Optical node device and signal superimposition method

Abstract

This optical node device comprises: a modulation amplitude correcting unit that generates correction information used for correcting the amplitude of a modulation signal based on a control signal such that the superimposition ratio in superimposing, on an optical signal, the control signal used for controlling a subscriber device is a desired superimposition ratio; a driver that converts an externally inputted control signal to the modulation signal and that adjusts the amplitude of the modulation signal by using the correction information generated by the modulation amplitude correcting unit; and a superimposition unit that superimposes, on the optical signal, the modulation signal as adjusted by the driver.　

Description

[Technical field]

[0001] The present invention relates to an optical node device and a signal superposition method. [Background technology]

[0002] Conventionally, a system has been proposed in which a subscriber device communicates with a counterpart subscriber device by optical signals via an optical node device called a photonic gateway. FIG. 8 is a diagram for explaining the configuration of a conventional optical communication system 100. As shown in FIG. 8, the conventional optical communication system 100 includes a plurality of subscriber devices 200-1 to 200-3, a plurality of subscriber devices 300-1 to 300-3, a plurality of optical node devices 350-1 to 350-2, and a plurality of control units 400-1 to 400-2. The optical node device 350-1 and the optical node device 350-2 are connected via an optical communication NW 600 configured by an optical transmission path.

[0003] The section between the subscriber devices 200-1 to 200-3 and the optical node device 350-1, and the section between the subscriber devices 300-1 to 300-3 and the optical node device 350-2 are called optical access sections. The section between the optical node device 350-1 and the optical node device 350-2 is called a relay section. In the example shown in Fig. 8, the subscriber devices 200-1, 200-2 and the optical node device 350-1 are connected by a single-core optical transmission path, and the subscriber device 200-3 and the optical node device 350-1 are connected by a two-core optical transmission path.

[0004] The optical node device 350-1 is composed of an optical SW 500, a plurality of transmission / reception separation units 510-1 to 510-2, a plurality of wavelength multiplexers / demultiplexers 520-1 to 520-2, and a plurality of signal superimposing units 530-1 to 530-3. The optical node device 350-2 is composed of an optical SW 550, a plurality of transmission / reception separation units 560-1 to 560-2, a plurality of wavelength multiplexers / demultiplexers 570-1 to 570-2, and a plurality of signal superimposing units 580-1 to 580-3. The control unit 400-1 manages the subscriber device 200 and controls the operation of the optical node device 350-1. The control unit 400-2 manages the subscriber device 300 and controls the operation of the optical node device 350-2.

[0005] Here, consider a state in which the subscriber device 200-1 and the subscriber device 300-1 are communicating with each other. Each of the subscriber devices 200 and 300 is equipped with a wavelength-tunable transceiver. For example, the subscriber device 200-1 transmits an optical signal using a wavelength previously assigned by the subscriber device management control unit 420-1 of the control unit 400-1. Regarding wavelength assignment, the methods described in, for example, non-patent documents 1 and 2 are used. Similarly, the subscriber device 300-1 transmits an optical signal using a wavelength previously assigned by the subscriber device management control unit 420-2 of the control unit 400-2. In this way, in the optical communication system 100, communication is performed between the subscriber device 200 and the subscriber device 300 using the wavelength previously assigned by each of the control units 400-1 and 400-2.

[0006] For example, in the subscriber devices 200-1 and 200-2, single-core bidirectional communication is performed within the optical SW 500, 550 in the optical access section and each optical node device 350-1, 350-2. Therefore, between the optical SW 500 and the wavelength multiplexer / demultiplexer 520-1, 520-2, a transmission / reception separator 510-1, 510-2 is provided, which separates or multiplexes the transmission and reception wavelengths. The transmission / reception separators 510-1, 510-2 and the wavelength multiplexers / demultiplexers 520-1, 520-2 are connected by optical transmission paths, respectively.

[0007] Similarly, between the optical SW 550 and the wavelength multiplexer / demultiplexer 570-1, 570-2, there are provided transmission / reception separators 560-1, 560-2, which separate or multiplex the transmission and reception wavelengths. The transmission / reception separators 560-1, 560-2 and the wavelength multiplexer / demultiplexer 570-1, 570-2 are connected by optical transmission lines, respectively. Therefore, the repeater section is connected by a two-core optical transmission line. Means for realizing the transmission / reception separators 510, 560 include, for example, a circulator.

[0008] For the subscriber devices 200-1 and 200-2, we considered a case where the optical access section is a single-core bidirectional communication like the conventional optical access communication, but it is also assumed that the optical access section is connected by separate optical fibers for transmission and reception, as in the subscriber devices 200-3 and 300-3. In this case, the connection between the optical SW and the wavelength multiplexer / demultiplexer is a connection configuration that does not go through a transmission / reception separation unit.

[0009] As shown in Fig. 8, by installing a signal superimposing unit 530 or 580 for superimposing a new optical signal between the wavelength multiplexer / demultiplexer 520 and the transmission / reception separator 510 or between the wavelength multiplexer / demultiplexer 570 and the transmission / reception separator 560, it is possible to superimpose a new signal on an optical signal transmitted from each optical node device to a subscriber device. For example, the signal superimposing unit 530 superimposes a new signal on an optical signal transmitted from the subscriber device 300 to the subscriber device 200. Here, an example of a signal newly superimposed on an optical signal is an AMCC (Auxiliary Management and Control Channel) signal (see, for example, Non-Patent Document 3). Meanwhile, the subscriber device can selectively receive not only the original optical signal but also the newly superimposed optical signal. [Prior art documents] [Non-patent literature]

[0010] [Non-Patent Document 1] Kanai, “Photonic Gateway Supporting All-Photonics Network,” IEICE General Conference, B-8-20, March 2021. [Non-Patent Document 2] K. Honda et al., “Photonic Gateway for Direct and Protocol-Independent End-to-End User Connections”, OFC2021. [Non-Patent Document 3] T. Kanai et al., “In-Line Protocol-Independent Control and Management Method in End-to-End Optical Connections via Photonic Gateway”, ECOC2021. Summary of the Invention [Problem to be solved by the invention]

[0011] When an optical signal output from a subscriber device is superimposed on another optical signal using a signal superimposing unit installed in the path, modulation is applied to the optical signal output from the opposing subscriber device. However, since there is variation in the optical signal strength output from the opposing subscriber device and in the transmission path environment (e.g., loss), the optical signal strength input to the signal superimposing unit is not constant. Therefore, it is unclear to what extent the amplitude of the modulated signal in the signal superimposing unit should be set, and there is a problem in that the modulation degree of the optical signal to be superimposed cannot be set to a desired value.

[0012] In this way, if the optimum superposition ratio cannot be set, the following adverse effects can be expected: If the superposition ratio is too large, the effect on the original optical signal (which becomes noise) will be large, and as a result, the subscriber device on the opposite side will not be able to demodulate the signal. On the other hand, if the superposition ratio is too small, the subscriber device on the opposite side will not be able to receive the newly superposed signal.

[0013] In view of the above circumstances, the present invention aims to provide a technology that, when a new signal is superimposed during transmission of an optical signal, can superimpose the new signal at a superimposition ratio that allows demodulation and reception by a subscriber device on the opposing side. [Means for solving the problem]

[0014] One aspect of the present invention is an optical node device comprising: a modulation amplitude correction unit that generates correction information for correcting the amplitude of a modulated signal based on a control signal for controlling a subscriber device so that the superposition ratio when the control signal is superimposed on an optical signal becomes a desired superposition ratio; a driver that converts the control signal input from outside into a modulated signal and adjusts the amplitude of the modulated signal using the correction information generated by the modulation amplitude correction unit; and a superposition unit that superimposes the modulated signal adjusted by the driver onto an optical signal.

[0015] One aspect of the present invention is a signal superposition method that generates correction information for correcting the amplitude of a modulated signal based on a control signal for controlling a subscriber device so that the superposition ratio when the control signal is superimposed on an optical signal becomes a desired superposition ratio, converts the control signal input from outside into a modulated signal, adjusts the amplitude of the modulated signal using the correction information, and superimposes the adjusted modulated signal on the optical signal. Effect of the Invention

[0016] According to the present invention, when a new signal is superimposed during transmission of an optical signal, it is possible to superimpose the new signal at a superimposition ratio that allows demodulation and reception by the subscriber device on the opposite side. [Brief description of the drawings]

[0017] [Figure 1] 1 is a diagram illustrating a configuration of an optical communication system according to a first embodiment. [Diagram 2] 4 is a diagram illustrating an example of the configuration of a signal superimposing unit in the first embodiment. FIG. [Diagram 3] 5 is a flowchart showing a flow of processing in the optical node device in the first embodiment. [Figure 4] FIG. 11 is a diagram illustrating an example of the configuration of a signal superimposing unit in the second embodiment. [Diagram 5] FIG. 13 is a diagram illustrating an example of the configuration of a signal superimposing unit in the third embodiment. [Figure 6] FIG. 13 is a diagram illustrating an example of the configuration of a signal superimposing unit in the fourth embodiment. [Figure 7] FIG. 13 is a diagram illustrating an example of the configuration of a signal superimposing unit in the fifth embodiment. [Figure 8] FIG. 1 is a diagram for explaining the configuration of a conventional optical communication system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (First embodiment) 1 is a diagram showing a configuration of an optical communication system 1 in the first embodiment. The optical communication system 1 includes a plurality of optical node devices 10, 15, a plurality of subscriber devices 20-1 to 20-3, a plurality of subscriber devices 30-1 to 30-3, and a plurality of control units 40-1 to 40-2. The number of subscriber devices 20 and 30 may be one or more. The configuration of the optical communication system 1 is basically the same as the configuration shown in FIG. 8, except for the configurations of the optical node devices 10 and 15.

[0019] The optical node device 10 and each subscriber device 20, and the optical node device 15 and each subscriber device 30 are connected by optical transmission paths. The optical transmission paths are, for example, optical fibers. The optical node device 10 and the optical node device 15 are connected via an optical communication NW 60 configured by the optical transmission paths.

[0020] In the following description, the section between the subscriber devices 20-1 to 20-3 and the optical node device 10, and the section between the subscriber devices 30-1 to 30-3 and the optical node device 15 are described as optical access sections, and the section between the optical node device 10 and the optical node device 15 is described as a relay section. In the example shown in Fig. 1, each of the subscriber devices 20-1, 20-2 and the optical node device 10 are connected by a single-core optical transmission line, and the subscriber device 20-3 and the optical node device 10 are connected by a two-core optical transmission line. Similarly, each of the subscriber devices 30-1, 30-2 and the optical node device 15 are connected by a single-core optical transmission line, and the subscriber device 30-3 and the optical node device 15 are connected by a two-core optical transmission line.

[0021] The optical node device 10 is composed of an optical SW 50, a plurality of transmission / reception separation units 51-1 to 51-2, a plurality of wavelength multiplexers / demultiplexers 52-1 to 52-2, and a plurality of signal superimposing units 53-1 to 53-3. Note that the numbers of the optical SW 50, transmission / reception separation units 51, wavelength multiplexers / demultiplexers 52, and signal superimposing units 53 included in the optical node device 10 are not limited to the numbers shown in FIG. 1, and may be changed as appropriate depending on the system configuration.

[0022] The optical SW50 is an optical switch having a plurality of ports 50-1 and a plurality of ports 50-2. An optical signal input to a certain port of the optical SW50 is output from another port. For example, an optical signal input to port 50-1 of the optical SW50 is output from port 50-2. In the optical SW50, a connection relationship between the port 50-1 and the port 50-2 is set under the control of the control unit 40-1.

[0023] The transmission / reception separators 51-1 to 51-2 are, for example, circulators. The transmission / reception separators 51-1 to 51-2 have at least three or more ports. In the following description, it is assumed that the transmission / reception separators 51-1 to 51-2 have three ports. A first port of the transmission / reception separator 51-1 is connected to any one of the ports 50-2 of the optical SW 50. A second port of the transmission / reception separator 51-1 is connected to the wavelength multiplexer / demultiplexer 52-2. A third port of the transmission / reception separator 51-1 is connected to the signal superimposing unit 53-1. An optical signal input to the first port of the transmission / reception separator 51-1 is output from the second port. An optical signal input to the second port of the transmission / reception separator 51-1 is output from the third port. An optical signal input to the third port of the transmission / reception separator 51-1 is output from the first port.

[0024] Similarly, a first port of the transmission / reception separator 51-2 is connected to any second port of the optical SW 50. A second port of the transmission / reception separator 51-2 is connected to the wavelength multiplexer / demultiplexer 52-2. A third port of the transmission / reception separator 51-2 is connected to the signal superimposing unit 53-2. An optical signal input to the first port of the transmission / reception separator 51-2 is output from the second port 54-2. An optical signal input to the second port of the transmission / reception separator 51-2 is output from the third port. An optical signal input to the third port of the transmission / reception separator 51-2 is output from the first port.

[0025] The wavelength multiplexers / demultiplexers 52-1 and 52-2 multiplex or demultiplex the input optical signals. The wavelength multiplexers / demultiplexers 52-1 and 52-2 are, for example, AWGs (Arrayed Waveguide Gratings).

[0026] The signal superimposing units 53-1 to 53-3 superimpose the optical signal output from the control unit 40-1 onto the optical signal transmitted on the optical transmission line. For example, the signal superimposing units 53-1 to 53-3 are provided on the optical transmission line through which the optical signal transmitted from the subscriber device 30 to the subscriber device 20 is transmitted. In this case, the signal superimposing units 53-1 to 53-3 superimpose the optical signal output from the control unit 40-1 onto the optical signal transmitted from the subscriber device 30 to the subscriber device 20. The optical signal output from the control unit 40-1 is a control signal including, for example, an instruction for setting the subscriber device 20 or changing the wavelength, and is, for example, an AMCC signal.

[0027] The optical node device 15 is composed of an optical SW 55, a plurality of transmission / reception separation units 56-1 to 56-2, a plurality of wavelength multiplexers / demultiplexers 57-1 to 57-2, and a plurality of signal superimposing units 58-1 to 58-3. Note that the numbers of the optical SW 55, transmission / reception separation units 56, wavelength multiplexers / demultiplexers 57, and signal superimposing units 58 included in the optical node device 15 are not limited to the numbers shown in FIG. 1, and may be changed as appropriate depending on the system configuration.

[0028] The optical SW55 is an optical switch having a plurality of ports 55-1 and a plurality of ports 55-2. An optical signal input to a certain port of the optical SW55 is output from another port. For example, an optical signal input to port 55-1 of the optical SW55 is output from port 55-2. The optical SW55 is set to have a connection relationship between the ports 55-1 and 55-2 under the control of the control unit 40-2.

[0029] The transmission / reception separators 56-1 to 56-2 are, for example, circulators. The transmission / reception separators 56-1 to 56-2 have at least three or more ports. In the following description, it is assumed that the transmission / reception separators 56-1 to 56-2 have three ports. A first port of the transmission / reception separator 56-1 is connected to any one of the ports 55-2 of the optical SW 55. A second port of the transmission / reception separator 56-1 is connected to the wavelength multiplexer / demultiplexer 57-2. A third port of the transmission / reception separator 56-1 is connected to the signal superimposing unit 58-1. An optical signal input to the first port of the transmission / reception separator 56-1 is output from the second port. An optical signal input to the second port of the transmission / reception separator 56-1 is output from the third port. An optical signal input to the third port of the transmission / reception separator 56-1 is output from the first port.

[0030] Similarly, a first port of the transmission / reception separator 56-2 is connected to one of the ports 55-2 of the optical SW 55. A second port of the transmission / reception separator 56-2 is connected to the wavelength multiplexer / demultiplexer 57-1. A third port of the transmission / reception separator 56-2 is connected to the signal superimposing unit 58-3. An optical signal input to the first port of the transmission / reception separator 56-2 is output from the second port. An optical signal input to the second port of the transmission / reception separator 56-2 is output from the third port. An optical signal input to the third port of the transmission / reception separator 56-2 is output from the first port.

[0031] The signal superimposing units 58-1 to 58-3 superimpose the optical signal output from the control unit 40-2 onto the optical signal transmitted on the optical transmission path. For example, the signal superimposing units 58-1 to 58-3 are provided on the optical transmission path along which the optical signal transmitted from the subscriber device 20 to the subscriber device 30 is transmitted. In this case, the signal superimposing units 58-1 to 58-3 superimpose the optical signal output from the control unit 40-2 onto the optical signal transmitted from the subscriber device 20 to the subscriber device 30. The optical signal output from the control unit 40-2 is a control signal including, for example, an instruction for setting the subscriber device 30 or changing the wavelength, and is, for example, an AMCC signal.

[0032] The subscriber devices 20 and 30 each have a tunable optical transmitter / receiver as an optical transceiver. Therefore, the subscriber devices 20 and 30 can communicate at any wavelength. The wavelengths used by the subscriber devices 20 and 30 for communication are assigned by the control unit 40. For example, the wavelength used by the subscriber device 20 for communication is assigned by the control unit 40-1, and the wavelength used by the subscriber device 30 for communication is assigned by the control unit 40-2. The optical transceiver may be an optical transceiver with an AMCC function. In this case, the wavelengths used by the subscriber devices 20 and 30 are controlled via a control signal superimposed by the AMCC. The subscriber devices 20 and 30 are, for example, ONUs (Optical Network Units) installed in subscriber homes.

[0033] The control units 40-1 and 40-2 control at least the subscriber devices 20 and 30 and the optical switches 50 and 55. Here, the control of the subscriber devices 20 and 30 includes, for example, allocation of emission wavelengths to the subscriber devices 20 and 30, an optical stop command, and a command to change the wavelength. The control unit 40-1 transmits an optical signal including an optical stop command and an command to change the wavelength, which are commands other than those for the initial connection, to the signal superimposing unit 53 to superimpose the optical signal addressed to the destination subscriber device 20. The control unit 40-2 transmits an optical signal including an optical stop command and an command to change the wavelength, which are commands other than those for the initial connection, to the signal superimposing unit 58 to superimpose the optical signal addressed to the destination subscriber device 30. The control of the optical switches 50 and 55 includes, for example, setting the connection between the ports of the optical switches 50 and 55 and setting the optical path. The control units 40-1 and 40-2 perform similar processes except for the control objects, so the control unit 40-1 will be taken as an example for explanation.

[0034] The control unit 40-1 includes an optical SW control unit 41-1 and a subscriber device management control unit 42-1. The optical SW control unit 41-1 controls the connection between the ports of the optical SW 50. Specifically, the optical SW control unit 41-1 controls the connection between the ports of the optical SW 50 so that an optical signal transmitted from the subscriber device 20 is forwarded to a destination subscriber device (e.g., the subscriber device 30-1). Controlling the connection between the ports means setting a path so that a certain port is connected to another port. Furthermore, the optical SW control unit 41-1 controls the connection between the ports of the optical SW 50 so that an optical signal addressed to the subscriber device 20 is forwarded to the subscriber device 20.

[0035] The subscriber equipment management and control unit 42-1 assigns wavelengths to each subscriber equipment 20. When the subscriber equipment management and control unit 42-1 assigns wavelengths to each subscriber equipment 20, the optical SW control unit 41-1 sets a path between the ports of the optical SW 50 so that the subscriber equipment 20 to which the wavelength is to be assigned is connected to the subscriber equipment management and control unit 42-1. Furthermore, the subscriber equipment management and control unit 42-1 transmits a control signal to be superimposed on the optical signal to the signal superimposing unit 53.

[0036] The subscriber device management control unit 42-1 stores a management table. The management table includes information for identifying the subscriber device 20, information on the wavelength assigned to the subscriber device 20, and information on the optical SW 50 to which the subscriber device 20 is connected (e.g., information on the port to which the subscriber device 20 is connected, etc.). Each control unit 40 is composed of one or more processors. Each functional unit of each control unit 40 is realized by mounting each control unit 40 on one server.

[0037] Fig. 2 is a diagram showing an example of the configuration of the signal superimposing units 53 and 58 in the first embodiment. Since the signal superimposing units 53 and 58 have the same configuration, the signal superimposing unit 53 will be described as an example in Fig. 2. The signal superimposing unit 53 includes, for example, a modulator driver 531, a modulator 532, a splitter 533, an optical power monitor 534, and a modulation amplitude correction unit 535.

[0038] The modulator driver 531 is a functional unit for driving the modulator 532. Specifically, a control signal output from the subscriber equipment management control unit 42 included in the control unit 40 is input to the modulator driver 531. The modulator driver 531 converts the control signal input from the subscriber equipment management control unit 42 into a modulated signal. For example, when the control signal output from the subscriber equipment management control unit 42 is a simple bit string, the modulator driver 531 generates a modulated signal having an electrical amplitude and a waveform that match the characteristics of the modulator 532 based on the input control signal. Note that the amplitude in the present invention is the modulation amplitude, which is different from the electric field amplitude. Furthermore, the modulator driver 531 adjusts the electrical amplitude of the modulated signal input to the modulator 532 using the value output from the modulation amplitude correction unit 535. Adjusting the electrical amplitude of the modulated signal means converting the electrical amplitude of the modulated signal so that it becomes the value output from the modulation amplitude correction unit 535.

[0039] The modulator 532 is an optical modulator that modulates an input optical signal using a modulation signal output from the modulator driver 531. As a result, the modulator 532 superimposes the modulated signal on the optical signal. Examples of optical modulators include an LN (LnNbO3) modulator, an EA (Electroabsorption) modulator, a semiconductor optical amplifier (SOA), and a variable optical attenuator (VOA). In the first embodiment, an LN modulator or an EA modulator is used as the optical modulator. The modulator 532 is one aspect of a superimposing unit.

[0040] The splitter 533 splits and outputs the optical signal output from the modulator 532. The optical signal split by the splitter 533 is input to an optical power monitor 534 via a first path, and is output to the outside via a second path. In the first embodiment, the optical signal input to the splitter 533 is a signal in which a control signal is superimposed on the optical signal output from the subscriber device 30.

[0041] The optical power monitor 534 monitors the optical intensity of the optical signal output from the modulator 532. The optical power monitor 534 transmits the monitoring result to the modulation amplitude correction unit 535.

[0042] The modulation amplitude correction unit 535 generates information (hereinafter referred to as "correction information") for correcting the electrical amplitude of the modulated signal output from the modulator driver 531 so as to achieve a desired superposition ratio based on the monitoring result output from the optical power monitor 534. The modulation amplitude correction unit 535 inputs the correction information to the modulator driver 531.

[0043] In the first embodiment, the overlap ratio is expressed by the following formula (1). Superposition ratio (%) = control signal optical amplitude / optical signal average power × 100 Equation (1)

[0044] Therefore, in order to realize a desired superposition ratio, it is necessary to set the optical amplitude of the control signal according to the average power of the optical signal. Here, the optical amplitude of the control signal means, for example, the difference in optical power when the control signal is a non-return-to-zero (NRZ) signal and when it is "1" and when it is "0". When the control signal is a sine wave, it corresponds to the difference in optical power between the peak and the valley. The modulation amplitude correction unit 535 generates correction information according to the optical average power input to the modulator 532 according to the above formula (1), and inputs it to the modulator driver 531. The modulator driver 531 outputs the control signal set to the specified amplitude as a modulation signal to the modulator 532 according to the input information.

[0045] When a signal specifying the superposition ratio is input from the subscriber equipment management control unit 42, the modulation amplitude correction unit 535 may input correction information including information for achieving the superposition ratio specified by the input signal to the modulator driver 531. In this case, the signal superposition unit 53 does not need to include the optical power monitor 534.

[0046] FIG. 3 is a flowchart showing the flow of processing of the optical node device 10 in the first embodiment. Assume that an optical signal is input to the signal superimposing unit 53 of the optical node device 10 (step S101). The modulator 532 of the signal superimposing unit 53 modulates the input optical signal (step S102). The optical signal modulated by the modulator 532 is input to the splitter 533. The splitter 533 splits the input optical signal. The optical signal split by the splitter 533 is input to the optical power monitor 534 and is also output to the subscriber device 20.

[0047] The optical power monitor 534 monitors the intensity of the optical signal split by the splitter 533 (step S103). The optical power monitor 534 outputs the monitoring result to the modulation amplitude correction unit 535. The modulation amplitude correction unit 535 generates correction information based on the monitoring result output from the optical power monitor 534 (step S104). The modulation amplitude correction unit 535 outputs the correction information to the modulator driver 531.

[0048] Here, it is assumed that a control signal is input from the control unit 40 to the signal superimposing unit 53 (step S105). The modulator driver 531 converts the control signal into a modulated signal (step S106). The modulator driver 531 adjusts the electrical amplitude of the modulated signal to be input to the modulator 532 using the correction information output from the modulation amplitude correcting unit 535 (step S107). The modulator driver 531 outputs the adjusted modulated signal to the modulator 532. The modulator 532 modulates the input optical signal using the adjusted modulated signal output from the modulator driver 531, thereby superimposing the control signal on the optical signal (step S108).

[0049] According to the optical communication system 100 configured as above, when a new signal is superimposed during the transmission of an optical signal, it is possible to superimpose the new signal at a superimposition ratio that allows the subscriber device on the opposite side to demodulate and receive the signal. Specifically, in the optical communication system 100, the optical intensity of the optical signal output from the modulator 532 is measured by the optical power monitor 534, and the value is fed back to the modulator driver 531, thereby controlling the modulation amplitude to be newly superimposed according to the optical intensity. This makes it possible to realize a desired superimposition ratio. Therefore, when a new signal is superimposed during the transmission of an optical signal, it is possible to superimpose the new signal at a superimposition ratio that allows the subscriber device on the opposite side to demodulate and receive the signal.

[0050] Second Embodiment In the second embodiment, the system configuration of the optical communication system 100 is similar to that of the first embodiment, but the configuration of the signal superimposing unit is different from that of the first embodiment. Specifically, in the first embodiment, the optical intensity of the optical signal modulated by the modulator is monitored, whereas in the second embodiment, the optical intensity of the optical signal before being modulated by the modulator is monitored, which is a difference from the first embodiment. The differences from the first embodiment will be described below.

[0051] 4 is a diagram showing an example of the configuration of a signal superimposing unit 53a in the second embodiment. The signal superimposing unit 53a includes, for example, a modulator driver 531, a modulator 532, a splitter 533, an optical power monitor 534, and a modulation amplitude correction unit 535.

[0052] When an optical signal is input to the signal superimposing unit 53a, the optical signal is first split by the splitter 533. The optical signal split by the splitter 533 is input to the optical power monitor 534 via the first path, and is input to the modulator 532 via the second path. In the second embodiment, the optical signal input to the splitter 533 is a signal before being modulated by the modulator 532. The subsequent processing is similar to that in the first embodiment.

[0053] According to the optical communication system 100 in the second embodiment configured as above, it is possible to obtain the same effects as those of the first embodiment.

[0054] (Third embodiment) In the third embodiment, the system configuration of the optical communication system 100 is similar to that of the first embodiment, but the configuration of the signal superimposing unit is different from that of the first embodiment. Specifically, in the first embodiment, only the optical intensity of the optical signal is monitored, whereas in the third embodiment, the signal amplitude is also monitored in addition to the optical intensity of the optical signal, which is a difference from the first embodiment. The differences from the first embodiment will be described below.

[0055] 5 is a diagram showing an example of the configuration of a signal superimposing unit 53b in the third embodiment. The signal superimposing unit 53b includes, for example, a modulator driver 531, a modulator 532, a splitter 533, a modulation amplitude correction unit 535b, and an optical power & amplitude monitor 536. The signal superimposing unit 53b differs in configuration from the signal superimposing unit 53 in that it includes an optical power & amplitude monitor 536 and a modulation amplitude correction unit 535b instead of the optical power monitor 534 and the modulation amplitude correction unit 535.

[0056] The optical power & amplitude monitor 536 monitors the optical intensity and amplitude of the optical signal output from the modulator 532. The optical power & amplitude monitor 536 transmits the monitor result to the modulation amplitude correction unit 535b.

[0057] The modulation amplitude correction unit 535b generates correction information so as to achieve a desired superposition ratio based on the monitor result output from the optical power & amplitude monitor 536. The modulation amplitude correction unit 535b inputs the correction information to the modulator driver 531.

[0058] In the third embodiment, the overlap ratio is expressed by the following formula (2). Superimposition ratio (%) = control signal amplitude / main signal amplitude × 100 Equation (2)

[0059] Therefore, in order to realize a desired superposition ratio, it is necessary to set the optical amplitude of the control signal according to the average power of the optical signal. Here, the optical amplitude of the control signal is, for example, the difference between when the control signal is "1" and when it is "0" when the control signal is an NRZ signal. When the control signal is a sine wave, it corresponds to the difference between the peak and the valley. In this case, it is assumed that the amplitude is measured as an electrical signal, not an optical signal. The modulation amplitude correction unit 535b generates correction information according to the optical average power and signal amplitude input to the modulator 532 according to the above formula (2), and inputs it to the modulator driver 531. The modulator driver 531 outputs the control signal set to the specified amplitude to the modulator 532 as a modulation signal according to the input information.

[0060] According to the optical communication system 100 of the third embodiment configured as described above, by monitoring the amplitude of the optical signal in addition to the intensity of the optical signal, it becomes possible to handle signals with different extinction ratios even with the same optical power.

[0061] The signal superimposing unit 53b may be configured to monitor both the optical power and the signal amplitude before input to the modulator 532, as in the second embodiment. In this case, the signal superimposing unit 53b has a configuration in which the optical power monitor 534 is replaced with an optical power & amplitude monitor 536 and the modulation amplitude correction unit 535 is replaced with a modulation amplitude correction unit 535b in the configuration shown in FIG. 4. As a result, when an optical signal is input to the signal superimposing unit 53b, the optical signal is first split by the splitter 533. The optical signal split by the splitter 533 is input to the optical power & amplitude monitor 536 via the first path and input to the modulator 532 via the second path. In this case, the optical signal input to the splitter 533 is a signal before modulation by the modulator 532. The optical power & amplitude monitor 536 monitors the optical intensity and the amplitude of the optical signal split by the splitter 533. The optical power & amplitude monitor 536 transmits the monitoring result to the modulation amplitude correction unit 535b. The subsequent processing is similar to the processing shown in the third embodiment.

[0062] (Fourth embodiment) In the fourth embodiment, the system configuration of the optical communication system 100 is similar to that of the first embodiment, but the configuration of the signal superimposing unit is different from that of the first embodiment. Specifically, the fourth embodiment differs from the first embodiment in that a variable optical attenuator is used as an optical modulator. The differences from the first embodiment will be described below.

[0063] 6 is a diagram showing an example of the configuration of a signal superimposing unit 53c in the fourth embodiment. The signal superimposing unit 53c includes, for example, a modulator driver 531, a splitter 533, an optical power monitor 534, a modulation amplitude correction unit 535, and a variable optical attenuator 537. The signal superimposing unit 53c differs in configuration from the signal superimposing unit 53 in that it includes a variable optical attenuator 537 instead of the modulator 532. The modulation amplitude correction unit 535 and the modulator driver 531 generate a modulation signal based on a control signal that matches the characteristics of the variable optical attenuator 537.

[0064] The variable optical attenuator 537 adjusts the intensity of the input optical signal. Specifically, the variable optical attenuator 537 attenuates the intensity of the input optical signal by modulating it with the modulation signal output from the modulator driver 531. The variable optical attenuator 537 is, for example, a VOA. In this way, the variable optical attenuator 537 superimposes the modulation signal on the optical signal. The variable optical attenuator 537 is one aspect of a superimposing unit.

[0065] The signal superimposing unit 53c may be configured to monitor the optical power before input to the modulator 532, as in the second embodiment. When configured in this way, the signal superimposing unit 53c is configured to use the variable optical attenuator 537 as a specific example of the modulator 532 configured as shown in Fig. 4. In this case, the signal superimposing unit 53c performs the same processes as in the second embodiment, except for the operations performed by the variable optical attenuator 537.

[0066] The signal superimposing unit 53c may be configured to monitor the signal amplitude in addition to the optical intensity of the optical signal as in the third embodiment. When configured in this manner, the signal superimposing unit 53c includes an optical power & amplitude monitor 536 instead of the optical power monitor 534.

[0067] Fifth embodiment In the fifth embodiment, the system configuration of the optical communication system 100 is similar to that of the first embodiment, but the configuration of the signal superimposing unit is different from that of the first embodiment. Specifically, the fifth embodiment differs from the first embodiment in that a semiconductor optical amplifier is used as an optical modulator. The differences from the first embodiment will be described below.

[0068] 7 is a diagram showing a configuration example of a signal superimposing unit 53d in the fifth embodiment. The signal superimposing unit 53d includes, for example, a modulator driver 531, a splitter 533, an optical power monitor 534, a modulation amplitude correction unit 535, and an optical gain medium 538. The signal superimposing unit 53d is different in configuration from the signal superimposing unit 53 in that it includes an optical gain medium 538 instead of the modulator 532. The modulation amplitude correction unit 535 and the modulator driver 531 generate a modulation signal based on a control signal that matches the characteristics of the optical gain medium 538.

[0069] The optical gain medium 538 adjusts the intensity of the input optical signal. Specifically, the optical gain medium 538 amplifies the intensity of the input optical signal by modulating it using the modulation signal output from the modulator driver 531. The optical gain medium 538 is, for example, an SOA. In this way, the optical gain medium 538 superimposes the modulation signal on the optical signal. The optical gain medium 538 is one aspect of a superimposing unit.

[0070] The signal superimposing unit 53d may be configured to monitor the optical power before input to the modulator 532, as in the second embodiment. When configured in this way, the signal superimposing unit 53d is configured to use an optical gain medium 538 as a specific example of the modulator 532 configured as shown in Fig. 4. In this case, the signal superimposing unit 53d performs the same processing as in the second embodiment, except for the operation performed by the optical gain medium 538.

[0071] The signal superimposing unit 53d may be configured to monitor the signal amplitude in addition to the optical intensity of the optical signal as in the third embodiment. When configured in this manner, the signal superimposing unit 53d includes an optical power & amplitude monitor 536 instead of the optical power monitor 534.

[0072] Some of the functional units of the optical node devices 10, 15 and the control unit 40 in the above-mentioned embodiments may be realized by a computer. In this case, a program for realizing this function may be recorded in a computer-readable recording medium, and the program recorded in the recording medium may be read into a computer system and executed to realize the function. Note that the "computer system" referred to here includes hardware such as an OS and peripheral devices.

[0073] In addition, the term "computer-readable recording medium" refers to portable media such as flexible disks, optical magnetic disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into computer systems. Furthermore, the term "computer-readable recording medium" may also include those that dynamically hold a program for a short period of time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, and those that hold a program for a certain period of time, such as a volatile memory inside a computer system that serves as a server or client in such a case. Furthermore, the above program may be one that realizes part of the above-mentioned functions, or may be one that can realize the above-mentioned functions in combination with a program already recorded in the computer system, or may be one that is realized using a programmable logic device such as an FPGA.

[0074] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and designs that do not deviate from the gist of the present invention are also included. [Industrial Applicability]

[0075] The present invention can be applied to an optical communication system in which a control signal is superimposed on an optical signal. [Explanation of symbols]

[0076] 10, 15...Optical node device, 20, 20-1 to 20-3, 30, 30-1 to 30-3...Subscriber device, 40, 40-1 to 40-2...Control unit, 41, 41-1 to 41-2...Optical SW control unit, 42, 42-1 to 42-2...Subscriber device management control unit, 51, 51-1 to 51-2, 56, 56-1 to 56-2...Transmitter / receiver separation unit, 52, 52-1 to 52-2, 57, 57-1 to 57-2...Wavelength multiplexer / demultiplexer, 53, 53a, 53b, 53c, 53d, 53-1 to 53-3, 58, 58-1 to 58-3...Signal superposition unit, 531...Modulator driver, 532...Modulator, 533...Splitter, 534...Optical power monitor, 535...modulation amplitude correction section, 536...optical power & amplitude monitor, 537...variable optical attenuator, 538...optical gain medium

Claims

1. a modulation amplitude correction unit that generates correction information for correcting the amplitude of a modulation signal based on a control signal for controlling a subscriber device so that a superposition ratio when the control signal is superimposed on an optical signal becomes a desired superposition ratio; a driver that converts the control signal input from outside into a modulation signal and adjusts the amplitude of the modulation signal using the correction information generated by the modulation amplitude correction unit; a superimposing unit that superimposes the modulated signal adjusted by the driver onto an optical signal; Equipped with a monitor for monitoring at least the intensity of the optical signal before or after the modulating signal is superimposed; the modulation amplitude correction unit generates the correction information based on the intensity of the optical signal obtained by the monitor; The optical node device further comprises a branching unit that branches the input optical signal and outputs the branched optical signal to the monitor and the superimposing unit when the monitor monitors at least the intensity of the optical signal before the superimposing of the modulated signal.

2. a modulation amplitude correction unit that generates correction information for correcting the amplitude of a modulation signal based on a control signal for controlling a subscriber device so that a superposition ratio when the control signal is superimposed on an optical signal becomes a desired superposition ratio; a driver that converts the control signal input from outside into a modulation signal and adjusts the amplitude of the modulation signal using the correction information generated by the modulation amplitude correction unit; a superimposing unit that superimposes the modulated signal adjusted by the driver onto an optical signal; Equipped with a monitor for monitoring at least the intensity of the optical signal before or after the modulating signal is superimposed; the modulation amplitude correction unit generates the correction information based on the intensity of the optical signal obtained by the monitor; When the monitor monitors at least the intensity of the optical signal after superimposition of the modulated signal, the optical node device further includes a branching unit downstream of the superimposition unit that branches the input optical signal and outputs it to the monitor and to the outside.

3. The monitor further monitors the amplitude of the optical signal; the modulation amplitude correction unit generates the correction information based on the intensity and amplitude of the optical signal obtained by the monitor.

3. The optical node device according to claim 1 or 2.

4. The superposition unit is any one of an LN (LnNbO3) modulator, an EA (Electroabsorption) modulator, a semiconductor optical amplifier (SOA), and a variable optical attenuator (VOA). The optical node device according to claim 1 .

5. generating correction information for correcting an amplitude of a modulated signal based on a control signal for controlling a subscriber device so that a superposition ratio when the control signal is superimposed on an optical signal becomes a desired superposition ratio; converting the control signal input from outside into a modulation signal, and adjusting the amplitude of the modulation signal using the correction information; superimposing the adjusted modulation signal on an optical signal; monitoring at least the intensity of the optical signal with a monitor before or after the modulating signal is superimposed; generating the correction information based on the intensity of the optical signal obtained by the monitor; A signal superposition method in which, when the monitor monitors at least the intensity of the optical signal before the modulated signal is superposed, the input optical signal is branched by a branching unit and output to the monitor and a superposition unit that superposes the modulated signal.

6. generating correction information for correcting an amplitude of a modulated signal based on a control signal for controlling a subscriber device so that a superposition ratio when the control signal is superimposed on an optical signal becomes a desired superposition ratio; converting the control signal input from outside into a modulation signal, and adjusting the amplitude of the modulation signal using the correction information; superimposing the adjusted modulation signal on an optical signal; monitoring at least the intensity of the optical signal with a monitor before or after the modulating signal is superimposed; generating the correction information based on the intensity of the optical signal obtained by the monitor; A signal superposition method in which, when the monitor monitors at least the intensity of the optical signal after the modulated signal is superimposed, a branching unit branches the optical signal on which the modulated signal is superimposed after the modulated signal is superimposed, and outputs the branched signal to the monitor and to an external device.

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