OPTICAL FIBER CONNECTOR AND METHOD FOR MAKING SAME

Abstract: An optical fiber connector comprises an elongate plug support member (12) having an interior bore extending between opposed first and second ends thereof, a plug (32) circumscribing a portion of the plug support member adjacent the second end thereof, extending therewithin and also being longitudinally outward of the second end. The plug defines an interior bore (18) extending therethrough into communication with the plug support member bore and may be in alignment or in intersecting relation therewith, in respective different types of connectors. An insert (16) is disposed in the plug interior bore and is successively radially circumscribed by the plug and the plug support member. The insert defines an interior passage for receiving an optical fiber and centers same with respect to the plug interior bore.

Description: A significant quality control standard for both of the foregoing types of biconical connectors is precise angular disposition of the fiber therein, i.e., inclined or coincident with the plug central axis. Rather substantial rejections of fabricated connectors have heretofore been seen in quality control inspection on the basis of this control standard. In heretofore known practice for making both types of connectors, the plug has been a molded member throughout, having a bore opening into an end thereof opposite the conical end and formed by a first mandrel upon which the plug was molded in a first molding jacket. This mandrel terminated slightly axially beyond the start of the cone and a second continuation mandrel, in the form of a wire of the diameter of the fiber and its cladding, was secured to the end of the first mandrel. The remote end of the wire was captured by a jewel of a companion molding jacket at a position according with the desired angulation of the fiber in the final assembly, i.e., coincident with the plug central axis in the case of the standard connector and inclined with respect to the plug central axis in the case of the '458 patent connector. In the described prior practice, the disposition of the wire, and subsequently the fiber inserted in the passage formed by the wire, was highly dependent on both displacement of the wire in response to molding material forces thereon and on the position of the jewel. Both of these factors bear particularly on failure to meet the above quality control standard. US-A-4,264,128 discloses an optical fiber connector comprising an elongate plug support with a plug circumscribing an end of the plug support. The plug extends into the interior of the plug support and projects from the end of the plug support. An interior bore extends through the interior of the plug and communicates with a bore in the plug support. The plug interior bore is molded over the centered optical fiber and thus no centring insert is disclosed. WO-A-84/00069 discloses an optical connector with a centring insert inside the bore of a plug, with the end of the bore being occupied by a jewel. The centring insert does not extend to the end of the bore, since this is occupied by the jewel. Summary of the Invention The present invention has as its primary object the provision of improved optical fiber connectors. A more particular object of the invention is to provide solutions to the aforementioned quality control yield problems heretofore faced by the art. According to the present invention there is provided an optical fiber connector, comprising: (a) an elongate plug support member having an interior bore extending between opposed first and second ends thereof; (b) a plug encompassing a portion of said plug support member adjacent said second end of said plug support member extending therewithin and also projecting longitudinally outward beyond said second end, said plug having an interior bore extending therethrough into communication with said plug support member bore, characterised by: (c) an insert disposed in said plug interior bore and lying, in part, within said plug and said plug support member, said insert extending out of said plug, said insert having an interior bore for receiving an optical fiber and centering same with respect to said plug interior bore. As will be more fully discussed below, the connector of the invention forces an expansion of the plug bore of the prior art to a measure vastly exceeding same and being a multiple of the composite diameter of the optical fiber and its cladding, thereby enhancing symmetry as between the plug bore end face and the frustro-conical exterior surface of the plug. There is also disclosed a method for making an optical fiber connector, comprising the steps of configuring a molding core to define an interior bore and closing the bore at a preselected axial location therealong by disposing a core mandrel therein and configuring a molding jacket for assembly with the molding core to circumscribe an end portion of the molding core and therewith define a molding cavity to form a plug exteriorly thereon, interiorly of the molding core up to such preselected location, and axially beyond the core mandrel. The molding jacket is further formed to have a molding jacket mandrel fixedly disposed therein and matable with the core mandrel upon assembly of the molding core and the molding jacket, thereby to form a passage extending throughout the molding core and the molding jacket. One assembles the molding mandrel defines a controlled circular surface, preferably provided as a machined metal component, and exhibits exposed cylindrical surface in the final connector, grinding operations are improved over those otherwise obtaining in the prior connectors, which exhibited molded plastic exteriors throughout the length of the connectors. While the foregoing discussion has centered on the connector type described in the '458 patent, it will be appreciated, as alluded to at the outset above, that method of the invention and its product structure are equally applicable to the making of the standard type of biconical connector wherein the fiber is to be disposed in coincidence with the connector central axis. Thus, the aforementioned control of fiber angle at zero to the connector central axis and orientation in the standard connector are served by the invention, as is the enhanced effectiveness of the grinding operation. Various changes may be made to the foregoing structure and modification may be introduced in the foregoing practices without departing from the invention. For example, while the insert is configured in Fig. 5 as an integral body, other fiber centering inserts may be employed, such as the well-known arrangement of three cylindrical rods having a fiber disposed therewithin. Further, the invention contemplates molding of such insert in situ. Accordingly, it is to be understood that the particularly disclosed and depicted embodiments and methods are intended in an illustrative and not in a limiting sense. The true scope of the invention is set forth in the following claims.

Claims: An optical fiber connector, comprising: (a) an elongate plug support member (12) having an interior bore (16) extending between opposed first (24) and second (26) ends thereof; (b) a plug (14) encompassing a portion of said plug support member (12) adjacent said second end (26) of said plug support member extending therewithin and also projecting longitudinally outward beyond said second end, said plug having an interior bore (18) extending therethrough into communication with said plug support member bore (16), characterised by: (c) an insert (44) disposed in said plug interior bore (18) and lying, in part, within said plug and said plug support member, said insert extending out of said plug, said insert having an interior bore (48) for receiving an optical fiber and centering same with respect to said plug interior bore. An optical fiber connector as claimed in claim 1 wherein said plug (14) has an exterior frustro-conical surface (20) tapering radially downwardly to an end face (14a) of said plug longitudinally outward of said plug support member second end (26). An optical fiber connector as claimed in claim 2 wherein said plug interior bore (18) is concentric with said plug frustro-conical surface (20) at said end face of said plug. An optical fiber connector as claimed in claim 3 wherein said plug interior bore (18) defines a further frustro-conical surface (40) interiorly thereof providing a transition from said plug support member interior bore (48) to said plug interior bore (18). An optical fiber connector as claimed in claim 4 wherein said plug interior bore (18) defines an inward stop surface (38) for said insert (44) adjacent said further frustro-conical surface (40). An optical fiber connector as claimed in claim 5 wherein the length of said plug interior bore (48) from said stop surface (38) to said plug end face (14a) is less than the length of said insert (44). An optical fiber connector as claimed in claim 6 wherein said insert (44) comprises a cylindrical body having a central bore (48) therethrough of diameter generally equal to the diameter of said optical fiber with its cladding. An optical fiber connector as claimed in claim 7 wherein said insert (44) includes a still further frustro-conical surface (50) therein providing a transition from said plug interior bore (18) to said insert cylindrical passage (48).

Inventors: GALIOTTI, GEORGE A. MINNESOTA MINING AND, KOFOD, MOGENS MINNESOTA MINING AND, PUCHAMMER, JULIUS T. MINNESOTA MINING AND, RAO, RAM A. C/O MINNESOTA MINING AND
Applicants: MINNESOTA MINING AND MANUFACTURING COMPANY
Application year: 1988
Main classification: G02B6
IPC codes: G02B6, B29C33, B29C70