JP7733345B2 - Transmitting device, receiving device, communication system, transmitting method, and receiving method - Google Patents

Description

The present invention relates to a transmitting device, a receiving device, a communication system, a transmitting method, and a receiving method.

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 the 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).

“Transmission equipment for multi-channel television signals over optical access networks by sub-carrier multiplexing (SCM)”, ITU-T Rec. J. 186, 2008. “Transmission equipment for transferring multi-channel television signals over optical access networks by frequency modulation conversion”, ITU-T Rec. J. 185, 2012.

Figure 11 is a diagram showing an example of communication quality degradation. The communication system illustrated in Figure 11 comprises 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. Depending on the specifications and characteristics of the communication system and the type of service of the communication system, a carrier frequency band that can be used for the carrier signal is predetermined.

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

Carrier signals include frequency division multiplexed signals (FDM signals). Here, interference waves (harmonics and distortion signals) caused by a carrier signal of a certain carrier frequency can interfere with other carrier signals of other carrier frequencies. Furthermore, in a communication system, relaying of an optical signal by the transmission network 4 can, for example, amplify distortion in the carrier signal, degrading communication quality and affecting the services provided by the communication system. As such, it may not be possible to suppress degradation of communication quality due to interference waves caused by carrier signals.

In consideration of the above circumstances, the present invention aims 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 carrier signals.

One aspect of the present invention is a transmitting device comprising: a selection unit that, 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 is equal to or less than a threshold, selects a third carrier frequency from among available carrier frequencies at which the difference exceeds the threshold; a signal transmission unit 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 and transmits the first carrier signal at the third carrier frequency when the difference is equal to or less than the threshold; 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.

One aspect of the present invention is a receiving device comprising: an information acquisition unit that acquires, from a transmitting device, information on the 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; 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.

One aspect of the present invention is a communication system comprising a transmitting device and a receiving device, wherein the transmitting device includes a selector that, 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, selects a third carrier frequency from among available carrier frequencies at which the difference exceeds 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 and transmits the first carrier signal at 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, wherein the receiving device comprises 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.

One aspect of the present invention is a transmission method executed by a transmitting device, the transmission method including the steps of: selecting a third carrier frequency from among available carrier frequencies at which 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 value when the difference is equal to or less than a threshold value; transmitting the first carrier signal at the first carrier frequency when the difference exceeds the threshold value; 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 when the difference is equal to or less than the threshold value; and transmitting 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.

One aspect of the present invention is a receiving method executed by a receiving device, which includes 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 the 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 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.

This invention makes it possible to suppress degradation of communication quality caused by interference waves resulting from carrier signals.

FIG. 1 is a diagram illustrating an example of the configuration of a communication system in a first embodiment. FIG. 4 is a diagram illustrating an example of frequency conversion in the first embodiment. FIG. 2 is a diagram illustrating an example of the configuration of a transmission device in the first embodiment. FIG. 2 is a diagram illustrating an example of the configuration of a receiving device in the first embodiment. 4 is a flowchart illustrating an example of the operation of the transmitting device in the first embodiment. 4 is a flowchart showing an example of the operation of the receiving device in the first embodiment. FIG. 1 is a diagram illustrating an example of the configuration of a communication system in a comparative example to the first embodiment. FIG. 10 is a diagram illustrating an example of the configuration of a communication system in a second embodiment. FIG. 10 is a diagram illustrating an example of the configuration of a communication system in a comparative example to the second embodiment. FIG. 2 is a diagram illustrating an example of a hardware configuration of an optical communication device in each embodiment. FIG. 10 is a diagram illustrating an example of communication quality degradation.

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 illustrating an example of the configuration of a communication system 1a according to a 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.

The transmitting device 2a is, for example, an optical line termination device. The optical line termination device 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.

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 amplifier 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.

The carrier signal may include a pilot signal. The pilot signal is used by a transmission device (not shown) and receiving device 3a within the transmission network 4 to check the normality of the transmission signal, etc. The pilot signal is generated, for example, by a head-end device (not shown) and input to transmitting device 2a in the same way as other input signals. The pilot signal may be generated, for example, by transmitting device 2a. When a pilot signal is generated by transmitting device 2a, the pilot signal generating unit 20 synchronizes with the input carrier signal and generates a pilot signal of 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.

A carrier signal including a frequency division multiplexed signal is input to the input signal analysis unit 21, for example, from 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.

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 below 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.

The input signal analysis unit 21 generates carrier frequency conversion information. The carrier frequency conversion information includes information on the combination of the carrier frequency before conversion and the carrier frequency after conversion.

The input signal conversion unit 22 removes the carrier signal of the pre-conversion carrier frequency from the carrier signal of the band input from the first system of the input signal analysis unit 21. The input signal conversion unit 22 outputs the carrier signal of the remaining band from which the carrier signal of the pre-conversion carrier frequency has been removed to the combiner 23.

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.

The combiner 23 combines 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 combined carrier signal may be amplified using an amplifier (not shown) before the combined carrier signal is input to the batch conversion unit 24.

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 according to the carrier signal after frequency modulation batch conversion. The optical dispersion compensation unit 26 performs dispersion compensation processing on the generated optical signal.

The optical amplifier 27 amplifies the level of the optical signal that has undergone 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.

Power is supplied to the power supply unit 28 from an external power source. The power supply unit 28 supplies power to each functional unit of the transmitting device 2a. The alarm monitoring unit 29 transmits specified information to the receiving 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 transmitting device 2a. If an abnormality is detected in any functional unit, the alarm monitoring unit 29 outputs an alarm (notification of the abnormality) to the outside according to the monitoring results.

Figure 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".

"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).

The input signal analysis unit 21 rearranges the carrier frequency of the carrier signal before transmitting it 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.

In the graph on the left side of Figure 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". The input signal analysis unit 21 also 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".

Therefore, the input signal analysis unit 21 decides to perform downconversion or upconversion processing on the carrier signal of carrier frequency "fa" so that the second-order distortion frequency "fb-fa" does not exist near the carrier frequency "fa".

In the graph on the left side of Figure 2, the input signal analysis unit 21 decides to perform down-conversion processing on the carrier signal with carrier frequency "fa". Based on the decision by the input signal analysis unit 21, the input signal conversion unit 22 performs down-conversion processing on the carrier signal with carrier frequency "fa". In other words, the input signal conversion unit 22 shifts the carrier frequency "fa" downward to the vacant carrier frequency "fc".

As a result, as illustrated in the graph on the right side of Figure 2, the frequency of each interference wave moves away on the frequency axis from the carrier frequency "fa" currently being used for the carrier signal. Also, the frequency of each interference wave moves away on the frequency axis from another carrier frequency "fb" currently being used for another carrier signal.

Returning to Figure 1, the receiving device 3a will now 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.

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 obtains carrier frequency conversion information from the input signal analysis unit 21 via the alarm monitoring unit 29.

The output signal analysis unit 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. 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.

The output signal conversion unit 33 converts the carrier signal with 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 with 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 with the converted carrier frequency "fc" has been deleted, to the multiplexer 34.

The multiplexer 34 multiplexes the carrier signal with the carrier frequency "fa" before conversion with the carrier signal of the remaining band from which the carrier signal with 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 with the amplified level to an external device (not shown). This external device is, for example, a display device. Power is supplied to the power supply 36 from an external power source. The power supply 36 supplies power to each functional unit of the receiving device 3a.

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 distributor 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.

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

The signal analysis unit 210 selects, from the band of carrier frequencies available to the communication system 1a, an unused carrier frequency (free 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, as the converted carrier frequency of the carrier signal. The signal analysis unit 210 generates carrier frequency conversion information.

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".

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".

The distributor 211 outputs (distributes) the carrier signal input from the signal analysis unit 210 to the variable bandpass filter 220 and the variable bandpass filter 221.

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

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

The signal generator 222 receives information (control signal) representing the frequency "ft" 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.

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, such as the converted carrier frequency "fc = fa + ft", the multiplier 223 outputs the carrier signal with the converted 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, such as the converted carrier frequency "fc = fa - ft", the multiplier 223 outputs the carrier signal with the converted carrier frequency "fc = fa - ft" as the multiplication result to the variable band-pass filter 224.

The variable bandpass filter 224 receives information (control signal) representing the converted carrier frequency "fc" from the signal analysis unit 210. The variable bandpass filter 224 passes the carrier signal with the converted carrier frequency "fc" and outputs it to the combiner 23. The combiner 23 combines the carrier signal with the converted carrier frequency "fc" with the carrier signal of the remaining band from which the carrier signal with the pre-conversion carrier frequency "fa" has been deleted. The amplifier 40 may amplify the level of the carrier signal combined by the combiner 23.

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.

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.

The signal analysis unit 320 outputs information (control signal) representing the converted carrier frequency "fc" to the variable bandpass filter 330 so that the variable bandpass filter 330 does not pass the carrier signal with the converted carrier frequency "fc".

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

The distributor 321 outputs (distributes) the carrier signal corresponding to the optical signal to the variable bandpass filter 330 and the variable bandpass filter 331.

The variable bandpass filter 330 removes the carrier signal with the converted carrier frequency "fc" from the carrier signals of the band input from the first system of the distributor 321. The variable bandpass filter 330 outputs the carrier signals of the remaining band, from which the carrier signal with the carrier frequency "fc" has been removed, to the combiner 34.

The variable bandpass 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 distributor 321. The variable bandpass filter 331 outputs the carrier signal with the converted carrier frequency "fc" to the multiplier 333.

The signal generator 332 receives information (control signal) representing the frequency "ft" 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.

The multiplier 333 multiplies the carrier signal with the converted carrier frequency "fc" by the analog signal with the frequency "ft". When converting the converted carrier frequency "fc" toward a lower frequency (returning it back to 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 the converted carrier frequency "fc" toward a higher frequency (returning it back to 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.

The variable bandpass filter 334 receives information (control signal) representing the pre-conversion carrier frequency "fa" from the signal analysis unit 320. The variable bandpass 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.

Next, an example of the operation of the communication system 1a will be described.
5 is a flowchart showing an example of the operation of the transmitting 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 measures carrier frequencies "fa _i " (i = 1, ..., n) currently being used for the carrier signals (step S102).

The input signal analysis unit 21 selects a combination of the carrier frequency "fa _i " to be determined and another carrier frequency "fb _j " that is being used for another carrier signal from among the carrier frequencies that are being used for the carrier signal (step S103).

The input signal analysis unit 21 determines whether the difference (absolute value) "|fa _i (d) - fb _j |" between the frequency of the interference wave caused by the carrier frequency being determined, "fa _i (d)," and the carrier frequency "fb _j " (i ≠ j) currently used for another carrier signal is less than or equal to the threshold value "ΔF" (step S104).

If it is determined that the difference is equal to or smaller than the threshold (step S104: YES), the input signal analysis unit 21 determines whether or not there is an unused carrier frequency "fc _k " among the carrier frequencies available for the carrier signal, at which the difference exceeds the threshold. That is, the input signal analysis unit 21 determines whether or not there is an unused carrier frequency "fc _k " that satisfies "|fc _k (d) - fb _j | >ΔF" (k ≠ j). Here, "fc _k (d)" represents the frequency of interference waves (such as harmonics) resulting from the carrier frequency "fc _k " (step S105).

If it is determined that there is no unused carrier frequency "fc _k " that causes the difference to exceed the threshold value (step S105: NO), the input signal analysis unit 21 proceeds to the process of step S107.

If it is determined that there is an unused carrier frequency "fc _k " whose difference exceeds the threshold value (step S105: YES), the input signal conversion unit 22 converts the carrier frequency "fa _i " to be determined to be an unused carrier frequency "fc _k " whose difference exceeds the threshold value (step S106).

The input signal analysis unit 21 determines whether or not an unused carrier frequency (vacant 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 less than the maximum value "k _max " (step S107). 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.

If it is determined that there are no unused carrier frequencies (step S107: NO), the input signal analysis unit 21 proceeds to step S109. An example of an unused carrier frequency not being present is when the carrier frequencies are densely packed together, or when the input signal analysis unit 21 has used up all unused carrier frequencies.

If it is determined in step S104 that the difference exceeds the threshold value (step S104: NO), the input signal analysis unit 21 determines whether or not there is an undetermined other carrier frequency "fb _j " among the other carrier frequencies "fb _j " used for the other carrier signals. That is, the input signal analysis unit 21 determines whether or not the index "j" of the other carrier frequency used for the other carrier signal is equal to or less than the maximum value "j _max " (step S108).

If it is determined that there is another undetermined carrier frequency "fb _j " (step S108: YES), the input signal analysis unit 21 returns the process to step S103.

If it is determined that there are no other undetermined carrier frequencies "fb _j " (step S108: NO), the input signal analysis unit 21 determines whether there is an undetermined carrier frequency "fa _i " to be determined. That is, the input signal analysis unit 21 determines whether the index "i" of the carrier frequency "fa _i " to be determined is equal to or less than the maximum value "i _max " (step S109).

If it is determined that there is an undetermined carrier frequency "fa _i " to be determined (step S109: YES), the input signal analysis unit 21 returns the process to step S103.

If it is determined that there is no undetermined carrier frequency "fa _i " to be determined (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).

Figure 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).

The output signal analysis unit 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 conversion unit 33 returns the converted carrier frequency to the carrier frequency before conversion based on the carrier frequency conversion information (step S204).

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 with a batch frequency conversion method. 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 the 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 to the receiving device 3a at the first carrier frequency. 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 to the receiving device 3a at the third carrier frequency. The alarm monitoring unit 29 (information transmitting unit) transmits information (conversion information) on the combination of the first carrier frequency before conversion and the third carrier frequency after conversion to the receiving device 3a when the difference exceeds the threshold value.

The receiving device 3a acquires a carrier signal including a frequency division multiplexed signal from the transmitting device 2a using an optical signal with a batch frequency conversion method. The output signal analysis unit 32 (information acquisition unit) acquires information from the transmitting device 2a regarding the 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 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 analysis unit 32 (signal acquisition 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 conversion unit 33 (conversion 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.

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

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.

The transmitting device 200a is, for example, an optical line termination device. The optical line termination device 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 compensation unit 26, an optical amplifier unit 27, a power supply unit 28, and an alarm monitoring unit 29.

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 optical-to-electrical conversion unit 30, a demodulation unit 31, an amplifier unit 35, and a power supply unit 36.

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

Second Embodiment
The second embodiment is different from the first embodiment in that the main signal is modulated by the intensity modulation method. The second embodiment will be described mainly focusing on the differences from the first embodiment.

Figure 8 is a diagram showing an example configuration of a communication system 1b in 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.

Transmitting device 2b is, for example, an optical line termination. The optical line termination is, for example, a V-OLT or a transmitter (TX). 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.

The receiving device 3b is, for example, an optical line terminal. The optical line terminal is, for example, a V-ONT. The receiving device 3a includes an optical-to-electrical conversion unit 30, an output signal analysis unit 32, an output signal conversion unit 33, a multiplexer 34, an amplifier unit 35, and a power supply unit 36.

In the transmitting device 2b, the electrical-to-optical converter 25 generates an optical signal in response to the carrier signal combined by the combiner 23. The optical amplifier 27 amplifies the level of the generated optical signal.

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 the carrier frequency conversion information.

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 with optical intensity modulation. 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 the 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. The alarm monitoring unit 29 (information transmitting unit) transmits information (conversion information) on the combination of the first carrier frequency before conversion and the third carrier frequency after conversion to the receiving device 3b when the difference exceeds the threshold value.

The receiving device 3b acquires a carrier signal including a frequency division multiplexed signal from the transmitting device 2b using an optical signal with an optical intensity modulation method. The output signal analysis unit 32 (information acquisition unit) acquires information from the transmitting device 2b regarding the 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 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 analysis unit 32 (signal acquisition 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 conversion unit 33 (conversion 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.

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

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.

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 conversion unit 25, an optical amplifier unit 27, a power supply unit 28, and an alarm monitoring unit 29.

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

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

(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 transmitting device 2a in the first embodiment, the example of the hardware configuration of the receiving device 3a in the first embodiment, the example of the hardware configuration of the transmitting device 2b in the second embodiment, and the example of the hardware configuration of the receiving device 3b in the second embodiment.

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 in memory 103. The programs may be recorded on a computer-readable recording medium. Examples of computer-readable recording media include portable media such as flexible disks, optical magnetic disks, ROMs (Read Only Memory), and CD-ROMs (Compact Disc Read Only Memory), as well as non-transitory recording media such as hard disks and other storage devices built into computer systems. The communication unit 105 performs optical communication processing.

Some or all of the functional units of the 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).

The above describes in detail an embodiment of the present invention with reference to the drawings, but the specific configuration is not limited to this embodiment and also includes designs that do not deviate from the gist of the present invention.

The present invention is applicable to systems that communicate using optical signals.

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...Processor 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 (5)

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 value. 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 the information of the combination. 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. 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;
and 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 smaller than the threshold value. 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;
and 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.