Abstract:
A passive optical network includes one or more multi-service terminals each having a housing and a plurality of ruggedized plug-receiving distribution ports accessible from outside the housing. The multi-service terminals also each include an optical power splitter or wave division multiplexer for splitting an optical signal and directing the split signal to the plug-receiving distribution ports. Some of the multi-service terminals provide a different power split ratio from others of the multi-service terminals.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of application Ser. No. 13/588,045, filed Aug. 17, 2012, which application claims the benefit of provisional application Ser. No. 61/524,745, filed Aug. 17, 2011, which applications are incorporated herein by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates generally to equipment for fiber optic communications networks. More particularly, the present disclosure relates to the components of passive optical networks and methods for deploying the same. 
       BACKGROUND 
       [0003]    Passive optical networks are becoming prevalent in part because service providers want to deliver high bandwidth communication capabilities to customers. Passive optical networks are a desirable choice for delivering high-speed communication data because they may not employ active electronic devices, such as amplifiers and repeaters, between a central office and a subscriber termination. The absence of active electronic devices may decrease network complexity and/or cost and may increase network reliability. 
       SUMMARY 
       [0004]    Certain aspects of the disclosure relate to fiber optic cable systems. 
         [0005]    In example systems, a distributed passive optical network includes one or more feeder terminals and one or more distribution terminals. In accordance with some aspects, each terminal includes an optical power splitter arrangement. In accordance with other aspects, one or more terminals include wave division multiplexers. 
         [0006]    A variety of additional inventive aspects will be set forth in the description that follows. The inventive aspects can relate to individual features and to combinations of features. It is to be understood that both the forgoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the broad inventive concepts upon which the embodiments disclosed herein are based. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  shows an example distributed passive fiber optic network; 
           [0008]      FIG. 2  is a schematic block diagram of one example feeder terminal suitable for use in the passive optical network of  FIG. 1 ; 
           [0009]      FIG. 3  is a schematic block diagram of a first example type of distribution terminal suitable for use in the passive optical network of  FIG. 1 ; 
           [0010]      FIG. 4  is a schematic block diagram of an example cascading type of distribution terminal suitable for use in the passive optical network of  FIG. 1 ; 
           [0011]      FIG. 5  is a network map showing the deployment of an example distributed passive optical network over an example neighborhood in accordance with the principles of the disclosure; 
           [0012]      FIG. 6  is a flow diagram illustrating a method of providing a distributed passive optical network in a neighborhood; 
           [0013]      FIGS. 7 and 8  are schematic diagrams showing the deployment of a cascading-type distribution terminal at one example section of a neighborhood; and 
           [0014]      FIG. 9  is a flow diagram illustrating a method of upgrading a distributed passive optical network in accordance with the principles of the disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Reference will now be made in detail to exemplary aspects of the present disclosure that are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
         [0016]      FIG. 1  shows an example network  100  deploying passive fiber optic lines. The example network  100  can include a central office  105  that connects a number of end subscribers  140  (also called end users herein) in a network. The central office  105  can additionally connect to a larger network such as the Internet (not shown) and/or a public switched telephone network (PSTN). The network  100  includes multiple break-out locations at which branch cables are separated out from the main cable lines. Feeder cables  152  may branch off from the main cable lines and connect to fiber distribution hubs (FDHs) or pedestals  110  that include connector interfaces for facilitating coupling of the fibers of the branch cables to multiple different subscriber locations  140 . Each FDH or pedestal  110  may accept a feeder cable  152  from the central office or other upstream portion of the network  100 . The feeder cable  152  may have one or more fibers. The hub or pedestal  110  may separate and/or split the fibers of the feeder cable  152  into one or more distribution fibers  154 . 
         [0017]    Each distribution fiber  154  may be routed to a feeder terminal  120 . Each feeder terminal  120  includes a splitter arrangement at which the distribution fiber  154  may be split into two or more drop fibers  156 . Each drop fiber  156  is routed to a distribution terminal arrangement  130 . Each distribution terminal arrangement  130  includes a splitter arrangement at which the respective drop fiber  156  is split into two or more subscriber fibers  158 . Some types of the distribution terminal arrangements  130  evenly split the signals received from the drop fibers  156  as will be disclosed in more detail herein. Other types of distribution terminal arrangements  130  split the signal ratios unevenly. 
         [0018]    In some implementations, the splitter arrangements include optical power splitting structures. In other implementations, the splitter arrangements include wavelength splitting/dividing structures. Optical power splitters are capable of splitting an entire optical signal carried by one optical fiber to two or more optical fibers (e.g., 1 by 2 splitters; 1 by 4 splitters; 1 by 8 splitters, 1 by 16 splitters; 1 by 32 splitters, etc.), and are also capable of combining optical signals from multiple fibers back to one optical fiber. Wavelength splitting/dividing structures (e.g., coarse wavelength dividing multiplexers and de-multiplexers, dense wavelength dividing multiplexers and de-multiplexers, array waveguide grading structures, etc.) are capable dividing an optical signal carried by one optical fiber into separate wavelength ranges with each range then being directed to and carried by a separate optical fiber, and are also capable of combining separate wavelength ranges carried by separate optical fibers back to one optical fiber. 
         [0019]    In the example shown in  FIG. 1 , the feeder terminal  120  includes a 1 by 4 optical power splitter that splits the distribution fiber  154  into four drop fibers  156 . Two of the drop fibers  156  are each routed to a first example type of distribution terminal  132  having 1 by 8 optical power splitters that split the drop fibers  156  into eight subscriber fibers  158 . Another two of the drop fibers  156  are each routed to a cascading distribution terminal arrangement  135  that includes an example second type of distribution terminal  134  and an example third type of distribution terminal  136 . The second type of distribution terminal  134  includes a splitter arrangement including a 1 by 2 optical splitter and a 1 by 4 optical splitter. A cascade fiber  157  output from the 1 by 2 optical power splitter is routed to the input of the third type of distribution terminal  136 , which includes a 1 by 4 optical splitter. Output of each 1 by 4 optical splitter is carried by the respective subscriber fiber  158  to one of the end users  140 . 
         [0020]    In some implementations, the feeder terminals  120  and/or the distribution terminals  130  may be implemented as multi-service terminals (MSTs). Non-limiting examples of a multi-service terminal housing a splitter arrangement are shown in U.S. Pat. No. 7,444,056 and U.S. Publication No. 2009/0208177, the disclosures of which are hereby incorporated herein by reference. In some implementations, one or more of the feeder terminals  120  and/or distribution terminals  130  may include fiber spools from which a respective fiber may be deployed. One example multi-service terminal housing a fiber spool is shown in U.S. application Ser. No. 12/487,318, filed Jun. 18, 2009, and titled “Methods and Systems for Distributing Fiber Optic Telecommunications Services to Local Area,” and U.S. application Ser. No. 13/195,939, filed Aug. 2, 2011, and titled “Cable Spool Assembly,” the disclosures of which are hereby incorporated herein by reference. 
         [0021]      FIG. 2  is a schematic block diagram of one example feeder terminal  120  suitable for use in the passive optical network  100  of  FIG. 1 . The feeder terminal  120  includes a body  121  defining an input port  122  and at least two output ports  128 . The distribution fiber  154  is received at the input port  122 . In the example shown, the feeder terminal body  121  defines four output ports  128 . In other implementations, however, the feeder terminal body  121  may define greater or fewer (e.g., three, five, eight, etc.) output ports  128 . The feeder terminal body  121  houses a splitter arrangement  125  that is configured to split optical signals carried over the distribution fiber  154  to the output ports  128  (see lines  126 ). In the example shown, the splitter arrangement  125  includes a 1 by 4 power splitter. 
         [0022]    In some implementations, an optical connector interface  123  is disposed at the input port  122  of the feeder terminal body  121  to enable a “plug and play” type connection. In certain implementations, the optical connector interface  123  is ruggedized (i.e., hardened) to seal the interior of the feeder terminal body  121  from contaminants. In some implementations, the optical connector interface  123  includes an optical connector from which a splitter input fiber  124  routes to the splitter arrangement  125 . In other implementations, the optical connector interface  123  includes an optical socket from which a splitter input fiber  124  routes to the splitter arrangement  125 . In still other implementations, the optical connector interface  123  includes an optical adapter configured to interface two optical connectors. Some non-limiting example ruggedized optical connector interfaces suitable for use with a feeder terminal  120  are disclosed in U.S. Pat. Nos. 7,744,288, 7,762,726, 7,744,286, 7,942,590, and 7,959,361, the disclosures of which are hereby incorporated herein by reference. 
         [0023]      FIG. 3  is a schematic block diagram of a first example type of distribution terminal  132  suitable for use in the passive optical network  100  of  FIG. 1 . The distribution terminal  132  includes a body  161  defining an input port  162  and at least two output ports  168 . The drop fiber  156  is received at the input port  162 . In the example shown, the feeder terminal body  161  defines eight output ports  168 . In other implementations, however, the distribution terminal body  161  may define greater or fewer (e.g., three, four, six, ten, twelve, etc.) output ports  168 . The distribution terminal body  161  houses a splitter arrangement  165  that is configured to split optical signals carried over the drop fiber  156  to the output ports  168  (see lines  166 ). In the example shown, the splitter arrangement  165  includes a 1 by 8 power splitter. 
         [0024]    In some implementations, an optical connector interface  163  is disposed at the input port  162  of the distribution terminal body  161  to enable a “plug and play” type connection. In certain implementations, the optical connector interface  163  is ruggedized (i.e., hardened) to seal the interior of the feeder terminal body  161  from contaminants. In some implementations, the optical connector interface  163  includes an optical connector from which a splitter input fiber  164  routes to the splitter arrangement  165 . In other implementations, the optical connector interface  163  includes an optical socket from which a splitter input fiber  164  routes to the splitter arrangement  165 . In still other implementations, the optical connector interface  163  includes an optical adapter configured to interface two optical connectors. Some non-limiting example ruggedized optical connector interfaces suitable for use with a distribution terminal  130  are disclosed in U.S. Pat. Nos. 7,744,288, 7,762,726, 7,744,286, 7,942,590, and 7,959,361, incorporated by reference above. 
         [0025]      FIG. 4  is a schematic block diagram of an example cascading type of distribution terminal  135  suitable for use in the passive optical network  100  of  FIG. 1 . The example cascading distribution terminal  135  includes an example second type of distribution terminal  134  and an example third type of distribution terminal  136 . The second distribution terminal  134  includes a body  171  defining an input port  172  and at least two output ports  179 . The drop fiber  156  is received at the input port  172 . In the example shown, the body  171  defines four output ports  179 . In other implementations, however, the body  171  may define greater or fewer (e.g., three, five, eight, etc.) output ports  179 . In certain implementations, the body  171  also defines a pass-through port  175 . 
         [0026]    The second type of distribution terminal  134  also includes a splitter arrangement  174  that is configured to split optical signals carried over the drop fiber  156  to the output ports  179 . In some implementations, the splitter arrangement  174  includes at least a first optical power splitter  177  and a second optical power splitter  178 . The first optical power splitter  177  splits signals carried by the drop fiber  156  and directs a first split signal to the second optical power splitter  178  and a second split signal to the pass-through port  175 . In the example shown, the first optical power splitter  177  is a 1 by 2 splitter, which splits the power of the optical signals  50 / 50 . In other implementations, the first optical power splitter  177  may split the signals unevenly (e.g., 25/75). The second optical power splitter  178  receives the first split signal from the first optical power splitter  177  and splits that signal into four signals, which are directed to the output ports  179 . In the example shown, the second optical power splitter  178  is a 1 by 4 splitter. 
         [0027]    In some implementations, an optical connector interface  173  is disposed at the input port  172  of the distribution terminal body  171  to enable a “plug and play” type connection. Indeed, in some implementations, a second optical connector interface  176  is disposed at the pass-through port  173  of the distribution terminal body  171  to enable a “plug and play” type connection. In other implementations, optical fiber (e.g., pigtail fibers, stub fibers, spliced fibers, etc.) may be routed through the ports  172 ,  175  to the splitter. In certain implementations, the optical connector interfaces  173 ,  176  are ruggedized (i.e., hardened) to seal the interior of the distribution terminal body  171  from contaminants. In various implementations, the optical connector interfaces  173 ,  176  include optical connectors, optical sockets, or optical adapter. Some non-limiting example ruggedized optical connector interfaces suitable for use with a distribution terminal  134  are disclosed in U.S. Pat. Nos. 7,744,288, 7,762,726, 7,744,286, 7,942,590, and 7,959,361, incorporated by reference above. 
         [0028]    The third type of distribution terminal  136  includes a body  181  defining an input port  182  and at least two output ports  188 . The cascade fiber  157  is received at the input port  182 . In the example shown, the distribution terminal body  181  defines four output ports  188 . In other implementations, however, the distribution terminal body  181  may define greater or fewer (e.g., three, six, ten, twelve, etc.) output ports  188 . The distribution terminal body  181  houses a splitter arrangement  185  that is configured to split optical signals carried over the cascade fiber  157  to the output ports  188 . In the example shown, the splitter arrangement  185  includes a 1 by 4 power splitter. 
         [0029]    In some implementations, an optical connector interface  183  is disposed at the input port  182  of the distribution terminal body  181  to enable a “plug and play” type connection. In certain implementations, the optical connector interface  183  is ruggedized (i.e., hardened) to seal the interior of the feeder terminal body  181  from contaminants. In various implementations, the optical connector interface  183  includes an optical connector, an optical socket, or an optical adapter. For example, in some implementations, the cascade fiber  157  is connectorized at both ends. A first end of the cascade fiber  157  plugs into a ruggedized socket or adapter at the pass-through port  175  of the first body  171  and a second end plugs into a ruggedized socket or adapter at the input  182  of the second body  181 . Some non-limiting example ruggedized optical connector interfaces suitable for use with a distribution terminal  136  are disclosed in U.S. Pat. Nos. 7,744,288, 7,762,726, 7,744,286, 7,942,590, and 7,959,361, incorporated by reference above. 
         [0030]      FIG. 5  is a network map showing the deployment of an example distributed passive optical network  1000  over an example neighborhood  1010 . For ease in viewing, only the feeder terminals  120  (labeled “F4”) and distribution terminals  130  (labeled “D8”) are shown. In use, however, each of the feeder terminals  120  would receive a feeder cable fiber  154  from a network hub or pedestal  110 . In the example shown, each feeder terminal  120  includes a 1 by 4 splitter and each distribution terminal  130  includes a 1 by 8 splitter. Each distribution terminal  130  provides service to a section  1020  of the neighborhood  1010 . For example, each section  1020  includes two or more structures (e.g., homes, offices, etc.)  1025  to which a subscriber fiber  158  is routed. 
         [0031]    The feeder terminals  120  are disposed at various locations in the neighborhood  1010 . Some types of feeder terminals  120  may be disposed within pedestals or cabinets. Other types of feeder terminals  120  may be disposed within handholes. Still other types of feeder terminals  120  may be disposed within wall boxes. Each drop fiber  156  is routed from one of the feeder terminals  120 , along one or more streets within the neighborhood  1010 , to a respective distribution terminal  130 . 
         [0032]    Each distribution terminal  130  is disposed within one of the neighborhood sections  1020 . Some types of distribution terminals  130  may be disposed in a pedestal or cabinet. Certain types of distribution terminals  130  may be disposed within a pedestal or cabinet with a corresponding feeder terminal  120 . Other types of distribution terminals  130  may be disposed within handholes. Still other types of distribution terminals  130  may be disposed within wall boxes. Each subscriber fiber  158  is routed from one of the distribution terminals  130 , along one or more streets within the neighborhood section  1020 , to a respective subscriber location  140 . 
         [0033]      FIG. 6  is a flow diagram  900  illustrating a method of providing a distributed passive optical network, such as network  100  of  FIG. 1  or network  1000  of  FIG. 5 , in a neighborhood. The method diagram  900  includes a deploy operation  902  during which a network framework is installed in the neighborhood. For example, the network framework may include pedestals, handholes, conduits, and other such components. The method diagram  900  also includes a connect operation  904  during which optical connections are made between the central office and the subscribers  140 . 
         [0034]    In some implementations, the connect operation  904  is implemented at a subsequent date to the deploy operations  902 . For example, the framework for the network (e.g., the conduits, pedestals, handholes, and optical fibers) may be laid at an initial date and the terminals  120 ,  130  may be added at a subsequent date when service is required. Indeed, in certain implementations, the terminals  120 ,  130  may be added incrementally as service is required. For example, a feeder terminal  120  and distribution terminals  130  may be added for one section  1020  of a neighborhood on a first date and a second feeder terminal  120  and corresponding distribution terminals  130  may be added at a later date. In other implementations, some or all of the terminals  120 ,  130  may be installed when the framework is laid. 
         [0035]    In some implementations, the deployment operation  902  includes installing handholes and/or pedestals at appropriate feeder locations and distribution locations. Conduits are laid between the feeder and distribution locations. In some implementations, the conduits are installed in small bores through the street. In certain implementations, the conduits include ducts having a diameter of about one inch. In other implementations, the conduits may have a larger or smaller diameter. Optical fibers may be routed along the conduits between the feeder locations and the distribution locations. In some implementations, a single optical fiber is routed through each conduit. Ends of the optical fibers may be stored at the respective handholes and/or pedestals. 
         [0036]    One or more feeder terminals  120  and two or more distribution terminals  130  are deployed during the connect operation  904 . The optical fibers are connected to the terminals  120 ,  130  during a connect operation  908 . For example, in one implementation, a connectorized end of an optical fiber may be plugged into a socket defined by one of the terminals  120 ,  130 . In another implementation, the optical fiber may define a combination connector and adapter that is configured to connect to a connector disposed at the terminal  120 ,  130 . 
         [0037]      FIGS. 7 and 8  are schematic diagrams showing the deployment of a cascading-type distribution terminal  135  at one example section  1020  of a neighborhood. The neighborhood section  1020  includes a street lined with four lots  1025  on each side.  FIG. 7  shows the deployment of the network framework including a first pedestal or handhole  137  at a first side of the street and a second pedestal or handhole  139  at a second side of the street. A first conduit is installed along the first side of the street (e.g., underground) to provide a pathway to the first pedestal or handhole  137 . A second conduit is installed across the street (e.g., underground) to connect the first pedestal  137  to the second pedestal  139 . 
         [0038]    A drop fiber  156  is routed along the first side of the street through the first conduit to the first pedestal or handhole  137 . In some implementations, excess length of the drop fiber  156  is stored in the pedestal or handhole  137 . In certain implementations, the drop fiber  156  has a connectorized end that is stored in the pedestal or handhole  137 . In other implementations the drop fiber  156  is terminated at a distribution terminal (e.g., distribution terminal  134 ) that is disposed in the pedestal or handhole  137 . 
         [0039]    A cascade fiber  157  is routed through the second conduit to the second pedestal or handhole  139 . In some implementations, excess length of the cascade fiber  157  is stored in the second pedestal or handhole  137 . In certain implementations, the cascade fiber  157  has a first connectorized end  158  that is stored in the first pedestal or handhole  137  and a second connectorized end  159  that is stored in the second pedestal or handhole  139 . In other implementations, the second end of the cascade fiber  157  may be terminated at a distribution terminal (e.g., distribution terminal  136 ) that is disposed in the second pedestal or handhole  139 . 
         [0040]    When service to one or more lots  1025  in the neighborhood section  1020  is desired, one or more terminals  120 ,  130  may be installed. For example, as shown in  FIG. 8 , one example distribution terminal  134  may be disposed in the first pedestal or handhole  137  and another example distribution terminal  136  may be disposed in the second pedestal or handhole  139 . A connectorized end of the drop cable  156  is plugged into the input (e.g., connector interface  173 ) of the distribution terminal  134  disposed in the first pedestal or handhole  137 . The first connectorized end  158  of the cascade fiber  157  is plugged into a connector interface  176  at the pass-through port  176  of the distribution terminal  134 . The second connectorized end  158  of the cascade fiber  157  is plugged into the input (e.g., connector interface  183 ) of the distribution terminal  136  disposed in the second pedestal or handhole  139 . 
         [0041]    In one such implementation, the signal power received at the distribution terminal  134  is split so that 50% of the power is routed through the cascade fiber  157  to the distribution terminal  136 . The remaining signal power is split evenly at the distribution terminal  134  so that about 12.5% of the initial signal power is provided to each output port  179  of the distribution terminal  134 . The distribution terminal  136  splits the received signal power evenly so that about 12.5% of the initial signal power is provided to each output port  188  of the distribution terminal  136 . 
         [0042]      FIG. 9  is a flow diagram  910  illustrating a method of upgrading a distributed passive optical network, such as network  100  of  FIG. 1  or network  1000  of  FIG. 5 . The method diagram  910  includes a provide operation  912  at which a distributed passive optical network is deployed or acquired. The distributed passive optical network includes optical power splitters disposed at one or more of the feeder terminals  120  and/or distribution terminals  130 . 
         [0043]    A swap operation  914  replaces one or more of the optical power splitters with wave division multiplexers. For example, in some implementations, the network may be upgraded by replacing the optical power splitters located within the feeder terminals  120  with wave division multiplexers. In certain implementations, the entire feeder terminal  120  may be replaced with an upgraded terminal housing the wave division multiplexers. In other implementations, the network may be upgraded by replacing the optical power splitters located within the distribution terminals  130  with wave division multiplexers. In certain implementations, the entire distribution terminal  130  may be replaced with an upgraded terminal housing the wave division multiplexers. 
         [0044]    In some implementations, the upgraded terminals (e.g., upgraded feeder terminals  120  and/or upgraded distribution terminals  130 ) may include plug and play type connections. For example, an upgraded terminal may include a ruggedized connector, socket, or adapter at which a connectorized end of an optical fiber may be connected.