Transmitting device, receiving device, communication system, transmitting method, and receiving method

Abstract

This transmission device comprises: a selection unit that, if the difference between the frequency of an interference wave, which occurs when a first carrier signal is transmitted at a first carrier frequency, and a second carrier frequency of a second carrier signal is less than or equal to a threshold value, selects a third carrier frequency from among unused carrier frequencies that will cause the difference to exceed the threshold value; a signal transmission unit that, if the difference exceeds the threshold value, transmits the first carrier signal at the first carrier frequency, and that, if the difference is less than or equal to the threshold value, converts the first carrier frequency of the first carrier signal into the third carrier frequency and transmits the first carrier signal at the third carrier frequency; and an information transmission unit that transmits information of the combination of the first carrier frequency before the conversion and the third carrier frequency after the conversion in the case of the difference exceeding the threshold value.

Description

[Technical Field]

[0001] The present invention relates to a transmitting device, a receiving device, a communication system, a transmitting method, and a receiving method. [Background technology]

[0002] A communication system may perform optical intensity modulation on a carrier signal including a frequency division multiplexing signal. A transmitter of the communication system transmits an optical signal generated by the optical intensity modulation to a receiver of the communication system (see Non-Patent Document 1). The communication system may also perform frequency modulation batch conversion (FM batch conversion) on the carrier signal in order to extend the transmission distance of the optical signal (see Non-Patent Document 2). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] “Transmission equipment for multi-channel television signals over optical access networks by sub-carrier multiplexing (SCM)”, ITU-T Rec. J. 186, 2008. [Non-patent document 2] “Transmission equipment for transferring multi-channel television signals over optical access networks by frequency modulation conversion”, ITU-T Rec. J. 185, 2012. Summary of the Invention [Problem to be solved by the invention]

[0004] Fig. 11 is a diagram showing an example of communication quality degradation. The communication system shown in Fig. 11 includes a transmission network 4, a transmitting device 200b, and a receiving device 300b. A carrier signal is input to the transmitting device 200b from a head-end device (not shown). The carrier signal is, for example, a radio frequency video signal. A carrier frequency band that can be used for the carrier signal is predetermined according to the specifications and characteristics of the communication system and the type of service of the communication system.

[0005] The transmitting device 200b transmits an optical signal generated in response to a carrier signal of a predetermined carrier frequency to the receiving device 300b. The transmission network 4 relays and transmits the optical signal. The receiving device 300b receives the relayed optical signal from the transmission network 4. The receiving device 300b converts the received optical signal into an electrical signal. The receiving device 300b performs demodulation processing on the electrical signal. As a result, the receiving device 300b generates a carrier signal in response to the optical signal.

[0006] The carrier signal includes a frequency division multiplexed signal (FDM signal). Here, interference waves (harmonics and distortion signals) caused by a carrier signal of a certain carrier frequency may interfere with other carrier signals of other carrier frequencies. Furthermore, in a communication system, relaying of an optical signal through a transmission network 4 may, for example, amplify distortion in the carrier signal, degrading communication quality and affecting the services provided by the communication system. As such, there are cases where it is impossible to suppress degradation of communication quality due to interference waves caused by carrier signals.

[0007] In view of the above circumstances, an object of the present invention is to provide a transmitting device, a receiving device, a communication system, a transmitting method, and a receiving method that are capable of suppressing degradation of communication quality due to interference waves caused by a carrier signal. [Means for solving the problem]

[0008] One aspect of the present invention is a transmitting device comprising: a selection unit that selects a third carrier frequency from among available carrier frequencies that cause a difference between the frequency of an interference wave generated when a first carrier signal is transmitted at a first carrier frequency and the second carrier frequency of a second carrier signal to exceed a threshold value when the difference is equal to or less than a threshold value; a signal transmission unit that transmits the first carrier signal at the first carrier frequency when the difference exceeds the threshold value, and converts the first carrier frequency of the first carrier signal to the third carrier frequency and transmits the first carrier signal at the third carrier frequency when the difference is equal to or less than the threshold value; and an information transmission unit that transmits information about the combination of the first carrier frequency before conversion and the third carrier frequency after conversion when the difference exceeds the threshold value.

[0009] One aspect of the present invention is a receiving device comprising: an information acquisition unit that acquires, from a transmitting device, information on a combination of a first carrier frequency before conversion and a third carrier frequency after conversion when the difference between the frequency of an interference wave generated when a first carrier signal is transmitted at a first carrier frequency and the second carrier frequency of a second carrier signal exceeds a threshold; a signal acquisition unit that acquires, from the transmitting device, the first carrier signal transmitted at the first carrier frequency or the third carrier frequency; and a conversion unit that converts the third carrier frequency of the first carrier signal transmitted at the third carrier frequency to the first carrier frequency based on the combination information.

[0010] One aspect of the present invention is a communication system including a transmitting device and a receiving device, wherein the transmitting device includes a selector that, when a difference between a frequency of an interference wave generated when a first carrier signal is transmitted at a first carrier frequency and a second carrier frequency of a second carrier signal is equal to or less than a threshold, selects a third carrier frequency from among available carrier frequencies that cause the difference to exceed the threshold; and a receiver that transmits the first carrier signal at the first carrier frequency when the difference exceeds the threshold, and converts the first carrier frequency of the first carrier signal to the third carrier frequency when the difference is equal to or less than the threshold. and an information transmitting unit that transmits information on a combination of the first carrier frequency before conversion and the third carrier frequency after conversion when the difference exceeds the threshold value, and the receiving device includes an information acquiring unit that acquires the information on the combination from the information transmitting unit, a signal acquiring unit that acquires the first carrier signal transmitted at the first carrier frequency or the third carrier frequency from the signal transmitting unit, and a converting unit that converts the third carrier frequency of the first carrier signal transmitted at the third carrier frequency to the first carrier frequency based on the information on the combination.

[0011] One aspect of the present invention is a transmission method executed by a transmitting device, the transmission method including the steps of: when a difference between the frequency of an interference wave generated when a first carrier signal is transmitted at a first carrier frequency and the second carrier frequency of a second carrier signal is equal to or less than a threshold, selecting a third carrier frequency from among available carrier frequencies that cause the difference to exceed the threshold; transmitting the first carrier signal at the first carrier frequency if the difference exceeds the threshold, and converting the first carrier frequency of the first carrier signal to the third carrier frequency and transmitting the first carrier signal at the third carrier frequency if the difference is equal to or less than the threshold; and transmitting information about the combination of the first carrier frequency before conversion and the third carrier frequency after conversion if the difference exceeds the threshold.

[0012] One aspect of the present invention is a receiving method executed by a receiving device, the receiving method including the steps of: acquiring, from a transmitting device, information on a combination of the first carrier frequency before conversion and the third carrier frequency after conversion when the difference between the frequency of an interference wave generated when a first carrier signal is transmitted at a first carrier frequency and the second carrier frequency of a second carrier signal exceeds a threshold; acquiring, from the transmitting device, the first carrier signal transmitted at the first carrier frequency or the third carrier frequency; and converting, based on the information on the combination, the third carrier frequency of the first carrier signal transmitted at the third carrier frequency to the first carrier frequency. [Effects of the Invention]

[0013] According to the present invention, it is possible to suppress deterioration of communication quality due to interference waves caused by carrier signals. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a communication system in a first embodiment. [Figure 2] FIG. 3 is a diagram illustrating an example of frequency conversion in the first embodiment. [Figure 3] FIG. 2 is a diagram illustrating an example of the configuration of a transmission device in the first embodiment. [Figure 4] FIG. 2 is a diagram illustrating an example of the configuration of a receiving device in the first embodiment. [Figure 5] 5 is a flowchart showing an example of the operation of the transmitting device in the first embodiment. [Figure 6] 5 is a flowchart showing an example of the operation of the receiving device in the first embodiment. [Figure 7] FIG. 10 is a diagram illustrating an example of the configuration of a communication system in a comparative example to the first embodiment. [Figure 8] FIG. 10 is a diagram illustrating an example of the configuration of a communication system in a second embodiment. [Figure 9] FIG. 10 is a diagram illustrating an example of the configuration of a communication system in a comparative example to the second embodiment. [Figure 10]FIG. 2 is a diagram illustrating an example of a hardware configuration of an optical communication device in each embodiment. [Figure 11] FIG. 10 is a diagram illustrating an example of communication quality degradation. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings. (First embodiment) 1 is a diagram showing an example of the configuration of a communication system 1a according to the first embodiment. The communication system 1a is a system that communicates using optical signals. The communication system 1a includes a transmitting device 2a, a receiving device 3a, and a transmission network 4.

[0016] The transmitting device 2a is, for example, an optical line termination. The optical line termination is, for example, a V-OLT (Video-Optical Line Terminal) or a transmitter (TX). The transmitting device 2a includes a pilot signal generating unit 20, an input signal analyzing unit 21, an input signal converting unit 22, a multiplexer 23, a batch converting unit 24, an electrical-to-optical converting unit 25, an optical dispersion compensating unit 26, an optical amplifying unit 27, a power supply unit 28, and an alarm monitoring unit 29.

[0017] The receiving device 3a is, for example, an optical line terminal. The optical line terminal is, for example, a V-ONT (Video-Optical Network Terminal). The receiving device 3a includes an opto-electrical conversion unit 30, a demodulation unit 31, an output signal analysis unit 32, an output signal conversion unit 33, a multiplexer 34, an amplification unit 35, and a power supply unit 36. The transmission network 4 (optical transmission network) is a relay network. The transmission network 4 includes, for example, optical fiber.

[0018] The carrier signal may include a pilot signal. The pilot signal is used by a transmission device (not shown) and a receiving device 3a in the transmission network 4 to check the normality of the transmission signal, for example. The pilot signal is generated, for example, by a head-end device (not shown), and input to the transmitting device 2a in the same way as other input signals. The pilot signal may be generated, for example, by the transmitting device 2a. When the pilot signal is generated by the transmitting device 2a, the pilot signal generating unit 20 synchronizes with the input carrier signal and generates a pilot signal having a frequency that does not overlap with the frequency of the input carrier signal. The generated pilot signal is multiplexed with the carrier signal at a predetermined point before the batch conversion unit 24.

[0019] A carrier signal including a frequency division multiplexed signal is input to the input signal analysis unit 21 from, for example, a head-end device (not shown). The carrier signal is, for example, a video signal (main signal). The input signal analysis unit 21 measures the carrier frequency (center frequency) of the input carrier signal in units of carrier width. The input signal analysis unit 21 divides the input carrier signal into two systems (first system and second system) and outputs them to the input signal conversion unit 22.

[0020] If the difference (absolute value) between the frequency of the interference wave caused by a specified carrier frequency in use and other carrier frequencies in use is less than a threshold value, the input signal analysis unit 21 selects, as the carrier frequency after conversion of the carrier signal, an unused carrier frequency (free carrier frequency) within the band of carrier frequencies available to the communication system 1a that satisfies the condition that the carrier signal of the converted carrier frequency will not become a new interference wave for other carrier signals.

[0021] The input signal analysis unit 21 generates carrier frequency conversion information, which includes information on a combination of a carrier frequency before conversion and a carrier frequency after conversion.

[0022] The input signal conversion unit 22 deletes the carrier signal of the pre-conversion carrier frequency from the carrier signals of the band input from the first system of the input signal analysis unit 21. The input signal conversion unit 22 outputs to the multiplexer 23 the carrier signals of the remaining band from which the carrier signal of the pre-conversion carrier frequency has been deleted.

[0023] The input signal conversion unit 22 generates a carrier signal with a converted carrier frequency based on the carrier signal of the band input from the second system of the input signal analysis unit 21. The input signal conversion unit 22 outputs the carrier signal with the converted carrier frequency to the multiplexer 23.

[0024] The multiplexer 23 multiplexes the carrier signal of the converted carrier frequency with the carrier signal of the remaining band from which the carrier signal of the pre-conversion carrier frequency has been deleted. The level of the multiplexed carrier signal may be amplified using an amplifier (not shown) before the multiplexed carrier signal is input to the batch conversion unit 24.

[0025] The batch conversion unit 24 performs frequency modulation batch conversion (FM batch conversion) on the combined carrier signal. The electrical-to-optical conversion unit 25 generates an optical signal in accordance with the carrier signal after frequency modulation batch conversion. The optical dispersion compensation unit 26 performs dispersion compensation processing on the generated optical signal.

[0026] The optical amplifier 27 amplifies the level of the optical signal that has been subjected to dispersion compensation processing. The optical amplifier 27 outputs the optical signal whose level has been amplified to the transmission network 4. The transmission network 4 (optical transmission network) transmits the optical signal whose level has been amplified by the optical amplifier 27 to the photoelectric conversion unit 30.

[0027] The power supply unit 28 is supplied with power from an external power source. The power supply unit 28 supplies power to each functional unit of the transmission device 2a. The alarm monitoring unit 29 transmits predetermined information to the reception device 3a. For example, the alarm monitoring unit 29 outputs carrier frequency conversion information (a list of combinations of pre-conversion frequencies and post-conversion frequencies for carrier waves that have undergone frequency conversion) to the output signal analysis unit 32. For example, the alarm monitoring unit 29 monitors the operation of each functional unit (each device) of the transmission device 2a. If an abnormality is detected in any of the functional units, the alarm monitoring unit 29 outputs an alarm (notification of the abnormality) to the outside according to the monitoring results.

[0028] FIG. 2 is a diagram showing an example of frequency conversion (relocation of carrier frequencies) in the first embodiment. "fa" represents the carrier frequency currently used for the carrier signal. "2fa" represents the frequency of the second harmonic of the carrier frequency "fa". "2fa" represents the frequency of the third harmonic of the carrier frequency "fa". "fb" represents another carrier frequency currently used for another carrier signal. "2fb" represents the frequency of the second harmonic of another carrier frequency "fb". "2fb" represents the frequency of the third harmonic of another carrier frequency "fb".

[0029] "fb+fa" and "fb-fa" respectively represent the frequencies of second-order distortion (second-order DU ratio). The DU ratio (Desired to Undesired signal ratio) represents the ratio between the desired signal and the interference signal. "2fb+fa" and "2fb-fa" respectively represent the frequencies of third-order distortion (third-order DU ratio).

[0030] The input signal analysis unit 21 rearranges the carrier frequency of the carrier signal before transmitting the carrier signal so that no harmonic or distortion frequencies exist near the carrier frequency of the carrier signal on the frequency axis. The input signal analysis unit 21 outputs carrier frequency conversion information (rearrangement information) to the output signal analysis unit 32.

[0031] In the graph on the left side of FIG. 2, the input signal analysis unit 21 detects as a measurement result that a second-order distortion frequency "fb-fa" exists near the carrier frequency "fa." In such a case, the signal with the second-order distortion frequency "fb-fa" becomes an interference wave for the carrier signal with the carrier frequency "fa." In addition, the input signal analysis unit 21 detects as a measurement result that a second-order harmonic frequency "2fa" exists near another carrier frequency "fb." In such a case, the signal with the second-order harmonic frequency "2fa" becomes an interference wave for the carrier signal with the carrier frequency "fb."

[0032] Therefore, the input signal analysis unit 21 decides to perform down-conversion or up-conversion processing on the carrier signal of the carrier frequency "fa" so that the second-order distortion frequency "fb-fa" does not exist near the carrier frequency "fa".

[0033] In the graph on the left side of Fig. 2, the input signal analysis unit 21 determines to perform down-conversion processing on the carrier signal having the carrier frequency "fa." The input signal conversion unit 22 performs down-conversion processing on the carrier signal having the carrier frequency "fa" based on the determination by the input signal analysis unit 21. In other words, the input signal conversion unit 22 shifts the carrier frequency "fa" downward to the vacant carrier frequency "fc."

[0034] As a result, as shown in the graph on the right side of Figure 2, the frequency of each interference wave is separated on the frequency axis from the carrier frequency "fa" currently used for the carrier signal, and the frequency of each interference wave is separated on the frequency axis from another carrier frequency "fb" currently used for another carrier signal.

[0035] Returning to Fig. 1, the receiving device 3a will be described. An optical signal relayed by the transmission network 4 is input from the transmission network 4 to the photoelectric conversion unit 30. The photoelectric conversion unit 30 converts the optical signal into an electrical signal. The demodulation unit 31 performs demodulation processing on the optical signal to generate a carrier signal corresponding to the optical signal.

[0036] A carrier signal corresponding to the optical signal is input to the output signal analysis unit 32 from the demodulation unit 31. The output signal analysis unit 32 acquires carrier frequency conversion information from the input signal analysis unit 21 via the alarm monitoring unit 29.

[0037] The output signal analysis unit 32 detects a carrier signal having a converted carrier frequency in the carrier signal corresponding to the optical signal based on the carrier frequency conversion information. The output signal analysis unit 32 outputs a control signal corresponding to the carrier frequency conversion information to the output signal conversion unit 33. The output signal analysis unit 32 divides the carrier signal corresponding to the optical signal into two systems (first system and second system) and outputs them to the input signal conversion unit 22.

[0038] The output signal conversion unit 33 converts the carrier signal having the converted carrier frequency in the carrier signal corresponding to the optical signal back to the carrier frequency before conversion based on a control signal corresponding to the carrier frequency conversion information. The output signal conversion unit 33 outputs the carrier signal having the pre-conversion carrier frequency "fa" to the multiplexer 34. The output signal conversion unit 33 outputs the carrier signal of the remaining band, from which the carrier signal having the converted carrier frequency "fc" has been deleted, to the multiplexer 34.

[0039] The multiplexer 34 multiplexes the carrier signal of the carrier frequency "fa" before conversion with the carrier signal of the remaining band from which the carrier signal of the carrier frequency "fc" after conversion has been deleted. The amplifier 35 may amplify the level of the multiplexed carrier signal. The amplifier 35 outputs the carrier signal whose level has been amplified to an external device (not shown). This external device is, for example, a display device. The power supply 36 is supplied with power from an external power source. The power supply 36 supplies power to each functional unit of the receiving device 3a.

[0040] Next, the transmitter 2a will be described in detail. 3 is a diagram showing an example of the configuration of the transmission device 2a in the first embodiment. The input signal analysis unit 21 includes a signal analysis unit 210 and a divider 211. The input signal conversion unit 22 includes a variable band pass filter 220, a variable band pass filter 221, a signal generator 222, a multiplier 223, and a variable band pass filter 224. The transmission device 2a may further include an amplifier 40.

[0041] A carrier signal including a frequency division multiplexed signal is input from, for example, a head-end device (not shown) to the signal analysis unit 210. The signal analysis unit 210 measures the carrier frequency (center frequency) of the input carrier signal in units of carrier width.

[0042] The signal analysis unit 210 selects, from the band of carrier frequencies available to the communication system 1a, an unused carrier frequency (empty carrier frequency) that satisfies the condition that the carrier signal of the converted carrier frequency will not become a new interfering wave for other carrier signals. The signal analysis unit 210 generates carrier frequency conversion information.

[0043] The signal analysis unit 210 outputs information (control signal) representing the pre-conversion carrier frequency "fa" to the variable band-pass filter 220 so that the variable band-pass filter 220 does not pass the carrier signal of the pre-conversion carrier frequency "fa".

[0044] The signal analysis unit 210 outputs information (control signal) representing the pre-conversion carrier frequency "fa" to the variable band-pass filter 221 so that the variable band-pass filter 221 passes the carrier signal of the pre-conversion carrier frequency "fa".

[0045] The distributor 211 outputs (distributes) the carrier signal input from the signal analysis unit 210 to the variable band pass filter 220 and the variable band pass filter 221 .

[0046] The variable band-pass filter 220 removes the carrier signal of the pre-conversion carrier frequency "fa" from the carrier signals input from the first system of the distributor 211. The variable band-pass filter 220 outputs the carrier signals of the remaining band, from which the carrier signal of the carrier frequency "fa" has been removed, to the multiplexer 23.

[0047] The variable band pass filter 221 generates a carrier signal with a pre-conversion carrier frequency "fa" based on the carrier signal of the band input from the second system of the divider 211. The variable band pass filter 221 outputs the carrier signal with the pre-conversion carrier frequency "fa" to the multiplier 223.

[0048] Information (control signal) representing the frequency "ft" is input to the signal generator 222 from the signal analysis unit 210. The frequency "ft" represents the amount of frequency shift. The signal generator 222 outputs an analog signal of the frequency "ft" to the multiplier 223.

[0049] The multiplier 223 multiplies the carrier signal with the pre-conversion carrier frequency "fa" by the analog signal with the frequency "ft". When converting the pre-conversion carrier frequency "fa" in the higher frequency direction to the post-conversion carrier frequency "fc=fa+ft", the multiplier 223 outputs the carrier signal with the post-conversion carrier frequency "fc=fa+ft" as the multiplication result to the variable band-pass filter 224. When converting the pre-conversion carrier frequency "fa" in the lower frequency direction to the post-conversion carrier frequency "fc=fa-ft", the multiplier 223 outputs the carrier signal with the post-conversion carrier frequency "fc=fa-ft" as the multiplication result to the variable band-pass filter 224.

[0050] Information (control signal) representing the converted carrier frequency "fc" is input to the variable band pass filter 224 from the signal analysis unit 210. The variable band pass filter 224 passes the carrier signal of the converted carrier frequency "fc" and outputs it to the multiplexer 23. The multiplexer 23 multiplexes the carrier signal of the converted carrier frequency "fc" with the carrier signal of the remaining band from which the carrier signal of the pre-conversion carrier frequency "fa" has been deleted. The amplifier 40 may amplify the level of the carrier signal multiplexed by the multiplexer 23.

[0051] Next, the receiving device 3a will be described in detail. 4 is a diagram showing an example of the configuration of the receiving device 3a in the first embodiment. The output signal analysis unit 32 includes a signal analysis unit 320 and a distributor 321. The output signal conversion unit 33 includes a variable band pass filter 330, a variable band pass filter 331, a signal generator 332, a multiplier 333, and a variable band pass filter 334. The receiving device 3a may further include an amplifier 35.

[0052] A carrier signal corresponding to the optical signal is input to the signal analysis unit 320 from the demodulation unit 31. The signal analysis unit 320 acquires carrier frequency conversion information (information on the combination of the carrier frequency "fa" before conversion and the carrier frequency "fc" after conversion) from the input signal analysis unit 21 via the alarm monitoring unit 29.

[0053] The signal analysis unit 320 outputs information (control signal) representing the converted carrier frequency "fc" to the variable band pass filter 330 so that the variable band pass filter 330 does not pass the carrier signal of the converted carrier frequency "fc".

[0054] The signal analysis unit 320 outputs information (control signal) representing the converted carrier frequency "fc" to the variable band pass filter 331 so that the variable band pass filter 331 passes the carrier signal of the converted carrier frequency "fc".

[0055] The distributor 321 outputs (distributes) a carrier signal corresponding to the optical signal to the variable band pass filter 330 and the variable band pass filter 331 .

[0056] The variable band-pass filter 330 removes the carrier signal of the converted carrier frequency "fc" from the carrier signals of the band input from the first system of the distributor 321. The variable band-pass filter 330 outputs the carrier signals of the remaining band from which the carrier signal of the carrier frequency "fc" has been removed to the multiplexer 34.

[0057] The variable band-pass filter 331 generates a carrier signal with a converted carrier frequency "fc" based on the carrier signal of the band input from the second system of the divider 321. The variable band-pass filter 331 outputs the carrier signal with the converted carrier frequency "fc" to the multiplier 333.

[0058] Information (control signal) representing the frequency "ft" is input to the signal generator 332 from the signal analysis unit 320. The frequency "ft" represents the amount of frequency shift. The signal generator 332 outputs an analog signal of the frequency "ft" to the multiplier 333.

[0059] The multiplier 333 multiplies the carrier signal with the converted carrier frequency "fc" by the analog signal with the frequency "ft". When converting (reverting) the converted carrier frequency "fc" in the direction of a lower frequency such as the pre-conversion carrier frequency "fa=fc-ft", the multiplier 223 outputs the carrier signal with the pre-conversion carrier frequency "fa=fc-ft" as the multiplication result to the variable band-pass filter 334. When converting (reverting) the converted carrier frequency "fc" in the direction of a higher frequency such as the pre-conversion carrier frequency "fa=fc+ft", the multiplier 223 outputs the carrier signal with the pre-conversion carrier frequency "fa=fc+ft" as the multiplication result to the variable band-pass filter 334.

[0060] Information (control signal) representing the pre-conversion carrier frequency "fa" is input to the variable band-pass filter 334 from the signal analysis unit 320. The variable band-pass filter 334 passes the carrier signal of the pre-conversion carrier frequency "fa" and outputs it to the combiner 34. The combiner 34 combines the carrier signal of the pre-conversion carrier frequency "fa" with the carrier signal of the remaining band from which the carrier signal of the post-conversion carrier frequency "fc" has been deleted. The amplifier 35 may amplify the level of the carrier signal combined by the combiner 34.

[0061] Next, an example of the operation of the communication system 1a will be described. FIG. 5 is a flowchart showing an example of the operation of the transmission device 2a in the first embodiment. The input signal analysis unit 21 acquires information on frequencies (center frequencies of carrier widths) that can be used for carrier signals in the communication system 1a from a predetermined storage device (step S101). The input signal analysis unit 21 analyzes the carrier frequency "fa" that is being used for the carrier signal. i ” (i=1, . . . , n) are measured (step S102).

[0062] The input signal analysis unit 21 selects the carrier frequency "fa" to be determined from the carrier frequencies currently used in the carrier signal. i " and other carrier frequencies "fb j " is selected (step S103).

[0063] The input signal analysis unit 21 analyzes the frequency of the interference wave caused by the carrier frequency to be determined, "fa i (d)" and the carrier frequency "fb" currently being used for other carrier signals. j (i≠j) difference (absolute value) "|fa i (d)-fb j It is determined whether or not "|" is equal to or smaller than the threshold value "ΔF" (step S104).

[0064] If it is determined that the difference is equal to or smaller than the threshold value (step S104: YES), the input signal analysis unit 21 selects an unused carrier frequency "fc" from among the carrier frequencies available for the carrier signal, at which the difference exceeds the threshold value. kThat is, the input signal analysis unit 21 determines whether or not "|fc" exists. k (d)-fb j |>ΔF" (k≠j) k Here, it is determined whether "fc k (d)" is the carrier frequency "fc k The frequency of the interference wave (harmonic wave, etc.) caused by the signal " is represented (step S105).

[0065] The unused carrier frequency fc k If it is determined that " does not exist" (step S105: NO), the input signal analysis unit 21 proceeds to the process of step S107.

[0066] The unused carrier frequency fc k If it is determined that there is an unused carrier frequency "fc" (step S105: YES), the input signal conversion unit 22 selects an unused carrier frequency "fc" ( k ", the carrier frequency to be judged "fa i " is converted (step S106).

[0067] The input signal analysis unit 21 determines whether or not an unused carrier frequency (empty carrier frequency) still exists. That is, the input signal analysis unit 21 determines whether or not the index "k" of the unused carrier frequency is equal to or greater than the maximum value "k max If it is determined that an unused carrier frequency still exists (step S107: YES), the input signal analysis unit 21 returns the process to step S105.

[0068] If it is determined that there is no unused carrier frequency (step S107: NO), the input signal analysis unit 21 proceeds to the process of step S109. If there is no unused carrier frequency, for example, this occurs when the carrier frequencies are densely packed together or when the input signal analysis unit 21 has used up all the unused carrier frequencies.

[0069] In step S104, if it is determined that the difference exceeds the threshold value (step S104: NO), the input signal analysis unit 21 analyzes the other carrier frequency "fb j ", other undetermined carrier frequencies "fb j That is, the input signal analysis unit 21 determines whether the index "j" of the other carrier frequency being used for the other carrier signal has the maximum value "j max It is determined whether the value is equal to or less than the predetermined value (step S108).

[0070] Other undetermined carrier frequencies "fb j If it is determined that "" exists (step S108: YES), the input signal analysis unit 21 returns the process to step S103.

[0071] Other undetermined carrier frequencies "fb j If it is determined that the undetermined carrier frequency "fa i That is, the input signal analysis unit 21 determines whether or not the carrier frequency "fa" to be determined exists. i " index "i" is the maximum value "i max It is determined whether the value is equal to or less than the predetermined value (step S109).

[0072] Undetermined carrier frequency to be determined "fa i If it is determined that "exists" (step S109: YES), the input signal analysis unit 21 returns the process to step S103.

[0073] Undetermined carrier frequency to be determined "fa i If it is determined that " does not exist" (step S109: NO), the input signal analysis unit 21 outputs the carrier frequency conversion information to the output signal analysis unit 32 via the alarm monitoring unit 29 (step S110).

[0074] 6 is a flowchart showing an example of the operation of the receiving device 3a in the first embodiment. The output signal analysis unit 32 acquires the demodulated carrier signal from the demodulation unit 31 (step S201). The output signal analysis unit 32 acquires carrier frequency conversion information from the input signal analysis unit 21 via the alarm monitoring unit 29 (step S202).

[0075] The output signal analyzer 32 detects the carrier signal of the converted carrier frequency in the carrier signal corresponding to the optical signal based on the carrier frequency conversion information (step S203). The output signal converter 33 restores the converted carrier frequency to the carrier frequency before conversion based on the carrier frequency conversion information (step S204).

[0076] As described above, the transmitting device 2a transmits a carrier signal including a frequency division multiplexed signal to the receiving device 3a using an optical signal in a batch frequency conversion system. When the difference between the frequency of an interference wave (such as a harmonic) generated when the first carrier signal is transmitted at the first carrier frequency "fa" and the second carrier frequency "fb" of the second carrier signal is equal to or less than a threshold, the input signal analyzing unit 21 (selecting unit) selects the third carrier frequency "fc" from among available carrier frequencies that cause the difference to exceed the threshold. When the difference exceeds the threshold, the input signal converting unit 22 (signal transmitting unit) transmits the first carrier signal at the first carrier frequency to the receiving device 3a. When the difference is equal to or less than the threshold, the input signal converting unit 22 (signal transmitting unit) converts the first carrier frequency of the first carrier signal to the third carrier frequency. When the difference is equal to or less than the threshold, the input signal converting unit 22 (signal transmitting unit) transmits the first carrier signal at the third carrier frequency to the receiving device 3a. When the difference exceeds the threshold, the alarm monitoring unit 29 (information transmitting unit) transmits information (conversion information) about the combination of the first carrier frequency before conversion and the third carrier frequency after conversion to the receiving device 3a.

[0077] The receiving device 3a acquires a carrier signal including a frequency division multiplexed signal from the transmitting device 2a using an optical signal in a batch frequency conversion method. The output signal analyzing unit 32 (information acquiring unit) acquires information on a combination of the first carrier frequency before conversion and the third carrier frequency after conversion from the transmitting device 2a when the difference between the frequency of an interference wave generated when the first carrier signal is transmitted at the first carrier frequency and the second carrier frequency of the second carrier signal exceeds a threshold. The output signal analyzing unit 32 (signal acquiring unit) acquires the first carrier signal transmitted at the first carrier frequency or the third carrier frequency from the transmitting device 2a. The output signal converting unit 33 (converting unit) converts the third carrier frequency of the first carrier signal transmitted at the third carrier frequency to the first carrier frequency based on the combination information.

[0078] This makes it possible to suppress degradation of communication quality due to interference caused by the carrier signal. If the carrier signal is a video signal, it is possible to suppress adverse effects on the correct reproduction and viewing of video. It is also possible to extend the transmission distance of the optical signal corresponding to the carrier signal.

[0079] <Comparative Example with First Embodiment> 7 is a diagram illustrating an example of the configuration of a communication system 100a in a comparative example to the first embodiment. The communication system 100a is a system that communicates using optical signals. The communication system 100a includes a transmitting device 200a, a receiving device 300a, and a transmission network 4.

[0080] The transmitting device 200a is, for example, an optical line termination. The optical line termination is, for example, a V-OLT or a transmitter (TX). The transmitting device 200a includes a pilot signal generating unit 20, a batch conversion unit 24, an electrical-to-optical conversion unit 25, an optical dispersion compensating unit 26, an optical amplifier 27, a power supply unit 28, and an alarm monitoring unit 29.

[0081] The receiving device 300a is, for example, an optical line terminal. The optical line terminal is, for example, a V-ONT. The receiving device 300a includes an opto-electrical conversion unit 30, a demodulation unit 31, an amplification unit 35, and a power supply unit 36.

[0082] The communication system 100a as a comparative example to the first embodiment does not include the input signal analysis unit 21, the input signal conversion unit 22, the output signal analysis unit 32, and the output signal conversion unit 33. Therefore, the communication system 100a cannot suppress degradation of communication quality due to interference waves caused by carrier signals.

[0083] (Second embodiment) The second embodiment is different from the first embodiment mainly in that the main signal is modulated by an intensity modulation method. The second embodiment will be described focusing on the differences from the first embodiment.

[0084] 8 is a diagram showing an example of the configuration of a communication system 1b according to the second embodiment. The communication system 1b is a system that communicates using optical signals. The communication system 1b includes a transmitting device 2b, a receiving device 3b, and a transmission network 4.

[0085] The transmitting device 2b is, for example, an optical line termination. The optical line termination is, for example, a V-OLT or a transmitter (TX). The transmitting device 2a includes a pilot signal generating unit 20, an input signal analyzing unit 21, an input signal converting unit 22, a multiplexer 23, an electrical-to-optical converting unit 25, an optical dispersion compensating unit 26, an optical amplifying unit 27, a power supply unit 28, and an alarm monitoring unit 29.

[0086] The receiving device 3b is, for example, an optical network terminal (ONT). The optical network terminal is, for example, a V-ONT. The receiving device 3a includes an optical-to-electrical converter 30, an output signal analyzer 32, an output signal converter 33, a multiplexer 34, an amplifier 35, and a power supply 36.

[0087] In the transmitting device 2b, the electrical-to-optical converter 25 generates an optical signal in response to the carrier signals multiplexed by the multiplexer 23. The optical amplifier 27 amplifies the level of the generated optical signal.

[0088] In the receiving device 3b, a carrier signal corresponding to the optical signal is input to the output signal analysis unit 32 from the photoelectric conversion unit 30. The output signal analysis unit 32 classifies the carrier signal corresponding to the optical signal into carrier signals whose carrier frequency has been converted and carrier signals whose carrier frequency has not been converted, based on carrier frequency conversion information.

[0089] As described above, the transmitting device 2b transmits a carrier signal including a frequency division multiplexed signal to the receiving device 3b using an optical signal in an optical intensity modulation system. When the difference between the frequency of an interference wave (such as a harmonic) generated when the first carrier signal is transmitted at the first carrier frequency "fa" and the second carrier frequency "fb" of the second carrier signal is equal to or less than a threshold, the input signal analyzing unit 21 (selecting unit) selects the third carrier frequency "fc" from among available carrier frequencies that cause the difference to exceed the threshold. When the difference exceeds the threshold, the input signal converting unit 22 (signal transmitting unit) transmits the first carrier signal at the first carrier frequency to the receiving device 3b. When the difference is equal to or less than the threshold, the input signal converting unit 22 (signal transmitting unit) converts the first carrier frequency of the first carrier signal to the third carrier frequency. When the difference is equal to or less than the threshold, the input signal converting unit 22 (signal transmitting unit) transmits the first carrier signal at the third carrier frequency to the receiving device 3b. When the difference exceeds the threshold, the alarm monitoring unit 29 (information transmitting unit) transmits information (conversion information) about the combination of the first carrier frequency before conversion and the third carrier frequency after conversion to the receiving device 3b.

[0090] The receiving device 3b acquires a carrier signal including a frequency division multiplexed signal from the transmitting device 2b using an optical signal in an optical intensity modulation system. The output signal analyzing unit 32 (information acquiring unit) acquires information on the combination of the first carrier frequency before conversion and the third carrier frequency after conversion from the transmitting device 2b when the difference between the frequency of an interference wave generated when the first carrier signal is transmitted at the first carrier frequency and the second carrier frequency of the second carrier signal exceeds a threshold. The output signal analyzing unit 32 (signal acquiring unit) acquires the first carrier signal transmitted at the first carrier frequency or the third carrier frequency from the transmitting device 2a. The output signal converting unit 33 (converting unit) converts the third carrier frequency of the first carrier signal transmitted at the third carrier frequency to the first carrier frequency based on the combination information.

[0091] This makes it possible to suppress degradation of communication quality due to interference caused by the carrier signal. If the carrier signal is a video signal, it is possible to suppress adverse effects on the correct reproduction and viewing of video. It is also possible to extend the transmission distance of the optical signal corresponding to the carrier signal.

[0092] <Comparative Example with Second Embodiment> 9 is a diagram illustrating an example of the configuration of a communication system 100b in a comparative example to the second embodiment. The communication system 100b is a system that communicates using optical signals. The communication system 100b includes a transmitting device 200b, a receiving device 300b, and a transmission network 4.

[0093] The transmitting device 200b (optical line termination device) is, for example, a V-OLT or a transmitter (TX). The transmitting device 200b includes a pilot signal generating unit 20, an electrical-to-optical converting unit 25, an optical amplifying unit 27, a power supply unit 28, and an alarm monitoring unit 29.

[0094] The receiving device 300b (optical line terminal) is, for example, a V-ONT, and includes an opto-electrical conversion unit 30, an amplifier unit 35, and a power supply unit 36.

[0095] The communication system 100b, which is a comparative example to the second embodiment, does not include the input signal analysis unit 21, the input signal conversion unit 22, the output signal analysis unit 32, and the output signal conversion unit 33. Therefore, the communication system 100b cannot suppress deterioration of communication quality due to interference waves caused by carrier signals.

[0096] (Example of hardware configuration) Fig. 10 is a diagram illustrating an example of the hardware configuration of a communication device in each embodiment. The example of the hardware configuration of the communication device 101 illustrated in Fig. 10 corresponds to the example of the hardware configuration of the transmission device 2a in the first embodiment, the example of the hardware configuration of the reception device 3a in the first embodiment, the example of the hardware configuration of the transmission device 2b in the second embodiment, and the example of the hardware configuration of the reception device 3b in the second embodiment.

[0097] Some or all of the functional units of the communication device 101 are realized as software by a processor 102, such as a CPU (Central Processing Unit) and a DSP (Digital Signal Processor), executing programs stored in a storage device 104 having a non-volatile recording medium (non-transitory recording medium) and a memory 103. The programs may be recorded on a computer-readable recording medium. Examples of computer-readable recording media include portable media such as a flexible disk, a magneto-optical disk, a ROM (Read Only Memory), and a CD-ROM (Compact Disc Read Only Memory), and non-transitory recording media such as a storage device built into a computer system, such as a hard disk. The communication unit 105 executes optical communication processing.

[0098] Some or all of the functional units of communication device 101 may be realized using hardware including electronic circuits (electronic circuits 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).

[0099] 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]

[0100] The present invention is applicable to systems that communicate using optical signals. [Explanation of symbols]

[0101] 1a, 1b... communication system, 2a, 2b... transmitting device, 3a, 3b... receiving device, 4... transmission network, 20... pilot signal generating unit, 21... input signal analyzing unit, 22... input signal converting unit, 23... multiplexer, 24... batch conversion unit, 25... electrical-to-optical converting unit, 26... optical dispersion compensating unit, 27... optical amplifying unit, 28... power supply unit, 29... alarm monitoring unit, 30... optical-to-electrical converting unit, 31... demodulating unit, 32... output signal analyzing unit, 33... output signal converting unit, 34... multiplexer, 35... amplifying unit, 36... power supply unit, 40... amplifying unit, 101... communication device, 102... processing unit processor, 103...memory, 104...storage device, 105...communication unit, 200a, 200b...transmitting device, 210...signal analysis unit, 211...distributor, 220...variable band pass filter, 221...variable band pass filter, 222...signal generator, 223...multiplier, 224...variable band pass filter, 300a, 300b...receiving device, 320...signal analysis unit, 321...distributor, 330...variable band pass filter, 331...variable band pass filter, 332...signal generator, 333...multiplier, 334...variable band pass filter

Claims

1. a selector that, when a difference between a frequency of an interference wave generated when the first carrier signal is transmitted at the first carrier frequency and the second carrier frequency of the second carrier signal is equal to or smaller than a threshold, selects a third carrier frequency from among available carrier frequencies that cause the difference to exceed the threshold; a signal transmitting unit that transmits the first carrier signal at the first carrier frequency when the difference exceeds the threshold, and that converts the first carrier frequency of the first carrier signal to the third carrier frequency and transmits the first carrier signal at the third carrier frequency when the difference is equal to or smaller than the threshold; an information transmitting unit that transmits information about a combination of the first carrier frequency before conversion and the third carrier frequency after conversion when the difference is equal to or less than the threshold; A transmitting device comprising:

2. an information acquiring unit that acquires, from a transmitting device, information on a combination of the first carrier frequency before conversion and the third carrier frequency after conversion, when a difference between a frequency of an interference wave generated when a first carrier signal is transmitted at a first carrier frequency and a second carrier frequency of a second carrier signal is equal to or smaller than a threshold, and converts the first carrier frequency of the first carrier signal to a third carrier frequency selected from available carrier frequencies that cause the difference to exceed the threshold; a signal acquisition unit that acquires the first carrier signal transmitted at the first carrier frequency or the third carrier frequency from the transmitting device; a conversion unit that converts the third carrier frequency of the first carrier signal transmitted at the third carrier frequency into the first carrier frequency based on information of the combination; A receiving device comprising:

3. A communication system comprising a transmitting device and a receiving device, The transmitting device a selector that, when a difference between a frequency of an interference wave generated when the first carrier signal is transmitted at the first carrier frequency and the second carrier frequency of the second carrier signal is equal to or smaller than a threshold, selects a third carrier frequency from among available carrier frequencies that cause the difference to exceed the threshold; a signal transmitting unit that transmits the first carrier signal at the first carrier frequency when the difference exceeds the threshold, and that converts the first carrier frequency of the first carrier signal to the third carrier frequency and transmits the first carrier signal at the third carrier frequency when the difference is equal to or less than the threshold; an information transmitting unit configured to transmit information about a combination of the first carrier frequency before conversion and the third carrier frequency after conversion, regarding conversion from the first carrier frequency of the first carrier signal to a third carrier frequency selected from available carrier frequencies that cause the difference to exceed the threshold value when the difference is equal to or less than the threshold value, The receiving device an information acquisition unit that acquires information about the combination from the information transmission unit; a signal acquiring unit that acquires the first carrier signal transmitted at the first carrier frequency or the third carrier frequency from the signal transmitting unit; a conversion unit that converts the third carrier frequency of the first carrier signal transmitted at the third carrier frequency into the first carrier frequency based on information of the combination, Communication system.

4. A transmission method executed by a transmission device, selecting a third carrier frequency from among available carrier frequencies at which a difference between a frequency of an interference wave generated when the first carrier signal is transmitted at the first carrier frequency and a second carrier frequency of the second carrier signal is equal to or smaller than a threshold; transmitting the first carrier signal at the first carrier frequency if the difference exceeds the threshold, and converting the first carrier frequency of the first carrier signal to the third carrier frequency and transmitting the first carrier signal at the third carrier frequency if the difference is equal to or less than the threshold; transmitting information about a combination of the first carrier frequency before conversion and the third carrier frequency after conversion when the difference is equal to or less than the threshold value; A transmission method including:

5. A receiving method executed by a receiving device, When a difference between a frequency of an interference wave generated when a first carrier signal is transmitted at a first carrier frequency and a second carrier frequency of a second carrier signal is equal to or smaller than a threshold, the method converts the first carrier frequency of the first carrier signal to a third carrier frequency selected from available carrier frequencies at which the difference exceeds the threshold, acquiring information on a combination of the first carrier frequency before conversion and the third carrier frequency after conversion from a transmitting device; acquiring the first carrier signal transmitted at the first carrier frequency or the third carrier frequency from the transmitting device; converting the third carrier frequency of the first carrier signal transmitted at the third carrier frequency to the first carrier frequency based on the combined information; Receiving method including.

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