Optical fiber connection system

An optical fiber connection system (100) for connecting a plurality of optical fibers is described. The connection system comprises a first bare fiber holder (120) comprising a first splice element (160) and a second bare fiber holder (120′) comprising a second splice element (160′). Each of the first and second splice elements (160,160′) comprises a splice body (161) having a first end (160a) and a second end (160b) and a plurality of alternating alignment and clamping channels (165,167) formed in a top surface (161b) of the splice body (161) that extend from the first end to the second end of the splice body. When the first and second bare fiber holders (120,120′) are mated, at least a portion of the alignment channels (165) of the first splice element (160) overlap a portion of the clamping channels (167) in the second splice element (160′) and at least a portion of the clamping channels (167) of the first splice element (160) overlap a portion of the alignment channels (165) of the second splice element (160′) to hold the first and second optical fibers in end to end alignment.

BACKGROUND

Field of the Invention

The present invention is directed to an optical fiber connections system to interconnect a plurality of first and second plurality of optical fibers.

Related Art

Communication network owners and operators are faced with increasing demands to deliver faster and better service to their customers. They can meet these needs for greater bandwidth by incorporating fiber optics in their networks. Optical fiber cables are used in the optical network to transmit signals between access nodes to transmit voice, video, and data information.

Some conventional optical fiber cables include optical fiber ribbons that includes a coated group of optical fibers that are arranged in a planar array. Optical fibers in the ribbon are generally disposed generally parallel to each other. Optical fiber ribbons are typically interconnected using multi-fiber optical connectors, for example, MPO/MTP connectors which can be used in data centers or other points in the network where parallel optical interconnections are needed.

Data centers rely on 10G and 40G transmission rates which are relatively mature technologies. The global data center Internet protocol (IP) traffic is anticipated to grow by about 31 percent annually within the next five years due to changes in the way people are using Internet. Cloud computing, mobile devices, access video and social media content around the globe are driving data centers to migrate from 10G and 40G transmission rates to 100G and 400G transmission rates.

Data centers are moving toward 40G/100G transmission rates which utilize multiple parallel network links that are then aggregated to achieve higher overall data rates. Polarity in fiber optic cabling is essentially the matching of the transmit signal (Tx) to the receive equipment (Rx) at both ends of the fiber optic link by providing transmit-to-receive connections across the entire fiber optic system. Polarity is managed by use of transmit and receive pairs (duplex cabling), but becomes more complex with multi-fiber connectivity which support multiple duplex pairs such as MPO/MTP connectors.

Higher bandwidth links will require more power to assure signal transmission integrity. Today, heat dissipation from the electronics is already a concern and increasing the power further will amplify the issues that data centers are already facing. This increasing need for more power as well as the desire to install future flexible structured cabling systems is driving interconnection performance to low loss performance (less than 0.1 dB per connection point).

Conventional single fiber ferrule type connectors offer easy reconfiguration, but have the drawback of high optical loss (0.2-0.3 dB) and even higher loss for multi-fiber ferruled connectors such as MPO/MTO connectors (0.35-0.7 dB). Ferruled connectors must be cleaned every time that they are mated. In addition, space required for ferruled connectors limits the interconnection density.

Fusion splicing is another conventional interconnection method, which creates low loss permanent reliable splices. However, handling 250 micron fiber during preparation, fuse, storage can be troublesome. Today, such fusion splices typically require their own splice rack in the data center.

Finally, traditional gel type mechanical splices offer permanent and reliable fiber slices with insertion loss better than connectors and approaching that of fusion splices. However, these mechanical splices employ index matching gels which are not solid materials and therefore, provide no structural integrity.

Thus, need exists for new multi-fiber interconnect technology that offer “fusion-like” optical performance to facilitate datacenter bandwidth migration from 10G and 40G transmission rates, today, to tomorrow's 100G and 400G transmission rates.

SUMMARY

According to an embodiment of the present invention, splice element for use in an optical fiber connection system is described which is configured to interconnect a plurality of first and second optical fibers. The splice element comprises a splice body having a plurality of alternating alignment and clamping channels formed in a top surface of splice body, wherein the alignment channels include sloped channel walls, wherein each of the sloped channel walls touches the optical fibers along a line of contact and wherein the clamping channel is configured to contact the optical fibers disposed therein along the bottom wall of the clamping channel.

According to an embodiment of the present invention, an optical fiber connection system configured to interconnect a plurality of first and second optical fibers is described herein. The connection system comprises a first bare fiber holder comprising a first splice element and a second bare fiber holder comprising a second splice element. Each of the first and second splice elements comprises a splice body having a first end and a second end and a plurality of alternating alignment and clamping channels formed in a top surface of splice body that extend from the first end to the second end of the splice body. When the first and second bare fiber holders are mated, at least a portion of the alignment channels of the first spice element overlap a portion of the clamping channels in the second splice element and at least a portion of the clamping channels of the first splice element overlap a portion of the alignment channels of the second splice element to hold the first and second optical fibers in end to end alignment.

The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and the detailed description that follows more particularly exemplify these embodiments.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1shows an optical fiber splice connection system100that provides a ferrule-less interconnection system to optically couple a plurality of first and second optical fibers. Optical fiber splice connection system100comprises first and second bare fiber holders120,120′. First and second bare fiber holders120,120′ can be secured together by a clamping member110in the form of a clamping sleeve as shown. The clamping sleeve is a generally tubular structure having a passage way extending therethrough and a means for securing the bare fiber holders within the sleeve. The passage way is sized to secure the first and second fiber holders together when in their mated condition. In an exemplary aspect, the securing means can include a pair of latch arms (not shown) disposed on opposite sides of the passageway at each end of the sleeve. The latch arms on the clamping sleeve can be configured to mate with a catch146disposed on a front or second housing portion140of each of the first and second bare fiber holders (FIG. 2A). Optionally, clamping member110can include a connection flange (such as flange112) extending from the external surface of the clamping member to secure the clamping member in a bulkhead, face plate or wall of an enclosure, module, cassette or patch panel. Each of the first and second bare fiber holders120,120′ can comprises a release collar125that can be pulled away from the clamping member allowing the latch arms to be released so that the bare fiber holders may be released from the clamping member. In an alternative embodiment, the bare fiber holders may be permanently connected within the clamping member such as by an adhesive.

Bare fiber holders120,120′, according to the current invention, manage and protect a fiber array of one or more optical fibers having an exposed glass portion adjacent to the end face or terminal end of the optical fiber(s). In other words, the polymer coatings have been removed from at least a portion of the optical fiber(s) circumferential diameter to facilitate alignment during mating a pair of bare fiber holders to optically interconnect the fiber arrays held by said bare fiber holders.

In an exemplary aspect, optical fiber splice connection system100includes first and second bare fiber holders120,120′ that can be field terminated or installed or mounted onto an optical fiber cable or fiber ribbon in the field followed by assembly of the first and second bare fiber holders to form either a semi-permanent or permanent optical connection. Alternatively, the first and second bare fiber holders can be factory terminated or installed or mounted onto an optical fiber cable or fiber ribbon in the factory followed by assembly of the first and second bare fiber holders to form either a semi-permanent or permanent optical connection in the field.

In an exemplary aspect, the bare fiber holders can be configured to resemble the look and feel of an MPO or MTP optical fiber connector, while at the same time providing the enhanced signal performance and in some embodiments permanence of an optical fiber splice.

Optical fiber splice connection system100is configured as a multi-fiber optical splice connection system. In the exemplary embodiments described herein, the optical fiber splice connection system is configured to connect first and second arrays of optical fibers. In the exemplary embodiment provided herein, the optical fiber splice connection system is configured to connect two 12 fiber arrays. As would be apparent to one of ordinary skill in the art given the present description, optical fiber splice connection system100can be modified to include fewer optical fibers or a greater number of optical fibers in each fiber array.

FIG. 2Ashows first bare fiber holder120in an assembled state;FIG. 2Bshows the first bare fiber holder without its release collar125; andFIG. 2Cshows an exploded view of the first bare fiber holder showing the bare fiber holder's internal components. The first bare fiber holder120has a first housing portion130and a second housing portion140that can be secured together to form the holder housing configured to arrange and hold the rest of the elements of the fiber holder. In an exemplary aspect, at least a portion of first housing portion can be inserted into a portion of the second housing portion to secure the two housing portions together.

A fiber alignment mechanism or splice element160is a precision element that is disposed in an element receiving pocket142adjacent to a first end of the second housing portion. A blocking element150is disposed behind splice element160within the internal cavity of the second housing potion which pushes on the element to ensure that it is properly positioned within the bare fiber holder. A fiber organizer135is disposed between the blocking element and first housing portion. The fiber organizer helps reduce the complexity of assembling the bare fiber holders onto the end of a fiber cable or fiber ribbon comprising a plurality of optical fibers. The fiber organizer includes a fiber comb structure138that provides a straightforward mechanism to simultaneously feed the plurality of optical fibers into alignment channels in a surface of the splice element of the first and second bare fiber holders, as shown inFIG. 7A.

A first intermediate spring element124can be disposed between a front portion of the fiber organizer and the blocking element to help control the force placed on the fiber ends when they are connected. Intermediate spring124can be a small spring element, such as a flat or leaf spring that is seated on a shelf or shoulder portion136adisposed around the opening of passage136through the body137of the fiber organizer135(see e.g.,FIG. 7A). In one aspect, the intermediate spring can provide a countering force to dampen the force placed on the mated fibers. As shown inFIGS. 6A-6B, the blocking element150includes a pair of protrusions or bumps155a,155blocated on a rear portion thereof that provides a point of contact with the intermediate spring and helps center the force applied by the intermediate spring element. The intermediate spring element enables a desired ratio of spring forces to be applied to the fibers being terminated and helps balance the forces within the bare fiber holder.

The actual force applied to the end of the fiber array can be controlled by tuning the compressive force of intermediate spring124and a compression spring122disposed between the fiber organizer135and the first housing portion130to create a variable resulting force on the fiber array. By using this configuration, the multi-fiber splice device(s) of the present invention can utilize the spring forces of the fiber array, the intermediate spring and the main compression spring to achieve a force balance.

In one exemplary aspect, this force balancing can be used to enable the exemplary remote grip bare fiber holders to be used to create a reliable dry splice interface (no optical coupling material or index matching gel or adhesive) in the optical path in conjunction with fiber end face shaping techniques known in the industry. For example, putting a spherical end face shape onto the fiber can eliminate the need for index matching material in the splice region and yield an insertion loss of less than 0.5 dB.

In a first embodiment, optical fiber connection system utilizes a pair of splice elements held by the first and second bare fiber holders120,120′. The structure of the first and second bare fiber holders is essentially the same apart from the orientation of the splice element160within an element receiving pocket142adjacent to a first end of the second housing portion140as shown inFIGS. 3A and 3Bas will be describe below.

FIGS. 4A-4Cshow an exemplary splice element160that is configured to join a plurality of parallel optical fibers54of first and second optical fiber ribbons50when mated with another slice element160′ as shown inFIG. 5. Splice elements160,160′ are structurally equivalent, but are rotated with respect to one another when mated.

Splice element160has a generally rectangular body161. In an exemplary aspect, the shape of the body161is a rectangular frustum. In alternative aspects, the body may have another shape such as a trapezoidal prism, semi-cylindrical solid, bisected prism or other three-dimensional shape having at least one generally flat major surface. The body161has a bottom surface161a, a smaller top surface161band four sloped side walls161c-161fextending from the bottom surface to the top surface. In an exemplary aspect, the side walls are sloped at an angle between about 45° and about 85°, preferably at an angle of about 60° relative to the bottom surface.

Splice element160has an integral alignment and clamping mechanism in the form of a plurality of alternating alignment and clamping channels165,167, respectively, formed in the top surface161bof body161. The alternating alignment and clamping channels extend from the first end160ato the second end160bof the body. Each alignment channel is configured to guide and support a single optical fiber and the clamping channels are configured to press on an optical fiber held in an alignment channel in a second splice element when two splice elements160are mated together. In the exemplary embodiment shown inFIG. 4A, the splice element has 12 parallel channels comprising6alignment channels and 6 clamping channels. In alternative embodiments, the exemplary optical fiber slice element can have fewer or more alignment and clamping channels depending on the final application and the number of optical fibers to be spliced. Thus, in some embodiments, the splice element can have two parallel channels (i.e. one alignment channel and one clamping channel) for joining a pair of duplex optical fiber cables. In other embodiments, the exemplary splice element can have a larger number of channels (e.g. the number of channels can be 16, 24, 32, etc.) so long as the splice element has an equal number of alternating alignment and clamping channels. In an alternative embodiment, the exemplary splice element can have alternating sets of alignment and clamping channels, wherein each set comprises a plurality of like channels.

Alignment channels165and the clamping channels167can be substantially flat or planar as they extend from the first and second ends of the splice element. In the exemplary embodiment shown inFIGS. 4A-4B, the alignment and clamping channels are continuous structures extending from the first entrance opening163aat the first end160aof splice body161to the second entrance opening163bat the second end160bof splice body161. The alignment channels and the clamping channels can have a characteristic cross-section, such as the trapezoidal profile shown inFIG. 4C. Alternatively, alignment channels and the clamping channels can have a semi-circular cross section, a rectangular cross section, a v-shaped cross section.

The fibers can be inserted into the alignment mechanism through entrance openings163aand163b. In some aspects, the entrance openings163a,163bcan comprise a funneling inlet portion formed by the tapering of the partitions164between adjacent channels to provide for more straightforward fiber insertion. In other embodiments, the entrance apertures can be fully or partially cone or funnel-shaped to guide the insertion of the optical fibers into the alignment channels165.

The entrance openings163a,163bare characterized by an interchannel pitch CP (i.e. the distance between the centerline of adjacent alignment channels). In the embodiment, shown inFIG. 4C, the channel pitch at the first end of the splice element is the same as the channel pitch at the second end of the splice element. In this exemplary embodiment, the interchannel pitch is approximately the same as the inter-fiber spacing in a conventional 12 fiber ribbon. In an alternative embodiment, the interchannel pitch at the first end of the splice element and the channel pitch at the second end of the splice element can be different. For example, the channel pitch at the first end of the splice element can be set to the fiber spacing of a conventional optical fiber ribbon, while the channel pitch at the second end of the splice element can be at a different value such as when splicing individual optical fibers or when splicing two or more smaller optical fiber ribbon ribbons or optical fiber modules to a larger ribbon fiber.

In the exemplary embodiment shown inFIGS. 4A-4C, while the inter channel pitch is uniform across splice element160, the width of the alignment channels and the clamping channels is different. The alignment channels are configured such that a fiber disposed in the alignment channel will contact each of the sloped channel walls165a,165bof the alignment channel along a line of contact54a,54bdisappearing into the page inFIG. 5along the length of the fiber disposed within the alignment channel, while the clamping channels167are configured such that a fiber disposed in the clamping channel will contact the bottom wall167aof the clamping channel along a line of contact54calong the length of the fiber disposed within the clamping channel as shown inFIG. 5. Thus, when two splice elements are brought together, each optical fiber will have three lines of contact with the splice elements to reliably position and hold said optical fibers. In an exemplary aspect, the three lines of contact can be spaced relatively uniformly around the optical fiber.

Referring toFIGS. 4C and 5, the sloped channel walls of the alignment channels can be disposed at an angle relative to the bottom wall165cof the alignment channel of between 45° and about 75°, preferably at an angle of about 60° relative to the bottom surface. The alignment channels can be characterized by a characteristic alignment channel width, w, between the lines of contact extending longitudinally along the sloped channel walls of the alignment channel where the optical fibers contact the alignment channel. In an exemplary aspect, the alignment channel width can be between about 85 microns and about 120 microns, preferably between about 95 microns and about 110 microns.

The clamping channels can be characterized by a characteristic clamping channel width, W, at the bottom167cof the clamping channel. In embodiments where the characteristic clamping channel width is less than the diameter of the optical fiber to be disposed therein, the sidewalls167a,167bof the clamping channel are angled so they will not contact the optical fiber disposed therein.

In an exemplary aspect, the splice elements of the present invention can be formed using a sol casting resin to generate net shape silica ceramic parts, such as is disclosed in U.S. Provisional Patent Application Nos. 62/382,944 and 62/394,547, herein incorporated by reference in its entirety.

Fiber organizer135, shown inFIGS. 7A-7D, is a multi-purpose element that provides for orderly insertion of the plurality of optical fibers into the splice element160. The fiber organizer has a body portion137having a passage136extending therethrough to permit insertion of a plurality of optical fibers through the body of the fiber organizer. The body of the fiber organizer supports securing the plurality of optical fibers in a remote gripping region or pocket137aof the fiber organizer so that the plurality of optical fibers can be firmly held in bare fiber holder120. In this way, the fibers do not need to be attached to splice element160but are free to move axially within the alignment channels of the splice element. In one aspect, the remote gripping region includes a pocket137aof the fiber organizer. A smaller slot or opening137bcan be formed opposite pocket137a. Additional slots and openings (such as slots137c,137dshown inFIG. 7A) can also be provided in in the fiber organizer to accommodate features of the clamping mechanism, if needed. In one aspect, a mechanical clamp (not shown) can be utilized to secure an array of optical fibers within the fiber organizer. Alternatively, an adhesive, such as a fast-curing UV or visible light initiated adhesive or a thermally activated adhesive, such as a hot-melt material can be utilized to secure an array of optical fibers within the fiber organize.

Fiber organizer135includes a fiber comb portion138that is used to support, align and guide the optical fibers to be terminated. The fiber comb portion includes a top surface138a(seeFIG. 7B) and an array of grooves138b(seeFIGS. 4A-4C), located on the underside of the top surface, disposed on an end of the fiber organizer (nearest the splice element when assembled), with each individual groove or channel138bconfigured to guide and support a single optical fiber of the fiber cable50. The fiber comb portion also includes a ramp section138cadjacent groove array138band disposed between the groove array and the main body portion of the fiber organizer. The ramp section includes gradual rising dividing structures138dthat separate the individual groove which can help align the individual fibers during the fiber insertion process. The structure of the fiber comb portion separates potentially tangled fibers, arranges the fiber array in a uniform pitch, and allows for straightforward feeding of the fiber array into the alignment channels of the splice element160. In addition, the groove array/ramp structure of the fiber comb portion allows for precision placement of the fiber array with the naked eye.

Fiber organizer135also includes a rear portion having an opening (not shown) that allows for insertion of the fiber cable50into the fiber organizer passage137. In one aspect, the rear portion includes extending support structures135aand135b(disposed opposite each other about the opening) that are configured to receive and support compression spring122. The compression spring can fit over the support structure such that it rests against a rear side of the fiber organizer on one side of the compression spring and against the first housing portion on the opposite side of the compression spring. A contact bump or protrusion135dcan be formed on the rear portion of the fiber organizer to contact compression spring122and to center the force of the spring relative to the fiber organizer. Thus, when first fiber holder120is assembled, the compression spring122will be disposed between the fiber organizer135and the first housing portion130.

In an exemplary aspect, fiber organized135can include a guide pin or protrusion139bextending from the sides of the fiber organizer to facilitate proper positioning of the fiber organizer in the second housing portion of the exemplary bare fiber holder. The guide pins fit into guide slots144formed in the interior side walls of the second housing portion140as illustrated inFIGS. 8D and 9A.

In addition, the fiber organizer may have one or more <-shaped notches139aformed in the sides thereof that can be further used to guide and position the fiber guide within the second housing portion140. The <-shaped notches139acan be guided by inclined side walls143which help form the element receiving pocket142.

According to an aspect of the present invention, fiber organizer135can be formed or molded from a polymer material, although metal and other suitable materials can also be utilized. For example, fiber organizer135can comprise an injection-molded, integral material. The choice of suitable materials for the fiber organizers can be made in accordance with the temperature stability parameters.

Referring again toFIGS. 4A and 4B, splice element160includes a rail168disposed along each longitudinal edge of splice body161. Splice element160can include standoff features that provide a controlled vertical offset between two splice elements during at least a portion of the mating process. For example, a first plurality of optical fibers can be disposed in in the alternating alignment and clamping channels165,167in first splice element160and a plurality of second optical fibers can be secured in the alternating alignment and clamping channels165,167in a second inverted splice element160. The optical connection is made by sliding the splice elements on the standoff features formed on one of the first and second splice elements until the standoff features fit into depressions formed in the surface of the other of splice elements. In the embodiment shown inFIGS. 4A-4B and 10A-10D, each rail168of the first and second splice elements can include a locking depression168aand/or locking protrusion168b. For example, splice element160includes a locking depression168aand a locking protrusion168bin each rail.

As mentioned previously in reference toFIGS. 3A and 3Bthe second bare fiber holder120′ is substantially similar to the first fiber holder120described above except with respect to the orientation of splice element160in the element receiving pocket142. InFIG. 3A, the second end160bof splice element160is disposed adjacent to the front wall142aof the element receiving pocket142, while inFIG. 3B, the first end160aof splice element160′ is disposed adjacent to the front wall142aof the element receiving pocket142. Rotating the splice element in the element receiving pocket ensures proper alignment of the locking protrusions(s) and locking projections of bare fiber holders120,120′ when they are mated together.

FIGS. 8A-8Dillustrate the features of the second housing portion140. Second housing portion140is a generally tubular structure having an interior cavity141configured to receive the internal components of the bare fiber holder (i.e. splice element160, blocking element150, intermediate spring124and fiber organizer135) through its second end140band a stepped first or front end140ahaving the splice element receiving pocket142formed therein. The splice element receiving pocket is formed by inclined side walls that are sloped at the same angle as the side walls161c-161f. In particular, the element receiving pocket includes two inclined side walls143(FIGS. 8A and 8C) extending longitudinally along the length of the element receiving pocket and an inclined front wall142a(FIG. 8D) disposed along the front end of the element receiving pocket adjacent to the first end of the second housing portion.FIG. 9Ais a cross-sectional view of the second housing portion140showing the splice element160disposed in the element receiving pocket with the first end160adisposed adjacent to the first end of the second housing portion with the inclined sidewall161dof the splice element disposed against the incline front wall of the element receiving pocket.

Referring toFIGS. 6A-6B and 9A-9B, blocking element150is the next component which is inserted into the second housing portion140as shown inFIG. 9B. Blocking element150anchors the splice element160in the element receiving pocket by forming the fourth wall of the receiving pocket. Blocking element150includes a front side150a, a back side150band an opening152, to permit passage of a portion of the comb structure of the fiber organizer which is holding the optical fibers to be spliced by the connection system of the present invention. The front side of the blocking element includes a vertical wall portion153a, a cutaway portion153band an angled wall portion153c. The angled wall portion153cis configured to push against inclined wall161fof splice element160to ensure that it is pushed fully into the element receiving pocket142as shown inFIG. 9B. The cutaway portion will rest against the top surface of the splice to control the vertical position of the splice element in the element receiving pocket. In an exemplary aspect, blocking element150can include alignment slots156along either side151of the blocking element that are configured to engage with inclined sidewalls143of the element receiving pocket. The back side of the blocking element is a generally vertical surface that includes a pair of protrusions or bumps155a,155blocated on a rear portion thereof that provides a point of contact with the intermediate spring and helps center the force applied by the intermediate spring element124.

FIGS. 10A-10Dillustrate the mating sequence for a pair of splice elements160,160′ to optically connect a first and a second plurality of optical fibers54,54′.FIG. 10Ashows splice elements160,160′ moving toward each other in a forward and slightly downward direction as provided by directional arrow195.FIG. 10Bshows the splice elements at the point where the rail168at the second end160bof splice element160contacts the locking protrusion168b′ of splice element160′. Splice element160slides across the surface of the locking protrusion as indicted by directional arrows196and197as shown inFIGS. 10B and 10C. Splice element160continues to slide forward riding on the surface of the locking protrusion168b′ of splice element160′ until said locking element is seated in locking depression168aof splice element160as shown inFIG. 10D.

A second embodiment of an exemplary optical fiber connection system is shown inFIGS. 11A-11E through 14A-14B. Optical fiber splice connection system200provides a ferrule-less interconnection system to optically couple a plurality of first and second optical fibers. Optical fiber splice connection system200comprises a pair of bare fiber holders, such as first and second bare fiber holders220,220′. In one aspect, the bare fiber holders may be secured together with an auxiliary clamping member (not shown) or by an adhesive. The first and second bare fiber holders220,220′ be field terminated, installed or mounted onto an optical fiber cable or fiber ribbon in the field followed by assembly of the first and second bare fiber holders to form either a semi-permanent or permanent optical connection. Alternatively, the first and second bare fiber holders can be factory terminated, installed or mounted onto an optical fiber cable or fiber ribbon in the factory followed by assembly of the first and second bare fiber holders to form either a semi-permanent or permanent optical connection in the field.

FIGS. 11A-11Eillustrate the features and components of bare fiber holder220.FIGS. 12A and 12Bare detail views of the element platform270of bare fiber holder220.FIGS. 13A-13Care three views on a bare fiber holder that is configured to mate with the bare fiber holder ofFIGS. 11A-11Eto form the alternative optical fiber connection system200.

Bare fiber holder220has a first housing portion230and a second housing portion240that can be secured together to form the holder housing221. Holder housing221is configured to arrange and hold the remaining components of the bare fiber holder and to protect the exposed bare glass portion55of the optical fibers54supported within the bare fiber holders. A crimp ring229can secure the first and second housing portions together. Optionally, additional latching features (not shown) can be added to further secure the first and second housings. Alternatively, the first and second housing portions can be adhesively bonded together, secured by a snap fit, or a latching system. In alternative embodiment, the holder housing can have a clam shell configuration having a first housing portion and a second housing portion that are joined by a living hinge. In the exemplary embodiment shown inFIGS. 11A-11E, each of the first and second housing230,240can include a semi-cylindrical anchoring portion233,243formed at their first ends230a,240a, respectively. The semi-cylindrical anchoring portion233,243form a cylindrical anchoring portion223when the first and second housing portions are assembled to form the holder housing221. A crimp ring229can be fitted over and secured to the cylindrical anchoring portion223to anchor the cable jacket or strength members an optical fiber cable to the bare fiber holder to enhance the cable retention strength in the bare fiber holder. In the exemplary aspect shown inFIG. 11A, the cylindrical anchoring portion has a smooth outer surface. In some embodiment, it can be desirable to add teeth or ribs to the outer surface of the cylindrical anchoring portion to further increase the retention force.

In an exemplary aspect, the first and second housing portions230,240can have a generally open rectangular channel profile having a base242aand a pair of parallel walls242bextending from the base, the side walls having a top edge242cextending along the length of the side walls. The top edge232cof the first housing portion230is joined to a portion of the top edge242cof the second housing portion240when the first and second housing portions are assembled to for the holder housing201.

Optionally, a strain relief boot (not shown) can be mounted over the crimp ring to provide strain relief and bend control to an optical fibers or optical fiber cable at the point where the optical fibers enter the holder housing of the bare fiber holder.

Referring toFIGS. 11C, 11E and 14B, a leaf spring280can be attached to second housing portion240of bare fiber holder220to provide a vertical mating force (represented by directional arrow292inFIG. 14B) on a bottom surface272d′ of element platform270′ of a mating bare fiber holder220′. Similarly, leaf spring280′ attached to second housing portion240′ of bare fiber holder220′ provides a vertical mating force (represented by directional arrow292′ inFIG. 14B) on a bottom surface272dof element platform270of a mating bare fiber holder220. The combination of the vertical mating forces292,292′ ensures the vertical alignment of the ends of the first and second optical fibers, while the sloped walls of the alignment channels in the splice elements160,160′ provide the lateral alignment of the optical fibers.

In an exemplary aspect, the second housing240can include a pair of spaced apart anchor bars247formed on the interior surface241of the second housing portion. Leaf spring280can be fitted into a slot248formed in the anchor bars to secure the leaf spring to the second housing portion. The leaf spring can have a generally arched profile comprising two arched arms282connected at both ends by a flat footer portion284. The footer portion fits into the slot formed in the anchor bars to secure the leaf spring to the second housing portion. In an exemplary aspect, the leaf spring can be stamped from a piece of spring steel and formed into the leaf spring as shown inFIG. 11C.

Bare fiber holder220further comprises a fiber alignment mechanism or splice element160that is held by an element platform270in a first orientation. In the exemplary aspect shown inFIGS. 11A, 11C and 12B, splice element160is the same splice element used in bare fiber holder120described previously. In this embodiment, the optical fibers can be secured directly to splice element160using an adhesive. For example, an adhesive such as a fast-curing UV or visible light initiated adhesive or a thermally activated adhesive, such as a hot-melt material can be utilized to secure an array of optical fibers within the entrance openings163aof the splice element. Securing the optical fibers in this area of the splice element still provides the advantages of remote gripping the optical fibers, but without the need for a separate fiber organizer such as that provided in bare fiber holder120, described above in reference toFIGS. 2A-2C.

Element platform270includes a collar portion271which is attached to an element stage272. Collar portion271can have a generally cylindrical shape that is configured to receive a portion of a compression spring222. As shown inFIG. 12A, the collar portion can have an opening271bthrough an end wall portion271dwhere the element stage attaches to the collar portion. The opening permits passage of the optical fibers through the end wall of the collar portion element platform.

Element stage272has a base and sidewalls272bextending from the base. The side walls extend along the longitudinal edges of the base from a second end270bof the element platform to the collar portion271. The base has a top surface272aand a bottom surface272d. Splice element160is anchored to the top surface by element catches273,274. In an exemplary aspect, the sidewalls can include a protrusion or bump272cformed on the top of the sidewalls272bto control the vertical offset between the splice elements held on the element platform during the mating of a pair of bare fiber holders220.

In an exemplary aspect, element stage272can include a window275that extends through the base of the element stage under the interconnection area on the splice element160where the first and second optical fibers are joined end-to-end (seeFIG. 11E). In an exemplary aspect, a pair of bare fiber holders220can be permanently joined together by an index matched optical adhesive. An exemplary optical adhesive can be cured with actinic radiation via a rapid and straightforward procedure using an eye-safe visible, e.g., blue, LED light source such as is described in U.S. patent application Ser. No. 15/695,842, herein incorporated by reference in its entirety. The curing radiation can be shined on the adhesive through at least one of the exemplary splice elements through window275.

Collar portion271can also include a pall271cthat extends from the outer surface271aof the collar portion either side of the collar portion. A translation gap279is formed between the pall and the end272dof the sidewall272b. Tapered ridges239,249disposed on the interior surface of the first and second housing portions230,240form a track that fits in gap279to control the relative position of the element platform when two of the exemplary bare fiber holders220are mated together.

The element platform270can be resiliently mounted in the holder housing221. In an exemplary aspect, a compression spring222can be disposed between the holder housing221and the element platform that applies a forward force (represented by directional arrows295inFIG. 14B) on the element platform and the splice element disposed thereon. For example, the holder housing can comprise a spring seating area224that is formed when the first and second housing portions230,240are assembled together.

Using this configuration, optical fiber connection system200can utilize the spring forces of the fiber array, and the main compression spring to achieve a force balance to create a reliable dry splice interface (no optical coupling material or index matching gel or adhesive) in the optical path in conjunction with fiber end face shaping techniques known in the industry.

FIGS. 13A-13Cshow the second bare fiber holder220′ that is configured to mate with the bare fiber holder220ofFIGS. 11A-11Eto form the alternative optical fiber connection system200. The structure of the first and second bare fiber holders is essentially the same apart from the orientation of the splice element160disposed on element platform270. In second bare fiber holder220′, the second end of splice element160abuts against element catch274on the element stage. When the splice element is in this orientation, the splice element will be referred to as splice element160′ and the bare fiber splice holder is referred to as second splice holder120′. Otherwise the first and second splice holders are structurally equivalent.

FIGS. 14A and 14Bare two cross-sectional views showing the mating of two bare fiber holders220,220′ of optical fiber splice connection system200.FIG. 14Aillustrate the bare fiber holders220,220′ at the beginning of the mating process. The bare fiber holders220,220′ are brought together until the top edge at the second ends240b,240b′ of the second housing240,240′ contact each other. As bare fiber holder220′ moves toward bare fiber holder220, as indicated by directional arrow295, element stage272′ of bare fiber holder220′ enters the space between stage element stage272of bare fiber holder220and the second housing240. Similarly, the element stage272of bare fiber holder220enters the space between stage element stage272′ of bare fiber holder220′ and the second housing240′ at the same time.

As bare fiber holder220′ continues to move toward bare fiber holder220, the cam surface of the locking protrusions168b,168b′ and the rails168′,168engage to roughly align the height of the splice elements160,160′ with respect to one another.FIG. 14Bshows the initial engagement between the rails (not shown) and the locking protrusions168b,168b′. As this occurs, leaf spring280,280′ begins to apply a vertical force to the back surface272d,272d′ of the element stages272pushing splice elements160,160′ toward each other. The vertical force increases as the leaf spring contact the camming feature277(best seen inFIG. 11B) on the bottom surface of the element stage, up to 3.5-4.5 lbs. Once the bare fiber holders220,220′ are fully mated. The leaf springs280,280′ continue to apply the vertical force to element holders270′,270and in turn the splice elements160′160. The vertical force is centered on the point where the first and second optical fibers54,54′ meet to secure and align the fibers in the alignment channels of the splice elements.

Provided that the second housing portion is made of a transparent or semi-transparent material, it may be desirable to permanently secure, the first and second bare fiber holders120,120′,220,220′ can be permanently secured together with an optical adhesive such as the optical adhesive described in U.S. patent application Ser. No. 15/696,901.

Alternatively, the first and second bare fiber holders can be semi-permanently secured together via a mechanical clamping element, such as clamping element110, in either a dry state or using an index patching material disposed between the terminal ends of the optical fiber arrays being joined in the exemplary an optical fiber splice connection system100exemplified byFIGS. 1-10as provided above.

An exemplary connection made in accordance with the present disclosure should have an insertion loss of less than 0.1 dB, a return loss variation of less than 5 dB when temperature cycled from −10° C. to +75° C. and have a pullout strength of greater than 0.45 lbf.

The exemplary optical fiber connection system can be used in a wide range of applications where low loss optical connections are needed, especially when the connections are semi-permanent or permanent. In some embodiments, the exemplary multifiber devices can be used in fiber optic cassettes, terminals, patch panels, etc. where the splice can be located at a bulkhead or through the wall of an enclosure.

For example, the exemplary connection system can be used in an optical cassette, such as is described in U.S. Provisional Patent Application No. 62/544,370, herein incorporated by reference, wherein the optical cassette or terminal comprises an enclosure having a top, a bottom and a plurality of side walls disposed between the top and the bottom, and at least one exemplary connection system of the present disclosure disposed through one of the plurality of sidewalls. A plurality signal paths can exit the cassette or through one of the plurality of sidewalls wherein the plurality signal paths can comprise a connection point at the sidewall where the plurality signal paths exit the cassette. The exemplary optical fiber connection system of the present disclosure can be used for the multifiber connection device and/or for the single fiber connection points. In an exemplary use in which the cassette or terminal can comprise a plurality of paired single fiber connection points, such that the first of the pair of single fiber connection points is designated as a transmit port and the second of the pair of single fiber connection points is designated as a receive port. In this aspect, signals carried by the plurality of outside optical fibers can be reordered within the cassette or terminal such that the signals leaving the cassette are in a different order than they enter the cassette. In some embodiments, this reordering of the signal paths is used to manage the polarity of the send and receive ports.

In an alternative application, the exemplary optical fiber connection system can be used to make an optical fiber harness assembly. For example, in the exemplary optical fiber connection system may be used to directly connect fiber fanout to a continuous transmission portion or cable in either the field or in the factory. This can be especially advantageous when the fanout portion is made in a first location, the transmission portion is made at a second location and where the fanout portion to a continuous transmission portion are brought together at a third location.

Various modifications, equivalent processes, as well as numerous structures to which the present invention may be applicable will be readily apparent to those of skill in the art to which the present invention is directed upon review of the present specification.