GB2097149A

GB2097149A - Apparatus for aligning an optical fiber with a collimating lens

Info

Publication number: GB2097149A
Application number: GB8211091A
Authority: GB
Original assignee: Malco
Current assignee: Malco
Priority date: 1981-04-20
Filing date: 1982-04-16
Publication date: 1982-10-27
Also published as: FR2504279A1; SE8202359L; JPS581114A; DE3214582A1; DK173582A; NL8201629A; NO821265L

Abstract

Apparatus for aligning a single optical fiber (23) with a collimating lens (21) includes an alignment bushing (25) having a chamfer (27) on a first side surface (29) adapted to receive the spherical collimating lens (21). An orifice (31) is arranged concentrically with the chamfer (27) and extends through to a second side (33) of the bushing (25). The orifice (31) is sized to securely hold a single optical fiber. In this way, a single relatively simple element accomplishes all of the axial alignment functions between the optical fiber and the spherical lens. <IMAGE>

Description

SPECIFICATION Apparatus for aligning an optical fiber with a collimating lens The present invention relates to an apparatus for aligning an optical fiber with a collimating lens.

Further, the present invention relates to a contact assembly for an optical fiber aligned with a collimating lens.

As the use of optical fibers increases, it is desirable to provide separable connectors for aligning the ends of two optical fibers. At present, it is known to align the fibers by mechanical devices such as precision ferrules, alignment sleeves and the like.

Because of the small size of the optical fibers, a very high degree of accuracy is required when producing such mechanical connectors. Consequently, it is difficult to achieve the necessary accuracy of the alignment in this type of connector and still be able to disconnect and reconnect the fibers as desired.

Various arrangement for overcoming the difficulty in aligning the fiber have been proposed. One such proposal includes the use of a lens to expand the radiation pattern of a single optical fiber into a collimated beam. Due to the increased diameter of the beam over the diameter of the fiber, and assuming that each fiber to be connected is terminated by such a lens, the criticality of the alignment across the connector interface is greatly reduced.

However, such a lens system produces a further problem of properly aligning the fiber with the lens.

One arrangement for aligning optical fibers using a pair of collimating lenses includes a pair of optical terminals for coupling the optical fibers. Each terminal includes a connector and a biconvex lens which is adapted to receive an end of the optical fiber. In such an arrangement, it is necessary to accurately position the ends of the optical fibers at the focal points of the respective lens. This positioning of the ends of the optical fibers is accomplished by mounting within each of the lenses a short length of an optical fiber having dimensions and optical characteristics similar to the optical fibers to be coupled. The fibers are then inserted into the connector until each fiber abuts the end of the short fiber length secured in the lens.A device of this type generally requires that the lenses be manufactured by a plastic molding which may present difficulties in maintaining consistency of manufacture. Also, the required orientation between the short fiber length and the lens in practice may limit this type of connector to very large fibers. A device of this type is disclosed in U.S. Patent No. 4,183,618 issued January 15, 1980 to Rush petal.

An arrangement has been proposed for mounting a spherical lens in an optical fiber light pen including an annular seat received within an opening in an end of the pen. An optical fiber bundle containing a multitude of optical fibers is arranged behind the seat within an opening in a ring member secured in a housing. A spherical lens rests on a curved portion of the seat and is held in contact with the seat by an outer sleeve. A device of this type does not relate to the alignment of a single optical fiber with a spherical lens. Further, the seat does not serve to align the fiber bundle with the lends but rather serves to space the bundle an appropriate axial distance from the lens. A device of this type is disclosed in U.S. Patent No. 3,904,277 issued Sep tember9, 1975 to Phillips et al.

It has also been proposed to couple a Lambertian source, such as an LED, to a fiber bundle with an arrangement for positioning a spherical lens with respect to the bundle and the LED. The fiber bundle is terminated in a ferrule which is press fitted into a plastic alignment sleeve containing a spherical lens.

A device of this type however requires that each of the fiber bundle diameter, the ferrule inside diameter, the ferrule inside diameter to outside diameter concentricity, and the concentricity of holes in the alignment sleeve all be considered in order to properly align the fiber bundle with the lens. It is further submitted that a device of this type is not readily suitable for aligning a single optical fiber with a spherical lens. A device of this type is disclosed in U.S. Patent No. 3,950,075 issued April 13, 1976 to Cook et al.

Other patents which relate generally to optical fibers or optical fiber bundles in combination with lenses include U.S. Patent Nos. 3,166,623 issued January 1965 to Waidelich, Jr.; 3,492,058 issued January 1970 to Waldman; and 3,656,832 issued April 1972 to Judin.

It is an object of the present invention to provide an improved apparatus for aligning a single optical fiber with a collimating lens.

It is a further object of the present invention to provide a relatively simple and inexpensive apparatus for utilizing a properly aligned spherical collimating lens to create a termination for an optical fiber.

Additionally, it is a further object of the present invention to provide a more reliable apparatus for aligning optical fibers by reducing the number of tolerances involved in the alignment process to a minimum.

Still a further object of the present invention is to provide a contact assembly for an optical fiber which contains no temperature sensitive materials and is substantially immune to the effects of aging. Additionally, it is an object of the present invention to provide a contact assembly which is immune from contamination of the face of the optical fiber and which is relatively rugged in mechanical construc- tion. It is still a further object of the present invention to provide an optical fiber contact assembly which is smaller than known assemblies and is small enough to fit within the space allotted for a contact in an electrical connector. In this way, the optical fiber alignment apparatus according to the present invention can be used in standard connectors without substantial redesign of these connectors.Still further, it is an object to permit the optical fiber alignment apparatus according to the present invention to be used for coupling optical fibers with electrical connectors.

According to the invention there is provided apparatus for aligning an optical fiber with a collimating lens comprising an alignment bushing, a right circular conical chamfer arranged in a first side surface of the bushing, an orifice concentric with the chamfer and extending through the bushing to a second side surface of the bushing at the apex of the conical chamfer, said orifice being sized for securely holding a single optical fiber, and a spherical lens pressed against the chamfer.

In a preferred embodiment of the present invention, the chamfer is in the form of a right circular cone and the orifice extends from an apex of the conical chamfer. Still further in the preferred embodiment, the chamfer and the orifice are simultaneously polished in a single operation to ensure concentricity.

By arrangement of the present invention for aligning an optical fiber with the collimating lens the number of tolerances involved is reduced to a minimum of three. Specifically, the fiber diameter, the diameter of the orifice in the alignment bushing, and the orifice to chamfer concentricity are the only tolerances which must be considered. Since the chamfer and the orifice can be finished in a single operation with a single tool, the chamfer to orifice concentricity is assured. The two other tolerances can be carefully controlled in a known manner during manufacture.

Further, according to the present invention, a first housing part is provided for surrounding and retaining the alignment bushing and the spherical lens.

The lens and the bushing are preferably insertable into the first housing part from a first end and are prevented from movement outwardly from a second end of the housing part. In the preferred embodiment, the lens is resliently urged against the chamfer of the alignment bushing by a sealing ring arranged between a flange of the first housing part and the lens.

Still further, a contact assembly according to the present invention includes a second housing part for surrounding a fiber-optic cable including an optical fiber which is successively surrounded by at least a buffer layer and a strength layer. The second housing part includes an annular clamping arrangement for securely holding the optical fiber generally centrally within the housing. The clamping arrangement in the preferred embodiment comprises a generally annular clamping assembly secured to the second housing part and having a central bore slightly larger than the diameter of the optical fiber.

An outside surface portion of the assembly urges the strength layer of the fiber-optic cable into tight engagement with an inside wall portion of the second housing part. Further, the clamping assembly comprises a chuck on the inside of the assembly for tightly resiliently engaging the optical fiber to thereby securely hold the optical fiber radially within the second housing part.

In the preferred embodiment, the first housing part is adapted to be secured to the second housing part such that the optical fiber extends through the orifice in the alignment bushing thereby aligning the fiber with the collimating lens.

Preferred embodiments of the present invention will be described in greater detail with reference to the accompanying drawings wherein like members bear like reference numerals and wherein: Figure l is a cross-sectional view of an apparatus for aligning an optical fiber with a collimating lens; Figure 2 is a perspective view of a preferred embodiment of the alignment bushing of Figure 1; Figure 3 is a longitudinal cross-sectional view of a first embodiment of a contact assembly according to the present invention; and Figure 4 is a longitudinal cross-sectional view of a second, preferred embodiment of a contact assembly according to the present invention.

When attempting to connect two single optical fibers into a single circuit, substantial problems are encountered due to the extremely small size of an optical fiber. In general, an optical fiber is of a diameter of approximately 0.1 millimeter. As can be seen, such a small size renders alignment of two fibers along a common axial line extremely difficult.

Since the fibers must be precisely axially aligned in order to complete a circuit through the connection, it is essential that a relatively simple and inexpensive apparatus for achieving the desired alignment be produced.

When employing a lens to expand the radiation pattern of the fiber into a collimated beam, the alignment across the connector interface is considerably simplified, assuming that each fiber to be connected is terminated by such a collimating lens, since the width of the collimated beams are more easily aligned by known mechanical apparatus.

However, the problem is transformed into the difficulty of properly aligning the small optical fiber with the center of the lens.

Further, in addition to the problems encountered when aligning the fiber with the lens, the lens itself may pose additional problems. It should be noted that a collimating lens for an optical fiber may be of a diameter of approximately only 2 to 3 millimeters.

Accordingly, manufacturing problems are encountered when attempting to design a complex lens in such a small size to be aligned with an optical fiber.

According to the present invention, a spherical lens is utilized for various reasons.

A spherical lens of the appropriate size is readily available commercially at a relatively low cost.

Further, since the spherical lens can be manufactured without utilizing a molding operation, the lens can be more easily obtained in an environmentally resistant material. In other words, a spherical lens can be comprised of a material which is relatively insensitive to temperature and humidity variations in the air and also can be comprised of a material which is relatively resistant to shocks. These characteristics are significant for use in optical fiber contacts which may be located where less than environmentally ideal conditions exist. Further, since it is desirable to utilize an optical fiber contact in cooperation with electrical contacts within readily available connecting assemblies, these environmental conditions take on added significance. Afurther advantage of a spherical lens is that the accuracy of manufacture of a spherical lens far exceeds that which can be obtained by a molding operation of a different form of lens, e.g., a biconvex lens and the like. Still further, because of the symmetrical geometry of a spherical lens, a structure for aligning the lens may be greatly simplified. Additionally, by using a spherical lens, the size of the lens can be reduced to be readily adaptable for use in existing electrical connectors.

With reference to Figure 1, the present invention provides a single, relatively simple element which accom plighes all of the required alignment functions between an optical fiber 23 and a spherical lens 21.

This element comprises an alignment bushing 25.

The alignment bushing 25 includes a chamfer 27 arranged in a first side surface 29 of the alignment bushing 25 which chamfer 27 provides a seating surface for the spherical lens 21.

An orifice 31 for securely holding the optical fiber 23 is provided concentrically with the chamfer 27.

The diameter of the orifice 31 is sized to securely hold the optical fiber 23 therein. The orifice 31 extends concentrically with the chamfer 27 from the deepest portion of the chamfer through the alignment bushing 25 to a second side surface 33 thereof.

In addition, a chamfer 35 may be provided in the second side surface 33 of the bushing 25 in order to facilitate insertion of the optical fiber 23 within the orifice 31.

According to the present invention, the number of tolerances involved in the arrangement for aligning the optical fiber with the lens is reduced to only three tolerances. Specifically, the fiber diameter, the diameter of the bushing orifice 31 and the concentricity of the bushing orifice 31 and the chamfer 27 are the three items whose tolerances must be considered.

The fiber diameter is relatively constant while the bushing orifice diameter can be carefully controlled by known precision machining operations. Since the chamfer 27 and the bushing orifice 31 may be polished to a finished condition by a single tool, the necessary concentricity will be inherent during the manufacturing process of the bushing 25.

Since the spherical lens is completely symmetrical and, as noted above, can be manufactured with high precision, the spherical lens 21 is easily seated within the chamfer 27. In other words, the lens 21 seats securely within the chamfer 27 and does not have a tendency to swivel or rock. Even if the lens 21 rolls or rotates, the center of the lens remains aligned with the concentric orifice 31. Accordingly, the alignment bushing 25 of the present invention ensures axial alignment of the optical fiber 23 with the spherical lens 21.

With reference to Figure 2, in the preferred embodiment, the chamfer 27 is in the form of a right circular cone. In this arrangement, the orifice 31 extends from the apex of the conical chamfer. The right circular cone is particularly simple to machine into the first surface 29 of the bushing 25 and further ensures concentricity of the orifice 31 with the chamfer 27 due to the simple geometry of the chamfer. As noted above, the polishing of the surface of the chamfer and the orifice 31 may be accomplished with a single tool thereby further assuring the concentricity of the orifice 31 and the chamfer 27.

Again with reference to Figure 1, the largest diameter of the chamfer 27, i.e. in the plane of the first surface 29 of the alignment bushing 25, is less than the diameter of the spherical lens 21. In this way, it is ensured that the spherical lens 21 will properly seat within the chamfer 27 and will remain spaced from the base of the chamfer (or the apex of the cone) where the orifice 31 is arranged. By this arrangement, fiber to lens spacing can be more easily maintained.

The fiber to lens spacing is not as critical as the axial alignment of the fiber with the spherical lens.

However, with the present invention the optical fiber can be precision cut to terminate a predetermined distance from the surface against which the second surface 33 of the alignment bushing 25 rests in a assembled contact. This distance is a predetermined amount less than the distance between the second bushing surface 33 and the periphery of the lens 21 pressed into the chamfer. After the fiber 23 has been precision cut to the desired length, the alignment bushing and spherical lens are placed over the optical fiber thereby assuring the spacing between the end of the optical fiber 23 and the spherical lens 21. The desired spacing is maintained because the spherical lens 21 is prevented from further movement toward the optical fiber by the surface of the chamfer 27.

In the preferred embodiment, both the alignment bushing 25 and the spherical lens 21 are comprised of sapphire. Sapphire is particularly desirable since it is substantially immune to environmental changes, is relatively durable in use, and can be relatively easily formed into a spherical lens and relatively easily machined to the proper form for use as the alignment bushing 25. Alternatively, the alignment bushing may be a suitable metal or a ceramic material. Additionally, the lens may be glass which is also relatively easily formed into the desired spherical shape. Further, the lens 21 may be optically coated to reduce reflections.

A further aspect of the present invention relates to a contact assembly for an optical fiber which assembly is preferably adapted to be installed in existing connector designs. It is preferred to utilize the contact assembly in existing connector designs in orderto minimize requirements for reinvention of the connector designs and to facilitate coupling of optical fiber channels with electrical channels if desired. Also, separate optical and electrical contacts can be arranged within a common housing as part of a single harness assembly.

In Figure 3, a first embodiment of a contact assembly 41 is illustrated with the alignment bushing 25 and the spherical lens 21 according to the present invention. However, it is to be understood that the contact assembly may be used with any other suitable mechanical alignment arrangement as desired.

The optical fiber 23 is normally encased within a fiber-optic cable 43. The fiber-optic cable 43 includes an outer casing 45 arranged concentrically around a Kevlar strength member layer 47 which surrounds an elastomeric buffer layer 49 within which the optical fiber 23 is arranged. The fiber-optic cable 43 may comprise additional layers as desired. However, the illustrated embodiment is typical of the present fiber-optic cables for facilitating handling of the small fiber and for protecting the relatively fragile optical fiber 23.

The contact assembly 41 includes a first housing part 51 for surrounding and holding the fiber-optic cable 43 placed within the first housing part 51. The fiber-optic cable is stripped to expose the Kevlar strength layer 47, the elastomeric buffer layer 49 and the optical fiber 23. The first housing part 51 is screwed onto the outside of the fiber-optic cable 43 forming thread-like deformations in the surface of the outer casing 45. The first housing part is screwed onto the fiber-optic cable 43 until the strength members 47 are disposed within a clamping zone 55 of the first housing part 51.

At this point, it may be necessary to insert a small conical bushing (not shown) between the strength member layer 47 and the elastomeric buffer layer 49 in order to fan open the Kevlar strands in the strength layer 47 toward the inside wall 57 of the clamping zone 55. After spreading the strength layer 47, a generally annular clamping assembly 59 is inserted in the first housing part 51 such that a spreader member 69 is arranged around the buffer layer 49 and between the buffer layer 49 and the strength layer 47. The spreader member 69 includes a central bore slightly larger than the diameter of the buffer layer 49. The clamping assembly 59 may be secured within the first housing part 51 by engagement of screw threads 61 on an outside surface portion of a securement member 63 with threads 65 arranged on an inside surface portion of the first housing part 51.The securement part 63 may also be provided with a hexagonal opening 67 to facilitate a screwing of the clamping assembly 59 within the first housing part 51.

The spreader member 69 includes a tapering front end 71 for facilitating insertion of the spreader member 69 between the strength layer 47 and the buffer layer 49. A portion of the spreader member 69 surrounds a portion 73 of the securement member 63 such that limited axial movement of the spreader member 69 relative to the securement member 63 is permitted. Axial movement of the spreader member 69 relative to the securement member 63 is limited by engagement of a metal split ring 77 with an annular stop flange 75 arranged at an end of the securement member 63. The ring 77 is arranged within a groove 79 on an inside surface portion of the spreader member 69.

Arranged within the spreader member 69 between the spreader member end 71 and the stop flange 75 are two split conical bushings 81 for engagement with the buffer layer 49. The bushings 81 are preferably separated by a conical washer 83. In a preferred embodiment, the bushings 81 are compris ed of Teflon.

After securing the fiber-optic cable 43 within the first housing part 51 and partially spreading the strength layer 47 if necessary, the clamping assem bly 59 is screwed within the first housing part 51 along the screw threads 65. As the securement member 63 is screwed along the threads 65, the entire clamping assembly 59 moves axially within the first housing part 51 toward the fiber-optic cable 43. It should be noted that due to the arrangement of the spreader member 69 around the securement member 63, relative axial and rotational movement is permitted between the two members. In this way, torsional and axial stresses between the spreader member 69 and the strength layer 47 and between the bushings 81 and the buffer layer 49 are reduced.

As the clamping assembly 59 moves further axially within the first housing part 51, the spreader member 69 compresses the strength layer 47 against the inside wall 57 of the clamping zone 55 within the first housing part 51. Simultaneously, a compressive force is exerted on the conical bushings 81 to securely hold the buffer layer 49 and the optical fiber 23 against radial and axial movement within the first housing part 51. It should be noted that the optical fiber 23 is arranged to extend a substantial distance outwardly from a forward side 85 of the clamping assembly 59 for reasons to be discussed below.

In a preferred embodiment, a second housing part 87 is provided for surrounding the spherical lens 21 and the alignment bushing 25 according to the present invention. As noted above, any suitable alignment arrangement may be provided if desired in lieu of the alignment bushing and lens according to the present invention. Also, the contact assembly 41 could be used without any collimating lens for direct connection of optical fibers if desired. The second housing part 87 includes threads 89 on an external surface portion which are adapted to engage threads 91 provided on an inside surface portion of the first housing part 51.The second housing part 87 includes an internal bore 93 having a diameter which is just slightly greater than the diameter of the alignment bushing 25 and the spherical lens 21, the diameters of which are generally about the same, to tightly engage the bushing 25 and the lens 21.

An inwardly directed flange 95 for preventing movement of the lens 21 outwardly from the second housing part 87 is provided at an end of the second housing part 87 opposite the end containing the screw threads 89. As illustrated, the flange 95 is integral with the second housing part 87. However, the flange for preventing movement of the lens 21 and the bushing 25 could be arranged as a separate member. Arranged between an inside surface of the flange 95 and the spherical lens 21 is a sealing ring 97 which provides a seal to prevent material from passing around the spherical lens and cor.+aminat- ing either the exposed face of the optical fiber or the contact area between the chamfer 27 and the spherical lens 21. Such contamination could cause interference with the signal emitted from the optical fiber face or could unseat the spherical lens 21 from the chamfer 27. Further, the sealing ring 93 is arranged to urge the lens 21 into tight engagement with the alignment bushing chamfer 27.

Prior to inserting the second housing part 87 within the first housing part 51, the optical fiber 23 is cut to a predetermined axial protrusion from the forward side 85 of the clamping arrangement 59.

This distance is determined by the distance between the second side 33 of the alignment bushing 25 and the desired termination point of the optical fiber 23 within the chamfer 27. The termination point lies a predetermined distance from the periphery of the lens 21 pressed into the chamfer 27. This cutting can be done with sufficient precision to maintain the axial spacing between the end of the optical fiber 23 and the spherical lens 21 at the desired distance.

After cutting the optical fiber 23 to the predetermined length, the second housing part 87 is screwed into the first housing part 51 until the second surface 33 of the alignment bushing 25 abuts with the forward side 85 of the clamping assembly 59. As the second housing part 87 is moved axially within the first housing part 51, the optical fiber 23 enters the alignment chamfer 35 and the orifice 31 within the alignment bushing 25 to thereby precisely align the optical fiber 23 with the spherical lens 21. It should be noted that in the assembled condition the sealing ring 97, in addition to preventing foreign matter from entering the contact assembly 41, ensures that the lens 21 is securely seated against the chamfer 27 of the alignment bushing 25.

Different fiber-optic cables have various configurations. Often, the buffer layer 49 does not securely contain the optical fiber 23 therein. In other words, the optical fibre 23 may be capable of small radial movements within the buffer layer 49. Accordingly, the contact assembly 41 according to Figure 3 may not be suitable for use with such a fiber-optic cable.

In order to accommodate a wider range of fiberoptic cables a second, preferred embodiment of a contact assembly 41' (Figure 4) is provided according to the present invention. The contact assembly 41' includes a first housing part 51' for surrounding and holding the fiber-optic cable 43 placed within the first housing part 51'. For ease of assembly, the first housing part 51' is separated into first and second portions 54, 56, respectively. It should be noted that the first housing part 51' may be a single unit as in the embodiment of Figure 3. The fiber-optic cable is stripped to expose the Kevlar strength layer 47, the elastomeric buffer layer 49. The buffer layer 49 is then stripped away inside the strength layer to expose the optical fiber 23.The first portion 54 of the first housing part 51' is screwed onto the outside of the fiber-optic cable 43 forming thread-like deformations in the surface of the outer casing 45. The first portion 54 is screwed onto the fiber-optic cable until the members of the strength layer 47 are disposed within a clamping zone 55' of the first housing part portion 54.

At this point, an expansion cone 101 is inserted between the strength layer 47 and the elastomeric buffer layer 49 in order to fan open the Kevlar strands in the strength layer 47 toward the inside wall 57' of the clamping zone 55' and to secure the buffer layer 49 with respect to the strength layer 47.

After insertion of the expansion cone 101, the second portion 56 of the first housing part 51' is secured to the first portion 54 by, for example, screw threads. A generally annular clamping assembly 59' is inserted in the first housing part 51' such that a spreader member 69' is arranged around the optical fiber 23 and between the optical fiber 23 and the strength layer 47. The spreader member 69' includes a central bore slightly larger than the diameter of the optical fiber 23. The clamping assembly 59' may be secured within the first housing part 51' by engagement of screw threads 61' on an outside surface portion of a securement member 63' with threads 65' arranged on an inside surface portion of the first housing part 51'.The securement member 63' may also be provided with a hexagonal opening 67' to facilitate a screwing of the clamping assembly 59' within the second portion 56 of the first housing part 51'.

The spreader member 69' includes a generally flat front end 103 for abutting engagement with an end of the expansion cone 101. A portion of the spreader member 69' surrounds a portion 73' of the securement member 63' such that limited axial movement of the spreader member 69' relative to the securement member 63' is permitted. Axial movement of the spreader member 69' relative to the securement member 63' is limited by engagement of a flange 105 on the spreader member 69' with an annular stop flange 75' arranged at an end ofthesecurement member 63'. Belleville washers 107 urge the spreader member 69' into tight engagement with the strength layer 47.

Arranged within central bores in the spreader member 69' and the securement member 63' is a chuck 109 for clampingly gripping the optical fiber 23. The chuck 109 is prevented from axial movement toward the front end 103 of the spreader member 69' by a radial flange 110 on the spreader member 69'.

The chuck 109 has a central bore 111 which is slightly larger than the outside diameter of the optical fiber 23. An outside surface portion 113 of the chuck 109 within the central bore in the securement member 63' tapers such that the cross-sectional area of the chuck 109 decreases in a direction away from the fiber-optic cable 43. The central bore in the securement member 63' may also be tapered if desired.

After securing the fiber-optic cable 43 within the first housing part 51', spreading the strength layer 47 with the expansion cone 101, and securing the second portion 56 to the first portion 54 of the first housing part 51', the clamping assembly 59' is screwed within the first housing part 51' along the screw threads 65'. As the secu rement member 63' is screwed along the threads 65', the entire clamping assembly 59' moves axially within the first housing part 51' toward the fiber-optic cable 43. It should be noted that due to the arrangement of the spreader member 69' around the securement member 63', relative axial and rotational movement is permitted between the two members. In this way, torsional and axial stresses between the spreader member 69' and the strength layer 47 and between the chuck 109 and the optical fiber 23 are reduced.

As the clamping assembly 59' moves further axially within the first housing part 51', the front end 103 of the spreader member 69' abuts the expansion cone 101 as the spreader member 69' further compresses the strength layer 47 against the inside wall 57' of the clamping zone 55' within the first housing part 51'. After abutting the expansion cone 101, further axial movement of the securement member 63 causes relative axial displacement be tween the securement member 63' and the spreader member 69'. Since the chuck 109 is confined within the spreader member 69', relative axial displacement between the securement member 63' and the chuck 109 also occurs.Due to the tapered surface portion 113 on the chuck 109, the axial displacement causes chuck 109 to be compressed within the bore in the securement member 63' to tightly resiliently hold the optical fiber 23 against radial and axial movement within the first housing part 51'. It should be noted that the optical fiber 23 is arranged to extend a substantial distance outwardly from a forward side 85' of the clamping assembly 59' for reasons discussed previously.

At this point, a second housing part 87' preferably containing the alignment bushing 25 and the spherical lens 21 according to the present invention may be secured to the second portion 56 of the first housing part 51' in a manner similar to the previously described contact assembly (Figure 3).

The assembled contact assembly 41' is then preferably inserted within an insulator cavity 117 provided in a connector 119 (partially shown).

Belleville washers 121 may also be provided to urge the contact assembly 41' toward a forward end of the connector 119.

After securing the second housing part 87' within the first housing part 51', the contact assembly 41' is complete. It should be noted that in the finished contact assembly there are no environmentally susceptible elements. The optical fiber 23 is held in alignment with the spherical lens and held within the housing part 51' without the use of any temperature dependent seal such as epoxy. Further, the contact assembly is relatively rugged in construction. The entire assembly is generally secured by mechanical means such as compression and/or screw threads.

While screwed connectors have been described with reference to the preferred embodiment, other suit able connections are contemplated within the pre sent invention.

It should be further noted that due to the construction of the contact assembly 41 ',foreign matter is not permitted to enter the inside of the housing parts to contaminate the optical fiber therein. Also, since the entire size of the contact assembly 41 ' according to the present invention is only slightly longer than 11 millimeters and only approximately 4 millimeters in diameter, the contact assembly according to the present invention can be arranged within standard connector designs. This adaptability offers the possi bility of combining optical and electrical contacts in existing connector designs.

Claims

1. Apparatus for aligning an optical fiber with a collimating lens comprising: an alignment bushing (25); a right circular conical chamfer (27) arranged in a first side surface (29) of the bushing; an orifice (31) concentric with the chamfer (27) and extending through the bushing to a second side surface (33) of the bushing at the apex of the conical chamfer; said orifice being sized for securely holding a single optical fiber (23); and a spherical lens (21) pressed against the chamfer (27).

2. The apparatus of claim 1, wherein the largest diameter of the chamfer (27) is less than the diameter of the spherical lens (21) whereby spacing between the lens and the orifice (31) is maintained when the lens (21) is pressed against the chamfer.

3. The apparatus of claim 1, further comprising first housing means (87) for surrounding and retaining the alignment bushing (25) and the spherical lens (21), said lens and said bushing being insertablein said first housing means (87) and being prevented from movement outwardly toward a first end of the first housing means.

4. The apparatus of claim 3, further comprising second housing means (51,51') for surrounding said optical fiber, said second housing means including clamping means (59, 59') for securely holding said optical fiber (23) within said second housing means, said first housing means (87) being adapted to be secured to the second housing means (51,51') such that the optical fiber (23) extends through the orifice (31) in the alignment bushing (25).

5. The apparatus of claim 3, further comprising seal means (97) arranged generally between the first end of the first housing means and the lens (21) for preventing contamination of both the chamfer-lens interface and an exposed face of the optical fiber (23), said seal means (97) also urging the lens (21) against the chamfer (27) in the alignment bushing (25).

6. The apparatus of claim 4, wherein the optical fiber is successively concentrically surrounded by at least a buffer layer (49) and a strength layer (47) and wherein the clamping means (59') comprises an annular member releasably secured to the second housing means (51'), said member having a central bore (111) slightly larger than the diameter of the optical fiber and having an outside surface portion (69') for urging said strength layer (47) into tight engagement with an inside wall portion (57') of the second housing (51').

7. The apparatus of claim 6, wherein the clamping means further comprises means (109) on an inside portion of said member for tightly resiliently engaging said optical fiber to hold said optical fiber radially within the second housing means.

8. The apparatus of claim 6, further ccmprising an expansion cone (101) for fanning open the strength layer (47) toward the inside wall portion (57') prior to securing the annular member to the second housing means (51').

9. Apparatus for aligning an optical fiber with a collimating lens, substantially as herein described with reference to the accompanying drawings.