JP2012029176A - Hinderance onu specification device, hinderance onu specification method and pon system - Google Patents

Abstract

【Task】
Identify a faulty ONU (Optical Network Unit) that generates interfering light.
[Solution]
The CPU (20) sequentially selects one of the plurality of subscriber-side optical terminators (ONUs) (56-1 to 56-n) connected to the optical transmission lines (50, 52, 54-1 to 54-n). Designated as a light emission control target, the control frame generation device (22) causes the light emission control target to transmit a control signal for periodically emitting light in a predetermined light emission cycle and light emission period. The optical / electrical converter (30) receives the upstream light including the upstream signal light from the light emission control target, and the signal level detection device (38) of the portion including the upstream signal light from the light emission control target from the received waveform. Detect the signal level. The CPU (20) determines whether the light emission control target is a normal ONU or a failure ONU based on the signal level detected by the signal level detection device (38).
[Selection] Figure 1

Description

  The present invention relates to a failure ONU identification device, a failure ONU identification method, and a PON system. More specifically, the station side optical terminal device (OLT: Optical Line Terminal) uses a plurality of subscriber side optical signals via a passive optical transmission line. The present invention relates to a failure ONU identification device, a failure ONU identification method, and a PON system for identifying a failure ONU that abnormally emits light in a PON (Passive Optical Network) system that accommodates an end device (ONU: Optical Network Unit).

  In order to provide an FTTH (Fiber to the Home) service economically, a PON system in which one optical transmission line and a communication band are shared by a plurality of subscribers is known. In the PON system, one station side optical terminator OLT (Optical Line Terminal) accommodates a plurality of subscriber side optical terminators ONU (Optical Network Unit) via a passive optical transmission line.

  In a PON system that employs a TDMA (Time Division Multiple Access) system that multiplexes upstream optical signals of each ONU on the time axis using a single wavelength for upstream, each ONU is shared on an optical transmission line shared by all ONUs. The OLT instructs the light emission time and light emission timing of each ONU so that the upstream optical signals do not collide with each other. When the ONU sends an upstream optical signal beyond the light emission time zone indicated by the OLT due to some trouble, user's malicious intention or malfunction, the upstream output of the ONU operating normally (hereinafter referred to as “normal ONU”) is output. As a result, the optical signal is obstructed, and as a result, the upstream communication of the entire PON system is disabled, and all normal ONUs are disconnected. Therefore, there is a need for a technique for quickly identifying an ONU that performs an abnormal light emission operation (hereinafter referred to as “failure ONU”).

  Patent Documents 1 to 7 describe techniques for identifying or blocking such a failure ONU.

  In the technique described in Patent Document 1, the OLT measures the received light power level when the band allocation of all ONUs is eliminated, and the received light power level when the maximum band is set for each ONU. Are sequentially compared to identify the fault ONU.

  Also in the technique described in Patent Document 2, the failure ONU is specified by the difference in the received light level of the upstream light incident on the OLT. When the OLT can receive the ONU transmission light exclusively, it calculates the value obtained by subtracting the light level when all ONUs are not emitting light from the light reception level from each ONU, and the OLT is the ONU. When the ONU transmission light cannot be exclusively received by the OLT, the ONU light reception level corresponding to the light reception timing previously held from the measured upstream light reception level and when no light is emitted A value obtained by subtracting the level is calculated, and the calculated value is compared with a value for each ONU, and an ONU whose comparison result matches is identified as a failure ONU.

  In the technology described in Patent Document 3, a light intensity detection unit for detecting the light reception level from each ONU and a light intensity reference table for writing the detection light reception level for each ONU are provided in the OLT, causing a failure that disables communication throughout the PON. In this case, the ONU in which the lowest light intensity is written or the ONU having the smallest light intensity change before and after the occurrence of the failure is identified as the failure ONU that continuously emits light.

  In the technique described in Patent Document 4, the OLT periodically sends a trigger optical signal including a specifier designating an ONU and an idle pattern, and the designated ONU is synchronized with the idle pattern in the assigned time slot. The test pattern optical signal is returned to the OLT, and the OLT sends out the interfering light by calculating the correlation between the test pattern optical signal and the reference pattern in the time slot assigned to the ONU. Determine if there is any.

  In the technique described in Patent Document 5, in the ONU, an optical switch is disposed between the laser diode and the WDM coupler, an optical demultiplexer for branching the upstream light is disposed at the tip of the WDM coupler, and the separated upstream light is separated. From this, a monitor device that monitors whether or not the upstream light is output outside the upstream light transmission permission period is arranged to monitor whether or not it is abnormal light, and when the upstream light is abnormal light, the optical switch is opened. Thus, the failure ONU is blocked.

  In the technique described in Patent Document 6, an optical breaker is provided between the OLT and the ONU, the time length of upstream light is measured in the optical breaker, and a continuous optical signal exceeding the time length of upstream light allowed on the PON system is measured. When an optical transmission line is detected, the optical transmission line is blocked.

  In Patent Document 7, the ONU is provided with a transmission abnormality detection unit that detects an abnormality in which the transmission timing of the upstream optical signal is outside the specified range, and a transmission stop unit that stops transmission of the upstream optical signal when an abnormality is detected. It is described.

Japanese Patent No. 4020597 JP 2008-104028 A JP 2008-277947 A Japanese Patent Laid-Open No. 2003-158531 Japanese Patent No. 4111163 JP 2006-304180 A JP 2007-194983 A

  In the techniques described in Patent Documents 1 to 3, the faulty ONU is identified from the light reception power level of each ONU. In an actual PON system, the difference between the interference light power level from the faulty ONU and the light reception power level from the normal ONU Alone, it is difficult to identify the fault ONU. The optical power level of the normal ONU may be significantly smaller than the interference light power level, and in such a case, the normal ONU may be erroneously determined as a faulty ONU.

  Moreover, although the techniques described in Patent Documents 1 to 3 are based on the premise that the interference light power level is constant, it cannot be asserted that the upstream light power level of the ONU is stable for a long time. In the case of interference light whose power level fluctuates irregularly with the passage of time, it is extremely difficult to detect a faulty ONU only with the light reception power level of each ONU.

  As described above, the techniques described in Patent Documents 1 to 3 are not techniques for correctly identifying the failure ONU under any circumstances.

  In the techniques described in Patent Documents 4 to 7, it is necessary to provide a new device on the ONU or the optical transmission line, and it is difficult to apply to the existing PON system. Installation costs and operation management costs also increase.

  An object of the present invention is to provide a failure ONU identification device, a failure ONU identification method, and a PON system that can accurately identify a failure ONU with an inexpensive configuration.

  The faulty ONU identifying device according to the present invention is an optical transmission system in which a plurality of subscriber-side optical terminators (ONUs) share an optical transmission line and its upstream communication band. A failure ONU identification device for identifying a failure ONU that transmits jamming light in the device, a designation means for sequentially designating one of the plurality of subscriber side optical termination devices as a light emission control target, and the light emission control Control signal transmitting means for transmitting a control signal for periodically emitting light at a predetermined light emission period and light emission period to the light emission control object via the light transmission path, and upstream signal light from the light emission control object A light receiving means for receiving the upstream light output from the optical transmission line, a level detecting means for detecting a signal level of a portion including the upstream signal light from the light emission control target from a reception waveform of the light receiving means, The signal level detected by said level detection means said light emission control target, characterized by comprising determination means for determining the normal ONU or fault ONU.

  The failure ONU identifying method according to the present invention is a method for optically terminating a plurality of subscriber-side optical terminations in an optical transmission system in which a plurality of subscriber-side optical termination units (ONUs) share an optical transmission line and its upstream communication band. A failure ONU identification method for identifying a failure ONU that transmits interfering light in a device, a designation step of sequentially designating one of the plurality of subscriber side optical termination devices as a light emission control target, and the light emission control A step of transmitting a control signal for periodically emitting light to a target in a predetermined light emission period and a light emission period, and receiving upstream light output from the optical transmission line including upstream signal light from the light emission control target and receiving A detection step for detecting the signal level of the portion including the upstream signal light from the light emission control target from the waveform, and the light emission control target is a normal ONU by the signal level detected in the detection step Characterized by comprising a determination step of determining failure ONU.

  In the optical transmission system according to the present invention, a plurality of subscriber-side optical terminators (ONUs) share an optical transmission line and its upstream communication band, and a station-side optical terminator (OLT: Optical Line Terminal) An optical transmission system for controlling the upstream signal optical transmission of the plurality of subscriber-side optical terminators, wherein the station-side optical terminator includes the above-described failure ONU identifying device.

  According to the present invention, a faulty ONU can be accurately identified without erroneously determining a normal ONU as a faulty ONU. Further, since it can be realized by installing a new device only in a station side device such as an OLT, a faulty ONU can be specified easily and inexpensively without extremely increasing the installation cost and the operation management cost.

It is a schematic block diagram of one Example of this invention. It is an example of ONU information. It is a schematic block diagram of a signal level detection apparatus. It is a flowchart of the failure ONU detection operation of the present embodiment. 4 is a waveform example in the signal level detection device shown in FIG. 3. It is an example of the square sum calculation result with respect to normal ONU. It is an example of a square sum calculation result with respect to a failure ONU. It is a schematic block diagram of another structure of a signal level detection apparatus. 9 is a flowchart of a fault ONU detection operation for the configuration shown in FIG. 8. It is a schematic block diagram of still another configuration of the signal level detection device. 11 is a flowchart of a failure ONU detection operation for the configuration shown in FIG. 10. It is an example of a waveform of operation | movement description of the signal level detection apparatus of a structure shown in FIG. It is a schematic block diagram of a station side optical terminal device (OLT) incorporating the failure ONU detection device having the configuration shown in FIG. 14 is a flowchart of a fault ONU detection operation having the configuration shown in FIG. 13.

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

  FIG. 1 is a block diagram of a schematic configuration of a failure ONU identifying apparatus according to an embodiment of the present invention.

  In this embodiment, when the OLT that is the station-side optical termination device detects the occurrence of a failure in any of the ONUs that are the subscriber-side optical termination devices, the operator replaces the OLT with the failure ONU identifying device 10. At the time of this replacement, the operator makes it possible for the faulty ONU specifying apparatus 10 to refer to the ONU information recognized immediately before the OLT detects the faulty ONU. Specifically, the ONU information held by the OLT is read to a removable memory device, and the memory device is connected to the failed ONU identifying device 10.

  The OLT is connected to the optical coupler 52 via the trunk optical fiber 50, and the optical coupler 52 is connected to the ONUs 56-1 to 56-n via the branch optical fibers 54-1 to 54-n. The optical coupler 52 equally distributes the optical signal incident from the OLT 10 and supplies it to the branch optical fibers 54-1 to 54-n, and combines the upstream light incident from the ONUs 56-1 to 56-n to the trunk line. It is a passive element that outputs to the optical fiber 50. The trunk optical fiber 50, the optical coupler 52, and the branched optical fibers 54-1 to 54-n constitute an optical transmission line of the PON system, a so-called PON optical transmission line. When the OLT detects continuous interfering light from any one of the ONUs or detects that a plurality of ONUs cause a link break at a time, the OLT notifies the operator of the occurrence of the faulty ONU.

  First, the configuration and basic operation of the failure ONU specifying device 10 will be described. The CPU 20 controls the failure ONU specifying device 10 as a whole. The ONU information storage device 40 stores ONU information registered immediately before the failure detection in the OLT that has detected the failure occurrence. As the ONU information acquisition method, for example, the ONU information stored in the memory of the OLT is read and transferred to the ONU information storage device 40 of the faulty ONU identification device 10 by batch processing, or the OLT stores the ONU information in a nonvolatile manner. The data is stored in a memory medium backed up by a memory or a battery, and the non-volatile memory or memory medium is removed from the OLT and connected to the failure ONU identifying device 10. FIG. 2 is an example of ONU information stored in the ONU information storage device 40. A serial number (or a registration order number) sequentially added to an ONU recognized by the OLT and a MAC (Media Access Control) address of the ONU are stored as a pair.

  The timer 24 measures the current time. The CPU 20 refers to the timer 24 in order to determine the light emission timing of each ONU. The control frame generator 22 generates a fixed-format control frame for a specified ONU according to a control signal from the CPU 20 and supplies the control frame to an electrical / optical (E / O) converter 26. More specifically, the control frame includes a Discovery_GATE message for confirming a registration request, a Register message for assigning a unique logical link to the new registration request ONU, and a GATE message that is a transmission permission signal.

  The E / O converter 26 converts the downlink electrical signal of the control frame supplied from the control frame generator 22 into an optical signal, and supplies the optical signal to a wavelength division multiplexing (WDM) optical coupler 28. The WDM optical coupler 28 outputs the wavelength of the downstream optical signal from the E / O converter 26 to the trunk optical fiber 50. This downstream optical signal propagates through the trunk optical fiber 50, is split by the optical coupler 52, and enters the ONUs 56-1 to 56-n via the branch optical fibers 54-1 to 54-n.

  The WDM optical coupler 28 also outputs upstream optical signals output from the ONUs 56-1 to 56-n and propagated through the branch optical fibers 54-1 to 54-n, the optical coupler 52, and the trunk optical fiber 50 to optical / electrical (O / O). E) Supply to the converter 30. The O / E converter 30 converts the upstream optical signal into an electrical signal and supplies the electrical signal to a low pass filter (LPF) 32. The LPF 32 is installed to prevent aliasing when sampling the reception waveform of the upstream optical signal from the ONUs 56-1 to 56-n. The analog / digital (A / D) converter 34 converts the analog electric signal output from the LPF 32 into a digital signal and inputs the digital signal to the signal level detection device 38.

  The clock generation device 36 refers to the timer 24, generates a clock that is completely synchronized with the light emission cycle and light emission period of the ONU that is controlled to emit light, and inputs the generated clock to the signal level detection device 38.

  The signal level detector 38 analyzes the waveform of the received data signal from the A / D converter 34, particularly the waveform level, according to the clock from the clock generator 36, and supplies the analysis result to the CPU 20. The CPU 20 determines from the detection result of the signal level detection device 38 whether the ONU whose light emission has been controlled is normal.

  FIG. 3 shows a schematic block diagram of the signal level detection device 38. The fault ONU continuously transmits upstream light or transmits upstream light at a timing unrelated to the light emission control signal from the fault ONU identifying device 10. Accordingly, the failure ONU identifying device 10 receives the interference light caused by the failure ONU and the upstream light from the normal ONU whose emission is controlled. In the signal level detection device 38 having the configuration shown in FIG. 3, the upstream light level from the normal ONU buried in the interference light is separated and detected by the correlation between the received upstream signal and the clock when the ONUs are sequentially controlled to emit light. Identify whether the ONU is normal or faulty.

  The 90 ° phase shifter 60 shifts the phase of the clock from the clock generator 36 by 90 °. The multiplier 62-1 multiplies the clock (phase 0 °) from the clock generator 36 by the output waveform of the A / D converter 34, and the multiplier 62-2 outputs the clock (from the 90 ° phase shifter 60). Multiply the output waveform of the A / D converter 34 by (phase 90 °).

The integrating circuits 64-1 and 64-2 integrate the received waveforms output from the multipliers 62-1 and 62-2 by the time width of the received waveforms, and divide the integration result by the time width to obtain time. The average is calculated and output to the sum of squares calculation circuit 66 as calculation results X and Y, respectively. The integrating circuits 64-1 and 64-2 are controlled by the CPU 20 so as to integrate (measure) the time width of the received waveform. The square sum calculation circuit 66 calculates the square sum X ² + Y ² of the output values X and Y of the integration circuits 64-1 and 64-2, and outputs the result as a signal level detection result Z (i).

  The signal level detection process in the configuration shown in FIG. 3 is equivalent to a process of synchronously detecting a received signal using a reference clock and calculating a correlation value with the reference clock.

  The CPU 20 can exclusively specify which one is the faulty ONU by sequentially executing the above reception waveform analysis processing on the ONUs 56-1 to 56-n.

  An operation for identifying the abnormal light emission failure ONU in this embodiment will be described. FIG. 4 shows a flowchart of the fault ONU specifying operation of the fault ONU specifying device 10.

  The CPU 20 sets, as initial parameters for determining the normality of each ONU, a cycle T for emitting each ONU, a light emission period D (<T), a light emission control count M, and a normality determination threshold W (S1). The CPU 20 acquires ONU information of each ONU from the ONU information storage device 40 (S2). Here, it is assumed that n ONUs (i) (i = 1, 2,..., N) communicate with each other before the OLT finds a faulty ONU. The CPU 20 determines normality one by one for the n ONUs in order.

  A variable i designating ONU is initialized with 1 (S3). That is, the ONU (i) to be controlled for light emission is designated. In recent PON systems, in order to control the light emission operation of ONU (i), it is necessary that the failure ONU identifying device 10 establishes a logical link with ONU (i). Therefore, the CPU 20 simulates the logical link assignment to the ONU (i) (S4). Specifically, the CPU 20 transmits a Discovery_GATE message to the ONU (i) and receives a Register_REQ message, which is a registration request signal from the ONU (i), immediately after the time of receiving the Register_REQ message, the logical link ID (LLID) is assigned to the ONU (i). ) Is sent. Thereby, even if it is a case where the upstream optical signal from ONU (i) cannot be received in presence of disturbance light, CPU20 can complete the provision of the logical link with respect to ONU (i) internally. Thereafter, the CPU 20 can transmit a light emission control signal to the ONU (i).

  After assigning a logical link to ONU (i), the CPU 20 transmits a light emission control signal (GATE message) for causing the ONU (i) to emit light in the light emission period T and the light emission period D, for the number of times of light emission control (S5 to S10). ). First, a variable k indicating the number of times of light emission is initialized with 1 (S5). Next, the failure ONU identification device 10 transmits the GATE message at the same period T as the ONU (i) emission period, and controls the ONU (i) to emit light after a predetermined time from the transmission time of each GATE message ( S6). As a result, if the ONU (i) is normal, it emits light as instructed by the light emission control signal from the faulty ONU specifying device 10; Or emits no light at all.

  The normal ONU (i) uplink transmission signal is the sum of the REPORT message for reporting the amount of data requested for transmission at the next opportunity and the uplink data transmitted this time. When uplink data to be transmitted is not accumulated in the ONU (i) buffer, the ONU (i) transmits an idle pattern only during the light emission period D.

  The period during which the failure ONU specifying device 10 controls the light emission of each ONU, for example, the number of times of control M may be an arbitrary period during which the normality of ONU (i) can be determined.

  The signal level detection device 38 calculates the index Z (i) indicating the upstream light level from the normal ONU buried in the interference light as described above, and supplies it to the CPU 20 (S7).

  FIG. 5 is a waveform example showing the relationship between the light emission control signal from the faulty ONU identification device 10 to the ONU (i), the received waveform, and the 0 ° clock and 90 ° clock for detecting the received waveform level. FIG. 5A shows a light emission control signal, and FIG. 5B shows an upstream light waveform (assuming that the interfering light is CW (continuous) light) incident on the faulty ONU identifying device 10 from the trunk optical fiber 50. 2C shows the 0 ° clock from the clock generator 36, and FIG. 2D shows the 90 ° clock by the phase shifter 60. In FIG. 5, the horizontal axis represents time. The reception waveform shown in FIG. 5B is illustrated as an analog waveform for easy understanding, but is represented by a digital value in the signal level detection device 38 shown in FIG.

  As shown in FIG. 5 (b), the upstream light input from the trunk optical fiber 50 to the faulty ONU specifying device 10 is generally a signal in which the upstream signal light whose emission is controlled from the normal ONU is superimposed on the interference light. FIG. 6 shows the time change of the output value of the sum-of-squares calculation circuit 66 when the upstream light input from the trunk optical fiber 50 to the faulty ONU specifying device 10 includes upstream signal light whose emission is controlled from the normal ONU. FIG. 7 shows the time change of the output value of the sum-of-squares calculation circuit 66 when the upstream light input from the trunk optical fiber 50 to the faulty ONU identification device 10 does not include the upstream signal light whose emission is controlled from the normal ONU. . FIG. 7 corresponds to the case where the ONU (i) whose light emission is controlled is a failure ONU.

  As can be understood from FIG. 6 and FIG. 7, the upstream signal light whose emission is controlled from the normal ONU by the multipliers 62-1-62-2, the integration circuits 64-1, 64-2, and the square sum calculation circuit 66. It can be separated and its level detected. That is, it can be determined whether or not the ONU (i) subject to light emission control is a normal ONU.

  The CPU 20 compares the signal level detection result Z (i) with the normality determination threshold value W (S8). When the ONU (i) specified by the variable i is a failure ONU, the light emission control by the GATE message is not followed, and the upstream light level Z (i) input to the failure ONU specifying device 10 at that time is remarkably small. Value. Accordingly, the CPU 20 determines that ONU (i) is a normal ONU when Z (i) is greater than the threshold W, and determines that ONU (i) is a faulty ONU when Z (i) is less than or equal to the threshold W. Yes (S9).

  When ONU (i) is a normal ONU (S8), M inspections are continued (S10, S11). On the other hand, if the ONU (i) is a faulty ONU (S8, S9), the CPU 20 checks whether all ONUs have been inspected (S12), and if there is an uninspected ONU (S12), i is incremented. (The next ONU is set as the inspection target) (S13), and step S4 and subsequent steps are repeated. When all the ONUs are inspected (S12), the process ends.

  In the present embodiment, even if the upstream light from the normal ONU is weaker than the interference light, it can be detected, and thereby the faulty ONU can be accurately identified.

  When the interference light from the faulty ONU has the same fundamental frequency component as the upstream light output from the ONU (i), there is a possibility that the normality of the ONU (i) may be erroneously determined. By performing the light emission control by changing the light emission period T at a certain interval, it is possible to avoid erroneous determination.

  Whether the interference light generated by the failure ONU is continuous light (CW), an idle pattern, or a pseudo-random signal, the failure ONU can be accurately identified.

  FIG. 8 shows a schematic block diagram of another configuration of the signal level detection device 38. Since upstream optical transmission of the ONU is controlled by the light emission period T, upstream light from the ONU has a fundamental frequency component of 1 / T (Hz). By detecting the signal level of the fundamental frequency component, the failure ONU and the normal ONU can be identified.

  The clock from the clock generator 36 is input to the trigger generator 68, and the output signal of the A / D converter 34 is input to the Fourier transformer 70. The trigger generation device 68 generates a trigger synchronized with the clock and supplies it to the Fourier transform device 70. The Fourier transform device 70 refers to the trigger from the trigger generation device 68 and Fourier transforms the output signal of the A / D converter 34. Further, the CPU 20 resets the Fourier transform device 70 by a reset signal instructing the reading of the received waveform and the end of measurement so that the Fourier transform is performed by the time width of the received waveform. The Fourier transform device 70 supplies the CPU 20 with the peak level F (i) of the fundamental frequency component of 1 / T (Hz).

  FIG. 9 shows an operation flowchart when the signal level detection device 38 having the configuration shown in FIG. 8 is used. Steps S21 to S33 correspond to steps S1 to S13 shown in FIG. 4, but only steps S21, S27, and S28 are slightly different from steps S1, S7, and S8, respectively. That is, step S21 is the same as step S1 except that the value E corresponding to the peak level F (i) measured by the Fourier transform apparatus 70 is set as the normality determination threshold value of the initial parameter. In step S27, the peak level F (i) measured by the Fourier transform apparatus 70 is captured. In step S28, the captured peak level F (i) is compared with the normality determination threshold value E.

  A bandpass filter that passes the fundamental frequency component of the frequency 1 / T (Hz) of the upstream light from the normal ONU whose emission is controlled is provided instead of the Fourier transform device 70, and the peak level of the output signal of the bandpass filter is set. It may be compared with a normality determination threshold value. In this case, the A / D converter 34 may not be provided.

  Even in this embodiment, even if the upstream light from the normal ONU is weaker than the interfering light, it can be detected, so that the faulty ONU can be accurately identified.

  When the interference light from the faulty ONU has the same fundamental frequency component as the upstream light output from the ONU (i), there is a possibility that the normality of the ONU (i) may be erroneously determined. By performing the light emission control by changing the light emission period T at a certain interval, it is possible to avoid erroneous determination.

  Whether the interference light generated by the failure ONU is continuous light (CW), an idle pattern, or a pseudo-random signal, the failure ONU can be accurately identified.

  A description will be given of an embodiment in which a failure ONU is specified by analyzing a received waveform in the time domain. FIG. 10 shows a schematic configuration block diagram of another configuration of the signal level detection device 38 for that purpose.

  The clock from the clock generator 36 is input to the trigger generator 72, and the output signal of the A / D converter 34 is input to the averaging processor 74. The trigger generation device 72 generates a trigger synchronized with the clock and supplies the trigger to the averaging processor 74. The averaging processor 74 refers to the trigger from the trigger generator 72 and adds and averages the output signal of the A / D converter 34 at intervals of the period T. The CPU 20 resets the addition average processing device 74 by a reset signal instructing the reading of the received waveform and the end of measurement so that the addition average processing device 74 performs addition averaging for the time width of the reception waveform of the upstream light from the ONU (i). To do. In this way, the addition average processing device 74 calculates the average intensity value of the upstream light and interference light from the ONU (i) by the addition average processing. From the calculated average value F (i), irregular noise components due to interference light are reduced. The addition average processing device 74 also follows the trigger from the trigger generation device 72 and the reset from the CPU 20, and the received light average level during the period in which the upstream light from the ONU (i) is not received, that is, the average level of only interference light And the CPU 20 is notified of the measurement result. The addition average processing device 74 notifies the CPU 20 of the average intensity value of the upstream light and interference light from the ONU (i) and the intensity value of only interference light calculated in this way.

  FIG. 11 is an operation flowchart when the signal level detection device 38 having the configuration shown in FIG. 10 is used. Steps S41 to S43 correspond to steps S1 to S13 shown in FIG. 4, but only steps S41, S47, and S48 are slightly different from steps S1, S7, and S8, respectively. That is, step S41 sets the threshold value P for the difference between the average intensity value of the upstream light and the interference light and the intensity value of only the interference light, which is measured by the addition averaging processor 74, as the normality determination threshold value of the initial parameter. It is the same as step S1 except doing. In step S47, the CPU 20 calculates a difference value Q (i) between the average intensity value of the upstream light and the interference light from the ONU (i) measured by the addition averaging processor 74 and the intensity value of only the interference light. In step S48, the difference value Q (i) is compared with the normality determination threshold value P.

  FIG. 12 shows the relationship between the added average intensity value of upstream light and interference light from ONU (i), the intensity value of interference light only, and the difference value Q (i) when ONU (i) is a normal ONU. Indicates. The peak levels of the normal light and the interference light can be calculated by referring to the peak levels in the normal light emission period D and other periods in the reception waveform after the averaging.

  Even in this embodiment, even if the upstream light from the normal ONU is weaker than the interfering light, it can be detected, so that the faulty ONU can be accurately identified. Further, this is effective for interference light whose power level varies irregularly with time. A normal ONU and a fault ONU can be identified only by simple waveform processing. Whether the interference light generated by the failure ONU is continuous light (CW), an idle pattern, or a pseudo-random signal, the failure ONU can be accurately identified.

  FIG. 13 shows a schematic block diagram of the OLT 100 in which the function of the failure ONU specifying device 10 is incorporated. The illustrated OLT 100 operates in a normal OLT mode for managing communication between the ONUs 56-1 to 56-n and the upper network and the failure ONU identification mode described in the above embodiment.

  The OLT 100 is connected to an upper network via a network interface (NW I / F) 110. The NW I / F 110 supplies the downlink signal from the upper network to the downlink frame transfer apparatus 112. The downlink frame transfer device 112 separates the signal to the OLT 100 from the downlink signal from the upper network and transfers it to the CPU 130, and directs it to any one of the ONUs 56-1 to 56-n from the downlink signal from the upper network. The downlink control frame generated by the CPU 130 is multiplexed on the time axis on the received signal and supplied to the electrical / optical (E / O) converter 114 in the frame structure for the PON system. That is, the downlink frame transfer device 112 functions as a demultiplexing device. The CPU 130 also preferentially controls the downstream signals to the ONUs 56-1 to 56-n by the downstream frame transfer device 112. The E / O converter 114 converts the downlink electrical signal transferred from the downlink frame transfer apparatus 112 into an optical signal, and supplies the optical signal to a wavelength division multiplexing (WDM) optical coupler 116. As in FIG. 1, the WDM optical coupler 116 is connected to the ONUs 56-1 to 56-n via the trunk optical fiber 50, the optical coupler 52, and the branched optical fibers 54-1 to 54-n, and is an E / O converter. The downstream optical signal from 114 is output to the trunk optical fiber 50.

  The WDM optical coupler 116 also receives an upstream optical signal input from the ONUs 56-1 to 56-n via the branch optical fibers 54-1 to 54-n, the optical coupler 52, and the trunk optical fiber 50 as optical / electrical (O / O). E) Connect to transducer 118. The O / E converter 118 converts the upstream optical signal from the WDM optical coupler 116 into an electrical signal.

  In this embodiment, a switch 120 is provided for identifying the fault ONU. In the normal OLT mode, the switch 120 supplies the output signal of the O / E converter 118 to the control frame separation device 122 to identify the fault ONU. In the mode, the output signal of the O / E converter 118 is supplied to the LPF 126.

  The control frame separation device 122 uses the upstream electrical signal supplied from the switch 120 as an upstream data frame directed to the upper network, and a control frame such as a registration / request signal transmitted from the ONUs 56-1 to 56-n to the OLT 100. The former is supplied to the upstream frame transfer device 124, and the latter is supplied to the CPU 130. The uplink frame transfer device 124 outputs the uplink signal from the control frame separation device 122 to the NW I / F 110 in the frame structure for the upper network under priority control by the CPU 130. The upstream frame transfer device 124 also outputs a control signal from the CPU 130 to a device on the upper network, for example, a network monitoring device, to the NW I / F 110. From this viewpoint, the upstream frame transfer device 124 is also a multiplexing device that multiplexes the signal from the CPU 130 and the signal from the control frame separation device 122 on the time axis. The NW I / F 110 transfers the signal from the upstream frame transfer device 124 to the upper network.

  More specifically, the uplink control frame separated by the control frame separation device 122 and supplied to the CPU 130 includes a Register_REQ message, a Register_ACK message, a REPORT message, or the like. When the control frame is received from each of the ONUs 56-1 to 56-n, the CPU 130 causes the control frame generation function 132 to generate a downlink control frame to the ONUs 56-1 to 56-n corresponding to the received control frame. More specifically, the downlink control frame includes a Discovery_GATE message, a Register message, or a GATE message. Regarding the light emission control of each ONU 56-1 to 56-n, the control frame generation function 132 refers to the ONU information storage device 134 and the timer 136, and the upstream optical transmission timing and light emission period of each ONU 56-1 to 56-n. And a downlink control frame that indicates the calculated upstream light transmission timing and light emission period is generated.

  In the fault ONU identification mode, the switch 120 supplies the output signal of the O / E converter 118 to the LPF 126. Similar to the LPF 32, the LPF 126 is installed to prevent aliasing during sampling of received waveforms from the ONUs 56-1 to 56-n. The analog / digital (A / D) converter 128 converts the analog signal from the LPF 126 into a digital signal with a sampling clock similar to that of the A / D converter 34 and supplies the digital signal to the signal level detection device 140. Similarly to the clock generation device 36, the clock generation device 138 refers to the output of the timer 136, generates a clock indicating the reception timing of upstream light from the normal ONU whose light emission has been controlled, and supplies the clock to the signal level detection device 140. . The operations of the clock generation device 138 and the signal level detection device 140 are the same as those of the clock generation device 36 and the signal level detection device 38, respectively, and the CPU 130 performs normal ONU and failure in the same procedure as described in the above embodiment. Identify the ONU.

  FIG. 14 shows an operation flowchart of the OLT 100. The fault ONU identification operation is shown in detail.

  When any of the ONUs 56-1 to 56-n that are turned on are operating normally, the switch 120 is connected to the contact A (control frame separation device 122 side), and the CPU 130 sets the OLT 100 as a normal OLT. Operate (S101). For example, an unregistered ONU is registered and a logical link is given. After the registration, the CPU 130 transmits a GATE message to each of the registered ONUs 56-1 to 56-n, and each ONU 56-1 to 56-n that has received the GATE message receives each ONU 56-1 to 56-n. The amount of data stored in the buffer is reported to the OLT 100 with a REPORT message. The CPU 130 analyzes the received REPORT message, schedules the transmission timing and the light emission period to the ONUs 56-1 to 56-n that desire transmission, and designates it with the GATE message.

  During the normal OLT operation (S101), when it is detected that any of the ONUs 56-1 to 56-n generates interference light (S102), the CPU 130 sets the switch 120 to the B contact (LPF 126). Side) (S103), the failure ONU specifying operation (S104 to S114) is entered.

  As described above, the light emission cycle T, the light emission period D, the light emission control count M, and the normality determination threshold are set as the initial parameters for the ONU normality determination (S104). Here, it is assumed that there are n ONUs that are normality determination targets. The normality determination threshold depends on which of the failure ONU identification methods described as the first to third embodiments is used.

  A variable i designating the ONU to be subjected to normality determination is initialized with 1 (S105), and normality determination for the ONU (i) is executed (S106 to S109). Here, the order of ONUs to be determined is the order of ONU numbers registered in the ONU information storage device 134, but is not limited to this order.

  A new logical link is assigned to ONU (i) (S106). If a logical link can be maintained regardless of the presence of interference light, the maintained logical link may be used. In general, assuming a situation in which the logical link is broken, the provision of the logical link is simulated as described above.

  Subsequently, a control signal (GATE message) for causing the ONU (i) to emit light in the light emission period T and the light emission period D is transmitted one by one for the light emission control count M (S107). As described above, the level of the optical signal received by the OLT 100 during the light emission control is detected (S108), and the normality of the ONU (i) is determined (S109).

  When the ONU (i) is a failure ONU (S109), the CPU 130 transmits a control signal for forcibly stopping the transmission of the upstream signal light to the ONU (i) (S112). At the same time, the CPU 130 notifies the PON system administrator that the ONU (i) is a faulty ONU by display on a monitor means (not shown) or via the host network. When the forced stop is successful, the PON system administrator is notified of this.

  When the ONU (i) is a normal ONU (S109), the next ONU (S111) is similarly determined whether it is a normal ONU (S106 to S109). Without detecting the failure ONU (S109), when the normal / failure determination is completed for all the ONUs that were activated before the failure occurred (S110), the CPU 130 displays on a monitor means (not shown) or Notify the PON system administrator of the non-detection via the host network.

  After steps S112 and S113, the CPU 130 switches the switch 120 to the contact A (control frame separation device 122 side) and executes a normal OLT operation (S101). At this time, the CPU 130 resumes from the provision of the logical links to the activated ONUs 56-1 to 56-n.

  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: Fault ONU identification device 20: CPU
22: control frame generator 24: timer 26: electrical / optical (E / O) converter 28: wavelength division multiplexing (WDM) optical coupler 30: optical / electrical (O / E) converter 32: low-pass filter ( LPF)
34: analog / digital (A / D) converter 36: clock generation device 38: signal level detection device 40: ONU information storage device 50: trunk optical fiber 52: optical couplers 54-1 to 54-n: branch optical fiber 56 -1 to 56-n: ONU
60: 90 ° phase shifters 62-1, 62-2: multiplication circuits 64-1, 64-2: integration circuit 66: sum of squares calculation circuit 68: trigger generation device 70: Fourier transform device 72: trigger generation device 74: Addition averaging processor 100: OLT
110: Network interface (NW / IF)
112: Downstream frame transfer device 114: Electrical / optical (E / O) converter 116: Wavelength division multiplexing (WDM) optical coupler 118: Optical / electrical (O / E) converter 120: Switch 122: Control frame separation device 124 : Upstream frame transfer device 126: Low-pass filter (LPF)
128: Analog / digital (A / D) converter 130: CPU
132: Control frame generation function 134: ONU information storage device 136: Timer 138: Clock generation device 140: Signal level detection device

Claims (14)

In an optical transmission system in which a plurality of subscriber-side optical terminators (ONU: Optical Network Unit) share an optical transmission line and its upstream communication band, the interfering light in the plurality of subscriber-side optical terminators is transmitted. A failure ONU identification device that identifies a failure ONU,
Designation means (20) for sequentially designating one of the plurality of subscriber-side optical terminal devices (56-1 to 56-n) as a light emission control target;
Control signal transmitting means (22) for transmitting a control signal for periodically emitting the light emission control target in a predetermined light emission period and light emission period to the light emission control target via the optical transmission path;
A light receiving means (30) for receiving upstream light output from the optical transmission line, including upstream signal light from the light emission control target;
Level detection means (38) for detecting the signal level of the portion including the upstream signal light from the light emission control target from the received waveform of the light receiving means;
Determination means (20) for determining whether the light emission control target is a normal ONU or a failure ONU based on the signal level detected by the level detection means
A faulty ONU identifying device.   2. The fault ONU identifying apparatus according to claim 1, wherein the specifying unit includes a unit that gives a logical link to the light emission control target. Furthermore, it comprises clock generation means (36) for generating a clock indicating the timing at which the light receiving means receives the upstream signal light from the light emission control target,
The level detection means calculates a correlation value between the received waveform and the clock,
3. The failure ONU identifying device according to claim 1, wherein the determination unit determines that the light emission control target is the failure ONU when the correlation value is equal to or less than a predetermined threshold. The level detection means (38)
A 90 ° phase shifter (60) for shifting the phase of the clock by 90 °;
A first multiplier (62-1) for multiplying the received waveform of the light receiving means by the clock;
A second multiplier (62-2) for multiplying the received waveform of the light receiving means by the output of the 90 ° phase shifter;
A first integration circuit (64-1) for time-integrating the output of the first multiplier by the time width of the received waveform and dividing the integration result by the time width to calculate a time average;
A second integration circuit (64-2) for time-integrating the output of the second multiplier by the time width of the received waveform and dividing the integration result by the time width to calculate a time average;
Sum-of-squares calculation circuit (66) for calculating the sum of squares of the outputs of the first and second integration circuits
The failure ONU identifying apparatus according to claim 3, wherein   The level detection means (38) includes means for Fourier-transforming the received waveform and calculating a peak level of a frequency component corresponding to the predetermined light emission period and light emission period instructed to the light emission control target. The failure ONU identification device according to claim 1 or 2.   The level detection means detects, as the signal level, a level of a frequency component corresponding to the predetermined light emission cycle and light emission period instructed to the light emission control target from the received waveform. The fault ONU identification device described in 1.   The level detection means includes an addition average of a portion corresponding to the upstream signal light from the light emission control target of the reception waveform and an addition average of a portion of the reception waveform not corresponding to the upstream signal light from the light emission control target. The failure ONU identification device according to claim 1, wherein the difference is detected as the signal level. In an optical transmission system in which a plurality of subscriber-side optical terminators (ONU: Optical Network Unit) share an optical transmission line and its upstream communication band, the interfering light in the plurality of subscriber-side optical terminators is transmitted. A failure ONU identification method for identifying a failure ONU,
A designation step (S3, S13, S4) for sequentially designating one of the plurality of subscriber-side optical terminal devices (56-1 to 56-n) as a light emission control target;
A step (S6) of transmitting a control signal for periodically emitting light to the light emission control target in a predetermined light emission period and light emission period;
Detection step of receiving upstream light output from the optical transmission line including upstream signal light from the light emission control target, and detecting a signal level of a portion including the upstream signal light from the light emission control target from a received waveform ( S7)
Determination step of determining whether the light emission control target is a normal ONU or a failure ONU based on the signal level detected in the detection step (S8)
A failure ONU identification method comprising:   The fault ONU identifying method according to claim 8, wherein the specifying step includes a step of assigning a logical link to the light emission control target. The detection step includes a step of generating a clock synchronized with a light emission period and a light emission period instructed to the light emission control target, and calculating a correlation value between the reception waveform and the clock,
10. The failure ONU identification method according to claim 8, wherein the determination step determines that the light emission control target is the failure ONU when the correlation value is equal to or less than a predetermined threshold value.   The detection step includes performing Fourier transform on the received waveform and detecting, as the signal level, a peak level of a frequency component corresponding to the predetermined light emission period and light emission period instructed to the light emission control target. The failure ONU identification method according to 8 or 9.   The detection step detects a level of a frequency component corresponding to the predetermined light emission cycle and light emission period instructed to the light emission control target as the signal level from the received waveform. The failure ONU identification method described.   The detection step includes an addition average of a portion corresponding to the upstream signal light from the light emission control target of the reception waveform and an addition average of a portion of the reception waveform not corresponding to the upstream signal light from the light emission control target. The fault ONU identification method according to claim 8 or 9, wherein the difference is detected as the signal level.   A plurality of subscriber side optical terminators (ONUs) share an optical transmission line and its upstream communication band, and a station side optical terminator (OLT: Optical Line Terminal) is the plurality of subscriber side optical terminators. An optical transmission system for controlling the upstream optical signal transmission, wherein the station side optical termination device comprises the failure ONU identifying device according to any one of claims 1 to 7. system.

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