Abstract:
A method of ensuring continuous receipt of video services based on certain conditions in a passive optical network (PON) is provided. The method includes (i) detecting at a PON element a condition indicating a change of states in receipt of video services, (ii) starting a timing mechanism having a default value stored in the PON element, and (iii) enabling receipt of video services at the PON element for an amount of time defined by the default value. The receipt of video services may be disabled after the amount of time defined by the default value.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     In a passive optical network (PON), a central office may communicate with a subscriber terminal using three wavelengths: (i) an analog video wavelength, (ii) a downstream communications wavelength, and (iii) an upstream wavelength. When the central office ranges the subscriber terminal, the central office provides the subscriber terminal with its actual video service mode that indicates whether receipt of video service is enabled or disabled. Oftentimes, the central office may lose communications with the subscriber terminal. When this happens, the video service mode defaults to either enabled or disabled. If the subscriber terminal defaults to the enabled video service mode, a user may connect the subscriber terminal to any optical video distribution network and receive free video service. If, on the other hand, the subscriber terminal defaults to the disabled video service mode, a field technician cannot determine whether the subscriber terminal is functional or whether other problems exist on the PON.  
       SUMMARY OF THE INVENTION  
       [0002]     A method of ensuring continuous receipt of video services based on certain conditions in a passive optical network (PON) is provided. A method according to one embodiment of the present invention includes (i) detecting at a PON element a condition indicating a change of states in receipt video services, (ii) starting a timing mechanism having a default value stored in the PON element, and (iii) enabling receipt of video services at the PON element for an amount of time defined by the default value. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0003]     The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred 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 the principles of the invention.  
         [0004]      FIG. 1  is a network diagram of an exemplary Passive Optical Network (PON) in which an optical network terminal (ONT) continues to provide video services for a limited length of time to a subscriber when an active communications link exists between a PON card and the ONT;  
         [0005]      FIG. 2  is a block diagram of an ONT card in accordance with embodiments of the present invention;  
         [0006]      FIG. 3  is a flow chart of an exemplary process performed by an ONT card in accordance with embodiments of the present invention; and  
         [0007]      FIG. 4  is a flow chart of an exemplary process performed by an ONT card in accordance with embodiments of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0008]     A description of preferred embodiments of the invention follows.  
         [0009]      FIG. 1  is a network diagram of an exemplary passive optical network (PON)  101 . The PON  101  includes an optical line terminal (OLT)  102 , wavelength division multiplexers  103   a , . . . ,  103   n , optical distribution network (ODN) devices  104   a , . . . ,  104   n , ODN device splitters (e.g.,  105   a , . . . ,  105   n  associated with ODN device  104   a ), optical network terminals (ONTs) (e.g.,  106   a ,  106   b , . . . ,  106   n  corresponding to ODN device splitters  105   a , . . . ,  105   n ), and customer premises equipment (e.g.,  110 ). The OLT  102  includes PON cards  120   a , . . . ,  120   n , each of which provides an optical feed ( 121   a , . . . ,  121   n ) to ODN devices  104   a , . . . ,  104   n . Optical feed  121   a , for example, is distributed through corresponding ODN device  104   a  by separate ODN device splitters  105   a , . . . ,  105   n  to respective ONTs  106   a ,  106   b , . . . ,  106   n  in order to provide communications to and from customer premises equipment  110 .  
         [0010]     The PON  101  may be deployed for fiber-to-the-business (FTTB), fiber-to-the-curb (FTTC), and fiber-to-the-home (FTTH) applications. The optical fibers  121   a , . . . ,  121   n  in PON  101  may operate at bandwidths such as 155 Mb/sec, 622 Mb/sec, 1.25 Gb/sec, and 2.5 Gb/sec or any other desired bandwidth implementations. The PON  101  may incorporate asynchronous transfer mode (ATM) communications, broadband services such as Ethernet access and video distribution, Ethernet point-to-multipoint topologies, and native communications of data and time division multiplex (TDM) formats. Customer premises equipment (e.g.,  110 ) that can receive and provide communications in the PON  101  may include standard telephones (PSTN and cellular), Internet Protocol telephones, Ethernet units, video devices (e.g.,  111 ), computer terminals (e.g.,  112 ), digital subscriber line connections, cable modems, wireless access, as well as any other conventional device.  
         [0011]     A PON  101  includes one or more different types of ONTs (e.g.,  106   a ,  106   b , . . . ,  106   n ). Each ONT  106   a ,  106   b , . . . ,  106   n , for example, communicates with an ODN device  104   a  through associated ODN device splitters  105   a , . . . ,  105   n . Each ODN device  104   a , . . . ,  104   n  in turn communicates with an associated PON card  120   a , . . . ,  120   n  through respective wavelength division multiplexers  103   a , . . . ,  103   n . Communications between the ODN devices  104   a , . . . ,  104   n  and the OLT  102  occur over a downstream wavelength and an upstream wavelength. The downstream communications from the OLT  102  to the ODN devices  104   a , . . . ,  104   n  may be provided at 622 megabytes per second, which is shared across all ONTs connected to the ODN devices  104   a , . . . ,  104   n . The upstream communications from the ODN devices  104   a , . . . ,  104   n  to the PON cards  120   a , . . . ,  120   n  may be provided at 155 megabytes per second, which is shared among all ONTs connected to ODN devices  104   a , . . . ,  104   n.    
         [0012]     A broadband source  124 , of which a cable television feed through an erbium doped fiber amplifier (EDFA) is just one example, may also provide video or other broadband data to the WDMs  103   a , . . . ,  103   n  using a single wavelength (hereinafter, video wavelength). The WDMs  103   a , . . . ,  103   n  multiplex the PON upstream and downstream communications wavelengths and the video wavelength and provide the resulting multiplexed signals to respective ODN devices  104   a , . . . ,  104   n . Each ONT (e.g.,  106   a ,  106   b , . . . ,  106   n ) may monitor a broadband overlay signal provided by broadband source  124 . One example of a broadband overlay signal is a 1550 nanometer signal used for downstream video applications.  
         [0013]      FIG. 2  is a block diagram of an ONT  200  according to an embodiment of the present invention. The ONT  200  comprises a splitter  210  which connects through a fiber to an ODN device splitter  105   a  of the optical network device  104   a  ( FIG. 1 ). The splitter  210  may split the optical signal from the ODN device splitter into its three respective wavelengths (e.g., upstream and downstream communications wavelengths and the video or broadband data wavelength). Thus, the ONT  200  (i) receives video or broadband data  212 , (ii) receives PON communications data, and (iii) transmits PON communications data  216 . The ONT  200  further includes a microprocessor  221  which monitors and controls the transmission and receipt of the video and PON communications data. The microprocessor  221  is coupled to non-volatile flash memory  223  which may be used to store settings of a video service mode according to an embodiment of the present invention. The microprocessor  221  is further coupled to a timing mechanism  225 , which may be used to enable video services for a given length of time.  
         [0014]     In normal operation, a PON card of the OLT ranges an ONT to enable communications between the PON card and the ONT. Once the ONT is ranged, the PON card may provision the ONT to enable or disable video services to the ONT. In existing FTTP systems, however, the ONT may lose communications with the OLT for a variety of reasons.  
         [0015]     First, there may be a fiber break in certain segments of the PON.  
         [0016]     Second, the ONT may reboot, for example, in response to a command by the OLT. Reboots most often occur when the ONT is upgraded. The OLT may issue an emergency management system (EMS) command to the ONT to perform a hard reboot for troubleshooting purposes. The ONT may also reboot in response to actuating a switch on the ONT or in response to an internal command from the microprocessor.  
         [0017]     Third, the ONT may lose communications with the OLT because there may be a problem in the OLT (e.g., a problem with a PON line card providing an OLT interface on the PON in which the ONT resides) or in the PON line cards (or other line cards that may be required to reboot or may be replaced with another line card.) When the PON line card is replaced with another line card, the communication between the ONT and the OLT is lost and an ONT loss of physical layer-loss of signal (ONT LOPL-LOS) condition occurs.  
         [0018]     Fourth, the ONT may lose communications with the OLT because (i) there may be a bad connection between some ODN device splitters and a PON line card, which may cause high bit-error-rates; (ii) the ODN device splitter may simply lose connection with its corresponding ONT; or (iii) a misbehaving ONT (e.g., often referred to as a “rogue” ONT) may cause bad communications between all ONTs and the PON line card and thus cause all ONTs&#39; ranging to go down.  
         [0019]     Fifth, the ONT may lose communication with the OLT because, in some PON troubleshooting scenarios, the ONT may be commanded to perform an emergency stop (per ITU-G.983.1) (“E-STOP”) via the disable_serial_number PLOAM messages, at which point the ONT must stop regular communications with the OLT until commanded to come out of the emergency stop state.  
         [0020]     The above list of reasons why an ONT may lose communications with a PON line card is not meant to be an exhaustive list. There are many other reasons for loss of communications between an ONT and a PON line card. For whatever reason the ONT loses ranging with the OLT, the ONT defaults to its video service enabled or disabled mode whether or not the ONT is provisioned to offer video services to its subtended subscriber.  
         [0021]     In the case when the ONT&#39;s default attribute for video services is enabled, a user can connect such an ONT in any PON network and receive video services at no charge from the service provider. Ideally, the service provider would want to change video services whether or not an ONT has lost communications with the OLT. In the case when the ONT&#39;s default video services mode is disabled (for example, when an ONT comes out of manufacturing), a field technician cannot connect an ONT to the PON to determine if the ONT even receives video. This is a useful troubleshooting technique in the home to ensure the ONT is functional and that fiber is linked to the home. Typically, an ONT defaults to the disabled video services mode.  
         [0022]     According to an embodiment of the present invention, a mechanism is provided that allows the ONT to continue offering video services even when the ONT loses communications with the OLT (e.g., across reboots). In one embodiment, the ONT may maintain the last known Video Services Mode in flash memory. After an OLT loses ranging with an ONT, the ONT maintains the last known video service mode for a predetermined length of time as defined by a timing mechanism. In this way, a user cannot connect an ONT in any PON network to receive free video services.  
         [0023]      FIG. 3  is a flow chart of a process  300  performed by an ONT card in accordance with embodiments of the present invention. The process  300  starts in step  301 . In decision step  305 , the process  300  determines whether or not the ONT detects a condition indicating a change of states in video services. A condition indicating a change of states in video services may include any of the conditions listed above (i.e., reasons why an ONT loses communications with a PON card at the OLT). If the process  300  does not detect a condition indicating a change of state in video services, then the process  300  repeats decision step  305 . If the process  300  does detect such a condition, then the process (i) starts a timing mechanism in step  310  and (ii) enables video services for an amount of time defined by the timing mechanism in step  315 . When the amount of time defined by the timing mechanism expires, the process  300  may resume a video service mode stored in memory before returning to step  301  to restart the process  300 . For example, if the video service mode stored in memory were set to disabled, then the process  300  would disable video services.  
         [0024]      FIG. 4  is a flow chart of a process according to an embodiment of the present invention  400 . The process  400  may be implemented in software, stored on a computer-readable medium (e.g., CD-ROM), and loaded and executed in the microprocessor of the ONT. In step  401 , the process  400  starts. In decision step  405 , the process  400  determines whether or not the ONT has been ranged and provisioned by the PON line card of the OLT. In a PON, after the PON line card ranges the ONT, it may provision the ONT to operate according to certain modes such as a video service mode. In this way, a service provider may control the services being provided to the ONT. If the ONT has not been ranged and provisioned by the PON line card, then the process  400  repeats decision step  405 .  
         [0025]     If, in decision step  405 , the ONT has been ranged and provisioned, then the process  400  stores the provisioned video service mode settings in the ONT&#39;s FLASH memory in step  415 . An ONT in inventory may be provisioned with a video service mode settings before being deployed, and thus, the video service mode settings would be stored in such an ONT&#39;s FLASH memory. Inventory may include new ONTs and used ONTs (e.g., refurbished ONTs ready for redeployment).  
         [0026]     In step  420 , the process  400  determines whether or not video services have been enabled. If video services have not been enabled, but instead they have been disabled, then the process  400  proceeds to step  425  to determine whether or not the ONT has lost ranging with the PON line card. If the process  400  determines that the ONT has lost ranging with the PON line card, then the process  400  determines in decision step  430  whether or not the ONT has been rebooted. If, on the other hand, the process  400  determines that the ONT has not lost ranging with the PON line card, then the process  400  repeats decision step  425 .  
         [0027]     If the ONT has lost ranging and the ONT has not been rebooted, then the process repeats decision step  430 . If the ONT has lost ranging and the ONT has been rebooted, then the process  400  proceeds to step  445  in which the process  400  enables video services and starts the range-fail video timer, which is set for a default amount of time. For example, the default amount of time may be sufficient for troubleshooting purposes or may be a value that is determined by the customer. Thus, the ONT does not need to range the OLT in order to provide video services for test or troubleshooting purposes. In a preferred embodiment, the technician troubleshoots the ONT before the range-fail video timer expires.  
         [0028]     The default timer value may be a few minutes or many hours (e.g., 1 to 72 hours). The timer value may be stored in the ONT, for example, in the FLASH memory. The timer value may also be updated, for example, locally by a technician or remotely by the Emergency Management System. The range-fail video timer may be any type of timing mechanism capable of measuring a given length of time such as a counter or a monitoring device monitoring a clock.  
         [0029]     Referring again to decision step  420 , when the process  400  determines that the video service mode has been set to enabled, the process  400  proceeds to step  435  to determine whether or not the ONT has lost ranging with the PON line card. If the ONT has indeed lost ranging with the PON line card, then the process  400  enables video services and starts the range-fail video timer. If, in decision step  435 , the ONT has not lost ranging with the PON line card, then the process  400  repeats decision step  435 , thereby monitoring whether or not the ONT has lost ranging with the PON line card.  
         [0030]     Referring again to decision step  415 , after the process  400  stores the provisioned video service mode settings in FLASH memory, the process  400  monitors whether or not the ONT has rebooted in step  440 . In other words, when the process  400  determines in step  440  that the ONT (or the ONT microprocessor) has not been rebooted, then the process  400  repeats step  440 . Once the process  400  determines that the ONT has rebooted, the process  400  proceeds to step  445  and enables video services and starts the range-fail video timer.  
         [0031]     After the process  400  enables video services and starts the range-fail video timer, the process  400  monitors in decision step  450  whether or not the ONT has been ranged and provisioned. If the ONT has been ranged and provisioned, then the process  400  stores the provisioned video service mode settings in the ONT&#39;s flash memory in step  415 . If, instead, the ONT has not been ranged and provisioned, then the process proceeds to decision step  455  and determines whether or not the range fail video timer has expired. If the range fail video timer has not expired, then the process  400  continues to monitor whether or not the ONT has been ranged and provisioned in decision step  450 . However, if the timer has expired, then in step  460  the process  400  resumes the video service mode according to the video service mode settings stored in the FLASH memory. Next, in step  465 , the process determines whether or not the stored video service mode settings are set to enabled. If the video service mode is set to enabled, then the process  400  returns to step  405  to determine whether or not the ONT has been ranged or provisioned. Otherwise, the process  400  disables video services in step  470  and then returns to step  405 .  
         [0032]      FIG. 4  is a flow chart of a process according to an embodiment of the present invention  400 . The process  400  may be implemented in software, stored on a computer-readable medium (e.g., CD-ROM), and loaded and executed in the microprocessor of the ONT. In step  401 , the process  400  starts. In decision step  405 , the process  400  determines whether or not the ONT has been ranged and provisioned by the PON line card of the OLT. In a PON, after the PON line card ranges the ONT, it may provision the ONT to operate according to certain modes such as a video service mode. In this way, a service provider may control the services being provided to the ONT. If the ONT has not been ranged and provisioned by the PON line card, then the process  400  repeats decision step  405 .  
         [0033]     If, in decision step  405 , the ONT has been ranged and provisioned, then the process  400  stores the provisioned video service mode settings in the ONT&#39;s FLASH memory in step  415 . An ONT in inventory may be provisioned with video service mode settings before being deployed, and thus, the video service mode settings would be stored in such an ONT&#39;s FLASH memory. Inventory may include new ONTs and used ONTs (e.g., refurbished ONTs ready for redeployment).  
         [0034]     In step  420 , the process  400  determines whether or not video services have been enabled. If video services have not been enabled, but instead they have been disabled, then the process  400  proceeds to step  425  to determine whether or not the ONT has lost ranging with the PON line card. If the process  400  determines that the ONT has lost ranging with the PON line card, then the process  400  determines in decision step  430  whether or not the ONT has been rebooted. If, on the other hand, the process  400  determines that the ONT has not lost ranging with the PON line card, then the process  400  repeats decision step  425 .  
         [0035]     If the ONT has lost ranging and the ONT has not been rebooted, then the process repeats decision step  430 . If the ONT has lost ranging and the ONT has been rebooted, then the process  400  proceeds to step  445  in which the process  400  enables video services and starts the range-fail video timer, which is set for a default amount of time. For example, the default amount of time may be sufficient for troubleshooting purposes or may be a value that is determined by the customer. Thus, the ONT does not need to range the OLT in order to provide video services for test or troubleshooting purposes. In a preferred embodiment, the technician troubleshoots the ONT before the range-fail video timer expires.  
         [0036]     The default timer value may be a few minutes or many hours (e.g., 1 to 72 hours). The timer value may be stored in the ONT, for example, in the FLASH memory. The timer value may also be updated, for example, locally by a technician or remotely by the Emergency Management System. The range-fail video timer may be any type of timing mechanism capable of measuring a given length of time such as a counter or a monitoring device monitoring a clock.  
         [0037]     Referring again to decision step  420 , when the process  400  determines that the video service mode has been set to enabled, the process  400  proceeds to step  435  to determine whether or not the ONT has lost ranging with the PON line card. If the ONT has indeed lost ranging with the PON line card, then the process  400  enables video services and starts the range-fail video timer. If, in decision step  435 , the ONT has not lost ranging with the PON line card, then the process  400  repeats decision step  435 , thereby monitoring whether or not the ONT has lost ranging with the PON line card.  
         [0038]     Referring again to decision step  415 , after the process  400  stores the provisioned video service mode settings in FLASH memory, the process  400  monitors whether or not the ONT has rebooted in step  440 . In other words, when the process  400  determines in step  440  that the ONT (or the ONT microprocessor) has not been rebooted, then the process  400  repeats step  440 . Once the process  400  determines that the ONT has rebooted, the process  400  proceeds to step  445  and enables video services and starts the range-fail video timer.  
         [0039]     After the process  400  enables video services and starts the range-fail video timer, the process  400  monitors in decision step  450  whether or not the ONT has been ranged and provisioned. If the ONT has been ranged and provisioned, then the process  400  stores the provisioned video service mode settings in the ONT&#39;s flash memory in step  415 . If, instead, the ONT has not been ranged and provisioned, then the process proceeds to decision step  455  and determines whether or not the range fail video timer has expired. If the range fail video timer has not expired, then the process  400  continues to monitor whether or not the ONT has been ranged and provisioned in decision step  450 . However, if the timer has expired, then in step  460  the process  400  resumes the video service mode according to the video service mode settings stored in the FLASH memory. Next, in step  465 , the process determines whether or not the stored video service mode settings are set to enabled. If the video service mode is set to enabled, then the process  400  returns to step  405  to determine whether or not the ONT has been ranged or provisioned. Otherwise, the process  400  disables video services in step  470  and then returns to step  405 .  
         [0040]      FIG. 5  is a flow chart of a process according to another embodiment of the present invention  500 . In step  501 , the process  500  starts. In decision step  505 , the process  500  determines whether or not the ONT has been ranged and provisioned by the PON line card of the OLT. If the ONT has not been ranged and provisioned by the PON line card, then the process  500  repeats decision step  505 .  
         [0041]     If, in decision step  505 , the ONT has been ranged and provisioned, then the process  500  stores the provisioned video service mode settings in the ONT&#39;s FLASH memory in step  515 . In step  520 , the process  500  determines whether or not the video service mode has been set to enabled. If the video service mode has not been set to enabled, but instead has been set to disabled, then the process  500  proceeds to step  525  to disable video services and returns to decision step  505 . Thus, the timing mechanism is disabled when the video service mode is set to disabled. If the video service mode has been set to enabled, the process  500  proceeds to step  535  to determine whether or not the ONT has lost ranging with the PON line card. If the ONT has indeed lost ranging with the PON line card, then the process  500  enables video services and starts the range-fail video timer. If, in decision step  535 , the ONT has not lost ranging with the PON line card, then the process  500  repeats decision step  535 , thereby monitoring whether or not the ONT has lost ranging with the PON line card.  
         [0042]     Referring again to decision step  520 , if the video service mode has been set to enabled, then the process  500  also monitors whether or not the ONT has rebooted in step  540 . In other words, when the process  500  determines in step  540  that the ONT (or the ONT microprocessor) has not been rebooted, then the process  500  repeats step  540 . Once the process  500  determines that the ONT has rebooted, the process  500  proceeds to step  545  and enables video services and starts the range-fail video timer.  
         [0043]     After the process  500  enables video services and starts the range-fail video timer, the process  500  monitors in decision step  550  whether or not the ONT has been ranged and provisioned. If the ONT has been ranged and provisioned, then the process  500  stores the provisioned video service mode settings in the ONT&#39;s flash memory in step  515 . If, instead, the ONT has not been ranged and provisioned, then the process proceeds to decision step  555  and determines whether or not the range fail video timer has expired. If the range fail video timer has not expired, then the process  500  continues to monitor whether or not the ONT has been ranged and provisioned in decision step  550 . However, if the timer has expired, then in the process  500  disables video services in step  570  and then returns to step  505 .  
         [0044]     It should be understood that the range-fail video timer should be long enough to allow a technician to troubleshoot the ONT and ensure it is able to receive video services and detect a valid 1550 nm from the PON line card. However, the length of time monitored by the timer should not be so long as to allow the customer to steal video services for extended periods of time. The length of time monitored by timer should be short enough to make it inconvenient to watch any video programming.  
         [0045]     While this invention has been particularly shown and described with references to preferred 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.  
         [0046]     Although described as “cards” herein, it should be understood that PON cards, OLT cards, or ONT cards may be systems or subsystems without departing from the principles disclosed hereinabove.  
         [0047]     The timer may be a count-up timer, count-down timer, or any form of timer that can be used for maintaining the ONT in an enabled state for a given length of time.  
         [0048]     Although described in reference to a passive optical network, the same or other embodiments of the present invention may be employed in an active optical network, data communications network, or any other type of network.