JP2004120105A - Node apparatus in hybrid transmission line - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission system to improve throughput and a node apparatus thereof. <P>SOLUTION: The node apparatus 100 mainly includes a router 112 and a CMTS (cable modem termination system) 114. The node apparatus 100 is installed at any point of a coaxial cable in the hybrid transmission line by using a branching unit, and at least one optical fiber cable 105 is extended from the router 112 of the node apparatus 100 and connected to a central unit. That is, a new optical transmission line is extended. Then the CMTS 114 converts an RF signal in the coaxial cable 104 into a base band signal and data are communicated through a newly extended path. Since an optical path is formed to each node apparatus 100 independently respectively, a channel can be shared with each of coaxial cables connected in parallel and each coaxial cable can divide terminals into cells in a data flowing direction. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a node device for mutually converting an RF signal and an optical baseband signal in a transmission system including an optical fiber cable and a coaxial cable. In particular, the node device includes a cable modem termination system device, a router device, and a photoelectric converter, and connects an optical fiber cable to the router device via the photoelectric converter to perform data communication using the optical fiber cable. To a device that enables Further, the node device of the present invention can divide a large number of terminal devices connected to the coaxial cable into a large number of cells by connecting the terminal device to an arbitrary portion of the coaxial cable, thereby improving the data communication throughput. This is a useful device for constructing
[0002]
[Prior art]
Conventionally, there is an Internet service using a CATV network system. It is generally called a wide area network (hereinafter, referred to as a WAN), and uses an optical fiber cable and a coaxial cable provided in the city as a transmission line, and data such as the Internet is transmitted and received by a plurality of terminal devices. In order to cope with the concentration of users, a central device is provided with a high-speed router device and a cable modem termination system device (hereinafter, CMTS).
[0003]
As shown in FIG. 4A, the system includes a central device 10, a high-speed router device 11 (L3SW (Layer 3 switch)), a CMTS 12, a CMTS 13, a downstream amplifier 14, an upstream amplifier 15, and optical fiber cables 18, 19. , An optical node device 16, coaxial cables 20 and 21, a bidirectional amplifier 22, and terminal devices 23 and 24. The CMTSs 12 and 13 are devices for mutually converting between an RF signal and a baseband signal. The reason why two CMTSs 12 and 13 are provided is to improve the data communication throughput by setting the number of channels for data communication to two.
[0004]
In the above configuration, a pair of a CMTS and a pair of a downlink channel and an uplink channel used are in one-to-one correspondence. For example, the signal on the downlink channel F1 is modulated by the CMTS 12, and the signal on the uplink channel R1 is demodulated by the CMTS 12. Similarly, the signal on the downlink channel F2 is modulated by the CMTS 13, and the signal on the uplink channel R2 is demodulated by the CMTS 13. As described above, the use channel and the CMTS shown in FIG. 4B have a one-to-one correspondence. As a result, in each coaxial cable, there are two downlink channels and two uplink channels for data communication. Therefore, for example, the terminal device connected to the coaxial cable 20 uses the channels F1 and R1, and the terminal device connected to the coaxial cable 21 uses the channels F2 and R2. Cells can be divided (grouped) for each terminal device connected to the cable. However, in the transmission path of the coaxial cable 20, the channels F2 and R2 are wasted, and in the transmission path of the coaxial cable 21, the channels F1 and R1 are wasted.
[0005]
[Problems to be solved by the invention]
If such cell division is adopted, there is a problem that the number of cell divisions is limited by the small number of usable channels in the narrow upstream band. That is, assuming that the cells are divided for each coaxial cable, the number of divided cells is limited by the number of available channels, and it is impossible to divide cells further. As a result, there is a problem that the throughput decreases with the increase in the number of terminal devices. As described above, the number of cell divisions is limited, and in a saturated state, the number of terminal devices per channel cannot be reduced. Therefore, the data communication throughput cannot be further improved.
[0006]
On the other hand, in order to break this state, it is necessary to lay each optical fiber from the central unit for each cell or for each coaxial cable connected in parallel to the optical node. There is a problem that costs and resources are required to improve the quality.
[0007]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to increase the number of cell divisions in a hybrid transmission line provided in a city or each business office, thereby increasing the data communication throughput. It is to provide a device which can improve this.
[0008]
Another object of the present invention is to realize a transmission system capable of efficiently realizing only data communication without affecting signal transmission of a coaxial cable mainly for transmitting a conventional TV signal.
[0009]
Means for Solving the Problems and Functions and Effects
In order to solve the above-mentioned problem, the transmission method according to claim 1, in a hybrid transmission line composed of an optical fiber cable and a coaxial cable, a signal input or output to the optical fiber cable is output or transmitted to the coaxial cable. An input node device, a cable modem termination system device for mutually converting an RF signal on a coaxial cable and a baseband signal on an optical fiber cable, and a router provided on the baseband input / output side of the cable modem termination system device Device, and a photoelectric converter provided on a branch line of the router device for mutually converting an electric signal and an optical signal and outputting or inputting a signal to a plurality of optical fiber cables. This is a node device in a hybrid transmission path.
[0010]
The device is connected at any point of the coaxial cable of the hybrid transmission line so as to output or input an RF signal to the coaxial cable. A cable modem termination system device (CMTS) in this device converts between an RF signal on a coaxial cable and a baseband signal on an optical fiber cable. Further, the CMTS outputs or inputs a baseband signal to a router device provided on the baseband signal input / output side. A plurality of optical fiber cables are connected to the router device via a photoelectric converter. Among these, one optical fiber is connected to, for example, a central device of a center or an optical fiber network. Thereby, the data (RF signal) transmitted from the consumer after the node is converted into a baseband signal by the CMTS in the node, and the transmission destination is allocated to a predetermined route by the router device and transmitted. For example, when using the Internet or the like, the upstream data signal is output to an optical fiber cable in order to transmit the upstream data signal to the central device.
[0011]
This node device can be provided in plural or in a single coaxial cable. Then, a plurality of node devices are cascaded by optical fibers. By configuring the transmission system in this way, it becomes possible to divide a large number of terminal devices connected to the coaxial cable into cells for each node device of the present invention.
That is, the coaxial cable can be divided into cells along the direction in which data flows. The channels assigned to each cell divided by the cell division can be assigned to another coaxial cable system which is in parallel with respect to data transmission. Since the node device and the central unit or optical fiber network are connected by optical fibers, signals of the same channel in each coaxial cable system are transmitted to the central unit or optical fiber network by wavelength-multiplexed optical fibers or individual optical fibers. Since transmission is possible, there is no data interference.
[0012]
As a result, when a terminal device is viewed from a center device that manages a large number of terminal devices, a common channel arrangement can be set for each coaxial cable that is arranged in parallel. Will increase. Therefore, when the number of terminal devices increases, a decrease in throughput can be prevented.
In other words, the cells can be divided into a plurality of cells along the direction in which the data of the transmission path of each coaxial cable flows, so that the number of cells can be increased as a whole network controlled by one center device.
[0013]
According to a second aspect of the present invention, the hybrid transmission line is a hybrid transmission line of a CATV system, and the node device is connected to a coaxial cable of the hybrid transmission line by a branch unit. Is a node device.
With this configuration, a video signal in a conventional CATV system can be transmitted on a conventional transmission path, and only a data signal can be transmitted between a node device and a central device or an optical fiber network by an optical fiber.
[0014]
The invention according to claim 3 is characterized in that the router device is connected to the plurality of optical fiber cables extending to the terminal device via a photoelectric converter, and the terminal device performs data communication using the optical fiber cable. A node device in a hybrid transmission path according to claim 1 or claim 2.
With this configuration, a video signal in a conventional CATV system can be transmitted on a conventional transmission path, and only a data signal can be transmitted between a node device and a central device or an optical fiber network by an optical fiber.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, this invention is not limited to a following example.
(Example)
FIG. 1 shows a node device installed in a hybrid transmission line according to the present invention. The node device of the present invention includes a media converter 110, a router device 112, a CMTS (cable modem termination system) 114, a frequency converter 116, a down amplifier 118, an up amplifier 120, and a duplexer 122.
[0016]
In the above configuration, the media converter is a photoelectric converter for mutually converting an electric signal and an optical signal. The router device 112 is a device that specifies an optimum route and transmits data to a different network or its own network. The CMTS 114 is a device for mutually converting an RF signal and a baseband signal of a coaxial cable. The frequency converter 116 is a device that converts a frequency in the downstream direction into any band (channel) of a predetermined coaxial cable band (for example, 88 MHz to 870 MHz). When this apparatus is used for a LAN, one coaxial cable 104 is branched from a coaxial cable (not shown), and the coaxial cable 104 and two optical fiber cables 105 and 106 are connected as shown in the figure. Thus, the signals from the optical fiber cables 105 and 106 are designated to the CMTS 114 by the router device 112, converted into RF signals by the CMTS 114, and transmitted to the terminal devices connected to the coaxial cable 104. Further, a signal from the terminal device is transmitted to the optical fiber cable 105 or the optical fiber cable 106 in a reverse route.
[0017]
FIG. 2 shows a LAN using this node device. For example, a general LAN includes a central device 200, a high-speed router device (L3SW) 201, a CMTS 204, a media converter (MC) 202, an optical node device 205, a bidirectional amplifier 207, optical fiber cables 210 and 211, and coaxial cables 212 and 213. Consists of A transmission line extends from the bidirectional amplifier 207 to the customer, and a terminal device 215 of the customer is connected. In this configuration, data is normally transmitted bidirectionally via optical fiber cables 210 and 211 and coaxial cables 212 and 213.
[0018]
As shown in FIG. 2, the node device 100 (FIG. 1) of the present invention is installed via a branching device 214, and one optical fiber cable 105 extends to the central device 200. That is, one optical path is added from the central device 200 to the coaxial cable 212 system. Similarly, one optical path is added from the central device 200 to the coaxial cable 213 system. Since the added paths are independent of each other, the same frequency band can be used. As a result, the central device 200 and the terminal device 215 can communicate with each other more efficiently than before. In particular, the central device can efficiently transmit image data via the Internet or the like to consumers. That is, by using the node device 100 of the present invention, the communication throughput can be improved without affecting the LAN having the existing coaxial cable. In addition, if the optical fiber cable 105 is transmitted by wavelength multiplexing, only one optical fiber cable is required. Of course, a plurality of optical fibers may be used.
As described above, according to the present invention, when a plurality of coaxial transmission lines 212 and 213 of different systems are arranged, the channel arrangement can be shared in each coaxial cable, so that the number of cell divisions can be increased, It is possible to prevent a decrease in throughput when the number of devices increases.
[0019]
A plurality of node devices 100 can be provided along each of the coaxial cables 212 and 213. Providing a plurality of node devices 100 in the direction in which data flows means that the terminal devices 215 after the node device 100 are classified into a plurality of cells. The cell refers to one integrated area when viewed from the central device 200. Then, in the coaxial cables 212 and 213 in a parallel relationship, the cells 220 and 221 in a parallel relationship can be assigned a common channel. Therefore, it is possible to increase the number of cell divisions in the whole system.
[0020]
(Modification)
As described above, one embodiment representing the present invention has been described, but various other modifications are possible. For example, in the node device 100 of the first embodiment, the router device 112 that designates and distributes the destination by referring to the destination by software is assumed, but the configuration of the node device 100 is not limited to this. For example, as shown in FIG. 3, the router device 112 is, for example, a high-speed router device (L3SW) 112A that specifies and distributes a destination by hardware, and is further converted into an optical signal by a media converter (MC) 110A that is a photoelectric converter. And input / output to / from the optical fiber cable 108. If the node device 100 is configured in this manner, services can be provided to more customers. In addition, since the customer can directly connect to the node device 100 with the optical fiber cable 108A, the throughput can be further improved.
[Brief description of the drawings]
FIG. 1 is a block circuit diagram of a node device according to a first embodiment of the present invention.
FIG. 2 is a system block diagram of a LAN to which the node device according to the first embodiment of the present invention is applied.
FIG. 3 is a block circuit diagram of a node device according to a modification of the present invention.
FIG. 4 is a system block diagram of a LAN according to a conventional example (a), and a frequency structure diagram of the system (b).
[Explanation of symbols]
100 node device 104 coaxial cable 105, 106, 108 optical fiber cable 110, 202 media converter 112 router device 114, 204 cable modem termination system (CMTS)
116 frequency converter 118 downlink amplifier 120 uplink amplifier 122 duplexer 200 central device 201 high-speed router device 207 bidirectional amplifier 214 branch device 215 terminal device 220 cell

Claims (3)

In a hybrid transmission path including an optical fiber cable and a coaxial cable, a node device that outputs or inputs a signal input or output to the optical fiber cable to the coaxial cable,
A cable modem termination system device for mutually converting an RF signal on the coaxial cable and a baseband signal on the optical fiber cable;
A router device provided on the baseband input / output side of the cable modem termination system device,
A hybrid provided on a branch line of the router device, the photoelectric converter for converting an electric signal and an optical signal to each other and outputting or inputting a signal to or from the plurality of optical fiber cables; Node device on the transmission path. The node device according to claim 1, wherein the hybrid transmission line is a hybrid transmission line of a CATV system, and the node device is connected to the coaxial cable of the hybrid transmission line by a branch. . The router device is connected to the plurality of optical fiber cables extended to a terminal device via the photoelectric converter, and the terminal device performs data communication using the optical fiber cable. 3. A node device in a hybrid transmission path according to claim 1.

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