Fiber optic connector and method for assembling

A connector and method for assembling a connector. The connector includes a ferrule that is retainably engaged within a hub. The connector further includes a rear housing and a front housing. The front housing is sized to receive and rotationally retain the hub. The front housing has a bore that receives and engages the exterior surface of a rear housing. The front and rear housing include engagement members that allow the rear housing to be retained within the front housing. A grip housing slideably mounts to the front housing. A boot mounts to the rear housing and terminates before the grip. An inner passage of the rear housing includes a flared passage adjacent to the hub.

FIELD OF THE INVENTION

The present invention relates to fiber optic connectors for use in optical fiber signal transmission systems, and to methods for assembling such fiber optic connectors.

BACKGROUND OF THE INVENTION

Fiber optic cables are used in the telecommunication industry to transmit light signals in high speed data and communication systems. A standard fiber optic cable includes a fiber with an inner light transmitting optical core. Surrounding the fiber typically is a reinforcing layer and an outer protective casing or jacket.

A fiber terminates at a fiber optic connector. Connectors are frequently used to non-permanently connect and disconnect optical elements in a fiber optic transmission system. There are many different fiber optic connector types. Some of the more common connectors are ST, FC and SC connectors. Small form factor connectors include LC and LX.5 (by ADC Telecommunications, Inc.).

A typical SC fiber optic connector includes a housing having a front end positioned opposite from a rear end. The front end of the SC connector housing is commonly configured to be inserted within an adapter. An example adapter is shown in U.S. Pat. No. 5,317,663, the disclosure of which is incorporated by reference. The SC connector typically further includes a ferrule that is positioned within the front and rear ends of the housing, and adjacent the front end. The ferrule is axially moveable relative to the housing, and is spring biased toward the front of the connector. The fiber optic cable has an end that is stripped. The stripped end includes a bare fiber that extends into the connector and through the ferrule.

A connector, such as the connector described above, is mated to another connector within an adapter like the adapter of U.S. Pat. No. 5,317,663. A first connector is received within the front portion of the adapter, and a second fiber is received within the rear portion of the adapter. When two connectors are fully received within an adapter, the ferrules (and hence the fibers internal to the ferrule) contact or are in close proximity to each other to provide for signal transmission between the fibers.

Another SC connector is shown in U.S. Pat. No. 6,428,215, the disclosure of which is incorporated by reference. The SC connector of U.S. Pat. No. 6,428,215 is tunable, if desired.

SUMMARY OF THE INVENTION

One aspect of the present invention relates to a fiber optic connector. The connector includes a ferrule that is retainably engaged within a hub. The connector further includes a rear housing and a front housing. The front housing and the rear housing are sized to receive the hub, the ferrule and a spring. The front housing has a bore that receives and engages the exterior surface of the rear housing. The front and rear housings include engagement members that allow the rear housing to be retained within the front housing. A grip housing mounts over the front housing for sliding relative movement. A strain relief boot mounts to the rear housing and terminates before the grip housing.

An interior passageway of the rear housing includes an entry end at a distal end connected to a main passage. A flared passage connects to the main passage at an opposite end. A spring passage at a proximal end is adjacent to the ferrule and hub, and connects to the flared passage. The main passage is sized to closely surround a 900 micron buffer coated fiber. The spring passage is wider than the main passage. The flared passage is positioned adjacent to the spring passage. The flared passage defines a flared shape connecting the main passage to the spring passage. Preferably, the flared passage is separated by a gap from the end of the hub of less than or equal to about 0.083 inches, and more preferably about 0.063 inches.

Another aspect of the present invention relates to a method for assembling a fiber optic connector including the above features. The location of the flared passage allows for easier passage of the fiber from the main passage to the ferrule during assembly. The strain relief boot does not occupy space within the grip housing as prior SC designs did, thereby allowing larger cables to be crimped to the rear housing.

A variety of advantages of the invention will be set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practicing the invention. It is to be understood that both the foregoing general description and the following detailed description are explanatory only and are not restrictive of the invention as claimed.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary aspects of the present invention that are illustrated in the accompanying drawings. Where ever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

FIGS. 1-6illustrate an SC-type connector20constructed in accordance with the principles of the present invention. The connector20includes a housing22having a front housing24that connects to a rear housing26. A strain relief boot28is mounted at the rear end23of the connector20. The front portion49of a ferrule48is shown extending out the front end25of the connector20. The ferrule48is mounted to a hub44which together are slidably mounted within the connector20. Connector20also includes a slidable outer grip housing92located at the front of the housing22that is typically found on an SC-type connector.FIGS. 1-3also show connector20mounted to a cable96.

The front housing24of the connector20extends along a longitudinal axis30and includes a front end32positioned opposite from a rear end34. The front housing24also defines a front chamber36and a rear chamber38. A transverse wall40separates the front and rear chambers36and38. An opening42centered about the longitudinal axis30is defined by the transverse wall40. The front and rear ends32and34of the front housing24are open with a bore33formed therebetween extending along longitudinal axis30.

Referring now toFIGS. 2,3,5and11-14, the connector20also includes a hub44positioned within the connector20. The hub44is mounted to slide longitudinally along the axis30relative to the front housing24. The hub44has openings45and47at its front and rear portions55and57with a bore53extending between the openings.

The hub44secures the ferrule48. The ferrule48includes a rear portion51mounted within the front opening45defined by the hub44. The ferrule48may be secured to the hub44using a conventional fastening technique, such as an epoxy adhesive. The hub44can also be mounted to the ferrule48with an interference fit or it can be molded around the ferrule48. The ferrule48includes a bore59for receiving a bare optical fiber98. The ferrule48extends along the longitudinal axis30from the hub44toward the front end32of the front housing24. The ferrule48extends through the central opening42of the transverse wall40between the front and rear chambers36and38of the front housing24, and protrudes out from the front end25of the connector20. Typically, fiber98is epoxied to the ferrule48.

The connector20further includes a coil spring56positioned within the rear chamber38. The coil spring56surrounds the rear portion57of the hub44and is captured between a forwardly facing shoulder58formed by the rear housing26and a rearwardly facing shoulder60formed by the hub44. The spring56functions to bias the hub44toward the front end32of the front housing24. Because the ferrule48is connected to the hub44, the spring56also functions to bias the ferrule48in a forward direction.

Referring now toFIGS. 2-10, the rear housing26also extends along longitudinal axis30and includes a front end62positioned opposite from a rear end64. The hub44and surrounding spring56slide into the opening27at the front end62of the rear housing26. The hub44and spring56, however, are not mechanically fastened to the rear housing26, and thus are free to move longitudinally along axis30with respect to the rear housing26. The only limit placed on the rearward movement of the hub44and spring56into the rear housing26is the forward facing shoulder58on the rear housing26which, as mentioned above, engages the spring56. The engagement of the spring56to the shoulder58functions to bias the hub44and connected ferrule48outwardly from the opening27at the front end62of the rear housing26.

The front portion55of the hub44and the chamber38at the rear end34of the front housing24are sized and/or shaped so that the hub44, when received within the housing22, cannot be rotated. Likewise, the ferrule48, which is secured to the hub44, does not rotate relative to the housing22when the hub44is inserted therein. This can be achieved by having a non-circularly shaped hub44and a corresponding non-circularly shaped chamber38at the rear end34of the front housing24. In the embodiment shown, slots63on the hub44and corresponding teeth65in chamber38of the front housing24prevent relative rotation at all times during use, including during rearward sliding movement. It can be appreciated that other configurations could be used which mount the hub44within the front and rear housings24,26but not be rotatable once assembled. This allows for the fiber at end49of the ferrule48to be polished at an angle if desired. Hub44and front housing24also include front angled surfaces67on hub44and line or edge contacts69on front housing24as described in U.S. Pat. No. 6,916,120, the disclosure of which is incorporated by reference. These allow for more precise alignment if the connector is disconnected and reconnected to the adapter.

Further details of the front housing24can be seen inFIGS. 2-6. The rear portion34of the front housing24includes two extensions66and68that define the opening29at the rear portion34. The extensions66and68also define two cut-outs70that extend longitudinally toward the front end32of the front housing24on two of the sides of the front housing24. The cut-outs70give the extensions66and68a resiliency allowing them to be deflected outward when suitable pressure is applied from within the opening29.

As noted above, the front housing24connects to the rear housing26. The front end62of rear housing26is received into the opening29at the rear end34of the front housing24. Two tabs82are positioned on the external surface of the rear housing26. When the rear housing26is inserted into the opening29of the front housing24, the tabs82press up against the extensions66,68. The tabs82snap into adjacent slots80formed in the front housing24. When that occurs, the resilient extensions66and68quickly return to their natural positions, which secures the rear housing26to the front housing24.

The connector20further includes grip housing92. The connector housing22inserts into a bore93formed within the grip housing92. The front housing24includes structure that mounts the connector housing22within the grip housing92as is known in the art. When the connector housing22is positioned within the grip housing92, the grip housing92restrains the resilient extensions66and68, preventing them from deflecting outward. The external surface of the connector housing22and the bore93of the grip housing92are configured such that the connector housing22can be fully inserted into the grip housing92in only one orientation. For example, see keyed front side surfaces102on the front housing24, and a matching profile for bore93. The external surface of the grip housing92includes a longitudinal key94that is sized to be received into a slot of an adapter (not shown), such as the adapter of U.S. Pat. No. 5,317,663, where the connector mates with a second SC-type connector.

An interior passageway81of the rear housing26receives an end of the cable96and includes an entry end83at a distal end connected to a main passage85. A flared passage87connects to the main passage85at an opposite end. A spring passage89at a proximal end is adjacent to the ferrule and hub, and connects to the flared passage87. The main passage85is sized to closely surround a 900 micron buffer coated fiber. The spring passage89is wider than the main passage85. The flared passage87is positioned adjacent to the spring passage89. The flared passage87defines a flared shape connecting the main passage85to the spring passage89. Preferably, the flared passage is separated by a gap from the end of the hub of less than or equal to about 0.083 inches, and more preferably about 0.063 inches. Ferrule48and hub44can push back 0.078 inches to be flush with the front end of the connector20.

One goal of the flared shape is that it generally defines a surface that does not damage the bare fiber as it is pushed axially from the rear end23toward the ferrule48. Sharp transitions and edges could cause burrs or cutting surfaces that could nick the fiber during insertion. By moving the flared shape fairly close to the hub44, there is less chance for the fiber to drift away from the longitudinal axis30and become misaligned during insertion. Compare the flared passage87with the cross-sections of a prior art SC design as shown inFIGS. 25-27. Preferably, main passage85is at 0.060 inches in diameter. Flared passage87extends from 0.060 inches in diameter to 0.109 inches in diameter.

As shown inFIGS. 1-4and15-21, connector20includes an internal crimp ring71for crimping the housing22to an end of cable96. The external boot28is snapped onto the housing22. Note that the boot28and the grip housing92do not overlap. The exterior shape of the grip housing92is a standard well-known SC type connector shape useable with mating SC adapters.

The present invention is further directed to a method for assembling the SC-type connector described above. The ferrule48is first mounted within the opening45formed in the front portion55of the hub44. The spring56is then positioned over the rear portion57of the hub44, and together these are inserted into the rear end34of the front housing24. Next, the rear housing26is snapped into the front housing24, thereby retaining the hub44and ferrule48(and spring56) within the connector housing22. This connection is made to prevent movement of the rear housing26relative to the front housing24. As mentioned above, the front portion55of the hub44is sized and shaped so that when it is inserted into the front housing24, the hub44(and connected ferrule48) cannot rotate relative to the front rear housings24,26.

At this point, a fiber optic cable96, having a central bare fiber98, is attached to the connector20using conventional techniques well known in the art. This includes stripping the end of the cable96to expose the fiber98. The fiber98is then fed into the connector20all the way through passage81including flared passage87and into the bore59in the ferrule48. The fiber may be either mechanically or adhesively retained within the ferrule48. The buffer coated portion99of the fiber (typically 900 microns) extends through the connector20up to the ferrule48. A reinforcement layer101(such as aramid yarn) of the fiber optic cable96is crimped with the crimp sleeve71. An outer jacket103of cable96is also crimped to the rear housing by the crimp sleeve71. The rear housing26has a first crimp surface105for the reinforcing layer101. First crimp surface105is preferably textured for improved gripping of the reinforcing layer, such as with knurling. The rear housing26has a second crimp surface106for the outer jacket103. The crimp sleeve71includes one or more crimp rings107to improve gripping of the jacket103. Crimp rings107project outwardly on crimp sleeve71. Crimp rings107provide localized gripping on the jacket103.

In the illustrated embodiment, cable96is a 5 millimeter cable. For smaller cables, a different crimp sleeve171can be used with a smaller rear end172as shown inFIGS. 22-24. Similar crimp rings175to rings107can be used. For example, a cable with a 3.6 millimeter outer dimension can be used with crimp sleeve71. In some cases, a different boot28may be needed to more closely surround cable96at distal end109. For still smaller cables, smaller rear ends172can be provided.

The boot28is positioned over the crimp sleeve71and helps provide strain relief. Slots108in boot28provide flexibility. The boot28is attached to the rear housing26by snapping a circumferential lip76over a circumferential tab78. Note that boot28terminates before grip92. A stop79prevents boot from being slid too far toward the grip housing92. In this manner, larger cables96can be used than connectors of the type shown in U.S. Pat. No. 6,428,215, noted above. The exposed bare fiber at the front end49of the ferrule48may then be removed and polished. The connector housing22is inserted within the grip housing92. The connector20can then be inserted into an adapter (not shown) for mating with a second SC-type connector.

It is anticipated that connector housing22can be used with a variety of cable sizes. As noted above, cable96can be 5.0 millimeters, or 3.6 millimeters. Other sizes are anticipated where only the crimp sleeves71,171and rear ends109of boots28would vary. Cable sizes that are anticipated include 1.7 millimeter, 2.0 millimeter and 3.0 millimeter. Also, connector20can be used with 900 micron cables, that have no reinforcing members.

With regard to the foregoing description, it is to be understood that changes may be made in detail, especially in matters of the construction materials employed and the shape, size and arrangement of the parts without departing from the scope of the present invention. It is intended that the specification and depicted aspects be considered exemplary only, with a true scope and spirit of the invention being indicated by the broad meaning of the following claims.