Note: Descriptions are shown in the official language in which they were submitted.
CA 02669799 2012-05-18
TITLE OF THE INVENTION
OPTICAL CONNECTOR ASSEMBLY
[0001] This application is a divisional of Canadian patent application Serial
No. 2,486,320 filed on October 29, 2004.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] Embodiments of the invention generally relate to an optical
connector assembly and method of fabricating the same, suitable for use in
harsh environments such as down hole gas and oil well applications.
Background of the Related Art
[0003] Transmitting information, such as temperature, strain and seismic
movement, through optical fibers utilized in down hole gas and oil (e.g.,
petroleum) field drilling applications is becoming more widely accepted as gas
and oil field producers embrace the advantages of optical fiber systems over
conventional metallic conductors. For example, optical fiber sensing systems
exhibit increased long-term reliability over convention conductors, often
having
a useful service life up to and exceeding four times the service life of
conventional sensing systems utilizing metallic conductors, thus allowing
efficient petroleum removal to continue long into the life of wells utilizing
optical
sensing systems, and thereby maximizing the profitability of older wells.
[0004] However, as optical fiber sensing systems for oil and gas well use
become more widespread, it has become apparent that convention optical
equipment commonly utilized in above-ground telephone and data transmission
is not compatible with the harsh environmental conditions present in down hole
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oil and gas well applications. For example, optical connector assemblies
utilized in down hole sensing applications must be able to operate reliably in
conditions that may include temperatures in excess of 300 degrees Celsius,
static pressures in excess of 20,000 pounds per square inch (psi), vibration,
corrosive chemistry and the presence of high partial pressures of hydrogen.
Experience has demonstrated that conventional optical connector assemblies
that utilize ceramic ferrules fastened to optical fiber by epoxy do not
provide
reliable and robust coupling of optical fibers at the elevated temperatures
present in down hole well environments. Particularly, the mismatch in the
thermal coefficient of expansion between the epoxy, the ceramic ferrules and
the optical fiber results in movement and misalignment of the mating optical
fibers in the connect assembly at high temperatures, causing an increase in
optical loss and instability of the optical connection.
[0005] Therefore, there is a need for an improved method and apparatus
for coupling optical fibers suitable for use in harsh environments.
SUMMARY OF THE INVENTION
[0006] Optical connector assemblies suitable for use in harsh
environments such as down hole oil and gas well applications and methods for
fabricating the same are provided. In one embodiment, an optical connector
assembly suitable for down hole oil field applications comprises a first and
second optical waveguide urged by a biasing member against a bracket. Each
of the waveguides has at least one base surface formed on the exterior of the
waveguide that is disposed against at least one of a plurality of reference
surfaces of the bracket. In another embodiment, flats comprise two of the base
surfaces on each optical waveguide.
[0007] In another embodiment, a method of fabricating an optical
connector assembly suitable for down hole oil field applications includes the
steps of forming a first flat on a first optical waveguide, forming a second
flat on
the first optical waveguide, forming a first flat on a second optical
waveguide,
forming a second flat on the second optical waveguide, and biasing the first
flats of the first and second optical waveguides against a first seating
surface
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and second flats of the first and second optical waveguides against a second
seating surface. In this manner, the waveguides are aligned.
[0008] According to an embodiment of the present disclosure there is
provided an optical connector assembly comprising: a first optical waveguide
having a core exposed to an end surface; a first registration feature formed
in
an outer diameter of the first optical waveguide at a predefined distance from
the core; a second registration feature formed in the outer diameter of the
first
optical waveguide at a predefined distance from the core; a second optical
waveguide having a core exposed to an end surface abutting the end surface of
the first optical waveguide; a first registration feature formed in an outer
diameter of the second optical waveguide at a predefined distance from the
core; a second registration feature formed in the outer diameter of the second
optical waveguide at a predefined distance from the core; and a bracket having
the first and second optical waveguides disposed therein. The bracket has a
first portion for aligning the first registration features of the first and
second
optical waveguides and a second portion for aligning the second registration
features of the first and second optical waveguides in an orientation that
aligns
the cores of the optical waveguides.
[0008a] According to another embodiment there is provided an optical
connector assembly comprising: a first optical waveguide having a core
circumscribed by a cladding; a first registration surface formed in the
cladding of
the first optical waveguide at a predefined distance from the core; a second
optical waveguide axially abutting the first optical waveguide and having a
core
circumscribed by a cladding; a first registration surface formed in the
cladding of
the second optical waveguide at a predefined distance from the core; and a
bracket disposed at least partially around the first and second optical
waveguides and engaging the registration surfaces of the waveguides to align
the cores.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0009] A more particular description of the invention, briefly summarized
above, may be had by reference to the embodiments thereof that are illustrated
in the appended drawings. It is to be noted, however, that the appended
drawings illustrate only typical embodiments of this invention and are
therefore
not to be considered limiting of its scope, for the invention may admit to
other
equally effective embodiments.
[0010] Figure 1 is a front perspective partial exploded view of one
embodiment of an optical connector assembly joining two optical waveguides
suitable for use in hazardous environments;
[0011] Figures 2A-B are cross-sectional views of the optical connector
assembly of Figure 1;
[0012] Figure 3 is a perspective view of one embodiment of a bracket;
[0013] Figure 4 is a sectional view of another embodiment of a bracket;
[0014] Figure 5 is a perspective view of one embodiment of an optical
waveguide;
[0015] Figure 6 is a perspective view of one embodiment of an optical
waveguide;
[0016] Figure 7 is a perspective view of a bundle of optical waveguides of
Figure 5;
[0017] Figure 8A is a perspective view of one embodiment of an optical
connector assembly;
[0018] Figure 8B is a sectional view of the connector assembly of Figure
8A;
[0019] Figure 8C is a sectional view of another embodiment of a
connector assembly; and
[0020] Figure 9 is an exploded perspective view of another embodiment
of a connector assembly.
[0021] To facilitate understanding, identical reference numerals have
been
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used, wherever possible, to designate identical elements that are common to
the figures.
DETAILED DESCRIPTION
[0022] Figures 1 and 2A-B are front perspective partial exploded and
cross-sectional views of one embodiment of an optical connector assembly 100
suitable for use in hazardous environments such as those found in oil or gas
wells. The reader is encouraged to refer to Figures 1 and 2A-B simultaneously.
The optical connector assembly 100 generally includes housing assembly 150,
a bracket 106, a biasing member 108 and a pair of optical waveguides 102,
104. The waveguides 102, 104 are disposed in the bracket 106. The biasing
member 108 retains the waveguides 102, 104 within the bracket 106 that is
disposed in the housing assembly 150. The bracket 106 has a plurality of
reference or seating surfaces against which at least one base surface of each
of the waveguides 102, 104 are registered, thus holding the waveguides
concentrically in a predefined position within the bracket 106.
[0023] The housing assembly 150 includes a male portion 152 that mates
with a female portion 154 to house the bracket 106, biasing member 108 and
waveguides 102, 104. A spring 156 is disposed in at least one of the male or
female portions 152, 154 to axially load the waveguides 102, 104 as the
housing assembly 150 is put together. It is contemplated that other housing
assemblies may be utilized to axially load and protect the waveguides 102,
104.
[0024] The first optical waveguide 102 has at least one core 112
surrounded by a cladding 114. The materials utilized to fabricate the core 112
and the cladding 114 are selected to provide reliable transmission of optical
signals through the waveguides 102, 104 when disposed in a down hole gas or
oil well application. For example, the first waveguide 102 may be fabricated
from a silica glass (Si02) based material having the appropriate dopants to
allow light to propagate in either direction along the core 112 and/or within
the
cladding 114 of the first waveguide 102. The first waveguide 102 may
alternatively be fabricated from other light propagating materials, for
example,
the first waveguide 102 may be made of any glass (e.g., silica, phosphate
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glass, or other glasses), plastic or other suitable material.
[0025] The cladding 114 generally has an outer dimension of at least
about 0.3 mm while the core 112 has an outer dimension such that it
propagates only a few spatial modes (e.g., less than about 6). For example for
single spatial mode propagation, the core 112 has a substantially circular
transverse cross-sectional shape with a diameter less than about 12.5 microns,
depending on the wavelength of light signal traveling through the first
waveguide 102. It is contemplated that larger or non-circular cores that
propagate a few (less than about 6) spatial modes, in one or more transverse
directions, may be utilized. The outer diameter and length of the cladding 114
are configured to resist buckling when the first waveguide 102 is placed in
axial
compression.
[0026] In one embodiment, the cladding 114 has an outer diameter of
greater than about 400 microns (0.4 mm) which has demonstrated good
buckling resistance for a waveguide length of 5 mm. It is contemplated that
other waveguide diameters may be used for waveguides having different
lengths. The second waveguide 104 may be similarly configured.
[0027] Mating ends 118 of the waveguides 102, 104 may be ground,
polished or etched to provide good and reliable optical transmission between
the waveguides 102, 104. the mating ends 118 may be square to the center
line of other waveguides 102, 104 or may be orientated at an angle. In one
embodiment, the ends 118 have a surface finish of about 0.006 RA and are
orientated at about 12 degrees relative to the centerline. Opposing ends 120
of
the waveguides 102, 104 positioned opposite the mating ends 110 may be
ground or etched to provide tapered (or beveled or angled) outer corners or
edges 116. The tapered edges 116 provide a seat for each waveguide 102,
104 that facilitates mating with another part (not shown) and/or to adjust the
force angles on each of the waveguides 102, 104, among other purposes.
Generally, a fiber optic conductor is spliced or fused to the opposing ends
120
of the waveguides 102, 104. For example, the opposing ends 120 of the
waveguides 102, 104 may be etched, turned down or ground to provide nubs
(not shown) for splicing a fiber optic pigtail assembly to the waveguides 102,
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104. In another embodiment, the waveguides 102, 104 may be formed by
collapsing a tube around an optical fiber core.
[0028] The waveguides 102, 104 may be made using conventional glass
fiber drawing techniques or later developed that provide the resultant desired
dimensions for the core 112 and the cladding 114 discussed above. As such,
the external surfaces of the waveguides 102, 104 will likely be optically
flat.
Because the waveguides 102, 104 have a large outer diameter compared to
that of a standard optical fiber (e.g., 125 microns), the exterior of the
cladding
114 to be ground, etched or machined while retaining the mechanical strength.
[0029] The waveguides 102, 104 may have end cross-sectional shapes
other than circular, such as square, rectangular, elliptical, clam-shell,
octagonal,
multi-sided, or any other desired shapes, discussed more hereinafter. Also,
the
waveguide may resemble a short "block" type or a longer "cane" type geometry,
depending on the length of the waveguide and outer dimension of the
waveguide.
[0030] Alternatively, the waveguides 102, 104 may be formed by heating,
collapsing and fusing a glass capillary tube to a fiber (not shown), for
example,
by heating with a laser, filament, flame, etc. Other techniques may be used
for
collapsing and fusing the tubes to the fiber, such as is discussed in United
States Patent No. 5,745,626, entitled "Method For And Encapsulation Of An
Optical Fiber", issued to Duck et al., and United States Patent No. 4,915,467,
entitled "Method of Making Fiber Coupler Having Integral Precision Connection
Wells", issued to Berkey. Alternatively, other techniques may be used to fuse
the fiber to the tube, such as using a high temperature glass solder, e.g., a
silica solder (powder or solid), such that the fiber, the tube and the solder
all
become fused to each other, or using laser welding/fusing or other fusing
techniques.
[0031] Each of the waveguides 102, 104 includes at least one registration
feature or base surface that is precision fabricated using the center axis of
the
respective waveguide cores 112 as dimensional coordinate origin. For
example, the base surface may be at least a portion of a diameter, slot, a
flat or
other registration feature formed on the surface of the waveguide by a
precision
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forming process (i.e., ground, etched, machined or the like) that is formed at
or
defines a predetermined distance from the centerline of the waveguide. The
distance of the base surface relative to the core 112 is generally less than
the
radius of the waveguide. The one or more base surfaces of the waveguides
102, 104 are positioned and biased against the reference surfaces of the
bracket 106 by the biasing member 108 to provide concentric alignment of the
waveguides 102, 104 with little or no temperature effect upon the alignment,
thereby making the optical connector assembly 100 advantageous for use in
down hole well applications. Moreover, as the base surfaces are fabricated
using the core 112 as a point of reference, the concentricity between the core
112 and cladding 114, along with the sectional shape of the cladding 114, are
eliminated as factors which often result in core misalignment in conventional
designs.
[0032] In the embodiment depicted in Figures 2A-B, the waveguides 102,
104 each include two base surfaces in the form of flats 220, 222, 224, 226.
The flats 220, 222, 224, 226 are generally smooth and in one embodiment,
have a surface finish of at least about O.15 RA. The first flats 220 and 224
formed on respective waveguides 102, 104 share the same dimensional
attributes as referenced from the waveguide's core center. For example, the
flats 220, 224 each share the same distance defined between the center of the
waveguide core 112 to a point where the flat is tangential to a radius line
extending from the waveguide's core center. The radial distance is generally
fabricated to submicron tolerances, and in one embodiment, is within plus or
minus about 0.250 microns-
[0033] The second flats 222 and 226 formed on respective waveguides
102, 104 also share the same dimensional attributes as references from the
waveguide core's center. For example, the second flats 222, 226 each share
the same distance defined between the center of the core 112 to a point where
the flat is tangential to a radius line extending from the waveguide core's
center.
The radial distance defined between the tangent points on the first flats 220,
224 and the second flats 222, 226 may be the same or different. The angular
orientation defined between the first flats 220, 224 and the second flats 222,
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226 may be varied, but is generally chosen to interface parallel to a mating
surface of the bracket 106 as further discussed below.
[0034] The bracket 106 is fabricated from a substantially rigid material
suitable for down hole applications. Examples of materials suitable for
fabrication of the bracket 106 include spring materials, such as spring
steels,
carbon steels, stainless steels, resilient plastics and the like.
[0035] The bracket 106 includes a plurality of reference or seating
surfaces against which the waveguides 102, 104 are registered. In the
embodiment depicted in Figures 2A-B, the bracket 106 includes a first seating
surface 202 and a second seating surface 202. The seating surfaces 202, 204
may be planar or include one or more contact points as further described with
reference to the embodiment depicted in Figure 3.
[0036] The seating surfaces 202, 204 are configured to have an orientation
parallel with a centerline of the waveguides 102, 104. The seating surfaces
202, 204 partially bound a waveguide receiving pocket 206 and are oriented
relative each other at an angle selected to match the angular orientation of
the
flats 220, 222, 224, 226 formed in the waveguides. The angle defined between
the seating surfaces 202, 204 may be varied, and generally equal to or greater
than about 90 degrees. Alternatively, the seating surfaces 202, 204 may define
an acute angle. In one embodiment, the seating surfaces 202, 204 are joined a
bend 208 to form from a single continuous element.
[0037] The biasing member 108 also bounds a portion of the waveguide
receiving pocket 206 and is adapted to maintain contact with the waveguides
102, 104 when disposed in the pocket 260, thereby biasing the waveguides
102, 104 against the seating surfaces 202, 204 of the bracket 106. The biasing
member 108 is generally fabricated from a materially having sufficient memory
such that when the waveguides 102, 104 are disposed in the receiving pocket
206 of the bracket 106, the biasing member 108 generates sufficient force upon
the waveguides 102, 104 to maintain the waveguides 102, 104 in contact with
the seating surfaces 202, 204 through the range of service temperatures
expected in a predefined application. For example, one embodiment of the
biasing member 108 is fabricated from a spring material, such as spring
steels,
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carbon steels, stainless steels, resilient plastics and the like.
Alternatively,
other spring materials may be utilized that are suitable for use in a down
hole
environment.
[0038] The biasing member 108 may be fabricated as a single member
with the seating surfaces 202, 204, or as a separate element. In the
embodiment depicted in Figures 2A-B, a first end 212 of the biasing member
108 is coupled to the second seating surface 204 opposite the first seating
surface 202. A second end 214 of the biasing member 108 is disposed in a
spaced-apart relation to an end 216 of the first seating surface 202, defining
a
gap 218. The gap 218 is generally narrower than the diameter of the
waveguides 102, 104 so that the biasing member 108 is flexed or displaced
away from the bend 208 as the waveguides 102, 104 pass through the gap 218
and into the waveguide receiving pocket 206. Once the waveguides 102, 104
are in the waveguide receiving pocket 206, the biasing member 108
substantially returns to its normal position while remaining in contact with
the
waveguides 102, 104, thus urging the waveguides against the seating surfaces
202, 204 of the bracket 106.
[0039] In one embodiment, the second end 214 of the biasing member
108 includes a waveguide entry facilitating feature 230 that allows biasing
member 108 to be displaced as the waveguide enters the gap 218, thereby
allowing the biasing member 108 and first surface 202 to spread apart, thus
allowing the waveguide to easily enter the receiving pocket 206. In the
embodiment depicted in Figure 2, the second end 214 of the biasing member
108 includes a section 234 that curves away from the first surface 202 of the
bracket 106. It is contemplated that other geometric configurations, such as
angled tabs, balls, or other structures may be utilized to provide a tapered
entry
passage for the waveguide into the receiving pocket 206.
[0040] Figure 3 is a perspective view of another embodiment of a bracket
300 that may be utilized to couple waveguides 102, 104 (shown removed from
the bracket 300 in Figure 3). The bracket 300 is substantially similar to the
bracket described above, except that seating surfaces 302, 304 of the bracket
300 include a plurality of contact members for contacting the waveguides.
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[0041] In one embodiment, the first seating surface 302 includes a contact
member 310 and a second contact member 312. The first and second contact
members 310, 312 are disposed equidistant from a reference line 330 running
through a waveguide receiving pocket 308 of the bracket 300 that is coaxial to
the core centerline of the waveguides 102, 104. The contact members 310,
312 may project an equal distance inward from the first seating surface 302
and
are positioned on the first seating surface 302 such that the first contact
member 310 is adapted to contact the first flat of the first waveguide 102
while
the second contact member 312 is adapted to contact the first flat of the
second waveguide 104.
[0042] The second seating surface 304 includes plurality of contact
members. In the embodiment depicted in Figure 3, a first pair of contact
members 314 and at least a second pair of contact members 316 are shown.
The first and second pairs of contact members 314, 316 are disposed
equidistant from the reference line 330 running through the waveguide
receiving pocket 308. The contact members 314, 316 may project an equal
distance inward from the second seating surface 304 and are positioned on the
second seating surface 304 such that the first pair of contact members 314 is
adapted to contact the second flat of the first waveguide 102 while the second
pair of contact members 316 is adapted to contact the second flat of the
second waveguide 104.
[0043] Generally, the contact members and pairs 312, 314, 316 and 318
are configured to minimize scratching, marring or otherwise damaging the
exterior surface of the waveguides. In one embodiment, one or more of the
contact members 312, 314, 316 and 318 may be dimples, ridges, posts or other
projections extending from the seating surfaces 302, 304 of the bracket 300.
[0044] Referring primarily back to Figures 1 and 2A-B, in operation, the
waveguides 102, 104 are inserted through the gap 218 into the waveguide
receiving pocket 206 of the bracket 106. The waveguides 102, 104 are
orientated in the bracket 106 so that the base surfaces of the waveguides 102,
104 are positioned facing the reference surfaces of the bracket 106. In one
embodiment, the first flats 220, 224 of the waveguides 102, 104 are disposed
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against the first surface 202 of the bracket 106 while the second flats 222,
226
are disposed against the second surface 204. The biasing member 108 urges
the waveguides 102, 104 against the bracket 106, the matched dimensions of
the first flats 220, 224 position the centerlines of each waveguide 102, 104
at
the common distance from the first surface of the bracket while the matched
dimensions of the second flats 222, 226 position the centerlines of each
waveguide 102, 104 at the common distance from the second surface, thereby
positioning the centerlines of the waveguides 102, 104 on separate axes
sharing a common plane that concentrically registers the waveguides within the
bracket 106.
[0045] Figure 4 is a sectional view of another embodiment of a bracket 400
that may be utilized to couple waveguides. The bracket 400 is substantially
similar to the brackets described above, except that seating surfaces 402, 404
of the bracket 400 are coupled by a biasing member 406.
[0046] The seating surfaces 402, 404 are configured similar to the seating
surfaces described above, defining a waveguide receiving pocket 408
therebetween. At least one of distal ends 410, 412 of the seating surfaces
402,
404 includes a waveguide entry facilitating feature 414 that allows the
seating
surfaces 402, 404 to be spread apart to allow entry of a waveguide (not shown)
into the receiving pocket 408. In the embodiment depicted in Figure 4, the
distal ends 410 of the first and second seating surfaces 402, 404 includes
tabs
416, 418 oriented to define an angle between about 45 and 120 degrees. The
tabs 416, 418 may alternatively be curved so that ends 420, 422 of the tabs
416, 418 diverge to provide a tapered entry passage for the waveguide.
[0047] The biasing member 406 is adapted to urge the seating surfaces
402, 404 toward each other. As the seating surfaces 402, 404 urge the
waveguide toward the biasing member 406, the base surfaces of the
waveguides are biased against the seating surfaces 402, 404, thereby
registering the centers of the waveguide cores coaxially within the bracket
400.
[0048] Figure 5 is a perspective view of one embodiment of a waveguide
500 suitable for use with the optical connector assembly 100 and bracket 106
described above. The waveguide 500 includes a core 112 suitable for optical
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transmission circumscribed by a cladding 114. The waveguide 500 has a first
end 506 and a second end 508. The first end 506 is adapted to be coupled to
an optical fiber, and in an embodiment shown in Figure 5, includes a reduced
diameter section 520 suitable for splicing.
[0049] The second end 508 is configured to mate with an end of a second
waveguide (not shown). The second end 508 may be square to a center line
510 of the waveguide 500, or may be disposed at an acute angle 506 relative to
a line 512 oriented perpendicular to the center line 510.
[0050] A first base surface 220 is ground or otherwise formed in the
cladding 114 at a predefined distance from the core 112. A second first base
surface 224 is also ground or otherwise formed in the cladding 114 at a
predefined distance from the core 112. The distances between the core 112
and base surfaces 220, 224 may be the same or different, and generally are
configured having a tolerance within about plus or minus 2.0 microns. The
base surfaces 220, 224 may also have a surface finish of less than about 0.20
RA to ensure a good fit with the reference surfaces of the bracket 106.
[0051] Figure 6 is a perspective view of one embodiment of a waveguide
600 suitable for use with another embodiment of a connector assembly 800
described with reference to Figure 8 below. The waveguide 600 is similar to
the waveguides described above, and includes a core 602 suitable for optical
transmission surrounded by a cladding 604. The waveguide 600 has a first end
606 and a second end 608. The first end 606 is adapted to be coupled to an
optical fiber, and in an embodiment shown in Figure 6, includes a reduced
diameter section 620 suitable for splicing.
[0052] The second end 608 is configured to mate with an end of a second
waveguide (not shown). The second end 608 may be square to a center line
610 of the waveguide 600, or may be disposed at an acute angle 614 relative to
a line 612 oriented perpendicular to the center line 610.
[0053] The waveguide 600 generally includes at least two registration
surfaces that are utilized to orientate the core 602 in a pre-determined
position
to facilitate alignment of the core 602 with a core of a mating optic fiber.
In the
embodiment depicted in Figure 6, the reference surfaces comprise a first flat
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616 and a second flat 618 formed in the cladding 604 of the waveguide 600.
[0054] Referring to additionally to Figure 7, the flats 616, 618 are
orientated at an angle 606 that facilitates the grouping of at least two
additional
waveguides (shown as a second, third and fourth waveguides 710, 712, 714) to
form a bundle 700. The waveguides 600, 710, 712, 714 comprising the bundle
700 have substantially parallel center lines. It is contemplated that the
angle
600 defined by the flats 618, 618 of the waveguide 600 may the same or
different than angles defined by the flats of the waveguides 710, 712, 714. In
the embodiment depicted in Figure 7, the angle 706 of the waveguide 600 is
about 90 degrees. It is contemplated that the waveguide 600 may be
configured with other angles, such that the bundle 700 may be comprised of
three or more waveguides.
[0055] The second through fourth waveguides 710, 712, 714 each have
respective reference surfaces 718, 720, 722, 724, 726, 728 that are formed at
predefined distances relative to the cores 730, 732, 734 of the respective
waveguides. In the embodiment depicted in Figure 7, the first flat 616 is
disposed against the first flat 718 of the second waveguide 710. The second
flat 720 of the second waveguide 710 is positioned against the first flat 722
of
the third waveguide 712. The second flat 724 of the third waveguide 712 is
positioned against a first flat 726 of the fourth waveguide 714. The second
flat
728 of the fourth waveguide 714 is positioned against the second flat 718 of
the
waveguide 600. Thus, as the waveguides 600, 710, 712, 714 are assembled
into the bundle 700, the cores 602, 730, 732, 734 are positioned in a pre-
defined orientation relative to each other to ensure alignment with a mating
bundle 750 (shown in phantom).
[0056] Referring to Figure 8A, the bundle 700 may be retained by a
bracket 802 to form a connector assembly 800. The bracket 802 generally
provides a bias force that urges the reference services of the waveguides 600,
710, 712, 714 against one another, thereby maintaining the cores 602, 730,
732, 734 in a pre-defined orientation. The bracket 802 is generally fabricated
from a material compatible with a down hole oil and gas well environment, or
may alternatively be fabricated from materials suitable for use in a pre-
defined
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environment.
[0057] One embodiment of a bracket 802 is depicted in the sectional view
of the connector assembly 800 depicted in Figure 8B. The bracket 802 is
shown as a sleeve 804 that radially compresses the wave guides 600, 710,
712, 714 toward the center of the sleeve 804. In one embodiment, the sleeve
804 is resilient and may be fabricated from an elastomer, heat-shrink plastic,
other material that may be temporarily expanded or enlarged to fit over the
bundle 700 than shrunk or swaged there round, or other material suitable for
radially biasing the waveguides 600, 710, 712, 714 toward a center of the
bundle 700. In another embodiment, the embodiment, the sleeve 804 may
comprise a spring. In yet another embodiment, the sleeve 804 may be a glass
tube collapsed around the bundle 804. It is also contemplated that the bracket
802 may be fabricated from a rigid material and configured to fit tightly
around
the bundle 700 or otherwise rigidly retain the bundle 700 in a predefined
orientation.
[0058] Figure 8C depicts an alternate embodiment of a bracket 802. The
bracket 802 comprises a band 806 that may be tightened or sprung around the
circumference of the bundle 700, thereby compressing the waveguides 600,
710, 712, 714 together. In one embodiment, the sleeve 804 includes two tabs
810 and 812, which are urged toward each other by a fastener 808 threaded
into the tab 810. The band 806 may alternatively be a spring form or clamp.
[0059] Figure 9 depicts another embodiment of a connector assembly 900
suitable for axially aligning a first optical waveguide 902 to a second
optical
waveguide 904. The waveguides 902, 904 are substantially similar to the
waveguides described above, wherein the waveguides 902, 904 have a
predefined registration surface 906 ground or otherwise formed in a cladding
908 surrounding each core 910.
[0060] In one embodiment, the registration surface 906 is a diameter
ground concentric to the cores 910 of each waveguide 902, 904. The
registration surface 906 generally has a diametrical tolerance within about
plus
or minus 2.0 microns and a surface finish of less than about O.20 RA.
[0061] A sleeve 920 is disposed around the waveguides 902, 904 and
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configured to interface with the registration surfaces 906 to maintain axial
alignment between the waveguides 902, 904. The sleeve 920 may be
fabricated from a material having a coefficient of thermal expansion similar
to
the waveguides 902, 904. Alternatively, the sleeve 920 may be fabricated from
a material that radially compresses the waveguides 902, 904.
[0062] The sleeve 920 includes a bore 922 that receives mating ends 924
of each waveguide 902, 904. In one embodiment, the bore 922 is configured to
tighten the surfaces 906 to ensure axial alignment between the waveguides
902, 904. In another embodiment, the bore 922 is configured to provide
interference or pressed fit between the waveguides 902, 904 and the sleeve
920. As the sleeve 920 tightly retains the waveguides 902, 904 in predefined
orientation that axially aligns the cores 910, optical signals may be reliably
transmitted through the connector assembly 900.
[0063] Thus, a fiber optic waveguide connector for use in harsh
environments such as down hole oil and gas well applications has been
provided. The novel optic cable has unique construction that advantageously
minimizes fabrication costs.
[0064] Although the invention has been described and illustrated with
respect to exemplary embodiments thereof, the foregoing and various other
additions and omissions may be made therein and thereto without departing
from the spirit and scope of the present invention.
