Signal Transmitter

Abstract

To suppress increase in circuit scale and a device cost.SOLUTION: A signal transmission apparatus includes a pilot signal generation unit that generates multiple pilot signals of different frequencies as a monitoring pilot signal used to detect abnormal levels in specific frequency bands of an input signal, a demultiplexing unit that demultiplexes the multiple pilot signals of different frequencies, one or more detection units that detect at least two or more pilot signals of the multiple pilot signals of different frequencies by using signals demultiplexed by the demultiplexing unit, a switching unit that switches an output target to output each of the multiple pilot signals of different frequencies demultiplexed by the demultiplexing unit at a predetermined cycle to the one or more detection units, a control unit that controls the switching unit so that the output target of the switching unit and an output destination are connected at a predetermined cycle.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a signal transmission device. [Background Art]

[0002] Conventionally, as a signal transmission device, there has been known a signal transmission device including a pilot signal generation unit that generates a pilot signal used to detect an abnormality in a processing unit that performs internal processing on an input signal (see, for example, Non-Patent Documents 1 and 2). In such a signal transmission device, when the frequency band of the input signal covers a wide band, a plurality of pilot signal generation units are provided to generate a plurality of pilot signals with different bands. The pilot signal is detected inside the signal transmission device and may be used for abnormality detection judgment of an intermediate processing unit. This mechanism is equivalent to the mechanism provided in a reception device.

[0003] FIG. 11 is a diagram showing a configuration example of a conventional signal transmission device 100. FIG. 8 shows a signal transmission device 100 included in a communication system to which an FM (Frequency Modulation) collective conversion method is applied, as an example of the signal transmission device. The signal transmission device 100 includes an electrical signal branching unit 110, a pilot signal generation unit 120, a multiplexing unit 130, an electrical signal abnormality detection unit 140, an electrical signal amplification unit 150, an FM collective conversion signal generation unit 160, an electrical-optical conversion unit 170, an optical signal amplification unit 180, an optical signal branching unit 190, a demodulated signal abnormality detection unit 200, a monitoring unit 210, and an alarm processing unit 220. Note that the dotted lines extending from some functional units to the monitoring unit 210 represent control signals.

[0004] The signal transmitting device 100 receives signals of multiple frequency bands as input signals. For example, the signal transmitting device 100 receives signals with frequency bands of 70 to 770 MHz (47 to 864 MHz in Non-Patent Literature 1) and signals with frequency bands of 1000 to 2100 MHz (1000 to 2150 MHz in Non-Patent Literature 1). Note that the frequency bands of the input signals input to the signal transmitting device 100 are just examples. In the following explanation, we will assume that, as an example, signals with frequency bands of 70 to 770 MHz and signals with frequency bands of 1000 to 2100 MHz are input to the signal transmitting device 100. The electrical signal branching unit 110 branches the input signals received from the outside and outputs them to the multiplexing unit 130 and the electrical signal anomaly detection unit 140. The pilot signal generation unit 120 generates pilot signals of multiple different frequencies. The pilot signal generation unit 120 generates pilot signals with frequencies around 70 MHz, around 885 MHz, and around 2100 MHz, for example.

[0005] The multiplexer 130 combines the input signal branched by the electrical signal branching unit 110 with multiple pilot signals output from the pilot signal generation unit 120 to generate a multiplexed signal. The multiplexer 130 outputs the generated multiplexed signal to the electrical signal amplification unit 150. The electrical signal amplification unit 150 amplifies the multiplexed signal output from the multiplexer 130 and outputs it to the FM batch conversion signal generation unit 160.

[0006] The electrical signal anomaly detection unit 140 detects an anomaly in the power level of the input signal. The electrical signal anomaly detection unit 140 outputs a detection result indicating whether or not there is an anomaly in the power level of the input signal to the monitoring unit 210. The FM batch conversion signal generation unit 160 performs FM batch conversion on the multiplexed signal amplified by the electrical signal amplification unit 150 to generate a broadband FM batch conversion signal, which is output to the electrical-optical conversion unit 170 and the monitoring unit 210. The electrical-optical conversion unit 170 converts the FM batch conversion signal generated by the FM batch conversion signal generation unit 160 into an optical signal and outputs it to the optical signal amplification unit 180 and the monitoring unit 210. The optical signal amplification unit 180 amplifies the optical signal output from the electrical-optical conversion unit 170 and outputs it to the optical signal branching unit 190 and the monitoring unit 210.

[0007] The optical signal splitter 190 splits the optical signal amplified by the optical signal amplifier 180 and outputs it to the external device and the demodulated signal anomaly detection unit 200. The demodulated signal anomaly detection unit 200 converts the optical signal split by the optical signal splitter 190 back into an electrical signal, performs FM demodulation, and then detects the state of the demodulated signal. For example, the state detection performed by the demodulated signal anomaly detection unit 200 is the detection of level anomalies in the frequency band of the pilot signal included in the input demodulated signal. The demodulated signal anomaly detection unit 200 outputs the measured level information to the monitoring unit 210.

[0008] The monitoring unit 210 detects abnormalities in each functional unit based on the signals output from the electrical signal abnormality detection unit 140, the FM batch conversion signal generation unit 160, the electrical-optical conversion unit 170, the optical signal amplification unit 180, and the demodulated signal abnormality detection unit 200. For example, the monitoring unit 210 detects the following abnormalities: Based on the signal output from the electrical signal abnormality detection unit 140, the monitoring unit 210 detects an abnormality in the power level of the input carrier signal. Furthermore, based on the signal output from the FM batch conversion signal generation unit 160, the monitoring unit 210 detects an abnormality in the center frequency of the input FM batch conversion signal. Furthermore, based on the signal output from the electrical-optical conversion unit 170, the monitoring unit 210 detects an abnormality in the optical conversion level in the electrical-optical conversion unit 170. Furthermore, based on the signal output from the optical signal amplification unit 180, the monitoring unit 210 detects an abnormality in the optical amplification output. Furthermore, the monitoring unit 210 compares the information on the signal level in a normal state, which is stored in memory, with the information on the signal level demodulated by the demodulated signal anomaly detection unit 200 to determine an abnormal state. If the monitoring unit 210 detects an anomaly, it causes the alarm processing unit 220 to output an alarm.

[0009] Figure 12 shows an example configuration of a conventional demodulated signal anomaly detection unit 200. The demodulated signal anomaly detection unit 200 comprises an optical-to-electrical conversion unit 201, a demodulation unit 202, a demultiplexing unit 203, and a plurality of detection units 204-1 to 204-3. The optical-to-electrical conversion unit 201 converts the optical signal branched by the optical signal branching unit 190 into an electrical signal. This restores the FM batch conversion signal. The demodulation unit 202 performs FM demodulation on the electrical signal (FM batch conversion signal) converted by the optical-to-electrical conversion unit 201. This demodulates the multiplexed signal output from the multiplexing unit 130.

[0010] The demultiplexer 203 demultiplexes the multiplexed signal demodulated by the demodulator 202 according to its frequency band. For example, the demultiplexer 203 demultiplexes signals in the 70MHz to 770MHz frequency band to the detector 204-1, signals in the 770MHz to 960MHz frequency band to the detector 204-2, and signals in the 960MHz to 2100MHz frequency band to the detector 204-3. The detectors 204-1 to 204-3 detect the pilot signal included in the signals demultiplexed by the demultiplexer 203. [Prior art documents] [Non-patent literature]

[0011] [Non-Patent Document 1] “Transmission equipment for transferring multi-channel television signals over optical access networks by frequency modulation conversion” ITU-T Rec. J. 185, 2012. [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. [Overview of the project] [Problems that the invention aims to solve]

[0012] As mentioned above, in devices that require detection of multiple pilot signals, the number of detection units increases in proportion to the number of pilot signals. This leads to a problem where the circuit size increases with the number of pilot signals, and consequently, the device cost also increases. This problem is not limited to the FM batch conversion signal transmission device shown in Figure 11, but is common to all signal transmission devices that receive wideband input signals.

[0013] In view of the above circumstances, the present invention aims to provide a technology that can suppress the increase in circuit size and equipment costs. [Means for solving the problem]

[0014] One aspect of the present invention is a signal transmitting device comprising: a pilot signal generation unit that generates a plurality of pilot signals of different frequencies as monitoring pilot signals used for detecting level anomalies in a specific frequency band of an input signal; a demultiplexing unit that separates the plurality of pilot signals of different frequencies; one or more detection units that detect at least two or more pilot signals of the plurality of pilot signals of different frequencies using the signals separated by the demultiplexing unit; a switching unit that switches the output target so as to output each of the plurality of pilot signals of different frequencies separated by the demultiplexing unit to the one or more detection units at a predetermined period; and a control unit that controls the switching unit so as to connect the output target of the switching unit and the output destination at the predetermined period. [Effects of the Invention]

[0015] This invention makes it possible to suppress increases in circuit size and equipment costs. [Brief explanation of the drawing]

[0016] [Figure 1] This figure shows an example of the configuration of a signal transmitting device in the first embodiment. [Figure 2] This figure shows an example of the configuration of the demodulated signal anomaly detection unit in the first embodiment. [Figure 3] This figure shows an example of the configuration of the switching unit in the first embodiment. [Figure 4] This figure illustrates the switching timing control of the switching unit in the signal transmission device of the first embodiment. [Figure 5] This figure shows an example of the configuration of the demodulated signal anomaly detection unit in the second embodiment. [Figure 6]FIG. 2 is a diagram showing a configuration example of a switching unit in a second embodiment. [Figure 7] FIG. 3 is a diagram for explaining switching timing control of a switching unit in the signal transmission device according to the second embodiment. [Figure 8] FIG. 4 is a diagram showing a configuration example of a demodulated signal abnormality detection unit in a third embodiment. [Figure 9] FIG. 5 is a diagram showing a configuration example of a switching unit in the third embodiment. [Figure 10] FIG. 6 is a diagram for explaining switching timing control of a switching unit in the signal transmission device according to the third embodiment. [Figure 11] FIG. 7 is a diagram showing a configuration example of a conventional signal transmission device. [Figure 12] FIG. 8 is a diagram showing a configuration example of a conventional demodulated signal abnormality detection unit. MODE FOR CARRYING OUT THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. (First Embodiment) FIG. 1 is a diagram showing a configuration example of a signal transmission device 10 according to a first embodiment. An input signal having a wide frequency band is input to the signal transmission device 10 from the outside. The input signal input from the outside may be, for example, a carrier signal obtained from a video signal. The signal transmission device 10 includes an electrical signal branching unit 11, a pilot signal generation unit 12, a multiplexing unit 13, an electrical signal abnormality detection unit 14, an electrical signal amplification unit 15, an FM collective conversion signal generation unit 16, an electrical-optical conversion unit 17, an optical signal amplification unit 18, an optical signal branching unit 19, a demodulated signal abnormality detection unit 20, a monitoring unit 21, and an alarm processing unit 22. Note that the dotted lines extending from some of the functional units to the monitoring unit 21 represent control signals.

[0018] The electrical signal branching unit 11, pilot signal generation unit 12, multiplexing unit 13, electrical signal anomaly detection unit 14, electrical signal amplification unit 15, FM batch conversion signal generation unit 16, electrical-optical conversion unit 17, optical signal amplification unit 18, optical signal branching unit 19, monitoring unit 21, and alarm processing unit 22 basically perform the same processing as the functional units of the same name shown in Figure 11 (electrical signal branching unit 110, pilot signal generation unit 120, multiplexing unit 130, electrical signal anomaly detection unit 140, electrical signal amplification unit 150, FM batch conversion signal generation unit 160, electrical-optical conversion unit 170, optical signal amplification unit 180, optical signal branching unit 190, monitoring unit 210, and alarm processing unit 220). The differences will be explained below.

[0019] To explain the differences, we will first describe the prerequisite of multiple pilot signals of different frequencies. The pilot signal generation unit 12 has the function of generating multiple pilot signals of different frequencies. The pilot signals generated by the pilot signal generation unit 12 are monitoring signals used to detect level anomalies in a specific frequency band of the input signal. In the following explanation, we will assume that the input signal includes signals in the 70-770 MHz frequency band and signals in the 1000-2100 MHz frequency band. Thus, the signal transmission device 10 receives input signals with a wide frequency bandwidth.

[0020] The pilot signal generation unit 12 generates a first pilot signal, a second pilot signal, and a third pilot signal to detect level anomalies in multiple frequency bands included in the input signal. For example, the first pilot signal is a pilot signal with a frequency near 70 MHz, the second pilot signal is a pilot signal with a frequency near 885 MHz, and the third pilot signal is a pilot signal with a frequency near 2100 MHz. The pilot signal generation unit 12 only needs to generate pilot signals having frequencies near the frequencies of the input signal, and the frequencies of the pilot signals are not limited to the above frequencies. Note that each of the above pilot signals may be generated by one pilot signal generation unit 12 or by multiple pilot signal generation units 12.

[0021] The demodulated signal anomaly detection unit 20 receives the optical signal branched by the optical signal branching unit 19 as input. The demodulated signal anomaly detection unit 20 converts the input optical signal back into an electrical signal and performs FM demodulation, and then detects each pilot signal included in the demodulated signal at different timings. For example, the demodulated signal anomaly detection unit 20 detects the first pilot signal at time a, the second pilot signal at time b, and the third pilot signal at time c. In this way, the demodulated signal anomaly detection unit 20 shares the detection unit by controlling the timing of the detection of the pilot signals. In the following explanation, times a, b, and c are assumed to be the same time interval, but times a, b, and c may be different time intervals.

[0022] Figure 2 shows an example of the configuration of the demodulated signal anomaly detection unit 20 in the first embodiment. The demodulated signal anomaly detection unit 20 comprises an optical-to-electrical conversion unit 31, a demodulation unit 32, a demultiplexing unit 33, a switching unit 34, a plurality of detection units 35-1 to 35-2, and a control unit 36.

[0023] The optical-to-electrical conversion unit 31 converts the optical signals branched by the optical signal branching unit 19 into electrical signals.

[0024] The demodulation unit 32 performs FM demodulation on the electrical signal converted by the optical-electrical conversion unit 31 (for example, the FM batch conversion signal). As a result, the multiplexed signal output from the multiplexing unit 13 is demodulated.

[0025] The demultiplexer 33 demultiplexes the multiplexed signal demodulated by the demodulator 32 according to its frequency band. For example, the demultiplexer 33 demultiplexes the signal into three frequency bands: 70MHz to 770MHz, 770MHz to 960MHz, and 960MHz to 2100MHz. The demultiplexer 33 outputs the signals of each demultiplexed frequency band to the switching unit 34.

[0026] The switching unit 34 switches the output target and output destination of the signals for each frequency band output from the demultiplexer 33, in accordance with the control of the control unit 36. For example, the switching unit 34 switches the path so that the output target instructed (switching instruction) by the control unit 36 ​​is output from the instructed output destination.

[0027] Detection units 35-1 to 35-2 receive the signal output from the switching unit 34 as input. Detection units 35-1 to 35-2 detect the pilot signals included in the input signal. For example, detection unit 35-1 detects the first pilot signal (pilot signal [1] in Figure 2), and detection unit 35-2 detects the second and third pilot signals (pilot signal [2] and pilot signal [3] in Figure 2). In this way, detection unit 35-2 detects the pilot signals included in the input signal's processing frequency range.

[0028] The detection units 35-1 to 35-2 may be configured to perform asynchronous detection or synchronous detection. If the switching unit 34 operates in synchronization with the pilot signal generation unit 12, the detection units 35-1 to 35-2 may be configured to perform asynchronous detection.

[0029] The control unit 36 ​​controls the pilot signal generation unit 12 and the switching unit 34. If synchronization with the pilot signal generation cycle of the pilot signal generation unit 12 is not required, the control unit 36 ​​only needs to control the switching unit 34. In the following explanation, however, it is assumed that synchronization with the pilot signal generation cycle of the pilot signal generation unit 12 is necessary. The control unit 36 ​​is, for example, a microcomputer.

[0030] The control unit 36 ​​changes the frequency of the pilot signal generated by the pilot signal generation unit 12 at a predetermined period. For example, the control unit 36 ​​causes the pilot signal generation unit 12 to generate a first pilot signal at time a, a second pilot signal at time b, and a third pilot signal at time c. Furthermore, the control unit 36 ​​switches the output target and output destination of the signals of each frequency band input to the switching unit 34 by outputting a switching instruction to the switching unit 34. The switching instruction is an instruction to switch the path so as to connect the output target and output destination of the switching unit 34, and includes information such as the input terminal into which the signal to be output is input and the output terminal that is the output destination.

[0031] The control unit 36, for example, at time a, switches the path to connect the input terminal to which a signal in the frequency band including the first pilot signal is input as the output target of the switching unit 34 to the output terminal to which the detection unit 35-1, which is the output destination, is connected; at time b, switches the path to connect the input terminal to which a signal in the frequency band including the second pilot signal is input as the output target of the switching unit 34 to the output terminal to which the detection unit 35-2, which is the output destination, is connected; and at time c, switches the path to connect the input terminal to which a signal in the frequency band including the third pilot signal is input as the output target of the switching unit 34 to the output terminal to which the detection unit 35-2, which is the output destination, is connected.

[0032] Figure 3 shows an example of the configuration of the switching unit 34 in the first embodiment. As shown in Figure 3, the switching unit 34 includes a switch unit 341. The switch unit 341 consists of a plurality of input terminals 342 to 344, a connection unit 345, and a plurality of output terminals 346 to 347. The switch unit 341 connects any input terminal to any output terminal via the connection unit 345 in response to a switching instruction from the control unit 36. As a result, the switching unit 34 outputs signals of each frequency band separated by the devolving unit 33 to the output destination at a predetermined period. In the example shown in Figure 3, a signal in the frequency band including the first pilot signal separated by the devolving unit 33 is input to input terminal 342, a signal in the frequency band including the second pilot signal separated by the devolving unit 33 is input to input terminal 343, and a signal in the frequency band including the third pilot signal separated by the devolving unit 33 is input to input terminal 344.

[0033] The switching unit 34 outputs a signal in the frequency band including the first pilot signal to the detection unit 35-1 connected to the output terminal 346 by connecting the input terminal 342 and the output terminal 346. The switching unit 34 outputs a signal in the frequency band including the second pilot signal to the detection unit 35-2 connected to the output terminal 347 by connecting the input terminal 343 and the output terminal 347. The switching unit 34 outputs a signal in the frequency band including the third pilot signal to the detection unit 35-2 connected to the output terminal 347 by connecting the input terminal 344 and the output terminal 347.

[0034] Figure 4 is a diagram illustrating the switching timing control of the switching unit 34 in the signal transmitting device 10 of the first embodiment. In Figure 4, (1) represents the first pilot signal, (2) represents the second pilot signal, and (3) represents the third pilot signal. In Figure 4, the horizontal axis represents time t, and the vertical axis represents the operating timing of the detection unit 35. As shown in Figure 4, the control unit 36 ​​controls the switching unit 34 at time a to connect the input terminal 342 and the output terminal 346. As a result, the switching unit 34 switches the connection to connect the input terminal 342 and the output terminal 346 during the period of time a, and outputs the signal input to the input terminal 342 to the detection unit 35-1. Consequently, the detection unit 35-1 detects the first pilot signal using the signal output from the switching unit 34 during the period of time a.

[0035] Next, when time b occurs, the control unit 36 ​​controls the switching unit 34 to connect the input terminal 343 and the output terminal 347. As a result, the switching unit 34 switches the connection so that the input terminal 343 and the output terminal 347 are connected during time b, and outputs the signal input to the input terminal 343 to the detection unit 35-2. Consequently, the detection unit 35-2 uses the signal output from the switching unit 34 during time b to detect the second pilot signal.

[0036] Next, when time c occurs, the control unit 36 ​​controls the switching unit 34 to connect the input terminal 344 and the output terminal 347. As a result, the switching unit 34 switches the connection so that the input terminal 344 and the output terminal 347 are connected during time c, and outputs the signal input to the input terminal 344 to the detection unit 35-2. Consequently, the detection unit 35-2 uses the signal output from the switching unit 34 during time c to detect a third pilot signal.

[0037] Note that the operation shown in Figure 4 is just one example. When the detection unit 35-1 detects multiple pilot signals of different frequencies, the control unit 36 ​​controls the switching unit 34 so that the signal in the frequency band containing the pilot signal detected by the detection unit 35-1 is output to the detection unit 35-1.

[0038] With the signal transmission device 10 configured as described above, the control unit 36 ​​shifts the timing of outputting signals in the frequency band containing the pilot signals to be output by the switching unit 34 so that pilot signals of different frequencies are detected by one detection unit 35. As a result, there will be periods in a particular time period when a pilot signal of a certain frequency is not present. However, if continuous monitoring is not performed, multiple pilot signals can be processed by one detection unit 35, thus reducing the number of detection units 35. This is applicable to video transmission systems, which have very strict monitoring conditions, but it can be sufficiently applied by shortening the time interval. In this way, since pilot signals of different frequencies are detected at different timings by one detection unit 35, the increase in circuit size in accordance with the increase in the number of pilot signals can be suppressed more than in conventional systems. As a result, equipment costs can also be reduced.

[0039] (Second embodiment) In the first embodiment, a configuration was shown in which the signals of each frequency band, separated by the demultiplexer, are sequentially switched by the switching unit and output to the detection unit to be processed. In the second embodiment, a configuration is described in which some detection units constantly monitor signals of a specific frequency band, and other detection units monitor signals of each frequency band separated by the demultiplexer by the demultiplexer by switching the switching unit at a specific period. In the second embodiment, the configuration of the signal transmission device is the same as in the first embodiment. In the second embodiment, the configuration of the demodulated signal anomaly detection unit differs from that of the first embodiment. The differences will be explained below.

[0040] Figure 5 shows an example of the configuration of the demodulated signal anomaly detection unit 20a in the second embodiment. The demodulated signal anomaly detection unit 20a comprises an optical-to-electrical conversion unit 31, a demodulation unit 32, a demultiplexing unit 33a, a switching unit 34a, a plurality of detection units 35-1 to 35-2, and a control unit 36a.

[0041] The demultiplexer 33a demultiplexes the multiplexed signal demodulated by the demodulator 32 according to its frequency band. For example, the demultiplexer 33a demultiplexes the signal into three frequency bands: 70MHz to 770MHz, 770MHz to 960MHz, and 960MHz to 2100MHz. The demultiplexer 33a outputs the demultiplexed signal of a specific frequency band to the detection unit 35-1 and outputs the signals of the other frequency bands to the switching unit 34a. For example, the demultiplexer 33a outputs the demultiplexed signal of the 70MHz to 770MHz frequency band to the detection unit 35-1 and outputs the signals of the 770MHz to 960MHz frequency band and the signals of the 960MHz to 2100MHz frequency band to the switching unit 34a.

[0042] The switching unit 34a switches the output target and output destination of the signals for each frequency band output from the demultiplexer 33a, in accordance with the control of the control unit 36a. For example, the switching unit 34a switches the path so that the output target instructed (switching instruction) by the control unit 36a is output from the instructed output destination.

[0043] The control unit 36a controls the pilot signal generation unit 12 and the switching unit 34a. If synchronization with the pilot signal generation cycle of the pilot signal generation unit 12 is not required, the control unit 36a only needs to control the switching unit 34a. The control unit 36a is, for example, a microcomputer.

[0044] The control unit 36a changes the frequency of the pilot signal generated by the pilot signal generation unit 12 at a predetermined period. For example, the control unit 36a causes the pilot signal generation unit 12 to generate a first pilot signal at a certain time a, a second pilot signal at a certain time b, and a third pilot signal at a certain time c. Furthermore, the control unit 36a switches the output target and output destination of the signals of each frequency band input to the switching unit 34a by outputting a switching instruction to the switching unit 34a.

[0045] The control unit 36a, for example, at a certain time a, switches the path to connect the input terminal to which a signal in the frequency band including the second pilot signal is input as the output target of the switching unit 34a to the output terminal to which the detection unit 35-2, which is the output destination, is connected, and at time b, switches the path to connect the input terminal to which a signal in the frequency band including the third pilot signal is input as the output target of the switching unit 34a to the output terminal to which the detection unit 35-2, which is the output destination, is connected.

[0046] As shown in Figure 5, the demultiplexer 33a is connected to the detection unit 35-1 without going through the switching unit 34a. In this way, in the second embodiment, the signal of a specific frequency band output from the demultiplexer 33a is input to the detection unit 35-1. As a result, the detection unit 35-1 constantly monitors the input signal of a specific frequency band.

[0047] Figure 6 shows an example of the configuration of the switching unit 34a in the second embodiment. As shown in Figure 6, the switching unit 34a includes a switch unit 341a. The switch unit 341a consists of a plurality of input terminals 343 to 344 and an output terminal 347. The switch unit 341a connects one of the input terminals to the output terminal in response to a switching instruction from the control unit 36a. As a result, the switching unit 34a outputs the signals of each frequency band separated by the devolving unit 33a to the output destination at a predetermined period.

[0048] In the example shown in Figure 6, a signal in the frequency band including the second pilot signal separated by the demultiplexer 33a is input to input terminal 343, and a signal in the frequency band including the third pilot signal separated by the demultiplexer 33a is input to input terminal 344. The switching unit 34a outputs the signal in the frequency band including the second pilot signal to the detection unit 35-2 connected to output terminal 347 by connecting input terminal 343 and output terminal 347. The switching unit 34a outputs the signal in the frequency band including the third pilot signal to the detection unit 35-2 connected to output terminal 347 by connecting input terminal 344 and output terminal 347.

[0049] Figure 7 is a diagram illustrating the switching timing control of the switching unit 34a in the signal transmitting device 10 of the second embodiment. In Figure 7, (1) represents the first pilot signal, (2) represents the second pilot signal, and (3) represents the third pilot signal. In Figure 7, the horizontal axis represents time t, and the vertical axis shows the operating timing of the detection unit 35. As shown in Figure 5, the demultiplexer 33a and the detection unit 35-1 are directly connected. Therefore, a signal in the frequency band including the first pilot signal is constantly output to the detection unit 35-1. As a result, the detection unit 35-1 constantly detects the first pilot signal using the signal output from the demultiplexer 33a.

[0050] The control unit 36a controls the switching unit 34a at time a to connect the input terminal 343 and the output terminal 347. As a result, the switching unit 34a switches the connection to connect the input terminal 343 and the output terminal 347 during time a, and outputs the signal input to the input terminal 343 to the detection unit 35-2. Consequently, the detection unit 35-2 uses the signal output from the switching unit 34a during time a to detect a second pilot signal.

[0051] Next, when time b occurs, the control unit 36a controls the switching unit 34a to connect the input terminal 344 and the output terminal 347. As a result, the switching unit 34a switches the connection to connect the input terminal 344 and the output terminal 347 during time b and outputs the signal input to the input terminal 344 to the detection unit 35-2. Consequently, the detection unit 35-2 uses the signal output from the switching unit 34a during time b to detect the third pilot signal.

[0052] In the second embodiment, compared to the first embodiment, signals of two frequency bands are input to the switching unit 34a. Therefore, when the third timing, time c, occurs, the control unit 36a controls the switching unit 34a to connect the input terminal 343 and the output terminal 347. As a result, the switching unit 34a switches the connection to connect the input terminal 343 and the output terminal 347 during time c, and outputs the signal input to the input terminal 343 to the detection unit 35-2. Consequently, the detection unit 35-2 detects a third pilot signal using the signal output from the switching unit 34a during time c. After that, the control unit 36a switches the connection of the switching unit 34a at regular intervals as time progresses, and outputs the signals output from the demultiplexer 33a in sequence.

[0053] Note that the operation shown in Figure 7 is just one example. When the detection unit 35-1 detects multiple pilot signals of different frequencies and the demultiplexer 33a and the detection unit 35-2 are directly connected, the control unit 36a controls the connection of the switching unit 34a to switch over time so that signals in the frequency band including the pilot signals detected by the detection unit 35-1 are output to the detection unit 35-1.

[0054] In the signal transmission device 10a configured as described above, among the multiple detection units 35, signals in a specific frequency band are constantly monitored by one detection unit 35 (for example, detection unit 35-1), while signals in other frequency bands are processed at different timings by one detection unit 35 (for example, detection unit 35-2). In this way, while constantly monitoring signals in a specific frequency band, the timing of outputting signals in frequency bands that include pilot signals to be output by the switching unit 34 is staggered so that, as in the first embodiment, one detection unit 35 detects pilot signals of different frequencies. This reduces the number of detection units 35, and the increase in circuit size in response to an increase in the number of pilot signals can be suppressed more than in the conventional method. As a result, equipment costs can also be reduced.

[0055] (Third embodiment) In the third embodiment, a configuration will be described in which the signals of each frequency band, separated by the demultiplexer, are sequentially switched by the switching unit and output sequentially to a single detection unit. In the third embodiment, the configuration of the signal transmission device is the same as in the first embodiment. The configuration of the demodulated signal anomaly detection unit in the third embodiment differs from that of the first embodiment. The differences will be explained below.

[0056] Figure 8 shows an example of the configuration of the demodulated signal anomaly detection unit 20b in the third embodiment. The demodulated signal anomaly detection unit 20b comprises an optical-to-electrical conversion unit 31, a demodulation unit 32, a demultiplexing unit 33, a switching unit 34b, a detection unit 35, and a control unit 36b.

[0057] The switching unit 34b switches the output target of the signals of each frequency band output from the demultiplexer 33 according to the control of the control unit 36b. The switching unit 34b switches the path so that the output target instructed (switching instruction) by the control unit 36b is output to the detection unit 35.

[0058] The control unit 36b controls the pilot signal generation unit 12 and the switching unit 34b. If synchronization with the pilot signal generation cycle of the pilot signal generation unit 12 is not required, the control unit 36b only needs to control the switching unit 34b. The control unit 36b is, for example, a microcomputer.

[0059] The control unit 36b changes the frequency of the pilot signal generated by the pilot signal generation unit 12 at a predetermined period. For example, the control unit 36b causes the pilot signal generation unit 12 to generate a first pilot signal at a certain time a, a second pilot signal at a certain time b, and a third pilot signal at a certain time c. Furthermore, the control unit 36b switches the output target and output destination of the signals of each frequency band input to the switching unit 34b by outputting a switching instruction to the switching unit 34b.

[0060] The control unit 36b, for example, at time a, switches the path to connect the input terminal to which a signal in the frequency band including the first pilot signal is input as the output target of the switching unit 34b to the output terminal to which the detection unit 35, which is the output destination, is connected; at time b, switches the path to connect the input terminal to which a signal in the frequency band including the second pilot signal is input as the output target of the switching unit 34b to the output terminal to which the detection unit 35, which is the output destination, is connected; and at time c, switches the path to connect the input terminal to which a signal in the frequency band including the third pilot signal is input as the output target of the switching unit 34b to the output terminal to which the detection unit 35, which is the output destination, is connected.

[0061] Thus, in the third embodiment, the signals of each frequency band output from the demultiplexer 33 are sequentially output from the switching unit 34b to a single detection unit 35. As a result, the detection unit 35 monitors the signals of the input frequency bands in sequence.

[0062] Figure 9 shows an example of the configuration of the switching unit 34b in the third embodiment. As shown in Figure 9, the switching unit 34b includes a switch unit 341b. The switch unit 341b consists of a plurality of input terminals 342 to 344 and an output terminal 348. The switch unit 341b connects one of the input terminals to the output terminal in response to a switching instruction from the control unit 36b. As a result, the switching unit 34b outputs the signals of each frequency band separated by the devolving unit 33 to the output destination at a predetermined period.

[0063] In the example shown in Figure 9, a signal in the frequency band including the first pilot signal, which has been devolved by the devolver 33, is input to input terminal 342, a signal in the frequency band including the second pilot signal, which has been devolved by the devolver 33, is input to input terminal 343, and a signal in the frequency band including the third pilot signal, which has been devolved by the devolver 33, is input to input terminal 344. The switching unit 34b outputs the signal in the frequency band including the first pilot signal to the detection unit 35 connected to output terminal 348 by connecting input terminal 342 and output terminal 348. The switching unit 34b outputs the signal in the frequency band including the second pilot signal to the detection unit 35 connected to output terminal 348 by connecting input terminal 343 and output terminal 348. The switching unit 34b outputs the signal in the frequency band including the third pilot signal to the detection unit 35 connected to output terminal 348 by connecting input terminal 344 and output terminal 348.

[0064] Figure 10 is a diagram illustrating the switching timing control of the switching unit 34b in the signal transmitting device 10 of the third embodiment. In Figure 10, (1) represents the first pilot signal, (2) represents the second pilot signal, and (3) represents the third pilot signal. In Figure 10, the horizontal axis represents time t, and the vertical axis shows the operation timing of the detection unit 35.

[0065] The control unit 36b controls the switching unit 34b at time a to connect the input terminal 342 and the output terminal 348. As a result, the switching unit 34b switches the connection to connect the input terminal 342 and the output terminal 348 during time a, and outputs the signal input to the input terminal 342 to the detection unit 35. Consequently, the detection unit 35 detects the first pilot signal using the signal output from the switching unit 34b during time a.

[0066] Next, when time b occurs, the control unit 36b controls the switching unit 34b to connect the input terminal 343 and the output terminal 348. As a result, the switching unit 34b switches the connection so that the input terminal 343 and the output terminal 348 are connected during time b, and outputs the signal input to the input terminal 343 to the detection unit 35. Consequently, the detection unit 35 uses the signal output from the switching unit 34b during time b to detect the second pilot signal.

[0067] Next, when time c occurs, the control unit 36b controls the switching unit 34b to connect the input terminal 344 and the output terminal 348. As a result, the switching unit 34b switches the connection so that the input terminal 344 and the output terminal 348 are connected during time c, and outputs the signal input to the input terminal 344 to the detection unit 35. Consequently, the detection unit 35 uses the signal output from the switching unit 34b during time c to detect a third pilot signal.

[0068] In the signal transmission device 10b configured as described above, the control unit 36b sequentially switches the signals to be input to one detection unit 35 using the switching unit 34b. In this third embodiment, one detection unit 35 processes all the pilot signals generated by the pilot signal generation unit 12. This reduces the number of detection units 35, and suppresses the increase in circuit size in response to an increase in the number of pilot signals more effectively than in the conventional design. As a result, equipment costs can also be reduced.

[0069] (Modification 1 common to the first to third embodiments) In the above-described embodiments, the signal transmitting device 10 is configured to perform FM batch conversion and optical signal conversion, but the signal transmitting device 10 may also be a signal transmitting device that transmits electrical signals. In this configuration, the signal transmitting device 10 in the first embodiment may be configured as a signal transmitting device comprising an electrical signal branching unit 11, a pilot signal generation unit 12, a multiplexing unit 13, an electrical signal anomaly detection unit 14, an electrical signal amplification unit 15, a demodulated signal anomaly detection unit 20, a monitoring unit 21, and an alarm processing unit 22. The electrical signal amplification unit 15 amplifies the multiplexed signal output from the multiplexing unit 13 and outputs it to the demodulated signal anomaly detection unit 20. The demodulated signal anomaly detection unit 20 comprises a demultiplexing unit 33, a switching unit 34, a plurality of detection units 35-1 to 35-2, and a control unit 36. The demultiplexing unit 33 demultiplexes the multiplexed signal output from the electrical signal amplification unit 15 according to the frequency band. The demultiplexing unit 33 outputs the signals of each demultiplexed frequency band to the switching unit 34. In this case, the demodulated signal abnormality detection unit 20 does not need to perform the conversion from optical signal to electrical signal and FM demodulation.

[0070] Furthermore, when the multiplexed signal output from the electrical signal amplification unit 15 is to be output externally, the signal transmission device 10 may be equipped with an electrical signal branching unit instead of the optical signal branching unit 19. The electrical signal branching unit branches the input multiplexed signal and outputs it externally and to the demodulated signal anomaly detection unit 20. The demodulated signal anomaly detection unit 20 receives the multiplexed signal branched by the electrical signal branching unit. The demodulated signal anomaly detection unit 20 performs state detection using the input multiplexed signal. In this case, the demodulated signal anomaly detection unit 20 does not need to perform conversion from optical signal to electrical signal and FM demodulation.

[0071] The signal transmitting device 10 in the second embodiment may be configured as a signal transmitting device comprising an electrical signal branching unit 11, a pilot signal generation unit 12, a multiplexing unit 13, an electrical signal anomaly detection unit 14, an electrical signal amplification unit 15, a demodulated signal anomaly detection unit 20a, a monitoring unit 21, and an alarm processing unit 22. The electrical signal amplification unit 15 amplifies the multiplexed signal output from the multiplexing unit 13 and outputs it to the demodulated signal anomaly detection unit 20a. The demodulated signal anomaly detection unit 20a comprises a demultiplexing unit 33a, a switching unit 34a, a plurality of detection units 35-1 to 35-2, and a control unit 36a. The demultiplexing unit 33a demultiplexes the multiplexed signal output from the electrical signal amplification unit 15 according to its frequency band. The demultiplexing unit 33a outputs the signal of a specific frequency band that has been demultiplexed to the detection unit 35-1 and outputs the signal of other frequency bands to the switching unit 34a. In this case, the demodulated signal abnormality detection unit 20a does not need to perform conversion from optical signal to electrical signal and FM demodulation.

[0072] Furthermore, when the multiplexed signal output from the multiplexing unit 13 is to be output externally, the signal transmitting device 10 in the second embodiment may be equipped with an electrical signal branching unit instead of the optical signal branching unit 19. The electrical signal branching unit branches the input multiplexed signal and outputs it externally and to the demodulated signal anomaly detection unit 20a. The demodulated signal anomaly detection unit 20a receives the multiplexed signal branched by the electrical signal branching unit. The demodulated signal anomaly detection unit 20a performs state detection using the input multiplexed signal. In this case, the demodulated signal anomaly detection unit 20a does not need to perform conversion from optical signal to electrical signal and FM demodulation.

[0073] The signal transmitting device 10 in the third embodiment may be configured as a signal transmitting device comprising an electrical signal branching unit 11, a pilot signal generation unit 12, a multiplexing unit 13, an electrical signal anomaly detection unit 14, an electrical signal amplification unit 15, a demodulated signal anomaly detection unit 20b, a monitoring unit 21, and an alarm processing unit 22. The electrical signal amplification unit 15 amplifies the multiplexed signal output from the multiplexing unit 13 and outputs it to the demodulated signal anomaly detection unit 20b. The demodulated signal anomaly detection unit 20b comprises a demultiplexing unit 33, a switching unit 34b, a detection unit 35, and a control unit 36b. The demultiplexing unit 33 demultiplexes the multiplexed signal output from the electrical signal amplification unit 15 according to its frequency band. The demultiplexing unit 33 outputs the signals of each demultiplexed frequency band to the switching unit 34b. In this case, the demodulated signal anomaly detection unit 20b does not need to perform optical signal to electrical signal conversion and FM demodulation.

[0074] Furthermore, when the multiplexed signal output from the multiplexing unit 13 is to be output externally, the signal transmitting device 10 in the second embodiment may be equipped with an electrical signal branching unit instead of the optical signal branching unit 19. The electrical signal branching unit branches the input multiplexed signal and outputs it externally and to the demodulated signal anomaly detection unit 20a. The demodulated signal anomaly detection unit 20b receives the multiplexed signal branched by the electrical signal branching unit. The demodulated signal anomaly detection unit 20b performs state detection using the input multiplexed signal. In this case, the demodulated signal anomaly detection unit 20b does not need to perform conversion from optical signal to electrical signal and FM demodulation.

[0075] (Modification 2 common to the first to third embodiments) In the above-described embodiments, the signal transmitting device 10 is configured to perform FM batch conversion, but the signal transmitting device 10 may be a signal transmitting device that does not perform FM batch conversion. In this configuration, the signal transmitting device 10 in the first embodiment may be configured as a signal transmitting device comprising an electrical signal branching unit 11, a pilot signal generation unit 12, a multiplexing unit 13, an electrical signal anomaly detection unit 14, an electrical signal amplification unit 15, an electrical-to-optical conversion unit 17, a demodulated signal anomaly detection unit 20, a monitoring unit 21, and an alarm processing unit 22. The electrical signal amplification unit 15 amplifies the multiplexed signal output from the multiplexing unit 13 and outputs it to the electrical-to-optical conversion unit 17. The electrical-to-optical conversion unit 17 converts the multiplexed signal amplified by the electrical signal amplification unit 15 into an optical signal and outputs it to the demodulated signal anomaly detection unit 20 and the monitoring unit 21. The demodulated signal anomaly detection unit 20 comprises an optical-to-electrical conversion unit 31, a demultiplexer unit 33, a switching unit 34, a plurality of detection units 35-1 to 35-2, and a control unit 36. The optical-to-electrical conversion unit 31 converts the optical signal converted by the electrical-to-optical conversion unit 17 into an electrical signal. The optical-to-electrical conversion unit 31 outputs the converted electrical signal to the demultiplexer unit 33. The demultiplexer unit 33 demultiplexes the electrical signal output from the optical-to-electrical conversion unit 31 according to the frequency band. The demultiplexer unit 33 outputs the signals of each demultiplexed frequency band to the switching unit 34. If the signal transmitting device 10 does not perform FM batch conversion, the demodulated signal anomaly detection unit 20 does not need to perform FM demodulation.

[0076] The signal transmitting device 10 in the second embodiment may be configured as a signal transmitting device comprising an electrical signal branching unit 11, a pilot signal generation unit 12, a multiplexing unit 13, an electrical signal anomaly detection unit 14, an electrical signal amplification unit 15, an electrical-to-optical conversion unit 17, a demodulated signal anomaly detection unit 20a, a monitoring unit 21, and an alarm processing unit 22. The electrical signal amplification unit 15 amplifies the multiplexed signal output from the multiplexing unit 13 and outputs it to the electrical-to-optical conversion unit 17. The electrical-to-optical conversion unit 17 converts the multiplexed signal amplified by the electrical signal amplification unit 15 into an optical signal and outputs it to the demodulated signal anomaly detection unit 20a and the monitoring unit 21. The demodulated signal anomaly detection unit 20a comprises an optical-to-electrical conversion unit 31, a demultiplexing unit 33a, a switching unit 34a, a plurality of detection units 35-1 to 35-2, and a control unit 36a. The optical-to-electrical conversion unit 31 converts the optical signal converted by the electrical-to-optical conversion unit 17 into an electrical signal. The optical-to-electrical conversion unit 31 outputs the converted electrical signal to the demultiplexer unit 33a. The demultiplexer unit 33a demultiplexes the electrical signal output from the optical-to-electrical conversion unit 31 according to its frequency band. The demultiplexer unit 33a outputs the signal of a specific frequency band to the detection unit 35-1 and outputs the signals of other frequency bands to the switching unit 34a. If the signal transmitting device 10 does not perform FM batch conversion, the demodulated signal abnormality detection unit 20a does not need to perform FM demodulation.

[0077] The signal transmitting device 10 in the third embodiment may be configured as a signal transmitting device comprising an electrical signal branching unit 11, a pilot signal generation unit 12, a wave multiplexing unit 13, an electrical signal anomaly detection unit 14, an electrical signal amplification unit 15, an electrical-to-optical conversion unit 17, a demodulated signal anomaly detection unit 20b, a monitoring unit 21, and an alarm processing unit 22. The electrical signal amplification unit 15 amplifies the multiplexed signal output from the wave multiplexing unit 13 and outputs it to the electrical-to-optical conversion unit 17. The electrical-to-optical conversion unit 17 converts the multiplexed signal amplified by the electrical signal amplification unit 15 into an optical signal and outputs it to the demodulated signal anomaly detection unit 20b and the monitoring unit 21. The demodulated signal anomaly detection unit 20b comprises an optical-to-electrical conversion unit 31, a wave demultiplexing unit 33, a switching unit 34b, a detection unit 35, and a control unit 36b. The optical-to-electrical conversion unit 31 converts the optical signal converted by the electrical-to-optical conversion unit 17 into an electrical signal. The optical-to-electrical conversion unit 31 outputs the converted electrical signal to the demultiplexing unit 33. The demultiplexing unit 33 demultiplexes the electrical signal output from the optical-to-electrical conversion unit 31 according to the frequency band. The demultiplexing unit 33 outputs the signals of each demultiplexed frequency band to the switching unit 34b. If the signal transmitting device 10 does not perform FM batch conversion, the demodulated signal abnormality detection unit 20b does not need to perform FM demodulation.

[0078] The signal transmission device 10 in the above-described embodiment may be implemented using a computer. In that case, the program for implementing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be loaded into a computer system and executed. Here, "computer system" includes hardware such as an OS (Operating System) and peripheral devices. Furthermore, "computer-readable recording medium" refers to portable media such as flexible disks, magneto-optical disks, ROMs (Read Only Memory), CD-ROMs, and storage devices such as hard disks built into a computer system.

[0079] Furthermore, "computer-readable recording media" may include those that dynamically hold programs for a short period of time, such as communication lines used when transmitting programs via networks such as the Internet or communication lines such as telephone lines, as well as those that hold programs for a fixed period of time, such as volatile memory inside computer systems that act as servers or clients in such cases. In addition, the above-mentioned program may be for the purpose of realizing a part of the aforementioned functions, or it may be a program that can realize the aforementioned functions in combination with a program already recorded in the computer system, or it may be implemented using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0080] While embodiments of this invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments and includes designs and the like that do not depart from the spirit of this invention. [Explanation of Symbols]

[0081] 10...Signal transmission device, 11...Electrical signal branching unit, 12...Pilot signal generation unit, 13...Multiplexing unit, 14...Electrical signal anomaly detection unit, 15...Electrical signal amplification unit, 16...FM batch conversion signal generation unit, 17...Electrical-to-optical conversion unit, 18...Optical signal amplification unit, 19...Optical signal branching unit, 20, 20a, 20b...Demodulation signal anomaly detection unit, 21...Monitoring unit, 22...Alarm processing unit, 31...Optical-to-electrical conversion unit, 32...Demodulation unit, 33, 33a...Diplexing unit, 34, 34a, 34b...Switching unit, 35, 35-1~35-2...Detection unit, 36, 36a, 36b...Control unit, 341, 341a, 341b...Switching unit, 342~344...Input terminals, 345...Connection unit 346~348…Output terminals

Claims

1. A pilot signal generation unit generates multiple pilot signals of different frequencies to be used as monitoring pilot signals for detecting level anomalies in a specific frequency band of the input signal, A dewave splitter that separates the multiple pilot signals of different frequencies, One or more detection units that detect at least two or more pilot signals of the plurality of pilot signals of different frequencies using the signals separated by the aforementioned demultiplexing unit, A switching unit that switches the output target so that each of the multiple pilot signals of different frequencies separated by the dewave splitting unit is output to the one or more detection units at a predetermined period, A control unit controls the switching unit to connect the output target and the output destination at a predetermined interval. A signal transmitting device equipped with the following features.

2. The control unit controls the switching unit to connect the output target and the output destination at a predetermined interval by synchronizing with the generation period of the pilot signal generated by the pilot signal generation unit. The signal transmitting device according to claim 1.

3. A combiner unit that combines the input signal and the plurality of pilot signals of different frequencies generated by the pilot signal generation unit, A first conversion unit that optically modulates the signal combined by the aforementioned multiplexing unit and converts it into an optical signal, A second conversion unit converts the optical signal converted by the first conversion unit into an electrical signal, Furthermore, The dewave splitter separates the multiple pilot signals of different frequencies included in the electrical signal converted by the second conversion unit. The signal transmitting device according to claim 1 or 2.

4. A combiner unit that combines the input signal and the plurality of pilot signals of different frequencies generated by the pilot signal generation unit, An FM batch conversion unit generates an FM batch conversion signal by batch converting the signals combined by the aforementioned multiplexing unit into an FM (Frequency Modulation) signal, A demodulation unit that demodulates the FM batch conversion signal generated by the FM batch conversion unit, Furthermore, The demultiplexing unit demultiplexes the multiple pilot signals of different frequencies included in the FM batch conversion signal demodulated by the demodulation unit. The signal transmitting device according to claim 1 or 2.

5. The aforementioned one or more detection units are multiple detection units, The demultiplexer is directly connected to some of the plurality of detection units, and connected to the remaining detection units via the switching unit. The demultiplexer outputs some of the pilot signals obtained by demultiplexing the plurality of pilot signals of different frequencies to the directly connected detection unit, and outputs the remaining pilot signals obtained by demultiplexing the plurality of pilot signals of different frequencies to the remaining detection unit via the switching unit. The signal transmitting device according to claim 1 or 2.

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