JP5434461B2 - Fault ONU identification method and fault ONU identification apparatus - Google Patents

Description

  The present invention relates to a failure ONU identifying method and apparatus, and more specifically, a station side optical terminal device OLT (Optical Line Terminal) such as a PON (Passive Optical Network) system has a plurality of subscriber optical terminal devices ONU ( BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for identifying a faulty ONU that emits interfering light in an optical transmission system that accommodates an optical network unit) via an optical transmission line partially shared by them.

  In the FTTH (Fiber To The Home) service using an optical fiber for an access line to a subscriber, a PON (Passive Optical Network) system is often used. In the PON system, a single station-side optical terminator OLT (Optical Line Terminal) is installed in an exchange station, etc., and multiple subscriber optical terminators ONU (Optical Network Unit) are accommodated in the OLT via passive optical transmission lines. It is a method to do. The passive optical transmission line is an optical fiber (shared optical fiber) connected to the OLT, an optical fiber (branched optical fiber) connected to each subscriber optical terminal unit ONU, and a passive connecting the shared optical fiber and the branched optical fiber. It consists of an optical coupler which is an optical element. By sharing the OLT and the shared optical fiber, the equipment cost and the optical fiber cost can be reduced.

  In a PON system that uses a single wavelength for upstream, a TDMA (Time Division Multiplexing Access) system is adopted for upstream optical signal transmission of each ONU. The OLT instructs the transmission timing of the upstream optical signal so that each ONU does not overlap with the upstream optical signal of another ONU on the optical transmission path, and each ONU transmits upstream light only at the instructed timing and time zone. The signal is output to the optical fiber.

  The ONU failure includes a case where control or an instruction from the OLT is not accepted including that the ONU does not operate, and a case where an optical signal (interfering light for other ONUs) is transmitted outside the permitted time zone. In the latter case, because the ONU shares the optical transmission line, the OLT may not be able to discriminate upstream optical signals from other ONUs. Such an optical signal exceeds the permitted time zone. A technique for early identification of a failure ONU that transmits (interfering light) is required. This failure can typically occur due to a runaway or control failure of the laser diode for upstream optical signal output.

  In Patent Document 1, all ON bands are sequentially given to each ONU to transmit an upstream optical signal, the upstream optical power at that time is measured, and an upstream optical signal having the same upstream optical power as when no upstream band is given is obtained. A technique for specifying an ONU to be output as a failure ONU is described.

  In Patent Document 2, an OLT transmits an idle pattern to each ONU, loops back, and calculates a correlation function with the received idle pattern to identify a normally operating ONU (hereinafter referred to as a normal ONU). How to do is described. An ONU that does not make such a loopback response has some kind of failure and needs to be replaced or repaired.

  Patent Document 3 describes that a database is created by monitoring the behavior of an ONU when it is disconnected from an optical fiber, and when an interference light is generated, the ONU that outputs the interference light is estimated by referring to the database. ing.

  Patent Document 4 describes that the reception power for each ONU is measured in advance, and the failure ONU is specified by comparison with the reception power when the failure occurs (the total power of normal light and interference light).

  Patent Document 5 describes that the reception power for each ONU is measured periodically, and the reception power at the time of failure occurrence is identified as the failure ONU with the least change compared to the previous measurement (normal time). Has been.

Patent No. 4020597 Japanese Patent Laid-Open No. 2003-158531 JP 2006-303673 A JP 2008-104028 A JP 2008-277947 A

  The conventional technology is based on the premise that a normal ONU responds to a control command from the OLT even in a situation where interference light is generated. However, this assumption is not applicable when the logical link of the normal ONU is disconnected due to the inability to perform upstream communication. Actually, in an EPON (Ethernet (registered trademark) PON) system used for commercial purposes, when uplink communication becomes impossible, the logical link is broken and the ONU cannot react to the OLT bandwidth allocation signal.

  It is difficult to identify a faulty ONU only by the difference between the optical power of normal light and interfering light and the optical power of only normal light. For example, when the fault ONU is at a short distance and the normal ONU is at a long distance, the light of normal light may be too small to determine the difference. Further, the output power of the upstream optical signal laser diode of each ONU changes with time, and if the laser diode and its driving circuit are made inexpensive to reduce the cost, the optical output of each ONU will be further increased. Power stability over time cannot be expected. In such a situation, a simple difference between the optical power of normal light and interfering light and the optical power of only normal light can make a determination error.

  It is an object of the present invention to provide a failure ONU identification method and a failure ONU identification device that solve such an inconvenience.

The failure ONU identification method according to the present invention is an optical transmission line in which a station side optical terminal unit (OLT) is partially shared by a plurality of subscriber optical terminal units (ONUs). In the optical transmission system accommodated via the optical transmission system, the station-side optical termination is specified in a state in which the plurality of subscriber optical termination devices are instructed not to output the upstream optical signal. An interference light power measurement step for measuring the optical power of interference light to be incident on the device, a designation step in which any one of the plurality of subscriber optical termination devices is designated subscriber optical termination device, and the designated subscriber A logical link establishment step for establishing a logical link in the optical terminal device, a request step for causing the designated subscriber optical terminal device to output an upstream optical signal in a predetermined upstream band, and the request step. The upstream optical power measurement step for measuring the optical power of the upstream light to be incident on the station side optical termination device, and the optical power of the upstream light measured in the upstream optical power measurement step becomes the optical power of the interference light. If the result is equal to or less than the result of adding the predetermined threshold, the designated subscription until the subscriber optical termination device is designated as a failure ONU candidate and all of the plurality of subscriber optical termination devices are targeted. A repetitive step of updating the optical terminal device and executing the logical link establishment step, the request step, the upstream optical power measurement step, and the failure ONU candidate designation step, and the station side of the failure ONU candidates A requesting step comprising: identifying a subscriber optical terminating device having the smallest transmission distance or transmission loss to the optical terminating device as a faulty ONU. However, this is characterized in that the station-side optical termination device repeatedly transmits a signal requesting a reply to the designated subscriber optical termination device to the designated subscriber optical termination device at a predetermined time interval.

The failure ONU identification method according to the present invention is an optical transmission line in which a station side optical terminal unit (OLT) is partially shared by a plurality of subscriber optical terminal units (ONUs). In the optical transmission system accommodated via the optical transmission system, the station-side optical termination is specified in a state in which the plurality of subscriber optical termination devices are instructed not to output the upstream optical signal. An interference light power measurement step for measuring the optical power of interference light to be incident on the apparatus, and an arrangement in which the plurality of subscriber optical terminators are rearranged in order from the smallest transmission distance or transmission loss to the station side optical terminator. A reordering step, a designating step in which the first one in the order of the reordering step is a designated subscriber optical termination device, and a logical link for establishing a logical link to the designated subscriber optical termination device. Step, requesting the designated subscriber optical terminating device to output an upstream optical signal in a predetermined upstream band, and measuring the optical power of upstream light to be incident on the local optical terminating device by the requesting step. An upstream optical power measurement step, a determination step for determining whether the optical power of the upstream light measured in the upstream optical power measurement step exceeds a result obtained by adding a predetermined threshold to the optical power of the interfering light, and In the determination step, when the optical power of the upstream light is equal to or less than the result of adding a predetermined threshold value to the optical power of the interfering light, a fault ONU specific step that sets the designated subscriber optical terminal device as a fault ONU; If the upstream optical power measured in the upstream optical power measurement step exceeds the result of adding a predetermined threshold to the optical power of the interfering light, the plurality of additional The designated subscriber optical terminator is updated in the order of the rearrangement step until all of the incoming optical terminators are targeted, the logical link establishment step, the request step, the upstream optical power measurement step, and the A repeat step for executing a determination step, wherein the request step repeatedly repeats a signal for requesting a reply from the designated subscriber optical terminator to the designated subscriber optical terminator at a predetermined time interval. It is the step which transmits to an apparatus, It is characterized by the above-mentioned.

  The failure ONU identification method according to the present invention is an optical transmission line in which a station side optical terminal unit (OLT) is partially shared by a plurality of subscriber optical terminal units (ONUs). A method for identifying a faulty ONU that emits interfering light in an optical transmission system accommodated via a designated step, wherein one of the plurality of subscriber optical terminators is a designated subscriber optical terminator, and the designated subscription A logical link establishment step for establishing a logical link in the subscriber optical termination device, a request step for causing the designated subscriber optical termination device to output an upstream optical signal in a predetermined upstream band, and the station side optical termination by the request step. An upstream optical power measuring step for measuring optical power of upstream light to be incident on the device, and the designated subscriber optical termination device until all of the plurality of subscriber optical termination devices are targeted. A new step of repeating the logical link establishment step, the request step, and the upstream optical power measurement step, and the upstream optical light by the upstream optical power measurement step for the plurality of subscriber optical terminal devices. A signal for requesting a reply to the designated subscriber optical terminator from the station side optical terminator, comprising a fault ONU identifying step for identifying a subscriber optical terminator having the minimum power as a faulty ONU. Is repeatedly transmitted at a predetermined time interval to the designated subscriber optical terminal device.

The faulty ONU identification device according to the present invention has an optical transmission line in which a station side optical terminal device (OLT) is partially shared by a plurality of subscriber optical terminal devices (ONU: Optical Network Unit). In the optical transmission system accommodated via the optical transmission system, the optical power of the upstream light transmitted through the optical transmission line output from the plurality of subscriber optical terminal devices is measured, and is a device for identifying the failure ONU that emits interfering light. A logical link is established between the power meter and any one of the plurality of subscriber optical terminators as a designated subscriber optical terminator, and the designated subscriber optical terminator is established. And a subscriber optical termination device control means for outputting an upstream optical signal in a predetermined upstream band, and the plurality of subscriber optical termination devices are instructed not to output an upstream optical signal and The Control means for causing the power meter to measure the upstream optical power for each designated subscriber optical termination device, while causing the subscriber optical termination device control means to update the designated subscriber optical termination device, When the power is equal to or less than the result of adding a predetermined threshold value to the optical power of the interfering light, the failure ONU candidate specifying means that sets the subscriber optical terminal device as a failure ONU candidate, and the failure ONU candidate, A subscriber optical terminator having the smallest transmission distance or transmission loss to the station-side optical terminator is specified as a failure ONU, and the subscriber optical terminator control means includes the designated subscriber optical terminator. A signal requesting a reply to the terminal is repeatedly transmitted to the designated subscriber optical termination apparatus at a predetermined time interval, thereby causing the designated subscriber optical termination apparatus to output an upstream optical signal in a predetermined upstream band. To do.

The faulty ONU identification device according to the present invention has an optical transmission line in which a station side optical terminal device (OLT) is partially shared by a plurality of subscriber optical terminal devices (ONU: Optical Network Unit). In the optical transmission system accommodated via the optical transmission system, the optical power of the upstream light transmitted through the optical transmission line output from the plurality of subscriber optical terminal devices is measured, and is a device for identifying the failure ONU that emits interfering light. Any one of the power meter, reordering means for reordering the plurality of subscriber optical terminators in descending order of transmission distance or transmission loss to the station side optical terminator , and any one of the plurality of subscriber optical terminators A designated optical subscriber unit, a logical link is established with the designated subscriber optical terminator, and the designated optical subscriber unit outputs an upstream optical signal in a predetermined upstream band. In a state in which the station control means and the plurality of subscriber optical termination devices are instructed not to output the upstream optical signal, the power meter measures the interference light power, and the subscriber optical termination device control means Control means for causing the power meter to measure the upstream optical power for each designated subscriber optical termination device while updating the designated subscriber optical termination device in the order of arrangement by the switching means, and the upstream optical power is the interference light It is determined whether or not the result of adding a predetermined threshold value to the power is exceeded, and when the optical power of the upstream light is equal to or less than the result of adding the predetermined threshold value to the optical power of the interfering light, the designated subscriber optical terminal device A failure ONU identifying unit that sets a failure ONU as a failure ONU, and the subscriber optical termination device control unit repeatedly transmits a signal requesting a reply to the designated subscriber optical termination device at a predetermined time interval. By transmitting to the terminating device, the designated subscriber optical terminating device is caused to output an upstream optical signal in a predetermined upstream band.

  The faulty ONU identification device according to the present invention has an optical transmission line in which a station side optical terminal device (OLT) is partially shared by a plurality of subscriber optical terminal devices (ONU: Optical Network Unit). In the optical transmission system accommodated via the optical transmission system, the optical power of the upstream light transmitted through the optical transmission line output from the plurality of subscriber optical terminal devices is measured, and is a device for identifying the failure ONU that emits interfering light. A logical link is established between the power meter and any one of the plurality of subscriber optical terminators as a designated subscriber optical terminator, and the designated subscriber optical terminator is established. Subscriber optical termination device control means for outputting an upstream optical signal in a predetermined upstream band, and updating the designated subscriber optical termination device to the subscriber optical termination device control means, light Control means for measuring upstream optical power for each end device, and failure ONU identifying means for identifying a subscriber optical termination device that minimizes the upstream optical power of the plurality of subscriber optical termination devices as a failure ONU. The subscriber optical terminator control means repeatedly transmits a signal requesting a reply to the designated subscriber optical terminator at a predetermined time interval to the designated subscriber optical terminator. The apparatus is characterized in that an upstream optical signal is output in a predetermined upstream band.

  According to the present invention, it becomes possible to accurately identify a fault ONU of a PON system.

It is a schematic block diagram of one Example of this invention. It is an example of ONU information. It is an operation | movement flowchart of the Example shown in FIG. It is another operation | movement flowchart of the Example shown in FIG. It is another operation | movement flowchart of the Example shown in FIG. 6 is an example of ONU (i) vs. upstream optical power measurement value Pi in the operation flow shown in FIG. 5. It is a schematic block diagram of a failure ONU identification device separated from the OLT.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic block diagram of an embodiment of the present invention.

  The configuration and basic operation of this embodiment will be briefly described. The OLT 10 deployed in the center station is connected to the optical coupler 14 via the shared optical fiber 12, and the optical coupler 14 is connected to the ONUs 18-1 to 18-1 of the subscriber's home via the individual branch optical fibers 16-1 to 16-n. Connect to 18-n. The optical coupler 14 divides the downstream optical signal input from the shared optical fiber 12 into n parts, supplies the divided downstream optical signals to the branched optical fibers 16-1 to 16-n, and branches the optical fibers 16-1 to 16-16. This is a passive optical element that outputs an upstream optical signal input from −n to the shared optical fiber 12. The shared optical fiber 12, the optical coupler 14, and the branched optical fibers 16-1 to 16-n constitute a PON optical transmission line that optically connects the OLT 10 and the ONUs 18-1 to 18-n.

  The OLT 10 also connects to the upstream network at its network network interface (NNI) 20. The NNI 20 supplies a downlink signal (downlink data frame) from the upstream network to any one of the ONUs 18-1 to 18-n to the downlink transfer device 22. Further, a control signal or a control frame for the OLT 10 to manage each of the ONUs 18-1 to 18-n is also input to the downlink transfer device 22 from the CPU 24 that controls the entire OLT 10. Details of this control signal will be described later.

  The downlink transfer device 22 multiplexes the control frame from the CPU 24 on the downlink data frame from the NNI 20 on the time axis, and supplies it to the electrical / optical converter (E / O converter) 26 with a predetermined frame configuration. In general, the downlink transfer device 22 supplies the control frame with priority over the downlink data frame to the E / O converter 26. The control frame includes a Band frame for bandwidth allocation and a Discovery_GATE frame.

  The E / O converter 26 includes a laser diode that oscillates at a predetermined wavelength, and converts an electrical signal from the downstream transfer device 22 into an optical signal (downstream optical signal). The WDM (wavelength division multiplexing) optical coupler 28 outputs the downstream optical signal from the E / O converter 26 to the shared optical fiber 12.

  The downstream optical signal is transmitted through the shared optical fiber 12, is divided by the optical coupler 14, is transmitted through the branched optical fibers 16-1 to 16-n, and reaches the ONUs 18-1 to 18-n. The ONUs 18-1 to 18-n determine whether or not they are addressed to themselves after converting the downstream optical signals input from the corresponding branch optical fibers 16-1 to 16-n into electric signals. A signal (downlink data or a control frame from the OLT 10) carried by the downstream optical signal is captured.

  Each of the ONUs 18-1 to 18-n sends an upstream optical signal to the corresponding branch optical fibers 16-1 to 16-n at the timing or time zone specified by the OLT 10 as long as it is normal. The wavelength of the upstream optical signal is different from the wavelength of the downstream optical signal. This upstream optical signal is transmitted through the branch optical fibers 16-1 to 16-n, multiplexed on the optical fiber 12 by the optical coupler 14 on the time axis, and input to the WDM optical coupler 28 of the OLT 10.

  The WDM optical coupler 28 supplies an upstream optical signal input from the shared optical fiber 12 to an optical / electrical converter (O / E converter) 30. The O / E converter 30 includes a light receiving element, and converts the upstream optical signal from the WDM optical coupler 28 into an electrical signal. The switch 32 normally connects the output electrical signal of the O / E converter 30 to the upstream transfer device 34, and connects to the power meter 38 at the time of power measurement for identifying the failure ONU. Of course, the switch 32 may be eliminated, and the output electrical signal of the O / E converter 30 may be supplied to both the upstream transfer device 34 and the power meter 38 at all times.

  The uplink signal input to the uplink transfer device 34 is composed of a control frame (control signal or response signal or the like) directed to the OLT 10 and an uplink data frame or uplink data signal directed to the upstream network. The CPU 24 is supplied, and the latter is supplied to the NNI 20. The former includes a Report frame used privately in response to the Gate frame, and a Register_REQ frame and a Register_ACK frame used in the discovery procedure. The NNI 20 outputs the upstream data frame from the upstream transfer device 34 to the upstream network with a predetermined transmission frame configuration and protocol.

  The OLT 10 recognizes the ONUs 18-1 to 18-n through a discovery procedure, and assigns logical links to the recognized ONUs 18-1 to 18-n. Details of the discovery procedure will be described later. The OLT 10 stores ONU information 36a in the memory 36 in order to manage each ONU 18-1 to 18-n. The ONU information 36a includes a record number (for example, a serial number) that identifies the ONU, a MAC address, and distance information for each of the ONUs 18-1 to 18-n. A round trip time RTT (Round Trip Time) may be used instead of the distance. FIG. 2 shows an example of the ONU information 36a. The distance information (or round-trip delay time) is necessary for each ONU 18-1 to 18-n to determine the timing and period for outputting upstream optical signals without colliding with each other by TDMA.

  The CPU 24 uses the power meter 38 to measure the optical power of the upstream optical signal when there is no fault ONU, and stores the power measurement value 36b in the memory 36 in order to identify the fault ONU. Details of this operation will be described later.

  FIG. 3 shows an operation flowchart of this embodiment. Until the failure ONU is detected (S3), the CPU 24 registers unregistered ONUs in the discovery procedure (S1), assigns a predetermined bandwidth to the registered ONUs in order, and permits upstream transmission (S2). Note that step S1 is activated at regular time intervals while allowing the registered ONU to perform upstream transmission in order.

  A procedure (S1) for registering an unregistered ONU in the case of an EPON standardized by IEEE 802.3-2008 will be specifically described. The OLT 10 transmits a Discovery_GATE frame via the optical fiber 12 to an unknown (unregistered) ONU among all the ONUs 18-1 to 18-n at the time of power-on startup or every certain period thereafter. To do. The Discovery_GATE frame notifies the transmission destination ONU of the time stamp information of the OLT 10 and designates a discovery slot size (Discovery Slot Size) including a time and a time width at which the ONU can return the registration request frame Register_REQ. The OLT 10 sets the discovery slot size so that all registration request (Register_REQ) frames from unregistered ONUs reach the OLT 10 within a predetermined time (in the Discovery Window).

  After receiving Discovery_GATE, the unregistered ONU that has received Discovery_GATE waits for a delay time determined at random, and transmits a registration request frame called Register_REQ to OLT 10. Since the delay time of each unregistered ONU is determined at random, the Register_REQ output by each unregistered ONU is uniformly distributed within the discovery slot size notified from the OLT 10 and collides on the optical transmission line. Can reduce the probability. Each unregistered ONU notifies the OLT 10 of its own MAC address in a registration request frame (Register_REQ).

  When the OLT 10 receives the registration request frame (Register_REQ), the OLT 10 returns a Register frame (registration frame) (and registration approval (Register_ACK) for returning a logical link) to the transmission source unregistered ONU. Gate frame) is transmitted. This Register frame notifies the identification number (LLID) of the assigned logical link. The unregistered ONU that has received the Register frame transmits a registration approval (Register_ACK) frame corresponding to the Register frame to the OLT 10. As a result, the OLT 10 registers the unregistered ONU and ends the discovery procedure. The basic information of the registered ONU is also recorded in the ONU information 36a. Each ONU that has received the registration (Register) frame stores the LLID notified in the registration frame and uses it for subsequent data communication.

  In step S2, the CPU 24 designates the registered ONUs in order and permits transmission using the Gate frame, and the registered ONU that has received the Gate frame transmits uplink data using the Report frame at the permitted transmission timing.

  Registered ONUs, for example, ONUs 18-1 to 18-n, can transmit uplink signals under permission of transmission by the OLT 10 through steps S1 and S2.

  Assume that the OLT 10 detects that any ONU has become a fault ONU that outputs disturbing light (S3). This can be determined by disconnecting all registered ONU links. As another means for detecting the failure ONU, when the upstream optical power is constantly monitored by the output signal of the O / E converter 30, the upstream light is present in a period that does not originally exist, which is stronger than the expected range. This can be determined by the presence of upstream light or the presence of upstream light having a certain level of optical power at all times.

  The CPU 24 switches the switch 32 to the terminal B (power meter 38) side, and causes the power meter 38 to measure the optical power of the upstream light (S4). The CPU 24 stores the optical power measurement value P0 by the power meter 38 at this time in the memory 36. When there is a possibility that a normally operating ONU outputs an upstream optical signal, the upstream optical signal output is prohibited, and the upstream optical power is measured after disconnecting the logical links of all ONUs. The optical power measurement value P0 represents the optical power of the interfering light output from the fault ONU.

  Next, a logical link is established for each registered ONU, and an upstream optical signal is transmitted in the entire band, and the upstream optical power at that time is measured (S5 to S8).

  First, 1 is substituted into a variable i that designates a target registered ONU (S5). i indicates the i-th ONU (denoted as ONU (i)) among the registered ONUs stored in the ONU information 36a.

  The OLT 10 provisionally establishes a logical link for the ONU (i) by a discovery procedure (S6). That is, the OLT 10 transmits a Discovery_GATE frame to the optical fiber 12. In response to this Discovery_GATE frame, the registered ONU and, if present, the unregistered ONU return a Register_REQ frame to the OLT 10. However, in this procedure, the OLT ignores the Register_REQ frame and returns a Register frame (registration frame) (and registration approval (Register_ACK)) for setting a logical link to the ONU (i). Normal Gate frame) is transmitted. The ONU (i) that has received the Register frame transmits a registration approval (Register_ACK) frame corresponding to the Register frame to the OLT 10, but the OLT 10 ignores the Register_ACK frame. This is because it may be buried in the jamming light and cannot be received properly, and it is not essential for permission to transmit all bands.

  When the logical link of the ONU (i) is established in this way (S6), the OLT 10 instructs the ONU (i) to output an upstream optical signal in the entire upstream band, and the ONU (i) responds to this instruction. On the other hand, an upstream optical signal using the entire upstream band is output (S7). Specifically, the OLT 10 continuously transmits Gate frames to the ONU (i) at predetermined intervals, and the ONU (i) transmits a Report frame in response to the Gate frame. Since ONU (i) continuously receives Gate frames, as a result, it continuously transmits Report frames. By transmitting such a continuous report frame, ONU (i) transmits an upstream optical signal that consumes the entire upstream bandwidth.

  In a normal PON system, when there is interference light in the upstream direction, the OLT cannot receive a signal from the ONU and does not receive a Report frame as a reply to the Gate frame periodically transmitted by the OLT. Stop sending. Then, since the ONU does not receive the Gate frame, it retains the logical link for a certain period, but finally erases the logical link assigned to itself.

  On the other hand, in this embodiment, the OLT 10 continuously and repeatedly transmits the Gate frame to the ONU (i) regardless of whether or not it receives the Report frame from the ONU (i). Keeps the logical link. That is, the OLT 10 transmits the Gate frame to the ONU (i) without waiting for the reception of the Report frame as a reply to the previously transmitted Gate frame. Since the Report frame can be transmitted even when there is no data to be transmitted, transmission of the upstream optical signal using the entire upstream band is possible even if the ONU (i) does not have the data to be transmitted. It becomes possible.

  The CPU 24 causes the power meter 38 to measure the upstream optical power Pi (S8). The upstream light measured at this time includes interference light from the fault ONU and upstream signal light from ONU (i), and Pi> P0 if power fluctuation is ignored. On the other hand, if ONU (i) is a faulty ONU, the upstream light consists only of interfering light, and Pi is equal to P0 if power fluctuations are ignored.

  The CPU 24 determines whether or not the difference Pi-P0 between Pi and P0 exceeds a predetermined threshold value Pt (S9). Pt is a positive value and is determined in advance in consideration of power fluctuations. When Pi-P0> Pt is not satisfied (S9), the CPU 24 stores ONU (i) as a failure ONU candidate (S10).

  After step S9 or S10, i is incremented (S11). Steps S6 to S11 are repeated until i exceeds the number of registered ONUs (S12).

  In this way, for all registered ONUs before detecting the failure ONU, optical transmission in the entire uplink band is individually executed to measure the upstream optical power, and only the failure ONU emits interference light. The failure ONU can be narrowed down by comparing with the upstream optical power.

  At this stage, there may be a plurality of failure ONU candidates. Therefore, in the present embodiment, the nearest ONU (the optically optically least ONU) among the failure ONU candidates is identified as the failure ONU (S13). When there is no failure ONU candidate, it means that the failure ONU has failed to be identified. For example, the threshold Pt may be reduced and the flow shown in FIG. 3 may be executed again.

  For example, it is assumed that there is no significant difference in upstream optical power measured by the OLT 10 when the entire band is given to the short-distance ONU 18-1 and when the full band is given to the long-distance ONU 18-2. Assuming that the long-distance ONU 18-2 is a faulty ONU, the latter is the case when the short-distance ONU 18-1 does not output an upstream optical signal and when the upstream optical signal is transmitted using the entire band. However, the upstream optical power measured by the OLT 10 is large. However, since the ONU 18-1 is located at a short distance, there should be a significant optical power difference between them.

On the other hand, when it is assumed that the short-distance ONU 18-1 is a faulty ONU, when the long-distance ONU 18-2 does not output an upstream optical signal, and when the upstream optical signal is transmitted using the entire band. , the latter being, but should be greater upstream optical power measured by the OLT 10, since ONU18-1 is located near distance, the optical power difference between them is small.

  Therefore, if any of the two ONUs having different distances is a faulty ONU, and no significant difference is detected in the upstream optical power in the OLT even if the entire bandwidth is given to any ONU, the ONUs in the short distance Is likely to be a faulty ONU. Therefore, in this embodiment, when there are a plurality of failure ONU candidates, the closest ONU is identified as a failure ONU.

  Since the transmission distance corresponds to the transmission loss, the same can be said for the transmission loss. That is, when there are a plurality of failure ONU candidates, the ONU with the smallest transmission loss is identified as the failure ONU. Even when there are three or more faulty ONU candidates with no significant difference in upstream optical power, the faulty ONU can be identified by the same logical development of distance or transmission loss. In a PON system in which any ONU is connected to the branch destination of an optical coupler, the correlation between distance and transmission loss is obvious. In the case of a bus-type PON system, the failure ONU can be identified by using transmission loss according to the branching ratio of the coupler network. Transmission distance, transmission loss, and branching ratio can all be evaluated uniformly as optical perspective.

  The CPU 24 notifies the specified failure ONU to the monitoring center (not shown) via the NNI 40 and the monitoring network (S14).

  In this embodiment, the upstream optical power in the case of only the interfering light is not simply compared with the upstream optical power in the case where the upstream signal light is added to the interfering light. Therefore, it is possible to reduce the erroneous determination due to the temporal change of the output optical power of the ONU.

  FIG. 4 shows a modification example of the flow shown in FIG. In the flow shown in FIG. 3, one ONU is designated from among registered ONUs (S5), logical link establishment (S6), upstream optical transmission using all upstream bands (S7), and comparison of upstream power ( S8, S9) are performed, but in FIG. 4, the registration ONU is performed in order from the short-distance (low transmission loss) registered ONU, and when a registered ONU that does not satisfy Pi-P0> Pt is found, the registered ONU is displayed. Identify the fault ONU.

  Steps S21 to S24 in FIG. 4 are the same as steps S1 to S4 in FIG.

  Before and after step S24 corresponding to step 4, the CPU 24 sorts the registered ONUs in order of increasing distance (or in order of decreasing transmission loss) (S25). The variable i indicates the order sorted in step S25. First, 1 is set (S26). Steps S27 to S30 correspond to steps S6 to S9 in FIG. That is, for the nearest registered ONU (i), establishment of a logical link (S27), upstream optical transmission using the entire upstream band (S28), and comparison of upstream power (S29, S30) are performed.

  When a registered ONU that does not satisfy Pi-P0> Pt is found (S30), the registered ONU is identified as a failed ONU (S31), and the failed ONU is monitored via the NNI 40 and the monitoring network (not shown). (S32) and the process ends.

  If Pi-P0> Pt (S30), i is incremented (S33), and steps S27 to S30 are repeated for the next registered ONU. When the incremented i exceeds the number of registered ONUs (S34), all the registered ONUs have been checked. In this case, the CPU 24 ends the failure ONU specifying process. As in the first embodiment, for example, the CPU 24 may decrease the threshold value Pt and re-execute the flow illustrated in FIG.

  FIG. 5 shows another modification of the flow shown in FIG. In the flow shown in FIG. 5, the ONU that minimizes the upstream optical power measurement value when the registered ONU performs upstream optical transmission using the entire upstream band is identified as a faulty ONU.

  Steps S41 to S43 in FIG. 5 are the same as steps S1 to S3 in FIG. The process corresponding to step S4 becomes unnecessary.

  When a failure is detected (S43), the CPU 24 sorts the registered ONUs in ascending order of distance (or in order of decreasing transmission loss) (S44). The variable i indicates the order sorted in step S44. First, 1 is set (S45). Steps S46 to S48 correspond to steps S6 to S8 in FIG. 3, respectively. That is, for the nearest registered ONU (i), logical link establishment (S46), upstream optical transmission using the entire upstream band (S47), and upstream optical power measurement (S48) are performed.

  The variable i specifying the ONU is incremented (S49), and steps S46 to S48 are repeated for the next registered ONU. When the incremented i exceeds the number of registered ONUs (S50), all the registered ONUs have been checked.

  The CPU 24 identifies an ONU (i) having a minimum uplink power measurement value Pi as a failure ONU (S51). This is because when the entire upstream band is given to the ONU that outputs the interference light, the upstream light incident on the OLT is only the interference light, and the optical power measurement value at this time is minimized. FIG. 6 is a measurement example of registered ONUs and upstream optical power arranged in order of increasing transmission distance. The horizontal axis indicates ONUs in order of transmission distance, and the vertical axis indicates the upstream optical power measurement value Pi. In the example shown in FIG. 6, the upstream light power for the eighth ONU is the lowest, and this ONU is identified as a faulty ONU. Arranging in order of distance makes it easier to identify the ONU with the smallest upstream optical power measurement value Pi.

  The CPU 24 notifies the specified failure ONU to the monitoring center (not shown) via the NNI 40 and the monitoring network (S52) and ends.

  Although the embodiment in which the function for identifying the fault ONU is incorporated in the OLT 10 has been described, it is obvious that the OLT 10 may be configured as a dedicated device separate from the OLT 10. The failure ONU identification device includes the failure ONU identification processing described in FIGS. 3 to 5 (after step S4 in FIG. 3, after step S24 in FIG. 4, and in FIG. 5), among the functions of the OLT 10 of the embodiment shown in FIG. What is necessary is just to comprise a functional element required for step S44 or later. FIG. 7 shows a schematic block diagram of a faulty ONU identification device configured separately from the OLT.

  In FIG. 7, the OLT 110 is an OLT that excludes the fault ONU identification function from the OLT 10, that is, an existing OLT. When the OLT 110 detects the failure ONU (step S3 in FIG. 3, step S23 in FIG. 4 or step S43 in FIG. 5), the operator or maintenance personnel removes the optical fiber 12 from the OLT 110 and connects it to the failure ONU identifying device 111. The failure ONU identification device 111 is activated.

  The CPU 124 that controls the entire failure ONU specifying device 111 receives information about the registered ONU at the time of failure detection from the OLT 110 and stores it as ONU information 36 a in the memory 136. The functions of the E / O converter 126, the WDM optical coupler 128, and the O / E converter 130 are the same as those of the embodiment shown in FIG. 1, the E / O converter 26, the WDM optical coupler 28, and the O / E converter 30, respectively. Is the same as that.

  The frame generation device 122 requires a Discovery_GATE frame, a Register frame (registration frame) (and a normal gate frame for returning a registration approval (Register_ACK)) required for link establishment (S6, S27, S46) of the ONU (i). And a continuous Gate frame at a predetermined interval necessary for transmission of upstream optical signals (S7, S28, S47) using the entire upstream band by ONU (i) is generated.

  The power meter 138 measures the upstream optical power (P0) in steps S4 and S24 and the upstream optical power (Pi) in steps S8, S29, and S48 under the control of the CPU 124, and each measurement result. Is transmitted to the CPU 124.

  The CPU 124 identifies the failure ONU using the upstream optical powers P0 and Pi measured by the power meter 138 according to the flow shown in FIGS. 3 to 5, and notifies the operator or the monitoring center as necessary.

  By preparing the failure ONU identifying device 111 separate from the OLT, it becomes possible to identify the failure ONU for the PON system using the existing OLT.

  Although the invention has been described with reference to specific illustrative embodiments, various modifications and alterations may be made to the above-described embodiments without departing from the scope of the invention as defined in the claims. This is obvious to an engineer in the field to which the present invention belongs, and such changes and modifications are also included in the technical scope of the present invention.

10: OLT
12: Shared optical fiber 14: Optical couplers 16-1 to 16-n: Branch optical fibers 18-1 to 18-n: ONU
20: Network Network interface (NNI)
22: Downlink transfer device 24: CPU
26: Electric / optical converter (E / O converter)
28: WDM (wavelength division multiplexing) optical coupler 30: optical / electrical converter (O / E converter)
32: Switch 34: Upward transfer device 36: Memory 36a: ONU information 36b: Power measurement value 38: Power meter 40: Network network interface (NNI)
110: OLT
111: Fault ONU identifying device 122: Frame generating device 124: CPU
126: Electric / optical converter (E / O converter)
128: WDM (wavelength division multiplexing) optical coupler 130: optical / electrical converter (O / E converter)
136: Memory 136a: ONU information 136b: Power measurement value 138: Power meter

Claims (8)

In an optical transmission system in which an optical line terminal (OLT) accommodates a plurality of optical terminal units (ONUs) through an optical transmission line partially shared by them. A method for identifying a faulty ONU that emits light,
An interference light power measurement step (S4) for measuring the optical power (P0) of interference light to be incident on the station side optical termination device in a state where the plurality of subscriber optical termination devices are instructed not to output the upstream optical signal. )When,
A designation step (S5) in which any one of the plurality of subscriber optical termination devices is designated subscriber optical termination device;
A logical link establishment step (S6) for establishing a logical link to the designated subscriber optical terminal unit (ONU (i));
A request step (S7) for causing the designated subscriber optical terminal unit (ONU (i)) to output an upstream optical signal in a predetermined upstream band;
An upstream optical power measurement step (S8) for measuring the optical power (Pi) of upstream light to be incident on the station side optical termination device in the request step;
When the optical power (Pi) of the upstream light measured in the upstream optical power measurement step is equal to or less than a result of adding a predetermined threshold to the optical power (P0) of the interfering light, the subscriber optical termination device is A failure ONU candidate designation step (S9, S10) as a failure ONU candidate;
The designated subscriber optical terminal unit (ONU (i)) is updated until all of the plurality of subscriber optical terminal units are targeted, the logical link establishment step (S6), the request step (S7), Repetitive steps (S11, S12) for executing the upstream optical power measurement step (S8) and the failure ONU candidate designation step (S9, S10);
Identifying step (S13) of identifying the subscriber optical terminal device with the smallest transmission distance or transmission loss to the station side optical terminal device as the defective ONU among the failed ONU candidates
And
In the request step, the designated optical terminal unit (ONU (i)) repeats a signal for the station side optical terminal unit to request a reply from the designated subscriber optical terminal unit (ONU (i)) at a predetermined time interval. The fault ONU identification method characterized by the above-mentioned step. In an optical transmission system in which an optical line terminal (OLT) accommodates a plurality of optical terminal units (ONUs) through an optical transmission line partially shared by them. A method for identifying a faulty ONU that emits light,
An interference light power measurement step (S24) for measuring the optical power (P0) of the interference light to be incident on the station side optical termination device in a state where the plurality of subscriber optical termination devices are instructed not to output the upstream optical signal. )When,
A reordering step (S25) for reordering the plurality of subscriber optical terminators in order from the transmission distance to the station side optical terminator or the one having the smallest transmission loss ;
A designation step (S26) in which the first one in the arrangement order of the rearrangement step is a designated subscriber optical termination device;
A logical link establishing step (S27) for establishing a logical link to the designated subscriber optical terminal unit (ONU (i));
A request step (S28) for causing the designated subscriber optical termination unit (ONU (i)) to output an upstream optical signal in a predetermined upstream band;
An upstream optical power measurement step (S29) for measuring the optical power (Pi) of upstream light to be incident on the station side optical termination device in the request step;
Determination step (S30) for determining whether the optical power (Pi) of the upstream light measured in the upstream optical power measurement step exceeds the result of adding a predetermined threshold to the optical power (P0) of the interfering light When,
In this determination step, when the optical power (Pi) of the upstream light is equal to or less than the result of adding a predetermined threshold to the optical power (P0) of the interfering light, the failure that causes the designated subscriber optical terminal device to be a failure ONU ONU specific step (S31),
If the optical power (Pi) of the upstream light measured in the upstream optical power measurement step exceeds the result of adding a predetermined threshold to the optical power (P0) of the interfering light, the plurality of subscriber optical termination devices Until all of the above are targeted, the designated subscriber optical terminal unit (ONU (i)) is updated in the order of the rearrangement step (S25), the logical link establishment step (S27), and the request step (S28). ), Repetitive steps (S33, S34) for executing the upstream optical power measurement step (S29) and the determination step (S30).
And
In the request step, the designated optical terminal unit (ONU (i)) repeats a signal for the station side optical terminal unit to request a reply from the designated subscriber optical terminal unit (ONU (i)) at a predetermined time interval. The fault ONU identification method characterized by the above-mentioned step. In an optical transmission system in which an optical line terminal (OLT) accommodates a plurality of optical terminal units (ONUs) through an optical transmission line partially shared by them. A method for identifying a faulty ONU that emits light,
A designation step (S45) in which one of the plurality of subscriber optical terminators is designated subscriber optical terminator;
A logical link establishing step (S46) for establishing a logical link to the designated subscriber optical terminal unit (ONU (i));
A request step (S47) for causing the designated subscriber optical terminal unit (ONU (i)) to output an upstream optical signal in a predetermined upstream band;
An upstream optical power measurement step (S48) for measuring the optical power (Pi) of upstream light to be incident on the station side optical termination device in the request step;
The designated subscriber optical terminator (ONU (i)) is updated until all of the plurality of subscriber optical terminators are targeted, the logical link establishment step (S46), the request step (S47), And repeating steps (S49, S50) for executing the upstream optical power measurement step (S48),
Failure ONU identification step (S51) for identifying the subscriber optical termination device that minimizes the optical power of the upstream light in the upstream optical power measurement step (S48) for the plurality of subscriber optical termination devices as a failure ONU.
And
In the request step, the designated optical terminal unit (ONU (i)) repeats a signal for the station side optical terminal unit to request a reply from the designated subscriber optical terminal unit (ONU (i)) at a predetermined time interval. The fault ONU identification method characterized by the above-mentioned step. Furthermore, prior to the designation step, a reordering step (S44) for reordering the plurality of subscriber optical termination devices in order from the transmission distance or transmission loss to the station side optical termination device is as follows.
In the designation step, the first one in the arrangement order of the rearrangement steps is designated subscriber optical terminal device,
4. The failure ONU identification method according to claim 3, wherein the repeating step updates the designated subscriber optical terminal unit (ONU (i)) in the order of the rearrangement step (S25). In an optical transmission system in which an optical line terminal (OLT) accommodates a plurality of optical terminal units (ONUs) through an optical transmission line partially shared by them. A device for identifying a faulty ONU that emits light,
A power meter (38) for measuring the optical power of upstream light transmitted through the optical transmission line output from the plurality of subscriber optical termination devices;
One of the plurality of subscriber optical terminators is used as a designated subscriber optical terminator, and a logical link is established with the designated subscriber optical terminator, and the designated subscriber optical terminator (ONU (i )) Subscriber optical terminator control means (22, 24, S6, S7) for outputting an upstream optical signal in a predetermined upstream band;
In a state where the plurality of subscriber optical terminators are instructed not to output the upstream optical signal, the power meter measures the interference light power (P0), and the subscriber optical terminator control means controls the designated subscriber light. Control means (24, S4, S8) for causing the power meter to measure the upstream optical power (Pi) for each designated subscriber optical termination device while updating the termination device;
When the upstream optical power (Pi) is equal to or less than the result of adding a predetermined threshold to the optical power (P0) of the interfering light, a fault ONU candidate specifying means (24 , S9, S10),
Identification means (24, S13) for identifying a subscriber optical terminating device with the smallest transmission distance or transmission loss to the station side optical terminating device among the failed ONU candidates as a failed ONU
And
The subscriber optical terminating device control means repeatedly sends a signal requesting a reply to the designated subscriber optical terminating device (ONU (i)) to the designated subscriber optical terminating device (ONU (i)) at predetermined time intervals. A faulty ONU identifying device that causes the designated subscriber optical termination unit (ONU (i)) to output an upstream optical signal in a predetermined upstream band by transmitting. In an optical transmission system in which an optical line terminal (OLT) accommodates a plurality of optical terminal units (ONUs) through an optical transmission line partially shared by them. A device for identifying a faulty ONU that emits light,
A power meter (38) for measuring the optical power of upstream light transmitted through the optical transmission line output from the plurality of subscriber optical termination devices;
Reordering means (24, S25) for reordering the plurality of subscriber optical terminators from the one with the smallest transmission distance or transmission loss to the station side optical terminator ;
One of the plurality of subscriber optical terminators is used as a designated subscriber optical terminator, and a logical link is established with the designated subscriber optical terminator, and the designated subscriber optical terminator (ONU (i )) Subscriber optical terminator control means (22, 24, S27, S28) for outputting an upstream optical signal in a predetermined upstream band;
In a state where the plurality of subscriber optical terminators are instructed not to output the upstream optical signal, the power meter measures the interference light power (P0), and the subscriber optical terminator control means causes the rearranging means Control means (24, S24, S29) for causing the power meter to measure the upstream optical power (Pi) for each designated subscriber optical termination device while updating the designated subscriber optical termination device in the order of arrangement according to
It is determined whether or not the upstream optical power (Pi) exceeds a result obtained by adding a predetermined threshold to the jamming light power (P0), and the optical power (Pi) of the upstream light is the optical power (P0) of the jamming light. Failure ONU specifying means (24, S30, S31) that makes the designated subscriber optical termination device a failure ONU when the result is equal to or less than the result of adding a predetermined threshold to
And
The subscriber optical terminating device control means repeatedly sends a signal requesting a reply to the designated subscriber optical terminating device (ONU (i)) to the designated subscriber optical terminating device (ONU (i)) at predetermined time intervals. A faulty ONU identifying device that causes the designated subscriber optical termination unit (ONU (i)) to output an upstream optical signal in a predetermined upstream band by transmitting. In an optical transmission system in which an optical line terminal (OLT) accommodates a plurality of optical terminal units (ONUs) through an optical transmission line partially shared by them. A device for identifying a faulty ONU that emits light,
A power meter (38) for measuring the optical power of upstream light transmitted through the optical transmission line output from the plurality of subscriber optical termination devices;
One of the plurality of subscriber optical terminators is used as a designated subscriber optical terminator, and a logical link is established with the designated subscriber optical terminator, and the designated subscriber optical terminator (ONU (i )) Subscriber optical terminator control means (22, 24, S46, S47) for outputting an upstream optical signal in a predetermined upstream band;
Control means (24, S48) for causing the power meter to measure the upstream optical power (Pi) for each designated subscriber optical termination device while causing the subscriber optical termination device control means to update the designated subscriber optical termination device. When,
Failure ONU specifying means (24, S51) for specifying a subscriber optical termination device that minimizes the upstream optical power of the plurality of subscriber optical termination devices as a failure ONU
And
The subscriber optical terminating device control means repeatedly sends a signal requesting a reply to the designated subscriber optical terminating device (ONU (i)) to the designated subscriber optical terminating device (ONU (i)) at predetermined time intervals. A faulty ONU identifying device that causes the designated subscriber optical termination unit (ONU (i)) to output an upstream optical signal in a predetermined upstream band by transmitting. Furthermore, it comprises rearranging means (24, S25) for rearranging the plurality of subscriber optical termination devices in order from the transmission distance or transmission loss to the station side optical termination device ,
8. The failure ONU identifying device according to claim 7, wherein the control unit causes the subscriber optical terminal device control unit to update the designated subscriber optical terminal device in the order of arrangement by the rearranging unit.

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