Optical transmission device, optical transmission system, and optical transmission method

Abstract

In order to provide a technology capable of realizing an APR control function of an optical transmission system with a simple configuration, this optical transmission device comprises: an optical amplifier that amplifies first signal light; a monitoring light generation unit that generates first monitoring light; an optical multiplexer that couples an output of the optical amplifier and an output of the monitoring light generation unit to output the resultant to a first optical transmission line; an optical demultiplexer for separating light that includes second signal light and second monitoring light and that is inputted through a second optical transmission line, into the second signal light and the second monitoring light; and a control unit that controls the optical amplifier and the monitoring light generation unit on the basis of the reception state of the second signal light and the duration time of emission and reduction of the second monitoring light.

Description

[Technical field]

[0001] The present invention relates to an optical transmission device, an optical transmission method, and a recording medium. In particular, the present invention relates to an APR (Automatic Power Reduction) control that automatically reduces the output of an optical amplifier included in the optical transmission device when a fault occurs in an optical transmission line connected to the optical transmission device. [Background technology]

[0002] In the event that an optical fiber in an optical transmission path connecting two optical transmission devices performing bidirectional communication is broken, some optical transmission devices are equipped with an APR control function to ensure the safety of maintenance workers at the broken optical fiber. APR control automatically reduces the output power of the signal light sent to the broken optical fiber, or stops the output of the signal light. In a typical terrestrial optical transmission system, a supervisory signal frame such as 1.544 Mb / s (megabits per second) is encoded to transmit information for APR control between optical transmission devices. The supervisory signal is also called an OSC (Optical Supervisory Channel) signal. In a typical terrestrial optical transmission system, the supervisory signal contains a lot of information used for purposes other than APR control. For this reason, the optical transmission device that receives the supervisory signal decodes the supervisory signal frame, and performs APR control if the information required for APR control is decoded from the supervisory signal.

[0003] Regarding the present invention, Patent Documents 1 and 2 describe a general APR control in which, when a loss of a main signal or a supervisory signal is detected, the loss is notified to an opposing device and the output of an optical amplifier is reduced. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2000-332695 A [Patent Document 2] JP 2002-077056 A Summary of the Invention [Problem to be solved by the invention]

[0005] A supervisory control circuit in a typical terrestrial optical transmission system includes an encoding circuit and a decoding circuit to transmit many types of supervisory control signals. Furthermore, signals for APR control are transmitted together with other supervisory control signals. For this reason, if a supervisory control circuit used in a typical terrestrial optical transmission system is applied to an optical transmission system that requires only signals for APR control as supervisory control signals, the function of the supervisory control circuit becomes unnecessarily complicated, which is a factor in increasing costs.

[0006] (Objective of the Invention) An object of the present invention is to provide a technique for realizing an APR control function in an optical transmission system with a simple configuration. [Means for solving the problem]

[0007] The optical transmission device of the present invention comprises: an optical amplifier for amplifying a first signal light; A supervisory light generating means for generating a first supervisory light; an optical multiplexing means for combining an output of the optical amplifying means and an output of the supervisory light generating means and outputting the combined output to a first optical transmission line; an optical demultiplexing means for demultiplexing light inputted from a second optical transmission line, the light including a second optical signal and a second optical supervisory signal, into the second optical signal and the second optical supervisory signal; a control means for controlling the optical amplifier means and the supervisory light generating means based on a receiving state of the second signal light and a duration of emission and dimming of the second supervisory light; Equipped with.

[0008] The optical transmission method of the present invention comprises the steps of: amplifying the first signal light; generating a first monitor light; combining the amplified first signal light with the first supervisory light and outputting the combined signal light to a first optical transmission line; a second optical signal and a second optical supervisory signal, and a light input from a second optical transmission line is separated into the second optical signal and the second optical supervisory signal; controlling amplification of the first signal light and generation of the first supervisory light based on a receiving state of the second signal light and duration of emission and dimming of the second supervisory light; It is characterized by:

[0009] The recording medium of the present invention comprises: an optical amplifier for amplifying a first signal light; A supervisory light generating means for generating a first supervisory light; an optical multiplexing means for combining an output of the optical amplifying means and an output of the supervisory light generating means and outputting the combined output to a first optical transmission line; an optical demultiplexing means for demultiplexing light inputted from a second optical transmission line, the light including a second optical signal and a second optical supervisory signal, into the second optical signal and the second optical supervisory signal; A computer of an optical transmission device comprising: A recording medium having recorded thereon a program for executing a procedure for controlling the optical amplification means and the supervisory light generating means based on the receiving status of the second signal light and the duration of emission and dimming of the second supervisory light. Effect of the Invention

[0010] The present invention can realize an APR control function in an optical transmission system with a simple configuration. [Brief description of the drawings]

[0011] [Figure 1] 1 is a block diagram showing an example of the configuration of an optical transmission system 1. FIG. [Diagram 2] FIG. 1 illustrates an example of a bidirectional failure in the optical transmission system 1. [Diagram 3] FIG. 2 is a block diagram showing an example of a detailed configuration of optical transmission devices 100 and 200. [Figure 4] 11 is a timing chart illustrating an example of APR control when a failure occurs in both directions. [Diagram 5]11 is a timing chart illustrating an example of APR control when failures in both directions are restored. [Figure 6] FIG. 1 illustrates an example of a unidirectional failure in the optical transmission system 1. [Figure 7] 11 is a timing chart illustrating an example of APR control when a unidirectional failure occurs. [Figure 8] 11 is a timing chart illustrating an example of APR control when a unidirectional failure occurs. [Figure 9] 11 is a timing chart illustrating an example of APR control when a one-way failure is restored. [Figure 10] 11 is a timing chart illustrating an example of APR control when a one-way failure is restored. [Figure 11] 1A to 1C are diagrams illustrating examples of operations in APR control and conditions under which the operations are executed. [Figure 12] 1A and 1B are diagrams illustrating examples of the output form of supervisory light and the operation of an optical switch in such a case. [Figure 13] 11A and 11B are diagrams illustrating examples of conditions for determining whether the received supervisory light is continuous light or pulsed light. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The embodiments of the present invention will be described below with reference to the drawings. The directions of the arrows shown in the drawings are illustrative and are not intended to limit the directions. In each embodiment and drawing, the same reference numerals are used to designate elements that have already been described, and duplicate descriptions will be omitted.

[0013] (First embodiment) 1 is a block diagram showing an example of a configuration of an optical transmission system 1 according to a first embodiment of the present invention. The optical transmission system 1 includes an optical transmission device 100 and an optical transmission device 200. The optical transmission device 100 and the optical transmission device 200 are connected by two optical transmission paths 20 and 30.

[0014] The optical transmission device 100 transmits an optical signal to the optical transmission path 20. The optical transmission device 200 receives the optical signal transmitted by the optical transmission device 100 from the optical transmission path 20. The optical transmission device 200 transmits an optical signal to the optical transmission path 30. The optical transmission device 100 receives the optical signal transmitted by the optical transmission device 200 from the optical transmission path 30. Hereinafter, the direction from the optical transmission device 100 to the optical transmission device 200 may be referred to as "downstream" and the direction from the optical transmission device 200 to the optical transmission device 100 may be referred to as "upstream". In this way, the optical transmission device 100 and the optical transmission device 200 communicate with each other via the optical transmission paths 20 and 30.

[0015] The optical transmission device 100 includes an optical amplifier 111, a light source 112, an optical switch 113, an optical multiplexer 114, an optical demultiplexer 122, a signal light monitor 123, a supervisory light monitor 125, and a control unit 180. The optical transmission device 200 includes an optical amplifier 211, a light source 212, an optical switch 213, an optical multiplexer 214, an optical demultiplexer 222, a signal light monitor 223, a supervisory light monitor 225, and a control unit 280. The signal light monitor 123 and the supervisory light monitor 125 may be included in the control unit 180. The signal light monitor 223 and the supervisory light monitor 225 may be included in the control unit 280.

[0016] The functions of each part of the optical transmission device 100 will be described. The optical amplifier 111 amplifies the signal light (hereinafter referred to as "downstream signal light") transmitted from the optical transmission device 100 to the optical transmission device 200. The downstream signal light is an optical signal including user data. An optical signal in which an optical carrier wave in the 1550 nm band is wavelength-multiplexed may be used as the signal light. The light source 112 is a light source of the supervisory light (hereinafter referred to as "downstream supervisory light") transmitted from the optical transmission device 100 to the optical transmission device 200. A semiconductor laser having a central wavelength of 1490 nm or 1510 nm may be used as the light source 112. The wavelength of the light source 112 does not overlap with the wavelength of the downstream signal light. The light source 112 may be provided outside the optical transmission device 100. The optical switch 113 transmits or blocks the light generated by the light source 112. Instead of the optical switch 113, an optical modulator may be used. The light that has passed through optical switch 113 is input to optical multiplexer 114 as downstream supervisory light. Under the control of control unit 180, optical switch 113 can output the downstream supervisory light as continuous light, or as pulsed light having a predetermined emission time and dimming time. Note that "dimming" refers to a state in which the power of pulsed light is lower than that of "emission." In other words, "dimming" includes a state in which the pulsed light is extinguished. In other words, the downstream supervisory light may be continuous light, or pulsed light whose optical output changes over time.

[0017] The optical multiplexer 114 multiplexes the downstream signal light output from the optical amplifier 111 and the downstream supervisory light output from the optical switch 113, and transmits the multiplexed signal light to the optical transmission line 20. Since the wavelengths of the downstream signal light and the downstream supervisory light are different, a WDM (Wavelength Division Multiplexing) filter can be used as the optical multiplexer 114.

[0018] The optical demultiplexer 122 separates the signal light (hereinafter referred to as "upstream signal light") and the supervisory light (hereinafter referred to as "upstream supervisory light") transmitted by the optical transmission device 200 according to wavelength. Since the wavelengths of the upstream signal light and the upstream supervisory light are different, a WDM filter can be used as the optical demultiplexer 122. The upstream signal light separated by the optical demultiplexer 122 is input to a signal light monitor 123, and the separated supervisory light is input to a supervisory light monitor 125.

[0019] The signal light monitor 123 outputs the receiving state of the upstream signal light in the optical transmission device 100 to the control unit 180. The supervisory light monitor 125 outputs the receiving state of the upstream supervisory light in the optical transmission device 100 to the control unit 180. The signal light monitor 123 and the supervisory light monitor 125 each include a PD (Photo Diode). The signal light monitor 123 outputs the upstream signal light received by the optical transmission device 100 as an optical signal, and outputs an electrical signal having an amplitude proportional to the intensity of the upstream signal light to the control unit 180. The optical transmission device 100 may include an optical amplifier 121 that amplifies the upstream signal light output by the signal light monitor 123. The optical amplifier 121 may amplify the input upstream optical signal and output it to another optical transmission device. However, the optical amplifier 121 is not essential for the optical transmission device 100. The supervisory light monitor 125 also outputs to the control unit 180 an electrical signal whose amplitude is proportional to the intensity of the upstream supervisory light received by the optical transmission device 100 .

[0020] The control unit 180 judges the receiving state of the upstream signal light and the upstream supervisory light based on the amplitude of the electrical signals input from the signal light monitor 123 and the supervisory light monitor 125, and further controls the optical amplifier 111 and the optical switch 113 based on the judgment results.

[0021] Each component of the optical transmission device 100 can be described as follows. That is, the optical amplifier 111 serves as an optical amplifying means for amplifying a first signal light (downstream signal light). The optical switch 113 serves as a supervisory light generating means for generating a first supervisory light (downstream supervisory light). The optical multiplexer 114 serves as an optical multiplexing means for combining the output of the optical amplifier 111 and the output of the optical switch 113 and outputting the combined output to the first optical transmission path (optical transmission path 20).

[0022] The optical splitter 122 also functions as an optical splitting means for splitting the light, which includes the second signal light (upstream signal light) and the second supervisory light (upstream supervisory light) input from the second optical transmission line (optical transmission line 30), into the second signal light and the second supervisory light. The control unit 180 also functions as a control means for controlling the optical amplifying means (optical amplifier 111) and the supervisory light generating means (optical switch 113) based on the receiving state of the second signal light (upstream signal light) and the duration of the emission and dimming of the second supervisory light (upstream supervisory light).

[0023] The optical transmission device 200 has a similar configuration to the optical transmission device 100. That is, the optical amplifier 211 amplifies the signal light (hereinafter referred to as "upstream signal light") transmitted from the optical transmission device 200 to the optical transmission device 100. The upstream signal light is an optical signal including user data. The light source 212 is a light source of the supervisory light (hereinafter referred to as "upstream supervisory light") transmitted from the optical transmission device 200 to the optical transmission device 100. The wavelength of the light source 212 does not overlap with the wavelength of the upstream signal light. The light source 212 may be provided outside the optical transmission device 200. The optical switch 213 transmits or blocks the light generated by the light source 212 for a predetermined period. An optical modulator may be used instead of the optical switch 213. The light transmitted through the optical switch 213 is input to the optical multiplexer 214 as the upstream supervisory light. Under the control of the control unit 280, the optical switch 213 can generate the upstream supervisory light as continuous light or pulsed light.

[0024] The optical multiplexer 214 multiplexes the upstream signal light output from the optical amplifier 211 and the upstream supervisory light output from the optical switch 213, and transmits the multiplexed signal light to the optical transmission line 30. Since the wavelengths of the upstream signal light and the upstream supervisory light are different, a WDM filter can be used as the optical multiplexer 214.

[0025] The optical demultiplexer 222 separates the downstream signal light and downstream supervisory light transmitted by the optical transmission device 100. Since the wavelengths of the downstream signal light and the downstream supervisory light are different, a WDM filter can be used as the optical demultiplexer 222. The downstream signal light separated by the optical demultiplexer 222 is input to a signal light monitor 223, and the separated supervisory light is input to a supervisory light monitor 225.

[0026] The signal light monitor 223 outputs the receiving state of the downstream signal light in the optical transmission device 200 to the control unit 280. The supervisory light monitor 225 outputs the receiving state of the downstream supervisory light in the optical transmission device 200 to the control unit 280. The signal light monitor 223 and the supervisory light monitor 225 each include a PD. The signal light monitor 223 outputs the downstream signal light received by the optical transmission device 200 and outputs an electrical signal having an amplitude proportional to the intensity of the downstream signal light to the control unit 280. The optical transmission device 200 may include an optical amplifier 221 that amplifies the downstream signal light output by the signal light monitor 223. The optical amplifier 221 may amplify the input downstream optical signal and output it to another optical transmission device. However, the optical amplifier 221 is not essential for the optical transmission device 200. The supervisory light monitor 225 outputs the receiving state of the downstream supervisory light received by the optical transmission device 200 to the control unit 280.

[0027] The control unit 280 judges the receiving state of the downstream signal light and downstream supervisory light based on the amplitude of the electrical signals input from the signal light monitor 223 and supervisory light monitor 225, and further controls the optical amplifier 211 and the optical switch 213 based on the judgment result.

[0028] Fig. 2 is a diagram showing an example of bidirectional faults in the optical transmission system 1. With reference to Fig. 2, an example of APR control when faults occur in the optical fibers at both the fault point 21 of the optical transmission line 20 and the fault point 31 of the optical transmission line 30 will be described.

[0029] (1-1) In a normal state before a fault occurs, the control unit 180 of the optical transmission device 100 and the control unit 280 of the optical transmission device 200 control the optical switches 113 and 213, respectively, so that both the downstream supervisory light and the upstream supervisory light are continuous light. Then, in the optical transmission device receiving the supervisory light, if the received supervisory light is continuous light, it determines that the optical transmission line is normal, and if the received supervisory light is input interruption or pulsed light, it determines that a fault has occurred in the optical transmission line. Because the downstream supervisory light does not pass through the optical amplifier 111, it is output to the optical transmission line 20 even if the optical output of the optical amplifier 111 is stopped.

[0030] (1-2) In the optical transmission device 100, when an input interruption of the upstream signal light and the upstream supervisory light is detected due to a fault at the fault point 31, the control unit 180 stops (shuts down) the optical output of the optical amplifier 111 and changes the downstream supervisory light from continuous light to pulsed light. The downstream supervisory light does not pass through the optical amplifier 111 and is therefore output to the optical transmission line 20 even if the optical amplifier 111 is shut down. However, due to the fault at the fault point 21, neither the downstream signal light nor the downstream supervisory light is received by the optical transmission device 200.

[0031] (1-3) Similarly, in the optical transmission device 200, when an input interruption of the downstream signal light and the downstream supervisory light is detected due to a fault at the fault point 21, the control unit 280 shuts down the optical amplifier 211 and changes the upstream supervisory light from continuous light to pulsed light. The upstream supervisory light is output to the optical transmission line 30 even if the optical amplifier 211 is shut down. However, due to the fault in the optical transmission line 30, neither the upstream signal light nor the upstream supervisory light is received by the optical transmission device 100.

[0032] In this way, when a fault occurs in both the optical transmission lines 20 and 30, the APR control is executed by automatically stopping the output of the signal light from the optical transmission devices 100 and 200 at both ends.

[0033] Next, a case where the optical transmission lines 20 and 30 are restored from failure will be described.

[0034] (1-4) Immediately after the failures in the optical transmission lines 20 and 30 are restored, the upstream signal light remains disconnected in the signal light monitor 123 of the optical transmission device 100, while the upstream supervisory light of pulsed light is input to the supervisory light monitor 125. The control unit 180 determines the time from off to on (dimming to emission) and the time from on to off (emission to dimming) of the upstream supervisory light, and changes the downstream supervisory light from pulsed light to continuous light when it confirms the reception of the first pulse of the upstream supervisory light. When it confirms in the supervisory light monitor 225 that the downstream supervisory light has changed from pulsed light to continuous light, the optical transmission device 200 determines that the optical transmission line 30 has returned to normal, and automatically releases the shutdown of the optical amplifier 211. Note that the power of the upstream supervisory light at the output of the optical transmission device 200 when it is emitting light and the power of the upstream supervisory light at the time of dimming may be determined as a power that allows the optical transmission device 100 to distinguish between "emission" and "dimming" when the upstream supervisory light is received. Similarly, the power of the downstream supervisory light at the output of the optical transmission device 100 when it is on and when it is dimmed may be defined as a power at which “on” and “dimming” can be distinguished when the downstream supervisory light is received by the optical transmission device 200.

[0035] (1-5) Similarly, immediately after the failures in the optical transmission lines 20 and 30 are restored, the downstream signal light remains disconnected in the signal light monitor 223 of the optical transmission device 200, while a pulsed downstream supervisory light is input to the supervisory light monitor 225. The control unit 280 determines the time from off to on and from on to off of the downstream supervisory light, and upon confirming the reception of the first pulse of the downstream supervisory light, changes the upstream supervisory light from pulsed light to continuous light. Upon confirming in the supervisory light monitor 125 that the upstream supervisory light has changed from pulsed light to continuous light, the optical transmission device 100 determines that the optical transmission line 20 has returned to normal, and automatically releases the shutdown of the optical amplifier 111.

[0036] In this way, when the failures in the optical transmission lines 20 and 30 are restored, the optical transmission devices 100 and 200 at both ends can automatically release the shutdown of the optical amplifiers 111 and 211.

[0037] That is, by the above procedure, the optical transmission devices 100 and 200 can execute and release APR control with a simple configuration without requiring an encoding circuit or a decoding circuit for the monitor and control signal.

[0038] Second embodiment In the second embodiment, an example of APR control and its recovery when a bidirectional fault occurs will be described in detail. Fig. 3 is a block diagram showing an example of a detailed configuration of the optical transmission devices 100 and 200 described in Fig. 1 and Fig. 2. The control unit 180 of the optical transmission device 100 described in Fig. 1 includes a signal light detection circuit 124, a supervisory light detection circuit 126, a supervisory light determination circuit 127, a supervisory light output determination circuit 131, a signal light output determination circuit 132, an optical switch control circuit 133, and an optical amplifier control circuit 134. These circuits included in the control unit 180 may be realized by electric circuits.

[0039] The signal light detection circuit 124 judges whether or not a signal light is being received from the optical transmission line 30 based on the intensity of the upstream signal light detected by the signal light monitor 123. The supervisory light detection circuit 126 judges whether or not a supervisory light is being received from the optical transmission line 30 based on the intensity of the upstream supervisory light detected by the supervisory light monitor 125. The judgment results of the signal light detection circuit 124 and the supervisory light detection circuit 126 are output to both the supervisory light output judgment circuit 131 and the signal light output judgment circuit 132. In addition, the supervisory light detection circuit 126 acquires the emission time and dimming time of the upstream supervisory light based on the temporal change in the intensity of the upstream supervisory light. The acquired results of the emission time and dimming time of the upstream supervisory light are output to the supervisory light judgment circuit 127.

[0040] The supervisory light determination circuit 127 determines whether the upstream supervisory light is continuous light or pulsed light based on the emission time and dimming time of the upstream supervisory light, and outputs the result to a supervisory light output determination circuit 131 .

[0041] The supervisory light output determination circuit 131 determines whether the supervisory light that the optical transmission device 100 transmits to the optical transmission line 20 is continuous light or pulsed light, based on inputs from the signal light detection circuit 124, the supervisory light detection circuit 126, and the supervisory light determination circuit 127. The signal light output determination circuit 132 determines whether the optical amplifier 111 is to operate normally or to stop (shut down), based on inputs from the signal light detection circuit 124 and the supervisory light detection circuit 126.

[0042] The optical switch control circuit 133 controls the optical switch 113 based on the determination result of the monitor light output determination circuit 131. The optical amplifier control circuit 134 operates or shuts down the optical amplifier 111 based on the determination result of the signal light output determination circuit 132.

[0043] The control unit 280 of the optical transmission device 200 includes a signal light detection circuit 224, a monitor light detection circuit 226, a monitor light determination circuit 227, a monitor light output determination circuit 231, a signal light output determination circuit 232, an optical switch control circuit 233, and an optical amplifier control circuit 234. The configuration of the control unit 280 is similar to that of the control unit 180. In the optical transmission device 200, blocks with the same names as those in the optical transmission device 100 also include corresponding functions in the optical transmission device 200, and therefore detailed description of the control unit 280 will be omitted.

[0044] 3, a fault location in the optical transmission line 20 is indicated by a fault point 21, and a fault location in the optical transmission line 30 is indicated by a fault point 31. The optical signals propagating through the optical transmission lines 20 and 30 are cut off at the fault points 21 and 31, respectively. Below, the APR control when a transmission line fault occurs will be described with reference to a timing chart.

[0045] 4 and 5 are timing charts illustrating an example of APR control of each part in the optical transmission devices 100 and 200 when a bidirectional fault occurs. In these timing charts, the horizontal axis represents time, and the vertical axis represents the state of each part in the optical transmission devices 100 and 200. The vertical dashed lines represent the time of fault occurrence or recovery. In other words, these timing charts show the change over time in the state of each part in the optical transmission devices 100 and 200 after the fault occurs or is recovered from at the fault points 21 and 31.

[0046] Taking the optical transmission device 100 as an example, in Figs. 4 and 5, "[1] Optical input of signal light" indicates the power of the input light to the signal light monitor 123 in Fig. 3. "[2] Input judgment of signal light" indicates the judgment result (normal or off) of the presence or absence of input of signal light in the signal light detection circuit 124. "[3] Optical output of signal light" indicates the power of the output light of the optical amplifier 111. "[4] Optical output of supervisory light" indicates the power of the output light of the optical switch 113. "[5] Optical input of supervisory light" indicates the power of the input light of the supervisory light monitor 125. "[6] Input judgment of supervisory light" indicates the judgment result (normal or off) of the presence or absence of input of supervisory light in the supervisory light detection circuit 126. "[7] Detection of pulsed light" indicates the detection result of pulsed light in the supervisory light judgment circuit 127 (presence or absence of pulsed light). "[8] Output form of supervisory light" indicates the judgment result of whether to output continuous light or a pulsed signal in the supervisory light output judgment circuit 131.

[0047] 7 to 10, items [1] to [8] have the same contents. In addition, the functions of the components of the optical transmission device 100 are also the same as those of the optical transmission device 200, so these timing charts will be used hereinafter to explain the operation of the optical transmission device 200.

[0048] Moreover, Fig. 11 shows an example of the operation in APR control and the conditions under which the operation is executed. Fig. 12 shows an example of the output form of the monitor light and the operation of the optical switches 113 and 213 at that time. Fig. 13 shows an example of the conditions for determining whether the received monitor light is continuous light or pulsed light in the monitor light determination circuit 127. The control units 180 and 280 include a storage unit, and the operations and conditions in Figs. 11 to 13 may be stored as data in the storage unit. The data in the storage unit is referenced by the circuits of each unit of the optical transmission devices 100 and 200.

[0049] (2-1) Operation when a bidirectional fault occurs When there is no fault in the optical transmission paths 20 and 30, the optical amplifiers 111 and 211 operate normally, and both the downstream supervisory light and the upstream supervisory light are continuous light. When a fault occurs at the fault point 31 in this state, the input power of the upstream signal light input to the signal light monitor 123 in the optical transmission device 100 decreases (4-a1 in FIG. 4). As a result, the signal light detection circuit 124 detects the input interruption of the upstream signal light (4-b1). In addition, the input power of the upstream supervisory light input to the supervisory light monitor 125 also decreases (4-a2), so the supervisory light detection circuit 126 detects the input interruption of the upstream supervisory light (4-b2). These detection results are notified to the supervisory light output determination circuit 131 and the signal light output determination circuit 132.

[0050] When the detection of input interruption of the upstream signal light and the upstream supervisory light is notified, the signal light output determination circuit 132 determines to shut down the optical amplifier 111 according to condition 501 in Fig. 11. Then, the signal light output determination circuit 132 outputs an instruction to shut down the optical amplifier 111 to the optical amplifier control circuit 134. The optical amplifier control circuit 134 shuts down the optical amplifier 111 based on this instruction (4-c1). The optical amplifier control circuit 134 may shut down the optical amplifier 111 by stopping the supply of pump light to the optical amplifier 111.

[0051] Moreover, according to condition 503 in Fig. 11, the supervisory light output judgment circuit 131 judges that the downstream supervisory light should be pulsed light. The supervisory light output judgment circuit 131 outputs an instruction to the optical switch control circuit 133 to make the downstream supervisory light pulsed light (4-c2). In response to this instruction, the optical switch control circuit 133 controls the optical switch 113 so that the downstream supervisory light becomes pulsed light (4-c3). The pulsed light is an optical pulse train having a predetermined emission time and dimming time. In this embodiment, the pulsed light is initially dimmed for 10 seconds, and then repeats emission for 3 seconds and dimming for 10 seconds (condition 602 in Fig. 12).

[0052] The pulsed light (downstream supervisory light) output from the optical switch 113 is input to the optical multiplexer 114. Because the downstream supervisory light does not pass through the optical amplifier 111, the downstream supervisory light is sent to the optical transmission line 20 via the optical multiplexer 114 even if the optical amplifier 111 is shut down. However, because the optical transmission line 20 is disconnected due to a fault, the downstream supervisory light does not reach the optical transmission device 200.

[0053] Meanwhile, due to the failure at the failure point 21, the optical transmission device 200 also operates in the same manner as the optical transmission device 100. That is, in the optical transmission device 200, the supervisory light output determination circuit 231 and the signal light output determination circuit 232 are notified that a loss of input of the downstream signal light and a loss of input of the downstream supervisory light have been detected. The signal light output determination circuit 232 outputs an instruction to shut down the optical amplifier 211 to the optical amplifier control circuit 234. The optical amplifier control circuit 234 shuts down the optical amplifier 211 in response to this instruction.

[0054] 12. Moreover, the supervisory light output judgment circuit 231 outputs an instruction to make the downstream supervisory light a pulsed light to the optical switch control circuit 233. In response to this instruction, the optical switch control circuit 233 controls the optical switch 213 so that the upstream supervisory light becomes a pulsed light that satisfies the condition 602 in FIG.

[0055] By the above operation, the optical transmission devices 100 and 200 shut down the optical amplifiers 111 and 211 when a fault occurs in the optical transmission paths 20 and 30. That is, the APR control is executed in the optical transmission system 1.

[0056] (2-2) Operation when both directions are restored The APR control recovery (APR recovery) operation of the optical transmission device 100 after the failures of the optical transmission paths 20 and 30 are recovered will be described. Immediately after the failures of the optical transmission paths 20 and 30 are recovered, the optical amplifiers 111 and 211 are shut down. Therefore, the signal light monitor 123 of the optical transmission device 100 does not detect the upstream signal light. However, the monitor light monitor 125 detects the upstream monitor light as light whose intensity changes in a pulsed manner (5-a1, 5-b1, 5-c1 in FIG. 5). The monitor light determination circuit 127 detects the emission time and the dimming time of the pulsed light received by the monitor light monitor 125, and outputs the detection result to the monitor light output determination circuit 131. The monitor light output determination circuit 131 controls the optical switch 113 based on the input information and the conditions in FIG. 11 and FIG. 12. Specifically, the monitor light determination circuit 127 detects the reception of the first pulse of the pulsed light in a state in which no pulsed light has been received (5-d1). This detection result is notified to the supervisory light output determination circuit 131. When the supervisory light output determination circuit 131 is notified of the reception of the first pulse, it outputs an instruction to change the downstream supervisory light from pulsed light to continuous light to the optical switch control circuit 133 (5-d2) in accordance with condition 504 in Fig. 11. As a result, the downstream supervisory light changes from pulsed light to continuous light (5-d3).

[0057] Next, the APR restoration operation of the optical transmission device 200 will be described. FIG. 5 is also used to describe the optical transmission device 200. Due to the APR restoration operation of the optical transmission device 100 described above, the downstream supervisory light received by the optical transmission device 200 changes from pulsed light to continuous light. As a result, the supervisory light input to the supervisory light monitor 225 of the optical transmission device 200 changes from pulsed light to continuous light (5-e1, 5-f1 in FIG. 5). Since the emission time of the pulsed light is 3 seconds, the supervisory light determination circuit 227 detects that the continuous light has continued for 6 seconds or more. As a result, the condition 701 in FIG. 13 is satisfied, so the supervisory light determination circuit 227 notifies the signal light output determination circuit 232 that the supervisory light has changed from pulsed light to continuous light (5-g1). The signal light output determination circuit 232 outputs an instruction to the optical amplifier control circuit 234 to release the stop of the optical amplifier 211 according to the condition 502 in FIG. 11. As a result, the upstream signal light is transmitted from the optical transmission device 200 to the optical transmission device 100 via the optical transmission line 30 .

[0058] On the other hand, immediately after the failures in the optical transmission paths 20 and 30 are restored, the optical transmission device 200 does not receive the downstream signal light, but starts receiving only the downstream supervisory light, which is a pulsed light. Therefore, like the optical transmission device 100, the optical transmission device 200 changes the upstream supervisory light from pulsed light to continuous light. As a result, the supervisory light input to the supervisory light monitor 125 of the optical transmission device 100 also changes from pulsed light to continuous light. Then, when the optical transmission device 100 detects that the continuous light has continued for six seconds or more, it resumes the stop of the optical amplifier 111 according to condition 502 in FIG. 11.

[0059] By the above operations, in the optical transmission devices 100 and 200, when the failures in the optical transmission paths 20 and 30 are restored, the shutdown of the optical amplifiers 111 and 211 is automatically released. This restores the APR control of the optical transmission system 1, and communication of the optical transmission system 1 is resumed.

[0060] As described above, the optical transmission system 1 of the present embodiment can achieve the APR control function of the optical transmission system with a simple configuration when a failure occurs in both directions.

[0061] (Third embodiment) In the third embodiment, an example of APR control when a unidirectional fault occurs will be described in detail. Fig. 6 is a diagram showing an example of a unidirectional fault in the optical transmission system 1. Fig. 6 shows that a fault occurs at a fault point 21 in the optical transmission line 20, but no fault occurs in the optical transmission line 30. That is, the downstream supervisory light and downstream signal light propagating through the optical transmission line 20 are blocked at the fault point 21, but the upstream supervisory light and upstream signal light propagate through the optical transmission line 30 and reach the optical transmission device 100. APR control in such a unidirectional fault will be described below.

[0062] 7 to 10 are timing charts for explaining an example of APR control of the optical transmission device 100 or 200 when a unidirectional failure occurs. FIG. 7 is a diagram for explaining APR control in the optical transmission device 200 when a unidirectional failure occurs at the failure point 21. FIG. 8 is a diagram for explaining APR control in the optical transmission device 100 when a unidirectional failure occurs at the failure point 21. FIG. 9 is a diagram for explaining APR control in the optical transmission device 200 when a unidirectional failure is restored. FIG. 10 is a diagram for explaining APR control in the optical transmission device 100 when a unidirectional failure is restored. The contents shown in [1] to [8] in FIGS. 7 to 10 correspond to those in FIGS. 4 and 5.

[0063] (3-1) Operation when a unidirectional fault occurs When a fault occurs at the fault point 21, the power of the downstream signal light in the optical transmission device 200 decreases (7-a1 in FIG. 7), and the power of the downstream supervisory light also decreases (7-a2). Therefore, the supervisory light detection circuit 226 and the signal light detection circuit 224 detect the input interruption of the downstream signal light and the input interruption of the downstream supervisory light, respectively (7-b1, 7-b2). These detection results are notified to the supervisory light output determination circuit 231 and the signal light output determination circuit 232.

[0064] When the detection of input interruption of the downstream signal light and the downstream supervisory light is notified, the signal light output judgment circuit 232 judges to shut down the optical amplifier 211 according to the condition 501 in Fig. 11. Moreover, the supervisory light output judgment circuit 231 judges to make the upstream supervisory light a pulsed light according to the condition 503 in Fig. 11. In this embodiment as well, the pulsed light is initially dimmed for 10 seconds, and then the light emission for 3 seconds and the dimming for 10 seconds are repeated. The operations and conditions in Figs. 11 to 13 are set in advance as data in a storage unit provided in the control unit 280.

[0065] The signal light output determination circuit 232 outputs an instruction to shut down the optical amplifier 211 to the optical amplifier control circuit 234. In response to this instruction, the optical amplifier control circuit 234 shuts down the optical amplifier 211 (7-c1).

[0066] Furthermore, the supervisory light output judgment circuit 231 outputs an instruction to the optical switch control circuit 233 to make the downstream supervisory light a pulsed light (7-c2). In response to this instruction, the optical switch control circuit 233 controls the optical switch 213 so that the upstream supervisory light becomes a pulsed light (7-c3).

[0067] The pulsed light (upstream supervisory light) output from the optical switch 213 is input to the optical multiplexer 214. Because the upstream supervisory light does not pass through the optical amplifier 211, the upstream supervisory light is sent to the optical transmission line 30 via the optical multiplexer 214 even if the optical amplifier 211 is stopped. Because no fault has occurred in the optical transmission line 30, the optical transmission device 100 does not receive the upstream signal light, but receives the upstream supervisory light, which is a pulsed light.

[0068] 8, the power of the upstream signal light drops in the optical transmission device 100 (8-a1 in FIG. 8), and the upstream supervisory light, which is a pulsed light, is received (8-a2). Therefore, the signal light detection circuit 124 detects the input interruption of the upstream supervisory light (8-b1). These detection results are notified to the supervisory light output determination circuit 231 and the signal light output determination circuit 232.

[0069] While the pulsed light is being attenuated, the power of the upstream supervisory light is reduced, and it is determined that the supervisory light is interrupted (8-b2). Therefore, when the signal light output judgment circuit 132 and the optical amplifier control circuit 134 are notified of the detection of the interruption of the input of the upstream signal light and the upstream supervisory light, they shut down the optical amplifier 111 (8-c1) in accordance with condition 501 in Fig. 11. In addition, the supervisory light output judgment circuit 131 and the optical switch control circuit 133 set the downstream supervisory light to pulsed light in accordance with condition 503 in Fig. 11 (8-c2).

[0070] On the other hand, since the optical transmission line 30 is normal, the first pulse of the upstream supervisory light arrives from the optical transmission device 200 (8-d1). If the upstream supervisory light is pulsed light, the emission time of the supervisory light is three seconds (8-e1 to 8-f1), and therefore the supervisory light determination circuit 127 determines that the upstream supervisory light is pulsed light (8-g1) in accordance with the condition 702 in Fig. 13. Then, in accordance with the condition 504 in Fig. 11, the downstream supervisory light transmitted by the optical transmission device 100 is changed from pulsed light to continuous light (8-g2 to 8-g3).

[0071] Note that the input of the upstream supervisory light is temporarily cut off due to the dimming of the first pulse of the upstream supervisory light (8-f1). However, the determination that the pulsed light has been received at 8-g1 in FIG. 8 is maintained due to condition 702 in FIG. 13. Therefore, condition 503 in FIG. 11 is not applied, and the determination that the downstream supervisory light is continuous light is maintained. Furthermore, when the second pulse of the pulsed light is received (8-h1), the state in which the supervisory light is normal again continues for three seconds (8-i1 to 8-j1). However, because this pulse is the second in a row, it does not meet condition 504 in FIG. 11.

[0072] By the above operation, the optical transmission devices 100 and 200 shut down the optical amplifiers 111 and 211 even if a fault occurs in only one of the optical transmission paths 20 and 30. That is, the APR control is executed in the optical transmission system 1.

[0073] (3-2) Operation when recovering from one-way failure A procedure for restoring APR control due to a one-way fault (APR restoration procedure) will be described. First, an APR restoration procedure of the optical transmission device 200 will be described. As described above, after the fault occurs at the fault point 21, the downstream supervisory light becomes continuous light (8-g3 in FIG. 8). Therefore, when the fault at the fault point 21 is restored, the supervisory light monitor 225 of the optical transmission device 200 receives the downstream supervisory light, which is continuous light (9-a1 in FIG. 9). Then, the supervisory light detection circuit 226 determines that the supervisory light is normally received (9-b1). When the continuous light is received for six seconds, the shutdown of the optical amplifier 211 is released (8-c1) and the upstream supervisory light is changed from pulsed light to continuous light (9-c2, 9-c3) due to the condition 502 in FIG. 11. As described below, this releases the shutdown of the optical amplifier 111 of the optical transmission device 100, so that the downstream signal light is received by the signal light monitor 223 (9-d1) and it is determined that the downstream signal light has been received normally (9-e1).

[0074] Next, the APR recovery operation of the optical transmission device 100 will be described with reference to Fig. 10. Immediately after the failure at the failure point 21 is recovered, the optical amplifier 211 of the optical transmission device 200 is shut down, so that the upstream signal light is determined to be input interrupted. Meanwhile, pulse light is being received as the upstream supervisory light (10-a1 in Fig. 10). Since this state does not satisfy any of the conditions 501-504 in Fig. 11, the optical transmission device 100 maintains the current state.

[0075] After that, due to the APR recovery operation of the optical transmission device 200 described in Fig. 9, the upstream signal light is received from the optical transmission device 200 (10-b1), and the upstream signal light is determined to be normal (10-c1). As described above, the upstream supervisory light is changed to continuous light in the optical transmission device 200 (9-c3 in Fig. 9). As a result, the upstream supervisory light received by the optical transmission device 100 changes from pulsed light to continuous light (10-b2 in Fig. 10), and therefore normal reception of the upstream supervisory light continues for six seconds or more (after 10-c2). As a result, due to the condition 701 in Fig. 13 and the condition 502 in Fig. 11, it is determined that the upstream supervisory light is not pulsed light (10-d2), and the shutdown of the optical amplifier 111 is released (10-d1).

[0076] By the above operation, in the optical transmission devices 100 and 200, even if a fault that occurred in only one of the optical transmission paths 20 and 30 is restored, the shutdown of the optical amplifiers 111 and 211 is automatically released. This restores the APR control of the optical transmission system 1, and communication between the optical transmission device 100 and the optical transmission device 200 is resumed.

[0077] As described above, the optical transmission system 1 of the present embodiment can achieve the APR control function of the optical transmission system with a simple configuration when a one-way failure occurs.

[0078] Although the present invention has been described above with reference to the embodiment, the present invention is not limited to the above embodiment. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0079] In each embodiment, the control units 180 and 280 may include a central processing unit (CPU). Some or all of the functions of the optical transmission devices 100 and 200 may be realized by the CPUs included in the devices executing programs. The programs may be recorded on a tangible and non-transitory recording medium. The recording medium is, for example, a non-volatile semiconductor memory, an optical disk, or a magnetic disk.

[0080] Furthermore, the configurations described in the respective embodiments are not necessarily mutually exclusive. The actions and effects of the present invention may be achieved by a configuration that combines all or part of the above-described embodiments. [Explanation of symbols]

[0081] 1. Optical transmission system 20, 30 Optical transmission line 21, 31 Failure points 100, 200 Optical transmission equipment 111, 121, 211, 221 Optical amplifiers 112, 212 light source 113, 213 Optical switch 114, 214 Optical multiplexer 122, 222 optical demultiplexer 123, 223 Signal Light Monitor 124, 224 Signal light detection circuit 125, 225 Surveillance light monitor 126, 226 Monitor light detection circuit 127, 227 Monitoring light judgment circuit 131, 231 Monitoring light output judgment circuit 132, 232 Signal light output determination circuit 133, 233 Optical switch control circuit 134, 234 Optical amplifier control circuit 180, 280 Control section

Claims

1. An optical amplifier for amplifying a first signal light; A supervisory light generating unit that generates a first supervisory light; an optical multiplexing means for combining an output of the optical amplifying means and an output of the supervisory light generating means and outputting the combined output to a first optical transmission line; an optical demultiplexing means for demultiplexing light inputted from a second optical transmission line, the light including a second signal light and a second supervisory light, into the second signal light and the second supervisory light; a control means for controlling the optical amplifier means and the supervisory light generating means based on a receiving state of the second signal light and a duration of emission and dimming of the second supervisory light, The monitor light generating means a light modulation means for generating continuous light or pulsed light whose optical output varies with time as the first monitor light; the control means includes a first monitoring means for determining whether or not the second signal light has been received, and a second monitoring means for acquiring whether or not the second monitor light has been received and a duration of emission and dimming of the second monitor light, The control means, based on the determination result of the first monitoring means and the acquired result of the second monitoring means, Activating or deactivating the optical amplifying means; Controlling the optical modulation means to generate the first monitor light as the continuous light or the pulsed light; The control means The optical amplifying means is stopped, and the first monitor light is the pulsed light, and When the second supervisory light is received for a period longer than a predetermined period, operating the optical amplifying means and changing the first supervisory light into the continuous light; Optical transmission equipment.

2. The control means Neither the second signal light nor the second supervisory light is received, and When the first supervisory light is the continuous light, the first supervisory light is changed to the pulsed light.

2. An optical transmission device according to claim 1.

3. An optical amplifier for amplifying a first signal light; A supervisory light generating unit that generates a first supervisory light; an optical multiplexing means for combining an output of the optical amplifying means and an output of the supervisory light generating means and outputting the combined output to a first optical transmission line; an optical demultiplexing means for demultiplexing light inputted from a second optical transmission line, the light including a second signal light and a second supervisory light, into the second signal light and the second supervisory light; a control means for controlling the optical amplifier means and the supervisory light generating means based on a receiving state of the second signal light and a duration of emission and dimming of the second supervisory light, The monitor light generating means a light modulation means for generating continuous light or pulsed light whose optical output varies with time as the first monitor light; the control means includes a first monitoring means for determining whether or not the second signal light has been received, and a second monitoring means for acquiring whether or not the second monitor light has been received and a duration of emission and dimming of the second monitor light, The control means, based on the determination result of the first monitoring means and the acquired result of the second monitoring means, Activating or deactivating the optical amplifying means; Controlling the optical modulation means to generate the first monitor light as the continuous light or the pulsed light; Neither the second signal light nor the second supervisory light is received, and When the first supervisory light is the continuous light, the first supervisory light is changed to the pulsed light. Optical transmission equipment.

4. the control means sets the first monitor light to the continuous light when the second monitor means detects a first pulse of the second monitor light based on a duration of emission and dimming of the second monitor light.

4. An optical transmission device according to claim 1.

5. An optical amplifier for amplifying a first signal light; A supervisory light generating unit that generates a first supervisory light; an optical multiplexing means for combining an output of the optical amplifying means and an output of the supervisory light generating means and outputting the combined output to a first optical transmission line; an optical demultiplexing means for demultiplexing light inputted from a second optical transmission line, the light including a second signal light and a second supervisory light, into the second signal light and the second supervisory light; a control means for controlling the optical amplifier means and the supervisory light generating means based on a receiving state of the second signal light and a duration of emission and dimming of the second supervisory light, The monitor light generating means a light modulation means for generating continuous light or pulsed light whose optical output varies with time as the first monitor light; the control means includes a first monitoring means for determining whether or not the second signal light has been received, and a second monitoring means for acquiring whether or not the second monitor light has been received and a duration of emission and dimming of the second monitor light, The control means, based on the determination result of the first monitoring means and the acquired result of the second monitoring means, Activating or deactivating the optical amplifying means; Controlling the optical modulation means to generate the first monitor light as the continuous light or the pulsed light; when the second monitoring means detects a first pulse of the second monitor light based on a duration of emission and dimming of the second monitor light, the first monitor light is set as the continuous light. Optical transmission equipment.

6. An optical transmission system in which a first optical transmission device and a second optical transmission device are communicatively connected via the first optical transmission path and the second optical transmission path, 6. An optical transmission system, wherein the first and second optical transmission devices are both optical transmission devices according to claim 1.

7. amplifying the first signal light by an optical amplifier; generating a first monitor light; combining the amplified first signal light and the first supervisory light and outputting the combined signal light to a first optical transmission line; a second optical supervisory light source that receives a second optical signal and a second optical supervisory light from a second optical transmission line and separates the second optical signal and the second optical supervisory light; an optical transmission method for controlling amplification of the first signal light and generation of the first supervisory light based on a receiving state of the second signal light and duration of emission and dimming of the second supervisory light, the first monitor light is a continuous light or a pulsed light whose optical output varies with time, determining whether the second signal light is received by a first monitoring means; acquiring by a second monitoring means whether the second monitor light is received and the duration of the emission and dimming of the second monitor light; Based on the determination result of the first monitoring means and the acquisition result of the second monitoring means, Executing or stopping the amplification of the first signal light in the optical amplifying means; generating the first monitor light as the continuous light or the pulsed light; when the optical amplifying means is stopped, the first supervisory light is the pulsed light, and the second supervisory light is received for more than a predetermined time, the optical amplifying means is operated and the first supervisory light is changed to the continuous light; Optical transmission method.

8. amplifying the first signal light by an optical amplifier; generating a first monitor light; combining the amplified first signal light and the first supervisory light and outputting the combined signal light to a first optical transmission line; a second optical supervisory light source that receives a second optical signal and a second optical supervisory light from a second optical transmission line and separates the second optical signal and the second optical supervisory light; an optical transmission method for controlling amplification of the first signal light and generation of the first supervisory light based on a receiving state of the second signal light and duration of emission and dimming of the second supervisory light, the first monitor light is a continuous light or a pulsed light whose optical output changes over time, determining whether the second signal light is received by a first monitoring means; acquiring by a second monitoring means whether the second monitor light is received and the duration of the emission and dimming of the second monitor light; Based on the determination result of the first monitoring means and the acquisition result of the second monitoring means, Executing or stopping the amplification of the first signal light in the optical amplifying means; generating the first monitor light as the continuous light or the pulsed light; changing the first supervisory light to the pulsed light when neither the second signal light nor the second supervisory light is received and the first supervisory light is the continuous light; Optical transmission method.

9. amplifying the first signal light by an optical amplifier; generating a first monitor light; combining the amplified first signal light and the first supervisory light and outputting the combined signal light to a first optical transmission line; a second optical supervisory light source that receives a second optical signal and a second optical supervisory light from a second optical transmission line and separates the second optical signal and the second optical supervisory light; an optical transmission method for controlling amplification of the first signal light and generation of the first supervisory light based on a receiving state of the second signal light and duration of emission and dimming of the second supervisory light, the first monitor light is a continuous light or a pulsed light whose optical output changes over time, determining whether the second signal light is received by a first monitoring means; acquiring by a second monitoring means whether the second monitor light is received and the duration of the emission and dimming of the second monitor light; Based on the determination result of the first monitoring means and the acquisition result of the second monitoring means, Executing or stopping the amplification of the first signal light; generating the first monitor light as the continuous light or the pulsed light; when the second monitoring means detects a first pulse of the second monitor light based on a duration of emission and dimming of the second monitor light, the first monitor light is set as the continuous light. Optical transmission method.

Images