The present invention relates generally to fiber optic connectors and, more particularly, to multifiber fiber optic connectors adapted for field installation.
Optical fibers are widely used in a variety of applications, including the telecommunications industry in which optical fibers are employed in a number of telephony and data transmission applications. Due, at least in part, to the extremely wide bandwidth and the low noise operation provided by optical fibers, the use of optical fibers and the variety of applications in which optical fibers are used are continuing to increase. For example, optical fibers no longer serve as merely a medium for long distance signal transmission, but are being increasingly routed directly to the home or, in some instances, directly to a desk or other work location.
With the ever increasing and varied use of optical fibers, it is apparent that efficient methods of coupling optical fibers, such as to other optical fibers, to a patch panel in a telephone central office or in an office building or to various remote terminals or pedestals, are required. However, in order to efficiently couple the signals transmitted by the respective optical fibers, a fiber optic connector must not significantly attenuate or alter the transmitted signals. In addition, the fiber optic connector must be relatively rugged and adapted to be connected and disconnected a number of times in order to accommodate changes in the optical fiber transmission path.
In order to provide the desired signal transmission characteristics, a number of fiber optic connectors have been developed which are mounted to the end portion of one or more optical fibers during a factory assembly process. By mounting the fiber optic connector to the optical fiber(s) and/or fiber optic cable (hereinafter optical fiber) during an assembly process at the factory, the assembly of the fiber optic connector can be standardized such that inconsistent assembly and other problems associated with the field installation of the connector are avoided.
However, the factory installation of fiber optic connectors is not altogether satisfactory for every application. In particular, the factory installation of fiber optic connectors does not customize the installation process to account for the myriad of design variations experienced in the field. For example, by installing fiber optic connectors to the end portion of an optical fiber at the factory, the length of the connectorized optical fiber is fixed, thus requiring excess length and coiling to insure sufficient length for all applications. In addition, in many instances, it is desirable to cut a length of optical fiber into a plurality of shorter lengths of optical fiber, each of which must be individually connected, such as by a fiber optic connector, to another optical fiber or to a patch panel or other type of terminal. However, the respective lengths of the shorter optical fibers cannot generally be determined until the optical fibers are installed in the field. Thus, in this instance, the requisite fiber optic connectors cannot be mounted to the fibers at the factory prior to installation of the optical fiber. Still further, it is desirable, in many instances, to package and ship optical fiber prior to the installation of the fiber optic connectors since the fiber optic connectors generally have a greater diameter than the respective optical fiber, and may unnecessarily complicate the packaging and shipping of the optical fiber.
Consequently, several fiber optic connectors have been developed which can be mounted to the end portion of an optical fiber in the field once the particular application of the optical fiber has been determined. For example, the UNICAM(trademark) connector which is manufactured and distributed by Siecor Corporation, the assignee of the present invention, is adapted to be mechanically spliced to an optical fiber. Unfortunately, the UNICAM(trademark) connector as well as most other standard field installable connectors are designed to be mounted upon the end portion of a single optical fiber. Accordingly, in order to connectorize two or more optical fibers, such as provided by a fiber optic ribbon cable or the like, the optical fibers must be separated and then individually terminated with single fiber connectors. As will be apparent, the individual connectorization of a plurality of optical fibers therefore requires significant time, labor and cost. Additionally, the separation of a fiber optic cable into individual optical fibers also mechanically weakens the fiber optic cable at the point of separation.
In order to connectorize two or more optical fibers with a single connection, a number of multifiber connectors have been developed which receive and maintain two or more optical fibers in respective predetermined positions during interconnection. For example, the ESCON(trademark) connector and the FCS(trademark) connector have been developed. These connectors include a pair of conventional ferrules, each of which receive and maintain a single optical fiber in a predetermined position during interconnection. The ESCON(trademark) and FCS(trademark) connectors also include a housing or yoke which surrounds and supports the ferrules in a side-by-side relationship. Accordingly, these fiber optic connectors can provide for the simultaneous connection of two or more optical fibers as known to those skilled in the art. However, these fiber optic connectors, such as the ESCON(trademark) and FCS(trademark) connectors, have a nonstandard size and are generally relatively large since they include at least two conventional ferrules positioned in a side-by-side relationship. See also U.S. Pat. Nos. 4,898,449 to Vroomen, et al.; 5,064,268 to Morency, et al.; 5,093,881 to Bartolin, et al., 5,123,072 to Kawanami, et al.; and 5,125,055 to Kawanami, et al. which describe several other types of customized or nonstandard multifiber connectors.
Therefore, while a number of customized or nonstandard multifiber connectors have been developed, these multifiber connectors typically include multiple components, such as multiple ferrules, which must be assembled to form the fiber optic connector. Due to the multiple components which must generally be precisely aligned, the assembly process can be relatively complicated and the resulting cost of the nonstandard fiber optic connectors can be correspondingly increased. For example, the end face of most nonstandard multifiber connectors must be precisely polished since those multifiber connectors are typically quite sensitive to polishing imperfections which may result in poor optical performance or failure of the multifiber connector. As a result, specially trained technicians may be required to mount these multifiber connectors to the end portions of two or more optical fibers. In addition, due to the customized or nonstandard designs of these fiber optic connectors, the fiber optic connectors typically cannot mate with standard fiber optic connectors or with terminals which have been designed to mate with standard fiber optic connectors. As such, other connector hardware must be provided to permit these nonstandard multifiber connectors to mate with a connector sleeve, a terminal or the like. Further, the relatively large size of a number of the nonstandard fiber optic connectors described above limits the applications in which such fiber optic connectors can be employed since they may be unable to mate with other fiber optic connectors or other types of terminals in areas of limited access.
According to one advantageous aspect of the present invention, a multifiber connector is provided which includes a multifiber ferrule, splice components and a crimp tube that defines a lengthwise extending passageway having a lateral cross-sectional shape which is generally oval for receiving a plurality of optical fibers and that is adapted to be crimped about the optical fibers so as to maintain the optical fibers in a lateral side-by-side relationship. As such, the crimp tube of this advantageous embodiment provides the optical fibers to the splice components in an aligned and properly spaced manner for alignment and optical interconnection with respective optical fiber stubs. By facilitating the alignment and spacing of the plurality of optical fibers, the multifiber connector including the crimp tube of this aspect of the present invention can be mounted upon a plurality of optical fibers, thereby obviating the conventional practice of separately connectorizing each optical fiber and permitting a plurality of optical fibers to be connectorized in a more efficient and less time consuming manner. In addition, since the multifiber connector including the crimp tube of this embodiment of the present invention appropriately aligns the plurality of optical fibers without requiring the optical fibers to be spaced widely apart, the fiber optic connector of this embodiment of the present invention can include conventional housings and shrouds, thereby facilitating connection of the multifiber connector of this advantageous embodiment with conventional fiber optic hardware, such as connector sleeves, terminals and the like.
According to one embodiment of the multifiber connector, the splice components are adapted to align and operably interconnect end portions of the plurality of optical fiber stubs and the plurality of optical fibers in a splice plane. As such, the passageway defined by the crimp tube of this embodiment preferably defines a major axis in lateral cross-section that extends laterally in a direction parallel to and, more preferably, coplanar with the splice plane such that the optical fibers can be appropriately aligned with respect to the splice plane. Additionally, the passageway defined by the crimp tube is preferably sized such that the major axis is at least twice as long as an orthogonal minor axis such that the crimp tube aligns the optical fibers in a side-by-side relationship along the major axis.
The crimp tube of one advantageous embodiment includes at least one projection, typically having a curved shape in lateral cross-section, that extends into the passageway for securing the optical fibers therein. According to one embodiment, each projection is formed by an elongate rib extending lengthwise through at least a portion of the passageway. In addition, the crimp tube of one advantageous embodiment includes a pair of aligned projections extending into a medial portion of the passageway from opposite sides thereof.
Although the inwardly extending projections facilitate the secure attachment of the crimp tube to the optical fibers, the crimp tube need not include inwardly extending projections but can, instead, have an elliptical shape in lateral cross-section in order to receive the plurality of optical fibers in a lateral side-by-side relationship. In addition, the outer surface of the crimp tube of this embodiment generally has a similar elliptical shape in lateral cross-section.
In order to insure that the end portions of the optical fiber stubs and the field fibers are aligned in the splice plane, the fiber optic connector can include a ferrule holder defining a lengthwise extending passageway for receiving the splice components and at least an end portion of the multifiber ferrule. According to one advantageous embodiment, both the multifiber ferrule and the ferrule holder can include at least two alignment features. For example, the multifiber ferrule can include as at least two lengthwise extending channels, while the ferrule holder can include at least two lengthwise extending ribs which extend into the passageway for engaging corresponding channels of the multifiber ferrule. Since the splice plane defined by the splice components is preferably disposed in a predetermined positional relationship to the alignment features of the ferrule holder, the engagement of the alignment features of the ferrule holder and the multifiber ferrule also aligns the end portions of the optical fiber stubs and the field fibers within the splice plane.
According to another advantageous aspect of the present invention, a fiber optic connector is provided that is adapted for field installation and which includes a ferrule, mechanical splice components, a ferrule holder, an associated cam member for actuating the mechanical splice components and means for controlling the position of the cam member relative to the mechanical splice components such that the cam member can be precisely moved from a first unactuated position to a second actuated position. As such, the fiber optic connector of this advantageous embodiment can be mechanically spliced to a plurality of optical fibers in a reliable manner so as to facilitate the field installation of a multifiber connector.
According to this embodiment, the ferrule holder defines at least one window through which a portion of the mechanical splice components, such as the keel, is exposed. By appropriately mounting the cam member upon the ferrule holder, the cam member will engage the exposed portion of the mechanical splice components as the cam member is moved from the first unactuated position to the second actuated position. More particularly, the cam member is adapted to actuate the splice components in order to mechanically splice the optical fiber stubs held by the ferrule and the optical fibers as the cam member is rotated relative to the ferrule holder from a first unactuated position to a second actuated position.
According to this aspect of the present invention, the cam member includes an inwardly extending projection. Correspondingly, the outer surface of the ferrule holder defines a groove for receiving the inwardly extending projection of the cam member and for guiding the cam member as the cam member is mounted on the ferrule holder and is thereafter rotated relative to the ferrule holder from the first unactuated position to the second actuated position. According to one advantageous embodiment, the groove defined by the outer surface of the ferrule holder includes a first section that extends lengthwise along a portion of the ferrule holder from one end of the ferrule holder to a medial portion of the ferrule holder. In addition, the groove defined by the outer surface of the ferrule holder of this embodiment also includes a second section that extends circumferentially about a portion of the ferrule holder and which intersects the first section of the groove in the medial portion of the ferrule holder.
Preferably, the first and second sections of the groove are defined by the outer surface of the ferrule holder of this advantageous embodiment such that the cam member is in the first unactuated position as the cam member is mounted upon the ferrule holder and the inwardly extending projection of the cam member moves through the first section of the groove. In addition, the first and second sections of the groove are also preferably defined by the outer surface of the ferrule holder of this embodiment such that the cam member moves to the second actuated position as the cam member is rotated relative to the ferrule holder and the inwardly extending projection of the cam member moves through the second section of the groove.
Advantageously, the cam member of one embodiment defines a lengthwise extending passageway having an enlarged portion and a camming portion. As such, the exposed portion of the mechanical splice is preferably disposed within the enlarged portion of the passageway of the cam member as the inwardly extending projection of the cam member moves through the first section of the groove. As a result, the splice components are not actuated as the cam member is mounted upon the ferrule holder. However, the exposed portion of the mechanical splice components is thereafter preferably moved along the camming portion of the passageway of the cam member as the inwardly extending projection of the cam member moves through the second section of the groove. As a result, the splice components are actuated so as to mechanically splice the optical fiber stubs and the optical fibers.
Accordingly, the fiber optic connector of this aspect of the present invention facilitates the field installation of the fiber optic connector upon one or more optical fibers. The fiber optic connector of this advantageous embodiment including the inwardly extending projection of the cam member and the generally L-shaped groove of the ferrule holder also insures that the mechanical splice components are fully actuated following assembly so as to securely engage end portions of the optical fiber stubs and the optical fibers. In addition, the fiber optic connector of this embodiment prevents the cam member from being removed from the ferrule holder without first moving the cam member to an unactuated position, thereby preventing damage to the components of the fiber optic connector which could occur if the cam member were forcibly removed from the ferrule holder while the splice components were actuated.
USPTO Backgrounds
USPTO Backgrounds