JP2007336442A - Center device, optical transmission system and system switching method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switchable center device including a security control function, an optical transmission system and a system switching method by solving the problem that communication is not normally recovered because by switching when security control is made compatible with switching in the optical transmission system including IF sections 800-1, 800-2, 800-3 and a switching section 900. <P>SOLUTION: After switching by optical reception interruption detection is performed in the case of switching in transmission line disconnection, re-switching is stopped only for a switching stop period based on pulse signal reception. Thus, after switching, optical security control can be performed and communication is normally recovered. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a center apparatus, an optical transmission system, and a system switching method, and more particularly to a center apparatus, an optical transmission system, and a system switching method for an optical transmission system that transmits a plurality of signal lights by wavelength multiplexing.

  Patent Document 1 or Patent Document 2 discloses a single-fiber bidirectional optical transmission system that switches an optical output to an intermittent pulse by using a pulse generation circuit built in a transmitter when reception of an optical signal is interrupted for a certain period of time. Is described. If there is a failure in the transmission optical fiber of the single-fiber bidirectional optical transmission system, both IF units at the communication end are in a reception-disconnected state, and a separate detection circuit for detecting the pulse is provided in the receiver to detect the pulse. Thus, it is determined that the optical fiber has been recovered from the fault, and normal optical signal output is permitted.

  In this way, the intermittent pulse is sent in order to suppress the amount of light energy directly incident on the retina of the worker when recovering the optical fiber failure and to avoid adverse effects on the eyes. Further, communication can be restored by detecting a pulse received when the line is reconnected.

  The configuration described above will be described with reference to FIGS. Here, FIG. 1 is a block diagram of an optical interface unit of the optical transmission apparatus. FIG. 2 is a diagram for explaining the occurrence and recovery of a failure in a transmission optical fiber of a single fiber bidirectional optical transmission system.

  In FIG. 1, the IF unit 50 includes an optical receiver 1 and an optical transmitter 2. An optical receiver 1 is connected to a fiber, and an optical-electrical converter 11 that performs optical-electrical conversion, a signal detector 12 that detects a signal from an electrical signal output from the optical-electrical converter 11, and an optical-electrical converter 11 includes a reception interruption detection unit 14 that detects reception interruption from the output of 11, and a pulse detection unit 13 that detects a pulse from the output of the photoelectric conversion unit 11. On the other hand, the optical transmission unit 2 includes a pulse generation unit 22 that generates a pulse electrical signal, a selector 23 that receives the output of the pulse generation unit 22 and the electrical signal, and an electrical-optical conversion that receives the output of the selector 23 as an input. And an electro-optical conversion unit 21 to be performed.

  Here, the selector 23 is controlled by the pulse detector 13 and the reception interruption detector 14. That is, when the pulse detector 13 detects a pulse signal, an electric signal input is selected as the output of the selector 23. On the other hand, when the reception interruption detection unit 14 detects reception interruption, a pulse is selected as the output of the selector 23.

  In FIG. 2, in the single-fiber bidirectional transmission system 500 in which the IF unit 50-1 and the IF unit 50-2 are connected by a single optical fiber 52, when the fiber 52 is broken, the bidirectional IF unit 50 is disconnected. Is switched to pulse output as shown in FIG. When the break of the fiber 52 is restored, the IF unit receives the pulse, so that the optical signal is output and the communication is normally restored as shown in FIG.

  On the other hand, as a typical technique for optical fiber switching control, there is a technique for switching signals by detecting an optical input signal and issuing a switching instruction when reception of an optical signal cannot be detected.

  However, when optical safety control and optical fiber switching control are combined, the optical input disconnection is detected even after the optical fiber switching occurs by erroneously judging that the optical input is interrupted during pulse transmission by the optical safety control. The problem that occurs.

Patent Document 3 describes a switchable optical transmission system having a main transmission line and a backup transmission line.
Patent Document 4 describes an optical switching device that distinguishes between a failure alarm detected due to an abnormality or failure and a pseudo alarm detected by a switching operation or the like to prevent malfunction. It is described that this optical switching device masks an alarm until it returns to normal operation when it detects an abnormality in the normal operation state and transitions to the autonomous redundancy switching state.

Japanese Patent Laid-Open No. 05-122154 JP 2001-217778 A JP 2005-269246 A Japanese Patent Laid-Open No. 2003-224872

  The present invention provides a center device that achieves both switching that ensures transmission path reliability so that signal transmission does not stop even when the transmission path is broken while reducing the influence on the human body when the transmission path is broken by a pulse output function based on safety control An optical transmission system and a system switching method are provided.

  The above-described problem is selected by the switching unit, which is connected to the local device via the first transmission path and the second transmission path, and is connected to the first transmission path and the second transmission path. An interface unit that performs bidirectional communication with the local device via the first transmission path, and when the interface unit detects a failure in the first transmission path, the interface unit controls the switching unit to switch to the second transmission path. When switching and detecting a failure in the second transmission path, this can be achieved by the center device that continues the connection with the second transmission path in a predetermined period.

  A local device including a first interface unit, a second interface unit, and a wavelength multiplexing / demultiplexing unit; a switching unit connected to the first interface unit and the second interface unit; A center device comprising a connected third interface unit, and the third interface unit controls the switching unit to detect the second interface when a failure is detected in the signal from the first interface unit. This can be achieved by an optical transmission system that switches to the signal from the unit and continues the connection with the second interface unit during a predetermined period when a failure is detected in the signal from the second interface unit.

  Further, the step of the third interface unit detecting a failure in the signal from the first interface unit, the step of controlling the switching unit to switch to the signal from the second interface unit, This can be achieved by a system switching method including a step of continuing connection with the second interface unit during a predetermined period when a failure is detected in the signal.

  According to the present invention, it is possible to provide a center device, an optical transmission system, and a system switching method that improve safety when a transmission line is broken and have high transmission reliability.

Hereinafter, embodiments of the present invention will be described using examples with reference to the drawings. The same reference numerals are assigned to substantially the same parts, and the description will not be repeated.
Here, FIG. 3 is a block diagram of the optical transmission system. FIG. 4 is a block diagram of the local device. FIG. 5 is a block diagram of the wavelength multiplexing / demultiplexing unit. FIG. 6 is a block diagram of the center device. FIG. 7 is a block diagram of the optical switch unit. FIG. 9 is a timing chart of the IF unit. FIG. 8 is a block diagram of the IF unit. FIG. 10 is a timing chart for explaining processing from transmission line disconnection to signal restoration by switching. FIG. 11 is a timing chart for explaining processing from transmission line disconnection to signal restoration by switching when the signal restoration condition is a plurality of pulses.

  In FIG. 3, the optical transmission system 510 includes a center station 2000 and two unmanned stations 1000. The user interface 100-1 in the unmanned station 1000 inputs a signal input to the local device 300, and receives the signal at the center device 600 in the center station 2000 via the transmission line optical fibers 400-1 and 400-2. . The center device 600 transmits the received signal to the user interface 100-2. The user interfaces 100-1 and 100-2 send signals to the local device 300 and the center device 600, and send signals from the local device 300 and the center device 600 to a user device (not shown).

  In FIG. 4, the local device 300 divides the signal received from the user interface 100-1 by the wavelength multiplexing / demultiplexing unit 200 and inputs the optical signal to the IF units 800-1 and 800-2, respectively. The IF units 800-1 and 800-2 that have received the optical signal convert the wavelength of the optical signal, and then transmit the optical signal to the transmission lines 400-1 and 400-2, respectively.

  On the other hand, the IF units 800-1 and 800-2 that have received the optical signals from the transmission lines 400-1 and 400-2 convert the wavelength of the optical signals, and then perform wavelength multiplexing by the wavelength multiplexing / demultiplexing unit 200, It transmits to the interface 100-1.

  In FIG. 5, the wavelength multiplexing / demultiplexing unit 200 includes two optical couplers 201-1 and 201-2. The optical coupler 201-1 branches the optical signal from the user interface 100-1 and transmits it to the IF units 800-1 and 800-2. On the other hand, the optical coupler 201-2 multiplexes the optical signals from the IF units 800-1 and 800-2 and transmits them to the user interface 100-1. The IF units 800-1 and 800-2 do not transmit an optical signal to the user interface 100-1 at the same time.

  In FIG. 6, the center device 600 includes two sets of a switching unit 900 and an IF unit 800. The center device 600 selects one of the transmission paths 400-1 and 400-2 by the switching section 900-1 that has received the optical signal, and transmits the optical signal from the transmission path to the user interface via the IF section 800-3. 100-2. The center device 600 may include N (N: positive integer) pairs of switching units 900 and IF units 800, but N = 2 is described here. The IF unit 800 controls switching of the switching unit 900.

  In FIG. 7, the switching unit 900 includes an optical switch unit 901 and an optical switch control unit 902. Here, the optical switch unit 902 always selects one of the transmission lines 400-M (M: positive odd number) and 400-M + 1. The selection state of the optical switch unit 902 is determined by the switch control unit 902. When there is no instruction from the optical switch control unit 902, the transmission path selection state is maintained.

  In FIG. 8, an IF unit 800 includes an optical-electric conversion unit 801, an electrical-optical conversion unit 802, signal regeneration units 803 and 804, an optical power detection unit 805, an optical reception determination unit 806, a pulse detection unit 807, and a pulse control unit. 808, a laser diode driving unit 809, and an optical multiplexing / demultiplexing unit 810. The optical multiplexing / demultiplexing unit 810 converts the received optical signal into an electrical signal by the optical / electrical conversion unit 801, reproduces it by the signal reproduction unit 803, converts it to an optical signal by the electrical / optical conversion unit 802, and sends it out. . The optical signal received by the optical-electric conversion unit 801 converts the received optical signal into an electrical signal, reproduces the signal by the signal reproduction unit 804, converts the optical signal into an optical signal by the electrical-optical conversion unit 801, and outputs an optical multiplexing / demultiplexing unit. Via 810.

The optical power detection unit 805 monitors the output of the photoelectric conversion unit 801 and transmits the output to the pulse detection unit 807 and the optical reception determination unit 806. When the pulse detection unit 807 detects that the received optical signal is a pulsed optical signal, the pulse detection unit 807 controls the laser diode driving unit 809 via the pulse control unit 808 and sets the transmission signal in the reverse direction as a normal signal. On the other hand, when the optical reception determining unit 806 detects that the received optical signal is in a disconnected state, the optical reception determining unit 806 controls the laser diode driving unit 809 via the pulse control unit 808 and uses the transmission signal in the reverse direction as a pulse signal. The description will be continued assuming that the transmission line fiber 400-1 shown in FIG. When the transmission line fiber 400-1 is broken, the optical power is not detected by the optical power detection unit 805 of the IF unit 800-3 of the center apparatus 600, and the optical reception determination unit 806 that receives a signal from the optical power detection unit 805 is received. The optical signal reception interruption is determined at.

  When the optical reception determination unit 806 determines that the reception is interrupted, it transmits a signal generation stop to the signal reproduction unit 803 and sends a signal to the pulse control unit 808, and the IF unit 800-3 transitions to the intermittent pulse output mode. Upon receiving the signal for stopping signal generation, the signal reproducing unit 803 stops signal reproduction. Upon receiving the pulse output mode transition signal, the pulse control unit 808 holds the signal output to the laser diode driving unit 809 at the Low level immediately after the mode transition, after a certain time tL, and at the High level for a certain time tH, and thereafter constant. A pulse signal is output at a cycle.

  9, (a) shows the optical signal reception level, (b) shows the control of the transmitted light, (c) shows the output of the pulse control unit, and (d) shows the optical output. In FIG. 9A, when the optical signal reception level becomes Low, the control of the transmission light is changed to intermittent pulses after tp. Further, after changing to the intermittent pulse, a pulse width tH is output after tL. Note that the output optical pulse has a width (tH−td) because of a rise delay of td.

  On the other hand, for the IF unit 800-1 of the local device 300, the received optical power is detected by the optical power detection unit 805. While the received pulse is low and the received signal is not detected, the optical reception determining unit 806 determines that the reception is interrupted after detection protection, and the IF unit 800-1 also shifts to the intermittent pulse output mode. As a result, in the pulse control unit 808 and the laser diode driving unit 809 of the IF unit 800-1, a low level output is obtained immediately after the transition to the pulse output mode, as in the IF unit 800-3. Since the Low level output time is constant, as shown in FIG. 9, while the reception pulse is Low, the transmission pulse is also Low.

  The IF unit 800-2 of the local device 300 has detected a reception interruption before the transmission line fiber 400-1 breaks because the signal from the IF unit 800-3 is not transmitted by the switching device 900-1. The light output is a pulse output.

  At the same time, if the optical signal determination unit 806 in the IF unit 800-3 determines that reception is interrupted when the transmission line 400-1 is broken, the optical signal determination unit 806 sends a switching signal to the optical switch control unit 902. When receiving the switching signal, the optical switch 902 sends the switching signal to the optical switch unit 901, and switches the optical switch 901 selection state from the transmission line 400-1 to the transmission line 400-2.

  10, (a) is a control of the transmission light of IF section 800-1, (b) is an optical signal reception level of IF section 800-1, and (c) is a control of transmission light of IF section 800-2. (D) is the optical signal reception level of the IF unit 800-2, (e) is the control of the transmission light of the IF unit 800-3, (f) is the optical signal reception level of the IF unit 800-3, and (g) is This is a selection state of the switching unit 900-1.

  When the IF unit 800-3 in FIG. 10 (f) detects a decrease in the optical signal reception level due to the transmission line breakage, the switching unit 900-1 in FIG. 10 (g) changes the selected state from the transmission line 400-1 to the transmission line. Switch to 400-2. At the same time, the IF unit 800-3 in FIG. 10E changes the control of the transmission light to the pulse output mode. Similarly, when the IF unit 800-1 in FIG. 10B detects a decrease in the optical signal reception level, the IF unit 800-1 in FIG. 10A changes the transmission light control to the pulse output mode.

  At this time, since the IF unit 800-2 in FIG. 10C is in the pulse output mode, the IF unit 800-3 in FIG. 10F that has received this pulse is the IF unit 800- in FIG. 3 starts normal optical output transmission from the pulse output mode. The IF unit 800-2 in FIG. 10D detects recovery of the optical signal reception level, and the IF unit 800-2 in FIG. 10C starts normal optical output transmission from the pulse output mode.

  The optical switch switching control unit 902 always maintains the switching state for the switching stop period tHold immediately after switching. If a pulse signal during safety control is received during the switching stop period, the switching stop period is extended until the optical reception signal of the IF unit 800-3 is recovered.

  If the transmission path is normal, IF unit 800-2 receives pulse signal 151 from IF unit 800-3 and IF unit 800-3 receives pulse signal 152 from IF unit 800-2 within the switching stop period. Receive. Note that the switching stop period tHold needs to be at least longer than (tL + tH).

  Due to the reception of the pulse signal of IF section 800-2, the transmission pulse of IF section 800-2 is received by IF section 800-3, and IF section 800-3 performs signal regeneration to signal regeneration section 803 by optical reception determination section 806. In addition to notifying the restart, the pulse output mode is stopped and the laser is driven to allow normal light output.

  Similarly, the transmission pulse of IF section 800-3 is received by IF section 800-2, and IF section 800-2 notifies signal regeneration section 803 of signal regeneration restart in optical reception determination section 806, and in pulse output mode. And the laser is driven to allow normal light output. Accordingly, IF units 800-2 and 800-3 are both in the state of detecting the reception of the optical signal, and the laser diode driving unit 809 operates to transmit the signal by leaving the pulse output mode and maintaining the optical output. Recovers normally.

  In the above embodiment, the signal is recovered by detecting one pulse. However, in the case of a safety control method in which the signal is recovered by detecting a plurality of pulses, a switching stop period by pulse reception is provided by receiving one pulse. Due to this switching stop period due to pulse reception, the IF units 800-2 and 800-3 can perform normal pulse reception after switching, and communication is restored to normal. An operation time chart in the case of signal restoration by multiple pulse detection is shown in FIG.

  11A is a control of the transmission light of the IF unit 800-1, FIG. 11B is an optical signal reception level of the IF unit 800-1, and FIG. 11C is a control of the transmission light of the IF unit 800-2. (D) is the optical signal reception level of the IF unit 800-2, (e) is the control of the transmission light of the IF unit 800-3, (f) is the optical signal reception level of the IF unit 800-3, and (g) is This is a selection state of the switching unit 900-1.

  In FIG. 10, when the IF unit 800-3 in FIG. 10F detects signal recovery, the IF unit 800-3 starts normal optical output transmission from the pulse output mode. On the other hand, in FIG. 11, when the IF unit 800-3 in FIG. 11 (f) detects signal recovery, a switching stop period due to pulse reception is started. Within this period, when the IF unit 800-3 in FIG. 11F detects signal recovery again, the IF unit 800-3 starts normal optical output transmission from the pulse output mode.

  Therefore, this modified embodiment can reliably detect signal recovery without being affected by noise or the like.

It is a block diagram of an optical transmission system optical IF unit. It is a block diagram and a timing chart of a single fiber bidirectional optical transmission system. It is a block diagram of an optical transmission system. It is a block diagram of a local device. It is a block diagram of a wavelength multiplexing / demultiplexing unit. It is a block diagram of a center apparatus. It is a block diagram of an optical switch part. It is a block diagram of IF section. It is a timing chart of IF section. It is a timing chart explaining the process from transmission line disconnection to signal restoration by switching. It is a timing chart explaining the process from the transmission line disconnection to the signal restoration by switching when the signal restoration condition is a plurality of pulses.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical receiving part, 11 ... Optical-electricity conversion part, 12 ... Signal detection part, 13 ... Pulse detection part, 2 ... Optical transmission part, 21 ... Electric-light conversion part, 22 ... Pulse generation part, 50 ... IF part 400 ... Transmission path optical fiber, 100 ... User side device, 151 ... Transmission pulse signal, 152 ... Reception pulse signal, 200 ... Wavelength multiplexing / demultiplexing unit, 201 ... Optical coupler, 300 ... Local device, 400 ... Optical transmission path, 600 ... Center device, 800 ... IF unit, 900 ... Switching unit, 801 ... Optical-electrical conversion unit, 802 ... Electrical-optical conversion unit, 803,804 ... Signal regeneration unit, 805 ... Optical power detection unit, 806 ... Optical reception Judgment unit, 807 ... pulse detection unit, 808 ... pulse control unit, 809 ... laser diode drive unit, 810 ... optical multiplexing / demultiplexing unit, 901 ... optical switch unit, 902 ... optical switch control unit, 1000 ... unmanned station (local ), 2000 ... the center station.

Claims (9)

A switching unit connected to the local device via the first transmission line and the second transmission line, and connected to the first transmission line and the second transmission line, and the switching unit selected by the switching unit In a center device including an interface unit that performs bidirectional communication with the local device via one transmission path,
When the interface unit detects a failure in the first transmission line, the interface unit controls the switching unit to switch to the second transmission line, and when a failure is detected in the second transmission line, the interface unit is predetermined. A center apparatus characterized in that the connection with the second transmission line is continued during a period. The center device according to claim 1,
The center device, when detecting a signal from the second transmission path in the predetermined period, ends the switching from the first transmission path to the second transmission path. The center device according to claim 1,
A center device characterized in that, when a pulse signal from the second transmission path is detected during the predetermined period, the connection with the second transmission path is continued during a second predetermined period. A local device including a first interface unit, a second interface unit, and a wavelength multiplexing / demultiplexing unit;
In an optical transmission system comprising: a center unit including a switching unit connected to the first interface unit and the second interface unit; and a third interface unit connected to the switching unit.
When the third interface unit detects a failure in the signal from the first interface unit, the third interface unit controls the switching unit to switch to the signal from the second interface unit, and from the second interface unit When a failure is detected in the signal, a connection with the second interface unit is continued for a predetermined period. The optical transmission system according to claim 4,
When the signal from the second interface unit is detected during the predetermined period, the switching from the first interface unit to the second interface unit is terminated. The optical transmission system according to claim 4,
An optical transmission system characterized in that, when a pulse signal from the second interface unit is detected during the predetermined period, the connection with the second interface unit is continued during a second predetermined period.   A step in which the third interface unit detects a failure in the signal from the first interface unit, a step of controlling the switching unit to switch to a signal from the second interface unit, and a signal from the second interface unit And a step of continuing the connection with the second interface unit during a predetermined period when a fault is detected in the system. The system switching method according to claim 7, wherein
The method further includes detecting a signal from the second interface unit during the predetermined period and ending switching from the first interface unit to the second interface unit. System switching method. The system switching method according to claim 7, wherein
A step of continuing connection with the second interface unit during a second predetermined period when a pulse signal from the second interface unit is detected during the predetermined period. System switching method.

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