GB2028534A

GB2028534A - Optical fiber connector

Info

Publication number: GB2028534A
Application number: GB7928467A
Authority: GB
Original assignee: Bunker Ramo Corp
Current assignee: Bunker Ramo Corp
Priority date: 1978-08-15
Filing date: 1979-08-15
Publication date: 1980-03-05
Also published as: SE442454B; DE2932986A1; IT1122760B; CA1121631A; FR2433766B1; IT7925110A0; SE7906775L; GB2028534B; FR2433766A1; JPS5528099A

Abstract

This invention relates generally to fiber optic connectors and, more specifically, to a separable in-line fiber optic connector for coupling a pair of optical fibers or a single optical fiber and a light source or detector. The fiber optic connector 10 of the present invention includes a terminal plug member 24 having a through hole extending axially therethrough for receiving an optical fiber 20. The plug member is axially split so as to comprise first and second separate longitudinal portions defining the through hole which are transversely matable for clamping the optical fiber therebetween. A housing 30 is provided for receiving the terminal plug member 24 and confining the split portions thereof to their mating position in which they firmly clamp the optical fiber 20. At least one of the longitudinal plug portions may be transversely ribbed along at least an axial section of the through hole for engaging the optical fiber to prevent axial displacement thereof. Interengaging surfaces may be provided on the two plug portions for preventing axial displacement therebetween. <IMAGE>

Description

SPECIFICATION Optical fiber connector TECHNICAL FIELD This invention relates generally to fiber optic connectors and, more specifically, to a separable in-line fiber optic connector for coupling a pair of optical fibers or a single optical fiber and a light source or detector.

BACKGROUND OF THE PRIOR ART The terminal end surface of an optical fiber for use in light wave transmission must be flat and highly polished to minimize insertion losses. The optical fibers typically must also be axially, laterally, and angularly aligned within certain parameters to establish an excellent optical coupling between two optical fibers. The success achieved in the development and production of optical fibers has therefore focused strongly upon connectors and couplers for such fibers including in-line connectors. The ability to design, manufacture, deploy and service a data transmission line, for instance, requires suitable connectors in order to assure the contiriued progress of the fiber optics field.Accordingly, connectors for this and other applications typically capable of plural mate-unmate cycles must be developed which can be used without any significant increase in insertion losses.

Many fiber optic connectors presently available are precision, expensive instruments providing very low insertion losses but they are not designed for repeated connection, disconnection, or servicing by untrained field perspnnel. This is particularly true in long distance applications such as telephonic systems and in other applications requiring extremely low insertion losses where expensive low loss connectors may be employed. It has been found however, that expensive low loss connectors are not always well suited for applications requiring a large number of connectors which need not achieve the same levei of low insertion losses.For instance, in such applications as computers and other data transmission applications, a large number of relatively short lengths of optical fibers are employed which are terminated at connectors which suitably must be capable of plural mate/unmate cycles for servicing in the field presenting a need for an improved low cost connector of the character described.

BRIEF SUMMARY OF THE INVENTION Accordingly, a principal object of the. present invention is to provide a new and improved low cost, separable inline fiber optic connector adapted for coupling a pair of optical fibers or between a single optical fiber and a light source or detector.

The structure of the fiber optic connector of the present invention is designed so as to include cooperating features in furtherance of this object.

The fiber optic connector of the present invention includes a terminal plug member having a through hole extending axially therethrough for receiving an optical fiber. The plug member is axially split so as to comprise first and second separate longitudinal portions defining the through hole which are transversely matable for clamping the optical fiber therebetween. A housing is provided for receiving the terminal plug member and confining the split portions thereof to their mating position in which they firmly clamp the optical fiber. The plug member includes at least one of the longitudinal plug portions being transversely ribbed along at least an axial section of the through hole for engaging the optical fiber to prevent axial displacement thereof.

Interengaging means is provided between the two plug portions for preventing axial displacement therebetween.

As shown herein, the fiber optic connector is adapted for receiving an optical fiber having an insulating layer or jacket comprising a thermoplastic coating. The through hole includes a first portion having a relatively large inner diameter substantially equal to the outer diameter of the jacket of the optical fiber extending axially from one end of the plug member, a second portion having a relatively small diameter substantially equal to the diameter of the optical fiber itself extending axially from the other end of the plug member, and a third portion generally at the juncture of the first and second portions and sized so as to receive strength members disposed between the optical fiber and the outer jacket.

Accordingly, the through hole advantageously includes three distinct portions sized and shaped to accommodate the optical fiber.

Complementary angular aligning means may advantageously be provided between the housing and one of the longitudinal plug portions for polarization of the connector. The aligning means comprises an axial interior groove formed in either the housing or the plug portion with a protrusion being formed on the other of the housing and the plug portion-axially positionable in the groove.

Detent means may also advantageously be provided between the housing and the plug member for holding the plug member axially within the housing. The detent means comprises d detent notch in either the housing or the plug member with a detent protrusion in the other of the housing and the plug member for snap fitting into the detent notch.

One of the plug portions of the split plug member advantageously extends from an outer end of the through hole to an inner end thereof. It is provided at the inner end thereof with a mating face defining a terminal end of the plug member.

Preferably, the mating face extends entirely across the terminal end of the plug member.

In one form of the invention disclosed herein, a pair of aforementioned plug members are provided and the housing is in the form of a sleeve. The housing is then axially dimensioned so that the sleeve receives both plug members in mated position. Advantageously, the sleeve and each of the plug members can have complementary angular aligning means providing for polarized engagement of the plug members with the housing and complementary detent elements for axially holding the opposing plug members within the housing so that the terminal ends of the optical fibers are in axial, lateral and angular alignment. The distance between the two detent elements of the two plug members and the axial dimensions between the corresponding detent elements of the housing can be varied to the mated plug members thereby controlling end separation of corresponding ones of the optical fibers.The plug members and the housing can be fabricated of elastomeric materials for low cost manúfacture but reliable production and functional use.

The present invention is therefore directed to a separable, in-line fiber optic connector adapted for coupling a pair of optical fibers or a single optical fiber and a light source or detector. It is among the objects of the present invention to provide a connector which is capable of plural mate/unmate cycles for servicing in the field by untrained field personnel in an industrial environment wherein the connector can be molded from a number of different thermoplastics in order to be compatible with existing electrical and optical components.

Still other objects and advantages of the present invention will be appreciated from a consideration of the details of construction and operation set forth in the accompanying specification, claims and drawings, BRIEF DESCRIPTION OF THE DRAWINGS The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with the further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings.In the drawings, like reference numerals identify like elements in the several figures in which: FIGURE 1 shows a psrspective view of the optical fiber connector of the present invention shown as used in various applications; FIGURE 2 is a central sectional view, on an enlarged scale, of the optical fiber connector as embodied for use with duplex fiber and including a pair of identical plug members coupled in line within a housing; FIGURE 3 is a fragmented vertical section of FIGURE 2, with one portion of the plug member removed and shown separately to facilitate the illustration; FIGURE 4 is a vertical section taken generally along line 4-4 of FIGURE 2; FIGURE 5 is a vertical section taken generally along line 5-5 of FIGURE 2; FIGURE 6 is a vertical section taken generally along line S6 of FIGURE 2; and FIGURE 7 is an end elevational view taken generally in the direction of arrows 7-7 oFFlGU'RE 2, with a section through the optical cable.

DETAILED DESCRIPTION OF THE INVENTION Referring to the drawings in greater detail, a separable in-line fiber optic connector, generally designated 10, is shown as adapted in its broadest sense for coupling a pair of optical fibers or a single optical fiber and a light source or detector.

As shown in the drawings, the fiber optic cable employed with the present invention is a duplex cable 1-2. However, as shown in the bottom righthand corner of FIGURE 1 , the fiber optic cable may comprise a single cable 14 for use with the connector of the present invention. As seen in FIGURE 2, the duplex cable 12 has an outer insulating layer or jacket 16 of thermoplastic material. Each individual optical fiber 20 of the duplex cable 1 2 also has an inner insulating layer or jacket 1 8 of thermoplastic material.As shown in the drawings, the outer jacket 1 6 and the inner jacket 1 8 have been trimmed so that the inner jackets 1 S extend beyond the outer jacket 16 and the optical fibers 20 extend beyond the corresponding inner jackets 18 to form the terminal end of the fiber optic cable 12. Strength members 22 are provided between the inner jackets 1 8 and the corresponding optical fibers 20 and are exposed in a flared fashion as shown in FIGURE 2.

FIGURE 2 shows the fiber optic connector 10 of the present invention as embodied for coupling a pair of fiber optic cables 12 in opposed in-line relationship. The connector 10 aligns the corresponding optical fibers 20 of the cables 1 2 to provide low insertion losses due to axial, lateral, or angular misalignment However, the advantages and features of the fiber optic connector 10 of the present invention are equally applicable for coupling a single fiber optic cable 12 to a light source or detector as described in more detail hereinafter.

Referring to FIGURES 2 through 7 in greater detail, the fiber optic connector 10 of the present invention includes one or more terminal plug members, generally designated 24, depending on the appiication for the connector 10. Each plug member 24 is axially split so as to comprise a first longitudinal plug portion 28 which are shown as the lower and upper plug portions as viewed in FIGURE 3. The plug portions 26,28 which define a contoured through hole extending axially through the terminal plug member 24 are transversely matable for clamping the fiber optic cable 12 and the optical fibers 20 within the through hole as described hereinafter.

A housing 30 is provided generally in the form of a rectangular sleeve which receives the plug members 24 to hold them in axial alignment and to confine the split plug portions 26, 28 to a mating position in which they firmly clamp the fiber optic cables 1 2. The outside of the plug members 24 are generally rectangularly shaped for insertion within the interior rectangular receiving hole extending entirely through the housing 30 from end to end. The outside of the plug members 24 on the split portions 26, 28 thereof may be ribbed as at 34 (as shown in FIGURE 3) at the outer exposed ends thereof to facilitate grasping during insertion and removal of the plug members into and out of the housing 30.

The plug members 24 also include shoulders 36 which abut against the ends of the housing 30 so that the terminal ends of the plug members 24, if desired, can be slightly spaced from each other at the mated ends thereof as at 38 (as shown in FIGURES 2 and 3) to prevent scratching' of the aligned optical fibers 20 when in a fully mated position.

Complementarily engageable detent means are provided between each of the plug members 24 and the housing 30 for releasably holding the plug members axially within the housing. Referring to FIGURE 3, the detent means comprises a bore 40 through the housing 30 communicating with each of the plug members 24 and a radially protruding detent projection or boss 42 formed on the lower split portion 26 of each of the plug members.

Referring to FIGURES 2 and 3, the distance between the detent holes 40 in the housing 30 can be slightly smaller than the cumulative dimension between the centre lines of fhe detent bosses 42. When coupling a pair of plug members 24 and their respective fiber optic cables 1 2 in an in-line relationship with this feature, the shoulders 36 are located so as to permit the plug members 24 to be driven towards each other minimizing end separation of corresponding ones of the optical fibers 20 within the housing 30.

Means are provided between the plug members 24 and the housing 30 to angularly relate the components so as to provide polarized interengagement thereof particularly for use with duplex cables 12 or multiple fiber bundles. More particularly, referring to FIGURE 6, an inwardly protruding axial rib 44 is formed on the inside of the housing 30 and axial groove 46 is formed on the outside of the plug member 24 for receiving the rib 44 so that the plug member can b inserted into the housing only in a predetermined angular orientation. The groove 46 may be formed on either of the plug portions 26, 28 of the plug member 24 depending upon the design and desired orientation of the plug member.

As stated above, each plug member 24 is comprised of first and second plug portions 26,28 (the lower and upper plug portions, respectively, as illustrated in FIGURE 3). Axial interengaging means is provided between the plug portions 26; 28 for preventing axial displacement therebetween. This means includes a pair of axially extending grooves 48 (as shown in FIGURE 2) along the inner face of the plug portion 26 and a pair of protruding axially extending ribs 50 on the corresponding inner face of the plug portion 28. In assembling the plug portions 26; 28 to sandwich a fiber optic cable 1 2 therebetween, the plug portion 26 simply is assembled in a lateral direction positioning the ribs 50 of the plug portion 28 into the grooves 48 of the plug portion 26 to clamp the fiber optic cable 12 therebetween.

After the plug members 24 have been assembled, they are then inserted axially into the housing 30 as described hereinabove. The plug portion 26 of each of the plug members 24 is longer than the corresponding plug portion 28 (as shown in FIGURE 3) and is dimensioned at its terminal end to extend across the terminal end of the plug portion 28 so as to substantially conform to the size and shape of the inside of the housing 30. Thus, the plug portion 26 has a single continuous mating face 52 extending entirely across the plug member 24 at the terminal end thereof which is opposite the corresponding mating face 52 of the mated plug member 24 when fully mated (as shown in FIGURES 2 or 3) or which is opposite a light source or detector when using a single plug member 24.Moreover, the non-segmented mating faces 52 of the plug members 24 assure proper mating of the plug members by entirely eliminating one source of alignment error which would otherwise exist. The relative dimensioning between the detent holes 40 of the housing 30 and the detent bosses 42 of the plug member 24 as well as the shoulders 36 of the plug members 24 as described above are effective to control the spacing, if any, between the mating faces 52 of the opposing plug members 24. Preferably, the optical fibers 20, after being assembled or clamped between the plug portions 26, 28 are trimmed so as to be flush with the mating face 52 of their respective plug members 24.

As mentioned abdve, the through hole extending axially throúgh each plug member 24 is contoured for receiving the components of the fiber optic cable such as the duplex cable 1 2.

More particularly, with the duplex cable 12 (as shown in FIGURE 2) the composite through hole includes a small diameter portion 54 for each optical fiber 20 and a relatively larger diameter portion 56 for receiving the inner jacket 18 of each optical fiber 20. Furthermore, the composite through hole includes a still larger portion 58 for receiving the integral outer jacket or sheath 1 6 of the duplex cable 12. Moreover, the interior of the through hole portion 58, including that which extends through both of the plug portions 26, 28, is interiorly ribbed as at 60 (as shown in FIGURE 3) to facilitate gripping engagement of the duplex cable 12 by the plug member 24.Referring to FIGURE 3, the through hole of each plug member 24 also includes-a flared portion 62 formed in the plug portion 28 at the juncture between the through hole portions 54 and 56 for accommodating strength members 22.

The housing 30 and the plug portions 26, 28 of each of the plug members 24 may be fabricated of thermoplastic material for ease of manufacture and assembly while yet providing a reliable, low loss, fiber optic connector which is relatively inexpensive to manufacture. The connector and the novel features thereof are readily adaptable for a wide variety of applications. For instance, the connector as shown in FIGURES 2 through 7 may be used for in-line applications, sometimes called a "flying splice" 70 (FIGURE 1). The connector of FIGURES 2 through 7 may also be used as a bulkhead connector secured to a panel 72 (FIGURE 1) by means of snap fingers 74 molded integrally along the sides of the housing 30.The connector as shown in FIGURES 2 through 7 also may be secured to a printed circuit board 76 (FIGURE 1) by means of bosses 78 molded integrally with the housing 30 for snap fit within holes 80 in the circuit board 76. The connector of FIGURES 2 through 7 may also be utilized with the housing 30 fabricated as at 82 (FIGURE 1) to provide an expandable section for use with multiple individual plug members 24. In addition, the plug member 24 may be used in input/output connector applications forming a part of an emitter or detector by use of complementary housings 84 (FIGURE 1) with the interior thereof fabricated similar two the housing 30.

With the present invention, it is possible to use a split design with the through hole contours molded into the plug member to accept the optical fiber, the inner jacket, the strength members, and the outer jacket. The strength members are retained by captivating them between the longitudinal plug portions as they are bonded together. It has been found that in addition to the traditional epoxy bonding techniques, the connector's design lends itself to ultrasonic welding of the plug portions by selecting and using suitable thermoplastics as the material for molding the connector elements. The connector design allows the optical fibers to be terminated by either polishing the fiber ends or cutting the fiber ends such as with a razor blade, when using plastic optical fibers.It has been found that providing a single continuous mating face which is not segmented at the terminal end of the plug member facilitates termination of the optical fibers as well as eliminating one common source of alignment error. The non-segmented surface at which the optical fibers terminate also eliminate the possibility of overlap of the plug portions which might otherwise be caused by deviations from acceptable manufacturing tolerances or possible assembly errors. Although particularly well suited for duplex fiber optic cable, the connector of the present invention can easily be modified to handle single channel fiber optic cables, multichannel fiber optic cables and planar arrays, i.e., ribbon fiber optic cables, of any number of channels, by forming the through hole or holes to conform to such cable in-a manner that will readily be appreciated by those skilled in the art.

While in the foregoing specification a detailed description of the invention has been set forth for purposes of illustration, variation of the details herein given may be made by those skilled in the art without departing from the spirit and scope of this invention.

Claims

1. A separable in-line fiber optic connector adapted for coupling a pair of optical fibers or a single optical fiber and a light source or detector, said connector comprising: a plug member having a through hole extending axially therethrough for receiving an optical fiber, said plug member being axially split so as to comprise first and second separate longitudinal portions defining said through hole and being transversely matable for clamping said optical fiber therebetween; and a housing member for receiving said plug member to hold said longitudinal plug portions thereof in mating position firmly clamping said optical fiber therebetween.

2. The fiber optic connector as claimed in Claim 1, wherein at least one of said longitudinal plug portions is transversely ribbed along at least an axial section of said through hole for engaging said optical fiber to prevent axial displacement thereof.

3. The fiber optic connector as claimed in Claim 1, including axial interengaging means between said first and second plug portions for preventing axial displacement therebetween.

4. The fiber optic connector as claimed in Claim 1 ,wherein said connector is adapted for receiving an optical fiber having an insulating jacket, said through hole including a first portion having a relatively large inner diameter substantially equal to the outer diameter of said insulating jacket extending axially from one end of said plug member, and a second portion having a relatively small diameter substantially equal to the diameter of said optical fiber extending axially from the other end of said plug member.

5. The fiber optic connector as claimed in Claim 4, wherein said through hole includes a third portion generally at the juncture of said first and second portions and sized so as to receive strength members disposed between said optical fiber and said insulating jacket.

6. The fiber optic connector as claimed in Claim 1, wherein said housing and one of said longitudinal plug portions have complementary angular aligning means providing for polarized interengagement of said plug member and said housing.

7. The fiber optic connector as claimed in Claim 6, wherein one of said housing and said one longitudinal plug portion has an axial interior groove and the other of said housing and said one longitudinal plug portion has a protrusion axially positionable in said groove.

8. The fiber optic connector as claimed in Claim 1, wherein said housing and said plug member have complementarily engageable detent means for releasably holding said plug member axially within said housing.

9. The fiber optic connector as claimed in Claim 8, wherein one of said housing and said plug member has a detent notch and the other of said housing and said plug member has a detent protrusion for snap fitting into said detent notch.

10. The fiber optic connector as claimed in Claim 1, wherein one of said longitudinal plug portions extends from an outer end of said through hole to an inner end thereof and is provided at said inner end with a mating face defining a terminal end of said plug member.

11. The fiber optic connector as claimed in Claim 10, wherein said mating face extends entirely across said terminal end of said plug member.

1 2. The fiber optic connector as claimed in Claim 1, including an opposing pair of said plug members and with said housing member being in the form of a sleeve axially dimensioned so as to receive both of said plug members inserted into opposite ends of said sleeve with said plug members mating position.

13. The fiber optic connector as claimed in Claim 1 2, wherein said sleeve and each of said plug members have complementary angular aligning means providing for polarized interengagement of said plug members and said sleeve.

1 4. The fiber optic connector as claimed in Claim 1 , wherein said connector is adapted for receiving a duplex fiber optic cable having an outer insulating jacket, strength members disposed within said outer insulating jacket, and a pair of optical fibers disposed within said strength members, each of said optical fibers being disposed within an inner insulating jacket.

1 5. The fiber optic connector as claimed in Claim 14, wherein said through hole includes a small diameter portion for accommodating each of said optical fibers, a relatively larger diameter portion for accommodating said inner insulating jacket of each of said optical fibers, and a still larger diameter portion for accommodating said outer insulating jacket of said fiber optic cable.

1 6. The fiber optic connector as claimed in Claim 1 5, wherein said through hole further includes a flared portion for accommodating said strength members of said fiber optic cable.