U.S. patent application number 10/852017 was filed with the patent office on 2005-01-27 for optical fiber connector system.
This patent application is currently assigned to 3M Innovative Properties Company. Invention is credited to Loder, Harry A., Smith, Duane T..
Application Number | 20050018973 10/852017 |
Document ID | / |
Family ID | 46278430 |
Filed Date | 2005-01-27 |
United States Patent
Application |
20050018973 |
Kind Code |
A1 |
Loder, Harry A. ; et
al. |
January 27, 2005 |
Optical fiber connector system
Abstract
A fiber optic connector system including a backplane housing
assembly defining at least one longitudinal receiving cavity, the
receiving cavity having a frontal opening along a first surface of
the backplane member and a rear opening along a second surface of
the backplane member; and one or both of a front door covering the
frontal opening and a rear door covering the rear opening.
Inventors: |
Loder, Harry A.; (Austin,
TX) ; Smith, Duane T.; (Round Rock, TX) |
Correspondence
Address: |
3M INNOVATIVE PROPERTIES COMPANY
PO BOX 33427
ST. PAUL
MN
55133-3427
US
|
Assignee: |
3M Innovative Properties
Company
|
Family ID: |
46278430 |
Appl. No.: |
10/852017 |
Filed: |
May 24, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10852017 |
May 24, 2004 |
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09992212 |
Nov 5, 2001 |
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09992212 |
Nov 5, 2001 |
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09643333 |
Aug 22, 2000 |
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6789950 |
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09643333 |
Aug 22, 2000 |
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09443713 |
Dec 1, 1999 |
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6419399 |
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Current U.S.
Class: |
385/53 |
Current CPC
Class: |
G02B 6/3885 20130101;
G02B 6/387 20130101; G02B 6/43 20130101; G02B 6/3825 20130101; G02B
6/3821 20130101; G02B 6/389 20130101; G02B 6/3829 20130101; G02B
6/3879 20130101; G02B 6/3893 20130101; G02B 6/3887 20130101; G02B
6/3849 20130101; G02B 2006/4297 20130101; G02B 6/3869 20130101;
G02B 6/4478 20130101; G02B 6/4277 20130101; G02B 6/3897
20130101 |
Class at
Publication: |
385/053 |
International
Class: |
G02B 006/36 |
Claims
What is claimed:
1. A fiber optic connector system for connecting at least one
optical fiber cable mounted near the edge of a planar substrate to
a backplane member having a first surface and a second surface, the
longitudinal orientation of the optical fibers defining a
longitudinal axis, the optical connector system comprising: a
backplane housing assembly defining at least one longitudinal
receiving cavity, the receiving cavity having a frontal opening
along the first surface of the backplane member and a rear opening
along the second surface of the backplane member; and at least one
of a front door covering the frontal opening and a rear door
covering the rear opening.
2. The fiber optic connecting system of claim 1 wherein the at
least one door comprises a spring element made of a flexible,
conductive material biased towards a closed position.
3. The fiber optic connecting system of claim 2 wherein the at
least one door is capable of folding to an open position upon
insertion of an object into the opening covered by the door and
capable of returning to a closed position upon removal of the
object from the opening.
4. The fiber optic connecting system of claim 1 wherein the at
least one door comprises a flat spring metal member hingedly
coupled to an opening.
5. The fiber optic connecting system of claim 4 wherein the at
least one door is made of a conductive metal material.
6. The fiber optic connecting system of claim 5 wherein the metal
material is selected from the group consisting of stainless steel
alloys and beryllium/copper alloys.
Description
RELATED APPLICATIONS
[0001] The present application is a continuation of commonly-owned
U.S. patent application Ser. No. 09/992,212, filed Nov. 6, 2001, a
divisional of commonly-owned U.S. patent application Ser. No.
09/643,333, filed Aug. 22, 2000, which is a continuation-in-part of
U.S. patent application Ser. No. 09/443,713, filed Dec. 1, 1999,
and now issued as U.S. Pat. No. 6,419,399 all of which are hereby
incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to an optical fiber connector
system. More particularly, the present invention relates to a
connector assembly for optically coupling a circuit card to a
backplane.
[0003] The use of optical fibers for high-volume high-speed
communication is well established. As the volume of transmitted
information grows, the use of optical fiber cables including
multiple optical fibers, and of systems using multiple optical
fiber cables, has increased.
[0004] It has long been desirable to increase the number of fibers
that can be removably connected within a given space. Until
recently fiber optic interconnects were limited to single or duplex
formats utilizing industry standard connectors, such as the SC, ST,
LC, and the like. These solutions are analogous to single end
electrical cable terminations prevalent prior to the invention of
electrical ribbon cable and mass-terminable IDC connectors.
[0005] Fiber optic terminations currently are evolving from single
terminations to mass terminations. Within the past few years,
ribbonized multi fiber cables have been developed. In conjunction
with these cable development efforts, multi-fiber mounting ferrules
also have been developed.
[0006] The design of traditional electronic cabinets is now being
utilized to accommodate optical and opto-electronic devices. In
traditional cabinet designs, the cabinet comprises a box having a
plurality of internal slots or racks, generally parallel to each
other. Components are mounted on planar substrates, called as
circuit boards or daughter cards, which are designed to slide into
the slots or racks within the cabinet.
[0007] As with electrical cables, the need exists to provide a
means to allow the fiber signals to be passed through the backplane
of electronic cabinets. A backplane derives its name from the back
(distal) plane in a parallelepipedal cabinet and generally is
orthogonal to the board cards. The term backplane in the present
invention refers to an interconnection plane where a multiplicity
of interconnections may be made, such as with a common bus or other
external devices. For explanation purposes, a backplane is
described as having a front or interior face and a back or exterior
face.
[0008] An example of a backplane connectivity application is the
interconnection of telephone switching equipment. In this
application, cards having optical and electronic telecommunication
components are slid into cabinets. The need exists to have a
removable fiber termination from both the front side and the
back-side of the backplane. Furthermore, as a function of inserting
and removing an optical driver card from a rack coupled to the
backplane, coupling and uncoupling of the optical connections in
the card is to be completed in a blind mating manner.
[0009] In order to maintain appropriate transmission of light
signals, optical fiber ends are to be carefully aligned along all
three movement (x, y, and z) axes, as well as angularly. Alignment
challenges increase and tolerances decrease geometrically as the
number of optical fibers to be aligned increases. Blind mating of a
card-mounted component to a backplane connector has been found to
create special challenges with regards to alignment and mating
force issues along the axis of interconnection.
[0010] For the purposes of the present description, the axis of
interconnection is called the longitudinal or x-axis and is defined
by the longitudinal alignment of the optical fibers at the point of
connection. Generally, in backplane applications, the longitudinal
axis is collinear with the axis of movement of the cards and the
axis of connection of the optical fibers in and out of the
cabinets. The lateral or y-axis is defined by the perpendicular to
the x-axis and the planar surface of the card. Finally, the
transverse or z-axis is defined by the orthogonal to the x-axis and
the backplane surface. The angular alignment is defined as the
angular orientation of the card with respect to the x-axis.
[0011] In preferred embodiments, the motion of sliding the card
into a receiving slot simultaneously achieves optical
interconnection. The "optical gap" distance along the longitudinal
axis between the optical fiber ends and interconnected optical
components is an important consideration. A large gap will prevent
effective connection, thereby causing the loss of the optical
signals. On the other hand, excessive pressure on the mating faces,
such as that caused by "jamming in" a card, may result in damage to
the fragile optical fiber ends and mating components. Traditional
optical gap tolerances are in the order of less than one
micron.
[0012] Current connector assemblies include forward biased spring
mounted ferrules. The purpose of the said bias springs is twofold,
one, to absorb a limited amount of over travel of the ferrules
during mating and two, to provide a predetermined spring biasing
force thus urging the ferrules intimately together when the
ferrules are in their mated position.
[0013] An additional subject of concern is card gap, especially
when dealing with backplane connector systems. Card gap is defined
as the space remaining between the rear edge of a circuit card and
the interior or front face of the backplane. In general, designers
and users of backplane connection systems find it exceedingly
difficult to control the position of a circuit card to a backplane
within the precision range required for optical interconnects. Card
gap, otherwise defined as card insertion distance, is subject to a
multiplicity of variables. Among these variables are card length,
component position on the surface of the card, card latch
tolerances, and component position on the backplane.
[0014] Over insertion of a circuit card relative to the interior
surface of a backplane presents a separate set of conditions
wherein the backplane connector's components are subjected to
excessive compressive stress when fixed in a mated condition. In
certain instances the said compressive stress may be sufficient to
cause physical damage to the connector's components and the optical
fibers contained therein.
[0015] The need remains for a connector system that prevents
component damage due to excessive operator force, compensates for
longitudinal card misalignment, yet provides accurate control of
optical gap distance and mating force.
[0016] Another consideration is radial misalignment of the card.
When an operator inserts a card on a slot, it is often difficult to
maintain the card edge perfectly aligned in parallel with the
lateral axis of the backplane. FIG. 1 illustrates an angularity
misaligned card 10 having a connector 12 mating to a backplane
connector 14. The card is otherwise correctly aligned along the y
and z-axes. At the point of contact between connectors 12 and 14,
the angular misalignment prevents correct gap spacing between
optical fibers 16 and causes undue pressure on one end of the
connector and the respective optical fiber end faces.
[0017] Other considerations exist in backplane interconnection
systems other than correct alignment. With the advent of laser
optical signals and other high-intensity light sources, eye safety
is a major concern associated with backplane connector users today.
The safety issues are further escalated by the fact that ribbonized
fiber arrays present a greater danger than the single fiber
predecessors because the amount of light is multiplied by the
number of fibers.
[0018] Previous systems, such as that discussed in U.S. Pat. No.
5,080,461, discuss the use of complex door systems mounted on
terminating fiber connectors, but mainly for the purpose of
preventing damage or contamination of fiber ends. As the
light-transmitting core of a single mode fiber measures only
.about.8 microns in diameter, even a minute accumulation of dust
particles may render the fiber inoperable. However, prior systems
require complex terminations at each fiber end and only may be
mated to another corresponding male-female connector pair, not to
standard connectors, making their use cumbersome.
[0019] EMI (electro-magnetic interference) control also has arisen
as an issue in backplane connector design. As connection of
optoelectronic devices through a backplane often necessitates
forming of a physical opening through the backplane of an
electronic cabinet, the potential exists for EMI leakage through
the said backplane. Electrical interconnection has attempted to
address this problem through the use of several elaborate EMI
shielding techniques. However, current optical fiber connectors
have failed to satisfy this concern.
[0020] Finally, another concern regarding backplane optical
connector applications is bend radius control. Horizontal cabinets
connections are often subject to bend stresses due to gravity,
operator misuse, or physical constraints, such as when a cabinet is
pressed against a wall. Optical fibers are made of glass and rely
on total internal reflection to transmit light signals. When an
optical fiber is bent beyond a certain critical angle, fractures
may appear in the glass, causing the fiber to break or become
damaged. Also, at certain bend angles, even if the glass fiber does
not break, the optical signal may be lost or may deteriorate, as
the complete light signal is no longer contained inside the
fiber.
[0021] Several methods and apparatus for controlling the bend
radius of an optical cable have been attempted. Among those are
pre-formed boots that are slid over the cable, external devices
such as clips or clamps, and elaborate injection molded components
that are shaped such that when attached to a cable, the cable
assumes the shape of the molded structure.
[0022] Because backplane connection frequently involves connecting
an increasing number of optical fibers in a small space, the need
exists for an apparatus for controlling the bend radius of the
optical fibers.
SUMMARY OF THE INVENTION
[0023] At least one aspect of the present invention relates to a
fiber optic connector system for connecting at least one optical
fiber cable mounted near the edge of a planar substrate to a
backplane member having a first surface and a second surface, the
longitudinal orientation of the optical fibers defining a
longitudinal axis, the optical connector system including a
backplane housing assembly defining at least one longitudinal
receiving cavity, the receiving cavity having a frontal opening
along the first surface of the backplane member and a rear opening
along the second surface of the backplane member; and at least one
of a front door covering the frontal opening and a rear door
covering the rear opening. In at least one embodiment, one or both
of the doors may include a spring element made of a flexible,
conductive material biased towards a closed position. The door may
be capable of folding to an open position upon insertion of an
object into the opening covered by the door and capable of
returning to a closed position upon removal of the object from the
opening. In at least one other embodiment, one or both of the doors
may include a flat spring metal member hingedly coupled to an
opening. The door may be made of a conductive metal material. The
metal may be stainless steel alloys and beryllium/copper
alloys.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a side elevation view of an angularly misaligned
card and a backplane connector.
[0025] FIG. 2 is an isometric cut-away view of a first embodiment
of a connector system in accordance with the present invention in a
coupled card position.
[0026] FIG. 3 is an isometric view of the connector system
illustrated in FIG. 2 in an uncoupled card position.
[0027] FIG. 4 is an exploded isometric view of the connector system
illustrated in FIG. 2.
[0028] FIG. 5 is an isometric cut-away view of the backplane
housing assembly of the connector system illustrated in FIG. 2.
[0029] FIG. 6 is an isometric view of the card housing assembly of
the connector system illustrated in FIG. 2.
[0030] FIG. 7 is an isometric view of the card-facing face of the
housing assembly of the connector system illustrated in FIG. 2.
[0031] FIG. 8 is a side elevation view of a backplane connection
system wherein the connector components are aligned along the axis
of the interconnection even though the circuit card is angular with
respect to the said axis of interconnection.
[0032] FIG. 9 is an isometric view of the plug portion of the
connection system illustrated in FIG. 4.
[0033] FIG. 10 is an isometric exploded view of plug illustrated in
FIG. 4 showing the plug fully assembled except for the installation
of the cover.
[0034] FIG. 11 is an isometric view of the plug illustrated in FIG.
4 with its cover being installed.
[0035] FIG. 12 is an isometric view of the plug illustrated in FIG.
4 fully assembled.
[0036] FIG. 13 is an isometric view of the plug assembly
illustrated in FIG. 11 wrapped about a forming fixture.
[0037] FIG. 14 is an exploded isometric view of a backplane housing
assembly.
DETAILED DESCRIPTION OF THE INVENTION
[0038] FIGS. 2 and 3 illustrate an embodiment of an optical
interconnect system 100 in accordance with the present invention.
The optical interconnect system 100 couples a circuit card or
daughter card 102 with and through a backplane 104. The card 102 is
a planar substrate, such as a circuit card or daughterboard, which
may include optical, optoelectronic, and electronic components. The
card 102 may be slideably inserted in a slot defined by card guides
106. The backplane 104 includes a through opening 108, a first
interior surface 110 and a second, exterior surface 112.
[0039] The optical interconnect system 100 includes a backplane
housing 120 disposed within opening 108. The backplane housing 120
includes, in the present embodiment, a first portion 122 and a
second portion 124. The first portion 122 includes male locating
features 126 that engage with corresponding female features (not
shown) on a rear face of the second portion 124. Locating features
three help ensure accurate alignment between the backplane housing
portions 122 and 124 during assembly. It should be understood that
in alternative embodiments housing portions 122 and 124 do not need
to be separate and could be molded as one piece. Splitting off the
housing portions 122 and 124, however, may allow for more freedom
in mold core design.
[0040] In the present embodiment, fasteners 128 secure the
backplane housing assembly 120 to the backplane 104. Fasteners 128
include threaded metal inserts inserted through matching bores 130
in the first and second portion 122 and 124 of the backplane
housing 120. Those skilled in the art will readily appreciate that
mounting screws are used in conjunction with fasteners 128 and that
a variety of fastening mechanisms, adhesives, interference fitting,
and other devices known in the art may be used to align and secure
the backplane housing assembly 120.
[0041] The backplane housing assembly 120 defines an array of four
receiving cavities 132. Alternative embodiments may include a
single receiving cavity or any other necessary number of cavities
to accommodate various optical fiber cable connections. Each one of
the cavities 132 includes a front opening 134 and a rear opening
136. For the purpose of the description of the present invention
the terms rear, front, forward or backward are merely illustrative
to help describe the depicted embodiments with respect to the
figures. The folding front doors 138 are coupled to close the front
opening 134 and rear doors 140 are coupled to close rear openings
136. The front and rear doors 138 and 140 in the present embodiment
include flat spring metal members hingedly coupled to the front and
rear openings 134 and 136. The doors 138 and 140 are designed to
fold down flat when a plug is inserted into the opening of the
receiving cavity 132. In the present embodiment, the backplane
housing assembly 120 comprises molded plastic pieces of a
dielectric material that exhibit the structural strength and
dimensional stability required to maintain control of the optical
fiber's position. Such materials include, but are not limited to,
thermoplastic injection moldable polymers that are filled or
unfilled with reinforcement agents, and transfer moldable polymers
such as epoxy. The doors 138 and 140 are made of a conductive metal
material, such as tempered stainless steel, beryllium/copper alloys
or other materials, and are coupled to provide a grounding
electrical path. The doors 138 and 140 provide three functions:
[0042] 1) to provide a physical barrier to limit ambient
contamination from entering the assembled connector housing,
[0043] 2) to absorb and route to ground electric magnetic
interference that may otherwise leak through the cavities 132
through the backplane 104; and
[0044] 3) to provide eye safety from emitted light signals from
either end of the backplane.
[0045] The backplane housing assembly 120 may include mating
features corresponding to common plugs or ferrules. The dual door
design allows for the sealing of the optical connection without the
need to include special gated terminations at each connector. The
double door arrangement also allows for at least one door to be
closed any time a receiving cavity is not filled by both a rear and
a front plug. Finally, the use of conductive metal doors retained
in a conductive housing assembly 24 allows for the containment and
grounding of EMI components, using a relatively simple and elegant
design. In embodiments where the user is not concerned with any of
the above issues, the use of doors may be optional without
effecting the performance and function of the backplane housing
assembly 120.
[0046] Another useful feature of the housing assembly 120 is the
use of side latch receiving features 142. While traditional plug
retaining features, such as that in a conventional phone plug, are
placed on top of a connector plug and receiving housing, it was
found that such an arrangement unnecessarily interfered with the
stacking of ribbon flat optical fiber cables. The present invention
addresses this problem by placing the latch receiving features
along the same plane defined by the optical fiber array in an
optical fiber ribbon cable. This allows for vertical stacking of a
number of flat ribbon cables in a reduced space.
[0047] The front end of the backplane housing assembly 120 mates
with a board housing assembly 150 when the card 102 is slid into
the guide slots 106. The board housing assembly includes a housing
member 152, including hollow protrusions 154 shaped in size to
correspond and fit into front openings 134 of the backplane housing
assembly 120. The board housing assembly 150 includes board
attachment features 156 having a barbed end 158. The board
attachment features 156 are designed to be inserted through a
receiving slot 160 in the planar substrate 102. While the board
attachment features 156 secures the board housing assembly to the
board in the transverse and lateral direction, a range of freedom
of movement along the longitudinal axis is allowed. The present
embodiment, the length of the slot 160 exceeds the width of the
alignment feature 156. Those skilled in the art will be readily
aware of additional methods for attaching the board housing
assembly 150 to the planar substrate 102, while allowing freedom of
movement in the x direction. Alternative embodiments may include
attachment means such as mechanical fasteners, spring clips or the
like.
[0048] The protrusions 154 in the present embodiment are hollow and
rectangular shaped and are terminated in a truncated pyramid shaped
lead 162. The pyramid shaped lead 162 allow for compensation of
certain mating misalignments by directing the board housing
assembly protrusions 154 into the receiving cavities 132 of the
backplane housing assembly. Furthermore, the protrusions 154 are
shaped to provide alignment with respect to the inside walls of
receiving cavities 132. Protrusions 154 also provide an automatic
pressure for opening front doors 138 during mating. The inner walls
of protrusion 154 define a stepped cavity 164 that provides
guidance to a fiber optic ferrule 170 to be seated inside of the
stepped cavity 164. The present embodiment, the stepped cavity 164,
is shaped to receive an industry standard ferrule, such as the
MT-Style optical ferrules. Step cavity 164 is designed in such a
manner that it comprises a front and a rear rectangular opening 166
and 168, respectively. The front opening 166 is sized to allow
insertion of the ferrule 170 up to an internal flange 172. A
typical MT-style connector includes a ferrule 170 mounted on a
stalk of optical fibers 174, slidably connected to a detente body
portion 176. The ferrule 170 has a limited range of motion x.sub.1
along the longitudinal axis. The stalk of optical fibers 174 is
allowed to move with respect to the detente body portion 176. A
spring element located between the ferrule and the detente body
portion forward biases the ferrule towards a forward end of the
range of motion.
[0049] In the present embodiment, the board housing assembly 150
includes rear openings 168 designed to accept the MT connector,
including the detente body portion 176. The detente body portion
176 is retained against flange 173 while the ferrule 170 is allowed
to extend inside of protrusion 154 up to and through the rear
opening 168. The detente member 176 is designed in such a manner
that as the member 176 is inserted into the front of the stepped
cavity 164, the spring 178 is compressed between detente member 176
and the ferrule 170. The ferrule 170 is prevented from travelling
freely through the rear opening 168 by a flange 180 formed in the
ferrule 170. The flange 180 is formed to act as a travel stop for
the ferrule 170 when flange 180 is engaged with internal flange
172. The detente member 176 is provided with a latch feature that
engages the rear opening 168 of the board housing assembly 150.
Preferably, latching features are provided on both side surfaces of
the housing assembly 150 and the detente member 176. It may be
desirable in some instances to remove detente member 176 from the
housing assembly, and for these situations, a release feature is
provided in the side of the housing. This release feature is
cantilevered and allowed to pivot and thereby allowing the release
feature to be sprung outwards to release the corresponding latch
feature.
[0050] The length of travel of the card 102 along the card guides
106 is selected such that when in the coupled position the board
housing assembly 150 exerts spring force on the backplane housing
assembly 120. In a preferred embodiment, the width of the card gap
should be greater than 0, preferably greater than the combined
travel of the spring biased ferrules (typically 1 to 2 mm) relative
to their respective housings.
[0051] The range of motion x.sub.2 of the board housing assembly
150 with respect to the card 102 is sufficient to correct for
tolerance errors in the range of movement of the card 102 along the
card guides 106, and to absorb any excessive force imparted by the
user when sliding the card before the card is stopped by the
backplane housing 120 or by the stop features if present in the
card guides 106. The present invention addresses issues or
overcompression by allowing the circuit card's attached connector
components to move relative to the said circuit card. Accordingly,
in the coupled position, the board housing assembly 150 is held
tightly against the back of the backplane housing assembly 120 and
is subject to a constant spring bias provided by spring assembly
184. The advantage of providing the constant spring bias is to
ensure that intimate contact is maintained between the housing
assemblies 150 and 120 even in the event that the card 102 is
subject to movement during its operation.
[0052] FIG. 5 illustrates a detailed cutaway view of backplane
housing assembly 120 having front and rear doors 138 and 140. The
doors 138 are designed such that when the protrusions 154 of board
housing assembly 150 are inserted into the front opening 134, the
pyramid shaped lead 162 of the protrusions 154 forces the front
door 138 to fold down. Similarly, when a plug 190 is inserted into
rear opening 136, the insertion of the plug 190 causes rear door
140 to fold down. Doors 138 and 140 are preferably formed of a
spring-like material that withstands numerous cycles of being
folded to an open position and then returning to a closed position
when the plug 190 or protrusion 154 is removed. In instances where
EMI protection is a concern, the rear doors 140 and the first
portion 124 of the backplane housing may be constructed of a
conductive material such as metal. When made of a conductive
material, the rear door 140 and the first portion 124 will absorb
the majority of any EMI radiation that would otherwise escape
through the cavities 132. The first portion 124 is then
electrically coupled to a ground end feature. In alternative
embodiment, either the doors 140 or the first portion of the
backplane housing 122 may be constructed of a dielectric material,
leaving only one conductive element. The remaining conductive
portion would then be coupled to ground.
[0053] By providing both a front door 138 and a rear door 140
covering both the front opening 134 and the rear opening 136, the
removal of either plug 190 or the card housing assembly 150 results
in the closing of one of the doors, thus alleviating any possible
visual safety risk. It should be understood that each door is
allowed to function independently of the other. Accordingly, that
means that if only one plug 190 is inserted into the rear opening
136, the rear doors 140 of the remaining receiving cavities 132
will remain closed. To further assure the tight fit of the doors
138 and 140 within the openings 134 and 136, frame features 144 may
be formed on the side walls of the receiving cavities 132 that
match the side profile and overlap the side edges of doors 138 and
140. This further creates a tighter seal to prevent contamination,
contain EMI, and prevent light leakage.
[0054] FIGS. 6 and 7 illustrate the positioning of springs 184
inserted into spring receiving openings 186 and housing assembly
150. Springs 184 are wire springs having a wire diameter sized such
that the wire springs 184 provide a slight pressed fit between the
spring, board attachment features 156 and the receiving boards
slots 160. With springs 184 inserted into the spring receiving
openings 186, the board attachment features 156 are prevented from
flexing, thereby locking the housing assembly 150 to the card 102.
Referring in particular to FIG. 6, one may appreciate how slots 160
provide passage through card 102 for the board attachment features
156. The barbed end 158 of the board attachment features 156 is
designed as to grip the back side of card 102 thereby securing the
housing assembly 150 along the transversed axis to the daughtercard
102. The slots 160 are sized such that the board housing assembly
150 has a range of movement x.sub.2 along the longitudinal axis on
the surface of the card 102. The combination of the forward bias of
the spring assembly 182 and the freedom of movement x.sub.2 of the
housing assembly 150 allows to compensate for incorrect tolerances
in the alignment of the card 102 with respect to the backplane 104.
The combined force of the springs 184 of spring assembly 182 is
selected to be greater than the summation of all opposing spring
forces such as those of the independent springs 178 of the
individual ferrule assemblies. Otherwise, the combined force of the
springs 178 of the ferrule assemblies would push the housing
assembly backwards thus preventing the desired coupling between the
board housing assembly 150 and the backplane housing assembly 120.
However, as the forward movement of the board housing assembly 150
will be limited by flange 151, the independent ferrules still
retain their range of movement, thus assuring a tight fit on each
individual optical cable connection.
[0055] As illustrated in FIGS. 6 and 7 the longitudinal movement of
the board housing assembly 150 is controlled by a spring assembly
182. The term spring refers to a resilient or elastic member, such
as a coiled spring, a biasing clip, an elastic band, a compression
foam, or other similar devices known in the art. In the present
embodiment, the spring assembly 182 includes two spring clips 184
laterally spaced with respect to each other and located generally
at the lateral ends of the board housing assembly 150. The spring
assembly 182 serves three functions (a) to exert a forward force
along the longitudinal axis on the board housing assembly 150, thus
creating a spring bias between board housing assembly 150 and the
board 102 that the board housing assembly 150 is mounted on; and
(b) to lock the board latching features 156, thus preventing the
board housing assembly 150 from inadvertently being removed from
the board; and (c) to provide compensation for angular misalignment
of the card.
[0056] The spring assembly 182 preferably biases the board housing
assembly 150 towards the front or mating edge of the daughter card,
such that the board housing assembly 150 is forced to move against
the resistance of springs 184 when the board housing assembly 150
is moved by an action opposite to that of the normal force of the
springs 184.
[0057] Furthermore, as illustrated in FIG. 8, the placement of the
two springs 184 at laterally spaced locations allows for the
correction of angular misalignments, thus reducing the pressure and
possible damage on the leading edge of the backplane housing
assembly 150 and compensating for angular misalignment of the
port.
[0058] FIGS. 9-11 illustrate the plug assembly 190. The plug
assembly 190 is designed to receive a conventional MT-style
connector ferrule and provide connectorization features to match
the backplane housing assembly 120. Those skilled in the art will
readily appreciate that the plug assembly may be molded to receive
different types of connectors. In alternative embodiments of the
present invention, the backplane housing assembly may be shaped to
receive directly traditional connector assemblies.
[0059] The plug assembly 190 is comprised of a lower housing member
192 and housing cover 194. As explained above, a MT style connector
assembly includes a ferrule 170, and a ferrule spring 178. The MT
style connector is used to terminate a multi-fiber ribbon cable 196
that is surrounded by a protective jacket 198.
[0060] The lower housing component 192 includes a front opening 200
defined by flange surfaces 202, a receiving well 204, and a
spring-retaining lip 206. The ferrule 170 has a front portion 171
and a flange 172. The front portion 171 passes through opening 200.
However, opening 200 is sized such that the flange 172 is too large
to pass through opening 200 and the flange 172 rests against the
flange surfaces 202. The end 179 of ferrule spring 178 when
positioned properly within lower housing 192, as seen in FIG. 10,
rests within receiving well 204 and is compressed between flange
172 and the spring-retaining lip 206. The compression of ferrule
spring 178 results in a force being exerted against flange 172 and
lip 206, therein spring biasing ferrule 170 forward through opening
200.
[0061] FIG. 11 illustrates housing cover 194 positioned for
attachment to lower housing 192. This attachment is facilitated by
placing engaging features 208 of housing cover 194 into engaging
cavity 210 present in the sidewalls of the lower housing component
192. As housing cover 194 is rotated in a downward direction,
engagement features 208 are trapped within engagement cavity 210.
As the rotation progresses male snap latches 212 are engaged with
the respective female latch receiving features 214, locking lower
housing component 192 and housing cover 194 together.
[0062] An opening 216 is provided in lower housing component 192 to
provide a path for strength members 218 to pass through. The
strength members 218 are generally present in fiber optic cables
and are typically attached to the housings of fiber optic
connectors to relieve axial stress on the cable's optical
fibers.
[0063] The lower housing component 192 also includes cavities 220
into which posts 222 of the housing cover 194 are inserted during
the assembly procedure to provide lateral locking and alignment of
the housing cover 194 to the lower housing component 192.
[0064] FIG. 12 illustrates plug assembly 190 assembled onto the
optical fiber cable 196 with a bend radius control member 230
installed. The bend radius control member 230 for purposes of this
illustration is comprised of a shrinkable tubing that has been
applied over a rear housing section 232 of plug assembly 190, the
cable's protective jacket 198, and the cable's strength members
218. The bend radius control member 230 is heated and shrunk into
position therein securing cable 196 to the plug 190.
[0065] FIG. 13 shows a cable forming device 250 comprising a
vertical support 255 fastened to a base plate 254 and one or more
forming mandrels 256 that are attached to vertical support 252. The
radius of the mandrels 256 exceeds the critical bend radius for the
optical fiber cable 196. The angles of the mandrels 256 with
respect to each other correspond to the expected or desired path
for the optical fibber cable 196.
[0066] To apply the bend radius control member 230, a shrinkable
tubing or jacket 262 is first slid or wrapped over the plug
assembly 190 and the optical fiber cable 196. The term
heat-shrinkable jacket or tubing is intended to include tubing,
jackets, tapes, wraps or coatings comprising heat-shrinkable
materials that may be wrapped around the desired portion of the
optical fiber cable. The term heat-shrinkable jacket refers to a
material that, when heated, collapses and compresses around the
optical fiber cable, and remains in this collapsed shape upon
returning to ambient temperature, such as heat-shrinkable
plastics.
[0067] The cable 196 and the shrinkable tubing 262 are wrapped
about mandrels 256. The illustrated device 250 produces a dual bend
wherein the cable 196 is formed down and left thus creating a
compound bend. The shrinkable tubing is then heated to a
temperature sufficient to cause the tubing to shrink. In the
present embodiment the heat exposure required to collapse the
heat-shrinkable material is selected to avoid any detrimental
effects to the optical fiber cable, yet to be higher than the
normal operating range for the optical fiber cable. Heat sources
may include hot air guns, irradiating heat elements, heated
mandrels or other suitable heat sources. The heating may be done
before placing the optical cable 196 on the mandrels 256 or
afterwards. The shrinkable tubing 262 and the cable 196 remain
wrapped about mandrels 256 while the tubing is allowed to cool.
Once cooled, the cable 196 will assume the desired shape and bend
radius . The stiffness of the formed cable may be controlled by the
thickness and the durometer of the material from which the
shrinkable tubing is formed.
[0068] In certain instances it may be desirable to coat the inner
surface of the shrinkable tubing with a heat activated adhesive
that forms a bond with the protective jacket of the optical cable
196 and with the rear housing section 232. The bend radius control
member may be applied to any portion of the cable where a bend is
expected or desired. Field applications may be performed using a
wrapable shrink material and a portable heat source, such as a heat
air gun or lamp.
[0069] FIG. 14 shows a backplane housing assembly 120 according to
the present invention including an alternative embodiment of the
folding front doors 238 and folding back doors 240. In this case,
the structure of the folding front doors 238 and the folding back
doors 240 includes a pair of substantially equally sized biasing
members 242,244 connected by an elongate hinge plate 246 located
between the biasing members 242,244 and integrally formed
therewith. The general appearance of each of the folding doors
238,240 is that of a V-folded planar element including a
substantially centrally located hinge plate 246 having biasing
members 242,244 joined at opposing longitudinal edges of the hinge
plate 246 and extending outwardly of the same side of the hinge
plate 246.
[0070] After installation in the housing assembly 120, the biasing
members 242,244 of each of the folding doors 238,240 provide
closure at either the front openings 134 or the rear openings 136
of a pair of adjacent receiving cavities 132. In the embodiment
shown in FIG. 14, installation of the folding doors 238,240
requires the placing of a first latch 248 and a second latch 250
adjacent to each of the longitudinal edges of the hinge plate 246.
The latches 248,250 engage an upper latch seat 252 and a lower
latch seat 254 formed as recesses in the upper and lower faces of
an intervening wall 256 between adjacent receiving cavities 132.
With the biasing members 242,244 positioned over e.g. openings 134
of an adjacent pair of receiving cavities 132, the hinge plate 246
being aligned with the intervening wall 256 and latches 248,250
positioned to engage the latch seats 252,254, application of
pressure to the hinge plate 246 attaches the folding door 240 to
the housing assembly 120. This provides connection of the folding
door 240 to the intervening wall 256 by interference-fit between
the latches 248,250 and the latch seats 252,254. Secure attachment
of the hinge plate 246 adjacent to the intervening wall restricts
movement of the hinge plate 246 but allows deflection of each
biasing member 242,244, independent of the other, during insertion
of a plug 190 into a receiving cavity 132 or withdrawal therefrom.
Fabrication of biasing members 242,244 requires the use of durable
material that retains its shape for repeated cycling between a
retracted condition, to allow access to a receiving cavity 132 and
a closed condition in which a biasing member 242,244 fills an
opening 134,136 and presents a barrier to contaminants such as
dirt, dust moisture and the like. Preferably the durable material
is a flexible metal, such as a stainless steel alloy, a
beryllium/copper alloy or similar springy materials that return
substantially to their original shape even after numerous
applications of shape altering forces.
[0071] It should be noted that this invention is not limited to the
use of shrinkable tubing to provide strain relief and bend radius
control; however the use of shrinkable tubing offers an inexpensive
solution to an otherwise costly problem.
[0072] Those skilled in the art will appreciate that the present
invention may be used when coupling a variety of optical devices
and even non-optical devices that require precise alignment. While
the present invention has been described with a reference to
exemplary preferred embodiments, the invention may be embodied in
other specific forms without departing from the spirit of the
invention. Accordingly, it should be understood that the
embodiments described and illustrated herein are only exemplary and
should not be considered as limiting the scope of the present
invention. Other variations and modifications may be made in
accordance with the spirit and scope of the present invention.
* * * * *