Abstract:
Separating Passive Optical Network (PON) functions in different mechanical devices, such as optical to electrical conversion of the PON protocol, allows installation of an optical termination device at an exterior of an installation premises and installation of a user interface device performing PON functions inside the installation premises. Various embodiments allow service providers first to install an optical device outside the premises and, later, to install an electrical device, optionally by a customer. This eliminates a service provider from entering the installation premises and enables the customer to complete installation in the interior of the installation premises. Further, more robust, hardened components may be used in the more-permanently installed exterior device, while less-expensive, lower-quality components may be used in the easily-replaceable indoor device, thus reducing cost.

Description:
RELATED APPLICATION(S) 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/994,100, filed on Sep. 17, 2007. The entire teachings of the above application are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    A Fiber-to-the-Premises (FTTP) network architecture extends optical fiber directly to subscribers&#39; premises. According to the FTTP network architecture, an Optical Network Terminal (ONT) is placed on the subscribers&#39; premises, typically inside the premises. In a typical FTTP deployment, a single network element, such as an Optical Line Terminal (OLT), in a Central Office (CO) may monitor and manage active components of hundreds, thousands, or millions of ONTs. However, service providers employing the FTTP network architecture experience high costs in bringing optical fiber to subscribers&#39; premises. Further, lengthy installation, itself, at the customer premises is very expensive to the service provider and disruptive to the customer. 
       SUMMARY OF THE INVENTION 
       [0003]    A method and corresponding apparatus for configuring an Optical Network Terminal (ONT) conducts physical layer ranging of the ONT with an upstream device, such as an Optical Line Terminal (OLT), and detects presence of a downstream device configured to support transport layer communications with the upstream device and user interface communications with end user devices. Optical signals are terminated, supporting communications of configuration data between the upstream device and downstream device. A configuration state of the ONT is changed based on configuration data initiated by the upstream device but presented by the downstream device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    The foregoing will be apparent from the following more particular description of example embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments of the present invention. 
           [0005]      FIG. 1  is a block diagram of an example network in which example embodiments of the present invention may be employed. 
           [0006]      FIG. 2  is a diagram of an example embodiment of the present invention in which an Optical Network Terminal (ONT) is physically divided into a Network Interface Device (NID) and a User Interface Device (UID). 
           [0007]      FIGS. 3A-3F  are diagrams illustrating example embodiments of the present invention in which a composite cable carries data, voice and video signals, as well as various arrangements of electrical power. 
           [0008]      FIGS. 4A-4C  are diagrams illustrating different types of packages used in example embodiments of the present invention. 
           [0009]      FIGS. 5A-5C  are flow diagrams illustrating example methods by which an example ONT according to the present invention may be configured. 
           [0010]      FIG. 6  is a block diagram illustrating an example apparatus for configuring an example ONT according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    A description of example embodiments of the invention follows. 
         [0012]      FIG. 1  is a block diagram of an example network  100  in which example embodiments of the present invention may be employed. The network  100  includes a Wide Area Network (WAN)  110  and a Passive Optical Network (PON)  117 . The WAN  110  may be a network such as the Internet, and the PON  117  is typically a more localized network in which optical signals, used to transmit information, traverse passive optical elements, such as splitters and combiners, to be communicated between network nodes. 
         [0013]    The example network  100  of  FIG. 1  includes one or more Optical Line Terminals (OLTs)  115 , an Element Management System (EMS)  120 , and a Content Server (CS)  105 , all connected, generally, by the WAN  110 . In the example network  100 , each OLT  115  transmits/receives information in the form of a frame of packets  122   a ,  122   b  embodied on optical signals to/from an optical splitter/combiner (OSC)  125  to communicate with, for example, thirty-two Optical Network Terminals (ONTs)  130 . Each ONT  130  receives primary power by local alternating current (AC) power  132  at respective points of installation. The ONTs  130  provide connectivity to customer premises equipment  140  that may include standard telephones  141 ,  149  (e.g., Public Switched Telephone Network (PSTN) and cellular network equipment), Internet Protocol (IP) telephones  142 , network routers  143 ,  147 , video devices (e.g., televisions  144  and digital cable decoders  145 ), computer terminals  146 ,  148 , digital subscriber line connections, cable modems, wireless access devices, as well as any other conventional, newly developed, or later developed devices that may be supported by the ONT  130 . 
         [0014]    ONTs  130  may be equipped with batteries or battery backup units (BBUs), interchangeably referred to herein as BBUs. In an event an ONT  130  equipped with a BBU experiences an interruption in primary power (e.g., local AC power  132 ), the ONT  130  may enable the BBU or otherwise accept receipt of power form the BBU to maintain services until the primary power source is restored or the BBU is drained of stored energy. 
         [0015]      FIG. 2  is a diagram of an example embodiment of the present invention in which an ONT  230  is physically divided into a Network Interface Device (NID)  205 , located in the outdoor  203  of a customer premises, and a User Interface Device (UID)  210 , located in the indoor  206  of the customer premises. Many service providers are reluctant to incur the cost of installing optical fiber cables to numerous installation locations and prefer that ONTs  230  remain outside  203  customer premises. In example embodiments of the present invention, the NID  205  performs an optical to electrical conversion for downstream data for processing by the UID  210  and an electrical to optical conversion for upstream data from the UID  210 . Further, the NID  205  may provide electrical power to the UID  210 , including battery backup power when AC main power becomes unavailable. 
         [0016]    A composite cable  215  may be connected through a wall  204  of a customer premises between the NID  205  and the UID  210  to carry electrical power as well as the service provider&#39;s data payload, including voice, data, video, physical layer information, such as converted Physical Layer Operations, Administration and Maintenance (PLOAM) cells or special protocol packets, and management data, such as ONT Management Control Interface (OMCI) channel data and upgrade data. 
         [0017]    The NID  205  facilitates communications between an upstream device  202  (e.g., OLT  115  of  FIG. 1 ), not shown, of the PON  217  and a downstream device  207  (e.g., UID  210 ). The ONT  230  is configured by conducting physical layer ranging, including a ranging request  218  and a ranging response  219 , with the upstream device  202 . Then the NID  205  detects  213  the presence of the downstream device  207  configured to support transport layer communications with the upstream device  202  and user interface communications with end user devices  240 . The NID  205  then terminates optical signals from the PON  217  to support communications of configuration data  223  between the upstream device  202  and the downstream device  207 . After terminating optical signals, the NID  205  changes a configuration state based on the configuration data  223  initiated by the upstream device  202  but presented  223 ′ by the downstream device  207 . The NID  205  also may transmit the configuration data  223  from an outdoor environment  203  to an indoor environment  206  with respect to a premises where the end user devices  240  are located. 
         [0018]    The physical layer ranging request  218  and a ranging response  219  may be performed automatically, or responsive to testing the downstream device  207 . Further, detecting the presence of the downstream device  207  and changing the configuration state may be separated in time from the physical layer ranging. An ONT Management Control Interface (OMCI) channel also may be established. A second downstream device different from the downstream device may be detected, after which the OMCI channel must be reestablished with the second downstream device. The ONT  230  may change the configuration state based on further configuration data initiated by the upstream device  202 , to configure an upgraded downstream device  207 , but presented by the upgraded downstream device  207 . The NID  205  may receive electrical power via the downstream device  207  or independent of the downstream device  207 . 
         [0019]    The NID  205  may convert data from an optical domain to an electrical domain and transmit the data via a non-fiber medium to the downstream device  207  to support data flow from the upstream device  202  to the end user devices  240 . The NID  205  also may report a state of the downstream device  207  in an event of a fault associated with the downstream device  207 , the fault including communications failure with the downstream device  207 . 
         [0020]    Example embodiments of the present invention allow various installation models, such as terminating the optical functions of the PON  217  outside  203  the installation premises at the NID  205  and transmitting the functions over a less-expensive medium, such as a copper interface of an existing coaxial cable, into the indoor  206  of the installation premises via a wall  204 , for example, to the UID  210 . This example embodiment allows easy upgrades of the UID  210 , which is more likely than the NID  205  (containing the PON interface) to change over time as new technologies are released. Further, a NID  205  intended for outdoor installation may be manufactured using more-robust, hardened components to withstand harsh outdoor environments, with an interior UID  210  using less-expensive, non-hardened components. 
         [0021]    Such installation models may reduce installations costs, both monetary and temporal. For example, a service provider may first install the NID  205  at the outside of a home. Later, a home owner may perform self-installation of the UID  210  so that the service provider may avoid entering the home altogether. 
         [0022]    If there are problems with the NID  205 , the UID  210  first detects them and then reports the problems to the EMS (e.g., EMS  120  of  FIG. 1 ) via a notification, such as a hardware failure alarm. The UID  210  also performs all ranging functions and all physical layer functions, such as generation of PLOAM messages, recognizing downstream data that is destined for the UID  210 , and other functions performed by a traditional ONT (e.g., ONT  130  of  FIG. 1 ). The NID  205  may perform the physical layer functions and convert data to relevant flows that the UID  210  may distinguish as voice, data, video, etc. The UID  210  may then convert these signals to the proper format and forward them to their respective devices  240 , include standard telephones  241 ,  249  (e.g., Public Switched Telephone Network (PSTN) and cellular network equipment), Internet Protocol (IP) telephones  242 , network routers  243 ,  247 , video devices (e.g., televisions  244  and digital cable decoders  245 ), computer terminals  246 ,  248 , digital subscriber line connections, cable modems, wireless access devices, as well as any other conventional, newly developed, or later developed devices that may be supported by the ONT  230 . 
         [0023]    A service provider may manage the NID  205  and UID  210  as a single logical ONT  230  or, alternatively, as separate devices  205 ,  210 . Logical management of the NID  205  and UID  210  as a single ONT  230  is beneficial to service providers that currently deploy traditional ONTs (e.g., ONT  130  of  FIG. 1 ) with all functions integrated in one device but want to transition to the use of NIDs  205  and UIDs  210 . However, there may be cases in which the NID  205  and UID  210  may be managed as separate devices. For example, a service provider may install the NID  205  before installing the UID  210 , but may want to communicate with and range the NID  205  without use of the UID  210 . 
         [0024]    In example embodiments of the present invention, an EMS/OLT (e.g., EMS/OLT  120 ,  115  of  FIG. 1 ) may manage with the NID  205  and UID  210  in a number of different ways: the EMS/OLT may communicate with the NID  205 , which may act as a proxy for both the NID  205  and the UID  210  (i.e., the NID  205  and UID  210  are managed logically as a single ONT  230 ), or the EMS/OLT may communicate with the UID  210 , which may act as a proxy for both the NID  205  and the UID  210  (i.e., the NID  205  and UID  210  are managed logically as a single ONT  230 ), or the EMS/OLT may communicate directly with the NID  205  and the UID  210  (i.e., the NID  205  and UID  210  are managed as separate devices). These management scenarios cover management categories, including Fault, Configuration, Accounting, Performance, Security (FCAPS), provisioning, alarms and upgrades. Note that in some example embodiments the EMS/OLT may communicate only with the UID  210  as long as it is first communicating with the NID  205 . 
         [0025]      FIGS. 3A-3F  are diagrams illustrating example embodiments of the present invention in which a composite cable  315  carries data, voice and video signals, as well as various arrangements of electrical power. As illustrated, electrical power becomes available when the UID  310  is installed and the composite cable  315  is connected between the UID  310  and the NID  305 . 
         [0026]      FIGS. 3A-3C  are diagrams illustrating example embodiments of the present invention in which the UID  310  receives electrical power via its own AC power source  332 . In  FIG. 3A , the UID  310  provides electrical power from its power source  332  to the NID  305  via the composite cable  315 , including battery backup power provided to the UID  310  when the AC main power  332  becomes unavailable. In  FIGS. 3B-3C , a separate power source  305  connected to the composite cable provides power to the NID  305 , which may include main AC power, backup power or both. In  FIG. 3C , the UID  310  additionally provides battery backup power to the NID  305  via the composite cable  315  when the AC main power  305  becomes unavailable. 
         [0027]      FIGS. 3D-3F  are diagrams illustrating example embodiments of the present invention in which the UID  310  receives electrical power via a separate power source  310  connected to the composite cable  315 . In  FIGS. 3D-3E , the separate power source  310  also provides AC power to the NID  305 . In  FIG. 3E , the UID  310  also provides backup power to the NID  305  via the composite cable  315 . In  FIG. 3F , the UID  310  provides electrical power to the NID  305  via the composite cable  315 . 
         [0028]    There are various configurations in which the NID  305  and UID  310  may be packaged. In addition to the separate installation locations (e.g., indoor and outdoor) as discussed above, as illustrated in  FIG. 4A , the NID  405  and UID  410  may be packaged as a single ONT  430 . In this example embodiment, although the NID  405 , or an internal optical device  407  of the NID  405 , is removed from the NID  405 , the NID  405  is physically connected to the UID  410 , so they both reside in a single location (e.g., outside or inside an installation premises), and they are still functionally independent. Thus, for example, the optical device  407  may be removed from the NID  405  and physically connected to the UID  410 . In this example, the optical device  407  may have a female connector corresponding to a male connector on the UID  410  for insertion or connection to the UID  410 . 
         [0029]    Alternatively, as illustrated in  FIG. 4B , the optical device  407  of the NID  405  may be physically collocated with the UID  410  with one of the composite cable connections described above with reference to  FIGS. 3A-3F . In this case, the UID  410  may have a compartment  408  that can accommodate the optical device  407  of the NID  405  and a composite cable  415 , which are connected to the NID  405  and also internally connected to the UID  410 . If a service provider desires to remove or replace the NID  405 , then the cable  415  may stay attached. 
         [0030]    In a further example embodiment, as illustrated in  FIG. 4C , a traditional ONT  450  enclosure may have a special compartment  405  or location that can accommodate the NID  405  and UID  410 , connected by a composite cable  415 . 
         [0031]      FIG. 5A  is a flow diagram  500   a  illustrating an example method of configuring an ONT. First, physical layer ranging with an upstream device (e.g., NID) is conducted  505 . Downstream devices (e.g., UID) configured to support transport layer communications with the upstream device and user interface communications with end user devices are then detected  510 . Optical signals are terminated to support communications of configuration data between the upstream device and downstream device  515 . Finally, a configuration state is changed based on configuration data initiated by the upstream device but presented by the downstream device  520 . 
         [0032]      FIG. 5B  is a flow diagram  500   b  illustrating an example method of configuring an ONT in which a UID of the ONT may be installed at a time after a time of installation of a NID of the ONT. First, physical layer ranging with an upstream device (e.g., NID) is conducted  505 . Then, after a delay  507  (e.g., at a time after a time of installation of the NID), downstream devices configured to support transport layer communications with the upstream device and user interface communications with end user devices are detected  510 . Optical signals are terminated to support communications of configuration data between the upstream device and downstream device  515 . Finally, a configuration state is changed based on configuration data initiated by the upstream device but presented by the downstream device  520 . 
         [0033]      FIG. 5C  is a flow diagram  500   c  illustrating an example method of configuring an ONT in which a UID of the ONT may be replaced or upgraded. First, physical layer ranging with an upstream device (e.g., NID) is conducted  505 . Downstream devices (e.g., UID) configured to support transport layer communications with the upstream device and user interface communications with end user devices are then detected  510 . Optical signals are terminated to support communications of configuration data between the upstream device and downstream device  515 . A configuration state is changed based on configuration data initiated by the upstream device but presented by the downstream device  520 . An OMCI channel then may be established  525 . Later, a second downstream device (e.g., UID) may be detected  530 , such as after a replacement or upgrade of a UID. The OMCI channel is then reestablished  535  with the second downstream device. 
         [0034]      FIG. 6  is a block diagram illustrating an example apparatus  600  for configuring an ONT. A ranging unit  605  conducts physical layer ranging with an upstream device. A detection unit  610  then detects the presence of a downstream device configured to support transport layer communications with the upstream device and user interface communications with end user devices. A termination unit  615  terminates optical signals to support communications of configuration data between the upstream device and the downstream device. A configuration unit  620  then changes a configuration state based on configuration data initiated by the upstream device but presented by the downstream device. 
         [0035]    In most situations, the NID performs the conversion of the 1550 nm optical signal to the radio frequency (RF) quadrature amplitude modulated (QUAM) signal that is utilized for analog video. However, the NID may also convert the 1550 nm signal to a digital format, which may then be reconverted by the to a format such as Internet Protocol Television (IPTV) or a RF video signal. 
         [0036]    Example cables that may be used as the composite cable between the NID and UID include Category 7 (CAT-7) cable. CAT-7 cable is a four twisted pair (TP) cable, similar to Category 5 (CAT-5) cable, except that each pair is individually shielded with an aluminum foil, with all four pairs shielded by a tinned copper braid shield. These layers of shielding allow transmission of frequency signals higher than those permitted by CAT-5, for example. Category 8 (CAT-8) cable, which will carry 1.2 MHz signals, may also be used but is not as common as CAT-7. The use of CAT-7 or CAT-8 cable is only an example of a possible solution to implement the Gigabit PON signal transmission. The actual implementation would likely require more than four pairs and may need a special cable and connector. 
         [0037]    While this invention has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.