Optical communication system, master unit, slave unit, and optical communication method

Abstract

To provide an optical communication system, master station equipment, slave station equipment, and optical communication method that transmit control information more efficiently with a simple configuration. [Solution] The optical communication system 301 comprises a master station and a slave station. The master station generates a digital signal containing a single frame in which multiple pieces of control information are stored, and transmits the generated digital signal and an analog master signal to the slave station via an optical fiber 191. The slave station obtains at least one of the multiple pieces of control information from the digital signal contained in the optical signal received from the master station via the optical fiber.

Description

Technical Field

[0001] The present disclosure relates to an optical communication system, a master station device, a slave station device, and an optical communication method. This application claims priority based on Japanese Patent Application No. 2022-30708 filed on March 1, 2022, and incorporates all of its disclosure herein.

Background Art

[0002] Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2021-64861) discloses an optical transmission device as follows. That is, the optical transmission device includes multiplexing means for multiplexing a first electrical signal for carrying information and a plurality of tone signals to generate a multiplexed signal, and modulation means for performing carrier-suppressed amplitude modulation of continuous light with the multiplexed signal.

[0003] Furthermore, Patent Document 2 (Japanese Patent Application Publication No. 2020-43488) discloses the following amplifier unit. Specifically, the amplifier unit comprises a digital signal generation unit that generates a digital signal with modulation frequency fm and outputs the digital signal; an analog signal generation unit that generates an analog signal with frequency fc having information in its amplitude and outputs the analog signal; a superposition unit that generates a superposition signal by superimposing the digital signal and the analog signal and outputs the superposition signal; an amplification unit that generates an amplified signal by amplifying the superposition signal and outputs the amplified signal; a detection unit that detects information regarding the voltage of the amplified signal; and an amplification degree determination unit that determines the amplification degree of the amplification unit based on the information detected by the detection unit. The relationship between the input voltage of the input signal input to the amplification unit and the output voltage of the output signal output from the amplification unit has a relationship that ranges from a region where the output voltage increases as the input voltage increases to a region where the amplification degree changes so that the output voltage becomes a predetermined constant value. The input voltage of the digital signal input to the amplification unit is the voltage at which the output voltage of the digital signal amplified by the amplification degree becomes the constant value. Furthermore, the input voltage of the analog signal input to the amplification unit is a voltage at which the output voltage of the analog signal amplified by the amplification factor is proportional to the amplification factor. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-64861 [Patent Document 2] Japanese Patent Publication No. 2020-43488 [Overview of the Initiative]

[0005] The optical communication system disclosed herein comprises a master station and a slave station, wherein the master station generates a digital signal including a single frame in which a plurality of control information is stored, transmits the generated digital signal and an analog master signal to the slave station via an optical fiber, and the slave station acquires at least one of the plurality of control information from the digital signal included in the optical signal received from the master station via the optical fiber.

[0006] The master station device of this disclosure comprises a generation unit that generates a digital signal including a single frame in which a plurality of control information is stored, and a transmission unit that transmits an optical signal including the digital signal and an analog master signal generated by the generation unit to another device via an optical fiber.

[0007] The slave station device of this disclosure includes a receiving unit that receives an optical signal from another device via an optical fiber, which includes a digital signal including a single frame containing a plurality of control information and an analog master signal, and an acquiring unit that acquires at least one of the plurality of control information from the digital signal included in the optical signal received by the receiving unit.

[0008] The optical communication method of the present disclosure is an optical communication method in an optical communication system comprising a master station device and a slave station device, comprising the steps of: the master station device generating a digital signal including a single frame in which a plurality of control information is stored, and transmitting an optical signal including the generated digital signal and an analog master signal to the slave station device via an optical fiber; and the slave station device obtaining at least one of the plurality of control information from the digital signal included in the optical signal received from the master station device via the optical fiber.

[0009] One aspect of this disclosure can be implemented not only as a master station device equipped with such characteristic processing, but also as an optical communication method in which such characteristic processing is performed in steps, or as a program for causing a computer to perform such steps. Furthermore, one aspect of this disclosure can be implemented as a semiconductor integrated circuit that implements part or all of the master station device.

[0010] Furthermore, one aspect of this disclosure can be implemented not only as a slave station device equipped with such characteristic processing, but also as an optical communication method in which such characteristic processing is performed in steps, or as a program for causing a computer to perform such steps. In addition, one aspect of this disclosure can be implemented as a semiconductor integrated circuit that implements part or all of the slave station device. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a diagram showing the configuration of an optical communication system according to the first embodiment of this disclosure. [Figure 2] Figure 2 shows the configuration of the master station device according to the first embodiment of this disclosure. [Figure 3] Figure 3 is a schematic diagram showing an example of the frequency spectrum of an electrical signal generated by the multiplexing unit in a master station device according to the first embodiment of this disclosure. [Figure 4] Figure 4 shows the configuration of a slave station device according to the first embodiment of this disclosure. [Figure 5] Figure 5 shows an example of a communication sequence in an optical communication system according to the first embodiment of this disclosure. [Figure 6] Figure 6 shows the configuration of an optical communication system according to a second embodiment of the present disclosure. [Figure 7] Figure 7 shows the configuration of the master station device according to the second embodiment of this disclosure. [Figure 8] Figure 8 is a schematic diagram showing an example of the frequency spectrum of an optical signal output by the multiplexing unit in a master station device according to a second embodiment of the present disclosure. [Figure 9] FIG. 9 is a diagram showing the configuration of a slave station device according to the second embodiment of the present disclosure.

Embodiments for Carrying Out the Invention

[0012] Conventionally, in an optical communication system that transmits an analog signal including communication data between devices via an optical fiber, a technique has been developed to multiplex control information for controlling the operation of one device onto the analog signal and transmit it.

[0013] [Problems to be Solved by the Present Disclosure] A technique that can transmit control information more efficiently with a simpler configuration beyond the techniques described in Patent Documents 1 and 2 is desired.

[0014] The present disclosure has been made to solve the above problems, and an object thereof is to provide an optical communication system, a master station device, a slave station device, and an optical communication method capable of transmitting control information more efficiently with a simpler configuration.

[0015] [Effects of the Present Disclosure] According to the present disclosure, control information can be transmitted more efficiently with a simpler configuration.

[0016] [Description of Embodiments of the Present Disclosure] First, the contents of the embodiments of the present disclosure will be listed and described.

[0017] (1) The optical communication system according to the embodiment of the present disclosure includes a master station device and a slave station device. The master station device generates a digital signal including one frame in which a plurality of control information is stored, and transmits an optical signal including the generated digital signal and an analog main signal to the slave station device via an optical fiber. The slave station device acquires at least one of the plurality of control information from the digital signal included in the optical signal received from the master station device via the optical fiber.

[0018] In this way, by adopting a configuration in which an optical signal including a digital signal and a main signal, which contains a plurality of control information in one frame, is transmitted via an optical fiber, it is possible to collectively transmit the plurality of control information without requiring strict control of the frequency of the main signal. Therefore, control information can be transmitted more efficiently with a simple configuration.

[0019] (2) In the above (1), the master station device may generate the optical signal based on an electrical signal in which the digital signal and the main signal are frequency multiplexed, and transmit the generated optical signal to the slave station device via the optical fiber.

[0020] With such a configuration, compared with a configuration that wavelength multiplexes a digital signal and a main signal, each signal can be transmitted with high frequency utilization efficiency using a single-wavelength optical signal including the digital signal and the main signal.

[0021] (3) In the above (2), the master station device may frequency multiplex the passed signal of the first low-pass filter that has received the digital signal and the main signal.

[0022] With such a configuration, in the master station device, noise derived from the digital signal can be reduced, and a decrease in the transmission quality of the main signal can be suppressed.

[0023] (4) In the above (2) or (3), the slave station device may generate an electrical signal based on the optical signal received from the master station device via the optical fiber, separate the digital signal from the electrical signal using a filter, and acquire the control information from the passed signal of the second low-pass filter that has received the separated digital signal.

[0024] With such a configuration, in the slave station device, noise derived from the digital signal can be reduced, and a decrease in the transmission quality of the main signal can be suppressed.

[0025] (5) In the above (1), the master station device may generate a first optical signal based on the digital signal, wavelength multiplex the generated optical signal with a second optical signal based on the main signal to generate the optical signal, and transmit the generated optical signal to the slave station device via the optical fiber.

[0026] This configuration, compared to a configuration that frequency-multiplexes the digital signal and the main signal, suppresses the influence of the digital signal on the main signal and improves the transmission quality of the main signal.

[0027] (6) The master station device according to the embodiment of the present disclosure comprises a generation unit that generates a digital signal including a single frame in which a plurality of control information is stored, and a transmission unit that transmits an optical signal including the digital signal and an analog master signal generated by the generation unit to another device via an optical fiber.

[0028] In this configuration, a digital signal containing a single frame with multiple control information stored within it, and an optical signal containing the main signal, are transmitted via optical fiber. This allows for the simultaneous transmission of multiple control information without requiring precise control of the main signal frequency. Therefore, control information can be transmitted more efficiently with a simpler configuration.

[0029] (7) A slave station device according to an embodiment of the present disclosure includes a receiving unit that receives an optical signal from another device via an optical fiber, which includes a digital signal including a single frame containing a plurality of control information and an analog main signal, and an acquiring unit that acquires at least one of the plurality of control information from the digital signal included in the optical signal received by the receiving unit.

[0030] In this configuration, a digital signal containing a single frame with multiple control information stored in it, and an optical signal containing the main signal are received, and control information is acquired from the digital signal contained in the received optical signal. This allows for the simultaneous transmission of multiple control information without requiring strict control of the main signal frequency. Therefore, control information can be transmitted more efficiently with a simpler configuration.

[0031] (8) An optical communication method according to an embodiment of the present disclosure is an optical communication method in an optical communication system comprising a master station and a slave station, the master station generating a digital signal including a single frame in which a plurality of control information is stored, and transmitting an optical signal including the generated digital signal and an analog master signal to the slave station via an optical fiber, and the slave station acquiring at least one of the plurality of control information from the digital signal included in the optical signal received from the master station via the optical fiber.

[0032] In this way, by transmitting a digital signal containing a single frame with multiple control information stored in it, and an optical signal containing the main signal, via optical fiber, multiple control information can be transmitted simultaneously without requiring strict control of the main signal frequency. Therefore, control information can be transmitted more efficiently with a simpler configuration.

[0033] Embodiments of this disclosure will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated. Furthermore, at least some of the embodiments described below may be combined in any way.

[0034] <First Embodiment> [Configuration and Basic Operation] Figure 1 shows the configuration of an optical communication system according to a first embodiment of the present disclosure. Referring to Figure 1, the optical communication system 301 comprises a master station 101 and a slave station 201. The master station 101 and the slave station 201 are connected to each other via an optical fiber 191. The optical communication system 301 may also be configured to include multiple slave station 201s. In this case, for example, the multiple slave station 201s are connected to the master station 101 via a single optical fiber 191 and an optical coupler. For example, the optical communication system 301 is an analog RoF (Radio over Fiber) system.

[0035] For example, the master station 101 and the slave station 201 transmit and receive communication data via the optical fiber 191.

[0036] More specifically, the master station 101 receives an OFDM (Orthogonal Frequency Division Multiplexing) modulated analog signal containing communication data from a base station device (not shown). The master station 101 generates an IF (Intermediate Frequency) signal by frequency-converting the received analog signal. The IF signal is an example of a main signal. The master station 101 transmits an optical signal containing the generated IF signal to the slave station 201 via the optical fiber 191.

[0037] The slave unit 201 receives an optical signal from the master unit 101 via the optical fiber 191. The slave unit 201 acquires an IF signal from the received optical signal and transmits an RF (Radio Frequency) signal based on the acquired IF signal via the antenna 161. The slave unit 201 may also be configured to transmit the signal based on the acquired IF signal to another device via a wired connection.

[0038] Furthermore, the slave unit 201 receives an OFDM-modulated millimeter-wave RF signal containing communication data from a mobile communication terminal (not shown) via antenna 161. The slave unit 201 generates an IF signal by frequency-converting the received RF signal and transmits an optical signal containing the generated IF signal to the master unit 101 via optical fiber 191. Alternatively, the slave unit 201 may be configured to receive a signal containing communication data via a wired connection and transmit an optical signal containing the received signal to the master unit 101 via optical fiber 191.

[0039] The master station 101 receives an optical signal from the slave station 201 via the optical fiber 191. The master station 101 obtains an IF signal from the received optical signal and transmits a signal based on the obtained IF signal to the base station equipment.

[0040] Furthermore, the master station 101 transmits multiple control information to the slave station 201 periodically or irregularly. More specifically, the master station 101 generates a digital signal that includes a single frame containing multiple control information.

[0041] The master station 101 transmits the optical signal, including the generated digital signal and IF signal, to the slave station 201 via the optical fiber 191. More specifically, the master station 101 generates an optical signal based on an electrical signal obtained by frequency multiplexing the digital signal and the IF signal, and transmits the generated optical signal to the slave station 201 via the optical fiber 191.

[0042] The slave unit 201 acquires a frame from the digital signal contained in the optical signal received from the master unit 101 via the optical fiber 191, and obtains multiple pieces of control information from the acquired frame. The slave unit 201 operates according to the multiple pieces of control information it has acquired.

[0043] (Master station device) Figure 2 shows the configuration of a master station device according to a first embodiment of the present disclosure. Referring to Figure 2, the master station device 101 comprises a signal receiving unit 11, a frequency conversion unit 12, a control information output unit 13, a framer 14, an 8B / 10B modulation unit 15, an LPF (Low Pass Filter) 16, a multiplexing unit 17, and an optical modulation unit 18. The framer 14 is an example of a generation unit. The optical modulation unit 18 is an example of a transmission unit. The LPF 16 is an example of a first low-pass filter. Some or all of the signal receiving unit 11, frequency conversion unit 12, control information output unit 13, framer 14, and 8B / 10B modulation unit 15 are implemented, for example, by a circuit including one or more processors.

[0044] The signal receiving unit 11 receives an OFDM-modulated analog signal containing communication data from a base station device (not shown). The signal receiving unit 11 may be configured to receive either an RF signal or a baseband signal as the analog signal. The signal receiving unit 11 outputs the received analog signal to the frequency conversion unit 12.

[0045] The frequency conversion unit 12 generates an IF signal having a center frequency fa by upconverting or downconverting the analog signal received from the signal receiving unit 11, and outputs the generated IF signal to the multiplexing unit 17.

[0046] The control information output unit 13 generates control information for controlling the slave station device 201. For example, the control information output unit 13 generates multiple types of control information. More specifically, the control information output unit 13 generates beamforming information for controlling the transmission direction of the RF signal, synchronization information for controlling the transmission timing of the RF signal according to TDD (Time Division Duplex), and register control information for controlling the registers of the FPGA (Field-Programmable Gate Array) in the slave station device 201, as control information. The control information output unit 13 outputs the generated control information to the framer 14. Alternatively, the control information output unit 13 may output control information acquired from a base station device (not shown) to the framer 14, in addition to outputting the generated control information to the framer 14.

[0047] The framer 14 generates a digital signal containing a single frame with multiple control information stored within it. For example, the framer 14 periodically or irregularly generates an Ethernet® frame destined for the slave device 201, in which multiple control information received from the control information output unit 13 is stored in the payload. For instance, the framer 14 generates an Ethernet frame in which the destination MAC address includes the MAC address of the slave device 201 and multiple types of control information are stored in the payload. Alternatively, the framer 14 may be configured to generate an Ethernet frame in which multiple pieces of a single type of control information are stored in the payload. The framer 14 outputs a binary digital signal containing the generated Ethernet frame to the 8B / 10B modulation unit 15.

[0048] Furthermore, the framer 14 may store control information in multiple fields within the Ethernet frame. This allows for the rapid transmission of control information, which requires frequent updates, to the slave station device 201.

[0049] The 8B / 10B modulation unit 15 modulates the digital signal received from the framer using 8B / 10B modulation and outputs it to the LPF 16. In other words, the 8B / 10B modulation unit 15 converts the 8-bit digital signal received from the framer into a 10-bit digital signal and outputs it to the LPF 16.

[0050] The LPF16 receives a digital signal from the 8B / 10B modulation unit 15 and attenuates frequency components in the received digital signal that are above a predetermined frequency. For example, the LPF16 is a Bessel filter of order 4 or higher that attenuates frequency components above the cutoff frequency fc. The cutoff frequency fc is smaller than the center frequency fa of the IF signal generated by the frequency conversion unit 12. The LPF16 outputs the digital signal, from which frequency components above the cutoff frequency fc have been attenuated, to the multiplexing unit 17.

[0051] For example, the multiplexer 17 frequency multiplexes the signal passed through the LPF 16 and the IF signal. More specifically, the multiplexer 17 frequency multiplexes the digital signal received from the LPF 16 and the IF signal received from the frequency conversion unit 12. The multiplexer 17 generates an electrical signal M1 by frequency multiplexing the digital signal and the IF signal and outputs it to the optical modulation unit 18.

[0052] The master station 101 may be configured to receive an IF signal from the base station equipment and transmit an optical signal including the received IF signal to the slave station 201 via the optical fiber 191. More specifically, the master station 101 may be configured without a frequency conversion unit 12. In this case, the signal receiving unit 11 receives an IF signal from the base station equipment and outputs the received IF signal to the multiplexing unit 17. The multiplexing unit 17 receives the IF signal from the signal receiving unit 11 and frequency multiplexes the digital signal received from the LPF 16 and the IF signal received from the signal receiving unit 11.

[0053] Figure 3 is a schematic diagram showing an example of the frequency spectrum of an electrical signal generated by the multiplexing unit in a master station device according to the first embodiment of this disclosure. In Figure 3, the horizontal axis represents frequency [GHz] and the vertical axis represents signal strength.

[0054] Referring to Figure 3, the frequency conversion unit 12 generates an IF signal having a center frequency fa in a frequency range other than the frequency range in which the harmonic intensity of the digital signal generated by the framer 14 drops, and outputs it to the multiplexing unit 17. More specifically, the frequency conversion unit 12 generates an IF signal having a center frequency fa that satisfies the following equation (1), and outputs it to the multiplexing unit 17. n × fd + k × fd <fa<(n+1)×fd-k×fd ··· (1)

[0055] Here, n is an integer greater than or equal to 1. k is a value greater than zero and less than 0.1. fd is the bandwidth of the control information. By configuring the frequency conversion unit 12 to generate an IF signal having a center frequency fa that satisfies the above equation (1), it is possible to suppress the degradation of the transmission quality of the IF signal due to the influence of DC component noise that may occur when the duty cycle of the digital signal generated by the framer 14 is not 50%.

[0056] The optical modulation unit 18 transmits the optical signal, including the digital signal and IF main signal generated by the framer 14, to the slave station device 201 via the optical fiber 191. More specifically, the optical modulation unit 18 receives an electrical signal M1 from the multiplexing unit 17, generates an optical signal by optically modulating the received electrical signal M1, and outputs the generated optical signal to the optical fiber 191.

[0057] (Slave station device) Figure 4 shows the configuration of a slave station device according to a first embodiment of the present disclosure. Referring to Figure 4, the slave station device 201 comprises an optical demodulation unit 21, a separation unit 22, amplification units 23A, 23B, a frequency conversion unit 24, an 8B / 10B demodulation unit 25, an LPF 26, a deframer 27, and a control information processing unit 28. The optical demodulation unit 21 is an example of a receiving unit. The deframer 27 is an example of an acquisition unit. The LPF 26 is an example of a second low-pass filter. Some or all of the frequency conversion unit 24, the 8B / 10B demodulation unit 25, the deframer 27, and the control information processing unit 28 are implemented, for example, by a circuit including one or more processors.

[0058] The optical demodulation unit 21 receives an optical signal from the master station device 101 via the optical fiber 191, which includes a digital signal containing a single Ethernet frame containing multiple control information and an IF signal, and generates an electrical signal M2 based on the received optical signal. More specifically, the optical demodulation unit 21 generates an electrical signal M2 at a level corresponding to the intensity of the received optical signal and outputs it to the separation unit 22.

[0059] The separation unit 22 receives the electrical signal M2 from the optical demodulation unit 21 and separates the digital signal, including the Ethernet frame, from the received electrical signal M2. More specifically, the separation unit 22 outputs some of the frequency components of the electrical signal M2 to the amplification unit 23A and the remaining frequency components to the amplification unit 23B.

[0060] For example, the separation unit 22 is a diplexer composed of an HPF (High Pass Filter) and an LPF. The separation unit 22 outputs electrical signal M2a, which is the frequency component of electrical signal M2 with a frequency of Fx or higher, to the amplification unit 23A, and electrical signal M2b, which is the frequency component with a frequency of less than Fx, to the amplification unit 23B. Here, frequency Fx is smaller than the center frequency fa of the IF signal. Electrical signal M2a includes the IF signal generated by the frequency conversion unit 12 in the master station device 101. Electrical signal M2b includes the digital signal that has passed through the LPF 16 in the master station device 101.

[0061] The amplification unit 23A receives the electrical signal M2a from the separation unit 22 and amplifies the received electrical signal M2a. For example, the amplification unit 23A is a linear amplifier. The amplification unit 23A outputs the amplified electrical signal M2a to the frequency conversion unit 24.

[0062] The amplification unit 23B receives the electrical signal M2b from the separation unit 22 and amplifies the received electrical signal M2b. For example, the amplification unit 23B is a limiting amplifier. The amplification unit 23B outputs the amplified electrical signal M2b to the 8B / 10B demodulation unit 25.

[0063] In this configuration, electrical signals M2a and M2b are separated from electrical signal M2, and the electrical signals M2a and M2b are amplified using amplification units 23A and 23B, respectively. This allows a linear amplifier to be used as amplification unit 23A and a limiting amplifier to be used as amplification unit 23B. This makes it possible to avoid waveform distortion of the digital signal that occurs when a linear amplifier is used as amplification unit 23B. Furthermore, the circuit size of the substation device 201 can be made smaller compared to a configuration in which electrical signal M2 is amplified without separating electrical signals M2a and M2b.

[0064] For example, the frequency conversion unit 24 generates an RF signal by upconverting the electrical signal M2a received from the amplification unit 23A, and outputs the generated RF signal to the antenna 161. Alternatively, the frequency conversion unit 24 generates a baseband signal by downconverting the electrical signal M2a received from the amplification unit 23A, and transmits the generated baseband signal to an external device of the slave station 201.

[0065] The 8B / 10B demodulation unit 25 demodulates the electrical signal M2b received from the amplification unit 23B using the 8B / 10B method and outputs it to the LPF 26. In other words, the 8B / 10B demodulation unit 25 converts the 10-bit electrical signal M2b received from the amplification unit 23B into an 8-bit electrical signal M2b and outputs it to the LPF 26.

[0066] The LPF26 receives the electrical signal M2b from the 8B / 10B demodulation unit 25 and attenuates components in the received electrical signal M2b that are above a predetermined frequency. For example, the LPF26 is a Bessel filter of order 4 or higher that attenuates frequency components above the cutoff frequency fc. The LPF26 outputs the electrical signal M2b, from which components above the cutoff frequency fc have been attenuated, to the deframer 27.

[0067] The deframer 27 acquires multiple pieces of control information from the digital signals contained in the optical signal received by the optical demodulator 21. For example, the deframer 27 acquires control information from the signal passed through the LPF 26.

[0068] More specifically, the deframer 27 receives an electrical signal M2b from the LPF 26 and obtains an Ethernet frame from the received electrical signal M2b. If the destination MAC address included in the obtained Ethernet frame does not match the MAC address of the slave device 201, the deframer 27 discards the Ethernet frame. On the other hand, if the destination MAC address included in the obtained Ethernet frame matches the MAC address of the slave device 201, the deframer 27 obtains multiple pieces of control information from the payload of the Ethernet frame. The deframer 27 outputs the multiple pieces of control information it has obtained to the control information processing unit 28.

[0069] The control information processing unit 28 receives multiple pieces of control information from the deframer 27 and processes each piece of control information it receives. For example, the control information processing unit 28 receives beamforming information, which is an example of control information, and processes the beam output from the antenna 161 according to the beamforming information it receives.

[0070] [Operation Flow] Figure 5 shows an example of a communication sequence in an optical communication system according to the first embodiment of this disclosure.

[0071] Referring to Figure 5, the master station 101 transmits an optical signal, in which the IF signal is optically modulated, to the slave station 201 via the optical fiber 191 (step S11).

[0072] Next, when the master unit 101 needs to control the slave unit 201, it generates a digital signal containing a single Ethernet frame that stores multiple control pieces of information for controlling the slave unit 201 (step S12).

[0073] Next, the master station device 101 generates an electrical signal M1 by frequency multiplexing the IF signal and the generated digital signal (step S13).

[0074] Next, the master station 101 transmits an optical signal, in which the electrical signal M1 is optically modulated, to the slave station 201 via the optical fiber 191 (step S14).

[0075] Next, the slave station 201 receives an optical signal from the master station 101 via the optical fiber 191 and generates an electrical signal M2 with a level corresponding to the intensity of the received optical signal (step S15).

[0076] Next, the slave station device 201 acquires an Ethernet frame from the electrical signal M2b, which is the frequency component of the electrical signal M2 with a frequency less than Fx, and acquires multiple pieces of control information from the payload of the Ethernet frame (step S16).

[0077] Next, the slave station device 201 processes the acquired control information (step S17).

[0078] While the master station device 101 in the first embodiment of this disclosure is configured to include an LPF 16, it is not limited to this configuration. The master station device 101 may also be configured without an LPF 16, depending on the required transmission quality and transmission bandwidth range for the optical communication system 301.

[0079] Furthermore, although the master station device 101 according to the first embodiment of this disclosure is configured to include one frequency conversion unit 12, it is not limited thereto. The master station device 101 may be configured to include multiple frequency conversion units 12 depending on the number of antennas 161 installed in different locations. In this case, the multiplexing unit 17 generates an electrical signal by frequency multiplexing multiple IF signals, each containing communication data for each antenna 161 generated by the multiple frequency conversion units 12, with a digital signal, and outputs it to the optical modulation unit 18.

[0080] Furthermore, although the slave station device 201 according to the first embodiment of this disclosure is configured to include an LPF 26, it is not limited thereto. The slave station device 201 may be configured without an LPF 26, depending on the transmission quality and transmission bandwidth range required for the optical communication system 301.

[0081] Furthermore, although the master station device 101 according to the first embodiment of this disclosure is configured to include an 8B / 10B modulation unit 15, it is not limited thereto. The master station device 101 may also be configured without an 8B / 10B modulation unit 15. However, in a configuration in which the master station device 101 includes an 8B / 10B modulation unit 15, the DC component of the digital signal can be reduced and the occurrence of baseline wander can be suppressed compared to a configuration in which the master station device 101 does not include an 8B / 10B modulation unit 15.

[0082] Furthermore, in the master station device 101 according to the first embodiment of this disclosure, the frequency conversion unit 12 is configured to generate an IF signal having a center frequency fa that satisfies the above-described equation (1), but the invention is not limited to this. The frequency conversion unit 12 may be configured to generate an IF signal having a center frequency fa that does not satisfy the above-described equation (1). In this case, for example, the master station device 101 further includes a DC (Direct Current) rejection unit that is downstream of the 8B / 10B modulation unit 15 and upstream of the LPF 16. The DC rejection unit receives a digital signal from the 8B / 10B modulation unit 15, removes the DC component of the received digital signal, and outputs the digital signal from which the DC component has been removed to the LPF 16.

[0083] Incidentally, there is a need for technology that can transmit control information more efficiently with a simpler configuration.

[0084] For example, in the technology described in Patent Document 1, a wireless device that receives a multiplexed signal consisting of multiple sinusoidal tone signals and an IF signal requires an FFT (Fast Fourier Transform) circuit to separate and process the tone signals from the received signal, which can complicate the circuit configuration of the wireless device. Furthermore, in order to suppress interference between tone signals and between tone signals and the IF signal, it is necessary to strictly control the frequencies of the tone signals and the IF signals, which can also complicate the configuration of the optical transmitter that transmits the multiplexed signal. In addition, the technology described in Patent Document 1 does not allow for the simultaneous transmission of multiple types of control information from the optical transmitter to the wireless device.

[0085] Similarly, the technology described in Patent Document 2 cannot transmit multiple types of control information from a transmitting device to a receiving device all at once.

[0086] In contrast, in the optical communication system 301 according to the first embodiment of this disclosure, the master station 101 generates a digital signal including a single frame containing multiple control information, and transmits the generated digital signal and IF signal, along with the optical fiber 191, to the slave station 201. The slave station 201 obtains at least one of the multiple control information from the digital signal included in the optical signal received from the master station 101 via the optical fiber 191.

[0087] In this configuration, a digital signal containing a single frame with multiple control information stored within it, and an optical signal containing an IF signal, are transmitted via optical fiber. This allows for the simultaneous transmission of multiple control information without requiring precise control of the IF signal frequency. Therefore, control information can be transmitted more efficiently with a simpler configuration. Furthermore, by changing the frame format, various types of control information can be flexibly transmitted.

[0088] Next, other embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0089] <Second Embodiment> This embodiment relates to an optical communication system 302 that transmits wavelength-multiplexed optical signals via an optical fiber 191, compared to the optical communication system 301 according to the first embodiment. Except for the contents described below, it is the same as the optical communication system 301 according to the first embodiment.

[0090] Figure 6 is a diagram showing the configuration of an optical communication system according to a second embodiment of the present disclosure. Referring to Figure 6, the optical communication system 302, compared to the optical communication system 301 shown in Figure 1, includes a master station 102 instead of a master station 101, and includes a slave station 202 instead of a slave station 201.

[0091] The master station 102 transmits an optical signal, including a digital signal and an IF signal, to the slave station 202 via the optical fiber 191. More specifically, the master station 102 generates an optical signal based on the digital signal, wavelength-multiplexes the generated optical signal with an optical signal based on the IF signal, and transmits it to the slave station 202 via the optical fiber 191.

[0092] The slave unit 202 acquires control information from the digital signals contained in the optical signal received from the master unit 102 via the optical fiber 191. The slave unit 202 operates according to the acquired control information.

[0093] (Master station device) Figure 7 shows the configuration of a master station device according to a second embodiment of the present disclosure. Referring to Figure 7, the master station device 102, compared to the master station device 101 shown in Figure 2, includes optical modulation units 31A, 31B and a multiplexing unit 32 instead of the LPF 16, multiplexing unit 17 and optical modulation unit 18. The multiplexing unit 32 is an example of a transmission unit.

[0094] The frequency conversion unit 12 receives an analog signal from the signal receiving unit 11, generates an IF signal by upconverting or downconverting the received analog signal, and outputs the generated IF signal to the optical modulation unit 31A.

[0095] The optical modulation unit 31A receives an IF signal from the frequency conversion unit 12, generates an optical signal with wavelength λ1 by optically modulating the received IF signal, and outputs the generated optical signal to the multiplexing unit 32. The optical signal with wavelength λ1 generated by the optical modulation unit 31A is an example of a second optical signal.

[0096] The 8B / 10B modulation unit 15 receives a digital signal, including an Ethernet frame, from the framer 14, modulates the received digital signal using the 8B / 10B method, and outputs it to the optical modulation unit 31B.

[0097] The optical modulation unit 31B receives a digital signal from the 8B / 10B modulation unit 15, generates an optical signal with wavelength λ2 by optically modulating the received digital signal, and outputs the generated optical signal to the multiplexing unit 32. The optical signal with wavelength λ2 generated by the optical modulation unit 31B is an example of the first optical signal.

[0098] The multiplexer 32 wavelength-multiplexes the optical signal with wavelength λ1 received from the optical modulation unit 31A and the optical signal with wavelength λ2 received from the optical modulation unit 31B. For example, the multiplexer 32 is an optical coupler. The multiplexer 32 outputs the wavelength-multiplexed optical signal to the optical fiber 191.

[0099] Figure 8 schematically shows an example of the frequency spectrum of an optical signal output by the multiplexing unit in a master station device according to a second embodiment of the present disclosure. In Figure 8, the horizontal axis represents frequency [THz], and the vertical axis represents signal intensity.

[0100] Referring to Figure 8, the multiplexer 32 combines an optical signal with a wavelength λ1 and a center frequency of 193.4 THz with an optical signal with a wavelength λ2 and a center frequency of 193.2 THz, and outputs it to the optical fiber 191.

[0101] (Slave station device) Figure 9 shows the configuration of a substation device according to a second embodiment of the present disclosure. Referring to Figure 9, the substation device 202, compared to the substation device 201 shown in Figure 4, includes a separation unit 41 and optical demodulation units 42A, 42B instead of the optical demodulation unit 21, separation unit 22, and LPF 26. The separation unit 41 is an example of a receiving unit.

[0102] The separation unit 41 receives an optical signal from the master station 102 via the optical fiber 191, which includes a digital signal containing a single Ethernet frame containing multiple control information and an IF signal, and separates the received optical signal according to its wavelength. For example, the separation unit 41 is an optical coupler. The separation unit 41 outputs the optical signal with wavelength λ1 from the received optical signal to the optical demodulation unit 42A and the optical signal with wavelength λ2 to the optical demodulation unit 42B. The optical signal with wavelength λ1 includes an IF signal generated by the frequency conversion unit 12 in the master station 102. The optical signal with wavelength λ2 includes a digital signal modulated by the 8B / 10B modulation unit 15 in the master station 102.

[0103] The optical demodulation unit 42A receives an optical signal of wavelength λ1 from the separation unit 41, generates an electrical signal M2a with a level corresponding to the intensity of the received optical signal, and outputs it to the amplification unit 23A.

[0104] The amplification unit 23A receives the electrical signal M2a from the separation unit 41, amplifies the received electrical signal M2a, and outputs the amplified electrical signal M2a to the frequency conversion unit 24.

[0105] For example, the frequency conversion unit 24 generates an RF signal by upconverting the electrical signal M2a received from the amplification unit 23A, and outputs the generated RF signal to the antenna 161. Alternatively, the frequency conversion unit 24 generates a baseband signal by downconverting the electrical signal M2a received from the amplification unit 23A, and transmits the generated baseband signal to an external device of the slave station device 202.

[0106] The optical demodulation unit 42B receives an optical signal with wavelength λ2 from the separation unit 41, generates an electrical signal M2b with a level corresponding to the intensity of the received optical signal, and outputs it to the amplification unit 23B.

[0107] The amplification unit 23B receives the electrical signal M2b from the separation unit 41, amplifies the received electrical signal M2b, and outputs the amplified electrical signal M2b to the 8B / 10B demodulation unit 25.

[0108] The 8B / 10B demodulation unit 25 demodulates the electrical signal M2b received from the amplification unit 23B using the 8B / 10B method and outputs it to the deframer 27. In other words, the 8B / 10B demodulation unit 25 converts the 10-bit electrical signal M2b received from the amplification unit 23B into an 8-bit electrical signal M2b and outputs it to the deframer 27.

[0109] The deframer 27 acquires multiple control information from the digital signals contained in the optical signal received by the separation unit 41. More specifically, the deframer 27 receives an electrical signal M2b from the 8B / 10B demodulation unit 25 and acquires an Ethernet frame from the received electrical signal M2b. If the destination MAC address contained in the acquired Ethernet frame matches the MAC address of the slave device 202, the deframer 27 acquires multiple control information from the payload of the Ethernet frame and outputs the acquired control information to the control information processing unit 28.

[0110] The control information processing unit 28 receives multiple pieces of control information from the deframer 27 and processes the received control information. For example, the control information processing unit 28 receives beamforming information, which is an example of control information, and processes the beam output from the antenna 161 according to the received beamforming information.

[0111] The embodiments described above should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the above description, and all modifications within the meaning and scope of the claims are intended to be included.

[0112] Each process (each function) of the above-described embodiment is implemented by a processing circuit (Circuitry) including one or more processors. The processing circuit may consist of one or more memories, various analog circuits, various digital circuits, etc., in addition to the one or more processors, as well as an integrated circuit. The one or more memories store programs (instructions) that cause the one or more processors to execute each of the above processes. The one or more processors may execute each of the above processes according to the programs read from the one or more memories, or they may execute each of the above processes according to logic circuits that have been pre-designed to execute each of the above processes. The processors may be various processors suitable for computer control, such as a CPU (Central Processing Unit), GPU (Graphics Processing Unit), DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), and ASIC (Application Specific Integrated Circuit). Furthermore, the physically separated multiple processors may cooperate with each other to execute each of the above processes. For example, the processors installed in each of several physically separated computers may cooperate with each other via a network such as a LAN (Local Area Network), WAN (Wide Area Network), and the Internet to perform the above processes. The program may be installed in the memory via the network from an external server device, or it may be distributed on a recording medium such as a CD-ROM (Compact Disc Read Only Memory), DVD-ROM (Digital Versatile Disk Read Only Memory), and semiconductor memory, and then installed in the memory from the recording medium.

[0113] The above description includes the following features. [Note 1] The master station and Equipped with a substation device, The master station device generates a digital signal including a single frame containing multiple pieces of control information, and transmits the generated digital signal and an analog main signal to the slave station device via an optical fiber. The slave station device acquires at least one of the plurality of control information from the digital signal included in the optical signal received from the master station device via the optical fiber, The master station device generates the digital signal, which includes the frame containing destination information for the slave station device, as part of an optical communication system. [Explanation of Symbols]

[0114] 11 Signal receiving section 12 Frequency conversion section 13 Control Information Output Unit 14 Frame 15 8B / 10B Modulation Section 16 LPF 17 Multiplex section 18 Optical Modulation Section 21 Optical demodulator 22 Separation part 23A, 23B Amplifier Section 24 Frequency conversion section 25 8B / 10B Demodulation Unit 26 LPF 27 Deframer 28 Control Information Processing Unit 31A, 31B Optical Modulation Section 32 Multiplex section 41 Separation part 42A, 42B Optical demodulator 101,102 Master station device 161 Antenna 201,202 Slave station device 191 Optical Fiber 301,302 Optical communication systems

Claims

1. The master station and It includes a substation that transmits and receives wireless signals via an antenna, The master station device generates a digital signal including a single frame containing multiple control information for controlling the slave station device, and transmits the generated digital signal and an analog main signal to the slave station device via an optical fiber. The slave station device is an optical communication system that acquires at least one of a plurality of control pieces of information from the digital signal included in the optical signal received from the master station device via the optical fiber.

2. The optical communication system according to claim 1, wherein the master station device generates the optical signal based on an electrical signal obtained by frequency multiplexing the digital signal and the master signal, and transmits the generated optical signal to the slave station device via the optical fiber.

3. The optical communication system according to claim 2, wherein the master station device frequency multiplexes the signal passed through the first low-pass filter that receives the digital signal with the main signal.

4. The optical communication system according to claim 2 or 3, wherein the slave station device generates an electrical signal based on the optical signal received from the master station device via the optical fiber, separates the digital signal from the electrical signal using a filter, and obtains the control information from the signal passed through a second low-pass filter that receives the separated digital signal.

5. The optical communication system according to claim 1, wherein the master station device generates a first optical signal based on the digital signal, wavelength multiplexes the generated optical signal with a second optical signal based on the master signal to generate the optical signal, and transmits the generated optical signal to the slave station device via the optical fiber.

6. The optical communication system according to claim 1, wherein the control information is information for controlling the transmission operation of the wireless signal by the slave station device.

7. A generation unit that generates a digital signal including a single frame containing multiple control pieces of information for controlling other devices that transmit and receive wireless signals via an antenna, A master station device comprising a transmitting unit that transmits an optical signal, including the digital signal and the analog master signal generated by the generating unit, to the other device via an optical fiber.

8. A substation device that transmits and receives wireless signals via an antenna, A receiving unit that receives from another device via optical fiber an optical signal including a digital signal and an analog main signal, which include a single frame containing multiple control information for controlling the aforementioned substation device, A substation device comprising: an acquisition unit that acquires at least one of a plurality of control information from the digital signal contained in the optical signal received by the receiving unit.

9. An optical communication method in an optical communication system comprising a master station device and a slave station device that transmits and receives wireless signals via an antenna, The steps include: the master station device generating a digital signal including a single frame containing multiple control information for controlling the slave station device, and transmitting an optical signal including the generated digital signal and an analog master signal to the slave station device via an optical fiber; An optical communication method comprising the step of the slave station device acquiring at least one of a plurality of control pieces of information from the digital signal included in the optical signal received from the master station device via the optical fiber.

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