Abstract:
Methods and apparatuses consistent with the present invention facilitate the transition from a legacy network to an upgraded network by providing a converter that communicates between the legacy network and the upgraded network. The converter is provisioned such that legacy devices, such as Optical Network Units (ONUs), appear as upgraded devices to the upgraded network, while the upgraded network looks like a legacy network to the legacy devices.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims the benefit of the provisional patent application filed on Apr. 9, 2004, and assigned application Ser. No. 60/561,005. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to the field of communication systems, and more particularly to a method and apparatus for transitioning from a legacy Passive Optical Network (PON) to an upgraded PON.  
       BACKGROUND  
       [0003]     The use of fiber optic cables to cary information signals continues to grow in popularity worldwide. Digital information signals modulate light traveling on the fiber optic cable between a source node and a receiving node. As is well known, fiber optic cable has a much higher information carrying capacity than copper wire, including the ubiquitous unshielded twisted copper pair commonly used for providing dial-up telephone service. As fiber continues to be deployed throughout telecommunications networks, its advantages over copper accrue to the user. Generally, fiber exhibits a higher bandwidth and lower signal losses than copper conductors. Fiber is also more reliable and has a longer useful life than copper conductors. Since fiber does not emit any electromagnetic radiation, it is a more secure tn ssion medium than copper.  
         [0004]     A Passive Optical Network (PON), including for example a Broadband Passive Optical Network (BPON) or a Gigabit Passive Optical Network (GPON), provides multiple data transmission paths, each capable of delivering high-bandwidth data services to multiple subscribers. An exemplary BPON comprises 32 or 64 such data paths, each data path comprising one fiber optic cable. A GPON comprises, for example, 64 or 128 data paths. A standardized PON protocol controls and manages the transmission and reception of signals across the PON.  
         [0005]     A network architecture reference model for the BPON is described in the Inteemational Telecommunications Union (ITU) Specification ITU-T G.983.1, entitled,  Broadband Optical Access Wstems Based on Passive Optical Networks (PON) , which is incorporated herens by reference. Additional information can be found in related rrU specifications G.983.x, which are incorporated by refence. GPON reference models are descnbed in the Inteuational Telecommunications Union Specifications ITU-T G.984.1 through 984-4, which is also incorporated by reference.  
         [0006]     The PON Optical Distribution Network (ODN) fiwther comprises optical splitters and combiners for directing information signals propagating between an Optical Line Terminal (OLT) and a plurality of Optical Network Units (ONUs). Various trnission speeds are consistent with the present invention, but according to current standards, the fiber optic path on a PON network operates at data rates of 155 Mbps, 622 Mbps, 1.25 Gbps, and 2.5 Gbps. Bandwidth allocated to each customer from this aggregate bandwidth can be statically or dynamically assigned to suwport voice, data, video, and multimedia applications.  
         [0007]     As GPON networks gain popularity over BPON networks, there exists a need to have methods and systems for trisitioning from the legacy BPON networks to GPON. One option is to replace all the BPON equipment with GPON equipment However, replacing the equipment would be cost prohibitive and labor intensive. Another option would be maintaining the existing BPON network as well as the new GPON network. This option would have a lower equipment cost than the first option; however, maintaining both network types would be administratively difficult and increase maintenance costs.  
         [0008]     Although the above options exist to trausfer from a BPON network to a GPON network, they are cost and maintenance intensive. A need exists for improved methods and systems to facilitate migration between networks having different transmission protocols, without necessarily replacing all equipment associated with a legacy network.  
       SUMMARY OF THE INVENTION  
       [0009]     Methods and apparatuses consistent with the present invention facilitate the transition from a legacy network to an upgraded network by providing a converter that communicates between the legacy network and the upgraded network. The converter is provisioned such that legacy devices, such as Optical Network Units (ONUs), appear as upgraded devices to the upgraded network, while the upgraded network looks like a legacy network to the legacy devices.  
         [0010]     In one aspect of the invention a method is descnrbed for upgrading a legacy BPON network, having a legacy BPON OLT and a plurality of legacy BPON ONUs, to facilitate communication between the legacy BPON ONUs and an upgraded GPON OLT. The method includes the steps of (a) installing a converter between the plurality of legacy BPON ONUs and the upgraded GPON OLT; (b) provisioning the converter and the legacy BPON ONUs to appear in the downstream direction to the upgraded GPON OLT as virtal GPON ONUs; and (c) provisioning the converter to appear in the upstream direction to the plurality of legacy BPON ONUs as a virtual BPON OLT.  
         [0011]     In another aspect of the invention a converter is provided for facilitating communication between a plurality of legacy BPON ONUs and a upgraded GPON OLT. The converter includes a central processing unit, a memory, and a queue for storing and processing data transmitted and received by the converter. The converter also includes a BPON transceiver for Unsmiling and receiving BPON frames between the converter and the legacy BPON ONUs. Additionally, the convert includes a BPON MAC for processing the BPON frames transmitted to and received from the legacy BPON ONUs. The converter further includes a converter managed entity and a plurality of ONU managed entities for storing and manipulating parameters related to the management of the legacy BPON ONUs and the upgraded GPON OLT.  
         [0012]     In still another aspect of the invention, a method is described for ranging an upgraded PON OLT with a converter and a plurality of legacy PON ONUs. The method includes the steps of (a) installing the converter between the legacy PON ONUs and a legacy PON OLT; (b) monitoring, by the converter, transmissions between the legacy PON OLT and the legacy PON ONUs to identify legacy ranging data in the trasmissions related to a prior ranging of the legacy PON ONUs with the legacy PON OLT; and (c) storing, by the converter, the legacy ranging data to facilitate the ranging of the legacy PON ONUs.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The above mentioned and other concepts of the present invention will now be described with reference to the following drawings. The illustrated embodiments are intended to illustrate, but not to limit Ihe invention. The drawings contain the following figures, in which like numbers refer to like parts throughout the description and drawings wherein:  
         [0014]      FIG. 1  illustrates a network consistent with an exemplary embodiment of the present invention  
         [0015]      FIG. 2  illustrates an exemplary downstream provisioning perspective consistent with the present invention.  
         [0016]      FIG. 3  illustrates an exemplary upstream provisioning perspective consistent with the present invention.  
         [0017]      FIG. 4  illustrates a converter consistent with an exemplary embodiment of the present invention.  
         [0018]      FIG. 5  illustrates an exemplary downstream transmission consistent with the present invention.  
         [0019]      FIG. 6  illustrates an exemplary upstream transmission consistent with the present invention.  
         [0020]      FIG. 7  illustrates an exemplary learning phase associated with provisioning the converter of  FIG. 4 . 
     
    
     DETAILED DESCRIPTION OF INVENTION  
       [0021]      FIG. 1  illustrates a network  10  consistent with one embodiment of the present invention comprising a legacy Broadband Passive Optical Network (BPON)  32 ( 1 ), a Gigabit Passive Optical Network (GPON)  32 ( 2 ), and an Internet and switched network  12 . The network  10  may comprise, for example, a data network, a Public Switched Telephone Network (PSTN), an Integrated Services Digital Network (ISDN), a Local Area Network (LAN), a Wide Area Network (WAN), or other communication systems or combination of communication systems at one or more locations. The network  10  may comprise wireless networks, wireline networks, or a combination of wireless and wireline networks. The network  10  may support, for example, cell based protocols, such as the Asynchronous Transfer Mode (ATM) or Frame Relay protocols, and/or streams assigned to a time slot such a Time Division Multiplexing (TDM), and/or packet based protocols, such as the Transmission Control Protocol/Internet Protocol (TCP/IP) or the User Datagram Protocol (UDP). Throughout this document, “legacy” equipment and/or network refers to an installed equipment or network relating to a PON network that will be migrated to an “upgraded” equipment and/or network relating to a different PON network Incompatibilities between the legacy and upgraded networks involve for example differences in protocols and/or bit rates. For example, BPON (also known as APON) is considered a legacy network with respect to GPON.  
         [0022]     The BPON network  32 ( 1 ) provides a communications link  14 ( 1 ) between the Internet and switched networks  12  and plurality of telecommunications users or subscribers (not shown) via a BPON Optical Line Terminal (OLT)  22 ( 1 ). Throughout this document, the term “communication link” refers to any suitable wireless, wireline, electrical, and/or optical based system that supports communication between network elements using ground-based and/or space-based components.  
         [0023]     The BPON OLT  22 ( 1 ) operates via an optical transceiver for broadcasting data, multimedia, and telephone signals to a plurality of BPON Optical Network Units (ONUs)  26  and for receiving data, multimedia, and telephone signals from the BPON ONUs  26 . Additionally, the BPON OLT  22 ( 1 ) operates as a network manager for managing the BPON ONUs  26 , executing its network management functions in accordance with an Optical Network Terminal Management and Control Interface (OMCI). The BPON OLT  22 ( 1 ) may be either centralized or decentralized. Throughout this document “centralized” means located at a central office (not shown), and “decentralized” means located away from the central office.  
         [0024]     The BPON network also comprises a BPON Optical Distribution Network (ODN)  20 ( 1 ) having an optical communication link to the BPON OLT  22 ( 1 ). The BPON ODN  20 ( 1 ) includes an optical splitter allowing multiple BPON ONUs  26  to be coupled to the BPON OLT  22 ( 1 ). Throughout this document, the terms “couple” and “coupled” refer to any direct or indirect communication between two or more elements in the network  10 , whether or not those elements are in physical contact with one another. For example, a typical BPON ODN  20 ( 1 ) may provide  32  optical connections to the BPON ONUs  26 .  
         [0025]     The BPON ONU  26  provides a communication link between one or more subscribers or users of the network  10  and the BPON network  32 ( 1 ) via a BPON ODN  20 ( 1 ). Throughout this document, the term “ONU refers to any device such as an ONU or ONT that provides a communication link from a customer premises terminal equipment of a subscriber or user of the network to the optical network The GPON network  32 ( 2 ) provides a communications link  14 ( 2 ) between an Internet and switched network  12  and a GPON OLT  22 ( 2 ). It may also provide a communication link between the GPON OLT  22 ( 2 ) and a telecommunication user or subscriber (not shown). The GPON network  32 ( 2 ) may also include a GPON ODN  20 ( 2 ), and a GPON ONU  28 .  
         [0026]     The GPON OLT  22 ( 2 ), which may be either centralized or decentralized, may operate via an optical transceiver for broadcasting data, multimedia, and telephone signals to a plurality of GPON ONUs  28  and for receiving data, multimedia, and telephone signals from the GPON ONUs  28 . Additionally, the GPON OLT  22 ( 2 ) may operate as a network manager for managing the GPON ONUs  28 , executing its network management functions in accordance with an OMCI.  
         [0027]     The GPON ODN  20 ( 2 ) has an optical communication link to the GPON OLT  22 ( 2 ). The GPON ODN  20 ( 2 ) includes an optical splitter allowing multiple GPON ONUs  28  to be coupled to a GPON OLT  22 ( 2 ). For example, a typical GPON ODN  20 ( 2 ) may provide up to 32, 64, or 128 optical connections to the GPON ONUs  28 .  
         [0028]     Communication in the direction from the OLT  22  to the ONUs  26 ,  28  is termed “downstream” and communication in the direction from the ONU  26 ,  28  to the OLT  22  is termed “upstream”.  
         [0029]     A converter  16  provides a communication link from the BPON ODN  20 ( 1 ) to the GPON OLT  22 ( 2 ). Although the illustration shows the converter  16  within the BPON network  32 ( 1 ), the converter may be located anywhere in the optical path between the GPON OLT  22 ( 2 ) and the BPON ODN  20 ( 1 ), including being co-located with the GPON OLT  22 ( 2 ) or the BPON ODN  20 ( 1 ). Additionally, the converter may provide a communication link  18  to the BPON OLT  22 ( 1 ).  
         [0030]     An optional splitter  30  splits the communication link from the GPON OLT  22 ( 2 ) to the BPON ODN  20 ( 1 ) and the GPON ODN  20 ( 2 ). The splitter  30  may be located anywhere along the optical path between the converter  16  and the GPON OLT  22 ( 2 ). If the converter  16  is co-located with the GPON OLT  22 ( 2 ), the splitter  30  may not be required.  
         [0031]     During the installation and operation of the legacy BPON network  32 ( 1 ), the BPON ONUs  26  are initialized via a process called ranging. Since the upstream communication is via Time Division Multiple Access (TDMA), the BPON ONUs  26  must be synchronized to communicate at a particular time slot to prevent communication collisions. Ranging establishes the synchronization by the BPON OLT  22 ( 1 ) by determining the distance of each BPON ONU  26  and assigning the time slot in which the ONU  26  may transmit. Subsequently, the BPON OLT  22 ( 1 ) sends grant messages via the Physical Layer Operation, Administration, and Maintenance (PLOAM) cells to provision the TDMA slots that are assigned to that BPON ONU  26 . The BPON OLT  22 ( 1 ) stores ranging and initialization information for each BPON ONU  26 .  
         [0032]     As the legacy BPON network  32 ( 1 ) is being upgraded to a GPON network  32 ( 2 ), the converter  16  is provisioned to appear like a BPON OLT  22 ( 1 ) to the BPON ONUs  26 . Provisioning the converter  16  to appear like a BPON OLT  22 ( 1 ) requires that the converter  16  have access to ranging information for the BPON ONUs  26  in order to range the BPON ONUs  26 . This may be done by a learning phase in which ranging information is obtained during normal BPON network  32 ( 1 ) operation. During the learning phase, the converter  16  sets up managed entities for the BPON ONUs  26 . Once the learning is complete, the BPON OLT  22 ( 1 ) and communications links  14 ( 1 ),  18  are removed. Alternatively, the converter  16  may gain ranging information via the messages sent by the GPON OLT  22 ( 2 ). Those skilled in the art will appreciate that there are other methods that would facilitate the converter  16  acquiring ranging information without deviating from the invention.  
         [0033]     Additionally, the converter  16  provides the networks the ability to communicate with each other even though they use different protocols. For one communication method, the converter  16  may convert downstream frames in the GPON network  32 ( 2 ) protocol to downstream frames in the BPON network  32 ( 1 ) protocol. Likewise, the converter may convert upstream frames in the BPON network  32 ( 1 ) to upstream frames in the GPON network  32 ( 1 ). In embodiments of the present invention that include a converter  16  that is not co-located with the OPON OLT  22 ( 2 ), the converter  16  may be provisioned to look like a GPON ONU  28  to establish a communications link between the GPON OLT  22 ( 2 ) and the converter  16 . In embodiments of the present invention that include a converter  16  that is co-located with the GPON OLT  22 ( 2 ), the converter  16  may covert messages from the Internet and switched networks  12  directly to the BPON network  32 ( 1 ) without requiring a GPON conversion.  
         [0034]      FIG. 2  illustrates how the converter  16  appears in terms of provisioning to the GPON OLT  22 ( 2 ). In this illustration, shaded items represent equipment with both an actual and a virtual provisioning appearance. The virtual appearance is indicated in quotes. In the virtual perspective, the BPON ONUs  26  and the converter  16  appear as “GPON ONUs”  26 , 16  to the GPON OLT  22 ( 2 ). In reality, however, the BPON ONUs  26  are legacy BPON ONUs and the converter  16  is connected upstream of these legacy BPON ONUs as illustrated in  FIG. 1 .  
         [0035]      FIG. 3  illustrates how the converter  16  appears in terms of provisioning to the BPON network  32 ( 1 ). Again, shaded items represent equipment with both an actual and a virtual provisioning appearance (virtual appearances are indicated in quotes). To the BPON ONUs  26 , the converter  16  appears as a “BPON OLT”  16 .  
         [0036]      FIG. 4  illustrates an exemplary embodiment of a converter  16  consistent with the present invention. The converter may include a first BPON Media Access Controller (MAC)  42 ( 1 ) for managing the data link layer of transmissions from a legacy BPON OLT during a learning phase. The converter may include a corresponding transceiver (XCVR)  40 ( 1 ) for receiving BPON transmissions from the legacy BPON OLT. A second BPON MAC  42 ( 2 ) may be provided for managing the data link layer of transmissions to and from one or more legacy BPON ONUs. A corresponding XCVR  40 ( 2 ) may be provided for transmitting and receiving BPON transmissions to and from the legacy BPON ONUs. The converter  16  may also include a GPON MAC  42 ( 3 ) and a corresponding XCVR  40 ( 3 ) for transmitting and receiving GPON transmissions to and from the GPON OLT  22 ( 2 ). However, in an alternate embodiment, the converter  16  is co-located with the GPON OLT  22 ( 2 ) and has direct access to the backplane of the GPON OLT. In this alternate embodiment, the converter  16  may act upon transmissions from the Internet and switched networks  12  before the transmissions are formatted as GPON transmissions, making the GPON MAC  42 ( 3 ) and XCVR  40 ( 3 ) unnecessary.  
         [0037]     The converter may further include a Central Processing Unit (CPU)  48  for executing processing functions for the converter  16 . The CPU may be coupled to the MACs  42  and to a memory  51 , a queue  49 , a Segment and Reassembly (SAR) unit  50 , and managed entities  44 ,  46 . The queue  49  is used to store and manage incoming and outgoing transmissions. The SAR unit  50  may comprise hardware, software or a combination thereof. The SAR unit  50  performs functions associated with segmenting and reassembling data during conversion of the data, for example, from TDM data to and from ATM data The managed entities may include a converter managed entity  44  and ONU managed entities  46 . The converter managed entity  44  stores and process parameters associated with converting transmissions between BPON and GPON format The ONU managed entities  46  store and process parameters associated with transmission between and management of ONUs and an OLT.  
         [0038]      FIG. 5  illustrates an exemplary downstream transmission consistent with the present invention. The transmission includes a frame  52 ( 1 ) formatted according to the GPON protocol traveling from the GPON OLT  22 ( 2 ) to the converter  16  (in the downstream direction). The frames  52 ( 1 ) have a fixed length of 125us. Each frame  52 ( 1 ) includes a Physical Control Block downstream (PCBd)  54  and a payload  58 ( 1 ). The PCBd  54  is a variable length field and includes a PLOAM dowstream (PLOAMd) field  56 . A typical PLOAMd field  56  has a 13-byte length and is embodied in accordance with the G.984.3 standard. The payload  58 ( 1 ) may include a “Pure” ATM section  60  and a TDM and Data Section. The “Pure” ATM section contains n number of 53 byte ATM cells. The TDM and Data Section  62  contains fragments of TDM, Ethernet, or data packets.  
         [0039]     A typical downstream frame  52 ( 2 ) format in the BPON protocol traveling from the converter  16  to the BPON ONU  26  is also illustrated. A typical downstream frame  52 ( 2 ) has 54 cells where each cell is 53 bytes. The first and 27 th  cells are PLOAM cells  66  and the others are ATM cells  68 . The converter receives a frame  52 ( 1 ) from the GPON OLT  22 ( 2 ) and puts the payload into the queue for further processing  49 . The PLOAMd  56  field is converted to a PLOAM cell  66  if necessary. In one embodiment, the GPON protocol uses the “Pure” ATM Section  60  the transport mechanism. ATM cells  68  from the “Pure” ATM Section  60  are received by the converter  16  and sent to the BPON ONU  26 . In another embodiment, the GPON protocol uses the TDM &amp; Data Section  62  that requires that the converter  16  be coupled to a SAR unit. The SAR unit  50  uses the ATM adaptation layer to segment the TDM &amp; Data Section  62  into ATM cell  68 . The ATM cells  68  are then sent to the BPON ONU  26 .  
         [0040]      FIG. 6  illustrates an exemplary upstream transmission consistent with the present invention. A typical upstream frame  52 ( 3 ) format is illustrated in BPON protocol format traveling from the BPON ONUs  26  to the converter  16 . The frames  52 ( 3 ) may, for example, be of a fixed size and consists of 53 header  80  and cell  82  pairs. The cell  82  may be an ATM type or a PLOAM type.  
         [0041]     A typical upstream frame  52 ( 4 ) formatted according to the GPON protocol traveling from the converter  16  to the GPON OLT  22 ( 2 ) is also illustrated. As with the downstream frame  52 ( 1 ) the typical upstream frame  52 ( 4 ) may have a fixed length of 125us. The upstream frame  52 ( 4 ) may include transmissions  90  from one or more ONUs  26 . Each ONU transmission  90  may include a PLOAM upstream (PLOAMu) field  84 , a PCB upstream (PCBu) field  86 , and a payload field  88 . A typical PLAOMu field  84  has a 13-byte length. The payload field  88  may contain a “Pure” ATM field or TDM and data field.  
         [0042]     The converter  16  receives a frame  52 ( 3 ) from the BPON ONUs  26  and puts the frame  52 ( 3 ) into a queue for further processing. The PLOAM cells  82  are converted to PLOAMu cells  84  if necessary.  
         [0043]     In one embodiment, the GPON protocol uses the “Pure” ATM Section in the transport mechanism. In another embodiment, the GPON protocol uses the TDM and Data Section, which requires that the converter  16  be coupled to a SAR unit  50 . The SAR unit  50  uses the ATM adaptation layer to reassemble the ATM cells  82  into TDM &amp; Data, which is then formatted into GEM frames and sent to the GPON OLT  22 ( 2 ).  
         [0044]      FIG. 7  illustrates a learning phase associated with the converter of  FIG. 4 . The learning phase comprises the following operating modes, a BPON transparent mode  70 , a GPON ONU mode  72 , BPON Monitor mode  74 , and a GPON-BPON bridge mode  76 . Preferably control of the operating modes is provided from the GPON OLT  22 ( 2 ) via the creation of a new managed entity. The BPON operating modes  70  and  74  are not mandatory; however, it is preferable that all the operating modes are exercised.  
         [0045]     In the BPON transparent mode  70 , the converter  16  is installed between the BPON OLT  22 ( 1 ) and the BPON ODN  20 ( 1 ). A minor service disruption occurs to introduce the converter  16  into the optical path The BPON transparent mode  70  may be the default mode of the converter  16  after a successful startup of the converter  16 . Alternatively, the GPON OLT  22 ( 2 ) may manage the operation of this mode  70  via an OMCI managed entity request of the converter managed entity  44 . While in this mode  70 , transmission transparently continues to pass through the legacy BPON network  32 ( 1 ) between the BPON ODN  20 ( 1 ) and the BPON OLT  22 ( 1 ). One purpose of the BPON transparent mode  70  is to ensure that the introduction of the converter hardware into the legacy BPON network  32 ( 1 ) does not affect the existing BPON network  32 ( 1 ) operation or ONU  26  user services. During this mode  70 , the BPON transmission convergence (TC) layer is not terminated or directed to active components within the converter  16 .  
         [0046]     One purpose of the GPON ONU mode  72  is to provision the converter  16  as a GPON ONU  28  within the GPON network  32 ( 2 ). Once provisioned, the OMCI channel is established, which allows creation of and control of managed entities. Also, the traffic paths between the priority queues  49  and the GPON OLT  22 ( 2 ) are established. During this mode  72 , the BPON ONU  26  transmission continues through the BPON network  32 ( 1 ).  
         [0047]     The BPON monitor mode  74  allows the converter  16  to learn the BPON ONU  26  TC layer configuration data as well as the user services provisioned. Transmission continues to transparently pass through the legacy BPON network  32 ( 1 ) between the BPON ODN  20 ( 1 ) and the BPON OLT  22 ( 1 ) while the converter monitors the upstream and downstream transmissions. This mode  74  may be activated, for example, via a GPON OLT  22 ( 2 ) managed entity request During this mode  74 , the converter monitors the TC layer to determine configuration and bandwidth information that is stored for later use in the GPON-BPON bridge mode  76 . Configuration and bandwidth information may include upstream bandwidth, downstream bandwidth, serial numbers, associated BPON ONU  26  identifiers, grant allocations, upstream overhead parameters, virtal path/virtual circuit assignments and churn control. Also during this mode  74 , the converter may monitor the OMCI traffic and store in memory  51  the managed entities related to user interfaces and services. In order to ensure a clean starting point for the monitoring and storage of the data, it may be required to restart all BPON ONUs  26  in the BPON ODN  20 ( 1 ).  
         [0048]     The GPON-BPON bridge mode  76  is an operational mode in which transmissions occur between the BPON ONUs  26  and the GPON network  32 ( 2 ). During the bridge mode  76 , the BPON OLT  22 ( 1 ) is disconnected and the converter takes over managing the BPON ONUs  26 . The converter  16  may range the BPON ONUs  26  either directly or via the GPON OLT  22 ( 2 ). The GPON OLT  22 ( 2 ) may retrieve and update the managed entities to mitigate any discrepancy between the learned parameters and the downloaded parameters.  
         [0049]     Once migrated to the GPON network  22 ( 2 ), the BPON ONU  26  maintenance activities such as reset, download, service status, alarm, and fault handling may be managed by the converter  16  acting as a BPON OLT. This may be facilitated by having each BPON ONU  26  appear as a “virtal GPON ONU  26 . The converter  16  may store managed entities within the converter  16  that are associated with the “virtal” GPON ONUs  26 .  
         [0050]     The present invention has been described in the context of communicating between a GPON and BPON network. The invention may, however, be embodied in many different forms and may be applied to many different types of networks and protocols and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will filly convey the scope of the invention to those skilled in the art Thus, the scope of the invention should be determined based upon the appended claims and their legal equivalents, rather than the specific embodiments described above.