WO2021093186A1

WO2021093186A1 - Fast detection and recovery of a rogue optical network unit using a reset signal

Info

Publication number: WO2021093186A1
Application number: PCT/CN2020/074124
Authority: WO
Inventors: Xingang Huang; Jun Shan Wey; Liquan Yuan; Yong Guo
Original assignee: Zte Corporation
Priority date: 2020-01-31
Filing date: 2020-01-31
Publication date: 2021-05-20

Abstract

Described are methods and apparatuses for optical digital communications. In one aspect a method includes assigning, by an optical line terminal (OLT), different time slots to different optical network units (ONUs) for data transmission by the different ONUs in a time domain multiple access (TDMA) system. The method further includes sending, by the optical line terminal (OLT), bandwidth allocations to the different ONUs, and determining an optical power in each time slot assigned to the different ONUs. The method further includes detecting a power change in a first assigned time slot between a previous first optical power and a first optical power associated with a first ONU, wherein the detecting the power change indicates a faulty ONU is transmitting to the OLT.

Description

FAST DETECTION AND RECOVERY OF A ROGUE OPTICAL NETWORK UNIT USING A RESET SIGNAL

TECHNICAL FIELD

This patent document relates to digital communication, and, in one aspect, optical communication systems.

BACKGROUND

There is an ever-growing demand for data communication in application areas such as wireless communication, fiber optic communication, and so on. The demands on core networks and access networks are increasing because user devices such as smartphones and computers are using more and more bandwidth due to multimedia applications, and because the number of devices carrying data is increasing. To maintain profitability, to meet increasing demand, and to improve reliability equipment manufacturers and network operators need new techniques to increase efficiency and throughput of optical networks, reduce down-time, and to reduce capital expenditures.

SUMMARY

Methods, apparatuses, systems, and computer readable media are disclosed. The present document discloses techniques for determining when an optical network unit is erroneously transmitting in one or more time slots not assigned to it and for returning the incorrectly transmitting optical network unit to normal operation. Among other benefits, the disclosed techniques can be used to increase the reliability of optical networks, increase throughput, and to restore the functioning of optical network units.

In one aspect, a method of digital communication is disclosed. The method includes assigning, by an optical line terminal (OLT) operating in a time-division multiple access (TDMA) system in which transmissions from different optical network units (ONUs) to the OLT are organized in time slots separated by time gaps, different time slots to the different ONUs for optical transmission by the different ONUs to the OLT. The method further includes transmitting a reset signal before each of the different time slots and following each of the different time slots, and identifying a faulty ONU from the different ONUs by receiving an identification frame from the faulty ONU in one or more incorrect time slots not assigned to the faulty ONU or in one or more of the time gaps.

In another aspect, a method of digital communication is disclosed. The method includes assigning, by an OLT operating in a TDMA system in which transmissions from different ONUs to the OLT are organized in time slots separated by time gaps, wherein different time slots are assigned to the different ONUs for optical transmission by the different ONUs to the OLT, identifying a faulty ONU from the different ONUs, and transmitting a control message to disable the faulty ONU.

In another aspect, a method of digital communication is disclosed. The method includes receiving, by an ONU from an OLT, at least one assigned time slot reserved for transmissions from the ONU, and receiving, by the ONU from the OLT, a message causing the ONU to stop transmitting in the one or more time slots not assigned to the ONU and to return to normal operation.

In yet another aspect, a method of digital communication is disclosed. The method includes assigning, by an OLT operating in a TDMA system in which transmissions from different ONUs to the OLT are organized in time slots separated by time gaps, different time slots to the different ONUs for optical transmission by the different ONUs to the OLT, receiving an upstream signal and decoding data from the upstream signal, and determining whether a rouge ONU identification frame is included in the decoded data, wherein a rouge behavior flag included in the rouge ONU identification frame identifies a faulty ONU from the different ONUs.

In another aspect, a method of digital communication is disclosed. The method includes assigning, by an OLT, different time slots to N different optical network units for data transmission by the N different ONUs in a TDMA system, wherein N is an integer greater than one, determining, during a time interval that the OLT is unable to successfully decoded optical transmissions received from (N-M) ONUs in corresponding time slots while the OLT is able to successfully decode optical transmissions received from a remaining M ONUs in corresponding time slots, and concluding based on the determining, that one of the remaining M ONUs is a faulty ONU operating in an erroneous transmission (ET) mode, wherein the faulty ONU has a lowest received power among the M ONUs.

In another aspect, a method of digital communication is disclosed. The method includes assigning, by an OLT, different time slots to different ONUs for data transmission by the different ONUs in a TDMA system, sending, by the OLT, bandwidth allocations to the different ONUs, determining an optical power in each time slot assigned to the different ONUs; and detecting a power change in a first assigned time slot between a previous first optical power and a first optical power associated with a first ONU, wherein the detecting the power change indicates a faulty ONU is transmitting to the OLT.

In yet another aspect, a method of digital communication is disclosed. The method includes assigning, by an OLT, different time slots to different ONUs for data transmission by the different ONUs in a TDMA system, sending, by the OLT, bandwidth allocations to the different ONUs, determining time slot optical powers for each time slot assigned to the different ONUs and a time gap optical powers for each time gap between the time slots, comparing the time gap optical powers to the time slot optical powers, wherein a first optical power in a first time slot assigned to a first ONU being equal to one or more of the time gap optical powers indicates that the first ONU is a faulty ONU.

In another aspect, a method of digital communication is disclosed. The method includes assigning, by an OLT, different time slots to different ONUs for data transmission by the different optical network units in a TDMA system, and generating a binary signal indicating whether an optical input power is present. The method further includes determining, based on the binary signal, whether the optical input power is above a threshold in the different time slots and at least one other time slot, wherein in a case that the binary signal indicates the optical input power is above the threshold only in the different time slots, then no optical network unit is continuously transmitting, and in another case that the binary signal indicates the optical input power is above the threshold in the other time slot in addition to the different time slots, then a faulty ONU is in an erroneous transmission (ET) mode. The method further includes determining the faulty ONU to be one of the different ONUs with a lowest optical input power that is decoded by the OLT.

In another aspect, an apparatus is disclosed. The apparatus includes an optical receiver configured to determine an optical power received in each of a plurality of time slots, wherein each of the plurality of time slots corresponds to one of a plurality of optical network units. The apparatus further includes a processor and memory including executable instructions that when executed perform at least the following operations: determining decoded data in one or more of the plurality of time slots, and determining a lowest optical power received in one of the plurality of time slots compared to other of the plurality of time slots, wherein data is decoded at the lowest optical power received, and wherein a faulty ONU from the plurality of optical network units corresponds to the one of the plurality of time slots, and wherein the faulty ONU is in an erroneous transmission (ET) mode.

These, and other, aspects are further described in the present document.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an optical network, in accordance with some example embodiments.

FIG. 2 depicts data flow between an optical line terminal (OLT) and an optical network unit (ONU) , in accordance with some example embodiments.

FIG. 3A depicts an example of a timeline with three optical network units each transmitting correctly in three different time slots, in accordance with some example embodiments.

FIG. 3B depicts another example of a timeline with three optical network units where two optical network units are transmitting in their assigned time slots and one optical network unit is erroneously transmitting in time slots not assigned to it, in accordance with some example embodiments.

FIG. 4A depicts an example of internal ONU data flow for an ONU operating normally, in accordance with some example embodiments.

FIG. 4B depicts an example of internal ONU data flow for an ONU that is erroneously transmitting continuously, in accordance with some example embodiments.

FIG. 4C depicts an example of internal ONU data flow for an ONU that is erroneously transmitting intermittently, in accordance with some example embodiments.

FIG. 5A depicts examples of timelines with three optical network units and a reset signal sent by an OLT, in accordance with some example embodiments.

FIG. 5B depicts examples of timelines with three optical network units and a reset signal sent by an OLT and a signal detect (SD) or optical power detection signal, in accordance with some example embodiments.

FIG. 5C depicts examples of timelines with three optical network units and a loss of signal (LOS) or loss of optical power signal, in accordance with some example embodiments.

FIG. 6A depicts an example of an optical network with three ONUs at different distances from the OLT.

FIG. 6B depicts examples of power received at an OLT from eight ONUs at different distances from the OLT.

FIG. 7A depicts a method performed at an OLT based on a received identification frame, in accordance with some example embodiments.

FIG. 7B depicts another method performed at an OLT based on a received identification frame, in accordance with some example embodiments.

FIG. 7C depicts another method performed at an OLT based on a received identification frame including a rogue behavior flag, in accordance with some example embodiments.

FIG. 7D depicts a method for causing a faulty ONU to return to normal operation, in accordance with some example embodiments.

FIG. 7E depicts another method performed at an ONU, in accordance with some example embodiments.

FIG. 7F depicts a method performed at an ONU and a method performed at an OLT, in accordance with some example embodiments.

FIG. 7G depicts a method for disabling a faulty ONU, in accordance with some example embodiments.

FIG. 7H depicts a method for determining a faulty ONU, in accordance with some example embodiments.

FIG. 7I depicts another method for determining a faulty ONU, in accordance with some example embodiments.

FIG. 7J depicts a method performed at an OLT for determining a faulty ONU based on received optical power, in accordance with some example embodiments.

FIG. 8 details a Disable_Serial_Number physical layer operations, administration, and maintenance (PLOAM) message, in accordance with some example embodiments.

FIG. 9 depicts an apparatus, in accordance with some example embodiments.

Where possible, like reference numeral refer to similar features.

DETAILED DESCRIPTION

The fast-growing data and services, such as cloud, mobile front-haul and HD video streaming applications, drive the demand of higher bit-rate optical communications, such as inter-and intra-data center connection and optical access networks, which benefit from systems that can support higher capacity. Cloud networking, 5G mobile fronthaul, and high bandwidth video applications, are driving the demand for increased capacity in access networks.

Disclosed herein are methods, apparatuses, systems, and computer readable media for digital optical communication in passive optical networks (PONs) .

FIG. 1 depicts an optical network, in accordance with some example embodiments. Optical network 100 includes optical line terminal (OLT) 110 connected to power splitter/combiner 116 (referred to herein as a splitter 116) via fiber 112, and optical network units (ONUs) 130A-130C connected to splitter 116 via fibers 132A-132C. Although FIG. 1 depicts splitter 116 multiplexing fiber 112 to three fibers 132A-132C, splitter 116 may multiplex fiber 112 to any other number of fibers such as eight, or 16, or 256, and so on.

OLT 110 may be located at a central location such as a central office of a network service provider. OLT 110 may include a one or more optical transmitters and a one or more optical receivers. For example, OLT 110 may include one optical transmitter such as a laser diode to produce an optical downlink signal that is broadcast via splitter/combiner 116 to all of the ONUs. OLT 110 may further include a single optical receiver. Uplink optical signals generated by each ONU which may be at the same wavelength are combined by splitter/combiner 116 and received at the OLT 110. Signals passed from the OLT to an ONU may be referred to as a downstream or downlink signal, and signals passed from an ONU to the OLT may be referred to as an upstream or uplink signal.

Power splitters may support time division multiple access (TDMA) where multiple links use the same fiber and signal transmissions are separated by time. Although FIG. 1 depicts one OLT, one splitter 116, and three ONUs 130A-130C, optical network 100 may include more than on OLT, more than one splitter, and any number of connected ONUs.

Depending on the locations of the optical network units, optical network 100 may include fibers of substantial length. As an illustrative example, OLT 110 may be located at a central office. Fiber 112 may be 3 km long and connect OLT 110 to splitter 116. Splitter 116 may break-out the downlink signal at a first wavelength into separate signals carried by separate fibers such as fibers 132A-132C. Splitter 116 may combine uplink signals at a second wavelength carried by fibers 132A-132C from ONUs 130A-130C. For example, fiber 132A may connect splitter 116 to optical network unit 130A located 10 km from splitter 116 and carry a downlink signal to be received at optical network unit 130A and carry an uplink signal transmitted from optical network unit 130A at a second wavelength to splitter 116. Fiber 132B may connect splitter 116 to optical network unit 130B located 8 km from splitter 116 and carry the downlink signal to be received at optical network unit 130B and carry an uplink signal transmitted from optical network unit 130B. Fiber 132C may connect splitter 116 to optical network unit 130C located 20 km from splitter 116 and carry the downlink signal to be received at optical network unit 130C and carry an uplink signal transmitted from optical network unit 130C. Additional optical network units may be connected via additional fibers to splitter 116. The foregoing example indicated example distances and three optical network units, any other distances and/or number of optical network units may be used as well.

Each ONU may be connected to one or more fibers. For example, ONU 130A may be connected to fiber 132A. An ONU may include an optical transmitter and an optical receiver. The optical transmitter may include an optical source that may be modulated to include data. In some example embodiments, the optical source may be coupled to a semiconductor optical amplifier (SOA) . The power output from the optical source may be adjusted via a bias voltage and the SOA may further adjust the optical power via gain in the SOA coupled to a fiber.

For some types of messages where low latency and higher robustness is preferred, a lower order modulation such as OOK may be used. For example, the registration or discovery of ONUs, frame preamble, and communications performed before training is completed, may use lower order modulation such as NRZ-OOK. Registration of one or more ONUs with the OLT may be performed before payload data is sent. Registration of an ONU with an OLT is referred to as auto-discovery in some Institute for Electrical and Electronic Engineers (IEEE) Ethernet Passive Optical Network (E-PON) standards. As used herein, registration and auto-discovery are synonymous.

FIG. 2 depicts data flow between an optical line terminal (OLT) and an optical network unit (ONU) , in accordance with some example embodiments. The description of FIG. 2 also refers to FIG. 1. In the example of FIG. 2, network 200 includes OLT 110 connected to ONU 130A. OLT 110 may communicate with optical network unit 130A by transmitting downstream signal 220 to ONU 130A and receiving upstream signal 230 from ONU 130A. FIG. 2 depicts information/data flow rather hardware components. In normal upstream operation of some embodiments, the ONU, transmits optical signals to the OLT in at least one assigned time slot.

FIG. 3A is an illustration of a timeline showing examples of times when each of three ONU’s is transmitting data to the OLT. ONU3 at 310C transmits first of the three ONU’s in timeslot 320C. For example, ONU3 at 310C may be ONU 130C in FIG. 1. The transmission in timeslot 320C may pass from ONU 130C through fiber 132C to splitter 116 which combines signals from

ONUs

130A and 130B and combines them onto a single fiber, fiber 112, which carries the signals to OLT 110.

If more than one ONU is transmitting at the same time and wavelength, their signals will interfere with one another. As a result of the interference, the OLT may not be able to receive either signal. Some caveats to this are described with respect to FIG. 5. ONU1 at 310A transmits second of the three ONU’s in timeslot 320A and ONU2 at 310B transmits third of the three ONU’s in timeslot 320B. In the example of FIG. 3A, none of the timeslots overlap one another. As such, there is no interference between ONUs 310A-310C.

FIG. 3B is another illustration of a timeline showing times when each of three ONUs is attempting to transmit data to the OLT. In this illustrative example, ONU1 at 350A is transmitting continuously. ONU1 is allocated to transmit in timeslot 360A but due to some type of failure is transmitting before timeslot 360A at 370A and after timeslot 360A at 370B. As a result of ONI1 transmitting in timeslot 370A which overlaps timeslot 360C assigned to ONU3 at 350C, the data from ONU3 will not be received at the OLT. Similarly, as a result of ONU1 transmitting in timeslot 370B which overlaps timeslot 360B assigned to ONU2 at 350B, the data from ONU2 will not be received at the OLT. Because there is no overlap by ONU2 or ONU3 with ONU1’s timeslot 360A, the OLT will detect and receive the data in timeslot 360A. ONU1 in the illustrative example of FIG. 3B is an example of an erroneously transmitting ONU that the disclosed subject matter detects and attempts to correct to normal functioning.

FIG. 4A depicts an example of internal ONU data flow for an ONU operating normally, in accordance with some example embodiments. The data flow shown in FIG. 4A corresponds to data flow that is internal to the ONU that results in data transmitted in an optical signal. An ONU includes electrical, optical, and optoelectronic hardware used in generating data transmitted in an optical signal. For example, ONU optical module 400 may be included in an ONU such as ONU 130A which may include electrical devices for receiving data 405 via an electrical interface 410 and optical/optoelectronic devices for transforming the data received via the electrical interface 405 into an optical signal 415 transmitted via an optical interface 420. A control signal 430 provided to the ONU optical module 400 may be used to indicate to the ONU optical module when to transmit an optical signal and may be determined by dynamic bandwidth allocation (DBA) information. For example, control signal 430 may indicate to ONU 130A including optical module 400 that time slot 436 is allocated to ONU 130A. In FIG. 4A, the ONU optical module receives data 405 including payload data 434 via electrical interface 410. At times where no payload data is sent, identification frames 432A, 432B, 432C, 432D, and so on may be passed via the electrical interface to ONU optical module 400 as shown at timeline 405A. The identification frames may include information such as an identity of the ONU such as ONU1, ONU2, ONU3, and so on. In correct and normal operation as shown in FIG. 4A, payload data 434A is transmitted across the optical interface 420 and the ID frames passed across the electrical interface 410 are not transmitted across the optical interface 420 by the optical module 400 as shown on timeline 415A. Data is passed across the optical interface 420 only during time slot 436 indicated by the control signal 430 as shown at timeline 430A.

As described above, the identification frames are electrical signals that may be sent during unassigned timeslots. Optical signals from the ONU are controlled by dynamic bandwidth allocation (DBA) and may be sent in assigned time slots. Some ONUs that cannot be controlled by DBA to turn ON/OFF their optical power may continue to send optical signals during the unassigned time slots. Normally in correct operation, ONUs send the identification frame only over the electrical interface and not the optical interface. Normally, optical signals sent by ONUs are controlled by DBA, and are only sent in authorized time slots, and the optical signal is turned off in unauthorized time slots, but a faulty ONU may have an uncontrolled optical signal that sends the identification frames in unauthorized time slots.

Identification frame 455 may be transmitted by an ONU and includes transmission and ONU identification information. Identification frame 455 may include preamble 453, delimiter 454, and identifier 456. The identifier 456 identifies a specific ONU and may include and ONU ID, and ONU serial number, or another parameter that may be used to identify and associated ONU that transmitted the identification frame. When the OLT receives the identification frame 455, the OLT can determine the ONU that transmitted the identification frame 455.

FIG. 4B depicts an example of internal ONU data flow for an ONU that is erroneously transmitting continuously. Erroneous continuous transmission is not desirable and mitigating an erroneously transmitting ONU is one of the purposes for the disclosed subject matter. FIG. 4B is similar to FIG. 4A except that in FIG. 4B the ONU is erroneously transmitting. In FIG. 4B, the same data and ID frames as in FIG. 4A are present at the electrical interface 410 and the same control signal 430 is provided to the ONU optical module 400. In FIG. 4A, the optical signal passed across the optical interface 420 only included payload data 434A, but in FIG. 4B, due to a failure at the ONU, the ONU optical module causes ID frames 432A-432D to be transmitted across the optical interface 420 as ID frames 438A-438D. Due to the failure at the ONU, control signal 430 does not limit the optical data transmission to payload data 434A. For example, either a failure may exist in the generation of the control signal or a failure may exist in the reception of the control signal at the ONU optical module that causes the ONU to erroneously continuously transmit. The erroneous data transmission shown at timeline 415B includes ID frames 438A-438D. Payload data 434A is passed across the optical interface 420 during time slot 436 as indicated by the control signal at timeline 430A, but ID frames 438A-438D are also transmitted at times outside time slot 436.

FIG. 4C depicts an example of internal ONU data flow for an ONU that is erroneously transmitting intermittently. FIG. 4C is similar to FIGs. 4A and 4B except that in FIG. 4C, the ONU is erroneously transmitting intermittently rather than operating normally or erroneously transmitting continuously. In FIG. 4C, the same data and ID frames as in FIGs. 4A and 4B are present at the electrical interface 410 and the same control signal 430 is provided to the ONU optical module 400. In FIG. 4A, the optical signal passed across the optical interface 420 only included payload data 434A, but in FIG. 4C, due to a failure at the ONU including the ONU optical module 400 causes some of the ID frames 432A-432D to be transmitted across the optical interface 420 as ID frames 438A, 438C, and 438D, but ID frame 432B is not transmitted over optical interface 420. Because some ID frames are erroneously transmitted (438A, 438C, 438D) and some are not (432B) , the erroneous operation in FIG. 4C is intermittent. FIG. 4C depicts an example or intermittent erroneous operation. Any other ID frame may be transmitted or not transmitted in addition to 432B or in addition to 432B when erroneously transmitting intermittently. Due to the failure at the ONU, control signal 430 did not limit the optical data transmission to payload data 434A. In another example, either a failure may exist in the generation of the control signal or a failure may exist in the reception of the control signal at the ONU optical module that causes the ONU to erroneously continuously transmit. The erroneous data transmission shown at timeline 415C includes ID frames 438A, 438C, and 438D. Payload data 434A is passed across the optical interface 420 during time slot 436 as indicated by the control signal at timeline 430A, but ID frames 438A, 438C, and 438D are also transmitted at times outside time slot 436.

FIG. 5A at 502 depicts a timeline showing timeslots assigned to three ONUs and a reset signal 540. In the example of FIG. 5A at 502, ONU1, ONU2, and ONU3 are operating correctly. ONU3 at 510C transmits to the OLT in a first timeslot 520C which starts at time 2 and ends at time 4. The OLT receives the data at 521C in the corresponding timeslot as shown at timeline 550A. ONU1 at 510A transmits to the OLT in a second timeslot 520A which starts at time 5 and ends at time 10. The OLT receives the data at 521A in the corresponding timeslot as shown at timeline 550A. ONU2 at 510B transmits data in timeslot 520B which starts at time 12 and ends at time 15. The OLT receives the data at 521B in the corresponding timeslot as shown at timeline 550A. The data sent by ONU1, ONU2, and ONU3 are received normally as expected. No ONU is transmitting in an incorrect time slot.

FIG. 5A at 502A depicts a timeline showing timeslots assigned to three ONUs with one of the ONUs being rogue and a reset signal 540. In the example of FIG. 5A at 502A, ONU3 at 510C transmits to the OLT in a first timeslot 520C which starts at time 2 and ends at time 4. The OLT receives the data at 521C as shown at timeline 550 in the corresponding timeslot. ONU1 at 510A transmits to the OLT in timeslot 520A which starts at time 5 and ends at time 10 but ONU1 510A erroneously continues to transmit identification frames 530A-530C immediately after timeslot 520A. The data sent by ONU1 to the OLT can be received correctly by ONU1. ONU2 at 510B transmits data in timeslot 520B which starts at time 12 and ends at time 15 but the OLT is not able to detect or receive the data because ONU1 is rogue by transmitting identification frames at the same time as ONU2 is transmitting data. As shown in timeline 550, the data from ONU2 in timeslot 520B cannot be received at the OLT due to the erroneous identification frames 530A-530B transmitted by ONU1 that collide with the data sent by ONU2 in timeslot 520B. Identification frame 530C can be received by the OLT because no signal collides with it. The identity of the faulty or rogue ONU can be determined by the OLT from identification information in the identification frame. In the example of FIG. 5A, the OLT will identify the faulty ONU as ONU1.

As used herein, an ONU that is “faulty” is an ONU that is transmitting in one or more time slots not assigned to it or is otherwise not transmitting correctly. A “faulty” ONU may also be referred to as a “rogue” ONU. The faulty ONU may be in an “erroneous transmission (ET) mode” in that the faulty ONU is operating by transmitting in time slots including one or more time slots not assigned to it. For example, an erroneous transmission mode may be a mode where a faulty ONU transmits continuously during all time slots. In another example, an erroneous transmission mode includes a faulty ONU that is transmitting in time slots not assigned to it but not continuously such as transmitting predictably or consistently but in the wrong time slots, or the faulty ONU may be transmitting intermittently that includes time slots not assigned to it.

In some implementations, the OLT sends a reset signal such as reset signal 540 to an OLT receiver such as an OLT burst mode receiver around the time of the start of each timeslot assigned to any of the ONUs and around the time of the end of each assigned timeslot. Around the time of the start of each timeslot includes a time slightly before the timeslot and a time slightly after the timeslot begins as shown at 541. Slightly before and slightly after the beginning of the timeslot are limited to not affect data reception in the timeslot. For example, slightly before and slightly after the beginning of a time slot or the end of a time slot is between several nanoseconds and tens of nanoseconds. Around the time of the end of each timeslot includes immediately after the end of the timeslot or slightly later. Around the time of the end of each timeslot excludes a time before the timeslot ends to prevent data in the timeslot form being lost as shown at 542. Although not shown in the Figures, the same allowable variation in time positioning of the reset signal applies to each time slot. The reset signal at the end of a time slot may not overlap the reset signal before the beginning of the next time slow. The reset signal at the beginning of a time slot may not extend too far into the time slot in order to not interfere with the preamble of the data frame in the time slot. The reset signal may cause the OLT receiver to quickly prepare to receive upstream data from an ONU. The reset signal before a timeslot allocated to any ONU may resolve any issues preventing the OLT from being ready to receive data from an ONU in the ONU’s allocated timeslot. The reset signal after a timeslot allocated to any ONU prepares the OLT to receive an identification frame that may be present from an ONU that is erroneously transmitting in one or more gaps between time slots assigned to ONUs or in unassigned time slots. For ONUs that are not scheduled to transmit immediately after the reset signal or did not stop sending data at the end of the timeslot, the reset signal ensures the OLT will be prepared to receive an identification frame that may be used to identify which ONU is transmitting erroneously in a time gap or an unassigned timeslot.

In some implementations, the presence of an optical signal during a time period no optical signal is expected may be used as a trigger to indicate to the OLT that one of the ONUs is transmitting at a time when no transmissions should be sent. For example, no transmissions should be sent during a guard period between one assigned time slot and the next time slot. In the example of FIG. 5A at 502A, no optical signal is expected during the guard time 532. Because when all ONUs are operating correctly such as shown at 502, the presence of the optical signal during guard time 532 is indicative of a rogue ONU that is transmitting when it should not be transmitting. The foregoing trigger is indicative of an incorrectly operating ONU but does not in itself indicate which ONU is rogue or operating incorrectly.

The OLT may use one or more techniques to determine which ONU is rogue by transmitting in time slots not assigned to it. In a first technique, the OLT is able to read an identifier sent by the rogue ONU to the OLT. In the example of FIG. 5A at 502A, ONU1 is rogue in that after its allocated timeslot 520A, ONU1 continues to transmit. For example, as shown in FIG. 5A at 502A, ONU1 continues to transmit by sending repeated identification frames 530A-530C. A rogue ONU such as ONU1 may fail and transmit other data instead of, or in addition to, identifier frames 530A-530C. In the example of FIG. 5A at 502A, because the identification frame is longer than the time gap between

timeslot

520A and 520B, the OLT is unable to receive the identification frame of the rogue ONU in the gap. The data in timeslot 520B is not received at the OLT due to the collision between the data transmitted in timeslot 520B and identification frames 530A and 530B. In the example of FIG. 5A, there is no collision or assigned data transmission during identification frame 530C. Accordingly, the OLT is able to receive identification frame 530C and identify that the rogue ONU is ONU1 from the data in the identification frame 530C.

In some example implementations, the OLT may detect and receive identification frames 530 and from the identification frames determine which ONU is transmitting (ONU1 in the example of FIG. 5A at 502A) . Because the OLT has information indicating in which timeslots each ONU should be transmitting, the OLT can determine in FIG. 5A at 502A that ONU1 is rogue because the OLT can determine which ONU is transmitting from the identification frame and that ONU1 is transmitting in a timeslot not allocated to it.

FIG. 5B depicts at 504 a timeline showing timeslots assigned to three ONUs, a reset signal 565A, and a signal detect (SD) signal 563A. The ONUs in FIG. 5B at 504 are operating correctly. In the example of FIG. 5B at 504, the OLT sends reset signal 565A to the OLT receiver before each timeslot assigned to any ONU but not after each time slot assigned to any ONU. In some implementations consistent with FIG. 5B at 504, the OLT may send a reset signal before each timeslot assigned to an ONU and after each time slot assigned to an ONU as in FIG. 5A.

In the example of FIG. 5B at 504, ONU1 at 510A transmits to the OLT in timeslot 552A which starts at time 5 and ends at time 10. The OLT receives the data as shown at timeline 567A in the corresponding timeslot 569A. ONU3 at 510C transmits to the OLT in timeslot 552C which starts at time 2 and ends at time 4. The OLT receives the data as shown at timeline 567A in the corresponding timeslot 569C. ONU2 at 510B transmits data in timeslot 552B which starts at time 12 and ends at time 15. The OLT receives the data as shown at timeline 567A in the corresponding timeslot 569B.

In FIG. 5B at 504, an OLT signal detection (SD) signal is shown at 563A. The SD signal indicates whether optical power is present on the uplink fiber from any of the ONUs. For example, the SD signal may be a logical one when optical power is present ( “power present state” ) and a logical zero when not present ( “no power state” ) , or alternatively a logical zero when optical power is present and a logical one when not present. The SD signal switches to the no optical power state when no optical power is present or when the reset signal is sent by the OLT to the OLT receiver and remains in the no power state until optical power is detected. In the example of FIG. 5B at 504, because no ONU is transmitting between time 0 to time 2, in the power present state between time 2 and time 4 while ONU3 is transmitting, in the no power state from after ONU3 finishes transmitting to when ONU1 starts transmitting at time 5 and completes transmitting at time 10, in the no power present state between after ONU1 finishes transmitting at time 10 and ONU2 starts transmitting at time 12 and completes transmitting at time 15, and in the no power state after ONU2 completes transmitting. As used herein, “just before” or “just after” means a short time period compared to a time slot.

In some commercial gigabit passive optical networks (GPON) , 10-gigabit passive optical networks (XGPON or 10GPON) systems, a signal detect, or an “SD” signal, indicates whether an optical signal is present on an optical fiber. A “low” logic state means no signal is present and a “high” logical state means an optical signal is present. The SD may be initially set to low and switched to high when an optical signal is received. The SD signal may be switched to low again upon receiving a reset signal after which the process repeats.

In some commercial Ethernet passive optical networks (EPON) , 10 gigabit Ethernet passive optical network (10G-EPON) , a loss of signal, or “LOS” signal, indicates a “loss of optical signal. ” A “high” logic state means that no optical signal is present, and a “low” logic state means an optical signal is present. In some implementations, an initial state of the LOS signal is set to “high. ”

FIG. 5B at 504A depicts a timeline showing timeslots assigned to three ONUs with one of the ONUs being rogue, a reset signal, and an SD signal. In the example of FIG. 5B at 504A, the OLT sends a reset signal 565 to the OLT receiver before each timeslot assigned to an ONU but not after each time slot assigned to an ONU. In some implementations consistent with FIG. 5B at 504A, the OLT may send a reset signal before each timeslot assigned to an ONU and after each time slot assigned to an ONU as in FIG. 5A.

In the example of FIG. 5B at 504A, ONU1 at 510A transmits to the OLT in timeslot 552A which starts at time 5 and ends at time 10. The OLT receives the data as shown at timeline 567 in the corresponding timeslot 569A. ONU3 at 510C attempts to transmit to the OLT in timeslot 552C which starts at time 2 and ends at time 4 but is corrupted or unusable due to ONU1 510A continuing to transmit before timeslot 552A. ONU2 at 510B attempts to transmit data in timeslot 552B which starts at time 12 and ends at time 15 but the OLT is not able to detect or receive the data because ONU1 is rogue by transmitting a signal at the same time that ONU2 is transmitting data. As shown in timeline 567, the data from ONU2 in timeslot 552B and the data sent by ONU3 in timeslot 552C are not received by the OLT.

An OLT SD signal is shown at 563. The SD signal indicates whether optical power is present on the uplink fiber from the ONUs. For example, the SD signal may indicate a power present state or a no power state as described above. In the example of FIG. 5B at 504A, if ONU1 was operating correctly by transmitting only in time slot 552A, the SD signal would be in the no power state from time 0 to time 2 when ONU3 is scheduled to transmit data, in the power present state between

times

2 and 4, in the no power state between after the ONU3 finishes transmitting data and time 5 when ONU1 is scheduled to transmit data, in the power present state between time 5 and time 10, in the no power state between time 10 and time 12 when ONU2 is scheduled to transmit data, in the power present state between time 12 and time 15, and in the no power state after time 15. But instead being in the foregoing states at the corresponding times, the SD signal 563 is in the power present state for all the times except when the reset signal is sent. This is because ONU1 is rogue and continuously transmitting. The SD signal can be used to determine the presence of a rogue ONU such as ONU1 in FIG. 5B at 504A because the SD signal is not in the expected state at corresponding times. For example, if the SD signal is in the power present state during an unassigned timeslot, then a rogue ONU is transmitting. In another example of use of the SD signal, if the SD signal is in the power present state during an assigned timeslot, but the OLT cannot decode any data in the timeslot, then the optical signal from the assigned ONU may be being interfered with by a rogue ONU. In some implementations, which ONU is rogue may be determined by which ONU’s data is detected and received. The ONU whose data is detected and received may be the rogue ONU.

Similar to FIG. 5B at 504, FIG. 5C at 506 depicts ONU1-ONU3 assigned to the same time slots as in FIG. 5B at 504 and 504A. ONU1-ONU3 in 506 are operating correctly. FIG. 5C at 506 includes loss of signal (LOS) indication 570A. The LOS signal indicates whether optical power is present on the uplink fiber from the ONUs. For example, the LOS indication 570A signal may be a logical zero when optical power is present ( “power present state” ) and a logical one when not present ( “no power state” ) , or alternatively a logical one when optical power is present and a logical zero when not present. In the example of FIG. 5C at 506, ONU1 in the no power state from time 0 to time 2 when ONU3 is scheduled to transmit data, in the power present state between time 2 and time 4, in the no power state between after the ONU3 finishes transmitting data at time 4 and time 5 when ONU1 is scheduled to transmit data, in the power present state between time 5 and time 10, in the no power state between after the ONU1 finishes transmitting data at time 10 and time 12 when ONU2 is scheduled to transmit data, in the power present state between time 12 and time 15, and in the no power state just after time 15 after the ONU2 finishes transmitting data. As used herein, “just before” or “just after” means a short time period compared to a time slot.

FIG. 5C at 506A depicts ONU1-ONU3 assigned to the same time slots as in FIG. 5C at 506. At 506A, ONU1 is rogue by transmitting continuously. FIG. 5C at 506A includes loss of signal (LOS) indication 570. The LOS signal indicates whether optical power is present on the uplink fiber from the ONUs as described above. In the example of FIG. 5C at 506A, if ONU1 was operating correctly by transmitting only in time slot 552A and ONU2 and ONU3 are operating correctly, the LOS signal would be as shown in 570A but since ONU1 is rogue, the LOS signal is in the optical power present state continuously because ONU1 is transmitting continuously. The LOS signal can be used to determine the presence of a rogue ONU such as ONU1 in FIG. 5C at 506A because the LOS signal is not in the expected state at corresponding times such as before 552C, in the time gaps between

slot

552C and 552A and between

slot

552A and 552B, and after slot 552B. For example, if the LOS signal is in the power present state during an unassigned timeslot, then a rogue ONU is transmitting. In another example of use of the LOS signal, if the LOS signal is in the power present state during an assigned timeslot, but the OLT cannot decode any data in the timeslot, then the optical signal from the assigned ONU may be being interfered with by a rogue ONU. In some implementations, which ONU is rogue may be determined by which ONU’s data is detected and received. The ONU whose data is detected and received may be the rogue ONU.

In some example implementations, instead of a binary no power state or power present state for an SD signal and/or LOS signal, the optical power may be measured over a range. For example, an optical power measurement device such as a photodiode or other photoelectric device may provide a signal that is digitized to provide a digital representation of the power level being carried on the fiber to the OLT. For example, the optical power may be digitized by a 16-bit analog-to-digital converter (ADC) or an ADC with a different resolution. Then, instead of, or in addition to, a power present state and a no power state, a power level such the power levels shown in the example of FIG. 6B may be determined at the OLT.

After the OLT has determined that an ONU is rogue, the OLT may send a message to disable the rogue ONU. For example, the message may include a Disable_Serial_Number physical layer operations, administration, and maintenance (PLOAM) message detailed in Table 1 of FIG. 8. Generally, a rogue ONU that is transmitting uplink signals that it should not be transmitting can still receive downlink signals including commands. Without loss of generality, the following will use the example of FIG. 6 for illustration. Normally the Disable_Serial_Number PLOAM message will disable ONU1 (FIG. 5A) . The OLT may send a PLOAM messages to all the other ONUs for dynamic bandwidth allocation (DBA) such as ONU2 and ONU3 in FIG. 6. Operation may then resume for all functioning ONUs.

If the Disable_Serial_Number PLOAM message cause the rogue ONU to recover to normal functioning, an Emergency_Stop message may be sent by the OLT to the rogue ONU. The Emergency_Stop message may cause the ONU to stop transmitting. In some implementations, an ONU optical module may support disabling the power to the transmitter in a revised PLOAM message such as an Optical_Power_Disable message. The Optical_Power_Disable message may be used to isolate the rogue ONU and stop it from interfering with transmissions from properly functioning ONUs. The Optical_Power_Disable message may cause the electrical power to the rogue ONU optical transmitter to be turned-off or disabled. For example, an electrical power supply supplying power to a laser diode used to generate the optical transmissions may be turned-off via a switch configured to remove electrical power from the laser diode or disabled via an electrical disable input or by removing an electrical enable input, or other method of disabling electrical power. In some implementations, the OLT may send a signal to cause the rogue ONU to reboot which may cause the rogue ONU to recover upon rebooting. If none of the foregoing cause the rogue ONU to return to normal functioning, power to the entire ONU may be shut down via a Power_Down command. In some implementations, the order of methods used to attempt to return a rogue ONU to normal functioning may be: Disable_Serial_Number, Emergency_Stop, Reboot, Optical_Power_Disable, Power_Down.

FIG. 6A depicts another example of an optical network. Similar to FIG. 1, FIG. 6A includes OLT 610 and ONU1-ONU3. The interference caused by a continuously transmitting ONU will be more or less severe depending on the relative fiber lengths or attenuation from the OLT to the ONUs that are being interfered with. In the illustrative example shown in FIG. 6A, fiber 625A connecting ONU1 at 630A to splitter 620 is the longest (or has the largest path loss) , fiber 625C connecting ONU3 at 630C to splitter 620 is the second longest (or has the second largest path loss) , and fiber 625B connecting ONU2 at 630B to splitter 620 is the shortest (or has the smallest path loss) . In this illustrative example, if each of the ONUs 630A-630C have the same optical transmit power, the optical signal power received at the OLT 610 from ONU2 at 630B will be the largest, the optical signal power received at the OLT 610 from ONU3 at 630C will be the second largest, and the optical signal power received at the OLT 610 from ONU1 at 630AC will be the smallest. As such, the interference if an ONU becomes rogue will be largest if the rogue ONU is 630B, next largest if the rogue ONU is ONU3, least if the rogue ONU is ONU1. Depending on the relative length of fibers 625A-625C, the interference will be larger or smaller. In some cases where the rogue ONU is much farther away (or a much greater path loss) than the non-rogue ONUs, the interference may be considered additional noise where the OLT may still be able to detect and receive the non-rogue ONU’s signals. In other cases, where fiber corresponding to the rogue ONU has a shorter length (or less path loss) than the non-rogue ONUs, the interference will be greater in which case the OLT will not be able to detect and receive the signals from the other ONUs.

FIG. 6B depicts examples of power received at an OLT from eight different ONUs. In this example, the OLT receives -8 dBm from ONU1 640A, -10 dBm from ONU2 640B, -14 dBm from ONU3 640C, -16 dBm from ONU4 640D, -20 dBm from ONU5 640E, -22 dBm from ONU6 640F, -23 dBm from ONU7 640G, and -28 dBm from ONU8 640H. The example of FIG. 6B can be used to illustrate three scenarios: where the power received at the OLT from the rogue ONU is greater than the power received from each of the other ONUs, where the power received at the OLT from the rogue ONU is greater than the power received from some of the other ONUs and less than others, and where the power received at the OLT from the rogue ONU is less than the power received from each of the other ONUs. In an example of the first scenario, if ONU1 in FIG, 6B is the rogue ONU, the power received from ONU1 is higher than the other ONUs which will cause interference such that the OLT cannot decode signals from the ONUs 2-8. In an example of the second scenario, if ONU4 is the rogue ONU, the power received from ONU4 is less than the powers received from ONUs 1-3, and greater than the powers received from ONUs 5-8. The OLT may be able to decode signals from ONUs 1-2 (higher power than ONU4) , may not be able to decode signals from ONU3 (power level comparable to ONU4) , and cannot decode signals from ONU5-ONU8 (lower power than ONU4) . In an example of the third scenario, if ONU8 is the rogue ONU, the power received from ONU8 is much lower than from ONUs 1-7. In this case, because the power received form ONU8 is low, the interference may act as added noise to the signals from ONUs 1-7 and the OLT can still decode signals from ONUs 1-7.

In some implementations, a rogue ONU may be identified by determining which ONU corresponds to the lowest power signal that can be decoded. The identification process may include the OLT sending bandwidth allocations to the ONUs. The OLT detects optical power in the assigned time slots for all of the ONUs. The OLT may decode signals from some of the ONUs, but not all of the ONUs. The OLT measures the received optical power in time slots corresponding to each ONU. The ONU corresponding to the lowest received power that the OLT can decode may be identified as the continuous-mode rogue ONU.

In some implementations, a rogue ONU may be identified by determining which ONU corresponds to the lowest power signal among the ONUs in which the OLT received power is unchanged. The identification process may include the OLT sending bandwidth allocations to the ONUs. The OLT may detect optical power in the assigned time slots for all of the ONUs. The OLT may measure the received optical power in time slots corresponding to each ONU. The OLT may determine that one or more ONUs are faulty based on a power change detected in a first ONU’s assigned time slot and the data in the first ONU’s time slot cannot be decoded. For example, the OLT may detect an increase in power compared to an earlier transmission from the first ONU in the time slot assigned to the first ONU. Normally, an increase in power would increase the likelihood of the OLT being able to decode the signal, but if the added power is from a rogue ONU that is transmitting in a slot not assigned to it, the slot assigned to the first ONU, then the OLT would be less likely to be able to decode the signal due to the interference from the rogue ONU. The OLT can save the measured received powers from each ONU, and the OLT can check the power values against values from previous measurement of each ONU that are stored in memory. The ONU with the lowest unchanged power value may be identified as the continuous-mode rogue ONU.

In some implementations, a rogue ONU may be identified by comparing the power received at the OLT in time slots to the power received in time gaps. Identifying a rogue ONU may include the OLT sending bandwidth allocations to the ONUs. The OLT may determine the received optical power at the assigned time slot for each ONU and in the time gaps. The OLT can compare the power value from each ONU to the power values in the time gaps. The ONU with a power value that is the same as the power value of time gaps may be identified as the rogue ONU. For example, a rogue ONU that is continuously transmitting sets a floor to the power level, or a lowest power level, that will be measured by the OLT because if any other ONU transmits a signal, the power in a corresponding time slot will be the sum of the power from the rogue ONU and the power transmitted from the other ONU.

FIG. 7J depicts a method performed at an OLT, in accordance with some example embodiments. At 702, the method includes assigning, by an optical line terminal (OLT) operating in a time-division multiple access (TDMA) system in which transmissions from different optical network units (ONUs) to the OLT are organized in time slots separated by time gaps, different time slots to the different ONUs for optical transmission by the different ONUs to the OLT. At 704, the method includes transmitting a reset signal before each of the different time slots and following each of the different time slots. In some embodiments, such as in some EPON and 10G-EPON systems, the reset signal may not be used. At 706, the method includes determining an optical signal power received in each time gap. In some embodiments an optical signal power received in each time slot may be determined. At 708, the method includes determining, based on optical signal power received in each time gap, whether one or more of the different ONUs in the TDMA system are faulty.

FIG. 7A depicts a method performed at an OLT, in accordance with some example embodiments. At 712, the method includes assigning, by an optical line terminal (OLT) operating in a time-division multiple access (TDMA) system in which transmissions from different optical network units (ONUs) to the OLT are organized in time slots separated by time gaps, different time slots to the different ONUs for optical transmission by the different ONUs to the OLT. At 714, the method further includes transmitting a reset signal before each of the different time slots and following each of the different time slots. At 716, the method includes identifying a faulty ONU from the different ONUs by receiving an identification frame from the faulty ONU in one or more incorrect time slots not assigned to the faulty ONU or in one or more of the time gaps.

FIG. 7B depicts a method performed at an OLT, in accordance with some example embodiments. At 722, the method includes assigning, by an optical line terminal (OLT) operating in a time-division multiple access (TDMA) system in which transmissions from different optical network units (ONUs) to the OLT are organized in time slots separated by time gaps, different time slots to the different ONUs for optical transmission by the different ONUs to the OLT. At 724, the method includes transmitting a reset signal before each of the different time slots and following each of the different time slots. At 726, the method includes receiving an upstream signal and decoding data from the upstream signal. At 728, the method includes determining whether an identification frame from a first ONU of the different ONUs is included in the decoded data in a time slot not assigned to the first ONU, wherein in a case that the decoded data includes an identification frame, the identification frame identifies a faulty ONU, and wherein in another case that the data does not include an identification frame, none of the different ONUs are faulty.

FIG. 7C depicts a method performed at an OLT, in accordance with some example embodiments. At 1722, the method includes assigning, by an optical line terminal (OLT) operating in a time-division multiple access (TDMA) system in which transmissions from different optical network units (ONUs) to the OLT are organized in time slots separated by time gaps, different time slots to the different ONUs for optical transmission by the different ONUs to the OLT. At 1726, the method includes receiving an upstream signal and decoding data from the upstream signal. At 1728, the method includes determining, whether a rouge ONU identification frame is included in the decoded data, wherein a rouge behavior flag included in the rouge ONU identification frame identifies a faulty ONU from the different ONUs.

Rogue Identification frame 459 may be transmitted by an ONU and includes transmission and ONU identification information. Identification frame 459 may include preamble 453, delimiter 454, identifier 456, and rogue behavior flag 457. The identifier 456 identifies a specific ONU and may include and ONU ID, and ONU serial number, or another parameter that may be used to identify and associated ONU that transmitted the identification frame. When the OLT receives the identification frame 455, the OLT can determine the ONU that transmitted the identification frame 455. The rogue behavior flag indicates that the ONU transmitting the rogue identification frame 455 acknowledges that the ONU is transmitting in a slot not assigned to

For an ONU, the ONU TC transmit data frame to the ONU optical module at the time slot assigned by OLT and transmit rouge ONU identification frames at the other time slots not assigned to the ONU. The control signal 430 turns on the ONU optical module 400 at the time slot assigned to the ONU and transmits optical signals to OLT. The control signal 430 turns off the ONU optical module 400 at the other time that not assigned to the ONU. If the ONU is an ET ONU, the ONU optical module may be uncontrollable by the control signal 430 and can transmit optical signals at any time.

FIG. 7D depicts a method performed at an ONU, in accordance with some example embodiments. At 732, the method includes receiving, by an ONU from an OLT, at least one assigned time slot reserved for transmissions from the ONU. At 734, the method includes transmitting, by the ONU, optical signals in the at least one assigned time slot, wherein the ONU also transmits in one or more incorrect time slots not assigned to the ONU. At 726, the method includes receiving, by the ONU from the optical line terminal, a message causing the ONU to stop transmitting in the one or more time slots not assigned to the ONU and to return to normal operation.

FIG. 7E depicts a method performed at an ONU, in accordance with some example embodiments. FIG. 7E also refers to FIG. 4A. At 742, the method includes receiving, by an ONU from an OLT at least one assigned time slot reserved for optical transmissions from the ONU. At 744, the method includes transmitting, by the ONU, an identification frame in one or more time slots not assigned to the ONU, or transmitting the identification frame in one or more time gaps, or transmitting the identification frame in both the one or more time slots not assigned to the ONU and in the one or more time gaps, and transmitting data in the at least one assigned time slot. Due to the failure at the ONU, control signal 430 may not limit the optical data transmission to payload data 434A. For example, either a failure may exist in the generation of the control signal or a failure may exist in the reception of the control signal at the ONU optical module that causes the ONU to erroneously continuously transmit

FIG. 7F depicts methods performed to cause a faulty ONU to return to normal operation, in accordance with some example embodiments. At 750 is a method performed at an OLT and at 755 is a method performed at an ONU. At 752, the method includes determining, by an OLT that an ONU is a faulty ONU. For example, of the methods described in this patent document can be used to determine whether an ONU is faulty. At 754, the method includes transmitting, by the OLT to the faulty ONU, a message causing the faulty ONU to stop transmitting in one or more time slots not assigned to the faulty ONU causing the faulty ONU to return to normal operation. The method shown at 755 for the ONU includes at 757 receiving, by a faulty ONU from an OLT, a message causing the faulty ONU to stop transmitting in one or more time slots not assigned to the faulty ONU. At 759, the method includes returning, by the faulty ONU, to normal operation that is not faulty.

FIG. 7G depicts a method performed at an OLT, in accordance with some example embodiments. At 762, the method includes assigning, by an optical line terminal (OLT) operating in a time-division multiple access (TDMA) system in which transmissions from different optical network units (ONUs) to the OLT are organized in time slots separated by time gaps, different time slots to the different ONUs for optical transmission by the different ONUs to the OLT. At 764, the method includes identifying a faulty ONU from the different ONUs based on optical signals received from the different ONUs. At 766, the method includes transmitting a physical layer operations, administration, and maintenance (PLOAM) message to disable the faulty ONU.

FIG. 7H depicts a method performed at an OLT, in accordance with some example embodiments. At 772, the method includes assigning, by an optical line terminal (OLT) , different time slots to N different optical network units for data transmission by the N different optical network units (ONUs) in a time domain multiple access (TDMA) system, wherein N is an integer greater than one. At 774, the method includes determining, during a time interval that the OLT is unable to successfully decoded optical transmissions received from (N-M) ONUs in corresponding time slots while the OLT is able to successfully decode optical transmissions received from a remaining M ONUs in corresponding time slots. At 776, the method includes concluding based on the determining, that one of the remaining M ONUs is a faulty ONU operating in an erroneous transmission (ET) mode, wherein the faulty ONU has a lowest received power among the M ONUs.

FIG. 7I depicts a method performed at an OLT, in accordance with some example embodiments. At 782, the method includes assigning, by an optical line terminal, different time slots to different optical network units for data transmission by the different optical network units in a time domain multiple access (TDMA) system. At 784, the method includes generating a binary signal indicating whether an optical input power is present. For example, the binary signal may indicate whether the optical input power is above a first threshold, wherein the binary signal is in a “power present” state when the optical input power is above the first threshold. The binary signal may be in a “no power” state when the optical input power is below, or equal to, a second threshold. The value of the first threshold may be equal to the value of the second threshold or may be lower than the second threshold value. At 786, the method includes determining, based on the binary signal, whether the optical input power is above the threshold in the different time slots and at least one other time slot, wherein in a case that the binary signal indicates the optical input power is above the threshold only in the different time slots, then no optical network unit is continuously transmitting, and in another case that the binary signal indicates the optical input power is above the threshold in the other time slot in addition to the different time slots, then a faulty ONU is in an erroneous transmission (ET) mode. At 788, the method includes determining the faulty ONU to be one of the different optical network units with a lowest received optical power that is decoded by the optical line terminal.

In some implementations a method may include assigning, by an optical line terminal, different time slots to different optical network units for data transmission by the different optical network units in a time domain multiple access (TDMA) system. The method may further include generating a binary signal indicating whether an optical input power is within an expected range of optical power. The expected range of optical power may change for the different ONUs and corresponding time slots assigned to the different ONUs. For example, closer ONUs may correspond to a higher expected optical input power and ONUs that are farther away may correspond to a lower expected optical input power. The expected range of optical power for an unassigned slot or for the gaps between slots may be at, or close to, the thermal noise limit (very low power) . The binary signal may indicate whether the optical input power is within the expected range on a per slot basis. In one state, the binary signal indicates that the optical input power is within the expected range and in the other state the binary signal indicates that the optical input power is out of range. In this way ONUs that are erroneously transmitting in unassigned slots or ONUs that are transmitting at an unexpected optical power can be identified. Additional steps described above may also be included. The method further includes determining a faulty ONU to be one of the different optical network units that is transmitting in a time slot not assigned to it or in one or more gaps between time slots.

FIG. 8 shows Table 1 with some example details of a Disable_Serial_Number PLOAM message.

FIG. 9 depicts an apparatus, in accordance with some example embodiments. The description of FIG. 9 also refers to FIGs. 1, 2, 3A, 3B, 4A, 4B, 4C, 5A, 5B, 5C, 6A, 6B, 7A, 7B, 7C, 7D, 7E, 7F, 7G, 7H, 7I, and 8.

Operations and management of the disclosed optical network unit such as optical network units 130A-130C and OLT 110 may include an apparatus such as 900. In an optical network unit, apparatus 900 may perform one or more of the processes described with respect to FIGs. 1, 2, 3A, 3B, 4A, 4B, 4C, 5A, 5B, 5C, 6A, 6B, 7A, 7B, 7C, 7D, 7E, 7F, 7G, 7H, 7I, and 8. Apparatus 900 may also perform other status and control functions and include interfaces to other devices. FIG. 9 at 900 is a block diagram of a computing system, consistent with various embodiments such as the OLT and/or ONU described above.

The apparatus 900 may include one or more central processing units ( “processors” ) 905, memory 910, input/output devices 925 (e.g., keyboard and pointing devices, display devices) , storage devices 920 (e.g., disk drives) , and network adapter (s) 930 (e.g., network interfaces) that are connected to an interconnect 915. Apparatus 900 may further include optical devices 940 including one or more of lasers, detectors, semiconductor amplifiers, and other optical and optoelectronic components. Optical devices 940 may connect to an optical line terminal, optical network unit via one or more fibers 945. The interconnect 915 is illustrated as an abstraction that represents any one or more separate physical buses, point to point connections, or both connected by appropriate bridges, adapters, or controllers. The interconnect 915, therefore, may include, for example, a system bus, a Peripheral Component Interconnect (PCI) bus or PCI-Express bus, a HyperTransport or industry standard architecture (ISA) bus, a small computer system interface (SCSI) bus, a universal serial bus (USB) , IIC (I2C) bus, or an Institute of Electrical and Electronics Engineers (IEEE) standard 1394 bus, also called “Firewire” .

The memory 910 and storage devices 920 are computer-readable storage media that may store instructions that implement at least portions of the described technology. In addition, the data structures and message structures may be stored or transmitted via a data transmission medium, such as a signal on a communications link. Various communications links may be used, such as the Internet, a local area network, a wide area network, or a point-to-point dial-up connection. Thus, computer-readable media can include computer-readable storage media (e.g., "non-transitory" media) and computer-readable transmission media.

The instructions stored in memory 910 can be implemented as software and/or firmware to program the processor (s) 905 to carry out actions described above. In some embodiments, such software or firmware may be initially provided to the apparatus 900 by downloading it from a remote system through the apparatus 900 (e.g., via network adapter 930 or optical devices 940) .

In accordance with the disclosed technology, an OLT may include an optical receiver configured to determine an optical power received in each of a plurality of time slots, wherein each of the plurality of time slots corresponds to one of a plurality of optical network units; and a processor and memory including executable instructions that when executed perform at least: determining decoded data in one or more of the plurality of time slots; and determining a lowest optical power received in one of the plurality of time slots compared to other of the plurality of time slots, wherein data is decoded at the lowest optical power received, and wherein a faulty ONU from the plurality of optical network units corresponds to the one of the plurality of time slots, and wherein the faulty ONU is in an erroneous transmission (ET) mode. The OLT may further be configured to implement methods described herein, e.g., FIGS. 7A-7J.

The above description and drawings are illustrative and are not to be construed as limiting. Numerous specific details are described to provide a thorough understanding of the disclosure. However, in some instances, well-known details are not described in order to avoid obscuring the description. Further, various modifications may be made without deviating from the scope of the embodiments. Accordingly, the embodiments are not limited except as by the appended claims.

Reference in this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but not for other embodiments.

The terms used in this specification generally have their ordinary meanings in the art, within the context of the disclosure, and in the specific context where each term is used. Terms that are used to describe the disclosure are discussed below, or elsewhere in the specification, to provide additional guidance to the practitioner regarding the description of the disclosure. For convenience, some terms may be highlighted, for example using italics and/or quotation marks. The use of highlighting has no influence on the scope and meaning of a term; the scope and meaning of a term is the same, in the same context, whether or not it is highlighted. It will be appreciated that the same thing can be said in more than one way. One will recognize that “memory” is one form of a “storage” and that the terms may on occasion be used interchangeably.

Consequently, alternative language and synonyms may be used for any one or more of the terms discussed herein, nor is any special significance to be placed upon whether or not a term is elaborated or discussed herein. Synonyms for some terms are provided. A recital of one or more synonyms does not exclude the use of other synonyms. The use of examples anywhere in this specification including examples of any term discussed herein is illustrative only, and is not intended to further limit the scope and meaning of the disclosure or of any exemplified term. Likewise, the disclosure is not limited to various embodiments given in this specification.

Without intent to further limit the scope of the disclosure, examples of instruments, apparatus, methods and their related results according to the embodiments of the present disclosure are given below. Note that titles or subtitles may be used in the examples for convenience of a reader, which in no way should limit the scope of the disclosure. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In the case of conflict, the present document, including definitions will control.

The disclosed and other embodiments, modules and the functional operations described in this document can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this document and their structural equivalents, or in combinations of one or more of them. The disclosed and other embodiments can be implemented as one or more computer program products, i.e., one or more modules of computer program instructions encoded on a computer readable medium for execution by, or to control the operation of, data processing apparatus. The computer readable medium can be a machine-readable storage device, a machine-readable storage substrate, a memory device, a composition of matter effecting a machine-readable propagated signal, or a combination of one or more them. The term “data processing apparatus” encompasses all apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, or multiple processors or computers. The apparatus can include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, or a combination of one or more of them. A propagated signal is an artificially generated signal, e.g., a machine-generated electrical, optical, or electromagnetic signal, that is generated to encode information for transmission to suitable receiver apparatus.

A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit suitable for use in a computing environment. A computer program does not necessarily correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document) , in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code) . A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.

The processes and logic flows described in this document can be performed by one or more programmable processors executing one or more computer programs to perform functions by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit) .

Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer. Generally, a processor will receive instructions and data from a read only memory or a random-access memory or both. The essential elements of a computer are a processor for performing instructions and one or more memory devices for storing instructions and data. Generally, a computer will also include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks. However, a computer need not have such devices. Computer readable media suitable for storing computer program instructions and data include all forms of non-volatile memory, media and memory devices, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto optical disks; and CD ROM and DVD-ROM disks. The processor and the memory can be supplemented by, or incorporated in, special purpose logic circuitry.

While this patent document contains many specifics, these should not be construed as limitations on the scope of an invention that is claimed or of what may be claimed, but rather as descriptions of features specific to particular embodiments. Certain features that are described in this document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or a variation of a sub-combination. Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results.

Only a few examples and implementations are disclosed. Variations, modifications, and enhancements to the described examples and implementations and other implementations can be made based on what is disclosed.

Claims

A method of digital communication, comprising:

assigning, by an optical line terminal (OLT) , different time slots to N different optical network units for data transmission by the N different optical network units (ONUs) in a time domain multiple access (TDMA) system, wherein N is an integer greater than one;

determining, during a time interval that the OLT is unable to successfully decoded optical transmissions received from (N-M) ONUs in corresponding time slots while the OLT is able to successfully decode optical transmissions received from a remaining M ONUs in corresponding time slots; and

concluding based on the determining, that one of the remaining M ONUs is a faulty ONU operating in an erroneous transmission (ET) mode, wherein the faulty ONU has a lowest received power among the M ONUs.
The method of claim 1, further comprising:

sending, by the OLT, bandwidth allocations to the N different optical network units.
A method of digital communication, comprising:

assigning, by an optical line terminal (OLT) , different time slots to different optical network units (ONUs) for data transmission by the different ONUs in a time domain multiple access (TDMA) system;

sending, by the optical line terminal (OLT) , bandwidth allocations to the different ONUs;

determining an optical power in each time slot assigned to the different ONUs; and

detecting a power change in a first assigned time slot between a previous first optical power and a first optical power associated with a first ONU, wherein the detecting the power change indicates a faulty ONU is transmitting to the OLT.
The method of claim 3, further comprising:

transmitting a control message to disable the faulty ONU.
The method of claim 4, wherein the control message is a physical layer operations, administration, and maintenance (PLOAM) message.
The method of claim 4, wherein the control message is one of:

a Disable_Serial_Number message causing the disabling of a particular optical network unit identified by Disable_Serial_Number message,

an Optical_Power_Disable message causing the faulty ONU to turn-off an electrical power supplied to an optical device to stop the optical device from transmitting,

a message causing the faulty ONU to reboot,

another message causing the faulty ONU to power down, or

an Emergency_Stop message causing the faulty ONU to stop transmitting.
The method of claim 4, wherein attempts to return the faulty ONU to normal operation follow an order from first attempt to last attempt, wherein the order includes:

a Disable_Serial_Number PLOAM message,

an Emergency_Stop PLOAM message,

a reboot message,

an Optical_Power_Disable PLOAM message, and

a Power_Down message.
The method of claim 3, wherein the faulty ONU transmits continuously.
A method of digital communication, comprising:

assigning, by an optical line terminal (OLT) , different time slots to different optical network units (ONUs) for data transmission by the different ONUs in a time domain multiple access (TDMA) system;

sending, by the optical line terminal (OLT) , bandwidth allocations to the different ONUs;

determining time slot optical powers for each time slot assigned to the different ONUs and a time gap optical powers for each time gap between the time slots;

comparing the time gap optical powers to the time slot optical powers, wherein a first optical power in a first time slot assigned to a first ONU being equal to one or more of the time gap optical powers indicates that the first ONU is a faulty ONU.
The method of claim 9, further comprising:

transmitting a control message to disable the faulty ONU.
The method of claim 10, wherein the control message is a physical layer operations, administration, and maintenance (PLOAM) message.
The method of claim 10, wherein the control message is one of:

a Disable_Serial_Number message causing the disabling of a particular optical network unit identified by Disable_Serial_Number message,

an Optical_Power_Disable message causing the faulty ONU to turn-off an electrical power supplied to an optical device to stop the optical device from transmitting,

a message causing the faulty ONU to reboot,

another message causing the faulty ONU to power down, or

an Emergency_Stop message causing the faulty ONU to stop transmitting.
The method of claim 10, wherein attempts to return the faulty ONU to normal operation follow an order from first attempt to last attempt, wherein the order includes:

a Disable_Serial_Number PLOAM message,

an Emergency_Stop PLOAM message,

a reboot message,

an Optical_Power_Disable PLOAM message, and

a Power_Down message.
The method of claim 8, wherein the faulty ONU transmits continuously.
A method of digital communication, comprising:

assigning, by an optical line terminal (OLT) , different time slots to different optical network units (ONUs) for data transmission by the different optical network units in a time domain multiple access (TDMA) system;

generating a binary signal indicating whether an optical input power is present;

determining, based on the binary signal, whether the optical input power is above a threshold in the different time slots and at least one other time slot, wherein in a case that the binary signal indicates the optical input power is above the threshold only in the different time slots, then no optical network unit is continuously transmitting, and in another case that the binary signal indicates the optical input power is above the threshold in the other time slot in addition to the different time slots, then a faulty ONU is in an erroneous transmission (ET) mode; and

determining the faulty ONU to be one of the different ONUs with a lowest optical input power that is decoded by the OLT.
The method of claim 15, wherein the binary signal is in a power present state when the optical input power is above a first threshold value and in a no power state when the optical input power is below, or equal to, a second threshold value.
The method of claim 16, wherein the first threshold value is equal to the second threshold value or is less than the second threshold value.
The method of claim 15, further comprising:

sending a reset signal, wherein the reset signal causes the binary signal to return to the no power state until the reset signal is deactivated and optical input power is above the first threshold.
The method of claim 15, further comprising:

transmitting a control message to disable the faulty ONU.
The method of claim 19, wherein the control message is a physical layer operations, administration, and maintenance (PLOAM) message.
The method of claim 19, wherein the control message is one of:

a Disable_Serial_Number PLOAM message causing the disabling of a particular optical network unit identified by Disable_Serial_Number PLOAM message,

an Optical_Power_Disable PLOAM message causing the faulty ONU to turn-off an electrical power supplied to an optical device to stop the optical device from transmitting,

a message causing the faulty ONU to reboot,

another message causing the faulty ONU to power down, or

an Emergency_Stop PLOAM message causing an identified optical network unit to stop transmitting.
The method of claim 19, wherein attempts to return the faulty ONU to normal operation follow an order from first attempt to last attempt, wherein the order includes:

a Disable_Serial_Number PLOAM message,

an Emergency_Stop PLOAM message,

a reboot message,

an Optical_Power_Disable PLOAM message, and

a Power_Down message.
The method of claim 15, wherein the faulty ONU transmits continuously.
An optical line terminal apparatus for digital communication, comprising:

an optical receiver configured to determine an optical power received in each of a plurality of time slots, wherein each of the plurality of time slots corresponds to one of a plurality of optical network units; and

a processor and memory including executable instructions that when executed perform at least:

determining decoded data in one or more of the plurality of time slots; and

determining a lowest optical power received in one of the plurality of time slots compared to other of the plurality of time slots, wherein data is decoded at the lowest optical power received, and wherein a faulty ONU from the plurality of optical network units corresponds to the one of the plurality of time slots, and wherein the faulty ONU is in an erroneous transmission (ET) mode.
[Rectified under Rule 91, 29.05.2020]

The apparatus of claim 24, wherein the executable instructions further perform at least:

sending bandwidth allocations to the plurality of optical network units.
[Rectified under Rule 91, 29.05.2020]

The apparatus of claim 25, wherein the executable instructions further perform at least:

transmitting to the OLT receiver a reset signal before each time slot assigned to one of the plurality of optical network unit.
[Rectified under Rule 91, 29.05.2020]

The apparatus of claim 24, further comprising:

transmitting a control message to disable the faulty ONU.
[Rectified under Rule 91, 29.05.2020]
The apparatus of claim 27, wherein the control message is a physical layer operations, administration, and maintenance (PLOAM) message.
[Rectified under Rule 91, 29.05.2020]

The apparatus of claim 27, wherein the control message is one of:

a Disable_Serial_Number message causing the disabling of a particular optical network unit identified by Disable_Serial_Number message,

an Optical_Power_Disable message causing the faulty ONU to turn-off an electrical power supplied to an optical device to stop the optical device from transmitting,

a message causing the faulty ONU to reboot,

another message causing the faulty ONU to power down, or

an Emergency_Stop message causing an identified optical network unit to stop transmitting.
[Rectified under Rule 91, 29.05.2020]

The apparatus of claim 27, wherein attempts by the optical line terminal to return the faulty ONU to normal operation follow an order from first attempt to last attempt, wherein the order includes:

a Disable_Serial_Number PLOAM message,

an Emergency_Stop PLOAM message,

a reboot PLOAM message,

an Optical_Power_Disable PLOAM message, and

a Power_Down PLOAM message.
[Rectified under Rule 91, 29.05.2020]
The apparatus of claim 24, wherein the faulty ONU transmits continuously.