Lens plate for ferrules

A lens plate for fiber-optic ferrules has an inner side and an outer side. The inner side of the lens plate has a plurality of lenses on an inner base in an inner central recessed portion of the inner side, the inner side facing an end face of the fiber-optic ferrule. The plurality of lenses are configured to collimate an optical beam received thereupon. There is an outer base in an outer central recessed portion on the outer side and at least partially circumscribed by an outer face, the inner central recessed portion and the outer central recessed portion at least partially overlie one another. There is also a method for collimating an optical beam output from a fiber-optic ferrule end face using a lens plate.

BACKGROUND OF THE INVENTION

Managing optical output from a fiber-optic ferrule to precisely mate with another fiber-optic ferrule is necessary to prevent excessive divergence of the output beam or back reflection. One current technique to address beam divergence is to place lenses on the exterior of the ferrule end face. An example of such a technique is discussed in European Patent Pub. No. EP 3451033A1 and US Pat. Pub. No. 2018/0314012. These lenses are external in the sense that they modify an optical beam at an exit/entry point in the ferrule. Alternatively, lens surface negatives may be part of the mold itself, in which case lenses are molded integrally as part of the ferrule end face and are therefore, externally positioned on the ferrule end-face. See, e.g., U.S. Pat. Nos. 9,563,027 and 9,465,170 owned by the Applicant. As another alternative, molding may be carried out internal to the ferrule such that one or more prescriptioned lens surfaces are inside the ferrule, thereby creating internally molded lenses.

Certain internal lens designs for fiber-optic ferrules have been proposed, for example, in Applicant's US Pat. Pub. No. 2018/0239092 and Applicant's U.S. Pat. No. 9,983,365. The internal lenses in these designs are integrally molded.

Molding a lens as a separate, external part of the fiber-optic ferrule is prone to tolerance errors, where lens to fiber pitch is critical. The fact that the fiber-optic ferrule has an extra part—the external lens—increases manufacturing costs. Externally-lensed fiber-optic ferrules may be relatively more susceptible to moisture on the end face, and may be slightly harder to clean than non-lensed ferrules.

Currently, integrally molded lenses external to the ferrule (i.e., one-piece external lensed ferrule) are difficult to make in terms of lens to fiber alignment due to a moving lens core.

Further, as the number of optical fibers increases and the fiber size decreases, internally-lensed ferrules are challenging, but not impossible, either with individual molding pins due to a sharper lens or due to maintaining a rigid core structure.

Thus, there is a need to collimate and manage optical output from a fiber-optic ferrule to precisely mate with optical features of the mating fiber-optic ferrule, without excessive divergence of the output beam or back reflection or the other issues previously noted. The inventive lens plate according to the present invention provides one solution thereto.

SUMMARY OF THE INVENTION

The present invention is directed to lens plate for a fiber-optic ferrule that includes a main body having an outer side and an inner side, the outer side configured to mate with another lens plate or another ferrule, and the inner side having a plurality of lenses on an inner base in an inner central recessed portion of the inner side, the inner side facing an end face of the fiber-optic ferrule, wherein at least one of the plurality of lenses are configured to collimate an optical beam received thereupon.

In some embodiments, the inner side has an inner face at least partially circumscribing the inner central recessed portion.

In some embodiments, there is also a standoff member extending from the inner face for engagement with the end face of the fiber-optic ferrule.

In some embodiments, there is also an outer base in an outer central recessed portion on the outer side and at least partially circumscribed by an outer face, the inner central recessed portion and the outer central recessed portion at least partially overlie one another.

In other embodiments, each of the plurality of lenses have prescription and the prescription of at least one of the plurality of lenses is different from the other of the plurality of lenses.

In yet another aspect, the invention is directed to a combination of a ferrule and a lens plate that includes a fiber optic ferrule having an end face through which at least one optical beam passes, and a lens plate attached to the end face via a cured adhesive, the lens plate having an inner side facing the end face of the fiber-optic ferrule, the inner face having a plurality of collimating lenses on an inner base in an inner central recessed portion of the inner side.

In some embodiments, wherein the inner side has an inner face at least partially circumscribing the inner central recessed portion and further comprising a further comprising a standoff member extending from the inner face for engagement with the end face of the fiber-optic ferrule.

In other embodiments, the inner side has an inner face at least partially circumscribing the inner central recessed portion and further comprising a further comprising a standoff member extending from the inner face for engagement with the end face of the fiber-optic ferrule.

In yet another aspect, the present invention is directed to a method of collimating an optical beam output from a fiber-optic ferrule end face that includes applying an adhesive to at least one of a lens plate and the fiber-optic ferrule end face, the lens plate having an inner side having a plurality of lenses in an inner central recessed portion facing the fiber-optic ferrule end face, aligning the lens plate with ends of optical fibers at the fiber-optic ferrule end face, and curing the adhesive to attach the lens plate to the fiber-optic ferule end face, wherein the optical output beam is collimated upon exit from an outer side of the lens plate.

DETAILED DESCRIPTION OF THE INVENTION

FIGS.1-4illustrate one embodiment of a lens plate100according to the present invention. The lens plate100has a main body102having an outer side104(FIG.2) and an inner side106(FIG.1). The main body102has two guide pin openings108a,108b, but may have only one or even none. The outer side104is configured to mate with another lens plate (like the present invention as illustrated inFIGS.7-10) or with another fiber optic ferrule that may have a number configuration of lenses (such as internal, external, or none). The outer side104has an outer face110that circumscribes an outer central recessed portion112. The outer face110is illustrated as completely circumscribing the entirety of the outer central recessed portion112, but the outer face110may circumscribe less than the whole outer central recessed portion112. In fact, there could be multiple breaks in the outer face110and there may be portions of the outer face110that are not contiguous with other portions of the outer face100. The outer side104also has an outer base114that is contained within the outer central recessed portion112. As described in more detail below, the optical beams passing between fiber-optic ferrules will pass through the outer base114. The outer central recessed portion112may also include the two guide pin openings108a,108b, but the outer central recessed portion112may be smaller (and the outer face110be larger) so that the two guide pin openings108a,108bexit through the outer face110. The outer central recessed portion112is preferably about 50 microns—meaning that when two of the lens plates100are mated there is about 100 microns between the exit surfaces of each of the lens plates100. This distance allows for the application of an anti-reflective (AR) coating on the outer surface (or a part of the outer surface) and for the AR coating to work as desired.

The inner side106is configured to face and engage the fiber-optic ferrule. SeeFIGS.5-7. The inner side106has an inner face120that at least partially circumscribes an inner central recessed portion122of the inner side106. The inner face120may circumscribe less than the whole inner central recessed portion122. In fact, there could be multiple breaks in the inner face120and there may be portions of the inner face120that are not contiguous with other portions of the inner face120. Within the inner central recessed portion122is an inner base124that includes a plurality of lenses126. Each lens in the plurality of lenses126has a prescription. The prescription of each of the plurality of lenses126may be the same or there may be intentional predetermined variations between each of the lenses in the plurality of lenses126. However, the prescriptions generally cause the light beam passing through to be collimated between fiber optic ferrules. For example, as a light beam leaves an optical fiber, it is an expanding beam. As the light passes through one of the plurality of lenses, it is collimated until it encounters a lens on the other (mated) fiber-optic ferrule. The collimated light beam is then focused on the optical fiber in the mated fiber-optic ferrule. The same beam manipulation occurs regardless of the direction the beam takes as it travels between fiber-optic ferrules. The depth of the inner central recessed portion122of the inner side106will depend on the specific use, the optical fibers, the fiber optic ferrules and other considerations. However, the goal is to have a collimated beam leave the lenses for receipt on the other side of a fiber optic junction.

The inner side106may be associated with the fiber-optic ferrule end face with the inner face120. The inner face120may directly engage the fiber-optic ferrule end face or there may be standoff members130that extend from the inner face120to engage the fiber-optic ferrule end face. Naturally, the lens plate100would be adhered to the fiber-optic ferrule end face in any appropriate fashion, e.g., adhesives, welding, etc. The faces132of the standoff members130are more easily fabricated in a single plane than the entirety of the inner face120. There is also a lower likelihood of debris affecting the positioning of the lens plate100relative to the fiber-optic ferrule with the standoff members130. The standoff members130also allow a space for adhesives to fit between the fiber-optic ferrule end face and the inner face120. It should also be noted that there may be similar standoff members on the outer face of the lens plate100to engage another lens plate or with another fiber-optic ferrule end face.

There may be a tab140that is at the top edge of the lens plate100. The tab140may aid in the handling of the lens plate100before, during, or after attachment to the fiber-optic ferrule end face.

Attaching the lens plate100to a fiber optic ferrule200, and its end face202, will be described with reference toFIGS.5and6. The lens plate100may be attached to the end face202either with active or passive alignment. With active alignment, optical fibers are secured within the fiber optic ferrule200by known processes and procedures. An adhesive is then applied to the inner side106of the lens plate100. If there are standoff members130on the inner side106, the epoxy should fill the entire space between the inner side106and the end face202(it would therefore be the same as the length of the standoff members). The adhesive is preferably as epoxy with an index as close to the optical fiber core as possible. Alternatively, the adhesive may be applied to the end face202, or both the end face202and the inner side106. For active alignment, the lens plate100then can be moved around (e.g., for example by use of the tab104) until the lens to fiber core alignment is optimized. This is indicated by one or more of several methods of measuring the light, including measuring the beam properties of the beam exiting the lens plate, measuring the insertion loss of the light when coupled into a mating fiber optic ferrule, or measuring the back reflection that is coupled back into the optical fiber while a mirror is placed in front of the lens plate. SeeFIG.5and the arrows indicating the movement of the lens plate100relative to the fiber optic ferrule200, although such movement may be in other non-Cartesian or non-planar directions too (e.g., circular, elliptical, etc.) until the lens plate100is in an optimal positioning with respect to the end face202for maximum optical output for active alignment. The epoxy is then cured by UV light or in an appropriate oven. Subsequently, depending upon the application the setup ofFIGS.5and6is used in, the ferrule and the lens tab may be connectorized, i.e., one or more housings or other standard connector components added around the ferrule200. The lens plate100may or may not be included as part of any such connector housing.

Turning toFIG.6, the fiber optic ferrule200has guide pin openings204(one is illustrated and there is a second one on the opposite side of the fiber optic ferrule200). Epoxy is applied to the inner side106of the lens plate100. The lens plate100is aligned with the end face202with a guide pin (not shown) that can be inserted into the guide pin opening204and the guide pin openings108a,108b. The epoxy is then cured as noted above and the guide pins can then be removed. Additionally, other passive alignment structures could be used to align the lens plate100with the fiber optic ferrule200.

FIGS.7-10illustrate two mated fiber optic ferrules200with a lens plate100on each of the fiber optic ferrules200and the relationships of the components to one another.FIGS.8-10are cross section of the mated fiber optic ferrules200and show the spacing between the lens plates100. For example, arrow A points to the spacing between the fiber optic ferrule end face202and outer face110of the outer side104. This spacing is, as noted above, the same as the distance as the standoff members130extend from the inner face120. Arrow B points to the space between the outer bases114of the two lens plates100. This area between the outer bases114is where the optical beams are collimated as they pass between the fiber optic ferrules200.

An alternative embodiment of a lens plate100′ according to the present invention is illustrated inFIGS.11and12. In this embodiment, the lens plate100′ has an outer side104′ that includes an outer face110′ that circumscribes an outer central recessed portion112′. The outer face110′ is illustrated as completely circumscribing the entirety of the outer central recessed portion112′, but as noted above the outer face110′ may circumscribe less than the whole. The outer side104′ also has an outer base114′ that is contained within an outer central recessed portion112′. The outer base114′ may also have a plurality of collimating lens pedestals118′. The plurality of lens pedestals118′ may be extensions of the plurality of lenses126′. Alternatively, the plurality of lens pedestals118′ may be separately molded. The diameter the plurality of pedestals118′ may generally correspond to a diameter or cross-section of the plurality of lenses126′. The plurality of pedestals118′ may have a convex end surface that mates with opposing ones of the plurality of pedestals118′ in the clearance space. A height of the plurality of pedestals118′ may (measured from the outer base114′) determines whether the convex end face of the plurality of pedestals118′ will make contact with a mating pedestal from the opposing lens plate100′. This structure would eliminate the need for an AR coating on the outer base114′, but would require the outer base remain clean to have physical contact of these structures.