WO2021148923A1

WO2021148923A1 - Optical ferrules

Info

Publication number: WO2021148923A1
Application number: PCT/IB2021/050335
Authority: WO
Inventors: Changbao Ma; Terry L. Smith
Original assignee: 3M Innovative Properties Company
Priority date: 2020-01-24
Filing date: 2021-01-18
Publication date: 2021-07-29

Abstract

An optical ferrule (200) includes a top major surface (10) and a bottom major surface (70) opposite the top major surface (10). The top major surface (10) has an attachment portion (20) for receiving and securing a plurality of optical waveguides (30). A light redirecting portion (60) receives along a first direction (51) the central light ray (50) transmitted by the optical waveguides (30) and redirecting the received central light ray (53) along a different second direction (52). When the optical ferrule (200) mates with a mating optical ferrule (300), the bottom major surface (70) makes physical contact or near physical contact with a corresponding surface of the mating optical ferrule (300) to define a contact or near contact interface (71) therebetween. An average gap defined between the optical ferrule (200) and the mating optical ferrule (300) in the near contact interface (71) is less than about 3 microns. The redirected central light ray (53) exits the optical ferrule (200) and enters the mating optical ferrule (300) through the contact or near contact interface (71).

Description

OPTICAL FERRULES

Technical Field

This disclosure relates generally to optical coupling devices such as optical ferrules.

Background

Optical communications are increasingly used in systems to achieve data communication with a greater bandwidth and/or lower electromagnetic interference as compared to electrical communications. In some systems, optical and electrical communication interconnections may be used. Optical fibers may be employed for optical input/output, and for some applications, optical fibers may be coupled to other optical fibers and/or system components by an optical connector. Optical connectors are used for optical communications in a variety of applications including telecommunications networks, local area networks, data center links, and internal links in computer devices. Optical connectors, including expanded beam optical connectors, can include optical ferrules having elements for receiving and securing optical waveguides, elements for affecting light from the optical waveguides, and features for aligning the optical ferrule to a mating optical ferrule.

Summary

Various aspects and embodiments described herein relate to optical connectors and optical ferrules.

Some aspects of the disclosure relate to an optical ferrule. The optical ferrule includes a top major surface including an attachment portion for receiving and securing a plurality of optical waveguides. The top major surface further includes an input surface portion for receiving and transmitting a central light ray from an optical waveguide received and secured in the attachment portion. A light redirecting portion on the top major surface receives, along a first direction, the central light ray transmitted by the light input surface portion, and redirects the received central light ray along a different second direction. The optical ferrule includes a bottom major surface opposite the top major surface. When the optical ferrule mates with a mating optical ferrule, the bottom major surface of the optical ferrule makes physical contact or near physical contact with a corresponding surface of the mating optical ferrule to define a contact or near contact interface therebetween. An average gap defined between the optical ferrule and the mating optical ferrule in the near physical contact interface is less than about 3 microns. The redirected central light ray exits the optical ferrule and enters the mating optical ferrule through the contact or near contact interface.

Some other aspects of the disclosure relate to an optical ferrule including a plurality of grooves for receiving and securing a plurality of optical fibers. A light redirecting portion of the optical ferrule receives along a first direction a central light ray from each optical fiber in the plurality of optical fibers and redirects the received central light ray along a different second direction. The optical ferrule includes a plurality of distinct spaced apart raised platforms. Each raised platform corresponds to a different groove and includes a compliant top surface curved in two orthogonal directions. When the optical ferrule mates with a mating optical ferrule the compliant top surface of each raised platform reversibly deforms upon physical contact with a corresponding surface of the mating optical ferrule to define a contact or near contact interface between the top and the corresponding surfaces. The redirected central light ray from the optical waveguide received and secured in the groove corresponding to the raised platform exits the optical ferrule and enters the mating optical ferrule through the contact or near contact interface between the raised platform and the corresponding surface of the mating optical ferrule.

Some other aspects of the disclosure relate to an optical ferrule assembly including an optical ferrule and a plurality of optical waveguides received and secured in the attachment portion of the optical ferrule.

These and other aspects of the present application will be apparent from the detailed description below. In no event, however, should the above summaries be construed as limitations on the claimed subject matter, which subject matter is defined solely by the attached claims.

Brief Description of Drawings

The various aspects of the disclosure will be discussed in greater detail with reference to the accompanying figures where,

FIGS. 1-3 schematically show different views of an optical ferrule according to certain embodiments;

FIG. 4 schematically shows an optical ferrule assembly according to an aspect of the disclosure;

FIG. 5 schematically shows an optical ferrule mated with a mating optical ferrule according to certain aspects of the disclosure

FIG. 6 schematically shows a cross sectional view of an optical ferrule mated with a mating optical ferrule according to certain aspects of the disclosure;

FIG. 7 schematically shows the light redirecting portion of the optical ferrule with reflective coating according to some aspects of the disclosure;

FIG. 8 schematically shows a bottom major surface of the optical ferrule according to some embodiments of the disclosure;

FIG. 9 schematically shows a cross sectional view of the optical ferrules mated with each other showing the physical/near physical contact between the two mating optical ferrules; and

FIGS. 10-11 schematically show different cross sectional views of the optical ferrules according to other aspects of the disclosure;

The figures are not necessarily to scale. Like numbers used in the figures refer to like components. However, it will be understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labelled with the same number.

Detailed Description of Illustrative embodiments

In the following description, reference is made to the accompanying drawings that form a part hereof and in which various embodiments are shown by way of illustration. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the present description. The following detailed description, therefore, is not to be taken in a limiting sense.

Optical connectors can be used to connect multi-fiber ribbon cables, for example. A ribbon cable typically includes a plurality of optical fibers organized and molded side by side in a plastic ribbon. An optical connector may include an optical ferrule configured to receive optical fibers from a ribbon cable. Two mating optical ferrules with the same fiber spacing may be placed in an abutting relationship so that the ends of the fibers of the respective ferrules are substantially co-axially aligned with one another, thereby forming a multi-fiber connection. Optical connectors described herein include one or more optical cable assemblies disposed in a housing. The optical cable assemblies may include one waveguide or arrays of multiple parallel waveguides (typically 4, 8 or 12 or more parallel waveguides) attached to one or more optical ferrules.

Expanded optical beams may be used in connectors to provide an optical connection that is less sensitive to dust and other forms of contamination so that alignment tolerances may be relaxed. Generally, an expanded beam is a beam that is larger in diameter than the core of an associated optical waveguide (usually an optical fiber, e.g., a multi -mode fiber for a multi -mode communication system). The connector is generally considered an expanded beam connector if there is an expanded beam at a connection point. The expanded beam is typically obtained by diverging a light beam from a source or optical fiber. In many cases, the diverging beam is processed by optical elements such as a lens or mirror into an expanded beam that is approximately collimated. The expanded beam is then received by focusing of the beam via another lens or mirror.

Optical ferrules include an optical window, e.g., a recessed optical window, on a side of a mating portion opposite the light redirecting portion. The optical window may be coated with an antireflective coating to avoid reflecting light propagating between the ferrules. The output windows of the optical ferrule and the mating optical ferrule through which light propagates do not physically contact each other for various reasons, for instance, to eliminate scratches on the lens or mirrors of the ferrules. In other words, there exists a gap (in the order of tens of microns) between the two output windows of the paired ferrule. Dust, moisture, and in some cases bubbles, if the optical connectors are immersed in bubbling liquid, may get trapped in this gap and may create undesirable results, which could compromise the optical performance of the connectors.

In some embodiments of the present disclosure, optical ferrules include features that eliminate, or substantially minimize, the gap between the output windows when the optical ferrules are mated with each other.

An optical ferrule (200) according to some embodiments is illustrated in FIGS. 1 to 3. The optical ferrule (200) is configured to mate with a mating optical ferrule as will be explained later. In some aspects, the optical ferrule (200) may have a unitary construction. In other aspects, the optical ferrule may be a ferrule that includes pieces formed separately and adhered or otherwise fastened together. The ferrule may be made from any suitable materials including polymers or ceramics. The ferrule may include one or more elements that guide or help guide the ferrule and a mating ferrule into alignment when the two ferrules are mated. In some aspects, the optical ferrule and/or the mating optical ferrule may be hermaphroditic.

In some embodiments, an optical connector may include a housing and the optical ferrules may be assembled to the housing. The housing may function to prevent dirt from interfering with optical connections, for example. The housing may provide, in some instances, retention force to maintain the ferrules in positive contact, as well as a latching and release mechanism formating and de-mating an optical connector. In addition, the housing can protect an optical ferrule from outputting stray light that can be a safety hazard to those nearby. In some embodiments, the housing may have a latching mechanism to prevent its accidental opening. In some embodiments, the housing may have a door mechanism that may be opened by the action of mating two connectors. The housing can have any suitable configuration for holding and securing the optical ferrule and for mating the optical connector to the mating optical connector.

In some aspects as illustrated in FIGS. 1-3, the optical ferrule (200) may include a plurality of grooves (21) for receiving and securing a plurality of optical waveguides (30). For instance, a top major surface (10) of the ferrule (200) may include an attachment portion (20) for receiving and securing a plurality of optical waveguides (30). The attachment portion (20) may include the plurality of grooves (21), substantially parallel to each other, for receiving and securing the plurality of optical waveguides (30). Each optical waveguide (30) may be received and secured in a different groove. The optical waveguides (30) according to some embodiments may be optical fibers. At the point of attachment, the fiber buffer coating and protective jacket, if any, of the optical fibers (30) are stripped away to allow only the bare optical fibers to lie aligned and permanently secured to the grooves in the attachment portion (20).

Fig. 4 shows an optical ferrule assembly (400) including an optical ferrule according to one or more embodiments described in this disclosure and a plurality of optical waveguides (30) received and secured in the attachment portion of the optical ferrule.

In some embodiments, the plurality of optical waveguides (30) may form a waveguide array of an optical cable . The term optical waveguide is used herein to refer to an optical element that propagates signal light. An optical waveguide may have at least one core with a cladding, wherein the core and cladding are configured to propagate light, e.g., by total internal reflection. An optical waveguide may be, for example, a single or multi-mode waveguide, a single core optical fiber, a multi-core optical fiber, a polymeric waveguide, or planar waveguides disposed on a substrate. A waveguide may have any suitable cross sectional shape, e.g., circular, square, rectangular etc. The individual waveguides in the waveguide array may be optical fibers made of glass with a protective buffer coating. Multiple parallel waveguides of a waveguide array may be enclosed by a jacket.

The top major surface (10) of the optical ferrule may include an input surface portion (40) for receiving and transmitting a central light ray (50) from an optical waveguide (30) received and secured in the attachment portion (20), as best shown in FIGS. 3 and 6. The optical ferrule includes a light redirecting portion (60), which, in some aspects, is provided on the top major surface (10) of the ferrule. The light redirecting portion (60) receives the central light ray (50) from each optical fiber in the plurality of optical fibers along a first direction (51) and redirects the received central light ray, as a redirected central light ray (53), along a different second direction (52). In some aspects, the light redirecting portion (60) may be configured to change the direction of light (50) received from the optical waveguide (30) received and secured in the attachment portion (20) by at least 45 degrees, or at least 60 degrees, or, in some cases, about 90 degrees.

In some embodiments, the optical ferrule (200) and the mating optical ferrule (300) may each include an array of light redirecting elements in the light redirecting portion (60), at least one for each optical waveguide (30). The exit ends of the optical waveguides (30) received and secured in the grooves (21) of the attachment portion (20) may be situated so as to be able to direct the central light ray (50) emanating from each optical waveguide (30) into the input side or face of a corresponding light redirecting element in the light redirecting portion of the mating ferrule (300). For example, in various embodiments, each light redirecting element in the light redirecting portion (60) has one or more of a prism, a lens, and a reflecting surface, such as a mirror or the like, to collimate light.

In some other aspects, the light redirecting portion (60) redirects the central light ray (50) primarily by total internal reflection (TIR). In some embodiments, the light redirecting elements in the light redirecting portion (60) may include a reflective coating, for example, or otherwise be made reflective. For instance, as illustrated in FIG. 7, the light redirecting portion (60) may include a coating (61) including at least one layer (6 la-6 Id) of at least one of a metal and a dielectric material. The coating may be configured to reflect and redirect at least 80% of the central light ray incident thereon. In some aspects, the coating (61) may be configured to reflect and redirect at least 90%, or, at least > 95% of the central light ray incident thereon. The reflective metal layer coating may be made of gold, silver, aluminum, etc.

As shown in Fig. 2, the optical ferrule (200) includes a bottom major surface (70) opposite the top major surface (10). In some embodiments, as best seen in Figs. 5 and 6, when the optical ferrule (200) mates with a mating optical ferrule (300), the bottom major surface (70) of the optical ferrule makes physical contact or near physical contact with a corresponding surface (310) of the mating optical ferrule (300) to define a contact or near contact interface (71) therebetween. The redirected central light ray (53) exits the optical ferrule (200) and enters the mating optical ferrule (300) through the contact or near contact interface (71). In the illustrated embodiment, when a plurality of optical waveguides (30) are received and secured in the attachment portion (20), and the optical ferrule (200) mates with the mating optical ferrule (300), a central light ray (50) from each optical waveguide, after entering the optical ferrule (200) through the input surface portion (40) and being redirected by the light redirecting portion (60), exits the optical ferrule (200) and enters the mating optical ferrule (300) through the contact or near contact interface.

In some embodiments, an average gap defined between the optical ferrule (200) and the mating optical ferrule (300) in the near contact interface (71) may be less than about 3 microns, or less than about 2 microns, or less than about 1 micron.

In some embodiments, as best illustrated in FIGS. 6 and 9, when the optical ferrule (200) mates with the mating optical ferrule (300), the bottom major surface (70) of the optical ferrule (200) makes physical or near physical contact with the corresponding surface (310) of the mating optical ferrule (300) to define a plurality of distinct spaced apart contact or near contact interfaces (7G) therebetween. When a plurality of optical waveguides (30) are received and secured in the attachment portion, a central light ray (50) from each optical waveguide enters the optical ferrule through the input surface portion (40) and is redirected by the light redirecting portion (60). The redirected central light ray (53, 53’) exits the optical ferrule (200) and enters the mating optical ferrule (300) through a corresponding different contact or near contact interface (7G).

In some embodiments, the optical ferrule includes a plurality of distinct spaced apart raised platforms (72). For instance, the plurality of distinct spaced apart raised platforms (72) may be formed on the bottom major surface (70) of the optical ferrule. Each raised platform (72) corresponds to a different groove in the plurality of grooves (21). In some aspects, each raised platform (72) may include a corresponding different contact or near contact interface (7G) in the plurality of contact or near contact interfaces. In some aspects, each raised platform (72) may include a compliant top surface (73). When the optical ferrule (200) mates with the mating optical ferrule (300), the compliant top surface (73) of each raised platform (72) reversibly deforms upon physical contact with the corresponding surface (310) of the mating optical ferrule (300). The deformed compliant top surface (73) of each raised platform (72) defines a contact or near contact interface (7G) between the top and the corresponding surfaces of the ferrules.

In some aspects, the reversibly deformed top surface includes a corresponding different contact or near contact interface (7 G) in the plurality of contact or near contact interfaces. The redirected central light ray (53’) from the optical waveguide (30) received and secured in the groove (21) corresponding to the raised platform (72) exits the optical ferrule (200) and enters the mating optical ferrule (300) through the contact or near contact interface (7 G) between the raised platform (72) and the corresponding surface (310) of the mating optical ferrule.

In some aspects, the raised platforms (72), or the compliant top surface (73) of each raised platform, may include any reversibly deformable material, such as elastic materials, e.g., silicone, rubber, etc. The material may be chosen to have good transparency in the working wavelength bands.

In some embodiments, the compliant top surface (73) of each raised platform (72) in the optical ferrule may be curved in two orthogonal directions (x, y), as best shown in Figs. 10 and 11. The compliant top surface curved in two orthogonal directions (x, y) provides a dome shape to the top surface (73). When the dome shaped top surface (73) of each raised platform (72) defines a contact or near contact interface (7 G) between the top and the corresponding surfaces of the ferrules, the dome shaped compliant top surface (73) in each raised platform (72) provides intimate physical contact over an area larger than the expanded beam spot with a diameter of tens of microns to more than 100 microns.

In other aspects, each raised platform (72) in the optical ferrule may be curved in one lateral direction, either in the x- or the y-direction. For instance, the raised platform may be of a cylindrical shape or alike, or a 2D array of domed dots, or a ID array of cylindrical strips, or the like.

In some other embodiments, a plurality of distinct spaced apart raised platforms may also be provided in the corresponding surface (310) of the mating optical ferrule (300). Each raised platform in the corresponding surface (310) may include a compliant top surface curved in two orthogonal directions (x, y). When the optical ferrule (200) mates with a mating optical ferrule (300), the compliant top surfaces of each raised platform of both of the optical ferrule (200) and mating optical ferrule (300) reversibly deforms upon physical contact with each other to define a contact or near contact interface (7G) between the compliant top surfaces. For example, each raised platform of the optical ferrule (200) and of the mating optical ferrule (300) can deform upon physical contact during mating such that when mated, the interface (7G) between the compliant top surfaces is a contact interface or a near contact interface. The redirected central light ray (53’) from the optical waveguide (30) received and secured in the groove corresponding to the raised platform of the optical ferrule (200) exits the optical ferrule (200) and enters the mating optical ferrule (300) through the contact or near contact interface (7G) between the raised platforms of the optical ferrule and mating optical ferrule. In other words, when the compliant domes of the ferrule and mating optical ferrule are pressed by appropriate forces through mating, the domes become flat and intimately contact each other. The mating mechanism may be appropriately designed to provide the normal force required to form the flat domes to make the physical or near physical contact surface.

In some aspects, the raised platforms (72) may be arranged in a row. The illustrated embodiment shows an example of an optical ferrule’s output window having a raised platform (72) with compliant top surface (73) corresponding to each groove having an optical fiber. The separation between each raised platform (72) cannot be in the optical path. The plurality of separated raised platforms (72) for optical fibers applies not only to protruded, but also to recessed and flushed output window. In some aspects, an average height of each raised platform (72) in the plurality of raised platforms may be greater than about 1 micron, or may be greater than 3 microns, or may be greater than 5 microns.

By making and maintaining the physical or near physical contact between the output windows of expanded beam optical ferrules, the paired ferrules become impermeable to moisture and dust. The optical ferrules according to these embodiments may be used for liquid cooling applications since bubbles cannot pass through the optical paths of the mated ferrules. Further, it may not be necessary to provide anti reflecting coating on the optical window since light can completely propagate through the physical or near physical contact between the optical ferrules.

Claims

1. An optical ferrule comprising: a top major surface comprising: an attachment portion for receiving and securing a plurality of optical waveguides; an input surface portion for receiving and transmitting a central light ray from an optical waveguide received and secured in the attachment portion; and a light redirecting portion for receiving along a first direction the central light ray transmitted by the light input surface portion and redirecting the received central light ray along a different second direction; and a bottom major surface opposite the top major surface, such that when the optical ferrule mates with a mating optical ferrule, the bottom major surface of the optical ferrule makes physical contact or near physical contact with a corresponding surface of the mating optical ferrule to define a contact or near contact interface therebetween, wherein an average gap defined between the optical ferrule and the mating optical ferrule in the near contact interface is less than about 3 microns, and wherein the redirected central light ray exits the optical ferrule and enters the mating optical ferrule through the contact or near contact interface.

2. The optical ferrule of claim 1, wherein when a plurality of optical waveguides are received and secured in the attachment portion and the optical ferrule mates with the mating optical ferrule, a central light ray from each optical waveguide exits the optical ferrule and enters the mating optical ferrule through the contact or near contact interface after the central light ray enters the optical ferrule through the input surface portion and is redirected by the light redirecting portion.

3. The optical ferrule of claim 1, wherein when the optical ferrule mates with the mating optical ferrule, the bottom major surface of the optical ferrule makes physical or near physical contact with the corresponding surface of the mating optical ferrule to define a plurality of distinct spaced apart contact or near contact interfaces therebetween, such that when a plurality of optical waveguides are received and secured in the attachment portion, a central light ray from each optical waveguide exits the optical ferrule and enters the mating optical ferrule through a corresponding different contact or near contact interface after the central light ray enters the optical ferrule through the input surface portion and is redirected by the light redirecting portion.

4. The optical ferrule of claim 3, wherein the bottom major surface comprises a plurality of distinct spaced apart raised platforms, each raised platform comprising a corresponding different contact or near contact interface in the plurality of contact or near contact interfaces.

5. The optical ferrule of claim 4, wherein each raised platform comprises a compliant top surface, such that when the optical ferrule mates with the mating optical ferrule, the compliant top surface of each raised platform reversibly deforms upon physical contact with the corresponding surface of the mating optical ferrule, the reversibly deformed top surface comprising a corresponding different contact or near contact interface in the plurality of contact or near contact interfaces.

6. The optical ferrule of claim 1, wherein the average gap defined between the optical ferrule and the mating optical ferrule in the near contact interface is less than about 1 micron.

7. The optical ferrule of claim 1, wherein the attachment portion comprises a plurality of substantially parallel grooves for receiving and securing the plurality of optical waveguides, wherein each optical waveguide is received and secured in a different groove.

8. An optical ferrule comprising: a plurality of grooves for receiving and securing a plurality of optical fibers; a light redirecting portion for receiving along a first direction a central light ray from each optical fiber in the plurality of optical fibers and redirecting the received central light ray along a different second direction; and a plurality of distinct spaced apart raised platforms, each raised platform corresponding to a different groove and comprising a compliant top surface curved in two orthogonal directions, such that when the optical ferrule mates with a mating optical ferrule, the compliant top surface of each raised platform reversibly deforms upon physical contact with a corresponding surface of the mating optical ferrule to define a contact or near contact interface between the top and the corresponding surfaces, wherein the redirected central light ray from the optical waveguide received and secured in the groove corresponding to the raised platform exits the optical ferrule and enters the mating optical ferrule through the contact or near contact interface between the raised platform and the corresponding surface of the mating optical ferrule.

9. The optical ferrule of claim 8, wherein the raised platforms are arranged in a row, and wherein an average height of each raised platform in the plurality of raised platforms is greater than about 1 micron.

10. The optical ferrule of claim 8, wherein the corresponding surface of the mating optical ferrule includes a plurality of distinct spaced apart raised platforms, each raised platform comprising a compliant top surface curved in two orthogonal directions, such that when the optical ferrule mates with a mating optical ferrule, the compliant top surfaces of each raised platform of both of the optical ferrule and mating optical ferrule reversibly deforms upon physical contact with each other to define a contact or near contact interface between the compliant top surfaces, wherein redirected central light ray from the optical waveguide received and secured in the groove corresponding to the raised platform of the optical ferrule exits the optical ferrule and enters the mating optical ferrule through the contact or near contact interface between the raised platforms of the optical ferrule and mating optical ferrule.