Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
1998-11-04
2001-04-17
Sanghavi, Hemang (Department: 2874)
Optical waveguides
With optical coupler
Particular coupling structure
C385S059000, C385S065000, C385S071000, C385S083000
Reexamination Certificate
active
06219479
ABSTRACT:
TECHNICAL FIELD
This invention relates to fiber optic couplers, and more particularly to a passive fiber optic star assembly.
BACKGROUND OF THE INVENTION
A passive fiber optic star is a device used to distribute the optical information from one fiber optic source to several fiber optic receivers simultaneously, without an external source of power. The heart of the fiber optic star is its mixing element, a device by which the optical signal coming in from any of several input fibers is distributed more or less evenly among the output fibers. Characteristic features of mixing elements include a number of input and output ports, connection method, uniformity, insertion loss and excess loss. Insertion loss of the amount of attenuation experience between an input and output port. Excess loss of the amount of attenuation of the input signal before reaching the output ports. Such a system as described in U.S. Pat. No. 5,367,595 issued to Jennings et al on Nov. 22, 1994.
U.S. Pat. No. 5,402,512 issued to Jennings et al on Mar. 28, 1995 describes a seven fiber optic line star connection with a retainer that forms a mixing element into a predefined shape. The retainer constraints the mixing element on all sides. The mixing element in one embodiment is made from polymethylmethaacyalate, a material which shrinks approximate two percent when heated and cooled repeatedly. Because the mixing element is constrained on all sides, shrinkage occurs at the ends of the mixing element causing a gap to appear between the linear arrayed fibers and the mixing element. This gap greatly increases the optical insertion loss of the star.
This fiber optic coupling system includes an individual spring and terminal for each fiber plug into the star. As each fiber is plugged into the star, it is retained by a plastic lock. Because the space required for the “push, click, tug” locking mechanism of the system, the fibers must be spaced on 5 mm center lines. The incoming fibers are transitioned in each of three dimensions or directions down into a linear array. In order to minimize light loss, the fiber should not be bent on a radius smaller than 25 mm. Because of the large spacing between the fibers, each fiber must be transitioned many mm in each direction in order to lineup in the linear array without substantially reducing light loss. Accordingly, under this type of system configuration, the transition occurs over a length of 50 mm.
Further, under this fiber optical coupling system a complex assembly of parts is utilized to create channels which guide individual fibers into their appropriate positions in the linear array. The channel was created by assembling a convergent piece with a stop. A combination of two parts creates the channel which guides each fiber into position. The channels are not significantly tight however. The fibers when heated, lose some of their column strength, and tend to relax resulting in extra space in the channels. As a result, the ends of the fibers in the array tend to back away from the mixing element creating a gap and increasing the optical loss. Thus, a solution to the drawbacks of this type of system is needed.
SUMMARY OF THE INVENTION
The invention generally includes an optical star assembly having a ribbon fiber optic mixing element with first and second ends. A first and second bundle of fiber optic cables are provided each with an engagement end for connection with a respective end of the ribbon fiber optic mixing element. The ribbon fiber optic mixing element and a portion of the fiber optic cables are carried in the housing so that the housing biases the ribbon fiber optic mixing element towards an engagement end of the first and second bundles of fiber optic cables respectively. The fiber optic cables may be connected to a plurality of optical receivers so that the ribbon fiber optic mixing element distributes optical information from each of the fibers to all of the optical receivers in the assembly.
In one embodiment of the invention, first and second ribbon holders are secured to respective ends of the ribbon fiber optic mixing element and a bridge extends between the ribbon holders. A stop with a sloped surface is provided on one the of the upper or lower housing halves. The stop is positioned so that when the upper and lower halves are connected together, the sloped surface of the stop engages the bridge to bias the ribbon holder ends, and thus the ends of the ribbon fiber optic mixing element, towards the first and second bundles of fiber optic cables respectively.
In another embodiment of the invention, a bundle of fiber optic cables is provided including a first row of cables aligned in a first plane and overlying a second row of cables aligned in a second plane. A star ferrule is provided including a plurality of channels formed therein each for receiving a fiber optic cable and constructed and arranged so that the fiber optic cable is transitioned in the X, Y and Z directions so that two fibers from the first row are transitioned into a linear array and are spaced apart a distance sufficient to receive a third fiber therebetween from the second row. Accordingly, all the fibers in the first and second row are transitioned into a single linear array engaging the engagement end of the ribbon fiber optic mixing element. More particularly, two fibers from one row are transitioned a distance just sufficient to receive another fiber from the other row therebetween and preferably so that the cables are positioned on 2.2 mm center lines.
These and other objects, features and advantages of the present invention will become apparent from the following brief description of the drawings, detailed description, and appended claims and drawings.
REFERENCES:
patent: 4995692 (1991-02-01), Dihiello et al.
patent: 5097522 (1992-03-01), Tackett et al.
patent: 5367595 (1994-11-01), Jennings et al.
patent: 5402512 (1995-03-01), Jennings et al.
Bungo Edward M.
Corso Anthony Joseph
Halbach Paul Gerhard
Madden William T.
Delphi Technologies Inc.
Jones Richard A.
Sanghavi Hemang
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