Optical fiber connectors are an essential part of substantially all optical fiber communication systems. For instance, optical connectors are used to join segments of fiber into longer lengths, to connect fiber to active devices such as radiation sources, detectors and repeaters, and to connect fiber to passive devices such as switches and attenuators. The principal function of an optical fiber connector is to hold a fiber end such that the core of the fiber is axially aligned with the optical path of the component to which the connector is mated (e.g., another fiber, a planar waveguide, or an opto-electric device). This way, light from the fiber is optically coupled to the other component.
One popular multi-fiber connector is the Lightray MPX™ connector by Tyco Electronics, Inc. (Harrisburg, Pa.). This connector is disclosed in U.S. Pat. No. 6,116,790 to Vergeest, which is incorporated herein by reference. A Lightray MPX™ connector is shown in FIG. 7. The connector comprises a multi-fiber ferrule 71 contained within a housing unit 73. A crimp member 75 is provided at the rear of the housing to secure the fiber optic cable to the connector. Upon mating, the front face of the multi-fiber ferrule 71 contacts the front face of a mating connector to join the fibers.
A popular configuration for the Lightray MPX™ connectors is a blind mate backplane system. FIG. 8 illustrates a blind mate backplane system utilizing a Lightray MPX™ connector 81. One connector 82 is located on a daughter card 83 with a mating connector 84 located on a motherboard or backplane 85. The connection process is a blind mate process, meaning the daughter card is inserted into an appropriate position on the backplane and the connection between the connectors is made without the need for the user to manipulate the connectors.
Typically, flexible fiber optic cable is used in blind mate fiber optic connector systems such as the one shown in FIG. 8. Flexible fiber optic cable has mechanical bending properties similar to copper wire cables; however, in order to maintain suitable performance, flexible fiber optic cable must not have any bends which exceed the minimum bend radius of the cable specification. Specifically, it is well known that as fiber optic cable is bent, there is a resulting loss in power. The loss in power increases as the bend radius decreases. Thus, there exists a minimum bend radius for every cable where a bend sharper than the minimum radius would create an unacceptable loss in power. The minimum bend radius varies depending on the cable type. A typical minimum bend radius for commonly used optical single mode fiber is approximately 25 mm (or 1 inch).
One commonly used method of preventing excessive bending is to employ a bend limiting device referred to as a bend limiter. A bend limiter is attached to the rear portion of an MPX connector plug to serve as a mechanical means of preventing the cable from bending too sharply. FIG. 7 illustrates an MPX connector in conjunction with a bend limiter. The bend limiter 77 is mounted to the rear crimp member 75 of the connector plug housing 73. The bend limiter 77 extends rearward from the crimp member 75 providing a guide path for the fiber optic cable to bend around, and insuring that the bend in the fiber does not exceed the minimum acceptable bend radius.
Many blindmate systems are used in enclosures where the space located behind the backplane is limited. Because of strict space constraints, it is often necessary to route the fiber optic cables to run parallel to the backplane. This requires a full 90° bend in the fiber path. To complete the full 90° bend desired using a Lightray MPX™ connector and a bend limiter, however, a certain amount of space behind the backplane is required. Referring again to FIG. 7, the fibers extend rearward from the front face of the ferrule 71 through the connector housing 73, through the crimp member 75, into the bend limiter 77, and around the controlled radius fiber path 79 of the bend limiter until the full 90° change in direction has been achieved. The total distance required behind the backplane is referred to as the effective connector length. The effective connector length is defined as the distance from the front face of the ferrule 71 to a line parallel with the front face of the ferrule and tangent to the arc radius of the curve at the point where the change in direction of the fiber is complete (shown as distance D on FIG. 7).
Despite the many advantages of the blind mate Lightray MPX™ connector system, occasionally its effective connector length proves to be excessive. Accordingly, there is a need for a blindmate connector system which controls fiber bend radius while minimizing effective connector length. The present invention fulfills this need among others.
USPTO Backgrounds
USPTO Backgrounds