Patent Publication Number: US-9432114-B2

Title: Method for identifying the optical network unit power off reason

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/756,764 filed Apr. 8, 2010 by Michael Shaffer, et al., and titled “Method for Identifying the Optical Network Unit Power Off Reason,” which claims priority to U.S. Provisional Patent Application No. 61/171,500 filed Apr. 22, 2009 by Michael R. Shaffer, et al., and entitled “A New Method for Identifying the Optical Network Unit Power Off Reason,” both of which are incorporated by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     REFERENCE TO A MICROFICHE APPENDIX 
     Not applicable. 
     BACKGROUND 
     A passive optical network (PON) is one system for providing network access over “the last mile.” The PON is a point-to-multi-point (P2MP) network comprised of an optical line terminal (OLT) at the central office, an optical distribution network (ODN), and a plurality of optical network units (ONUs) at the customer premises. Some ONUs are configured to send a message indicating power loss at the ONU. The message does not include a reason for the power loss, and receiving a power loss message without a reason for the power loss can be problematic for the recipient of the message. 
     SUMMARY 
     In an embodiment, the disclosure includes a passive optical network (PON) component comprising a power switch, a detector configured to monitor the power switch, and a processor configured to receive an interrupt from the detector and transmit a message comprising a first indicator that the PON component has powered down, and a second indicator giving a reason for the power down. 
     In another embodiment, the disclosure includes a passive optical network (PON) component comprising a processor configured to implement a method comprising receiving an interrupt message from a detector, determining a reason for the interrupt, and transmitting a dying gasp message comprising an indicator of the reason for the interrupt. 
     In yet another embodiment, the disclosure includes a method comprising transmitting an alarm message comprising an optical network terminal (ONT) manual power off indicator that indicates the ONT is shutting down because a subscriber has turned off its power switch. 
     These and other features will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts. 
         FIG. 1  is a schematic diagram of an embodiment of a PON. 
         FIG. 2A  is a schematic diagram of a first embodiment of an ONU with hardware centric power detection. 
         FIG. 2B  is a schematic diagram of a second embodiment of an ONU with hardware centric power detection. 
         FIG. 2C  is a schematic diagram of a third embodiment of an ONU with hardware centric power detection. 
         FIG. 3A  is a schematic diagram of a first embodiment of an ONU with software centric power detection. 
         FIG. 3B  is a schematic diagram of a second embodiment of an ONU with software centric power detection. 
         FIG. 3C  is a schematic diagram of a third embodiment of an ONU with software centric power detection. 
         FIG. 3D  is a schematic diagram of a fourth embodiment of an ONU with software centric power detection. 
         FIG. 3E  is a schematic diagram of a fifth embodiment of an ONU with software centric power detection. 
         FIG. 4  is a block diagram of an embodiment of a physical layer operation, administration, and management (PLOAM) message. 
         FIG. 5  is a block diagram of an embodiment of ONT management and control interface (OMCI) alarm extensions. 
         FIG. 6  is a block diagram of an embedded operation, administration, and management (OAM) message. 
         FIG. 7  is a flow chart of an embodiment of a method for indicating a power loss reason. 
         FIG. 8  is a schematic diagram of an embodiment of a general purpose computer. 
     
    
    
     DETAILED DESCRIPTION 
     It should be understood at the outset that although an illustrative implementation of one or more embodiments are provided below, the disclosed systems and/or methods may be implemented using any number of techniques, whether currently known or in existence. The disclosure should in no way be limited to the illustrative implementations, drawings, and techniques illustrated below, including the exemplary designs and implementations illustrated and described herein, but may be modified within the scope of the appended claims along with their full scope of equivalents. 
     One type of PON is a gigabit PON (GPON), which has been standardized by International Telecommunication Union (ITU) Telecommunication Standardization Sector (ITU-T) G.984. GPON performs OAM functions using three channels: embedded OAM, PLOAM, and OMCI. Embedded OAM utilizes structured overhead fields of downstream GPON transmission convergence (GTC) frames and upstream GTC bursts. Embedded OAM is defined by the ITU-T G.984.3 standard, which is incorporated herein as if reproduced in its entirety. The PLOAM channel is a message-based OAM channel between the OLT and the ONUs that supports the GTC layer management functions, including ONU activation, ONU management and control channel establishment, encryption configuration, key management, and alarm signaling. The PLOAM channel and message types are defined by the ITU-T G.984.3 standard. OMCI is a management channel between the OLT and the ONUs that supports Ethernet, equipment, subscriber interface, and subscriber feature management. OMCI is standardized in the ITU-T G.984.4 standard, which is incorporated herein as if reproduced in its entirety. OMCI supports alarm reporting, and one type of alarm presently supported by OMCI is a Dying Gasp alarm. The Dying Gasp alarm is reported to the OLT by an ONU when the ONU loses power. Dying Gasp may be reported via the PLOAM channel and/or the OMCI channel. 
     Disclosed herein is a system and method for identifying an ONU power off reason. Some subscribers may power down an ONU when not in use to conserve electricity. A dying gasp message may be sent responsive to the subscriber power down of the ONU. If the dying gasp message does not contain a reason for the message, an OLT may interpret the power down as an area wide power disruption rather than an intentional subscriber action. Thus, a dying gasp message may be sent to an OLT with a reason for the ONU power loss which may prevent erroneous action by the OLT or central office. The ONU may implement a hardware centric power switch, a software centric power switch, or both. The ONU may monitor the state of the power switch, input power level, or a battery power level, in order to identify the cause for power loss at the ONU. After a power loss, the ONU may send a message identifying the cause for the power loss before powering down. 
       FIG. 1  illustrates one embodiment of a PON  100  configured to implement the concepts described herein. The PON  100  comprises an OLT  110 , a plurality of ONUs  120 , and an ODN  130 , which may be coupled to the OLT  110  and the ONUs  120 . The PON  100  may be a communications network that does not require any active components to distribute data between the OLT  110  and the ONUs  120 . Instead, the PON  100  may use the passive optical components in the ODN  130  to distribute data between the OLT  110  and the ONUs  120 . The PON  100  may be Next Generation Access (NGA) system, such as ten gigabits per second (Gbps) GPONs (or XGPONs), which may have a downstream bandwidth of about ten Gbps and an upstream bandwidth of at least about 2.5 Gbps. Other examples of suitable PONs  100  include the asynchronous transfer mode PON (APON) and the broadband PON (BPON) defined by the ITU-T G.983 standard, the GPON defined by the ITU-T G.984 standard, the Ethernet PON (EPON) defined by the Institute of Electrical and Electronics Engineers (IEEE) 802.3ah standard, 10G EPON as defined by the IEEE 802.3av standard, and the wavelength division multiplexed (WDM) PON (WPON), all of which are incorporated herein by reference as if reproduced in their entirety. 
     In an embodiment, the OLT  110  may be any device that is configured to communicate with the ONUs  120  and another network (not shown). Specifically, the OLT  110  may act as an intermediary between the other network and the ONUs  120 . For instance, the OLT  110  may forward data received from the network to the ONUs  120 , and forward data received from the ONUs  120  onto the other network. Although the specific configuration of the OLT  110  may vary depending on the type of PON  100 , in an embodiment, the OLT  110  may comprise a transmitter and a receiver. When the other network is using a network protocol, such as Ethernet or Synchronous Optical Networking/Synchronous Digital Hierarchy (SONET/SDH), that is different from the PON protocol used in the PON  100 , the OLT  110  may comprise a converter that converts the network protocol into the PON protocol. The OLT  110  converter may also convert the PON protocol into the network protocol. The OLT  110  may be typically located at a central location, such as a central office, but may be located at other locations as well. 
     In an embodiment, the ONUs  120  may be any devices that are configured to communicate with the OLT  110  and a customer or user (not shown). Specifically, the ONUs  120  may act as an intermediary between the OLT  110  and the customer. For instance, the ONUs  120  may forward data received from the OLT  110  to the customer, and forward data received from the customer to the OLT  110 . Although the specific configuration of the ONUs  120  may vary depending on the type of PON  100 , in an embodiment, the ONUs  120  may comprise an optical transmitter configured to send optical signals to the OLT  110  and an optical receiver configured to receive optical signals from the OLT  110 . Additionally, the ONUs  120  may comprise a converter that converts the optical signal into electrical signals for the customer, such as signals in the Ethernet or asynchronous transfer mode (ATM) protocol, and a second transmitter and/or receiver that may send and/or receive the electrical signals to a customer device. In some embodiments, ONUs  120  and optical network terminals (ONTs) are similar, and thus the terms are used interchangeably herein. The ONUs  120  may be typically located at distributed locations, such as the customer premises, but may be located at other locations as well. 
     In an embodiment, the ODN  130  may be a data distribution system, which may comprise optical fiber cables, couplers, splitters, distributors, and/or other equipment. In an embodiment, the optical fiber cables, couplers, splitters, distributors, and/or other equipment may be passive optical components. Specifically, the optical fiber cables, couplers, splitters, distributors, and/or other equipment may be components that do not require any power to distribute data signals between the OLT  110  and the ONUs  120 . Alternatively, the ODN  130  may comprise one or a plurality of active components, such as optical amplifiers. The ODN  130  may typically extend from the OLT  110  to the ONUs  120  in a branching configuration as shown in  FIG. 1 , but may be alternatively configured in any other point-to-multi-point (P2MP) configuration. 
     In an embodiment, the OLT  110  and/or the ONUs  120  may comprise a data framer, which may be coupled to the transmitter and/or the receiver. The data framer may be any device configured to process the data between the OLT  110  and the ONUs  120  by framing the data into frames or obtaining the data from the frames according to a PON protocol, such as IEEE 802.3ah and/or 802.3av. The data framer may be hardware, such as a processor, comprising electronic or logic circuitry, which may be designed for such purpose. Alternatively, the data framer may be software or firmware, which may be programmed for such purpose. Specifically, the data framer may be configured to generate media access control (MAC) control messages, which may be used to promote OAM functions in the PON  100 . The data framer may be configured to generate different control messages, for instance to implement different OAM functions according to different organizations or architectures. For example, the data framer may frame control data for different providers, customer networks, or standardization and/or regulatory organizations (e.g. IEEE, ITU-T, etc.) into a MAC control message. 
       FIG. 2A  is a schematic diagram of a first embodiment of an ONU with hardware centric power detection  200 . The ONU with hardware centric power detection  200  may comprise an external power detector  203  coupled to an external power source  201  and a controller  205 . The ONU with hardware centric power detection  200  may further comprise a hardware switch  202  coupled to a switch detector  204 , an optional capacitor  208 , and an internal circuit power module  207 . The controller  205  may be coupled to the switch detector  204  and a host processor  206 . The host processor  206  may be coupled to the internal circuit power module  207  and a gigabit media access controller (GMAC) (not shown). The internal circuit power module  207  may be coupled to other functional modules not shown in the schematic diagram. The internal circuit power module  207  may provide power for all of the modules in the ONU with hardware centric power detection  200 . 
     The switch detector  204  may be configured to monitor and detect the position of the hardware switch  202 , e.g. on or off. If the hardware switch  202  is moved to the off position, the switch detector  204  may detect the position of the switch and send an indicator to the controller  205 . The indicator may notify the controller  205  of the position of the hardware switch  202 . The controller  205  may store the occurrence of the hardware switch  202  changing to off. The controller  205  may also store the time of the change and other relevant data related to the hardware switch  202  being changed to the off position. Upon receiving the indicator from the switch detector  204 , the controller  205  may notify the host processor  206  of the change. The notification may be in the form of an interrupt sent to the host processor  206 . Upon receiving the interrupt, the host processor  206  may use system software to generate and transmit an ONU manual power off message comprising a reason for power loss indicator, e.g. ONU switched off. The generation and transmission of the ONU manual power off message may be performed by hardware and/or software available on the ONU with hardware centric power detection  200 . The ONU manual power off message may be transmitted to an OLT at a central office. The central office or the OLT may take actions based upon the reason for power loss contained in the ONU manual power off message. 
     The external power detector  203  may be configured to monitor and measure the power level received from the external power source  201 . If the power level received from the external power source  201  drops below a predefined level, e.g. the level necessary for operation of the ONU with hardware centric power detection  200 , the external power detector  203  may alert the controller  205 . Upon receiving the alert from the external power detector  203 , the controller  205  may notify the host processor  206  of the alert. The notification may be in the form of an interrupt sent to the host processor  206 . The host processor  206  may then transmit a message comprising the power loss reason to an OLT connected to the ONU with hardware centric power detection  200 , e.g. power loss due to external power source  201  failure. 
     The amount of time available for the ONU with hardware centric power detection  200  to generate and transmit a message after power loss is dependant upon the capacity of the capacitor  208 . A capacitor  208  may be selected based upon the predetermined power required to generate and transmit the dying gasp reports. The ONU with hardware centric power detection  200  may determine the power loss reason by indicators received at the controller  205 . If the controller receives a first indicator from the switch detector  204  and a subsequent indicator from the external power detector  203 , the ONU with hardware centric power detection  200  may determine that the power switch has been formally shut off. If the controller only receives an indicator from the external power detector  203 , the ONU with hardware centric power detection  200  may determine that power has been abnormally lost. 
       FIG. 2B  is a schematic diagram of a second embodiment of an ONU with hardware centric power detection  230 . The ONU with hardware centric power detection  230  may be configured and function substantially similar to the ONU with hardware centric power detection  200 . However, the ONU with hardware centric power detection  230  comprises a controller/host processor module  209 . The controller/host processor module  209  may combine the functionality of the controller  205  and the host processor  206  into a single module. Combining modules into a single module may reduce cost and size of the ONU with hardware centric power detection  230 . The functionality of other modules may also be combined into other single modules, e.g. to reduce cost, power consumption, size, and other improvements to the various embodiments disclosed herein. 
       FIG. 2C  is a schematic diagram of a third embodiment of an ONU with hardware centric power detection  260 . The ONU with hardware centric power detection  260  may be substantially similar to the ONU with hardware centric power detection  200 , however the ONU with hardware centric power detection  260  further comprises an external battery  211 , and battery power detector  210 . The external battery  211  may allow the ONU with hardware centric power detection  260  to continue to function if external power  201  is lost. The functionality of ONU with hardware centric power detection  260  remains substantially similar to that of the ONU with hardware centric power detection  200 . The battery power detector  210  monitors the power output from the external battery  211 . If the power level received from the external battery  211  drops below a predefined level, e.g. the level necessary for operation of the ONU with hardware centric power detection  260 , the battery power detector  210  may alert the controller  205 . Upon receiving the alert from the battery power detector  210 , the controller  205  may notify the host processor  206  of the alert. The notification may be in the form of an interrupt sent to the host processor  206 . The host processor  206  may then transmit a message comprising the power loss reason to an OLT connected to the ONU with hardware centric power detection  260 , e.g. power loss due to external battery  211  failure. 
       FIG. 3A  is a schematic diagram of a first embodiment of an ONU with software centric power detection  300 . The ONU with software centric power detection  300  may comprise an external power detector  305  coupled to an external power source  301 , and a controller  306 . The ONU with software centric power detection  300  may further comprise a software switch  303  coupled to a switch detector  304 . The controller  306  may be coupled to the switch detector  304  and a host processor  307 . The host processor  307  may be coupled to an internal circuit power module  308  and a GMAC (not shown). The internal circuit power module  308  may be coupled to an optional capacitor  309 , a hardware switch  302 , and other functional modules not shown in the schematic diagram. 
     The switch detector  304  may be configured to monitor and detect the state of the software switch  303 , e.g. on or off. If the software switch  303  is changed to the off state, the switch detector  304  may detect the state of the software switch  303  and send an indicator to the controller  306  to notify the controller  306  of the state of the software switch  303 . The state of the software switch  303  may have changed to off, however power may still be applied to the ONU with software centric power detection  300 . The controller  306  may store the occurrence of the software switch  303  state changing to off. The controller  306  may also store the time of the state change and other relevant data related to the software switch  303  state being changed to the off position. Upon receiving the indicator from the switch detector  304 , the controller  306  may notify the host processor  307  of the state of the software switch  303 . The notification may be in the form of an interrupt sent to the host processor  307 . Upon receiving the interrupt, the host processor  307  may use system software to generate and transmit an ONU manual power off message comprising a reason for power loss indicator, e.g. ONU switched off. The generation and transmission of the ONU manual power off message may be performed by hardware and/or software available on the ONU with software centric power detection  300 . The ONU manual power off message may be transmitted to an OLT at a central office for tracking purposes. Upon transmitting the ONU manual power off message, the system software may send an indicator to the controller  306  indicating that it is safe to power down. The controller  306  may then power down the ONU with software centric power detection  300 . In some embodiments, the system software may store any critical data in non-volatile memory prior to sending the power down indicator to the controller  306 . 
     The external power detector  305  may be configured to monitor and measure the power level received from the external power source  301 . If the power level received from the external power source  301  drops below a predefined level, e.g. the level necessary for operation of the ONU with software centric power detection  300 , the external power detector  305  may alert the controller  306 . Upon receiving the alert from the external power detector  305 , the controller  306  may notify the host processor  307  of the alert. The notification may be in the form of an interrupt sent to the host processor  307 . The host processor  307  may then transmit a power loss message comprising the power loss reason to an OLT connected to the ONU with software centric power detection  300 , e.g. power loss due to external power source  301  failure. 
     In the case of power loss at the external power source  301 , the amount of time available for the ONU with software centric power detection  300  to generate and transmit the power loss message is dependant upon the capacity of the capacitor  309 . A capacitor  309  may be selected based upon the predetermined power required to generate and transmit the power loss message. The ONU with software centric power detection  300  may determine the power loss reason by indicators received at the controller  306 . If the controller receives an indicator from the switch detector  304 , the ONU with software centric power detection  300  may determine that the software power switch  303  has been formally shut off. If the controller receives an indicator from the external power detector  305 , the ONU with software centric power detection  300  may determine that power has been abnormally lost. 
       FIG. 3B  is a schematic diagram of a second embodiment of an ONU with software centric power detection  320 . The ONU with software centric power detection  320  may be configured and function substantially similar to the ONU with software centric power detection  300 . The functionalities of the switch detector  304  and the external power detector  305  have been combined into a single module: detector  310 . Detector  310  may be coupled to a software switch  303 , an external power source  301 , and a controller  306 . The detector  310  may serve as a substitute for the switch detector  304  and the external power detector  305  in any of the embodiments disclosed herein. Combining modules into a single module may reduce cost and size of the ONU with software centric power detection  320 . The functionality of other modules may also be combined into other single modules, e.g. to reduce cost, power consumption, size, and other improvements to the various embodiments disclosed herein. 
       FIG. 3C  is a schematic diagram of a third embodiment of an ONU with software centric power detection  340 . The ONU with software centric power detection  340  may be configured and function substantially similar to the ONU with software centric power detection  300 . In this embodiment, the functionality of the switch detector  304 , the external power detector  305 , and the controller  306  may be combined into a single module, detector/controller  311 . The detector/controller  311  may be coupled to the host processor  307 , the soft switch  303 , and the external power source  301 . As described above, combining modules into a single module may reduce cost and size of the ONU with software centric power detection  340 . 
       FIG. 3D  is a schematic diagram of a fourth embodiment of an ONU with software centric power detection  360 . The ONU with software centric power detection  360  may be configured and function substantially similar to the ONU with software centric power detection  300 . The functionalities of the switch detector  304  and external power detector  305  have been combined into a single module, detector  310 . The functionalities of the host processor  307  and controller  306  have been combined into a single module, controller/host processor  312 . Detector  310  may be coupled to the software switch  303 , the external power source  301 , and the controller/host processor  312 . The controller/host processor  312  may be coupled to the internal circuit powering module  308  and the GMAC. As described above, combining modules into a single module may reduce cost and size of the ONU with software centric power detection  360 . 
       FIG. 3E  is a schematic diagram of a fifth embodiment of an ONU with software centric power detection  380 . The ONU with software centric power detection  380  may be configured substantially similar to the ONU with hardware centric power detection  300 . The ONU with software centric power detection  380  further comprises an external battery  313 , and battery power detector  314 . The external battery  313  may allow the ONU with software centric power detection  380  to continue to function if external power  301  is lost. The functionality of the ONU with software centric power detection  380  remains substantially similar to that of the ONU with software centric power detection  300 . The battery power detector  314  monitors the power output from the external battery  313 . If the power level received from the external battery  313  drops below a predefined level, e.g. the level necessary for operation of the ONU with software centric power detection  380 , the battery power detector  314  may alert the controller  306 . Upon receiving the alert from the battery power detector  314 , the controller  306  may notify the host processor  307  of the alert. The notification may be in the form of an interrupt sent to the host processor  307 . The host processor  307  may then transmit a message comprising the power loss reason to an OLT connected to the ONU with software centric power detection  380 , e.g. power loss due to external battery  313  failure. The external battery  313  and external battery power detector  314  may be added to any of the embodiments disclosed herein to provide backup power in the case of external power  301  loss. 
       FIG. 4  is a block diagram of an embodiment of a PLOAM message  400 , which may be used in conjunction with existing PLOAM alarm messages. PLOAM message  400  may be configured as a dying gasp message. The PLOAM message  400  may comprise  12  octets. The first octet  410  may comprise an ONU-identifier (ID). The ONU-ID may indicate the ONU that is sending the dying gasp message to an OLT. The second octet  420  may comprise a message identification corresponding to a dying gasp message, e.g. ‘00000011’. The third octet  430  may comprise a reason indicator. The reason indicator may indicate to the OLT receiving the message the reason for the dying gasp message. A value of ‘00000001’ in the third octet  430  may indicate that the power switch at the ONU was formally turned off. A value of ‘00000010’ in the third octet  430  may indicate that the external power at the ONU is abnormally off. A value of ‘00000100’ in the third octet  430  may indicate that there is an internal circuit fault at the ONU. The fourth through twelfth octets  440  may be reserved for future use. While several reason indicators are described herein, other reason indicators may be used by the ONU to transmit a reason for power loss at the ONU over the PLOAM channel. 
       FIG. 5  is a block diagram of an embodiment of OMCI alarm extensions  500 , which may be used in conjunction with existing OMCI alarm messages. The OMCI alarm extensions  500  may comprise new OMCI alarms indicating the cause of power loss at an ONT. OMCI alarm 7  510  may be a dying gasp alarm that indicates the ONT is powering off immediately due to loss of power to the ONT itself, rather than being turned off manually. This alarm may be sent in conjunction with the powering alarm if a backup unit cannot supply power and the ONT is shutting down. OMCI alarm 12  520  may be an ONT manual power off alarm used to indicate that ONT is shutting down because a subscriber (e.g. a user) has turned off the ONT&#39;s power switch. OMCI alarm 13  530  may be a dying gasp caused by external power loss message used to indicate that the ONT is powering off because of an external power loss. OMCI alarm 14  540  may be a dying gasp caused by a circuit fault message used to indicate that the ONT is powering off because of an internal circuit fault. While several OMCI alarms are described herein, other OMCI alarms may be used by the ONT to transmit a reason for power loss at the ONT over the OMCI channel. 
       FIG. 6  is a block diagram of an embedded OAM message  600 , which may be used in conjunction with existing embedded OAM alarm messages. The embedded OAM message  600  may comprise  8  bits. The embedded OAM message  600  may correspond to the indication (Ind) field contained in the structured overhead of upstream GTC frames. Bit seven  610  may be used to indicate if a PLOAM is waiting for the OLT. If bit seven  610  is set to one, then a PLOAM message may be waiting. If bit seven  610  is set to zero, then a PLOAM message may not be waiting. Bit six  620  may be used to indicate the status of forward error correction (FEC). If bit six  620  is set to one then FEC is on. If bit six  620  is set to zero, then FEC is off. Bit five  630  may contain the remote defect indication (RDI) status. If bit five  630  is set to one, then a remote defect is present. If bit five  630  is set to zero, then a remote defect is not present. Bit four  640  may be reserved, and may be ignored by the OLT. Bits three through one  650  may be used as a reason indicator. If bits three though one  650  contain the sequence ‘001’, then the power switch at the ONU may have bee formally shut off. If bits three though one  650  contain the sequence ‘010’, then the external power source at the ONU may be abnormally off. If bits three though one  650  contain the sequence ‘100’, then there may be an internal circuit fault at the ONU. Bit zero  660  may be reserved for future use. While several bit sequences for bits three through one  650  are described herein, other bit sequences for bits three through one  650  may be used by the ONU to transmit a reason for power loss at the ONU over the embedded OAM channel. 
       FIG. 7  is a flow chart of an embodiment of a method for indicating a power loss reason  700 . The method  700  starts at block  720 , an ONU may monitor its power switch and/or external power source. The monitoring may be accomplished by a single module or a plurality of modules within the ONU. The external power source may be monitored for output power level. The power switch may be monitored for the current position, e.g. on or off. The method continues at block  730  when the ONU may detect a change of the power switch, or power loss at the external power supply. At block  740 , the ONU may send a message indicating the power loss reason to an OLT or some other upstream monitoring device. The message may be one or more of a PLOAM message, an embedded OAM message, or an OMCI message. The ONU may send the message via one, two, or three of a PLOAM channel, an embedded OAM channel, or an OMCI channel. 
     The network components described above may be implemented on any general-purpose network component, such as a computer or network component with sufficient processing power, memory resources, and network throughput capability to handle the necessary workload placed upon it.  FIG. 8  illustrates a typical, general-purpose network component  800  suitable for implementing one or more embodiments of the components disclosed herein. The network component  800  includes a processor  802  (which may be referred to as a central processor unit or CPU) that is in communication with memory devices including secondary storage  804 , read only memory (ROM)  806 , random access memory (RAM)  808 , input/output (I/O) devices  810 , and network connectivity devices  812 . The processor  802  may be implemented as one or more CPU chips, or may be part of one or more application specific integrated circuits (ASICs). 
     The secondary storage  804  is typically comprised of one or more disk drives or tape drives and is used for non-volatile storage of data and as an over-flow data storage device if RAM  808  is not large enough to hold all working data. Secondary storage  804  may be used to store programs that are loaded into RAM  808  when such programs are selected for execution. The ROM  806  is used to store instructions and perhaps data that are read during program execution. ROM  806  is a non-volatile memory device that typically has a small memory capacity relative to the larger memory capacity of secondary storage  804 . The RAM  808  is used to store volatile data and perhaps to store instructions. Access to both ROM  806  and RAM  808  is typically faster than to secondary storage  804 . 
     At least one embodiment is disclosed and variations, combinations, and/or modifications of the embodiment(s) and/or features of the embodiment(s) made by a person having ordinary skill in the art are within the scope of the disclosure. Alternative embodiments that result from combining, integrating, and/or omitting features of the embodiment(s) are also within the scope of the disclosure. Where numerical ranges or limitations are expressly stated, such express ranges or limitations should be understood to include iterative ranges or limitations of like magnitude falling within the expressly stated ranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). For example, whenever a numerical range with a lower limit, R l , and an upper limit, R u , is disclosed, any number falling within the range is specifically disclosed. In particular, the following numbers within the range are specifically disclosed: R=R l +k*(R u −R l ), wherein k is a variable ranging from 1 percent to 100 percent with a 1 percent increment, e.g., k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, . . . , 50 percent, 51 percent, 52 percent, . . . , 95 percent, 96 percent, 97 percent, 98 percent, 99 percent, or 100 percent. Moreover, any numerical range defined by two R numbers as defined in the above is also specifically disclosed. Use of the term “optionally” with respect to any element of a claim means that the element is required, or alternatively, the element is not required, both alternatives being within the scope of the claim. Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of. Accordingly, the scope of protection is not limited by the description set out above but is defined by the claims that follow, that scope including all equivalents of the subject matter of the claims. Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present disclosure. The discussion of a reference in the disclosure is not an admission that it is prior art, especially any reference that has a publication date after the priority date of this application. The disclosure of all patents, patent applications, and publications cited in the disclosure are hereby incorporated by reference, to the extent that they provide exemplary, procedural, or other details supplementary to the disclosure. 
     While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented. 
     In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled or directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.