JP5397115B2 - In-station apparatus, subscriber apparatus, optical communication system, failure apparatus identification method, and apparatus program - Google Patents

Description

  The present invention is a point-to-multipoint light configured by connecting a plurality of subscriber units (ONU: Optical Network Unit) to an intra-station device (OLT: Optical Line Terminator) such as a PON (Passive Optical Network) system. The present invention relates to an intra-station apparatus, a subscriber apparatus, an optical communication system, a failure apparatus identification method, and an apparatus program used in a communication system.

Generally, a PON system is configured by connecting a plurality of ONUs to an OLT via an optical splitter.
Since the same wavelength is used for the upstream optical signal output from each ONU, the OLT schedules upstream traffic by a DBA (Dynamic Bandwidth Allocation) scheduler and grants transmission permission to each ONU. . This prevents transmission data from each ONU from colliding on an optical transmission line shared by a plurality of ONUs.

  Also, in an optical communication system, when the duration of an idle pattern transmitted from an ONU during idle time is longer than a specified value defined in the standard, and only one logical connection is established, the connected ONU is There are some which are determined to be abnormal (see, for example, Patent Document 1).

  Also, when there is no periodic response from the ONU in the optical communication system, the connected ONUs are divided into two groups and extinction commands are transmitted to the two groups, and the optical signals that have been received so far disappear. Alternatively, there is one in which a malfunctioning ONU is specified by returning a periodic response from another ONU (see, for example, Patent Document 2).

JP 2008-28451 A JP 2004-112746 A

  However, when a certain ONU always outputs light due to a failure (always light-emitting mode) among a plurality of ONUs connected to the same optical fiber, it collides with an optical signal transmitted by another ONU. The service to other users is affected, and in the worst case, the service to other users is stopped.

When such a failure ONU in the constant light emission mode occurs, in order to identify the failure ONU, a maintenance staff is dispatched to all user homes connected to the same optical fiber, contacted with the maintenance staff on the center side, and the ONU It was necessary to identify the faulty ONU by turning off the power of each unit.
For this reason, it takes time to identify the faulty device, time is required to restore the service, and there is a problem that maintenance costs due to dispatch of maintenance personnel to the site are required.

  In addition, the above-mentioned Patent Document 1 is intended to be specified when there is only one failure ONU in the always light emission state, and it is not considered even when there are a plurality of failure ONUs in the always light emission state. There wasn't. That is, when there are a plurality of failure ONUs that are always in a light emitting state, the links of all ONUs including the failure ONUs are unstable (links are not established), so it is difficult to identify the failure ONUs. It was.

The above-mentioned Patent Document 2 assumes a failure mode in which the ONU does not respond. For example, the ONU responds due to a failure in the signal processing unit or the optical transmission unit of the ONU, but is always in the light emission mode. It was not considered even about the failure state to become.
Further, since the extinction command is transmitted in two groups, there are a plurality of failure ONUs that are always in a light emitting state, and there is a possibility that the failure ONUs cannot be specified if they exist in both groups.

  The present invention has been made in view of such a situation, and even when a plurality of failure devices in a constantly light-emitting state occur, an in-station device, a subscriber device, which can automatically identify the failure device, An object of the present invention is to provide an optical communication system, a faulty device identification method, and a device program.

  In order to achieve the above object, an intra-station apparatus according to the present invention is an intra-station apparatus used in a system configured by connecting a plurality of subscriber apparatuses to an intra-station apparatus via an optical branching unit. Measuring means for measuring the amount of light received from the apparatus, stop instruction means for transmitting a light output stop instruction to the subscriber apparatus, and causing the stop instruction means to transmit a stop instruction to one subscriber apparatus, to another subscriber The received light quantity of the device is measured by the measuring means, and when the measured received light quantity is smaller than a received light quantity before the stop instruction transmission by the stop instruction means by a predetermined threshold or more, the subscriber apparatus that has transmitted the stop instruction And a failure device specifying means for determining that the subscriber device that has transmitted the stop instruction is not a failure device in other cases.

  The subscriber device according to the present invention receives a setting of a standard ID assigned by a procedure defined in the standard and a fixed ID assigned in association with a MAC (Media Access Control) address, and transmits a signal for measurement. When the request is received by the fixed ID, pattern sending means for sending a predetermined measurement pattern is provided.

  An optical communication system according to the present invention is characterized in that a plurality of subscriber devices according to the present invention described above are connected to the above-mentioned intra-station device according to the present invention via an optical branching means. .

  The faulty device specifying method according to the present invention is a faulty device specifying method in a system in which a plurality of subscriber devices are connected to an intra-station device via an optical branching means. An output stop instruction is transmitted, the received light quantity of other subscriber devices is measured, and when the measured received light quantity is smaller than the received light quantity before transmission of the stop instruction, the stop instruction is issued. It is characterized by comprising a failure device specifying step of specifying the transmitted subscriber device as a failed device, and otherwise determining that the subscriber device that transmitted the stop instruction is not a failed device.

  An in-station device program according to the present invention is a program for an in-station device used in a system configured by connecting a plurality of subscriber devices to an in-station device via an optical branching unit. A light output stop instruction is transmitted to the other subscriber device, and the received light quantity of another subscriber unit is measured. If the measured received light quantity is smaller than the received light quantity before transmission of the stop instruction, the stop is performed. The subscriber device that has transmitted the instruction is identified as a failed device, and in other cases, the failed device identifying procedure for determining that the subscriber device that has transmitted the stop instruction is not a failed device is executed by the computer of the in-station device. Features.

  As described above, according to the present invention, it is possible to automatically identify a faulty device even when a plurality of faulty devices that are always in a light emitting state are generated.

It is a block diagram which shows the structural example of the PON system as embodiment of this invention. It is a flowchart which shows the operation | movement as this embodiment schematically. It is a sequence diagram which shows a Discovery process. It is a figure which shows the example of allocation of Static LLID. It is a flowchart which shows the normality confirmation operation | movement by this embodiment. It is a figure explaining the normality confirmation by this embodiment. It is a flowchart which shows the normal light emission ONU specific operation by this embodiment. It is a figure explaining the always light emission ONU specific operation by this embodiment. It is a figure which shows the example of allocation of Static LLID. It is a figure which shows the specific example of a normal state in the normality confirmation by this embodiment. It is a figure which shows the example of a failure occurrence state in the normality confirmation by this embodiment. It is a figure which shows the specific example of the always light emission ONU specific operation 1 by this embodiment. It is a figure which shows the specific example of the always light emission ONU specific operation 2 by this embodiment. It is a figure which shows the specific example of the always light emission ONU specific operation 3 by this embodiment. It is a figure which shows the specific example of the always light emission ONU specific operation 4 by this embodiment.

  Next, an embodiment in which an in-station apparatus, a subscriber apparatus, an optical communication system, a failure apparatus specifying method, and an apparatus program according to the present invention are applied to a PON system will be described in detail with reference to the drawings.

First, an outline of the present embodiment will be described.
In this embodiment, the OLT device installed on the local office side in the PON system is fixedly allocated in advance different from the logical link established by the process defined in the standard (defined in IEEE802.3ah). By using a link, even if multiple ONUs are always in the issuing state at the same time, the optical output power of each ONU is monitored at the timing when each ONU connected to the same PON line outputs light. It is possible to do.

  In this embodiment, by comparing the optical output power of each ONU measured in this way with the power in a normal state, it is possible to identify a faulty ONU that has fallen into a constant light emission state. Further, the ONU for which the failure is specified is removed from the system by being stopped by remote control from the OLT, and the service can be continued.

Next, the configuration of the PON system as the present embodiment will be described with reference to FIG.
As shown in FIG. 1, the PON system according to this embodiment includes an OLT 101 installed on the center side, which includes a plurality of ONUs 104 via an optical transmission path 102 and an optical splitter 103 (optical branching unit) using a single-core optical fiber. It is configured to accommodate.
Each ONU 104 converts a signal from the end user terminal 105 into an optical signal and transmits / receives to / from the OLT 101.

  Next, the outline of the operation according to the present embodiment will be described with reference to the flowchart of FIG.

  When the ONU is activated, the Discovery process specified in IEEE802.3ah is performed, handshaking is performed between the ONU 104 and the OLT 101, the dynamic LLID is assigned to the MAC address of the activated ONU 104, and a logical link is established Established.

  The logical link established by this discovery process is once again broken by the discovery process once the link is disconnected due to the power off of the ONU, optical fiber disconnection, external failure (such as constant light emission), etc. Need to be established. The LLID assigned by this Discovery process is hereinafter referred to as Dynamic LLID (standard ID).

  In this embodiment, a fixed LLID (hereinafter, Static LLID; fixed ID) is allocated in advance separately from the LLID allocation in the Discovery process (step S1).

  When installing each ONU 104, the OLT 101 measures the optical output power (the amount of received light) in the received signal received from the ONU as an initial value. The OLT 101 stores the initial value of the optical output power in association with the specific information (for example, MAC address, Static LLID, etc.) of the ONU 104 as a reference value of the optical output power in the ONU 104 (step S2).

  The OLT 101 performs a normality confirmation operation for each ONU 104 for each predetermined period using this Static LLID (step S3). When it is detected that there is a failure ONU in the constant light emission mode (step S4; Yes), a specific operation for the constant light emission ONU is performed (step S5).

  Next, details of each operation according to the present embodiment will be described with reference to the drawings.

<1> Allocation of LLID (Logical Link Identification) by Discovery Process Since the same wavelength is used for the upstream optical signal output from each ONU 104, the PON system according to this embodiment outputs the signal from each ONU. In order to avoid the collision of upstream optical signals, the following procedure is taken.

  When the ONU is activated, a Discovery process defined in IEEE 802.3ah is performed as shown in FIG.

  First, the OLT 101 transmits a Discovery Gate in order to accept a link registration request from the ONU 104 (step S11). When receiving the Discovery Gate, the ONU 104 transmits a link registration request (step S12).

  When the OLT 101 receives the link registration request, the OLT 101 determines an LLID (Dynamic LLID) to be assigned to the ONU MAC address and transmits the LLID to the ONU 104 (step S13).

  The ONU 104 recognizes the assigned Dynamic LLID and stores it in a storage unit (not shown) in the apparatus.

The OLT 101 transmits a transmission permission signal to the allocated Dynamic LLID (step S14). The ONU 104 recognizes the allocated Dynamic LLID normally and notifies the OLT 101 that it has been saved (step S15).
The OLT 101 receives the response from the ONU, and a logical link is established (step S16).

  When the logical link is established in this way, the ONU 104 thereafter transmits a frame (Report) for confirming the normality of the link at a maximum period of 50 ms (step S17). The OLT 101 sets the link to an unestablished state when no Report frame is received for 1 second or longer.

<2> Fixed LLID assignment (step S1 in FIG. 2)
In this embodiment, as shown in FIG. 4, apart from the Dynamic LLID assigned in the Discovery process, Static LLID is assigned in advance and set in the OLT 101 and the ONU 104.

  Since the MAC address of each ONU connected under the OLT 101 is usually known, this MAC address and Static LLID are associated one-to-one, and the mapping is determined in advance when the ONU 104 is installed. This mapping is set in the OLT 101 and the ONU 104 and stored in the respective storage units (not shown).

<3> Traffic Scheduling by DBA in LLID Units With the DBA scheduler installed in the OLT 101, the OLT 101 schedules the emission permission times for each LLID (Dynamic LLID, Static LLID), and sets the determined emission permission times. Notify each ONU. Each ONU 104 performs optical output according to the time notified from the OLT 101.
In this light emission permission time allocation and scheduling, the OLT 101 performs scheduling by a well-known DBA for each of the Dynamic LLID and Static LLID. For Static LLID, scheduling is performed periodically at predetermined time intervals.

  Here, in this embodiment, Dynamic LLID and Static LLID are used separately for user traffic, Dynamic LLID is used, and Static LLID is used as a LLID for power monitoring for detecting a constantly emitting ONU. And

<4> Normality confirmation by optical output power measurement for Static LLID (step S3 in FIG. 2)
In this embodiment, as shown in FIGS. 5 and 6, the optical output power is periodically measured for the Static LLID of each ONU (step S21).

  When measuring the optical output power, the OLT transmits a signal transmission request for measurement to the ONU by Static LLID, and the ONU assigned with the Static LLID transmits a predetermined measurement pattern. The OLT measures the optical output power for the measurement pattern and stores it in association with the specific information of the ONU.

  The measured values for each ONU-i (104-1, 104-2,..., 104-n) thus measured and the initial value of the optical output power stored in the OLT as the reference value in step S2 of FIG. Are compared for each ONU (step S22).

As a result of this comparison, as illustrated in FIG. 6, if the measurement result for each ONU does not vary with respect to the initial value at the time of station installation (if the variation is less than a predetermined threshold), it is determined to be normal (step S23). .
On the other hand, by comparison with the measurement result, when there is an ONU that is larger than the initial value at the time of station installation by a predetermined threshold value or more, it is determined that a faulty ONU in the constant light emission mode exists (step S24). .

  The measurement period of the optical output power for performing the normality confirmation operation of <4> may be every arbitrary period as long as it is a preset period, such as once per minute or once per hour. . Thus, the normality confirmation operation according to the present embodiment can be performed so as not to affect the user traffic by setting the measurement cycle to such an extent that the user traffic band (data communication amount) is not compressed.

<5> Method for identifying the always-on failure ONU (step S5 in FIG. 2)
With reference to FIG. 7, the failure ONU specifying operation when it is determined that the failure ONU in the always light emitting state exists as a result of the normality confirmation operation of <4> described above will be described.

First, the OLT performs optical output stop control on the ONU 1 (104-1) (step S31). In this state, as shown in FIG. 8, the optical output power of each other ONU is measured, and the measured value is compared with the measured value before the optical output stop control of the ONU 1 (step S32).
The measured value before the optical output stop control is stored in the storage means in association with the specific information of the ONU to be measured, the previous measured value in the periodic optical output power measurement by the normality confirmation operation of <4>. The initial value stored as the reference value when the ONU is installed may be used.

  By performing the comparison in step S32 in this way, if the ONU 1 performs the light output stop control, the measured value of the other ONU is a level lower than the measured value before the light output stop control by a predetermined threshold or more. If it is, ONU1 will be specified as ONU of a light emission state always (step S34).

When the measurement value of each other ONU has not changed compared to the measurement value before performing the light output stop control by the comparison in step S32 (the change is less than a predetermined threshold value), the ONU 1 is always in the light emitting state. Therefore, the optical output stop control is canceled (step S33).
Thereafter, in the same procedure, it is determined whether or not the ONU-i after the ONU 2 (104-2) is in the failure state of the constant light emission mode.

  Further, the OLT removes the ONU identified as a failure state from the system by stopping it by remote control, and allows the service to continue.

  Normally, if there is an ONU that always emits light, it is difficult to transmit and receive data using an optical signal due to a collision of optical signals, and there is a risk that control such as optical output stop control and cancellation may become impossible. In this embodiment, Static LLID By using, it is possible to control them.

Next, the specific operation of the always light emitting ONU by the PON system as the present embodiment will be described in detail using specific examples shown in FIGS.
In this specific example, it is assumed that four ONUs (ONU1, ONU2, ONU3, ONU4) are connected to the OLT, and ONU1 and ONU4 are always in failure in the light emission mode.

  As illustrated in FIG. 9, each of the ONU 1, ONU 2, ONU 3, and ONU 4 is assigned with a static LLID associated with a MAC address in advance and stored in the storage unit of each of the OLT and ONU.

As shown in FIG. 10, the OLT measures the optical output power when each ONU is installed, and determines the reference value of the optical output power for each Static LLID. In the example of FIG. 10, ONU1 = 0.5 mW, ONU2 = 1.0 mW, ONU3 = 0.3 mW, and ONU4 = 0.1 mW.
Thereafter, when the normality confirmation operation described above is performed periodically, if the optical output power for each Static LLID is the reference value, there is no ONU that is always in a light emitting state.

Here, it is assumed that the ONU 1 and the ONU 4 are constantly in a light emitting state from a certain point in time, and the optical output power for each Static LLID changes as shown in FIG.
In this case, during the periodic normality confirmation operation, the OLT has an ONU in which a value obtained by adding the optical output power of the always light-emitting ONU to the reference value is measured. Detect that occurred.

  When the presence of the constant light ONU is detected, the OLT shifts to a detection operation for the constant light ONU. First, the OLT forcibly stops the optical output of the ONU 1 and measures the optical output power for other Static LLIDs. As a result of the measurement, as shown in FIG. 12, the ONU 1 can always be identified as having a failure in light emission because the measured value of the other ONU has decreased compared to before the ONU 1 was forcibly stopped. In this case, the OLT is excluded from system operation by keeping the optical output forcibly stopped for the ONU 1.

  Next, the OLT forcibly stops the optical output of the ONU 2 and measures the optical output power for other Static LLIDs. As a result of the measurement, as shown in FIG. 13, the ONU 2 can be identified as a normal ONU because the measured values of other ONUs are not different from those before the ONU 2 is forcibly stopped. In this case, the OLT transmits an instruction to cancel the forced stop of the optical output to the ONU 2.

  Next, the OLT forcibly stops the optical output of the ONU 3 and measures the optical output power for other Static LLIDs. As a result of the measurement, as shown in FIG. 14, the ONU 3 can be identified as a normal ONU because the measured values of other ONUs are not different from those before the ONU 3 is forcibly stopped. In this case, the OLT transmits an instruction to cancel the forced stop of the optical output to the ONU 3.

  Next, the OLT forcibly stops the optical output of the ONU 4 and measures the optical output power for other Static LLIDs. As a result of the measurement, as shown in FIG. 15, it is possible to specify that the ONU 4 is always in a light emitting failure because the measured value of other ONUs is lower than before the ONU 4 is forcibly stopped. In this case, the OLT is excluded from the system operation by keeping the optical output forcibly stopped with respect to the ONU 4.

  As described above, the OLT can specify that the ONU 1 and the ONU 4 are always in the light emission mode. Further, by stopping the ONU identified as a faulty device by remote control from the OLT, it can be excluded from the system and the service can be continued.

  As described above, according to the above-described automatic detection method for a constant light emission failure according to the present embodiment, the following effects can be obtained.

  Even when a plurality of faulty ONUs that are in the constant light emission state are generated under the same PON line, the optical output is stopped and checked one by one, so that the faulty ONU can be automatically identified.

  In addition, after the failure ONU is specified, the optical output stop can be controlled remotely from the OLT.

  In addition, in order to identify a faulty ONU that is always on, a maintenance staff is dispatched to all users' homes connected to the same fiber, contacted with the maintenance staff on the center side, and the power is turned off one by one. There is no need to specify the ONU. For this reason, the maintenance cost by such a trouble can be held down.

  In addition, since the time for identifying the fault ONU can be shortened, the service stop time can be shortened.

  Each of the above-described embodiments is a preferred embodiment of the present invention, and the present invention is not limited to this, and various modifications can be made based on the technical idea of the present invention.

For example, by recording the processing procedure for realizing the OLT as the above-described embodiment on a recording medium as a program, the above-described functions according to the embodiment of the present invention can be performed by the program supplied from the recording medium. It can be realized by causing the CPU of the computer constituting the processing to perform processing.
In this case, the present invention can be applied even when an information group including a program is supplied to the output device from the above recording medium or from an external recording medium via a network.
That is, the program code itself read from the recording medium realizes the novel function of the present invention, and the recording medium storing the program code and the signal read from the recording medium constitute the present invention. It will be.
As this recording medium, for example, flexible disk, hard disk, optical disk, magneto-optical disk, CD-ROM, CD-R, CD-RW, DVD-ROM, DVD-RAM, DVD-RW, DVD + RW, magnetic tape, non-volatile A memory card, ROM or the like may be used.

  According to the program according to the present invention, each function in the above-described embodiment can be realized by the OLT controlled by the program.

101 OLT (Intra-station equipment)
102 Optical transmission line 103 Optical Splitter
104 ONU (subscriber equipment)

Claims (20)

An in-station device used in a system configured by connecting a plurality of subscriber devices to an in-station device via an optical branching means,
Measuring means for measuring the amount of light received from the subscriber unit;
Stop instruction means for transmitting a light output stop instruction to the subscriber unit;
The stop instruction means transmits a stop instruction to one subscriber apparatus, the received light quantity of another subscriber apparatus is measured by the measurement means, and the measured received light quantity is measured before the stop instruction transmission by the stop instruction means. When the received light quantity is smaller than a predetermined threshold or more, the subscriber device that transmitted the stop instruction is identified as a failed device, and in other cases, the subscriber device that transmitted the stop instruction is determined not to be a failed device. Device identification means;
An in-station device comprising: A reference value storage means for storing a reference value of the amount of received light measured at a predetermined timing by the measurement means in association with the specific information of the subscriber device that is the measurement target;
The received light amount of the subscriber device is measured by the measuring means, and the measured received light amount is compared with a reference value stored in the reference value storage means in association with the specific information of the subscriber device to be measured. A failure detecting means for detecting that there is a subscriber device having a constant light emission failure when the measured received light quantity is larger than the stored reference value by a predetermined threshold value;
With
2. The intra-station device according to claim 1, wherein the faulty device specifying unit specifies a faulty device when the fault detection unit detects that a subscriber unit having a constant light emission failure exists.   3. The intra-station apparatus according to claim 2, wherein the failure detection means measures the amount of received light periodically at a predetermined cycle.   The specific information is a fixed ID that is provided separately from a standard ID assigned by a procedure defined in a standard and assigned in association with a MAC (Media Access Control) address of the subscriber device. Item 2. The intra-station device according to item 2 or 3. The stop instruction means transmits the light output stop instruction using the fixed ID,
5. The intra-station device according to claim 4, wherein the failure device specifying means specifies the failure device using the fixed ID.   6. The intra-station device according to claim 2, wherein the reference value is an initial value measured when the subscriber device is installed. In response to the setting of the standard ID assigned by the procedure defined in the standard and the fixed ID assigned in association with the MAC (Media Access Control) address,
A subscriber unit comprising pattern sending means for sending a predetermined measurement pattern when a measurement signal sending request is received by the fixed ID.   An optical communication system, comprising: the intra-station apparatus according to any one of claims 1 to 6; and a plurality of subscriber apparatuses according to claim 7 connected via an optical branching unit. A failure device identification method in a system configured by connecting a plurality of subscriber devices to an in-station device via an optical branching means,
An optical output stop instruction is transmitted to one subscriber device, the received light amount of the other subscriber device is measured, and the measured received light amount is smaller than the received light amount before transmission of the stop instruction by a predetermined threshold or more. A failure device specifying step of identifying the subscriber device that has transmitted the stop instruction as a failed device in other cases, and determining that the subscriber device that has transmitted the stop instruction is not a failed device in other cases. The failure device identification method. A reference value storing step of storing a reference value of the amount of light received from the subscriber unit measured at a predetermined timing in association with the specific information of the subscriber unit that is the measurement target;
Measuring the amount of received light of the subscriber unit, comparing the measured amount of received light with the reference value stored in the reference value storing step in association with the specific information of the subscriber unit to be measured; A failure detection step of detecting that there is a subscriber device having a constant light emission failure when the received light intensity is greater than a stored reference value by a predetermined threshold or more;
With
10. The faulty device specifying method according to claim 9, wherein the faulty device specifying step is performed when it is detected by the fault detecting step that there is a subscriber device having a constant light emission fault.   11. The fault device identification method according to claim 10, wherein in the fault detection step, the amount of received light is periodically measured at a predetermined cycle.   The specific information is a fixed ID that is provided separately from a standard ID assigned by a procedure defined in a standard and assigned in association with a MAC (Media Access Control) address of the subscriber device. Item 12. The fault device identification method according to Item 10 or 11.   13. The failure device identification step transmits an optical output stop instruction to the one subscriber device using the fixed ID, and identifies the failure device using the fixed ID. Faulty device identification method.   14. The faulty device specifying method according to claim 10, wherein the reference value is an initial value measured when the subscriber device is installed. A program for an in-station device used in a system configured by connecting a plurality of subscriber devices to an in-station device via an optical branching means,
An optical output stop instruction is transmitted to one subscriber device, the received light amount of the other subscriber device is measured, and the measured received light amount is smaller than the received light amount before transmission of the stop instruction by a predetermined threshold or more. In this case, a faulty device specifying procedure for determining a subscriber device that has transmitted the stop instruction as a faulty device and in other cases determining that the subscriber device that has transmitted the stop instruction is not a faulty device A program for an in-station device that is executed by A reference value storing procedure for storing a reference value of the amount of light received from the subscriber unit measured at a predetermined timing in association with the specific information of the subscriber unit that is the measurement target;
Measuring the amount of received light of the subscriber unit, comparing the measured amount of received light with the reference value stored in the reference value storing procedure in association with the specific information of the subscriber unit to be measured; A failure detection procedure for detecting that there is a subscriber device with a constant light emission failure when the received light intensity is greater than the stored reference value by a predetermined threshold or more;
Is executed by a computer of the in-station device,
16. The in-station device program according to claim 15, wherein the failure device identification procedure is executed when it is detected by the failure detection procedure that a subscriber device having a constant light emission failure exists.   The in-station apparatus program according to claim 16, wherein in the failure detection procedure, the amount of received light is periodically measured according to a predetermined period.   The specific information is a fixed ID that is provided separately from a standard ID assigned by a procedure defined in a standard and assigned in association with a MAC (Media Access Control) address of the subscriber device. Item 18. A program for an in-station device according to Item 16 or 17.   19. The failure device identification procedure transmits a light output stop instruction to the one subscriber device using the fixed ID, and identifies the failure device using the fixed ID. In-station device program.   20. The in-station device program according to any one of claims 16 to 19, wherein the reference value is an initial value measured when the subscriber device is installed.

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