Optical waveguides – With disengagable mechanical connector – Optical fiber/optical fiber cable termination structure
Reexamination Certificate
2000-02-04
2001-04-03
Ullah, Akrn E. (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber/optical fiber cable termination structure
Reexamination Certificate
active
06210047
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to the art of fiber optic connectors and, particularly, to a method of fabricating a connector ferrule.
BACKGROUND OF THE INVENTION
In fiber optic transmission systems, signals are transmitted along optical fibers by optical frequency waves (light) generated by such source as LED's, lasers and the like. Optical fibers typically are fabricated of glass materials and, as optical fiber circuitry developed, it became necessary to provide connecting devices which could couple one optical fiber to another, only in an end-to-end relationship.
A traditional procedure for making a connection between ends of optical fibers is to, first, remove a protective jacket from a given length of fiber at the end of the fiber to be joined. After the jacket is removed, a 250 micron (OD) buffer is exposed which can then be stripped to expose a 125 micron (OD) fiber. The fiber is then threaded through a passage in a ferrule where it is affixed in place by adhesive and/or crimping. The fiber is inserted so as to extend well beyond a front surface of the ferrule. The exposed fiber material is then cleaved and polished. Any remaining adhesive is removed. The ferrules then are assembled into a connector assembly which is intended to position the optical fibers with their optical axes in alignment for connection to the fibers of a mating connector or other appropriate connecting device.
A fiber optic ribbon cable has become increasingly popular to provide multiple channels in a single cable structure. An optical ribbon cable is similar to any other well known ribbon electrical cable to the extent that a plurality of generally parallel optical fibers or channels are disposed in a line or generally coplanar relationship. Terminating the optical fibers of a fiber optic ribbon cable is generally similar to the procedure described above. In general, the unitary protective jacket surrounding the line of fibers is removed so that the buffered fibers are exposed which are then stripped and the unprotected fibers project from the flat cable in a line. Typically, these individual fibers must be inserted into respective individual holes or passages in a prefabricated connector ferrule. The passages align the fibers at a predetermined spacing for coupling to the ends of the fibers in a complementary connector ferrule or other connecting device.
This terminating process of the individual fibers of a multi-fiber cable, creates a number of problems. First, because of the very thin size and extremely fragile nature of the fibers, it can be tedious to insert a fiber into a single aligning hole or passage. However, inserting a plurality of such fibers from a single cable into a plurality of passages can be extremely difficult. If a single fiber of the cable is broken, the stripped cable end and ferrule either must be discarded and/or reworked. Since these processes typically are carried out by hand, they can be rather inefficient and result in unnecessary expense.
In the prior art, placing individual fibers of a multi-fiber cable into individual holes or passages in a connector ferrule results in a high percentage of rejects. The ferrules must be inspected hole by hole. In addition to fibers being broken, the holes, themselves, may be too large or too small or not circular. Connector ferrules comprise bodies which are crystalline in nature, typically of ceramic material. However, they can be molded of plastic or like material. For multiple channel ferrules, the fiber-receiving holes or passages must be formed precisely to maintain proper form or alignment and spacing between the fibers to prevent tolerance problems causing transmission losses during mating.
The above alignment/tolerance problems are further complicated in connector assemblies wherein a pair of mating connector ferrules, themselves, are placed in the mating condition by two alignment pins. These alignment pins typically have one end of each pin extending into a passage of the connector ferrule, and the opposite end of the pin being inserted into a passage in the mating connector ferrule, with a chamfered lead-in on the pin for alignment. The problems of maintaining precise tolerances with the alignment pins and their passages must be added to the tolerance problems in maintaining precise spacing and alignment of the individual holes for the optical fibers of the fiber optic cable. It can be understood why there is such a high number of rejects during the fabrication of prior art connector ferrules. The present invention is directed to solving these problems in the fabrication of a multi-fiber ferrule.
SUMMARY OF THE INVENTION
An object, therefore, of the invention is to provide a new and improved method of fabricating a connector ferrule for a fiber optic cable. The invention is particularly applicable for terminating a multi-fiber optic cable which includes a plurality of generally parallel optical fibers, such as a fiber optic ribbon cable having the fibers in a straight line or coplanar relationship, but the invention is not limited to such multi-fiber cables.
In the exemplary embodiment of the invention, the method includes the steps of providing a pair of ferrule clamping members which define at least one fiber passage therebetween for receiving an optical fiber and which define at least one pin passage therebetween of a given diameter. A ferrule body is formed about the clamping members. A spreader pin larger than the given diameter is inserted into the pin passage to spread the clamping members and open the fiber passage. The optical fiber then is inserted into the opened fiber passage, and the spreader pin is removed to allow the clamping members to close onto the optical fiber.
As disclosed herein, the clamping members define a plurality of generally parallel fiber passages of diameters equal to or less than the outside diameters of optical fibers. The pin passage is of a given diameter for receiving a standard alignment pin projecting from the ferrule to align the ferrule with an appropriate complementary connecting device. The ferrule body is molded about the clamping members, and the spreader pin spreads the clamping members within the constraints of the molded body.
Still further, the clamping members herein are provided with opposing generally planar surfaces defining the fiber passages therebetween in a generally straight line for receiving the optical fibers of a fiber optic ribbon cable. The clamping members are provided with fiber half-passages in each of the opposing planar surfaces combining to form the complete fiber passages. One of said pin passages is spaced from each end of the line of fiber passages for receiving a pair of the spreader pins.
Other objects, features and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings.
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Grois Igor
Margolin Mark
Migo Stephen Z.
Molex Incorporated
Tirva A. A.
Ullah Akrn E.
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