Optical waveguides – With splice – Including splice joint reinforcement
Reexamination Certificate
2000-02-03
2002-01-15
Healy, Brian (Department: 2874)
Optical waveguides
With splice
Including splice joint reinforcement
C385S068000, C385S095000, C385S097000, C385S098000
Reexamination Certificate
active
06338579
ABSTRACT:
BACKGROUND OF INVENTION
1. Technical Field
The present invention relates to a fiber optic cable; and more particularly to a fiber protection sleeve assembly for use in a splice junction of a fiber optic cable.
2. Description of Related Art
Over the years, fiber optic cables have gained popularity and are used in a variety of fields. One such field is oil and gas exploration where fiber optic systems, such as that shown in
FIG. 1
, are used for measuring various conditions underground, such as temperature, pressure, acceleration and vibration. A gas and/or oil exploration environment is harsh, characterized by well gases and fluids, extreme temperatures and pressures, and multiple other cables and equipment extending downwardly through a well into a deep underground region.
FIG. 1
shows one such system
10
for detecting the various conditions in an underground region
12
and transmitting data indicating the status of those conditions to the surface
14
that includes a fiber optic cable
16
having a surface end
20
and an underground end
22
. The surface end
20
of the fiber optic cable
16
attaches to an instrumentation box
24
on the surface
14
, while the underground end
22
extends into the underground region
12
, passing through a well
26
and supporting one or more measuring devices
28
. The fiber optic cable
16
has one or more optical fibers that are typically fragile and must be shielded from the harsh well environment. To effectively protect the optical fiber from the well environment, the optical fiber is placed into protective metal tubing and is environmentally sealed therein, like that shown in
FIGS. 2 and 3
.
FIGS. 2 and 3
show the fiber optic cable
16
which has optical fibers
32
,
33
ultimately shielded by a protective outer capillary tube
34
. Typically, the optical fibers
32
,
33
are encased in a thin layer of flexible coating
35
. The optical fibers
32
,
33
are affixed to the inner capillary tube
37
using a pliable material
36
, such as grease for example. A blocking polymer
38
is disposed between inner capillary tube
37
and outer capillary tube
34
. The fiber optic cable
16
ensures that the optical fibers
32
,
33
are protected from the harsh environment and from any mechanical loads imparted on the fiber optic cable
16
. The subject matter of
FIGS. 1
,
2
and
3
is shown and described in more detail in a commonly-owned co-pending United States Patent Application, filed with Express Mail No. EL
4
19975708US on Feb. 3, 2000 also hereby incorporated by reference in its entirety. Also see commonly-owned copending U.S. patent application Ser. No. 09/121,468, hereby incorporated by reference in its entirety, for a detailed description of another such optical fiber cable.
During installation and maintenance of the system
10
in
FIG. 1
, segments of the fiber optic cable
16
must be joined and sealed to form and maintain a continuous protective covering for the optical fibers
32
,
33
. For example, when the fiber optic cable
16
is either connected to another fiber optic cable, terminated on either end at a well head, a junction box or other instrument, or spliced and repaired for any other reason at some intermediate cable point, the metal inner and outer capillary tubes
34
,
37
are cut and opened to gain access to the optical fibers
32
,
33
. After splicing the optical fibers
32
,
33
to other optical fibers, ends of the metal inner and outer capillary tubes
34
,
37
must be joined together or terminated at a splice junction.
By way of example,
FIG. 4
shows a splice junction for a fiber optic cable
42
that is set forth in the commonly-owned co-pending United States Patent Application, filed with Express Mail No. EL419975708US on Feb. 3, 2000. In summary, the fiber optic cable and splice junction includes the optical fibers
32
,
33
, the outer capillary tube
34
, a buffer material
36
, the capillary tube
37
, a blocking polymer
38
, a splice protection assembly generally indicated as
40
, slice couplings
46
,
48
, an outer tube
50
, welds
52
,
54
,
56
,
58
, carrier tubes or heat sink tubes
60
,
62
, swage crimps
64
,
66
, swage crimps
80
,
82
, a splice protection
91
, a splice area
144
, and fiber splices
148
,
150
.
During installation and maintenance of the system
10
in
FIG. 1
, segments of the fiber optic cable
16
must also be cut and opened to gain access to the optical fibers
32
,
33
. There are known methods in the art of cutting and opening the metal inner and outer capillary tubes
34
,
37
to gain access to the optical fibers
32
,
33
. In particular, the focus of this patent application is on the cutting and opening of the metal inner capillary tube
37
, which is a metal tube about
2
.
4
millimeters in diameter. Typically, a knife file is used to provide a radial score on the metal inner capillary tube
37
, which is then flexed until it breaks-off to expose the optical fibers
32
,
33
.
However, when the metal inner capillary tubes
34
,
37
are cut and opened to gain access to the optical fibers
32
,
33
, then reassembled, problems arise due to the potential for cutting of the fiber jacket
35
caused by exposed edges of the capillary tube
37
, when the spliced junction of the fiber optic cable
16
is subjected to vibration.
Because of this, various scoring, breaking and deburring tests were conducted by the inventor. In one test, visual inspections of the tube samples showed that a broken end of the metal inner capillary tube
37
was deformed with varying degrees of metal wings or tabs by the separation process. The deeper the score of the tube, the greater likelihood of a thin “tab or wing” of metal being produced. This “tab or wing” of metal may be bent either inwardly, outwardly or both. Any surface obstruction or restriction of the inner diameter of the broken end of the metal inner capillary tube
37
will pose a threat for fiber damage by abrasion over time. All samples exhibited this type of result to some extent.
In a second test, the samples were visually inspected after the deburring of the metal inner capillary tube
37
. The inner diameter of the metal inner capillary tube
37
was opened by the deburring tool, but there was evidence of metal wings or tabs still present. A review of the separation process indicated that the metal inner capillary tube
37
had a tendency to rotate or twist with the deburring tool as it was being applied. This reduced the effectiveness of the deburring tool to remove the burrs, as did the rocking motion that is required to prevent possible fiber twist damage due to the tight inner diameter of the tool on the fiber. The combination of the twist, the required tightness of the inner diameter of the tool and the tool geometry (hex outer diameter surface) resulted in a poor end preparation of the inner tube
37
, that could cause fiber damage.
In a third test, samples were visually inspected after the deburring of the metal inner capillary tube
37
held stationary. The inner diameter of the metal inner capillary tube
37
was opened and clear, but the deburring tool produced a counter bore on the inner diameter and flared the end of the outer diameter, i.e. the “tab or wings” were bent outward. This flare is a more favorable condition for the fiber interface; however, it does pose a problem with the splice procedure, because the copper heatsink centering washer will not pass over the flare.
These tests indicate that the aforementioned splicing procedure may present a reasonable risk of damage to the optical fibers
32
,
33
in the spliced junction of the fiber optic cable
16
. Failure of the transmission of optical signals on the optical fibers
32
,
33
would be catastrophic to the performance of a signal transmission system like the system
10
shown in FIG.
1
.
SUMMARY OF THE INVENTION
The present invention features a fiber protection sleeve assembly and method for installing the same in a splice junction of a fiber optic cable, which reduces any likelihood of damage to optical fibers in the fib
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