Signal transmitting device

Abstract

To allow an abnormality due to a mistake in connection or the like of a transmission line in a relay transmission section to be quickly determined by a simple method in a system including an active system and a standby system.SOLUTION: A signal transmitting device is provided in either an active network or a standby network. The signal transmitting device includes: a system information setting unit that performs system settings; a pilot signal setting unit that determines the frequency of a pilot signal for monitoring or the frequency of a modulated signal to be carried by the pilot signal based on information of the system settings performed by the system information setting unit; and a pilot signal generation unit that generates a pilot signal based on the frequency determined by the pilot signal setting unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a signal transmitting device. [Background technology]

[0002] Conventionally, a signal transmission device equipped with a pilot signal generator that generates a pilot signal used for monitoring an input signal has been known (see, for example, Non-Patent Documents 1 and 2). In such a signal transmission device, the pilot signal is multiplexed with an input signal, and then the signal is adjusted and transmitted. In conventional signal transmission systems, a network is configured to be duplicated in order to improve reliability and fault tolerance.

[0003] 11 is a diagram showing an example of the configuration of a conventional signal transmission system 100. The signal transmission system 100 includes two signal transmitting devices 110-1 and 110-2, two relay transmitting devices 120-1 and 120-2, a distribution transmitting device 130, and a receiving device 140. In the signal transmission system 100, the signal transmitting device 110-1 and the relay transmitting device 120-1 belong to a 0-system network, and the signal transmitting device 110-2 and the relay transmitting device 120-2 belong to a 1-system network. The 0-system network is an active system network, and the 1-system network is a standby system network.

[0004] The signal transmitting device 110 transmits an optical signal in which a pilot signal is multiplexed with an input signal. The signal transmitting device 110 can improve noise resistance during long-distance transmission by performing FM (Frequency Modulation) batch conversion. The relay transmitting device 120 converts the optical signal transmitted from the signal transmitting device 110 into an electrical signal, and then measures the state of the pilot signal to determine a CNR (Carrier-to-Noise Ratio) error. If FM batch conversion is performed in the signal transmitting device 110, the relay transmitting device 120 performs FM demodulation after converting to an electrical signal. If an abnormality is found as a result of measuring the state of the pilot signal, the relay transmitting device 120 notifies an error. Furthermore, the relay transmitting device 120 transmits the optical signal transmitted from the signal transmitting device 110 to the distribution transmitting device 130.

[0005] The distribution transmission device 130 switches between the 0-system network and the 1-system network, and transmits the optical signal transmitted from either the relay transmission device 120-1 or the relay transmission device 120-2 to the receiving device 140. The receiving device 140 demodulates the optical signal transmitted from the distribution transmission device 130 back to the original signal format.

[0006] Fig. 12 is a diagram showing an example of the configuration of a conventional signal transmission device 110. Fig. 12 shows, as an example of a signal transmission device, a signal transmission device 110 provided in a communication system to which an FM batch conversion method is applied. The signal transmission device 110 includes a pilot signal generation unit 111, a multiplexing unit 112, an electric signal amplification unit 113, an FM batch conversion signal generation unit 114, an electric-to-optical conversion unit 115, an optical signal amplification unit 116, a sending unit 117, and a system information setting unit 118.

[0007] The pilot signal generating unit 111 generates a pilot signal used for monitoring an input signal. The multiplexing unit 112 multiplexes the input signal input to the signal transmitting device 110 with the pilot signal output from the pilot signal generating unit 111 to generate a multiplexed signal. The multiplexing unit 112 outputs the generated multiplexed signal to the electric signal amplifying unit 113. The electric signal amplifying unit 113 amplifies the multiplexed signal output from the multiplexing unit 112 and outputs it to the FM batch converted signal generating unit 114.

[0008] The FM batch converted signal generation unit 114 performs FM batch conversion on the multiplexed signal amplified by the electrical signal amplification unit 113 to generate an FM batch converted signal that is a wideband FM signal and outputs it to the electrical-optical conversion unit 115. The electrical-optical conversion unit 115 converts the FM batch converted signal generated by the FM batch converted signal generation unit 114 into an optical signal and outputs it to the optical signal amplification unit 116. For example, the electrical-optical conversion unit 115 converts the FM batch converted signal into an optical signal by intensity modulation. The optical signal amplification unit 116 amplifies the optical signal output from the electrical-optical conversion unit 115 and outputs it to the transmission unit 117. The transmission unit 117 transmits the optical signal amplified by the optical signal amplification unit 116 as an output signal. The system information setting unit 118 accepts and holds system information settings from a communication device such as a personal computer connected via IP or Ethernet (registered trademark). [Prior art documents] [Non-patent literature]

[0009] [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]

[0010] As shown in FIG. 11, in a fully redundant network with one network serving as an active system and the other as a standby system, the relay transmission device 120 cannot determine whether it is the active system or the standby system. Therefore, even if a transmission line (e.g., optical fiber) is connected incorrectly in the relay transmission section, there is no way to detect this. Here, the relay transmission section includes at least the section between the signal transmission device 110 and the distribution transmission device 130. One possible method is to install monitoring software or the like in the relay transmission device 120 and input its own system settings to the device. However, this requires manual intervention, which may result in an incorrect setting that differs from the value in the signal transmission device 110, resulting in an incorrect system determination. While it is also possible to notify the settings of the system information setting unit 118 of the signal transmission device 110 to the subordinate relay transmission device 120, this requires the preparation of a separate communication network for this purpose, and there is also the possibility of incorrect connection or configuration of the communication network itself. Thus, in conventional systems with an active system and a standby system, there is a problem in that it is not possible to quickly determine an abnormality due to a transmission line connection error or the like in the relay transmission section using a simple method. This problem also occurs when the signal transmitting device transmits an analog signal (electrical signal).

[0011] In view of the above circumstances, the present invention aims to provide a technology that can quickly determine, in a system having an active system and a standby system, an abnormality due to a mistaken connection of a transmission line in a relay transmission section in a simple manner. [Means for solving the problem]

[0012] One aspect of the present invention is a signal transmission device that is provided in either an operational network or a standby network, and that includes a system information setting unit that performs system settings, a pilot signal setting unit that determines the frequency of a pilot signal for monitoring or the frequency of a modulated signal to be carried by the pilot signal based on information about the system settings performed by the system information setting unit, and a pilot signal generation unit that generates a pilot signal based on the frequency determined by the pilot signal setting unit. [Effects of the Invention]

[0013] According to the present invention, in a system having an active system and a standby system, it is possible to quickly determine, by a simple method, whether or not there is an abnormality due to a mistake in the connection of a transmission line in a relay transmission section. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram illustrating an example of the configuration of a signal transmission system according to a first embodiment. [Figure 2] 1 is a diagram illustrating an example of the configuration of a signal transmitting device according to a first embodiment. [Figure 3] FIG. 4 is a diagram illustrating an example of a frequency generation table according to the first embodiment. [Figure 4] FIG. 2 is a diagram illustrating an example of the configuration of a pilot signal generating unit in the first embodiment. [Figure 5] FIG. 2 is a diagram illustrating an example of the configuration of a relay transmission device according to the first embodiment. [Figure 6] 1 is a diagram illustrating an example of the configuration of a distribution transmission device according to a first embodiment. [Figure 7] FIG. 3 is a sequence diagram showing the flow of processing performed by the signal transmission system in the first embodiment. [Figure 8] FIG. 10 is a diagram illustrating an example of the configuration of a signal transmitting device according to a second embodiment. [Figure 9]FIG. 10 is a diagram illustrating an example of the configuration of a signal transmitting device according to a third embodiment. [Figure 10] 10A and 10B are diagrams illustrating another example of a frequency generation table and an explanation of the another example. [Figure 11] FIG. 1 is a diagram illustrating an example of the configuration of a conventional signal transmission system. [Figure 12] FIG. 1 is a diagram illustrating an example of the configuration of a conventional signal transmission device. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] (First embodiment) 1 is a diagram showing an example of the configuration of a signal transmission system 1 in the first embodiment. The signal transmission system 1 includes two signal transmission devices 10-1 and 10-2, two relay transmission devices 20-1 and 20-2, a distribution transmission device 30, and a receiving device 40. In the signal transmission system 1, the signal transmission device 10-1 and the relay transmission device 20-1 belong to a 0-system network, and the signal transmission device 10-2 and the relay transmission device 20-2 belong to a 1-system network. In the following description, the 0-system network is a working system network, and the 1-system network is a standby system network.

[0017] The signal transmitting device 10 converts a multiplexed signal generated by multiplexing a pilot signal with an input signal into an optical signal and transmits the optical signal. In the first embodiment, a configuration in which the signal transmitting device 10 transmits an optical signal using an FM batch conversion method will be described. The signal transmitting device 10 is a device equivalent to a TA (Transmitter and Amplifier) ​​in Non-Patent Documents 1 and 2.

[0018] The relay transmission device 20 amplifies the optical signal sent from the signal transmission device 10 and transmits the optical signal. The relay transmission device 20 performs dispersion compensation processing on the optical signal, filtering of frequencies outside the transmission band, etc. as necessary. Furthermore, the relay transmission device 20 monitors the main signal. The relay transmission device 20 is a device equivalent to the V-OLT (Video-Optical Line Terminal) in Non-Patent Documents 1 and 2.

[0019] The distribution transmission device 30 switches between the 0-system network and the 1-system network, and selects either the 0-system or 1-system optical signal to amplify and transmit. If the distribution transmission device 30 detects an abnormality, such as a drop in level, in the optical signal being transmitted, it autonomously switches the connected network to the other. For example, if the distribution transmission device 30 is connected to the 0-system network and detects an abnormality, such as a drop in level, in the optical signal being transmitted, the distribution transmission device 30 switches the connection to the 1-system network. The distribution transmission device 30 is a device equivalent to the V-OLT in Non-Patent Documents 1 and 2.

[0020] The receiving device 40 demodulates the optical signal transmitted from the distribution transmission device 30 back to the original signal format. When the signal transmitting device 10 performs an FM batch conversion method, the receiving device 40 has an FM demodulation function. The receiving device 40 is a device equivalent to the V-ONT (Video-Optical Network Terminal) in Non-Patent Documents 1 and 2.

[0021] FIG. 2 is a diagram illustrating an example of the configuration of a signal transmission device 10 according to the first embodiment. The signal transmission device 10 includes a pilot signal generation unit 11, a multiplexing unit 12, an electric signal amplification unit 13, an FM batch converted signal generation unit 14, an electric-to-optical conversion unit 15, an optical signal amplification unit 16, a transmission unit 17, a system information setting unit 18, and a pilot signal setting unit 19. Note that FIG. 2 shows only the configuration necessary for explaining the present invention. The multiplexing unit 12, the electric signal amplification unit 13, the FM batch converted signal generation unit 14, the electric-to-optical conversion unit 15, the optical signal amplification unit 16, and the transmission unit 17 basically perform the same processing as the functional units with the same names shown in FIG. 12 (the multiplexing unit 112, the electric signal amplification unit 113, the FM batch converted signal generation unit 114, the electric-to-optical conversion unit 115, the optical signal amplification unit 116, and the transmission unit 117). The following description will focus on the differences. In the following description, the processes executed in the electrical signal amplifier 13, the FM batch converted signal generator 14, the electrical-to-optical converter 15, the optical signal amplifier 16 and the transmitter 17 are collectively referred to as signal transmission processes.

[0022] The system information setting unit 18 receives and stores system information settings as communication signals from communication devices such as personal computers connected via IP or Ethernet (registered trademark). The system information settings received by the system information setting unit 18 indicate whether the device is considered to operate as an active system or a standby system. The system information settings received by the system information setting unit 18 are expressed as numerical values ​​such as 0, 1, 2, etc. When the system information setting unit 18 sets a value of “0,” the device is considered to operate as an active system, and when the system information setting unit 18 sets a value of “1” or greater, the device is considered to operate as a standby system. Generally, one standby system is sufficient, and therefore the system information settings received by the system information setting unit 18 only need to be at least 0 or 1. However, since it is anticipated that two or more standby systems may be required depending on the usage situation, the system information settings are set as numerical values ​​such as 0, 1, 2, etc., as described above. The system information setting unit 18 transmits information indicating the stored system information settings to the pilot signal setting unit 19 as an information signal. For example, if the system information (number) is 0, it is 0V (no signal), if it is 1, it is 1V, if it is 2, it is 2V, and so on. Here, V in the above 0V, 1V, 2V, and so on represents voltage. The system information setting unit 18 is, for example, a microcomputer.

[0023] The pilot signal setting unit 19 determines the frequency of the pilot signal to be generated by the pilot signal generating unit 11 or the frequency of the modulation signal that modulates the pilot signal, based on the system information held by the system information setting unit 18. Specifically, the pilot signal setting unit 19 determines the frequency of the pilot signal to be generated by the pilot signal generating unit 11 or the frequency of the modulation signal that modulates the pilot signal, based on the system information held by the system information setting unit 18, with reference to the frequency generation table shown in FIG.

[0024] FIG. 3 is a diagram showing an example of a frequency generation table in the first embodiment. As shown in FIG. 3, the frequency generation table is made up of a plurality of records in which system information and signal frequencies are associated with each other. As shown in FIG. 3, the signal frequency differs for each piece of system information. In other words, the frequency determined by the pilot signal setting unit 19 differs for each piece of system information. Taking the frequency generation table shown in FIG. 3 as an example, when the system information held by the system information setting unit 18 is "0", the pilot signal setting unit 19 determines the frequency of the pilot signal generated by the pilot signal generating unit 11 or the frequency of the modulation signal that modulates the pilot signal to be "300 kHz".

[0025] Pilot signal setting unit 19 outputs a control signal based on the determined frequency to pilot signal generation unit 11. The control signal is a rectangular signal required to generate a pilot signal or a modulated signal having the frequency determined by pilot signal setting unit 19 in pilot signal generation unit 11. Pilot signal setting unit 19 is, for example, a microcomputer.

[0026] The pilot signal generator 11 generates a pilot signal based on the control signal output from the pilot signal setting unit 19. Examples of pilot signals used in the present invention include unmodulated signals, analog modulated signals, and digitally modulated signals. In addition to the above-mentioned signals, the pilot signal may also be pulse modulated, in which the carrier wave is a rectangular wave, and any of these may be used. Whether the pilot signal generator 11 generates an unmodulated signal, an analog modulated signal, or a digitally modulated signal depends on the system. For example, if the pilot signal needs to be demodulated in the relay transmission device 20, the distribution transmission device 30, or the like, a modulated signal can be generated by modulating it using the appropriate modulation method. If the pilot signal does not need to be demodulated in the relay transmission device 20, the distribution transmission device 30, or the like, an unmodulated signal can be generated as the pilot signal.

[0027] An unmodulated signal is a signal that is not modulated. When the pilot signal generating unit 11 generates an unmodulated signal as a pilot signal, the pilot signal generating unit 11 changes the frequency of the pilot signal itself instead of changing the frequency of a modulated signal in accordance with system information. An analog modulated signal is a signal in which a carrier wave is continuously changed. An analog modulated signal is generated based on a modulation method such as amplitude modulation (AM), frequency modulation (FM), or phase modulation (PM). A digital modulated signal is a signal in which a carrier wave is discontinuously changed. A digital modulated signal is generated based on a modulation method such as amplitude shift keying (ASK), frequency shift keying (FSK), or phase shift keying (PSK). The modulation method is not particularly limited. The pilot signal generating unit 11 may change the frequency of the pilot signal or the frequency of the modulated signal at a specific time period.

[0028] 4 is a diagram showing an example of the configuration of the pilot signal generation unit 11 in the first embodiment. The pilot signal generation unit 11 is made up of an oscillator 2 and a PLL 3. The oscillator 2 generates a modulated signal based on a control signal output from a pilot signal setting unit 19. The oscillator 2 outputs the generated modulated signal to the PLL 3. The PLL 3 is a phase-locked loop circuit, and generates a pilot signal based on the modulated signal output from the oscillator 2 and a reference signal generated internally. The PLL 3 outputs the generated pilot signal to the multiplexing unit 12.

[0029] Fig. 5 is a diagram showing an example of the configuration of relay transmission device 20 in the first embodiment. Relay transmission device 20 includes an optical amplifier 21 and a main signal monitor 22. Optical amplifier 21 amplifies an input optical signal. Main signal monitor 22 includes an optical-electrical converter 23, an FM batch signal demodulator 24, an electrical signal amplifier 25, and a pilot signal measurer 26. Note that Fig. 5 shows only the configuration necessary to explain the present invention.

[0030] The optical-electrical conversion section 23 converts the optical signal amplified by the optical amplification section 21 into an electrical signal.

[0031] The FM batch signal demodulation unit 24 performs FM demodulation on the electrical signal converted by the optical-electrical conversion unit 23. In this way, the FM batch signal demodulation unit 24 restores the multiplexed signal.

[0032] The electrical signal amplifier 25 amplifies the multiplexed signal restored by the FM batch signal demodulator 24 .

[0033] The pilot signal measuring unit 26 is a spectrum analyzer that displays the multiplexed signal amplified by the electrical signal amplifier 25, or an audio receiving device such as a radio if the modulated signal is within the audible frequency range.

[0034] Fig. 6 is a diagram showing an example of the configuration of a distribution transmission device 30 in the first embodiment. The distribution transmission device 30 includes a switching unit 31, a main signal monitoring unit 32, and an optical amplifier unit 33. Note that Fig. 6 shows only the configuration necessary to explain the present invention.

[0035] The switching unit 31 selects an optical signal from either the 0-system network or the 1-system network and outputs it to the optical amplification unit 33. That is, the switching unit 31 switches the network to which the distribution transmission device 30 is connected to either the 0-system network or the 1-system network. Furthermore, the switching unit 31 autonomously switches the network to which the distribution transmission device 30 is connected to the other network in response to a switching control signal output from the main signal monitoring unit 32. The switching control signal is a control signal that instructs the switching unit 31 to switch the connection destination.

[0036] The main signal monitoring unit 32 demodulates the optical signal input to the distribution transmission device 30 and monitors the state of a signal (pilot signal) of a specific frequency included in the signal. If the main signal monitoring unit 32 detects an abnormality as a result of monitoring the state of the pilot signal, it notifies an error. Furthermore, if the main signal monitoring unit 32 detects an abnormality, such as a level drop, in the signal being transmitted, it sends a switch control signal to the switching unit 31.

[0037] The optical amplifier 33 amplifies the optical signal output from the switch 31. The optical amplifier 33 outputs the amplified optical signal to the receiver 40.

[0038] FIG. 7 is a sequence diagram showing the flow of processing performed by the signal transmission system 1 in the first embodiment. The system information setting unit 18 receives system information settings from an external device (step S101). The system information setting unit 18 outputs information indicating the received system information settings to the pilot signal setting unit 19. The pilot signal setting unit 19 determines the frequency of the pilot signal generated by the pilot signal generating unit 11 or the frequency of the modulation signal that modulates the pilot signal, based on the information indicating the system information settings output from the system information setting unit 18 and a frequency generation table (step S102). The pilot signal setting unit 19 outputs a control signal based on the determined frequency to the pilot signal generating unit 11.

[0039] The pilot signal generating unit 11 generates a pilot signal based on the control signal output from the pilot signal setting unit 19 (step S103). The pilot signal generating unit 11 outputs the generated pilot signal to the multiplexing unit 12. In addition to the pilot signal output from the pilot signal generating unit 11, an input signal is also input to the multiplexing unit 12. The multiplexing unit 12 multiplexes the input pilot signal with the input signal to generate a multiplexed signal (step S104). The multiplexed signal generated by the multiplexing unit 12 is input to the electric signal amplifying unit 13. Thereafter, signal transmission processing is performed in the electric signal amplifying unit 13, the FM batch converted signal generating unit 14, the electric-to-optical converting unit 15, the optical signal amplifying unit 16, and the transmitting unit 17 (step S105). As a result, an optical signal is transmitted from the signal transmitting device 10 to the relay transmission device 20.

[0040] The optical amplifier 21 of the relay transmission device 20 amplifies the optical signal sent from the signal transmission device 10 (step S106). The main signal monitoring unit 22 monitors the status of the pilot signal based on the optical signal amplified by the optical amplifier 21 (step S107). For example, the main signal monitoring unit 22 converts the optical signal into an electrical signal, performs FM demodulation on the electrical signal, and amplifies the electrical signal. Thereafter, the main signal monitoring unit 22 outputs the status of the pilot signal visually by displaying an electrical signal, or audibly by outputting a sound if the frequency band allows sound output. The relay transmission device 20 transmits the optical signal amplified by the optical amplifier 21 to the distribution transmission device 30 (step S108).

[0041] The switching unit 31 of the distribution transmission device 30 outputs the optical signal transmitted from the relay transmission device 20 to the main signal monitoring unit 32 and the optical amplifying unit 33. The main signal monitoring unit 32 monitors the state of the optical signal output from the switching unit 31 (step S109). If the main signal monitoring unit 32 detects an abnormality, such as a level drop, in the signal being transmitted, it transmits a switching control signal to the switching unit 31. The optical amplifying unit 33 of the distribution transmission device 30 amplifies the optical signal output from the switching unit 31 (step S110). The distribution transmission device 30 transmits the optical signal amplified by the optical amplifying unit 33 to the receiving device 40 (step S111).

[0042] For convenience of explanation, in Fig. 7, step S108 is performed after step S107, but steps S107 and S108 are actually performed in parallel. Similarly, in Fig. 7, step S109 is performed after step S110, but steps S109 and S110 are actually performed in parallel.

[0043] According to the signal transmission system 1 configured as described above, the signal transmission device 10 includes a system information setting unit 18 that performs system setting, a pilot signal setting unit 19 that determines the frequency of a pilot signal for monitoring or the frequency of a modulated signal to be carried by the pilot signal based on the system setting information performed by the system information setting unit 18, and a pilot signal generating unit 11 that generates a pilot signal based on the frequency determined by the pilot signal setting unit 19. This allows the main signal monitoring unit 22 of the relay transmission device 20 to visually confirm the frequency of the pilot signal or the modulated signal output from the pilot signal measuring unit 26 using a measuring device such as a spectrum analyzer, thereby recognizing the system information. However, this requires that the user knows the system information and the frequency of the pilot signal or the modulated signal being used at that time. Alternatively, if the modulated signal is in a frequency band that can be distinguished as sound, the system information can also be distinguished audibly by connecting a device that can reproduce the demodulated signal (for example, an FM radio if the pilot signal is FM-modulated). In this way, the signal transmitting device 10 can quickly detect human errors such as incorrect optical fiber connections by using the pilot signal used for monitoring the main signal for system determination without changing the configuration of the downstream relay transmission device 20. Therefore, in a system having an active system and a standby system, it becomes possible to quickly determine abnormalities due to incorrect connections of transmission lines in the relay transmission section using a simple method.

[0044] (Second embodiment) In the second embodiment, a configuration in which a signal transmission device does not perform FM batch conversion will be described. The system configuration of a signal transmission system 1 in the second embodiment is the same as that in the first embodiment. The following description will focus on the differences from the first embodiment.

[0045] 8 is a diagram showing an example of the configuration of a signal transmission device 10a in the second embodiment. The signal transmission device 10a includes a pilot signal generation unit 11, a multiplexing unit 12, an electric signal amplification unit 13, an electric-to-optical conversion unit 15, an optical signal amplification unit 16, a sending unit 17, a system information setting unit 18, and a pilot signal setting unit 19. The signal transmission device 10a differs in configuration from the signal transmission device 10 in that it does not include the FM batch converted signal generation unit 14. The following description will focus on the differences from the first embodiment.

[0046] The electrical signal amplifier 13 amplifies the multiplexed signal output from the multiplexer 12 and outputs it to the electrical-to-optical converter 15. The electrical-to-optical converter 15 converts the multiplexed signal amplified by the electrical signal amplifier 13 into an optical signal and outputs it to the optical signal amplifier 16. If the signal transmitter 10a does not perform FM batch conversion, the main signal monitoring unit 22 of the relay transmission device 20 does not need to include the FM batch signal demodulator 24. In other words, the optical-to-electrical converter 23 of the relay transmission device 20 only needs to output an electrical signal to the electrical signal amplifier 25.

[0047] According to the signal transmission system 1 of the second embodiment configured as above, it is possible to obtain the same effects as those of the first embodiment even when the signal transmission device 10 does not perform FM batch conversion.

[0048] (Third embodiment) In the third embodiment, a configuration will be described in which a signal transmission device transmits an electrical signal without performing FM batch conversion and conversion to an optical signal. The system configuration of the signal transmission system 1 in the third embodiment is the same as that in the first embodiment. The following description will focus on the differences from the first embodiment.

[0049] 9 is a diagram showing an example of the configuration of a signal transmission device 10b in the third embodiment. The signal transmission device 10b includes a pilot signal generation unit 11, a multiplexing unit 12, an electric signal amplification unit 13, a sending unit 17, a system information setting unit 18, and a pilot signal setting unit 19. The signal transmission device 10b differs in configuration from the signal transmission device 10 in that it does not include the FM batch converted signal generation unit 14, the electric-to-optical conversion unit 15, and the optical signal amplification unit 16. The following description will focus on the differences from the first embodiment.

[0050] The electrical signal amplifier 13 amplifies the multiplexed signal output from the multiplexer 12 and outputs it to the transmitter 17 .

[0051] As described above, since the signal transmitting device 10b does not transmit an optical signal, the configurations of the relay transmission device 20 and the distribution transmission device 30 also differ from those of the first embodiment. Specifically, the relay transmission device 20 may be provided with an electrical signal amplifier that amplifies an electrical signal instead of the optical amplifier 21. Furthermore, the main signal monitoring unit 22 of the relay transmission device 20 does not include the optical-electrical converter 23 and the FM batch signal demodulator 24. Note that if the relay transmission device 20 is provided with an electrical signal amplifier that amplifies an electrical signal instead of the optical amplifier 21, the main signal monitoring unit 22 does not need to include the electrical signal amplifier 25. The electrical signal amplifier outputs the electrical signal sent from the signal transmitting device 10b to the pilot signal measuring unit 26 and the distribution transmission device 30.

[0052] The distribution transmission device 30 includes an electrical signal amplifier that amplifies the electrical signal instead of the optical amplifier 33, and the main signal monitoring unit 32 does not need to include an optical-electrical converter that converts the optical signal into an electrical signal. An electrical signal is input to the switching unit 31 of the distribution transmission device 30 from the 0-system network or the 1-system network. The electrical signal amplifier amplifies the electrical signal output from the switching unit 31 and outputs it to the receiving device 40.

[0053] According to the signal transmission system 1 of the third embodiment configured as described above, it is possible to obtain the same effects as those of the first embodiment even if the signal transmission device 10 does not perform FM batch conversion and conversion to an optical signal.

[0054] (Modifications common to the first to third embodiments) In the first to third embodiments, the frequency in the frequency generation table referred to by the pilot signal setting unit 19 is a constant output independent of time. Alternatively, the pilot signal setting unit 19 may use the frequency generation table shown in FIG. 10 . FIG. 10 is a diagram illustrating another example of the frequency generation table and an explanation of the another example. As shown in FIG. 10A , multiple signal frequencies may be set for one piece of system information. The multiple signal frequencies are periodically changed. For example, in the example shown in FIG. 10A , when the system information is “0,” the pilot signal setting unit 19 determines the frequency of the pilot signal generated by the pilot signal generating unit 11 or the frequency of the modulation signal that modulates the pilot signal to be “300 kHz” at the timing of period a, and determines the frequency of the pilot signal generated by the pilot signal generating unit 11 or the frequency of the modulation signal that modulates the pilot signal to be “600 kHz” at the timing of period b.

[0055] As shown in Fig. 10(B), two cycles, cycle a and cycle b, are alternately repeated. The times a and b may be set in advance or may be input from the system information setting unit 18. Note that three or more signal frequencies may be set for one piece of system information. In the case where three or more signal frequencies are set for one piece of system information, they may be similarly divided by cycle.

[0056] The signal transmission devices 10, 10a, and 10b in the above-described embodiments may be implemented by a computer. In this case, a program for implementing the functions may be recorded on a computer-readable recording medium, and the program may be loaded into a computer system and executed. Note that the term "computer system" as used herein includes hardware such as an operating system (OS) and peripheral devices. Furthermore, the term "computer-readable recording medium" refers to portable media such as a flexible disk, a magneto-optical disk, a read-only memory (ROM), and a CD-ROM, as well as storage devices such as a hard disk built into a computer system.

[0057] Furthermore, the term "computer-readable recording medium" may include a medium that dynamically stores a program for a short period of time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, or a medium that stores a program for a fixed period of time, such as a volatile memory within a computer system that serves as a server or client in such a case. The program may also be one that realizes part of the above-mentioned functions, or one that can realize the above-mentioned functions in combination with a program already stored in the computer system, or one that can be realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0058] 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. [Explanation of symbols]

[0059] 1...signal transmission system, 2...oscillator, 3...PLL, 10, 10a, 10b, 10-1 to 10-2...signal transmitting device, 20, 20-1 to 20-2...relay transmission device, 30...distribution transmission device, 40...receiving device, 11...pilot signal generating unit, 12...multiplexing unit, 13...electrical signal amplifier unit, 14...FM batch converted signal generating unit, 15...electrical-to-optical converter unit, 16...optical signal amplifier unit, 17...transmission unit, 18...system information setting unit, 19...pilot signal setting unit, 21...optical amplifier unit, 22...main signal monitoring unit, 23...optical-to-electrical converter unit, 24...FM batch signal demodulation unit, 25...electrical signal amplifier unit, 26...pilot signal measuring unit, 31...switching unit, 32...main signal monitoring unit, 33...optical amplifier unit

Claims

1. A signal transmission device provided in either an active network or a standby network, a system information setting unit for setting the system; a pilot signal setting unit that determines a frequency of a pilot signal for monitoring or a frequency of a modulated signal carried by the pilot signal based on information on the system setting performed by the system information setting unit; a pilot signal generating unit that generates a pilot signal based on the frequency determined by the pilot signal setting unit; A signal transmitting device comprising:

2. The pilot signal setting unit determining the frequency of the pilot signal or the frequency of a modulated signal carried by the pilot signal for a specific time period; 2. The signal transmitting device according to claim 1.

3. the system setting information is a value indicating a specific state, The pilot signal setting unit referencing a table in which values ​​indicated by the system setting information correspond to information on one frequency, and determining one frequency associated with the value indicated by the system setting information performed by the system information setting unit as the frequency of the pilot signal or the frequency of a modulated signal carried by the pilot signal; 3. A signal transmitting device according to claim 1 or 2.

4. the system setting information is a value indicating a specific state, The pilot signal setting unit referencing a table in which values ​​indicated by the information on the system setting are associated with information on a plurality of frequencies that differ in period, and determining a frequency with a corresponding period from among the plurality of frequencies associated with the values ​​indicated by the information on the system setting performed by the system information setting unit as the frequency of the pilot signal or the frequency of a modulated signal carried by the pilot signal; 3. A signal transmitting device according to claim 1 or 2.

5. a multiplexing unit that multiplexes an input signal with a pilot signal generated by the pilot signal generating unit; a conversion unit that optically modulates the signal multiplexed by the multiplexing unit to convert it into an optical signal, 3. A signal transmitting device according to claim 1 or 2.

6. a multiplexing unit that multiplexes an input signal with a pilot signal generated by the pilot signal generating unit; an FM batch conversion unit that performs FM (Frequency Modulation) batch conversion on the signals multiplexed by the multiplexing unit to generate FM batch converted signals; a converter that optically modulates the FM batch converted signal generated by the FM batch converter to convert it into an optical signal, 3. A signal transmitting device according to claim 1 or 2.

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