Note: Descriptions are shown in the official language in which they were submitted.
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PLANAR OPTICAL DEVICE CONNECTOR AND METHOD FOR MAKING SAME
The present invention relates to optical components.
More particularly, the present invention relates ~o planar
optical device connectors.
BACK ~ROZTND OF TH . TNV .NTTnN
Planar optical devices, such as planar waveguides,
lightwave optical circuits, and optical devices on planar
glass and semiconductor substrates are becoming
increasingly important in multi-wavelength transmissions
systems, fiber-to-the-home, and personal handy set
systems.
To function, a light guiding region in the planar
optical devices must be interconnected or pigtailed with a
light guiding region in an optical fiber or another planar
optical device. The interconnection requires low loss,
typically less than 0.2 db per connection, environmental
reliability against heat and humidity, and cost
effectiveness. Achieving a low loss connection requires
extremely high precision alignment of the light guiding
regions.
One way to align the waveguide region in pla:_ar
optical devices with the light guiding regions in another
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planar optical device or optical fiber is by active
alignment, wherein the waveguide regions are butted
together, the alignment is monitored with an optical
monitoring tool, and the abutting waveguide regions are
then secured together. The optical monitoring tool can be
a photodetector device to measure the amount of optical
radiation lost at the interconnection. One disadvantage
associated with the active alignment of two abutting
waveguide regions is that it can be expensive and time
consuming, especially when the active alignment is
performed at the job site.
Another approach is passive alignment, which involves
aligning the waveguide regions by mechanical means. For
example, a planar optical device may be aligned with an
array of fibers or another planar device by using a pair
of MT type connector devices, fabricated by forming V-
grooves on a silicon wafer which support a planar
waveguide surrounded by a plastic molded MT type connector
plug. The V-grooves are precisely located on the wafer,
and the V-grooves support guide pins. The guide pins are
positioned to be received by guide holes on an oppositely
disposed MT-type connector plug which contains an array of
optical fibers. Connection of the two plug ends passively
aligns the planar waveguide and the array of fibers. An
example of a device utilizing a MT connector and V-grooves
is described in IEEE Photonics Letters, Volume 7, No. 12,
December 1995, which is relied upon and incorporated by
reference.
There are several disadvantages to using the passive
alignment V-groove approach described above. Because of
the small core diameters of the waveguides that must be
connected, the accuracy to which a V-groove can be
machined is insufficient to achieve desired losses of less
than 0.2 db per connection. Another problem is that the
pins are supported and aligned by silicon, which is
brittle and subject to fracture from the torques and
stresses created when the pins and the MT type connector
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plug are joined. Furthermore, fabrication requires high
precision V-groove grinding referenced to a fiducial
marker line, which is an expensive process. In addition,
forming V-grooves on a semiconductor surface uses
extremely valuable chip surface area that could be better
devoted to optical circuitry.
In view of the above disadvantages there is an
explicit need for a planar optical device connector which
combines the advantages of the above-noted active and
passive alignment approaches. Thus, it would be
advantageous to provide a connector device that produces
losses less than 0.2 db per connection in which the
abutting waveguide regions do not have to be actively
aligned, and which avoids the disadvantages associated
with placing V-grooves on a semiconductor substrate.
Accordingly, the present invention generally provides
a planar optical device connector comprising a body having
an annulus and datums. A planar optical device is
actively aligned to the datums and located within the
annulus, and preferably secured to the annulus with an
adhesive. Preferably the body of the device is molded,
more preferably, plastic molded, and the datums are either
guide pins or bores for receiving guide pins.
Another aspect of the invention includes a method of
fabricating a planar optical device connector by providing
a body having an annulus therein adapted to receive a
planar optical device and datums. The planar optical
device is actively aligned to the datums, and the planar
optical device is secured in the annulus. The datums can
be guide pins or guide pin bores, and the guide pins may
be integrally molded with the body of the connector, or
separately made and inserted into body of the connector.
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The principal advantage of the device and method of
the present invention is providing a device having a low
connection loss in which valuable semiconductor surface
area is not wasted by forming V-grooves thereon. Another
advantage of the present invention is that low connection
loss can be achieved without having to actively align
abutting waveguide regions of optical devices. Additional
features and advantages of the invention will become
apparent by the device and method particularly pointed out
in the written description and claims hereof as well as
the appended drawings. It is to be understood that both
the foregoing general description and the following
detailed description are exemplary and explanatory and are
intended to provide further explanation of the invention
I5 as claimed.
The accompanying drawings are included to provide a
further understanding of the invention by illustrating one
embodiment of the invention, and together with the
description serve to explain the principles of the
invention. In the drawings, wherever possible, like or
similar parts are identified throughout the drawings by
the same reference numerals. It is to be understood that
various elements of the drawings are not intended to be
drawn to scale, but instead are sometimes purposely
distorted for the purposes of illustrating the invention.
FIG. 1 is a perspective view of an embodiment of a
planar optical device connector in accordance with the
present invention.
FIG. 2 is an end view of a planar optical device
connector in accordance with the present invention.
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Reference will now be made in detail to the present
preferred embodiment of the invention, an example of which
is illustrated in the accompanying drawing.
The exemplary embodiment of the planar optical device
connector of the present invention is shown in Fig. 1 and
is designated generally by reference numeral 10. As
embodied herein and referring to Fig. 1, planar optical
device connector 10 includes an a body 12, having an
annulus 14 therein adapted to receive a planar optical
device 16. Planar optical device 16 contains waveguide
regions 17 for receiving and transmitting optical signals.
As used herein, the term "waveguide region.'" means the
region in an optical waveguide device that transmits an
optical signal. Waveguide region 17 is preferably silica
or doped silica, but it can be other materials such as
silicon, lithium niobate, etc. Body 12 is similar in
shape to typical MT type connectors and is fabricated by
any suitable well known methods such as injection molding.
Datums 18 are aligned with the annulus during manufacture
of body 12. As used in this invention, a datum is a point
with reference to which positions can be measured. Datums
18 may be guide pins as shown in Fig. 1, or they may be
bores for receiving guide pins (not shown).
If the datums 18 are guide pins, they may be made of
metal, stainless steel, ceramic or plastic. The guide
pins can be fixed permanently into the guide pin bores
with an adhesive such as epoxy, or they can be removable
from guide pin bores to facilitate disconnection and
reconnection. The guide pins may be separately fabricated
or made integral with the body of the connector device of
the present invention. It is understood that while the
cross sectional area of datums 18 are shown in the
drawings as generally cylindrical, datums 18 can have
other cross sectional areas, for example, square or
rectangular.
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Referring now to Fig. 2, which is an end view of a
planar optical device connector according to the present
invention, waveguide regions 17 of the planar optical
device 14 are actively aligned to the centerline of datums
18. As shown in Fig. 2, the cross sectional area of
annulus 14 is slightly larger than planar optical device
16 inserted therein. Annulus 14 will generally be
rectangularly shaped to accommodate a similarly shaped
planar optical device and is fabricated to only moderate
dimensional tolerances of about ~10 microns.
Another embodiment of the invention includes a method
of fabricating a planar optical device connector 10
including a step of providing a body 12 having an annulus
14 adapted to receive a planar optical device 16 and
datums 18. As mentioned above, annulus 14 is of only
moderate dimensional precision (about t10 microns), and is
sized slightly larger than the cross sectional area of the
planar optical device 16 to be inserted therein. This
embodiment further includes a step of actively aligning
planar optical device 16 to the datums after the planar
optical device has been inserted into annulus 14.
Active alignment of the datums 18 and the planar
optical device 16 may be achieved by using a suitable well
known method. For example, a power peaking method may be
utilized in which an MT type connector containing light
waveguides may be plugged into the body 12, and the
interconnect between the MT type connector and the planar
optical device 16 may be optically monitored by a
photodetector to determine optimal alignment of the
waveguide regions 17 in the planar optical device 16 and
the waveguide regions in the MT type connector (not
shown). Active alignment may also include other methods
such as an image analysis technique wherein an image of
the datums 18 and the planar optical device 16 are
utilized to actively align the planar optical device 6 to
the datums 18 either manually or automatically. This
embodiment finally includes a step of securing the planar
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optical device 16 in the annulus 14 by a suitable method.
For example, an adhesive or epoxy may be~used to secure
the actively aligned planar optical device 16 in the
annulus 14. After the planar optical device 16 has been
aligned to the datums 18, the adhesive or epoxy is cured
to secure the actively aligned planar optical device.
Curing of the adhesive may occur, for example by using
heat or light radiation, such as ultraviolet light.
After the planar optical device has been secured to
l0 the annulus, it may be desirable to polish the endface of
the device, or to cut the end of the planar optical device
at an angle to minimize back reflections. Advantageously,
after the planar optical device has been actively aligned
to the datums and secured in the annulus, the planar
optical device connector of the present invention can be
connected to an MT type connector containing waveguide
regions without having to actively align the abutting
waveguide regions. Since the waveguide regions on a
planar optical device are typically formed by a high
precision process such as photolithography, the alignment
of the waveguide regions is inherent.
In the embodiments described above, the datums are
located near the external lateral edge along the face of
the connector, with the planar optical device located in
between. The arrangement is logical, but exemplary only,
and other configurations are within the scope of this
invention.
The invention has been described in terms of a device
for connecting a planar optical device to an MT type
connector. The planar optical device may include a planar
waveguide having an array of waveguide regions, or an
optical integrated circuit having an array of waveguides.
The optical integrated circuit may be associated with a
modulator, switch, amplifier, multiplexer, etc. It will
be understood that the MT connector which is
interconnected to the device of the present invention may
contain an array of fibers or a planar optical device
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containing an array of waveguide regions in an optical
integrated circuit. Accordingly, it is within the scope
of this invention to use the device of the present
invention to interconnect a variety of planar optical
devices to a variety of devices capable of transmitting
optical signals.
It will also be apparent that the guide pins used to
interconnect the device of the present invention to an MT
connector plug are part of the final interconnection when
the two parts are connected together, and pins are not
necessarily associated with one part or the other.
It will be apparent to those skilled in the art that
various modifications and variations can be made in the
of the present invention without departing from the spirit
or scope of the invention. Thus, it is intended that the
present invention cover the modifications and variations
of this invention provided they come within the scope of
the appended claims and their equivalents.
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