U.S. patent application number 09/761877 was filed with the patent office on 2002-08-08 for optical fiber connector assembly.
Invention is credited to Cairns, James L..
Application Number | 20020106163 09/761877 |
Document ID | / |
Family ID | 25063486 |
Filed Date | 2002-08-08 |
United States Patent
Application |
20020106163 |
Kind Code |
A1 |
Cairns, James L. |
August 8, 2002 |
OPTICAL FIBER CONNECTOR ASSEMBLY
Abstract
An optical fiber connector assembly has releasably mating first
and second units each having a through bore and a respective
ferrule mounted in the through bore and having a front end face
having a plurality of optical contacts for mating, face-to-face
engagement with corresponding contacts in the front end face of the
other ferrule. At least one of the ferrules is movably mounted in
the through bore for movement between an advanced and retracted
position. A ribbon fiber extends through each through bore and the
individual fibers in the ribbon fiber extend through the respective
ferrule and are terminated at respective contacts in the end face.
A biasing device is mounted in the through bore of at least one
unit behind the movable ferrule and bears against the rear end of
the ferrule to bias it towards its advanced position. The biasing
device includes a spring spaced rearwardly from the rear end of the
ferrule by a spacer assembly having a flat forward end face bearing
against the flat rear end of the ferrule.
Inventors: |
Cairns, James L.; (Ormond
Beach, FL) |
Correspondence
Address: |
BROWN, MARTIN, HALLER & MCCLAIN LLP
1660 UNION STREET
SAN DIEGO
CA
92101-2926
US
|
Family ID: |
25063486 |
Appl. No.: |
09/761877 |
Filed: |
January 17, 2001 |
Current U.S.
Class: |
385/60 |
Current CPC
Class: |
G02B 6/3869 20130101;
G02B 6/3821 20130101; G02B 6/3822 20130101; G02B 6/3885
20130101 |
Class at
Publication: |
385/60 |
International
Class: |
G02B 006/38 |
Claims
1. An optical fiber connector assembly, comprising: a first unit
having a first housing with a through bore and a first ferrule
movably mounted in the through bore for movement between an
advanced and retracted position, the ferrule having a forward end
face and a rear end face; a second unit for releasable mating
engagement with the first unit, the second unit having a housing
with a through bore and a second ferrule mounted in the through
bore and having a forward end face for face to face engagement with
the forward end face of the first ferrule when the units are mated
together; the forward end face of each ferrule having a plurality
of contacts for engagement with corresponding contacts in the end
face of the other ferrule when the units are mated; and a biasing
device mounted in the through bore in the first unit behind the
first ferrule and bearing against the rear end face of the ferrule
to bias it towards its advanced position, the biasing device
comprising a spring having a rear fixed end and a forward end, a
bushing having a front end and a rear end, the forward end of the
spring bearing against the rear end of the bushing, the front end
of the bushing having a seat, and a ball member rotatably seated in
the seat at the forward end of the bushing, the ball member having
a flat face bearing against the rear face of the ferrule.
2. The connector assembly as claimed in claim 1, wherein the second
ferrule is movably mounted in the through bore in the second unit
for movement between an advanced position and a retracted position,
and a second biasing device is mounted in the through bore in the
second unit to bias the second ferrule into the advanced position,
whereby both ferrules are moved into the respective retracted
position on mating of the first and second units with the ferrule
end faces in face to face engagement, and are biased into the
advanced positions on separation of the units.
3. The assembly as claimed in claim 2, wherein the second biasing
device comprises a second spring having a rear fixed end and a
forward end, a second bushing having a front end and a rear end,
the forward end of the second spring bearing against the rear end
of the second bushing, the front end of the second bushing having a
seat, and a second ball member rotatably seated in the seat at the
forward end of the bushing, the ball member having a flat face
bearing against the rear face of the ferrule.
4. The assembly as claimed in claim 1, wherein the ball member has
an indent and a locating tail projects from the rear end face of
the ferrule into the indent for axial alignment of the ball member
and bushing, whereby the ferrule rear end face and ball member flat
face are held in face-to-face engagement.
5. The assembly as claimed in claim 1, including a first optical
fiber ribbon containing a plurality of optical fibers extending
into the through bore of the first unit, and a second optical fiber
ribbon containing a corresponding number of optical fibers
extending into the through bore of the second unit, the fibers of
each ribbon extending through the respective ferrule and
terminating in the respective optical contacts of the respective
ferrule end faces.
6. The assembly as claimed in claim 1, wherein the bushing
comprises an elongate member having a through bore.
7. The assembly as claimed in claim 6, wherein the bushing seat is
radiused at a curvature matching that of the ball member for
rotatable engagement with the ball member.
8. The assembly as claimed in claim 1, wherein the mating end face
of each ferrule is angled at a taper matching that of the end face
of the other ferrule.
9. An optical fiber connector assembly, comprising: a first unit
having a first housing with a through bore and a first ferrule
movably mounted in the through bore for movement between an
advanced and retracted position, the ferrule having a forward end
face having a plurality of optical contacts and a rear end; a first
group of optical fibers extending through the through bore and
first ferrule and terminated at the respective optical contacts; a
second unit for releasable mating engagement with the first unit,
the second unit having a housing with a through bore and a second
ferrule mounted in the through bore and having a forward end face
for face to face engagement with the forward end face of the first
ferrule when the units are mated together, the forward end face
having a plurality of optical contacts for optical contact with
respective contacts in the first ferrule end face when the units
are mated together; a second group of optical fibers extending
through the through bore in the second unit and through the second
ferrule, each fiber of the second group being terminated at a
respective one of the optical contacts; a biasing device mounted in
the through bore of the first unit behind the ferrule and bearing
against the rear end face of the ferrule to bias it towards its
advanced position, the biasing device comprising a spring having a
rear fixed end and a forward end spaced from the rear end of the
ferrule, and a spacer between the forward end of the spring and the
rear end of the ferrule, the spacer having a flat forward end face
for face-to-face engagement with the rear end of the ferrule.
10. The assembly as claimed in claim 9, wherein the spacer
comprises an elongate bushing having a rear end engaging the
forward end of the bushing and a forward end comprising a seat, and
a ball member mounted in the through bore between the bushing seat
and the ferrule rear end, the ball member having a spherical face
engaging the bushing seat and a flat forward face comprising said
forward end face.
11. The assembly as claimed in claim 9, wherein the spacer has an
indent extending inwardly from said forward end face, and the
ferrule has a tail portion of shape and dimensions substantially
matching those of said indent, the tail portion of the ferrule
engaging in said spacer indent to maintain said spacer and ferrule
in axial alignment.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to optical fiber
connectors of the type used to connect multiple optical fibers or
ribbon fibers.
[0002] Optical fiber connectors are known in which each half of the
connector comprises a ferrule in which a plurality of optical
fibers are terminated. The ferrule is mounted in a housing with a
small amount of free play, and is biased by a spring into a forward
position in the housing. The outer end face of the ferrule is
exposed for face to face contact with the ferrule end face in the
mating opposite half of the connector. Each fiber is terminated at
a respective contact face at the outer end of the respective
ferrule, and the optical contact faces engage one another to
provide optical communication between the connector halves when
mated together. The arrangement is such that the ferrules will be
moved back slightly when the connection is made, compressing the
biasing springs and ensuring a good optical contact between the
fiber end faces. This type of optical fiber connector can connect a
ribbon fiber containing up to 48 fibers.
[0003] One problem with known connectors for connecting a plurality
of optical fibers is potential misalignment, side loading and
torque in the connection. One reason for this is that the spring
end acting on the inner end face of the ferrule does not present a
flat surface, and thus may tend to apply some side loading or
torque to the ferrule.
SUMMARY OF THE INVENTION
[0004] It is an object of the present invention to provide a new
and improved optical fiber connector assembly.
[0005] According to the present invention, an optical fiber
connector assembly is provided, which comprises a first unit having
a first housing with a through bore and a first ferrule movably
mounted in the through bore for movement between an advanced and
retracted position, the ferrule having a forward end face, a second
unit for releasable mating engagement with the first unit, the
second unit having a housing with a through bore and a second
ferrule mounted in the through bore having a forward end face for
face to face engagement with the forward end face of the first
ferrule when the units are mated together, each ferrule having a
plurality of optical contacts at its end face for optical contact
with the contacts in the end face of the opposing ferrule when the
units are connected together, the arrangement being such that the
ferrules are pushed back into a retracted position when the units
are mated together, the first ferrule having a rear end face, and a
biasing device mounted in the through bore behind the first ferrule
and bearing against the rear end face of the ferrule to bias it
towards its forward position, the biasing device comprising a
spring having a rear fixed end and a forward end, a bushing having
a front end and a rear end, the forward end of the spring bearing
against the rear end of the bushing, the front end of the bushing
having a part spherical seat, and a ball member rotatably seated in
the seat at the forward end of the bushing, the ball member having
a flat face bearing against the rear face of the ferrule.
[0006] This arrangement provides a biasing force in a direction
perpendicular to the end face of the ferrule, reducing the risk of
misalignment between the optical contacts, and avoiding torque or
twisting forces which may result in improper alignment. The flat
face of the ball member will be in full face to face contact with
the flat rear end face of the ferrule at all times. The ball and
socket type engagement between the bushing and ball member will
compensate for any non-perpendicular force applied by the end of
the spring on the bushing. The assembly will act in the manner of a
universal joint to allow better alignment between the optical
contacts.
[0007] In an exemplary embodiment of the invention, the connector
assembly is an optical fiber assembly, and a plurality of optical
fibers extend through the respective ferrule and have end faces
terminated at the respective ferrule end face. Preferably, the
second ferrule is also slidably mounted in the second housing for
movement between advanced and retracted positions, and spring
biased towards the advanced or forward position by a biasing device
identical to that in the first housing. The amount of movement
provided on each side of the connector is very small, preferably of
the order of fifty thousandths of an inch, and the movement
together with the spring loading of the ferrules ensures good face
to face contact between the optical contacts.
[0008] To improve optical performance, the mating end faces of the
two ferrules may in some cases each be angled slightly. One of the
end faces has a pair of alignment pins projecting outwardly, while
the other end face has alignment holes for receiving the pins as
the units are mated together, to ensure proper alignment of the
optical contacts. It is these pins that cause the fined mechanical
alignment of the ferrules. But even with the pins, which have some
small clearance with the bores, mis-alignment of the ferrules can
occur if there is axial or rotational mis-alignment, or axial
tilting between the ferrules. The universal joint like connection
at the ball member allows compensation for any such mis-alignments
with the ball member swiveling to allow proper alignment of the
pins in the alignment holes. This ensures that the optical contacts
are properly aligned.
[0009] In an exemplary embodiment of the invention, each bushing
and ball member has a through bore and each ferrule has a
rearwardly projecting tail portion which engages in the through
bore for locating purposes. A plurality of optical fibers extend
into each housing through bore, through the bushing and ball member
through bores, and through the ferrule, with each fiber being
terminated in a respective optical contact at the mating end face
of the respective ferrule.
[0010] The optical fiber connector assembly of this invention
reduces the risk of misalignment or torque on the fibers which
could result in previous ribbon fiber connectors where the non-flat
end face of the biasing spring bore directly against a flat end
face of the ferrule. In this invention, a flat end face of an
otherwise spherical ball member bears against the flat rear end
face of the respective ferrule, and the ball member engages in a
radiused seat at one end of bushing which is biased by the spring.
This provides a universal joint type of connection, allowing much
better alignment of the ferrule end faces and helping to ensure
that the spring applies an axial biasing force to the ferrule.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The present invention will be better understood from the
following detailed description of an exemplary embodiment of the
invention, taken in conjunction with the accompanying drawings in
which like reference numerals refer to like parts and in which:
[0012] FIG. 1 is a side view of the plug portion of the optical
connector according;
[0013] FIG. 2 is a side view of the receptacle portion of the
connector;
[0014] FIG. 3 is a sectional view taken on line 3-3 of FIG. 1;
[0015] FIG. 4 is a sectional view taken on line 4-4 of FIG. 2;
[0016] FIG. 5 is a sectional view of the two portions
connected;
[0017] FIG. 6 is a right hand end view of the plug portion in FIG.
1;
[0018] FIG. 7 is a left hand end view of the receptacle portion of
FIG. 2;
[0019] FIG. 8 is a sectional view taken on line 8-8 of FIG. 5;
[0020] FIG. 9 is a perspective view of the separated internal
components of the receptacle unit; and
[0021] FIG. 10 is a sectional view of the ball and socket
elements.
DETAILED DESCRIPTION OF THE DRAWINGS
[0022] The drawings illustrate an optical connector assembly
according to an exemplary embodiment of the present invention which
is suitable for connection of two lengths of fiber ribbon which may
contain up to 48 or more individual optical fibers. The assembly
basically comprises a first or plug unit 10 as illustrated in FIGS.
1 and 3, and a second, receptacle unit 12 as illustrated in FIGS.
2, 4, 9 and 10, which is designed for releasable mating engagement
with the plug unit, as indicated in FIG. 5.
[0023] As illustrated in FIGS. 1 and 3, the plug unit 10 basically
comprises an outer housing 14 of hard plastic or the like having a
through bore 16 of varying shape and dimensions, and a ferrule 18
of ceramic or similar material slidably mounted in a front end
portion of the housing 14 and biased outwardly by a biasing
assembly 20 mounted in bore 16 to the rear of ferrule 18. As
illustrated in FIGS. 1 and 6, the housing is of generally
cylindrical shape with a rectangular projection 22 from its forward
end face, and may be made in two semicylindrical halves which are
secured together by screws 24 extending through aligned through
bores in the two halves of the housing, for ease of assembly. The
through bore has a first end portion 25 extending from the rear of
the housing which is of generally cylindrical shape, an enlarged
portion 26 of rectangular cross section at the inner end of bore
portion 25, and a rectangular portion 28 of reduced dimensions
extending forwardly from enlarged portion 26 to the outer end of
rectangular projection 22.
[0024] The optical ferrule 18 is a solid member of shape and
dimensions designed for sliding engagement in the rectangular bore
portions 26,28. Ferrule 18 may be of ceramic, metal, or hard
plastic material, and has an enlarged end portion 30 which engages
in bore portion 26 and a rectangular portion of reduced dimensions
which extends forwardly from portion 30 through bore portion 28 and
projects forwardly from the forward end 32 of housing 14. The front
end face 34 of ferrule 18 is slightly angled in one direction, as
indicated in FIG. 1, and has a plurality of spaced optical contacts
35 extending in a line, some of which are illustrated in FIG. 6.
The optical contacts may be provided over substantially the entire
outer end face if necessary, depending on the number of optical
fibers to be connected. A pair of alignment holes or slots 36 are
provided adjacent opposite side edges of the end face 34, as
indicated in FIGS. 1, 3 and 6. A rectangular tail or locating
portion 38 of reduced dimensions projects rearwardly from the inner
end of the enlarged end portion 30 of the ferrule.
[0025] The biasing assembly 20 is in three parts, comprising a
biasing spring 40, a cylindrical bushing 42, and a ball member 44,
all mounted in the cylindrical bore portion 25. The spring 40 acts
between an annular stop member 45 and a rear end of bushing 42. The
ball member 44 is of substantially spherical shape and engages in a
part spherical or radiused seat 46 at the forward end of bushing
42. Member 44 has a flat front end face 48 which bears against the
rear end face of the enlarged portion 30 of the ferrule. Bushing 42
has a through bore 50, and the ball member 44 has an aligned,
elongate or generally rectangular through bore 52 for sliding
engagement over the locating or tail end portion 38 of the ferrule
18. A first ribbon fiber 54 extends into the rear end of the
through bore 16, through the spring 40 and bushing 42, and into the
bore 52 in the ball member. The outer casing of the ribbon fiber is
stripped back to enable individual fibers 55 in the ribbon fiber to
extend through appropriate epoxy filled grooves or bores in the
ferrule up to the front end face 34 in a conventional manner, and
the outer end of each fiber is machined to form a respective
optical contact 35 at the ferrule end face.
[0026] The spring 40 biases the bushing 42 and ball member 44
outwardly so that the flat end face 48 of the ball member acts
against the flat rear end face of the ferrule 18 in order to bias
the ferrule outwardly into the extended position illustrated in
FIGS. 1 and 3. The flat, face-to-face engagement between ball
member 44 and ferrule 18 will help to compensate for any non-planar
engagement between the end of spring 44 and the bushing 42,
ensuring that the biasing force is applied in a direction
transverse to the end face of the ferrule, helping to avoid any
misalignment or torque between the ferrules as they are mated
together.
[0027] The receptacle unit 12 also comprises an outer housing 60
having a through bore 62 in which a ferrule 64 of ceramic or
similar material is slidably mounted and biased into an extended
position by a biasing assembly 65. The ferrule 64 and biasing
assembly 65 are illustrated in more detail in FIGS. 9 and 10, and
it will be understood that the ferrule 18 and biasing assembly 20
of the plug unit are of identical structure to that illustrated in
FIGS. 9 and 10. A second optical fiber ribbon 66 carrying multiple
optical fibers extends through the bore 62 up to the ferrule 64,
and the individual, stripped fibers 68 extend from the end of
ribbon 66 through grooves or bores in the ferrule 64, and are
terminated to form respective optical contacts 70 in the front end
face 72 of the ferrule.
[0028] The housing 60 is of generally cylindrical shape with an
indent or recess 74 of rectangular cross-section at its forward end
75 shaped and dimensioned for receiving the projecting forward end
portion 22 of the plug housing 14. Housing 60 is also made in two
semicylindrical halves secured together by screws 76 or the like,
as best illustrated in FIG. 8. As in the plug unit, the through
bore has a rear, cylindrical portion 78 receiving the biasing
assembly 65, an enlarged portion 80 of rectangular cross-section,
and a rectangular portion 82 of smaller dimensions extending up to
the indent or enlarged counter-bore 74.
[0029] The optical ferrule 64 in the receptacle unit is of similar
shape and dimensions to ferrule 18, and is designed for close
sliding engagement in the rectangular bore portions 80 and 82, as
best illustrated in FIG. 4. Unlike ferrule 18, the ferrule 64 does
not extend outwardly from the end face 75 of the receptacle
housing, but the front end face 72 is recessed inwardly from indent
or recess 74 in the extended position of FIG. 4. As best
illustrated in FIG. 9, ferrule 64 has an enlarged end portion 85 of
rectangular shape which engages in the enlarged bore portion 80 and
has a flat rear end face 86 engaged by biasing assembly 65, as
discussed in more detail below. A rectangular portion of reduced
dimensions extends forwardly from portion 80 into the smaller bore
bortion 82. The front end face 72 is slightly angled at a taper
matching that of the end face 34 of the mating ferrule, as
indicated in FIGS. 1 and 2. The optical contacts 70 are suitably
arranged in a line as indicated in FIGS. 7 and 9. It will be
understood that only a few of the optical contacts are illustrated
in FIGS. 7 and 9, and that in practice up to 48 or more such
contacts may be provided, depending on the number of optical fibers
to be connected.
[0030] A pair of locating pins 84 extend outwardly from end face 72
for engagement in the alignment slots or holes 36 in the mating
ferrule 18. A rectangular tail or locating portion 88 extends from
rear end face 86 of the ferrule for engagement in the biasing
assembly.
[0031] The biasing assembly 65 is identical to that of the plug
unit, and comprises a biasing spring 90, a cylindrical bushing 92
having a through bore 94, and a ball member 95 located between the
bushing 92 and the rear end face 86 of the ferrule. The bushing and
ball member are illustrated in more detail in FIGS. 9 and 10.
Biasing spring 90 acts between an annular seat 96 and the rear end
of bushing 92. As best illustrated in FIG. 9, ball member 95 is
part spherical in shape, and has a rectangular through bore 97 in
which tail or locating portion 88 of the ferrule 64 is engaged, and
a flat end face 98 which bears against the rear end face 86 of the
ferrule. The ball member seats against a radiused seat 99 at the
forward end of bushing 92, as illustrated in FIG. 10. The ribbon
fiber 66 extends through the spring 90, the bore in bushing 92, and
the through bore in ball member 95 up to ferrule 64, as in the plug
unit.
[0032] When the plug and receptacle units are separate as in FIGS.
3 and 4, the two ferrules are biased outwardly by the respective
biasing assemblies into the extended position illustrated in the
drawings. As the two units are brought together, the projecting
outer end portion 36 of the ferrule 18 will first enter the indent
74, followed by the projecting end portion 22 of the housing which
helps to position the ferrule 18 in the correct orientation
relative to ferrule 64. The alignment pins 84 of ferrule 64 will
then enter the slots or holes 36, ensuring that the optical
contacts 35 and 70 are properly aligned. As the parts are brought
into full engagement, the optical contact ends of the fibers will
be brought into face-to-face engagement, and each ferrule will be
pushed slightly rearwardly against the action of biasing spring 40
and 90, respectively. This helps to ensure proper optical
engagement between the optical contacts. Each ferrule is designed
to be moved rearwardly through a distance of around 50 microns as
the units are fully mated together between the extended positions
of FIGS. 3 and 4 and the retracted, mated positions of FIG. 5.
[0033] Unlike a conventional ribbon fiber connector, where a
biasing spring acts directly against the rear end face of each
ferrule, the biasing assemblies of this invention move the biasing
spring rearwardly away from direct contact with the ferrule, and
provide a flat end face bearing against the flat rear face of the
ferrule. The engagement of the tail portion of each ferrule in the
respective bore in the adjacent ball member ensures that these
parts remain in co-axial alignment and the flat end face of the
ball member engages flat or face-to-face with the respective
ferrule end face. Any offset in the force applied by the biasing
spring will be accommodated by the universal joint connection
between the ball member and radiused seat in the bushing. This
reduces the problem of misalignment and torque at the optical
junction as a result of non-axial biasing forces on the two
ferrules, due to the non-flat end face of a spring acting directly
against the ferrule as was characteristic of prior art ribbon fiber
connectors. Instead, with this arrangement, the two ball members
rotatably seated in the radiused seats at the end of respective
elongate bushings will allow better alignment of the spring force
with the axis of the ferrule, ensuing that the biasing force is
applied in a direction perpendicular to the ferrule end face.
[0034] Although an exemplary embodiment of the invention has been
described above by way of example only, it will be understood by
those skilled in the field that modifications may be made to the
disclosed embodiment without departing from the scope of the
invention, which is defined by the appended claims.
* * * * *