Burst power measurements using averaged power measurement

An apparatus comprising an individual optical power level calculation (IOPLC) module and a transceiver coupled to the IOPLC module and configured to communicate with a plurality of optical network units (ONUs). Also disclosed is an apparatus comprising a control and management (CM) module, an average power level measurement (APLM) module coupled to the CM module, a first transceiver coupled to the CM module and configured to communicate with an optical line terminal (OLT), and a second transceiver coupled to the CM module and the APLM module, and configured to communicate with a plurality of ONUs.

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 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. The ODN comprises optical fibers, couplers, splitters, distributors, filters, and other passive optical devices, which connect the OLT to the ONUs. A PON may be a long reach PON (LR-PON), where the OLT and the ONUs may communicate along longer distances in comparison with other PONs. An LR-PON may comprise an Extender Box, which may be coupled to the OLT and the ONUs. The Extender Box may amplify the optical signals forwarded between the OLT and the ONUs and along at least some of the other LR-PON components. As such, the amplified optical signals may be less affected by increased signal attenuations, which are introduced at the various LR-PON components, along longer distances between the OLT and the ONUs.

SUMMARY

In one embodiment, the disclosure includes an apparatus comprising an individual optical power level calculation (IOPLC) module and a transceiver coupled to the IOPLC module and configured to communicate with a plurality of ONUs.

In another embodiment, the disclosure includes an apparatus comprising a control and management (CM) module, an average power level measurement (APLM) module coupled to the CM module, a first transceiver coupled to the CM module and configured to communicate with an OLT, and a second transceiver coupled to the CM module and the APLM module, and configured to communicate with a plurality of ONUs.

In yet another embodiment, the disclosure includes a method comprising at least one processor configured to implement a method comprising obtaining a plurality of average power levels over a plurality of time intervals for a plurality of burst power levels corresponding to a plurality of optical signals from a plurality of ONUs, obtaining a plurality of timeslots associated with the optical signals, and determining values for the burst power levels using the average powers levels, the time intervals, and the timeslots.

DETAILED DESCRIPTION

Disclosed herein is a method and system for estimating a plurality of unknown burst power levels corresponding to a plurality of optical signals, which may be transmitted from a plurality of ONUs in a PON. The burst power levels may be estimated based on a plurality of known average power levels. The average power levels may be measured over a plurality of corresponding time intervals at an Extender Box coupled to the ONUs and an OLT without using timing information for the individual optical signals. Accordingly, the average power levels and the corresponding time intervals may be processed, in addition to bandwidth information, to calculate the unknown burst power levels corresponding to the ONUs. Specifically, a plurality of timeslots may be obtained based on the bandwidth information, and may be associated with the corresponding unknown burst power levels. The sum of the individual products of the unknown burst power levels and the corresponding timeslots may be equated to a product of one known average power level and one corresponding time interval to obtain one equation. As such, a plurality of equations, corresponding to each measured average power level, may be obtained and processed using a numerical procedure to obtain the unknown burst power levels. Once obtained, the burst power levels may be analyzed to assess the performances of or detect problems in the individual ONUs.

FIG. 1illustrates one embodiment of a PON100. The PON100may comprise an OLT110, an optical trunk line (OTL)120, an Extender Box130, an ODN140, and a plurality of ONUs150. The PON100may be a communications network that does not require any active components to distribute data between the OLT110and the ONUs150. Instead, the PON100may use the passive optical components in the ODN140to distribute data, in the form of optical signals, between the OLT110and the ONUs150. Examples of suitable PONs100include the asynchronous transfer mode PON (APON) and the broadband PON (BPON) defined by the ITU-T G.983 standard, the Gigabit PON (GPON) defined by the ITU-T G.984 standard, the Ethernet PON (EPON) defined by the IEEE 802.3ah standard, and the wavelength division multiplexing PON (WDM-PON). Further, the PON100may be an LR-PON, where the optical signals forwarded between the OLT110and the ONU150may be amplified, for instance using the Extender Box130, to tolerate increased signal attenuations introduced along increased distances between the OLT110and the ONUs150.

The OLT110may be any device that is configured to communicate with the ONUs150and another network (not shown). Specifically, the OLT110may act as an intermediary between the other network and the ONUs150. In an embodiment, the OLT110may communicate with the network using a server network interface (SNI) and with the ONUs150or other components of the PON100coupled to the ONUs150using a send/receive point or interface (S/R). The OLT110may forward data received from the network to the ONUs150and forward data received from the ONUs150onto the other network. For instance, the OLT110may forward the data in the form of optical signals to the ONUs150and in the form of electrical or radio signals to the network. Although the specific configuration of the OLT110may vary depending on the type of PON100, in an embodiment, the OLT110may comprise a transmitter, a receiver, a transceiver, or combinations thereof. When the other network is using a protocol, such as Ethernet or Synchronous Optical Networking (SONET)/Synchronous Digital Hierarchy (SDH), that is different from the communications protocol used in the PON100, the OLT110may comprise a converter that converts the other network's data into the PON's protocol. The converter may also convert the PON's data into the other network's protocol. The OLT110may be located at a central location, such as a central office, but may be located at other locations as well.

The OTL120may be a single optical fiber or a plurality of aggregated fibers coupled to the OLT110and the Extender Box130. In an alternative embodiment, the OTL120may be configured similar to the ODN140and comprise optical fibers, couplers, splitters, distributors, filters, other passive optical devices, or combinations thereof.

The Extender Box130may be configured to receive, amplify, and retransmit or forward the optical signals between the OLT110and the ONUs150. Specifically, the Extender Box130may act as a signal booster or regenerator for the optical signals, which may be transported over longer distances or through more optical components with respect to other PONs, such as in an LR-PON. For instance, the Extender Box130may comprise a repeater or amplifier, such as an optical-electrical-optical (OEO) converter or a semiconductor optical amplifier (SOA) inserted between the OTL120and the ODN140. In an embodiment, the Extender Box130may exchange the optical signals with the OTL120using an interface to the trunk (IFT), and exchange the optical signals with the ODN140using an interface to the distribution (IFD). Further, the Extender Box130may comprise a transmitter, a receiver, a transceiver, other modules, or combinations thereof.

The ODN140may be a data distribution system that 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 are 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 as optical signals between the OLT110and the ONUs150. The ODN140may extend from the Extender Box130to the ONUs150in a branching configuration or in any alternative configuration.

The ONUs150may be any devices that are configured to communicate with the OLT110and at least one customer or user (not shown). Specifically, the ONUs150may act as an intermediary between the OLT110and the customer. For instance, the ONUs150may forward data received from the OLT110to the customer and forward data received from the customer onto the OLT110. In an embodiment, the ONUs150may exchange the optical signals with the ODN140using a receive/send point or interface (R/S), and exchange the optical signals with the customer using a user network interface (UNI). Although four ONUs150are shown inFIG. 1, the PON100may comprise any number of ONUs150.

Although the specific configuration of the ONUs150may vary depending on the type of PON100, in an embodiment, the ONUs150may comprise an optical transmitter configured to send optical signals to the OLT110. Additionally, the ONUs150may comprise an optical receiver configured to receive optical signals from the OLT110and a converter that converts the optical signal into electrical signals for the customer, such as signals in the asynchronous transfer mode (ATM) or Ethernet protocol. The ONUs150may also comprise a second transmitter and/or receiver that may send and/or receive the electrical signals to a customer device. In some embodiments, the ONUs150and optical network terminals (ONTs) are similar, and thus the terms are used interchangeably herein. The ONUs150may be located at distributed locations, such as the customer premises, but may be located at other locations as well.

The optical signals transmitted from the ONUs150may be burst optical signals, e.g., optical signals that are transmitted intermittently or separated by time delays or pauses, which may have signal power levels referred to as burst power levels. In normal operating conditions, the burst power levels of the transmitted optical signals may be equal to at least one power level associated with the transmitters' standard performances at the ONUs150. However, when the operating condition at an ONU150deteriorates due to a decrease in the transmitters' performance, the burst power level may decrease or may fluctuate over time. Hence, measuring the burst power level corresponding to the optical signal may be advantageous to assess the performance of the ONU150or to detect a problem in the ONU150or the transmitter.

However, measuring the burst power levels of the optical signals at the OLT110may be difficult in the PON100in the presence of the Extender Box130. Specifically, the transmitted optical signals from the ONUs150may be amplified at the Extender Box130at variable amplification levels, for instance due to design or physical limitations, before being forwarded to the OLT110. Thus, it may be difficult to correlate the power levels of the amplified optical signals received at the OLT110with the burst power levels of the optical signals transmitted from the ONUs150. Hence, measuring the power levels of the amplified optical signals at the OLT110may not be an accurate evaluation of the burst power levels of the optical signals from the ONUs150. Moreover, the burst power levels of the optical signals may not be directly measured at the Extender Box130. Specifically, the Extender Box130may not be configured to implement a PON protocol, for instance to reduce the impact of adding the Extender Box130on system design. Hence, the Extender Box130may be configured as a passive device, which may not associate the individual burst power levels with the corresponding optical signals.

To overcome the difficulty in measuring the burst power levels of the optical signals at the OLT110or associating the optical signals with corresponding ONUs150at the Extender Box130, a plurality of average power levels corresponding to the optical signals may be measured at the Extender Box130. The average power levels may be measured over a plurality of corresponding time intervals or durations, which may each comprise the total time for receiving at least some of the optical signals at the Extender Box130. In an embodiment, the measured average power levels and the corresponding time intervals may then be forwarded from the Extender Box130to the OLT110, where they may be processed, in addition to timing information, to evaluate or estimate the corresponding burst power levels for the transmitted optical signals from the individual ONUs150. Specifically, the timing information may be needed to associate the burst power levels with the corresponding ONUs150. For instance, the timing information may comprise a plurality of timeslots or durations corresponding to the transmitted optical signals. In an embodiment, the timing information may be obtained from bandwidth information, which may be stored at the OLT110. The bandwidth information may be historic bandwidth information, which may be acquired by recording the time bandwidth of previously transmitted optical signals from the ONUs150. Hence, the timing information or timeslots may be extracted from the recorded time bandwidth. Alternatively, the bandwidth information may be statistical bandwidth information, which may be obtained based on anticipated traffic from the ONUs150, historic traffic in the PON100, or both.

FIG. 2illustrates one embodiment of an OLT200, which may be used to estimate the burst power levels at a PON, such as the PON100. The OLT200may comprise an IOPLC module210, which may be coupled to a PON adapter220and a transceiver230. The IOPLC module210may be configured to evaluate or calculate the burst power levels using the average power levels and the corresponding time intervals, which may be obtained from the Extender Box130, and the timing information, which may be stored in the OLT200. In an embodiment, the IOPLC module210may be a software, hardware, firmware, or combinations thereof, which may be programmed to receive as inputs the average power levels, the time intervals, and the timeslots corresponding to the burst power levels. Hence, the IOPLC210may process the inputs based on an algorithm or program to provide the burst power levels as outputs.

The PON adapter220may be coupled to a server or a network, for instance via an SNI, and may be used to exchange data between the OLT200and the server or network. For instance, the PON adapter220may forward at least some of the inputs or outputs of the IOPLC210, including the burst power levels, to a network operator or manager in charge of detecting problems in the PON's ONUs. Additionally, the PON adapter220may exchange other data, including data received from the ONUs, with the server or network. Accordingly, the PON adapter220may convert the exchanged data based on the protocols and the transport layer architectures of the OLT200and the network. In some embodiments, the PON adapter220may comprise a transmitter, receiver, transceiver, or combinations thereof.

The transceiver230may be coupled, for instance via an S/R, to an Extender Box, which may be in turn coupled to the ONUs. The transceiver230may be an integrated device comprising an optical transmitter and receiver or alternatively may comprise an optical transmitter coupled to an optical receiver. The transceiver230may be used to exchange data between the OLT200and the Extender Box, as well as the ONUs. For instance, the transceiver230may forward the average power levels and the time intervals from the Extender Box to the IOPLC210. Additionally, the transceiver230may forward data between the OLT200and the ONUs via the Extender Box.

FIG. 3illustrates one embodiment of an Extender Box300, which may be used to measure the average power levels of the optical signals transmitted from a plurality of ONUs, such as the ONUs150described above. The Extender Box300may comprise a CM module310, an average power level measurement (APLM) module320, a first transceiver330, which may be coupled to the CM module310, and a second transceiver340, which may be coupled to the CM module310and the APLM module320. The CM module310may be configured to set the time intervals over which the average power levels may be measured. For instance, the CM module310may set a plurality of about equal or different time intervals for measuring a plurality of average signals. In some embodiments, the CM module310may set a discrete number equal to the quantity of the average power levels to be measured, a discrete number equal to the quantity of burst power levels to be detected for each average power level, or both. The CM module310may forward the time intervals, and in some embodiments the discrete numbers, to the APLM module320via the second transceiver340. For instance, the CM module310may comprise a software, hardware, firmware, or combinations thereof, which may be programmed to provide the time intervals as an input to the APLM module320. In other embodiments, the CM module310may be configured to receive such measurement settings via the first transceiver330, for instance from an OLT coupled to the Extender Box300, and to forward it to the APLM module320.

The APLM module320may be configured to measure the average power levels over the time intervals set by the CM module310. To measure each of the average power levels, the APLM module320may receive a plurality of optical signals from the individual ONUs, via the second transceiver340, and detect the corresponding individual burst power levels. For instance, the APLM module320may detect a quantity of burst power levels equal to the discrete number set by the CM module310. Hence, the APLM module320may sum the burst power levels, and divide the sum by the discrete number to obtain a corresponding average power level. Alternatively, the APLM module320may detect and average a plurality of burst power levels in a continuous manner over the time interval, for instance using a low pass filter. The APLM module320may comprise at least a software, hardware, firmware, or combinations thereof, which may be programmed to receive, as inputs, the burst power levels and provide, as outputs, the average power levels, which may then be forwarded to the CM module310, via the second transceiver340. In turn, the CM module310may forward the average power levels and the corresponding time intervals to the OLT, via the first transceiver330.

The first transceiver330and the second transceiver340may be integrated devices comprising a plurality of optical transmitters and receivers or alternatively may comprise a plurality of optical transmitters coupled to a plurality of optical receivers. The first transceiver330may be coupled to an OLT, for instance via an IFT, and may be used to exchange data between the OLT and the Extender Box300. For instance, the first transceiver330may forward at least some of the inputs or outputs of the CM module310, as described above. Additionally, the first transceiver330may exchange other data, including data received from the ONUs, with the OLT. The second transceiver340may be coupled, for instance via an IFD, to an ODN, which may be in turn coupled to the ONUs. The second transceiver340may be used to detect the burst power levels of the optical signals. For instance, the second transceiver340may comprise an optical detector, such as a detector array, a photodiode, or other types of detectors, which may detect the strength or power of the optical signal, or convert the optical signal into an electrical signal, which may be measured. The second transceiver340may also exchange data between the ONUs and the Extender Box300or the OLT, in addition to the measurements described above. For instance, the second transceiver340may forward the data from the ONUs and the average power levels from the APLM module320, via the CM module310, to the first transceiver330, which may in turn forward it to the OLT.

In other embodiments, instead of measuring the average power levels at the Extender Box300and forwarding the average power levels to the OLT200to estimate the burst power levels, the OLT may forward to the Extender Box the timing information, bandwidth information, or timeslots needed to estimate the burst power levels. Accordingly, the Extender Box may comprise an IOPLC module in addition to the APLM module320. The Extender Box may receive the needed information from the OLT, measure the average power levels, and estimate the burst power levels using the average power levels, the corresponding time intervals, and the received timeslots. In alternative embodiments, the Extender Box may send the sum of the detected power levels to the OLT. Accordingly, the OLT may comprise an APLM module320in addition to the IOPLC module, and may evaluate the average power levels and estimate the burst power levels.

FIG. 4illustrates one embodiment of a plurality of burst optical signals, including a first burst optical signal410, a second burst optical signal420, and an nth burst optical signal430, which may be detected over a time interval equal to about Ti. The nth burst optical signal430may be the last detected burst optical signal in a sequence of n burst optical signals, where n may be equal to an integer or a discrete number set by a CM module. The time interval Timay be equal to the time interval, for instance set by a CM module, over which an average power of the ONUs' optical signals may be measured. The burst power levels of the burst optical signals may be detected at about equal or different values by the optical detector. For instance, the first burst optical signal410, the second burst optical signal420, and the nth burst optical signal430may have a first burst power level equal to about P1, a second burst power level equal to about P2, and an nth burst power level equal to about Pn, respectively. The burst power levels of the detected burst optical signals may be summed and divided by the quantity of the detected burst optical signals to measure or obtain the average power level. For instance, a total of n values, including P1, P2, and Pn, may be summed up and divided by n to obtain a value of Pafor the average power level.

Further, each detected burst optical signal may be associated with a timeslot, for instance using bandwidth information, which may be a portion of the time interval Ti. For instance, the first burst optical signal410, the second burst optical signal420, and the nth burst optical signal430may be associated with a first timeslot Ti1, a second timeslot Ti2, and an nth timeslot Tin, respectively. The timeslots Ti1, Ti2, Tin, as well as the remaining timeslots corresponding to the remaining detected burst optical signals over the time interval Ti, may or may not be about equal to one another. The time interval Timay include other time portions, in addition to the timeslots corresponding to the detected burst optical signals, such as time gaps that may exist between the timeslots. The time gaps may correspond to time durations where no burst power levels may be detected or no burst optical signals may be transmitted.

The burst power levels corresponding to the ONUs' optical signals may be estimated, for instance at the IOPLC, using the average power levels measurements and based on a plurality of mathematical equations. The mathematical equations may define the relationship between the burst power levels, which may be unknown variables, with the corresponding timeslots, the average power levels, and the corresponding time intervals, which may be known values. If there are a sufficient number of equations to resolve the unknown variables, the mathematical equations may be solved to obtain values for the burst power levels. For example, the mathematical equations may comprise a system of n mathematical equations that relate n unknown burst power levels and n known average power levels, where n is an integer. Specifically, a total or sum of the products of each burst power level and its corresponding timeslot may be equated to a product of one average power level and its corresponding time interval. The system of n mathematical may be represented in a generic form, such as:
(P1×Ti1)+(P2×Ti2)+ . . . +(P(n-1)×Ti(n-1))+(Pn×Tin)=Pai×Ti.
For instance, the above equation may be the ith equation in the system of n equations, where Paiis the ith average power level, Tiis the ith corresponding time interval, P1, P2, . . . , P(n-1), and Pnare n burst power levels, Ti1, Ti2, . . . , Ti(n-1), and Tinare n corresponding timeslots, n is equal to the number of burst power levels, and i is an integer less than or equal to the number of average power levels. The number of average power levels may be equal to or greater than n, e.g., the number of the unknown burst power levels to be estimated. Increasing the number of measured average power levels may reduce the amount of errors or uncertainties in the calculated burst power levels, for instance due to measurement errors or noise from the optical detector. Further, each average power level may be measured a plurality of times or repeatedly at a predetermined rate over the time interval, which may be set by the CM module. The measured values may then be averaged to obtain an average power level value with less error or uncertainty, and hence more accurate burst power level values.

The n equations may be solved simultaneously using standard solution methods or any solution methods that may be used to obtain the values of the burst power levels from the average power levels. The standard solution methods may include statistical solution methods, linear and non-linear regression techniques, least error solutions, or any other solution methods that may be used to solve the burst power levels. For instance, using a least error solution, the estimated values of the burst power levels may correspond to an acceptable fitting error for the measured average power levels. In other words, using the least error solution, the obtained values of the burst power levels may correspond to measurement values that are substantially equal to the acquired values of the average power levels.

In another embodiment, one burst power level for an optical signal from a single ONU may be estimated without estimating the remaining burst power levels. The burst power level may be estimated using two equations that represent the relation between the unknown burst power levels for all the optical signals from the ONUs, with two measured average power levels. Specifically, the burst power level may be estimated based on a first average power level measured over a first time interval and a second average power level measured over a second time interval, which may be consecutive to the first time interval. Further, the burst power level may be associated with a first timeslot during the first time interval and a second timeslot during the second time interval, which may not be equal to the first timeslot. For instance, the second timeslot may be longer than the first timeslot. However, the remaining burst power levels may be associated with corresponding timeslots which may be about equal during the first time interval and the second time interval. The system of two equations may be represented such as:
(P1×T11)+(P2×T12)+ . . . +(P(n-1)×T1(n-1))+(PnT1n)=Pa1×T1
(P1×T21)+(P2×T22)+ . . . +(P(n-1)×T2(n-1))+(Pn×{T2n+δ})=Pa2×T2,
wherein Pa1is the first average power level, T1is the first time interval, Pa2is the second average power level, T2is the second time interval, Pnis the burst power level, T1nis the first timeslot at the first time interval, {T2n+δ} is the second timeslot at the second time interval and δ is equal to about the time difference between the second timeslot and the first timeslot. Additionally, P1, P2, . . . , and Pn-1are the remaining burst power levels, T11, T12, . . . , and T1(n-1)are the corresponding timeslots at the first time interval, T21, T22, . . . , and T2(n-1)are the corresponding timeslots at the second time interval and n is equal to the number of burst power levels.

FIG. 5illustrates an embodiment of a burst power level estimation method500, which may be used in a PON system comprising an Extender Box, such as an LR-PON. The burst power level estimation method500may be implemented at the OLT. Alternatively, the burst power level estimation method500may be implemented at another PON component in communication with the OLT, such as the Extender Box. At block510, the burst power level estimation method500may obtain a plurality of average power levels, which may be measured at the Extender Box, and at least one time interval. For instance, the average power levels and the time interval may be forwarded from the Extender Box to the OLT via an OTL. Alternatively, the average power levels and the time interval may be obtained and stored within the Extender Box, for instance from the APLM and CM modules.

At block520, the burst power level estimation method500may obtain a plurality of timeslots corresponding to the burst power levels, for instance from historic or statistical bandwidth information. The bandwidth information may be stored at the OLT or may be forwarded from a network server or manager to the OLT, which may also receive the average power levels and the time interval. Alternatively, the bandwidth information or timeslots may be forwarded from the OLT to the Extender Box, where the average power levels and the time interval may be obtained and stored.

At block530, the relation between the burst power levels, the timeslots, the average power levels, and the time intervals may be established, for instance using a system of mathematical equations, as described above. The system of mathematical equations may comprise a number of equations equal to the number of measured average power levels, and equal to or greater than the number of unknown burst power levels. Additionally or alternatively, another system of equations, comprising at least two equations, may be established to estimate the value of any burst power level associated with a selected ONU, as described above.

At block540, the relation or system of equations that relates the unknown burst power levels to the measured average power levels and the other known values may be processed or solved to calculate or resolve at least one of the burst power levels, as described above. The system of equations may be established and solved at the OLT, for instance using an IOPLC module. Alternatively, the an IOPLC module may be present at or coupled to the Extender Box, where the burst power levels may be estimated, and then forwarded to the OLT. Additionally, the burst power levels may optionally be forwarded to other PON components, such as the ONUs or a PON component in charge of monitoring or detecting problems in the ONUs.

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. 6illustrates a typical, general-purpose network component600suitable for implementing one or more embodiments of the components disclosed herein. The network component600includes a processor602(which may be referred to as a central processor unit or CPU) that is in communication with memory devices including secondary storage604, read only memory (ROM)606, random access memory (RAM)608, input/output (I/O) devices610, and network connectivity devices612. The processor602may be implemented as one or more CPU chips, or may be part of one or more application specific integrated circuits (ASICs).

The secondary storage604is 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 RAM608is not large enough to hold all working data. Secondary storage604may be used to store programs that are loaded into RAM608when such programs are selected for execution. The ROM606is used to store instructions and perhaps data that are read during program execution. ROM606is a non-volatile memory device that typically has a small memory capacity relative to the larger memory capacity of secondary storage604. The RAM608is used to store volatile data and perhaps to store instructions. Access to both ROM606and RAM608is typically faster than to secondary storage604.