a rear slack-management region and a front connector region;a support structure that constrains a relative vertical position of the backbone tube assemblies while permitting each backbone tube assembly to translate laterally in a direction normal to the stacking direction;wherein each backbone tube assembly is free to laterally displace independently of adjacent backbone tube assemblies in response to tension vectors applied by the optical fiber passing therethrough, such that adjacent backbone tube assemblies separate from one another at locations proximate fiber exit regions; andwherein each backbone tube assembly includes a rigid tubular segment and at least one flexible strain-relief segment configured to limit bending of the optical fiber as the backbone tube assembly reorients under tension.

11. The optical fiber routing assembly of claim 10, wherein lateral displacement of each backbone tube assembly occurs passively under fiber tension without active actuation.

12. The optical fiber routing assembly of claim 10, wherein the backbone tube assemblies are configured to accommodate fiber exit divergence angles of at least 45 degrees in a horizontal plane.39© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patent13. The optical fiber routing assembly of claim 10, wherein adjacent backbone tube assemblies separate laterally by at least 2 mm at fiber exit regions under nominal operating tension.

14. The optical fiber routing assembly of claim 10, wherein the flexible strainrelief segment limits a minimum bend radius of the optical fiber to not less than 5 mm during reorientation.

15. The optical fiber routing assembly of claim 10, wherein each backbone tube assembly comprises a thin-walled metal tube forming the rigid tubular segment.

16. The optical fiber routing assembly of claim 15, wherein the thin-walled metal tube is stainless steel having a wall thickness not exceeding 0.075 mm.

17. The optical fiber routing assembly of claim 10, wherein each backbone tube assembly includes a low-friction liner disposed along at least a portion of the internal passage.

18. The optical fiber routing assembly of claim 17, wherein the low-friction liner comprises a PTFE sleeve extending substantially the full length of the rigid tubular segment.

19. The optical fiber routing assembly of claim 18, wherein the PTFE sleeve is surface-etched to modify surface chemistry before assembly within the rigid tubular segment.

20. The optical fiber routing assembly of claim 19, wherein the surface etching comprises chemical or plasma etching of the PTFE sleeve.

21. The optical fiber routing assembly of claim 18, wherein the PTFE sleeve is bonded to the rigid tubular segment or to an adjacent strain-relief segment using an adhesive.

22. The optical fiber routing assembly of claim 21, wherein the adhesive comprises a UV-curable adhesive, cyanoacrylate adhesive, acrylate adhesive, or epoxy adhesive.

23. The optical fiber routing assembly of claim 10, wherein the flexible strainrelief segment comprises a polymer tube bonded to an end of the rigid tubular segment.

24. The optical fiber routing assembly of claim 23, wherein the polymer tube comprises a Pebax material.

25. The optical fiber routing assembly of claim 10, wherein the support structure comprises a plurality of rigid divider plates stacked in parallel and defining laterally open slots for receiving respective backbone tube assemblies.

26. The optical fiber routing assembly of claim 25, wherein the divider plates have a thickness in a range of 0.13 mm to 0.25 mm (0.005 to 0.010 inch).

27. The optical fiber routing assembly of claim 25, wherein the divider plates are spaced to define a stacking pitch of approximately 1.02 mm (0.040 inch).40© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patent28. The optical fiber routing assembly of claim 10, wherein the support structure comprises a comb of elongated wire elements arranged to laterally constrain and vertically separate the backbone tube assemblies while permitting lateral translation.

29. The optical fiber routing assembly of claim 28, wherein the elongated wire elements comprise piano wire having a diameter of approximately 0.25 mm (0.010 inch).

30. The optical fiber routing assembly of claim 10, wherein each backbone tube assembly is configured to rotate about its longitudinal axis as the optical fiber is displaced vertically.

31. The optical fiber routing assembly of claim 10, wherein the optical fiber is maintained under static tension in a range of 28 g to 57 g (1 to 2 ounces) during operation.

32. The optical fiber routing assembly of claim 10, wherein the backbone tube assemblies are configured to withstand at least 10,000 reorientation cycles under nominal operating tension without mechanical failure.

33. The optical fiber routing assembly of claim 10, wherein an axial sliding coefficient of friction between the optical fiber and each backbone tube assembly is less than 0.2 under nominal operating conditions.

34. The optical fiber routing assembly of claim 10, wherein the backbone tube assemblies are located at an intermediate span of the optical fibers between a rear slackmanagement pulley system and a front two-dimensional connector array.

35. The optical fiber routing assembly of claim 10, wherein each backbone tube assembly comprises:a rigid tubular segment having a first inner diameter;a low-friction liner disposed within the rigid tubular segment along substantially its entire length; andfirst and second flexible strain-relief segments coupled to opposite ends of the rigid tubular segment,wherein the rigid tubular segment, the low-friction liner, and the flexible strain-relief segments are fixed relative to one another to form a unitary backbone tube assembly configured to slide and reorient as a single body.

36. The optical fiber routing assembly of claim 35, wherein the backbone tube assembly is dimensioned to receive an optical fiber assembly comprising one or two optical fibers, and wherein:the rigid tubular segment has an inner diameter of approximately 0.58 mm and an outer diameter of approximately 0.71 mm;41© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentthe low-friction liner has an inner diameter of approximately 0.51 mm and an outer diameter of approximately 0.56 mm; andeach flexible strain-relief segment has an inner diameter of approximately 0.74 mm and an outer diameter of approximately 1.02 mm.

37. The optical fiber routing assembly of claim 35, wherein the backbone tube assembly is dimensioned to receive a bundled optical fiber assembly comprising eight or more optical fibers, and wherein:the rigid tubular segment has an inner diameter of approximately 0.74 mm and an outer diameter of approximately 0.83 mm;the low-friction liner has an inner diameter of approximately 0.66 mm and an outer diameter of approximately 0.71 mm; andeach flexible strain-relief segment has an inner diameter of approximately 0.84 mm and an outer diameter of approximately 1.09 mm.

38. A robotic optical fiber cross-connect system, comprising:an enclosure defining an internal three-dimensional fiber routing volume;a plurality of optical fibers extending between a rear slack-management subsystem and a front connector array disposed in a two-dimensional arrangement;a robotic actuator disposed within an upper region of the enclosure and configured to reposition selected optical fibers among the front connector array while traversing between adjacent optical fibers;a backbone assembly located at an intermediate span of the optical fibers between the rear slack-management subsystem and the front connector array, the backbone assembly comprising:a plurality of backbone tube assemblies arranged in a vertically stacked array, each backbone tube assembly defining an internal passage through which at least one optical fiber passes; anda support structure that constrains a relative vertical position of the backbone tube assemblies while permitting each backbone tube assembly to translate laterally in a direction normal to the stacking direction;wherein each backbone tube assembly is configured to reorient and laterally displace independently in response to tension vectors applied by the optical fiber passing therethrough, such that adjacent backbone tube assemblies passively separate from one another at fiber exit locations as optical fibers are repositioned by the robotic actuator; and42© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentwherein each backbone tube assembly comprises a rigid tubular segment and at least one flexible strain-relief segment coupled to the rigid tubular segment and dimensioned to limit a minimum bend radius of the optical fiber to not less than 5 mm.

39. A robotic optical fiber cross-connect system, comprising:an enclosure defining an internal fiber routing volume;a plurality of optical fibers extending between a rear slack-management subsystem and a front connector array;a robotic actuator configured to transport selected optical fibers across and between other optical fibers to effect reconfiguration of connections at the front connector array; and a backbone assembly located at an intermediate span of the optical fibers, wherein the backbone assembly comprises a plurality of backbone tube assemblies arranged in a vertically stacked array and supported by a structure that:mechanically constrains a relative vertical positions of the backbone tube assemblies; mechanically permits independent lateral translation of each backbone tube assembly in a horizontal direction normal to the stacking direction; andmechanically prevents fixation of the backbone tube assemblies in the horizontal direction,such that, during robotic reconfiguration, backbone tube assemblies associated with optical fibers experiencing differing tension vectors laterally displace and separate from one another at fiber exit regions,and wherein each backbone tube assembly includes a rigid tubular segment and at least one flexible strain-relief segment configured to limit bending of the optical fiber to a minimum bend radius of not less than 5 mm during lateral displacement.

40. An optical fiber routing system for a robotic fiber cross-connect, comprising: a slack-management subsystem including a plurality of fiber storage elements configured to apply controlled tensile force to optical fibers;a plurality of optical fibers extending forward from the slack-management subsystem toward a connector region;a backbone assembly positioned along the optical fibers between the slackmanagement subsystem and the connector region, the backbone assembly comprising a plurality of backbone tube assemblies arranged in a vertically stacked array;wherein each backbone tube assembly defines an internal passage through which at least one optical fiber passes and is supported by a structure that permits lateral translation of43© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentthe backbone tube assembly in response to tensile forces applied by the optical fiber while maintaining vertical separation from adjacent backbone tube assemblies;wherein the slack-management subsystem maintains the optical fibers under static tension in a range of 28 g to 57 g; andwherein variations in fiber length introduced by robotic reconfiguration at the connector region cause corresponding passive lateral displacement of the backbone tube assemblies, thereby maintaining straight-line fiber paths forward of the backbone assembly and preventing loss of fiber tension.

41. An optical fiber routing assembly comprising:a plurality of backbone tube assemblies in a vertically stacked array, each defining a passage for at least one optical fiber support structure constraining vertical position while permitting lateral translation, wherein each backbone tube assembly is independently laterally displaceable in response to tension applied by optical fiber passing therethrough.

42. A backbone tube assembly comprising:a tubular segment defining longitudinal passage configured to laterally translate when supported in a vertically stacked arrangement that reorients under tensile forces applied by an optical fiber.

43. An optical fiber routing assembly for a robotic fiber cross-connect system, comprising:a plurality of backbone tube assemblies arranged in a vertically stacked array; each backbone tube assembly defining an internal passage for at least one optical fiber; anda support structure that constrains a relative vertical position of the backbone tube assemblies while permitting each backbone tube assembly to translate laterally, wherein each backbone tube assembly laterally displaces independently in response to tension applied by the optical fiber passing therethrough.

44. An optical fiber routing assembly comprising:a vertically stacked array of backbone tube assemblies,wherein each backbone tube assembly passively translates laterally without active actuation in response to tension vectors applied by optical fibers.

45. A method of preventing fiber congestion in a robotic optical fiber cross-connect system, comprising:arranging a plurality of backbone tube assemblies in a vertically stacked array; and supporting the backbone tube assemblies such that vertical positions are constrained 44© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentwhile permitting lateral translation, and allowing the backbone tube assemblies to independently displace laterally in response to tension applied by optical fibers passing therethrough,wherein straight-line fiber paths are maintained, and tension loss is prevented.

46. An optical fiber routing system that prevents fiber congestion by independently displacingbackbone tube assemblies laterally in response to varying fiber tension vectors while maintaining vertical separation between adjacent backbone tube assemblies.

47. An optical switch element comprised of a stacked arrangement of movable backbone tube assemblies providing strain relief to optical fibers sliding therein and exiting at large angles, the tube assemblies selected of a combination of tubes and materials to provide low fiber sliding friction, fatigue resistance during cyclic loading at large fiber divergence angles, minimum optical fiber bend radius of 5 mm, and low wear of fiber coating, and wherein the structure supporting tube assemblies allows tubes to shift in a direction normal to stacking direction so that tube assemblies are substantially separated at locations in which optical fibers exit the tube assemblies.

48. An optical switch element in accordance with claim 47, wherein the backbone tube assembly comprises a thin-walled, stiff stainless-steel tube with Pebax strain relief tube tips at ends thereof and lined along its entirety by an etched PTFE sleeve, wherein the stainless-steel tube, Pebax 7233 strain relief tips, and PTFE sleeve are permanently attached to one another with UV-cured adhesive.

49. An optical switch element in accordance with claim 48, wherein the tube dimensions are selected to allow a 0.016 inch outer diameter optical fiber assembly comprised of one or two optical fibers to slide therein, and the stainless steel tube dimensions are about 1 inch long, 0.023 inch inner diameter, 0.028 inch outer diameter, Pebax strain relief is 8 mm long, 0.029 inch inner diameter, 0.040 inch outer diameter, and etched PTFE sleeve is 0.020 inch inner diameter, 0.022 inch outer diameter.

50. An optical switch element in accordance with claim 48, wherein the tube dimensions are selected to allow a 0.024-inch outer diameter optical fiber assembly comprised of 8 or more fibers to slide therein, and the dimensions are 0.026-inch inner diameter, 0.028-inch outer diameter PTFE sleeve, 0.029-inch inner diameter, 0.0325-inch outer diameter SS tube and 0.033-inch inner diameter, 0.043-inch outer diameter Pebax 7233 tube.45© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patent51. An optical switch element in accordance with claim 47, wherein the tubes are separated by rigid divider plates that are uniformly spaced apart in the stacked arrangement.

52. An optical switch element in accordance with claim 51, wherein the rigid divider plates are 0.005- to 0.010-inch-thick stainless steel and stacked to produce a 0.040-inch pitch.

53. An optical switch element located between an array of optical fiber slack tensioning pulleys on the rear side and an array of moveable fiber connectors on the front side, the rear and front sides spanned by contiguous optical fibers under slight tension so that they follow straight-line paths in the volume between the front side and the optical switch element, wherein each optical fiber passes through an intermediate tube comprised of a rigid element, one or more flexible elements and a low friction element.

54. An optical switch element in accordance with claim 53, wherein the flexible elements are selected to limit the bend radius experienced by the tensioned optical fiber to be greater than or equal to 5 mm.

55. An optical switch element in accordance with claim 54, wherein static tension on the optical fibers is in the range of approximately 1 to 2 ounces.

56. An optical switch element comprised of a stacked arrangement of movable backbone tube assemblies providing strain relief to optical fibers sliding therein and exiting at large divergence angles in excess of 45 degrees, the tube assemblies selected of a combination of tubes and materials to provide low fiber sliding friction with a coefficient of friction less than 0.2, fatigue resistance during cyclic loading of 10,000 or more cycles at large fiber divergence angles, minimum optical fiber bend radius of 5 mm, and low wear of fiber coating, and wherein the structure supporting tube assemblies allows tubes to shift in a direction normal to the stacking direction so that tube assemblies are substantially separated by more than 2 mm at the locations in which optical fibers exit the tube assemblies.

57. An optical switch element in accordance with claim 56, wherein the backbone tube assembly comprises a thin-walled ( < 0.003 inch of 0.075 mm) thick, stiff stainless-steel tube with Pebax strain relief tube tips at the ends thereof and lined along its entirety by an etched PTFE sleeve, wherein the stainless-steel tube, Pebax 7233 strain relief tips, and PTFE sleeve are permanently attached to one another with UV-cured adhesive.

58. An optical switch element in accordance with claim 57, wherein the tube dimensions are selected to allow a 0.016 inch (0.41 mm) outer diameter optical fiber assembly comprised of one or two optical fibers to slide therein, and the stainless-steel tube dimensions are about 25.4 mm long, 0.023 inch (0.58 mm) inner diameter, 0.028 inch (0.7146© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patentmm) outer diameter, Pebax strain relief is 8 mm long, 0.029 inch (0.74 mm) inner diameter, 0.040 inch (1.02 mm) outer diameter, and etched PTFE sleeve is 0.020 inch (0.51 mm) inner diameter, 0.022 inch (0.56 mm) outer diameter.

59. An optical switch element in accordance with claim 57, wherein the tube dimensions are selected to allow a 0.024 inch (0.61 mm) outer diameter optical fiber assembly comprised of 8 or more fibers to slide therein, and the dimensions are 0.026 inch (0.66 mm) inner diameter, 0.028 inch (0.71 mm) outer diameter PTFE sleeve, 0.029 inch (0.74 mm) inner diameter, 0.0325 inch (0.83 mm) outer diameter SS tube and 0.033 inch (0.84 mm) inner diameter, 0.043 inch (1.09 mm) outer diameter Pebax 7233 tube.

60. An optical switch element in accordance with claim 56, wherein the tubes are separated by rigid divider plates that are uniformly spaced apart in the stacked arrangement.

61. An optical switch element in accordance with claim 60, wherein the rigid divider plates are 0.005-inch (0.13 mm) to 0.010-inch (0.25 mm) thick stainless steel and stacked to produce a 0.040-inch (1.02 mm) pitch.

62. An optical switch element located between an array of optical fiber slack tensioning pulleys on the rear side and an array of moveable fiber connectors on the front side, the rear and front side spanned by contiguous optical fibers that follow straight-line paths in the volume between the front size and the optical switch element, wherein each optical fiber passes through an intermediate tube comprised of a rigid element, one or more flexible elements, and a low friction element.

63. An optical switch element in accordance with claim 62, wherein the flexible elements are selected to limit the bend radius experienced by the tensioned optical fiber to be greater than or equal to 5 mm.

64. An optical switch element in accordance with claim 63, wherein static tension on the optical fibers is in the range of approximately 28 to 57 grams (1 to 2 ounces).47© TELESCENT INC All Rights Reserved Proprietary and Confidential until published as patent application or issued patent

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