U.S. patent application number 12/862614 was filed with the patent office on 2011-11-24 for fiber optic connector microlens with self-aligning optical fiber cavity.
Invention is credited to Reid Greenberg, Subhash Roy, Igor Zhovnirovsky.
Application Number | 20110286698 12/862614 |
Document ID | / |
Family ID | 45723985 |
Filed Date | 2011-11-24 |
United States Patent
Application |
20110286698 |
Kind Code |
A1 |
Greenberg; Reid ; et
al. |
November 24, 2011 |
Fiber optic connector microlens with self-aligning optical fiber
cavity
Abstract
A fiber optical connector microlens is provided with a
self-aligning optical fiber cavity. The microlens includes a convex
first lens surface and a second lens surface. A fiber alignment
cavity is integrally formed with the second lens surface to accept
an optical fiber core. A lens body is interposed between the first
and second lens surfaces, having a cross-sectional area with a lens
center axis, and the fiber alignment cavity is aligned with the
lens center axis. In a first aspect, the fiber alignment cavity
penetrates the lens second surface. In a second aspect, an
integrally formed cradle with a cradle surface extends from the
lens second surface, and a channel is formed in the cradle surface,
with a center axis aligned with the lens center axis. The fiber
alignment cavity includes a bridge covering a portion of the
channel.
Inventors: |
Greenberg; Reid; (Mountain
View, CA) ; Zhovnirovsky; Igor; (Newton, MA) ;
Roy; Subhash; (Lexington, MA) |
Family ID: |
45723985 |
Appl. No.: |
12/862614 |
Filed: |
August 24, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12793513 |
Jun 3, 2010 |
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12862614 |
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12784849 |
May 21, 2010 |
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12793513 |
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12756087 |
Apr 7, 2010 |
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12784849 |
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12652705 |
Jan 5, 2010 |
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12756087 |
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12581799 |
Oct 19, 2009 |
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12652705 |
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12483616 |
Jun 12, 2009 |
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12581799 |
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Current U.S.
Class: |
385/33 ;
385/81 |
Current CPC
Class: |
G02B 6/322 20130101;
G02B 6/4206 20130101; G02B 6/3853 20130101; G02B 6/4292
20130101 |
Class at
Publication: |
385/33 ;
385/81 |
International
Class: |
G02B 6/32 20060101
G02B006/32; G02B 6/36 20060101 G02B006/36 |
Claims
1. A fiber optical connector microlens with a self-aligning optical
fiber cavity, the microlens comprising: a convex first lens
surface; a second lens surface; and, a fiber alignment cavity
integrally formed with the second lens surface, the fiber alignment
cavity having a proximal end adjacent the lens second surface with
a first diameter to accept an unclad optical fiber core without a
ferrule, and a distal end with a second diameter to accept an
optical fiber cladding layer.
2. The microlens of claim 1 wherein the second lens surface is
selected from a group consisting of convex, aspheric, holographic,
and planar surfaces.
3. The microlens of claim 1 further comprising: a lens body
interposed between the first and second lens surfaces, having a
cross-sectional area with a lens center axis; and, wherein the
fiber alignment cavity has a center axis aligned with the lens
center axis.
4. The microlens of claim 1 wherein the fiber alignment cavity
penetrates the lens second surface.
5. The microlens of claim 4 further comprising: a lens body
interposed between the first and second lens surfaces, having a
lens body length, and a cross-sectional area with a lens center
axis; and, wherein the fiber alignment cavity has a length with a
center axis, aligned with the lens center axis, that is in a range
of 5 to 10% of the lens body length.
6. The microlens of claim 1 wherein the fiber alignment cavity has
a minimal cross-section with a shape selected from a group
consisting of a triangle, a square, a rectangle, circle, and an
oval.
7. The microlens of claim 6 wherein the fiber alignment cavity
accepts an optical fiber core having a first diameter, and the
cavity minimal cross-section area is about 5% greater than the
first diameter.
8. The microlens of claim 1 wherein a focal point is formed inside
the fiber alignment cavity, when transceiving light in a collimated
beam via the first lens surface.
9. The microlens of claim 1 wherein the first and second lens
surfaces are formed from a polycarbonate resin thermoplastic
selected from a group consisting of lexan and ultem.
10. The microlens of claim 1 further comprising: a lens body
interposed between the first and second lens surfaces, having a
cross-sectional area with a lens center axis; an integrally formed
cradle with a cradle surface extending from the lens second
surface; a channel formed in the cradle surface, with a center axis
aligned with the lens center axis; and, wherein the fiber alignment
cavity includes a bridge covering a portion of the channel.
11. The microlens of claim 10 wherein the bridge includes a first
end connected to the second lens surface, and an exposed second
end.
12. The microlens of claim 10 wherein the bridge includes an
exposed first end separated from the second lens surface by an
opening, and an exposed second end.
13. The microlens of claim 1 further comprising: a lens body
interposed between the first and second lens surfaces, having a
cross-sectional area with a lens center axis; and, wherein the
fiber alignment cavity includes an integrally formed tube extending
from the lens second surface, with a center axis aligned with the
lens center axis.
14. The microlens of claim 13 wherein the tube has a proximal end
adjacent the lens second surface with a first diameter to accept
the unclad optical fiber core, and a distal end with a second
diameter to accept the optical fiber cladding layer.
15. The microlens of claim 1 further comprising: a lens body
interposed between the first and second lens surfaces, having a
cross-sectional area with a lens center axis; an integrally formed
cradle with a cradle surface extending from the lens second
surface; a cradle channel formed in the cradle surface, with a
center axis aligned with the lens center axis; and, a crimping
plate with an interior surface, mechanically secured to the cradle;
a crimping channel formed in the crimping plate interior surface,
with a center axis aligned with the lens center axis; and, wherein
the fiber alignment cavity is formed between the cradle channel and
crimping channel.
16. A fiber optic connector plug with an optical fiber
self-alignment mechanism, the plug comprising: a mechanical body
shaped to selectively engage and disengage a jack housing, and a
microlens, the microlens having a convex first lens surface to
transceive light in a collimated beam with a jack optical
interface, a second lens surface, and a fiber alignment cavity
integrally formed with the second lens surface, the fiber alignment
cavity having a proximal end adjacent the lens second surface with
a first diameter to accept an unclad optical fiber core without a
ferrule, and a distal end with a second diameter to accept an
optical fiber cladding layer.
17. The plug of claim 16 further comprising a plurality of
microlenses, each first plug microlens having a convex first
surface to transceive light in a corresponding collimated beam with
a first jack optical interface, a second lens surface, and a fiber
alignment cavity integrally formed with each second lens surface to
accept a corresponding unclad optical fiber core.
18. The plug of claim 16 wherein the mechanical body and microlens
are a single injection molded piece made from a polycarbonate resin
thermoplastic selected from a group consisting of lexan and
ultem.
19. The plug of claim 16 wherein the fiber alignment cavity
penetrates the lens second surface.
20. The plug of claim 16 wherein the microlens forms a focal point
inside the fiber alignment cavity, when transceiving light in a
collimated beam via the first lens surface.
21. The plug of claim 16 further comprising: a lens body interposed
between the first and second lens surfaces, having a
cross-sectional area with a lens center axis; a cradle, integrally
formed with the mechanical body and microlens, with a cradle
surface extending from the lens second surface; a cradle channel
formed in the cradle surface, with a center axis aligned with the
lens center axis; and, a crimping plate with an interior surface,
mechanically secured to the cradle; a crimping channel formed in
the crimping plate interior surface, with a center axis aligned
with the lens center axis; and, wherein the fiber alignment cavity
is formed between the cradle channel and crimping channel.
22. The plug of claim 16 further comprising: a lens body interposed
between the first and second lens surfaces, having a
cross-sectional area with a lens center axis; a cradle, integrally
formed with the mechanical housing and microlens, with a cradle
surface extending from the lens second surface; a channel formed in
the cradle surface, a center axis aligned with the lens center
axis; and, wherein the fiber alignment cavity includes a bridge
covering a portion of the channel, with a first end connected to
the second lens surface, and an exposed second end.
23. The plug of claim 16 further comprising: a lens body interposed
between the first and second lens surfaces, having a
cross-sectional area with a lens center axis; and, wherein the
fiber alignment cavity includes a tube, integrally formed with the
mechanical body and microlens, extending from the lens second
surface, with a center axis aligned with the lens center axis.
24. (canceled)
25. The microlens of claim 1 further comprising: a fiber core
interface in the fiber alignment channel adjacent the second lens
surface to accept an index matching fluid.
26. The plug of claim 16 further comprising: a fiber core interface
in the fiber alignment channel adjacent the second lens surface to
accept an index matching fluid.
Description
RELATED APPLICATIONS
[0001] This application is a Continuation-in-Part of a pending
application entitled, FIBER OPTIC JACK WITH HIGH INTERFACE MISMATCH
TOLERANCE, invented by Igor Zhovnirovsky et al., Ser. No.
12/793,513, filed Jun. 3, 2010, attorney docket no.
applied.sub.--321_CIP3;
[0002] which is a Continuation-in-Part of a pending application
entitled, FIBER OPTIC CABLE WITH HIGH INTERFACE MISMATCH TOLERANCE,
invented by Igor Zhovnirovsky et al., Ser. No. 12/784,849, filed
May 21, 2010, attorney docket no. applied.sub.--321_CIP2;
[0003] which is a Continuation-in-Part of a pending application
entitled, PUNCH-DOWN FIBER OPTIC CABLE TERMINATION, invented by
Igor Zhovnirovsky et al., Ser. No. 12/756,087, filed Apr. 7, 2010,
attorney docket no. applied.sub.--352:
[0004] which is a Continuation-in-Part of a pending application
entitled, CONNECTOR JACK PROCESSING BACKCAP, invented by Igor
Zhovnirovsky et al., Ser. No. 12/652,705, filed Jan. 5, 2010,
attorney docket no. applied.sub.--354:
[0005] which is a Continuation-in-Part of a pending application
entitled, OFF-AXIS MISALIGNMENT COMPENSATING FIBER OPTIC CABLE
INTERFACE, invented by Igor Zhovnirovsky et al., Ser. No.
12/581,799, filed Oct. 19, 2009, attorney docket no.
applied.sub.--321_CIP1;
[0006] which is a Continuation-in-Part of a pending application
entitled, FIBER OPTIC CABLE INTERFACE, invented by Igor
Zhovnirovsky et al., Ser. No. 12/483,616, filed Jun. 12, 2009,
attorney docket no. applied.sub.--321. All the above-referenced
applications are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0007] 1. Field of the Invention
[0008] This invention generally relates to optical cables and, more
particularly, to a fiber optical plug connector with a mechanism
for aligning the core of an optical fiber with a plug
microlens.
[0009] 2. Description of the Related Art
[0010] Conventionally, optical fiber connectors are spring-loaded.
The fiber endfaces (optical interfaces) of the two connectors are
pressed together, resulting in a direct glass to glass or plastic
to plastic, contact. The avoidance of glass-to-air or
plastic-to-air interfaces is critical, as an air interface results
in higher connector losses. However, the tight tolerances needed to
eliminate an air interface make these connectors relatively
expensive to manufacture.
[0011] FIG. 1 is a partial cross-sectional view of a Transmission
Optical SubAssembly (TOSA) optical cable plug (prior art). The plug
100 is made from a plastic housing 102 with a bored ferrule 106 to
secure an optical fiber 108. The plug 100 also includes a plastic
lens 110, manufactured as a subassembly, integrated into the plug.
The lens 110 has a curved surface to create a focal plane where the
plug mates with a jack 112. The lens permits a low loss air gap to
be formed between the plug and a connecting jack. In addition to
the expense of manufacturing a 2-part plug, the plug must be made
to relatively tight tolerances, so that the lens focal plane aligns
with the jack, which also increases the cost of the plug.
[0012] FIG. 2 is a partial cross-sectional view of an 8 Position 8
Contact (8P8C) interface (prior art). The ubiquitous 8P8C connector
is a hardwired electrical connector used commercially and
residentially to connect personal computers, printers, and routers.
The 8P8C is often referred to as RJ45. Although the housing/body
can be made as a one-piece plastic molding, the spring-loaded
contacts and the necessity of cable crimping add to the complexity
of manufacturing the part. Advantageously however, the
spring-loaded contacts permit the part to be made to relatively lax
tolerances.
[0013] As noted in Wikipedia, plastic optical fiber (POF) is an
optical fiber which is made out of plastic. Conventionally,
poly(methyl methacrylate) (PMMA), a transparent thermoplastic
(acrylic) alternative to glass, is the core material, and
fluorinated polymers are the cladding material. Since the late
1990s however, much higher-performance POF based on perfluorinated
polymers (mainly polyperfluorobutenylvinylether) has begun to
appear in the marketplace.
[0014] In large-diameter fibers, 96% of the cross section is the
core that allows the transmission of light. Similar to conventional
glass fiber, POF transmits light (or data) through the core of the
fiber. The core size of POF is in some cases 100 times larger than
glass fiber.
[0015] POF has been called the "consumer" optical fiber because the
fiber and associated optical links, connectors, and installation
are all inexpensive. The conventional PMMA fibers are commonly used
for low-speed, short-distance (up to 100 meters) applications in
digital home appliances, home networks, industrial networks
(PROFIBUS, PROFINET), and car networks (MOST). The perfluorinated
polymer fibers are commonly used for much higher-speed applications
such as data center wiring and building LAN wiring.
[0016] For telecommunications, the more difficult to use glass
optical fiber is more common. This fiber has a core made of
germania-doped silica. Although the actual cost of glass fibers is
lower than plastic fiber, their installed cost is much higher due
to the special handling and installation techniques required. One
of the most exciting developments in polymer fibers has been the
development of microstructured polymer optical fibers (mPOF), a
type of photonic crystal fiber.
[0017] In summary, POF uses PMMA or polystyrene as a fiber core,
with refractive indices of 1.49 & 1.59, respectively. The fiber
cladding overlying the core is made of silicone resin (refractive
index .about.1.46). A high refractive index difference is
maintained between core and cladding. POF have a high numerical
aperture, high mechanical flexibility, and low cost.
[0018] Generally, POF is terminated in cable assembly connectors
using a method that trims the cables, epoxies the cable into place,
and cures the epoxy. ST style connectors, for example, include a
strain relief boot, crimp sleeve, and connector (with ferrule). The
main body of the connector is epoxied to the fiber, and fiber is
threaded through the crimp sleeve to provide mechanical support.
The strain relief boot prevents to fiber from being bent in too
small of a radius. Some connectors rely upon the connector shape
for mechanical support, so a crimp sleeve is not necessary.
[0019] First, the strain relief boot and crimp sleeve are slid onto
the cable. A jacket stripping tool must be used to remove the end
portion of the fiber, exposing an aramid yarn (e.g., Kevlar.TM.)
covered buffer or cladding layer. Next, a buffer stripping tool is
used to remove a section of the buffer layer, exposing the core.
After mixing, a syringe is filled with epoxy. A bead of epoxy is
formed at the end of the ferrule, and the ferrule back-filled with
epoxy. The exposed fiber core is threaded through the connector
ferrule with a rotating motion, to spread the epoxy, until the
jacket meets the connector. At this point the crimping sleeve is
slide onto the connector body and crimped in two places. Then, the
strain relief boot can be slide over the crimp sleeve. After the
epoxy cures, the core extending through the ferrule is polished
with a lapping film. Then, the core is scribed at the point where
it extends from the epoxy bead. The extending core potion is then
cleaved from the connector and polished in multiple steps.
[0020] As noted in the above-referenced parent applications, the
advantages of using a microlens in a plug or jack connector include
the ability to focus light on point, such as a photodiode or
optical fiber core face, while transceiving light in a collimated
beam between connectors. However, the focusing of light on a fiber
core face requires that the fiber core and microlens be properly
aligned.
[0021] It would be advantageous if an optical connector plug had a
mechanism for self-aligning an optical fiber core with a plug
microlens.
SUMMARY OF THE INVENTION
[0022] According, a fiber optical connector microlens is provided
with a self-aligning optical fiber cavity. The microlens includes a
convex first lens surface and a second lens surface. A fiber
alignment cavity is integrally formed with the second lens surface
to accept an optical fiber core. A lens body is interposed between
the first and second lens surfaces, having a cross-sectional area
with a lens center axis, and the fiber alignment cavity is aligned
with the lens center axis. In a first aspect, the fiber alignment
cavity is formed in (penetrates) the lens second surface.
[0023] In a second aspect, an integrally formed cradle with a
cradle surface extends from the lens second surface, and a channel
is formed in the cradle surface, with a center axis aligned with
the lens center axis. The fiber alignment cavity includes a bridge
covering a portion of the channel. In a related aspect, a crimping
plate with an interior surface is mechanically secured to the
cradle, and a crimping channel formed in the crimping plate
interior surface, with a center axis aligned with the lens center
axis. The fiber alignment cavity is formed between the cradle
channel and crimping channel.
[0024] In yet another aspect, the fiber alignment cavity is an
integrally formed tube extending from the lens second surface, with
a center axis aligned with the lens center axis. The tube has a
proximal end adjacent the lens second surface with a first diameter
to accept an optical fiber core, and a distal end with a second
diameter to accept an optical fiber with a cladding layer.
[0025] Additional details of the above-described microlens with
self-aligning optical fiber cavity, and a fiber optic connector
plug with an optical fiber self-alignment mechanism, are provided
below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a partial cross-sectional view of a Transmission
Optical SubAssembly (TOSA) optical cable plug (prior art).
[0027] FIG. 2 is a partial cross-sectional view of an 8 Position 8
Contact (8P8C) interface (prior art).
[0028] FIG. 3 is a diagram depicting a fiber optic cable.
[0029] FIGS. 4A and 4B are a more detailed depiction of the first
plug microlens of FIG. 3.
[0030] FIGS. 5A and 5B are partial cross-sectional and plan views,
respectively, of the first plug of FIG. 3.
[0031] FIG. 6 is a partial cross-sectional view of the first plug
microlens of FIG. 3.
[0032] FIGS. 7A and 7B are drawings depicting a fiber optic cable
with a cable section that includes a first plurality of fiber optic
lines.
[0033] FIG. 8 is a diagram depicting communicating jack and plug
microlens.
[0034] FIG. 9 is a model calculation graphically depicting the
coupling efficiency of the system of FIG. 8.
[0035] FIG. 10 is a diagram depicting the fiber core acceptance
angle.
[0036] FIG. 11 is a graph depicting the relationship between
coupling efficiency and fiber lateral decentering (.DELTA.).
[0037] FIG. 12 is a diagram depicting the effective focal length of
the plug microlens.
[0038] FIG. 13 is a table of tolerances cross-referenced to fiber
lateral decentering.
[0039] FIG. 14 is a graph depicting coupling efficiency as a
function of photodiode (PD) decentering.
[0040] FIG. 15 is a diagram depicting the relationship between
fiber decentering and lens tilt.
[0041] FIG. 16 is a diagram depicting the relationship between PD
decentering and lens tilt.
[0042] FIG. 17 is a diagram depicting the relationship between PD
decentering and groove (channel) placement error.
[0043] FIG. 18 is a diagram depicting the consequences of
shortening the focal length of the plug, without a corresponding
change in the jack lens.
[0044] FIGS. 19A and 19B are partial cross-sectional views
depicting a first variation of a fiber optical connector microlens
with a self-aligning optical fiber cavity.
[0045] FIGS. 20A, 20B, and 20D are partial cross-sectional views
depicting a second variation of the fiber optical connector
microlens with self-aligning optical fiber cavity, and FIGS. 20C
and 20E are perspective drawings.
[0046] FIGS. 21A through 21B are partial cross-sectional views
depicting a third variation of the fiber optical connector
microlens with self-aligning optical fiber cavity.
[0047] FIGS. 22A and 22B are partial cross-sectional views
depicting a fourth variation of the fiber optical connector
microlens with self-aligning optical fiber cavity.
[0048] FIGS. 23A through 23C are partial cross-sectional views
depicting a first variation of a fiber optic connector plug with an
optical fiber self-alignment mechanism.
[0049] FIGS. 24A and 24B are partial cross-sectional views
depicting a second variation of a fiber optic connector plug with
an optical fiber self-alignment mechanism.
[0050] FIGS. 25A and 25B are partial cross-sectional views
depicting a third variation of a fiber optic connector plug with an
optical fiber self-alignment mechanism.
[0051] FIGS. 26A through 26C are partial cross-sectional views
depicting a fourth variation of a fiber optic connector plug with
an optical fiber self-alignment mechanism.
DETAILED DESCRIPTION
[0052] FIG. 3 is a diagram depicting a fiber optic cable. The fiber
optic cable 300 comprises a cable section 302 including at least
one length of fiber optic line or core 304 having a first end 306
and a second end 308. A first plug 310 includes a mechanical body
312 shaped to selectively engage and disengage a first jack housing
314 (shown in phantom), and a microlens 316. As defined herein, the
plug is mechanically engaged with the jack when the plug is fully
inserted into the jack. In some aspects, a locking mechanism is
enabled when the plug and jack are mechanically engaged. An RJ-45
connector is one example of such a locking type mechanical
engagement (as shown). In other aspects, mechanical engagement is
obtained with a pressure or friction type fit. A universal serial
bus (USB) connector, microUSB, HDMI, and DisplayPort are some
examples of a pressure/friction type of mechanical engagement.
Alternately stated, a plug and jack are mechanically engaged when
they are mated sufficiently to perform their intended electrical or
optical functions.
[0053] The first plug microlens 316 has a planar surface 318 to
engage the fiber optic line first end 306 and a convex surface 320
to transceive light in a first collimated beam 322 with a first
jack optical interface 324. Likewise, a second plug 326 includes a
mechanical body 328 shaped to selectively engage and disengage a
second jack housing 330 (shown in phantom), and a microlens 332.
The second plug microlens 332 has a planar surface 334 to engage
the fiber optic line second end 308 and a convex surface 336 to
transceive light in a second collimated beam 338 with a second jack
optical interface 340.
[0054] A collimated beam is light whose rays are parallel, and
therefore the beam spreads slowly as it propagates. Laser light
from gas or crystal lasers is naturally collimated because it is
formed in an optical cavity between two mirrors, in addition to
being coherent. However, diode lasers do not naturally emit
collimated light, and therefore collimation into a beam requires a
collimating lens. A perfect parabolic mirror will bring parallel
rays to a focus at a single point. Conversely, a point source at
the focus of a parabolic mirror will produce a beam of collimated
light. Spherical mirrors are easier to make than parabolic mirrors
and they are often used to produce approximately collimated light.
Many types of lenses can also produce collimated light from
point-like sources.
[0055] The fiber optic cable first end 306 is formed in a focal
plane 342 of the first plug microlens 316, and the fiber optic
cable second end 308 is formed in a focal plane 344 of the second
plug microlens 332. In one aspect, the first and second plug
microlenses 316/332 are made from a polycarbonate resin
thermoplastic such as lexan or ultem, and have respective focal
lengths 342 and 344 in the range of 2 to 4 mm. The first and second
plug microlens 316 and 332 transceive the collimated beams with a
beam diameter 346 in the range of 1.2 to 1.3 mm.
[0056] As used herein, a jack is the "female" connector and a plug
is a mating "male" connector. Note, a portion of the first plug
body has been cut away to show the fiber line 304. In some aspects,
a crimping plate is connected to a cradle portion of the body, to
hold the fiber line in place. See parent application Ser. No.
12/581,799 for additional details.
[0057] FIGS. 4A and 4B are a more detailed depiction of the first
plug microlens of FIG. 3. For clarity, only the microlens 316 is
shown. The first plug microlens 316 has a lens center axis 400. As
shown in FIG. 4B, there is a lens axis tolerance defined by a cone
angle 402 of up to 0.5 degrees (+/-0.5 degrees from a perfectly
aligned, or tolerance midpoint lens center axis) as a result of the
first plug mechanical body tolerances, when engaging the first jack
mechanical body. That is, due to "play" between the jack and plug
housings, resulting from design and manufacturing tolerances, the
lens axis may be misaligned as much as 0.5 degrees. Note: although
misalignment is only shown in an XY plane, the lens axis tolerance
may define a circular cone with respect to a perfectly aligned
center axis.
[0058] The first plug microlens has a diameter 404 in the range of
2 to 3 mm, and the first collimated beam diameter (see FIG. 3,
reference designator 346) is transceived within the microlens
diameter 404. The first plug microlens 316 includes a cylindrical
section 406 interposed between the planar surface 318 and the
convex surface 320.
[0059] In one aspect, the first plug microlens cylindrical section
406 has a length 408 in the range of 4 to 6 mm and the convex
surface 320 has a radius of curvature in the range of 1.5 to 2.5
mm. The second plug microlens, not shown, has the same lens
dimensions and tolerances as the first plug microlens.
[0060] FIGS. 5A and 5B are partial cross-sectional and plan views,
respectively, of the first plug of FIG. 3. A first plug cradle 500
has a channel or groove 502 to accept the fiber optic line first
end 306 (not shown in FIG. 5A). The channel 502 has a center axis
504 with a tolerance 506 of up to 30 microns with respect to the
lens center axis 400. Alternately stated, the center axis of the
fiber line core may have a tolerance of up to 30 microns with
respect to the lens center axis. The first plug includes a gap 508
between the microlens planar surface 318 and the first fiber optic
cable first end of up to 0.4 mm. The second plug (not shown)
likewise has a cradle, channel, dimensions, and tolerance as
described above.
[0061] FIG. 6 is a partial cross-sectional view of the first plug
microlens of FIG. 3. The first plug microlens modifies the
magnification of light between the collimated beam 322 at convex
surface 320 and a point 600 on the planar surface 318 along the
lens center axis 400, forming a cone with an angle 602 of 10 to 11
degrees with respect the lens center axis 400. The second plug (not
shown) likewise has the same magnification/demagnification features
as the first plug microlens.
[0062] FIGS. 7A and 7B are drawings depicting a fiber optic cable
with a cable section that includes a first plurality of fiber optic
lines. In FIG. 7A, lines 304a through 304d are shown. Each fiber
optic line 304 has a first end 306 and a second end 308. In the
example of FIG. 7A, the first plurality is equal to four, but the
cable section 302 is not limited to any particular number of lines.
The first and second plugs 310/326 include the first plurality of
microlenses, respectively 316a-316d and 332a-332d. Each microlens
316/332 has a planar surface 318/334 to engage a corresponding
fiber optic line end and a convex surface 320/336 to transceive
light in a corresponding collimated beam with a jack optical
interface (not shown). Each fiber optic cable end 306/308 is formed
in a focal plane 342/344 of a corresponding first plug microlens
316/332. A layer of cladding 700 is also shown surrounding the
fiber cores 304. In one aspect the cladding diameter is about 0.49
mm and the core diameter is about 0.0625 mm. Typically, the
cladding is covered with a buffer and plenum jacket, which is not
shown because it is stripped away.
[0063] As shown in FIG. 7B, there may be multiple rows of
microlenses, e.g., a top row and a bottom row. Note: a completely
assembled plug would include top and bottom crimping plates (not
shown), to secure the fiber lines 304 to the cradle 500. In one
aspect, the first plug mechanical body has the form factor of an 8
Position 8 Contact (8P8C) plug mechanical body.
[0064] FIGS. 19A and 19B are partial cross-sectional views
depicting a first variation of a fiber optical connector microlens
with a self-aligning optical fiber cavity. The microlens 1900
comprises a convex first lens surface 1902 and a second lens
surface 1904. Although the second lens surface 1904 is shown as
planar, in other aspects it may also be convex (see FIG. 20A).
Further, in other aspects the second lens surface can be aspheric
or holographic. As is well known in the art, a convex lens surface
can be described by a portion of a circular circumference. That is,
a convex surface be can defined by a radius with respect to a
center point. An aspheric or aspherical lens is a more complicated
shape that may include a surface portion defined by a radius, and
other portions defined by a hyperbola or parabola, for example. A
holographic lens might be fabricated from a plurality of closely
packed, distinct convex (or aspheric) lens. For example, a
holographic lens might be a fly's-eye or integral lens array.
[0065] A fiber alignment cavity 1906 is integrally formed with the
second lens surface 1904 to accept an optical fiber core 1908. In
this aspect, the fiber alignment cavity 1906 is formed in the lens
second surface 1904. That is, the fiber alignment cavity penetrates
the lens second surface 1904.
[0066] A lens body 1910 is interposed between the first lens
surface 1902 and second lens surface 1904. The lens body 1910 has a
lens body length 1912, and a cross-sectional area 1914 with a lens
center axis 1916. In one aspect, the fiber alignment cavity 1906
has a center axis 1928 aligned with the lens center axis 1916.
Typically, the fiber alignment cavity 1906 has a length 1918,
aligned with the lens center axis 1916, which is in the range of 5
to 10% of the lens body length 1912. In one aspect, a focal point
1924 is formed inside the fiber alignment cavity 1906, when
transceiving light in a collimated beam 1926 via the first lens
surface 1902. Note, when the second lens surface 1904 is planar, it
can be said that the focal point is formed as a result of the first
lens surface, as the planar surface does not modify magnification.
When the second lens surface is convex, the focal point is
ultimately formed as a result of the second (convex) lens surface.
Alternately stated, the focal point is formed in the focal plane of
the first lens surface, as modified by the second lens surface. The
effect of such a microlens with two convex lens surfaces can be
seen in FIGS. 15-17, in the transceiving of light between a jack
lens and an optical element (VCSEL or photodiode).
[0067] The first and second lens surfaces 1902/1904 may be formed
from a polycarbonate resin thermoplastic such as lexan or ultem.
The fiber alignment cavity 1906 has a minimal cross-section 1920
with a shape such as a triangle, a square, a rectangle, circle, or
an oval (a circle is shown). Typically, the fiber. alignment cavity
1906 accepts an optical fiber core 1908 having a first diameter
1922, and the cavity minimal cross-section 1920 is about 5% greater
than the first diameter 1922. Note: these same dimensional features
also apply to the other aspects of the fiber alignment cavity
presented below.
[0068] FIGS. 20A, 20B, and 20D are partial cross-sectional views
depicting a second variation of the fiber optical connector
microlens with self-aligning optical fiber cavity, and FIGS. 20C
and 20E are perspective drawings. An integrally formed cradle 2000
with a cradle surface 2002 extends from the lens second surface
1906. A channel 2004 is formed in the cradle surface 2002, with a
center axis 2006 aligned with the lens center axis 1916. The fiber
alignment cavity 1906 includes a bridge 2008 covering a portion of
the channel 2004. As shown in FIGS. 20A and 20B, the bridge 2008
includes a first end 2010 connected to the second lens surface
1904, and an exposed second end 2012. FIG. 20C is a perspective
drawing illustrating the variation of FIGS. 20A and 20B. As shown
in FIG. 20D, the bridge 2008 includes an exposed first end 2010
separated from the second lens surface 1904 by an opening 2014, and
an exposed second end 2012. FIG. 20E is a perspective drawing
illustrating the variation of FIG. 20 D.
[0069] FIGS. 21A through 21C are partial cross-sectional views
depicting a third variation of the fiber optical connector
microlens with self-aligning optical fiber cavity. In this aspect,
the fiber alignment cavity 1906 includes an integrally formed tube
2100 extending from the lens second surface 1904, with a center
axis aligned 2102 with the lens center axis 1916. As shown in FIG.
21A, the tube 2100 has a proximal end 2104 adjacent the lens second
surface 1906 with a first diameter 2106 to accept an optical fiber
core 1908, and a distal end 2108 with a second diameter 2110 to
accept an optical fiber with a cladding layer 2112.
[0070] FIGS. 22A and 22B are partial cross-sectional views
depicting a fourth variation of the fiber optical connector
microlens with self-aligning optical fiber cavity. An integrally
formed cradle 2000 with a cradle surface 2002 extends from the lens
second surface 1904. A cradle channel 2004 is formed in the cradle
surface 2002, with a center axis 2006 aligned with the lens center
axis 1916. A crimping plate 2200 with an interior surface 2202 is
mechanically secured to the cradle 2000. A number of means are
known in the art to permanently or selectively secure the crimping
late 2200 to the cradle 2000. The microlens alignment mechanism is
not limited to any particular mechanism. In some aspects, the
crimping plate 2200 is used to compress the fiber core and/or fiber
cladding layer, to hold the fiber in place with respect to the
microlens and cradle.
[0071] As shown, a crimping channel 2204 is formed in the crimping
plate interior surface 2202, with a center axis 2206 aligned with
the lens center axis 1916 (and channel center axis 2006). The fiber
alignment cavity 1906 is formed between the cradle channel 2006 and
crimping channel 2204. In another aspect not shown, the cradle and
crimping channels have a first diameter to accommodate the fiber
core and a second diameter to accommodate a fiber cladding
layer.
[0072] FIGS. 23A through 23C are partial cross-sectional views
depicting a first variation of a fiber optic connector plug with an
optical fiber self-alignment mechanism. The plug 2300 comprises a
mechanical body 2302 shaped to selectively engage and disengage a
jack housing 2304 (shown in phantom), and a microlens 1900. As
described above in the explanation of FIGS. 19 through 22B, the
microlens 1900 has a convex first lens surface 1902 to transceive
light in a collimated beam 2306 with a jack optical interface 2308,
and a second lens (convex or planar) surface 1904. A fiber
alignment cavity 1906 is integrally formed with the second lens
surface 1904 to accept an optical fiber core. Typically, the
mechanical body 2302 and microlens 1900 are a single injection
molded piece made from a polycarbonate resin thermoplastic such as
lexan or ultem. As in FIGS. 19A and 19B, the fiber alignment cavity
1906 penetrates the lens second surface 1904. As above, the
microlens 1900 forms a focal point 1924 inside the fiber alignment
cavity 1906, when transceiving light in a collimated beam 2306 via
the first lens surface 1902.
[0073] FIG. 23B depicts a plug with a first plurality of
microlenses, 1900a through 1900n, where n is a variable not limited
to any particular value. Each microlens 1900 has a convex first
surface 1902 to transceive light in a corresponding collimated beam
2306 with a first jack optical interface (not shown), the second
lens surface 1904, and the fiber alignment cavity 1906 variation
depicted in FIG. 23A. FIG. 23C is another partial cross-sectional
view. Shown are m rows of microlenses 1900, where m is not limited
to any particular value.
[0074] FIGS. 24A and 24B are partial cross-sectional views
depicting a second variation of a fiber optic connector plug with
an optical fiber self-alignment mechanism. As in FIGS. 20A through
20D, a lens body 1910 is interposed between the first and second
lens surfaces 1902/1904, having a cross-sectional area with a lens
center axis 1916. A cradle 2000 is integrally formed with the
mechanical housing 2302 and microlens 1900, with a cradle surface
2002 extending from the lens second surface 1904. A channel 2004 is
formed in the cradle surface 2002, with a center axis 2006 aligned
with the lens center axis 1916. The fiber alignment cavity 1906
includes a bridge 2008 covering a portion of the channel 2004, with
a first end 2010 connected to the second lens surface 1904, and an
exposed second end 2012. In another aspect not shown here (see FIG.
20D), there is an opening between the bridge first end 2010 and the
lens second surface 1904.
[0075] FIG. 24B depicts a plug with a first plurality of
microlenses, 1900a through 1900n, where n is a variable not limited
to any particular value. Each microlens 1900 has a convex first
surface 1902 to transceive light in a corresponding collimated beam
2306 with a first jack optical interface (not shown), the second
lens surface 1904, and the fiber alignment cavity 1906 variation
depicted in FIG. 24A. Although not explicitly shown, the plug may
comprise m rows of microlenses, where m is not limited to any
particular value.
[0076] FIGS. 25A and 25B are partial cross-sectional views
depicting a third variation of a fiber optic connector plug with an
optical fiber self-alignment mechanism. As in FIGS. 21A and 21B, a
lens body 1901 is interposed between the first and second lens
surfaces 1902/1904, having a cross-sectional area with a lens
center axis 1916. The fiber alignment cavity 1906 includes a tube
2100, integrally formed with the mechanical body 2302 and microlens
1900, extending from the lens second surface 1904, with a center
axis 2102 aligned with the lens center axis 1916. Although only a
constant diameter variation is explicitly depicted here, the tube
may have a second diameter to accept a fiber cladding layer as
shown in FIG. 21B
[0077] FIG. 25B depicts a plug with a first plurality of
microlenses, 1900a through 1900n, where n is a variable not limited
to any particular value. Each microlens 1900 has a convex first
surface 1902 to transceive light in a corresponding collimated beam
2306 with a first jack optical interface (not shown), the second
lens surface 1904, and a fiber alignment cavity 1906 variation
depicted in FIG. 25A. Although not explicitly shown, the plug may
comprise m rows of microlenses, where m is not limited to any
particular value.
[0078] FIGS. 26A through 26C are partial cross-sectional views
depicting a fourth variation of a fiber optic connector plug with
an optical fiber self-alignment mechanism. As in FIGS. 22A and 22B,
a lens body 1910 is interposed between the first and second lens
surfaces 1902/1904, having a cross-sectional area with a lens
center axis 1916. A cradle 2000 is integrally formed with the
mechanical body 2302 and microlens 1900, with a cradle surface 2002
extending from the lens second surface 1904. A cradle channel 2004
is formed in the cradle surface 2002, with a center axis 2006
aligned with the lens center axis 1916. A crimping plate 2200 with
an interior surface 2202 is mechanically secured to the cradle
2000. A crimping channel 2204 is formed in the crimping plate
interior surface 2202, with a center axis 2206 aligned with the
lens center axis 1916 and cradle channel 2004. The fiber alignment
cavity 1906 is formed between the cradle channel 2004 and crimping
channel 2204.
[0079] FIGS. 26B and 26C depicts a plug with a first plurality of
microlenses, 1900a through 1900n, where n is a variable not limited
to any particular value. Each microlens 1900 has a convex first
surface 1902 to transceive light in a corresponding collimated beam
2306 with a first jack optical interface (not shown), the second
lens surface 1904, and the fiber alignment cavity 1906 variation
depicted in FIG. 26A. Although not explicitly shown, the plug may
comprise m rows of microlenses, where m is not limited to any
particular value. Note: only the cradle channel 2004 can be seen in
FIG. 26B.
[0080] FIG. 8 is a diagram depicting communicating jack and plug
microlens. A transmitting vertical-cavity surface-emitting laser
(VCSEL) 800 has a numerical aperture (NA) of 0.259, so that light
is emitted into a 30 degree cone at the 1/e.sup.2 point:
NA=1 sin 15.degree.=0.259.
[0081] The NA of the fiber line 304 is 0.185, which translates into
an acceptance angle cone of about 21 degrees.
[0082] One aspect of coupling efficiency is reflection (R). A
normally incident reflection of .about.4.9% is typical of each
air/lexan interface. For rays not normally incident, R is a
function of angle of incidence and polarization:
n for lexan@850 nm.about.1.568;
n' for air=1;
R=((n-n')/(n+n'))2.about.4.9%;
[0083] Assuming each jack and plug use a microlens, there are 3
air-to-lexan interfaces. The fiber/plug interface is filled with
index-matching fluid, so no reflection is assumed for this
interface;
(1-0.049).sup.3=86% optimal coupling efficiency.
[0084] FIG. 9 is a model calculation graphically depicting the
coupling efficiency of the system of FIG. 8. The model shows that
86% of the transmitted light falls within a circle of about 0.07
mm, which is about the diameter of a particular POF optical fiber
core.
[0085] FIG. 10 is a diagram depicting the fiber core acceptance
angle. Assuming a 70 micron diameter gradient index (GRIN) fiber
core, the NA is 0.185, which translates to an acceptance angle of
+/-10.7.degree.. This assumption ignores the fact that the
acceptance angle falls of towards to core edges.
[0086] Many of the system tolerances can be converted into an
effective fiber lateral decenter. For example, VCSEL lateral
decentering can be multiplied by the system magnification. Plug
tilt can be accounted for by taking the taking the tangent of the
tilt and multiplying it by the effective focal length of the plug
lens. Most of the other tolerances tend to change the shape of the
beam rather than causing the beam to "walk off" the face of the
fiber end. With respect to the fiber line of FIG. 10, "lateral"
refers to the X plane (in and out of the page) and Y plane (from
the page top to the page bottom). The Z plane would be left to
right on the page.
[0087] FIG. 11 is a graph depicting the relationship between
coupling efficiency and fiber lateral decentering (.DELTA.). The
relationship is nonlinear, steeply degrading at about 30 microns of
decentering, or about half the core diameter.
[0088] FIG. 12 is a diagram depicting the effective focal length of
the plug microlens. Assuming a radius of curvature of 1.971 mm, an
overall lens length of 5.447 mm, and a lexan material, the
effective focal length of the plug is:
eflplug.about.5.447 mm/n.sub.lexan;
eflplug=3.471 mm.
[0089] FIG. 13 is a table of tolerances cross-referenced to fiber
lateral decentering.
[0090] The following is an equation for worst-case effective fiber
decentering using tolerances T1 through T5 from the Table of FIG.
13:
effective fiber decenter = T 1 ( 1.36 ) + T 2 ( 1.36 ) + 3.471 tan
( T 3 ) + T 4 + T 5 ; = 1.36 ( T 1 + T 2 ) + 3.471 [ tan ( T 3 ) ]
+ T 4 + T 5 ~ 1.36 ( T 1 + T 2 ) + 3.471 ( T 3 ) + T 4 + T 5
##EQU00001##
[0091] The tolerances T1 and T2 are proportional to the system
magnification (1.36), and the lens tilt is expressed as a tangent
in radians, assuming a small-angle approximation. Note: T2 circuit
misalignment refers to the relationship between the circuit board
on which the optical elements (VCSEL and PD) are mounted and the
microlens. T1 VCSEL/PD misalignment refers to misalignment between
the VCSEL/PD and the circuit board. The T4 and T5 tolerances are
outside the system magnification, and need not be system
normalized.
[0092] In matrix form the equation is:
[ T 1 T 2 T 3 T 4 T 5 ] [ 1.36 1.36 3.471 1 1 ] ##EQU00002##
[0093] where [0094] 1.36=current system magnification; [0095] 3.471
mm=plug focal length; and, [0096] Ti=ith tolerance.
[0097] FIG. 14 is a graph depicting coupling efficiency as a
function of photodiode (PD) decentering.
[0098] FIG. 15 is a diagram depicting the relationship between
fiber decentering and lens tilt:
.DELTA. = effective fiber decenter = fplug * tan .theta. ; = 3.471
mm * tan .theta. ; ##EQU00003##
[0099] If .theta.=0.5.degree., then .DELTA.=30.3 .mu.m. Note: the
angle .theta. has been exaggerated.
[0100] FIG. 16 is a diagram depicting the relationship between PD
decentering and lens tilt.
.DELTA. = effective PD decenter = fjack * tan .theta. = 2.504 mm *
tan .theta. ##EQU00004##
[0101] If .theta.=0.5.degree., then .DELTA.=21.9 .mu.m.
[0102] FIG. 17 is a diagram depicting the relationship between PD
decentering and groove (channel) placement error. The channel
placement error may also be understood as a lens placement error
relative to the channel.
The effective PD decenter=channel placement error*Msys;
[0103] where Msys is the system magnification (0.727=1/1.36).
[0104] A channel placement error of 7.1 .mu.m results in effective
PD decentering of 7.1 .mu.m*0.727=5.2 .mu.m in both the X and Y
planes. The overall decentering (the hypotenuse of the triangle)
is:
sqrt(5.sup.2+5.sup.2)=7.1 microns.
[0105] A placement error of 10 microns results in a PD decentering
of about 10 microns.
[0106] FIG. 18 is a diagram depicting the consequences of
shortening the focal length of the plug, without a corresponding
change in the jack lens. If the plug focal length (fplug) is
decreased, the loss in coupling efficiency due to plug angular
misalignment can be reduced. However, the fiber core would be
overfilled (exceeding the NA 0.185), which would result in some
lost energy.
[0107] A fiber optic plug and microlens fiber alignment mechanism
have been provided. Some examples of particular housing designs,
tolerances, and dimensions have been given to illustrate the
invention. However, the invention is not limited to merely these
examples. Other variations and embodiments of the invention will
occur to those skilled in the art.
* * * * *