Abstract:
A device may include a component, a first switch, a repeater, and a second switch. The component may configure optical paths between ports. The component may comprise a first pair of optical ports connected to a first pair of optical fibers, and a second pair of optical ports connected to a second pair of optical fibers. The first switch may be configured to output one of two optical signals received by the first pair of optical ports from the first pair of optical fibers. The repeater may reshape or amplify the outputted optical signal. The second switch may be configured to direct the reshaped or amplified signal to one of the second pair of optical ports.

Description:
BACKGROUND INFORMATION 
     Optical amplifiers and regenerators may restore power and shape to degraded optical signals. Optical signals between a central office to a customer premise often pass through either optical amplifiers and/or regenerators, because, as the optical signals travel through a fiber, the signals may attenuate and/or become distorted. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an exemplary optical network in which concepts described herein may be implemented; 
         FIGS. 2A through 3B  are diagrams of an exemplary portion of the optical network of  FIG. 1 ; 
         FIG. 4  is a diagram of an exemplary self-healing (SH) repeater node of  FIGS. 2A  and/or  2 B; 
         FIG. 5  is a flow diagram of an exemplary process that is associated with operation of the SH repeater node of  FIG. 4 ; and 
         FIGS. 6 and 7  illustrate an example of the operation of the SH repeater node of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The following detailed description refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements. 
     As described below, a self-healing (SH) repeater node may be used instead of an optical regenerator node and/or amplifier node. When a component of the SH repeater node fails (e.g., an optical fiber, an amplifier pump, etc.), the SH repeater node may detect the failure and/or fix the component. For example, if the SH repeater node detects a fault/flaw (e.g., a break) in optical fiber, the SH repeater node may allow a network operator to test the broken fiber, identify the location of the fault/flaw, and re-route a communication signal from the broken fiber to another fiber. The SH repeater node may perform these operations automatically or in accordance with commands issued from a remote device. 
     In addition, the SH repeater node may be compact. Typically, a legacy regenerator or amplifier is installed in a large housing to provide convenient access to an engineer, service person, etc. Because the SH repeater node may repair itself, it may not need to provide such access, and consequently, may be placed in a compact container, manhole, hand hole, etc. In addition, because the SH repeater node may be environmentally hardened, it may withstand temperature changes, moisture, wind, radiation, vibrations, etc. 
     The SH repeater node may integrate many different components (e.g., a test equipment for remote troubleshooting) to lower the failures-in-time (e.g., to less than  5000  failures/billion unit-hours of operating time), and to support, if necessary, local maintenance activity. In addition, the SH repeater node may be energy efficient (e.g., 100 W). 
       FIG. 1  shows an exemplary optical network  100  in which the concepts described herein may be implemented. As shown, optical network  100  may include metro/regional networks  102  and  104 , long haul or ultra-long haul optical lines  106 , and edge network  108 . Depending on the implementation, optical network  100  may include additional, fewer, or different optical networks and optical lines than those illustrated in  FIG. 1 . For example, in one implementation, optical network  100  may include additional edge networks and/or metro/regional networks that are interconnected by Synchronous Optical Network (SONET) rings. 
     Metro/regional network  102  may include optical fibers and central office hubs that are interconnected by the optical fibers. The optical fibers, which may form the backbone of metro/regional optical network  102 , may span approximately 50 to 500 kilometers (km). The central office hubs, one of which is illustrated as central office hub  110 , may include sites that house telecommunication equipment, including switches, optical line terminals, etc. In addition to being connected to other central offices, central office hub  110  may provide telecommunication services to subscribers, such as telephone service, access to the Internet, cable television programs, etc., via optical line terminals. 
     Metro/regional network  104  may include similar components as metro/regional network  102  and may operate similarly. In  FIG. 1 , metro/regional network  104  is illustrated as including central office hub  112 , which may include similar components as central office hub  110  and may operate similarly. 
     Long haul optical lines  106  may include optical fibers that extend from metro/regional optical network  102  to metro/reginal optical network  104 . In some implementations, long haul optical lines  106  may span approximately 500 km or more. 
     Edge network  108  may include optical networks that provide user access to metro/regional optical network  104 . As shown in  FIG. 1 , edge network  108  may include access points  114  (e.g., office buildings, residential area, etc.) via which end customers may obtain communication services from central office hub  112 . 
       FIG. 2A  is a diagram of an exemplary portion  200 A of optical network  100 . Portion  200 A may be part of metro/regional network  102 , metro/regional network  104 , or long haul optical lines  106 . As shown, portion  200 A may include central office hubs  202  and  204 , optical fibers  206 , and node facilities  208  and  210 . Depending on the implementation, portion  200 A may include additional, fewer, or different components than those illustrated in  FIG. 2A  (e.g., additional node facilities). 
     Central office hub  202  or central office hub  204  may include telecommunication equipment, including switches, optical line terminals, etc., and may provide telecommunication services to subscribers, such as telephone service, access to the Internet, cable television programs, etc., via optical line terminals. 
     For example, in  FIG. 2A , central office hub  202  may include terminal equipment  202 - 1 , a battery  202 - 2 , and an air-conditioning unit  202 - 3 . Terminal equipment  202 - 1  may include components for optical telecommunications (e.g., optical switches, optical line terminals, etc.). Battery  202 - 2  (or a power adaptor) may provide power to terminal equipment  202 - 1 . Air conditioning unit  202 - 3  may provide a stable temperature for terminal equipment  202 - 1 . 
     Optical fibers  206  may connect central office hubs  202  and  204 , and may convey optical signals from/to central office hub  202  to/from central office hub  204 . As shown, optical fibers  206  pass through node facilities  208  and  210 . 
     Node facility  208  or  210  may include SH repeater nodes  208 - 1  or  210 - 1  to amplify and/or regenerate an optical signal that arrives from central office hub  202  or  204  via optical fibers  206  and transmit the amplified signal toward central office hub  204  or  202 . As shown in  FIG. 2A , node facilities  208  and  210  may include enclosures (e.g., cabinets) in which SH repeater nodes  208 - 1  and  210 - 1 , respectively, may be housed. SH repeater nodes  208 - 1  and  210 - 1  may be powered by, respectively, batteries  208 - 2  and  210 - 2  that are included in node facilities  208  and  210 . In a different implementation, node facilities  208  and  210  may include different components (e.g., a power adaptor). 
       FIG. 2B  is a diagram of another exemplary portion  200 B of optical network  100 . Portion  200 B may be part of metro/regional network  102 , metro/regional network  104 , or long haul optical lines  106 . As shown, portion  200 B may include central office hubs  202  and  204 , optical fibers  206 , and node facilities  218  and  220 . Depending on the implementation, portion  200 B may include additional, fewer, or different components than those illustrated in  FIG. 2B  (e.g., additional node facilities). 
     Node facility  218  and node facility  220  may include components (e.g., SH repeater node  218 - 1  and battery  218 - 2 ) that correspond to components of node facility  208  (e.g., SH repeater node  208 - 1  and battery  208 - 2 ) and node facility  210 , respectively. In addition, node facilities  218  and  220  may operate similarly as node facilities  208  and  210 . 
     In contrast to node facilities  208  and  210 , however, node facilities  218  and  220  may include enclosures that are under-or in-ground (e.g., man-hole, hand-hole, etc.). The enclosures may house SH repeater nodes  218 - 1  and  220 - 1  and batteries  218 - 2  and  220 - 2 . 
     In the exemplary embodiments of  FIGS. 2A and 2B , the enclosures in node facilities  208 ,  210 ,  218 , and  220  may be constructed just large enough to house SH repeater nodes  208 - 1 ,  210 - 1 ,  218 - 1  and  220 - 1 , and/or batteries  208 - 2 ,  210 - 2 ,  218 - 2 , and  220 - 2 . Such implementations may save space and reduce cost that is associated with a larger housing. SH repeater nodes  208 - 1 ,  210 - 1 ,  218 - 1 , and  220 - 1  may be environmentally hardened, and may be capable of withstanding large swings in temperature, moisture, vibration, etc. 
       FIG. 3A  is a diagram of yet another exemplary portion  300 A of optical network  100 . Portion  300 A may be part of metro/regional network  102 , metro/regional network  104 , or long haul optical lines  106 . As shown, portion  300 A may include central office hubs  202  and  204 , optical fibers  206 , and node facilities  302  and  304 . Depending on the implementation, portion  300 A may include additional node facilities that are approximately 30 to 80 km apart. 
     Node facility  302  and node facility  304  may include legacy regenerator nodes  302 - 1  and  304 - 1  and batteries  302 - 2  and  304 - 2  that correspond to components  208 - 1 ,  210 - 1 ,  208 - 2 , and  210 - 2  of node facilities  208  and  210 , respectively. In addition, node facilities  302  and  304  may include air conditioning units  302 - 3  and  304 - 3 , respectively. Air conditioning units  302 - 3  and  304 - 3  may provide stable environments (e.g., constant temperature) for node facilities  302  and  304 . 
     In contrast to SH repeater nodes  208 - 1  and  210 - 1 , legacy regenerator nodes  302 - 1  and  304 - 1  may be large, and therefore, may occupy more space. Furthermore, legacy regenerator nodes  302 - 1  and  302 - 2  may not be environmentally hardened, and may require the inclusion of air conditioning units  302 - 3  and  304 - 3 , resulting in increased power consumption. 
     In implementations that are similar to the one shown in  FIG. 3A , but with more node facilities, optical signal may be regenerated at each of the node facilities, which may be 30-80 km apart. With advances in modern optical communication technology, however, the optical signal may only need to be boosted in power once every ˜20-30 km, and regenerated once every ˜1,000 km. Consequently, many of regenerator facilities, such as, for example, regenerator facility  302 , that are 30 to 80 km apart, may be replaced with node facilities that include optical amplifiers or SH repeater nodes instead of legacy regenerator nodes. 
       FIG. 3B  is a diagram of portion  300 B of optical network  100  in which regenerator nodes are replaced with amplifiers. As shown in  FIG. 3B , portion  300 B may include similar components as portion  300 A in  FIG. 3A . However, in contrast to  FIG. 3A , node facilities  302  and  304  in  FIG. 3B  may include amplifiers  302 - 4  and  304 - 4 , respectively, instead of legacy regenerator nodes  302 - 1  and  304 - 1  in  FIG. 3A . 
     Because amplifiers  302 - 4  and  304 - 4  may be small (e.g., size of notebook) relative to legacy regenerator nodes  302 - 1  and  304 - 1 , it may be possible to decrease the size of the housing for node facilities  302  and  304  by using amplifiers  302 - 4  and  304 - 4  in place of legacy regenerator nodes  302 - 1  and  304 - 1 . 
     In addition, SH repeater nodes  208 - 1  and  210 - 1  ( FIG. 2A ), which may include optical amplifiers, may also be used instead of legacy regenerator nodes  302 - 1  and  304 - 1  in node facilities  302  and  304  to reduce the size of the housing. In such an implementation, because SH repeater nodes  208 - 1  and  210 - 1  may be environmentally hardened, air conditioning units  302 - 3  and  304 - 3  can be eliminated. 
       FIG. 4  is a diagram of an exemplary SH repeater node  402 . SH repeater node  402  may represent any of SH repeater nodes  208 - 1 ,  210 - 1 ,  218 - 1 , and  220 - 1 . As shown, SH repeater node  402  may include primary fibers  404 - 1  and  404 - 2 , backup fibers  406 - 1  and  406 - 2 , automated fiber patch panel  408 , visible light source  410 , optical time domain reflectometer (OTDR)  412 , cable locator  414 , optical service channel (OSC) equipment  416 , and amplifier modules  418  and  420 . Depending on the implementation, SH repeater node  402  may include additional, fewer, or different components than those illustrated in  FIG. 4 . For example, in one implementation, SH repeater node  402  may include a fiber optics switch (FOS). 
     Primary fibers  404 - 1  and  404 - 2  may carry optical signals to/from remote devices. Each of primary fibers  404 - 1  and  404 - 2  may include a pair of optical fibers. Backup fibers  406 - 1  and  406 - 2  may carry optical signals when one or both of the pairs of optical fibers of primary fibers  404 - 1  and/or  404 - 2  fail. 
     Each of fibers in primary fibers  404 - 1  and  404 - 2  and backup fibers  406 - 1  and  406 - 2  may provide a large number of individual data/service channels (e.g.,  80  channels) via which data may be transmitted. In one implementation, the optical fibers may carry troubleshooting and/or error messages in a service channel to/from a remote device, without interfering with other messages on data channels on the same optical fiber. 
     In some implementations, primary fibers  404 - 1  and  404 - 2  and backup fibers  406 - 1  and  406 - 2  may carry optical signals that are wavelength division multiplexed (WDM), In WDM, multiple optical carrier signals are transmitted on a single optical fiber by using different wavelengths of laser light or electromagnetic radiation. In some implementations, optical signals may be dense wave division multiplexed (DWDM). DWDM uses the C band (i.e., frequencies between 1530 and 1565 nanometers (nm)) and/or L band (i.e., wavelengths between 1565 and 1625 nm). 
     Automated fiber patch panel  408  may include optical ports to which different components of SH repeater node  402  (e.g., primary fibers  404 - 1 ) may be attached and may send/or receive optical signals. In addition, depending on the configuration, automated fiber patch panel  408  may optically couple two of the ports, such that an optical signal received at one of the coupled ports is routed to the other. 
     For example, in  FIG. 4 , automated fiber patch panel  408  may couple a port (not shown in  FIG. 4 ) that is connected to one of primary fibers  404 - 1  to a port (not shown in  FIG. 4 ) connected to amplifier module  418 . Accordingly, an optical signal may travel from one of primary fibers  404 - 1  to amplifier module  418  via automated fiber patch panel  408 . 
     Visible light source  410  may include a source of light that may be used to locate a particular optical fiber. A field engineer may direct visible light source  410  into a selected optical fiber, for example, to physically see which optical fiber end emits the light. 
     OTDR  412  may include instruments to measure parameters that are associated with an optical fiber. In one implementation, OTDR  412  may transmit optical pulses into an end of an optical fiber, and monitor, at the same end, pulses that are reflected from various points on the fiber where the index of refraction changes. OTDR  412  may detect and/or record the strength of reflected pulses and times at which the reflected pulses are received. Such information may be used to characterize the fiber (e.g., locate breaks in the fiber). 
     Cable locator  414  may emit electrical signals (e.g., encoded physical coordinates) to allow a field engineer to locate SH repeater node  402  by using a receiver/decoder. 
     OSC equipment  416  may send/receive information over service channels, via primary fibers  404 - 1  or  404 - 2  and/or backup fibers  406 - 1  or  406 - 2 . For example, when OSC equipment  416  detects a break in primary fibers  404 - 2 , OSC equipment  416  may send data that is provided by OTDR  412  to a remote device. In addition, OSC equipment  416  may receive commands/requests from the remote device to reconfigure repeater node  402  or to perform tests to isolate a fault/flaw on an optical fiber. 
     Amplifier module  418  and  420  may amplify an optical signal. For example, amplifier module  418  may amplify an optical signal that is received from one of primary fibers  404 - 1  and output the amplified signal to one of primary fibers  404 - 2  via automated fiber patch panel  408 . 
     As further shown in  FIG. 4 , amplifier module  418  may include switches  418 - 1  and  418 - 2  and an optical amplifier  418 - 3 . Depending on the implementation, amplifier module  418  may include additional, fewer, or different components than those illustrated in  FIG. 4 . 
     Switch  418 - 1  may select, depending on its setting or configuration, an input signal from a pair of optical fibers that include one of primary fibers  404 - 1  and one of backup fibers  406 - 1 , and route the selected signal to optical amplifier  418 - 3 . For example, in  FIG. 4 , when switch  418 - 1  is in the “up” configuration, switch  418 - 1  may route the optical signal from primary fibers  404 - 1  to optical amplifier  418 - 3 . 
     Switch  418 - 2  may output, depending on its setting of configuration, optical signal from optical amplifier  418 - 3  to one of a pair of optical fibers that include one of primary fibers  404 - 2  and one of backup fibers  406 - 2 . For example, in  FIG. 4 , when switch  418 - 2  is in the “up” configuration, switch  418 - 2  may route the optical signal from optical amplifier  418 - 3  to primary fibers  404 - 2 . 
     Optical amplifier  418 - 3  may amplify optical signal received from switch  418 - 1  and output the amplified signal to switch  418 - 2 . Optical amplifier  418 - 3  may include a primary laser pump and a backup laser pump. The backup laser pump may operate instead of the primary laser pump when the primary laser pump fails. Optical amplifier  418 - 3  may be smaller than legacy regenerators, such as a regenerator in regenerator node  302 - 1 . In a different implementation, SH repeater node may include a compact, optical regenerator instead of optical amplifier  418 - 3 . 
     Amplifier module  420  may include similar components as amplifier module  418  and may operate similarly. 
     Although not illustrated in  FIG. 4 , depending on the implementation, repeater node  402  may include additional circuits, one or more processors, logic, or mechanisms to control switches in amplifier module  418  and/or other components, such as automated fiber patch panel  408 , visible light source  410 , OTDR  412 , cable locator  414 , and/or OSC equipment  416 , etc. For example, in one implementation, OSC equipment  416  may include a processor for communicating with a remote device over a service channel (e.g., receive a command to conduct a test using OTDR  412 ), for monitoring and/or controlling OTDR  412  (e.g., obtain measurement of magnitude of reflected optical pulses), for reconfiguring switch settings for switches  418 - 1  and  418 - 2 ), and/or for performing other functions (e.g., report the failure of a primary laser pump, activating the backup pump, etc.). In a different implementation, SH repeater node  402  may include such a processor or control circuit as a separate component. The component may configure automated fiber patch panel  408 , to cause automated fiber patch panel  408  to couple two specific ports. 
       FIG. 5  is a flow diagram of an exemplary process  500  that is associated with operation of SH repeater node  402 . Although process  500  is depicted as starting at block  502 , in different embodiments, process  500  may start at other blocks. In addition, depending on situations or the configuration of SH repeater node  402 , each block may be performed independently of other blocks. 
     SH repeater node  402  may detect a component failure (block  502 ). In one example, SH repeater node  402  may detect a failure of the primary laser pump in optical amplifier  418 - 3 . In another example, SH repeater node  402  may detect a break in primary fibers  404 - 2  by sending test pulses at one end of primary fibers  404 - 2 , and monitoring reflected pulses at the same end. 
     When SH repeater node  402  detects the failure, SH repeater node  402  may send a message to a remote device over a service channel (block  502 ). For example, assume that SH repeater node  402  has tested primary fibers  404 - 2  and detected a break. SH repeater node  402  may send one or more messages that describe the test (e.g., magnitudes of transmitted pulses, magnitudes of reflected pulses, time differences between the transmitted and reflected pulses, etc.) to the remote device. In another example, SH repeater node  402  may send a message to the remote device about a failure of the primary laser pump in optical amplifier  418 - 3 . 
     SH repeater node  402  may receive a communication over a service channel (block  504 ). For example, SH repeater node  402  may receive a command from a remote device. The command may instruct SH repeater node  402  to address the failure (e.g., activate a backup laser pump, reroute an optical signal to backup fibers  406 - 2 , etc.), test specific fibers (e.g., primary fibers  404 - 1 , backup fibers  406 - 1 , etc.), to reconfigure automatic fiber patch panel  408 , to provide information (e.g., a result of testing a fiber) to the remote device, and/or to perform any other functions that are associated with changing the configuration of SH repeater node  402 . 
     SH repeater node  402  may reconfigure automated fiber patch panel  408  (block  506 ). For example, assume that SH repeater node  402  receives a command to test primary fibers  404 - 2 . In such an instance, SH repeater node  402  may cause automated fiber patch-panel  408  to couple a port connected to OTDR  412  and a port connected to primary fibers  404 - 2 . This may provide an optical path between OTDR  412  and primary fibers  404 - 2 . 
     SH repeater node  402  may select and test an optical fiber (block  508 ). For example, assume that SH repeater node  402  receives a command from a remote device to test primary fibers  404 - 1 . In such an instance, SH repeater node  402  may cause automated fiber patch panel  408  to provide an optical path from OTDR  412  to primary fibers  404 - 1 , and direct OTDR  412  to perform a test on primary fibers  404 - 1 . Consequently, OTDR  412  may send a series of pulses at one end of primary fibers  404 - 1  and monitor reflected pulses at the same end. After performing the test, OTDR  412  may provide a test result (e.g., data) to OSC equipment  416 , which may send the test result to the remote device over primary fibers  404 - 1 . 
     SH repeater node  402  may address the component failure (block  510 ). For example, SH repeater node  402  may activate the backup laser pump in amplifier  418 - 3  to operate in place of the failed primary laser pump in amplifier  418 - 3 . In another example, referring to  FIG. 4 , assume one of primary fibers  404 - 1  that carries an incoming optical signal fails. Upon detecting the failure, SH repeater node  402  may reconfigure switch  418 - 1 , such that amplifier  418 - 3  no longer receives optical signals from primary fibers  404 - 1 , but from backup fibers  406 - 1 . Similarly, SH repeater node  402  may modify configurations of other switches (e.g., switch  418 - 2 , switches in amplifier module  420 , etc.) to change other optical paths through SH repeater node  402 . 
     SH repeater node  402  may send data to a remote device (block  512 ). Depending on the circumstance, SH repeater node  402  may send data (e.g., data from testing optical fibers, information about a failed pump, etc.) in response to a request from the remote device or as a result of performing a test. 
     The following example, in conjunction with  FIGS. 6 and 7 , illustrates processes involved in operation of SH repeater node  402  in accordance with implementations described above. 
     In the example, as illustrated in  FIG. 6 , assume that one of primary fibers  404 - 2  includes a break  424 . Also assume that a user at a remote device decides to perform a diagnostic test on SH repeater node  402 . In  FIG. 6 , optical paths through automated fiber patch  408  are shown in dotted lines. As explained above, each optical path may couple two optical ports of automated fiber patch  408 . 
     The user sends a command to SH repeater node  402  from a remote device. Via OSC equipment  416 , SH repeater node  402  receives the command over an un-broken optical fiber of primary fibers  404 - 2 . The command instructs SH repeater node  402  to conduct a diagnostic test on primary fibers  404 - 2 . 
     Upon receiving the command, SH repeater node  402  reconfigures automated fiber patch panel  408  so that OTDR  412  is coupled to primary fibers  404 - 2  via an optical path, which is shown in  FIG. 6  as optical path  422 . Subsequently, OTDR  412  sends optical pulses to one of primary fibers  404 - 2 , and monitors reflected optical signals. SH repeater node  402  collects data from the OTDR  412 , and sends the data to the remote device over a service channel via the unbroken fiber of primary fibers  404 - 2 . 
     From examining the data, the user determines that there is break  424  on primary fibers  402 - 1  and decides to deploy backup fibers  406 - 2 . The user sends a command over the service channel to reconfigure amplifier module  418 . 
     Upon receiving the command, SH repeater node  402  reconfigures switch  418 - 2  in amplifier module  418  to reroute the optical signal from the output of optical amplifier  418 - 3  to one of backup fibers  406 - 2 . Optical paths that result from the reconfiguration are shown in  FIG. 7  as dotted lines. 
     Later, when a field engineer visits a node facility that houses SH repeater node  402  for maintenance, the field engineer activates cable locator  414 , which transmits a homing signal. Upon locating the node facility, the field engineer detaches and examines primary and backup fibers  404 - 1 ,  404 - 2 ,  406 - 1 , and  406 - 2 , and re-attaches them to correct ports on automated fiber patch panel  408 . In addition, the field engineer replaces the broken optical fiber. 
     The above example illustrates how SH repeater node  402  may operate. More generally, as described prior to the example, SH repeater node  402  may be used instead of an optical regenerator node and/or amplifier node. When a component of SH repeater node  402  fails (e.g., an optical fiber, an amplifier pump, etc.), SH repeater node  402  may detect the failure and/or fix the component. For example, if an optical fiber breaks, SH repeater node  402  may detect the break, may allow a network operator to test the broken fiber, may identify the location of the break, and may route optical signal that travels on the fiber to another fiber. SH repeater node  402  may perform these operations automatically or in accordance with commands issued from a remote device. 
     In addition, SH repeater node  402  may be compact. Typically, a legacy regenerator or amplifier is installed in a large housing to provide convenient access to an engineer, service person, etc. Because SH repeater node  402  is capable of repairing itself, it may not need to provide such access, and consequently, may be placed in a compact container, manhole, hand hole, etc. In addition, because SH repeater node  402  is environmentally hardened, it may withstand temperature changes, moisture, wind, radiation, vibration, etc. 
     SH repeater node  402  may integrate many different components (e.g., a test equipment for remote troubleshooting) to lower the failures-in-time, and to support, if necessary, local maintenance activity. In addition, SH repeater node  402  may be energy efficient. 
     In this specification, various preferred embodiments have been described with reference to the accompanying drawings. It will, however, be evident that various modifications and changes may be made thereto, and additional embodiments may be implemented, without departing from the broader scope of the invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative rather than restrictive sense. 
     For example, while a series of blocks have been described with regard to the process illustrated in  FIG. 5 , the order of the blocks may be modified in other implementations. In addition, non-dependent blocks may represent blocks that can be performed in parallel. 
     No element, block, or instruction used in the present application should be construed as critical or essential to the implementations described herein unless explicitly described as such. Also, as used herein, the article “a” is intended to include one or more items. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.