ALIGNMENT DEVICE

CROSS REFERENCE TO RELATED APPLICATIONS

This application is being filed on August 20, 2015, as a PCT International Patent Application and claims priority to U.S. Patent Application Serial No. 62/052,816 filed on September 19, 2014, and claims priority to U.S. Patent Application Serial No. 62/092,021 filed on December 15, 2014, the disclosures of which are incorporated herein by reference in their entireties.

TECHNICAL FIELD

The present disclosure relates to optical fiber connection systems and to devices and methods for aligning two fibers end-to-end.

BACKGROUND

Modern optical devices and optical communications systems widely use fiber optic cables. Optical fibers are strands of glass fiber processed so that light beams transmitted through the glass fiber are subject to total internal reflection wherein a large fraction of the incident intensity of light directed into the fiber is received at the other end of the fiber.

Many approaches to achieve fiber alignment can be found in the prior art, among them are V-grooves and ferrules. Ferrule based alignment systems including include ferruled connectors which use cylindrical plugs (referred to as ferrules) that fit within an alignment sleeve (e.g., a cylindrical split sleeve with elastic characteristics) to perform fiber alignment. Precision holes are drilled or molded through the centers of the ferrules. Optical fibers are secured (e.g., potted) within the precision holes with polished ends of the optical fibers located at end faces of the ferrules. Precise fiber alignment depends on the accuracy of the central hole of each ferrule. Fiber alignment occurs when two ferrules are inserted into an alignment sleeve such that the end faces of the ferrules oppose one another and the optical fibers supported by the ferrules are co-axially aligned with one another. Normally, ferruled connectors use ceramic or metal ferrules in which the precision center holes are drilled. Disadvantageously, drilling of such a central hole that is accurate enough for aligning can be difficult. In addition, a connector containing a ferrule has very high manufacturing costs. Therefore looking for adequate alignment solutions containing ferrule-less connectors would be more desirable.

V-grooves are commonly used in prior-art ferrule-less fiber optic alignment devices. An example is the V-groove method described in US 6,516,131 used for alignment of optical fiber ends. The V-groove is uni-directionally or bi-directionally tapered for enabling easy positioning of the fibers. Optical fibers are pressed into the V- grooves and line contact between the optical fibers and the surfaces of the V-grooves assists in providing precise alignment of the optical fibers. In one example, two optical fibers desired to be optically connected together are positioned end-to-end within a V- groove such that the V-groove functions to co-axially align the optical fibers. End faces of the aligned optical fibers can abut one another.

SUMMARY

One aspect of the present disclosure relates to a device and method for aligning two fibers end-to-end. Co-axial alignment can be provided between the optical fibers of two fiber optic connectors so as to provide an optical coupling between the optical fibers. In such an embodiment, the optical connectors can be ferrule-less optical connectors. Co-axial alignment can also be provided between the end of an optical fiber of a fiber optic cable and a stub end of an optical fiber supported by a ferrule. In certain embodiments, fiber alignment devices in accordance with the principles of the present disclosure can accurately align optical fiber while using a minimal number of parts to reduce cost and facilitate assembly.

The term "fiber" as used herein relates to a single, optical transmission element having a core usually having a diameter of 8-12 μιη and a cladding usually having a diameter of 120-130 μιη, wherein the core is the central, light-transmitting region of the fiber, and the cladding is the material surrounding the core to form a guiding structure for light propagation within the core. The core and cladding can be coated with a primary coating usually comprising one or more organic or polymer layers surrounding the cladding to provide mechanical and environmental protection to the light-transmitting region. The primary coating may have a diameter ranging e.g. between 200 and 300 μιη. The core, cladding and primary coating usually are coated with a secondary coating, a so- called "buffer", a protective polymer layer without optical properties applied over the primary coating. The buffer or secondary coating usually has a diameter ranging between 300-1100 μιη, depending on the cable manufacturer. The term "light" as used herein relates to electromagnetic radiation, which comprises a part of the electromagnetic spectrum that is classified by wavelength into infrared, the visible region, and ultraviolet.

Index matching gel can be used with alignment devices in accordance with the principles of the present disclosure to improve the optical connection between the open light transmission paths of the first and second optical fibers. The index matching gel preferably has an index of refraction that closely approximates that of an optical fiber is used to reduce Fresnel reflection at the surface of the bare optical fiber ends. Without the use of an index-matching material, Fresnel reflections will occur at the smooth end faces of a fiber and reduce the efficiency of the optical connection and thus of the entire optical circuit.

A self-centering structure is provided in accordance with a fiber alignment system to align fibers from ferrule-less connector plugs or other structures. The fibers protruding from the plugs are guided and aligned by a self-centering device, including a cantilever member which projects at least partially at an angle toward the fiber axis.

The self-centering devices can be assembled in a module, such as positioned within a split sleeve or other structure, or held together by other methods, wherein each self-centering device includes at least one cantilever member.

In one example implementation, each self-centering device includes three cantilever members positioned around the fiber axis.

Preferably more than one self-centering device is provided per fiber. In one implementation, two self-centering structures are provided for each fiber.

In one example, if the self-centering structures are provided with a single cantilever member, the cantilever member presses the fiber toward a groove structure, such as a V-groove, or a gap or slot. The V-groove can be defined by two parallel rods.

In another example, if the self-centering structures are provided with plural cantilever members spaced around the fiber axis, the cantilever members press the fiber toward the other one or more cantilever members to centralize the fiber at the fiber axis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a first embodiment in perspective view of a self-centering structure for centering two optical fibers;

FIG. 2 is a partial cross-sectional perspective view of the self-centering structure of FIG. 1; FIG. 3 is a perspective view of a self-centering device of the self-centering structure of FIGS. 1 and 2;

FIG. 4 is a perspective view of the self-centering device of FIG. 3;

FIG. 5 is a sectional view of a portion of the self-centering device of FIGS.

3 and 4;

FIG. 6 is a second embodiment in perspective view of a self-centering structure for centering two optical fibers;

FIG. 7 is a top view of the self-centering structure of FIG. 6;

FIG. 8 is a side view of the self-centering structure of FIG. 6;

FIG. 9 is an end view of the self-centering structure of FIG. 6;

FIG. 10 is a cross-sectional end view of the self-centering structure of FIG. 6 taken along lines 10-10 of FIG 8;

FIG. 11 is an exploded perspective view of the self-centering structure of

FIG. 6;

FIG. 12 is an end view of a self-centering device of the self-centering structure of FIGS 6-11;

FIG. 13 is an opposite end view of the self-centering device of FIG 12;

FIG. 14 is a first cross-sectional view of the self-centering device of FIG 12 taken along lines 14-14;

FIG. 15 is a second cross-sectional view of the self-centering device of FIG 12 taken along lines 15-15;

FIG. 16 is a top view of a fiber optic adapter useable with the self-centering structures of FIGS 1-15;

FIG. 17 is a cross-sectional side view of the fiber optic adapter of FIG. 16;

FIG. 18 is a cross-sectional side view of a fiber optic connector useable with the fiber optic adapter of FIGS 16-17;

FIG. 19 is a third embodiment in perspective view of a self-centering structure

for centering two optical fibers;

FIG. 20 is a top view of a portion of the self-centering device of FIG. 19;

FIG. 21 is a side perspective view of FIG. 20;

FIG. 22 is a front perspective view of a portion of the self-centering device of FIG. 19;

FIG. 23 is a top perspective view of FIG. 22; FIG. 24 is a front view of the self-centering device of FIG. 19;

FIG. 25 is a sectional view of a portion of the self-centering device of FIG. 19 without the fibers; and

FIG. 26 is a perspective view of the self-centering structure of FIG. 19 shown having two parts.

DETAILED DESCRIPTION

A self-centering structure 100, 200 is provided in accordance with a fiber alignment construction or system 10 to align fibers from ferrule-less connector plugs 600 or other structures. The fibers 302 protruding from the plugs are guided and aligned by a self-centering device 110, 210, including at least one cantilever member 120, 220 which projects at least partially at an angle toward the fiber axis 124, 224, and terminates at a distal end 122, 222. The cantilever members 120, 220 are flexible to centralize the fiber 302 for alignment with another fiber 302. FIGS 2, 5, and 14 show the angling of the cantilever members. Such a construction allows for the funnel shape for fiber feeding, and for bending to create clamping forces on the fibers. The alignment construction 10 includes a fiber alignment region 103, 203 at an intermediate location between the first and second ends.

The self-centering structures can be assembled in a module or unit 105, 205, such as including a split sleeve 130 or other structure 230, wherein each self- centering structure includes at least one cantilever member 120, 220. Split sleeve 130 holds the separate parts together to form a single unit with an aligned fiber axis. Structure 230 is a press fit arrangement of the parts that remain as a single unit, also for maintaining the aligned fiber axis. Each unit 105, 205 includes opposite ends 107, 207.

In one example implementation, each self-centering structure 100 includes three cantilever members 120.

Preferably more than one self-centering device 110, 210 is provided per fiber. In one implementation, two self-centering devices 110, 210 are provided for each fiber.

If the self-centering structures 200 are provided with a single cantilever member 220, the cantilever member 220 presses the fiber toward a groove structure, such as a V-groove 228, or a gap or slot defined by two parallel rods 226. If the self-centering structures 100 are provided with plural cantilever members 120, the cantilever members 120 press the fiber toward the other one or more cantilever members to centralize the fiber.

The self-centering devices 110, 210 each define a funnel shape 160, 260 to facilitate entry of the fiber 302 along the fiber axis 124, 224 or fiber alignment axis. The self-centering devices 110, 210 are positioned front to back in a stack for single fiber alignment (same direction of projection of the cantilever members). The pairs of stacked self-centering devices 110, 210 are positioned front to front relative to the centerline mating plane for alignment of two fibers end to end (opposite direction of projection of the cantilever members).

With the example embodiments showing four self-centering devices, the outer two serve as a pre-alignment structure. The inner two align the two mating fibers. At the contact zone, a gap 170, 270 is desired between the opposing cantilever members 120, 220 from opposite self-centering devices 110, 210. The gap can range from 100 microns to 1 millimeter. Less than or equal to 1 millimeter is desired. Less than or equal to 750 microns is more preferred, and less than or equal to 500 microns, and even less than 100 microns is useful. The gap avoids interference and allows for good fiber alignment. Index matching gels or oils can be used in the self-centering structures 100, 200. Hole 290 can be used to apply the index matching material.

In the case of self-centering device 110, the component can be made as an integral body 116, including the three cantilever members 120. In the case of self- centering device 210, the component can be made as an integral body 216 with the single cantilever member 220, and a passage 270. Passage 270 receives the two parallel rods 226 in a press-fit manner.

Integral bodies 116, 216 can be made from molded materials. Central passage 180, 280 through the structures 100, 200 is preferably smaller than the outer diameter of the fiber. In one example, forces in the range of 0.1-0.2 Newtons can be generated on the fiber 302 for alignment and centering.

Distal ends 122, 222 of cantilever members 120, 220 include a small center groove 150, 250 to facilitate centering and alignment of the fibers.

The self-centering structures 100, 200 can be used in an adapter 400.

Adapter 400 receives at least on connector 600 on each end 402, 404 for defining a signal path between the two fibers 302 of the two connectors 600. The self-centering structures 100, 200 can be placed in alignment areas 500 within adapter 400. In the example shown, adapter 400 is a duplex adapter for joining two fibers, with each end 402, 404 receiving two connectors 600.

Connector 600 is an example connector, such as further shown in PCT Publication WO2013/117598, the disclosure of which is incorporated by reference.

Connector 600 includes a connector body 602, and a moveable cover 604. A latch 606 latches the connector 600 to the adapter 400. Fiber 302 is shown protruding from the front end 608 of connector 600.

The optical fiber alignment devices can be incorporated into both ends of a fiber optic adapter. The optical fiber alignment devices can be incorporated into an adapter wherein the fiber optic adapter receives a ferrule-less connector on one end and a ferruled connector on an opposite end. The optical fiber alignment devices can also be incorporated into a converter for converting a ferrule-less connector into a ferruled connector.

In other examples, it may be desired to include another alignment structure for fiber optic ribbon cables. The alignment structure can be used to align each of the optical fibers as part of a process to optically connect each of the optical fibers precisely to a fiber optic connector. The optical fibers are held in alignment when provided in the ribbon matrix. FIG. 19 shows an example alignment self-centering structure 300 in accordance with a fiber ribbon alignment construction or system to align fibers from ferrule-less connector plugs or other structures. In one example, a fiber optic ribbon cable may include a plurality of optical fibers 308. Each of the plurality of optical fibers 308 includes a fiber axis 330 and each of the plurality of optical fibers 308 includes a bare optical fiber and a coating surrounding the bare optical fiber to form an external surface of the optical fiber.

The self-centering structure 300 can be made from molded materials. The self-centering structure 300 includes a body 310 having a first end 312, a second end 314, a top 316 and a bottom 311. The first end 312 defines a first opening 303 and the second end 314 defines an opposite second opening 304. The first and second openings 303, 304 each provide for optical fibers 308 to be centered and oriented in the bottom 311 of the self-centering structure 300. The bottom 311 has a plurality of groove structures 306 integrally formed, such as a V-grooves, or gaps, or slots. It will be appreciated that the groove structures 306 can include other groove profiles using various materials and manufacturing processes. FIGS. 20-21 show the groove structures 306 in parallel alignment that extend along the fiber axis 330. Each of the plurality of optical fibers 308 may be inserted through the bottom 311 of the first and second openings 303, 304 such that the fibers are disposed within the groove structures 306 in a substantially uniform orientation to facilitate centering and alignment of a first plurality of optical fiber 308a with a second plurality of optical fiber 308b. In this manner, as a non-limiting example, the self- centering structure 300 provides an alignment of the first plurality of optical fibers 308a in the first opening 303 to the second plurality of optical fibers 308b in the second opening 304.

As depicted in FIG. 19, twelve optical fibers 308 are aligned in each of the first and second openings 303, 304 relative to one another. The first plurality of optical fibers 308a extend from the first opening 303 at the first end 312 into the self-centering structure 300 to align with the second plurality of optical fibers 308b extending from the second opening 304 at the second end 314 of the self-centering structure 300.

The top 316 of the body 310 of the self-centering structure 300 comprises a planar region 318. The planar region 318 contains a recess 320 including a plurality of cantilever members 322. In one example, the plurality of cantilever members 322 extend from the planar region 318 and project at least partially downward at an angle toward the optical fibers 308. It will be appreciated that the plurality of cantilever members 322 may be configured to press the optical fibers in the grooves without being angled down. For example, a cantilever member may include a bump (e.g., projection) that extends from the body of the cantilever to engage the fibers and press the fibers into a respective groove.

Referring again to FIG. 19, a first set of cantilever members 322a are generally on the first end 312 of the self-centering structure 300 and can extend downwardly in the recess 320 at an angle toward the first plurality of optical fibers 308a at the first opening 303. A second set of cantilever members 322b are generally on the second end 314 of the self-centering structure 300 and can extend downwardly at an angle toward the second plurality of optical fibers 308b at the second opening 304. As described above, the arrangement and configuration of the first and second plurality of cantilever members 322a, 322b may vary in other embodiments such that they do not angle downward into the recess 320.

In one example, the first set of cantilever members 322a are flexible and configured for urging each of the first plurality of optical fibers 308a into their respective groove structures 306 and the second set of cantilever members 322b are flexible and configured for urging each of the second plurality of optical fibers 308b into their respective groove structures 306. In other words, the first and second sets of cantilever members 322a, 322b respectively align the first and second plurality of optical fibers 308a, 308b to one another.

Referring to FIGS. 22-23, the recess 320 has an open bottom 324 such that a fiber alignment region 305 (see FIG. 19) is made visible between the first and second sets of cantilever members 322a, 322b. The fiber alignment region 305 can help to facilitate centering and alignment of the optical fibers 308 with another optical fiber 308. The cantilever members are arranged and configured on opposite sides of the fiber alignment region 305. The cantilever members are shown having one row on each side of the fiber alignment region 305. It will be appreciated that other embodiments can include two or more rows on each side of the fiber alignment region 305. The cantilever members 322 are flexible to centralize the optical fibers 308 for alignment with another optical fiber 308 in the fiber alignment region 305. FIGS. 23 and 25 show one configuration of the cantilever members 322 being angled downward to allow for bending to create clamping forces on the optical fibers 308 while in the groove structures 306 as shown in FIG. 24. It will be appreciated that other arrangements and configurations of the cantilever members 322 may be used.

The self-centering structure 300 can be assembled as a single module or unit including the groove structures 306 and cantilever members 322. The self-centering structure 300 can be made as an integral body including the twelve cantilever members 322 and groove structures 306. In other examples, a self-centering structure 300a can include two parts as shown in FIG. 26. A first part 326 including the groove structures 306 and a second part 328 including the cantilever members 322. The first and second parts 326, 328 can be press fit together to form a single unit with an aligned fiber axis. The cantilever members 322 press the fibers toward the other respective cantilever members 322 to centralize the fibers.

From the forgoing detailed description, it will be evident that modifications and variations can be made without departing from the spirit and scope of the disclosure. PARTS LIST

10 Alignment construction

100 Self-centering structure

103 Fiber alignment region

105 Alignment construction

107 Ends

1 10 Self-centering devices

116 Integral body

120 Cantilever member

122 Distal end

124 Fiber axis

130 Split sleeve

150 Alignment groove

160 Funnel shape

170 Gap

180 Central passage

203 Fiber alignment region

205 Unit

207 Ends

210 Self-centering devices

216 Integral body

220 One cantilever member

222 Distal end

224 Fiber axis

226 Alignment rods

228 V-groove

230 Structure

250 Alignment groove

260 Funnel shape

270 Passage

280 Central passage

290 Hole

300 Self-centering structure

302 Fiber

303 First opening 304 Second opening

305 Fiber alignment region

306 Groove structure

308 Optical fibers

308a First plurality of optical fibers

308b Second plurality of optical fibers

310 Body

312 First end

311 Bottom

314 Second end

316 Top

318 Planar region

320 Recess

322 Cantilever members

322a First set of cantilever members

322b Second set of cantilever members

324 Open bottom

326 First part

328 Second part

330 Fiber axis

400 Adapter

402 End

404 End

500 Alignment areas

600 Connector

602 Connector body

604 Moveable cover

606 Latch

608 Front end