JP5655019B2 - Optical communication system - Google Patents

Description

  The present invention relates to an optical communication system including a plurality of subscriber-side communication devices and a station-side communication device connected to the plurality of subscriber-side communication devices via an optical coupler. The present invention is applied to an ONU (Optical Network Unit) and a PON (Passive Optical Network) system in which a station side communication device is an OLT (Optical Line Terminater).

  In recent years, a PON system has been widely used as a technology for realizing an optical communication network. In the PON system, an optical signal is branched using a passive element such as an optical coupler, whereby one optical fiber connected to a station side communication device (OLT) is connected to a plurality of subscriber side communication devices ( ONU) and the price of the optical communication network can be reduced.

  In the PON system, the downstream optical signal from the station side communication device to each subscriber side communication device is composed of signals in the same wavelength band obtained by time-division multiplexing data to a plurality of subscriber side communication devices. And is transmitted to each subscriber-side communication device. Each subscriber-side communication device extracts only data addressed to itself from the optical signal received from the station-side communication device, and discards other data. On the other hand, each optical signal in the upstream direction transmitted from each subscriber-side communication device to the station-side communication device is transmitted at a timing that does not overlap each other in the same wavelength band, and is joined by an optical coupler and transmitted to the station-side communication device. It is done. For this reason, the data transmission timing and data transmission amount of each subscriber side communication device are controlled by the station side communication device so that optical signal data transmitted from a plurality of subscriber side communication devices do not collide, The subscriber side communication device needs to transmit data at the permitted transmission timing.

  A function is used to transmit a power-off signal (dieing gasp) to the station-side communication device before the operation of the device stops when the power-off occurs in the subscriber-side communication device. As a result, when the station side communication device detects the disconnection of the link with the subscriber side communication device, it is due to the power failure of the subscriber side communication device or the failure of the optical fiber connected to the subscriber side communication device. The cause can be isolated.

  However, conventionally, when an uplink signal of a diving gasp is issued, it is necessary to transmit the dining gasp after performing a sequence for obtaining transmission timing assignment with the OLT. For this reason, the apparatus had to be operated for a period of time until the diving gasp was transmitted after the power was turned off, and a capacitor having a large capacity had to be mounted. In particular, a dedicated supercapacitor known as a large-capacitance capacitor is expensive, so it is common to use general-purpose capacitors connected in parallel, which increases the height of the board or mounts the original circuit of the device There were various problems such as a small mounting area.

  Therefore, a method for saving power as much as possible by stopping unnecessary circuit operations when the power is turned off has been studied (for example, see Patent Document 1). Alternatively, studies have been made such as mounting a large-capacity capacitor in an external circuit (for example, see Patent Document 2).

JP 2008-118290 A JP 2010-252192 A

  However, in the past, since the dicing gasp is transmitted using a wavelength band in which normal data communication is performed, a sequence for obtaining transmission timing assignment has to be performed with the OLT before transmission, and power is cut off. Since the dieing gasp cannot be transmitted immediately afterward, the problem that the apparatus has to be operated only for the time until the dieing gasp is transmitted has not been solved.

  In view of the above problems, an object of the present invention is to provide an optical communication system that does not require a large-capacitance capacitor to be mounted by allowing a diving gasp to be transmitted immediately when the power is turned off.

An optical communication system according to the present invention includes a plurality of ONUs and an OLT connected to the plurality of ONUs via an optical coupler, and transmits an upstream signal in the same wavelength band from the plurality of ONUs to the OLT . in division multiplexing to PON system in communication, the ONU includes a subscriber-side communication optical receiver for receiving downlink signals of the first wavelength or fourth wavelength from the OLT, the uplink signal of the second wavelength to the OLT A subscriber-side communication optical transmitter for transmitting, a subscriber-side control optical transmitter for transmitting an uplink signal of the third wavelength to the OLT , a subscriber-side controller for controlling communication with the OLT , A power-off detection unit that detects a power- off of the device, and a pulse modulation unit that turns on and off the subscriber-side control optical transmission unit to transmit a 1-bit pulse signal, and the subscriber-side control unit includes: Optical reception for subscriber side communication And to communicate the OLT and the user data by the subscriber-side communication optical transmission unit, the power the power-off detection unit via the subscriber-side control optical transmitter only when it detects the power-off of the device itself the disconnection signal is sent to the OLT, the power failure detecting unit, when detecting the power-off of the device itself, a detection signal is output directly to the pulse modulator not via the subscriber-side control unit the transmitted from the subscriber side control optical transmitter pulse signals of 1bit to the OLT in place of Daiin Gugya spool signal corresponding to the OAM standard, the OLT first wavelength or downstream of the fourth wavelength to the plurality of ONU An optical transmitter for communication on the station side that transmits a signal, an optical receiver for communication on the second wavelength that receives an upstream signal of the second wavelength from the plurality of ONUs, and an upstream signal of the third wavelength from the plurality of ONUs Station-side control light receiver Parts and the station side control unit that controls the communication with the plurality of ONU, and the link detecting section for detecting the state of the logical link to be formed between said plurality of ONU, logical that the link detecting section detects A log storage unit that stores in the history the time information when the link state has changed and the device identification information of the ONU corresponding to the logical link, and the station-side control unit includes the station-side control optical receiving unit When the 1-bit pulse signal is received from the ONU via the network, it is determined that a power failure has occurred in the ONU that detects a logical link break immediately after receiving the pulse signal with reference to the history. It is characterized by.

  The optical communication system according to the present invention can cope with a capacitor having a smaller capacity than the conventional one by enabling the diving gasp to be transmitted immediately when the power is cut off. Thereby, the mounting area of the base that can be used for the original circuit is increased, the height of the base can be reduced, and the size of the subscriber-side communication device can be reduced.

1 is a diagram illustrating a configuration example of a PON system 100. FIG. 2 is a diagram illustrating a configuration example of an ONU 103. FIG. It is a figure which shows the structural example of ONU103 when there exists a large capacity | capacitance capacitor | condenser. It is a figure which shows the structural example of OLT101. It is a flowchart which shows the process example at the time of a power supply interruption. It is a figure which shows the structural example of ONU103a. It is a figure which shows an example of a log. It is a figure which shows the structural example of ONU103b.

  Hereinafter, the PON system 100 will be described in detail as an embodiment of an optical communication system according to the present invention. The PON system 100 does not have to be the same, and is similarly applied to an optical communication system including a plurality of slave stations that transmit data by time-division multiplexing the same wavelength band at a timing assigned from the master station. Is possible.

  FIG. 1 is a diagram illustrating a configuration example of a PON system 100 according to the present embodiment. In FIG. 1, a PON system 100 includes an OLT 101 that is a station-side communication device, an optical coupler 102, and ONUs 103 (103a, 103b, and 103c) that are subscriber-side communication devices. Here, in the following description, when explaining matters common to the ONU 103a, ONU 103b, and ONU 103c, the alphabet at the end of the code is omitted and expressed as ONU 103, and when indicating a specific subscriber side communication apparatus, the alphabet is added to the code. In addition, for example, it is expressed as ONU 103a. The same applies to the subscriber terminal 104.

  Here, the OLT 101 is a station-side PON communication device, and has circuits corresponding to, for example, 10 G-EPON having a communication speed of 10 Gbps and GE-PON having a communication speed of 1 Gbps according to the communication speed of the ONU 103. The ONU 103 is a PON communication device on the subscriber side, and is a device corresponding to, for example, 10G-EPON or GE-PON. The subscriber terminal 104 is configured by a user terminal device such as a personal computer or a router.

  In FIG. 1, the PON system 100 includes a data a for the ONU 103a and an ONU 103b in a downstream optical signal (wavelength band: λ1 for 10G-EPON or λ4 for GE-PON) transmitted from the OLT 101 to each ONU 103. The data b for the ONU 103c and the data c for the ONU 103c are time-division multiplexed. The downstream optical signal is simply branched into a plurality of optical signals by the optical coupler 102 which is a passive element, and all data (data a, data b, and data c) are transmitted to all ONUs 103 that are the branch destinations. Then, the ONU 103 extracts only the data addressed to its own device and discards the data addressed to the other device. For example, the ONU 103a extracts only the data a and outputs it to the subscriber terminal 104a side, and the data b and data c are discarded.

  On the other hand, data transmitted from a device such as a user's personal computer or router connected to the subscriber terminal 104 is a downstream signal as an upstream optical signal (wavelength band: λ2) from the ONU 103 on each subscriber terminal 104 side. Are transmitted to the OLT 101 in different wavelength bands λ2. Here, since each ONU 103 uses the same wavelength band λ2, the transmission timing of the uplink data, the transmission data amount, and the like are specified from the OLT 101, and the data is transmitted at the specified timing. For example, the ONU 103a transmits data A of the subscriber terminal 104a at the transmission timing Ta, and the ONU 103b transmits data B of the subscriber terminal 104b at the transmission timing Tb. Similarly, the ONU 103c transmits the data C of the subscriber terminal 104c at the transmission timing Tc. All the data are merged by the optical coupler 102, time-division multiplexed, and transmitted to the OLT 101. In this manner, the transmission timings Ta, Tb, and Tc and the transmission data amount are controlled by the OLT 101 so as not to overlap other data when the optical coupler 102 joins.

  The OLT 101 also assigns a logical link ID (LLID) to each ONU 103 to manage communication with each ONU 103, monitors the status of the logical link, and saves the date of connection or disconnection in the history. However, when a logical link disconnection of the ONU 103 is detected, it is necessary to determine for maintenance whether an optical fiber failure with the ONU 103 is a cause or a power failure of the ONU 103 is a cause. Therefore, in the general ONU 103, a large-capacity capacitor is arranged in the power supply so that it can operate only for a certain time when the power supply is cut off. Then, a sequence for obtaining permission for the upstream signal in the wavelength band λ2 is performed with the OLT 101 for a fixed time until the large-capacity capacitor is no longer charged, and a power-off signal called diing gasp is transmitted to the OLT 101. . As a result, the OLT 101 can determine that there is no problem with the optical fiber between the ONU 103 and the ONU 103 when the diing gasp is received from the ONU 103 even when the logical link disconnection of the ONU 103 is detected.

  However, the ONU 103 must execute a sequence for obtaining the transmission permission of the upstream signal in the wavelength band λ2 in order to transmit the diving gasp, and it is necessary to mount a large capacity capacitor. In particular, since components such as a dedicated supercapacitor are expensive, an inexpensive ordinary electrolytic capacitor is often arranged in parallel, which requires a large mounting area for the capacitor and raises the problem that the height of the base becomes high. Therefore, in the PON system 100 according to the present embodiment, a third wavelength different from the downlink signal (wavelength band λ1 or λ4) and the uplink signal (wavelength band λ2) for transmitting / receiving user data between the ONU 103 and the OLT 101 is used. A circuit for transmitting an upstream signal in the band (λ3) is mounted, and a dicing gasp is transmitted in the third wavelength band. As a result, it is not necessary to worry about a collision with an upstream signal of another ONU 103, and therefore it is not necessary to execute a sequence for obtaining an upstream signal permission from the OLT 101. Since the ONU 103 can transmit the dieing gasp immediately after the power interruption occurs, it can be completed with a capacitor having a smaller capacity than the conventional one, and the problem of the mounting area and the height of the base can be avoided. In the example of FIG. 1, there is a possibility that a collision may occur when the three ONUs 103 ONU 103a, ONU 103b, and ONU 103c transmit the diing gasp DG at the same time, but the probability that the power failure of the ONU 103 will occur completely simultaneously is low. In addition, since the transmission time of the diving gasp is very short, the probability of signal collision is very small. In addition, there is a possibility that ONUs 103 in the same area will send diing gasp at the same time when a power outage occurs in the wide area. By referring to the power outage information of the power company, etc., the cause of the logical link breakage is not due to an optical fiber failure. Because it can be judged that there is no problem.

[Configuration example of ONU 103]
Next, a configuration example of the ONU 103 will be described with reference to FIG. In FIG. 2, the ONU 103 includes an optical transmission / reception circuit 201, a PONLSI 202, a LAN I / F 203, a power supply circuit 204, and a voltage monitoring circuit 205.

  The optical transmission / reception circuit 201 is a circuit for mutually converting an optical signal and an electric signal for transmitting / receiving user data and control data to / from the OLT 101 via an optical fiber. In the example of FIG. 251, an optical receiver 252, an optical transmitter 253, and a dedicated optical transmitter 254. The optical receiver 252 includes an optical module that converts an optical signal having a wavelength λ1 corresponding to 10GE-PON into an electrical signal. The optical receiver 252 converts a downstream signal in the wavelength band λ1 transmitted from the OLT 101 into received data and outputs the received data to the PONLSI 202. To do. The optical transmitter 253 includes a laser having a wavelength λ2 corresponding to 10G-EPON, converts transmission data output from the PON LSI 202 into an optical signal, and transmits the optical signal to the OLT 101 as an upstream signal in the wavelength band λ2. The dedicated optical transmitter 254 is configured by a laser or the like that converts an electrical signal of a diving gasp into an optical signal and transmits it, and is a dedicated transmitter for transmitting a diing gasp signal (DG signal) to the OLT 101 side. The wavelength band uses λ3.

  Note that the dedicated optical transmitter 254 may be 10G-EPON, GE-PON, or an original method as long as it can communicate with the receiver on the OLT 101 side. In addition, the wavelength band λ1, the wavelength band λ2, and the wavelength band λ3 have different wavelengths. For example, in the 10G-EPON standard, the upstream wavelength band is 1260 nm to 1280 nm, and the downstream wavelength band is 1575 nm to 1580 nm. Vacant wavelength bands other than these wavelength bands are used for dicing gasp signals. Then, these optical signals having different wavelength bands are multiplexed or demultiplexed according to each wavelength band by an optical multiplexer / demultiplexer 251 having a WDM function, and an optical receiver 252, an optical transmitter 253, and a dedicated optical transmitter. Input / output at 254.

  The PON LSI 202 is a control unit configured by a dedicated chip or the like that controls communication in accordance with the PON standard, and includes an ONU control unit 255 and a control signal generation unit 256 in the example of FIG. The control signal generator 256 is a separate block from the ONU controller 255 so that the features of the PON system 100 according to the present embodiment can be easily understood. However, the same block may be used, and in either case, the PON LSI 202 is used. This is one of the functions. In FIG. 2, the ONU control unit 255 transmits user data transmitted and received by the subscriber terminal 104 connected via the LAN I / F 203 according to the PON standard and various control data according to the PON standard generated by the control signal generation unit 256. Data is transmitted to and received from the OLT 101 via the optical transmission / reception circuit 201. In particular, in the present embodiment, the control signal generator 256 generates and transmits a Dying Gasp signal.

  The LAN I / F 203 is equipped with a dedicated chip that provides an interface for LAN connection of the subscriber terminal 104 to the ONU 103.

  The power supply circuit 204 is a circuit that converts power (for example, direct current power) supplied from an external power supply via a power supply line 206 into a voltage required for each part of the ONU 103. The power supply circuit 204 is illustrated in the optical transceiver circuit 201, the PONLSI 202, the LAN I / F 203, and the like. It is supplied by the wiring indicated by the dotted line power 2. The external power input is a power supplied from the outside such as an AC adapter.

  The voltage monitoring circuit 205 monitors the voltage drop of the external power supply input. For example, when the voltage of the power supply supplied from the external power supply via the power supply line 206 is monitored and becomes equal to or lower than a preset voltage value, A detection signal indicating disconnection is output. In the example of FIG. 2, the detection signal is output to the control signal generation unit 256 of the PONLSI 202, and the control signal generation unit 256 generates ON and transmits a Dying Gasp signal using the detection signal input as a trigger. Output to the unit 255. Upon receiving this, the ONU control unit 255 immediately transmits a dicing gasp signal (DG signal) from the dedicated optical transmitter 254 of the optical transmission / reception circuit 201 in the wavelength band λ3. Here, conventionally, the ONU control unit 255 communicates with the OLT 101 in order to transmit a dicing gasp signal (DG signal) in the wavelength band λ <b> 2 from the optical transmitter 254 for user data transmission of the optical transmission / reception circuit 201. Since the DG signal was transmitted at the transmission timing assigned from the OLT 101 after executing a predetermined sequence for acquiring the transmission timing and the like, it was necessary to operate the ONU 103 for a certain period of time before transmitting the DG signal. It was. For this reason, as shown in FIG. 3, a large-capacity capacitor 207 must be mounted on the external power supply input. In the example of FIG. 2, as soon as the voltage monitoring circuit 205 detects a voltage drop of the external power supply input, Since the DG signal is transmitted from the dedicated optical transmitter 254, the large-capacity capacitor 207 is not necessary, and a small-capacitance capacitor built in the power supply circuit 204 can be used.

[Configuration example of OLT 101]
Next, a configuration example of the OLT 101 will be described with reference to FIG. In FIG. 4, the OLT 101 includes an optical transmission / reception circuit 301, an OLT control unit 302, an optical transceiver 303, and a supervisory communication I / F 304.

  The optical transmission / reception circuit 301 is a circuit for transmitting / receiving user data and control data to / from a plurality of ONUs 103 via optical fibers. In the example of FIG. 4, an optical multiplexing / demultiplexing device 351, an optical transmitter 352, It has an optical receiver 353, a dedicated optical receiver 354, and an optical transmitter 352b.

  The optical transmitter 352 converts the transmission data output from the OLT control unit 302 into an optical signal, and transmits the optical signal as a downstream signal in the wavelength band λ1 by time division multiplexing to the plurality of ONUs 103, and the optical receiver 353 receives the signals from the plurality of ONUs 103. The upstream signal in the wavelength band λ <b> 2 transmitted in time division is converted into reception data and output to the OLT control unit 302. The dedicated optical receiver 354 is a dedicated receiver for receiving a dicing gasp signal (DG signal) from the ONU 103 in which the power interruption has occurred, and uses a wavelength band of λ3. Here, the OLT 101 is a station-side device that supports the PON standards with communication speeds of 10 Gbps and 1 Gbps, the optical transmitter 352 supports communication with the ONU 103 having a communication speed of 10 Gbps, and the optical receiver 353 An optical signal in the wavelength band λ2 is received, and the optical transmitter 352b supports communication with the ONU 103 having a communication speed of 1 Gbps using the wavelength band λ4. Here, the wavelength band λ1, the wavelength band λ2, the wavelength band λ3, and the wavelength band λ4 have different wavelengths. These optical signals are multiplexed or demultiplexed according to each wavelength by the optical multiplexer / demultiplexer 351, and enter the optical transmitter 352, optical receiver 353, dedicated optical receiver 354, and optical receiver 353b, respectively. Is output.

  The OLT control unit 302 is a control unit that operates according to the PON standard, and transmits / receives user data and various control data according to the PON standard via the optical transmission / reception circuit 301 to / from a plurality of ONUs 103. User data is transmitted / received to / from the higher level network via the optical transceiver 303, and the control data related to the PON control is processed, and the transmission timing and transmission data amount of the plurality of ONUs 103, alarm management and logical links of the subordinate ONUs 103 are processed. Status detection and history management. In particular, in the present embodiment, when a logical link disconnection of the ONU 103 is detected, it is determined whether it is due to a failure of the optical fiber or a power failure of the ONU 103, and is output to the monitoring device 305 via the monitoring communication I / F 304. , Notify the administrator. In this way, the administrator can manage the operation of the PON system 100.

  The optical transceiver 303 is an optical interface connected to the upper network.

The monitoring communication I / F 304 is connected to another monitoring network different from the communication of user data, and provides an interface for transmitting and receiving alarms and control commands to and from a remote monitoring device 305. For example, the OLT control unit 302 notifies the monitoring apparatus 305 when a change occurs in the logical link connection status with the ONU 103 or when an alarm is received.
[Processing when the power of the ONU 103 is turned off]
Next, processing when the ONU 103 is powered off will be described with reference to the flowchart of FIG.

  (Step S101) The voltage monitoring circuit 205 of the ONU 103 monitors the voltage of the external power supply.

  (Step S102) The voltage monitoring circuit 205 determines whether or not the voltage value measured in step S101 is less than or equal to a preset threshold value. If the power supply voltage is less than or equal to the threshold value, the voltage monitoring circuit 205 determines that a power interruption has occurred. Proceeding to S103, if the power supply voltage is greater than the threshold, the process returns to step S101 to continue monitoring the power supply voltage.

  (Step S103) When the power interruption is detected in Step S102, the ONU 103 transmits a Dying Gasp signal to the OLT 101 side. For example, in the case of FIG. 2, the voltage monitoring circuit 205 outputs a power-off detection signal to the PONLSI 202. Upon receiving this, the control signal generator 256 of the PON LSI 202 generates a Dying Gasp signal corresponding to the same OAM (Operation Administration and Maintenance) standard as before and outputs it to the ONU controller 255 using the OAM flag for ONU control. The unit 255 immediately transmits the DG signal to the OLT 101 side via the dedicated transceiver 254 of the optical transceiver circuit 201. Note that another method for transmitting the DG signal in step S103 will be described in detail later.

  (Step S104) Since the external power is not supplied, the power supply of the power supply circuit 204 is down and the operation of the ONU 103 is stopped. It should be noted that the ONU 103 operates only for a short period of time in which step S103 is executed by the capacitor in the power supply circuit 204.

  Here, conventionally, since it was necessary to execute step S151 “perform a predetermined sequence for transmitting the dicing gasp signal with the OLT 101” between step S102 and step S103, step S151 is executed. The ONU 103 had to be operated for a time, and it was necessary to mount a large-capacity capacitor 207 in addition to the capacitor in the power supply circuit 204 as described with reference to FIG.

  On the other hand, in the PON system 100 according to the present embodiment, the ONU 103 transmits the diing gasp signal as soon as it detects the power failure of the external power supply. Therefore, the processing in step S151 can be omitted, and the processing time is shortened. No need to mount the capacitor 207.

[Application Example 1]
In the above embodiment, the dicing gasp signal corresponding to the OAM standard similar to the conventional one is transmitted from the PONLSI 202. However, time is required for processing via the PONLSI 202. Therefore, in Application Example 1, as shown in FIG. 6, the ONU 103 ′ transmits a dicing gasp signal to the OLT 101 without going through the PONLSI 202. In FIG. 6, the same reference numerals as those in FIG. 2 denote the same components. The ONU 103 ′ in FIG. 6 and the ONU 103 in FIG. 2 are different from each other in that a pulse modulation unit 261 is provided in the optical transmission / reception circuit 201a and that the power-off detection signal of the voltage monitoring circuit 205a is not the PONLSI 202 but the pulse modulation unit 261. To be output.

  In FIG. 6, the pulse modulation unit 261 that has received the detection signal from the voltage monitoring circuit 205a turns on the laser diode of the dedicated optical transmitter 254 for a short time and transmits a 1-bit pulse signal in the wavelength band λ3 to the OLT 101. Thus, since it is not necessary for the PON LSI 202 to generate and transmit a diing gasp signal corresponding to the OAM standard, a diing gasp signal (DG signal) for notifying the power-off is faster than the case of the ONU 103 in FIG. Can be sent to. Since the diing gasp signal is a signal having a name corresponding to the OAM standard, strictly speaking, it is different from the pulse signal, but here, a signal for notifying the OLT 101 of power-off is referred to as a diing gasp signal.

  In this way, the ONU 103 ′ of Application Example 1 transmits a dicing gasp signal based on a pulse signal without passing through the PONLSI 202, so that a quicker power-off notification can be made and a large-capacity capacitor 207 is mounted. There is no need.

  Here, when a plurality of ONUs 103 are accommodated in the OLT 101, there arises a problem that the OLT 101 that has received the pulse signal does not know which ONU 103 has transmitted. Therefore, the OLT control unit 302 performs processing for identifying the ONU 103 that has transmitted the pulse signal with reference to a history (log) such as an alarm of the subordinate ONU 103 and a status of the logical link. FIG. 7 shows an example of a log. Here, the logical link ID (LLID) of the ONU 103a in FIG. 1 is LLID: 1, the logical link ID (LLID) of the ONU 103b is LLID: 2, and the logical link ID (LLID) of the ONU 103c is LLID: 3.

  In FIG. 7, the logical link with the ONU 103a is established at 10:25:30 on January 1, 2012, and the logical link with the ONU 103b is established at 15:11:05 on January 1, 2012, Date: 2012/1/1 at 17:35:28 A logical link with the ONU 103c is established. Then, the OLT control unit 302 receives the pulse signal (DG signal indicating power-off) described above at 21:45:00 on the date and time: 2012/1/1, and the date and time immediately after that: 2012/1/1 At 21:45:01, the disconnection of the logical link with the ONU 103a (LLID: 1) is detected. Therefore, the OLT control unit 302 determines that the ONU 103 that has transmitted the pulse signal is the ONU 103a of LLID: 1 that has detected the logical link disconnection immediately after reception of the pulse signal.

  In this way, the ONU 103 ′ of the application example 1 transmits a dicing gasp signal based on a pulse signal without passing through the PONLSI 202, so that a quicker power-off notification is possible and the history is referred to. Thus, it becomes possible to identify the ONU 103 in which the power interruption has occurred. This eliminates the need to mount a large-capacitance capacitor 207 in the ONU 103 while maintaining the same function of the dicing gasp as in the prior art.

[Application 2]
In the application example 1, since a simple 1-bit pulse signal for on / off is transmitted as a dicing gasp signal, it is necessary to perform processing for identifying the ONU 103 that transmitted the pulse signal with reference to the history on the OLT 101 side. there were. Thus, as in Application Example 1, Application Example 2 that can easily identify the ONU 103 that has transmitted the Dying Gasp signal while transmitting the Dying Gasp signal without passing through the PON LSI 202 will be described.

  The difference from the ONU 103 ′ in FIG. 6 is that a modulation unit 262 and a memory 263 are provided in the optical transmission / reception circuit 201 b. Note that the power-off detection signal of the voltage monitoring circuit 205a is output not to the PONLSI 202 but to the modulation unit 262, similarly to the ONU 103 'in FIG.

  In the ONU 103 ″ in FIG. 8, the modulation unit 262 that has received the detection signal from the voltage monitoring circuit 205 a modulates the laser diode of the dedicated optical transmitter 254 according to the digital information stored in the memory 263. As a modulation method, for example, digital “1” and “0” may be a modulation method such as NRZ (Non Return to Zero), or another modulation method may be used.

  Here, the digital information stored in the memory 263 may be a 6-byte MAC address unique to the ONU 103 or a 2-byte logical link ID assigned from the OLT 101.

  In this way, the ONU 103 ″ of the application example 2 transmits the diing gasp signal with the MAC address and the logical link ID for specifying the ONU 103 without passing through the PONLSI 202, so that a quick power-off notification can be made. Therefore, it is not necessary to mount a large capacity capacitor 207.

  The optical communication system according to the present invention has been described with reference to each embodiment, but can be implemented in various other forms without departing from the spirit or main features thereof. For this reason, the above-described embodiment is merely an example in all respects and should not be interpreted in a limited manner. The present invention is defined by the claims, and the present invention is not limited to the text of the specification. Further, all modifications and changes belonging to the equivalent scope of the claims are within the scope of the present invention.

100 ... PON system 101 ... OLT
102 ... Optical couplers 103, 103a, 103b, 103c, 103 ', 103''... ONU
104, 104 a, 104 b, 104 c... Subscriber terminals 201, 201 a, 201 b... Optical transceiver circuit 202.
203 ... LAN I / F
204 ... Power supply circuit 205, 205a ... Voltage monitoring circuit 251 ... Optical multiplexer / demultiplexer 252 ... Optical receiver 253 ... Optical transmitter 254 ... Dedicated optical transmitter 255 ... ONU controller 256 ... control signal generator 301 ... optical transceiver circuit 302 ... OLT controller 303 ... optical transceiver 304 ... supervisory communication I / F
351: Optical multiplexer / demultiplexer 352 ... Optical transmitter 353 ... Optical receiver 354 ... Dedicated optical receiver 352b ... Optical transmitter

Claims (1)

A plurality of ONU, wherein is composed of a plurality of OLT connected via an optical coupler to ONU, the PON system for communicating time division multiplexed upstream signals of the same wavelength band to the OLT from the plurality of ONU ,
The ONU is
An optical receiver for communication on the subscriber side that receives a downlink signal of the first wavelength or the fourth wavelength from the OLT ;
A subscriber-side communication optical transmitter that transmits an upstream signal of the second wavelength to the OLT ;
A subscriber-side control optical transmitter that transmits an upstream signal of the third wavelength to the OLT ;
A subscriber-side control unit that controls communication with the OLT ;
A power-off detector that detects power-off of the device itself ;
A pulse modulation unit for turning on and off the subscriber-side control optical transmission unit and transmitting a 1-bit pulse signal ;
The subscriber-side control unit communicates the user data with the OLT by the subscriber-side communication optical receiving unit and the subscriber-side communication optical transmission unit, and the power-off detection unit turns off the power of the own device. Only when it is detected, a power-off signal is transmitted to the OLT via the subscriber-side control optical transmitter,
The power-off detection unit outputs a detection signal directly to the pulse modulation unit without going through the subscriber-side control unit and detects from the subscriber-side control optical transmission unit when detecting the power-off of the own device. A 1-bit pulse signal is transmitted to the OLT instead of a diing gasp signal corresponding to the OAM standard.
The OLT is
An optical transmitter for station side communication that transmits a downlink signal of the first wavelength or the fourth wavelength to the plurality of ONUs ;
An optical receiver for communication on the station side that receives upstream signals of the second wavelength from the plurality of ONUs ;
A station-side control optical receiver that receives an upstream signal of the third wavelength from the plurality of ONUs ;
A station-side control unit that controls communication with the plurality of ONUs ;
A link detection unit for detecting a state of a logical link formed between the plurality of ONUs;
A log storage unit that stores in the history the time information when the logical link state detected by the link detection unit has changed and the device identification information of the ONU corresponding to the logical link ;
When the station-side control unit receives the 1-bit pulse signal from the ONU via the station-side control optical receiving unit, the station-side control unit detects a logical link break immediately after receiving the pulse signal with reference to the history. PON system, characterized in that to power-off the ONU has is determined to have occurred.

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