Abstract:
A segmented optical node exploits a configuration module having arrayed all elements to go from a 1×4 to a 4×4 configuration, save optional redundant switches. A jumper board in the 1×, 2× path configures the node for 1×4 in one orientation and for 2×4 when flipped around 180 degrees. The 4×4 configuration is achieved by rotating the configuration module 90 degrees. In this orientation power to the module is also off, since the 4× configuration is passive.

Description:
PRIORITY CLAIM 
     This application claims priority to the Provisional application on file under Ser. No. 61/559,629 filed on Nov. 14, 2011. 
    
    
     FIELD OF THE INVENTION 
     A configurable optical node, more specifically, a segmented bidirectional node is presented. 
     BACKGROUND OF THE INVENTION 
     Cable Operators are continually seeking means to meet the demand placed upon them to provide consumers with more services such as video on demand, Internet access, and voice over internet services. Because the laying of fiber is one of the very high costs incumbent upon a provider, Operators strive to configure networks to satisfy the greatest number of customers through existing fiber by understanding that generally the customers have two distinct needs. First, there are needs for broadcast content such as network television contact where content sent in the forward direction is the same across a broad number of consumers. In the business, this is described as point-to-multipoint services. Generally broadcast services are both analog (extending from Channel 2 at (55 MHz) to Channel 79 (553 MHz)) and digital (extending up to, alternatively 650 MHz or 750 MHz depending upon system design parameters). 
     For consumers there remains a second type of service known as narrowcast services such as Internet Access, telephony, or video on demand. For these services, known in the industry as multipoint-to-multipoint and carried on spectrum above that of broadcast services generally up to 1 GHz, content is unique on each path and there is no means by which to split and amplify a single signal to reach a large number of consumers. Rather each narrowcast signal is generally a single signal that reaches each consumer distinctly and generally is not split. Return path signals are a special case of narrowcasting in that they are unique signals from the consumer back up to the network headend. Return path signals include video on demand control signals, return Internet data, return telephony data. Return path signals are carried to the headend in frequency bands from 5 MHz to 40 MHz. 
     Optical nodes facilitate the transmission of data in both directions by serving as the connecting device between the higher capacity fiber optic cable that extends from the headend down to the lower capacity coaxial cable that is generally used to connect individual consumers to the network and carries a signal in that part of the signal spectrum known as radio frequency or RF. In its simplest configuration a conventional optical node is said to be in 1×1 configuration when, it receives one set of downstream content from the headend and transmits just one set of upstream return path signals. (1×1 does not refer to the specific relation between numbers of RF ports used but only to the signal relationship between the node and the headend.) For example, in a broadcast forward mode, an optical signal might enter an optical node having four RF ports for output. In this example, the optical node is in 1×1 configuration meaning that the single downstream signal is split and amplified such that all four ports have the same downstream content and all upstream return signals are combined into a single upstream optical signal. If, in this example, the optical node services a community with 1000 consumer households, each RF port might, if the load was perfectly balanced, carry an RF signal sufficient to serve 250 homes. 
     Distinct from a 1×1 configuration, a 4×4 configuration can be advantageous. As the name indicates the 4×4 optical node receives for forward distinct optical inputs and returns four distinct optical outputs to the headend. In this example, where four RF ports are present, the optical node converts the optical signals to four distinct electrical radio frequency (RF) signals, which it outputs each to one of the four ports. In essence, the system acts as four distinct optical to RF converters and in the reverse direction as RF to optical converts such that the signals inbound have a one to one relationship with the signals outbound. Thus, using a 4×4 optical node to transmit downstream may be costly in terms of fiber needed to service the network. 
     Because broadcast service can be carried by fewer optical fibers to serve the same community than is required to service the same community with narrowcast service, operators have found that fully segmentable optical nodes (i.e. those that can be configured to either split or combine signals in traversing between optical and RF ports) have great utility in networks. Operators find it difficult and costly to obtain the rights to place a large number of optical nodes at ground level because, often, many other utility providers must compete for the same space. Thus segmented optical nodes are extremely attractive to operators. 
     Without disturbing the basic fiber complement extending between a headend and the optical node, operators can install distinct configuration modules to distinctly task both optical interfaces and RF ports and can split signals as needed between them to create distinct configurations for both downstream and upstream signal transmission through the node. 
     Making an optical node capable to serve several distinct segmentation schemes incorporates very distinct power and hardware requirements. A first basic segmentation scheme is known as a 2×2 requires that a second receiver and a second transmitter be installed in the optical node and a pair of two-way splitters is introduced to replace the four-way splitter between the original single receiver/transmitter and the four RF ports. 
     In a second basic segmentation is known as the 4×4 configuration discussed above, two receivers and two transmitters are added to the two existing receivers and two existing transmitters such that a set of four jumpers is introduced into the system to replace the previous splitter pairs. This 4×4 allows each of a receiver/transmitter pair within the optical node to be commissioned for dedicated service to each of the 4 RF output ports. 
     Further complications result from the fact that traditional optical nodes rely on passive splitting for the 1×4 and 2×2 configurations, usually combined onto a device often known as a configuration module. As these often passive configuration modules have different split losses, the node is designed such that an amplifier is added to supply enough gain between the receiver and RF output section (called a launch amplifier) to overcome the split loss of the 1×4 split. When configure to facilitate the 2×2 split, the optical node now provides excess gain available because exchanging the two-way splitter for the four-way splitter results a lower loss which designers typically address by introduction of a corresponding amount of fixed attenuation. Similarly the loss of splitters in a 4×4 configuration also requires addition of still further attenuation. One consequence of this process is that, as the number of receivers and transmitters increase, the node consumes proportionately more power. 
     Unfortunately, as can readily be comprehended, each of these distinct modules with their distinct amplification and attenuation as employed in conventional optical node platforms must be separately designed and constructed. Further, the operator electing to reconfigure an optical node must also accommodate unique traffic management configurations, such as dedicating a receiver to 1 port or splitting 2 ports and dedicating a receiver each to the remaining 2 ports. So apart from requiring separate modules for splitting and amplification must also warehouse custom traffic modules. Individuals servicing the nodes are required to warehouse and keep a complete set of distinct modules on hand in order to configure each optical node as the need arises. 
     What is needed in the art is a readily configurable optical node that allows configuration with a single configurable module which does not require either unnecessary amplification or power loss. 
     SUMMARY OF THE INVENTION 
     A segmented optical node exploits a configuration module having arrayed all elements to go from a 1×4 to a 4×4 configuration, save optional redundant switches. A jumper board in the 1×, 2× path configures the node for 1×4 in one orientation and for 2×4 when flipped around 180 degrees. The 4×4 configuration is achieved by rotating the configuration module 90 degrees. In this orientation power to the module is also off, since the 4× configuration is passive. 
     In its role managing amplification and splitting across the optical node, the configuration module is a “unity gain” device. That is, no matter what configuration, 1×4, 2×2, 4×4, or other, the gain of the module is zero dB. This means that the split loss is overcome in the module itself, and the path configurations are done by a means of an internal jumper board instead of by changing to a new module. In the 4×4 configuration, the module is simply rotated 90 degrees to completely remove power from the module while establishing the required 4 passive RF paths between each receiver and each launch amplifier port. 
     Because of the unity gain across the module, the module allows conservation of power compared to all other segmentation designs. Because the configuration module is unity gain, the receiver and launch amplifier gain combined can be sized to provide 8 dB less than in a conventional design (8 dB is the rule-of-thumb split loss of a 4-way splitter). The conservation of amplification allows power saving opportunities in the receiver and launch amplifiers by the reduction of gain requirements in those sections. 
     Further, the configuration module adds segmentation options that have been impractical to introduce into other node designs due to the need to offer such a large number of configuration board options. Those two additional options are 3+1 and 2+2. Additionally, trans-hinge coaxial cables enable a patch panel, allowing the individual servicing the optical node to configure the ports to manage traffic by simple cable arrangement. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred and alternative examples of the present invention are described in detail below with reference to the following drawings: 
         FIG. 1  is a block diagram of an inventive optical node with configuration modules; 
         FIG. 2  is a block diagram depicting the configuration module oriented in a socket at 0°; 
         FIG. 3  is a block diagram depicting the configuration module oriented in a socket at 90°; 
         FIG. 4  is a switching diagram depicting the configuration module in a 1×4 with a single jumper board; 
         FIG. 5  is a switching diagram depicting the configuration module in a 2×4 with a single jumper board; 
         FIG. 6  is a switching diagram depicting the configuration module in a 1×4 with a single jumper board with a 1×4 redundant relay; 
         FIG. 7  is a switching diagram depicting the configuration module in a 2×4 with a single jumper board with 1×4 redundant relays; and 
         FIGS. 8-13  depict various configurations of coaxial patch cords shown to balance traffic at optical transmitters in response to distinct traffic situations. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  is a block diagram of an inventive optical node  10  comprising three distinct and identifiable elements named for their distinct physical locations: a fiber tray  12 ; a lid  14  containing each of an inventive forward module  147  along with four optical to RF receivers  141  and an inventive reverse traffic manager module  145  and its four RF to optical transmitters  143 ; and a base  16  having four distinct launch amplifiers  161   a - d  and RF ports  163   a - d . Two additional hardline RF ports  165   a, b  are included for dedicated power entry but add no additional RF functionality. As set forth, these two hardline RF ports  165   a, b  allow for more flexibility in the placement of the power inserter wile alleviating power inserter insertion loss occasioned by relying upon the functional RF ports  163   a - d  for power insertion. Two power supplies  149   a, b  are present to condition power supplied to the forward  147  and reverse  145  configuration modules. 
     The fiber tray  12  includes a series of optical connectors  129  for selectively connecting optical fiber to the fiber tray  12  for input and output of optical signals. The arrangement of connectors  129  with the reverse multiplexers  121 ,  123  and the forward multiplexers  125 ,  127  allow user configurable selection of optical connectors  129  for suitable configuration in any of the onboard multiplexers to facilitate several alternate configurations allowing the injection of optical signals in distinct configurations depending upon the needs of the operator. 
     The lid  14  includes, as indicated above, four transmitters  143  and four receivers  141  which together serve as the interface between the optical fiber that ties the connectors  129  to the multiplexers  121 - 127  and on into the lid  14 . The reverse traffic manager module  145  presents the upstream signal to such of its four RF to optical transmitters  143  as it is configured to use to present to the reverse multiplexers  121 ,  123  for introduction into such fiber optic fibers as are connected to the connectors  129 . In a similar manner, downstream signals are received from the forward multiplexers  125 ,  127  at the receivers  147 . The forward multiplexers  125 ,  127  receive downstream signals through the connectors  129  to convey through such of the four optical to RF receivers  141  as the forward configuration module  147  tasks. Below the discussion moves to treat the operation of the forward  147  and the reverse  145  configuration modules in greater detail than in this overview of the system. 
     A series of patch cords  15  are configurable to selectively connect the forward  147  and the reverse  145  configuration modules to the several launch amplifiers  161   a - d , through trans-hinge coaxial cables. The trans-hinge coaxial cables allow the user to intuitively connect output of the forward  147  and the reverse  145  configuration modules to such of four launch amplifiers  161   a - d  located in the base  16  according to the desired configuration. Simple columnar tables can be included within the base to facilitate the connections necessary. 
     In the base  16 , four bidirectional launch amplifiers  161   a - d  are each arranged to condition the signals for the inbound and outbound signals through dedicated RF ports  163   a - d  coupled to each of the launch amplifiers  161   a - d . Because these are the principle power consumption devices within the optical node  10 , the arrangement of the launch amplifiers  161   a - d , within the base (in the presently preferred embodiment an aluminum casting having heat sink convection fins to dissipate heat generated in signal amplification). 
     Referring to  FIG. 2 , the forward control module  147  (and similarly the reverse control module  145 ) provides conductivity paths or traces from the receivers  141   a - d  to the RF ports  163   a - d . Within the module  147 , a first set of four traces  1472  extends from a redundant switching section  1471  to a gain and split section  1473  to provide multiple switchably configurable unity gain paths through the module  147 . When the module  147  is oriented as depicted in  FIG. 2  a first set of pins  1475  engage the socket set  1479  on a base printed circuit board to provide switchably configurable set of four traces through the module  147  appropriate for any but the 4×4 configuration of the module (The 4×4 configuration being enabled by a purely unswitched path through the module (extending from a first set of pins  1477  to a second set of pins  1477 , shown) as discussed with reference to  FIG. 3  below). In such a manner, the physical configuration of the module  147  with the two sets of pins  1475  and  1477  and two sets of traces connecting those pins are two means to configure the module to present unity gain across the module  147  for each of the configurations in which the module splits and combines signals across the module  147 . A user achieves further configuration of the fully configurable module by use of the jumper switch and the gain and split section  1473  as discussed in greater detail below. 
     In contrast, when oriented as depicted in  FIG. 3 , a second set of pins  1477  engage the socket  1479  which then connect a second set of traces  1476  for a purely passive path from the first set of pins  1477  to the second set of pins  1477  with no switching capacity needed. As these traces are simple straight and nowhere split along the module  147 , they have no need for amplification to make up splitting losses. For that reason, when the orientation of the module is rotated as depicted in  FIG. 3  unity gain simply describes conductivity along these traces  1476 . 
     The further innovation that is a key to the versatility of the configuration module is depicted in  FIGS. 4-7 . By judicious selection and geometric configuration of several elemental components, specifically three splitters  14731   a - c , two amplifiers  14732   a, b  (selected to impart gain selected to exactly balance splitter losses), a transverse trace  14735 , and two redundant relays  14737   a, b , the configuration module can be configured to allow for four distinct configurations in response to positions of a single jumper switch having three positions. The positions for the jumper switch are “1×4”, “3+1”, and “2×2”. When the control module configuration module oriented in the socket at 0°, this switch enables tailoring of the module for any of these three modes and with jumper settings, the presence of the redundant relays allows exploitation of second receivers as backups to first receivers providing a failover capacity in the optical node. 
     By way of overview,  FIG. 4  depicts a switching diagram depicting the configuration module  147  in a 1×4;  FIG. 5  depicts the configuration module  147  in a 2×4;  FIG. 6  depicts the configuration module  147  in a 1×4 with a 1×4 redundant relay  14737   a ; and  FIG. 7  depicts the configuration module  147  in a 2×4 with 1×4 redundant relays  14737   a, b . The user readily configures the module  147  by simply moving the switch from position to position thereby changing the conductive path through the module  147  and its eight elemental components. 
     In  FIG. 4 , though not pictured as such, the jumper switch is in a first position, specifically the “1×4” position. By virtue of being the in first position, only one of the four receivers  141   a - d , specifically the first receiver  141   a , is placed in electrical contact with the a first amplifier  14732   a  through movement of one of the switch arms  14733   f  connecting contacts cu and cv. From the first amplifier  14732   a , the electrical path extends to another contact cj. At contact cj, another switch arm is positioned to close the path between contact cj and contact ci thereby incorporating the transverse trace  14735  completing the electrical pathway to contact cq. At contact cq, a third electrical switch arm  14732   e  connects contact cq to contact cr thereby completing a pathway from the receiver through the first and second amplifiers  14732   a, b  for a gain four times that of the output of receiver  1   141   a  to counter losses imparted by a four-way split of the signal. A fourth switch arm  14733   d , takes the output of the second amplifier  14732   b  and directs it from a contact cn to the contact cm for splitting at the splitter  14731   c . A fifth switch arm closes contacts ca and cb connecting a second splitters  14731   a , while a sixth switch arm closes contacts ce and cf to similarly connect the third splitter  14733   b  thereby conveying the output signal at unity gain to each of four RF ports. 
     In  FIG. 5 , depicts the configuration module  147  as the jumper switch is in a second position, specifically the “2×4” position. All but one of the six switch arms  14733   a - e  has moved and by that movement, the output of two of the four receivers  141   a - d , specifically the first and second receivers  141   a  will be conducted through the module  147 . Additionally, while in this “3+1” position, the first splitter  14731   c  and the transverse trace  13735  have been isolated, they not being necessary to constitute either of the two conductivity paths through the module  147 . 
     It is worth noting, at this juncture, there are no physical switches nor switch arms. In the presently preferred embodiment, positions of the switch selectively activate transistors to provide the actual switching function that the switch arms  14733   a - f  portray in these drawings. While a physical switch could be used, the present invention can be enabled by either electronic switching or physical switching, but in this depiction the physical switch is used as a valid analogy to portray movement of the signal through the module  147 . 
     In this second position or “2×4” of the jumper switch, two receivers are placed in electrical contact with separately with either the first amplifier  14732   a  through movement of one of the switch arms  14733   f  connecting contacts cu and cv and the second amplifier  14732   b  when the switch arm  14733   e  closes contact between contact cr and cy. Switch arms  14733   c  and  14733   d  respectively close contacts between contacts cj and ca to communicate the output of the first amplifier  14732   a  to the second splitter  14731   a  and between contacts cn and cf to, likewise, connect the second amplifier  14732   b  to the third splitter  14732   b , thereby completing paths between receiver  1   141   a  and ports  1  and  3 ,  163   a, c  and between receiver  2 ,  141   b  and ports  2  and  4 ,  163   b , and d. Thus, the module  147  now enables the “2×4” configuration that the jumper switch indicates. 
       FIG. 6  is a nearly identical depiction of a “1×4” configuration as is shown in  FIG. 4 , but is included to demonstrate the virtue of the virtue of the module configuration when considered in the context of the redundant relay  14737   a . The redundant relay provides failover protection allowing a relay to bring a second receiver, in this case, receiver  3   141   c  online in the event that receiver  1   141   a  should fail. This can be done remotely and, thus, prevents outages necessitating service calls. In a similar manner,  FIG. 7  is identical to  FIG. 5  except a second relay  14737   b  is also included to allow redundancy between receivers  2   141   b  and  4141   d.    
     Having seen the “1×4” and “2×4” modes, it is easy to comprehend that the “3+1” is simply a hybrid of the two achieved by switching. Just as in the “2×4” and “2×4” redundant modes shown in  FIGS. 4 and 6 , respectively, the output of the first amplifier  14732   a  is fed to the first splitter  14731   c . While one side of the output of the first splitter  14732   a  is fed to the second splitter  14732   b , just as in the  FIGS. 4 and 6 , the second side is fed to a pass-through that attenuates the signal by half, thereby providing the RF port  2 ,  163   b  with a signal having unity gain. With reference to the output of receivers  2  and  4 ,  141   b  and  d , the path is identical to that portrayed in either of  FIGS. 5 and 7  except that the first output of the third splitter  14731   b  that is depicted as flowing into RF port  2   163   b  (currently receiving the output from the pass-through instead), now is fed into a signal trap that completely attenuates the energy and, thus, the signal at RF port  4  arrives with the same unity gain as its three sisters. 
       FIGS. 8 through 15  depict various patching arrangements that are possible with the coaxial cords used to place the output from the receivers suitably at the inputs of the bidirectional launch amplifiers. Depicted in each is a block diagram of the base  16  having four launch amplifiers  161   a - d  and four corresponding RF ports  163   a - d . Each of the four launch amplifiers  161   a - d  are bidirectional and will amplify a signal coming upstream or flowing down with a suitable input or output for each as appropriate. Importantly, for clarity, the configuration modules have been removed from the paths for illustrative purposes. To function as discussed herein, however, the configuration modules must be present. 
     In each of the several depictions, a series of four coaxial jumper cables is shown acting as “patch cords.” A patch cable or patch cord connects (“patches-in”) one electronic device to another for signal routing. Generally, as here, patch cords are used to connect devices of different types (e.g., a switch connected to a computer, or a switch to a router). While the patch cords are numbered  151 ,  152 ,  153 , and  154 , this convention is not meant to suggest that the patch cords, as numbered, are the same cords from figure to figure. Rather, they are numbered simply to locate them for the reader in each of the distinct drawings. The use of all other reference numbers herein are according to the standard convention of identifying the component uniquely and consistently from one figure to the next. 
     In  FIG. 8 , two of the four receivers, the first receiver  141   a  and the third receiver  141   c , are depicted as connected to individual launch amplifiers  161   a - d , likely to show a broadcast configuration of the device as well as its flexibility. In this example, the north RF ports  163   a, c  are experiencing heavy traffic. Assuming that this load is based upon a relatively stable demand such that it is advantageous to configure the optical node to address this demand. An operator can then split the heavier load between two receivers rather than to assign one to the two RF ports  163   a, c , bearing the heavier traffic and one to those ports  163   b, d , bearing the lighter traffic. Thus, an operator would want, optimally, to take the output of Receiver  1  and split it between a heavy and a medium traffic port such as RF ports  1  and  2 ,  163   a  and  163   b . Thus, the operator will connect Receiver  1   141   a  to the RF ports  1  and  2 ,  163   a, b , with coaxial cable patch cords  151  and  153  at the launch amplifiers on the downstream side  161   ar  and  161   br  respectively. In a similar manner, Receiver  3 ,  141   c  will send its output through patch cords  152  and  154  to the downstream side of launch amplifiers  161   dr  and  161   cr  respectively. Hence,  FIG. 8  depicts the use of the patch cords to suitably address long-term changes in traffic. 
       FIG. 9  portrays the upstream configuration of the same traffic issues as  FIG. 8  portrays. Once again, heavy traffic on RF ports  1  and  3 ,  161   a  and  161   c , dictates a need to balance load as between transmitters  1  and  3 ,  143   a , and  143   c . To that end, coaxial cables  151  and  153  connect transmitter  1  to each of launch amplifiers  161   ar  and  br  on the upstream side. Again, the transmitter  3  is connected to the upstream sides of launch amplifiers at  161   ct  and  dt  using patch cords  152  and  154  respectively. In this manner, the load on either transmitter  143   a  and  143   c  is balanced relative to the other. 
       FIG. 10  shows a situation nearly identical configuration but configured as the coaxial cable is, to split the load between heavy traffic and regular traffic, the split is shown to be advantageous when demand shifts. As can be appreciated, when the heavy traffic has shifted from RF Port  1   163   a  to RF Port  2   163   b  and likewise from RF Port  3   163   c  to RF Port  4   163   d , the exact same coaxial configuration continues to allow a balanced traffic between Transmitter  1   143   a  and Transmitter  3   143   c . Given these two depicted examples, one can easily see how even shifting loads can be accommodated by judicious selection of correspondence between transmitters and RF ports. 
       FIG. 11  shows that traffic has moved to a region that had, in  FIGS. 9 and 10  had been served by Transmitter  3  alone. A simple exchanging of the patch cords  151  and as they are connect to input ports  161   bt  and  161   ct  results in the configuration shown in  FIG. 11 , thereby returning the balance of traffic as between Transmitter  1   143   a  and Transmitter  3   143   c . Clearly any service interruption necessitated by the exchange of the patch cords  152  and  153  will be minimal given the highly intuitive and extremely simple procedure the patch cord arrangement facilitates. 
     Thus far, we have discussed balanced shifting of traffic such that pairs of ports are experiencing increased or diminished demand. In  FIG. 12  a different situation. As discussed in reference to  FIGS. 4-7 , the configuration module  147  can be configured to a “3+1” configuration just as it can also be configured to a “1×1” with redundancy. Assuming that a service person has suitably adjusted the jumper switches as they are labeled, the output of Transmitter  3 ,  141   c  can be dedicated to a single RF port (RF Port  4   163   d  as illustrated) in response to heavy traffic on that single port. The remaining ports can be serviced by the single Transmitter  1  in “3+1” configuration. Coaxial patch cords  151 ,  152 , and  153  connect RF Ports  1 ,  2 , and  3   163   a - c , respectively, to, suitably, balance the traffic between the transmitters. 
     Again,  FIG. 13  demonstrates the versatility of the configuration node  10  as traffic loads shift. In this example, the heavy traffic has shifted from RF port  4   163   d  to RF port  3   163   c . Simple exchange of terminal ends of patch cords  152  and  154  results in dedication of Transmitter  3  to the heavy traffic on RF port  3   163   c.    
     While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. For example, patch cords may be configured to meet other needs according to the earlier explanation. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.