USRE35935E - Fiber optic connectors - Google Patents

Abstract

A fiber optic terminus assembly for use in a fiber optic connector is disclosed in which a gripper element and a radially deformable ferrule are compressed into gripping engagement with the optical fiber portion of an optical cable. A terminus body and a contact sleeve engage the outer layer of the optical cable and the ferrule and position the fiber at a preselected distance from a lens surface.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of application Ser. No. 07/403,097, filed Sep. 5, 1989, and now abandoned, the text of which is hereby incorporated by reference.

The invention relates to connectors for providing the mechanical and optical interconnection between optical fibers. More particularly, the invention relates to a fiber optic terminus that provides strain relief for the fiber portion as well as surrounding strength layers of the cable and that self-aligns the end of the fiber portion within a focal zone in a lens-type connection. The terminus of the present invention is relatively simple in construction, and is simple to install while being effective in operation.

BACKGROUND OF THE INVENTION

The use of fiber optics as a transmission medium provides communication of data at high speeds, great reliability, and relatively low cost. However, the installation and maintenance requirements of fiber optic networks have posed practical difficulties. Principal among these difficulties is the interconnection of pairs of fiber optic cables. Typically, fiber optic termini require precise alignment between two extremely small fiber cores in order to provide low-loss signal transmission. Alternatively, a lens arrangement may be placed between the two fibers, but precise alignment and axial positioning over a wide range of environmental conditions are still necessary. With either mode of connection, it is important to capture the fiber end at a closely controlled location, because the position of the fiber end, relative to either the other fiber end or to a lens, has a critical impact on the efficiency of the optical interconnection.

Fiber optic connectors in general are very susceptible to longitudinal forces on the fiber. Retention of the fiber forming the interconnection is therefore another frequent problem. Each fiber must be secured to prevent relative movement of the fibers since virtually any movement will adversely effect the quality of the interconnection. The physical attachment of the fiber, however, must avoid the application of undue stress on the fiber, which may cause microbend attenuation or, possibly, eventual breakage of the fiber due to stress fatigue. Further, the fiber ends must be kept clean and protected, both in the mated condition and in the open, unmated position. The fiber core sizes which are typically of interest, usually 50 to 200 microns, necessitate attention to the control of dirt and field cleanability.

Known fiber optic connectors usually employ the coupling of the ends of two connecting fibers. The ends of the fibers are glued or otherwise secured into ferrule subassemblies which are then brought into actual or virtual contact within a common alignment sleeve. Such connectors, however, tend to fail when the glue or adhesive employed to secure the fibers degrades after extended use. Further, such connectors tend to misalign upon the application of rotational, longitudinal or lateral forces.

Other types of fiber optic connectors, including known lens types, while they perform satisfactorily under certain circumstances, are overly complex and difficult to install and maintain. The assembly of complex mechanical parts associated with such connectors involves considerable wasted effort owing to aligning the fiber within the connector and completing the mechanical connection of the cable. Moreover, such complex systems typically suffer breakdowns after extended periods of use.

SUMMARY OF THE PRESENT INVENTION

Therefore, it is an object of the present invention to provide an improved fiber optic terminus. More specifically, it is an object of the present invention to provide a novel mode for capturing an optical fiber against the forces that tend to displace it.

It is another object of the present invention to provide a fiber optic terminus having separate locations for securing the fiber core and the surrounding strength layer of a fiber optic cable.

It is still another object of the present invention to provide a fiber optic terminus which is self aligning upon completion of the interconnection between two fiber cores.

It is still another object of the present invention to provide a fiber optic terminus that may be easily installed, even with hand tools, requiring far less time than known termini, yet which provides good gripping of the fiber and accurate positioning of the fiber end and also maintains a high degree of stress relief engagement with the cable.

It is still another object of the present invention to provide a fiber optic terminus that is durable and reliable.

It is a further object of the present invention to provide fiber optic termination within a small profile such as within a space normally providing a conventional electrical contact.

Generally, the objects of the present invention are accomplished in a terminus that provides one half of an optical connection in a lens type arrangement by securing a fiber optic cable at its fiber and its surrounding strength layer. To effect the termination, at least a portion of the strength layer is removed from the fiber. A novel compressible ferrule is placed between the exposed fiber and the removed strength layer and includes a head section having a reference surface at its distal end and a serrated tail section. The ferrule includes a compressible fiber gripping insert having a centrally disposed aperture that receives the exposed fiber. Advantageously, the head section surrounds the insert and is crimped around the insert directly on the fiber to securely grip the fiber. The strength layer is placed between the serrated portion of the ferrule and the inner surface of a compressible sleeve member. The strength layer is thereafter backfolded over the outer surface of the sleeve member. The fiber is then cleaved to length, as by an appropriate tool. A terminus body including an annular end section is advanced over the assembly including the ferrule, insert, sleeve, and cable. In accordance with an important feature of the invention, the terminus body includes a reference stop which is positioned at a preselected distance from a lens surface. When the body is crimped in place, the ferrule reference surface abuts the reference stop, thereby aligning the fiber end at a known distance from the lens surface.

While the invention disclosed herein has been described primarily with reference to termini for interconnection of a pair of fiber, it is understood that it is within the scope of the invention to provide termini having an array of locations for interconnecting multiple fibers which incorporates the same novel features. Further, while the terminus of the present invention will be described herein as generally cylindrical, it will be understood that other geometrical configurations may be utilized.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a detailed cross sectional view of a fiber optic terminus subassembly employing teachings of the present invention.

FIG. 2 is a detailed cross sectional view of the subassembly of FIG. 1 mating within an outer contact body to form a fiber optic pin terminus.

FIG. 3 is an exploded perspective view of the ferrule and gripping insert of FIG. 1.

FIG. 4 is a cross sectional view of a pin terminus assembly for forming one half of an optical fiber termination, as in FIG. 1 but without the optical fiber cable.

FIG. 5 is an exploded cross sectional view of the pin assembly of FIG. 4.

FIG. 6 is a cross sectional view of a corresponding complementary socket assembly which mates with the pin assembly of FIG. 4 to form a fiber optic termination employing the present invention.

FIG. 7 is an exploded cross sectional view of the socket assembly of FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following detailed description will permit a more complete understanding of this invention. However, the embodiments described below are simply examples of the invention and the invention is not limited to these embodiments. Furthermore, the drawings are not necessarily to scale. In certain instances, details may have been omitted which are not necessary for an understanding of the present invention.

Generally, the present invention relates to a terminus for interconnecting a pair of fiber optic cables. The device of this invention is intended to be used in the type of optical terminating arrangement using a lens expanded beam system wherein a first lens is employed to capture and collimate the light emerging from one fiber and project the light to a second lens. The second lens receives the light and refocuses the light on a receiving fiber.

Turning first to FIG. 4 and also to FIG. 5, therein is shown the assembled components of apin terminus assembly 8 for forming one half of a fiber optical connection. Thepin terminus 8 includes abuffer ferrule 10 and grippinginsert 12, and acrimp sleeve 14, for forming asubassembly 15 which is further illustrated in FIGS. 1-3. As discussed further below, theterminus 8 also includes anouter terminus body 36, alens 34, analignment sleeve 42 and afiber guide 44.

Turning now to FIG. 1, thefiber optic connector 8 has a particular application for use with a fiber optic cable 17 having afiber portion 20 which transmits and receives optical waves, aninner jacket layer 19 anintermediate strength layer 18 that encloses thefiber portion 20 and theinner jacket layer 19, and anouter layer 16. Typically, theintermediate strength layer 18 of the cable 17 is formed of a durable material. For example, thestrength layer 18 may be fabricated of braided Kevlar or fiberglass to minimize stress on the fiber. The fiber portion in the illustrated embodiment is a single cylindrical fiber having, for example, a diameter of 140 or 250 microns.

As is shown in FIG. 1 and also in FIG. 3, theferrule 10 is formed with ahead portion 22 including anend surface 28 that provides a reference plane for thebuffer ferrule subassembly 15 as will be noted further below, and atail section 26 which includes a serratedgripping portion 24. Thetail section 26 interfits between thestrength layer 18 and theinner jacket layer 19 of the fiber optic cable 17 when the end portion of thestrength layer 18 is removed or loosened from thefiber portion 20.

It has been found that use of a deformable metal of low elasticity for theferrule 10 permits crimping engagement of theferrule head 22 onto theinsert 12 and the encompassed fiber adequately to assure firm engagement without undue risk of crushing or overstressing the fiber during the crimping step.

Thebuffer ferrule subassembly 15 also includes the annulargripping insert 12, best shown in FIGS. 1-3, placed within thehead portion 22 of theferrule 10. Thebuffer ferrule 10 and thegripping insert 12 are crimped directly onto thefiber portion 20 in order to effectuate a suitable connection. Preferably, the grippinginsert 12 is fabricated of polyethersulfone (PES) and the coatings on the engaged portion of fiber are removed to provide a bare glass fiber engagement portion of the fiber prior to assembly. This has been found to provide an excellent gripping action over a wide operating range of temperatures between minus 55° C. to well over 200° C. Other materials may be substituted in place of PES provided they have a high coefficient of friction on the fiber and are formable and suitably resilient.

Advantageously, the grippinginsert 12 permits minimized pistoning and vibration offiber portion 20. For example, when such abuffer ferrule 10 is crimped onto such an insert about 1/16" long and the enclosed fiber portion in the manner described herein, theinsert 12 resists tension on the engagedfiber portion 20, e.g. up to approximately two pounds of force on the engagedfiber portion 20. Such a retention force is adequate for maintaining the optical fiber in position against forces typically encountered in thermal cycling and vibration. Thebuffer ferrule subassembly 15, however, must not transfer too great a compressive force to theoptical fiber 20 to avoid the problem of crushing or otherwise over-stressing the glass fiber.

It has been found that thebuffer ferrule 10 may be fabricated of stainless steel of high hardness, e.g. a Rockwell B scale of 92-95 to minimize elasticity and obtain a high degree of strength when compressively deformed onto theinsert 12 and encompassed fiber by crimping.

As best shown in FIG. 2, thecrimp sleeve 14 is placed in surrounding relation to thestrength layer 18 over the serrated grippingportion 24 of thebuffer ferrule 10 to "tie off" thestrength layer 18. Thesleeve 14 preferably is formed of a metal or a similar material which, like thebuffer ferrule 10, is non-elastically deformable to effect crimping retention of the enclosed layers. Thus, when thesleeve 14 is thereafter compressed, thestrength layer 18 is securely held between theserrated portion 24 and thesleeve 14. In the preferred embodiment, thesleeve 14 andouter body 36 are also fabricated of a stainless steel, e.g., 302 EZ or 303, hardness not being as significant for these components.

Theend surface 28 serves as a reference plane or surface for determining the plane of cleaving thefiber 20 after the fiber is gripped in thesubassembly 15.

FIGS. 2 and 5 also show theouter body 36 of thepin terminus 8, which has a cavity therethrough to receive the various components. Theouter body 36 includes anannular sleeve portion 38 that forms a receptacle to receive theferrule subassembly 15 and respective grippedfiber portion 20 of the cable 17. Theouter terminus body 36 also includes acentral bore portion 33, apin end portion 35 and areference stop surface 32 located at a predetermined distance from the inwardly disposed proximal surface of alens 34 which is mounted within the outerpin end portion 35. In the preferred embodiment, thelens 34 may be either a gradient index rod lens or a precision ball lens. When the ferrule subassembly is mated within theouter terminus body 36, theend reference surface 28 of thebuffer ferrule 10 abuts thereference stop surface 32 of theterminus body 36. Thereference surface 28 thereby serves as a reference surface both for cleaving the end of thefiber 20 and for positioning the fiber cable 17 and theferrule assembly 15, which results in highly accurate positioning of the end of thefiber 20 relative to thelens 34.

Thus, simply by cleaving thefiber portion 20 of the fiber optic cable 17 at an appropriate predetermined distance from thereference end surface 28 of thebuffer ferrule 10 in the subassembly stage, the end of thefiber portion 20 will be precisely positioned within the focal zone of thelens 34 when the terminus is assembled. Such alignment is necessary to obtain an efficient optical interconnection.

After the entire ferrule andcable assembly 15 is placed within theannular sleeve portion 38 of theouter terminus body 36, theannular portion 38 is crimped to clamp the underlying layers of thestrength material 18 and thesleeve 14 onto theserrated portion 24 of theferrule 10, with corresponding crimp deformation also of thesleeve 14. This arrangement provides strong strain relief retention for the cable to theterminus housing 36 on the order of approximately 50 pounds. The resulting strong mechanical interconnection of thestrength member 18 between theferrule 24 and theterminus body 36 provides strain relief against external forces on the cable being imposed on the fiber, such as tension forces and vibrational forces. Thus, this strong interconnection fixes thesubassembly 15 in position as with the reference surfaces 28 and 32 in abutment with one another, to maintain the cleaved end of the fiber in its desired position relative to thelens 34 despite external stresses transmitted through the cable or thehousing 36.

It will be appreciated that another advantage of the present invention is that a defective termination of the fiber cable 17 results in a minimum loss of componentry. Since theouter body 36 ofpin terminus 8 is mated with the ferrule and cable assembly after termination of the fiber cable 17, any shortcomings in the mechanical or optical termination of fiber cable 17 result only in the loss offerrule 10 and not in the loss of theentire pin terminus 8.

Lateral alignment of thefiber portion 20 in connection with thelens 34 is provided by aprecision fiber guide 44 which fits within thepin section 35 adjacent thelens 34. Thefiber guide 44 may, for example, be fabricated of sapphire or ceramic. The alignment advantages of such material will be appreciated by those skilled in the art. Adjacent thefiber guide 44 is thealignment sleeve 42 which also is mounted in thepin end portion 35. Thealignment sleeve 42 mechanically secures thefiber guide 44 in proper alignment and also provides a passive guide for thefiber portion 20 entering thealignment sleeve 42.

The pitch of thelens 34 is chosen so that thefiber portion 20 must be a small distance from thelens 34 in order for the image to be properly focused. One important advantage of this arrangement is that thefiber portion 20, when cleaved, never comes in contact with thelens 34. Damage to thelens 34, either during termination of the fiber optic cable 17 or during subsequent environmental or mechanical stress, is thereby avoided.

The other half of the optical interconnection is provided by asocket terminus assembly 46, shown in FIGS. 6 and 7 which is generally similar to the afore-described pin terminus in the manner of engaging the respective optical fiber and cable, but with appropriate modifications in the outer housing portions for complementary mating with apin terminus 8. Thesocket assembly 46 includes anouter body 48 which is similar to thebody 36 of thepin terminus 8, but modified in certain respects to a socket configuration for its mating engagement with thepin terminus 8. Thus, it also receives analignment sleeve 42,fiber guide 44 andlens 34 within its socket bore 49. The fiber and cable are gripped in the same manner in anidentical subassembly 15. Thus, as withpin assembly 8,socket assembly 46 includes abuffer ferrule 10, insert 12 and acrimp sleeve 14. The location and operation of these elements are the same as described in connection withpin assembly 8.

Acoupler sleeve 52 and "napkin" or clampingring 54 are provided for joining the pin andsocket connectors 8 and 46. Thecoupler sleeve 52 is pre-fitted over acylindrical end portion 56 ofsocket assembly 46 and includes a resilientsplit barrel portion 58 to receive the cylindricalpin end section 35 of thepin assembly 8, to provide a mating interconnection betweensocket assembly 46 andpin assembly 8. Thering 54 is thereafter compressed over the end of the coupler sleeve which engagesconnector 8 to conveniently secure this interconnection. When thecoupler sleeve 52 is in place, the interconnection provides lateral and angular alignment of the twotermini 8 and 46 and thus of the mating fibers. The telescopic connection afforded by the coupler sleeve allows for variations in the relative longitudinal positions of thetermini 8 and 46, such as may be attributable to tolerances in the connectors in which the termini are supported.

While particular outer shapes for thehousings 36 and 46 are disclosed, a variety of different termini housing shapes may be provided. The outer geometry of the termini will, of course, be dictated by constraints of the various interconnecting housings depending on the particular application. By employing the teachings of the present invention, the termini may fit within a small profile, such as for fitting within the envelope of space allowed for a conventional electrical contact, as in a hybrid connector.

To effect termination of an optical fiber in either terminus, therespective sleeve 14 is first propositioned over theouter layer 16 of the fiber optical cable 17. Theouter layer 16 of the cable 17 is removed from the distal end portion of the cable 17. Thestrength layer 18 is thereafter pulled away from theinner jacket 19. Theinner jacket 19 is removed from the fiber to expose a bare portion of theoptical fiber 20 and the fiber is preferably cleaned of any remaining coating.

The buffer ferrule subassembly, including theferrule 10 and grippinginsert 12, is then assembled directly onto the cable, with the serrated grippingportion 24 and thetail portion 26 sliding over theinner jacket 19 until thetail portion 26 abuts an unremoved portion of thestrength layer 18. In this operation, thefiber portion 20 is threaded through theinsert 12 in thebuffer end 22. It has been found that preparation of the fiber surface with a chemical agent may enhance the fiber strength and improve the engagement of thegripping insert 12. Thehead portion 22 of thebuffer ferrule 10 is then crimped or otherwise compressed radially inward to compress theinsert 12 against the exposedfiber portion 20 for gripping the fiber. The dimensions and conditions of theinsert 12 preferably are controlled such that theinsert 12 does not project from the end of theferrule 10. Some elongation of theinsert 12, particularly along thefiber surface 20, will typically occur. Once thebuffer ferrule 10 is crimped onto thefiber portion 20, theend reference surface 28 of theferrule 10 provides a reference plane relative to the gripped fiber for subsequent operations. These include scribing and cleaving the fiber at a fixed predetermined distance from theend surface 28 which take place after the strength layer is secured to theferrule 10.

Thereafter, thestrength layer 18 is urged forward over thebuffer ferrule 10. Thecrimp sleeve 14 is advanced over the serrated grippingportion 24 of theferrule 10, and the outer ends of thestrength layer 18 are folded back over the outer surface of thecrimp sleeve 14, as best seen in FIG. 2.

The assembled fiber and ferrule assembly is then advanced within theannular sleeve 38 of theouter terminus body 36. This fiber and ferrule assembly is advanced until thereference surface 28 abuts areference stop surface 32 in theterminus body 36. This operation precisely positions the end of thefiber portion 20 within the focal zone of thelens 34. Theannular portion 38 of the terminus body which surrounds thesleeve 16 and respective portions of thestrength elements 18 is then crimped or otherwise deformed inward to clamp the underlying layers of thestrength material 18 and thesleeve 14 onto theferrule gripping portion 24 for strain relief retention of the fiber contact assembly. In this arrangement, the two layers of thestrength material 18 are clamped between the metal layers 24, 14, and 36.

From the description thus far provided, a fiber optic connector that meets the aforestated objectives by providing a simple crimp and cleave assembly without the use of epoxies or other fillers has been described. It will be apparent that the proposed fiber optic connector may be used in a number of applications and that a number of modifications can be made in the invention disclosed, particularly by those having the benefit of the foregoing teachings, without departing from the spirit of these principles. For example, it will be understood that the mode of crimping and engaging thefiber portion 20 in thebuffer ferrule subassembly 15 may be utilized in assemblies where there is no joinder of thestrength layer 18 to theferrule 10, for example where the individual fibers are part of a multi-fiber cable having a single strength layer which is secured to other components of a connector. Also, the stress relief gripping arrangement may be utilized with other fiber holders. However, these features preferably are utilized together in the advantageous assembly described herein. Accordingly, while the invention disclosed herein has been described with reference to the presently contemplated best mode for practicing the invention, it is intended that this invention be limited only by the scope of the appended claims.

Claims (26)

What is claimed is:

1. A fiber optic terminus positioning assembly for closely controlling the axial position of an optical fiber end in a fiber optic connector, said terminus assembly comprising a single optical fiber having a bare portion of said fiber free of covering . .and coating.!., said bare portion having a terminal end, a resilient fiber gripper element of . .a material.!. .Iadd.polyethersulfone .Iaddend.which has a high coefficient of friction with the material of which said fiber is formed, said gripper element being distinct from any such fiber covering . .or coating.!. and in direct surface-to-surface contact with the surface of said bare portion of said fiber, and a metal support element surrounding said fiber portion and said gripper element in a predetermined axial position relative to said terminal end, said support element being in compressive engagement with said gripper element and thereby compressing said gripper element into gripping engagement with said bare fiber portion for retaining said terminal end of said fiber in said predetermined axial position relative to said support element.

2. The invention as in claim 1 wherein said support element forms a unitary continuous annulus around said gripper element and said fiber portion and is formed of a hard material having a low coefficient elasticity and includes at least a part thereof which is . .inelasticity.!. .Iadd.inelastically .Iaddend.deformed formed inwardly to effect such compressive engagement with said gripper element.

3. The invention as in claim 2 wherein said fiber is formed of glass . .and said gripper element is composed of polyethersulfone.!..

4. The invention as in claim 3 wherein said support element is composed of stainless steel.

5. The invention as in claim 2 wherein said support element is composed of stainless steel.

6. The invention of claim 2 wherein said gripper element is a unitary continuous sleeve surrounding said bare portion of said fiber, and said support element is a unitary continuous sleeve portion surrounding said gripper element.

7. The invention of claim 1 wherein said optical fiber is covered substantially throughout its length by a protective covering, said covering having a proximal terminal end, said bare portion projecting beyond said proximal terminal end of said covering, and said resilient fiber gripping element is located on said bare portion beyond said proximal terminal end of said covering.

8. . .The invention of claim 7.!. .Iadd.A fiber optic terminus positioning assembly for closely controlling the axial position of an optical fiber end in a fiber optic connector, said terminus assembly comprising a single optical fiber having a bare portion of said fiber free of covering, said bare portion having a terminal end, a resilient fiber gripper element of a material which has a high coefficient of friction with the material of which said fiber is formed, said gripper element being distinct from any such fiber covering and in direct surface-to-surface contact with the surface of said bare portion of said fiber, and a metal support element surrounding said fiber portion and said gripper element in a predetermined axial position relative to said terminal end, said support element being formed of a hard material having a hardness of at least about 92 on the Rockwell B scale and having a low coefficient of elasticity and including at least a part thereof which is inelastically deformed inwardly in compressive engagement with said gripper element and thereby compressing said gripper element into gripping engagement with said bare fiber portion for retaining said terminal end of said fiber in said predetermined axial position relative to said support element, wherein said optical fiber is covered substantially throughout its length by a protective covering, said covering having a proximal terminal end, said bare portion projecting beyond said proximal terminal end of said covering, and said resilient fiber gripping element is located on said bare portion beyond said proximal terminal end of said covering, and .Iaddend.wherein said terminus assembly includes first mating means, said fiber optic connector including a complimentary terminus assembly with second mating means for engaging said first mating means to form a fiber optic connection, said terminal end of said bare portion projecting to a predetermined axial distance in relation to said complimentary terminus assembly when said first and second mating means are engaged.

9. A terminus assembly for use in an optical fiber connector by securing, at a predetermined distance from a lens surface, a fiber optic cable having a fiber surrounded by a strength layer with at least a portion thereof removed from said fiber to expose a portion of said fiber comprising:

a radially deformable ferrule . .for placement between said exposed fiber portion and said removed strength layer.!., said ferrule having a head section with a reference surface at its distal end and a tail section .Iadd.for placement between said exposed fiber portion and said removed strength layer.Iaddend.,

an insert disposed within said head section and having a centrally disposed aperture therethrough for receiving said fiber portion, said insert being resilient and compressible into gripping engagement with such a fiber disposed in said aperture, said head section engaging and compressing said insert with said fiber portion therein when deformed radially inward, and

a terminus body having a cavity therethrough and a compressible annular portion for receiving said ferrule . .means.!., an optical coupler lens disposed in said cavity and having opposite end surfaces exposed therewithin, said terminus body including a reference stop fixed at a preselected distance from said lens for engagement by said reference surface of said ferrule whereby an end of a fiber retained in said ferrule by said insert will be in a predetermined position relative to the proximal surface of said lens when said reference surface abuts said terminus body reference stop and said annular portion is compressed to retain said ferrule . .means.!. and said . .contact sleeve.!. .Iadd.terminus body .Iaddend.in position with said reference stop against said reference surface.

10. The invention of claim 9 further comprising a deformable sleeve member received within said annular portion and over said tail section for engaging said removed strength layer with said tail section when said strength layer is disposed over said tail section and said sleeve member is compressed radially inward.

11. The invention of claim 10 wherein said ferrule . .means.!. and said sleeve member are fabricated of stainless steel.

12. The invention of claim 11 wherein said . .contact.!. .Iadd.terminus .Iaddend.body is fabricated of stainless steel.

13. A terminus assembly including the assembly as in claim 10 and a fiber optic cable including an optical fiber and a strength layer, a portion of said strength layer being disposed between said tail portion of said ferrule and the inside surface of said sleeve member and then back folded between the outside surface of said sleeve member and the inside surface of said annular portion of said . .contact.!. .Iadd.terminus .Iaddend.body to provide multiple locations of gripping engagement with said strength layer when said annular portion and said sleeve member are compressed radially inward.

14. The invention as in claim 13 wherein said ferrule, said sleeve member and said terminus body are of stainless steel.

15. The invention of claim 9 wherein said radially compressible insert is fabricated of polyethersulfone to reduce vibration of said fiber and to promote operability over a wide temperature range.

16. The invention of claim 9 wherein said terminus assembly includes first mating means, said fiber optic connector including a complimentary terminus assembly with second mating means for engaging said first mating means, . .said.!. .Iadd.the .Iaddend.terminal end of said . .bare portion.!. .Iadd.fiber .Iaddend.projecting to a predetermined axial distance in relation to said complimentary terminus assembly when said first and second mating means are engaged.

17. A terminus assembly for use in forming a termination of a fiber optic cable which includes an optical fiber and a flexible strength layer surrounding said fiber, said assembly comprising a metal support element formed of a deformable metal having a low coefficient of elasticity and having a cavity therethrough, a resilient fiber gripper element of a material which has a high coefficient of friction with the material of which said optical fiber is formed, said gripper element being mounted in said cavity in a first portion of said support element and being of a configuration to receive a portion of such an optical fiber therethrough and to be disposed between such fiber received therein and the inner surface of said cavity, whereby said first portion of said support element and said gripper element may be compressed for thereby compressing said gripper element into resilient gripping engagement with said fiber portion for retaining such a fiber in a predetermined position relative to said support element, said metal support element including a further portion at one end thereof including an annular wall of a configuration to receive such a strength layer thereover, an inelastically deformable metal sleeve of a size and configuration to be disposed in surrounding relation to such a strength layer over said further portion, and a metal housing for surrounding said support element and including a crimp portion to be disposed over said sleeve and a further layer of such strength layer overlying said sleeve when said sleeve is assembled over said further portion, and said crimp portion being inelastically deformable, whereby said crimp portion and said sleeve may be crimped radially inward to effect gripping engagement of such layers of strength material between said further portion and said sleeve and between said sleeve and said crimp portion for strain relief engagement of said cable to said support element and positioning retention of said fiber by said gripper element.

18. A method of forming a terminus assembly for an optical fiber provided with . .coating and.!. .Iadd.at least one .Iaddend.covering . .layers.!. .Iadd.layer .Iaddend.comprising the steps of removing coverings . .and coatings.!. from a portion of said fiber to form a bare portion of said fiber

providing a fiber support housing element formed of a hard metal having a low coefficient of elasticity and having a cavity therethrough,

providing a gripper element formed of an elastic .Iadd.polyethersulfone .Iaddend.material having a high coefficient of friction with said bare portion of said fiber,

positioning said gripper element and said optical fiber in said cavity with said gripper element in surrounding relation to said bare portion of said fiber,

crimping at least a portion of said support housing element circumjacent said gripper element to inelastically deform said portion of said support housing element and thereby compressing said gripper element into firm resilient surface-to-surface contact with said bare portion of said fiber in position in said terminus assembly

and, forming a terminal end of said fiber at a predetermined longitudinal position relative to said support housing element.

19. The invention as in claim 18 wherein said fiber is formed of glass . .and said gripper element is composed of polyethersulfone.!..

20. The invention as in claim 19 wherein said support housing element is composed of stainless steel.

21. The invention as in claim 18 wherein said support housing element is composed of stainless steel.

22. A method for positioning a fiber optic cable having a fiber surrounded by a strength layer at a predetermined distance from a lens surface to provide one half of an optical connection comprising the steps of:

separating said strength layer from said fiber along an end portion of said fiber optic cable to expose a portion of said fiber;

threading a ferrule between said fiber and said strength layer, said ferrule having a compressible head section including a compressible insert with an aperture to receive said exposed fiber portion and a reference edge at its distal end, said ferrule having a tail section with serrations along at least a portion thereof:

compressing said head section to firmly engage said insert with said fiber;

advancing a sleeve over said strength layer to surround said serrated portion;

folding said strength layer over the outer surface of said sleeve . .member.!.;

advancing said ferrule within a terminus body having an annular section for receiving said ferrule, said terminus body having a reference stop whereby when said ferrule reference edge abuts said terminus body reference stop said fiber is aligned with said lens surface; and

compressing said terminus body annular section to engage the inside surface of said terminus body annular section with said strength layer thereunder and to engage said strength layer with said sleeve . .member.!. and to engage said strength layer .Iadd.under said sleeve .Iaddend.with said tail portion.

23. A fiber optic connector comprising:

a pin terminus assembly for securing, at a predetermined distance from a lens surface, a first fiber optic cable having a fiber surrounded by a strength layer with at least a portion thereof removed from said fiber to expose a portion of said fiber, said pin terminus assembly including first radially deformable ferrule means for placement between said exposed fiber portion and said removed strength layer, said first ferrule means having a head section with a reference surface at its distal end and a tail section, a first insert disposed within said head section and having a centrally disposed aperture therethrough for receiving said fiber portion, said insert being resilient and compressible into gripping engagement with such a fiber disposed in said aperture, said head section engaging and compressing said insert with said fiber portion therein when deformed radially inward, and a pin terminus body having a cavity therethrough and a compressible annular portion for receiving said first ferrule means, a first optical coupler lens disposed in said cavity and having opposite end surfaces exposed therewithin, said pin terminus body including a reference stop fixed at a preselected distance from said first lens for engagement by said reference surface of said ferrule .Iadd.means .Iaddend.whereby an end of a fiber retained in said ferrule .Iadd.means .Iaddend.by said insert will be in a predetermined position relative to the proximal surface of said .Iadd.first .Iaddend.lens when said reference surface abuts said terminus body reference stop and said annular portion is compressed to retain said ferrule means . .and said contact sleeve.!. in position with said reference stop against said reference surface; and

a socket terminus assembly for securing, at a predetermined distance from a lens surface, a second fiber optic cable having a fiber surrounded by a strength layer with at least a portion thereof removed from said fiber to expose a portion of said fiber, said socket terminus assembly including second radially deformable ferrule means for placement between said exposed fiber portion and said removed strength layer, said second ferrule means having a head section with a reference surface at its distal end and a tail section, a second insert disposed within said head section and having a centrally disposed aperture therethrough for receiving said second fiber portion, said second insert being resilient and compressible into gripping engagement with such a fiber disposed in said aperture, said head section engaging and compressing said second insert with said fiber portion therein when deformed radially inward, and a socket terminus body having a cavity therethrough and a compressible annular portion for receiving said second ferrule means, a second optical coupler lens disposed in said cavity and having opposite end surfaces exposed therewithin, said socket terminus body including a reference stop fixed at a preselected distance from said .Iadd.second .Iaddend.lens for engagement by said reference surface of said .Iadd.second .Iaddend.ferrule .Iadd.means .Iaddend.whereby an end of a fiber retained in said second ferrule means by said insert will be in a predetermined position relative to the proximal surface of said second lens when said reference surface abuts said terminal reference stop and said annular portion is compressed to retain said second ferrule means . .and said contact sleeve.!. in position with said reference stop against said reference surface, said socket body engaging said pin body to align said first lens with said second lens so that light emerging from said first fiber may be projected from said first lens to said second lens. .Iadd.

24. The invention as in claim 1 wherein bare portion is free of any coating. .Iaddend..Iadd.25. The invention as in claim 2 wherein said support element is formed of a material having a hardness of at least about 92 on the Rockwell B scale. .Iaddend..Iadd.26. The invention as in claim 2 wherein said support element has a hardness of about 92-95 on the Rockwell B scale. .Iaddend..Iadd.27. The invention as in claim 5 wherein said support element is formed of a material having a hardness of at least about 92 on the Rockwell B scale. .Iaddend..Iadd.28. The invention as in claim 18 wherein said removing step includes removing all coatings from said portion of said fiber to form said bare portion thereof.

.Iaddend..Iadd.29. A fiber optic terminus positioning assembly for closely controlling the axial position of an optical fiber end in a fiber optic connector, said terminus assembly comprising a single optical fiber having a bare portion of said fiber free of covering, said bare portion having a terminal end, a resilient fiber gripper element of a material which has a high coefficient of friction with the material of which said fiber is formed, said gripper element being distinct from any such fiber covering and in direct surface-to-surface contact with the surface of said bare portion of said fiber, and a hard metal support element having a hardness of at least about 92B on the Rockwell B scale and a low coefficient of elasticity surrounding said fiber portion and said gripper element in a predetermined axial position spaced from said terminal end, said support element being compressed into compressive engagement with said gripper element and thereby compressing said gripper element into gripping engagement with said bare fiber portion for retaining said terminal end of said fiber in said predetermined spaced axial position relative to said support element, wherein said bare portion including said terminal end extends axially from one end of said support element and said terminal end is spaced a predetermined distance from said one end of said support element. .Iaddend..Iadd.30. A fiber optic terminus positioning assembly for closely controlling the axial position of an optical fiber end in a fiber optic connector, said terminus assembly comprising a fiber optic cable having a fiber surrounded by a strength layer with a portion thereof removed from a portion of said fiber whereby said fiber has a bare portion free of covering, said bare portion having a terminal end, a resilient fiber gripper element of a material which has a high coefficient of friction with the material of which said fiber is formed, said gripper element being distinct from any such fiber covering and in direct surface-to-surface contact with the surface of said bare portion of said fiber, and a metal support element surrounding said fiber portion and said gripper element in a predetermined axial position relative to said terminal end, said support element including a head section in compressive engagement with said gripper element and thereby compressing said gripper element into gripping engagement with said bare fiber portion for retaining said terminal end of said fiber in said predetermined axial position relative to said support element, said support element further including a tail section extending between said fiber and a portion of said strength layer, and an element circumscribing said strength layer over said tail section and engaging said strength layer with said tail section for strain relief engagement of said strength layer with said

support element. .Iaddend..Iadd.31. The invention as in claim 29 and wherein said gripper element is formed of a polyethersulfone. .Iaddend.

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