Optical waveguides – With disengagable mechanical connector – Optical fiber/optical fiber cable termination structure
Reexamination Certificate
2003-01-15
2004-11-16
Palmer, Phan T. H. (Department: 2874)
Optical waveguides
With disengagable mechanical connector
Optical fiber/optical fiber cable termination structure
C076S087000
Reexamination Certificate
active
06817780
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to fiber-optic cable used for the conducting optical signals. More particularly, the present invention relates to a guide boot for bending a fiber-optic cable, and maintaining the bend radius of the fiber-optic cable at or above a predetermined value.
BACKGROUND OF THE INVENTION
Fiber-optic cables are commonly used to transmit optical signals between optoelectronic devices. A conventional fiber-optic cable can include an optically-conductive optical fiber, and a protective inner jacket that surrounds the optical fiber and protects the optical fiber from buckling. The inner jacket can be surrounded by a layer of protective fibers having sufficient strength to withstand the maximum anticipated tensile forces on the fiber-optic cable. The protective fibers can be enclosed in a flexible outer jacket.
Excessive bending or twisting of a fiber-optic cable can degrade the quality of the optical signals transmitted through the fiber-optic cable. In extreme cases, excessive bending or twisting can break the optical fiber within the fiber-optic cable. In practice, fiber-optic cables must often be bent to facilitate routing to, from, or within equipment such as computers, connector panels, junction boxes, etc. Accordingly, fiber-optic cables are typically evaluated to determine a minimum bend radius. The minimum bend radius represents the minimum radius at which the fiber-optic can be bent without potentially degrading signal-transmission quality, or damaging the optical fiber within the fiber-optic cable.
Connectors are commonly used to couple fiber-optic cables to other fiber-optic cables, or to optoelectronic devices such as sources, detectors, repeaters, switches, attenuators, etc. The point at which a fiber-optic cable enters a connector is particularly susceptible to being bent in excess of, i.e., more sharply than, the minimum bend radius for the fiber-optic cable.
A guide boot is often used to maintain the bend radius of a fiber-optic cable at or above the minimum bend radius as the fiber-optic cable approaches and enters a connector.
FIGS. 1A and 1B
depict a conventional guide boot
100
used in conjunction with an LC-type connector
102
and a fiber-optic cable
104
. The figures are each referenced to a common coordinate system
11
depicted therein.
The cable
104
is mechanically coupled to the connector
102
using a metallic crimp sleeve
106
and a shrink tube
108
(see FIG.
1
B). The crimp sleeve
106
is crimped over a substantially cylindrical rear mating portion
102
a
of the connector
102
. The shrink tube
108
securely grasps the crimp sleeve
106
and the outer jacket of the cable
104
, and thereby secures the cable
104
to the crimp sleeve
106
(and the connector
102
).
The guide boot
100
has passages formed therein for receiving the cable
104
. The guide boot
100
is mated with the connector
102
by threading a free end of the cable
104
through the passages, and advancing the guide boot
100
along the cable
104
.
A forward, or mating, portion
112
of the guide boot
100
eventually reaches the crimp sleeve
106
as the guide boot
100
is advanced along the cable
104
, as shown in
FIG. 1B. A
force (hereinafter referred to as an “insertion force”) is exerted on the guide boot
100
to advance the mating portion
112
over the crimp sleeve
106
(and over the portion of the shrink tube
108
installed over the crimp sleeve
106
), in the direction denoted by the arrow
120
in FIG.
1
B.
The crimp sleeve
106
becomes disposed within the passage in the mating portion
112
as the guide boot
100
is advanced over the crimp sleeve
106
. The insertion force needed to advance the guide boot
100
is due, in part, to friction between an inner surface
116
of the mating portion
112
, and the portion of the shrink tube
108
installed over the crimp sleeve
106
. The guide boot
100
is retained on the connector
102
primarily by friction between the inner surface
116
of the mating portion
112
and the crimp sleeve
106
.
The guide boot
100
includes a curved body portion
116
. The body portion
116
should have a radius of curvature approximately equal to or greater than the minimum bend radius of the cable
104
. The body portion
116
imparts a corresponding curve to the cable
100
when the cable
100
is installed the passage
110
. The body portion
116
is sufficiently rigid to prevent the cable
104
from being bent in excess of its minimum bend radius.
The guide boot
100
can be rotated in relation to the connector
102
to direct the cable
104
toward a desired location. The guide boot
100
is rotated by imparting a torque to the guide boot
100
sufficient to overcome the friction between the inner surface
116
of the mating portion
112
and the crimp sleeve
106
. (The cable
104
, which is secured to the connector
102
by way of the shrink tube
108
and the crimp sleeve
106
, normally rotates with the mating portion
112
, and in a perfect world would do so without any twist being imparted thereon.)
However, the insertion force needed to advance the guide boot
100
over the shrink tube
108
until it reaches the crimp sleeve
106
in many instances damages the shrink tube
108
. Such is shown in
FIGS. 1C and 1D
. In particular, the force needed to overcome the friction between the inner surface
116
of the mating portion
112
and the portion of the outer surface of the shrink tube
108
installed over the crimp sleeve
106
will deform, tear, or otherwise damage the shrink tube
108
.
This damage to the shrink tube
108
can cause the shrink tube
108
to lose its firm grasp of the rear mating portion
102
a
of the connector
102
. Furthermore, damage to the shrink tube
108
will result in a loss of the frictional/interference fit between the shrink tube
108
and inner surface
116
. Thus, rotating the guide boot
100
to a desired orientation on the connector
102
when the shrink tube
108
has been damaged and its grasp on the rear mating portion
102
a
of the connector
102
lost, can cause a corresponding rotation of the cable
104
. Rotating the cable
104
in this manner will twist the underlying optical fiber, which is independently restrained from rotation within the connector
102
. Twisting the optical fiber can degrade the light-conducting characteristics thereof, and can thereby decrease the quality of the signals transmitted through the cable
104
. Moreover, twisting of the optical fiber, if extreme, can break the optical fiber.
SUMMARY OF THE INVENTION
A preferred embodiment of a guide boot for a fiber-optic cable mechanically coupled to a connector comprises a mating portion having an interior surface defining a passage for receiving a portion of the connector and the fiber-optic cable, and a plurality of ribs formed on the interior surface and extending along at least a portion of a length of the mating portion. A preferred embodiment also comprises a body portion adjoining the mating portion and having an interior surface that defines a passage for receiving the fiber-optic cable. The interior surface of the body portion is curved so that the body portion bends the fiber-optic cable.
A preferred embodiment of a guide boot for bending a fiber-optic cable mechanically coupled to a connector by way of a crimp sleeve and a shrink tube comprises a mating portion. The mating portion has an interior surface defining a passage for receiving the crimp sleeve and a portion of the shrink tube installed over the crimp sleeve. The passage has a diameter greater than an outer diameter of the portion of the shrink tube installed over the crimp sleeve and the interior surface has a plurality of ribs formed thereon for contacting the crimp sleeve. A preferred embodiment also comprises a body portion adjoining the mating portion and having an interior surface defining a passage for receiving the fiber-optic cable.
A preferred embodiment of a system for conducting optical signals comprises a connector, a crimp sleeve fixed to the connector, a fiber-optic cab
FCI Americas Technology Inc.
Palmer Phan T. H.
Woodcock & Washburn LLP
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