Abstract:
Systems and methods for optically connecting first and second fiber arrays at different locations with paired transmit and received fibers are disclosed. A method includes establishing at a first location first and second fiber arrays of fibers T and R, and establishing at a second location third and fourth fiber arrays of fibers T′ and R′. A trunk cable is then used to optically connect fibers T to fibers R′ and fibers R′ to fibers T to form first fiber pairs (T,R) where T=1 to (N/2) and R=[(N/2)+1] to N, and second fiber pairs (T′, R′), where T′=1′ to (N/2)′ and R′=[(N/2)+1]′ to N′, wherein N is an even number greater than 2.

Description:
PRIORITY APPLICATION 
       [0001]    This application claims the benefit of priority under 35 U.S.C. §119 of U.S. Provisional Application Ser. No. 61/994,446 filed on May 16, 2014, the content of which is relied upon and incorporated herein by reference in its entirety. 
     
    
     FIELD 
       [0002]    The present disclosure relates to optical fiber cabling systems, and in particular relates to pre-terminated modular cabling components and methods of optically connecting fiber arrays at two different locations with paired transmit and receive fibers. 
         [0003]    The entire disclosure of any publication or patent document mentioned herein is incorporated by reference, including U.S. Pat. Nos. 6,758,600 and 7,689,079. 
       BACKGROUND 
       [0004]    Pre-terminated optical fiber cabling, systems are used to dramatically streamline the process of deploying an optical networking infrastructure in the premises environment, particularly in data center applications. Such systems significantly reduce installation time and cost. Pre-terminated modular components of the system are simple to configure and can be installed, connected and operational in a fraction of the time when compared to using conventional, field-terminated methods. Commonly used pre-terminated modular components include jumper cables (“jumpers”), trunk cables, breakout modules, and breakout harnesses. 
         [0005]    One important aspect of designing, manufacturing and deploying components in a pre-terminated and modular optical cabling system (or network) is ensuring that the duplexed transmitters and receivers connection locations on one end of the optical path defined by the system are in optical communication with select receive and transmit connection locations at the opposite end of the optical path. Management of how the transmit and receive connections locations are interconnected is commonly known as “polarity management.” 
         [0006]    Most modular optical cabling systems in commercial use are based upon cable assemblies having 12-fiber MPO-style connectors. In particular, these systems utilize trunk cables having fiber counts in multiples of 12 and that are furcated into one or more 12-fiber legs, with each leg terminated with a 12-fiber MPO-style connector. These trunk cables are placed into cable pathways to span the distance between various equipment locations, patching locations (cross-connects and interconnects) and other network access points. 
         [0007]    To establish connectivity with duplex transceiver ports commonly used on active equipment, these trunk cables must be transitioned to duplexed single-fiber connectors or 2-fiber connectors. This is accomplished by mating the trunk&#39;s 12-fiber MPO connectors to breakout harnesses or breakout modules having 12-fiber MPO connectors on one end and either (a) 2-fiber connectors such as MT-RJ® connectors, or more commonly (b) duplexed single fiber connectors such as SC or LC connectors that are duplexed together with a duplexing adapters, clips or boots. These breakout assemblies are therefore sometimes collectively referred to as “transition assemblies” or “fan-out assemblies.” 
         [0008]    Bandwidth performance of some conventional optical fibers can be extended beyond their original performance specifications by concatenating them with engineered lengths of special optical fibers at optimal proximity to either the transmit or receive end of an optical link. Although these special fibers could be incorporated into the jumpers, there are practical considerations that make it more attractive to incorporate the special fibers into a breakout assembly, thereby extending the conventional functionality of a breakout assembly beyond that of merely transitioning from MPO connectors to duplex or 2-fiber connectors. Since a breakout assembly conventionally comprises duplexed fiber pairs terminated at one end into the same MPO connector, this means that the breakout assembly would need to comprise two different optical fibers or perhaps fibers of significantly different lengths. While it is possible to manufacture and test breakout assemblies with differing optical fibers and lengths, these requirements introduce complexities in manufacturing and testing that are undesirable and which conventional designs of breakout assemblies never anticipated. 
         [0009]    Consequently, there is a need for a new type of breakout assembly and methods of concatenating such assemblies to form optical pathways that are capable of extending the performance of existing and future fiber installations while properly manage the polarity requirements of the cabling system while exploiting the benefits associated with factory pre-terminated modular components. Furthermore, it is desirable that these breakout assemblies be easy to manufacture and test when they contain more than one type or length of fiber. 
       SUMMARY 
       [0010]    An aspect of the disclosure is a method of optically connecting first fiber pairs at a first location to second fiber pairs at a second location to form an optical path between the first and second locations. The method includes: establishing at the first location first and second fiber arrays comprising fibers T and R, respectively; establishing at the second location third and fourth fiber arrays comprising fibers T′ and R′, respectively; and optically connecting fibers T to fibers R′ and fibers R to fibers T′ so that first fiber pairs are defined by (T,R), where T=1 to (N/2) and R=[(N/2)+1] to N, and second fiber pairs are defined by (T′, R′), where T′=1′ to (N/2)′ and R′=[(N/2)+1]′ to N′, wherein N is an even number greater than 2. 
         [0011]    Another aspect of the disclosure is a method of optically connecting first fiber pairs at a first location to second fiber pairs at a second location to form an optical path between the first and second locations. The method includes: defining a first fiber array comprising fibers T=1 to N/2, a second fiber array comprising fibers R=[(N/2)+1] to N, a third fiber array comprising fibers T′=1′ to (N/2)′, and a fourth fiber array comprising fibers R′=[(N/2)+1]′ to N′, where N is an even number greater than 2; using at least one trunk cable, optically connecting the first fiber array to the fourth fiber array and optically connecting the second fiber array to the third fiber array to establish optical communication between the fibers in the respective fiber arrays as follows: 
         [0000]      { T}→{R′}={ 1 to ( N/ 2)}→{[( N/ 2)+1]′ to  N′};  
 
         [0000]      { R}→{T ′}={[( N/ 2)+1] to  N}→{ 1′ to [( N/ 2)]′};
 
         [0000]    and wherein the first fiber pairs are defined by (T,R), and the second fiber pairs are defined by (T′, R′). 
         [0012]    Another aspect of the disclosure is an optical assembly in the form of a module for providing N optical connections for N/2 pairs of fibers, for N even and greater than 2. The module includes: a housing having at least one wall that defines an interior; at least one multifiber connector adapter penetrating the at least one wall; at least one of duplexed single-fiber connector adapters or 2-fiber connector adapters penetrating the least one wall; a first fiber array of fibers T=1 to N/2 terminated at one end by at least one multifiber connector inserted into the at least one multifiber connector adapter and terminated at the other end by either first single-fiber or first 2-fiber connectors inserted into the single-fiber or the 2-fiber connector adapters; a second fiber array of fibers R=[(N/2)+1] to N terminated at one end by the at least one multifiber connector inserted into the at least one multifiber connector adapter and terminated at the other end by either second single-fiber or second 2-fiber connectors inserted into the single-fiber or the 2-fiber connector adapters; and wherein the fibers T and R are paired as (T,R). 
         [0013]    Another aspect of the disclosure is an optical assembly in the form of a harness for providing N optical connections for N/2 pairs of fibers, for N even and greater than 2. The harness includes: a first fiber array of fibers T=1 to N/2 terminated at one end by at least one multifiber connector and terminated at the other end by either first single-fiber or first 2-fiber connectors; a second fiber array of fibers R=[(N/2)+1] to N terminated at one end by the at least one multifiber connector and terminated at the other end by either second single-fiber or second 2-fiber connectors; and wherein the fibers T and R are paired as (T,R). 
         [0014]    Additional features and advantages are set forth in the Detailed Description that follows, and in part will be readily apparent to those skilled in the art from the description or recognized by practicing the embodiments as described in the written description and claims hereof, as well as the appended drawings. It is to be understood that both the foregoing general description and the following Detailed Description are merely exemplary, and are intended to provide an overview or framework to understand the nature and character of the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiment(s), and together with the Detailed Description serve to explain principles and operation of the various embodiments. As such, the disclosure will become more fully understood from the following Detailed Description, taken in conjunction with the accompanying Figures, in which: 
           [0016]      FIG. 1  is a schematic diagram of an example pre-terminated optical fiber cabling system that includes an example of a pre-terminated optical pathway as disclosed herein that utilizes a trunk cable and breakout modules; 
           [0017]      FIG. 2A  is an front elevated and partial cut-away view of an example breakout module according to the disclosure, that shows some of the fibers of the first fiber array and some of the fibers of the second fiber array, and that shows a close-up end-on view of an example of a back-end connector adapter and corresponding connector with example connection locations; 
           [0018]      FIG. 2B  is a close-up side and partial cut-away view of an example breakout module that shows the front-end adapters and a back-end adapter, corresponding front-end and back-end connectors, along with the internal fibers of the fiber array, and an end portion of a jumper cable showing the jumper cable connector; 
           [0019]      FIG. 2C  is a front-end view of the breakout module of  FIGS. 2A and 2B , illustrating duplex front-end adapters and an example polarity configuration of the transmit and receive connection locations (T,R) for an example 24-fiber module. 
           [0020]      FIG. 3A  is a schematic diagram of an example pre-terminated optical fiber cabling system that includes an example of a pre-terminated optical pathway as disclosed herein that utilizes a trunk cable and breakout harnesses; 
           [0021]      FIG. 3B  is a close-up view of an example breakout harness suitable for use in the pre-terminated optical fiber cabling system of  FIG. 3A ; 
           [0022]      FIG. 4A  is a schematic diagram of an example optical pathway according to the disclosure as defined by a trunk cable and two breakout modules; 
           [0023]      FIGS. 4B and 4C  are similar to  FIG. 4A , but only showing the first and second optical paths, respectively; 
           [0024]      FIG. 5A  is similar to  FIG. 4A , and illustrates an example of an optical pathway according to the disclosure as defined by a trunk cable and two breakout harnesses; 
           [0025]      FIGS. 5B and 5C  are similar to  FIG. 5A , but only showing the first and second optical paths, respectively; 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    Reference is now made in detail to various embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Whenever possible, the same or like reference numbers and symbols are used throughout the drawings to refer to the same or like parts. The drawings are not necessarily to scale, and one skilled in the art will recognize where the drawings have been simplified to illustrate the key aspects of the disclosure. 
         [0027]    The claims as set forth below are incorporated into and constitute part of this Detailed Description. 
         [0028]    Designations of “left” and “right” and “front” and “back” are used in some of the Figures for the sake of reference and to facilitate explanation and understanding and are not intended to be limiting as to position, direction, orientation, etc. 
         [0029]    The discussion below and the claims refer to optical fibers, and in particular to different optical fibers. Optical fibers in the present disclosure may be differentiated by differences in attributes such as refractive index profile, core size, mode field diameter, cladding diameter, composition, or length. Optical fibers in the present disclosure may also be differentiated according to performance characteristics such bandwidth-distance product, skew, differential modal delay, attenuation performance, bend sensitivity, modal dispersion, chromatic dispersion, polarization mode dispersion, cutoff wavelength, or transmission modes supported under given operating conditions. 
       Optical Fiber Cabling System 
       [0030]      FIG. 1  is a schematic diagram of an example pre-terminated optical fiber cabling system (“system”)  100 . System  100  includes a first and second (left and right) device equipment racks  120  (denoted  120 L and  120 R) that respectively support at least one electronic device  122  (denoted  122 L and  122 R), such as switches, routers, servers or data storage devices having optical transceivers (not shown). The transceivers typically have duplex optical communications connection locations (also referred to as “ports” in some embodiments) to accommodate transmit and receive signals. Each electronic device  122  has a front end  124 . 
         [0031]    System  100  also includes first and second (left and right) housing racks  130  (denoted  130 L and  130 R). Housing racks  130 L and  130 R each supports one or more housings  132  ( 132 L and  132 R, respectively), wherein each houses one or more breakout modules  200  ( 200 L and  200 R, respectively). In an example, breakout modules  200 L and  200 R have the same configuration, i.e., are identical modules. 
         [0032]      FIG. 2A  is a front elevated and partial cut-away view of an example breakout module  200 , while  FIG. 2B  is a close-up side and partial cut-away view and  FIG. 2C  is a front-end view. Each breakout module  200  includes a casing or housing  201  having at least one wall  201 W that in an example defines a front end  202 , a back end  204  and an interior  206 . Interior  206  houses two optical fiber arrays  208 A and  208 B made up of connectorized optical fibers  209 , i.e., fibers of each array are terminated individually at one end with connectors  210  and collectively at the other end with at least one multifiber connector  211 , such as an MPO connector. 
         [0033]    The module-based system  100  includes two breakout modules  200 L and  200 R, with breakout module  200 L having two optical fiber arrays  208 LA and  208 LB and breakout module  200 R having two optical fiber arrays  2008 RA and  2008 RB. Thus, there are a total of four optical fiber arrays in the module-based system  100 , and their configuration is explained in greater detail below. 
         [0034]    The front end  202  of module  200  includes a face plate  203  used to mount the module into housing  132  using mounting pins  205 . The face plate  203  of module  200  supports one or more connector adapters  212  (“front-end adapters”) that have pairs of alignment sleeves  213  each sized to accommodate a single fiber connector, e.g. LC or SC connectors. In the case of a 2-fiber MT-RJ® connectors, the two fibers  209  share a single ferrule and the ferrule fits into a single alignment sleeve  213  on the adapter. 
         [0035]    Alignment sleeves  213  are also referred to as “ports” and define connection locations. In an example, face plate  203  supports twelve front-end adapters  212  each configured to accommodate a pair of connectors  210  connected to one end of fibers  209 , with one fiber at a transmit (T) location and one fiber at a receive (R) location. Front-end adapters  212  extend through face plate  203  and into casing interior  206 , as best shown in  FIG. 2B . Each front-end adapter  212  is configured to mate on the module-interior side with connectors  210  of fibers  209 , and on the outside to connectors  252  of jumpers  250 , as described below. 
         [0036]    With reference again to  FIG. 2A , module  200  also includes one or more connector adapters  214  (“back-end adapters”) at back end  204 . In the example shown, there are two back-end multifiber adapters  214 , e.g., each are 12-fiber adapters. The back-end adapters  214  each includes alignment sleeves or connection locations  215 , as shown in  FIG. 2B . The back-end adapters are configured to support back-end connector  210 . The connection location numbers for the twenty-four connection locations  215  and their transmit (T) and receive (R) designation for module  200  are also shown in table form on the right side of  FIG. 2C . The management of the polarity configuration for optical pathway OP based on the connection location numbers or fiber numbers is discussed in greater detail below. 
         [0037]    It is noted that the connection locations numbers and their T and R designations can be reversed from what is shown in  FIG. 2A  and as discussed below and not impact the fundaments polarity management as disclosed herein. 
         [0038]    The close-up inset of  FIG. 2A  shows an end-on view of an example multifiber MPO back-end adapter  214 , along with the endface of a multifiber connector  211  that has two rows or planes of connection locations  215 , with the connection locations for optical fiber array  208 A residing on one plane and the connection locations for optical fiber array  208 B residing in the other plane, as indicated in parenthesis in the close-up inset of the back-end adapter. Thus, fibers  209  of the first fiber array  208 A are not coplanar with the fibers  209  of the second fiber array  209 A when there is a single multifiber connector  211  supported by a single back-end adapter  214 . 
         [0039]    In an example, each optical fiber array  208 A and  208 B originates at one or more back-end adapters  214 , with one fiber  209  from each optical fiber array forming a fiber pair at one or more front-end adapters  212 . Said differently, in an example the two fibers  209  that form a fiber pair originate from different back-end adapters. 
         [0040]    In an example configuration, module  200  can have a single back-end adapter  214  configured to receive all of the fibers  222  from trunk cable  200 , e.g., in two 12-fiber rows. In another example configuration, module  200  can have first and second back-end adapter  214 , with each configured to receive optical fibers  209  for first and second fiber arrays  208 A and  208 B, respectively. Also, front end  202  of module  200  can support a single front-end adapter  212  that is configured to support multiple duplex connections, as illustrated in  FIG. 2A . In an example, front-end and back-end adapters  212  and  214  are configured as MPO adapters. In other embodiments, multiple front-end adapters  212  are employed. 
         [0041]    In an example, fiber arrays  208 A and  208 B are made of different types of fibers  209 , e.g., one array includes single mode fibers while the other array includes multimode fibers. 
         [0042]    As noted above in connection with  FIGS. 1 and 2B , system  100  also includes optical jumper cables or patch cords (hereinafter, “jumpers”)  250  (denoted  250 L and  250 R). Jumpers  250  are connectorized, i.e., they include connectors  252  at each end, with one connector configured to plug into the one or more front-end adapters  212  of module  200 , and the other connector configured to plug into the front end  124  of one of the devices  122 . Jumpers  250  are typically 2 m to 10 m in length, but can be much longer if necessary. In an example, jumpers  250  are duplex jumpers and connectors  252  are duplex connectors (e.g., LC connectors, SC connectors, RT-MJ connectors, etc.), while front-end adapters  212  are duplex adapters, so that each front-end adapter  212  supports a 2-fiber or duplexed single-fiber connection. 
         [0043]    With reference again to  FIG. 1 , modules  200 L and  200 R are optically connected by a trunk cable  220  that carries trunk fibers  222 . Trunk cable  220  can include a main section  221  and one or more or legs  224  on either end of the main section that each includes two or more fibers  222 . In an example, legs  224  are connectorized, i.e., they include connectors  226  that plug into back-end adapters  214  of modules  200 L and  200 R, thereby establishing optical communication with first and second fiber arrays  208 L and  208 R therein. Trunk cable  220  can be very long (e.g., hundreds of meters, many kilometers, etc.) and typically spans a section of a large building or a data center. An example connector  226  is an MPO connector, e.g., a 12-fiber MPO connector. 
         [0044]    Trunk cable  220  can support a relative large number N of trunk fibers  222  (e.g., multiples of 24, such as 24, 48, 72, 96, etc.). Trunk cable  220  can include one or more ribbonized sections that operably support a portion (e.g., N/2) of the total number N of trunk fibers, e.g., twelve trunk fibers  222  of a total of N=24 trunk fibers. Generally, N is an even number equal to 2 or greater, i.e., the trunk cables  220  considered herein carry N trunk fibers  222 , for N=4, 6, 8, . . . . 
         [0045]    Trunk optical fibers  222  define first and second trunk optical fiber arrays  228 A and  228 B, as show in the close-up inset of  FIG. 1 . Trunk cables  220  that have legs  224  also typically include furcation locations  230  where the individual optical fibers  222  branch off into the different legs  224 . A feature of trunk fiber arrays  228 A and  228 B as employed herein is that trunk cable legs  224  contain fibers  222  that carry signals in only a single direction, i.e., one leg carries optical signals that travel from device  122 R to device  122 L while the other leg carries optical signals that travel from device  122 L to device  122 R. In particular, first trunk fiber array  228 A carries optical signals in one direction second trunk fiber array  228 B carries optical signals in a second direction. 
         [0046]    The portion of system  100  that includes trunk fiber arrays  228 A and  228 B, first and second left-side fiber arrays  208 LA and  208 LB, and first and second right-side fiber arrays  208 RA and  208 RB is referred to herein as an “optical pathway system”  102  that defines an optical pathway OP. A total of six fiber arrays are thus used to define this example optical pathway system  102 . 
         [0047]      FIG. 3A  is a schematic diagram of an example pre-terminated optical fiber cabling system  100  that includes an example of optical pathway OP as disclosed herein that utilizes trunk cable  220  and left and right breakout harnesses  270 , denoted  270 L and  270 R. The example trunk cable  220  includes two legs  224  at each of its ends. Each trunk leg  224  its terminated by a connector  226 . 
         [0048]      FIG. 3B  is a close-up view of an example breakout harness  270 . Breakout harness  270  supports N optical fibers  272 . Breakout harness  270  includes a main section  271  that encases all N fibers  272 . Breakout harness  270  includes front and rear furcation locations  274 F and  274 R that terminate respective ends of main section  271 . Front furcation location  274 F is where the N fibers  272  branch out into branches  276  that each carries a pair of fibers  272 . Branches  276  are terminated by connectors  277 . Connectors  277  can be 2-fiber connectors such as MT-RJ® connectors, or duplexed single fiber connectors such as SC or LC connectors that are duplexed together with a duplexing adapter or duplexing clip. Connectors  277  obviate the need for jumpers  250  to connect to devices  212 . The N fibers  272  of breakout harness  270  define two fibers arrays  275 A and  275 B, as shown in the close-up inset view of the main section  271  in  FIGS. 3A and 3B . 
         [0049]    Rear furcation location  274 R is where the N fibers  272  branch out into two legs  278 A and  278 B that each carrying N/2 fibers  272  that respectively define fiber arrays  275 A and  275 B. The two legs  278 A and  278 B are terminated by multifiber connectors  279 A and  279 B, which are configured to connect to multifiber connectors  226  of legs  224  of trunk cable  220 . The two fibers  272  that make up the pairs of fibers for each branch  276  come from different legs  278 , i.e., each branch  276  is made up of one fiber from each of legs  278 A and  278 B. 
         [0050]    Thus, the breakout harness embodiment of optical pathway OP is defined by the two trunk fiber arrays  228 A and  228 B and the two fiber arrays  275 A and  275 B of each breakout harness  270 L and  270 R, for a total of six fiber arrays. Breakout module  200  and breakout harness  270  are two different types of a breakout assembly that includes a fiber array, which constitutes part of the optical pathway OP of the optical pathway system  102 . 
       Module-Based Optical Path 
       [0051]      FIG. 4A  is schematic diagram of an example optical pathway system  102  based on the module-based configuration of system  100  of  FIG. 1 . As discussed above, optical pathway system  102  includes the first and second fiber arrays  208 LA and  208 LB on the left-hand side, first and second trunk fiber arrays  228 A and  228 B, and first and second fiber arrays  208 RA and  208 RB on the right-hand side. Optical signals  300  travel only in one direction each fiber array. One optical signal  300  is shown in system  100  for each direction of travel over the optical pathway OP defined by optical system  102  for ease of illustration. 
         [0052]    As noted above, in an example, modules  200 L and  200 R are identical modules, i.e., they have the same configuration for fiber arrays  208 A and  208 B and the same configuration for the front-end and back-end adapters  212  and  214 . For ease of illustration and explanation, the connection location numbering for module  200 R on the right-hand side of the optical path system  102  uses prime notation, i.e., (1′, 13′), (2′, 14′), etc. Thus, connection locations 1-12 are T connection locations; Connection locations 1′-12′ are T′ connection locations. Connection locations 13-24 are R connection locations. Connection locations 13′-24′ are R′ connection locations. 
         [0053]    Because fibers  209  define the connection locations T and R, the connection locations numbers for T and R also define the “fiber numbers” for fibers  209  in fiber arrays  208 LA and  208 LB, respectively. For example, the fibers  209  in fiber array  208 LA have fiber numbers T=1 through 12, while the fibers  209  in fiber array  208 LB have fiber numbers R=13 through 24. Likewise, the fibers  209  in fiber arrays  208 LB and  208 RB have fiber numbers T′=1′ through 12′, and R′=13′ through 24′, respectively. In the discussion below, the term “connection location” is used for T, R and T′ and R′ for ease of discussion, but it will be understood that this is synonymous with “fiber number.” 
         [0054]    The polarity management with respect to the connection locations or fiber numbers T and R on the left-hand side (module  200 L) and the connection locations or fiber numbers T′ and R′ on the right-hand side (module  200 R) that define the optical pathway OP can be stated as follows:
       Optical pathway section OP 1  defined by fiber arrays  208 LA,  228 A and  208 RB connects the transmit connection locations or fiber numbers T={1-12} to respective receive connection locations or fiber numbers R′={13′-24′} (i.e., transmit connection location 1 on the left-side module  200 L connects to receive connection location 13′ on the right-side module  200 R; transmit connection location 2 on the left-side module connects to receive connection location 14′ on the right-side module, . . . transmit connection location 12 on the left-side module connects to receive connection location 24′ on the right-side module).   optical pathway section OP 2  defined by fiber arrays  208 LB,  228 B and  208 RA maps receive connection locations or fiber numbers R={13-24} on the left-side module  200 L to transmit connection locations or fiber numbers T′={1′-12′} on the right-side module  200 R (i.e., receive connection location 13 on the left-side module  200 L connects to transmit connection location 1′ on the right-side module  200 R; receive connection location 14 on the left-side module connects to transmit connection location 2′ on the right-side module, . . . receive connection location 24 on the left-side module connects to transmit connection location 12′ on the right-side module).       
 
         [0057]    In shorthand notation, these connection or fiber number mappings for optical path sections OP 1  and OP 2  of optical path OP can be represented as: 
         [0000]      { T}→{R ′}={fiber array 208 LA }→{fiber array 208 RB}={ 1-12}→{13′-24′}
 
         [0000]      { R}→{T ′}={fiber array 208 LB }→{fiber array 208 RA}={ 13-24}→{1′-12′}
 
         [0058]      FIG. 4B  is similar to  FIG. 4A  but only shows optical path OP 1  and the associated left-to-right transmission of optical signals  300 . Likewise,  FIG. 4C  is similar to  FIG. 4A  but only showing optical path OP 2  and the associated right-to-left transmission of signals  300 . 
         [0059]    The above-described connection mapping results in pairs of transmit and receive connection locations or fiber numbers {T,R′}={1,13′}, {2,14′}, {3,15′} . . . {12,24′} for the first optical path OP 1  and pairs of transmit and receive connection locations or fiber numbers {R,T′}={13,1′}, {14,2′}, {15,3′} . . . {24,12′} for the second optical path. Here, the brackets {•} are used to denote left-to-right mapped pairs of connection locations or fiber numbers. Parenthesis (•) are used to denote pairs of fibers at the same connection location, i.e., pairs (T,R) and pairs (T′,R′). 
         [0060]    The connection polarity management defined by {T}→{R′}={1-12}→{13′-24′} and {R}→{T′}={13-24}→{1′-12′} is for an example embodiment of optical pathway OP that involves a total of N=24 fibers. Corresponding polarity managements apply generally to embodiments of optical pathway OP that include N fibers in each fiber array. Accordingly, for a total of N fibers (for N even and greater than 2), the fiber arrays  208 LA,  208 LB,  208 RA and  208 RB can be defined as follows: 
         [0061]      208 LA=T=1 to N/2, 
         [0062]      208 LB=R=((N/2)+1) to N, 
         [0063]      208 RA=T′=1′ to (N/2)′; and 
         [0064]      208 RB=R′=((N/2)+1)′ to N′. 
         [0065]    The connections between fiber arrays  208 LA and  208 RB and the connections between fiber arrays  208 LB and  208 RA can be written as follows: 
         [0000]      { T}→{R′}={ 208 LA}{ 208 RB}={ 1 to ( N/ 2)}→{(( n/ 2)+1)′ to  N′}   Eq. 1A
 
         [0000]      { R}→{T′}={ 208 LB}→{ 208 RA }={(( N/ 2)+1) to  N}→{ 1′ to ( N/ 2)}.  Eq. 1B
 
         [0066]    The connections or fiber numbers for 1 to N/2 are all one type, i.e., either all transmit T or all receive R. The connections or fiber numbers [(N/2)+1] to N are all of the other type, i.e., receive R or transmit T. 
         [0067]    In the examples set forth herein, connections 1 to N/2 are transmit T while connections (N/2)+1 to N are receive R. It is noted that it is the physical locations of the connection locations and the actual interconnections of fiber arrays  208 LA,  208 LB on the left and  208 RA,  208 RB on the right side of the optical pathway system  102  and how they are interconnected to one another to define the optical pathway OP that matters, and not the numbering of these locations or the particular numbering scheme for the fibers  209  per se. 
         [0068]    Note also that the notation N′ is to be read as (N)′, which is to say that N′ is not another integer but instead represents the primed connector locations or fiber numbers (e.g., 1′, 2′, . . . . 24′) on the right-hand side of optical pathway OP. 
         [0069]    The optical pathway connection between the transmit and receive connection locations or fiber numbers of the first and second fiber arrays  208 LA,  208 LB,  208 RA and  208 RB based on Eq. 1 above can be written as: 
         [0000]      { T,R′}={ 1 to ( N/ 2),[(( N/ 2)+1)′ to  N′ }   Eq. 2a
 
         [0000]      { T,R ′}={(( N/ 2)+1) to  N, 1′ to ( N/ 2)′ }  Eq. 2b
 
         [0070]    The pairings (T,R) of transmit and receive connection locations or fiber numbers at the left and right sides of the optical pathway system  102 S can be respectively written as: 
         [0000]      ( T,R ), where  T= 1 to ( N/ 2) and  R =(( N/ 2)+1) to  N.    
         [0000]      ( T′,R ′) where  T= 1′ to ( N/ 2)′ and  R =(( N/ 2)+1)′ to  N′.  
 
         [0000]    Optical Path with Breakout Harnesses 
         [0071]      FIGS. 5A through 5C  are similar to  FIGS. 4A through 4C  and illustrate an example optical path OP that utilizes breakout harnesses  270 L and  270 R rather than breakout modules  200 . The two optical paths OP 1  and OP 2  are shown separately in  FIGS. 5B and 5C , respectively. Rather than having front-end and back-end adapters  212  and  214 , breakout harnesses  270  have connectors  276  that define the transmit and receive locations and can connect directly to devices  212 . 
         [0072]    The explanation of the polarity management of the transmit and receive connection locations or fiber numbers T and R for the left side and T′ and R′ for the right side of the optical path system  102  are the same as discussed above for the module-based embodiment. 
         [0073]    It is further disclosed that proper maintenance of system polarity requires that the fiber arrays  228  of the trunk  220  be mated to fiber assemblies  200  or  270  at each end of the trunk in a manner so that each transmit fiber of fiber arrays  208 LA and  208 RA are placed in optical communication with a receive fiber of fiber arrays  208 LB and  208 RB and that the fiber paths so formed should be paired at each end. As an example, for a 24-fiber trunk  220  having two legs  224  on each end, each leg terminated with a 12-fiber MPO connector and subsequently mated on each end to a fiber assembly embodying the schematic diagram of  FIG. 4A  and where the assemblies  200  or  270  comprise 12-fiber MPO style connectors, the desired polarity can be achieved by orienting and terminating the fibers of each trunk leg  224  on one end of trunk  220  into the MPO connectors in a forward fiber order from 1 to 12 and orienting and terminating the fibers of each trunk leg  224  on the other end of the trunk  220  into the MPO connectors in a reverse fiber order from 12 to 1. 
         [0074]    It will be apparent to those skilled in the art that various modifications to the preferred embodiments of the disclosure as described herein can be made without departing from the spirit or scope of the disclosure as defined in the appended claims. For example, implementations involving modules could rather take the form of optical harness implementations and implementations involving optical harnesses could rather take the form of optical module implementations. Thus, the disclosure covers the modifications and variations provided they come within the scope of the appended claims and the equivalents thereto.