A device-to-device optical connector assembly is configured to provide an optical signal as an expanded beam to an expanded beam plug cable. The connector assembly includes an active receptacle having a lead-in portion that receives a light beam from an opto-electronic device, a lead-out portion and a turn portion that turns the light beam and delivers a collimated light beam to the lead-out portion. A waveguide rod is optically coupled to the lead-out portion of the active receptacle that receives the collimated light beam and carries the collimated light beam from the active receptacle to the expanded beam plug cable. In one embodiment, the waveguide rod has a step index core waveguide profile with its fundamental mode generally matching the coupling optics of a complementary cable assembly or the like within a predetermined value.

BACKGROUND

The present specification relates generally to optical connectors and, more particularly to device-to-device optical connectors.

Optical connectors are used in a variety of applications where one or more optical fibers of a set of optical fibers are in optical communication with another set of one or more optical fibers, circuit boards, or other devices. Various small form factor connectors have been proposed. However, many of the small form factor connectors must be fabricated precisely and are susceptible to dust and other environmental factors.

For device-to-device optical connector (DDOC) type consumer applications, expanded beam optical connector assemblies have been proposed. Expanded beam connectors include optics that increase beam diameter and/or collimate a light beam, which can mitigate the effects of dust and other factors. Such connectors are expected to be used to transfer high bandwidth data between electronic devices, such as smart phones, laptop personal computers, high speed processors, graphic modules, and other such electronic and mobile communication or consumer devices. The connectors are also expected to meet a variety of consumer electronic related criteria, such as small form factor, low cost, low loss for bandwidth performance, ease of cleaning, etc. Although, the received light beam is manipulated for improved performance there still are challenges for alignment and preserving optical performance of optical connector assemblies.

One type of optical connector assembly is an optical receptacle optical connector that may be used on an electronic device. These connectors are assembled into links with the active devices and coupling optics located centrally on the circuit board. A relay fiber is typically used to relay optical signals to an expanded beam connector located at an edge of the circuit board. A cable assembly having an expanded beam plug cable may then be used to optically couple a pair of devices together by receiving and/or delivering optical signals to and/or from the expanded beam connector. In another variation, the passive receptacle can be aligned with opto-electronic devices such as laser diodes and/or photodiodes disposed on the circuit board, thereby eliminating the need for relay fibers. However, in this configuration the opto-electronic devices must be located relatively close to the edge of the circuit board which can be challenging for the design of the circuit board and/or the electronic device.

SUMMARY

In one embodiment, an optical connector assembly providing an optical signal as an expanded beam for an expanded beam plug cable is disclosed. The connector assembly includes an active receptacle having a collimator having a lead-in portion that receives a light beam from an opto-electronic device, a lead-out portion and a turn portion that turns the light beam and delivers a collimated light beam to the lead-out portion and a waveguide rod. The waveguide rod is optically coupled to the lead-out portion of the collimator and receives the collimated light beam and carries the collimated light beam from the active receptacle to an optical interface of the connector assembly.

In another embodiment, a device comprises a circuit board comprising an optical connector assembly for connecting to an expanded beam cable for delivering optical signals thereto along with an opto-electronic device. The opto-electronic device is carried by the circuit board that is configured to convert electrical signals to optical signals in the form of a light beam. The optical connector assembly includes an active receptacle comprising a collimator with a lead-in portion that receives a light beam from the opto-electronic device, a lead-out portion and a turn portion that turns the light beam and carries the collimated the light beam from the active receptacle to an optical interface of the optical connector assembly. The optical connector assembly also comprises a waveguide rod optically coupled to collimator that receives the collimated light beam and carries the collimated light beam from the active receptacle to an optical interface of the optical connector assembly.

In another embodiment, a method of providing an optical signal as an expanded beam using an optical connector assembly is disclosed. The method includes providing a light beam from an opto-electronic device carried by a circuit board to an optical connector assembly, expanding and collimating the light beam using the optical connector assembly. The optical connector assembly comprising an active receptacle comprising a collimator with a lead-in portion that receives a light beam from the opto-electronic device, a lead-out portion and a turn portion that turns the light beam and delivers a collimated light beam to the lead-out portion, and a waveguide rod optically coupled to the collimator that receives the collimated light beam and carries the collimated light beam from the active receptacle to an optical interface of the optical connector assembly. The method also comprises delivering the collimated light beam to a waveguide rod optically coupled to the collimator and carrying the collimated light beam to the optical interface of the optical connector assembly.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings, in which some, but not all embodiments are shown. Indeed, the concepts may be embodied in many different forms and should not be construed as limiting herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Whenever possible, like reference numbers will be used to refer to like components or parts.

Embodiments described herein generally relate to optical connector assemblies such as device-to-device optical connector (DDOC) assemblies for consumer applications; however, the DDOC assemblies could be used in non-consumer contexts as well or for applications other than device-to-device purposes. The DDOC optical connector assemblies are generally associated with a circuit board and utilize a waveguide rod in conjunction with expanded beam optics to deliver a collimated beam from the expanded beam optics toward an expanded beam connector of, for example, an expanded beam plug cable, without any use of intervening relay components, such as a relay fiber therebetween. Such an arrangement can allow placement of active devices near an edge of the circuit board, while delivering the collimated beam to the edge with low losses. If the waveguide rod is formed of glass material, the waveguide rod can also provide a durable and surface accessible interface than can readily be cleaned of any contamination, such as dust, oils, etc.

Referring toFIG. 1and by way of introduction, an exemplary active approach to deliver optical signals to a device10from another device12is illustrated. This exemplary approach demonstrates a DDOC optical connector assembly14that sends optical signals as an expanded beam as an output to an expanded beam plug cable16, which then delivers the optical signals to the device10. However, the same principles can be applied in reverse for receiving optical signals by the device12from the device10. Additionally, the same or similar principles can be applied in either electrical-to-optical or optical-to-optical contexts.

In the illustrative embodiment ofFIG. 1, the device10includes a circuit board18and the device12includes a circuit board20. In some embodiments, the circuit boards18and20include connection interface components (e.g., USB ports) located at and represented by edges22and24of the circuit boards18and20. The interface components may be placed at or near edges22and24of the circuit boards18and20to facilitate exposure through a housing and access by a user. As examples of devices, the circuit boards18and20may be found in smart phones, computers, printers, digital versatile disk (DVD) drives, compact disk read-only-memory (CD-ROM) drives, CD-ROM Writer (CDRW) drives, pointing devices (e.g., computer mouse), keyboards, joy-sticks, hard-drives, speakers cameras, and the like. Opto-electronic devices26and28may also be provided by the circuit boards18and20. The opto-electronic devices26and28may include optical transmitter components (e.g., optical transmitter arrays, broad area emitters, vertical-cavity surface-emitting laser (VCSEL), LED etc.) and/or optical detector components (e.g., optical detector arrays, broad area detectors, photodectors, etc.).

The DDOC optical connector assembly14includes an active receptacle30, such as one or more molded lenses or prisms. The active receptacle30receives a light beam from the opto-electronic device28, collimates the light beam (represented by element32) and delivers the light beam32to an expanded beam connector34of the expanded beam plug cable16. In the illustrated embodiment, the active receptacle30includes a lead-in portion38that receives the light beam and a lead-out portion40that delivers the light beam32to the expanded beam connector34. Between the lead-in portion38and the lead-out portion40is a turn portion42that turns the light beam in a direction (e.g., 90 degrees) that is different from the direction the light beam is received. As one example, the turn portion42may include a reflective surface that is used to reflect the light beam. In other embodiments, a prism or some other beam turning component may be used.

As represented byFIG. 1, the active devices, such as opto-electronic device28are located relatively close to the edge24of circuit board20, which reduces the need for any relay fiber and associated optics. However, such an arrangement can result in precise placement of the active devices a short distance from the edge24and can restrict the freedom to locate the active devices and their associated electronics on the circuit board20.

FIGS. 2A and 2Bschematically depict misalignment tolerance issues that can occur if the optical receptacle has an optical component that has lengthened leg so that the active devices and associated electronics can be located further from the edge of circuit board20. Referring toFIG. 2A, if the optical path P of the light beam32is extended to place the active devices further from the edge24, misalignment of the light beam transmitted by the optical component45may also be increase due to the optical lever effect. Optical lever effects increase as the length of light path in the optical component increases so that the light beam being transmitted is displaced from its desired target location at the lead-out portion of the optical component.FIG. 2Ashows the desired target location for light beam32in solid lines and the dashed lines of optical path represent the misalignment effects that may occur with the lengthened leg of the optical component. Further, the adverse misalignment effects increase as the length of the optical path of the optical component increases as shown inFIG. 2B.FIG. 2Bis similar toFIG. 2Aand shows an extended horizontal leg for the optical component which can cause increased misalignment issues. As represented by the dashed lines the optical path may be farther from the desired target location for light beam32as represented by the solid lines. Consequently, the optical connectivity provided by optical receptacles having optical components which such extended legs such as shown inFIGS. 2A and 2Bmay suffer optical performance issues.

FIG. 2Cdepicts an improvement for addressing the optical lever effects for an optical connector assembly20such as an optical receptacle. An optical connector assembly20provides an expanded beam connector assembly comprising an active receptacle30having a collimator31with a lead-in portion38that receives a light beam from an opto-electronic device28, a lead-out portion40and a turn portion42that turns the light beam32and delivers a collimated light beam to the lead-out portion40and a waveguide rod60. The waveguide rod60is optically coupled to the lead-out portion40of the collimator31and receives the collimated light beam32and carries the collimated light beam32from the active receptacle to an optical interface47of the connector assembly20. Thus, the optical connector assembly is an active receptacle having a collimator for making the optical turn that is optically coupled to a waveguide rod that provides the optical interface for the optical connector.

Referring toFIG. 3, another embodiment of an optical connector assembly100for use with device102and circuit board104is illustrated schematically. As depicted, the optical connector assembly100includes many of the features described above including an active receptacle106and an opto-electronic device108carried by the circuit board104. An expanded beam plug cable110includes an expanded beam connector112that is located at an edge114of the circuit board104. The expanded beam connector112is connected to an optical fiber115that delivers optical signals between the device102and another device connected thereto.

The active receptacle106includes a collimator118including a lens120(e.g., a positive lens) and a turn portion122including a prism structure124. The opto-electronic device108and active receptacle106are located a short distance from the edge114of the circuit board104providing a gap126between the active receptacle106and the edge114. A waveguide rod128is provided that spans at least part of the gap126between the active receptacle106and the edge114.

The waveguide rod128includes a coupling face130that is physically and optically coupled to the turn portion122. For example, an index matching gel or adhesive132may be used to couple the waveguide rod128to the turn portion122. The waveguide rod128further includes an edge facing face134that is located flush or in close proximity of the edge114. Referring briefly toFIG. 4, the waveguide rod128may be a multimode waveguide having a core134with a refractive index n1and a cladding136having a refractive index n2, where n2is less than n1providing a low index difference step index core waveguide.

As mentioned, the waveguide rod128can be a low index difference, step index core waveguide. The waveguide rod128can be formed such that the fundamental mode of the waveguide rod128matches or nearly matches the collimated beam exiting the active receptacle106. The fundamental mode of the waveguide rod128can be evaluated based on the core diameter Dc(FIG. 3) and the refractive index difference between the core134and the cladding136. Such waveguide rods128can be formed using standard fabrication techniques, which can lead to low loss waveguide rods128with precise diameters and concentricity. As one example, the waveguide rods128can be formed using a silica core and fluorine doped cladding blank.FIG. 5illustrates a refractive index profile of such an exemplary waveguide rod including a silica core and fluorine doped cladding formed using a vapor deposition process for depositing the cladding. As can be seen, the refractive index of the cladding is approximately 0.005 lower than the core. Even with a refractive index difference of about 0.5 percent, the waveguide rod can capture the collimated light beam, even with some misalignment (e.g., of about one to two degrees).

Referring toFIG. 6, operation of the optical connector assembly100is illustrated. To excite the fundamental mode of the waveguide rod128, such as one including a silica core and fluorine doped cladding, the arrangement ofFIG. 6may be used. The fundamental mode140generated by the active receptacle106when producing the collimated light beam is coupled to the waveguide rod128with the waveguide rod adjacent the exit of the active receptacle106. The fundamental mode140excites the fundamental mode142of the waveguide rod128. In some embodiments, the core diameter Dcclosely matches the collimated beam diameter (e.g., between about 100 μm and about 350 μm). The index matching adhesive132can be used to couple the active receptacle106and the waveguide rod128. This arrangement couples all of the light from the collimated light beam very efficiently to the fundamental mode142of the waveguide rod128. The mode size does not change with propagation distance and is centered with respect to the waveguide axis. With such a low loss waveguide feature, any optical lever effect is minimized, but at the same time, the expanded beam can propagate longer distances to the card edge114while confined to the waveguide rod128. The output facet134of the waveguide rod128can be used as a reference for connecting an expanded beam plug cable154very precisely for a low loss optical connection.

The optical connector assemblies and methods can be flexible and can cover a broad range of beam sizes. For expanded beam connectors, to provide the benefit low losses, the beam diameter can be in the range of about 100 to about 300 μm and still have the small form factors needed for consumer-type applications. Commercially available optical components such as VCSEL and detector arrays are generally spaced at 250 μm pitch. Thus, the pitch for the active receptacle array can be 250 μm or some multiple of 250 μm, but other suitable values for the pitch are possible. With a 250 μm pitch, the diameter of the waveguide rod can be at most 250 μm with a core diameter Dcof about 200 μm and a 25 μm thick cladding. The corresponding fundamental mode with near Gaussian shape can be calculated for the known value of the core diameter Dcand the core/clad index difference and operating wavelength. The coupling optics of the active receptacle can be designed such that the expanded beam matches the fundamental mode of the waveguide rod. Arrays with other pitch values can be used. For example, an array160with 500 μm pitch with a corresponding v-groove array162is shown byFIG. 7.

Referring toFIG. 8, another embodiment of an optical connector assembly162uses an appropriate length gradient index (GRIN) lens as part of waveguide rod164. In this embodiment, the waveguide rod164includes the GRIN lens portion168and a turn portion170that is formed as an integral part of the waveguide rod164. The turn portion170may be formed using any suitable process, such as polishing, laser shaping or any combination of processes. The GRIN lens length can be increased by ((n/2)+¼) L, where L is the pitch length of the GRIN lens portion168and n is the refractive index.

Referring toFIG. 9, another embodiment of an optical connector assembly171includes a step core172as part of waveguide rod174with a turn portion176that can be formed of a beam bending prism structure178and a shaped refractive lens structure180integrated with the step core172. The prism structure178can be formed using any suitable process such as dicing and polishing.FIG. 10illustrates another embodiment formed of a step index waveguide rod182with integrated beam bending prism structure184. In addition to beam bending active receptacles, in some embodiments, an in-line configuration may be provided where the turn (e.g., 90 degrees) is incorporated in an active device. In these embodiments, the active device, instead of being mounted on a circuit board with light emission perpendicular to the circuit board, the active device can be mounted so that the light beam is parallel to the circuit board and the electrical leads have a 90 degree turn, as an example.FIG. 11illustrates such an in-line arrangement including the active device190that directs a light beam192parallel to the circuit board194to a step index waveguide rod196that has an input facet198that is shaped to provide a lens structure200. Referring toFIG. 12, another embodiment of an optical connector assembly210uses a mirror212or a combination of a refractive lens and a mirror. In this embodiment, the mirror212can be shaped on a beam bending facet214of waveguide rod216. It is also possible to include a refractive lens on a bottom facet218of the waveguide rod216. In some embodiments, a surface of the cladding of the waveguide rod may be shaped (e.g., flat or bi-conic), for example, to provide beam bending and/or shaping properties.

As used herein, it is intended that terms “fiber optic cables” and/or “optical fibers” include all types of single mode and multi-mode light waveguides, including one or more optical fibers that may be upcoated, colored, buffered, ribbonized and/or have other organizing or protective structure in a cable such as one or more tubes, strength members, jackets or the like. The optical fibers disclosed herein can be single mode or multi-mode optical fibers. Likewise, other types of suitable optical fibers include bend-insensitive optical fibers, or any other expedient of a medium for transmitting light signals. An example of a bend-insensitive, or bend resistant, optical fiber is ClearCurve® Multimode fiber commercially available from Corning Incorporated. Suitable fibers of this type are disclosed, for example, in U.S. Patent Application Publication Nos. 2008/0166094 and 2009/0169163, the disclosures of which are incorporated herein by reference in their entireties.

It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the application. Since modifications combinations, sub-combinations and variations of the disclosed embodiments incorporating the spirit and substance of the application may occur to persons skilled in the art, the application should be construed to include everything within the scope of the appended claims and their equivalents.