WO2022155342A1

WO2022155342A1 - Two-piece pluggable fiber ferrule

Info

Publication number: WO2022155342A1
Application number: PCT/US2022/012319
Authority: WO
Inventors: Marc Epitaux; R. Brad Bettman
Original assignee: Samtec, Inc.
Priority date: 2021-01-13
Filing date: 2022-01-13
Publication date: 2022-07-21

Abstract

A two-piece pluggable fiber ferrule assembly is described. The two-piece pluggable fiber ferrule assembly includes an optical fiber cable having a plurality of optical fibers, a ferrule that permanently secures the plurality of optical fibers in position relative to an alignment feature, and a rigid adaptor having a first alignment feature configured to mate with the alignment feature of the ferrule and a second alignment feature configured to mate with an optical element. The two-piece pluggable fiber ferrule assembly may be configured to mate with an optical interconnect module.

Description

Two-Piece Pluggable Fiber Ferrule

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This claims priority to U.S. Patent Application Serial No. 63/136,914 filed January 13, 2021, the disclosure of which is hereby incorporated by reference as if set forth in its entirety herein.

BACKGROUND

[0002] Standardized interconnections are used in many systems, such as electrical and optical systems. A ubiquitous example of a standardized electrical interconnect is a wall mounted household electrical socket and its mating plug. The plug typically is permanently connected to a multi-conductor wire, which is connected to an electrical component on the end of the wire opposite the plug. Inserting the plug into the socket powers the electrical component.

[0003] Similarly, various standard interconnections have been established in optical communication systems, where light is transmitted through an optical fiber. Standardized optical interconnections may be used to connect two optical fibers together or to connect an optical fiber to an optical element or optical module having optical functionality. There are many types of standardized optical interconnections. Some standardized optical interconnections are designed for multimode fiber, whereas some standardized optical interconnections are designed for single mode fiber. Some standardized optical interconnections are designed to connect a single fiber to another fiber or module, whereas some standardized optical interconnections are designed to connect a plurality of fibers together simultaneously. These multi-fiber optical interconnections can be used to connect to a module having a plurality of parallel optical channels. The optical interconnection may be designed to be mated and unmated multiple times.

[0004] A standardized optical interconnection typically has a ferrule into which one or more fibers are permanently mounted. The ferrule precisely registers the fiber within the ferrule relative to one or more alignment features. For example, a single fiber may be centered relative to an outer diameter of a cylindrical ferrule. The fiber end face is positioned so that it lies in a plane formed by an end of the cylindrical ferrule. The ferrule diameter is tightly controlled so that it may be inserted into a mating barrel having a tightly controlled inner diameter. The inner diameter of the barrel and end of the cylindrical ferrule serve as alignment features for a mating fiber ferrule. By abutting the mating fiber ferrule with the original fiber ferrule, an optical connection is established between the optical fibers positioned in each ferrule. An example of this type of standardized optical interconnection is a FC optical fiber interconnection system.

[0005] An example of a standard multi-fiber ferrule is a MT (mechanical transfer) ferrule. This ferrule type has a generally rectangular parallel opiped, i.e. box-like, shape that supports a plurality of optical fibers arranged in one or more rows. A fiber ribbon cable extends out of one side of the ferrule and the opposing side has polished fiber end faces. The fiber end faces extend a very short distance past a substantially planar end face of the ferrule. The fibers are registered relative to two precision holes that extend through the ferrule. Precision guide pins are inserted into these holes and extend from the planar face to form a male version of the ferrule. The holes are left open to form a female version of the ferrule. A hermaphroditic version of the ferrule may be formed by leaving one hole open and inserting a guide pin in the other hole. Two ferrules with the appropriate pin arrangement may be mated by inserting the pins into the holes and applying a force pressing the planar surfaces of the ferrules together. This forces the fibers ends in the two ferrules into mechanical contact establishing an optical connection between the fibers in the two ferrules.

[0006] In some situations, standardized optical interconnections are not available that provide the necessary functionality. For example, the interconnection may be exposed to environmental conditions that the interconnection system was not designed to handle. In other situations, the mating direction of the optical interconnection may be incompatible with other system constraints. In some cases, the alignment tolerance in the optical interconnection is too limited to allow the connection to operate with sufficiently low optical loss. An optical system and method to overcome these limitations is needed.

SUMMARY

[0007] In one aspect, a two-piece pluggable fiber ferrule assembly is described. The two-piece pluggable fiber ferrule assembly may be configured to mate with an optical interconnect module.

[0008] In one example, the two-piece pluggable fiber ferrule assembly includes an optical fiber cable having a plurality of optical fibers, a ferrule that permanently secures the plurality of optical fibers in position relative to an alignment feature, and a rigid adaptor having a first alignment feature configured to mate with the alignment feature of the ferrule and a second alignment feature configured to mate with an optical element.

[0009] In another example, the two-piece pluggable fiber ferrule assembly includes an optical fiber cable having a plurality of optical fibers, a ferrule that permanently secures the plurality of optical fibers in position relative to an alignment feature, and an adaptor having a first face mounted to a coupling end face of the ferrule and a second face arranged to couple light into or out of the plurality of optical fibers, either the ferrule or the adaptor has an optical power surface between an end face of each fiber in the plurality of optical fibers and the second face of the adaptor.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Fig. 1 is a perspective view of a prior art MT connector;

[0011] Fig. 2 is a perspective view of a prior art PRIZM® MT connector;

[0012] Fig. 3 is a perspective view of a prior art PRIZM® LightTum® connector;

[0013] Fig. 4 is an exploded perspective view of an optical interconnect module using a two-piece pluggable fiber ferrule assembly;

[0014] Fig. 5 is a cross-sectional perspective view of the two-piece pluggable fiber ferrule assembly shown in Fig. 4 mated to the optical interconnect module shown in Fig. 4;

[0015] Fig. 6 is an exploded perspective view of a two-piece pluggable fiber ferrule assembly according to one example;

[0016] Fig. 7 is a perspective view of the two-piece pluggable fiber ferrule assembly of Fig. 6;

[0017] Fig. 8 is a cross-section view of a two-piece pluggable fiber ferrule assembly of Fig. 6;

[0018] Fig. 9 is an exploded view of a two-piece pluggable fiber ferrule assembly according to another example;

[0019] Fig. 10 is a perspective view of the two-piece pluggable fiber ferrule assembly of Fig. 9; and

[0020] Fig. 11 is a cross-section view of a two-piece pluggable fiber ferrule assembly of Fig. 9.

DETAILED DESCRIPTION

[0021] These limitations described above may be overcome by mating an adaptor with a ferrule to form a two-piece fiber ferrule assembly. The adaptor may allow mating of elements that would otherwise be incompatible. Adaptors may also be used to enable different mating geometries, different mating directions, or withstand certain environmental conditions. The adaptor may also have looser mating tolerances for a sufficiently low loss optical connection. For example, in electrical systems a commonly used adaptor allows mating of a three-pronged plug into a two-slot socket.

[0022] Adaptors would be desirable for standardized optical interconnections. Adaptors compatible with ferrules supporting multiple rows of optical fibers would be advantageous for optical communication networks having a number of parallel channels. Adaptors that allow the light path to be sealed would allow optical interconnections to be used in harsh environments, such as a salt fog environment or submerged in a liquid, such as a liquid coolant. Furthermore, it would be desirable if the adaptor had relaxed alignment tolerances when being mated to an adjoining optical element.

[0023] Fig. 1 illustrates a representative standardized optical connector, a MT optical connector 10. The MT optical connector 10 may have one or more rows of optical fibers supported by a mechanical transfer (MT) ferrule 12. The MT optical connector 10 shown in Fig. 1 has two rows of optical fibers, a first fiber row 14 and a second fiber row 16. The MT ferrule 12 has an end face 18. The first and second row of optical fibers 14 and 16 are centered between two guide pins 20a and 20b. The fiber end faces protrude slightly from the ferrule end face 18, which is a flat surface except for the protruding fiber end faces. The position of the fiber end faces is tightly controlled relative to the two guide pins 20a and 20b and the ferrule end face 18, which form reference surfaces that serve as alignment features to mate the MT optical connector 10 with a mating optical element (not shown in Fig. 1). The alignment is such that optical signals can pass between the fibers and the optical element with acceptable losses and signal fidelity. An optical fiber cable 22, such as a fiber ribbon cable, extends out of a back side the MT ferrule 12 opposite the ferrule end face 18. Since in Fig. 1 there are two rows of optical fibers, there are two fiber ribbon cables.

[0024] An optical connection between two MT connectors 10 may be formed by positioning a second MT connector adjacent the original connector. The second MT connector has the same arrangement of fibers as the original connector, but rather than having guide pins 20a and 20b, it has guide holes. An optical connection between the two connectors is made by inserting the guide pins of the original MT connector into the guide holes of the second MT connector. The fiber ends in the two connectors contact each other and are forced together by a compressive force provided by a spring or clip.

[0025] Fig. 2 shows another type of standardized, multi-fiber optical connector, a PRIZM® MT connector 30 manufactured by USConec of Hickory, North Carolina. This interconnection system is similar to the MT interconnection system described relative to Fig. 1 in that a PRIZM® MT ferrule 32 has a box-like shape, an optical fiber cable 22 emerges from one side of the PRIZM® MT ferrule 32, the optical connection is made on a ferrule end face 38 opposite the optical fiber cable 22, the fibers are arranged in one or more rows, and the PRIZM® MT ferrule 32 has two precision guide features 34a and 34b aligned with the fibers. These alignment features can be either pins or holes, but, as shown in Fig 2, PRIZM® MT ferrules are currently provided by USConec with a guide pin 34a molded into the ferrule 32 and a guide hole 34b formed in the ferrule 34b. A difference between the PRIZM® MT connector 30 and MT connector 10 is that rather than the fiber ends protruding from the PRIZM® MT ferrule end face 38, they are recessed into the ferrule 32. A lens array 40 on the PRIZM® MT ferrule end face 38 (a coupling end face) is arranged to couple light into or out of optical fibers in the optical fiber cables 22. For light propagating from the optical fiber cables 22 into the PRIZM® MT ferrule 32, the lens array 40 collimates the propagating light. For light propagating from the PRIZM® MT ferrule end face 38 into the optical fiber cables 22, the lens array 40 focuses collimated light propagating into the ferrule end face 38 into end faces of the optical fibers in the optical fiber cables 22. As used herein collimated light or a collimated light beam refers to light within a Rayleigh length of a beam waist. The Rayleigh length being defined as the distance between the beam waist and a point along the propagation path where the cross-sectional size of the beam has doubled.

[0026] The example PRIZM® MT connector 30 shown in Fig. 2 has four rows of lens with each lens row having twelve lenses. This example also shows a PRIZM® MT connector 30 with a the molded-in hermaphroditic guide pin configuration, that is there is one guide pin 34a and one guide hole 34b, which may be inserted into a guide hole 34b and guide pin 34b of a mating connector (not shown in Fig. 2).

[0027] As with the MT interconnection system shown in Fig. 1, an optical connection between two PRIZM® MT connectors may be made by inserting the guide pins from one connector into the guide holes of the other connector. An advantage of the PRIZM® MT interconnection system is that debris that may be present in an interconnection region between the two connectors induces less optical loss because the beam size where the two connectors mate is larger. Another advantage of the PRIZM® MT interconnection system is that the positional alignment tolerance between mating connectors is relaxed as compared to connectors that do not expand the light path cross-sectional area in the interconnection region between mating connectors.

[0028] Fig. 3 shows another standardized optical connector, the PRIZM® LightTum® connector 50 manufactured by USConec of Hickory, North Carolina. This connector has a single optical fiber cable 22 with up to twelve optical fibers. The optical fiber cable 22 may be a fiber ribbon cable. A light path 56 through the PRIZM® LightTum® connector 50 is bent by approximately 81°. This is the angle between the optical fiber cable 22 and the light paths 56 adjacent a bottom surface 58 of the PRIZM® LightTum® ferrule 52, which is a coupling end face 60. The light paths 56 are arranged in a single row along the bottom surface 58 and a propagation direction of the light paths 56 is substantially perpendicular to the bottom surface 58. Light propagating in the light paths 56 is collimated in a region below the PRIZM® LightTum® ferrule 52. Two guide pins 54a and 54b are situated on the bottom surface 58 of the PRIZM® LightTum® ferrule 52. While Fig. 3 shows the light paths 56 leaving the bottom surface 58, some or all of the light paths may be entering the bottom surface 58.

[0029] All of these three prior art optical interconnection systems have limitations. The MT connector 10 and PRIZM® MT connector 30 have their coupling end face perpendicular to the optical fiber cable 22. This coupling geometry makes these connectors cumbersome to mate with VCSEL (Vertical Cavity Surface Emitting Laser) based light sources used in many optical interconnect modules, which often are configured so that light is directed perpendicular to a large substrate to which the VSCEL is mounted. To mate with optical interconnect modules, a coupling geometry similar to that of the PRIZM® LightTum® connector 50, which has its coupling end face 60 nearly parallel to the optical fiber cable 22 orientation, is desirable. However, the PRIZM® LightTum® connector is only available in a single row configuration, which limits the maximum number of fibers to twelve. Moreover, the PRIZM® LightTum® connector 50 uses total internal reflection (TIR) on a curved surface having optical power to both change the light propagation direction and alter the light’s wavefront curvature. If the PRIZM® LightTum® connector 50 was submerged in a liquid, the TIR surface would no longer work as designed. What is needed is a fermle arrangement that overcomes these limitations in the prior art.

[0030] Fig. 4 shows an exploded perspective view of a two-piece pluggable fiber fermle assembly 100 arranged to mate with an optical interconnect module 102, such as an optical transceiver, according to one example. To better understand the operation and features of the two-piece pluggable fiber ferrule assembly 100, a cover has been removed from the optical interconnect module 102 in Fig. 4. The optical interconnect module 102 may include an optical engine 104 and a ferrule receptacle 106 configured to mate with the two-piece pluggable fiber fermle assembly 100. The optical interconnect module 102 may be configured as a transceiver, transmitter, or receiver that transmits and/or receives optical signals from the optical fiber cable 22. The optical engine 104 converts optical signals into electrical signals and/or electrical signals into optical signals. The optical interconnect module 102 may convert electrical signals from a host substrate or integrated circuit package (not shown in Fig. 4) to optical signals transmitted through the optical fiber cable 22. Likewise, the optical interconnect module 102 may convert optical signals transmitted through the optical fiber cable 22 to electrical signals transmitted to a host substrate or integrated circuit package (not shown in Fig. 4). The optical interconnect module 102 may include a module substrate 108 having a major surface 110 (see Fig. 5) to which electrooptical components and the ferrule receptacle 106 are mounted. An example of an electrooptical component is a VCSEL that may be mounted to the module substrate 108 and emit light perpendicular to the major surface 110 of the module substrate 108. Another example of an electrooptical component is a photodetector, such as a PIN photodiode, that may be mounted to the module substrate 108 and receive light perpendicular to the major surface 110 of the module substrate 108. A PIN photodiode has a p-type semiconductor layer separated from an n-type semiconductor layer by an undoped intrinsic semiconductor region. Both the VSCEL and photodetector may consist of multiple, independent VSCEL and photodetector elements, respectively, arranged along a monolithic substrate.

[0031] The two-piece pluggable fiber ferrule assembly 100 may include an optical fiber cable 22. The fiber cable may be arranged as two rows of fiber ribbon cable. Each row may contain a plurality of fibers, such as 4, 8, or 12 or other multiples of these numbers such as 16, 24 or 32, etc. A clip 112 may secure the two-piece pluggable fiber ferrule assembly 100 into the optical interconnect module 102. The two-piece pluggable fiber ferrule assembly 100 is not permanently attached to the optical interconnection module 102 but is detachable and can be mated and unmated as desired. More details on the optical interconnect module 102 are described in Patent Cooperation Treaty patent application No. PCT/US2021/054749. It should be appreciated that the two-piece pluggable fiber ferrule assembly 100 may be used with other types of optical interconnect modules.

[0032] Fig. 5 shows an exploded, perspective cross-sectional view of the two-piece pluggable fiber ferrule assembly 100 shown in Fig. 4. For brevity, a description of previously described elements will not be repeated. Fig. 5 shows a cover 114 that may be part of the optical interconnect module 102. The cover 114 may have an opening 116 that is configured to accept the two-piece pluggable fiber ferrule assembly 100.

[0033] An optical connection between the two-piece pluggable fiber ferrule assembly 100 and the optical interconnect module 102 may be made by inserting the two- piece pluggable fiber ferrule assembly 100 into the optical interconnect module 102 in a direction substantially perpendicular to the major surface 110 of the module substrate 108. The two-piece pluggable fiber ferrule assembly 100 may be held in place by the clip 112 or some other mechanism once it is installed. The two-piece pluggable fiber ferrule assembly 100 may be removed from the optical interconnect module 102 by removing the clip 112 and then lifting the two-piece pluggable fiber ferrule assembly 100 up and away from the optical interconnect module 102. Having the ability to mate and unmate the two-piece pluggable fiber ferrule assembly 100 from the optical interconnect module 102 is often advantageous, since it eliminates the requirement for a cumbersome optical fiber pigtail on the optical interconnect module 102. When the two-piece pluggable fiber ferrule assembly 100 is mated with the optical interconnect module 102 it may be considered as part of the optical interconnect module.

[0034] Referring now to Fig. 6, a two-piece pluggable fiber ferrule assembly 200 may include an adaptor 202 mounted to a ferrule 204. The ferrule 204 may be part of a standardized optical connector 206, such as, but not limited to, a PRIZM® MT connector. The standardized optical connector 206 may be manufactured by a plurality of different companies under a multi-source supply agreement. The ferrule 204 permanently secures and registers a position and orientation of a plurality of optical fibers and their respective end faces relative to one or more alignment features. The ferrule 204 may have a coupling end face 208, which is configured to receive or accept light and couple light into or out of the optical fibers mounted in the ferrule 204. The coupling end face 208 may include a plurality of surfaces having optical power, such as lenses, which are surrounded by a nominally flat region. The coupling end face 208 may have an alignment feature 210, such as a guide hole or guide pin. The coupling end face alignment feature 210 is registered with respect to the position of the optical fibers in the ferrule 204. A flat region 212 of the coupling end face 208 also may serve as an alignment feature. The alignment features 210 and 212 of the ferrule 204 may orient the fiber end faces in three orthogonal linear dimensions and three orthogonal rotational dimensions.

[0035] The adaptor 202 may have at least two optical surfaces, denoted as a first face 214 and a second face 216, where light can enter or exit the adaptor 202. Collectively the first face 214 and the second face 216 may be known as the coupling faces. The adaptor 202 also has at least two alignment features, a first alignment feature 218 and second alignment feature 220, arranged to register a mating optical element to the first face 214 and second face 216, respectively. The adaptor 202 can additionally have other optical surfaces that redirect light within the adaptor 202. The adaptor depicted in Fig. 6 has three optical surfaces, the first face 214, the second face 216, and a reflective surface 222. The optical surfaces of the adaptor 202 are precisely registered relative to each other. Likewise, the first alignment feature 218 and second alignment feature 220 of the adaptor 202 are precisely registered relative to each other. The adaptor 202 may be rigid such that alignment between the optical surfaces and alignment features is fixed at the time of adaptor fabrication. The position and direction of light paths entering or exiting the coupling end face 208 of the ferrule 204 are precisely registered relative to the coupling end face alignment feature 210 and coupling end face 208 surface. By mating the adaptor first face 214 with the coupling end face 208, the precise registration of the ferrule 204 is transferred to a precise registration of the light path position and direction relative to the first face 214 and the first alignment feature 218 of the adaptor 202. The precise registration of the optical surfaces within the adaptor 202 enables the precise position and direction of light paths on the adaptor second face 216 to be known relative to the adaptor second alignment feature 220.

[0036] The adaptor 202 may have alignment features on the first face 214, which is arranged to mate with alignment features on the standardized optical ferrule 204. Both the adaptor first face 214 and coupling end face 208 of the optical ferrule 204 may be flat and configured to mated with each other. Into the flat adaptor first face 214 a first alignment feature 218 may be formed by at least one guide pin or guide hole arranged to mate with at least one guide hole or guide pin in the coupling end face 208 of the standardized optical ferrule 204. The first alignment feature 218 may be a guide pin or guide hole arranged to mate with a guide hole or guide pin in the standardized optical ferrule 204, such as the guide pin or guide hole of a PRIZM® MT ferrule. In some cases, the first alignment feature 218 may be two guide holes or guide pins. In other words, a combination of the flat surface and at least one guide pin or guide hole on the first face 214 of the adaptor 202 serves as the alignment feature of the adaptor 202 that enables the adaptor 202 to mate the corresponding flat surface and at least one guide hole or guide pin on the coupling end face 208 of the standardized optical ferrule 204.

[0037] The adaptor second face 216 may be arranged to mate with an optical element, such as an optical interconnect module, for example, optical interconnect module 102 shown in Fig. 5. The second face 216 may include a second alignment feature 220, such as one or more guide holes, guide pins, or grooves (grooves shown in Fig. 6). Light traveling in the adaptor 202 may be redirected by reflection off a reflective surface 222. The reflective surface 222 may use total internal reflection or the reflective surface may be coated, for example, with a metal or dielectric reflective coating. By coating the reflective surface 222, the reflective properties of the reflective surface 222 are unaffected by the external environment contacting the reflective surface. This contrasts with a reflective surface using total internal reflection, which may have its reflective properties spoiled if it is contacting a liquid. The reflective surface 222 may redirect light traveling in the adaptor by an angle close to or equal to 90°. For example, an angle between 75° and 100°. The reflective surface may redirect light at other angles outside this range. A coated reflective surface can redirect light at any desired angle, since the angle of incidence can be smaller than a critical angle for total internal reflection. Also, some adaptors 202 may have more than one reflective surface.

[0038] Light can propagate through the adaptor 202 in two directions. In a first direction, light propagates from a fiber end face in the ferrule 204 into the first face 214 of the adaptor 202. From the adaptor first face 214, the light propagates to the reflective surface 222, where it is redirected and from there propagates out through the second face 216. Light can also propagate in a second opposed direction, that is from the adaptor second face 216, to the reflective surface 222, then through the adaptor first face 214 and hence into a fiber end face located in the ferrule 204. To reduce reflective losses at the first 214 and second face 216 of the adaptor 202, either or both faces may be coated with an anti-reflective optical coating.

[0039] The precise registration of the light paths position and direction on the second face 216 allows an optical element, such as an optical interconnect module (not shown in Fig. 6), to be mated with the adaptor second face 216. The optical interconnect module may have an alignment feature that is arranged to engage with the adaptor second alignment feature 220. The interface region between the second face 216 and optical interconnect module may be sealed, so that environmental contaminants cannot reach the light paths between the adaptor and optical interconnect module.

[0040] Fig. 7 shows a two-piece pluggable fiber ferrule assembly with the adaptor 202 now mated to the ferrule 204. Mating of the adaptor 202 to the ferrule 204 results in the position and orientation of the adaptor 202 precisely registered with the alignment features of the ferrule 204. Fig. 7 shows a plurality of light paths 224. The light path 224 direction is shown as leaving the adaptor 222, but the light path 224 direction can be reversed so that light is propagating into the adaptor 202. In some examples, some light paths 224 may be directed into the adaptor 202 and some light paths 224 directed away from the adaptor 202 as shown in Fig. 7. In other examples, all the light paths 224 may be propagating away from the adaptor 202 or alternatively all the light paths 224 may be propagating into the adaptor 202. An interface region 226 between the adaptor 202 and ferrule 204 may be sealed, so that the light path between the ferrule 204 and adaptor 202 is isolated from the environment by a seal (not visible in Fig. 7). The seal may be made using an O-ring mounted in an O-ring groove fabricated in the first face of the adaptor 202 or the seal may be made using an adhesive or filler in the interface region 216. If the adaptor 202 is also sealed against its mating optical element that interfaces with the adaptor second face 216, the two-piece pluggable fiber ferrule assembly 200 may be used in a hostile environment, such as immersed in a liquid or in a saltwater spray.

[0041] Fig. 8 shows a cross-section view of a portion of the two-piece pluggable fiber ferrule assembly 200 shown in Figs. 6 and 7. Fig. 8 also shows representative light paths 224 in the assembly 200. Two light paths are shown, first light path 224a and second light path 224b. The ferrule 204 may secure an optical fiber 228. There may be a plurality of optical fibers 228 arranged in two rows, a first row 230 and a second row 232. Each optical fiber 228 may have a fiber end face 234 secured in the ferrule 204. Each optical fiber 228 may be said to terminate in the ferrule 204. Fig. 8 shows an example with two rows 230 and 232 of optical fibers 228, but more or fewer rows may be present. The ferrule 204 may be a PRIZM® MT ferrule, which is shown in Fig. 8, but the invention is not so limited. The PRIZM® MT ferrule has a plurality of lenses, which serve as optical power surfaces 236, on a coupling end face 208 that abuts the adaptor 202. The fiber end faces 234 are spaced away from the optical power surface 236 and abut a wall 240 internal to the ferrule 204. Each optical power surface 236 is arranged to collimate light emitted by a fiber end face 234 or focus collimated light directed at the optical power surface 236 into a fiber end face 234. Each optical power surface 236 is surrounded by air or something with a refractive index substantially equal to air, such as a vacuum or a different gas, to properly focus or collimate light. Alternatively, the curvature of the optical power surface 236 may be selected so that it has the correct optical power when surrounded by a low index liquid, solid, or gel, such as an adhesive or potting compound, to properly focus or collimate light. Whether the optical power surface 236 collimates or focuses depends on the propagation direction of light propagating through the adaptor 202 and ferrule 204. In the example shown, light in the first row 230 of optical fibers 228 is emitted by the optical fibers 228 and propagates in the first light path 224a. The optical power surface 236 collimates the light and the light propagates through the adaptor 202, emerging at the second face 216 of the adaptor 202. In the second light path 224b, collimated light is directed into the second row 232 of optical fibers 228 from the second face 216 through the adaptor 202 to an optical power surface 236 and from there into an optical fiber 228 in the second row 232. As noted previously, the interface region 226 between the adaptor 202 and ferrule 204 may be sealed to avoid contamination of the light paths 224 in the interface region 226.

[0042] The two-piece fiber ferrule assembly depicted in Fig. 8 has the optical power surface 236 on an internal surface of the two-piece pluggable fiber ferrule assembly 200. In Fig. 8 it is on the coupling end face 208 of the ferrule 204. Since the optical power surface 236 is internal to the two-piece fiber ferrule assembly 200, the optical power surface 236 may be sealed from the environment and hence unaffected by immersing the two-piece fiber ferrule assembly 200 in a liquid. If the optical power surface 236 was exposed, its optical properties may be altered by contact with the liquid. In this example, the adaptor 202 has no optical power surface, i.e. all the surfaces that transmit or reflect light are substantially flat so that they do not deliberately alter the wavefront curvature of light propagating in the optical paths 224. [0043] Fig. 9 shows an exploded view of a two-piece pluggable fiber ferrule assembly 300 according to another example. The arrangement of this two-piece pluggable fiber ferrule assembly 300 is similar to that depicted in Figs. 6-8 with use of a different type of ferrule. Instead of using a PRIZM® MT, the two-piece pluggable fiber ferrule 300 uses a MT ferrule 304. The MT ferrule 304 has a coupling end face 308, which is configured to receive or accept light and couple light into or out of optical fibers 328 mounted in the ferrule 304. The coupling end face 308 may have an alignment feature 306, such as a guide hole or guide pin. There may be two alignment features 306 as shown in Fig. 9. The coupling end face alignment features 306 are registered with respect to the position of the optical fibers 328 in the ferrule 304. The ferrule 304 permanently secures a position and orientation of the plurality of optical fibers 328 and their respective end faces relative to the alignment features 306.

[0044] An adaptor 302 may have a first alignment feature 318 on a first face 314, which is arranged to mate with the alignment feature 306 on the coupling end face 308 of the ferrule 304. For example, the first alignment feature 318 may be a guide pin or guide hole arranged to mate with a guide hole or guide pin in the coupling end face 308 of the ferrule 304. The first alignment feature 318 may be two guide pins or guide holes arranged to mate with guide holes or guide pins in the ferrule 304, such as the guide pins or guide holes of the MT ferrule 304. The adaptor 302 may include a second face 316, which is arranged to mate with an optical element, such as an optical interconnect module. The second face 316 may include a second alignment feature 320, such as one or more guide holes, guide pins, or grooves (grooves shown in Fig. 9). Light traveling in the adaptor 302 may be redirected by reflection off a reflective surface 322. The reflective surface 322 may use total internal reflection or the reflective surface 322 may be coated, for example, with a metal or dielectric reflective coating. By coating the reflective surface 322, the reflective properties of the reflective surface 322 are unaffected by the environment contacting the reflective surface 322. This contrasts with a reflective surface using total internal reflection, which may have its reflective properties spoiled if it is contacting a liquid. The reflective surface 322 may redirect light traveling in the adaptor 302 by an angle close to or equal to 90°. For example, an angle between 75° and 100°. The reflective surface 322 may redirect light at other angles outside this range. A coated reflective surface can redirect light at any desired angle, since the angle of incidence can be smaller than a critical angle for total internal reflection. Also, some adaptors may have more than one reflective surface.

[0045] Light can propagate through the adaptor 302 in two directions. In a first direction, light propagates from a fiber end face in the ferrule 304 into the first face 314 of the adaptor 302. From the adaptor first face 314, the light propagates to the reflective surface 322, where it is redirected and from there propagates out through the second face 316. Light can also propagate in a second opposed direction, that is from the adaptor second face 316, to the reflective surface 322, then through the adaptor first face 314 and hence into a fiber end face located in the ferrule 304.

[0046] The adaptor 302 has at least two optical surfaces, denoted as the first face 314 and the second face 316, where light can enter or exit the adaptor 302. The adaptor 302 also has at least two alignment features, a first alignment feature 318 and a second alignment feature 320, arranged to register a mating optical element to the first face 314 and second face 316, respectively. The adaptor 302 can additionally have other optical surfaces that redirect light within the adaptor 302. The adaptor depicted in Fig. 9 has three optical surfaces, the first face 314, the second face 316, and the reflective surface 322. The optical surfaces of the adaptor 302 are precisely registered relative to each other. Likewise, the first alignment feature 318 and second alignment feature 320 of the adaptor 302 are precisely registered relative to each other. The adaptor 302 may be rigid such that alignment between the optical surfaces and alignment features 318 and 320 is fixed at the time of adaptor fabrication. The position and direction of light paths entering or exiting the coupling end face of the ferrule 304 are precisely registered relative to the coupling end face alignment feature 306 and coupling end face surface. By mating the adaptor first face 314 with the coupling end face 308, the precise registration of the ferrule 304 is transferred to a precise registration of the light path position and direction relative to the first face 314 and first alignment feature 318 of the adaptor 302. The precise registration of the optical surfaces within the adaptor 302 enables the precise position and direction of the light paths on the adaptor second face 316 to be known relative to the adaptor second alignment feature 320.

[0047] The precise registration of the light paths position and direction on the second face 316 allows an optical element, such as an optical interconnect module (not shown in Fig. 9), to be mated with the adaptor second face 316. The optical interconnect module may have an alignment feature that is arranged to engage with the adaptor second alignment feature 320. An interface region between the second face 316 and an optical interconnect module may be sealed, so that environmental contaminants cannot reach the light paths between the adaptor and optical interconnect module.

[0048] Fig. 10 shows the two-piece pluggable fiber ferrule assembly 300 depicted in Fig. 9 with the adaptor 302 now mated to the ferrule 304. In some examples, some light paths 324 may be directed into the adaptor 302 and some light paths 324 directed away from the adaptor 302 as shown in Fig. 10. In other examples, all the light paths 324 may be propagating away from the adaptor 302 or alternatively all the light paths 324 may be propagating into the adaptor 302. An interface region 326 between the adaptor 302 and ferrule 304 may be sealed, so that the light paths 324 between the ferrule 304 and adaptor 302 are isolated from the environment. The seal may be made using an O-ring mounted in an Ciring groove fabricated in the first face 314 of the adaptor 302 (hidden in Fig. 10, see Fig. 9) or the seal may be made using a compliant adhesive or filler in the interface region 326. The adaptor 302 may also be sealed against a mating optical element (not shown in Fig. 10) which is arranged to mate with the second face 316 of the two-piece pluggable fiber ferrule assembly 300. Sealing this interface allows the two-piece pluggable fiber ferrule assembly 300 and mating optical element to be used in a hostile environment, such as immersed in a liquid or in a saltwater spray.

[0049] Fig. 11 shows a cross-section view of a portion of the two-piece pluggable fiber ferrule 300 assembly shown in Figs. 9 and 10. Fig. 11 also shows representative light paths 324 in the assembly 300. There may be two light paths 324a and 324b. The ferrule 304 has at least one row of optical fibers 328 terminating in the ferrule 304. Fig. 11 shows an example with two rows, a first row 330 of optical fibers 328 and a second row 332 of optical fibers 328, but more rows may be present. Fig. 11 shows the ferrule 304 being a MT ferrule, but the invention is not so limited. The ferrule 304 may have optical fiber 328 end faces that extend to the coupling end face 308 of the ferrule 304. The fiber end faces may protrude slightly from the coupling end face 308. In this example, the first face 314 of the adaptor 302 may have a plurality of optical power surfaces 336, such as a plurality of lenses. Each optical power surface is spaced apart from the ferrule coupling end face 308 by having a recessed region 340 in the first face 314 of the adaptor 302. The optical power surface 336 may be arranged to collimate light emitted by a fiber end face, or focus collimated light directed at the optical power surface 336 into a fiber end face. In the first light path 324a, light in the first row 330 of optical fibers 328 is emitted by the fibers 328. The optical power surface 336 collimates the light and the light propagates through the adaptor 302, emerging at the second face 316 of the adaptor 302. In the second light path 324b, collimated light is directed into the second row 332 of optical fibers 328 from the second face 316 through the adaptor 302 to an optical power surface 336 located in the recessed region 340 of the first face 314 of the adaptor 302 and from there into a fiber 328 in the second row 332. Each optical power surface 328 is surrounded by air or something with a similar refractive index, such as a vacuum or a different gas, in order to properly focus or collimate light. Alternatively, the curvature of the optical power surface 336 may be selected so that it has the correct optical power when surrounded by a low index liquid, solid, or gel, such as an adhesive or potting compound, to properly focus or collimate light. Each optical power surface 336 may be arranged in a light path 324 emanating from, or directed toward, an optical fiber 328. As noted previously, the interface region 326 between the adaptor 302 and ferrule 304 may be sealed to avoid contamination of the light paths 324 in the interface region 326.

[0050] The two-piece fiber ferrule assembly depicted in Fig. 11 has the optical power surface 336 on an internal surface of the two-piece pluggable fiber ferrule assembly 300. In Fig. 10, the optical power surfaces 336 are located in the recessed region 340 of the first face 314 of the adaptor 302. The optical power surface 336 may be a lens situated in the recessed region 340 of the adaptor 302. Each light path 324 may have an associated lens. Since the optical power surface 336 is internal to the two-piece fiber ferrule assembly 300, the optical power surface 336 may be sealed from the environment and hence unaffected by immersing the two-piece fiber ferrule assembly 300 in a liquid. If the optical power surface 336 was exposed, its optical properties may be altered by contact with the liquid.

[0051] It should be appreciated that the adapter can be permanently mated to a two- piece pluggable fiber ferrule assembly, or it may be detachably mated to a two-piece pluggable ferrule assembly. If the adaptor is permanently mated, the first face of the adaptor may be adhesively attached to the coupling end face of the ferrule. The same adhesive used to bond the adaptor and ferrule may be used to seal the light path in the two-piece pluggable fiber ferrule assembly. The adhesive may be distributed so that it surrounds, but does not intersect, the light paths in the two-piece pluggable fiber ferrule assembly. In this manner light propagation through the two-piece pluggable fiber ferrule assembly is not impacted by application of the adhesive.

[0052] An advantage a two-piece pluggable fiber ferrule assembly of the type described herein is that the cross-sectional area of a light path on the second face of the adaptor, which is arranged to either deliver or receive light from a mating optical element, is enlarged relative to the cross-section area of the light path in an optical fiber. Having an enlarged cross-sectional area, or equivalently an expanded beam size, relaxes the positional or translational alignment tolerance between the adaptor and mating optical element. Use of a collimated expanded beam trades positional sensitivity for rotational sensitivity. The relaxed positional tolerance may make the resultant optical system easier to manufacture and more tolerate of changes in environmental conditions, such as temperature. Having the optical beam collimated at the second face of the adaptor facilitates low loss optical coupling to the mating optical element.

[0053] The terms "upward," "upper," "up," "above," and derivatives thereof are used herein with reference to the upward direction. The terms "downward," "lower," "down," "below," and derivatives thereof are used herein with reference to the downward direction. Of course, it should be appreciated that the actual orientation of the optical interconnection system shown in Figs. 4 and 5 can vary during use, and that the terms upward and downward and their respective derivatives can be consistently used as described herein regardless of the orientation of the optical interconnection system and components thereof during use.

[0054] It should be appreciated that the illustrations and discussions of the embodiments shown in the figures are for exemplary purposes only and should not be construed as limiting the disclosure. One skilled in the art will appreciate that the present disclosure contemplates various embodiments. For example, rather than the optical power surface being a lens on the first face of the adaptor or the coupled end face of the ferrule, the optical power surface may be on the reflective surface. That is the reflective surface may be curved rather than a flat surface where the reflective surface intersects with each of the light paths. The optical power surface may be a parabolic surface formed in the reflective surface in the intersection regions. The two-piece fiber ferrule assembly may have two optical power surfaces, one internal to the assembly and one on an external surface of the assembly, such as the reflective surface. While the optical power surface has been generally described as a simple lens or curved reflective surface, an optical power surface is not so limited. For example, the optical power surface may be a Fresnel lens, a gradient refractive index (GRIN) lens, or may include diffractive surface features. Features other than those previously described may be included with the adaptor. The recessed region has been described as being on the first face of the adaptor adjacent the ferrule; however, in other examples the recessed region may be on the second face of the adaptor. These features include, but are not limited to, focusing or collimating the optical beam, attenuating the optical beam, picking off a fraction of the optical beam so that it can be monitored, splitting the optical beam in two or more beams, and/or shuffling the position of the optical beams in the adaptor. While the guide pins and holes have been described as round, it should be appreciated that the guide pins and holes can have any cross-sectional shape. Additionally, it should be understood that the concepts described above with the above-described embodiments may be employed alone or in combination with any of the other embodiments described above. It should be further appreciated that the various alternative embodiments described above with respect to one illustrated embodiment can apply to all embodiments as described herein, unless otherwise indicated.

Claims

What is claimed:

1. A two-piece pluggable fiber ferrule assembly comprising: an optical fiber cable having a plurality of optical fibers; a ferrule having an alignment feature, wherein the ferrule permanently secures the plurality of optical fibers in position relative to the alignment feature; and a rigid adaptor having a first alignment feature configured to mate with the alignment feature of the ferrule and having a second alignment feature configured to mate with an optical element.

2. The two-piece pluggable fiber ferrule assembly as recited in claim 1, wherein the adaptor is permanently mated to the ferrule.

3. The two-piece pluggable fiber ferrule assembly as recited in any one of the preceding claims, wherein the adaptor is detachably mated to the ferrule.

4. The two-piece pluggable fiber ferrule assembly as recited in any one of the preceding claims, wherein mating of the adaptor to the ferrule results in the position and orientation of the adaptor precisely registered with the alignment feature of the ferrule.

5. The two-piece pluggable fiber ferrule assembly as recited in any one of the preceding claims, wherein the ferrule alignment feature is a combination of a flat surface and at least one guide pin.

6. The two-piece pluggable fiber ferrule assembly as recited in claim 5, wherein the adaptor first alignment feature is a combination of a flat surface and at least one guide hole configured to accept the at least one guide pin of ferrule.

7. The two-piece pluggable fiber ferrule assembly as recited in claim 1 wherein the ferrule alignment feature is a combination of a flat surface and at least one guide hole.

8. The two-piece pluggable fiber ferrule assembly as recited in any one of claims 1 to 5, wherein the adaptor first alignment feature is a combination of a flat surface and at least one guide pin configured to be inserted into the at least one guide hole of the ferrule.

9. The two-piece pluggable fiber ferrule assembly as recited in any one of the preceding claims, wherein the optical element is an optical interconnect module.

10. The two-piece pluggable fiber ferrule assembly as recited in any one of the preceding claims, wherein the adaptor includes a reflective surface arranged to deflect a plurality of light paths extending between the plurality of optical fibers and the optical element.

11. The two-piece pluggable fiber ferrule assembly as recited in claim 10, wherein each of the plurality of light paths includes a section of collimated light.

12. The two-piece pluggable fiber ferrule assembly as recited in claim 11, wherein the ferrule includes a lens in each of the plurality of light paths.

13. The two-piece pluggable fiber ferrule assembly as recited in claim 11, wherein the adaptor includes a lens in each of the plurality of light paths.

14. The two-piece pluggable fiber ferrule assembly as recited in any one of claims 11 to 13, wherein the reflective surface is curved in each of the plurality of light paths.

15. The two-piece pluggable fiber ferrule assembly as recited in any one of claims 11 to 14, wherein the section of collimated light extends to a surface of the adaptor adjacent the optical element.

16. The two-piece pluggable fiber ferrule assembly as recited in any one of the preceding claims, wherein the plurality of optical fibers are arranged in a plurality of rows.

17. The two-piece pluggable fiber ferrule assembly as recited in claim 16, wherein the plurality of rows is two rows.

18. The two-piece pluggable fiber ferrule assembly as recited in any one of claims 3-17, further comprising a clip to secure the ferrule to the adaptor.

19. The two-piece pluggable fiber ferrule assembly as recited in any one of the preceding claims, wherein characteristics of the ferrule are defined by a multi-source supply agreement.

20. The two-piece pluggable fiber ferrule assembly as recited in claim 19, wherein the ferrule is a MT ferrule or PRIZM® MT ferrule.

21. The two-piece pluggable fiber ferrule assembly as recited in any one of the preceding claims, wherein an interface region between the ferrule and adaptor is sealed.

22. The two-piece pluggable fiber ferrule assembly as recited in any one of the previous claims, further comprising an optical power surface on an internal surface of the two-piece pluggable fiber ferrule assembly.

23. An optical interconnect module comprising: an optical engine mounted on a module substrate; a ferrule receptacle mounted on the module substrate; and the pluggable fiber ferrule assembly as recited in any one of the previous claims.

24. The optical interconnect module as recited in claim 23, wherein an interface between the optical engine and pluggable fiber ferrule is sealed.

25. The optical interconnect module as recited in any one of claims 23 to 24, wherein the two-piece pluggable fiber ferrule assembly mates with the optical interconnect module by inserting the two-piece pluggable fiber ferrule assembly into the ferrule receptacle in a direction substantially perpendicular to a major surface of the substrate.

26. A two-piece pluggable fiber ferrule assembly comprising: an optical fiber cable having a plurality of optical fibers; a ferrule permanently securing the plurality of optical fibers in position relative to an alignment feature of the ferrule; wherein the ferrule has a coupling end face arranged to couple light into or out of the plurality of optical fibers; and an adaptor having a first face mounted to the coupling end face of the ferrule and a second face arranged to couple light into or out of the plurality of optical fibers, wherein either the ferrule or the adaptor has an optical power surface between an end face of each fiber in the plurality of optical fibers and the second face of the adaptor.

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27. The two-piece pluggable fiber ferrule assembly as recited in claim 26 wherein the adaptor is permanently mated to the ferrule.

28. The two-piece pluggable fiber ferrule assembly as recited in claim 26 wherein the adaptor is detachably mated to the ferrule.

29. The two-piece pluggable fiber assembly as recited in any one of claims 26 to 28, wherein an interface region between the adaptor and ferrule is sealed.

30. The two-piece pluggable fiber ferrule assembly as recited in any one of claims 26 to 29, wherein the optical fibers are arranged in a plurality of rows.

31. The two-piece pluggable fiber ferrule assembly as recited in claim 30, wherein the plurality of rows is two rows.

32. The two-piece pluggable fiber ferrule assembly as recited in any one of claims 26 to 31, wherein the optical power surface is located on the coupling end face of the ferrule.

33. The two-piece pluggable fiber ferrule assembly as recited in any one of claims 26 to 31, wherein the optical power surface is located on the first face of the adaptor.

34. The two-piece pluggable fiber ferrule assembly as recited in any one of claims 26 to 33, wherein the optical power surface comprises a plurality of optical power surfaces, each optical power surface corresponding to one of the plurality of optical fibers.

35. The two-piece pluggable fiber ferrule assembly as recited in any one of claims 26 to 34, wherein the adaptor further comprises a reflective surface.

36. The two-piece pluggable fiber ferrule assembly as recited in any one of claims 26 to 32 and claim 34, wherein all surfaces of the adaptor that transmit or reflect light are substantially flat so that they do not deliberately alter a wavefront curvature of light propagating through the two-piece pluggable fiber ferrule.

37. The two-piece pluggable fiber ferrule assembly as recited in any one of claims 26 to 36, wherein the adaptor includes a recessed region.

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