Data Center Interconnect for Optical Trunk Cables Having Miniature Multi-fiber Ferrules

An optical interconnect assembly includes a pre-terminated trunk cable assembly with a cable bundle having a plurality of optical fiber trunk cables terminating in ribbonized groups of optical fiber and a plurality of terminated small form factor fiber optic connectors for inclusion in a pulling sock attached to the plurality of optical fiber trunk cables. Each of the connectors has a push-pull stick with a pair of side latches on opposing sides of the central portion, a ferrule push, a housing configured to engage the push-pull stick and the ferrule push, a miniature multi-fiber ferrule, and a dust cap. The components are provided inside the pulling sock with at least one additional one of the plurality of terminated small form factor fiber optic connector identical to the first small form factor fiber optic connector.

BACKGROUND OF THE INVENTION

Interconnect systems for MT ferrules involving pre-installed MPO connector housings in an adapter are known. In such systems, the MT ferrule is pre-installed with a ferrule push on a group of optical fibers in a trunk cable of a cable bundle and resides inside a pulling sock of the trunk cable, along with several other MT ferrules. During installation at the adapter, the pulling sock is opened and the MT ferrules are pushed into the pre-populated adapter having the MPO connector housings. The pre-installed MT ferrule is part of a pre-terminated trunk cable on a reel, and a pulling grip assembly (also referred to as the “pulling sock”) is installed over an end portion of the pre-terminated trunk cable. The pulling sock covers all of several such MT ferrules, the ferrule push components, and dust caps associated with the MT ferrule. One such setup is described in Applicant's co-owned U.S. patent application Ser. No. 17/227,750 (published as US 2021/0325614, hereinafter “the '614 publication”), incorporated by reference herein in its entirety. The MPO connector, when fully assembled with the housing (which is instead pre-assembled with the adapter in the '614 publication above), is too big to fit inside the pulling sock. Hence, only the conventional MT ferrule with the associated ferrule push have thus far been utilized inside the pulling sock, while the adapter panel with adapters is pre-populated separately with the MPO housing components (that only accept the terminated MT ferrules from the pulling sock). To complete the interconnect, the conventional MT ferrules are pulled out of the pulling sock, and the respective ferrule push is used to push the MT ferrule into the pre-assembled MPO housing at the adapters.

However, interconnect components are getting smaller to address higher spatial density of connectors in data centers, and also to accommodate higher bandwidth requirements. To this end a miniature MT ferrule, referred to as the TMT ferrule, has been introduced by the Applicant, and disclosed in Applicant's WIPO Publication No. WO 2021/217050 (“the '050 publication”), incorporated by reference herein in its entirety. The TMT ferrule has a significantly smaller footprint compared to the MT ferrule to meet industry small form factor standards and multi-source agreements (MSAs), such as QSFP-DD. The TMT ferrule is also referred to as a miniature multi-fiber ferrule since it is significantly smaller than the conventional MT-ferrule and has typical dimensions of 1.25 mm height, 4 mm length (between the front end and the rear end), and a width of 6.4 mm side-to-side. The associated housing for the TMT ferrule is also smaller than a comparable MPO housing per such standards. Once assembly with the TMT ferrule and associated housing is complete, the resulting combination is referred to as the MMC connector.

With smaller fiber optic connector footprints being increasingly adopted, there is a desire to have the TMT ferrule be included inside the pulling sock, while at the same time, utilizing the smaller size of the TMT ferrule housing to have the whole MMC connector inside the trunk cable. As a result, the pulling sock needs to be opened and the MMC connector that is pulled out can then be directly inserted into an adapter. To further increase the packing density of components inside the pulling sock, it is also desired that only the miniature multi-fiber ferrule and the ferrule push be included inside the pulling sock (with a smaller ferrule dust cap) during manufacture of the pre-terminated trunk assembly inside a cable bundle on a reel.

SUMMARY OF THE INVENTION

According to one aspect, the present invention is directed to a cable bundle attached to an optical fiber trunk cable having ribbonized optical fibers that includes a plurality of terminated small form factor fiber optic connectors for inclusion in a pulling sock attached to the optical fiber trunk cable, each small form factor fiber optic connector includes a push-pull stick with a rear portion, a central portion and a forward extension extending away from the central portion and the rear portion, wherein the push-pull stick further includes a pair of side latches on opposing sides of the central portion, the side latches also extending forward and away from the central portion and the rear portion, a ferrule push positioned underneath the forward extension of the push-pull stick and at least partially between the side latches, there being a space to receive the ferrule push between the side latches of the push-pull stick, a housing configured to engage the two side latches of the push-pull stick and the at least one projection from the ferrule push, a miniature multi-fiber ferrule configured to support at least two optical fibers of the ribbonized optical fibers and engaged to a front portion of the housing, the miniature multi-fiber ferrule engageable directly or indirectly to a front surface of the ferrule push, wherein the miniature multi-fiber ferrule has an end face that is outside the housing when the miniature multi-fiber ferrule is seated inside the housing, and a dust cap engaged to the housing from a front end of the housing, the end face of the miniature multi-fiber ferrule being fully covered by the dust cap, wherein the dust cap, the housing, the miniature multi-fiber ferrule with the at least two optical fibers, the ferrule push, and the push-pull stick of a first of the plurality of terminated small form factor fiber optic connectors are provided inside the pulling sock with at least one additional one of the plurality of terminated small form factor fiber optic connector identical to the first small form factor fiber optic connector.

In some embodiments, there is also an adapter panel having a plurality of adapters, the plurality of adapters are each shorter than 5 mm.

In some embodiments, the at least a portion of a rear end of the ferrule push extends underneath the rear end of the push-pull stick.

In some embodiments, the ferrule push has at least one projection with a latch at a front portion thereof.

In some embodiments, the dust cap has an opening for a polarity key on the push-pull stick.

In some embodiments, the ferrule push has a non-circular opening to receive the at least two optical fibers therethrough.

In some embodiments, the ferrule push has a circular opening to receive the at least two optical fibers therethrough.

In some embodiments, the rear portion of the push-pull stick is an elongated projection parallel to and not engaging the at least two optical fibers.

In some embodiments, the ferrule push extends rearwardly of all other components for each of the plurality of terminated small form factor fiber optic connectors to allow a user to push and pull on one or more of the plurality of terminated small form factor fiber optic connectors.

In another aspect, the present invention is directed to an optical cable bundle that includes a plurality of fiber optic connectors, each of the plurality of fiber optic connectors further includes a miniature multi-fiber ferrule having respective ribbonized optical fibers terminated therein, the miniature multi-fiber ferrule has dimensions smaller than a standard MT ferrule, a ferrule push associated with the miniature multi-fiber ferrule and having an opening for the respective ribbonized optical fibers, the ferrule push being loosely positioned rearward of miniature multi-fiber ferrule, a ferrule dust cap engaged to the ferrule push and covering an end face of the miniature multi-fiber ferrule, and a pulling sock for retaining the plurality of fiber optic connectors.

In some embodiments, the miniature multi-fiber ferrule in each of the plurality of fiber optic connectors are TMT ferrules.

In some embodiments, there is also a push-pull stick with a rear portion, a central portion and a forward extension extending away from the central portion and the rear portion, wherein the push-pull stick further includes a pair of side latches on opposing sides of the central portion, the side latches also extending forward and away from the central portion and the rear portion.

In another aspect, the present invention is directed to an optical cable bundle that includes a plurality of fiber optic connectors, each of the plurality of fiber optic connectors further comprising a miniature multi-fiber ferrule having respective ribbonized optical fibers terminated therein, the miniature multi-fiber ferrule has dimensions smaller than a standard MT ferrule, a ferrule push associated with the miniature multi-fiber ferrule and having an opening for the respective ribbonized optical fibers, the ferrule push being loosely positioned rearward of miniature multi-fiber ferrule, a ferrule dust cap engaged to the ferrule push and covering an end face of the miniature multi-fiber ferrule, and a boot with a rear portion surrounding at least a portion of the ferrule push, a central portion and a forward extension extending away from the central portion and the rear portion, wherein the boot further includes a pair of side latches on opposing sides of the central portion, the side latches also extending forward and away from the central portion and the rear portion; and a pulling sock for retaining the miniature multi-fiber ferrule, the ferrule push and the ferrule dust cap.

DETAILED DESCRIPTION OF THE INVENTION

Applicant notes that the term “front” or “forward” as used herein means that direction where the fiber optic connectors100would meet with another fiber-optic connector or device or mating ferrules, while the term “rear” or “rearward” is used to mean the direction from which the optical fibers enter into the fiber optic connectors100. Each of the components will therefore have a front and rear, and the two respective fronts or forward portions of opposing ferrules, for example, would engage one another. Thus, for example, inFIG.1, the “front” of the fiber-optic connectors100is on the left side and “forward” is to the left and out of the page. “Rearward” or “rear” is that part of the fiber-optic connectors100that is on the right side of the page and “rearward” and “backward” is toward the right and into the page.

Illustrated inFIGS.1-8is one example of a small form factor fiber optic connector100(connector100) that, along with the pulling sock (pulling plug/grip)208makes up a cable bundle200, which in turn is attached to an optical fiber trunk cable202on a reel204according to one embodiment of the present invention. SeeFIGS.9and11.

As noted above, the optical fiber trunk cable202has a plurality of optical fibers206(see, e.g.FIG.1) and there are a plurality of small form factor fiber optic connectors100that are connected to the plurality of optical fibers206of the optical fiber trunk cable202. In this way, a larger number of connectors100can be installed faster, easier, and with fewer complications normally associated with such installations.

The connectors100to be used with the cable bundle200according to the present invention have a push-pull stick102, a ferrule push104, a housing106, a miniature multi-fiber ferrule108, and a dust cap110(also referred to herein as “ferrule dust cap110”). There may be other components of the connector100that are not shown here but may include a pin keeper or spacer, a spring to bias the miniature multi-fiber ferrule108, etc. See alsoFIG.10. The details of each of these components will now be discussed with particular reference toFIG.6, but alsoFIGS.1-8.

The push-pull stick102has a rear portion114, a central portion116and a forward extension118extending away from the central portion116and the rear portion114. The rear portion114of the push-pull stick102is an elongated projection parallel to but does not engage the optical fibers206. SeeFIGS.1and7.

The push-pull stick102further includes a pair of side latches120on opposing sides of the central portion116(seeFIGS.6and8). As explained in more detail below, the pair of side latches120engage an opening in the housing106. The pair of side latches120also extend forward and away from the central portion116and the rear portion114. The front122of each of the pair of side latches120has a chamfered surface124that engages the housing106as the push-pull stick102is mated to the housing106. The pair of side latches120are urged toward each other when making contact with the housing106and when the pair of side latches120is sufficiently inserted into the housing106, the pair of side latches120return to their normal configuration with the side latches120engaging openings170in the housing106. As will be recognized fromFIG.6, the mating of the push-pull stick102with the housing106retains the other elements of the connectors100(e.g., the ferrule push104and the miniature multi-fiber ferrule108) therein.

Preferably the push-pull stick102also has two downwardly extending tabs126in the central portion116to engage a portion of the housing106and act as a stop surface. The two downwardly extending tabs126will engage a front surface of the housing106if the push-pull stick102is pushed too far into the housing106and past the openings170. The pair of side latches120may be attached to or formed integrally with the two downwardly extending tabs126in the central portion116of the push-pull stick102. SeeFIGS.6and8, for example. Alternatively, the pair of side latches120may be separately attached to the tabs126.

The push-pull stick102has features128that allow for the push-pull stick102to movably engage the housing106. The features128are a dove-tail or undercut feature of the forward extension118that engages and slides in a groove130on the housing106. SeeFIGS.6and8. The forward extension118of the push-pull stick102also has a latch mechanism132that allows the connector100to be secured within an adapter300that is disposed within an adapter panel302or some other type of appropriate receptacle. See, e.g.,FIG.12. The latch mechanism132is disposed mostly under the forward extension118but extends rearwardly towards the central portion116. The latch mechanism132has a projection134that rises through an opening136in the forward extension118to engage the adapter300. Thus, pulling on the push-pull stick102moves the latch mechanism132downward into the push-pull stick102and disengages it from the adapter300, releasing the connector100. Pushing on the push-pull stick102pushes the connector100into the adapter300or other receptacle and the projection134is pushed downward as the connector100is inserted into the receptacle. Once the connector is fully inserted, the projection134rises back up and engages a structure on the receptacle thereby allowing the connector100to be locked into the adapter300.

In one aspect of this disclosure, the housing106, the latch mechanism,132, and the push-pull stick102are pre-installed on the adapter300to save space in a pulling sock208. That is the pulling sock208will then only include several of the miniature multi-fiber ferrule108terminated with the optical fibers206, the ferrule push104, and the dust cap110. The pin clamp (e.g., pin clamp412) may also be included inside the pulling sock208. After pulling the combination of the fiber ferrule108terminated with the optical fibers206, the ferrule push104, and the dust cap110from the pulling grip208, these may be installed into the adapter300that is pre-populated with the housing106, the latch mechanism132, and the push-pull stick102. The adapter300is provided on the adapter panel302having a plurality of adapters similar to the adapter300, each of the plurality of adapters300are shorter than 5 mm.

The connector100may also include a ferrule push104positioned underneath the forward extension108of the push-pull stick102and at least partially between the pair of side latches120. Due to the separation of the pair of side latches120, there is a space122to receive the ferrule push104between the pair of side latches120of the push-pull stick102.

The ferrule push104has a main body140with a central opening142that continues along the main body140internally from a front end144to a rear end146of the main body140. SeeFIGS.6and7. The rear end146is generally rectangular but could be of other shapes including circular (seeFIG.10) or non-circular. The central opening142may narrow between the front end144and the rear end146, with a transition area148in between (see alsoFIG.10for another embodiment). The central opening142may be generally uniform to accommodate a ribbon format for the optical fibers between the front end144and the rear end146. Since the optical fibers206are already in a ribbonized form, a width of the central opening142through which the ribbonized optical fibers206pass is preferably less than a width of the ribbon (in a top to bottom direction inFIG.7), at least at the front end144, and possibly all throughout a length of the ferrule push104. Such a width prevents the ferrule push104from being rotated relative to the ribbonized optical fibers206and the miniature multi-fiber ferrule108(TMT ferrule, for example), when inside the pulling grip208, and even afterwards when the miniature multi-fiber ferrule108engages the ferrule push104. This relative dimension between the ribbonized optical fibers206and the central opening142prevents the terminated ribbonized optical fibers206from falling out of or disassociating from the ferrule push104. The ferrule push104has substantially the same footprint as the miniature multi-fiber ferrule108, at least at the front end of the ferrule push104.

The ferrule push104has at least one projection150with a latch152that extends from the main body140to engage a corresponding opening154in the housing106(seeFIG.7). The projection150extends rearward within a cutout into the main body140and ends at the latch152. For example, the top side and the bottom side of the housing106may each have an opening154(a top and a bottom opening, respectively) to receive the at least one projection150. Preferably, there are two such projections150, but only one may be necessary to retain the ferrule push104within the housing106. As illustrated in figures, the projections150take the form of cantilevered arms that include a front facing chamfered surface156and a rear facing flat surface158. See, e.g.,FIG.6. As the miniature multi-fiber ferrule108and the ferrule push104are inserted into the housing106from the rear end thereof, the front chamfered surface156engages the housing106, causing the projection150to be flexed into a space of the top or bottom opening154in the main body140. Once the ferrule push104is inserted into the housing106a sufficient distance, the projection150will return to its initial position and the rear facing flat surface158will engage the opening154in the housing. The ferrule push104cannot be removed from the housing106until and unless the projections150are removed from the opening154, although once assembled as a full connector100, there is no need for the ferrule push104to be removed from the housing106. It is also possible that the latch or projection(s)150/152could be on the inside of the housing106and engage a cut-out, depression or other feature on the ferrule push104at a location where the projections150are currently shown inFIG.7, although that may not be preferable for reasons related to ferrule stubbing during an insertion of the miniature multi-fiber ferrule108into the housing106.

The ferrule push104may have an optional polarity key or polarity indicator160. An example of such a polarity key is illustrated inFIG.6. This allows the ferrule push104to be oriented in only one way in the housing106. The housing106has a receptacle162on an inside surface thereof to receive the polarity key160. SeeFIG.3. Thus, if a user were to attempt to insert the ferrule push104into the housing106in some other orientation, the ferrule push104would be blocked since there would be interference at the key160between the ferrule push104and the housing106. It will be appreciated by one of ordinary skill in the art that other locations or means for proper insertion of the ferrule push104into the housing106may be provided. For example, the polarity key160may disposed inside the housing106while the ferrule push104may have a receptacle. Alternatively, the polarity key160may be at a different location on the main body of the ferrule push, e.g., on any one of the sides.

The housing106is dimensioned to receive the miniature multi-fiber ferrule108with optical fibers206from a rear opening164in the housing106. See, e.g.,FIGS.3and7. It should be noted that the housing106is shortened to fit inside an MMC adapter (about 4.8 mm in length). There is an opening166at a front end168of the housing106that may have a configuration that matches the configuration of the miniature multi-fiber ferrule108. As noted above, a guide pin clamp or a spacer may be provided rearward of the miniature multi-fiber ferrule108(seeFIGS.6,7, and10). The ferrule push104is positioned rearward of the miniature multi-fiber ferrule108, and is mostly inside the housing106, but partially within the side latches120of the push-pull stick102. The ferrule push104can optionally seat within a span or width of the push-pull stick102, although typically it does not engage the push-pull stick102.

The housing106, as noted above, has a groove130on the top surface to receive the forward extension108of the push-pull stick102. There are also openings170in the housing106to receive the pair of side latches120from the push-pull stick102. Finally, there is preferably a wedge172along the bottom edges of the housing106to fit within a notch174on the dust cap110.

The dust cap110covers the front end of the connector100—where the miniature multi-fiber ferrule108extends beyond the housing106. The fit between the dust cap110and the connector100is tight, as the main purpose of the dust cap110is to keep dust and debris from contaminating the miniature multi-fiber ferrule108. While guide pins are not shown in the connector100, they may be inserted and extend beyond the end face of the miniature multi-fiber ferrule108. The dust cap110has sufficient space to accommodate the guide pins. There is also a slot176on the top of the dust cap110that receives a portion of the push-pull stick102. See, e.g.,FIG.4. In particular, the projection134that rises through the opening136is received therein. The slot176of the dust cap110may also receive more or fewer components therein. The dust cap110is similar to those shown in Applicant's application Ser. No. 18/063,050, the contents of which are incorporated herein in their entirety.

The dust cap110also includes the notch174that receives the wedge172on the housing106. The combination of the notch174and the wedge172also make for a more robust connection between the dust cap110and the housing106to prevent the dust caps110from being separated one another while in the pulling sock208.

Another embodiment of a small form factor fiber optic connector400(connector400) is illustrated inFIG.10. The connector400is also used with the pulling sock (pulling plug)208to make the optical cable bundle. The connector400includes a shortened push-pull stick402, a ferrule push404, a housing406, a miniature multi-fiber ferrule408, and a dust cap110. The dust cap110for this connector400would be the same as for connector100. The housing406, the miniature multi-fiber ferrule408, and the latch mechanism432are preferably the same as in connector100. Illustrated inFIG.10is a pin keeper412with guide pins412a. The difference in connector400is the elongated ferrule push404that has a round rear end146. The connector400also has a boot438that surrounds the elongated ferrule push404and cooperates with the push-pull stick402to install and remove the connector400from the adapter300. It should be noted that the elongated ferrule push404extends rearwardly of all of the other components of the connector400(except the optical fibers). The elongated ferrule push404has similar projections450and a polarity key460as connector100. The elongated rear portion of the ferrule push404extending rearwardly past the boot438also allows the user to push on the ferule push404to install the miniature multi-fiber ferrule408and the ferrule push404through the housing106and the boot438. The housing106and the boot438are already pre-installed on the adapter300.