JP6693901B2 - Optical amplifier, wavelength division multiplexer, and optical splitter - Google Patents

Description

  The present invention relates to a wavelength division multiplexing optical communication system.

  In a wavelength division multiplexing optical communication system, a wavelength path (optical signal of wavelength) is usually set according to demand. That is, in the wavelength division multiplexing optical communication system, there is a period in which the maximum number of wavelength paths that can be set and the number of wavelength paths that are actually set (set number) do not match. This is because the initial investment can be suppressed by increasing the number of devices according to the demand balance. On the other hand, the optical amplifier is designed based on the maximum number of wavelength paths. For example, in an optical amplifier device with a constant total gain, such as used in an optical submarine cable system, the total gain is set based on the maximum number of wavelength paths. The gain of the wavelength path increases, which causes each wavelength path to be amplified more than necessary, which may rather deteriorate the quality of the wavelength path. Therefore, Patent Documents 1 and 2 disclose that a dummy light source is provided in the wavelength division multiplexer. The dummy light source transmits the optical signal of the wavelength of the wavelength path that is not set, and the gain given to the set wavelength path becomes constant regardless of the number of wavelength paths set, preventing the quality deterioration of the wavelength path. can do.

Japanese Patent No. 5076660 Japanese Patent No. 564829

  However, the number of required dummy light sources decreases as the set number of wavelength paths increases, and when the set number of wavelength paths reaches the maximum number, all dummy light sources are no longer needed. Therefore, a configuration that does not require a dummy light source is desired.

  The present invention provides a technique for preventing quality deterioration of each wavelength path without using a dummy light source.

According to an aspect of the present invention, an optical amplification device includes a first amplification unit that amplifies an input first optical signal and outputs a second optical signal, and the second optical signal with one or more first wavelengths. A third optical signal including the optical signal and a demultiplexing unit that demultiplexes into a fourth optical signal including an optical signal of a second wavelength other than the one or more first wavelengths of a predetermined wavelength, and outputting the fourth optical signal. The second amplifying means for amplifying the fourth optical signal and outputting the fifth optical signal, and the multiplexing means for multiplexing and outputting the third optical signal and the fifth optical signal are provided . The above-mentioned optical signal of the first wavelength is a signal light included in the first optical signal .

  According to the present invention, it is possible to prevent quality deterioration of each wavelength path without using a dummy light source.

The figure which shows a part of wavelength division multiplexing optical communication system by one Embodiment. 1 is a configuration diagram of an optical amplification device according to an embodiment. 1 is a configuration diagram of an optical amplification device according to an embodiment. The figure which shows a part of wavelength division multiplexing optical communication system by one Embodiment. The block diagram of the optical branching device by one embodiment. 1 is a configuration diagram of an optical amplification device according to an embodiment. 1 is a configuration diagram of a wavelength division multiplexer according to an embodiment.

  Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. The following embodiments are exemplifications, and the present invention is not limited to the contents of the embodiments. Further, in each of the following drawings, components that are not necessary for explaining the embodiment are omitted from the drawings.

<First embodiment>
FIG. 1 shows a part of a wavelength division multiplexing optical communication system, more specifically, a wavelength division multiplexer 1 and an optical amplifier 2 connected to the wavelength division multiplexer 1 for amplifying a wavelength division optical signal transmitted by the wavelength division multiplexer 1. Shows. The wavelength division multiplexer 1 is equipped with a maximum of six light sources 10 of light sources # 1 to # 6. The light sources # 1 to # 6 are assumed to generate continuous light of wavelengths # 1 to # 6, respectively. In addition, each light source 10 has a modulator that modulates the emitted continuous light with an input electric signal (not shown). Therefore, each light source 10 outputs the modulated light of the corresponding wavelength to the wavelength multiplexing unit 11. The wavelength multiplexer 11 wavelength-multiplexes the modulated light from each light source 10 and outputs a wavelength-multiplexed optical signal. In FIG. 1, a total of three light sources 10, light sources # 1 to # 3, are mounted in the wavelength multiplexing device 1, and light sources # 4 to # 6 are not mounted in the wavelength multiplexing device 1. That is, the wavelength-multiplexed optical signal output from the wavelength-multiplexing apparatus 1 includes optical signals of three wavelengths # 1 to # 3 (indicated by solid lines), as indicated by reference numeral 51 in FIG. Optical signals of wavelengths # 4 to # 6 (indicated by dotted lines) corresponding to the light sources # 4 to # 6 are not included.

  The optical amplifier device 2 according to the present embodiment receives a wavelength-multiplexed optical signal indicated by reference numeral 51, amplifies optical signals of three wavelengths of wavelengths # 1 to # 3, and also outputs dummy light of wavelengths # 4 to # 6. The wavelength-multiplexed optical signal with the signal added is output. More specifically, the optical amplification device 2 according to the present embodiment receives a wavelength-multiplexed optical signal including an optical signal of a wavelength being used in a wavelength-multiplexed optical communication system, A wavelength-multiplexed optical signal including an optical signal of a wavelength that is unused in the multiplex optical communication system is output. Therefore, in the wavelength-multiplexed optical communication system, each optical amplifier connected to the downstream side of the optical amplifier 2 always has a wavelength-multiplexed optical signal including optical signals of all wavelengths used in the wavelength-multiplexed optical communication system. Is input, the gain of the optical signal of each wavelength can be made constant regardless of the number of wavelengths of the optical signal actually used, and the quality of the optical signal can be maintained.

  FIG. 2 is a configuration diagram of the optical amplification device 2 according to the present embodiment. The amplification unit 20 is, for example, an erbium-doped optical fiber (EDF), and amplifies the wavelength-division-multiplexed optical signal 51 (FIG. 1) input by pumping light from a pumping light source (not shown). In the EDF, a broadband noise component called spontaneous emission light (ASE light) is generated. Therefore, as indicated by reference numeral 52, the wavelength-multiplexed optical signal output from the amplification unit 20 is obtained by adding the ASE light to the optical signals of wavelengths # 1 to # 3 included in the input wavelength-multiplexed optical signal 51. Become. The wavelength selective switch 21, which is controlled by a control unit (not shown) or an external control device, separates the input wavelength-multiplexed optical signal for each wavelength and outputs it to either the amplification unit 22 or the multiplexing unit 23. Here, the optical signals of wavelengths # 1 to # 3 (hereinafter, also referred to as signal light) included in the input wavelength-multiplexed optical signal 51 are output to the multiplexing unit 23, and the input wavelength-multiplexed optical signal 51. The wavelength selective switch 21 is set so that the wavelengths # 4 to # 6 not included in # 1 are output to the amplification unit 22. Therefore, the optical signal output from the wavelength selective switch 21 to the multiplexing unit 23 is as indicated by reference numeral 53. The optical signal output from the wavelength selective switch 21 to the multiplexing unit 23 is a combination of the signal lights # 1 to # 3 (shown by shading) and the ASE light in the same band as the signal lights # 1 to # 3. However, since the level of the ASE light is smaller than that of the signal lights # 1 to # 3, only the signal lights # 1 to # 3 are shown in the figure. On the other hand, the signal output from the wavelength selective switch 21 to the amplification unit 22 is, as indicated by reference numeral 54, the ASE light of wavelengths # 4 to # 6 (hereinafter, also referred to as ASE light # 4 to # 6, and displayed in white. Yes.) Since the wavelength selective switch 21 also functions as a bandpass filter for optical signals of respective wavelengths, the ASE lights # 4 to # 6 are band-limited as shown in FIG.

  The amplification unit 22 is, for example, an erbium-doped optical fiber (EDF), and amplifies the input ASE light # 4 to # 6 light by pumping light from a pumping light source (not shown). Since the ASE light is also generated in the amplifier 22, the optical signal output by the amplifier 22 includes the amplified ASE light # 4 to # 6 and the ASE light generated in the amplifier 22, as indicated by reference numeral 55. Will be things. Since the power given to the amplification by the amplification section 22 is given to the inputted optical signal with priority, the levels of the ASE lights # 4 to # 6 included in the signal outputted by the amplification section 22 are determined by the amplification section 22. It becomes stronger than the level of the ASE light included in the output signal. The multiplexing unit 23 multiplexes the signal from the wavelength selective switch 21 and the signal from the amplification unit 22, and outputs a wavelength multiplexed optical signal indicated by reference numeral 56. Note that the levels of the ASE light generated in the amplification unit 22 and the ASE light of wavelengths # 1 to # 3 generated in the amplification unit 20 are lower than those of the signal lights # 1 to # 3 and the ASE lights # 4 to # 6. The ASE light is omitted also in the wavelength division multiplexed optical signal 56.

  As described above, in this embodiment, the ASE light generated in the optical amplification section such as the EDF is used as the dummy light. Therefore, a dummy light source for outputting dummy light is not required, and a wavelength-multiplexed optical signal including optical signals of a fixed number of wavelengths can always be output. Therefore, even if the optical amplifiers connected to the downstream side of the optical amplifier 2 are the same optical amplifiers as the conventional ones, the fluctuation of the power for amplification given to the optical signal of each wavelength is suppressed and the gain is increased. Can be suppressed from deteriorating the quality of the set wavelength path. The optical amplifier 2 is used on the most upstream side of the wavelength division multiplexing optical communication system. Therefore, the wavelength multiplexer 1 and the optical amplifier 2 of FIG. 1 can be configured as one wavelength multiplexer. Further, in the present embodiment, the optical signal output by the wavelength selective switch 21 and the optical signal output by the amplifier 22 are multiplexed by the multiplexer 23, but a wavelength selective switch is used instead of the multiplexer 23. You can also By using the wavelength selective switch instead of the multiplexing unit 23, for example, the amplification unit 22 generates a wavelength different from the ASE light (wavelengths # 4 to 6 in the example of FIG. 2) that the amplification unit 22 amplifies. The ASE light (wavelengths # 1 to # 3 in the example of FIG. 2) to be generated can be prevented from being included in the wavelength multiplexed optical signal 56.

<Second embodiment>
The wavelength division multiplexer 1 of FIG. 1 is provided with a light source 10 and performs modulation in the wavelength division multiplexer 1. Here, if the light source 10 becomes an obstacle, the optical signal emitted by the light source 10 is not included in the wavelength-multiplexed optical signal. Further, as the wavelength multiplexing device, there is also a device that performs wavelength multiplexing by directly converting an optical signal input from an external device or by converting the wavelength. In such a case, the wavelength path passing through the wavelength division multiplexer may be disconnected due to a failure of another device in the network. Also in this case, the optical signal of a certain wavelength of the wavelength-multiplexed optical signal output by the wavelength-multiplexed device is not included in the wavelength-multiplexed optical signal due to a failure of another device in the network. That is, the number of optical signals included in the wavelength-multiplexed optical signal output by the wavelength-multiplexing device changes not only according to demand but also due to a failure. Therefore, in the present embodiment, the optical amplifying device 2 monitors the input wavelength-multiplexed optical signal and determines which wavelength of the optical signals of each wavelength that can be used does not include the optical signal of The wavelength selective switch 21 is dynamically controlled based on the determination result.

  FIG. 3 is a configuration diagram of the optical amplification device 2 according to the present embodiment. The same components as those already described are designated by the same reference numerals, and the description thereof will be omitted. The monitoring controller 24 monitors the output of the amplifier 20 and determines which wavelength of the optical signal is actually included in the wavelength-multiplexed optical signal input to the optical amplifier 2. More specifically, the monitoring controller 24 determines that a wavelength having a signal level equal to or higher than the threshold value is the wavelength of the optical signal included in the wavelength-multiplexed optical signal input to the optical amplification device 2, and inputs the wavelength. Of the optical signals of each wavelength that can be included in the wavelength-multiplexed optical signal, it is determined that the optical signal of the wavelength whose level is less than the threshold value is not included. Then, the wavelength selective switch 21 is controlled so that the optical signal of the wavelength actually included is output to the multiplexer 23 and the optical signal of the wavelength not included is output to the amplifier 22.

  With the above configuration, even if the number of optical signals included in the wavelength-multiplexed optical signal changes due to a failure, the wavelength-multiplexed optical signal output from the optical amplifier 2 is an optical signal with a fixed number of wavelengths. And the quality of each optical signal included in the wavelength division multiplexed optical signal can be prevented from deteriorating. Further, the monitoring controller 24 amplifies when the levels of the optical signals of all the wavelengths that can be included in the input wavelength-multiplexed optical signal are equal to or higher than the threshold value, that is, when there is no optical signal of the wavelength that is not included. The operation of the unit 22 can be stopped. As a result, it is possible to prevent only unnecessary ASE light from being generated by the amplification unit 22 and being multiplexed by the multiplexing unit 23. The monitoring controller 24 may monitor the input of the amplifier 20 instead of the output of the amplifier 20.

<Third embodiment>
The optical branching device 3 including the optical amplifying device 2 of FIG. 2 or 3 will be described below. FIG. 4 is an explanatory diagram of the optical branching device 3 used in, for example, an optical submarine cable system. The optical branching device 3 respectively receives wavelength-multiplexed optical signals from the wavelength-multiplexing device A and the wavelength-multiplexing device B in the so-called upstream direction, multiplexes them, and transmits them to the wavelength-multiplexing device C. In the example of FIG. 4, the wavelength division multiplexer A transmits a wavelength division multiplexed optical signal obtained by wavelength multiplexing the signal lights # 1 to # 3. On the other hand, the wavelength division multiplexer B transmits a wavelength division multiplexing optical signal obtained by wavelength multiplexing the signal lights # 4 to # 6. Then, the optical branching device 3 multiplexes these and transmits a wavelength division multiplexed optical signal including the signal lights # 1 to # 6. In the downstream direction, the optical branching device 3 receives the wavelength-multiplexed optical signals of the signal lights # 1 to # 6 from the wavelength-multiplexer C and outputs the wavelength-multiplexed optical signals including the signal lights # 1 to # 3. A wavelength division multiplexing optical signal including the signal lights # 4 to # 6 is transmitted to the wavelength multiplexing apparatus B.

  FIG. 5 is a configuration diagram of the optical branching device 3 according to the present embodiment. The optical amplifiers 2-1 and 2-2 are, for example, the same as the optical amplifier 2 of FIG. 3, and monitor the input wavelength-multiplexed optical signal. The optical amplifier 2-1 receives the wavelength multiplexed optical signal from the wavelength multiplexer A, and the optical amplifier 2-2 receives the wavelength multiplexed optical signal from the wavelength multiplexer B. FIG. 5 shows each signal when the wavelength-multiplexed optical signal from the wavelength-multiplexed device B is no longer input to the optical amplifier 2-2 due to a failure in the section between the wavelength-multiplexed device B and the optical branching device 3. Is shown. Since the optical signal is no longer input to the optical amplification device 2-2, the monitoring control unit 24 of the optical amplification device 2-2 outputs the wavelengths # 4 to # 6 to the amplification unit 22 so as to output the wavelength selective switch 21. To control. Therefore, the optical amplification device 2-2 outputs an optical signal including the ASE lights # 4 to # 6. The multiplexer 31 multiplexes the optical signals output by the optical amplifiers 2-1 and 2-2. Therefore, the optical branching device 3 always transmits the wavelength multiplexing optical signal including the optical signals of wavelengths # 1 to # 6, regardless of the failure in the section between the wavelength multiplexing device A or B and the optical branching device 3. . Therefore, it is possible to suppress the variation in the gain applied to the signal light of each wavelength by the optical amplifying device in the section from the optical branching device 3 to the wavelength multiplexing device C, and to suppress the deterioration of the quality due to the variation in the gain.

<Other forms>
For example, the optical branching device 3 described with reference to FIGS. 4 and 5 includes the first wavelength-multiplexed optical signal including the signal lights # 1 to # 3 received from the wavelength-multiplexing device A in the upstream direction, and the wavelength-multiplexing device. The second wavelength-multiplexed optical signal including the signal lights # 4 to # 6 received from B is multiplexed and output, and at the time of failure, the input of the first wavelength-multiplexed optical signal and / or the second wavelength-multiplexed optical signal is interrupted. Instead of optical signals, ASE light was used. In such a case, as the optical branching device 3, the optical amplifying device 4 shown in FIG. 6 can be used instead of the optical amplifying device 2 shown in FIGS.

  In FIG. 6, for example, the first wavelength-multiplexed optical signal including the signal lights # 1 to # 3 from the wavelength-multiplexing apparatus A is input to the amplification unit 20. The bandpass filter 25 is a bandpass filter that passes the bands of the signal lights # 1 to # 3, and normally, outputs the first wavelength-multiplexed optical signal including the signal lights # 1 to # 3 amplified by the amplification unit 20. Output. The monitoring controller 24 monitors the output of the bandpass filter 25, determines that the first wavelength-multiplexed optical signal is disconnected when the signal level becomes equal to or lower than the threshold value, and increases the gain of the amplifier 20. As a result, the amplification unit 20 outputs the ASE light of a predetermined level, as indicated by reference numeral 57. The bandpass filter 25 limits the band of each wavelength of the input ASE light, and thus outputs an optical signal including the ASE light # 1 to # 3, as indicated by reference numeral 58. The monitoring controller 24 controls the gain of the amplifier 20 based on the output level of the bandpass filter 25. More specifically, the monitoring control unit 24 adjusts the gain of the amplification unit 20 so that the output level of the bandpass filter 25 becomes constant regardless of whether the first wavelength-multiplexed optical signal is input to the amplification unit 20. Control. Therefore, by using the optical amplifying device 4 shown in FIG. 6 instead of the optical amplifying devices 2-1 and 2-2 of FIG. 5, the same operation as that of the optical branching device 3 described with reference to FIGS. 4 and 5 is performed. It is possible to realize an optical branching device that

  Further, the optical amplifying device 4 shown in FIG. 6 can be used not only for the optical branching device but also for the wavelength multiplexing device. FIG. 7 shows the configuration of a wavelength division multiplexer using the optical amplifier 4 of FIG. The wavelength multiplexer of FIG. 6 has three light sources (including a modulation function) and a wavelength multiplexer that wavelength-multiplexes the optical modulation signals output from the three light sources on one substrate. In FIG. 7, the board 61-1 is mounted, but the boards 61-2 and 61-3 are not mounted. Further, the optical amplification device 4 of FIG. 6 is mounted corresponding to each substrate, and is shown as optical amplification devices 4-1 to 4-3 in FIG. 7. Since the substrate 61-1 corresponding to the optical amplifier 4-1 is mounted, the optical amplifier 4-1 amplifies and outputs the wavelength-multiplexed optical signal including the signal lights # 1 to # 3. On the other hand, since the substrates 61-2 and 61-3 corresponding to the optical amplifiers 4-2 and 4-3 are not mounted, the optical amplifiers 4-2 and 4-3 are the ASE lights # 4 to # 6. , ASE lights # 7 to # 9 are output. Therefore, the wavelength multiplexing unit 11 always outputs the optical signals of wavelengths # 1 to # 9 regardless of the mounting state of the board.

  20, 22: Amplifying unit, 21: Wavelength selective switch, 23: Multiplexing unit

Claims (9)

First amplification means for amplifying the input first optical signal and outputting a second optical signal;
A third optical signal including the second optical signal including one or more first wavelength optical signals, and a fourth including a second optical signal including a second wavelength other than the one or more first wavelengths of a predetermined wavelength. Separation means for separating and outputting to an optical signal,
Second amplifying means for amplifying the fourth optical signal and outputting a fifth optical signal;
Multiplexing means for multiplexing and outputting the third optical signal and the fifth optical signal,
Equipped with
The optical amplification device , wherein the one or more optical signals of the first wavelength are signal lights included in the first optical signal . First amplification means for amplifying the input first optical signal and outputting a second optical signal;
A third optical signal including the second optical signal including one or more first wavelength optical signals, and a fourth including a second optical signal including a second wavelength other than the one or more first wavelengths of a predetermined wavelength. Separation means for separating and outputting to an optical signal,
Second amplifying means for amplifying the fourth optical signal and outputting a fifth optical signal;
Multiplexing means for multiplexing and outputting the one or more optical signals of the first wavelength contained in the third optical signal and the optical signal of the second wavelength contained in the fifth optical signal;
Equipped with
The optical amplification device , wherein the one or more optical signals of the first wavelength are signal lights included in the first optical signal . Claim 1 or 2, characterized by further comprising control means for controlling said separating means to determine the optical signal of the second wavelength by monitoring the first optical signal or the second optical signal The optical amplification device according to. The optical amplifying device according to claim 3 , wherein the control means stops the operation of the second amplifying means when there is no optical signal of the second wavelength. A wavelength division multiplexer comprising the optical amplifier according to any one of claims 1 to 4 . A first optical amplifier,
A second optical amplifier,
A multiplexing device that multiplexes and outputs the outputs of the first optical amplification device and the second optical amplification device;
An optical branching device comprising:
The first optical amplification device is the optical amplification device according to any one of claims 1 to 4 ,
An optical branching device, wherein the second optical amplifying device is the optical amplifying device according to any one of claims 1 to 4 . Amplification means for amplifying a first optical signal including optical signals of a plurality of wavelengths and outputting a second optical signal;
A band-pass filter to which the second optical signal is input and which passes each of the optical signals of the plurality of wavelengths;
Control means for monitoring the output of the bandpass filter, and controlling the gain of the amplification means based on the monitoring result,
Equipped with
The control means controls the gain of the amplification means such that the output of the bandpass filter becomes constant regardless of whether or not the first optical signal is input to the amplification means. Amplification device. A wavelength division multiplexer comprising the optical amplifier according to claim 7 . A first optical amplifier,
A second optical amplifier,
A multiplexing device that multiplexes and outputs the outputs of the first optical amplification device and the second optical amplification device;
An optical branching device comprising:
The first optical amplification device is the optical amplification device according to claim 7 ,
The optical branching device, wherein the second optical amplifying device is the optical amplifying device according to claim 7 .

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