Miniature mechanical transfer optical coupler

[0001] This nonprovisional patent application claims priority benefit, with regard to all common subject matter, of earlier-filed U.S. provisional patent application titled “Miniature MT Optical Coupler (MMTOC)”, Ser. No. 60/895,326, filed Mar. 16, 2007. The identified earlier-filed application is hereby incorporated by reference in its entirety into the present application.

[0002] The present invention was developed with support from the U.S. government under Contract No. DE-AC04-01AL66850 with the U.S. Department of Energy. Accordingly, the U.S. government has certain rights in the present invention.

[0003] 1. Field

[0004] Embodiments of the present invention relate to an optical coupler for optical fibers. More particularly, the invention relates to a miniature mechanical transferring (MT) optical coupler (“MMTOC”) which can passively and communicatively connect at least two ribbons of optical fibers.

[0005] 2. Related Art

[0006] Fiber optic technology generally refers to the transmission of light through transparent glass or plastic fibers. The light beams transmitted through the fibers, known as optical fibers, may be encoded with data by modulating the light beams.

[0007] Optical fibers are often bundled together in an optical fiber ribbon. In order to connect one optical fiber ribbon (or one set of optical fibers) to another optical fiber ribbon, a variety of fiber optic connectors may be used. Fiber optic connectors typically mechanically couple and align the cores of fiber so that light can pass from one fiber to another. One type of fiber optic connector is a mechanical transfer (MT) connector. The MT connector may be male or female, having a plurality of small openings or ferrules through which individual fibers may be threaded. The male MT connector is designed to physically connect with the female MT connector to communicatively connect the fibers of the optical fiber ribbons.

[0008] Currently, if an application requires one optical fiber ribbon to send light beams to two different optical fiber ribbons, the cores of the fibers must be actively aligned. Two commercially available methods exist for splitting the signals from one optical fiber ribbon into two optical fiber ribbons. One method for splitting signals from one optical fiber ribbon into two optical fiber ribbons requires the formation of a star coupler, which is formed by laying fibers next to each other and fusing them together. Manufacturing a star coupler is time intensive and requires a great deal of precision to get the light beam to split evenly. Another method for splitting the signals from one optical fiber ribbon into two optical fiber ribbons requires the formation of optical wave guides, which involves laying down the optical fibers onto a piece of silicon and then overcoating the silicon dioxide to form optical “tunnels”. These tunnels can be shaped to split the optical signal into multiple paths. This method is expensive and complex. Each of these prior art methods require that the fibers be actively coupled, meaning that at least a portion of each individual fiber must be physically adapted in a substantially permanent way, such as fusing two fibers together or bonding the fibers together with another substance. This type of active coupling is time consuming and can not easily be altered or disconnected without cutting the fiber.

[0009] Accordingly there is a need for a method and apparatus for communicatively coupling two or more sets of optical fibers that does not suffer from the problems and limitations of the prior art.

[0010] Various embodiments of the invention provide a miniature mechanical transfer (MT) optical coupler (“MMTOC”) for communicatively connecting a first set of optical fibers with at least one other set of optical fibers without the fibers touching one another, being cut, spliced, fused, chemically bonded, or otherwise physically altered. The MMTOC may comprise a beam splitting element, a first collimating lens, a second collimating lens, a third collimating lens, a fourth collimating lens, and at least one alignment element. The beam splitting element may comprise a first, second, third, and fourth side as well as a reflective portion for partially transmitting and partially reflecting light beams. The first collimating lens may be fixed at the first side of the beam splitting element, the second collimating lens may be fixed at the second side of the beam splitting element, the third collimating lens may be fixed at the third side of the beam splitting element, and the fourth collimating lens may be fixed at the fourth side of the beam splitting element.

[0011] The first and second collimating lenses may be fixed at opposing first and second sides of the beam splitting element and may share a center axis, while the third and fourth collimating lenses may be fixed at opposing third and fourth sides of the beam splitting element and share a center axis perpendicular to the center axis of the first and second collimating lenses. Additionally, the collimating lenses may be collimating lens arrays manufactured to collimate a plurality of parallel beams. Also, the beam splitting element may be an optical prism that allows a portion of light to be transmitted and a portion to be reflected at an angle. Additionally, the beam splitting element may be customized with an optical bandpass filter coating or other optical coatings known in the art.

[0012] The MMTOC may be mechanically attachable to at least a first, second, third, and fourth MT connector by the at least one alignment element. A plurality of optical fibers may be disposed in a plurality of ferrules of the MT connectors. The alignment elements may align each of the MT connectors with one of the collimating lenses such that, for example, a plurality of light beams extending from the first MT connector may be collimated and then split by the beam splitting element, with a portion of each of the plurality of light beams being reflected into the third collimating lens and the third MT connector and another portion of each of the light beams being transmitted through the beam splitting element into the second collimating lens and the second MT connector.

[0013] Additionally, a plurality of light beams extending from the fourth MT connector may be collimated and then split by the beam splitting element, with a portion of each of the plurality of light beams being reflected into the second collimating lens and the second MT connector and another portion of each of the light beams being transmitted through the beam splitting element into the third collimating lens and the third MT connector.

[0014] These and other important aspects of the present invention are described more fully in the detailed description below.

[0031] The drawing figures do not limit the present invention to the specific embodiments disclosed and described herein. The drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the invention.

[0032] The following detailed description of the invention references the accompanying drawing figures that illustrate specific embodiments in which the present invention can be practiced. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments can be utilized and changes can be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense.

[0033] Embodiments of the present invention, as illustrated in FIGS. 1-3, provide a miniature mechanical transferring (MT) optical coupler (“MMTOC”) 10 for optically coupling a plurality of optical fiber ribbons 12 each comprising a plurality of optical fibers 14 whose ends are disposed in ferrules 16 (illustrated in FIG. 5) of one of a plurality of MT connectors 18,20,22,24. The MMTOC 10 may comprise a mount 26, a beam splitting element 28; a plurality of collimating lenses 30,32,34,36; and at least one alignment element 38 for connecting the MT connectors 18-24 to the MMTOC 10.

[0034] The mount 26, illustrated in FIGS. 3 and 4, may be composed of metal, plastic, or any substantially solid material. The mount 26 may be attached to each of the beam splitting element 28, the collimating lenses 30-36, and the alignment element 38, maintaining these elements in a fixed relationship with one another. In various embodiments of the invention, the mount 26 may fix the collimating lenses 30-36 at right angles relative to each other in a substantially rectangular configuration, with the beam splitting element 28 fixed inward of the mount 26 and the collimating lenses 30-36.

[0035] The beam splitting element 28 may have a plurality of sides 40,42,44,46 and a reflective portion 48 for partially transmitting and partially reflecting light beams, as illustrated in FIG. 1. The beam splitting element 28 may be an optical prism with partially reflective properties or a partially reflective coating. However, the beam splitting element 28 may be any apparatus for splitting an individual beam of light into multiple light beams, as known in the art. The partially reflective coating may be any thin film optical coating known in the art. Changing the coating or reflective properties of the beam splitting element 28 may allow a greater portion of the beam to pass through the beam splitting element 28 and a smaller portion to be reflected, or vice versa. In this way, the beam splitting element 28 may be customized for a variety of applications. The coatings may also be used to manipulate incoming light beams in other ways. For example, a bandpass filter coating may be used to customize the beam splitting element 28, providing a bandpass filter to the incoming signal. Additionally or alternatively, various optical coatings may be applied to the collimating lenses 30-36 for particular applications.

[0036] Each of the collimating lenses 30-36 may be manufactured to collimate multiple parallel light beams, as known in the art. For example, as illustrated in FIGS. 6-7, each of the collimating lenses 30-36 may comprise a fiber collimating lens array 50 such as the Multi-mode Micro Lens Arrays manufactured by OMRON ELECTRONIC COMPONENTS LLC. Alternatively, the collimating lenses 30-36 may be any lens or apparatus known in the art for collimating a plurality of light beams simultaneously.

[0037] The collimating lenses 30-36 may be configured to collimate light beams from the plurality of fibers 14 disposed in the plurality of ferrules 16 of the MT connectors 18-24. For example, one of the collimating lenses 30-36 may collimate twelve light beams from twelve optical fibers 14 disposed in twelve ferrules 16 in a 1×12 channel MT connector 18 illustrated in FIG. 5. However, the collimating lenses 30-36 may be customized for a fewer or a greater number of parallel light beams without substantially increasing the physical size of the collimating lens 30-36, due to the compact nature of MT connectors and collimating lens arrays. For example, collimating lenses 30-36 may be customized to collimate 72 channels for use with a 6×12 channel MT connector 18. A 6×12 channel MT connector 18 as manufactured by US CONEC is illustrated in FIGS. 8-9. Furthermore, in various other embodiments of the invention, lenses 30-36 for collimating 100 or more parallel beams of light may be used.

[0038] The collimating lenses 30-36 may comprise a first collimating lens 30 fixed at a first side 40 of the beam splitting element 28, a second collimating lens 32 fixed at a second side 42 of the beam splitting element 28, a third collimating lens 34 fixed at a third side 44 of the beam splitting element 28, and a fourth collimating lens 36 fixed at a fourth side 46 of the beam splitting element 28. In various embodiments of the invention, the first and second collimating lenses 30,32 may be disposed on opposing sides of the beam splitting element 28 and aligned with each other such that they share a center axis 52. Additionally, the third and fourth collimating lenses 34,36 may be disposed on opposing sides of the beam splitting element 28 and aligned with each other such that they share a center axis 54, which may be perpendicular to the center axis 52, as illustrated in FIG. 3. Furthermore, the reflective portion 48 of the beam splitting element 28 may be fixed at a 45 degree angle relative to each of the center axes 52,54 of the collimating lenses 30-36.

[0039] The alignment elements 38 may be any alignment device for aligning at least one of the MT connectors 18-24 with at least one of the collimating lenses 30-36. For example, the alignment elements 38 may be cross-pins, as illustrated in FIGS. 2 and 10, having four appendages. One appendage of each of a pair of the cross-pins may slide into one of two openings 56,58 (illustrated in FIGS. 8-9) of a first MT connector 18, aligning the first MT connector 18 with the first collimating lens 30. Additionally, another appendage of each of the pair of cross-pins may slide into one of two openings (not shown) of a second MT connector 20, aligning the second MT connector 20 with the second collimating lens 32. The alignment elements 38 may also align a third and a fourth MT connector 22,24 with the third and fourth collimating lenses 34,36 respectively.

[0040] In use, the beam splitting element 28 may split a plurality of parallel light beams 60 in a plurality of directions to be received by multiple optical fiber ribbons 12. For example, the beam splitting element 28 may allow a portion of a beam of light to pass laterally through the reflective portion 48, while another portion of the beam of light may impinge the reflective portion 48 at a 45 degree angle and be reflected at a 90 degree angle from its original path of travel, as illustrated in FIG. 11.

[0041] Specifically, the plurality of fibers 14 disposed in the plurality of ferrules 16 of the first MT connector 18 may be optically coupled to the plurality of fibers 14 disposed in the plurality of ferrules 16 of the second MT connector 20 via the MMTOC 10, such that at least a portion of each light beam extending from the plurality of fibers 14 of the first MT connector 18 may be received by the plurality of fibers 14 of the second MT connector 20. Additionally, the plurality of fibers 14 disposed in the plurality of ferrules 16 of the third MT connector 22 may be optically coupled to the first MT connector 18 via the MMTOC 10. In this embodiment of the invention, the beam splitting element 28 may transmit a portion of each beam of light extending from the plurality of fibers 14 of the first MT connector 18 to the plurality of fibers 14 of the second MT connector 20 and reflect another portion of each beam of light extending from the plurality of fibers 14 of the first MT connector 18 to the plurality of fibers 14 of the third MT connector 22.

[0042] For example, as illustrated in FIG. 11, if the first MT connector 18 is aligned with the first collimating lens 30, the second MT connector 20 is aligned with the second collimating lens 32, and the third MT connector 22 is aligned with the third collimating lens 34, then the optical fibers 14 of the first MT connector 18 are optically coupled with the optical fibers 14 of the second and third MT connectors 20,22. In this configuration, a first portion of each of the plurality of light beams 60 from the plurality of fibers 14 of the first MT connector 18 is received by the plurality of fibers 14 of the second MT connector 20 and a second portion of each of the plurality of light beams 60 from the plurality of fibers 14 of the first MT connector 18 is received by the plurality of fibers 14 of the third MT connector 22.

[0043] Additionally, when the fourth MT connector 24 is aligned with the fourth collimating lens 36 as in FIG. 3, a portion of each of the plurality of light beams 60 extending from the fourth MT connector 24 may be transmitted through the beam splitting element 28 into optical fibers 14 of the third MT connector 22 while another portion of each of the plurality of light beams 60 extending from the fourth MT connector 24 may be reflected at a 90 degree angle by the beam splitting element 28 into the second MT connector 20.

[0044] In various embodiments of the invention, a laser (not shown) may be actively aligned to the MMTOC 10 proximate at least one collimating lens for diagnostic purposes. For example, a laser beam may be sent through the third lens 34 and be partially transmitted through the beam splitting element 28 and partially reflected at a 90 degree angle through the first lens 30 to a monitor (not shown) on the first MT connector 18, thereby notifying the user or system that the first MT connector 18 is properly aligned with the beam splitting element 28.

[0045] Although the invention has been described with reference to the embodiments illustrated in the attached drawings, it is noted that equivalents may be employed and substitutions made herein without departing from the scope of the invention as recited in the claims. For example, in alternative embodiments of the invention illustrated in FIGS. 12-14, the first and third collimating lenses 30,34 may be positioned such that their center axes 52,54 are perpendicular to each other and the second lens 32 may be omitted. In this arrangement, the light beams 60 transmitted by the optical fibers 14 of the first MT connector 18 may be reflected at a 90 degree angle by the beam splitting element 28 into the third MT connector 22, or vice versa. This configuration is particularly useful for situations in which the physical path of the optical fibers 14 turns by 90 degrees, since bending optical fibers at right angles may damage the fibers.

[0046] In other alternative embodiments of the invention, as illustrated in FIG. 15, a right angle prism 62 may be attached at the third side 44 of the beam splitting element 28 for routing purposes. In this configuration, the third collimating lens 34 may be positioned such that its center axis 54 is parallel with the center axis 52 of the first and second lenses 30,32. So, for example, in this configuration, light beams 60 transmitted from the first MT connector 18 may be both reflected at a 90 degree angle by the beam splitting element 28 and transmitted laterally through the beam splitting element 28 to the second MT connector 20. The reflected portion of the beams 60 may impinge the right angle prism 62 and reflect at another 90 degree angle toward the third MT connector 22.