JP4228693B2 - PON (Passive Optical Network) system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical data communication network connecting between a master station and a plurality of slave stations, and more particularly to a PON (Passive Optical Network) system.
[0002]
[Prior art]
In a system for bidirectional communication between a master station and a plurality of slave stations using an optical data communication network, there is a network configuration in which the master station and each slave station are radially connected by a single optical fiber. It has been put into practical use (Single Star). In this network configuration, the system and device configuration are simplified, but each slave station occupies one optical fiber, so it is difficult to reduce the cost of the system.
[0003]
Therefore, a PON (Passive Optical) that shares one optical fiber among multiple slave stations.
Network) system has been proposed.
In this PON system, packets are distributed in broadcast form from a master station to a slave station. Since the upstream packet from the slave station collides unless some sort of traffic control is performed, the upstream optical signal from the slave station is transmitted in a time division manner.
[0004]
[Problems to be solved by the invention]
However, the optical link circuit of the slave station may break down and be always on. Since the management of the slave station is usually performed by the master station administrator rather than the terminal user, it is necessary for the master station administrator to identify the slave station that is lit and repair or replace the slave station. is there.
However, since the master station cannot identify the upstream packet from the slave station, it is very difficult to identify the slave station that is in the lighting state.
[0005]
Therefore, an object of the present invention is to realize a PON system that can easily specify a slave station in a quenching failure state by transmitting a downlink command signal from the master station.
[0008]
[Means for Solving the Problems]
According to the PON system of the present invention, the master station designates a slave station and transmits a signal including a command for turning off the light emission of the slave station, and the slave station transmits its own signal based on the command. The master station turns off the light emission, and when the slave station with poor extinction extinguishes its own station based on the command, the optical signal that has been continuously received disappears, or from the other slave station When a normal optical signal is returned, it is determined that the slave station is out of order. In this case, the master station is grouped slave station, signal to downlink transmission including the command to turn off the light emission of the slave station for each group (Claim 1).
In the present invention, by specifying the group and narrowing down the group, it is only necessary to perform optical transmission at the maximum log2N times. Therefore, the number of times of optical transmission until a faulty slave station is found can be reliably reduced.
[0011]
Further, according to the PON system of the present invention, the master station designates the slave stations one by one, and sequentially transmits a signal including a command to turn off the optical link circuit of the slave station, The station turns off the power of its own optical link circuit based on the command, and the master station continues until now when the slave station with poor extinction causes the station to turn off the power based on the command. When the received optical signal disappears, it is determined that the slave station is faulty. When the power of the optical link circuit is turned off, the slave station automatically turns on the power after a certain period of time. Return (claim 3 ).
According to the present invention, even when the extinction / re-emission of the slave station cannot be controlled using a command from the master station, the power of the optical link circuit of the slave station can be turned off. If the slave station is turned off, it cannot receive commands from the master station. Therefore, after the check of the master station is completed, the power cannot be restored by a command from the master station. However, according to the present invention, the slave station can automatically restore power.
[0012]
The time to automatically restore the power is set to be longer than the time when the check of all the slave stations by the master station is completed. This is necessary to complete the check of all the slave stations by the master station. (Claim 4 ).
It should be noted that it is preferable to transmit a command including the content prohibiting the automatic power supply recovery to the faulty slave station because the system does not start up after the power supply automatically recovers (claim 5 ).
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
―Network configuration―
FIG. 1 is a configuration diagram of a PON (Passive Optical Network). Main terminal station (referred to as “parent station”) 1 and a plurality of remote terminal stations (referred to as “child stations”) 5A, 5B,. . . (Referred to collectively as “slave station 5”) through a passive optical branching device 3 through an optical network. The distance from the passive optical branching device 3 to the slave station 5 varies depending on the slave station.
[0016]
The downlink direction in which transmission is performed from the master station 1 to the plurality of slave stations 5 and the opposite uplink direction are separated by the difference in optical transmission direction or wavelength.
―Configuration of slave stations and master stations―
The configuration of the slave station 5 when communicating between the master station 1 and the slave station 5 will be described with reference to FIG.
The downlink transmission signal from the master station 1 to the slave station 5 and the uplink transmission signal from the slave station 5 to the master station 1 are each composed of packets.
[0017]
As shown in FIG. 2, the slave station 5 includes an optical link circuit (O / E) 51, a PHY circuit 52, an FPGA (Flexible Programmable Gate Array) circuit 53, and a LAN cable connected to the master station 1 through the optical fiber 4. An L2SW (Layer 2 Switch) circuit 54 connected to a device (for example, a computer installed in a home or office) is provided. A transmission buffer 56 and a reception buffer 55 are attached to the FPGA circuit 53.
Since the downstream packet transmitted from the master station 1 includes a clock signal, the slave station 5 uses this clock signal as the transmission clock of the PHY circuit 52. Thus, all the slave stations 5 can be synchronized with the clock of the master station 1.
[0018]
The upstream packet supplied from the home device to the slave station 5 is composed of a MAC frame having an indefinite time length. This packet is input to the FPGA circuit 53 through the L2SW circuit 54, and the upper layer (MII interface) processing is performed in the FPGA circuit 53. Then, it is sent to the PHY circuit 52 and is sent to the optical link circuit 51 from here.
On the other hand, the downstream packet received from the master station 1 through the optical link circuit 51 is input to the FPGA circuit 53 through the PHY circuit 52, the upper layer (MII interface) is processed by the FPGA circuit 53, and is sent to the L2SW circuit 54. From here, it is transmitted to the home device through the LAN cable.
[0019]
In the above, the configuration of the slave station 5 in the case where communication is performed between the master station 1 and the slave station 5 has been described. However, almost the same configuration as this configuration is also adopted in the master station 1. The master station 1 transmits a packet sent from the in-station device or a higher-level network (such as the Internet) to the slave station 5 through the optical fiber 4, and the packet sent from the slave station 5 Send it to the network.
FIG. 3 is a block diagram showing the configuration of the master station 1. The master station 1 includes an optical link circuit (O / E) 11 connected to a slave station through an optical fiber 4, a PHY circuit 12, an FPGA circuit 13, and an L2SW circuit 14 connected to a host network through a LAN cable. A transmission buffer 16 and a reception buffer 15 are attached to the FPGA circuit 13.
[0020]
The master station 1 transmits the clock signal generated by the clock generation PLL 17 in a downlink packet to the slave station. Thus, all the slave stations 5 can be synchronized with the clock of the master station 1.
Downstream packets supplied from the upper network to the master station 1 are input to the FPGA circuit 13 through the L2SW circuit 14, and the upper layer (MII interface) processing is performed in the FPGA circuit 13. Then, it is sent to the PHY circuit 12, and is transmitted from here through the optical link circuit 11 to the slave station.
[0021]
On the other hand, the upstream packet received from the slave station through the optical link circuit 11 is input to the FPGA circuit 13 through the PHY circuit 12, and after the upper layer (MII interface) processing is performed in the FPGA circuit 13, the L2SW circuit 14 Sent from here to the upper network.
The level of the optical signal received from the slave station is determined by the level monitoring circuit 18 connected to the optical link circuit 11, and the result is input to the FPGA circuit 13. In the FPGA circuit 13, a slave station abnormality determination unit 19 is provided, in which a faulty slave station is specified as described later.
[0022]
―Packet configuration―
FIG. 4A is a packet configuration diagram including a MAC frame. The MAC frame is divided into a header and data. The header is composed of data such as a destination address DA (destination address), a self address SA (sauce address), and a time length LEN (length).
A preamble PA is added to the MAC frame. As shown in FIG. 4 (b), the preamble PA includes a part for data synchronization, a terminal ID for designating a master station or a slave station for communication, a command from the master station to the slave station, or a slave station to the master station. Response, various parameters, error check code FCS, and start packet demilita SFD.
[0023]
-Failure diagnosis of slave stations-
FIG. 5 is a block circuit diagram showing a transmission unit of the optical link circuit 51. A burst signal having a waveform corresponding to the transmission packet is input to the laser diode LD through the control unit 51a and the driver 51b. The light emitted from the laser diode LD enters the optical fiber 4 and is received by the photodiode PD. This received light signal is averaged (referred to as PD monitor output) through the low-pass filter 51c, and fed back to the control unit 51a. The control unit 51a controls the light emission intensity to be constant.
[0024]
On the other hand, the PD monitor output is input to the monitoring unit 51d. The monitoring unit 51d checks whether normal light emission is performed based on the PD monitor output waveform.
Check items are a repetition period of the PD monitor output waveform, a signal level during light emission, and a signal level during extinction. The repetition period of the PD monitor output depends on the polling period tp.
[0025]
FIG. 6 is a signal waveform diagram of each part, where (a) shows a burst signal waveform, and (b) and (c) show PD monitor output waveforms. (b) shows normal time, (c) shows abnormal time. Dashed lines X and Y indicate threshold values.
Based on the PD monitor output, the monitoring unit 51d determines whether or not the light emission / quenching repetition period is within a certain time (for example, a time obtained by adding a certain margin to the polling period tp), that is, always emits and extinguishes within a certain period. It monitors whether or not state transitions occur.
[0026]
It is also monitored whether the signal level at the time of light emission is equal to or higher than the threshold value X and the signal level at the time of extinction is equal to or lower than the threshold value Y.
If the slave station emits light normally, as shown in FIG. 6 (b), the repetition cycle of light emission / quenching occurs within the above time, and the signal level at the time of light emission is equal to or higher than the threshold value X. The signal level is less than or equal to the threshold value Y. The monitoring unit 51d performs normality determination based on these determinations.
[0027]
If the slave station fails (extinction failure), the repetition cycle of light emission / extinction becomes infinite as shown in FIG. 6 (c), and the signal level during extinction always exceeds the threshold value Y. End up. Therefore, the monitoring unit 51d can determine the failure of the own station.
The monitoring unit 51d notifies the FPGA circuit 53 of this determination content. The FPGA circuit 53 immediately reduces the intensity of the optical signal of the local station to 0 to prevent the entire PON system from being down.
[0028]
A method for dropping an optical signal will be described with reference to FIG.
FIG. 7 is a control system diagram when optical signal on / off control is performed from the FPGA circuit 53 to the optical link circuit 51.
There are two types of optical on / off control systems from the FPGA circuit 53 to the optical link circuit 51. One is to turn off the driver of the laser diode LD while the optical link circuit 51 is energized, and the other is the optical link circuit. The power supply of 51 is cut off.
[0029]
A control signal to be performed while the former optical link circuit 51 is energized is indicated by reference symbol a in FIG. 7, and a control signal for turning off the power supply of the latter optical link circuit 51 is indicated by reference symbol b in FIG.
When the slave station determines that its own station has failed, the slave station sends out a control signal a to drop the optical link circuit 51 to prevent the entire PON system from going down. If the optical link circuit 51 does not go down even if the control signal a is sent, the control signal b is sent to turn off the power of the entire slave station. In this case, the slave station sends a power-off alarm to the master station.
[0030]
Even if the above measures are taken, the slave station may not be extinguished alone. If the optical signal received by the master station is always in the input state, all the uplink packets from the slave stations are destroyed, and the entire system becomes incapable of uplink communication. Therefore, the master station enters the following procedure in order to identify the slave station with a poor extinction.
Further, as shown in FIG. 8, the slave station may not have a failure self-diagnosis in which the light emission of the laser diode LD is monitored by the photodiode PD. In this case, even if the slave station becomes defective in extinction, it cannot be detected by the slave station alone, so it is necessary for the master station to identify and repair the slave station having the poor extinction.
[0031]
-Identification of faulty slave stations from the master station-
A slave station specifying procedure performed by the master station when the optical signal received by the master station is always in the input state will be described.
First, a procedure for determining a faulty slave station will be described using a flowchart.
FIG. 9 is a flowchart showing a procedure for discriminating a faulty slave station, and the master station periodically polls the slave station (step S1). If a predetermined response signal cannot be received from the slave station (step S2), the master station checks whether a power-off alarm is received (step S3).
[0032]
If the power-off alarm is received, the faulty slave station can be specified, but if the power-off alarm is not received, the process of determining the faulty slave station is started (step S4).
Hereinafter, the determination procedures A, A ′, B, and C in the case of extinction failure will be described.
Procedure A.
The master station designates the slave stations 5A, 5B,... One by one as the “terminal ID”, and uses the signal a for the optical link circuit 51 of the slave station in the “command” in the preamble. The polling packets A, B,... Including the command to turn off the light are sequentially transmitted downstream.
[0033]
The slave station that has received the polling packets A, B,...
When the slave station with abnormal light emission extinguishes its own station, the master station determines that the optical signal received so far by the level monitoring circuit 18 has disappeared. Can be determined.
If the master station does not have the level monitoring circuit 18, a faulty slave station can be identified by transmitting a command from the master station and returning a normal response from the slave station that is not abnormal in light emission.
[0034]
After that, a command to turn on the light emission is sent to other than the faulty slave station. Dispatch personnel to the failed child station for repair.
Procedure A ′.
This procedure is a modification of the procedure A, and the master station groups the slave stations 5A, 5B,... And transmits an extinction command in units of groups.
This will be described with reference to the flowchart of FIG. When the number of slave stations is N (N is an integer equal to or greater than 1), the master station selects an integer m satisfying 1 ≦ m ≦ N, and sets the slave stations as group A from the first to m-th stations. , The group B is divided into the (m + 1) th to Nth groups (step S11).
[0035]
The master station transmits a command to turn off light emission to the slave stations belonging to group A using the signal a to the optical link circuit 51 of the slave station (step S12). If the light that has arrived at the master station disappears or the periodic response returns (YES in step S13), it can be determined that there is a slave station with poor extinction among the slave stations belonging to group A. All the slave stations belonging to the group are again grouped (step S14). That is, the number of slave stations N is set to m, and it is determined whether N = 1 (step S15). If N = 1, the process returns to step S11, and the master station selects an integer m satisfying 1 ≦ m ≦ N, and sets the slave stations from the first to m-th group A and the m + 1-th station. It is divided again into the Nth group B and the procedure from step S12 is repeated.
[0036]
If it is not extinguished, or if a periodic response does not return (NO in step S13), it can be determined that there is a slave station with poor extinction among the slave stations belonging to group B, so all the slave stations belonging to group B Are grouped again (step S16). That is, the number of slave stations N is set to N−m, and it is determined whether N = 1 (step S17). If N = 1, the process returns to step S11, and the master station selects an integer m satisfying 1 ≦ m ≦ N, and sets the slave stations from the first to m-th group A and the m + 1-th station. It is divided again into the Nth group B and the procedure from step S12 is repeated.
[0037]
If N = 1 in step S15 or S17, the slave station is identified as having failed (step S18).
If the faulty slave station is specified, the process proceeds to step S5 in FIG. 9 to repair or replace the slave station (step S6).
Procedure B.
The master station sets a global address designating all the slave stations as the “terminal ID”, and turns off the light emission using the signal “a” to the optical link circuit 51 of all the slave stations in the “command” in the preamble. Packet including the command to be transmitted.
[0038]
Since all the slave stations receiving this packet stop emitting light, the optical signal received by the master station disappears.
Next, as shown in FIG. 11, the master station designates the slave stations 5A, 5B,... One by one as the “terminal ID”, and sets the optical link of the slave station in the “command” in the preamble. Polling packets A, B,... Including a command for turning on light emission and returning a packet are sequentially transmitted to the circuit 51 using the signal a.
[0039]
The slave station that has received the polling packets A, B,... Emits light only for a necessary period and returns a predetermined packet.
However, as shown in FIG. 11, the slave station with abnormal emission (for example, 5B) keeps its own station emitting light, so that the master station continues to receive the optical signal, It can be determined that there is a failure (extinction failure).
A command to turn off the light is sent to the failed slave station. Dispatch personnel to repair or replace the failed slave station.
[0040]
Procedure C.
When the optical link circuit 51 does not respond to the control signal a, the faulty slave station is not found even if the procedure for turning on and off with the control signal a is taken. In this case, the optical link circuit 51 itself is turned off.
The master station designates the slave stations 5A, 5B,... One by one as the “terminal ID”, and gives a command to turn off the power of the optical link circuit 51 of the slave station to the “command” in the preamble. The included polling packets A, B,.
[0041]
The slave station that has received the polling packets A, B,... Turns off the optical link circuit 51 by turning off the optical link circuit 51 of the local station.
When the slave station with abnormal light emission extinguishes its own station, the master station can determine that the slave station has failed (quenching failure) by extinguishing the optical signal that has been received.
When the power of the optical link circuit 51 is turned off, the light receiving circuit in the optical link circuit 51 also does not work (this is not necessary if the power supply on the transmission side and the reception side are separated), so the power is restored from the master station to the slave station. The command cannot be sent. In order to restore the power, the slave 58 automatically restores the power after a certain period of time by the timer 58. This “certain time” needs to be set to a time longer than the time when the check of all the slave stations is terminated due to the power interruption.
[0042]
When power is restored, the faulty slave station emits light again, so the second command to turn off the power of the optical link circuit 51 to the slave station (this command includes contents prohibiting automatic power recovery). ) To transmit only the slave station. Then, dispatch personnel to the slave station for repair or exchange.
If the power supply of the transmission side and the reception side of the optical link circuit 51 of the slave station is separated, the reception function is working, so that the power supply of the slave station is restored by sending a power recovery command from the master station. Can be made. Since it is not necessary to provide a timer for automatically returning the power to the slave station after a predetermined time has elapsed, the configuration of the slave station can be simplified.
[0043]
Although the embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention.
[0044]
【The invention's effect】
As described above, according to the present invention, the master station can identify a faulty slave station even when one of the slave stations becomes defective in extinction and cannot receive a signal from another slave station. The child station can be repaired or replaced.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a PON (Passive Optical Network).
FIG. 2 is a block configuration diagram of a slave station 5;
FIG. 3 is a block configuration diagram of a master station 1;
FIG. 4 is a configuration diagram of a frame. (a) shows the entire frame, and (b) shows the details of the preamble part.
FIG. 5 is a block circuit diagram showing a transmission unit of the optical link circuit 51;
6 is a signal waveform diagram of each part of the optical link circuit 51, where (a) shows a burst signal waveform, and (b) and (c) show a PD monitor output waveform. FIG. (b) shows the waveform when normal, and (c) shows the waveform when abnormal.
FIG. 7 is a control system diagram when optical signal on / off control is performed from the FPGA circuit 53 to the optical link circuit 51;
FIG. 8 is a block circuit diagram showing a transmission unit of the optical link circuit when the slave station does not have a failure self-diagnosis for monitoring the light emission of the laser diode LD with the photodiode PD.
FIG. 9 is a flowchart showing a procedure by which a master station determines a faulty slave station.
FIG. 10 is a flowchart showing a procedure for identifying a faulty slave station by grouping slave stations and transmitting an extinction command in units of groups.
FIG. 11 is a sequence diagram showing a state in which polling packets A, B,... Including a command for returning a packet are sequentially transmitted from a master station by specifying slave stations 5A, 5B,. It is.
[Explanation of symbols]
1 Master station 3 Passive optical splitter 4 Optical fibers 5, 5A, 5B,. . Slave station 11 Optical link circuit 12 PHY circuit 13 FPGA circuit 14 L2SW circuit 15 Reception buffer 16 Transmission buffer 51 Optical link circuit 51a Control unit 51b Driver 51c Low pass filter 51d Monitoring unit 52 PHY circuit 53 FPGA circuit 54 L2SW circuit 55 Reception buffer 56 Transmission Buffer 57 Relay 58 Timer LD Laser diode PD Photo diode

Claims (5)

In a PON (Passive Optical Network) system that connects a master station and multiple slave stations,
The master station includes a transmission means for transmitting a signal including a command to turn off the light emission of the slave station by designating the slave station,
The slave station includes quenching means for turning off the light emission of the local station based on the command,
When a slave station with poor extinction extinguishes its own station based on the command, the master station determines that the slave station is faulty by extinguishing the optical signal that has been continuously received. A discriminating means for
The PON system is characterized in that the transmission means of the master station divides the slave stations into groups and transmits a signal including a command for turning off the light emission of the slave stations for each group. In a PON (Passive Optical Network) system that connects a master station and multiple slave stations,
The master station includes a transmission means for transmitting a signal including a command to turn off the light emission of the slave station by designating the slave station,
The slave station includes quenching means for turning off the light emission of the local station based on the command,
When a slave station with poor extinction extinguishes its own station based on the command, the master station determines that the slave station is faulty by returning a normal optical signal from another slave station. With a discrimination means,
The PON system is characterized in that the transmission means of the master station divides the slave stations into groups and transmits a signal including a command for turning off the light emission of the slave stations for each group. In a PON (Passive Optical Network) system that connects a master station and multiple slave stations,
The master station includes transmission means for sequentially specifying a slave station one by one and sequentially transmitting a signal including a command to turn off the power of the optical link circuit of the slave station.
The slave station includes a power-off means for turning off the power of the optical link circuit of the local station based on the command,
When the slave station with poor extinction turns off its own station based on the command, the master station has a failure of the slave station because the optical signal that has been continuously received disappears. A determination means for determining
The PON system is characterized in that the slave station is provided with a power recovery means for automatically recovering the power after a predetermined time elapses by a timer when the power of the optical link circuit is turned off. 4. The PON system according to claim 3, wherein the “predetermined time” is set to a time longer than a time at which checking of all slave stations by the master station is completed. The transmission means of the master station is capable of downlink transmitting a signal including a command including a content prohibiting automatic power return of the optical link circuit to a predetermined slave station. 4. The PON system according to 4 .

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