AU729723C - Planar optical device connector and method for making same - Google Patents

Description

PLANAR OPTICAL DEVICE CONNECTOR AND METHOD FOR MAKING SAME

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The present invention relates to optical components. More particularly, the present invention relates zo planar optical device connectors.

BACKGROUND OF THE INVENTION

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 planar optical devices with the light guiding regions in another 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 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.

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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. 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 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.

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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. nFTATT.F.π D .qr^TP TON

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 . 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 ±10 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 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 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 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 .

Claims (10)

CT .A TMSWhat is claimed is :

1. A planar optical device connector comprising a body having an annulus and datums and a planar optical device actively aligned to the datums and located within the annulus .

2. The connector of claim 1 wherein the planar optical device is secured to the annulus with an adhesive.

3. The connector of claim 1 wherein the body is plastic molded.

4. The connector of claim 1 wherein the datums are guide pins .

5. The connector of claim 1 wherein the datums are guide pins integrally molded into the body.

6. The connector of claim 1 wherein the datums are bores for receiving guide pins.

7. A method of fabricating a planar optical device connector comprising the steps of : providing a body having an annulus adapted to receive a planar optical device and datums; actively aligning a planar optical device to the datums; securing the actively aligned planar optical device in the annulus .

8. The method of claim 7 wherein the datums are bores for receiving guide pins.

9. The method of claim 7 wherein the datums are guide pins .

10. The method of claim 9 wherein the guide pins are integrally molded with the body.