GLASS-BASED FERRULE ASSEMBLIES AND COUPLING APPARATUS FOR OPTICAL INTERFACE DEVICES FOR PHOTONIC SYSTEMS

Ferrule assemblies and coupling apparatus as used to form optical interface devices for photonics systems are disclosed. The ferrule assemblies include a ferrule made of a glass substrate and a pair of spaced apart alignment members, which can be made of a glass or a polymer. The ferrule assembly supports an array of optical fibers. The coupling apparatus is incorporated into a photonic integrated circuit assembly that has optical waveguides and that includes spaced apart alignment members, which can also be made of a glass or a polymer. The ferrule assembly and the coupling apparatus have complementary alignment features that align the optical waveguides and the optical fibers when forming the optical interface device. The alignment members have a geometry that allows them to be used to form both the ferrule assemblies and the coupling apparatus.

FIELD

The present disclosure relates to integrated photonics, and in particular relates to glass-based ferrule assemblies and coupling apparatus for optical interfaces devices for photonic systems.

BACKGROUND

Photonic systems are presently used in a variety of applications and devices to communicate information using light (optical) signals. Photonic systems may include photonic integrated circuits (PICs), which are analogous to electronic integrated circuits in that they integrate multiple components into a single material where those components operate using light only or a combination of light and electricity. A typical PIC has a combination of electrical and optical functionality, and can include light transmitters (light sources) and light receivers (photodetectors), as well as electrical wiring and like components that serve to generate and carry electrical signals for conversion to optical signals and vice versa.

A PIC includes one or more optical waveguides that carry light in analogy to the way metal wires carry electricity in electronic integrated circuits. Just as the electricity traveling in the wires of an electronic integrated circuit carries electrical signals, the light traveling in the waveguides of a PIC carries optical signals.

To transmit the optical signals from the PIC to a remote device, the optical signals carried by a waveguide in the PIC need to be transferred or “optically coupled” to a corresponding optical fiber connected to the remote device, This optical coupling should have a suitable optical efficiency and the optical coupling apparatus should have a compact footprint, as well as being low-cost and able to be reliably connected and disconnected. In addition, the optical coupling should be optically efficient even at relatively high operating temperatures since the PICs may generate significant amounts of heat. These relatively high operating temperatures may result in thermal expansion due to differences in the coefficients of thermal expansion (CTE) of the various components of the optical interface device and can adversely impact the optical coupling efficiency.

SUMMARY

A first aspect of the disclosure is a ferrule assembly for optically coupling to a coupling apparatus of a PIC assembly. The ferrule assembly includes: a glass support substrate having opposite upper and lower surfaces, opposite sides, and opposite front and back ends; first and second alignment members having respective first and second long axes and that are attached to the upper surface and spaced apart about their long axes, the first and second alignment members having respective first and second alignment features that respectively operably engage with first and second complementary alignment features of the coupling apparatus; and an array of optical fibers disposed on the upper surface of the glass support substrate between the first and second support members, with the optical fibers running generally parallel to the first and second long axes and that extend from the back end of the support substrate, the optical fibers having end faces that reside substantially at the front end of the support substrate.

Another aspect of the disclosure is a PIC assembly configured to couple to a ferrule assembly. The PIC assembly includes: a PIC having an upper surface, a front end, and an array of optical waveguides, with each optical waveguide having an end face that resides substantially at the PIC front end; and first and second alignment members having respective first and second front ends and first and second long axes, the first and second alignment members being attached to the upper surface and spaced apart along the first and second long axes, the first and second alignment members having respective first and second alignment features that respectively operably engage with first and second complementary alignment features of the ferrule assembly.

Another aspect of the disclosure is a coupling apparatus for a PIC assembly that has a PIC having an array of optical waveguides, for coupling to a ferrule assembly having an array of optical fibers, The coupling apparatus includes: first and second glass alignment members having respective first and second long axes and that are attached to the upper surface of the PIC and spaced apart along the first and second long axes; and first and second alignment features formed in the first and second glass alignment members and that are configured to engage with respective first and second complementary alignment features of the ferrule assembly.

Another aspect of the disclosure is an optical interface device that includes the ferrule assembly and the PIC assembly configured to operably couple to each other.

Another aspect of the disclosure is a photonic system that includes the optical interface device, a printed circuit board to which the PIC assembly is electrically connected, and a remote device operably connected to at least one of the optical fibers of the ferrule assembly.

DETAILED DESCRIPTION

Reference is now made in detail to various embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Whenever possible, the same or like reference numbers and symbols are used throughout the drawings to refer to the same or like parts. The drawings are not necessarily to scale, and one skilled in the art will recognize where the drawings have been simplified to illustrate the key aspects of the disclosure.

The claims as set forth below are incorporated into and constitute part of this Detailed Description.

Cartesian coordinates are shown in some of the Figures for the sake of reference and are not intended to be limiting as to direction or orientation.

Methods of forming the glass-based ferrule assemblies, the PIC assemblies, the coupling apparatus and the optical interface devices, including the various components that make up these assemblies, sub-assemblies and devices are described in the aforementioned patent application, entitled “Methods of forming glass-based ferrules and glass-based coupling apparatus,” which as noted above is incorporated by reference herein in its entirety.

Photonic System and PIC Assembly

FIG. 1is an elevated view of an example photonic system6in an unmated state. The photonic system6includes an integrated photonic assembly10and a ferrule assembly100. The integrated photonic assembly includes alignment members42configured to be operably coupled to alignment members142of ferrule assembly100via complementary alignment features for making an optical connection therebetween. The integrated photonic assembly10includes a PIC assembly20shown mounted to an interposer substrate (“interposer”)70, which is configured to provide electrical connections between PIC assembly20and a printed circuit board (PCB)80, The PIC assembly20includes or is configured as coupling apparatus40. The coupling apparatus40includes alignment members42.

The coupling apparatus40is configured to operably couple to ferrule assembly100via respective alignment members42and142so that the ferrule assembly is in optical communication with PIC assembly20of integrated photonic assembly10when mated. The combination of PIC assembly20and ferrule assembly100define an optical interface device200, which is shown as being disconnected inFIG. 1. The main components of photonic system6are now discussed in greater detail below.

PIC Assembly

FIG. 2Ais a close-up front-on view of an example PIC assembly20. The PIC assembly20includes PIC21, which has opposite upper and lower surfaces22and24, a front end26, opposite sides28A and28B, and supports an array30of optical waveguides (“waveguides”)32that run longitudinally in the x-direction along a medial portion35of the PIC21. Each waveguide32has an end face34that terminates at front end26. The end faces34may be disposed at any suitable location such as near lower surface24, or near upper surface22as shown inFIG. 2A. In an example, waveguides32are made of glass. In an example, waveguides32comprise channel waveguides that comprise a core and a cladding for guiding the optical signal. Also in an example, waveguides32are single-mode, but other types of waveguides may be used with the concepts disclosed herein. Although, array30is depicted as a single-row for explanation purposes, the array30may comprise multiple rows if desired for use with the concepts disclosed.

The PIC21can also include other components that are not shown, such as photoemitters, photodetectors, metal wiring, optical redirecting elements, electrical processing circuitry, optical processing circuitry, contact pads, etc., as is known in the art. In an example, PIC21is formed mainly from silicon (i.e., is silicon-based) and constitutes a silicon photonics (SIP) device. In another example, PIC21is formed mainly from glass, i.e., is glass-based) and may constitute a passive planar lightwave circuit.

Example Coupling Apparatus

As noted above, in an example PIC assembly20includes coupling apparatus40, which is configured to allow for the alignment of the optical coupling of the PIC assembly with ferrule100, as introduced above and as described in greater detail below. The coupling apparatus40as described below is shown in the form of a receptacle having guide holes44A and44B configured to receive respective alignment pins146A and146B from ferrule assembly100, as shown inFIG. 1and as discussed below. Alternatively, the coupling apparatus40can also be configured as a plug by providing alignment pins146A and146B on the coupling apparatus40and leaving the ferrule assembly configured with guide holes144A and144B for receiving alignment pins. The alignment pins and guide holes represent one example of complementary alignment features, and coupling apparatus40and ferrule assembly100can have other configurations for the complementary alignment features.

The coupling apparatus40includes spaced apart alignment members42, denoted42A and42B. The alignment members42A and42B are disposed on upper surface22of PIC21and are configured to receive alignment pins146A and146B of ferrule assembly100. PIC21has alignment members42A,42B attached thereto in a suitable manner so that a device such as ferrule100may be mated with the assembly for making an optical connection to the optical waveguides32of PIC21, Using separate alignment members42A,42B may be advantageous since they are easier to form with precision geometry than a monolithic component. Also by using individual alignment members and or components for the coupling apparatus40the impact due to the mismatch of CTEs of different materials (i.e., stress, strain and optical misalignment at elevated temperatures) may be reduced.

In an example, alignment members42A and42B reside on upper surface22atop respective side portions38A and38B of PIC21near sides28A and28B of PIC21. In an example, alignment members42A and42B are attached (fixed) to upper surface22of PIC21using a suitable structure for the materials of the PIC21and the alignment members42A,42B. By way of explanation, alignment members42A and42B may be attached to PIC21using an adhesive, such as an epoxy (e.g., a UV-cured epoxy). In another example, if alignment members42A and42B are glass-based they may be attached (fixed) to PIC21using a thin absorbing film or thin film of low melting glass or a glass frit or by using direct glass bonding techniques known in the art.

Coupling apparatus40comprises alignment members42A and42B and a PIC coupling assembly comprises PIC21with a coupling apparatus40(comprising alignment members42A and42B) attached thereto. The coupling apparatus40provides a precision alignment registration to the optical waveguides32of PIC21with another device such as ferrule assembly100or the like. Consequently, it is advantageous to have a coupling assembly that allows a precise and repeatable method of manufacture for placing and securing the coupling apparatus40to PIC21relative to the optical waveguides32.

Variations of coupling apparatus40may include other structure or features that aids in placing and securing the coupling apparatus in a precise and repeatable manner according to the concepts disclosed herein. Several explanatory examples are briefly introduced and then described in more detail below. In a first example, coupling apparatus40may comprise alignment members42A and42B and alignment spacer50(FIG. 3A). In another example, coupling apparatus40may comprise of alignment members42A and42B and alignment features52(FIG. 3B). In still another example, coupling apparatus40may comprise of alignment members42A and42B, and a support structure60(FIG. 3C). In other variations of the concepts disclosed, the coupling apparatus may use any suitable combinations of structures or features disclosed such as for the coupling apparatus. For instance, coupling apparatus40may comprises of alignment members42A and42B, alignment spacer50, and a support structure60(FIG. 3D).

In an example, alignment members42A and42B reside outside of medial portion35where array30of waveguides32resides. In one example, alignment members42A and42B are made a molded polymer (e.g., polyphenylene sulfide or PPS), while in another example the alignment members are made of glass, such as silica, PYREX® glass, or a chemically strengthened glass. One example of a chemically strengthened glass is GORILLA® glass, available from Corning, Inc., Corning, N.Y. Other chemically strengthened glasses can also be effectively employed.

FIG. 2Bis a front elevated view of an example alignment member42with a central axis AC, illustrating an example in which the two alignment members42A and42B are similar. With reference toFIGS. 2A and 2B, alignment members42A and42B include respective longitudinal central axes ACAand ACBthat run in the y-direction. The alignment members42A and42B also have respective front ends43A and43B and respective axial guide holes44A and44B that respectively run along or generally parallel to central axes ACAand ACBand that are open at the front ends. As used herein, the terms “parallel” or “generally parallel” means parallel within ±5 degrees. The guide holes44A and44B are configured to receive respective alignment pins146A and146B from ferrule assembly100and form a close fit thereto, thereby providing precision alignment of the optical channels upon mating. In one example, alignment members42A and42B are formed from a suitable glass material and may be formed using a glass-drawing process similar to a process used for drawing optical fibers for providing precision geometry, However, other manufacturing processes may be used depending on the materials selected for the coupling apparatus40and PIC21.

Alignment members may have any suitable cross-sectional shape or size. In an example, guide holes44A and44B have a circular cross-sectional shape (x-z plane) to closely accommodate guide pins146A and146B that in an example also have a circular cross-sectional shape, Other cross-sectional shapes for guide holes44A and44B can be used consistent with the cross-sectional shapes of alignment pins146A and146B. Also in an example, alignment members42A and42B have a substantially rectangular (x-z plane) cross-sectional shape of height and width dimensions h and w, and further in an example have a substantially square cross-sectional shape, i.e., h=w. In another example, the cross-sectional shape of alignment members42A and42B have an aspect ratio h:w of no greater than 1:5 or 5:1, while in another example have an aspect ratio of no greater than 1:2 or 2:1, In another example, the aspect ratio h:w is substantially 1:1. In an example, the edges of alignment members42A and42B need not be perfectly square, e.g., they can be rounded.

In an example, dimensions h and w are each in the range from 350 microns to 1500 microns, while in another example are each in the range from 600 microns to 650 microns, with exemplary values being nominally h=w=625 microns. Alignment members42A and42B also have respective lengths length LA and LB, which in an example are in the range from 2 millimeters (mm) to 12 mm, or 2 mm to 4 mm, with an exemplary lengths LA and LB being equal and nominally 3 millimeters.

With reference again toFIG. 2A, alignment members42A and42B have a center-to-center spacing SC when secured to PIC21along with a precise location relative to the optical waveguides32. Generally speaking, the center-to-center spacing SC is based upon the size and pitch of the optical waveguides32of the PIC along with the number of optical channels in array30and arrangement of the optical waveguides32of the array30. In an example, spacing SC may be between 2 mm and 10 mm, with an exemplary spacing between 2 and 3 mm, e.g., 2.3 mm. The alignment members42A and42B also have an inside edge-to-edge spacing SE of between 1 mm and 5 mm, or between 1.5 mm and 2 mm, with an exemplary spacing SE of nominally 1.675 mm.

The array30of waveguides32also has a width WG. By way of example, an array30of n=12 optical waveguides32with a pitch p=127 microns is WG=(n)(p)=(12)×(127)=1524 microns. Other suitable values for the pitch p can be used, e.g., 125 microns or 250 microns, and in an example the number n of waveguides32can be from n=2 to n=24, but other suitable values are possible. For n=12 and a pitch p=250 microns, WG can be about 3 millimeters. In an example, WG is as large as 5 millimeters. In an example, PIC21has a thickness TH of between 300 and 1000 microns, or in another example is between 500 microns and 800 microns, with an exemplary thickness TH being nominally 750 microns.

Thus, in an example, coupling apparatus40has an overall or total width height HT, a total or overall width WT and a total or overall length LT (seeFIG. 1). In an example, the overall length LT is defined by the overall lengths LA, LB of alignment members42, while in another example the overall length is defined as the length of PIC21(seeFIG. 1), or by an outer cover or housing (not shown).

In one example, the overall width WT is in the range from 2.5 mm to 7 mm, while in another example is in the range from 2.5 mm to 3.5 mm, with an exemplary value being about 3 mm. However, the coupling apparatus may have any suitable size, shape or dimension.

Also in an example, the overall or total height HT of coupling apparatus40is equal to height h, which as discussed above can have exemplary value of h=625 microns. In an example, the total height HT can include thickness TH of PIC21and can be in the range from 350 microns to 3500 microns (i.e., from 0.3 mm to 3.5 mm). In one example, the overall length LT of coupling apparatus40is LT=LA=LB, while in another example, the overall length LT>LA, LB and is defined by the length of PIC21.

In an example, coupling apparatus40can have a size that is about half the size of a standard MT connector and can range from about that size to about the same size as a standard MT connector. Thus, in one example, the overall dimensions height HT, width WT and length LT of coupling apparatus40are about the same as that for a standard MT connector, e.g., HT×WT×LT=3 mm×7 mm×8 mm, or can be about half the size, e.g., 1.5 mm×3.5 mm×4 mm. In an example, the dimensions HT×WT×LT can be in the range from 5 mm×15 mm×20 mm to 1 mm×3 mm×2 mm; however, any suitable dimension may be used with the concepts disclosed. In an example, PIC assembly20has the dimensions HT×WT×LT.

FIG. 3Ais similar toFIG. 2Aand illustrates an example wherein coupling apparatus40further comprises an alignment spacer50that resides between alignment members42A and42B and on upper surface22of PIC21. The alignment spacer50is formed to have a length defined to be the select edge spacing SE required to operably couple to ferrule assembly100(i.e., the alignment spacer matches the distance so the holes and alignment pins have the same spacing). The alignment spacer50acts a jig to control the spacing between alignment members42A and42B during manufacturing. The alignment spacer50can be formed from any suitable material such as a glass or a polymer, and can be secured to upper surface22of PIC21using the same techniques discussed above that can be used to fix alignment members42A and42B.

FIG. 3Bis similar toFIG. 3Aand illustrates another example of a coupling apparatus40that comprises alignment features52that reside on upper surface22of PIC21. InFIG. 3B, the alignment members42A and42B have respective outer sides48A and48B closest to opposite sides28A and28B, respectively, of PIC21. In the example, alignment features52are in the form of small blocks (i.e., smaller than alignment members42A and42B). The alignment features52can be used to facilitate proper spacing, placement and relative alignment of the alignment members42A and42B on the upper surface22of PIC21(e.g., relative to waveguide array30). Alignment features52act as stops for alignment members42A,42B on the outboard sides . The alignment features52can be formed from any suitable material such as a glass or a polymer and can be secured to upper surface22of PIC21and to alignment members42A and42B using the same techniques discussed above that can be used to fix alignment members42A and42B to the upper surface.

FIG. 3Cis similar toFIG. 3Aand illustrates another example of coupling apparatus40that includes a support structure60that mechanically connects alignment members42A and42B, which are shown inFIG. 3Cto have top surfaces49A and49B, respectively. The support structure60resides on top surfaces49A and498and spans the gap that separates the two alignment members42A and42B, thereby forming a bridge between the two alignment members. The support structure60serves to provide the desired spacing and additional structural support for coupling apparatus40. In an example, alignment spacer50can be used in combination with or incorporated into support structure60, as shown inFIG. 3D. The support structure60can be formed from any suitable glass or a polymer material and can be secured to top surfaces49A and40B using the same techniques discussed above that can be used to fix alignment members42A and42B to the upper surface22of PIC21. In another variation, the support structure60may be formed with an integrally formed spacer feature by having outboards ledges formed in the support structure for the precision alignment and placement of the alignment members42A,42B on relative to the support structure.

In one example, coupling apparatus40as disclosed herein is glass-based, i.e., at least a portion of the coupling apparatus is made of at least one type of glass. In another example, coupling apparatus40is polymer-based, i.e., a portion of the coupling apparatus is made of at least one type of polymer, or a combination of glass and polymer as part of a “hybrid” configuration. For example, alignment members42A and42B can be made of a polymer while the other components, such as the alignment spacer50, the alignment feature(s)52and/or the support structure60, can be made of glass (i.e., a so-called “hybrid” configuration), Coupling apparatus40formed from glass-based materials may be advantageous since they can be formed with a precise geometry, which is advantageous for optical alignment and coupling. Moreover, the glass-based materials may have a CTE that is closer match to CTE of the PIC21.

In another example configuration, alignment members42A and42B can be made of either a polymer or a glass. In an example, coupling apparatus40is made of a single type of glass, all of the components of the coupling apparatus are made of the same glass material. In another example, coupling apparatus40is made entirely of glass, but at least some of the components are made of different glass materials—for example, the alignment members42A and42B are made of a first glass material while all of the other components are made of a second glass material. In an example of coupling apparatus40that includes PIC21, the coupling apparatus is hybrid, with PIC21being silicon based while alignment members42A and42B can be made of either a glass or a polymer.

Example Ferrules and Ferrule Assemblies

As discussed above, optical interface device200includes ferrule assembly100, which is configured to mate to and optically couple to coupling apparatus40of PIC assembly20.FIG. 4Ais a back-side elevated view andFIG. 4Bis a partially exploded front-on view of the example ferrule assembly100.FIG. 4Cis similar toFIG. 2Band is an elevated view of an example alignment member142used to form ferrule assembly100

With reference now toFIGS. 4A through 4C, ferrule assembly100has a front side or front end102and a back side or back end104. The ferrule assembly100includes a support substrate110, that can have any suitable geometry. Generally speaking, support substrate has generally parallel upper and lower surfaces112and114, opposite front and back ends122and124, a central portion126, and opposite edges (sides)128A and128B. In an example, support substrate110is in the form of a generally planar sheet and is made of any suitable material. By way of example, support substrate may be a glass, such as a float glass or a fusion-drawn glass, which could be chemically strengthened glass if desired. Although, the term “planar” is used, the support substrate110may include fiber alignment features such as V-grooves or other geometry for aligning and fixing the optical fibers in a desired spacing. For instance, the support substrate110may have the fiber alignment features etched into the surface for seating and spacing the optical fibers. The support substrate110has a thickness TH′. The ferrule assembly has a total or overall width WT′, a total or overall length LT′ and a total or overall height HT′.

The ferrule assembly100includes an array130of optical fibers132each having core133a,a cladding133bsurrounding the core (see close-up inset inFIG. 4A), and an end face134. The optical fibers132reside on upper surface112of substrate110at central portion126and run in the y-direction. In an example, fiber end faces134are terminated near the front end122of support substrate110. The optical fibers132in array130define a pitch p′. In an example, optical fibers132each have a diameter d′, which in one example is 125 microns. In an example, optical fibers132are arranged side-by-side so that the optical fiber pitch p′ of array130is substantially equal to the fiber diameter d′. In another example, the optical fiber pitch p′ is 250 microns. In an example, optical fibers132are single-mode fibers, but other types of optical fibers may be used with the concepts disclosed. Also in an example, optical fibers132are small-clad optical fibers, i.e., the cladding133bof optical fiber132is substantially smaller than that of the cladding used in a conventional optical fiber.

By way of explanation, a standard single-mode optical fiber can have a core diameter of about10microns and a cladding diameter ranging from50microns up to125microns. An advantage of using small-clad optical fibers for optical fibers132is that the pitch p′ can be made smaller than for conventional optical fibers, and can be made as small as the diameter d′ of the optical fiber, where the diameter d′ is defined by the diameter of cladding133b.Thus, small-clad optical fibers132can be more densely packed in ferrule assembly100while also affording greater latitude in matching the period p′ of the optical fibers to the period p of waveguides32of PIC assembly20. Although ferrule assembly100is depicted with a single-row of optical fibers, the ferrule assembly100may have multiple rows of optical fibers to mate with a suitable PIC coupling assembly20.

The ferrule assembly100also includes first and second spaced apart alignment members142, denoted142A and142B. As noted above,FIG. 4Cis an elevated view of an example alignment member142, which can be used as alignment members142A and142B.

The alignment members142A and142B are disposed on upper surface122adjacent respective sides128A and128B. In an example, alignment members142A and142B are formed using a drawing process similar if not identical to that used to draw optical fibers. In an example, alignment members142are similar to alignment members42. In other examples, alignment members142can be formed using a molding process, a 3D printing process or an extrusion process.

The alignment member142has a central axis AC, and alignment members142A and142B include respective central axes ACAand AC′Bthat run in the y-direction. The alignment members142A and142B also have respective front ends143A and143B and include respective axial guide holes144A and144B that in an example run along or parallel to the central axes AC′Aand AC′B. The axial guide holes144A and144B respectively contain alignment pins146A and146B that extend in parallel from respective front ends143A and143B. The alignment pins146A and146B are configured to be received by respective guide holes44A and44B of alignment members42A and42B of coupling apparatus40so that ferrule assembly100can operably couple to the coupling apparatus. Consequently, the operable coupling results in the connection of optical interface device200, with optical fibers132of the ferrule assembly being axially aligned with corresponding waveguides32of PIC21of PIC coupling assembly20. In an example, alignment pins146A and146are made of a metal.

In an example, alignment pins146A and146B have a circular cross-sectional shape (x-z plane). Other cross-sectional shapes can be used consistent with the cross-sectional shape of guide holes44A and44B of alignment members42A and42B. Also in an example, alignment members142A and142B have a rectangular (x-z plane) cross-sectional shape of dimensions h′ and w′, and further in an example has a substantially square cross-sectional shape, i.e., h′=w′. In another example, the cross-sectional shape of alignment members142A and142B have an aspect ratio h′:w′ of no greater than 1:5 or 5:1, while in another example the aspect ratio is no greater than 1:2 or 2:1. In another example, the aspect ratio h′:w′ is substantially 1:1.

In an example, alignment members142A and142B are fixed to upper surface112of support substrate110using an adhesive, such as an epoxy (e.g., a UV-cured epoxy). In another example, alignment members142A and142B are fixed to upper surface112using a thin absorbing film or thin film of ow melting glass or a glass frit or by using direct glass bonding techniques known in the art. The alignment members142A and142B and the support substrate110define a ferrule body (“ferrule”)145. In an example, ferrule145can include securing member160, introduced and discussed below.

In an example, alignment members142A and142B reside outside of center portion126where array130of waveguides32resides. In one example, alignment members142A and142B are made of a molded polymer (e.g., polyphenylene sulfide or PPS), while in another example the alignment members are made of glass, such as silica, PYREX® glass, or a chemically strengthened glass. One example of chemically strengthened glass is GORILLA® glass, available from Corning, Inc., Corning, N.Y. Other chemically strengthened glasses can also be effectively employed.

In one example, dimensions h′ and w′ are each in the range from 300 microns to 2000 microns, while in another example are each in the range from 600 microns to 650 microns, with exemplary values being nominally h′=w′=625 microns. The alignment members142A and142B also have respective lengths length LA′ and LB′, which in one example are each in the range from 2 millimeters (mm) to 12 mm, while in another example are each in the range from 2 mm to 4 mm, with an exemplary lengths LA′ and LB′ being equal and nominally 3 millimeters. However, the concepts disclosed herein may be practiced with devices of any suitable size.

With reference toFIG. 4B, alignment members142A and142B have any suitable a center-to-center spacing SC′ for mating with the desired PIC, By way of example, the center-to-center spacing SC′ of between 2 mm and 10 mm, while in another example are in the range from 2 mm to 3 mm, with an exemplary spacing being 2.3 mm. The alignment members142A and142B also have an inside edge-to-edge spacing SE′ of between 1.5 and 5 mm, or between 1.5 mm and 2 mm, with an exemplary spacing SE′ of nominally 1.675 mm.

The array130of optical fibers132also has a width WG′, which in an example for an array of n′=12 optical fibers with a pitch p′=127 micron is WG′=(n′)(p′)=(12)×(127)=1524 microns. Other values for the pitch p′ can be used, e.g., 125 microns or 250 microns, and in an example the number n′ of optical fibers132can be from n=2 to n=24. For n′=12 and a pitch p′=250 microns, WG′ can be about 3 mm. In an example, WG′ is as large as 5 mm. In an example, support substrate110a thickness TH′ of between 300 and 2000 microns, or in another example is between 500 microns and 1000 microns, with an exemplary thickness TH′ being nominally 700 microns.

The array130of optical fibers132of ferrule assembly100is configured to optical couple to array30of waveguides32when ferrule assembly100is operably coupled to coupling apparatus40of PIC coupling assembly . Thus, in an example, the optical fiber pitch p′ is equal to the waveguide pitch p, and the number n′ of optical fibers132is equal to the number n of waveguides32.

In one example, the overall width WT′ is in the range from 2.5 mm to 7 mm, while in another example is in the range from 2.5 mm to 3.5 mm, with an exemplary value being about 3 mm. In an example, the overall dimensions HT′, WI′ and LT′ of ferrule assembly100are about the same as that for a standard MT connector, e.g., HT′×LT′=3 mm×mm×8 mm, or can be about half the size, e.g., 1.5 mm×3.5 mm×4 mm. In an example, the dimensions HT′×WT′×LT′ can be in the range from 3 mm×7 mm×8 mm to 1.5 mm×3.5 mm×4 mm.

In an example, the height h′ of alignment member142is not the same as the height h of alignment member42. This is because in some cases, these two heights need to be different in order for optical fibers132of ferrule assembly100to align with the optical waveguides32of PIC assembly40when the alignment pins146are inserted into alignment holes44. This is referred to as the fiber-to-waveguide alignment condition, and arises due to an offset Δz between optical fibers132and waveguides32when the upper surface112of support substrate110and the upper surface22of PIC21. reside in the same plane. This offset is referred to herein as the fiber-waveguide offset Δz.

FIG. 4Dis a close-up cross-sectional view of an example optical interface device200that shows ferrule assembly100operably mated with PIC assembly40and illustrates an example of where the height h′ is greater than the height h. The alignment members42and142are shown in phantom since they would not otherwise appear in a cross-sectional view that includes waveguides32and optical fibers132. The different heights h and h′ account for the offsets in the upper surface112of support substrate110and the upper surface22of PIC21.

Thus, in an example, alignment members42and142have the same cross-sectional geometry but are rotated by 90 degrees relative to each other when attached to their respective surfaces22and112. In other words, in an example, the height h′, the width w′ and the location of guide hole144are selected so that the alignment member142can be used in one orientation in ferrule145to form ferrule assembly100and in another orientation to serve as alignment member42on PIC21to form coupling apparatus40. In an equivalent manner, in an example the height h, the width w and the location of guide hole44are selected so that the alignment member42can be used in one orientation on PIC21to form coupling apparatus40and in another orientation to serve as alignment member142for ferrule145of ferrule assembly100. Thus, in an example, alignment member42or142can be a “dual use” alignment member, i.e., it can be used for either ferrule assembly100or coupling apparatus40.

In another example, h=h′ but the distance between central axis AC′ and upper surface112for ferrule assembly100is made larger than the distance between central axis AC and upper surface122. This can be accomplished by adjusting the locations of either guide holes44of alignment member42or guide holes144of alignment member44.

In an example, alignment members42or142can be configured with a rectangular cross-sectional shape wherein h′=w and h=w′, and with h′ greater than h, to compensate for the fiber-waveguide offset Δz in order to satisfy the fiber-to-waveguide alignment condition. In an alternative example, alignment members42and142can have square cross-sectional shapes with offset respective offset guide holes44and144to compensate for the fiber-waveguide offset Δz in order to satisfy the fiber-to-waveguide alignment condition.

FIGS. 4E through 4Hare similar toFIG. 4Band shows example ferrule assemblies100in their assembled form. With reference toFIG. 4E, in an example, ferrule assembly100includes a securing member160that has an upper surface162and a lower surface164. The securing member160resides atop optical fiber array130with lower surface164in contact with optical fibers132to keep the optical fibers in place on upper surface112of support substrate110, as shown inFIGS. 4E and 4F. In an example, securing member160is in the form of a planar sheet that has a width WS′ and a height HS′ (FIG. 4B). In an example, the width WS′ is substantially the same as the width WG′ of optical fiber array130. In an example, with width WS′ is slightly less than the width WG′ of optical fiber array130. In an example, the width WG′ of optical fiber array100is substantially the same as or equal to the edge-to-edge with SE′ of alignment members142A and142B, such as shown in example ofFIG. 4E. Thus, in an example, optical fiber array100spans the entire space between alignment members142A and142B. Also in an example, securing member160spans the entire space between alignment members142A and142B.

In an example, the height HS′ of securing member160is relatively small as compared to height h′ of alignment members142A and142B, e.g., is in the range from 100 microns to 500 microns. In another example, the height HS′ is substantially the same as or equal to the height h′ of alignment members142A and142B, as illustrated in the example shown inFIG. 4G. The configuration of ferrule assembly100ofFIG. 4Gprovides ferrule145with a solid, block-like structure.

FIG. 4His similar toFIG. 4Fand illustrates an example ferrule assembly100wherein securing member160includes fiber alignment features166on lower surface164. The fiber alignment features166are configured (e.g., shaped) to receive at least a portion of optical fibers132and to keep the optical fibers in place and aligned on surface112of support substrate110so that the end faces134of the optical fibers are aligned with the end faces34of waveguides32of PIC21when the ferrule assembly100is operably coupled to coupling apparatus40. In an example, the fiber alignment features166are in the form of grooves, such as V-grooves (as shown inFIG. 4F), U-grooves, notches, etc.

In an example, securing member160is used as a jig to ensure the proper placement of alignment members142A and142B on upper surface112of support substrate110. The securing member160can be fixed to optical fiber array130and/or to alignment members142A and142B using adhesive, such as an epoxy (e.g., a UV-cured epoxy). In another example, securing member160can be fixed to alignment members142A and142B and/or to optical fiber array130using a thin absorbing film or thin film of low melting glass or a glass frit or by using direct glass bonding techniques known in the art.

In an example, support substrate110is made of black glass, a glass doped with metal such as iron or titanium, which can facilitate the use of a glass fusion process in assembling ferrule assembly100. In an example, support substrate100can have a layer of glass that has a relatively low melting temperature (i.e., “low-melt glass”), e.g., of about 300 C. This can enable the use of bonding in an oven or other low-temperature non-localized heat source rather than using a laser or other relatively high-temperature and localized heating means to secure alignment members142A and142to upper surface112of support substrate110.

The ferrule145of ferrule assembly100as disclosed herein can be glass-based or a combination of glass and polymer as part of a “hybrid” configuration, i.e., at least a portion of ferrule145is made of at least one type of glass. Thus, embodiments of ferrule assembly100are also glass based and can have a hybrid configuration.

In an example, the support substrate110, alignment members142A and142B and the optional securing member160of ferrule145can be made of glass only, while in another example can be made with only some of the components being glass as part of a “hybrid” configuration. For example, support substrate110can be made of glass while alignment members142A and142B can be made of a polymer (i.e., a so-called “hybrid” configuration). In another example, ferrule145is made of a single type of glass, i.e., all of the components of the ferrule are made of the same glass material. In another example, ferrule145is made entirely of glass, but at least some of the components are made of different glass materials—for example, support substrate110is made of a first glass material while the two alignment members142A and142B are made of a second glass material.

Thus, in an example, optical interface device200has a hybrid construction wherein at least a portion of the optical interface device is made of glass since the ferrule assembly100and coupling apparatus40can each be glass-based, as described above.

Other Example Ferrule Assembly Configurations

The ferrule assembly100disclosed herein can have a number of configurations beyond those example configurations described above.FIGS. 5A through 5Eare front-on views of five additional example configurations for ferrule assembly100as disclosed herein.

FIG. 5Ashows an example ferrule assembly100wherein alignment members142A and142B have a generally rectangular shape but with respective rounded outer edges147A and147B. Such rounded outer edges147A and147B can arise for example during a drawing process used to form alignment members142A and142B. The rounded outer edges147A and1478can also be obtained by using a molding process or drawing process or extrusion process or 3D printing process to form alignment members142A and142B.

FIG. 5Bis similar toFIG. 5Aand shows an example ferrule assembly100wherein alignment members142A and142B have a generally circular cross-sectional shape with respective flat sections149A and149B for mounting the alignment members to upper surface112of support substrate110. In other words, the flat sections149A and149B reside upon upper surface112. An advantage of having a generally circular cross-sectional shape for alignment members142A and142B is that it may be easier to form the alignment members using standard drawing processes such as used in optical fiber manufacturing.

FIG. 5Cis similar toFIG. 5Band shows an example ferrule assembly100wherein alignment members142A and142B have respective alignment features in the form of alignment notches151A and151B. The alignment notches151A and151B are configured to receive alignment protrusions171A and171B of a removable alignment fixture170. The alignment protrusions171A and171B are configured to have a select spacing so that alignment members142A and142B can be positioned to have the same select spacing (e.g., center-to-center spacing SC′) prior to being secured to upper surface112of support substrate110. Once alignment members142A and142B are aligned and secured to support substrate110, alignment fixture170can be removed from ferrule assembly100.

FIG. 5Dis similar toFIG. 5Cand toFIG. 4Fand shows an example ferrule assembly100wherein the removable alignment fixture170is configured to also align optical fibers132by aligning securing member160on optical fiber array100. Once alignment members142A and142B and optical fibers132are aligned and secured to support substrate110, alignment fixture170can be removed from ferrule assembly100.

FIG. 5Eis similar toFIG. 5Aand shows an example ferrule assembly100wherein the alignment members142A and142B have their respective guide holes144A and144B defined by respective grooves144AG and144BG and an overlying cap member180. The alignment pins146can be arranged in the open grooves144AG and144BG and then overlying cap member180can be fixed to the alignment members142A and142B to form closed guide holes144A and144B.

In other examples, alignment members42can have the same or substantially the same shapes as the alignment members142as described above in connection with example ferrule assemblies100ofFIGS. 5A through 5E. Thus, in coupling apparatus40can also have similar example configurations to the example configurations of ferrule assemblies100ofFIGS. 5A through 5E.

Photonic System with Connected Optical Interface Device

FIG. 6Ais similar toFIG. 1Aand shows photonic system6with optical interface device200operably connected, i.e., with ferrule assembly100operably coupled to coupling apparatus40of PIC assembly20. The operably coupling is accomplished by alignment pins146A and146B of alignment members142A and142B of ferrule assembly100(seeFIGS. 4A, 4B) being received and closely engaged by respective guide holes44A and448of alignment members42A and42B of coupling apparatus40of PIC assembly20(seeFIGS. 2A, 28). The optical interface device200has an interface201defined by the respective confronting front ends102and26of ferrule assembly100and PIC assembly20.

FIG. 6Bis a close-up, cross-sectional view of optical interface device200ofFIG. 6Aas taken in a y-z plane along a waveguide32of PIC assembly20and a corresponding optical fiber132of ferrule assembly100.FIG. 6Balso includes a remote device220optical coupled to ferrule assembly100via one of optical fibers132. InFIG. 6B, the mating of alignment pins146A and146B with respective guide holes44A and44B of alignment members42A and42B is not shown because these features are not part of the cross-sectional view.

The PIC21of PIC assembly20is shown by way of example as having an optical emitter (e.g., light transmitter)210optically coupled to an input end32E of waveguide32. The optical emitter210emits light212that enters waveguide32at input end32E and that travels in the waveguide as guided light212G. The guided light212G exits waveguide end face34of waveguide32, crosses interface201and optical fiber132at end face134. The guided light212G then travels in optical fiber132and is carried away from ferrule assembly100to remote device220.

As noted above, the mating engagement of alignment pins146A and146B of alignment members142A and142B of ferrule assembly100with respective guide holes44A and44B of alignment members42A and42B of coupling apparatus40provides the required axial alignment of waveguides32in waveguide array30with optical fibers132of optical fiber array130in the connected optical interface device200. This allows for optical communication to take place between PIC assembly20and remote device220. This optical communication includes sending information as embodied in guided light212G, which in an example comprises optical signals. In other examples, the optical communication can be in the reverse direction in the case where the optical device210includes an optical transmitter and wherein the optical emitter210is an optical detector (e.g., photodetector).

In an example, waveguides32and optical fibers132have the same or substantially similar sizes and the same pitches p and p′ (to within manufacturing tolerances) to optimize the optical coupling efficiency (i.e., to minimize optical loss) between the waveguides and the optical fibers. In an example, waveguides32and optical fibers132are both single mode and the guided light212G carried by each has substantially the same mode-field diameter.

Features and Advantages

The embodiments of PIC assembly20and ferrule assembly100offer a number of important features and advantages as compared to existing PIC and ferrule assemblies and optical interface devices. A first advantage is that the glass-based construction of coupling apparatus40and ferrule assembly100avoids a substantial mismatch of the coefficients of thermal expansion (CTEs) between the two assemblies when they are operably coupled to one another. The coupling between fibers and waveguides can also occur over a broad optical wavelength range.

The ferrule assemblies and the coupling apparatus disclosed herein can also be made about twice as small as conventional ferrule assemblies and coupling apparatus that utilize standard sized connector components. The use of small-clad optical fibers132allows for a reduced optical fiber pitch p′ and allows for greater ability to match the waveguide pitch p of PIC21.

In addition, optical interface device200has a side-mount configuration because ferrule assembly100and PIC assembly20are engaged at their front “sides” (i.e., at their respective front ends102and26). A side-mount configuration has advantages over a top-mount configuration, which presents the risk of damage to PIC21. It also allows for a small form factor in the vertical (z) direction.

It will be apparent to those skilled in the art that various modifications to the preferred embodiments of the disclosure as described herein can be made without departing from the spirit or scope of the disclosure as defined in the appended claims. Thus, the disclosure covers the modifications and variations provided they come within the scope of the appended claims and the equivalents thereto.