JP5805165B2 - Broadcast system - Google Patents

Description

  The present invention relates to a broadcasting system.

  Patent Document 1 discloses a broadcasting system based on an HFC (Hybrid Fiber Coaxial) system. In a broadcasting system based on the HFC system, an optical fiber is used for the main part, and a coaxial cable is used for drawing into the user's home.

  FIG. 6 is a diagram showing a configuration of a broadcasting system based on a conventional HFC scheme. As shown in this figure, the broadcasting system based on the HFC system includes a center device 10, an optical transmission line 20, an optical node device 30, a coaxial transmission line 40, an amplification device 50, a coaxial transmission line 60, and a terminal device 70. doing.

  FIG. 7 shows the configuration of the optical node device 30 and the amplification device 50 of the broadcasting system shown in FIG. As shown in this figure, an optical node device 30 includes a PD (Photo Diode) 31, an LD (Laser Diode) 32, amplification units 33 and 34, a monitoring control unit 35, a distribution unit 36, a combining unit 37, an HPF (High Pass). Filter) 38 and LPF (Low Pass Filter) 39. The amplification device 50 includes an HPF 51, an LPF 52, amplification units 53 and 54, a monitoring control unit 55, a distribution unit 56, a combining unit 57, an HPF 58, and an LPF 59.

  FIG. 8 is a diagram illustrating signals transmitted through the broadcasting system illustrated in FIGS. 6 and 7. The center apparatus 10 illustrated in FIG. 6 transmits a downstream signal having a frequency band of 70 to 770 MHz to the optical node apparatus 30 via the optical fiber 21. Such a downlink signal is converted into an electric signal by the PD 31 of the optical node device 30, amplified by the amplifying unit 33, and then sent to the coaxial transmission line 40 via the HPF 38. The amplifying apparatus 50 receives a downstream signal transmitted through the coaxial transmission line 40 via the HPF 51, amplifies the signal by the amplifying unit 53, and then sends it to the coaxial transmission line 60 via the HPF 58. The terminal device 70 receives a downstream signal transmitted through the coaxial transmission line 60, extracts a broadcast signal, and supplies the broadcast signal to a television receiver or the like.

  The upstream signal output from the terminal device 70 is transmitted to the amplifying device 50 via the coaxial transmission line 60. The amplifying apparatus 50 receives the upstream signal transmitted through the coaxial transmission line 60 via the LPF 59, amplifies the amplified signal by the amplifying unit 54, and then sends it out to the coaxial transmission line 40 via the LPF 52. The optical node device 30 receives the upstream signal transmitted through the coaxial transmission line 40 via the LPF 39, amplifies it by the amplifier 34, converts it to an optical signal by the LD 32, and sends it to the optical fiber 22. The center device 10 receives an upstream signal transmitted through the optical fiber 22.

  As shown in FIG. 8, the center apparatus 10 adds a 73.5 MHz monitoring signal to a downstream signal having a frequency band of 70 to 770 MHz, and sends it to the optical fiber 21. The reason why the monitoring signal is included in the frequency band of the downlink signal in this way is that the monitoring signal needs to be transmitted to the terminal device 70, and for that purpose, it needs to pass through the HPFs 38 and 58. The supervisory control units 35 and 55 of the optical node device 30 and the amplifying device 50 extract the 73.5 MHz supervisory signal added to the downlink signal by the center device 10, and based on this supervisory signal, for example, the signal of the downlink signal The level is detected, the temperature of the device is detected, and the detection result is added to the upstream signal as a 54.5 MHz monitoring signal and transmitted to the center device 10. As shown in FIG. 8, the upstream signal has a frequency band of 10 to 60 MHz, and the upstream monitoring signal is 54.5 MHz and is included in the upstream signal frequency band. The center apparatus 10 that has received the monitoring signal refers to the level of the downstream signal, for example, and adjusts the downstream signal level to be appropriate.

JP 2003-9112 A

  By the way, in the conventional broadcasting system, since the monitoring signal is added in the band of the upstream signal and the downstream signal, there is a problem that a part of the band cannot be used by this monitoring signal.

  The present invention has been made in view of the above points, and an object thereof is to provide a broadcasting system capable of transmitting a monitoring signal without limiting an upstream or downstream signal band.

In order to solve the above-described problems, the present invention includes a center device, an optical node device, and a terminal device. Between the center device and the optical node device, a downstream signal and an upstream signal including a broadcast signal are transmitted as an optical signal. In a broadcasting system for transmitting a downlink signal and an uplink signal including a broadcast signal between the optical node device and the terminal device by an electrical signal via a coaxial transmission line between the optical node device and the terminal device, the coaxial transmission line The downlink signal and the uplink signal transmitted are assigned frequency bands that do not overlap each other, and the downlink signal and the uplink signal transmitted through the optical transmission path are monitored to monitor the state of the broadcasting system. signals are respectively added, the monitoring signal added to the downlink signal transmitted through the optical transmission line, the upstream signal and the frequency band of the downlink signal Assigned to the band between the frequency bands, the optical node device, after attenuated the monitoring signal added to the downlink signal, and sends it to the coaxial transmission line, characterized in that.
According to such a configuration, it is possible to transmit the monitoring signal without limiting the upstream or downstream signal band.

Further, the present invention is characterized in that the monitoring signal added to the uplink signal transmitted through the optical transmission line is assigned to a band different from the frequency band of the uplink signal.
According to such a configuration, the monitoring signal can be transmitted without limiting the bandwidth of the upstream signal.

Further, the present invention is characterized in that the monitoring signal is assigned to a frequency band lower than the downlink signal or the uplink signal to be added.
According to such a configuration, a circuit having a low frequency characteristic can be used as a circuit for processing the monitoring signal, so that the manufacturing cost can be reduced.

In addition, the present invention includes a center device, an optical node device, and a terminal device, and between the center device and the optical node device, a downstream signal including a broadcast signal and an upstream signal are transmitted by an optical signal through an optical transmission line. In a broadcasting system that transmits a downlink signal including a broadcast signal and an uplink signal via an electric signal between the optical node device and the terminal device via a coaxial transmission line, the downlink signal transmitted through the coaxial transmission line is transmitted. The signal and the upstream signal are assigned frequency bands that do not overlap with each other, and the downstream signal and the upstream signal transmitted through the optical transmission path are each added with a monitoring signal for monitoring the state of the broadcasting system, The monitoring signal added to the downlink signal transmitted through the optical transmission line is different from the frequency band of the downlink signal, and Assigned to the band that overlaps a frequency band, the optical node device, after attenuated the monitoring signal added to the downlink signal, and sends it to the coaxial transmission line, characterized in that.
According to such a configuration, it is possible to prevent the monitoring signal from affecting the upstream signal in the coaxial transmission line.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the broadcasting system which can transmit a monitoring signal, without restrict | limiting an upstream or downstream signal band.

It is a figure which shows the structural example of the broadcasting system which concerns on 1st Embodiment of this invention. It is a figure which shows the detailed structural example of the center apparatus and optical node apparatus of 1st Embodiment. It is a figure which shows the structural example of the downstream signal of 1st Embodiment, an upstream signal, and an extension band. It is a figure which shows the structural example of the downlink signal of 2nd Embodiment, an uplink signal, an extended band, and a monitoring signal. It is a figure which shows the structural example of the down signal of 3rd Embodiment, an up signal, an extension band, and a monitoring signal. It is a figure which shows the structure of the conventional broadcast system. It is a figure which shows the detailed structural example of the optical node apparatus and amplification apparatus of the conventional broadcasting system. It is a figure which shows the structural example of the downstream signal of a conventional broadcast system, an upstream signal, and a monitoring signal.

  Next, an embodiment of the present invention will be described.

(A) 1st Embodiment FIG. 1: is a figure which shows the structural example of the broadcasting system which concerns on 1st Embodiment of this invention. As shown in FIG. 1, the broadcasting system according to the first embodiment of the present invention includes a center device 10, an optical transmission line 20, an optical node device 30, a coaxial transmission line 40, and a terminal device 70.

  The center device 10 is arranged in, for example, a broadcaster's office, and transmits a downlink signal including a broadcast signal to the optical node device 30 via the optical fiber 21 and includes a communication signal from the optical node device 30. The upstream signal is received via the optical fiber 22. The downlink signal includes a communication signal of a personal computer, a video on demand signal, and an audio signal such as a telephone in addition to the broadcast signal. Further, the uplink signal includes a voice signal such as a telephone, a request signal for the center apparatus 10 and the like in addition to a communication signal of the personal computer. The above is an example, and signals other than these may be included.

  The optical transmission line 20 includes optical fibers 21 and 22, a downstream signal is transmitted to the optical fiber 21, and an upstream signal is transmitted to the optical fiber 22.

  The optical node device 30 receives a downlink signal transmitted from the center device 10 via the optical fiber 21, converts it into an electrical signal, and transmits it to the terminal device 70 via the coaxial transmission line 40. Further, the optical node device 30 converts an upstream signal transmitted from the terminal device 70 via the coaxial transmission line 40 into an optical signal and transmits the optical signal to the center device 10 via the optical fiber 22.

  The terminal device 70 is an STB (Set Top Box) or home terminal disposed at a user's home, and outputs a downstream signal transmitted from the optical node device 30 via the coaxial transmission line 40 to a television receiver or a personal computer. At the same time, a signal output from the television receiver or the personal computer is transmitted to the optical node device 30 as an upstream signal via the coaxial transmission line 40. In FIG. 1, only one terminal device 70 is shown to simplify the drawing, but a plurality of terminal devices may be connected. In addition, a television receiver may be connected without an STB or home terminal. That is, the terminal device 70 may be a television receiver.

  FIG. 2 is a diagram illustrating a detailed configuration example of the center device 10 and the optical node device 30 illustrated in FIG. 1. As shown in FIG. 2, the center device 10 includes a downstream signal facility 11, an upstream signal facility 12, a combining unit 13, a distributing unit 14, a monitoring control unit 15, amplification units 16 and 17, an LD (Laser Diode) 18, and , A PD (Photo Diode) 19.

  Here, the downlink signal facility 11 is a facility that generates and outputs a downlink signal, and generates and outputs a broadcast signal, a video on demand signal, a communication signal, and an audio signal. In FIG. 2, the plurality of signals are generated by a single facility for the sake of simplification of the drawing. However, an individual configuration for each signal may be used.

  The monitoring control unit 15 generates a monitoring signal for monitoring the optical node device 30 and outputs the monitoring signal to the combining unit 13. For example, the monitoring control unit 15 generates a signal requesting transmission of information indicating the reception level of the downlink signal of the optical node device 30 and outputs the signal to the combining unit 13. In addition, the monitoring control unit 15 extracts a monitoring signal added to the signal supplied from the distribution unit 14 and monitors the state of the optical node device 30 based on the monitoring signal.

  The amplifying unit 16 amplifies the electrical signal output from the combining unit 13 and outputs the amplified signal to the LD 18. The LD 18 converts the electrical signal output from the amplification unit 16 into an optical signal and outputs the optical signal to the optical fiber 21.

  The PD 19 converts an optical signal transmitted through the optical fiber 22 into an electrical signal and outputs the electrical signal to the amplifying unit 17. The amplifying unit 17 amplifies the electric signal output from the PD 19 and outputs it to the distributing unit 14. The distribution unit 14 distributes the electric signal output from the amplification unit 17 and supplies the electric signal to the monitoring control unit 15 and the upstream signal facility 12.

  The upstream signal facility 12 is a facility that extracts various signals from the upstream signal transmitted from the terminal device 70. In FIG. 2, for simplification of the drawing, the plurality of signals are extracted by one facility, but individual configurations may be used for each signal.

  The PD 31 of the optical node device 30 converts an optical signal transmitted through the optical fiber 21 into an electrical signal and outputs the electrical signal to the amplification unit 33. The amplifying unit 33 amplifies the electric signal output from the PD 31 and outputs the amplified electric signal to the distributing unit 36. The distributor 36 distributes the signal output from the amplifier 33 and supplies the signal to the monitoring controller 35 and the HPF 38. The HPF 38 attenuates the monitoring signal included in the electrical signal supplied from the distribution unit 36 and then outputs the attenuated signal to the coaxial transmission line 40 as a downlink signal.

  The monitoring control unit 35 extracts a monitoring signal from the signal supplied from the distribution unit 36, controls each unit based on the monitoring signal, and transmits information obtained as a result of the control unit to the combining unit 37 as a monitoring signal. Output.

  The LPF 39 attenuates components other than the uplink signal from the signal transmitted through the coaxial transmission line 40, passes the uplink signal, and outputs the signal to the combining unit 37. The combining unit 37 adds the monitoring signal output from the monitoring control unit 15 to the upstream signal output from the LPF 39 and outputs the added signal to the amplifying unit 34. The amplifying unit 34 amplifies the signal output from the combining unit 37 and outputs the amplified signal to the LD 32. The LD 32 converts the electrical signal output from the amplifying unit 34 into an optical signal and outputs the optical signal to the optical fiber 22.

  Next, the operation of the first embodiment will be described. The downlink signal facility 11 generates a downlink signal including a broadcast signal, a communication signal, an audio signal, and the like, and outputs the downlink signal to the synthesis unit 13. The monitoring control unit 15 generates a monitoring signal for monitoring the optical node device 30 and outputs the monitoring signal to the combining unit 13. The combining unit 13 adds the monitoring signal output from the monitoring control unit 15 to the downlink signal output from the downlink signal facility 11 and outputs the added signal.

  FIG. 3 is a diagram illustrating a relationship between an extension signal including a downlink signal, an uplink signal, and a monitoring signal. FIG. 3A shows a signal output from the combining unit 13. The downlink signal output from the downlink signal facility 11 has a band of 70 to 770 MHz, and the monitoring signal output from the monitoring controller 15 is added to the extension band of 60 to 70 MHz by the synthesis unit 13 for this downlink signal. Is done. That is, in the first embodiment, an extension band of 60 to 70 MHz is added to a downlink signal having a band of 70 to 770 MHz, and a monitoring signal is added within this extension band. Note that the monitoring signal may use the entire extension band or a part thereof.

  The signal shown in FIG. 3A is amplified by the amplification unit 16, converted into an optical signal by the LD 18, and sent to the optical fiber 21. The optical signal transmitted through the optical fiber 21 is converted into an electrical signal by the PD 31 of the optical node device 30 and then supplied to the amplifying unit 33. Note that the electrical signal output from the PD 31 is the same signal as in FIG. The amplifying unit 33 amplifies the electric signal supplied from the PD 31 and supplies it to the distributing unit 36. The distributor 36 distributes the electric signal output from the amplifier 33 and supplies the electric signal to the HPF 38 and the monitoring controller 35.

  Since the HPF 38 is a high-pass filter having a cut-off frequency of 70 MHz, the monitoring signal having a frequency band of 60 to 70 MHz is attenuated, and a downstream signal having a frequency band of 70 to 770 MHz is allowed to pass through. To send. As a result, only the downstream signal of 70 to 770 MHz as shown in FIG. 3C is transmitted to the coaxial transmission line 40.

  The monitoring control unit 35 extracts a monitoring signal included in the extended band of the signal supplied from the distribution unit 36, and executes various controls based on the monitoring signal. For example, the signal level of the downstream signal is detected by detecting the level of the signal output from the PD 31. Further, the temperature inside the optical node device 30 is detected by a temperature measuring unit (not shown). The information acquired in this way is supplied to the combining unit 37 as a monitoring signal and transmitted to the center apparatus 10 as will be described later.

  The downstream signal transmitted through the coaxial transmission line 40 is received by the terminal device 70, converted into a video signal, a communication signal, and an audio signal, and supplied to a television receiver, a personal computer, a telephone, and the like.

  For example, the terminal device 70 transmits the communication signal of the personal computer, the voice signal of the telephone, and the request signal to the center device to the coaxial transmission line 40 as an upstream signal having a band of 10 to 60 MHz shown in FIG. Send it out.

  Since the LPF 39 of the optical node device 30 is a low-pass filter having a cutoff frequency of 60 MHz, the upstream signal is extracted from the signal transmitted through the coaxial transmission line 40 and supplied to the combining unit 37. The combining unit 37 adds the monitoring signal supplied from the monitoring control unit 35 to the upstream signal supplied from the LPF 39 and outputs the added signal to the amplifying unit 34. More specifically, the combining unit 37 adds an extension band of 1 to 10 MHz to the uplink signal having a band of 10 to 60 MHz shown in FIG. 3B, and the monitoring control unit 15 is included in this extension band. A monitoring signal supplied from is added. Note that the monitoring signal may use the entire extension band or a part thereof.

  The amplifying unit 34 amplifies the electric signal supplied from the combining unit 37 and supplies it to the LD 32. The LD 32 converts the electrical signal supplied from the amplification unit 34 into an optical signal and sends it to the optical fiber 22.

  The PD 19 of the center device 10 converts an optical signal transmitted through the optical fiber 22 into an electrical signal and outputs the electrical signal to the amplification unit 17. The amplifying unit 17 amplifies the electric signal supplied from the PD 19 and outputs it to the distributing unit 14. The distribution unit 14 distributes the electric signal supplied from the amplification unit 17 and supplies the electric signal to the monitoring control unit 15 and the upstream signal facility 12.

  The monitoring control unit 15 extracts a monitoring signal included in the extension band of the upstream signal supplied from the distribution unit 14. The supervisory control unit 15 can know the state of the optical node device 30 by referring to the information included in the supervisory signal. For example, referring to information indicating the signal level received by the optical node device 30, and when the signal level is low, the level of the optical signal can be increased by increasing the gain of the amplifying unit 16. When the temperature of the optical node device 30 is higher than the threshold value, it can be determined that an abnormality has occurred in the optical node device 30, and the administrator can be notified.

  The upstream signal facility 12 separates the communication signal of the personal computer, the voice signal of the telephone, and the request signal for the center device included in the upstream signal and supplies them to the corresponding devices.

As described above, in the first embodiment of the present invention, the downstream signal having a band of 70 to 770 MHz is provided with an extension band having a frequency band of 60 to 70 MHz, and the upstream signal having a frequency band of 10 to 60 MHz. Since the extension band having the frequency band of 1 to 10 MHz is provided and the monitor signal is added to these extension bands, the monitor signal is transmitted without limiting the band of the downlink signal and the uplink signal. can do.

  In addition, since the extension band is provided in the frequency band lower than the downlink signal and the uplink signal, a circuit having low frequency characteristics can be used as a circuit for transmitting and receiving the monitoring signal, so that the manufacturing cost of the apparatus can be reduced. .

  Further, since the optical node device 30 is provided with the HPF 38 so as to attenuate the monitoring signal, it is possible to prevent unnecessary signals from being transmitted to the terminal device 70.

(B) Second Embodiment Next, a second embodiment of the present invention will be described. In the second embodiment, the configuration of the broadcast system is the same as the configuration shown in FIGS. 1 and 2, but the configurations of the downlink signal, the uplink signal, and the extension band are different from those of the first embodiment. Therefore, hereinafter, the signal configuration of the second embodiment will be described with reference to FIG.

  FIG. 4A shows a configuration example of the downlink signal and the extension band of the second embodiment. In this example, the frequency band of the downlink signal is set to 500 to 1700 MHz, the extension band is set to 70 to 500 MHz, and the monitoring signal is set to 73.5 MHz. FIG. 4B shows a configuration example of the uplink signal and the extension band. In this example, the frequency band of the uplink signal is set to 5 to 400 MHz, the extension band is not set, and the monitoring signal is set to 54.5 MHz that is within the band of the uplink signal. Note that the bandwidth of the downstream signal and upstream signal is assumed to be DOCSIS (Data Over Cable Service Interface Specifications) 3.1.

  Next, the operation of the second embodiment will be described. The downlink signal equipment 11 generates a downlink signal of 500 to 1700 MHz shown in FIG. The synthesizing unit 13 sets the downstream signal 70 to 500 MHz supplied from the downstream signal facility 11 as an extension band, adds a 73.5 MHz monitoring signal to the extension band, and outputs it. The amplifying unit 16 amplifies the signal shown in FIG. 4A, and the LD 18 converts the signal into an optical signal and outputs it to the optical fiber 21. The optical signal transmitted through the optical fiber 21 is converted into an electrical signal by the PD 31 of the optical node device 30, amplified by the amplification unit 33, and then supplied to the distribution unit 36. The distributor 36 distributes the signal output from the amplifier 33 and supplies it to the monitoring controller 35 and the HPF 38. The monitoring control unit 35 extracts a 73.5 MHz monitoring signal from the extension band. Since the HPF 38 is a high-pass filter having a cutoff frequency of 500 MHz, only the downstream signal of 500 to 1700 MHz shown in FIG.

  An upstream signal having a frequency band of 5 to 400 MHz transmitted from the terminal device 70 to the coaxial transmission line 40 is extracted by the LPF 39 and supplied to the combining unit 37. The synthesizer 37 adds a 54.5 MHz monitoring signal in the upstream signal band having a bandwidth of 5 to 400 MHz output from the LPF 39 and outputs the result to the amplifier 34. The electric signal amplified by the amplifying unit 34 is converted into an optical signal by the LD 32 and transmitted to the center apparatus 10 via the optical fiber 22. In the center apparatus 10, the PD 19 converts the optical signal into an electric signal, is then amplified by the amplification unit 17, and is output to the distribution unit 14. The distribution unit 14 distributes the signal output from the amplification unit 17 and supplies the signal to the monitoring control unit 15 and the upstream signal facility 12. The supervisory control unit 15 can know the state of the optical node device 30 by extracting the supervisory signal of 54.5 MHz included in the uplink signal and referring to this supervisory signal. The upstream signal facility 12 separates the communication signal of the personal computer, the voice signal of the telephone, and the request signal for the center device included in the upstream signal and supplies them to the corresponding devices.

  As described above, in the second embodiment of the present invention, an extension band of 70 to 500 MHz is provided for a downlink signal having a band of 500 to 1700 MHz, and a monitoring signal of 73.5 MHz is provided in this extension band. Since it is added, the monitoring signal can be transmitted without limiting the bandwidth of the downstream signal.

  In the second embodiment, the 54.5 MHz band is used for the upstream signal and the 73.5 MHz band is used for the downstream signal. Therefore, even if the upstream and downstream signal bands are expanded, Since the circuit for processing the monitoring signals of 54.5 MHz and 73.5 MHz used in the existing equipment can be diverted, an increase in cost can be suppressed.

  In the second embodiment, the extension band overlaps with the upstream signal band. However, when transmitted through the coaxial transmission line 40, the extension band is attenuated by the HPF 38, so that the extension band is arranged in the extension band. It is not affected by the signal.

(C) Third Embodiment Next, a third embodiment of the present invention will be described. In the third embodiment, the configuration of the broadcasting system is the same as that shown in FIGS. 1 and 2, but the configurations of the downlink signal, the uplink signal, the extension band, and the monitoring signal are different from those in the first embodiment. . Therefore, hereinafter, the signal configuration of the third embodiment will be described with reference to FIG.

  FIG. 5A shows a configuration example of the downlink signal and the extension band of the third embodiment. In this example, the frequency band of the downlink signal is set to 500 to 1700 MHz, no extension band is provided, and the monitoring signal is set to 600 MHz. FIG. 5B shows a configuration example of the uplink signal, the extension band, and the monitoring signal. In this example, the frequency band of the upstream signal is set to 5 to 400 MHz, the extension band is set to 1 to 5 MHz, and the monitoring signal is set to 2 MHz that is within the extension band.

  Next, the operation of the third embodiment will be described. The downlink signal equipment 11 generates a downlink signal of 500 to 1700 MHz shown in FIG. The synthesizing unit 13 adds the 600 MHz monitoring signal supplied from the monitoring control unit 15 to the band of the downlink signal supplied from the downlink signal facility 11 and outputs the added signal. The amplification unit 16 amplifies the signal shown in FIG. 5A supplied from the synthesis unit 13 and outputs the amplified signal to the LD 18. The LD 18 converts an electrical signal into an optical signal and outputs it to the optical fiber 21. The optical signal transmitted through the optical fiber 21 is converted into an electrical signal by the PD 31 of the optical node device 30, amplified by the amplification unit 33, and then supplied to the distribution unit 36. The distributor 36 distributes the signal output from the amplifier 33 and supplies the signal to the monitoring controller 35 and the HPF 38. The monitoring control unit 35 extracts a monitoring signal of 600 MHz and executes various control processes based on the monitoring signal. Since the HPF 38 is a high-pass filter having a cutoff frequency of 500 MHz, a downstream signal of 500 to 1700 MHz including the monitoring signal shown in FIG.

  An upstream signal (see FIG. 5C) having a bandwidth of 5 to 400 MHz output from the terminal device 70 to the coaxial transmission line 40 is extracted by the LPF 39 and supplied to the combining unit 37. As shown in FIG. 5B, the synthesizer 37 sets 1 to 5 MHz, which is lower than the uplink signal having a frequency band of 5 to 400 MHz output from the LPF 39, as an extension band, and 2 MHz within the extension band. A monitoring signal is added and output to the amplifying unit 34. The electric signal amplified by the amplifying unit 34 is converted into an optical signal by the LD 32 and transmitted to the center apparatus 10 via the optical fiber 22. In the center apparatus 10, the PD 19 converts the optical signal into an electric signal, amplifies the amplified signal by the amplifying unit 17, and outputs the amplified signal to the distributing unit 14. The distribution unit 14 distributes the signal output from the amplification unit 17 and outputs the signal to the monitoring control unit 15 and the upstream signal facility 12. The supervisory control unit 15 can know the state of the optical node device 30 by extracting the 2 MHz supervisory signal included in the uplink signal and referring to this supervisory signal. The upstream signal facility 12 separates the communication signal of the personal computer, the voice signal of the telephone, and the request signal for the center device included in the upstream signal and supplies them to the corresponding devices.

  As described above, in the third embodiment of the present invention, an extension band of 1 to 5 MHz is provided for an upstream signal having a band of 5 to 400 MHz, and a 2 MHz monitoring signal is added to the extension band. As a result, the monitoring signal can be transmitted without limiting the bandwidth of the upstream signal.

(D) Description of Modified Embodiment Each of the above embodiments is an example, and it is needless to say that the present invention is not limited to the case described above. For example, in each of the embodiments described above, the extension band is provided in the frequency band lower than the downlink signal or the uplink signal, but the extension band may be provided in a higher frequency band. When an extension band is provided in a frequency band higher than that of the downlink signal, the HPF 38 is replaced with a BPF (Band Pass Filter) having a pass band in the frequency band of the downlink signal, so that the extension band signal is provided in the coaxial transmission line 40 Can be prevented from being output.

  In the second and third embodiments, a monitoring signal having a single frequency is added, but a monitoring signal having a predetermined bandwidth may be added. For example, a monitoring signal that uses part or all of the extended band may be added.

  In each of the above embodiments, the upstream signal and the downstream signal are transmitted via different optical fibers 21 and 22. For example, by assigning different wavelengths to the upstream signal and the downstream signal, the same light is transmitted. It is also possible to transmit via a fiber.

  In each of the above embodiments, the downlink signal equipment 11, the uplink signal equipment 12, the synthesis section 13, the distribution section 14, the monitoring control section 15, the amplification sections 16, 17, the LD 18, and the PD 19 are integrated. For example, these may be integrated in a predetermined unit to form another independent configuration. For example, the amplification unit 16 and the LD 18 may be configured as transmission units, and the PD 19 and the amplification unit 17 may be configured as independent reception units.

DESCRIPTION OF SYMBOLS 10 Center apparatus 11 Downstream signal equipment 12 Upstream signal equipment 13 Synthesis | combination part 14 Distribution part 15 Monitoring control part 16, 17 Amplification part 18 LD
19 PD
20 Optical transmission path 21, 22 Optical fiber 30 Optical node device 31 PD
32 LD
33, 34 Amplifying unit 35 Monitoring control unit 36 Distribution unit 37 Combining unit 38 HPF
39 LPF
40 Coaxial transmission line 70 Terminal device

Claims (4)

A center device, an optical node device, and a terminal device, wherein a downlink signal and an uplink signal including a broadcast signal are transmitted between the center device and the optical node device by an optical signal via an optical transmission line, In a broadcasting system for transmitting a downlink signal and an uplink signal including a broadcast signal between a node device and the terminal device by an electrical signal via a coaxial transmission line,
The downlink signal and the uplink signal transmitted through the coaxial transmission line are assigned frequency bands that do not overlap each other,
A monitoring signal for monitoring the status of the broadcasting system is added to the downstream signal and the upstream signal transmitted through the optical transmission path, respectively.
The monitoring signal added to the downlink signal transmitted through the optical transmission line is assigned to a band between the frequency band of the downlink signal and the frequency band of the uplink signal,
The optical node device attenuates the monitoring signal added to the downlink signal and then sends it to the coaxial transmission line.
A broadcasting system characterized by that.   The broadcast system according to claim 1, wherein the monitoring signal added to the uplink signal transmitted through the optical transmission path is assigned to a band different from the frequency band of the uplink signal. The broadcast system according to claim 1 or 2, wherein the monitoring signal is assigned to a frequency band lower than the downlink signal or the uplink signal to be added. A center device, an optical node device, and a terminal device, wherein a downlink signal and an uplink signal including a broadcast signal are transmitted between the center device and the optical node device by an optical signal via an optical transmission line, In a broadcasting system for transmitting a downlink signal and an uplink signal including a broadcast signal between a node device and the terminal device by an electrical signal via a coaxial transmission line,
The downlink signal and the uplink signal transmitted through the coaxial transmission line are assigned frequency bands that do not overlap each other,
A monitoring signal for monitoring the status of the broadcasting system is added to the downstream signal and the upstream signal transmitted through the optical transmission path, respectively.
The monitoring signal added to the downlink signal transmitted through the optical transmission path is assigned to a band that is different from the frequency band of the downlink signal and overlaps the frequency band of the uplink signal,
The optical node device attenuates the monitoring signal added to the downlink signal and then sends it to the coaxial transmission line.
A broadcasting system characterized by that.

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