JP2000068944A - Two-way optical coaxial transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend the outgoing/incoming transmission capacity of the system. SOLUTION: Broad band transmission in outgoing signal transmission from a node device 5 to a subscriber terminal 34 is realized by optical transmission by using an outgoing transmitter 9, an optical amplifier section 10 and light distributors 11, 12. Since a frequency band for the broad band transmission part conventionally used in coaxial transmission is not used, thin frequency band is used for incoming transmission. Thus, the transmission band is extended for both outgoing transmission and incoming transmission, and the transmission capacity for the outgoing and incoming transmission is extended.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bidirectional optical coaxial transmission system, and more particularly to a bidirectional optical coaxial transmission system in which optical transmission is performed between a head end and a node device, and coaxial transmission is performed between the node device and a subscriber terminal. It relates to a coaxial transmission system.

[0002]

2. Description of the Related Art A transmission system having both optical transmission and coaxial transmission (hereinafter, sometimes referred to as an HFC system; HFC is an abbreviation of Hybrid Fiber Coax) is known.

First, the configuration of a conventional HFC transmission system will be described. FIG. 6 is a configuration diagram showing a configuration example of a conventional optical coaxial transmission network.

Referring to FIG. 6, the total service area is about 5
Node area 1 divided into cells in units of 00 to 1000 households
41 to 149, two-way transmission is performed by optical transmission between the head end 100 and the node device 103.
From 3 the coaxial distribution network is used between the subscriber terminals.

In the coaxial distribution network, a main line amplifier and an extension system amplifier are appropriately disposed to compensate for coaxial cable loss.

FIG. 7 is a configuration diagram showing an example of the configuration of the entire conventional optical coaxial transmission network.

Referring to FIG. 7, a head end (HE) 1
Optical transmission is performed from 00 to n (n is a positive integer) node devices 103.

Here, the transmission from the head end 100 to the subscriber terminal is called downlink transmission, and the transmission from the subscriber terminal to the head end 100 is called uplink transmission.

In general, bidirectional optical transmission between the head end 100 and the node device 103 is spatially divided, that is, optically separated. In some cases, wavelength division multiplexing (WDM) may be used.

FIG. 8 is a diagram showing details of an example of a conventional HFC configuration. The same components as those in FIGS. 6 and 7 are denoted by the same reference numerals, and description thereof will be omitted.

Referring to FIG. 8, a conventional HFC includes a head end 100 and cells 141 to 149.

The head end 100 is a downstream optical transmitter 1
01, and the upstream optical receiver 102,
Each of the nodes 149 includes the node device 103 and the areas 1 and 2.

The node device 103 is connected to the downstream optical receiver 10.
4 and an upstream optical transmitter 105.

An optical cable 151 connects between the downstream optical transmitter 101 and the downstream optical receiver 104, and an optical cable 152 connects between the upstream optical receiver 102 and the upstream optical transmitter 105.
Are connected respectively.

Then, the node device 103 and the areas 1 and 2
The spaces are connected by coaxial cables 153 and 154, respectively.

With this configuration, the downstream optical signal output from the downstream optical transmitter 101 in the head end 100 is received by the downstream optical receiver 104 in the node device 103 via the optical cable 151.

The upstream optical transmitter 1 in the node device 103
The upstream optical signal output from the head end 100 is received by the upstream optical transmitter 105 in the head end 100 via the optical cable 152.

Next, from the node device 103 to the subscriber terminal 3
4 will be described in detail. In addition, the area 1 will be described, but the same applies to the area 2.

The downstream electrical signal, which is optically / electrically converted by the downstream optical receiver 104 of the node device 103, is transmitted to the coaxial cable 15
The signal is distributed to the subscriber terminal 34 using the medium 4 as a medium.

In order to compensate for the loss of the coaxial cable 154 and to perform signal distribution, a coaxial amplifier (main line amplifier 10)
7 and an extension amplifier 108) are installed to amplify the signal.

The amplified downstream electric signal is tapped off 22
And the signal is split into the subscriber terminal 34.

In this configuration example, the signal is distributed by the distributor 106 in the subscriber terminal 34, and one of them is a television (hereinafter referred to as a TV) having a channel selection function and a descrambling function.
This is received by the TV 15 via the receiving terminal 14).

The other is received by a personal computer (PC) 17 via a cable modem 16 and can be connected to a high-speed communication service such as the Internet.

Next, uplink transmission will be described. The video signal transmitted from the cable modem 16 of the subscriber terminal 34 or the subscriber or the tap-off 22 to the head end 100 is appropriately amplified by a coaxial amplifier and input to the upstream optical transmitter 105 of the node device 103. After the electrical / optical conversion by the upstream optical transmitter 105, the head end 1
00 is transmitted optically.

Next, the configuration of a conventional node device will be described. FIG. 9 is a configuration diagram of an example of a conventional node device.

Referring to FIG. 9, downstream broadband signal S11 is input from downstream optical input terminal 161 and is received by downstream optical receiver 10
4, the signal S11a is output from the high-pass terminal 163a of the directional filter 163 to the input / output terminal 166 via the common terminal 163b, Input to area 1.

The other signal S11b is output from the high-pass terminal 167a of the directional filter 167 to the input / output terminal 168 via the common terminal 167b, and further input to the area 2.

On the other hand, the upstream narrow band signal S12a from the area 1 input from the input / output terminal 166 is input from the common terminal 163b of the directional filter 163 to the coupler 169 via the low pass terminal 163c.

The upstream narrowband signal S12b from the area 2 input from the input / output terminal 168 is supplied to the directional filter 1
67 are input to the coupler 169 from the common terminal 167b via the low-pass terminal 167c.

After these two signals S12a and S12b are combined by a combiner 169, the upstream optical transmitter 105
The optical signal is converted into a signal light S12 from the upstream optical output terminal 170 to the head end 100 which is the center.

Next, the configuration of the conventional trunk amplifier will be described. FIG. 10 is a configuration diagram showing an example of a configuration of a conventional main line amplifier. Referring to FIG. 10, a downstream frequency band signal S11, which is a high frequency band, is input to common terminal 121a of directional filter 121 via downstream main line input / upstream main output terminal 175. One of the outputs is output to the common terminal 123b via the high-pass terminal 123a of the directional filter 123, and further output from the common terminal 123b to the downstream trunk output / up trunk input terminal 176. Is output.

The other of the outputs is amplified by the down-converter 124, and then is passed to the high-pass terminal 126 of the directional filter 126.
a is distributed by the distributor 177 via the common terminal 126b, and the downstream branch output / up branch input terminals 178, 17
9 to the outside line.

On the other hand, the upstream transmission signal S12 in the low frequency band is input from the downstream main line output / upstream main input terminal 176 and the downstream branch output / up branch input terminals 178 and 179.

In the up signal S12a input from the down trunk output / up trunk input 176, the directional filter 1
From the common terminal 123b of the directional filter 121, the signal is amplified to a required level through the low-pass terminal 123c and then to the common terminal 1c.
The signal is output from the downstream main line input / up output terminal 175 to an external line via 21a.

Also, the down-branch output / up-branch input terminal 17
Uplink signals S12b and S12c input from 8,179
After the signals are combined by the divider 127, the common terminal 126b of the directional filter 126 is connected to the low-pass terminal 126.
c, the signal is amplified to a required level by the up-amplifier 125, and the up-signal S12a
And input to the amplifier 125.

The upstream signal S12 amplified by the amplifier 125
Are output from the downstream main line input / up output terminal 175 to the outside line in the same manner as the upstream signal S12a from the main line.

Next, the configuration of a conventional extension amplifier will be described. FIG. 11 is a configuration diagram showing an example of a configuration of a conventional extension amplifier.

Referring to FIG. 11, a downstream signal, which is a high frequency band, is input from a downstream input / up output terminal 181, and is transmitted from a common terminal 131a of the directional filter 131 to a downstream amplifying unit via a high-pass terminal 131b. 132, and is further amplified by a high-pass terminal 133 of the directional filter 133.
a from the downstream output / up input terminal 182 via the common terminal 133b.

On the other hand, the upstream signal S12, which is a low frequency band,
Is input from the down input / up output terminal 182, and is sent from the common terminal 131b of the directional filter 133 to the low pass terminal 1
The amplified signal is amplified by the upstream amplifying unit 134 via 33c, and further output from the low-pass terminal 131c of the directional filter 131 via the common terminal 131a to the downstream output / up input terminal 181.

In such two-way transmission, the optical transmission section (between the head end 100 and the node device 103) performs space division transmission by separate centering and the coaxial transmission section (the node device 10).
3 to the subscriber terminal 34) perform frequency division transmission.

An example of this type of bidirectional optical coaxial transmission system is disclosed in Japanese Patent Application Laid-Open No. 9-55868 (hereinafter referred to as Prior Art 1).

According to this technique, each signal propagating to the head end side of each electric transmission line is frequency-multiplexed at a coupling portion between the optical transmission line and a plurality of electric transmission lines, and a carrier light is multiplexed with the obtained multiplexed signal. A converter for amplitude-modulating and transmitting the signal on the optical transmission path to the head end side is provided.

Other examples of this type of bidirectional optical coaxial transmission system are disclosed in JP-A-7-240912 and JP-A-7-240912.
No. -107058 (hereinafter referred to as Prior Art 2 and 3, respectively).

[0044]

FIG. 2 is a diagram showing an example of a frequency arrangement of a transmission signal. 2, (A) and (B) show the frequency arrangement of the present invention described later, and (C) shows the conventional H
4 shows a frequency array of FC.

The frequency arrangement of the above-mentioned conventional HFC is shown in FIG.
As shown in (C), the downlink transmission band S11 on the high frequency side
And the upstream transmission band S12 on the lower frequency side, and the upstream transmission band 1S12 is smaller than the downstream transmission band S11.
This has been a bottleneck in constructing a large-capacity two-way transmission system.

However, the conventional HFC transmission system has the following problems.

The first problem is that when capturing multimedia in the future, it is conceivable to communicate a large amount of information in two directions. This means that the upstream transmission capacity of the conventional HFC system is insufficient.

The second problem is that when digital multi-channels provided by downlink satellites or the like are distributed as a service, the operation of changing the distribution of downlink and uplink in the above-mentioned frequency arrangement (shift of a split band to a higher frequency band) is a relative problem. This means that the downstream signal band is narrowed, and it is impossible to cope with further increase in capacity required in the downstream.

On the other hand, these solutions are not disclosed in the prior arts 1 to 3 described above.

Therefore, an object of the present invention is to provide a bidirectional optical coaxial transmission system capable of increasing downlink and uplink transmission capacities.

Another object is to provide a mechanism that can be easily upgraded from the current HFC configuration.

[0052]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a head for performing optical transmission between a head end and a node device and performing coaxial transmission between the node device and a subscriber terminal. A bidirectional optical coaxial transmission system between an end and the subscriber terminal, wherein transmission between the node device and the subscriber terminal is performed, and transmission from the node device to the subscriber terminal includes the optical transmission. It is characterized by comprising transmission means for performing the transmission.

According to the present invention, broadband transmission is performed by optical transmission among downlink transmissions. Because of this, the frequency band of this broadband transmission part, which was conventionally performed by coaxial transmission, becomes vacant,
This free frequency band is used for uplink transmission.

As a result, the transmission band can be expanded for both the downlink transmission and the uplink transmission, so that the downlink and uplink transmission capacity can be increased.

[0055]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a configuration diagram of a preferred embodiment of a bidirectional optical coaxial transmission system according to the present invention. FIG. 1 shows an example of a network configuration according to the present invention.

In FIG. 1, downlink transmission (signals S1 and S
2), all-optical transmission is performed for wideband transmission such as TV video and high-speed data, coaxial transmission is performed for narrow-band transmission such as low-speed data, and all-coaxial transmission is performed for upstream transmission (indicated by signal S5).

In particular, the present invention provides a system for extending the upstream band for overcoming the small upstream transmission band in bidirectional transmission, and also provides a system for expanding the downstream transmission band.

Further, the conventional HFC configuration is replaced with the HFC of the present invention.
It also includes systems that facilitate the upgrade to FC configurations.

Next, the configuration and operation of an example of the network configuration according to the present invention shown in FIG. 1 will be described in detail.

Referring to FIG. 1, head end 1 is CAT
This is a center in a V (Cable Television) system, and performs a narrow-band downlink transmission such as a multi-channel TV or a downlink optical transmitter 2 for downlink transmission of high-speed data, an uplink optical receiver 3 for receiving broadband uplink signal light, and low-speed data. And a downstream optical receiver 4.

The node device 5 is disposed, for example, with a subscriber area of 500 households as a cell.
And an upstream optical transmitter 7 and a downstream optical receiver 8.

Further, between the downstream optical receiver 4 and the downstream optical receiver 8,
Between the upstream optical receiver 3 and upstream optical transmitter 7 and downstream optical transmitter 2
And the downstream optical receiver 6 are connected by optical cables 81 to 83, respectively.

First, downlink transmission will be described. In the downstream optical receiver 6 of the node device 5, after the wideband downstream signal S1 such as multi-channel TV and high-speed data from the downstream optical transmitter 2 in the head end 1 is optically / electrically converted,
The splitter 31 splits the signal S1 into two signals, one of which is S1.
“a” intensity-modulates an optical signal of 1.5 μm band in the downstream optical transmitter 9 in the area 1 via the coaxial cable 84, and the optical amplifier 10 located at the subsequent stage is an optical amplifier represented by EDFA. The light is amplified.

On the other hand, the signal S1b is processed similarly in the area 2 via the coaxial cable 85.

The signal light S1a optically amplified by the optical amplifier 10
Are distributed by the optical distributors 11 and 12 and are drawn into the subscriber terminal 34.

In the subscriber terminal 34, the downstream optical signal S1a is received by the ONU 13 which is a line terminating device, where it is optically / electrically converted, appropriately signal-divided (in the example of FIG. 1, divided into two), and received by a multi-channel TV. Is connected to the TV 15 via the TV receiving terminal 14.

On the other hand, a PC is connected via a cable modem 16.
17 are connected to perform, for example, an Internet connection.

At this time, the wideband frequency band of, for example, 50 to 1000 MHz band shown in FIG. 2B is assigned to the downstream signal.

Further, the downstream optical transmitter 4 of the head end 1
2A, the signal light S2 is transmitted to the node device 5 at a low frequency of, for example, 10 to 55 MHz, as shown in FIG. 2A, and the signal light S2 is transmitted to the downstream optical receiver 8. After the optical / electrical conversion, the directional filter 32
Via the distributor 33 and the coaxial cable 86 (the coaxial cable 87 in the case of the area 2), the main line amplifier 19, the branching device 21, and the extension amplifier 2 provided in the area 1 and the area 2 are provided.
0, input to the subscriber terminal 34 via the tap-off 22.

Then, it becomes a downlink data signal to the data terminal 18 installed in the subscriber terminal 34 and the like. The downlink signal S2 at this time is, for example, 10 to 55 MH shown in FIG.
A narrow band of the z band is allocated.

Next, uplink transmission will be described. Uplink signal S for communication from the cable modem 16 or the like of the subscriber terminal 34
5 is input to the node device 5 via the tap-off 22, the extension amplifier 20, the branching device 21, the main line amplifier 19, and the coaxial cable 86 (the coaxial cable 87 in the case of the area 2).

In the node device 5, the distributor 33 (positioned as a multiplexer as a function in uplink transmission),
Through the high-pass terminal of the directional filter 32, the optical signal is subjected to electrical / optical conversion by the upstream optical transmitter 7 and optically transmitted to the upstream optical receiver 3 of the head end 1.

At this time, the broadband frequency band of, for example, 70 to 750 MHz band shown in FIG. 2A is allocated to the upstream signal S5.

As described above, according to the present invention, the transmission (down) from the head end 1 to the subscriber terminal 34 is transmitted coaxially with the optical transmission, and the transmission (up) from the subscriber terminal 34 to the head end 1 is transmitted coaxially. It is characterized by providing a system in which the downstream transmission band and the upstream transmission band are greatly expanded as compared with the conventional HFC.

Further, by including a system for easily realizing a change from the conventional HFC configuration, it is possible to upgrade at low cost.

Next, the configuration of each device in the cell will be described with reference to embodiments.

[0077]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a first embodiment will be described. In the first embodiment, a detailed configuration of the node device 5 will be described. FIG. 3 is a configuration diagram of the node device.

Referring to FIG. 3, downstream broadband signal S1 is input from downstream optical input terminal 51, is subjected to optical / electrical conversion by downstream optical receiver 6, is distributed by signal distributor 31, and is then subjected to downstream signal External coaxial cable 8 via output terminals 42 and 43
4, 85 are output to area 1 and area 2.

On the other hand, the downstream narrow-band signal S2 is input from the downstream optical input terminal 44, and is subjected to optical / electrical conversion by the downstream optical receiver 8, and then from the low-pass terminal 32a of the directional filter 32 to the directional filter 32. Are distributed by the distributor 33 and output to the area 1 and the area 2 from the downstream output / up input terminals 45 and 46 via the common terminal 32b.

The broadband upstream signal S5 input from the downstream output / upstream input terminals 45 and 46 is combined by the distributor 33, and then from the common terminal 32b of the directional filter 32 via the high-pass terminal 32c. The optical signal is subjected to electrical / optical conversion in the upstream transmitter 7. Then, the signal light S5 after the light conversion is transmitted to the head end 1 which is the center via the light output terminal 47.

Next, a second embodiment will be described. Second
In the embodiment, a detailed configuration of the trunk amplifier 19 will be described. FIG. 4 is a configuration diagram of the main line amplifier.

Referring to FIG. 4, a downstream frequency band signal S2, which is a low-frequency band input to downstream main line input / upstream main line output terminal 53, is supplied to common terminal 52 of directional filter 52.
a is amplified by the down-amplifying unit 54 via the low-pass terminal 52b, and one of its outputs is output from the low-pass terminal 55a of the directional filter 55 to the main terminal 56 via the common terminal 55b.

On the other hand, the other of the outputs is the directional filter 5
The signal is distributed by the distributor 58 from the low-pass terminal 57a through the common terminal 57b, and output from the branch terminals 59 and 60 to the outside line.

On the other hand, the upstream transmission signal S5 in the high frequency band is inputted from the downstream main line output / upstream main input terminal 56 and the downstream branch output / up branch input terminals 59 and 60.

The upstream signal S5a input from the downstream main line output / upstream main line input 56 is amplified to a required level by the upstream amplifying section 62 from the common terminal 55b of the directional filter 55 through the high-pass terminal 55c. Filter 52
From the high-pass terminal 52c through the common terminal 52a, and from the downstream trunk input / up output terminal 53 to the outside line.

Further, the down-branch output / up-branch input terminal 5
The upstream signals S5b and S5c input from the signals 9 and 60 are signal-coupled by the distributor 58, and then from the common terminal 57b of the directional filter 57 to the required level in the upstream amplifier 63 via the high-pass terminal 57c. Amplified, upstream amplifier 6
2 is coupled to the upstream signal S5a from the main line and input to the amplifier 62.

The upstream signal S5 amplified by the amplifying section 62 has the same path as the upstream signal S5a from the main line and has a downstream main line input / output signal.
The signal is output from the upstream output terminal 53 to an external line.

Next, a third embodiment will be described. Third
In the embodiment, a detailed configuration of the extension amplifier 20 will be described. FIG. 5 is a configuration diagram of the extension amplifier.

Referring to FIG. 5, a down signal S2, which is a low frequency band, is input from a down input / up output terminal 71, and is downstream amplified from a common terminal 72a of the directional filter 72 via a low pass terminal 72b. The signal is amplified by the unit 73, and further output from the low-pass terminal 74 a of the directional filter 74 via the downstream output / up output terminal 75 via the common terminal 74 b.

On the other hand, the up signal S5, which is a high frequency band, is inputted from the down output / up input terminal 75, and is sent from the common terminal 74b of the directional filter 74 to the high frequency pass terminal 74.
c, and is amplified by the up-amplifier 76. The signal is further amplified by the high frequency pass terminal 72c of the directional filter 72 to the common terminal 7c.
It is output from the downstream input / up output terminal 71 via 2a.

Next, a fourth embodiment will be described. 4th
In this embodiment, a description will be given of an example in which the main amplifier 19 and the extension amplifier 20 are plug-in replaceable.

As can be seen from the network configuration example of the optical coaxial transmission system of the present invention shown in FIG. 1 and the network configuration example of the conventional optical coaxial transmission system shown in FIG. There is no difference in the installation positions of 107, extension amplifiers 20 and 108, branching device 21, and tap-off 22.

However, referring to FIG. 2, in the conventional coaxial transmission, as shown in FIG. 2C, the upstream signal uses a low frequency band and the downstream signal uses a high frequency band.

Therefore, referring to FIGS. 10 and 11, the conventional main line amplifier 107 and extension amplifier 108 use a low-frequency amplifier for upstream and a high-frequency amplifier for downstream.

On the other hand, in the coaxial transmission of the present invention, as shown in FIG. 2A, a downstream signal uses a low frequency band and an upstream signal uses a high frequency band.

Therefore, referring to FIGS. 4 and 5, the trunk amplifier 19 and the extension amplifier 20 of the present invention use a high-frequency amplifier in the upstream and a low-frequency amplifier in the downstream.

Therefore, according to the present invention, the conventional main line amplifier 10
7 and the extension amplifier 108 cannot be used as they are.

Therefore, in the present invention, referring to FIG. 4, the main amplifier 19 is provided with plug-in terminals 81 to 84 at input / output signal lines near input / output terminals 53, 59, 56, 60, respectively. From 65, the amplification unit 66 is configured to be plug-in replaceable.

Similarly, referring to FIG.
In this configuration, plug-in terminals 85 and 86 are provided at input / output signal lines near input / output terminals 71 and 75, respectively, so that the amplifier 78 can be plugged in and replaced from the housing 78.

That is, the trunk amplifier 107 and the extension amplifier 10 in the coaxial transmission network constructed by the conventional HFC system.
By connecting the main line amplifier 19 and the extension amplifier 20 of the present invention at the position 8 so as to be pluggable, it is possible to upgrade to the present invention without redoing the external connection to the housing.

Although a power supply system to each amplifier is omitted in FIGS. 1 and 8, a plurality of amplifiers are usually supplied from a single power supply device to a remote place via a coaxial cable. It is possible to eliminate the need to review the power supply system when shifting to the configuration of the present invention.

Although the configuration of the embodiment has been described in detail, the branching device 21 and the distributors 11, 12, 31, and 3 shown in FIG.
The functions and circuits such as 3, tap-off 22 and the like are well known to those skilled in the art, and are not directly related to the present invention.

In another embodiment of the present invention, the basic configuration is as described above, but there is no limitation on the number of areas per unit node device 5 in a cell.

There is no particular limitation on the connection method and the number of connected TV receiving terminals 14, TV 15, cable modem 16, PC 17 and data terminals 18 in the subscriber terminal 34 configuration.

The installation positions of the downstream optical transmitter 9 and the optical amplifier 10 include a case where they are built in the node device 5.

In addition, it is assumed that the restrictions on the number of optical distributors 11 and 12 to be used and the number of distributions are limited by the optical input level to ONU 13 in subscriber terminal 34 and can be arbitrarily selected within the range.

Further, FIG. 2 shows the frequency arrangement. Both the present invention and the conventional example can be set to a system-specific setting, and the example shown here is only an example.

[0108]

According to the present invention, optical transmission is performed between a head end and a node device, and coaxial transmission is performed between the node device and a subscriber terminal. In the optical coaxial transmission system, transmission between the node device and the subscriber terminal is configured by a transmission unit that performs transmission from the node device to the subscriber terminal including the optical transmission. Thus, it is possible to increase the uplink transmission capacity.

Further, since the amplifying section of the coaxial transmission section has a plug-in configuration, it is possible to easily upgrade from the current HFC configuration.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a preferred embodiment of a bidirectional optical coaxial transmission system according to the present invention.

FIG. 2 is a diagram illustrating an example of a frequency arrangement of a transmission signal.

FIG. 3 is a configuration diagram of a node device.

FIG. 4 is a configuration diagram of a main line amplifier.

FIG. 5 is a configuration diagram of an extension amplifier.

FIG. 6 is a configuration diagram showing a configuration example of a conventional optical coaxial transmission network.

FIG. 7 is a configuration diagram showing a configuration example of an entire conventional optical coaxial transmission network.

FIG. 8 is a diagram showing details of an example of a conventional HFC configuration.

FIG. 9 is a configuration diagram of an example of a conventional node device.

FIG. 10 is a configuration diagram showing a configuration of an example of a conventional trunk amplifier.

FIG. 11 is a configuration diagram showing a configuration of an example of a conventional extension amplifier.

[Explanation of symbols]

 Reference Signs List 1 head end 2 downstream optical transmitter 3 upstream optical receiver 4 downstream optical receiver 5 node device 6 downstream optical receiver 7 upstream optical transmitter 8 downstream optical receiver 9 downstream optical transmitter 10 optical amplifier 19 trunk amplifier 20 extension amplifier 34 subscriber terminal

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[Procedure amendment]

[Submission date] July 19, 1999 (1999.7.1)
9)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0052

[Correction method] Change

[Correction contents]

[0052]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a head for performing optical transmission between a head end and a node device and performing coaxial transmission between the node device and a subscriber terminal. A bidirectional optical coaxial transmission system between an end and the subscriber terminal, wherein the node device
Narrowband transmission to subscriber terminal is converted to coaxial transmission
And the broadband transmission is performed by the optical transmission.
The transmission from the subscriber terminal to the node device before the broadband
It is characterized by having transmission means for performing the coaxial transmission.
I do.

Claims (10)

[Claims] 1. A bidirectional optical coaxial transmission system between the head end and the subscriber terminal, wherein optical transmission is performed between the head end and the node device, and coaxial transmission is performed between the node device and the subscriber terminal. Wherein the transmission between the node device and the subscriber terminal is constituted by transmission means for performing transmission from the node device to the subscriber terminal including the optical transmission. Coaxial transmission system. 2. The transmission means causes narrowband transmission to be performed by the coaxial transmission and broadband transmission to be performed by the optical transmission in transmission from the node device to the subscriber terminal. The bidirectional optical coaxial transmission system according to claim 1. 3. The bidirectional optical coaxial transmission system according to claim 1, wherein said transmission means causes transmission from said subscriber terminal to said node device to be performed by said coaxial transmission in a wide band. 4. The apparatus according to claim 1, wherein said transmission means includes a bidirectional amplifier for causing bidirectional transmission between said node device and said subscriber terminal to be performed by coaxial transmission.
3. The bidirectional optical coaxial transmission system according to any one of 3). 5. The optical transmission device according to claim 1, wherein the transmission unit includes an optical transmission device for performing transmission from the node device to the subscriber terminal by the optical transmission. Bidirectional optical coaxial transmission system. 6. The bidirectional amplifying device comprises a main line amplifier for inputting and outputting a signal to and from the node device, and an extension amplifier for inputting and outputting a signal between the main line amplifier and the subscriber terminal. The bidirectional optical coaxial transmission system according to claim 4, wherein: 7. An optical / optical converter for converting an electrical signal from the node device into an optical signal, an optical amplifier for amplifying an optical signal output from the electrical / optical converter, 6. A bidirectional optical coaxial transmission system according to claim 5, further comprising an optical distributor for distributing an output of said optical amplifier to said subscriber terminal. 8. The bidirectional optical coaxial transmission system according to claim 4, wherein said bidirectional amplifier is configured so that plug-in exchange is possible. 9. The bidirectional optical coaxial transmission system according to claim 2, wherein the data transmitted from the node device to the subscriber terminal in a wide band is television video data and other high-speed data. 10. The bidirectional optical coaxial transmission system according to claim 2, wherein data transmitted in a narrow band from said node device to said subscriber terminal is low-speed data.