Apparatus and method for maintaining alignment of optical ferrules during thermal expansion or contraction - Patent Application 20070122999

Abstract

The optical ferrule has a different coefficient of thermal expansion than the substrate on which the optical device is mounted, and the ferrule optically couples the device to one or more optical fibers. The cradle on which the optical ferrule is mounted includes lateral and longitudinal engagement features that ensure alignment with the optical device at the operating temperature, and the ferrule expands relative to the substrate when transitioning to the operating temperature.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to connector assemblies and methods relating to connector assemblies. [Background technology]

[0002] Optical connectors can be used in a variety of applications, including telecommunications networks, local area networks, data center links, and internal links in computer equipment. Optical functions are increasingly being incorporated into small integrated devices such as photonic integrated circuits (PICs). PIC devices may contain optical elements such as waveguides, grating detectors, lasers, etc., fabricated using processes such as material deposition, photolithography, and etching. PICs may also be coupled to external optical devices via optical fibers. One challenge in utilizing PICs in this manner is the efficient coupling of light between the optical fiber and the small-core PIC waveguide or other small-scale optical devices on the PIC. Existing solutions involve active alignment of the fiber followed by permanent attachment to the device, which is expensive, time-consuming, and often has high loss. Summary of the Invention

[0003] One embodiment is directed to an optical ferrule having a mounting area for receiving and permanently attaching a plurality of optical fibers. A light redirection member of the ferrule receives light along a first direction from the plurality of fibers received by and permanently attached to the mounting area and redirects the received light along a different second direction. The redirected light exits the ferrule at an exit location on the mating face. The exit location is substantially centered on a first alignment surface perpendicular to the first direction. A pair of first engagement features protrude from opposite sides of the optical ferrule. The first engagement features are substantially centered on the first alignment surface. A second engagement feature, different from the first pair of engagement features, protrudes from a front side of the ferrule and is substantially centered on a second alignment surface perpendicular to the first alignment surface. The second alignment surface substantially bisects the exit location.

[0004] In some configurations, the output positions may include a row of optical output positions along the first alignment surface. The first engagement feature may include first and second tabs extending from opposite sides of the ferrule. The first and second tabs may be located within corresponding first and second cavities of a cradle that secures the ferrule. The first and second cavities constrain the two tabs along the first direction when the ferrule is mated with the cradle. In such cases, the ferrule may further include first and second lateral clearances between the first and second tabs and the corresponding first and second cavities to allow the tabs to be displaced laterally, with little or no clearance in the first direction between the first and second tabs and the corresponding first and second cavities.

[0005] In other configurations, the second engagement feature may comprise a tab extending from the front side, the tab being disposed within a cavity of a cradle configured to secure the ferrule, in which case clearance is included between the tab and the cavity to allow the tab to be displaced in the first direction, with little or no clearance laterally between the first and second tabs and the corresponding first and second cavities.

[0006] In some configurations, the optical ferrule may be formed of a polymer. The optical ferrule may further include a mating surface that optically interacts with an optical device on the substrate. The optical ferrule may be configured to fit loosely into the cradle at an assembly temperature and to fit tightly into the cradle at an operating temperature. In such cases, the assembly temperature may be lower than the operating temperature.

[0007] In another embodiment, the optical ferrule includes a mounting end configured to receive and secure an optical waveguide. A distal tip is longitudinally opposed to the mounting end. The light redirecting element is configured to redirect light between the optical waveguide and the mating surface of the optical ferrule. The longitudinal restraint member is operable to interact with a corresponding longitudinal restraint member of a cradle that receives and secures the optical ferrule. The lateral restraint member is operable to interact with a corresponding lateral restraint member of the cradle. The longitudinal and lateral restraint members minimize displacement of a reference point on the optical ferrule relative to a corresponding reference point on the cradle due to different thermal expansion coefficients of the optical ferrule and the cradle, which cause a change in size of the optical ferrule relative to the cradle in response to changes in temperature.

[0008] In some configurations, the mating surface includes an array of optical output positions along a lateral line, with the reference point being at the center of the lateral line. The longitudinal restraint member may include two tabs extending from opposite sides of the ferrule and aligned with the lateral line. Furthermore, the corresponding longitudinal restraint member of the cradle may include two cavities that longitudinally restrain the two tabs and allow lateral displacement of the two tabs when the ferrule is seated in the cradle. The lateral restraint member may include tabs extending from a distal tip aligned with the center of the lateral line. Furthermore, the corresponding lateral restraint member may include a cavity that restrains lateral displacement of the tabs and allows longitudinal displacement of the tabs when the ferrule is seated in the cradle.

[0009] In one configuration, the first coefficient of thermal expansion of the optical ferrule is greater than the second coefficient of thermal expansion of the cradle. The optical ferrule may be formed of a polymer. The mating surface may be operable to optically interact with an optical device on the substrate, and the cradle aligns the optical ferrule with the optical device. The optical ferrule may be configured to fit loosely in the cradle at an assembly temperature and to fit tightly in the cradle at an operating temperature, where the assembly temperature may be lower than the operating temperature.

[0010] In another embodiment, a cradle is configured to receive and secure an optical ferrule. The cradle includes corresponding longitudinal restraining members operable to interact with the longitudinal restraining members of the optical ferrule. The corresponding lateral restraining members are operable to interact with the lateral restraining members of the optical ferrule. The longitudinal and lateral restraining members minimize displacement of reference points on the mating surface of the optical ferrule with corresponding reference points on the cradle due to changes in size of the optical ferrule relative to the cradle. The size changes are induced by different coefficients of thermal expansion of the optical ferrule and the cradle and changes in temperature.

[0011] In some configurations, the mating surface may include an array of optical output positions along a lateral line, with the reference point being the center of the lateral line. The longitudinal restraint member of the ferrule may include two tabs extending from opposite sides of the ferrule and aligned with the lateral line. Further, the corresponding longitudinal restraint member of the cradle may include two cavities that restrain the two tabs and allow lateral displacement of the two tabs when the ferrule is seated in the cradle. The lateral restraint member may include tabs extending from a distal tip aligned with the center of the lateral line, and the corresponding lateral restraint member may include cavities that restrain lateral displacement of the tabs and allow longitudinal displacement of the tabs when the ferrule is seated in the cradle.

[0012] In some configurations, the first coefficient of thermal expansion of the optical ferrule is greater than the second coefficient of thermal expansion of the cradle. The cradle is formed of silica or other ceramic, or a low-thermal-expansion metal alloy such as Invar or Covar. The cradle may align and secure the optical ferrule to the substrate such that the mating surface optically interacts with an optical device on the substrate. The optical ferrule may be configured to fit loosely in the cradle at an assembly temperature and to fit tightly in the cradle at an operating temperature, which may be lower than the operating temperature.

[0013] In some configurations, the cradle may further include a lens configured to modify an optical path between the optical ferrule and the optical device, the optical device being located on a substrate to which the cradle is mounted. The lens may comprise a collimating lens. The cradle may further include a second corresponding longitudinal restraint member and a second corresponding lateral restraint member configured to minimize a second displacement of a second reference point of the second optical ferrule with respect to a corresponding second reference point of the cradle due to a change in size of the second optical ferrule relative to the cradle.

[0014] In another embodiment, an optical assembly includes an optical ferrule including a light redirecting element configured to redirect light between an optical waveguide and a mating surface of the optical ferrule. The optical ferrule has a first coefficient of thermal expansion. The cradle is configured to hold the optical ferrule and secure it to the substrate. The cradle has a second coefficient of thermal expansion different from the first coefficient of thermal expansion. The optical ferrule may be configured to fit loosely within the cradle at an assembly temperature and to expand into the cradle at an operating temperature.

[0015] In some configurations, the optical ferrule may include at least one restraining member, and the cradle may include at least one corresponding restraining member. The restraining member and the corresponding restraining member interact to minimize displacement between a reference point on the optical ferrule and a reference point on the cradle between an assembly temperature and an operating temperature. The optical ferrule may include an array of optical output locations arranged in a lateral line along the mating surface, with the reference point being centered on the lateral line. The at least one restraining member may include a longitudinal restraining member and a lateral restraining member, and the at least one corresponding restraining member may include a corresponding longitudinal restraining member that interacts with the longitudinal restraining member and a corresponding lateral restraining member that interacts with the lateral longitudinal restraining member. The optical assembly may further include lateral clearance between the longitudinal restraining member and the corresponding longitudinal restraining member to allow the longitudinal restraining member to displace in the lateral direction, with little or no clearance in the longitudinal direction between the longitudinal restraining member and the corresponding longitudinal restraining member.

[0016] In some configurations, the assembly temperature may be lower than the operating temperature. The optical ferrule may be formed of a polymer, and the cradle may be formed of a ceramic. The optical assembly may further include an optical device mounted on a substrate, the cradle aligning one or more optical output positions of the optical ferrule with the optical device. At least a portion of the one or more optical output positions may be misaligned with the optical device at the assembly temperature, and the one or more optical output positions may be optimally aligned with the optical device at the operating temperature. The cradle may further include a lens configured to modify an optical path between the optical ferrule and the optical device, the optical device being located on the substrate. The lens may include a collimating lens. The cradle may be further configured to hold and secure a second optical ferrule to the substrate, the second optical ferrule being located laterally relative to the optical ferrule. The cradle and the optical ferrule may be integrally formed.

[0017] In another embodiment, a method involves coupling an optical ferrule to a substrate with a cradle at an assembly temperature. The optical ferrule fits loosely within the cradle at the assembly temperature. The optical ferrule has a first coefficient of thermal expansion and the cradle has a second coefficient of thermal expansion different from the first coefficient of thermal expansion. One or more devices are coupled to the substrate such that the substrate, cradle, and optical ferrule reach an operating temperature. Relative expansion of the optical ferrule and cradle at the operating temperature aligns one or more output locations of the optical ferrule with an optical device mounted on the substrate.

[0018] In some configurations, relative expansion of the ferrule and the cradle at operating temperatures results in a tight fit of the ferrule within the cradle. The method may further include transmitting light between the ferrule and the optical device at the operating temperature through one or more output locations on the mating face of the ferrule. Transmitting light between the ferrule and the optical device may include redirecting light between the mating face and an optical waveguide coupled to the end of the ferrule. The method may further include minimizing displacement between a reference point on the ferrule and a reference point on the cradle between the assembly temperature and the operating temperature. Displacement may be minimized via at least one longitudinal member of the ferrule interacting with at least one corresponding longitudinal restraint member of the cradle and at least one lateral restraint member of the ferrule interacting with at least one corresponding lateral restraint member of the cradle.

[0019] In another embodiment, a cradle is configured to receive and secure an optical ferrule, the cradle including a hold-down member configured to hold down the optical ferrule. The two or more bonding pads are operable with a bonding material that bonds the cradle to a substrate at a bonding temperature. The cradle has a first coefficient of thermal expansion, and the substrate has a second coefficient of thermal expansion different from the first coefficient of thermal expansion. The two or more mounting members mechanically couple the two or more corresponding bonding pads to the cradle. The two or more mounting members reversibly deflect in response to a force applied to the cradle between the bonding pads and attachment regions of the two or more mounting members. The force results from the difference between the first and second coefficients of expansion.

[0020] In some configurations, the two or more mounting members may include two or more legs fixed near the top surface of the cradle opposite the two or more bonding pads. The two or more legs may include four or more legs fixed to different corners of the cradle. The two or more legs may include three or more legs fixed to different edges of the cradle. The two or more mounting members may include two or more hollow cylinders or hollow prisms extending from the bottom surface of the cradle facing the substrate. The two or more mounting members may be symmetrically positioned with respect to the cradle such that reversible deflection minimizes displacement of a reference point on the optical ferrule relative to a corresponding reference point on the substrate. Displacement may be minimized when the cradle expands or contracts relative to the substrate due to temperature changes.

[0021] In some configurations, the cradle may further comprise a lens configured to modify the optical path between the optical ferrule and the optical device, the optical device being located on the substrate to which the cradle is mounted. The lens may comprise a collimating lens.

[0022] In another embodiment, a cradle is configured to receive and secure an optical ferrule. The cradle includes a hold-down member configured to hold down the optical ferrule and two or more bonding pads comprising a bonding material that bonds the cradle to a substrate at a bonding temperature. The cradle has a first coefficient of thermal expansion, and the substrate has a second coefficient of thermal expansion different from the first coefficient of thermal expansion. The two or more mounting members mechanically couple the two or more corresponding bonding pads to the cradle. The two or more mounting members are deformable in response to expansion of the cradle relative to the substrate. The relative change in expansion is due to a change between the bonding temperature and an operating temperature. The two or more mounting members are deformable such that the cradle maintains alignment between the optical ferrule and an optical device attached to the substrate at least at the operating temperature.

[0023] In some configurations, the two or more mounting members may include two or more legs fixed near the top surface of the cradle opposite the two or more bonding pads. The two or more legs may include four or more legs fixed to different corners of the cradle. The two or more legs may include three or more legs fixed to different edges of the cradle. The two or more mounting members may include two or more hollow cylinders or hollow prisms extending away from the bottom surface of the cradle facing the substrate. The two or more mounting members may be symmetrically positioned with respect to the cradle such that reversible deflection minimizes displacement of a reference point on the optical ferrule relative to a corresponding reference point on the substrate. Displacement may be minimized when the cradle expands or contracts relative to the substrate due to temperature changes. In some configurations, the cradle may further include a lens configured to modify the optical path between the optical ferrule and the optical device. The lens may include a collimating lens.

[0024] In another embodiment, a method includes bonding two or more bonding pads of a cradle to a substrate at a bonding temperature. The cradle includes two or more mounting members that mechanically couple the corresponding two or more bonding pads to the cradle. The cradle and substrate reach an assembly temperature. A difference between the bonding temperature and the assembly temperature causes deformation of the mounting members due to differences in the thermal expansion coefficients of the cradle and the substrate. An optical ferrule is inserted into the cradle such that the cradle secures the optical ferrule to an optical device mounted on the substrate.

[0025] In some configurations, the method may further include activating one or more devices coupled to the substrate such that the substrate, cradle, and optical ferrule reach an operating temperature, where expansion of the cradle relative to the substrate at the operating temperature aligns the optical ferrule with the optical device. The method may further include transmitting light between the optical ferrule and the optical device through one or more output locations on a mating face of the optical ferrule at the operating temperature. Transmitting light between the optical ferrule and the optical device may include redirecting light between the mating face and an optical waveguide coupled to an end of the optical ferrule.

[0026] In another embodiment, the optical component includes a mounting area for receiving and permanently mounting a plurality of optical fibers. The light redirecting member receives light from the plurality of optical fibers along a first direction and redirects the light along a different second direction. The redirected light exits the optical component at an exit location on the mating surface. The exit location is substantially centered on a first alignment surface perpendicular to the first direction. Two or more bonding pads of the component are operable with a bonding material that bonds the optical component to a substrate at a bonding temperature. The optical component has a first coefficient of thermal expansion, and the substrate has a second coefficient of thermal expansion different from the first coefficient of thermal expansion. Two or more mounting members mechanically couple corresponding two or more bonding pads to the optical component. The two or more mounting members reversibly deflect in response to a force applied to the optical component between the bonding pads and the mounting areas of the two or more mounting members, thereby minimizing the effect of temperature on the location of the intersection of the first alignment surface with the substrate. In one configuration, the optical component may further include a lens configured to modify the optical path between the component and the optical device, the high value device being located on the substrate. [Brief explanation of the drawings]

[0027] [Figure 1] 1A-1C are cross-sectional and top views of an optical ferrule and cradle according to some embodiments. [Figure 2] 1A-1C are cross-sectional and top views of an optical ferrule and cradle according to some embodiments. [Figure 3] 1A-1C are cross-sectional and top views of an optical ferrule and cradle according to some embodiments. [Figure 4] FIG. 2 is a perspective view of an optical ferrule according to an exemplary embodiment. [Figure 5] 1 is an exploded perspective view of an optical connector system according to an exemplary embodiment; [Figure 6] 6A and 6B are a perspective view and a top view of the optical connector system of FIG. 5. [Figure 7] 6A and 6B are a perspective view and a top view of the optical connector system of FIG. 5. [Figure 8] FIG. 10 is a top view of an optical ferrule and cradle according to another embodiment. [Figure 9] FIG. 10 is a top view of an optical ferrule and cradle according to another embodiment. [Figure 10] 1 is an exploded perspective view of an optical connector system according to an exemplary embodiment; [Figure 11] FIG. 11 is a perspective view of the optical connector system of FIG. [Figure 12] FIG. 11 is a perspective view of a cradle used in the optical connector system of FIG. [Figure 13] FIG. 10 is a perspective view of a cradle according to another exemplary embodiment. [Figure 14A] 10A-10C are bottom and side views of a cradle according to another exemplary embodiment. [Figure 14B] 10A-10C are bottom and side views of a cradle according to another exemplary embodiment. [Figure 15] 1 is a diagram of optical input / output locations of an optical ferrule according to an exemplary embodiment. [Figure 16] 1 is a diagram of optical input / output locations of an optical ferrule according to an exemplary embodiment. [Figure 17] 1 is a flowchart of a method according to an example embodiment. [Figure 18] 1 is a flowchart of a method according to an example embodiment. [Figure 19]FIG. 1 is a side view of an optical ferrule and cradle according to some embodiments. [Figure 20] FIG. 1 illustrates a top view of a plurality of optical ferrules and a cradle according to some embodiments. [Figure 21] FIG. 2 is a side view of an optical component according to an exemplary embodiment.

[0028] The drawings are not necessarily to scale. Like numbers used in the drawings refer to like components. However, it will be understood that the use of a number to refer to a component in a particular drawing is not intended to limit the component in another drawing bearing the same number. DETAILED DESCRIPTION OF THE INVENTION

[0029] Embodiments described herein relate to optical cable subassemblies, optical connectors, and packages for photonic integrated circuits (PICs). Connector interfaces are described that allow one or more optical fiber waveguides to mate with corresponding optical devices mounted on or integrated with a substrate. In some cases, the optical device and substrate may be integrally formed as part of the PIC. In other cases, the optical device may be mounted (e.g., bonded, soldered) to a circuit board, with the circuit board acting as the substrate. In other cases, the optical device may be mounted on an interposer or other carrier, which is then mounted on the circuit board. In any case, the optical device may include a waveguide, a diffraction grating, a detector, a modulator, a light source (e.g., a laser), and may include other integrated optical features such as lenses, collimators, mirrors, filters, etc.

[0030] The optical connectors described below may include a ferrule attached to multiple parallel waveguides (e.g., four, eight, or twelve or more parallel waveguides). The individual waveguides are typically glass optical fibers (e.g., single-mode or multimode fibers) with protective buffer coatings, and the parallel buffered fibers are surrounded by a jacket to form a ribbon. The ferrule may include a light redirecting element that redirects light (e.g., by an angle near 90 degrees) from the optical waveguides to the mating face, where the light is directed through an output window. The optical ferrule may be configured to expand the output beam from the mating face, thereby enabling non-contact optical coupling and reducing mechanical alignment requirements between connectors compared to other types of optical connectors, such as physical contact connectors.

[0031] Optical ferrules may be made of polymers with desirable optical properties that can be mass-produced, for example, by injection molding. Optical-grade polymers such as Zeonex K26R may have a coefficient of thermal expansion (CTE) (also referred to herein as the thermal expansion coefficient) on the order of 63 ppm / °C. In contrast, the substrate to which the optical ferrule mates may be formed from a material such as silicon, which has a CTE on the order of 2.6 ppm / °C. This difference in CTE can complicate the alignment of the optical ferrule with the substrate or an optical device integrated into the substrate. For example, assembly of the optical ferrule to the substrate may occur at room temperature, while the optical device (and any other devices thermally coupled to the substrate) may be assembled at temperatures significantly higher than room temperature. The substrate and optical ferrule expand or contract by different amounts at their different temperatures due to their CTE.

[0032] Differential expansion between the substrate and the optical ferrule can cause misalignment of the optical beam over a temperature range. Because maximum optical coupling between the optical ferrule and the optical device is required at the device's operating temperature, the optical ferrule is sized to expand to a desired size at the operating temperature. At the operating temperature, the beams entering or exiting the optical ferrule are substantially similarly spaced as the elements on the device that couple to the optical beam. However, assembly of the optical ferrule, substrate, and device typically occurs at a temperature different from (e.g., lower than) the operating temperature. At this lower temperature, it can be expected that at least some of the optical output positions of the ferrule will be misaligned. Therefore, the system has features that ensure that the ferrule is properly aligned during operation. Furthermore, the assembled system can be expected to cycle between the operating temperature and room temperature during operation, for example, when the optical device is powered on and off. This results in repeated expansion and contraction of the optical connector relative to the substrate and optical device. This can cause movement between them, resulting in misalignment of the optical beam.

[0033] Two approaches are described below to ensure that optical ferrules with a different CTE than the device to which they are mated maintain alignment even when exposed to a range of temperatures. Both approaches use a cradle that receives the optical ferrule and secures it to a substrate. In one approach, the cradle is made of a material with a CTE similar to that of the substrate. The cradle and optical ferrule include features that ensure the ferrule remains aligned with the substrate over the operating temperature range. In another approach, the cradle and ferrule are made of a similar CTE material. In this approach, the cradle is tightly attached to the ferrule over a wide range of temperatures. The cradle, which expands differently from the substrate, includes features that ensure the cradle remains aligned with the substrate at operating temperatures, which in turn aligns the ferrule.

[0034] The simplified diagrams of FIGS. 1 and 2 show side and cross-sectional views of an optical ferrule 100 and cradle 102 according to an exemplary embodiment. In this embodiment, the optical ferrule 100 and cradle 102 are made of materials having different CTEs. In this particular example, it is assumed that the ferrule has a higher thermal expansion coefficient than the cradle. The optical ferrule 100 includes a mounting end 101 configured to receive and secure an optical waveguide 106 (in this example, a plurality of optical fibers, as seen in FIG. 2 ). The interface between the waveguide 106 and the ferrule 100 is referred to as the mounting area 103, which receives and permanently attaches the plurality of optical fibers 106. A distal tip 104 of the optical ferrule 100 faces the mounting end 101 along a longitudinal direction 116. It should be noted that in this and other embodiments, the term "longitudinal" generally refers to the orientation of the elongated waveguide / fiber 106 at the mounting end 101 and is not meant to be limiting as to the relative shape or dimensions of the optical ferrule 100.

[0035] The optical ferrule 100 includes a light redirecting member 108 that accepts light 109 from a plurality of fibers 106 along a first direction (longitudinal direction 116). The light redirecting member 108 redirects the accepted light along a different second direction 115, which in this example is perpendicular to a substrate 120 to which the cradle 102 is mounted. It should be noted that the light redirecting member 108 may act in other ways to accept light in direction 115 and transmit it through the fibers 106 along direction 116. It will be understood that any discussion herein regarding light exiting or outputting from a ferrule is equally applicable to light entering or inputting into the ferrule, and such terminology is not intended to limit how the ferrule and the optical device may interact.

[0036] As best seen in Figure 2, redirected light 109 exits the optical ferrule at an exit location on mating face 117 (see exit location 210 in Figure 2, also referred to herein as the optical output location), which in this example corresponds to mating face 110 of ferrule 100. Exit location 210 is substantially centered on alignment face 119 that is perpendicular to first direction 116.

[0037] 1, the ferrule 100 is shown separated from the cradle 102. The cradle 102 is configured to receive and secure the optical ferrule 100 when the ferrule 100 is moved downward in a first direction 116. For example, the cradle 102 may include a surface 114 upon which or adjacent the ferrule 100 is positioned and at least partially restrained. The ferrule 100 may be further restrained by a cap (not shown) that captures it within the cradle 102.

[0038] Generally, at assembly temperatures, the ferrule 100 can fit loosely within the cradle 102, e.g., so that minimal force is required to insert the ferrule 100 into the cradle 102. At operating temperatures, the ferrule 100 expands more than the cradle 102, resulting in a tighter fit. The tight fit at operating temperatures is at least such that deflections caused by external forces, e.g., forces acting on the optical waveguide 106, do not cause excessive optical misalignment of a beam coupled between the optical ferrule 100 and the optical device 122. A tight fit may involve contact or interference between at least a portion of the ferrule 100 and the cradle 102, but may have some gap between them in at least some areas. The cradle 102 is fabricated from a material, such as a ceramic (e.g., silica) or metal alloy, that has a similar CTE to the substrate 120, minimizing relative expansion therebetween due to similar temperature changes.

[0039] 2 illustrates the optical ferrule 100 and cradle 102 in a loosely fitted configuration, e.g., at assembly temperatures. Also visible in this view is a longitudinal restraining member 200 operable to interact with a corresponding longitudinal restraining member 202 of the cradle 102. In this example, the longitudinal restraining members 200 are configured as a pair of first engagement features (e.g., tabs) projecting in a lateral direction 208 from opposite sides of the optical ferrule 100. The engagement features 200 are substantially centered on the alignment surface 119. The corresponding longitudinal restraining member 202, in this example, is configured as a cavity surrounding the engagement feature 200. Note the lateral clearance 203 between the longitudinal restraint member 200 and the corresponding longitudinal restraint member 202, which allows the longitudinal restraint member 200 to be displaced in the lateral direction 208 (e.g., due to expansion of the ferrule 100), but note that there is little or no clearance between them in the longitudinal direction 116.

[0040] The optical ferrule 100 includes a lateral restraint member 204 operable to interact with a corresponding lateral restraint member 206 of the cradle 202. In this example, the lateral restraint member 204 is configured as a second engagement feature, distinct from the pair of first engagement features 200, protruding from the front side (distal end 104) of the optical ferrule 100. A second alignment surface 214 passes through the second engagement feature 204, is perpendicular to the alignment surface 119, and substantially bisects the exit location 210. Note that the longitudinal clearance 205 between the longitudinal restraint member 200 and the corresponding longitudinal restraint member 204 is such that the longitudinal restraint member 200 can be displaced in the longitudinal direction 116 (e.g., due to expansion of the ferrule 100), but there is little or no clearance between them in the lateral direction 208.

[0041] The exit locations 210 are geometric locations defined by the shape and position of features of the ferrule 100, such as light redirection members, and correspond to the locations of light beams coupled into or out of the ferrule 100. In this illustration (at the assembled temperature), the pitch of the exit locations 210 is different from the pitch of the corresponding optical features (not shown) of the optical device 122. The pitch of the exit locations 210 is approximately equal to the pitch of the corresponding optical features of the optical device 122 at the operating temperature.

[0042] The longitudinal restraint member 200 and the lateral restraint member 204 are configured to align the output location 210 with a corresponding optical feature of the optical device 122 at operating temperatures. This can be done by minimizing displacement of the reference point 212 of the optical ferrule 100 relative to a corresponding reference point 215 on the cradle 102 due to changes in size of the optical ferrule 100 relative to the cradle 102 caused by changes in temperature. Figure 3 shows the optical ferrule 100 within the cradle 102 at or near operating temperatures. The optical ferrule 100 has expanded more than the cradle 102 due to its larger CTE, so that the ferrule 100 now fits tightly within the cradle 102, e.g., filling a cavity within the cradle 102. Due to the positioning of the restraining members 200, 204 relative to the alignment surfaces 119, 214, displacement between the reference points 212 and 215 is minimized, so that the exit locations 210 are substantially aligned with the optical devices 122. The exit locations 210 are expanded in the lateral direction 208 so that the pitch of the exit locations 210 also matches the pitch of the optical devices 122.

[0043] Note that more than the restraining members shown may be used. As indicated by dashed box 300, additional lateral restraints may supplement 204 and 206. Alternatively, other lateral restraints may be used in place of lateral restraints 204 and 206, as indicated by dashed boxes 301 and 302. Similar longitudinal hold-down members may be used as well. In some configurations, restraint members may be located elsewhere or in addition to the sides of the ferrule. This can be seen in the exemplary embodiment shown in the perspective view of FIG. 4. In this view, the mating face 402 of the ferrule 400 appears to be an exit window 404 through which the optical input / output location 406 can be viewed. The longitudinal restraint member includes a ridge 408, and the lateral restraint member includes a ridge 410. A cradle (not shown) includes corresponding channels into which ridges 408, 410 fit. Any combination of the ridges 408, 410 shown in Figure 4 and the tabs 202, 204 shown in Figure 2 may be used in other embodiments.

[0044] It should be noted that in the above embodiment, it was assumed that the CTE of the optical ferrule was greater than the CTE of the cradle and substrate, and that the assembly temperature was lower than the operating temperature. However, in this and other embodiments, a system with the opposite characteristics (the CTE of the optical ferrule is less than the CTE of the cradle and substrate, and the assembly temperature is higher than the operating temperature) may achieve similar results by providing a restraining member in the cradle that fits into a cavity in the ferrule, resulting in a tight fit between the cradle and ferrule at operating temperatures and a loose fit at assembly temperatures.

[0045] In FIG. 5 , a perspective exploded view illustrates an optical connection configuration according to another exemplary embodiment. An optical ferrule 500 and a cradle 502 are made of materials having different CTEs. The optical ferrule 500 includes an attachment area 503 that receives and permanently attaches an optical fiber ribbon 506. A distal tip 504 of the optical ferrule 500 faces the attachment area 503 along a longitudinal direction 516. The ferrule 500 includes a light redirecting member 508 that redirects light 509 between the optical fiber ribbon 506 in the direction 516 and an optical device 522 in a direction 515 perpendicular to a substrate 520 to which the cradle 502 is mounted. In other embodiments, the redirected direction 515 may not be perpendicular to the substrate. The redirected light 509 exits the optical ferrule 500 at an exit location (not shown) on a mating face 517 that corresponds to a mating face (not shown) of the ferrule 500. The exit position is substantially centered on an alignment plane 519 perpendicular to the first direction 516. An anti-reflective coating may be used to reduce reflections of light entering or exiting the ferrule. Note that the cradle 502 includes an air gap 511 that facilitates the passage of light 509 between the ferrule 500 and the optical device 522.

[0046] In FIG. 5 , the ferrule 500 is shown separated from the cradle 502. The cradle 502 is configured to receive and secure the optical ferrule 500 when the ferrule 500 is moved downward in a first direction 515. For example, the cradle 502 includes a surface 514 on top of or adjacent to which the ferrule 100 is positioned and at least partially restrained. The ferrule 500 may be further restrained by a cover 522 that captures it within the cradle 502. The illustrated cover 522 is held in place by a screw 524 that is fastened to a nut 526. It should be noted that other attachment means, such as clips or bonding, may be used to secure the cover 522 to the cradle 502 and substrate 520.

[0047] Prior to assembling the ferrule 500 with the cradle 502, the cradle 502 may be permanently attached to the substrate 520. This attachment may include soldering or other types of bonding, as indicated by the pads 518. In the case of a solder bond, the pads are metal wetted by the solder. The cradle 502 may be precisely positioned over the optical device 522, for example, by a pick-and-place machine, and then secured to the substrate 520 by application of heat, a light-cured adhesive, or the like. The cradle 502 and substrate 520 then form a subassembly to which the ferrule 500 and optical fiber ribbon 506 may be attached, for example, at room temperature, manually or by a robotic device. Final assembly, including the attachment of the cover 522, can be seen in the perspective view of FIG. 6. Note that, as seen in FIG. 6, the distal tip 514 extends outside of the cradle 502. The tip 514 corresponds to the molded gate in this design, so by extending the tip 514 outside the cradle 502, any gate cut marks will not affect alignment.

[0048] Generally, at assembly temperatures, the ferrule 500 can fit loosely within the cradle 502, such that minimal force is required to insert the ferrule 500 into the cradle 502. This can be seen in the top view of Figure 7, where a gap 700 is visible between the contour of the ferrule 500 and the receiving cavity of the cradle 502. At operating temperatures above the assembly temperature, the ferrule 500 expands more than the cradle 502, resulting in a tighter fit, e.g., an interference fit.

[0049] 5 , the longitudinal restraint members (tabs 530) of the ferrule 500 are operable to interact with corresponding longitudinal restraint members (cavities 532) of the cradle 502. The engagement tabs 530 are substantially centered on alignment surfaces 519 that define the center of the optical output position in direction 526. The optical ferrule 100 includes lateral restraint members (tabs 534) operable to interact with corresponding lateral restraint members (cavities 536) of the cradle 202. The alignment surfaces 514 pass through the lateral restraint members 534, are perpendicular to the alignment surfaces 519, and substantially bisect the exit / entrance positions of the light redirection member 508.

[0050] In another exemplary embodiment shown in FIG. 20 , a cradle 2002 is configured to receive and secure two or more ferrules 2000. The ferrules 2000 may include similar features as those described above, for example, the ferrule 100 of FIG. 1 . The ferrules 2000 and the cradle 2002 have different CTEs. The ferrules 2000 are offset from one another and configured to optically couple to a device 2006 on a substrate 2008. The cradle 2002 may be made of a material described above (e.g., ceramic, silica) and maintains alignment between the ferrules 2000 and the device 2006 during transitions from assembly temperatures to operating temperatures. The cradle 2006 may further include a plurality of corresponding longitudinal 2010 and lateral restraint members 2012 configured to minimize displacements between a plurality of second reference points 2015 on the cradle 2006 and a plurality of reference points 2014 on the plurality of optical ferrules 2000 due to changes in size of the plurality of optical ferrules 2000 relative to the cradle 2002.

[0051] 8 , a top view shows an optical ferrule 800 and cradle 802 according to another exemplary embodiment. In this example, the optical ferrule 800 and cradle 802 have the same or similar CTEs, which are different from the CTEs of the substrate 820 and the optical device 822 to which the ferrule 800 is mated. The optical ferrule 800 includes a light redirecting member 808 and an attachment area 803 that receives and permanently attaches an optical fiber ribbon 806. A distal tip 804 of the optical ferrule 800 faces the attachment area 803 along a longitudinal direction 816.

[0052] Because the optical ferrule 800 and cradle 802 have the same or similar CTE, they can have a relatively tight fit at assembly temperatures. The components may be configured with a hold-down member 801 such that assembly and disassembly of the optical ferrule 800 and cradle 802 can be performed, for example, by hand without significant installation force, while still having features such as snaps, springs, or the like that ensure a tight fit to hold down the ferrule 800. In this example, the hold-down member 801 includes at least the outer periphery of the cavity in the cradle 802, and the shape of the outer periphery matches the profile of the ferrule 800 as viewed from above. To aid in ferrule assembly, a small gap may exist between the surface of the hold-down member 801 and the lateral surface of the ferrule 800. Additionally, other components, such as a cover, may hold down the ferrule 800 after placement in the cradle 802. In other embodiments, the ferrule 800 may be integrally formed with the cradle 802, for example, molded as a single piece.

[0053] Before assembling the optical ferrule 800 to the cradle 802 (if the components are formed separately), the cradle 802 is attached to the substrate 820. This may involve a high-temperature process such as soldering. The cradle therefore includes two or more bonding pads 826 that can be used with a bonding material to bond the cradle to the substrate at a bonding temperature. The bonding pads 826 represent attachment points between the cradle 802 and the substrate 820, which may have similar pads (not shown). This bonding temperature is different from the assembly temperature (the temperature at which the ferrule 800 is inserted into the cradle 802) and may also be different from (e.g., higher than) the operating temperature of the assembly. Because these temperature differences result in greater dimensional change in the cradle 802 than in the substrate 820, the cradle 802 includes two or more mounting members 828 with controlled compliance that mechanically couple the corresponding two or more bonding pads 826 to the cradle 802.

[0054] In this illustration, the two or more mounting members 828 are represented schematically as springs at the corners of the cradle 802. The two or more mounting members 828 reversibly deflect in response to forces applied to the cradle 802 between the bond pads 826 and the attachment regions 830 of the two or more mounting members 828. Typically, these forces result from different coefficients of expansion between the cradle 802 and the substrate 820, but may also result from other forces, such as forces acting on the optical fiber 806. The stiffness of the mounting members 828 can be selected so that the mounting members are sufficiently rigid to prevent excessive movement in response to forces expected during use, yet flexible enough to allow the cradle 802 to contract and grow relative to the substrate 820 without breaking or other damage.

[0055] The mounting member 828 is configured so that forces acting on the cradle 802 through the mounting member 828 due to thermal expansion or contraction of the cradle 802 relative to the substrate minimize misalignment between the cradle 802 and the optical device 822 in at least one region. One example is shown in the simplified diagram of FIG. 9. The cradle 802 and ferrule 800 in an expanded configuration (e.g., at the bonding temperature) are shown using solid lines, and the cradle 802 and ferrule 800 in a contracted configuration (e.g., at the assembly temperature) are shown using dashed lines. Note that the ferrule 800 is typically not located within the cradle 802 during bonding, but is illustrated to show the effect that expansion / contraction of the cradle 802 has on the alignment of the ferrule 800 with the optical device 822. Similar expansion / contraction may occur between the assembly temperature and the operating temperature, and the ferrule 800 would then be located within the cradle 802. As indicated by dashed line configuration 840, the mounting members and associated pads may include three or more mounting members, each attached to a different edge of cradle 802.

[0056] Shown is an array of optical output locations 900 associated with the ferrule 800 in both the expanded and contracted configurations. These output locations 900 will align with optical features (e.g., facets, lenses, waveguides, detectors) of the optical device. To minimize the net displacement of these output locations 900 during operation, the mounting members 828 minimize misalignment between reference points on the cradle 802 and corresponding reference points on the optical device 822 and / or substrate 820 as the cradle 802 expands or contracts due to temperature changes. In this illustration, the centers of the circles 902, 904 define the reference points and corresponding reference points in this example.

[0057] In FIG. 10 , a perspective exploded view shows an optical connection configuration according to another exemplary embodiment. An optical ferrule 1000 and a cradle 1002 are made of materials having the same or similar CTE. The optical ferrule 1000 includes an attachment area 1003 that receives and permanently attaches an optical fiber ribbon 1006. A distal tip 1004 of the optical ferrule 1000 faces the attachment area 1003 along a longitudinal direction 1016. The ferrule 1000 includes a light redirecting member 1008 that redirects light between the optical fiber ribbon 1006 in the direction 1016 and an optical device 1022 in a direction 1015 directed toward a substrate 1020 to which the cradle 1002 is mounted. Redirected light 1009 exits the optical ferrule 1000 at an exit location (not shown) on a mating face 1017 that corresponds to a mating face (not shown) of the ferrule 1000. The output position is substantially centered on an alignment plane 1019 perpendicular to the first direction 1016. Note that the cradle 1002 includes an air gap 1011 that facilitates the passage of light 1009 between the ferrule 1000 and the optical device 1022.

[0058] In FIG. 10 , the ferrule 1000 is shown separated from the cradle 1002. The cradle 1002 is configured to receive and secure the optical ferrule 1000 when the ferrule 1000 is moved downward in a first direction 1015. For example, the cradle 1002 includes a surface 1014 on top of or adjacent to which the ferrule 1000 is positioned and at least partially restrained. The ferrule 1000 may be further restrained by a cover 1022 that is captured within the cradle 1002. The illustrated cover 1022 is held in place by a screw 1024 that tightens into a nut captured in a recess 1206 in the cradle. It should be noted that other attachment means, such as clips or bonding, may be used to secure the cover 1022 to the cradle 1002 and substrate 1020.

[0059] Prior to assembling the ferrule 1000 with the cradle 1002, the cradle 1002 may be permanently attached to the substrate 1020. This attachment may include soldering or other types of bonding, as indicated by the pads 1018. The bonding pads 1018 may be used with a bonding material that bonds the cradle 1002 to the substrate 1020 at a bonding temperature. The cradle 1002 may be precisely positioned over the optical device 1022, for example, by a pick-and-place machine, and then secured to the substrate 1020 by application of heat, light-cured adhesive, or the like. The cradle 1002 and substrate 1020 then form a subassembly to which the ferrule 1000 and optical fiber ribbon 1006 may be attached, for example, at room temperature, manually or by a robotic device. Final assembly, including the attachment of the cover 1022, can be seen in the perspective view of FIG. 11.

[0060] The cradle 1002 includes two or more mounting members, which in this example are configured as legs 1032 fixed near the cradle's top surface 1030, opposite two additional bonding pads (see bonding pads 1200 in FIG. 12 ). The cradle 1002 has a first coefficient of thermal expansion, and the substrate 1020 has a second coefficient of thermal expansion that is different from the first coefficient of thermal expansion. Due to these differences in thermal expansion coefficients, the cradle 1002 will expand or contract relative to the substrate 1020 at various temperatures. As can be seen from the perspective view of FIG. 12 , the legs 1032 can deflect, as indicated by the dashed lines. The legs 1032 can also deflect in other directions due to a gap 1201 between the legs 1032 and the body of the cradle 1002. In other embodiments, three or more legs may be secured to different edges of the cradle 1002 instead of or in addition to the corner legs (see mounting member 840 in FIG. 8).

[0061] The legs 1032 are located around the periphery of the cradle 1002 and all have the same dimensions. Flexure of the legs 1032 due to thermal expansion will minimize deflection of a reference point 1202 on the cradle 1002 relative to a corresponding reference point on the optical device 1022 (see point 1034 in FIG. 10 ). Therefore, the legs 1032 are symmetrically positioned around the reference point 1202, which may be different from the center point of the cradle. Note that the cradle includes a cavity 1204 through which light passes between the ferrule 1000 and the optical device 1022. Thus, the reference point 1202 is located within this cavity. In general, the reference points described here and elsewhere are abstract geometric features and need not correspond to physical features (e.g., surfaces, volumes) of the objects being aligned.

[0062] In Figure 13, a perspective view shows a cradle 1302 according to another exemplary embodiment. This cradle 1302 may be used with a ferrule previously described (e.g., the ferrule 1000 shown in Figure 10) and has the same or a similar CTE as the ferrule. The cradle 1302 includes two or more mounting members, which in this example are configured as hollow prisms 1304 extending from a bottom surface 1306 of the cradle 1302. The bottom surface 1306 faces the substrate to which the cradle 1302 is bonded.

[0063] The cradle 1302 has bonding pads 1308 operable with a bonding material that bonds the cradle 1302 to the substrate at a bonding temperature. The cradle 1302 has a first coefficient of thermal expansion, and the substrate has a second coefficient of thermal expansion different from the first coefficient of thermal expansion. The mounting members are capable of flexing when the cradle 1302 expands or contracts relative to the substrate due to changes in temperature. The hollow prisms 1304 are located around the periphery of the cradle 1302 and all have the same dimensions. Hollow cylinders may be used instead of or in addition to the hollow prisms 1304. The prisms 1304 are also symmetrically positioned around a reference point 1310 (located within the light-passing cavity 1312) of the cradle 1302. Therefore, flexing of the hollow prisms 1304 due to thermal expansion minimizes deflection of the reference point 1310 relative to a corresponding reference point of an optical device mounted on or part of the substrate. The cradle also has a recess 1310 that is used to hold a nut 1026 that mates with the screw 1024 to hold the top 1022 in place and thus restrain the ferrule within the cradle.

[0064] 14A-14B, bottom and side views show a cradle 1402 according to another exemplary embodiment. This cradle 1402 can be used with ferrules having the same or similar CTE as the cradle 1402. In general, the ferrule geometry is different from those previously illustrated, e.g., it has a larger row or array of light output locations in the lateral direction 1403 than those previously illustrated. The cradle 1402 includes two mounting members, which in this example are configured as legs 1404 extending from a top surface 1406 of the cradle 1402. A bottom surface 1412 faces a substrate to which the cradle 1402 is bonded.

[0065] The cradle 1402 has bonding pads 1408 that can be used with a bonding material to bond the cradle 1402 to a substrate at a bonding temperature. The cradle 1402 has a first coefficient of thermal expansion, and the substrate has a second coefficient of thermal expansion that is different from the first coefficient of thermal expansion. The mounting members 1404 can flex when the cradle 1402 expands or contracts relative to the substrate due to changes in temperature. The mounting members 1404 are located around the periphery of the cradle 1402 and all have the same dimensions. The mounting members 1404 are also symmetrical about a reference point 1410 (located within the light-passing cavity 1412) of the cradle 1402. Therefore, flexing of the hollow prism 1404 due to thermal expansion will minimize deflection of the reference point 1410 relative to a corresponding reference point of an optical device mounted to or part of the substrate.

[0066] In the above embodiments, the cradle geometry is designed to minimize displacement of the reference point of the ferrule held within the cradle. Generally, this minimizes the net displacement of the ferrule's multiple optical input / output locations relative to the optical device. One example is shown in the diagram of FIG. 15. Multiple optical input / output locations 1500 are arranged in two columns. Reference point 1502 is horizontally centered in the middle of the column and vertically centered between the rows. During ferrule expansion or contraction, input / output locations 1500a-d will experience the greatest displacement because the distances 1504a-d between the centers of these locations are the furthest from reference point 1502. If reference point 1502 were to move to another location, at least one of distances 1504a-d would increase, and therefore there is a risk that at least one of input / output locations 1500a-d would be misaligned more than the other output locations.

[0067] In general, the reference point may be selected to minimize the distance to the furthest input / output location. This may optionally apply to asymmetric patterns. An asymmetric arrangement of input / output locations 1600 according to an exemplary embodiment is shown in the diagram of FIG. 16. In this case, reference point 1602 is horizontally centered in the middle of the top row and vertically centered between the rows. As a result, input / output locations 1600a-c will experience the greatest displacement upon scaling when the distances 1604a-c of the centers of these locations are furthest from reference point 1602. In other embodiments, the center of gravity of the shape formed by input / output locations 1600 may be used instead, whereby the reference point is shifted slightly left and upward from that shown in this example.

[0068] 17, a flowchart illustrates a method according to an exemplary embodiment. The method involves coupling 1700 an optical ferrule to a substrate with a cradle at an assembly temperature. The optical ferrule fits loosely within the cradle at the assembly temperature. The optical ferrule has a first coefficient of thermal expansion, and the cradle has a second coefficient of thermal expansion different from the first coefficient of thermal expansion. One or more devices coupled to the substrate are activated 1701 so that the substrate, cradle, and optical ferrule reach an operating temperature. Due to the relative expansion of the optical ferrule and the cradle at the operating temperature, one or more output locations of the optical ferrule are aligned with an optical device mounted on the substrate 1702.

[0069] In FIG. 18 , a flowchart illustrates another method according to an exemplary embodiment. The method includes bonding 1800 two or more bonding pads of a cradle to a substrate at a bonding temperature. The cradle has two or more mounting members that mechanically couple two or more corresponding bonding pads to the cradle. The cradle and substrate are allowed to reach an assembly temperature 1801. An optical ferrule is inserted into the cradle such that the cradle secures the optical ferrule to an optical device mounted on the substrate 1802. The cradle and substrate are allowed to reach an operating temperature 1803. The difference between the bonding temperature and the operating temperature causes deformation of the mounting members due to differences in the thermal expansion coefficients of the cradle and the substrate. The deformation maintains alignment between the optical device and the optical ferrule.

[0070] In FIG. 19 , a side view shows an optical subassembly according to another exemplary embodiment. The optical ferrule 1900 and cradle 1902 may be configured similarly to the other ferrules described above. The cradle 1902 is configured to receive and secure the ferrule 1900 to a substrate 1904 such that the ferrule is optically aligned with an optical device 1906 at operating temperatures. The cradle 1902 includes a lens 1908 configured to modify the optical path between the optical ferrule 1900 and the optical device 1906. Part or all of the cradle 1902 may be formed of a material transparent to the wavelength of light of interest. The lens 1908 may be a collimating lens that substantially collimates the light transmitted between the optical ferrule 1900 and the optical device 1906. Two or more mounting members 1910 mechanically couple the cradle 1902 to the substrate 1904. The two or more mounting members 1910 reversibly deflect in response to a force applied to the ends of the members 1910 when the members 1910 are coupled with the substrate 1904 .

[0071] 21 , a side view shows an optical component 2100 according to another exemplary embodiment in which the ferrule and cradle are formed as a single, integral part. In another embodiment, the optical component includes a mounting area 2102 for receiving and permanently mounting a plurality of optical fibers 2104. A light redirecting member 2106 accepts light from the plurality of optical fibers 2102 along a first direction 2108 and redirects the light along a different, second direction 2110. The redirected light exits the optical component 2100 at an exit location on a mating face 2112. The exit location is substantially centered on a first alignment face 2114 that is perpendicular to the first direction.

[0072] The two or more bonding pads 2116 can be used with a bonding material that bonds the optical component 2100 to the substrate 2118 at a bonding temperature. The component 2100 is formed of a material (e.g., a clear optical-grade plastic) with a first coefficient of thermal expansion, and the substrate 2118 has a second coefficient of thermal expansion different from the first coefficient of thermal expansion. The two or more mounting members 2120 mechanically couple the corresponding two or more bonding pads 2116 to the optical component 2100. The two or more mounting members 2120 reversibly deflect in response to a force applied to the component 2100 between the bonding pads and the attachment regions of the two or more mounting members, thereby minimizing the effect of temperature on the position of the intersection of the first alignment surface 2114 with the substrate 2118. The optical component 2100 may further include a lens 2122 configured to modify an optical path between the component and an optical device 2124, the optical device 2124 being located on the substrate 2118.

[0073] Further information regarding connectors that may be used in conjunction with the techniques described herein is provided in the following commonly owned, commonly filed, U.S. patent application Ser. No. __________ entitled "Optical Connector" and identified by Attorney Docket No. 70228US002; U.S. patent application Ser. No. ___________ entitled "Optical Connector with Tilted Mirror" and identified by Attorney Docket No. 78847US002; and U.S. patent application Ser. No. ___________ entitled "Optical Ferrules and Optical Ferrule Molds" and identified by Attorney Docket No. 75985US002, which are incorporated herein by reference.

[0074] Embodiments described in this disclosure include: Item 1. An optical ferrule, an attachment area for receiving and permanently attaching the plurality of optical fibers; a light redirection member for receiving light from a plurality of fibers received by and permanently attached to the attachment area along a first direction and redirecting the received light along a different second direction, the redirected light exiting the ferrule at an exit location on the mating face, the exit location being substantially centered on a first alignment face perpendicular to the first direction; a pair of first engagement features projecting from opposite sides of the optical ferrule, the first engagement features being substantially centered on the first alignment surface; a second engagement feature different from the pair of first engagement features, the second engagement feature protruding from a front side of the optical ferrule and substantially centered on a second alignment surface orthogonal to the first alignment surface, the second alignment surface substantially bisecting the exit location; and An optical ferrule comprising:

[0075] Item 2. The optical ferrule of item 1, wherein the output locations comprise an array of optical output locations along the first alignment surface.

[0076] Item 3. An optical ferrule according to item 1 or 2, wherein the first engagement feature comprises first and second tabs extending from opposite sides of the optical ferrule, the first and second tabs being positioned within corresponding first and second cavities of a cradle that secures the optical ferrule, and the first and second cavities restrain the two tabs along a first direction when the optical ferrule is fitted into the cradle.

[0077] Item 4. The optical ferrule according to item 3, further comprising first and second lateral clearances between the first and second tabs and the corresponding first and second cavities so that the tabs can be displaced laterally, and little or no clearance exists in the first direction between the first and second tabs and the corresponding first and second cavities.

[0078] Item 5. An optical ferrule according to any one of items 1 to 4, wherein the second engagement feature comprises a tab extending from the front side, the tab being disposed within a cavity of a cradle configured to secure the ferrule.

[0079] Item 6. The optical ferrule of item 5, further comprising a clearance between the tab and the cavity so that the tab can be displaced in a first direction, and little or no clearance exists in the lateral direction between the first and second tabs and the corresponding first and second cavities.

[0080] Item 7. The optical ferrule according to any one of Items 1 to 6, wherein the optical ferrule is formed of a polymer.

[0081] Item 8. The optical ferrule according to any one of Items 1 to 7, further comprising a mating surface that optically interacts with an optical device on the substrate.

[0082] Item 9. The optical ferrule according to any one of Items 1 to 8, wherein the optical ferrule is configured to fit loosely into the cradle at assembly temperature and to fit tightly into the cradle at operating temperature.

[0083] Item 10. The optical ferrule according to Item 9, wherein the assembly temperature is lower than the operating temperature.

[0084] Item 11. An optical ferrule, a mounting end configured to receive and secure an optical waveguide; a distal tip longitudinally opposed to the attachment end; a light redirecting element configured to redirect light between the optical waveguide and a mating surface of the optical ferrule; a longitudinal restraining member operable to interact with a corresponding longitudinal restraining member of a cradle that receives and secures the optical ferrule; lateral restraint members operable to interact with corresponding lateral restraint members on the cradle, the longitudinal and lateral restraint members minimizing displacement of a reference point on the optical ferrule relative to a corresponding reference point on the cradle due to different thermal expansion coefficients of the optical ferrule and the cradle causing a change in size of the optical ferrule relative to the cradle in response to changes in temperature; An optical ferrule comprising:

[0085] Item 12. The optical ferrule according to item 11, wherein the mating surface comprises a row of optical output positions along a lateral line, and the reference point is at the center of the lateral line.

[0086] Item 13. An optical ferrule as described in Item 12, wherein the longitudinal restraint member has two tabs extending from opposite sides of the optical ferrule and aligned with the lateral line, and the corresponding longitudinal restraint member of the cradle has two cavities that longitudinally restrain the two tabs and allow lateral displacement of the two tabs when the optical ferrule is fitted within the cradle.

[0087] Item 14. An optical ferrule according to any one of items 12 to 13, wherein the lateral restraint member comprises a tab extending from the distal tip aligned with the center of the lateral line, and the corresponding lateral restraint member comprises a cavity that restrains lateral displacement of the tab and allows longitudinal displacement of the tab when the optical ferrule is fitted into a cradle.

[0088] Item 15. The optical ferrule according to any one of Items 11 to 14, wherein the first thermal expansion coefficient of the optical ferrule is greater than the second thermal expansion coefficient of the cradle.

[0089] Item 16. The optical ferrule according to Item 15, wherein the optical ferrule is formed of a polymer.

[0090] Item 17. An optical ferrule according to any one of items 11 to 16, wherein the mating surface is operable to optically interact with an optical device on the substrate, and the cradle aligns the optical ferrule with the optical device.

[0091] Item 18. An optical ferrule according to any one of Items 11 to 17, wherein the optical ferrule is configured to fit loosely into the cradle at assembly temperature and to fit tightly into the cradle at operating temperature.

[0092] Item 19. The optical ferrule according to item 18, wherein the assembly temperature is lower than the operating temperature.

[0093] Item 20. A cradle configured to receive and secure an optical ferrule, a corresponding longitudinal restraining member operable to interact with the longitudinal restraining member of the optical ferrule; corresponding lateral restraint members operable to interact with corresponding lateral restraint members of the optical ferrule, the longitudinal restraint members and the lateral restraint members minimizing displacement of reference points on the mating surface of the optical ferrule with corresponding reference points on the cradle due to changes in size of the optical ferrule relative to the cradle, the changes in size induced by different thermal expansion coefficients of the optical ferrule and the cradle and changes in temperature; A cradle.

[0094] Item 21. The cradle of item 20, wherein the mating surface comprises a row of light output positions along a lateral line, and the reference point is at the center of the lateral line.

[0095] Item 22. A cradle as described in Item 21, wherein the longitudinal restraint member of the optical ferrule has two tabs extending from opposite sides of the optical ferrule and aligned with the lateral line, and the corresponding longitudinal restraint member of the cradle has two cavities that restrain the two tabs and allow lateral displacement of the two tabs when the optical ferrule is fitted within the cradle.

[0096] Item 23. A cradle according to any one of items 21 to 22, wherein the lateral restraint member has a tab extending from a distal tip aligned with the center of the lateral line, and the corresponding lateral restraint member has a cavity that restrains lateral displacement of the tab and allows longitudinal displacement of the tab when an optical ferrule is fitted in the cradle.

[0097] Item 24. The cradle according to any one of Items 20 to 23, wherein the first thermal expansion coefficient of the optical ferrule is greater than the second thermal expansion coefficient of the cradle.

[0098] Item 25. The cradle according to Item 24, wherein the cradle is made of ceramic.

[0099] Item 25a. The cradle of Item 24, wherein the cradle is formed of silica.

[0100] Item 26. A cradle according to any one of Items 20 to 25a, wherein the cradle aligns the optical ferrule and secures it to the substrate so that the mating surface optically interacts with an optical device on the substrate.

[0101] Item 27. A cradle according to any one of Items 20 to 26, wherein the optical ferrule is configured to fit loosely into the cradle at assembly temperature and to fit tightly into the cradle at operating temperature.

[0102] Item 28. The cradle according to item 27, wherein the assembly temperature is lower than the operating temperature.

[0103] Item 28a. A cradle described in any of items 20 to 28, further comprising a lens configured to modify the optical path between the optical ferrule and the optical device, the optical device being located on a substrate to which the cradle is mounted.

[0104] Item 28b. The cradle of item 28a, wherein the lens comprises a collimating lens.

[0105] Item 28c. A cradle described in any of items 20 to 28b, further comprising a second corresponding longitudinal restraint member and a second corresponding lateral restraint member configured to minimize a second displacement of a second reference point of the second optical ferrule relative to a corresponding second reference point of the cradle due to a change in size of the second optical ferrule relative to the cradle.

[0106] Item 28d. The cradle of any of items 20-28c, further configured to receive and secure two or more ferrules.

[0107] Item 29. an optical ferrule having a first coefficient of thermal expansion, the optical ferrule including a light redirecting element configured to redirect light between the optical waveguide and a mating surface of the optical ferrule; a cradle configured to hold an optical ferrule and secure it to the substrate, the cradle having a second coefficient of thermal expansion different from the first coefficient of thermal expansion, the optical ferrule configured to fit loosely within the cradle at an assembly temperature and expand into the cradle at an operating temperature; An optical assembly comprising:

[0108] Item 30. An optical assembly as described in Item 29, wherein the optical ferrule includes at least one restraining member and the cradle includes at least one corresponding restraining member, and the restraining member and the corresponding restraining member interact to minimize displacement between a reference point on the optical ferrule and a corresponding reference point on the cradle between an assembly temperature and an operating temperature.

[0109] Item 31. The optical assembly of item 30, wherein the optical ferrule comprises an array of optical output positions arranged in a lateral line along the mating surface, and the reference point is at the center of the lateral line.

[0110] Item 32. An optical assembly described in any of items 29 to 30, wherein at least one restraining member comprises a longitudinal restraining member and a lateral restraining member, and at least one corresponding restraining member comprises a corresponding longitudinal restraining member that interacts with the longitudinal restraining member and a corresponding lateral restraining member that interacts with the lateral longitudinal restraining member.

[0111] Item 33. The optical assembly of item 32, further comprising lateral clearance between the longitudinal restraint member and the corresponding longitudinal restraint member so that the longitudinal restraint member can be displaced in the lateral direction, and wherein there is little or no clearance in the longitudinal direction between the longitudinal restraint member and the corresponding longitudinal restraint member.

[0112] Item 34. An optical assembly according to any one of Items 29 to 33, wherein the assembly temperature is lower than the operating temperature.

[0113] Item 35. An optical assembly according to any one of Items 29 to 34, wherein the optical ferrule is formed of a polymer and the cradle is formed of a ceramic.

[0114] Item 36. The optical assembly of any one of Items 29 to 35, further comprising an optical device attached to the substrate, wherein the cradle aligns one or more optical output positions of the optical ferrule with the optical device.

[0115] Item 37. The optical assembly of item 36, wherein at least a portion of the one or more light output locations are misaligned with the optical device at the assembly temperature, and the one or more light output locations are optimally aligned with the optical device at the operating temperature.

[0116] Item 37a. An optical assembly described in any of Items 29 to 37, wherein the cradle further comprises a lens configured to modify the optical path between the optical ferrule and the optical device, and the optical device is located on the substrate.

[0117] Item 37b. The optical assembly of item 37a, wherein the lens comprises a collimating lens.

[0118] Item 37c. An optical assembly according to any one of Items 29 to 37b, wherein the cradle is further configured to hold and secure two or more optical ferrules to the substrate.

[0119] Item 37d. An optical assembly according to any one of Items 29 to 37c, wherein the cradle and the optical ferrule are integrally formed.

[0120] Item 38. Coupling the optical ferrule to the substrate with a cradle at an assembly temperature, the optical ferrule fitting loosely within the cradle at the assembly temperature, the optical ferrule having a first coefficient of thermal expansion and the cradle having a second coefficient of thermal expansion different from the first coefficient of thermal expansion; activating one or more devices coupled to the substrate such that the substrate, cradle, and optical ferrule reach an operating temperature, whereby relative expansion of the optical ferrule and cradle at the operating temperature aligns one or more output locations of the optical ferrule with an optical device attached to the substrate; A method comprising:

[0121] Item 38a. The method of item 38, wherein the relative expansion of the optical ferrule and cradle at operating temperatures results in a tight fit of the optical ferrule within the cradle.

[0122] Item 39. The method of any one of Items 38 to 38a, further comprising transmitting light between the optical ferrule and the optical device through one or more output locations on the mating surface of the optical ferrule at an operating temperature.

[0123] Item 40. The method of item 39, wherein transmitting light between the optical ferrule and the optical device includes redirecting light between the mating surface and an optical waveguide coupled to the end of the optical ferrule.

[0124] Item 41. The method of item 40, further comprising minimizing displacement between the reference point of the optical ferrule and the reference point of the cradle between the assembly temperature and the operating temperature.

[0125] Item 42. Displacement is at least one longitudinal restraining member of the optical ferrule that interacts with at least one corresponding longitudinal restraining member of the cradle; and At least one lateral restraining member of the optical ferrule that interacts with at least one corresponding lateral restraining member of the cradle Item 42. The method according to Item 41, wherein the amount of the oxidative stress is minimized by

[0126] Item 43. A cradle configured to receive and secure an optical ferrule, a holding member configured to hold down the optical ferrule; two or more bonding pads operable with a bonding material to bond the cradle to the substrate at a bonding temperature, the cradle having a first coefficient of thermal expansion and the substrate having a second coefficient of thermal expansion different from the first coefficient of thermal expansion; two or more mounting members mechanically coupling a corresponding two or more bonding pads to the cradle, the two or more mounting members reversibly deflecting in response to a force applied to the cradle between the bonding pads and attachment areas of the two or more mounting members, the force resulting from different first and second coefficients of expansion; A cradle.

[0127] Item 44. The cradle of item 43, wherein the two or more mounting members comprise two or more legs fixed near the top surface of the cradle opposite the two or more bonding pads.

[0128] Item 45. The cradle according to item 44, wherein the two or more legs comprise four or more legs each secured to a different corner of the cradle.

[0129] Item 46. A cradle according to any one of Items 44 to 45, wherein the two or more legs include three or more legs each fixed to a different edge of the cradle.

[0130] Item 47. The cradle of any of items 43 to 46, wherein the two or more mounting members comprise two or more hollow cylinders or hollow prisms extending from a lower surface of the cradle facing the substrate.

[0131] Item 48. The cradle of any one of items 43 to 47, wherein the two or more mounting members are symmetrically arranged with respect to the cradle so that reversible deflection minimizes displacement of a reference point on the optical ferrule relative to a corresponding reference point on the substrate.

[0132] Item 49. The cradle of item 48, wherein displacement is minimized when the cradle expands or contracts relative to the substrate due to changes in temperature.

[0133] Item 49a. A cradle described in any of items 43 to 49, further comprising a lens configured to modify the optical path between the optical ferrule and the optical device, the optical device being located on a substrate to which the cradle is mounted.

[0134] Item 49b. The cradle of item 49a, wherein the lens comprises a collimating lens.

[0135] Item 50. A cradle configured to receive and secure an optical ferrule, a holding member configured to hold down the optical ferrule; two or more bonding pads comprising a bonding material that bonds a cradle to a substrate at a bonding temperature, the cradle having a first coefficient of thermal expansion and the substrate having a second coefficient of thermal expansion different from the first coefficient of thermal expansion; two or more mounting members mechanically coupling the two or more corresponding bonding pads to the cradle, the two or more mounting members being deformable in response to expansion of the cradle relative to the substrate, the relative change in expansion being due to changes between a bonding temperature and an operating temperature, the two or more mounting members being deformable such that the cradle maintains alignment between the optical ferrule and an optical device attached to the substrate at least at the operating temperature; A cradle.

[0136] Item 51. The cradle of item 50, wherein the two or more mounting members comprise two or more legs fixed near the top surface of the cradle opposite the two or more bonding pads.

[0137] Item 52. The cradle according to item 51, wherein the two or more legs comprise four or more legs each secured to a different corner of the cradle.

[0138] Item 53. The cradle according to any one of Items 51 to 52, wherein the two or more legs include three or more legs each fixed to a different edge of the cradle.

[0139] Item 54. The cradle of any of items 50 to 53, wherein the two or more mounting members comprise two or more hollow cylinders or hollow prisms extending away from the underside of the cradle facing the substrate.

[0140] Item 55. The cradle of any of Items 50 to 54, wherein the two or more mounting members are symmetrically arranged with respect to the cradle so that reversible deflection minimizes displacement of a reference point on the optical ferrule relative to a corresponding reference point on the substrate.

[0141] Item 56. The cradle of item 55, wherein displacement is minimized when the cradle expands or contracts relative to the substrate due to changes in temperature.

[0142] Item 56a. The cradle of any one of Items 50 to 56, further comprising a lens configured to modify the optical path between the optical ferrule and the optical device.

[0143] Item 56b. The apparatus of item 56a, wherein the lens comprises a collimating lens.

[0144] Item 57. bonding two or more bonding pads of a cradle to the substrate at a bonding temperature, the cradle including two or more mounting members mechanically coupling the corresponding two or more bonding pads to the cradle; allowing the cradle and substrate to reach an assembly temperature, where the difference between the bonding temperature and the assembly temperature causes deformation of the mounting member due to differences in the thermal expansion coefficients of the cradle and the substrate; Inserting the optical ferrule into the cradle such that the cradle secures the optical ferrule to the optical device mounted on the substrate; A method comprising:

[0145] Item 58. The method of Item 57, further comprising activating one or more devices coupled to the substrate so that the substrate, cradle, and optical ferrule reach an operating temperature, wherein expansion of the cradle relative to the substrate at the operating temperature aligns the optical ferrule with the optical device.

[0146] Item 59. The method of item 58, further comprising transmitting light between the optical ferrule and the optical device through one or more output locations on a mating face of the optical ferrule at an operating temperature.

[0147] Item 60. The method of item 59, wherein transmitting light between the optical ferrule and the optical device includes redirecting light between the mating surface and an optical waveguide coupled to the end of the optical ferrule.

[0148] Item 61. Optical components, a mounting area for receiving and permanently mounting a plurality of optical waveguides; a light redirection member for receiving light along a first direction from a plurality of optical fibers received and permanently attached by the attachment area and redirecting the light along a different second direction, the redirected light exiting the ferrule at an exit location on the mating face, the exit location being substantially centered on a first alignment face perpendicular to the first direction; two or more bonding pads operable with a bonding material to bond a component to a substrate at a bonding temperature, the component having a first coefficient of thermal expansion and the substrate having a second coefficient of thermal expansion different from the first coefficient of thermal expansion; two or more mounting members mechanically coupling a corresponding two or more bonding pads to the component, the two or more mounting members reversibly deflecting in response to a force applied to the component between the bonding pads and the attachment areas of the two or more mounting members, thereby minimizing the effect of temperature on the location of the intersection of the first alignment surface with the substrate; and An optical component comprising:

[0149] Item 62. The optical assembly of Item 61, wherein the component further comprises a lens configured to modify an optical path between the component and the optical device, the optical device being located on the substrate.

[0150] Unless otherwise noted, all numbers expressing feature sizes, quantities, and physical properties used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless specifically indicated to the contrary, the numerical parameters set forth in the above specification and appended claims are approximations that may vary depending upon the desired properties sought to be obtained by those of ordinary skill in the art utilizing the teachings disclosed herein. The use of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range.

[0151] Various modifications and variations of the above-described embodiments will be apparent to those skilled in the art, and it should be understood that the present disclosure is not limited to the exemplary embodiments described herein. The reader should assume that, unless otherwise indicated, features of one disclosed embodiment can also be applied to all other disclosed embodiments. It should also be understood that all U.S. patents, patent applications, patent application publications, and other patent and non-patent literature referenced herein are incorporated by reference to the extent they do not contradict the above disclosure.

Claims

1. An optical ferrule, a mounting area for receiving and permanently mounting a plurality of optical fibers; a light redirection member for receiving light from a plurality of fibers received by and permanently attached to the attachment area along a first direction and redirecting the received light along a different second direction, the redirected light exiting the optical ferrule at an exit location on a mating face, the exit location being substantially centered on a first alignment face perpendicular to the first direction; a pair of first engagement features projecting from opposite sides of the optical ferrule, the pair of first engagement features being substantially centered on the first alignment surface; a second engagement feature different from the pair of first engagement features, the second engagement feature protruding from a front side of the optical ferrule and substantially centered on a second alignment surface orthogonal to the first alignment surface, the second alignment surface substantially bisecting the exit location; and Equipped with The optical ferrule is configured to fit loosely within a mating optical component at room temperature and to expand into the mating optical component at an operating temperature greater than room temperature.

2. 1. An optical assembly comprising: an optical ferrule having a first coefficient of thermal expansion, the optical ferrule including a light redirecting element configured to redirect light between the optical waveguide and a mating surface of the optical ferrule; a cradle configured to hold the optical ferrule and secure it to a substrate, the cradle having a second coefficient of thermal expansion less than the first coefficient of thermal expansion; The optical assembly, wherein the optical ferrule is configured to fit loosely within the cradle at room temperature and to expand into the cradle at an operating temperature greater than room temperature.

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