U.S. patent application number 09/307530 was filed with the patent office on 2001-11-01 for multifiber ferrule defining alignment holes having a tapered lead-in portion.
Invention is credited to DEAN, DAVID L. JR., GIEBEL, MARKUS A., KNECHT, DENNIS M., LUTHER, JAMES P., ROSSON, JOEL C., WAGNER, KARL M..
Application Number | 20010036342 09/307530 |
Document ID | / |
Family ID | 23190155 |
Filed Date | 2001-11-01 |
United States Patent
Application |
20010036342 |
Kind Code |
A1 |
KNECHT, DENNIS M. ; et
al. |
November 1, 2001 |
MULTIFIBER FERRULE DEFINING ALIGNMENT HOLES HAVING A TAPERED
LEAD-IN PORTION
Abstract
A multifiber ferrule is provided that includes a ferrule body
that defines at least one elongate hole opening through the front
face of the ferrule body that, in turn, includes a lead-in portion
proximate the front face for guiding the respective alignment
member into the elongate hole. The ferrule body at least partially
defines one or more elongate holes, such as a guide pin hole or an
alignment groove, each having a longitudinal axis extending
therethrough. Each elongate hole includes the lead-in portion
proximate the front face and an adjacent alignment portion. The
lead-in portion expands radially outward from the longitudinal axis
in a direction extending from the adjacent alignment portion to the
front face of the ferrule body. As such, the opening of the lead-in
portion through the front face of the ferrule body is larger in
lateral cross-section than the opening of the lead-in portion into
the adjacent alignment portion. The lead-in portion is therefore
capable of guiding the respective alignment member into the
adjacent alignment portion that, in turn, is sized to snugly
receive the alignment member, thereby serving to properly align the
ferrule with the alignment members. In addition, the lead-in
portion of each elongate hole defined by the multifiber ferrule
serves as a receptacle for dirt or other particulates that are
transferred from the alignment member as the alignment member is
inserted into the respective elongate hole.
Inventors: |
KNECHT, DENNIS M.; (HICKORY,
NC) ; ROSSON, JOEL C.; (HICKORY, NC) ; GIEBEL,
MARKUS A.; (HICKORY, NC) ; LUTHER, JAMES P.;
(HICKORY, NC) ; WAGNER, KARL M.; (HICKORY, NC)
; DEAN, DAVID L. JR.; (HICKORY, NC) |
Correspondence
Address: |
CORNING CABLE SYSTEMS LLC
P O BOX 489
HICKORY
NC
28603
US
|
Family ID: |
23190155 |
Appl. No.: |
09/307530 |
Filed: |
May 7, 1999 |
Current U.S.
Class: |
385/84 |
Current CPC
Class: |
G02B 6/3833 20130101;
G02B 6/3837 20130101; G02B 6/3885 20130101; G02B 6/3834 20130101;
G02B 6/3882 20130101; G02B 6/3874 20130101 |
Class at
Publication: |
385/84 |
International
Class: |
G02B 006/36 |
Claims
That which is claimed:
1. A multifiber ferrule comprising: a ferrule body having a front
face and an opposed rear face and defining a plurality of bores
extending therebetween for receiving end portions of respective
optical fibers, said ferrule body also at least partially defining
at least one elongate hole opening through the front face and
adapted to receive a respective alignment member in order to align
the multifiber ferrule, wherein the elongate hole that is at least
partially defined by said ferrule body defines a longitudinal axis
extending therethrough, and wherein the elongate hole includes a
lead-in portion proximate the front face and an adjacent alignment
portion, the lead-in portion expanding radially outward from the
longitudinal axis in a direction extending from the adjacent
alignment portion to the front face of said ferrule body such that
the lead-in portion is capable of guiding the respective alignment
member into the adjacent alignment portion.
2. The multifiber ferrule according to claim 1 wherein said ferrule
body fully defines the hole such that the resulting guide pin hole
is adapted to receive a respective guide pin.
3. The multifiber ferrule according to claim 1 wherein said ferrule
body only partially defines the hole such that the resulting groove
is adapted to receive a respective alignment rib.
4. The multifiber ferrule according to claim 1 wherein the lead-in
portion linearly expands in a radially outward direction from the
longitudinal axis.
5. The multifiber ferrule according to claim 1 wherein the lead-in
portion expands radially outward from the longitudinal axis in a
nonlinear manner such that the smooth wall of the lead-in portion
is curved.
6. The multifiber ferrule according to claim 1 wherein a ratio of
the length of the alignment portion to the length of the lead-in
portion is at least 4:1.
7. A multifiber ferrule comprising: a ferrule body having a front
face and an opposed rear face and defining a plurality of bores
extending therebetween for receiving end portions of respective
optical fibers, said ferrule body also defining at least one guide
pin hole opening through the front face and adapted to receive a
respective guide pin in order to align the multifiber ferrule,
wherein the guide pin hole defines a longitudinal axis extending
therethrough and includes a lead-in portion proximate the front
face and an adjacent alignment portion, the lead-in portion
expanding radially outward from the longitudinal axis in a
direction extending from the adjacent alignment portion to the
front face of said ferrule body such that the lead-in portion is
capable of guiding the respective guide pin into the adjacent
alignment portion.
8. The multifiber ferrule according to claim 7 wherein the lead-in
portion linearly expands in a radially outward direction from the
longitudinal axis such that the lead-in portion has a frustoconical
shape.
9. The multifiber ferrule according to claim 7 wherein the lead-in
portion expands radially outward from the longitudinal axis in a
nonlinear manner such that the wall of the lead-in portion is
curved.
10. The multifiber ferrule according to claim 7 wherein the lead-in
portion is shorter than the adjacent alignment portion as measured
along the longitudinal axis.
11. The multifiber ferrule according to claim 10 wherein a ratio of
the length of the alignment portion to the length of the lead-in
portion is at least 4:1.
12. The multifiber ferrule according to claim 7 wherein the lead-in
portion is sized such that the lead-in portion proximate the front
face is at least 50% larger in lateral cross-section than the
alignment portion.
13. A multifiber ferrule comprising: a ferrule body having a front
face and an opposed rear face and defining a plurality of bores
extending therebetween for receiving end portions of respective
optical fibers, said ferrule body also defining at least one groove
extending along a side surface of said ferrule body and adapted to
receive a respective alignment rib in order to align the multifiber
ferrule, wherein the groove defines a longitudinal axis extending
therethrough and includes a lead-in portion proximate the front
face and an adjacent alignment portion, the lead-in portion
expanding radially outward from the longitudinal axis in a
direction extending from the adjacent alignment portion to the
front face of said ferrule body such that the lead-in portion is
capable of guiding the respective alignment rib into the adjacent
alignment portion.
14. The multifiber ferrule according to claim 13 wherein the
lead-in portion linearly expands in a radially outward direction
from the longitudinal axis.
15. The multifiber ferrule according to claim 13 wherein the
lead-in portion expands radially outward from the longitudinal axis
in a nonlinear manner such that the wall of the lead-in portion is
curved.
16. The multifiber ferrule according to claim 13 wherein the
lead-in portion is shorter than the adjacent alignment portion as
measured along the longitudinal axis.
17. The multifiber ferrule according to claim 16 wherein a ratio of
the length of the alignment portion to the length of the lead-in
portion is at least 4:1.
18. The multifiber ferrule according to claim 17 wherein a ratio of
the length of the alignment portion to the length of the lead-in
portion is at least 5:1.
19. The multifiber ferrule according to claim 18 wherein a ratio of
the length of the alignment portion to the length of the lead-in
portion is at least 6:1.
20. The multifiber ferrule according to claim 13 wherein the
lead-in portion is sized such that the lead-in portion proximate
the front face is at least 50% larger in lateral cross-section than
the alignment portion.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to multifiber
ferrules and, more particularly, to the alignment holes, such as
the guide pin holes and the alignment grooves, defined by
multifiber ferrules that cooperate with alignment members to
appropriately align the multifiber ferrules.
BACKGROUND OF THE INVENTION
[0002] As a result of the ever increasing utilization of optical
communications for both voice and data applications, multifiber
connectors are being more frequently utilized in order to
simultaneously interconnect a plurality of optical fibers. Not only
are multifiber connectors being utilized in larger numbers, but
increased performance demands are being placed upon multifiber
connectors, as well as all other portions of the optical network.
For example, in order to maximize signal transmission between pairs
of optical fibers, multifiber connectors are required to align each
of the optical fibers very precisely, especially for single mode
applications. In this regard, multifiber connectors are typically
required to align each optical fiber to within 7 to 14 microns for
multimode applications and to within 0 to 3 microns for single mode
applications.
[0003] In order to provide the desired alignment, conventional
multifiber connectors include multifiber ferrules that at least
partially define a pair of elongate alignment holes that receive
and cooperate with respective alignment members, such as guide pins
or alignment ribs, in order to appropriately align the multifiber
ferrule and, in turn, the optical fibers upon which the multifiber
ferrule is mounted. For example, one conventional type of
multifiber ferrule is the MT ferrule, such as described by U.S.
Pat. No. 5,214,830 to Sinji Nagasawa, et al., and assigned to
Nippon Telephone and Telegraph Corporation of Tokyo, Japan. The MT
ferrule has a generally rectangular shape in lateral cross-section
and defines a pair of guide pin holes opening through the front
face for receiving respective guide pins. As such, a pair of
multifiber connectors having respective MT ferrules that are to be
interconnected are typically configured such that one of the
multifiber connectors has a male configuration and the other
multifiber connector has a female configuration. The male
configuration of the multifiber connector includes a pair of guide
pins that have been inserted within the guide pin holes defined by
the respective MT ferrule and that extend beyond the front face of
the multifiber ferrule. In contrast, the female configuration of
the multifiber connector includes a female MT ferrule that defines
a pair of guide pin holes for receiving those portions of the guide
pins that extend beyond the front face of the MT ferrule of the
male connector. During mating, the insertion of the guide pins into
the guide pin holes defined by the MT ferrule of the female
connector aligns the connectors and, in turn, aligns the optical
fibers upon which the MT ferrules are mounted. In order to snugly
receive the guide pins, the guide pin holes defined by a
conventional MT ferrule are cylindrical in lateral cross-section so
as to have the same size and shape along their entire length. By
utilizing cylindrical guide pin holes, the sidewalls that form the
cylindrical guide pin holes contact the guide pins along their
entire length, thereby correspondingly maximizing the alignment
provided by the guide pins.
[0004] Another advantageous type of multifiber ferrule is the SC-DC
multifiber ferrule provided by Siecor Corporation of Hickory, N.C.,
the assignee of the present invention. The SC-DC ferrule has a
generally circular shape in lateral cross-section and defines a
pair of alignment grooves extending along opposed side surfaces.
During the mating of an SC-DC ferrule with another SC-DC ferrule,
the elongate grooves defined by the opposed side surfaces of the
ferrule engage respective alignment ribs or pins to align the
ferrules and, in turn, the optical fibers upon which the ferrules
are mounted. For example, alignment ribs are generally defined by
and extend inwardly from the inner sidewalls of an alignment
sleeve. Upon inserting the SC-DC ferrules into the opposed ends of
the alignment sleeve, the alignment ribs or pins engage and are
slidably advanced through the grooves defined by the respective
ferrules, thereby aligning the ferrules within the alignment
sleeve. As described above in conjunction with the guide pin holes
defined by an MT ferrule, the alignment grooves defined by the
opposed side surfaces of an SC-DC ferrule typically have the same
semi-circular size and shape in lateral cross-section along their
entire length. As such, the sidewalls that form the alignment
grooves contact the alignment ribs or pins along their entire
length, thereby correspondingly maximizing the alignment afforded
by the alignment grooves and the alignment ribs or pins.
[0005] While conventional multifiber ferrules, such as the MT and
SC-DC ferrules described above, effectively cooperate with
alignment members, such as guide pins and alignment ribs, in order
to align the optical fibers upon which the ferrules are mounted,
conventional alignment techniques still suffer from several
limitations. For example, attempts to insert those portions of the
guide pins that protrude beyond the front face of the male
configuration of an MT ferrule into the guide pin holes defined by
the female configuration of an MT ferrule can sometimes initially
stub the ends of the guide pins against the front face of the
female MT ferrule. As such, the guide pins and/or the front face of
the female MT ferrule may be damaged. At the least, this pin
stubbing will increase the care and, therefore, the time that must
be taken by a technician during the interconnection of a pair of
multifiber ferrules. In an attempt to reduce the stubbing, the
leading portion of most guide pins are tapered to facilitate
insertion of the guide pins into the respective guide pin holes. As
a result of the relatively small size of most guide pins that
typically have a diameter of 700 microns, MT ferrules may still be
misaligned by more than the diameter of the guide pin as the MT
ferrules are brought into contact. In these instances, the tapered
leading end of the guide pin will not serve to guide the guide pin
into the respective guide pin hole, but will instead stub against
the front face of the female MT ferrule.
[0006] With respect to the interaction of the alignment ribs or
pins of an alignment sleeve and the elongate grooves defined by the
opposed side surfaces of an SC-DC ferrule, it has been found that
the alignment ribs or pins are sometimes damaged as the SC-DC
ferrule is inserted into the respective alignment sleeve, thereby
diminishing the precision with which the alignment ribs or pins
align the optical fibers upon which the SC-DC ferrule is mounted.
In this regard, it is believed that the sharp edge that defines the
opening of the elongate grooves through the front face of an SC-DC
ferrule oftentimes gouges the alignment ribs or pins as the SC-DC
ferrule is being inserted into the respective alignment sleeve
since the SC-DC ferrule is oftentimes oriented in a direction that
is slightly offset from the longitudinal axis of the sleeve during
its insertion into the sleeve. After being gouged by the sharp
edges defined by the opening of the elongate grooves through the
front face of an SC-DC ferrule, the alignment ribs or pins may no
longer have the desired size and shape to cooperate with the
elongate grooves for precisely aligning the respective
ferrules.
[0007] Additionally, the precision with which all types of
multifiber ferrules can be alignment is diminished as dirt and
other particulates collect in or about the alignment holes defined
by the multifiber ferrule, such as the guide pin holes defined by
an MT ferrule or the elongate grooves defined by an SC-DC ferrule.
In this regard, dirt and other particulates are oftentimes carried
by an alignment member, such as a guide pin or an alignment rib.
Upon insertion of a guide pin into a guide pin hole defined by an
MT ferrule, any dirt or other particulates carried by the guide pin
are typically wiped from the guide pin and collect about the
circumference of the guide pin hole on the front face of the MT
ferrule. Likewise, the insertion of an SC-DC ferrule into an
alignment sleeve and the corresponding insertion of the alignment
rib into the elongate groove defined by the SC-DC ferrule will
oftentimes cause the dirt or other particulates carried by the
alignment rib to be wiped from the alignment rib and collect on the
front face of the SC-DC ferrule proximate the groove. While the
accumulation of any amount of dirt or other particulates upon the
front face of the ferrule is disadvantageous, it is possible that
sufficient dirt and other particulates may accumulate upon the
front face of the multifiber ferrule to prevent physical contact
between the front faces of a pair of multifiber ferrules following
mating of the multifiber ferrules. Without achieving physical
contact between the front faces of a pair of mated multifiber
ferrules, the quality of the resulting optical interconnection will
likely be somewhat impaired.
SUMMARY OF THE INVENTION
[0008] These and other shortcomings of conventional multifiber
ferrules are addressed by the multifiber ferrule of the present
invention that includes a ferrule body that defines at least one
elongate hole opening through the front face of the ferrule body
that, in turn, includes a lead-in portion proximate the front face
for guiding the respective alignment member into the elongate hole.
As such, the multifiber ferrule of the present invention
significantly reduces the occurrences of pin stubbing during the
alignment of MT-type ferrules. In addition, the multifiber ferrule
of the present invention significantly reduces gouging or other
damage incurred by an alignment rib during the insertion of an SC
or DC-type ferrule into a corresponding alignment sleeve. Finally,
the lead-in portion of each elongate hole defined by the multifiber
ferrule of the present invention serves as a receptacle for dirt or
other particulates that are transferred from the alignment member
as the alignment member is inserted into the respective elongate
hole. As a result, the dirt or other particulates do not collect on
the front face of the multifiber ferrule such that physical contact
can continue to be established between the front faces of a pair of
multifiber ferrules.
[0009] Regardless of the type of multifiber ferrule, the ferrule
body at least partially defines one or more elongate holes, each
having a longitudinal axis extending therethrough. Each elongate
hole includes the lead-in portion proximate the front face and an
adjacent alignment portion. The lead-in portion expands radially
outward from the longitudinal axis in a direction extending from
the adjacent alignment portion to the front face of the ferrule
body. As such, the opening of the lead-in portion through the front
face of the ferrule body is larger in lateral cross-section than
the opening of the lead-in portion into the adjacent alignment
portion. The lead-in portion is therefore capable of guiding the
respective alignment member into the adjacent alignment portion
that, in turn, is sized to snugly receive the alignment member,
thereby serving to properly align the ferrule with the alignment
members.
[0010] In one advantageous embodiment, the ferrule body fully
defines the elongate hole to form a guide pin hole adapted to
receive a respective guide pin. As such, the multifiber ferrule of
this embodiment may be an MT-type ferrule. Alternatively, the
ferrule body may only partially define the hole to thereby form an
elongate groove adapted to receive a respective alignment rib. As
such, the multifiber ferrule of this embodiment can be an SC or
DC-type ferrule having at least one and, more typically, a pair of
elongate grooves extending along the opposed side surfaces
thereof.
[0011] In order to guide the respective alignment member into the
adjacent alignment portion, the lead-in portion preferably has a
smooth wall that expands radially outward from the longitudinal
axis in the direction extending from the adjacent alignment portion
toward the front face of the ferrule body. In one embodiment, the
lead-in portion linearly expands in a radially outward direction
from the longitudinal axis. In another embodiment, the lead-in
portion expands radially outward from the longitudinal axis in a
nonlinear manner such that the smooth wall of the lead-in portion
is curved.
[0012] In order to guide the respective alignment member into the
elongate hole while at the same time snugly engaging the alignment
member so as to provide sufficiently precise alignment, the lead-in
portion is preferably shorter than the adjacent alignment portion,
as measured along the longitudinal axis. In this regard, the ratio
of the length of the alignment portion to the length of the lead-in
portion is preferably at least 4:1 and, more preferably, at least
6:1. As such, once the alignment member has been inserted into the
respective hole, such as a respective guide pin hole or an elongate
groove, the alignment portion snugly engages the alignment member
so as to align the multifiber ferrule with another multifiber
ferrule.
[0013] While the length of the lead-in portion is generally much
shorter than the length of the adjacent alignment portion, the
lead-in portion is preferably sized such that the lead-in portion
proximate the front face is at least 50% larger in lateral
cross-section than the alignment portion. As such, the multifiber
ferrule of the present invention significantly reduces pin stubbing
since the lead-in portion of the hole defined by the ferrule body
cooperates with the tapered leading end of a guide pin to
significantly increase the size of the region in which a guide pin
will be appropriately guided into the hole without pin stubbing. In
addition, the enlarged lead-in portion reduces gouging and other
damage to an alignment rib during the insertion of an SC or DC-type
ferrule into a corresponding alignment sleeve. Finally, the
enlarged lead-in portion serves as a receptacle for dirt or other
particulates that are wiped from the alignment member as the
alignment member is inserted into the hole. As such, the dirt or
other particulates do not accumulate upon the front face of the
ferrule body. The multifiber ferrule of the present invention can
therefore make physical contact more reliably with other multifiber
ferrules during the mating process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a perspective view of a multifiber ferrule
according to one embodiment of the present invention.
[0015] FIG. 2 is a cross-sectional view taken along line 2-2 of
FIG. 1 that illustrates the relative size and shape of the lead-in
portion and the adjacent alignment portion of the guide pin hole
defined by the multifiber ferrule.
[0016] FIG. 3 is a cross-sectional view similar to FIG. 2 depicting
a guide pin hole defined by the multifiber ferrule of another
embodiment of the present invention that has a lead-in portion with
curved walls.
[0017] FIGS. 4A-4C are sequential schematic views illustrating the
insertion of a guide pin into a guide pin hole defined by the
ferrule body of a multifiber ferrule according to one advantageous
embodiment of the present invention.
[0018] FIGS. 5A and 5B are a perspective and end views,
respectively, of a multifiber ferrule according to another
embodiment of the present invention that has a ferrule body that
defines elongate grooves along opposed side surfaces thereof, each
of which has an enlarged lead-in portion.
[0019] FIG. 6 is a perspective view of an alignment sleeve for
receiving the multifiber ferrule of FIGS. 5A and 5B.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The present invention now will be described more fully
hereinafter with reference to the accompanying drawings, in which
preferred embodiments of the invention are shown. This invention
may, however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein; rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. Like numbers refer to like
elements throughout.
[0021] Referring now to FIG. 1, a multifiber ferrule 10 according
to one advantageous embodiment of the present invention is
illustrated. The illustrated embodiment of the multifiber ferrule
is an MT-type ferrule having a ferrule body 12 that is generally
rectangular in lateral cross-section. As described below, however,
the multifiber ferrule need not be an MT-type ferrule, but can be
another type of ferrule, such as an SC-DC type of ferrule.
Regardless of the type, the multifiber ferrule extends lengthwise
between opposed front and rear faces 14,16. In addition, the
ferrule body defines a plurality of bores 18 through which the end
portions of respective optical fibers extend. Although the
illustrated embodiment of the multifiber ferrule defines four bores
such that the multifiber ferrule can be mounted upon the end
portions of four optical fibers, the multifiber ferrule can define
any number of bores, such as 2, 4, 8 or more.
[0022] The ferrule body 12 also at least partially defines at least
one elongate hole 20, i.e., an alignment hole, opening through the
front face 14 and adapted to receive a respective alignment member
22 in order to align the multifiber ferrule 10. In instances in
which the multifiber ferrule is an MT-type ferrule, the ferrule
body preferably fully defines at least one and, more typically, a
pair of guide pin holes for receiving respective guide pins. In
embodiments in which the multifiber ferrule is an SC-DC ferrule,
such as shown in FIGS. 5A and 5B, the ferrule body only partially
defines at least one and, more typically, a pair of holes in the
form of a pair of elongate grooves 21 extending lengthwise along
opposed side surfaces of the ferrule body. Regardless of the type
of ferrule, each elongate hole that is at least partially defined
by the ferrule body, in turn, defines a longitudinal axis 24
extending therethrough.
[0023] In contrast to conventional guide pin holes and alignment
grooves that have the same size and shape along their entire
length, each elongate hole 20 defined by the ferrule body 12 of the
present invention includes a lead-in portion 26 proximate the front
face 14 and an adjacent alignment portion 28 that are sized and
shaped differently, as described hereinbelow. In particular, the
lead-in portion extends radially outward from the longitudinal axis
24 in a direction extending from the adjacent alignment portion
toward the front face of the ferrule body. In other words, the
lead-in portion adjacent the front face of the ferrule body is
larger than the lead-in portion adjacent the alignment portion. As
such, the lead-in portion is capable of guiding an alignment member
into the adjacent alignment portion. The alignment portion is, in
turn, sized to snugly receive the alignment member so as to provide
the desired alignment of the multifiber ferrule 10 and, in turn,
the optical fibers upon which the multifiber ferrule is mounted
relative to the alignment member.
[0024] The lead-in portion 26 can extend radially outward in a
variety of manners without departing from the spirit and scope of
the present invention. In preferred embodiments, however, the
sidewall of the lead-in portion is preferably smooth to further
facilitate insertion of the alignment member into the adjacent
alignment portion 28. As shown in FIG. 2, the lead-in portion can
linearly expand in a radially outward direction from the
longitudinal axis 24. Although the lead-in portion can be designed
to expand at a variety of angles .A-inverted., the lead-in portion
of one advantageous embodiment linearly expands so as to define an
angle of 45.degree. with respect to the longitudinal axis of the
respective elongate hole 20. In this manner, the resulting lead-in
portion has a generally frustoconical shape. Alternatively, the
lead-in portion can expand radially outward from the longitudinal
axis in a nonlinear manner such that the smooth wall of the lead-in
portion is curved. As shown in FIG. 3, for example, the lead-in
portion can be shaped such that the sidewall of the lead-in portion
is concave. Although not illustrated, the lead-in portion can
expand in other nonlinear manners to define other curved shapes,
such as convex shapes without departing from the spirit and scope
of the present invention.
[0025] Regardless of the shape of the lead-in portion 26, the
lead-in portion serves to guide the respective alignment member
into the adjacent alignment portion 28. In embodiments in which the
multifiber ferrule 10 is an MT-type ferrule defining a pair of
guide pin holes 20, each guide pin hole has a respective lead-in
portion that significantly reduces pin stubbing during mating of a
pair of multifiber connectors 10, as described below. In this
regard, since the lead-in portion is larger at the front face 14 of
the ferrule body 12 than at the alignment portion, a technician can
more easily insert the leading end of the guide pins 22 into the
lead-in portion of the guide pin holes, as opposed to the smaller
alignment portion that typically has the same size as the guide pin
holes defined by conventional MT ferrules. In instances in which at
least the leading end of the guide pin is tapered, the lead-in
portion cooperates with the tapered leading end of the guide pin to
further facilitate the insertion of the guide pins into the
respective guide pin holes. As shown in FIG. 4A, which is greatly
enlarged for purposes of illustration, the lead-in portion can
capture the leading end of a guide pin even in instances in which
the guide pin would otherwise have missed the guide pin holes and
been stubbed against the front face of the ferrule body. After
capturing the leading end of the guide pin, the lead-in portion
funnels the leading end of the guide pin into the adjacent
alignment portion as the guide pin is further inserted into the
guide pin hole.
[0026] In addition to reducing instances of pin stubbing, the
lead-in portion 26 defined by the multifiber ferrule 10 of the
present invention serves as a repository or receptacle for dirt and
other particulates that are carried by the alignment member 22,
such as by a guide pin or alignment rib, and that may be wiped from
the alignment member as the alignment member is inserted into the
alignment hole 20. In addition, dirt or other particulates carried
by an alignment member may be wiped from the alignment member as
the alignment member is inserted into the respective alignment hole
since the hole is sized to snugly receive the alignment member. For
example, MT-type ferrules designed for multimode applications
generally define the guide pin holes to be only 2 to 3 microns
larger than the respective guide pins. In this regard, the
tolerances are even further diminished in single mode applications
in which MT-type ferrules only permit the guide pin holes to be
about 1 micron larger than the respective guide pins. As a result
of the extremely snug fit of the alignment members within the
respective holes, the dirt and other particulates carried by the
alignment members are wiped from the surface of the alignment
member as the alignment member is inserted into a respective hole.
As shown in FIG. 4B, for example, the dirt and other particulates
are generally wiped from the alignment member as the alignment
member is inserted into the portion of the alignment hole that is
designed to snugly receive the alignment member, that is, as the
guide pin is inserted into the alignment portion 28. As such, the
dirt and other particulates collect within that portion of the
lead-in portion proximate the alignment portion. By collecting the
dirt and other particulates, the lead-in portion protects the front
face 14 of the ferrule from having dirt and other particulates
deposited thereon, as typically occurs with conventional multifiber
ferrules. As shown in FIG. 4C, physical contact can therefore be
established between a pair of multifiber ferrules even after a
significant amount of dirt and other particulates have been wiped
from the alignment members since the dirt and other particulates
collect within the lead-in portion and do not obstruct the front
face of the ferrules. By permitting physical contact between the
front faces of the multifiber ferrules, the quality of the
resulting optical connection is maintained at a high level.
[0027] The ferrule body 12 can define the lead-in portion 26 and
the adjacent alignment portion 28 to have a variety of different
lengths as measured along the longitudinal axis 24. During the
design process, however, the alignment function provided by the
snug fit of the alignment member 22 within the alignment portion
must be balanced against the size and length of the lead-in
portion. In this regard, as the lead-in portion becomes longer, the
alignment portion becomes shorter and, as a result, the length of
the alignment hole that will snugly engage the alignment member is
likewise shortened. In one advantageous embodiment, the length of
the alignment portion L.sub.a and the length of the lead-in portion
L.sub.li, as measured along the longitudinal axis, define the ratio
of at least 4:1, such as 5:1 and, more preferably, 6:1. In this
regard, the length of the alignment portion L.sub.a refers to the
length of the alignment portion that will engage the alignment
member, i.e., the effective length, and not other portions of the
alignment hole that are spaced from the front face 14 by a distance
greater than the depth to which the alignment member will be
inserted into the alignment hole. With respect to an MT-type
ferrule, for example, the guide pin is generally inserted about
1.75 millimeters into the respective guide pin hole. As such, it
has been determined that sufficient alignment precision can be
maintained by defining the lead-in portion to have a length
L.sub.li of about 0.25 millimeters such that the alignment portion
will have an effective length L.sub.a of about 1.50 millimeters.
However, the lead-in portion can be shorter or longer and the
alignment portion can be correspondingly longer or shorter without
departing from the spirit and scope of the present invention.
[0028] The lead-in portion 26 can be designed such that the
relationship of the size of the lead-in portion adjacent the front
face 14 of the ferrule body 12 and the size of the lead-in portion
proximate the alignment portion 28 is tailored as desired for the
particular application. In one advantageous embodiment, for
example, the lead-in portion adjacent the front face is at least
50% larger than the alignment portion, thereby serving to guide
guide pins that are in the vicinity of the hole into the respective
alignment portion.
[0029] While the multifiber ferrule 10 of one advantageous
embodiment that is in the form of an MT-type ferrule has been
illustrated and described, the multifiber ferrule of the present
invention can be of other types and can have other shapes and sizes
without departing from the spirit and scope of the present
invention. In this regard, the multifiber ferrule can be an SC or
DC-type ferrule having a generally circular shape in lateral
cross-section as shown in FIGS. 5A and 5B. As depicted, the
alignment holes that are partially defined by the ferrule body 12
of this embodiment are in the form of at least one and, more
typically, a pair of elongate grooves 20 that extend lengthwise
along opposed side surfaces of the ferrule body. These grooves are
designed to slidably receive an alignment rib 42 as the multifiber
ferrule is inserted into one end of an alignment sleeve 40. See,
for example, FIG. 6 in which an alignment sleeve for receiving a
multifiber ferrule as shown in FIGS. 5A and 5B is depicted. As
known to those skilled in the art, the alignment ribs or pins of an
alignment sleeve typically serve to align a pair of multifiber
ferrules and, in turn, the optical fibers upon which the multifiber
ferrules are mounted.
[0030] According to the present embodiment, each groove 20 includes
a lead-in portion 26 proximate the front face 14 and an adjacent
alignment portion 28. The alignment portion has a generally
semi-circular shape and is sized to snugly receive a respective
alignment rib. As described above in conjunction with other
embodiments with the multifiber ferrule 10, however, the lead-in
portion expands radially outward from the longitudinal axis 24 in a
direction extending from the adjacent alignment portion to the
front face of the ferrule body 12. As such, the lead-in portion is
capable of guiding the respective alignment rib into the adjacent
alignment portion. As described above, the lead-in portion reduces
the stubbing of the alignment rib 40 into the front face of the
ferrule body as the alignment rib is inserted into the respective
groove. Since the multifiber ferrule of this embodiment of the
present invention no longer includes the sharp 90.degree. edge
proximate the front face of the ferrule, the lead-in portion also
serves to guide the alignment rib into the alignment portion of the
groove without gouging or otherwise damaging the alignment rib. As
such, the alignment sleeve, including the alignment ribs or pins,
can continue to reliably and precisely align multifiber ferrules as
described above.
[0031] The lead-in portion 26 of the elongate grooves 20 defined by
an SC or DC-type ferrule 16 also preferably has a smooth wall that
expands radially outward from the longitudinal axis 24 in the
direction extending from the adjacent alignment portion 28 to the
front face 14 of the ferrule body 12. In one embodiment, the
lead-in portion linearly expands in a radially outward direction
from the longitudinal axis so as to define an angle .alpha. with
respect to the longitudinal axis, such as between about 20.degree.
and 45.degree. in one advantageous embodiment. See FIG. 5A. In
another embodiment, however, the lead-in portion expands radially
outward from the longitudinal axis in a nonlinear manner such that
the smooth wall of the lead-in portion is curved. As explained
above, in conjunction with other embodiments of the multifiber
ferrule, the smooth wall of the lead-in portion can be curved in
either a concave or convex manner.
[0032] As described above in conjunction with other embodiments of
the multifiber ferrule 10, the lead-in portion 26 can be sized in a
variety of manners without departing from the spirit and scope of
the present invention. In one advantageous embodiment, for example,
the lead-in portion expands in a radially outward direction such
that the size of the elongate groove 20 adjacent the front face 14
is at least 50% larger than the alignment portion 28 of the
elongate groove. As also described above, the alignment portion of
the elongate groove is preferably sized to snugly receive the
alignment rib 40 such that dirt and other particulates carried by
the alignment rib are wiped from the alignment rib and collected
within the lead-in portion of the groove. As such, the dirt and
other particulates do not accumulate on the front face of the
ferrule, thereby permitting the front face of the ferrule to
physically contact the front face of another ferrule inserted into
the opposed end of the alignment sleeve.
[0033] In addition, the respective lengths of the lead-in portion
26 and the alignment portion 28 can be selected as desired for a
particular application. As explained above, the respective lengths
of the lead-in portion and the alignment portion are preferably
selected such that the lead-in portion is sufficiently large to
guide the alignment rib 40 into the elongate groove 20 while
insuring that a sufficient length of the alignment rib is snugly
received within the alignment portion of the elongate groove in
order to properly align the ferrule 10. As described above, the
multifiber ferrule typically defines the elongate grooves such that
the length of the alignment portion L.sub.a to the length of the
lead-in portion L.sub.li has a ratio of about 4:1, such as 5:1 and,
more typically, about 6:1. For example, the lead-in portion of one
embodiment has a length L.sub.li, as measured along the
longitudinal axis 24, of about 0.25 millimeters. As such, an
alignment rib that is about 1.75 millimeters in length will engage
an alignment portion that is about 1.50 millimeters in length,
thereby providing suitable alignment precision for most
applications.
[0034] As exemplified by the foregoing description, the multifiber
ferrule 10 of the present invention can have a number of different
embodiments. However, the multifiber ferrule of each of these
embodiments at least partially defines at least one elongate hole
20 having a lead-in portion 26 that guides the respective alignment
member 22, 40 into an adjacent alignment portion 28, thereby
reducing instances of pin stubbing for MT-type ferrules and
significantly reducing gouging or other damage to the alignment
ribs or pins by SC-DC type ferrules. In addition, the lead-in
portion serves as a repository or receptacle for dirt and other
particulates that are wiped from the alignment member upon its
insertion into the snug fitting alignment portion. As such, the
dirt and other particulates do not accumulate upon the front face
14 of the ferrule such that the multifiber ferrule of the present
invention can continue to physically contact other ferrules during
the alignment and interconnection process, thereby maintaining the
quality of the optical interconnection of the respective optical
fibers upon which the multifiber ferrules are mated.
[0035] Many modifications and other embodiments of the invention
will come to mind to one skilled in the art to which this invention
pertains having the benefit of the teachings presented in the
foregoing descriptions and the associated drawings. Therefore, it
is to be understood that the invention is not to be limited to the
specific embodiments disclosed and that modifications and other
embodiments are intended to be included within the scope of the
appended claims. Although specific terms are employed herein, they
are used in a generic and descriptive sense only and not for
purposes of limitation.
* * * * *