JP5887698B2 - Optical coupling / branching device and optical coupling / branching method - Google Patents

Description

  The present invention relates to an optical combining / branching device and an optical combining / branching method, and more particularly to a failure handling technique in an optical combining / branching device.

  FIG. 1 is a diagram illustrating an example of a configuration of an optical combining / branching device according to a conventional technique. 1 is used for a submarine optical cable system and is connected between an optical repeater 31 and an optical repeater 32. The optical multiplexer / demultiplexer 50 branches (drops) a part of the wavelength multiplexed optical signal of the wavelength multiplexed optical signal communication input from the repeater 31 to the add / drop station 30 and wavelength multiplexed light from the add / drop station 30. The signal is inserted (added) into the wavelength division multiplexing optical signal communication in the main route X connecting the repeater 31 and the repeater 32.

  The optical multiplexer / demultiplexer 50 shown in FIG. 1 includes an optical demultiplexer 51, an optical filter 52, and an optical multiplexer 53. The optical demultiplexer 51 branches the intensity of the wavelength multiplexed optical signal 300 (wavelength band: Band A + Band B1) input from the submarine cable 41 to the main route X side and the drop route Y side. The optical filter 52 extracts only a signal in the wavelength band “Band A”, which is a communication signal transmitted to the main route X, from the wavelength multiplexed optical signal 300 (Band A + Band B1), and outputs it as a wavelength multiplexed optical signal 301. The optical multiplexer 53 includes a transmission signal (wavelength multiplexed optical signal 301) output from the optical filter 52 and a wavelength multiplexed optical signal 303 (wavelength band: Band B2) output from the add / drop station 30 via the submarine cable 44. ) And output to the submarine cable 42 as a wavelength multiplexed optical signal 400 (wavelength band: Band A + Band B2).

  The wavelength division multiplexed optical signal 300 branched from the optical coupling / branching device 50 is input to the optical filter 45 via the submarine cable 43. The optical filter 45 extracts only the signal of the wavelength band “Band B1” from the input wavelength multiplexed optical signal 300 and outputs it to the add / drop station 30 as the wavelength multiplexed optical signal 302 (Band B1). On the other hand, the add / drop station 30 inserts a wavelength multiplexed optical signal (wavelength band: Band B2) into the optical multiplexer / demultiplexer 50 via the submarine cable 44.

  With the configuration as described above, the optical multiplexer / demultiplexer 50 branches (drops) the wavelength multiplexed optical signal 302 (Band B1) from the main route X out of the input wavelength multiplexed optical signal 300 (Band A + Band B1). The wavelength multiplexed optical signal 303 (Band B2) from the add / drop station 30 is inserted (added) into the main route X and output as a wavelength multiplexed optical signal 400 (Band A + Band B2).

  However, in the system shown in FIG. 1, when the submarine cable 44 is cut and the wavelength multiplexed optical signal 303 (Band B2) from the add / drop station 30 is not inserted into the optical add / drop device 50, it is transmitted to the submarine cable 42. This reduces the number of wavelengths of signals to be transmitted (bandwidth decreases). In this case, since the signal light of each channel in the wavelength multiplexed optical signal 301 (Band A) is excessively amplified by the optical repeater 32, the signal quality in the transmission path after the optical repeater 32 deteriorates.

  In order to solve such a problem, for example, in JP 2006-180417 A, a signal branched from the main route is inserted into the main route again in accordance with the light intensity of the signal inserted in the optical multiplexing and branching device. An optical add / drop device is described that maintains the strength of signals input and output via a main route (see Patent Document 1).

  FIG. 2 is a diagram illustrating a configuration of the optical coupling / decoupling device described in Patent Document 1. Referring to FIG. 2, an optical add / drop device 60 described in Patent Document 1 includes an optical branch switch 61 that branches one signal (wavelength λ1) of a wavelength multiplexed optical signal, and a signal ( And an optical insertion switch 62 for inserting the wavelength λ1 ′) into the wavelength-multiplexed optical signal. The add / drop device 60 further includes an optical coupler 63, an optical switch 64, an optical amplifier 65, a switch control circuit 66, and an amplifier control circuit 67.

  The optical coupler 63 outputs the signal (wavelength λ1) branched by the optical branch switch 61 to the transmission device 70 and the optical switch 64. The optical switch 64 selects and outputs one of the signal (wavelength λ1) branched by the optical branching switch 61 and the signal (λ1 ') input from the optical transmission device 70. The optical amplifier 65 amplifies the signal selected by the optical switch 64 and outputs the amplified signal to the optical add switch 62. The switch control circuit 66 monitors the signal level of the signal (wavelength λ1 ′) input from the optical transmission device 70, and controls the selection operation of the optical switch 64 according to the monitoring result. For example, when the signal level of the signal (wavelength λ1 ′) is lower than a specified value, the optical switch 64 selectively outputs the signal (wavelength λ1) from the optical coupler 63. ') Is selected and output. The amplifier control circuit 67 monitors the output level from the optical amplifier 65 and changes the amplification factor of the optical amplifier 65 according to the monitoring result.

  With the configuration as described above, the optical add / drop device 60 described in Patent Document 1 branches and outputs to the optical transmission device 70 when the signal level of the signal (wavelength λ1 ′) inserted from the optical transmission device 70 is lower than the specified value. The signal (wavelength λ1) is looped back to the wavelength-division multiplexed optical signal of the main route. As a result, even if a failure occurs on the transmission path between the transmission device 70 and the optical add / drop device 60, it is possible to suppress the occurrence of power level fluctuation of the wavelength multiplexed optical signal.

  However, since the apparatus described in Patent Document 1 can only perform loopback control in wavelength units (single channel), it can handle gain fluctuation when the number of inserted signals (number of wavelengths) in wavelength band units (multi-channel) fluctuates. Can not do it. In addition, when the apparatus described in Patent Document 1 is changed so as to perform loopback control in units of wavelength bands, an optical switch 64, an optical amplifier 65, a switch control circuit 66, and an amplifier control circuit 67 are provided for each signal (each channel). It is necessary to provide it. For this reason, when the technique described in Patent Document 1 is applied to the system shown in FIG. 1, the circuit scale of the device for avoiding the failure becomes large. Further, in Patent Document 1, when a failure occurs in the transmission line, an optical amplifier 65 for amplifying the looped back signal level is required, so that power consumption increases.

JP 2006-180417 A

  An object of the present invention is to prevent deterioration in communication quality of an optical communication system having an optical add / drop device that controls branching and insertion of wavelength multiplexed optical signals.

  Another object of the present invention is to suppress an increase in cost for maintaining the communication quality of an optical communication system having an optical add / drop device that controls branching and insertion of a wavelength multiplexed optical signal.

  Still another object of the present invention is to reduce the failure occurrence rate of an optical multiplexer / demultiplexer that controls the branching and insertion of a wavelength multiplexed optical signal and to prevent the communication quality of an optical transmission system from deteriorating.

  In order to solve the above problems, the present invention employs the means described below. In the description of technical matters constituting the means, in order to clarify the correspondence between the description of [Claims] and the description of [Mode for Carrying Out the Invention] The number / symbol used in [Form] is added. However, the added numbers and symbols should not be used to limit the technical scope of the invention described in [Claims].

  An optical multiplexer / demultiplexer (10) according to the present invention includes a branching circuit, a first variable attenuator (17), and a multiplexing circuit. The demultiplexing circuit converts the wavelength multiplexed optical signal (100) input from the first transmission line (41) into a first wavelength multiplexed optical signal (101) and a second wavelength multiplexed optical signal (102) having different frequency bands. Demultiplex. The first variable circuit (17) attenuates the second wavelength multiplexed optical signal (102) by the loss amount corresponding to the optical level of the third wavelength multiplexed optical signal (103) input from the second transmission line (44). The multiplexing circuit that performs the second wavelength multiplexed optical signal (102), the first wavelength multiplexed optical signal (101), and the third wavelength multiplexed optical signal (103) input via the first variable attenuator (17). ) And the third transmission path (42).

  According to the optical multiplexing and branching method of the present invention, a wavelength multiplexed optical signal (100) input from the first transmission line (41) is divided into a first wavelength multiplexed optical signal (101) and a second wavelength multiplexed optical signal (102) having different frequency bands. ), And the first variable attenuator (17) causes the first variable attenuator (17) to perform the first loss by the amount of loss corresponding to the optical level of the third wavelength multiplexed optical signal (103) input from the second transmission line (44). Attenuating the two-wavelength multiplexed optical signal (102); a second wavelength-multiplexed optical signal (102) input through the first variable attenuator (17); and a first wavelength-multiplexed optical signal (101); And a step of combining the third wavelength multiplexed optical signal (103) and outputting it to the third transmission line (42).

  As described above, the optical multiplexing / demultiplexing device (10) according to the present invention uses the second transmission line (41) by the second wavelength division multiplexed optical signal (102) even if the optical level of the third wavelength division multiplexed optical signal (103) decreases. ) And the third transmission line (42), the number of wavelengths on the main route can be maintained. As a result, even if an optical repeater is provided on the third transmission line, it is possible to prevent excessive amplification due to fluctuations in the number of wavelengths.

  According to the present invention, it is possible to prevent deterioration in communication quality of an optical communication system having an optical add / drop device that controls branching and insertion of wavelength multiplexed optical signals.

  In addition, it is possible to suppress an increase in cost for maintaining the communication quality of an optical communication system having an optical add / drop device that controls branching and insertion of wavelength multiplexed optical signals.

  Furthermore, it is possible to reduce the failure occurrence rate of the optical multiplexer / demultiplexer that controls the branching and insertion of the wavelength multiplexed optical signal, and to prevent the communication quality of the optical transmission system from deteriorating.

FIG. 1 is a diagram illustrating an example of a configuration of an optical combining / branching device according to a conventional technique. FIG. 2 is a diagram illustrating another example of the configuration of the optical coupling / branching device according to the related art. FIG. 3 is a diagram showing an example of a configuration in the first embodiment of the optical add / drop device according to the present invention. FIG. 4 is a wavelength arrangement diagram showing an example of the wavelength band used for the wavelength multiplexed optical signal according to the present invention. FIG. 5 is a diagram showing an example of the relationship between the optical level of the wavelength multiplexed optical signal to be monitored and the threshold value in the present invention. FIG. 6 is a diagram showing another example of the configuration of the first embodiment of the optical add / drop device according to the present invention. FIG. 7 is a diagram showing an example of the configuration of the optical add / drop device according to the second embodiment of the present invention. FIG. 8 is a diagram showing another example of the relationship between the optical level and the threshold value of the wavelength multiplexed optical signal to be monitored in the present invention. FIG. 9 is a diagram showing another example of the configuration in the third embodiment of the optical add / drop device according to the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same or similar reference numerals indicate the same, similar, or equivalent components. In this embodiment, an optical coupling / branching device that is used in an optical communication system (example: submarine optical cable system) and adds / drops a wavelength multiplexed optical signal to / from an add / drop station will be described as an example.

1. First Embodiment With reference to FIG. 3 to FIG. 6, the details of the configuration and operation of a first embodiment of an optical multiplexing / branching device according to the present invention will be described. FIG. 3 is a diagram showing an example of a configuration in the first embodiment of the optical add / drop device according to the present invention.

  Referring to FIG. 3, the optical coupling / branching device 10 according to the present invention is used in a submarine optical cable system and is provided between a submarine cable 41 and a submarine cable 42 serving as a main route X. In order to compensate for the optical loss of the main route X, the optical repeaters 31 and 32 amplify the input wavelength-multiplexed optical signal and output it to the next stage submarine cable. For example, the optical repeaters 31 and 32 are preferably optical amplifiers in which the repeater output level becomes substantially constant by the pumping light constant control generally used in the submarine cable system.

  The optical add / drop device 10 branches (drops) a part of the wavelength multiplexed optical signal input from the optical repeater 31 to the add / drop station 30 and wavelength multiplexed from the add / drop station 30. The optical signal is inserted (added) into the wavelength division multiplexing optical signal communication in the main route X connecting the optical repeater 31 and the optical repeater 32. Hereinafter, a route for taking out (dropping) the wavelength multiplexed optical signal from the optical add / drop device 10 to the add / drop station 30 is referred to as a drop route Y, and the wavelength multiplexed optical signal is inserted from the add / drop station 30 to the optical add / drop device 10. A route for (adding) is referred to as an add route Z.

  In the present embodiment, the optical multiplexing / demultiplexing device 10 drops the wavelength multiplexed optical signal 102 in the wavelength band “Band B1” from the wavelength multiplexed optical signal 100 in the wavelength band “Band A + Band B1” to the drop route Y. In addition, a wavelength multiplexed optical signal 101 in the wavelength band “Band A” is output to the main route X, and a wavelength multiplexed optical signal 103 in the wavelength band “Band B2” is inserted from the add route Z. FIG. 4 is a wavelength arrangement diagram showing an example of the wavelength band used for the wavelength multiplexed optical signal according to the present invention. Referring to FIG. 4, “Band B1” and “Band B2” are preferably in the same wavelength band, and “Band A” is preferably arranged in a different wavelength band from “Band B1 (B2)”. Further, “Band B1” and “Band B2” may be different wavelength bands unless they are within the “Band A” wavelength band.

  The optical multiplexer / demultiplexer 10 shown in FIG. 3 includes optical demultiplexers 11, 12, 18, optical filters 13, 16, optical multiplexers 14, 15, an optical variable attenuator 17, and a photodetector 19. The wavelength multiplexed optical signal 100 (wavelength band: Band A + Band B1) output from the optical repeater 31 is input to the optical demultiplexer 11 via the submarine cable 41. The optical demultiplexer 11 splits the intensity of the wavelength-multiplexed optical signal 100 (Band A + Band B1) and outputs it to the optical demultiplexer 12 on the main route X side and the optical filter 45 on the drop route Y side. The optical demultiplexer 12 splits the intensity of the wavelength-multiplexed optical signal 100 output to the main route X side and outputs it to the optical filter 13 and the optical filter 16. The optical filter 13 transmits only the wavelength band “Band A”, which is a communication signal of the main route X, from the wavelength multiplexed optical signal 100 (Band A + Band B1), and outputs the wavelength multiplexed optical signal 101 to the optical multiplexer 14. On the other hand, the optical filter 16 transmits only the same wavelength band “Band B1” as the communication signal dropped to the drop route Y from the wavelength multiplexed optical signal 100 (Band A + Band B1), and is an optical variable attenuator as the wavelength multiplexed optical signal 102. 17 to output. The wavelength multiplexed optical signal 102 is input to the optical multiplexer 14 via the optical variable attenuator 17. The optical variable attenuator 17 attenuates the optical level of the wavelength multiplexed optical signal 102 (the output level of the optical filter 16), and determines the input level of the wavelength multiplexed optical signal 102 to the optical multiplexer 14. The attenuation amount (loss amount) by the optical variable attenuator 17 is set by the control signal 110 from the photodetector 19.

  The optical multiplexer 14 combines the output signal from the optical filter 13 and the output signal from the optical variable attenuator 17 and outputs the resultant signal to the optical multiplexer 15. On the other hand, the optical demultiplexer 18 branches the intensity of the wavelength-multiplexed optical signal 103 (wavelength band: Band B2) output from the add / drop station 30 via the submarine cable 44, and the optical multiplexer 15 and the optical detector 19. Output to. For example, the optical demultiplexer 18 branches the intensity of the total power of the wavelength multiplexed optical signal 103 at a predetermined ratio, and outputs it to the optical multiplexer 15 and the photodetector 19. Alternatively, the optical demultiplexer 18 branches the intensity of the channel power of a specific wavelength in the wavelength multiplexed optical signal 103 at a predetermined ratio, and outputs it to the optical multiplexer 15 and the photodetector 19. The optical multiplexer 15 intensity-combines the output signal from the optical multiplexer 14 and the output signal from the optical demultiplexer 18 and outputs the resultant signal to the optical repeater 32 via the submarine cable 42.

  The photodetector 19 monitors the optical level of the output (wavelength multiplexed optical signal 103) from the optical demultiplexer 18, and outputs a control signal 110 corresponding to the monitoring result to the optical variable attenuator 17. For example, the photodetector 19 monitors the total power of the entire wavelength range in the wavelength division multiplexed optical signal 103 cut by the optical demultiplexer 8 from the entire wavelength band passing through the submarine cable 44. Alternatively, the photodetector 19 monitors the light level of a specific wavelength through the submarine cable 44. A threshold value as shown in FIG. 5 is set in the photodetector 19, and it is monitored whether or not the optical level of the monitoring light (for example, the wavelength multiplexed optical signal 103) is equal to or higher than the threshold value. The threshold value set here is preferably set to an optical level that can be regarded as the input of the wavelength multiplexed optical signal 103 to the optical add / drop device 10 being cut off.

  When the optical level of the wavelength multiplexed optical signal 103 or the monitoring light of a specific wavelength is greater than or equal to the threshold, the photodetector 19 has the maximum loss (greater than a predetermined value, preferably infinite) of the optical variable attenuator 17. To control. As a result, the input of the wavelength multiplexed optical signal 102 to the optical multiplexer 14 is cut off, and the optical multiplexer 14 outputs only the wavelength multiplexed optical signal 101 (Band A) to the optical multiplexer 15. In this case, the optical multiplexer 15 intensity-multiplexes the wavelength multiplexed optical signal 101 and the wavelength multiplexed optical signal 103 from the add / drop station 30, and the wavelength multiplexed optical signal 200 whose wavelength band is “Band A + Band B2” is the main. Output to the submarine cable 42 of route X. On the other hand, when the optical level of the wavelength multiplexed optical signal 103 falls below the threshold value, the photodetector 19 controls the loss of the optical variable attenuator 17 to be a minimum (a value smaller than a predetermined value, preferably a loss of 0). . As a result, the wavelength multiplexed optical signal 102 is input to the optical multiplexer 14, and the optical multiplexer 14 wavelength-multiplexes the wavelength multiplexed optical signal 101 (Band A) and the wavelength multiplexed optical signal 102 (Band B1). The optical signal 201 (wavelength band: Band A + Band B1) is output. The optical multiplexer 15 intensity-multiplexes the wavelength multiplexed optical signal 201 and the wavelength multiplexed optical signal 103. However, since the optical level of the wavelength multiplexed optical signal 103 is lower than the threshold, the wavelength band is substantially “Band A + Band B1”. Is output to the submarine cable 42 of the main route X. When a large threshold is set for the photodetector 19, the optical level of the wavelength multiplexed optical signal 103 below the threshold is a level that cannot be ignored (a level that cannot be regarded as substantially 0). In this case, it is preferable that the optical variable attenuator 17 attenuates the wavelength-multiplexed optical signal 102 with an attenuation factor considering the size of the wavelength-multiplexed optical signal 103 input to the optical multiplexer 15. For example, the optical variable attenuator 17 calculates the total power of “Band B1 and Band B2” in the submarine cable 42 so that the band A channel power in the submarine cable 42 does not change before and after the fault in the submarine cable 44. Adjustment is made so as to match the channel power of the multiplexed optical signal 102 (Band B1).

  In the above description, when the optical level that can be regarded as the input of the wavelength division multiplexed optical signal 103 to the optical add / drop device 10 being blocked is set as the threshold, and the optical level of the wavelength multiplexed optical signal 103 is below the threshold, the optical variable attenuator One example is controlling the loss to be zero. However, the magnitude of the threshold is not limited to this, and a predetermined light level may be set as the threshold. In this case, among the wavelength multiplexed optical signals output from the optical multiplexer 15, the optical variable is performed so that the optical level of the wavelength multiplexed optical signal in the wavelength band other than the communication (Band A) in the main route X is equal to or higher than the threshold value. The attenuation amount of the attenuator 17 is preferably set. For example, referring to FIG. 5, when the threshold is set to “a” and the optical level of the wavelength multiplexed optical signal 103 monitored by the photodetector 19 is “b” (a> b), the optical variable attenuation By setting the optical level of the wavelength multiplexed optical signal 102 output from the optical unit 17 to “c” which is equal to or higher than “b−a”, the wavelength multiplexed optical signal 201 output from the optical multiplexer 15 (wavelength band: Band A + Band B1 + BandB2). ) To the wavelength band “Band B1 + Band B2)” excluding the wavelength band “BandA” can be set to the threshold “a” or more.

  With the configuration as described above, the optical add / drop device 10 in the first embodiment transmits the wavelength multiplexed optical signal 102 (Band B1) out of the input wavelength multiplexed optical signal 100 (Band A + Band B1) to the main route X. The wavelength multiplexed optical signal 103 (Band B2) from the add / drop station 30 is inserted (added) into the main route X and output as a wavelength multiplexed optical signal 200 (Band A + Band B2). Also, the optical add / drop device 10 in the first embodiment adds / drops when the optical level (optical power) of the wavelength multiplexed optical signal 103 (Band B2) inserted from the add / drop station 30 is lower than the threshold value. The wavelength division multiplexed optical signal 102 (Band B1) branched and output to the station 30 is combined with the wavelength division multiplexed optical signal of the main route X. As a result, even when the wavelength multiplexed optical signal 103 (Band B2) is not inserted into the optical multiplexer / demultiplexer 10 due to a fault in the submarine cable 44 or the add / drop station 30, the number of wavelengths (bands) Width) does not decrease. Therefore, the repeater 32 can maintain the communication quality in the transmission path after the optical repeater 32 without excessively amplifying the signal light of each channel in the optical wavelength multiplexed optical signal 101 (Band A). That is, according to the present invention, even if a failure occurs on the transmission line between the optical add / drop device 10 and the add / drop station 30, the power level fluctuation of the wavelength multiplexed optical signal 101 (Band A) in the main route X is changed. It is suppressed and the deterioration of communication quality can be prevented.

  In the present invention, since the wavelength multiplexed optical signal to be multiplexed with the wavelength multiplexed optical signal on the main route X is determined using an attenuator, the wavelength band unit (multi-channel) is used without increasing the circuit scale. Thus, it is possible to cope with gain fluctuations due to fluctuations in the number of inserted signals (number of wavelengths). Furthermore, in the present invention, since there is no significant difference in the loss between the wavelength multiplexed optical signal 101 and the wavelength multiplexed optical signal 102 in the main route X, the wavelength multiplexed optical signal 102 combined with the wavelength multiplexed optical signal on the main route X is changed. Does not require an optical amplifier to amplify. For this reason, according to this invention, the power consumption which concerns on the operation | movement for maintaining communication quality can be reduced. In addition, unlike the case where a switch is provided as in the prior art, since an attenuator is used, the configuration is simplified without using a mechanically operated device such as an optical switch. In addition, since the number of devices having a simple configuration and a high failure rate is small, the failure occurrence rate is lower than the conventional one. Therefore, the reliability of the optical transmission system can be improved by using the optical add / drop device 10 according to the present invention.

(Operation)
Next, details of the operation of the optical add / drop device 10 shown in FIG. 3 will be described.

  First, the operation in a state where the submarine cable system is normally operated (no failure has occurred) will be described. The wavelength multiplexed optical signal 100 (Band A + Band B1) input from the submarine cable 41 to the optical add / drop device 10 is branched into the main route X and the drop route Y by the optical demultiplexer 11. The wavelength multiplexed optical signal 100 (Band A + Band B1) output from the optical demultiplexer 11 to the submarine cable 43 is extracted only by the optical filter 45 with the wavelength multiplexed optical signal 102 (Band B1) necessary for drop route Y communication. Thereafter, the data is output to the add / drop station 30. The wavelength division multiplexed optical signal 100 (Band A1 + Band B1) branched to the main route X side by the optical multiplexer / demultiplexer 10 is branched into the optical filter 13 and the optical filter 16 by the optical demultiplexer 12, respectively. The optical filter 13 transmits only the wavelength multiplexed optical signal 101 (Band A) from the wavelength multiplexed optical signal 100 (Band A + Band B1). On the other hand, the optical filter 16 transmits only the wavelength multiplexed optical signal 102 (Band B1) from the wavelength multiplexed optical signal 100 (Band A + Band B1) and outputs it to the optical variable attenuator 17.

  In the normal state, the light monitor level detected by the light detector 19 detects a light level that exceeds the break detection threshold. The control signal 110 at this time is controlled so that the loss amount of the optical variable attenuator 17 becomes the maximum loss. As a result, the wavelength multiplexed optical signal 102 (Band B1) transmitted from the optical filter 16 is not output from the optical variable attenuator 17. In this case, the optical multiplexer 14 outputs only the wavelength multiplexed optical signal 101 (Band A) from the optical filter 13 to the optical multiplexer 15. On the other hand, the wavelength division multiplexed optical signal 103 (Band B2) input from the add / drop station 30 via the submarine cable 44 to the optical multiplexer / demultiplexer 10 is output to the optical multiplexer 15 via the optical demultiplexer 18. The optical multiplexer 15 multiplexes the wavelength multiplexed optical signal 101 (Band A) from the optical multiplexer 14 and the wavelength multiplexed optical signal 103 (Band B2) from the optical demultiplexer 18 and combines the wavelength multiplexed optical signal 200 (Band B2). A + Band B2) is transmitted to the submarine cable 42. With the above operation, the optical add / drop device 10 drops the wavelength multiplexed optical signal 102 (Band B1) from the main route X, and adds the wavelength multiplexed optical signal 103 (Band B2) to the main route X.

  Next, an operation when a failure occurs in which the submarine cable 44 that is a branch route (add route Z) is disconnected will be described. When a failure occurs in which the submarine cable 44 is disconnected, the monitoring light of the wavelength multiplexed optical signal 103 (Band B2) detected by the photodetector 19 is cut off. When the monitor light is interrupted, the monitor light falls below the threshold value, so that the photodetector 19 determines that the wavelength multiplexed optical signal 103 is interrupted and uses the control signal 110 to reduce the loss of the optical variable attenuator 17. Reduce. As a result, the wavelength-multiplexed optical signal 102 (Band B1) is transmitted from the optical variable attenuator 17 and combined with the wavelength-multiplexed optical signal 101 (Band A) from the optical filter 13 by the optical multiplexer 14. Since there is no input light from the optical demultiplexer 18 in the optical multiplexer 15, only the wavelength multiplexed optical signal 201 (Band A + B1) from the optical multiplexer 14 is output to the submarine cable 42. Therefore, in the submarine cable 42, the number of wavelengths does not decrease even if the wavelength-multiplexed optical signal 103 (Band B2) disappears due to a failure. Therefore, each channel of the wavelength-multiplexed optical signal 101 (Band A) that is a communication signal of the main route X The signal light power is not excessively high, and degradation of signal quality can be suppressed.

  As described above, according to the present invention, the optical level (optical power) of the wavelength multiplexed optical signal propagated on the transmission path (submarine cable 44) on the add route Z is monitored, and dropped according to the monitoring result. By multiplexing the wavelength multiplexed optical signal 102 with the wavelength multiplexed optical signal 101 on the main route X, it is possible to maintain the number of wavelengths of the main route X and prevent deterioration in communication quality.

  FIG. 6 is a diagram showing another example of the configuration of the first embodiment of the optical add / drop device according to the present invention. In the example shown in FIG. 3, the demultiplexer 12 and the optical filter 16 are used to multiplex the dropped wavelength-multiplexed optical signal demultiplexer 102 with the wavelength-multiplexed optical signal of the main route X. A wavelength splitter 20 shown in FIG. 6 may be used. In this case, the wavelength splitter 20 branches the wavelength multiplexed optical signal 100 (Band A + Band B1) into a wavelength multiplexed optical signal 101 (Band A) and a wavelength multiplexed optical signal 102 (Band B1).

  Similarly, in the optical multiplexer / demultiplexer 10 shown in FIG. 3, an intensity demultiplexer or an intensity multiplexer is used as the optical demultiplexer 11 or the optical multiplexers 14, 15. A wavelength demultiplexer or a wavelength multiplexer that demultiplexes or multiplexes may be used. In this case, it goes without saying that the optical filters 45 and 13 are unnecessary.

2. Second Embodiment With reference to FIG. 7 to FIG. 9, the configuration and operation of a second embodiment of the optical coupling / branching device according to the present invention will be described. In the optical add / drop device 10 in the second embodiment, a wavelength multiplexed optical signal 103 (Band B2) having the same wavelength band as the dropped wavelength multiplexed optical signal 102 is inserted (added), and on the main route X Dummy light (wavelength multiplexed optical signal 105) in the same wavelength band “Band C” as the wavelength multiplexed optical signal 101 (Band A) is selectively inserted (added). In the second embodiment, in addition to the control to multiplex the wavelength multiplexed optical signal 102 with the wavelength multiplexed optical signal on the main route X according to the optical level of the added wavelength multiplexed optical signal 103, on the main route X Control for inserting (adding) the wavelength multiplexed optical signal 105 is performed in accordance with the optical level of the wavelength multiplexed optical signal 101.

  FIG. 7 is a diagram showing an example of the configuration of the optical add / drop device according to the second embodiment of the present invention. Hereinafter, a configuration and operation different from those of the first embodiment will be described in detail.

  7 includes an optical demultiplexer 21, a photodetector 22, optical filters 24 and 26, an optical multiplexer 25, and an optical variable attenuator in addition to the configuration of the optical multiplexer / demultiplexer 10 illustrated in FIG. 27. Also, the add / drop station 30 shown in FIG. 7 has a wavelength including the wavelength multiplexed optical signal 105 and the wavelength multiplexed optical signal 103 (Band B2) in the same wavelength band “Band C” as the wavelength band Band A of the wavelength multiplexed optical signal 101. The multiplexed optical signal 104 is output to the optical add / drop device 10. Other configurations are the same as those of the first embodiment.

  The optical demultiplexer 11 splits the intensity of the wavelength-multiplexed optical signal 100 (Band A + Band B1) and outputs it to the optical demultiplexer 21 on the main route X side and the optical filter 45 on the drop route Y side. The optical demultiplexer 21 splits the intensity of the wavelength-multiplexed optical signal 100 output to the main route X side and outputs it to the optical filter optical demultiplexer 12 and the photodetector 22. The photodetector 22 monitors the optical level of the output from the optical demultiplexer 21 (wavelength multiplexed optical signal 100), and outputs a control signal 111 corresponding to the monitoring result to the optical variable attenuator 27. A threshold value as shown in FIG. 8 is set in the photodetector 22, and it is monitored whether or not the optical level of the wavelength multiplexed optical signal 100 (Band A + Band B1) is equal to or higher than the threshold value. The threshold value set here is preferably set to an optical level that can be regarded as the input of the wavelength division multiplexed optical signal 100 to the optical add / drop device 10 being cut off.

  On the other hand, the optical demultiplexer 18 according to the second embodiment splits the intensity of the wavelength multiplexed optical signal 104 (Band C + Band B2) output from the add / drop station 30 via the submarine cable 44, and the optical demultiplexer. 23 and the light detector 19. The optical demultiplexer 23 branches the intensity of the wavelength-multiplexed optical signal 104 output to the add route Y side, and outputs it to the optical filter 24 and the optical filter 26. The optical filter 24 transmits only the wavelength band “Band B2”, which is the communication signal of the add route Y, from the wavelength multiplexed optical signal 104 (Band C + Band B2), and outputs it to the optical multiplexer 25 as the wavelength multiplexed optical signal 103. On the other hand, the optical filter 26 transmits only the same wavelength band “Band C” as the communication signal of the main route X from the wavelength multiplexed optical signal 104 (Band C + Band B2) to the optical variable attenuator 27 as the wavelength multiplexed optical signal 105. Output. The wavelength multiplexed optical signal 105 is input to the optical multiplexer 25 via the optical variable attenuator 27. The optical variable attenuator 27 attenuates the optical level of the wavelength multiplexed optical signal 105 (the output level of the optical filter 26), and determines the input level of the wavelength multiplexed optical signal 105 to the optical multiplexer 25. The attenuation amount (loss amount) by the optical variable attenuator 27 is set by a control signal 111 from the photodetector 22.

  When the optical level of the wavelength-multiplexed optical signal 100 is equal to or higher than the threshold value, the photodetector 22 performs control so that the loss of the optical variable attenuator 27 is maximized. Thereby, the input of the wavelength multiplexed optical signal 105 to the optical multiplexer 25 is cut off, and the optical multiplexer 25 outputs only the wavelength multiplexed optical signal 103 (Band B2) to the optical multiplexer 15. In this case, the optical multiplexer 15 intensity-multiplexes the wavelength multiplexed optical signal 101 and the wavelength multiplexed optical signal 103 from the add / drop station 30, and the wavelength multiplexed optical signal 200 whose wavelength band is “Band A + Band B2” is the main. Output to the submarine cable 42 of route X. On the other hand, when the optical level of the wavelength-multiplexed optical signal 100 falls below the threshold value, the photodetector 22 performs control so that the loss of the optical variable attenuator 27 is minimized (preferably loss 0). As a result, the wavelength multiplexed optical signal 105 is input to the optical multiplexer 25, and the optical multiplexer 25 performs wavelength multiplexing by intensity multiplexing the wavelength multiplexed optical signal 105 (Band C) and the wavelength multiplexed optical signal 103 (Band B2). The optical signal 104 (wavelength band: Band C + Band B2) is output. The optical multiplexer 15 intensity-multiplexes the wavelength multiplexed optical signal 201 and the wavelength multiplexed optical signal 104. However, since the optical level of the wavelength multiplexed optical signal 201 is lower than the threshold, the wavelength band is substantially “Band C + Band B2”. Is output to the submarine cable 42 of the main route X.

  The photodetector 19 in the second embodiment controls the attenuation (loss) of the optical variable attenuator 17 according to the optical level of the wavelength multiplexed optical signal 104 (Band C + Band B2). The attenuation control method is the same as that of the photodetector 22, and the attenuation of the optical variable attenuator 17 is determined according to the comparison result between the threshold and the wavelength multiplexed optical signal 104 (Band C + Band B2) as shown in FIG. To do. Other operations of the optical demultiplexer 12, the optical filters 13, 16, and the optical multiplexer 15 are the same as those in the first embodiment.

  With the configuration as described above, in the optical add / drop device 10 according to the second embodiment, when the wavelength multiplexed optical signal 100 (Band A + Band B1) is not inserted into the optical add / drop device 10 due to a failure in the submarine cable 41 or the like, A dummy light (wavelength multiplexed optical signal 105) in the wavelength band “Band C” corresponding to the wavelength band “Band A” is transmitted from the station 30. For this reason, when a failure occurs that causes the submarine cable 41 to be disconnected, the number of wavelengths (bandwidth) of the wavelength multiplexed optical signal transmitted to the submarine cable 42 does not decrease, and the signal quality of the ad-route Z can be ensured. It becomes. Similarly to the first embodiment, even when the wavelength multiplexed optical signal 103 (Band B2) is not inserted into the optical multiplexer / demultiplexer 10 due to a fault in the submarine cable 44 or the add / drop station 30, it is transmitted to the submarine cable 42. Since the number of wavelengths (bandwidth) of the wavelength multiplexed optical signal does not decrease, it is possible to prevent deterioration in communication quality of the main route X. That is, according to the optical add / drop device 10 in the second embodiment, it is possible to prevent the communication quality of the main route X from being deteriorated even if a failure occurs in the add route Z, and the add route even if a failure occurs in the main route X. A decrease in communication quality of Z can be prevented.

3. Third Embodiment FIG. 9 is a diagram illustrating a configuration of an optical add / drop device 10 according to a third embodiment. As shown in FIG. 9, the optical add / drop device 10 according to the present invention can also be applied when repeaters 46 and 47 are provided on the drop route Y and the add route Z. The optical add / drop device 10 according to the third embodiment includes an optical filter 28 that blocks dummy light (wavelength band: Band C) on the side of the submarine cable 44 with respect to the optical demultiplexer 18. The configuration is the same as that shown in FIG.

  In the present embodiment, an optical repeater 47 having the same capability (for example, output power) as the optical repeaters 31 and 32 is provided on the submarine cable 44. In this case, if only the wavelength multiplexed optical signal (wavelength band: Band B2) as an add signal is input, the channel power of the signal in the submarine cable 44 becomes higher than necessary by the optical repeater 47, and the optical multiplexer 15 The combined signal may be degraded. For this reason, in this embodiment, in order to keep the optical level of the wavelength multiplexed optical signal (Band B2) constant, in addition to the wavelength multiplexed optical signal (wavelength band: Band B2) that is an add signal, dummy light (wavelength band: Band C) is inserted into the submarine cable 44. In other words, the add / drop station 30 in the present embodiment outputs the wavelength multiplexed optical signal 104 including the wavelength multiplexed optical signal (Band B2) which is an add signal and the dummy light (Band C) to the submarine cable 44.

  The dummy light (Band C) is inserted in order to keep the channel power of the wavelength multiplexed optical signal (Band B2) in the submarine cable 44 constant. For this reason, the dummy light (Band C) is arranged at least in a wavelength band other than the wavelength bands “Band B1, B2”. Preferably, the dummy light (Band C) is a wavelength multiplexed optical signal having the same wavelength band as the wavelength band “Band A” of the wavelength multiplexed optical signal 101.

  The optical filter 28 blocks the dummy light (Band C) from the wavelength multiplexed optical signal 104 input through the repeater 47 and transmits the wavelength multiplexed optical signal (Band B2). The light that has passed through the optical filter 28 is branched by the optical demultiplexer 18, multiplexed by the optical multiplexer 15 to the submarine cable 18, and input to the photodetector 19. The operation of the configuration after the optical demultiplexer 18 is the same as the configuration shown in FIG.

  As described above, in the optical add / drop device 10 according to the present embodiment, even if a wavelength multiplexed optical signal including dummy light for keeping the optical level of the add signal constant is input, the same as in the first embodiment. In response to the signal degradation on the add route Z, the dropped wavelength multiplexed optical signal 102 can be combined with the wavelength multiplexed optical signal 101 on the main route X to prevent degradation of communication quality in the main route X.

  In FIG. 9, only one optical repeater 46, 47 is shown, but a plurality of similar optical repeaters may exist in the submarine cables 43, 44.

  As described above, the optical add / drop device 10 according to the present invention uses the wavelength-division multiplexed optical signal 102 in the same frequency band as the add signal (wavelength multiplexed optical signal 103) in response to the detection of the disconnection of the submarine cable 44 in the add route Z. The signal is multiplexed to the X wavelength multiplexed signal 101. Thereby, the fluctuation | variation (gain fluctuation | variation) of the signal light power of the main route X is suppressed, and deterioration of communication quality can be prevented. At this time, the wavelength multiplexed optical signal 102 input from the submarine cable 41 together with the wavelength multiplexed optical signal 101 as the main route signal is used as dummy light instead of the add signal (wavelength multiplexed optical signal 103). It is not necessary to install a dummy light source.

  Furthermore, since the dummy light combined with the wavelength multiplexed optical signal on the main route X is controlled by the optical attenuator when a failure occurs, it is not necessary to provide an amplifier or a switch for each wavelength (each channel). Compared to this, the circuit scale and power consumption can be reduced. Further, since the circuit configuration is simplified as compared with the conventional one, the failure occurrence rate is reduced and the reliability is improved.

  The embodiment of the present invention has been described in detail above, but the specific configuration is not limited to the above-described embodiment, and changes within a scope not departing from the gist of the present invention are included in the present invention. . In the above-described embodiment, the optical coupling / branching device used in the submarine cable system using the optical fiber as the transmission path has been described. However, the present invention can be applied to other systems. For example, any one of the main route X, the drop route Y, and the add route Z may be an electrical line (including free space) instead of an optical line. In this case, it goes without saying that the optical add / drop device 10 performs communication with the transmission line using a photoelectric converter.

  Further, the order of the multiplexing circuit (the circuit optical multiplexer 14 and the optical multiplexer 15) is not limited to the above example, and may be combined in the reverse order. For example, in FIG. 3 or FIG. 6, the result of combining the wavelength multiplexed optical signal 101 and the wavelength multiplexed optical signal 103 and the output of the optical variable attenuator 17 may be combined and output to the submarine cable 42. . Alternatively, in FIG. 7 or FIG. 9, the result of combining the wavelength multiplexed optical signal 101 and the output of the optical multiplexer 25 and the output of the optical variable attenuator 17 may be combined and output to the submarine cable 42. .

  Furthermore, although the optical filter 45 for extracting the drop signal in the above-described embodiment is provided outside the optical multiplexing / demultiplexing device 10, the optical filter 45 is not limited to this and may be provided in the optical multiplexing / demultiplexing device 10, or The drop station 30 may be provided.

10: Optical multiplexer / demultiplexer 11, 12, 18, 23: Optical demultiplexer 13, 16, 24, 26, 45: Optical filter 14, 15, 21, 25: Optical multiplexer 17, 27: Optical variable attenuator 19, 22: Optical detector 20: Wavelength splitter 30: Add / drop station 31, 32, 40: Optical repeater 41, 42, 43, 44: Submarine cable 100, 101, 102, 103, 104, 105: Wavelength multiplexing Optical signal 110, 111: Control signal

Claims (10)

A demultiplexing circuit for demultiplexing the wavelength multiplexed optical signal input from the first transmission path into a first wavelength multiplexed optical signal and a second wavelength multiplexed optical signal having different frequency bands;
A first variable attenuator for attenuating the second wavelength-multiplexed optical signal by an amount of loss corresponding to the optical level of the third wavelength-multiplexed optical signal input from the second transmission line;
The second wavelength multiplexed optical signal, the first wavelength multiplexed optical signal, and the third wavelength multiplexed optical signal input through the first variable attenuator are combined and output to the third transmission line. An optical multiplexing / branching device comprising a multiplexing circuit. The optical coupling / branching device according to claim 1,
The second wavelength multiplexed optical signal is output to a fourth transmission line,
The optical multiplexing / branching device, wherein a frequency band of the third wavelength multiplexed optical signal is the same as that of the second wavelength multiplexed optical signal. In the optical coupling / branching device according to claim 1 or 2,
A photodetector for monitoring an optical level of the third wavelength-multiplexed optical signal;
The optical detector controls the first variable attenuator so that the loss amount is equal to or greater than a predetermined value when the optical level of the third wavelength multiplexed optical signal is equal to or greater than a threshold, and the third wavelength multiplexed An optical coupling / branching device that controls the first variable attenuator so that the loss amount becomes smaller than a predetermined value when an optical level of an optical signal is lower than a threshold value. The optical coupling / branching device according to claim 3,
The optical detector is configured to control the first variable attenuator so that the loss amount becomes zero when the optical level of the third wavelength multiplexed optical signal is lower than a threshold value. The optical coupling / branching device according to claim 1,
Another demultiplexing circuit for demultiplexing the third wavelength multiplexed optical signal into a first output signal and a second output signal;
A first optical filter that transmits only a first wavelength band of the first output signal and outputs a dummy signal;
A second optical filter that transmits only the second wavelength band different from the first wavelength band of the second output signal and outputs another wavelength multiplexed optical signal;
A second variable attenuator for attenuating the dummy signal by a loss amount according to an optical level of the wavelength-multiplexed optical signal input from the first transmission line ;
Further comprising a separate multiplexing circuit outputting another third wavelength-multiplexed optical signal to the dummy signal inputted through said other wavelength-multiplexed optical signal and the second variable attenuator multiplexed to,
The multiplexing circuit includes a second wavelength division multiplexed optical signals inputted through said first variable attenuator, and the first wavelength-multiplexed optical signal, said further input via said further multiplexing circuit An optical multiplexing / branching device for combining the third wavelength multiplexed optical signal and outputting the multiplexed signal to the third transmission line. The optical coupling / branching device according to claim 5,
A first photodetector for monitoring an optical level of the wavelength multiplexed optical signal input from the first transmission line ;
A second photodetector for monitoring the optical level of the third wavelength multiplexed optical signal,
The first photodetector controls the second variable attenuator so that the loss amount is equal to or greater than a predetermined value when the optical level of the wavelength-multiplexed optical signal is equal to or greater than a threshold value, and the wavelength-multiplexed optical signal The second variable attenuator is controlled so that the amount of loss is smaller than a predetermined value when the light level of
The second photodetector controls the first variable attenuator so that the loss amount is equal to or greater than a predetermined value when the optical level of the third wavelength multiplexed optical signal is equal to or greater than a threshold value. An optical multiplexing / branching device that controls the first variable attenuator so that the loss amount becomes smaller than a predetermined value when the optical level of the wavelength multiplexed optical signal is lower than a threshold value. Demultiplexing the wavelength multiplexed optical signal input from the first transmission path into a first wavelength multiplexed optical signal and a second wavelength multiplexed optical signal having different frequency bands;
A first variable attenuator attenuating the second wavelength-multiplexed optical signal by a loss amount according to the optical level of the third wavelength-multiplexed optical signal input from the second transmission path;
The second wavelength multiplexed optical signal, the first wavelength multiplexed optical signal, and the third wavelength multiplexed optical signal input through the first variable attenuator are combined and output to the third transmission line. Comprising steps,
The second wavelength multiplexed optical signal is output to a fourth transmission line,
The optical multiplexing and branching method, wherein a frequency band of the third wavelength multiplexed optical signal is the same as that of the second wavelength multiplexed optical signal. The optical coupling / branching method according to claim 7,
Monitoring the optical level of the third wavelength multiplexed optical signal;
When the optical level of the third wavelength multiplexed optical signal is equal to or greater than a threshold, controlling the first variable attenuator so that the loss amount is equal to or greater than a predetermined value;
And a step of controlling the first variable attenuator so that the loss amount becomes smaller than a predetermined value when the optical level of the third wavelength multiplexed optical signal is lower than a threshold value. The optical coupling / branching method according to claim 7,
Demultiplexing the third wavelength multiplexed optical signal into a first output signal and a second output signal;
Transmitting only a first wavelength band of the first output signal and outputting a dummy signal;
Transmitting only a second wavelength band different from the first wavelength band of the second output signal and outputting a wavelength multiplexed optical signal;
A second variable attenuator attenuating the dummy signal by a loss amount according to an optical level of the wavelength-multiplexed optical signal input from the first transmission path ;
Another multiplexing circuit multiplexes the other wavelength multiplexed optical signal and the dummy signal input via the second variable attenuator to output another third wavelength multiplexed optical signal;
Said second wavelength-multiplexed optical signals inputted through said first variable attenuator, said a first wavelength-multiplexed optical signal, said further input via a multiplexing circuit said further third wavelength-multiplexed optical Combining the signal and outputting the signal to the third transmission line. The optical combining and branching method according to claim 9,
Monitoring the optical level of the wavelength multiplexed optical signal input from the first transmission line ;
Monitoring the optical level of the third wavelength-multiplexed optical signal; and controlling the second variable attenuator so that the amount of loss exceeds a predetermined value when the optical level of the wavelength-multiplexed optical signal is greater than or equal to a threshold value. And steps to
Controlling the second variable attenuator so that the loss amount is smaller than a predetermined value when the optical level of the wavelength-multiplexed optical signal is below a threshold;
When the optical level of the third wavelength multiplexed optical signal is equal to or greater than a threshold, controlling the first variable attenuator so that the loss amount is equal to or greater than a predetermined value;
And a step of controlling the first variable attenuator so that the loss amount becomes smaller than a predetermined value when the optical level of the third wavelength multiplexed optical signal is lower than a threshold value.

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