JP4272959B2 - CATV transmission system and CATV transmission method - Google Patents

Description

  The present invention is a CATV in which a redundant configuration is constructed while reducing the number of optical fiber core wires in the application of an HFC (Hybrid Fiber Coaxial), which is a CATV (Cable Television) transmission system having both optical transmission and coaxial transmission. The present invention relates to a transmission system and a CATV transmission method.

7 to 10 show examples of the configuration of a conventional CATV transmission system.
A conventional example 1 of the HFC system will be described with reference to FIG. First, the downward direction in which a signal flows from the center 1001 toward the subscriber will be described. A CATV signal is input to a downstream optical transmitter installed in the center 1001, and the CATV optical signal subjected to electro-optical conversion is received by a downstream optical receiver in the node device 1002 installed in a field or the like through an optical fiber. . When a redundant configuration is achieved by using a plurality of optical fiber transmission lines and center optical transmitters, a plurality of optical receivers are installed, and the output of each optical receiver is input to the switch to switch.

  The CATV signal that has been photoelectrically converted here passes through the subsequent coaxial transmission line 1003 (coaxial cable, relay amplification device, branching device, protector, etc.), and then at the STB (set top box) of each subscriber home 1004. The video and audio signals are transmitted to the TV. The data signal is received by a CM (cable modem) and transmitted to a PC (personal computer) or the like.

Next, uplink signal transmission in which a signal flows from the subscriber side toward the center will be described.
Viewing control signal of STB (set top box) of subscriber's house 1004, data signal of CM (cable modem), etc. (also called uplink CATV signal) are coaxial transmission lines (coaxial cable, protector, branching device, relay amplification device) Etc.) It passes through 1003 and reaches the node device 1002. This upstream CATV signal is converted into a CATV optical signal by an optical transmitter in the node device 1002, propagates through an upstream optical fiber, and is received by an upstream optical receiver in the center 1001. When a redundant configuration is achieved by using a plurality of optical fiber transmission lines and optical transmitters in the node device, a plurality of optical receivers are installed, and the output of each optical receiver is input to the switch and switched.

As described above, in the conventional conventional HFC system, a redundant configuration is constructed between the center and the node device, and about 1000 to 2000 households per node device are serviced by the coaxial cable after the node device. I never took it.
With respect to the conventional HFC system, various types of HFC systems are currently being studied, in which an optical fiber is laid to a location closer to the subscriber and the transmission capacity when using a cable modem is largely increased. In the case of this system, it is necessary to reduce the number of optical fiber cores used and to efficiently lay the optical fiber as close to the subscriber as possible.

  In order to reduce the number of optical fiber cores used, it is effective to use a tree & branch topology (dendritic network) or a WDM (wavelength division multiplexing) system. Conventional example 2 of such a conventional HFC system is shown in FIG. In FIG. 8, a hub device 703 is installed between the center 701 and the node device 702, and a coaxial transmission line 705 is laid from each node device 702 to the subscriber 704. As a result, the number of target households of each node device is set to several tens to several hundreds. The distance between the center and the hub device is also relatively long, and the distance between the hub device and each node device is relatively short.

  Next, Conventional Example 3 in FIG. 9 will be described in detail. In Conventional Example 3, it is possible to reduce the number of optical fiber cores used in the downstream direction by using a dendritic network. The CATV optical signal is transmitted from the downstream optical transmitter in the center 801 to the downstream optical receiver in the hub device 803. When a redundant configuration is adopted, switching is performed by the switch, and again by the optical transmitter in the hub device 803. Electro-optical conversion is performed, and N light is branched by a nearby closure 804 or the like, and is received by an optical receiver in N node devices 802.

  According to the above conventional example, in the upstream direction, the number of used optical fibers can be reduced by the WDM method. An upstream CATV optical signal is transmitted from the upstream optical transmitter in each node device 802 to the N-wave WDM filter in the hub device 803 and multiplexed. The upstream CATV optical signal multiplexed by the hub device 803 or the nearby closure 804 is transmitted to the center 801, separated into each wavelength by an N-wave WDM filter, received by each optical receiver, and has a redundant configuration. In this case, the switch is selected by the switch, and the upstream CATV signal reaches the center. Furthermore, it is of course possible to reduce the number of optical fiber cores used by WDM multiplexing the upstream direction with the downstream direction. FIG. 10 shows Conventional Example 4 in the case where the optical fibers from the hub device 903 to the node device 902 are also made redundant.

  In Patent Document 1, coaxial cables extend from an integrated optical terminal station in a plurality of distribution directions, each of which forms one network, and the subsequent distribution of coaxial cables is reduced. For this reason, particularly in urban systems, it is possible to suppress the rise in construction costs.

  In Patent Document 2, an optical node device and an optical node device that supply a signal such as a CATV signal to a coaxial transmission line system in which a transmission line device is operating by adopting a specific power backup method for the optical node apparatus. It is an object of the present invention to provide a power supply system for the camera.

Patent Document 3 provides a CATV transmission method that can be economically introduced while considering transferability at an appropriate timing while effectively utilizing an existing CATV system represented by the HFC method. It is an issue.
Utility Model Registration No. 3038269 JP 2001-144658 A JP 2003-009112 A

In the conventional system example of FIGS. 8 and 9, it is possible to reduce the number of optical fiber cores and perform optical transmission as close to the subscriber as possible. However, the number of lines between the hub device and the node device is large, and the node devices are installed in a star shape from the hub. For this reason, there is a problem that it is difficult to adopt a redundant configuration without increasing the number of optical fiber cores as much as possible.
FIG. 10 shows an example in which the optical fibers from the hub device 903 to the node device 902 are also configured redundantly. In this conventional example, between the hub device and the node device, the number of facings is large at a location corresponding to a branch of the dendritic network, and the number of optical fibers and optical passive devices at the location is approximately doubled. .

  The problem to be solved by the present invention is to provide a CATV transmission system and a CATV transmission method that enable a redundant configuration without increasing the number of optical fiber cores as much as possible.

To achieve the above object, according to a first aspect of the present invention, a center device, a hub device connected to the center device via an optical fiber, and a hub device connected to the hub device via an individual optical fiber are provided. A CATV transmission system including at least two node devices that perform electro-optic conversion of an upstream CATV signal to be transmitted to a center device and photoelectric conversion of a downstream CATV signal received from the center device. Each of the node devices is connected to one or two other node devices via a cable that distributes the power supplied by the power supply device, and either one of the node devices or a hub. When a communication failure occurs in the optical fiber with the device, it is transmitted from the node device in which the communication failure has occurred in the optical fiber with the hub device to the center device. The CATV signal is transmitted as an electrical signal to another node device via a cable, and the other node device performs light-optical conversion and transmits it to the center device. A communication failure occurs in the optical fiber with the hub device. The downlink CATV signal from the center device to the node device is subjected to photoelectric conversion in another node device, and is transmitted as an electrical signal to the node device in which a communication failure has occurred in the optical fiber with the hub device via the cable. The CATV transmission system characterized by the above is provided.

In the first aspect of the present invention, each of the node devices preferably has switching means for switching whether or not to exchange signals with the center device via other node devices. .

In the first aspect of the present invention, a coaxial cable is preferably used as the cable.

In any configuration of the first aspect of the present invention described above, the cable is joined to the electric signal line in each node device via a power supply filter, and is input from another node device via the cable. It is preferable that the electric signal is input to the electric signal line through the power supply filter.

In order to achieve the above object, the present invention provides, as a second aspect, a center device, a hub device connected to the center device via an optical fiber, and a connection to the hub device via an individual optical fiber. And a CATV transmission method by a system comprising at least two node devices that perform optical conversion of an upstream CATV signal to be transmitted to a center device and photoelectric conversion of a downstream CATV signal received from the center device, Power is supplied from one of the power supply devices to one of the node devices, and each of the node devices is connected to one or two other node devices via a cable that distributes the power supplied by the power supply device. When a communication failure occurs in the optical fiber with the hub device, transmission is sent from the node device in which the communication failure has occurred in the optical fiber to the hub device to the center device. The upstream CATV signal is transmitted as an electrical signal to another node device via a cable, and the other node device performs light-optical conversion and transmits it to the center device, causing a communication failure in the optical fiber with the hub device. The downstream CATV signal from the center device to the node device is subjected to photoelectric conversion in another node device, and is transmitted as an electrical signal to the node device in which a communication failure has occurred in the optical fiber with the hub device via the cable. The present invention provides a CATV transmission method characterized by the above.

In the second aspect of the present invention, it is preferable that each node device is provided with switching means for switching whether or not to perform signal transmission / reception with the center device via another node device. .

In the second aspect of the present invention, a cable is joined to an electric signal line in each node device via a power supply filter, and an electric signal input from another node device via a cable is used as a power supply filter. It is preferable to input to the electric signal line.

The CATV transmission system and the CATV transmission method according to the present invention can simultaneously provide power supply from a power supply apparatus to a plurality of apparatuses and a redundant configuration while reducing the number of optical fiber cores. Play.
Et al is not limited to the embodiments of the present invention, as the use of only applications or signal system backups only feeding system, it is possible to use to simplify the circuit.

  Embodiments of a CATV transmission system and a CATV transmission method according to the present invention will be described in detail with reference to the accompanying drawings. 1 to 6, an embodiment of the CATV transmission system and CATV transmission method of the present invention is shown.

  An object of the present invention is to provide a CATV transmission system and a CATV transmission method in which a redundant configuration is provided between a hub device and a node device. This redundant configuration method between the hub device and the node device is to construct a redundant configuration between the node devices by diverting the power supply cable of each node device without increasing the number of optical fiber cores. It is characterized by.

Example 1 is shown in FIG. 1 and FIG. The configuration of the first embodiment of the present invention will be described in detail with reference to FIG. FIG. 2 is a diagram for explaining a signal flow in the CATV transmission system of FIG.
As described above with reference to FIG. 7 of the conventional example, the distance between the hub device and the node device is a relatively short distance. Therefore, the power supply device for supplying power to the node device is not a single power supply device for each node device, but a plurality of node devices that are relatively close to each other and an active device such as a relay amplification device on the coaxial transmission line associated therewith, It is desirable to supply power to as many node devices as possible from one power supply device.

  In FIG. 1, the power feeding device 105 feeds power to the node a device 102 and further feeds power far away to the node a + 1 device 121 through the coaxial cable 106. The coaxial cable 106 is a commonly used cable that can also transmit a CATV signal. The coaxial cable 106 is used for power feeding and has a role of backing up the CATV signal of each node device. In this description, a coaxial cable is used as a representative example, but the type of cable is not particularly limited. The feed current from the feed device 105 supplies power to the power panel of the node a device 102 and is combined with the backup CATV signal by the feed filter, passes through the coaxial cable 106, and reaches the feed filter of the node a + 1 device 121. . The power supply filter of the node a + 1 device 121 separates the backup CATV signal and the power supply current, and the power supply current supplies power to the power supply panel in the node a + 1 device 121.

  FIG. 2 shows the signal flow during backup. 1 and 2 have the same configuration. A broken line indicates the flow of the downstream signal, and a dashed line indicates the flow of the upstream signal. It is assumed that an accident or the like has occurred between the hub device 203 and the node a device 202, and the optical fiber cable has been broken. In the downstream optical receiver of the node a apparatus 202, when the received light level is lowered, that is, when an abnormality occurs, the monitoring controller sends a signal notifying the node a + 1 apparatus 221 of the abnormality via the coaxial cable 206. . Alternatively, the monitoring control device of the center 201 detects an abnormality or no response of the node a device 202 and preferentially transmits a signal reporting the abnormality of the node a device 202 to the node a + 1 device 221.

  In the node a + 1 apparatus 221 that has received the signal reporting the abnormality, the downstream CATV signal that has been photoelectrically converted by the downstream optical receiver passes through the downstream switch 223, the directional filter 2, the common switch 222, and the power supply filter, and the power supply cable 206. Is output. In the node a device 202, the downlink CATV signal that has passed through the feed filter passes through the common switch 207, the directional filter 1, and the downlink switch 208 and is output to the coaxial transmission line 204. The upstream CATV signal from the coaxial transmission line 204 is input to the node a device 202 and then output from the upstream switch 209 to the coaxial cable 206 through the directional filter 1, the common switch 207, and the feed filter.

  In the node a + 1 apparatus 221, the uplink CATV signal that has passed through the power supply filter is transmitted to the optical transmitter in the node a + 1 apparatus 221 via the common switch 222, the directional filter 2, and the uplink switch 224, and the downlink signal • Backup between node devices is established for both upstream signals. In the center 201, the upstream CATV signal output unit of the node a device 202 and the node a + 1 device 221 is combined, or a signal backed up by an instruction from a monitoring control device or the like based on abnormality information in the node device is used. The uplink switch 210 is controlled so as to pass the signal to the regular output unit. This enables upstream backup.

  Configuration examples of the CATV transmission system and the CATV transmission method to which the second embodiment is applied are shown in FIGS. 3, 4, and 5. FIG. 3 shows an embodiment of the present invention with three node devices. The power feeding device 305 supplies power to the power supply panel of the node a + 1 device 321, and further feeds power to the node a device 302 and the node a + 2 device 331 through coaxial cables 306 and 311 through the power feeding filters 1 and 2 of the node a + 1 device 321, respectively. Is done.

  With reference to FIG. 4, the flow of the downlink signal at the time of backup will be described in detail. It is assumed that the optical fiber between the hub device 403, the node a device 402, and the node a + 1 device 421 is broken due to an accident or the like. In the downstream optical receiver of the node a device 402, the received light level decreases, that is, an abnormality occurs, and a signal notifying the abnormality is sent to the node a + 1 device 421 and the node a + 2 device 431 via the coaxial cables 406 and 411. The node a + 1 device 421 also sends a signal notifying the abnormality to another node device. Alternatively, the monitoring control device of the center 401 detects an abnormality or no response of the node a device 402 and the node a + 1 device 421, and transmits a signal notifying the node a + 2 device 431 of the abnormality of the node a device 402 and the node a + 1 device 421. To do.

  In the node a + 2 device 431 that has received the report of the abnormality, the downstream CATV signal that has been photoelectrically converted by the downstream optical receiver passes through the downstream switch 433, the directional filter 2, the common switch 432, and the feed filter, and is output to the coaxial cable 411. Is done. In the node a + 1 device 421, the downlink CATV signal that has passed through the feed filter 2 passes through the common switch 2 (425), the directional filter 1, and the downlink switch 423, and is output to the coaxial transmission line 412. From the downlink switch 423 in the node a + 1 apparatus 421, it further passes through the directional filter 2, the common switch 1 (422), the feed filter 1, and the coaxial cable 406, and in the node a apparatus 402, the feed filter and the common switch 407. The signal passes through the directional filter 1 and the down switch 408 and is also transmitted to the coaxial transmission line 404.

  The flow of the uplink signal will be described in detail with reference to FIG. 3, 4, and 5 have the same configuration. The upstream CATV signal from the coaxial transmission line 504 is input to the node a device 502, and then passes from the upstream switch 509 through the directional filter 1, the common switch 507, the feed filter, the coaxial cable 506, and in the node a + 1 device 521. , The feed filter 1, the common switch 1 (522), the directional filter 2, the uplink switch 524, the directional filter 1, the common switch 525, and the feed filter 2 to be output to the coaxial cable 511. . Here, the uplink CATV signal on the coaxial transmission line 512 is also coupled by the uplink switch 524 in the node a + 1 apparatus 521. In the node a + 2 device 531, the signal is transmitted to the upstream optical transmitter via the feed filter, the common switch 532, the directional filter 2, and the upstream switch 534, and both the downstream signal and the upstream signal are transmitted to the node a device 502 and the node a + 1 device. The backup of 521 is established.

  In the center 501, the output unit for the upstream CATV signal of the node a device 502, the node a + 1 device 521, and the node a + 2 device 531 is combined or backed up by an instruction from the monitoring control device or the like based on abnormality information in the node device The uplink switch 510 is controlled so as to pass the signal to the normal output unit of the center device. This enables upstream backup.

  A configuration example to which the third embodiment is applied is shown in FIG. FIG. 6 shows an embodiment of a redundant configuration of a plurality of node devices as still another embodiment. A node device equivalent to the node a + 1 device 321 of FIG. 3 showing the second embodiment is installed in each node, and backup monitoring control is performed. With this, it is possible to further develop a backup between a plurality of units.

  As an example of the node range to be fed and backed up according to the present invention, the power consumption (apparent power) of the node device is 50 VA, two extension amplifiers connected to the node device are 50 VA (100 VA per node for convenience), and coaxial The loop resistance of the cable is about 4 Ω / km. When a general medium-sized uninterruptible power supply device with a capacity of 320 VA (60 V x about 5.3 A) is used, the received voltage of the node device 800 m away from the coaxial cable is about 54 V, and the interval is about 800 m. With respect to the three installed node devices (and extension amplifiers), a power feeding device can be installed near the central node device to supply power (current consumption is about 5.3 A). In this case, power can be supplied from one power supply device to three node devices and six extension amplifiers, and backup can be performed when the optical fiber is in an emergency. By using a type with a large power supply capacity of the power supply device or a type with a high power supply voltage such as 90V, it is possible to construct a backup for each active device while supplying more active devices with one power supply device. become.

It is a figure which shows Example 1 of the CATV transmission system and CATV transmission method of this invention. It is a figure which shows the signal flow of Example 1 shown in FIG. It is a figure which shows Example 2 of the CATV transmission system and CATV transmission method of this invention. It is a figure which shows the flow of the downstream signal of Example 2 shown in FIG. It is a figure which shows the flow of the upstream signal of Example 2 shown in FIG. It is a figure which shows Example 3 of the CATV transmission system and CATV transmission method of this invention. It is a figure which shows the structural example of the HFC system of the prior art example 1. FIG. It is a figure which shows the structural example of the HFC system of the prior art example 2. FIG. It is a figure which shows the structural example of the HFC system of the prior art example 3. FIG. It is a figure which shows the structural example of the HFC system of the prior art example 4. FIG.

Explanation of symbols

1, 2, Directional filter (feed filter)
102, 202, 302, 402, 502 Node-a device 105, 305 Power feeding device 106, 206, 306, 311, 406, 411, 506, 511 Coaxial cable (power feeding cable)
121,221,321,421,521 Node a + 1 device 201,401,501 Center 203,403 Hub device 204,404,412,504,512 Coaxial transmission line 207,222,407,432,507,525,532 Common switching 208, 223, 408, 423 Downlink switch 209, 210, 224, 409, 509, 524, 534 Uplink switch 331, 431, 531 Node a + 2 device 422 Common switch 1
425 Common switch 2

Claims (7)

A center device, a hub device connected via the optical fiber to the center apparatus, is connected via a separate optical fiber to the hub device, electro-optic conversion and the center device of the uplink CATV signals to be transmitted to the center apparatus A CATV transmission system comprising at least two node devices that perform photoelectric conversion of a downstream CATV signal received from
A power supply device for supplying power to any one of the node devices ;
Each of the node devices is connected to one or two other node devices via a cable that distributes the power supplied by the power feeding device.
When a communication failure occurs in an optical fiber between any of the node devices and the hub device,
An uplink CATV signal transmitted from the node device in which a communication failure has occurred in the optical fiber to the hub device to the center device is transmitted as an electrical signal to the other node device via the cable, and the other node device The light is converted into light and transmitted to the center device.
A downlink CATV signal from the center device to the node device in which a communication failure has occurred in the optical fiber with the hub device undergoes photoelectric conversion in another node device, and the hub device is passed through the cable as an electrical signal. A CATV transmission system for transmitting to a node device in which a communication failure has occurred in an optical fiber between 2. The CATV according to claim 1 , wherein each of the node devices includes switching means for switching whether or not to perform signal transmission / reception with the center device via another node device. 3. Transmission system.   The CATV transmission system according to claim 1, wherein a coaxial cable is used as the cable. The cable is joined to an electric signal line in each node device via a power supply filter, and an electric signal input from another node device via the cable is connected to the electric signal via the power supply filter. 4. The CATV transmission system according to claim 1 , wherein the CATV transmission system is input to a signal line . Center device, hub device connected to center device via optical fiber, electro-optic conversion of upstream CATV signal transmitted to center device connected to hub device via individual optical fiber, and center device A CATV transmission method by a system comprising at least two node devices that perform photoelectric conversion of a downstream CATV signal received from
Supply power from a power supply device to any of the node devices ,
Each of the node devices is connected to one or two other node devices via a cable that distributes the power supplied by the power supply device;
When a communication failure occurs in an optical fiber between any of the node devices and the hub device,
An uplink CATV signal transmitted from the node device in which a communication failure has occurred in the optical fiber to the hub device to the center device is transmitted as an electrical signal to the other node device via the cable, and the other node device The light is converted into light and transmitted to the center device.
A downlink CATV signal from the center device to the node device in which a communication failure has occurred in the optical fiber with the hub device undergoes photoelectric conversion in another node device, and the hub device is passed through the cable as an electrical signal. A CATV transmission method comprising: transmitting to a node device in which a communication failure has occurred in an optical fiber between the first and second optical fibers . 6. The CATV according to claim 5 , wherein each of the node devices is provided with switching means for switching whether or not a signal is exchanged with the center device via another node device. Transmission method. The cable is joined to an electric signal line in each node device via a power supply filter, and an electric signal input from another node device via the cable is connected to the electric signal line via the power supply filter. The CATV transmission method according to claim 5, wherein the CATV transmission method is input .

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