Patent Publication Number: US-2021175699-A1

Title: Submarine cable architecture with redundancy for facilitating shared landing site

Description:
RELATED APPLICATIONS 
     This application claims priority to and the benefit of U.S. Provisional Application No. 62/943,600, entitled “SUBMARINE CABLE ARCHITECTURE WITH REDUDANCY FOR FACILITING SHARED LANDING SITE” filed on Dec. 4, 2019. The contents of the aforementioned application are incorporated by reference in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     This disclosure relates generally to the field of undersea communication networks and relates more particularly to an architecture for implementing multiple undersea fiberoptic cables with redundant connections to a shared landing site. 
     BACKGROUND 
     Undersea fiber optic cables are commonly employed for transmitting data across expanses of ocean between terrestrial landing sites which are often located in different countries and on different continents. Implementing new undersea fiber optic cables generally necessitates the acquisition of government-issued cable landing licenses in order to own and operate undersea fiber optic cables and associated landing stations that must be installed at each terrestrial landing site and in adjoining territorial waters. The process for obtaining such cable landing licenses can be difficult, time-consuming, and expensive. It would therefore be advantageous to provide an undersea fiber optic cable architecture in which a plurality of cables can share a single terrestrial landing site. It would be a further advantage to provide such an architecture that facilitates the incorporation of additional cables (i.e., cables added after initial installation) using the same terrestrial landing site. It would be a further advantage to provide such an architecture that facilitates redundant routing of signal traffic between multiple cables and landing sites for enhancing the reliability of the architecture. 
     It is with respect to these and other considerations that the present improvements may be useful. 
     SUMMARY 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended as an aid in determining the scope of the claimed subject matter. 
     An undersea fiber optic cable architecture in accordance with an exemplary embodiment of the present disclosure may include a beach manhole (BMH) installed at a terrestrial site, a terrestrial station connected to the BMH by a terrestrial fiber optic cable, a first landing cable extending from the BMH into territorial waters adjacent the terrestrial site and connected to a first enhanced branching unit (EBU) located in the territorial waters, a second landing cable extending from the BMH into the territorial waters and connected to a second EBU located in the territorial waters, a recovery path cable connecting the first EBU to the second EBU, a first trunk cable extending from the first EBU into international waters, and a second trunk cable extending from the second EBU into the international waters. 
     An undersea fiber optic cable architecture in accordance with another exemplary embodiment of the present disclosure may include a first beach manhole (BMH) installed at a first terrestrial site, a second BMH installed at a first terrestrial site, a first landing cable extending from the first BMH into territorial waters adjacent the terrestrial site and connected to a first enhanced branching unit (EBU) located in the territorial waters, a second landing cable extending from the second BMH into the territorial waters and connected to a second EBU located in the territorial waters, a recovery path cable connecting the first EBU to the second EBU, a first trunk cable extending from the first EBU into international waters, and a second trunk cable extending from the second EBU into the international waters. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram illustrating an exemplary embodiment of an undersea fiber optic cable architecture in accordance with the present disclosure; 
         FIG. 2A  is a schematic diagram illustrating another exemplary embodiment of an undersea fiber optic cable architecture in accordance with the present disclosure; 
         FIG. 2B  is a schematic diagram illustrating a fault condition in the undersea fiber optic cable architecture of  FIG. 2A ; 
         FIG. 2C  is a schematic diagram illustrating another fault condition in the undersea fiber optic cable architecture of  FIG. 2A ; 
         FIG. 3  is a schematic diagram illustrating electrical power distribution in the undersea fiber optic cable architecture of  FIG. 2A . 
     
    
    
     DETAILED DESCRIPTION 
     An undersea fiber optic cable architecture in accordance with the present disclosure will now be described more fully with reference to the accompanying drawing, in which a preferred embodiment of the undersea fiber optic cable architecture is presented. The undersea fiber optic cable architecture, however, may be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein. Rather, this embodiment is provided so that this disclosure will convey certain exemplary aspects of the undersea fiber optic cable architecture to those skilled in the art. 
     Referring to  FIG. 1 , an undersea fiber optic cable architecture  10  (hereinafter “the architecture  10 ”) in accordance with an exemplary embodiment of the present disclosure is presented. The architecture  10  may include a beach manhole (BMH)  12  installed at a terrestrial site  13  (e.g., along a shoreline) for coupling undersea fiber optic cables  14 ,  16  to a terrestrial fiber optic cable  18 . The terrestrial fiber optic cable  18  may extend to a terrestrial station  20  which may be configured to transmit and receive communication signals via the terrestrial fiber optic cable  18 . The land-based elements of the architecture  10  (i.e., the beach manhole  12 , the terrestrial fiber optic cable  18 , and the terrestrial station  20 ) may be of conventional construction/configuration familiar to those of ordinary skill in the art and will therefore not be discussed in any greater detail herein. 
     The undersea fiber optic cables  14 ,  16  of the architecture  10 , hereinafter referred to as “the first and second landing cables  14 ,  16 ,” may extend from the BMH  12  into territorial waters  21  that adjoin the terrestrial site  13  and that are subject to the jurisdiction of an entity that owns/governs the terrestrial site  13 . The first and second landing cables  14 ,  16  may extend to, and may be coupled to, respective first and second enhanced branching units (EBUs)  22 ,  24  that are located within the territorial waters  21  and that are connected to one another by an undersea fiber optic cable  26 , hereinafter referred to as “the recovery path cable  26 .” Thus, the BMH  12 , the first EBU  22 , and the second EBU  24  are interconnected by the first and second landing cables  14 ,  16  and the recovery path cable  26  to define a ring topology. 
     Undersea fiber optic cables  28 ,  30 , hereinafter referred to as “the first and second trunk cables  28 ,  30 ,” may extend from the first and second EBUs  22 ,  24 , respectively, and may extend into international waters for connecting the first and second EBUs  22 ,  24  to distant terrestrial stations (e.g., terrestrial stations located in different countries and on different continents, not shown). In a non-limiting embodiment of the present disclosure, the first and second trunk cables  28 ,  30  may each include a group of  8  bidirectional fiber pairs  32 ,  34 , and each of the first and second landing cables  14 ,  16  and the recovery path cable  26  may include a first group of 8 bidirectional fiber pairs  36   a ,  36   b ,  36   c , respectively, and a second group of 8 bidirectional fiber pairs  38   a ,  38   b ,  38   c , respectively. Thus, the ring topology of the architecture  10  may include a total of  16  bidirectional fiber pairs. The present disclosure is not limited in this regard. It is contemplated that the first and second trunk cables  28 ,  30 , the first and second landing cables  14 ,  16 , and the recovery path cable  26  may include a greater or fewer number of fiber pairs without departing from the present disclosure. 
     Each of the first and second EBUs  22 ,  24  may contain optical switches for selectively routing individual fiber pairs in the respective trunk cables  28 ,  30  directly to the BMH  12  through the first and second landing cables  14 ,  16 , respectively, or through the recovery path cable  26 . For example, during normal operation of the architecture  10 , the first EBU  22  may route incoming signal traffic from the bidirectional fiber pairs  32  of the first trunk cable  28  through the first group of bidirectional fiber pairs  36   a  in the first landing cable  14  to the BMH  12 . However, if the first landing cable  14  were to be damaged, the optical switches in the first EBU  22  could reroute the incoming signal traffic from the bidirectional fiber pairs  32  of the first trunk cable  28  to the first group of bidirectional fiber pairs  36 c of the recovery path cable  26 , where the traffic could then be transmitted to the BMH  12  via the second EBU  24  and the first group of bidirectional fiber pairs  36   b  in the second landing cable  16 . Similarly, during normal operation of the architecture  10 , the second EBU  24  may route incoming signal traffic from the bidirectional fiber pairs  34  of the second trunk cable  30  through the second group of bidirectional fiber pairs  38   b  in the second landing cable  16  to the BMH  12 . However, if the second landing cable  16  were to be damaged, the optical switches in the second EBU  24  could reroute the incoming signal traffic from the bidirectional fiber pairs  34  of the second trunk cable  30  to the second group of bidirectional fiber pairs  38   c  of the recovery path cable  26 , where the traffic could then be transmitted to the BMH  12  via the first EBU  22  and the second group of bidirectional fiber pairs  38   a  in the first landing cable  14 . In various embodiments, the first and second EBUs  22 ,  24  may be controlled by telemetry transceivers located in the terrestrial station  20  via the first landing cable  14  and/or the second landing cable  16 . 
     Thus, it will be appreciated that the architecture  10  of the present disclosure facilitates redundant routing of signal traffic between multiple cables and a single landing site for providing enhanced reliability. Additionally, the architecture  10  of the present disclosure provides a further advantage in that it facilitates the connection of additional trunk cables to the BMH  12  in the future (i.e., after initial installation of the architecture  10 ) without requiring an operator to acquire additional cable landing licenses. For example, during installation of the architecture  10 , extra EBUs can be provided in the ring topology of the architecture  10  for accommodating the connection of additional trunk cables at a later time. Alternatively, additional EBUs can be spliced into the ring topology without interrupting signal traffic. For example, referring to the exemplary embodiment of the architecture  10  shown in  FIG. 1 , incoming signal traffic on the second trunk  30  can be rerouted from the second landing cable  16  to the recovery path cable  26  by the second EBU  24  (as described above), thereby allowing an additional EBU to be spliced to second landing cable  16  without interrupting signal traffic in the architecture  10 . 
     Referring to  FIG. 2A , another undersea fiber optic cable architecture  100  (hereinafter “the architecture  100 ”) in accordance with an exemplary embodiment of the present disclosure is presented. The architecture  100  may include a first beach manhole (BMH)  112  installed at a first terrestrial site (e.g., along a shoreline) and a second BMH  114  installed at a second terrestrial site. The first and second BMHs  112 ,  114  may couple undersea fiber optic cables  116 ,  118  to respective terrestrial fiber optic cables (not shown) extending to respective terrestrial stations (not shown) which may be configured to transmit and receive communication signals via the terrestrial fiber optic cables. The land-based elements of the architecture  100  (i.e., the BMHs  112 ,  114 , the terrestrial fiber optic cables, and the terrestrial stations) may be of conventional construction/configuration familiar to those of ordinary skill in the art and will therefore not be discussed in any greater detail herein. 
     The undersea fiber optic cables  116 ,  118  of the architecture  100 , hereinafter referred to as “the first and second landing cables  116 ,  118 ,” may extend from the BMHs  112 ,  114 , respectively, into territorial waters  121  that adjoin the terrestrial sites where the BMHs  112 ,  114  are located. The first and second landing cables  116 ,  118  may extend to, and may be coupled to, respective first and second enhanced branching units (EBUs)  122 ,  124  that are also located within the territorial waters  121  and that are connected to one another by an undersea fiber optic cable  126 , hereinafter referred to as “the recovery path cable  126 .” Thus, the first and second BMHs  112 ,  114  and the first and second EBUs  122 ,  124  are interconnected by the first and second landing cables  116 ,  118  and the recovery path cable  126  to define a ring topology. 
     Undersea fiber optic cables  128 ,  130 , hereinafter referred to as “the first and second trunk cables  128 ,  130 ,” may extend from the first and second EBUs  122 ,  124 , respectively, and may extend into international waters for connecting the first and second EBUs  122 ,  124  to distant terrestrial stations (e.g., terrestrial stations located in different countries and on different continents, not shown). In a non-limiting embodiment of the present disclosure, the recovery path cable  126  and the first and second trunk cables  128 ,  130  may each include a group of  12  bidirectional fiber pairs  131 ,  132 ,  134 , and each of the first and second landing cables  116 ,  118  and may include a first group of  12  bidirectional fiber pairs  136   a ,  136   b , respectively, and a second group of  12  bidirectional fiber pairs  138   a ,  138   b , respectively. Each of the aforementioned groups of bidirectional fiber pairs is represented schematically by a single pair of inbound and outbound lines in  FIG. 2A  for clarity. The present disclosure is not limited to specific number of bidirectional fiber pairs listed above, and it is contemplated that the first and second trunk cables  128 ,  130 , the first and second landing cables  116 ,  118 , and the recovery path cable  126  may include a greater or fewer number of bidirectional fiber pairs without departing from the present disclosure. Generally, however, the recovery path cable  126  and the first and second trunk cables  128 ,  130  will include half as many bidirectional fiber pairs as the first and second landing cables  116 ,  118 . 
     Each of the first and second EBUs  122 ,  124  may contain optical switches for selectively routing individual fiber pairs in the respective trunk cables  128 ,  130  to the respective BMHs  112 ,  114  through the first and second landing cables  116 ,  118 , or to the BMH  112  or  114  associated with the other EBU  122  or  124  through the recovery path cable  126 . For example, during normal operation of the architecture  100 , the first EBU  122  may facilitate signal traffic between the bidirectional fiber pairs  132  of the first trunk cable  128  and the first group of bidirectional fiber pairs  136   a  in the first landing cable  116  to the first BMH  112 . Similarly, during normal operation of the architecture  100 , the second EBU  124  may facilitate signal traffic between the bidirectional fiber pairs  134  of the second trunk cable  130  and the second group of bidirectional fiber pairs  138   b  in the second landing cable  118  to the second BMH  114 . However, if the first landing cable  116  is disabled (e.g., cut) as shown in  FIG. 2B , the optical switches in the first EBU  122  may reroute the signal traffic from the bidirectional fiber pairs  132  of the first trunk cable  128  to the bidirectional fiber pairs  131  of the recovery path cable  126 , where the traffic could then be transmitted to the second BMH  114  via the second EBU  124  and the first group of bidirectional fiber pairs  136   b  in the second landing cable  118 . Similarly, if the second landing cable  118  were to be disabled as shown in  FIG. 2C , the optical switches in the second EBU  124  could reroute the signal traffic from the bidirectional fiber pairs  134  of the second trunk cable  130  to the bidirectional fiber pairs  131  of the recovery path cable  126 , where the traffic could then be transmitted to the first BMH  112  via the first EBU  122  and the second group of bidirectional fiber pairs  138   a  in the first landing cable  116 . In various embodiments, the first and second EBUs  122 ,  124  may be controlled by telemetry transceivers located in the terrestrial stations (not shown) associated with the first and second BMHs  112 ,  114  via the first and second landing cables  116 ,  118  and/or by telemetry transceivers located in terrestrial stations (not shown) associated with BMHs at distant termini of the first and second trunk cables  128 ,  130 . 
     Thus, it will be appreciated that the architecture  100  of the present disclosure allows signal traffic on multiple trunk cables to be maintained even if a landing cable of the architecture is disabled. 
     Referring now to  FIG. 3 , a schematic diagram illustrating electrical power distribution in the above-described architecture  100  is shown. In addition to the components of the architecture  100  shown in  FIGS. 2A-2C ,  FIG. 3  includes components located at the distal ends of the trunk cable  128 ,  130  relative to the first and second BMHs  112 ,  114 . These components include third and fourth BMHs  142 ,  144  located at respective terrestrial sites (e.g., along a shoreline), third and fourth landing cables  146 ,  148  extending from the BMHs  142 ,  144 , respectively, third and fourth EBUs  152 ,  154  connecting the third and fourth landing cables  146 ,  148  to the first and second trunk cables  128 ,  130 , and a recovery cable  156  connecting the first and second EBUs  152 ,  154  to one another. These components may be configured in substantially the same manner as the components of the architecture described above and shown in  FIGS. 2A-2C . 
     During normal operation of the architecture  100 , and as indicated by the arrowed lines shown in  FIG. 3 , power feed equipment (PFE) associated with the first BMH  112  may supply power through the first landing cable  116  and the first trunk cable  128 ; PFE associated with the second BMH  114  may supply power through the second landing cable  118  and the recovery cable  126 ; PFE associated with the third BMH  142  may supply power through the third landing cable  146  and the recovery cable  156 ; and PFE associated with the fourth BMH  144  may supply power through the fourth landing cable  148  and the second trunk cable  130 . However, if there is a fault (e.g., a shunt faults, a cable cut, etc.) in any of the cables, the EBUs  112 ,  114 ,  152 ,  154  may be configured to redirect the flow of electrical power to undamaged cables. Various non-limiting examples of fault conditions and corresponding rerouting of electrical power in the architecture  100  will now be described. 
     In the case of a shunt fault in the recovery cable  126 , power feed equipment (PFE) associated with the first BMH  112  may supply power through the first landing cable  116 , the first trunk cable  128 , and the third landing cable  146 ; PFE associated with the second BMH  114  may supply power through the second landing cable  118  and the second trunk cable  130 ; and PFE associated with the fourth BMH  144  may supply power through the fourth landing cable  148  and the recovery cable  156 . 
     In the case of a shunt fault in the recovery cable  156 , power feed equipment (PFE) associated with the first BMH  112  may supply power through the first landing cable  116 , the first trunk cable  128 , and the third landing cable  146 ; PFE associated with the second BMH  114  may supply power through the second landing cable  118  and the recovery cable  126 ; and PFE associated with the fourth BMH  144  may supply power through the fourth landing cable  148  and the second trunk cable  130 . 
     In the case of a shunt fault in the recovery cable  126  and a cable cut in the second landing cable  118 , power feed equipment (PFE) associated with the first BMH  112  may supply power through the first landing cable  116 , the first trunk cable  128 , and the third landing cable  146 ; and PFE associated with the fourth BMH  144  may supply power through the fourth landing cable  148  and the recovery cable  156 . 
     In the case of a shunt fault in the recovery cable  126  and a cable cut in the fourth landing cable  148 , power feed equipment (PFE) associated with the first BMH  112  may supply power through the first landing cable  116 , the first trunk cable  128 , and the third landing cable  146 ; and PFE associated with the second BMH  114  may supply power through the second landing cable  118 , the second trunk cable  130 , and the recovery cable  156 . 
     In the case of a shunt fault in the recovery cable  126  and a cable cut in the third landing cable  146 , power feed equipment (PFE) associated with the first BMH  112  may supply power through the first landing cable  116 , the first trunk cable  128 , the recovery path cable  156 , and the fourth landing cable  148 ; and PFE associated with the second BMH  114  may supply power through the second landing cable  118  and the second trunk cable  130 . 
     In the case of a cable cut in the first trunk cable  128 , power feed equipment (PFE) associated with the first BMH  112  may supply power through the first landing cable  116  and the recover path cable  126 ; PFE associated with the second BMH  114  may supply power through the second landing cable  118  and the second trunk cable  130 ; and PFE associated with the fourth BMH  144  may supply power through the fourth landing cable  148  and the recovery cable  156 . 
     As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. 
     While the present disclosure makes reference to certain embodiments, numerous modifications, alterations and changes to the described embodiments are possible without departing from the sphere and scope of the present disclosure, as defined in the appended claim(s). Accordingly, it is intended that the present disclosure not be limited to the described embodiments, but that it has the full scope defined by the language of the following claims, and equivalents thereof.