JP5557670B2 - GEPON system, ONU and OLT - Google Patents

Description

  The present invention includes a GEPON having a plurality of subscriber-side optical line terminators (ONUs) and a station-side optical line terminator (OLT) that communicates with each ONU. The present invention relates to a Gigabit Ethernet Passive Optical Network) system.

The GEPON system is an optical subscriber access network that provides subscribers with Internet services with a maximum transmission rate of 1 gigabit / second or 2.5 gigabit / second by means of FTTB (Fiber to The Building) or FTTH (Fiber To The Home). System.
This GEPON includes an ONU installed in each subscriber premises, an OLT installed in the center station, an optical splitter that branches each transmission line into a maximum of 32 to 64, and connects each ONU to the ONU. It consists of an optical splitter. Communication is performed between each ONU and the OLT via an optical distribution device.

A wavelength in the 1310 nm band is assigned to the upstream digital data signal transmitted from each ONU to the OLT via the optical splitter. Further, a downstream digital data signal (including a digital audio signal) transmitted from the OLT to each ONU via the optical branching unit is assigned a wavelength of 1490 nm band, and the downstream video signal (analog video signal) 1550 nm band wavelength is assigned.
In this way, in the GEPON system, by using a wavelength division multiplexing (WDM) system in which a plurality of wavelengths are assigned, single-core bidirectional optical communication for transmitting an upstream signal and a downstream signal using one optical fiber is performed. Is going.

  Here, the transmission timing of uplink signals from a plurality of ONUs is controlled so that individual uplink signals arrive at the OLT at different timings without overlapping each other, in units of clusters called packets or cells. Each upstream signal is simply superimposed by an optical splitter and transmitted to the OLT.

In addition, the GEPON system operating as described above has a problem of communication quality deterioration due to optical signal multiple reflection on the line. Therefore, there is a GEPON system that suppresses communication quality degradation due to optical signal multiple reflection by monitoring the optical reception level at each ONU and adjusting the optical transmission level for each ONU on the OLT side (for example, patents). Reference 1).
In the GEPON system disclosed in Patent Document 1, each ONU is provided with a level monitor circuit such as an analog-digital converter (ADC) that detects an optical reception level, and transmits the detected optical reception level to the OLT. In the OLT, the optical reception level from each ONU is monitored, and the optical transmission level for each ONU is adjusted so that the communication quality with each ONU becomes appropriate.

Japanese Patent No. 4169878

As described above, in the GEPON system, one OLT communicates with a plurality of ONUs. For this reason, when a communication failure occurs in a specific ONU, it is important to restore only the ONU in which the communication failure has occurred so as not to cause a communication failure to other operating ONUs.
In such a case, the maintenance person goes to the user's home where the ONU where the communication failure has occurred is installed to investigate the communication failure and replace the parts. For this reason, there is a problem that the time until the user line is restored and the maintenance cost due to the dispatch of the maintenance personnel are generated.

  Also, ONU communication failures are various, and ONU failures (in this case, replacement), optical reception level deterioration, ONU power supply interruption, and the like are assumed. However, communication failures caused by factors other than ONU failures can often be easily solved by performing primary failure isolation (for example, cleaning of optical fibers). In the future, it is expected that the DIY (Do It Yourself) work for users to connect ONUs with optical fibers by themselves will increase, and communication failures that can be easily solved will also increase.

  Further, in the optical communication system disclosed in Patent Document 1, in order to suppress communication quality deterioration due to optical signal multiple reflection on the line, the optical reception level is detected by a level monitor circuit, and each ONU is detected based on the optical reception level. The optical transmission level is adjusted. However, the configuration of the level monitor circuit is complicated, and the optical transmission level control for each ONU is necessary, which causes a problem of high cost. In particular, since ONUs are arranged for many users, there is a problem that they must be realized at as low a cost as possible.

  The present invention has been made to solve the above-described problems, and realizes low-cost detection of degradation of the optical reception level in the ONU and performs maintenance by performing the primary fault isolation by the user himself / herself. It aims at providing the GEPON system, OLT, and ONU which can reduce the maintenance cost by dispatching a worker.

The GEPON system according to the present invention includes a plurality of ONUs and an OLT that communicates with each ONU. The ONU has an ONU side optical receiving unit that receives an optical signal from the OLT and a preset threshold value. Based on a degradation level detection circuit for detecting degradation of the optical level of the optical signal received by the ONU side optical receiver, and degradation of the optical level when the degradation of the optical level is detected by the degradation level detection circuit superimposes the level degradation information indicating the data, when receiving the OLT or is bell degradation alarms through the ONU-side optical receiving unit, notifies the execution content of the fault primary isolation of the level degradation alarm indicates to the user An ONU side PON control unit, and an ONU side optical transmission unit that converts data from the ONU side PON control unit into an optical signal and transmits the optical signal to the OLT. And the OLT-side optical receiving unit for converting an optical signal from a side light transmitting unit to the data, when detecting the level degradation information from the transformed data by OLT-side optical receiving unit, the deterioration of the light level indicated by the level degradation information The OLT side PON control unit that superimposes a level deterioration alarm that indicates the content of the primary failure isolation on the data, and the OLT side light that converts the data from the OLT PON control unit into an optical signal and transmits it to the corresponding ONU And a transmission unit.

According to the present invention, since it is configured as described above, a complicated level monitoring circuit such as an ADC and optical transmission level control are not required, and it is possible to realize detection of deterioration of the optical reception level in the ONU at a low cost. Moreover, the maintenance cost by dispatching the maintenance personnel can be reduced by performing the primary isolation of the failure by the user himself / herself.
Communication quality degradation due to optical signal multiple reflection on the line can be avoided by appropriately designing the reflection level diagram in the line design. In addition, in the GEPON system, it is only necessary to pay attention to ONUs whose optical reception level is deteriorated, and in particular, there is an example in which reflection more than the line design occurs at the connection part of the ONU whose optical reception level is deteriorated. Therefore, it is not necessary to control the ONU with good communication.

It is a figure which shows the structure of the GEPON system which concerns on Embodiment 1 of this invention. It is a flowchart which shows the optical reception level degradation detection operation | movement of the GEPON system which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the GEPON system which concerns on Embodiment 2 of this invention. It is a figure which shows the threshold value which each degradation level detection circuit in Embodiment 2 of this invention hold | maintains. It is a flowchart which shows the optical reception level degradation detection operation | movement of the GEPON system which concerns on Embodiment 2 of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
1 is a diagram showing a configuration of a GEPON system according to Embodiment 1 of the present invention.
As shown in FIG. 1, the GEPON system includes a subscriber-side optical line terminator (ONU) 1 installed in each of a plurality of subscriber premises and a station-side optical line terminator (OLT) 2 installed in a center station. And an optical branching device 3 such as an optical splitter for branching the transmission path into a maximum of 32 to 64 and connecting each ONU 1 and the OLT 2. In FIG. 1, only ONU # N among the plurality of ONUs 1 is illustrated.
Further, each ONU 1 and the optical branching unit 3 and between the OLT 2 and the optical branching unit 3 are connected by an optical fiber 4, and each ONU 1 and the OLT 2 perform one-core bidirectional optical communication. It is assumed that the transmission direction from ONU 1 to OLT 2 is upstream, and the transmission direction from OLT 2 to ONU 1 is downstream.

The ONU 1 includes an optical transceiver 11, a deterioration level detection circuit 12, and a PON control unit (ONU side PON control unit) 13.
The optical transceiver 11 includes an optical receiver (ONU side optical receiver) 14 and an optical transmitter (ONU side optical transmitter) 15.
The optical receiver 14 receives the downlink communication optical signal from the OLT 2 and converts it into an electrical signal. The electrical signal converted by the optical receiver 14 is transmitted to the PON controller 13 as downlink communication data. The optical receiver 14 also transmits the received downlink communication optical signal to the deterioration level detection circuit 12.
The optical transmission unit 15 receives uplink communication data from the PON control unit 13 and converts it into an optical signal. The optical signal converted by the optical transmitter 15 is transmitted to the OLT 2 as an upstream communication optical signal.

The degradation level detection circuit 12 detects degradation of the optical level (optical reception level) of the downlink communication optical signal from the optical receiver 14. This degradation level detection circuit 12 detects a degradation of the optical reception level by setting a threshold value for the optical level in advance and comparing the optical level of the downstream communication optical signal with the threshold value. Note that the minimum reception sensitivity level (the light level before communication with the OLT 2 is disconnected) is used as the threshold value.
Here, when the degradation level detection circuit 12 determines that the optical level of the downlink communication optical signal is less than the threshold and the optical level of the downlink communication optical signal is degraded, the optical reception level is degraded. The level deterioration information indicating this is transmitted to the PON control unit 13.

  Further, after detecting the deterioration of the optical reception level, the deterioration level detection circuit 12 detects the recovery of the optical level of the downlink communication optical signal from the optical receiver 14 based on the threshold value. Here, when the degradation level detection circuit 12 determines that the optical level of the downlink communication optical signal is equal to or higher than the threshold value and the optical level of the downlink communication optical signal has recovered, the level recovery indicating that the optical reception level has recovered. Information is transmitted to the PON control unit 13.

The PON control unit 13 transmits downlink communication data from the optical reception unit 14 to a lower level device (not shown), and transmits uplink communication data from the lower level device to the optical transmission unit 15.
Further, when receiving the level deterioration information from the deterioration level detection circuit 12, the PON control unit 13 superimposes the level deterioration information on the uplink communication data and transmits it to the optical transmission unit 15.
In addition, the PON control unit 13 notifies the optical reception level deterioration from the OLT 2 via the optical reception unit 14 and also receives a level deterioration alarm instructing execution of primary failure isolation for the optical reception level deterioration. In such a case, this level deterioration alarm is displayed on a monitor (not shown) or the like to notify the user.
Further, when the level recovery information is received from the deterioration level detection circuit 12, the PON control unit 13 superimposes the level recovery information on the uplink communication data and transmits it to the optical transmission unit 15.

The OLT 2 includes an optical transceiver 21 and a PON control unit (OLT side PON control unit) 22.
The optical transceiver 21 includes an optical receiver (OLT side optical receiver) 23 and an optical transmitter (OLT side optical transmitter) 24.
The optical receiver 23 receives an upstream communication optical signal from the ONU 1 and converts it into an electrical signal. The electrical signal converted by the optical receiving unit 23 is transmitted to the PON control unit 22 as upstream communication data.
The optical transmission unit 24 receives downlink communication data from the PON control unit 22 and converts it into an optical signal. The optical signal converted by the optical transmitter 24 is transmitted to the corresponding ONU 1 as a downlink communication optical signal.

The PON control unit 22 transmits uplink communication data from the optical reception unit 23 to a higher-level device (not shown), and transmits downlink communication data from the higher-level device to the optical transmission unit 24.
When the PON control unit 22 detects the ONU2 level deterioration information from the upstream communication data converted by the optical receiving unit 23, the optical transmission unit 24 superimposes the level deterioration alarm for the ONU2 on the downstream communication data. Send to.
Further, when the PON control unit 22 detects the level recovery information of the ONU 2 from the upstream communication data converted by the optical receiving unit 23, the PON control unit 22 displays this level recovery information on a monitor (not shown), etc. Notify

Next, the optical reception level deterioration detection operation of the GEPON system configured as described above will be described.
FIG. 2 is a flowchart showing an optical reception level deterioration detection operation of the GEPON system according to Embodiment 1 of the present invention. In the following, the operation between ONU # N and OLT 2 will be described.

  In the optical reception level deterioration detection operation by the GEPON system, as shown in FIG. 2, first, the optical reception unit 14 of the ONU # N receives the downlink communication optical signal from the OLT 2 (step ST21). The downstream communication optical signal received by the optical receiver 14 is converted into an electrical signal, and then transmitted to the lower-level device via the PON controller 13 as downstream communication data. Further, the downlink communication optical signal received by the optical receiver 14 is also transmitted to the deterioration level detection circuit 12.

Next, the degradation level detection circuit 12 determines whether or not degradation of the optical level of the downlink communication optical signal from the optical receiver 14 has been detected based on a preset threshold value (step ST22).
In step ST22, when the degradation level detection circuit 12 determines that the optical level of the downlink communication optical signal is equal to or greater than the threshold and the optical level of the downlink communication optical signal is not degraded, the sequence ends.

  On the other hand, in step ST22, when the degradation level detection circuit 12 determines that the optical level of the downlink communication optical signal is less than the threshold and the optical level of the downlink communication optical signal is degraded, the degradation level detection circuit 12 On the other hand, level deterioration information is transmitted (step ST23).

  Next, the PON control unit 13 receives the level deterioration information from the deterioration level detection circuit 12, superimposes this level deterioration information on the uplink communication data, and transmits it to the optical transmission unit 15 (step ST24). The uplink communication data on which the level deterioration information is superimposed and transmitted to the optical transmitter 15 is converted into an optical signal and then transmitted to the OLT 2.

  Next, the PON control unit 22 of the OLT 2 receives the ONU # N level deterioration information from the upstream communication data converted by the optical receiving unit 23, and superimposes the level deterioration alarm for the ONU # N on the downstream communication data. It transmits to the transmission part 24 (step ST25). The downlink communication data on which the level alarm transmitted to the optical transmitter 24 is superimposed is converted into an optical signal and then transmitted to the ONU # N.

Next, the PON control unit 13 of the ONU # N receives a level deterioration alarm from the OLT 2 via the optical receiving unit 14, and notifies the user by displaying the level deterioration alarm on a monitor (step ST26).
Thereafter, the user performs primary fault isolation according to the content of the instruction by the notified level deterioration alarm (for example, handling based on a manual or contacting a maintenance center).

Here, primary fault isolation refers to, for example, changing the routing method of the optical fiber 4 of ONU # N, cleaning the optical fiber connector, or the like.
If the degradation level detection circuit 12 detects an optical reception level that is equal to or greater than the threshold value after the failure primary isolation, level recovery information is transmitted to the OLT 2 in the same procedure as described above. The OLT 2 can confirm that the ONU #N has recovered to the normal state by detecting the level recovery information.
If the optical reception level does not recover even when the user performs primary fault isolation, an investigation by dispatching maintenance personnel is performed as usual.

  Thus, by detecting the degradation of the optical reception level in the ONU 1 and notifying the OLT 2, it is possible to identify the ONU 1 in which the optical reception level is degraded on the OLT 2 side. Further, the OLT 2 can instruct the ONU user whose optical reception level is deteriorated to carry out the primary fault isolation so as to recover to the normal state before the communication abnormality occurs. For this reason, it is possible to improve communication quality (avoid communication interruption).

As described above, according to the first embodiment, a complicated level monitoring circuit such as an ADC and an optical transmission level control are not required, and the optical reception level deterioration detection in the ONU 1 is realized with a simple configuration and at a low cost. can do. In addition, since the OLT 2 side detects the level deterioration information from the ONU 1 and instructs the execution of the primary fault isolation, the maintenance by dispatching the maintenance personnel can be performed by performing the primary fault isolation by the user himself / herself. Cost can be reduced.
Communication quality degradation due to optical signal multiple reflection on the line can be avoided by appropriately designing the reflection level diagram in the line design. In addition, in the GEPON system, only the ONU 1 whose optical reception level is deteriorated needs to be focused. In particular, there is an example in which reflection more than the line design occurs at the connection portion of the ONU 1 where the optical reception level is deteriorated. Since there are many, control of ONU1 with favorable communication is unnecessary.

Embodiment 2. FIG.
FIG. 3 is a diagram showing a configuration of a GEPON system according to Embodiment 2 of the present invention.
In the GRPON system according to the second embodiment shown in FIG. 3, the deterioration level detection circuit 12 of the GEPON system according to the first embodiment shown in FIG. 1 is changed to a plurality (M pieces) of deterioration level detection circuits 16a to 16m. Is. Other configurations are the same, and the same reference numerals are given and the description thereof is omitted.

Each of the deterioration level detection circuits 16a to 16m has the same configuration and operation as those of the deterioration level detection circuit 12 shown in the first embodiment. However, the plurality of deterioration level detection circuits 16a to 16m have different threshold values. As the threshold value, for example, as shown in FIG. 4, the light level divided at equal intervals with the initial value −3 dB of the light reception level as the maximum value and the minimum reception sensitivity level as the minimum value is used.
When each of the deterioration level detection circuits 16a to 16m determines that the optical level of the downlink communication optical signal is less than the threshold and the optical level of the downlink communication optical signal is deteriorated, the detection level indicating the threshold used. The level deterioration information including the information is transmitted to the PON control unit 13.

Further, when the PON control unit 13 receives the level deterioration information including the detection level information from the deterioration level detection circuits 16a to 16m, the PON control unit 13 superimposes the level deterioration information on the uplink communication data and transmits it to the optical transmission unit 15. . When level degradation information is received from a plurality of degradation level detection circuits 16a to 16m, the level degradation information having the smallest threshold (the most severe degradation) is superimposed on the uplink communication data.
Further, when the PON control unit 22 receives the level deterioration information from the ONU 1 via the optical receiving unit 23, the PON control unit 22 selects the failure primary isolation content based on the detection level information included in the level deterioration information. A level deterioration alarm instructing the execution of primary separation is superimposed on the data.

Next, the optical reception level deterioration detection operation of the GEPON system configured as described above will be described.
FIG. 5 is a flowchart showing an optical reception level deterioration detection operation of the GEPON system according to Embodiment 2 of the present invention. In the following, the operation between ONU # N and OLT 2 will be described.

  In the optical reception level deterioration detection operation by the GEPON system, as shown in FIG. 5, first, the optical receiver 14 of the ONU # N receives the downlink communication optical signal from the OLT 2 (step ST51). The downstream communication optical signal received by the optical receiver 14 is converted into an electrical signal, and then transmitted to the lower-level device via the PON controller 13 as downstream communication data. Further, the downlink communication optical signal received by the optical receiver 14 is also transmitted to the respective degradation level detection circuits 16a to 16m.

Next, each of the degradation level detection circuits 16a to 16m determines whether or not the degradation of the optical level of the downlink communication optical signal from the optical receiving unit 14 is detected based on a preset threshold value (step ST52).
In step ST52, when all the degradation level detection circuits 16a to 16m determine that the optical level of the downlink communication optical signal is equal to or higher than the threshold value and the optical level of the downlink communication optical signal is not degraded, the sequence is finish.

  On the other hand, in step ST52, the deterioration level detection circuits 16a to 16m that have determined that the optical level of the downlink communication optical signal is less than the threshold and the optical level of the downlink communication optical signal has deteriorated are transmitted to the PON control unit 13. Level degradation information including detection level information is transmitted (step ST53).

  Next, the PON control unit 13 receives the level deterioration information from the deterioration level detection circuits 16a to 16m, and superimposes the level deterioration information on the uplink communication data and transmits it to the optical transmission unit 15 (step ST54). When level deterioration information is received from a plurality of deterioration level detection circuits 16a to 16m, the level deterioration information having the smallest threshold is superimposed on the uplink communication data. The uplink communication data on which the level deterioration information transmitted to the optical transmission unit 15 is superimposed is converted into an optical signal and then transmitted to the OLT 2.

  Next, the PON control unit 22 of the OLT 2 receives the ONU # N level deterioration information from the upstream communication data converted by the optical reception unit 23, and the failure primary isolation content based on the detection level information included in the level deterioration information The level degradation alarm for this ONU # N is superimposed on the downlink communication data and transmitted to the optical transmitter 24 (step ST55). The downlink communication data on which the level alarm transmitted to the optical transmitter 24 is superimposed is converted into an optical signal and then transmitted to the ONU # N.

Next, the PON control unit 13 of the ONU # N receives a level deterioration alarm from the OLT 2 via the optical receiving unit 14, and notifies the user by displaying the level deterioration alarm on a monitor (step ST56).
Thereafter, the user performs primary fault isolation according to the instruction content by the notified level deterioration alarm.

Here, as the primary fault isolation, for example, when the optical reception level is only slightly deteriorated, only the routing method of the optical fiber 4 is changed, and when the optical reception level is severely deteriorated, the optical fiber connector is further cleaned. Etc. As a result, when the degradation of the optical reception level is slight, it may be possible to restore the normal state by performing the primary fault isolation without disconnecting the line.
If the degradation level detection circuits 16a to 16m that have detected the degradation of the optical reception level detect the optical reception level that is equal to or higher than the threshold after the primary fault isolation, the level recovery information is sent to the OLT 2 in the same procedure as described above. Send. In the OLT 2, it can be confirmed from the level recovery information that the ONU #N has recovered to the normal state.
If the optical reception level does not recover even after the primary fault isolation by the user, an investigation by dispatching maintenance personnel is performed as before.

As described above, according to the second embodiment, the deterioration of the optical reception level is detected using a plurality of thresholds, and the failure primary isolation content is selected for each threshold. The primary failure isolation can be performed, and if the deterioration is slight, the normal state may be recovered without disconnecting the line.
In addition, by setting M threshold values (M is an integer of 2 or more) according to the situation, it is possible to monitor the communication quality level in M stages, and it is possible to take early measures against degradation of the optical reception level. Become.

  It should be noted that the embodiments can be appropriately combined, changed, omitted, etc. within the scope of the present invention.

  1 subscriber-side optical line terminator (ONU), 2 station-side optical line terminator (OLT), 3 optical branching unit, 4 optical fiber, 11 optical transceiver, 12, 16a, 16b, 16m deterioration level detection circuit, 13 PON control unit (ONU side PON control unit), 14 optical reception unit (ONU side optical reception unit), 15 optical transmission unit (ONU side optical transmission unit), 21 optical transceiver, 22 PON control unit (OLT side PON control unit) ), 23 optical receiver (OLT side optical receiver), 24 optical transmitter (OLT side optical transmitter).

Claims (9)

In a GEPON (Gigabit Ethernet Passive Optical Network) system comprising a plurality of ONUs (Optical Network Units) and OLTs (Optical Line Terminals) that communicate with each ONU,
The ONU is
An ONU side optical receiver that receives an optical signal from the OLT;
A degradation level detection circuit that detects degradation of the optical level of the optical signal received by the ONU side optical receiver based on a preset threshold;
If the deterioration of the light level is detected by the deterioration level detecting circuit superimposes the level degradation information indicating the deterioration of the light level data, the OLT or is bell degradation through the ONU-side optical receiving unit When receiving an alarm, the ONU side PON control unit for notifying the user of the content of the primary fault isolation indicated by the level degradation alarm;
An ONU side optical transmission unit that converts data from the ONU side PON control unit into an optical signal and transmits the optical signal to the OLT;
The OLT is
An OLT side optical receiver that converts an optical signal from the ONU side optical transmitter of each ONU into data;
When level degradation information is detected from the data converted by the OLT side optical receiver, a level degradation alarm is superposed on the data for instructing the content of the primary fault isolation for the degradation of the optical level indicated by the level degradation information. An OLT side PON control unit;
A GEPON system comprising: an OLT-side optical transmission unit that converts data from the OLT-side PON control unit into an optical signal and transmits the optical signal to the corresponding ONU. The degradation level detection circuit detects recovery of the optical level of the optical signal received by the ONU side optical receiver based on the threshold value,
The ONU side PON control unit superimposes level recovery information indicating the recovery of the light level on the data when recovery of the light level is detected by the deterioration level detection circuit,
2. The GEPON according to claim 1, wherein when the OLT side PON control unit detects level recovery information from the data converted by the OLT side optical receiving unit, the OLT side PON control unit notifies the maintenance person of the level recovery information. system. The deterioration level detection circuit comprises a plurality of deterioration level detection circuits having different threshold values,
The ONU side PON control unit superimposes level deterioration information including detection level information indicating a used threshold value on data when the deterioration of the light level is detected by the deterioration level detection circuit,
When the OLT side PON control unit detects level deterioration information from the data converted by the OLT side optical receiving unit, the OLT side PON control unit selects a failure primary isolation content based on detection level information included in the level deterioration information. 2. The GEPON system according to claim 1, wherein a level deterioration alarm instructing execution of the primary failure isolation is superimposed on the data. In a plurality of ONUs that communicate with the OLT,
An ONU side optical receiver that receives an optical signal from the OLT;
A degradation level detection circuit that detects degradation of the optical level of the optical signal received by the ONU side optical receiver based on a preset threshold;
If the deterioration of the light level is detected by the deterioration level detecting circuit superimposes the level degradation information indicating the deterioration of the light level data, the OLT or is bell degradation through the ONU-side optical receiving unit When receiving an alarm, the ONU side PON control unit for notifying the user of the content of the primary fault isolation indicated by the level degradation alarm;
An ONU comprising: an ONU side optical transmission unit that converts data from the ONU side PON control unit into an optical signal and transmits the optical signal to the OLT. The degradation level detection circuit detects recovery of the optical level of the optical signal received by the ONU side optical receiver based on the threshold value,
5. The ONU side PON control unit superimposes level recovery information indicating the recovery of the optical level on the data when the recovery of the optical level is detected by the deterioration level detection circuit. ONU. The deterioration level detection circuit comprises a plurality of deterioration level detection circuits having different threshold values,
The ONU side PON control unit superimposes level degradation information including detection level information indicating a used threshold on data when the degradation of the optical level is detected by the degradation level detection circuit, and receives the ONU side optical reception. When a level deterioration alarm instructing execution of the primary fault isolation selected based on the detection level information is received from the OLT via a unit, the user is notified of the level deterioration alarm. The ONU according to claim 4. In OLT that communicates with multiple ONUs,
An OLT side optical receiver for converting an optical signal from each ONU into data;
When the level degradation information indicating the degradation of the optical level of the optical signal received by the ONU is detected from the data converted by the OLT side optical receiver, the failure 1 against the degradation of the optical level indicated by the level degradation information An OLT-side PON control unit that superimposes a level deterioration alarm on the data to instruct the execution contents of the next carving ,
An OLT comprising: an OLT side optical transmission unit that converts data from the OLT side PON control unit into an optical signal and transmits the optical signal to the corresponding ONU. When the OLT side PON control unit detects level recovery information indicating recovery of the optical level of the optical signal received by the ONU from the data converted by the OLT side optical receiving unit, the OLT side PON control unit outputs the level recovery information. The OLT according to claim 7, wherein the OLT is notified. When the OLT side PON control unit detects level deterioration information including detection level information indicating a threshold value used for detection of optical level deterioration from the data converted by the OLT side optical receiving unit, the detection level 8. The OLT according to claim 7, wherein the content of primary fault isolation is selected based on the information, and a level deterioration alarm instructing execution of the primary fault isolation is superimposed on the data.

Images