Optical transmitter, optical receiver, optical communication system, and control signal superimposition method

Abstract

An optical transmitter comprising a main signal generation unit that generates a main signal, a control signal generation unit that generates a control signal which is slower than the main signal, a variable-wavelength driver that converts the control signal generated by the control signal generation unit to a signal for wavelength control, and a variable-wavelength transmitter that generates a modulated optical signal on the basis of the main signal and the signal for wavelength control.

Description

[Technical Field]

[0001] The present invention relates to an optical transmitter, an optical receiver, an optical communication system, and a control signal superimposing method. [Background technology]

[0002] Conventionally, a method using a control signal called AMCC (Auxiliary Management and Control Channel) has been used as a method for simultaneously transmitting and receiving a main signal and a control signal using a single optical transmitter. In the method using the AMCC signal, the AMCC signal is superimposed on the main signal in a low-frequency region, so that the main signal and the AMCC signal can be simultaneously transmitted and received without affecting the main signal (see, for example, Non-Patent Document 1). Generally, the modulation speed of the AMCC signal is several hundred kbps compared to the main signal with a modulation speed of 10 Gbit / s. The modulation method used is intensity modulation, and there are two types: baseband modulation and modulation using a carrier signal.

[0003] According to Non-Patent Document 1, there are two methods for superimposing an AMCC signal. The first method, "baseband modulation," is a method in which an AMCC signal is superimposed on a main signal as a baseband signal on the transmitter side. In the "baseband modulation" superimposition method, the AMCC signal is separated on the receiver side using a filter such as an LPF (Low-Pass Filter).

[0004] The second method, "low-frequency pilot tone," involves upconverting the AMCC signal to a specific carrier frequency at the transmitter and superimposing it onto the main signal. With the "low-frequency pilot tone" superimposition method, the AMCC signal is obtained by demodulating it using signal processing at the receiver. In each superimposition method, the ratio of the amplitudes of the main signal and the AMCC signal is defined as the modulation index, and an appropriate value is set according to the system requirements. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] ITU-T G.989.2 Amendment 1, “40-Gigabit-capable-passive optical networks 2 (NG-PON2): Physical media dependent (PMD) layer specification”, Oct. 2020. Summary of the Invention [Problem to be solved by the invention]

[0006] The modulation depth must be set to an appropriate value according to the system requirements and the required system budget for each of the main signal and AMCC signal. In other words, the modulation depth must be set so that both the main signal and the AMCC signal meet the desired budget. The modulation depth is mainly adjusted by controlling the signal amplitude of the AMCC signal.

[0007] However, because AMCC signals generally use intensity modulation methods (such as OOK (On-Off-Keying) and PSK (Phase Shift Keying)), there is a trade-off between the modulation depth and the signal characteristics of the main signal. Therefore, increasing the modulation depth and improving the signal characteristics (such as receiving sensitivity) of the AMCC signal results in a degradation of the signal characteristics of the main signal. This problem is not limited to AMCC signals, but is common to control signals that are superimposed on the main signal and transmitted and received simultaneously with the main signal.

[0008] In view of the above circumstances, an object of the present invention is to provide a technique that can superimpose a control signal without affecting the strength of a main signal. [Means for solving the problem]

[0009] One aspect of the present invention is an optical transmitter comprising: a main signal generating unit that generates a main signal; a control signal generating unit that generates a control signal slower than the main signal; a wavelength-tunable driver that converts the control signal generated by the control signal generating unit into a signal for wavelength control; and a wavelength-tunable transmitter that generates a modulated optical signal based on the main signal and the signal for wavelength control.

[0010] One aspect of the present invention is a receiver comprising: a main signal generating unit that generates a main signal; a control signal generating unit that generates a control signal slower than the main signal; a wavelength-tunable driver that converts the control signal generated by the control signal generating unit into a signal for wavelength control; and a wavelength-tunable transmitter that generates a modulated optical signal based on the main signal and the signal for wavelength control; a branching unit that receives the modulated optical signal transmitted from an optical transmitter and branches the received modulated optical signal; a main signal receiving unit that acquires the main signal based on the modulated optical signal branched by the branching unit; and a received wavelength identifying unit that converts the modulated optical signal branched by the branching unit into an electrical signal and acquires wavelength information indicating the control signal from the electrical signal.

[0011] One aspect of the present invention is an optical communication system comprising an optical transmitter, an optical receiver, and a photonic gateway that relays communications between the optical transmitter and the optical receiver, wherein the optical transmitter comprises: a main signal generation unit that generates a main signal; a control signal generation unit that generates a control signal slower than the main signal; a wavelength-tunable driver that converts the control signal generated by the control signal generation unit into a signal for wavelength control; and a wavelength-tunable transmitter that generates a modulated optical signal based on the main signal and the signal for wavelength control and transmits the generated modulated optical signal to the optical receiver via the photonic gateway, and the optical receiver receives the modulated optical signal via the photonic gateway and comprises: a separation unit that demultiplexes or branches the received modulated optical signal; and a control signal processing unit that acquires the control signal based on the demultiplexed or branched modulated optical signal.

[0012] One aspect of the present invention is a control signal superimposing method that generates a main signal, generates a control signal slower than the main signal, converts the generated control signal into a signal for wavelength control, and generates a modulated optical signal based on the main signal and the signal for wavelength control. [Effects of the Invention]

[0013] The present invention makes it possible to superimpose a control signal without affecting the strength of the main signal. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram illustrating an example of the configuration of an optical communication system according to a first embodiment. [Figure 2] FIG. 3 is a sequence diagram showing a processing flow of the optical communication system in the first embodiment. [Figure 3] FIG. 10 is an explanatory diagram of a wavelength-tunable light source according to a second embodiment. [Figure 4] FIG. 10 is a diagram showing the relationship between the DBR current and the oscillation wavelength of the wavelength-tunable light source in the second embodiment. [Figure 5] FIG. 10 is an explanatory diagram of a wavelength-tunable light source according to a third embodiment. [Figure 6] FIG. 11 is a diagram showing the relationship between the phase current and the oscillation wavelength of the wavelength-tunable light source according to the third embodiment. [Figure 7] FIG. 10 is a diagram illustrating an example of the configuration of an optical receiver according to a fourth embodiment. [Figure 8] FIG. 10 is a diagram illustrating an example of the configuration of an optical receiver according to a fifth embodiment. [Figure 9] FIG. 11 is a diagram for explaining the characteristics of an optical filter in the fifth embodiment. [Figure 10] FIG. 13 is a diagram illustrating an example of the configuration of an optical communication system according to a sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (First embodiment) Fig. 1 is a diagram showing an example of the configuration of an optical communication system 100 according to the first embodiment. The optical communication system 100 includes one or more optical transmitters 10 and one or more optical receivers 20. Fig. 1 shows one optical transmitter 10 and one optical receiver 20. The optical transmitter 10 and the optical receiver 20 are connected via an optical transmission path. The optical transmission path is, for example, an optical fiber.

[0016] The optical transmitter 10 includes a main signal generator 11, a modulator driver 12, a control signal generator 13, a wavelength-tunable driver 14, a wavelength-tunable light source 15, and an optical modulator 16. The wavelength-tunable light source 15 and the optical modulator 16 are configured as a wavelength-tunable transmitter.

[0017] The main signal generator 11 generates a main signal (for example, binary data).

[0018] The modulator driver 12 converts the main signal generated by the main signal generator 11 into a signal to be used for modulation by the optical modulator 16 (for example, an NRZ (Non-Return-to-Zero) electrical signal).

[0019] The control signal generator 13 generates a control signal. The control signal is, for example, an AMCC signal. The AMCC signal is a signal used for management and control.

[0020] The tunable wavelength driver 14 converts the control signal generated by the control signal generator 13 into a wavelength control signal (for example, an NRZ electrical signal). Here, the wavelength control signal differs depending on the tunable wavelength laser used as the tunable wavelength light source 15. For example, if the wavelength changes linearly with respect to the wavelength control signal (for example, voltage), a modulation signal like the main signal can be applied. On the other hand, if the wavelength changes discontinuously with respect to the wavelength control signal, such as in a DBR (Distributed Bragg Reflector)-LD, a control signal that matches the characteristics of the laser must be used. The tunable wavelength driver 14 is a device used to limit the oscillation wavelength of the tunable wavelength light source 15.

[0021] When the control signal is a binary bit string, the wavelength tunable driver 14 assigns a mark ("1") to a wavelength with lower transmission path loss (e.g., λ1) and a space ("0") to a wavelength with higher transmission loss (e.g., λ2). This suppresses deterioration of the signal-to-noise ratio of the mark and enables higher sensitivity (longer transmission distance).

[0022] The tunable light source 15 changes the oscillation wavelength in accordance with the wavelength control signal converted by the tunable driver 14. The tunable light source 15 outputs light of a wavelength corresponding to the oscillation wavelength.

[0023] As described above, by allocating a control signal to a wavelength, the wavelength-tunable light source 15 can include the control signal as wavelength information in an optical signal. A wavelength sweep light source whose oscillation wavelength can be controlled externally can be used as the wavelength-tunable light source 15. Note that a wavelength-tunable semiconductor laser (for example, a DBR laser, a DFB (Distributed-Feedback) laser, a TDA-DFB (Tunable Distributed Amplification - DFB) laser, or an external cavity laser) may also be used as the wavelength-tunable light source 15.

[0024] The optical modulator 16 modulates the light output from the wavelength-tunable light source 15 with the signal (corresponding to the main signal) output from the modulator driver 12. In this way, the optical modulator 16 generates a modulated optical signal.

[0025] The optical receiver 20 includes a branching unit 21, a main signal receiving unit 22, a receiving wavelength identifying unit 23, and a control signal processing unit 24.

[0026] The branching device 21 branches the modulated optical signal transmitted from the optical transmitter 10. The modulated optical signal branched by the branching device 21 is output to a main signal receiving unit 22 and a reception wavelength identifying unit 23.

[0027] The main signal receiving unit 22 acquires the main signal based on the modulated optical signal branched by the branching unit 21. For example, the main signal receiving unit 22 converts the modulated optical signal into an electrical signal and acquires the main signal from the electrical signal.

[0028] The receiving wavelength identifying unit 23 converts the modulated optical signal branched by the branching device 21 into an electrical signal. The receiving wavelength identifying unit 23 acquires wavelength information from the electrical signal. For example, the receiving wavelength identifying unit 23 acquires wavelength information by monitoring the electrical signal. The wavelength information acquired by the receiving wavelength identifying unit 23 is information indicating a control signal. For example, as described above, if the control signal is a binary bit string, a mark (“1”) is assigned to a wavelength with lower transmission path loss (e.g., λ1), and a space (“0”) is assigned to a wavelength with higher transmission loss (e.g., λ2). Therefore, the receiving wavelength identifying unit 23 can acquire wavelength information based on the electrical signal. For example, a device capable of acquiring wavelength information, such as an optical spectrum analyzer, is used as the receiving wavelength identifying unit 23. Therefore, the receiving wavelength identifying unit 23 is not limited to an optical spectrum analyzer, and a wavelength multiplexer / demultiplexer using a diffraction grating or the like may be used.

[0029] The control signal processing unit 24 receives the wavelength information acquired by the receiving wavelength identification unit 23 as input. The control signal processing unit 24 acquires a control signal based on the input wavelength information. For example, the control signal processing unit 24 acquires a control signal from the wavelength indicated by the wavelength information. Information on the wavelength to which the control signal is assigned is notified in advance from the optical transmitter 10.

[0030] FIG. 2 is a sequence diagram showing the flow of processing in the optical communication system 100 in the first embodiment. The main signal generator 11 of the optical transmitter 10 generates a main signal (step S101). The main signal generator 11 outputs the generated main signal to the modulator driver 12. The modulator driver 12 converts the main signal generated by the main signal generator 11 into a signal to be used for modulation by the optical modulator 16 (step S102). The modulator driver 12 outputs the converted signal to the optical modulator 16.

[0031] The control signal generating unit 13 generates a control signal (step S103). The control signal generating unit 13 outputs the generated control signal to the wavelength tunable driver 14. The wavelength tunable driver 14 converts the control signal output from the control signal generating unit 13 into a signal for wavelength control (step S104). The wavelength tunable driver 14 outputs the signal for wavelength control to the wavelength tunable light source 15. The wavelength tunable light source 15 outputs light of a wavelength corresponding to the wavelength control signal output from the wavelength tunable driver 14 (step S105).

[0032] The light output from the wavelength-tunable light source 15 is input to the optical modulator 16. The optical modulator 16 modulates the light output from the wavelength-tunable light source 15 with the changed signal output from the modulator driver 12 (step S106). As a result, the optical modulator 16 generates a modulated optical signal. The optical modulator 16 outputs the generated modulated optical signal to the optical transmission path (step S107). The modulated optical signal output from the optical transmitter 10 is input to the optical receiver 20.

[0033] The splitter 21 of the optical receiver 20 splits the input modulated optical signal (step S108). The modulated optical signal split by the splitter 21 is input to the main signal receiving unit 22 and the reception wavelength identifying unit 23. The main signal receiving unit 22 acquires the main signal from the input modulated optical signal (step S109). The reception wavelength identifying unit 23 converts the input modulated optical signal into an electrical signal and acquires wavelength information from the electrical signal (step S110). The reception wavelength identifying unit 23 outputs the acquired wavelength information to the control signal processing unit 24. The control signal processing unit 24 acquires a control signal based on the wavelength information (step S111).

[0034] In the optical communication system 100 configured as described above, the optical transmitter 10 modulates the main signal and the control signal separately. Specifically, the main signal is modulated by the optical modulator 16, and the control signal is modulated as the oscillation wavelength of the wavelength-tunable light source 15. In this way, the wavelength-tunable light source 15 changes the oscillation wavelength depending on the input signal. For example, if the control signal is a binary bit string, assigning marks to wavelengths with lower transmission path loss and spaces to wavelengths with higher transmission loss suppresses deterioration of the signal-to-noise ratio of the marks and increases sensitivity. In this way, transmitting and receiving the control signal as wavelength information makes it possible to superimpose the control signal on the main signal without affecting the intensity of the main signal.

[0035] (Modification 1 of the first embodiment) In the above-described embodiment, a configuration has been shown in which the wavelength-tunable transmitter included in the optical transmitter 10 modulates light output from the wavelength-tunable light source 15 with the optical modulator 16 to generate a modulated optical signal. However, the wavelength-tunable transmitter included in the optical transmitter 10 may be configured to perform direct modulation to generate a modulated optical signal. In such a configuration, the optical transmitter 10 generates a modulated optical signal by inputting a signal output from the modulator driver 12 to the wavelength-tunable light source 15.

[0036] (Second embodiment) In the second embodiment, a configuration will be described in which a DBR laser is used as a wavelength-tunable light source of an optical transmitter.

[0037] 3 is an explanatory diagram of a tunable light source 15 in a second embodiment. As shown in FIG. 3, the tunable light source 15 includes a front DBR region ("Front DBR" in FIG. 3), an active region ("Active" in FIG. 3), a phase region ("Phase" in FIG. 3), and a rear DBR region ("Rear DBR" in FIG. 3). In the second embodiment, the tunable driver 14 controls the wavelength by controlling the current input to the front DBR region and the rear DBR region included in the tunable light source 15.

[0038] Fig. 4 is a diagram showing the relationship between the DBR current and the oscillation wavelength of the wavelength-tunable light source 15 in the second embodiment. As shown in Fig. 4, the oscillation wavelength can be controlled by adjusting the DBR current, which represents the current input to the DBR region. Therefore, in the wavelength-tunable driver 14 in the second embodiment, by selecting any wavelength from the range of oscillation wavelengths shown in Fig. 4 as the wavelength for allocating a control signal, it becomes possible to transmit and receive the control signal as wavelength information.

[0039] (Modification 1 of the second embodiment) In the above-described embodiment, an example has been shown in which a DBR laser is used as the wavelength-tunable light source 15, but an SSG-DBR (Super Structure Grating - DBR) laser, an SG-DBR (Sampled Grating - DBR) laser, or a TDA (Tunable Distributed Amplification)-DFB laser may also be used. A method of using a DFB laser as the wavelength-tunable light source 15 and selecting the wavelength by controlling the chip temperature may also be used.

[0040] (Third embodiment) In the third embodiment, a configuration will be described in which a DBR laser is used as a wavelength-tunable light source of an optical transmitter.

[0041] Fig. 5 is an explanatory diagram of a tunable light source 15 in a third embodiment. As shown in Fig. 5, the tunable light source 15 includes a front DBR region ("Front DBR" in Fig. 5), an active region ("Active" in Fig. 5), a phase region ("Phase" in Fig. 5), and a rear DBR region ("Rear DBR" in Fig. 5). In the third embodiment, the tunable driver 14 controls the wavelength by controlling the current input to the phase region included in the tunable light source 15.

[0042] 6 is a diagram showing the relationship between the phase current and the oscillation wavelength of the wavelength-tunable light source 15 in the third embodiment. Here, the phase current represents the current input to the phase region. As shown in FIG. 4, the oscillation wavelength can be controlled by adjusting the phase current representing the current input to the phase region. Therefore, in the wavelength-tunable driver 14 in the third embodiment, by selecting any wavelength from the range of oscillation wavelengths shown in FIG. 6 as the wavelength for allocating the control signal, it becomes possible to transmit and receive the control signal as wavelength information.

[0043] (Modification 1 of the third embodiment) In the above-described embodiment, an example has been shown in which a DBR laser is used as the wavelength-tunable light source 15, but an SSG-DBR (Super Structure Grating - DBR) laser or an SG-DBR (Sampled Grating - DBR) laser may also be used. A method may also be used in which a DFB laser is used as the wavelength-tunable light source 15 and the wavelength is selected by controlling the chip temperature.

[0044] (Fourth embodiment) In the fourth embodiment, a configuration will be described in which an optical communication system including an optical transmitter according to any one of the first to third embodiments includes an optical receiver different from the optical receivers in the first to third embodiments.

[0045] An optical communication system including an optical transmitter according to any one of the first to third embodiments includes an optical receiver 20a, which is different from the optical receivers according to the first to third embodiments. Fig. 7 is a diagram showing an example of the configuration of the optical receiver 20a according to the fourth embodiment. The optical receiver 20a includes main signal receiving units 22-1, 22-1, a control signal processing unit 24, an optical multiplexer / demultiplexer 25, a signal separation unit 26, and a main signal processing unit 27.

[0046] The optical multiplexer / demultiplexer 25 demultiplexes the modulated optical signal transmitted from the optical transmitter 10. The optical multiplexer / demultiplexer 25 has a plurality of ports that output optical signals of different wavelengths, and a main signal receiver 22 is connected to each port. For example, the port that outputs an optical signal of wavelength λ1 is connected to main signal receiver 22-1, and the port that outputs an optical signal of wavelength λ2 is connected to main signal receiver 22-2. The modulated optical signals demultiplexed by the optical multiplexer / demultiplexer 25 are input to the main signal receivers 22-1 and 22-2. For example, the modulated optical signal of wavelength λ1 is input to the main signal receiver 22-1, and the modulated optical signal of wavelength λ2 is input to the main signal receiver 22-2.

[0047] Main signal receiving units 22-1 and 22-2 receive modulated optical signals of different wavelengths that have been demultiplexed by optical multiplexer / demultiplexer 25. When main signal receiving units 22-1 and 22-2 receive the modulated optical signal output from optical multiplexer / demultiplexer 25, they each output the received modulated optical signal to signal separator 26. The modulated optical signals output to signal separator 26 have different wavelengths.

[0048] The signal separator 26 determines which main signal receiver 22 has received the modulated optical signal, based on the modulated optical signal output from at least one of the main signal receivers 22-1 and 22-2. That is, the signal separator 26 determines whether the modulated optical signal has been received by the main signal receiver 22-1 or 22-2. The signal separator 26 determines the wavelength assigned to the control signal, based on the main signal receiver 22 that received the modulated optical signal. The signal separator 26 outputs the modulated optical signal to the main signal processor 27, and outputs the determination result and the modulated optical signal to the control signal processor 24. The determination result includes information on the wavelength assigned to the control signal.

[0049] The control signal processing unit 24 receives the determination result and the modulated optical signal output from the signal separation unit 26. The control signal processing unit 24 acquires a control signal based on the wavelength information indicated by the input determination result and the modulated optical signal.

[0050] The main signal processing unit 27 converts the modulated optical signal output from the signal separation unit 26 into an electrical signal, and obtains the main signal from the electrical signal.

[0051] In the optical communication system 100 of the fourth embodiment configured as described above, the modulated optical signal is demultiplexed by wavelength in the optical multiplexer / demultiplexer 25 of the optical receiver 20a. The modulated optical signal output from the port corresponding to the wavelength of the modulated optical signal is received by one of the main signal receivers 22. The signal separator 26 of the optical receiver 20a determines the wavelength of the control signal by the main signal receiver 22 that output the modulated optical signal, and notifies the control signal processor 24. This makes it possible to separate and acquire the main signal and the control signal.

[0052] (Fifth embodiment) In the fifth embodiment, a configuration will be described in which an optical communication system equipped with an optical transmitter according to any one of the first to third embodiments includes an optical receiver different from the optical receivers in the first to third embodiments.

[0053] An optical communication system including an optical transmitter according to any one of the first to third embodiments includes an optical receiver 20b as an optical receiver different from the optical receivers according to the first to third embodiments. Fig. 8 is a diagram showing an example of the configuration of the optical receiver 20b according to the fifth embodiment. The optical receiver 20b includes a branching unit 21, a main signal receiving unit 22, a control signal processing unit 24, a control signal receiving unit 28, and a received signal identifying unit 29.

[0054] The branching device 21 branches the modulated optical signal transmitted from the optical transmitter 10. The modulated optical signal branched by the branching device 21 is input to the main signal receiving unit 22 and the control signal receiving unit .

[0055] The main signal receiving unit 22 converts the modulated optical signal branched by the branching unit 21 into an electrical signal, and obtains the main signal from the electrical signal.

[0056] The control signal receiving unit 28 is composed of an optical filter 281 and a PD 282. The optical filter 281 is an optical filter having the characteristics shown in Fig. 9. Examples of the optical filter 281 include a multilayer filter and an etalon filter. Note that the optical filter 281 may be an optical filter using an optical interferometer such as a Mach-Zehnder filter.

[0057] 9 is a diagram for explaining the characteristics of the optical filter 281 in the fifth embodiment. As shown in FIG. 9, the optical filter 281 has a characteristic in which the transmittance differs for each wavelength. In this case, if the optical transmitter 10 assigns wavelengths λ1 and λ2 as control signals, the modulated optical signal after passing through the optical filter 281 will have different intensities for each wavelength. Therefore, it is converted into an intensity-modulated optical signal.

[0058] The PD 282 receives the modulated optical signal that has passed through the optical filter 281. The PD 282 converts the received modulated optical signal into an electrical signal. In this way, the PD 282 receives the modulated optical signal that has passed through the optical filter 281, and can treat it as a normal OOK signal (for example, NRZ). The electrical signal converted by the PD 282 is output to the received signal identification unit 29.

[0059] The received signal identifying unit 29 identifies the electrical signal output from the PD 282. Specifically, the received signal identifying unit 29 acquires the voltage value of the electrical signal. For example, a TIA (Trans Impedance Amplifier) ​​is provided between the PD 282 and the received signal identifying unit 29, and the TIA converts the electrical signal output from the PD 282 into a voltage signal. The received signal identifying unit 29 acquires the voltage value based on the voltage signal output from the TIA.

[0060] The control signal processing unit 24 receives the discrimination result obtained by the received signal discrimination unit 29 and the electrical signal as input. The control signal processing unit 24 acquires a control signal based on the discrimination result and the electrical signal that have been input.

[0061] In the optical communication system 100 of the fifth embodiment configured as described above, the modulated optical signal is branched in the branching device 21 of the optical receiver 20b. The branched modulated optical signal is converted into an intensity-modulated signal by the optical filter 281. The received signal identifying unit 29 of the optical receiver 20b identifies the intensity-modulated signal and notifies the control signal processing unit 24. This makes it possible to separate and acquire the main signal and the control signal.

[0062] (Sixth embodiment) In the sixth embodiment, a configuration will be described in which an optical transmitter according to any one of the first to third embodiments and an optical receiver according to any one of the first to fifth embodiments are applied to a subscriber device and a photonic gateway of an all-photonic network.

[0063] 10 is a diagram showing an example of the configuration of an optical communication system 110 in the sixth embodiment. The optical communication system 110 includes a plurality of subscriber devices 30 (e.g., subscriber devices 30-1 to 30-3), a plurality of subscriber devices 40 (e.g., subscriber devices 40-1 to 40-3), a plurality of control units 50 (e.g., control units 50-1 to 50-2), and a plurality of photonic gateways 60 (e.g., photonic gateways 60-1 to 60-2).

[0064] Optical transmission lines are used to connect subscriber device 30 and photonic gateway 60-1, between photonic gateway 60-1 and photonic gateway 60-2, and between photonic gateway 60-2 and subscriber device 40. An optical communication network 70 is configured between photonic gateway 60-1 and photonic gateway 60-2. In the following description, subscriber device 30 is the transmitting side, and subscriber device 40 is the receiving side.

[0065] The subscriber device 30 includes the optical transmitter 10 according to any one of the first to third embodiments. The subscriber device 30 transmits an optical signal using the optical transmitter 10. The subscriber device 30 is, for example, an ONU (Optical Network Unit) installed in a subscriber's home.

[0066] The subscriber device 40 is a device that communicates with the subscriber device 30. The subscriber device 40 includes the optical receivers 20, 20a, and 20b according to any one of the first to fifth embodiments. The subscriber device 40 receives an optical signal by the optical receivers 20, 20a, and 20b. The subscriber device 40 is, for example, an ONU installed in a subscriber's home.

[0067] The photonic gateway 60-1 includes an optical SW 61-1 and a wavelength multiplexing / demultiplexing unit 62-1. The photonic gateway 60-2 includes an optical SW 61-2 and a wavelength multiplexing / demultiplexing unit 62-2. Since the photonic gateways 60-1 and 60-2 perform similar processing, they will be described as an optical SW 61 and a wavelength multiplexing / demultiplexing unit 62 without distinguishing between the photonic gateways 60.

[0068] The optical SW61 has M (M is an integer of 2 or more) first ports and N (N is an integer of 2 or more) second ports. An optical signal input to one port of the optical SW61 is output from another port. For example, an optical signal input to the first port of the optical SW61 is output from the second port.

[0069] 10, a subscriber device 30 is connected to a first port of the optical SW61-1 via an optical transmission line, and a photonic gateway 60-2 is connected to a second port of the optical SW61-1 via an optical transmission line. In the example shown in Fig. 10, a subscriber device 40 is connected to a first port of the optical SW61-2 via an optical transmission line, and a photonic gateway 60-1 is connected to a second port of the optical SW61-2 via an optical transmission line.

[0070] The wavelength multiplexing / demultiplexing unit 62 multiplexes or demultiplexes the input optical signals.

[0071] The control unit 50 controls at least the subscriber devices 30 and 40 and each photonic gateway 60. Here, the control of the subscriber devices 30 and 40 includes, for example, allocating emission wavelengths to the subscriber devices 30 and 40, issuing instructions to stop light, and issuing instructions to change wavelengths. The control of the photonic gateway 60 includes, for example, switching connections between ports of the optical SW 61 provided in the photonic gateway 60 and setting optical paths.

[0072] Each control unit 50 controls each photonic gateway 60 and the subscriber device 30 or 40 connected to the photonic gateway 60. For example, the control unit 50-1 controls the photonic gateway 60-1 and the subscriber device 30 connected to the photonic gateway 60-1. For example, the control unit 50-2 controls the photonic gateway 60-2 and the subscriber device 40 connected to the photonic gateway 60-2.

[0073] The control unit 50-1 includes a subscriber device control unit 51-1 and an optical SW control unit 52-1. The control unit 50-2 includes a subscriber device control unit 51-2 and an optical SW control unit 52-2. The control units 50-1 and 50-2 perform similar processing except for the objects they control. Therefore, they will be described as the subscriber device control unit 51 and the optical SW control unit 52 without distinguishing between the control units 50.

[0074] When a new subscriber device is connected to the photonic gateway 60, the subscriber device control unit 51 identifies to which port of the optical SW provided in the photonic gateway 60 the subscriber device newly connected to the photonic gateway 60 is connected, and performs processing to open an optical path, such as issuing a wavelength instruction to the subscriber device. Note that the optical path opening processing in the subscriber device control unit 51 is the same as in the conventional case, and therefore a description thereof will be omitted.

[0075] The optical SW control unit 52 sets up and switches connections between ports of the optical SW provided in the photonic gateway 60, and sets up optical paths. As shown in Fig. 10, when an optical path is opened that communicably connects the subscriber device 30-1 connected to the photonic gateway 60-1 and the subscriber device 40-1 connected to the photonic gateway 60-2, the control unit 50 assigns wavelengths to the end-end optical path so that the transmission wavelength (λm) of the subscriber device 30-1 becomes the reception wavelength of the subscriber device 40-1, and the transmission wavelength (λn) of the subscriber device 40-1 becomes the reception wavelength of the subscriber device 30-1. The functions of the subscriber device control unit 51 and the optical SW control unit 52 may be realized by one or more processors executing programs.

[0076] The optical communication system 110 configured as above can also be applied to an all-photonic network.

[0077] (Modification 1 of the sixth embodiment) In the above-described embodiment, a one-way communication configuration has been described as an example. Therefore, the subscriber devices 30 and 40 are equipped with either the optical transmitter 10 or the optical receivers 20, 20a, and 20b. On the other hand, bidirectional communication is generally performed in the optical communication system 110. Therefore, the subscriber devices 30 and 40 provided in the optical communication system 110 may be configured to have the functions of both the optical transmitter 10 and the optical receiver 20. In this case, the functions of the optical transmitter 10 and the optical receiver 20 provided in the subscriber devices 30 and 40 may be any combination. For example, the subscriber devices 30 and 40 are equipped with a combination of the optical transmitter 10 of any one of the first to third embodiments and the optical receivers 20, 20a, and 20b of any one of the first to fifth embodiments.

[0078] (Modification 2 of the sixth embodiment) The photonic gateway 60 may include an optical transmitter according to any one of the first to third embodiments and an optical receiver according to any one of the first to fifth embodiments to exchange control signals with the subscriber devices 30 and 40. In this case, the subscriber devices 30 and 40 include a combination of an optical transmitter 10 according to any one of the first to third embodiments and an optical receiver 20, 20a, 20b according to any one of the first to fifth embodiments.

[0079] Some or all of the functional units of the optical transmitter 10 or the optical receivers 20, 20a, and 20b described above are realized as software by a processor such as a CPU (Central Processing Unit) executing a program stored in a storage device having a nonvolatile storage medium (non-transitory storage medium) and a storage unit. The program may be recorded on a computer-readable non-transitory storage medium. Examples of computer-readable non-transitory storage media include portable media such as flexible disks, magneto-optical disks, ROMs (Read Only Memory), and CD-ROMs (Compact Disc Read Only Memory), and storage devices such as hard disks built into computer systems.

[0080] Some or all of the functional units of the optical transmitter 10 or the optical receivers 20, 20a, 20b described above may be realized using hardware including an electronic circuit (electronic circuit or circuitry) using, for example, an LSI (Large Scale Integrated circuit), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array).

[0081] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention. [Industrial Applicability]

[0082] The present invention can be applied to an optical communication system in which a control signal such as AMCC is superimposed on a main signal and transmitted / received. [Explanation of symbols]

[0083] 10...optical transmitter, 11...main signal generating unit, 12...modulator driver, 13...control signal generating unit, 14...wavelength tunable driver, 15...wavelength tunable light source, 16...optical modulator, 20, 20a, 20b...optical receiver, 21...branching unit, 22, 22-1 to 22-2...main signal receiving unit, 23...receiving wavelength identifying unit, 24...control signal processing unit, 25...optical multiplexer / demultiplexer, 26...signal separating unit, 27...main signal processing unit, 28...control signal receiving unit, 29...receiving signal identifying unit, 30, 40...user equipment, 50...control unit, 51...user equipment control unit, 52...optical SW control unit, 60...photonic gateway, 61...optical SW, 62...wavelength multiplexing / demultiplexing unit, 100, 110...optical communication system, 281...optical filter, 282...PD

Claims

1. a main signal generating unit that generates a main signal; a control signal generating unit that generates a control signal slower than the main signal; a wavelength tunable driver that converts the control signal generated by the control signal generating unit into a signal for wavelength control; a wavelength-tunable transmitter that generates a modulated optical signal based on the main signal and the wavelength control signal; Equipped with the wavelength-tunable transmitter is composed of an optical modulator and a wavelength-tunable light source; the wavelength-tunable light source outputs light of a wavelength corresponding to the wavelength control signal; the optical modulator modulates the light output from the wavelength-tunable light source based on the main signal to generate the modulated optical signal; Optical transmitter.

2. the wavelength-tunable light source is any one of a DBR (Distributed Bragg Reflector) laser, an SSG-DBR (Super Structure Grating - DBR) laser, and an SG-DBR (Sampled Grating - DBR) laser, which are capable of controlling the wavelength according to an input current, or a DFB (Distributed-Feedback) laser, which is capable of controlling the wavelength by controlling the chip temperature; the wavelength tunable driver inputs the wavelength control signal to the wavelength tunable light source, thereby assigning an arbitrary wavelength from a range of oscillation wavelengths of the wavelength tunable light source to the wavelength control signal; 2. The optical transmitter according to claim 1.

3. a demultiplexing unit that receives the modulated optical signal transmitted from an optical transmitter comprising: a main signal generating unit that generates a main signal; a control signal generating unit that generates a control signal slower than the main signal; a wavelength tunable driver that converts the control signal generated by the control signal generating unit into a signal for wavelength control; and a wavelength tunable transmitter that generates a modulated optical signal based on the main signal and the signal for wavelength control, and demultiplexes the received modulated optical signal according to wavelength; a plurality of main signal receiving units that receive the modulated optical signals with different wavelengths demultiplexed by the demultiplexing unit; a signal separation unit that determines which of the plurality of main signal receiving units has received the modulated optical signal, and acquires wavelength information indicating the control signal by determining that a wavelength corresponding to the main signal receiving unit that has received the modulated optical signal is assigned to the control signal; and a control signal processing unit that acquires the control signal based on the wavelength information acquired by the signal separation unit and the modulated optical signal; A receiver comprising:

4. An optical communication system comprising an optical transmitter, an optical receiver, and a photonic gateway that relays communication between the optical transmitter and the optical receiver, The optical transmitter comprises: a main signal generating unit that generates a main signal; a control signal generating unit that generates a control signal slower than the main signal; a wavelength tunable driver that converts the control signal generated by the control signal generating unit into a signal for wavelength control; a wavelength-tunable transmitter that generates a modulated optical signal based on the main signal and the wavelength control signal and transmits the generated modulated optical signal to the optical receiver via the photonic gateway; Equipped with The optical receiver includes: a demultiplexer that receives the modulated optical signal via the photonic gateway and demultiplexes or splits the received modulated optical signal; a control signal processing unit that acquires the control signal based on the demultiplexed or branched modulated optical signal; Preparation, the wavelength-tunable transmitter is composed of an optical modulator and a wavelength-tunable light source; the wavelength-tunable light source outputs light of a wavelength corresponding to the wavelength control signal; the optical modulator modulates the light output from the wavelength-tunable light source based on the main signal to generate the modulated optical signal; Optical communication system.

5. The optical receiver includes: a plurality of main signal receiving units that receive the modulated optical signals with different wavelengths demultiplexed by the demultiplexing unit; a signal separation unit that determines which of the plurality of main signal receiving units has received the modulated optical signal and determines that a wavelength corresponding to the main signal receiving unit that has received the modulated optical signal is assigned to the control signal; Furthermore, the control signal processing unit acquires the control signal based on the result of the determination by the signal separation unit and the modulated optical signal.

5. The optical communication system according to claim 4.

6. The optical receiver includes: an optical filter having a characteristic that transmittance varies depending on wavelength, and converting the modulated optical signal branched by the branching unit into an intensity-modulated signal; a photodiode that converts the intensity-modulated signal that has passed through the optical filter into an electrical signal; a received signal identifying unit that identifies the electrical signal output from the photodiode; Furthermore, the control signal processing unit acquires the control signal based on the result of identification by the received signal identification unit.

5. The optical communication system according to claim 4.

7. A main signal generating unit generates a main signal, a control signal generating unit generating a control signal slower than the main signal; a wavelength tunable driver converting the generated control signal into a signal for wavelength control; a wavelength tunable transmitter generating a modulated optical signal based on the main signal and the wavelength control signal; the wavelength-tunable transmitter is composed of an optical modulator and a wavelength-tunable light source; the wavelength-tunable light source outputs light of a wavelength corresponding to the wavelength control signal, the optical modulator modulates the light output from the wavelength-tunable light source based on the main signal to generate the modulated optical signal; Control signal superposition method.

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