Configuring pigtails in a fiber distribution hub

[0001] This application is a continuation of U.S. patent application Ser. No. 10/714,814 filed on Nov. 17, 2003, now U.S. Pat. No. 6,983,095 the disclosure of which is hereby incorporated by reference herein.

[0002] In Fiber-to-the-Premises broadband network applications optical splitters are used to split the optical signals at various points in the network. Recent network specifications call for optical splitters to be incorporated in Fiber Distribution Hubs which are re-enterable outdoor enclosures. These enclosures allow easy re-entry for access to optical splitters allowing splitter ports to be utilized effectively and for additional splitter ports to be added on an incremental basis.

[0003] In typical applications to date, optical splitters are provided prepackaged in optical splitter module housings and are provided with splitter outputs in pigtails that extend from the module. The splitter output pigtails are typically connectorized with high performance low loss SC or LC connectors. This optical splitter cassette provides protective packaging for the optical splitter components in the housing and thus provides for easy handling for otherwise fragile splitter components. This approach allows the optical splitter modules to be added incrementally to the Fiber Distribution Hub, for example, as required.

[0004] A problem arises due to the lack of protection and organization of the connectorized ends of the splitter output pigtails. These pigtails can sometimes be left dangling in a cable trough or raceway within the enclosure. This method of leaving an exposed optical component such as a high performance connector exposed in an open area leaves it susceptible to damage. The high performance connectors, if damaged, can cause delays in service connection while connectors are repaired. Leaving connectorized splitter output pigtails dangling in a cabling trough also exposes them to dirt and debris in the cabling trough. In current network deployments, it is desirable to maintain clean optical connectors to maximize the performance of the network.

[0005] In addition, the fiber pigtails in the current art are not organized in a manner conducive to rapid service delivery. In many cases, the splitters may have sixteen or thirty-two output pigtails bundled together making it difficult to find a particular pigtail. Also the bundle of loose hanging pigtails can easily become entangled causing further delays in service delivery. The tangles can actually cause congestion and in some cases result in bend induced loss on the pigtails resulting in overall lower system performance.

[0006] To solve some of these issues, a separate storage tray or enclosure has been utilized to take up slack and/or store and protect splitter output pigtail connectorized ends. However, these auxiliary devices tend to take up additional space and often hide the pigtail in an enclosure that can cause further delays in deployment depending on how much time is required to access on the tray or enclosure. Thus, there still remains a need for a solution that does not take up additional space and that provides direct access and identification to splitter output pigtail ends.

[0007] In addition, some network applications may require equipping splitter outputs with fiber optic terminators in order to eliminate reflections caused by unterminated splitter outputs. Other methods of storing connectorized pigtails in cable troughs or auxiliary trays may make it difficult to equip splitter output ports with fiber optic terminators.

[0008] Finally, current methods tend to result in a disassociation of the splitter module from the splitter output pigtail end. This usually results because the pigtail, once deployed, gets lost in the midst of other pigtails in the fiber jumper trough. When subscribers are taken out of service, it is desirable to disconnect the splitter output and redeploy or store it for ready redeployment. It is further desirable for administrative purposes to maintain association of splitter module to splitter output pigtails so that resources are used effectively over time.

[0009] In accordance with an implementation, a method for configuring an enclosure used in a communications network is provided. The method may include providing a group of pigtails. The method may include routing the group of pigtails circumferentially around a subscriber termination field, where the group of pigtails is associated with an optical splitter module used to convey optical signals to a destination, and where the routing is performed in a manner that does not substantially obstruct access to at least one of a group of subscriber terminations that are associated with the subscriber termination field.

[0010] In accordance with another implementation, an optical splitter module for use in an optical communications network is provided. The optical splitter module may include an optical splitter configured to split an incoming optical signal into a group of outgoing optical signals. The splitter module may include a faceplate configured to make the group of outgoing optical signals available to a group of pigtails, where each of the group of pigtails is configured to couple a respective one of the group of optical signals to one of a group of subscriber terminations associated with a subscriber termination field. The faceplate may be configured to facilitate incremental deployment of the optical splitter module on a shelf in a manner that facilitates making optical signals from the group of optical splitter modules available to the subscriber termination field.

[0011] In accordance with yet another implementation, an enclosure for distributing optical communication signals is provided. The enclosure may include a subscriber termination field mounting area configured to support a subscriber termination field including a group of subscriber terminations, where each of the group of subscriber terminations is associated with a subscriber. The enclosure may include an optical splitter shelf configured to support a group of optical splitter modules, where each of the group of optical splitter modules has a group of pigtails that includes a transition member, and where the group of pigtails is adapted to convey optical communication signals to at least some of the group of subscriber terminations. The enclosure may include a transition member mounting area configured to support a group of transition members to facilitate circumferential routing of the group of pigtails around the subscriber termination field.

[0012] In accordance yet another implementation, a method for connecting a subscriber to an optical communications network is provided. The method may include removing a pigtail connector from a parked location associated with a receptacle. The method may include coupling the pigtail connector to a subscriber termination associated with a subscriber, where the subscriber termination is one of a group of subscriber terminations associated with a subscriber termination field. The method may include storing slack associated with the pigtail in a vertical channel within an enclosure to facilitate routing the pigtail in a manner that does not substantially interfere with others of the group of subscriber terminations.

[0013] The foregoing and other features and advantages of the systems and methods for fiber distribution and management will be apparent from the following more particular description of preferred embodiments of the system and method as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention.

[0026] The preferred embodiments of the present invention are directed to an optical splitter module that is equipped with adapters for storing connectorized optical splitter pigtail ends. Adapters are administratively located on the optical splitter module bulkhead, for example, but not limited to, in octal count arrangements ideally suited to identify splitter ports having sixteen or thirty-two output ports. The adapters in accordance with preferred embodiments are used to store or stage the connectorized ends of the optical splitter for rapid location, identification, easy access and removal of pigtail output ends. In accordance with preferred embodiments, the optical splitter outputs extending from the bulkhead on the module are wrapped back and secured to adapters on the splitter bulkhead. The preferred embodiments also include methods for installing optical splitter modules and associated fixed length output pigtails, storing the connectorized ends of the pigtails in a position ready for deployment and then individually connecting the splitter outputs as required to connect service to subscriber terminations.

[0027] FIG. 1 illustrates schematically a broadband access network 10, for example, a Fiber-to-the-Premises (FTTP) network using passive optical network (PON) components in accordance with a preferred embodiment of the present invention. The architecture can be a point to multi-point PON construction, which utilizes 1:32 splitters at a fiber hub enclosure within the distribution area. The architecture can be fiber rich 1:1 distribution between the fiber hub and a customer's premise. The broadband services capability of the network to distribute source information include, for example, data signals (622 Mbps×155 Mbps (shared)), and video signals (860 MHz, ˜600 analog and digital channels, high definition television (HDTV), and video on demand (VOD)). Signaling is accomplished using wavelength division multiplexing (WDM) and fiber sharing. The network includes the optical network terminals 26 that are scalable, provide high bandwidth, multi-service applications that serve residences and small/medium businesses. The network 10 includes passive components that are located outside the plant and require minimal maintenance.

[0028] The broadband access network 10 includes digital subscriber plug-in line cards that have a broadband terminal adapter configured for receiving a digitally multiplexed broadband data stream and outputting a group of demultiplexed broadband data streams for the respective subscriber loops.

[0029] FIG. 2 illustrates schematically further details of an FTTP network 50 in accordance with a preferred embodiment of the present invention. In Fiber-to-the-Premises broadband network applications optical splitters 64 are used to split the optical signals at various points in the network. In FTTP networks optical splitters are typically located in both indoor and outdoor environments including a Central Office/Head End, environmentally secure cabinets, enclosures or drop terminals. In some outdoor applications, optical splitters have been deployed in tightly sealed environmental closures that are not easily re-enterable. Preferred embodiments of the present invention provide optical splitter enclosures to effectively utilize splitter ports or to incrementally deploy additional splitters as the need arises. Preferred embodiments include optical splitters incorporated in Fiber Distribution Hubs 54 which are re-enterable outdoor enclosures. These enclosures allow easy re-entry for access to optical splitters allowing splitter ports to be utilized effectively and for additional splitter ports to be added on an incremental basis.

[0030] Preferred embodiments of the present invention include optical splitters that are provided prepackaged in optical splitter module housings that are mounted in a fiber patch panels to facilitate routing of jumpers interconnected from fibers in adjacent subscriber ports to the splitter outputs. This optical splitter cassette provides protective packaging and thus easy handling for otherwise fragile splitter components. The optical splitter modules can be added incrementally to the patch panel.

[0031] FTTP broadband networks are designed to achieve low optical insertion loss in order to achieve maximum network reach from electronics having fixed power output. Each optical component and subsystem utilized in the network is optimized to provide minimum insertion loss. The optical loss budget in a preferred embodiment is approximately 23 to 25 dB with 1:32 passive splitting. The components and factors contributing to the optical loss include splitters (1:32, single or cascaded), WDMs, connectors (optical line terminal (OLT), FDF, splitters, drop, ONT), fiber attenuation (at least three wavelengths: 1310 nm, 1490 nm, 1550 nm), and splicing.

[0032] The splitter hub 54 serves at least 128 splitter ports/premises. It includes multiple distribution cables, connectorized or fused between splitter and distribution. The preferred embodiments of the present invention provide efficient fiber connection and management with easy access, and low maintenance requirements. The splitter hubs of the preferred embodiments are pole or ground mountable. The drop terminals can be with or without splitters and include various number of drops, both aerial and buried.

[0033] In preferred embodiments, optical connectors are used in the network to provide the desired flexibility however they are restricted to those points in the network where flexibility is absolutely required. Optical connectors are required to provide flexible access to optical splitter outputs. The preferred embodiments of the present invention provide connector flexibility and yet minimize optical loss using the optical splitter module with connectorized pigtails. The pigtails have standard SC or LC type connectors on the ends.

[0034] FIG. 3 illustrates an optical splitter module 100 in a fiber distribution network having connectorized pigtails in accordance with a preferred embodiment of the present invention. The module 100 includes a bulkhead faceplate 102 having storage receptacles 112. In a preferred embodiment, the optical splitter module 100 provides for a high density ribbon cabling harness 106 to protect the splitter outputs extending from the splitter module 100. The optical splitter module ribbon harness 106 is secured to the module 100 with a strain relief mechanism 104 to provide high pull strength and bend radius control. The compact nature of the ribbon harness 106 allows for higher packing density and better space utilization in the cabling trough. The module ribbon harness cabling 106 is converted to individual pigtails with connectors to allow splitter outputs to be administered and rearranged individually.

[0035] The module 100 may be equipped with either half non-functional adapters or full functioning adapters as a means for storing pigtail ends. In a preferred embodiment, the half non-functional adapters are used in applications not requiring fiber optic terminators but for storage functionality. The full functional adapters are used in applications requiring connection of fiber optic terminators to the optical splitter output port. Access to the pigtail ferrule tip may be required for attaching fiber optic terminators to eliminate undesirable reflections caused by unterminated connectors. The module 100 provides a home position from which optical splitter output pigtails can be deployed and where they can be returned to once taken out of service. This administrative use of adapters provides protection for the connectorized pigtails ends 110, maintains cleanliness of the connector ends, and enables rapid service connection and deployment.

[0036] The preferred embodiments of the present invention address configuring a fiber distribution hub with optical splitter modules having fixed length connectorized pigtails. One aspect of the preferred embodiment determines where to position the optical splitter modules relative to other fiber terminations needing access to the optical splitter ports. The preferred embodiments also addresses installing the pigtails in a configuration that requires minimal pigtail rearrangement and slack yet allowing for enough slack to reach any of the fiber terminations requiring access to splitter ports. The methods of installing optical splitter module pigtails include determining how to route the pigtails in order to provide an optimal routing scheme that does not get congested and wherein slack can be controlled within set limits of the enclosure. The methods in accordance with a preferred embodiment of the present invention include making all pigtails the same length for ease of manufacturing and ordering by the customer. Splitter modules all having the same pigtail length also allow ease of flexibility for allowing a splitter module to be installed in any available slot within the patch panel without regard to sequential order.

[0037] A preferred embodiment of the method for installing the splitter module pigtails also provides for fiber management in the enclosure so that rearrangement and churn does not congest this management. To accomplish this, the slack and any chance of blocking access because of fiber entanglement is minimized. The preferred embodiments allow for churn over time including initial pigtail storage, service connection, service disconnection and repeat storage to provide ready access to pigtails for future use. The methods of the present invention are non-blocking and non-congesting for jumpers routed into cable pathways and fiber patch panels. The method of a preferred embodiment is fully contained within the confines of the enclosure.

[0038] FIG. 4A schematically illustrates the installation of the optical splitter module pigtails in accordance with a preferred embodiment of the present invention. A preferred embodiment of the present invention includes a cabling installation method 125 including splitter modules incrementally installed on a shelf adjacent to a subscriber termination field 128. The connectorized pigtails 138 from the splitter modules 132 having fixed identical length are routed in a circumferential path 130 surrounding the subscriber termination field 128. The connectorized ends of the pigtails are stored at a position on the front of the splitter module 132 via storage receptacle 134. The method in accordance with a preferred embodiment employs a fan through placement so that the splitter module pigtails can be installed without disturbing installation of pigtails already connected to subscriber terminations. This installation method in accordance with a preferred method of the present invention also ensures that the splitter module 132 can be preconfigured with the pigtail connectors in the storage position and left in the storage position throughout the pigtail installation process.

[0039] FIG. 4B schematically illustrates a service connection configuration 150 of the optical splitter module in accordance with the preferred embodiment of the present invention shown in FIG. 4A. The preferred embodiments of the present invention, include a service connection method to connect a subscriber into service by first disconnecting an individual splitter output pigtail from the storage position and then routing the pigtail to the desired subscriber port 152. Since the pigtail harness has been preconfigured and routed circumferentially around the subscriber termination the pigtail inherently reaches any of the desired subscriber ports within the target population by simply reducing the circumferential path distance. By reducing the circumferential path the pigtail slack exhibits additional slack. The additional slack may be taken up using slack-half loops 154 in the vertical channel where the pigtails are routed. The random nature of connecting splitter output pigtails to subscriber ports may result in a family of various size half-loops 154 that are managed in the vertical channel within the confines of the cabinet.

[0040] FIGS. 5A and 5B schematically illustrate the installation of the optical splitter module pigtails and the service connection configuration of the optical splitter module, respectively, in a network having modules adjacent to each other in accordance with a preferred embodiment of the present invention. A preferred embodiment of the present invention includes a method to connect subscriber ports that are in an adjacent field but not initially contained within the circumference of the splitter pigtail harness. In this extension the splitter output pigtail is routed to the adjacent field which by virtue of a juxtaposed position has a path at the same distance to the subscriber port within the circumference. The subscriber ports in the adjacent field also are assigned randomly therefore the resultant slack is managed using a family of various size half-loops in the vertical channel 176.

[0041] FIGS. 5C and 5D schematically illustrate the service connection configurations 194, 206 of the termination and splitter fields in adjacent fiber distribution hubs in accordance with a preferred embodiment of the present invention. The pigtails 198, 208 of the left module 196, 214 are routed circumferentially clockwise while the right pigtails 204, 210 of the module 202, 216 are routed circumferentially counterclockwise in a preferred embodiment. The fiber distribution hubs in this embodiment are located adjacent to one another, each having a splitter shelf with splitter modules and a termination shelf. The counter rotating feed provide for routing of the splitter module output pigtails circumferentially around the subscriber termination fields. The pigtail slack is stored in the vertical channels 200, 212.

[0042] A preferred embodiment includes a method of removing a splitter pigtail from a subscriber port and either redeploying that output pigtail to a new subscriber or storing the pigtail back to the original storage position at the splitter module. The method is completely non-blocking and non-congesting due to the planned slack management.

[0043] FIG. 6 is a flow chart illustrating a method for installing and connecting optical splitter module pigtails in accordance with a preferred embodiment of the present invention. The method includes the step 222 of installing a splitter module with output pigtails in a patch panel position. Further, the method includes the step 224 of routing the splitter module output pigtails circumferentially around a subscriber termination field. The method includes the step 226 of connecting an individual splitter pigtail connectorized ends at splitter module storage receptacles. These storage receptacles can be initially preconditioned in the factory. The method includes a next step 228 of storing the pigtail slack in half-loops in an adjacent vertical channel. Further, the method includes the step 230 of deciding whether to connect or disconnect the service order. If a service order needs to be connected, the method includes the decision in step 232 of determining if a splitter output is available for assignment. If it is determined that the splitter output is available for assignment then the method progresses to step 242 of disengaging connectorized pigtail from the storage position. If it is determined that the splitter output is not available per step 238 then it is determined if a position is available for adding a module. If yes, then the method steps are reiterated starting back from step 222. If, however, it is determined that there is no position available then the maximum module capacity of the system has been reached.

[0044] The method also includes the option of disconnecting the service order per step 234. The step 234 includes disengaging the connectorized pigtail from the subscriber position and per step 236 routing the pigtail through an expanded circumferential path around the subscriber termination field 236.

[0045] The method further includes the step 244 of connecting the splitter pigtail to the subscriber position and the step 246 of routing the pigtail through a reduced circumferential path around the subscriber termination field. The method includes the step 248 of storing the pigtail slack in graduated half-loops in an adjacent vertical channel.

[0046] FIGS. 7A–7E illustrate views of a fiber distribution hub in accordance with a preferred embodiment of the present invention. The fiber distribution hub (FDH) in accordance with a preferred embodiment administers connections between fiber optic cables and passive optical splitters in the outside plant (OSP) environment. These enclosures are used to connect feeder and distribution cables via power splitters providing distributed service in a FTTP network application. The preferred embodiment FDH provides a vital cross-connect/interconnect interface for optical transmission signals at a location in the network where fiber hubbing, operational access and reconfiguration are important requirements. In addition the FDH is designed to accommodate a range of sizes and fiber counts and support factory installation of pigtails, fanouts and splitters.

[0047] In a preferred embodiment, the FDH enclosure is designed for front access via a two-door configuration (FIG. 7E). The FDH provides termination, splicing, interconnection and splitting in one compartment. The unit accommodates either metallic or dielectric OSP cables via sealed grommet entry. Cables are secured with standard grip clamps. The FDH provides grounding for metallic members and for the cabinet.

[0048] The enclosure provides environmental and mechanical protection for cables, splices, connectors and passive optical splitters. These heavy gauge aluminum enclosures are NEMA-4X rated and provide the necessary protection against rain, wind, dust, rodents and other environmental contaminants. At the same time, they remain lightweight for easy installation, and breathable to prevent accumulation of moisture in the unit. The aluminum construction with a heavy power coat finish also provides for corrosion resistance. The enclosure is accessible through secure doors that are locked with standard tool or pad-lock.

[0049] In accordance with preferred embodiments, the FDH is provided in pole mount or pedestal mount configurations. The same cabinet and working space is available in both pole mount (FIGS. 7A and 7B) and pedestal mount units (FIGS. 7C, 7D and 7E). Three sizes of the fiber distribution hubs are available, for example, to correspond to three different feeder counts, for example, 144, 216 and 432.

[0050] FIG. 8 illustrates a view of the internal components of a fiber distribution hub enclosure 350 in accordance with a preferred embodiment of the present invention. The FDH enclosure 350 can be configured in a number of different ways to support fiber cable termination and interconnection to passive optical splitters. The configuration illustrated in the preferred embodiment provides for a termination shelf 352, a splitter shelf and optical component modules 354 and a channel for fiber management 358.

[0051] The termination shelf 352 can be based on the standard main distribution center (MDC) enclosure line that provides complete management for fiber terminations in accordance with a preferred embodiment of the present invention. In a preferred embodiment, the termination shelf is preterminated in the factory with a stub cable containing either 144-fibers, 216-fibers or 432-fibers. This stub cable is used to connect services to distribution cables routed to residences. The distribution fibers are terminated on certified connectors. The termination shelf uses standard 12-pack or 18-pack adapter panels, for example, that have been ergonomically designed to provide easy access to fiber terminations in the field. The panels can be mounted on a hinged bulkhead to allow easy access to the rear for maintenance. The fiber jumpers are organized and protected as they transition into the fiber management section 358 of the enclosure.

[0052] The splitter shelf 354 can be based on a standard fiber patch panel that accepts standard optical component modules (OCM) holding optical splitters in accordance with a preferred embodiment of the present invention. In a preferred embodiment, the splitter cassettes are designed to simply snap into the shelf and therefore can be added incrementally as needed. The splitter shelf serves to protect and organize the input and output fibers connected to the cassettes. Splitter shelves are available in various sizes and the shelf size can be optimized for different OCM module configurations.

[0053] FIG. 9 illustrates a schematic view of a fiber distribution hub enclosure 380 having a side-by-side equipment configuration in accordance with a preferred embodiment of the present invention. There are two adjacent termination shelves 388, 390 and two adjacent splitter shelves 384, 386, separated by a central fiber management channel 382 in accordance with a preferred embodiment of the present invention.

[0054] FIG. 10 illustrates a view of the optical component modules in a fiber distribution hub enclosure in accordance with a preferred embodiment of the present invention. The FDH configuration in a preferred embodiment provides for fiber management hardware on one side of the cabinet. This allows fiber jumpers to be routed between the termination shelf and the splitter shelf. Excess slack can be managed on the side of the cabinet using slack loops.

[0055] In accordance with a preferred embodiment, OCM modules can also be equipped with pigtails to reduce the number of connections in the network. The module shown in FIG. 10 contains a 1×32 splitter with pigtails provided on the input and 32 outputs. The connectorized ends of the pigtails are stored on bulkhead adapters on the front of the module. These storage adapters provide a familiar locating scheme for spare pigtails so that connector ends can be quickly identified and connected to distribution fibers. The spacing on the adapters is the same as on standard connector panels.

[0056] In preferred embodiments, OCM modules can also be equipped with standard terminators. Modules terminated with bulkhead adapters may be equipped with terminators on the front of the module. Modules connected via pigtails and equipped with storage adapters are equipped with terminators on the rear of the panel.

[0057] The claims should not be read as limited to the described order or elements unless stated to that effect. Therefore, all embodiments that come within the scope and spirit of the following claims and equivalents thereto are claimed as the invention.