JPH0946364A - Network and device and method for connecting network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a network connection device and method with simple constitution and to attain a network including the device and method. SOLUTION: First and second networks consisting of plural nodes 106 to 133 having plural transmission lines and transmitting/receiving parts less than the number of transmission lines are mutually connected. Single or plural transmission lines in the 1st network are extracted and inserted into the 2nd network and the extracted transmission lines are prevented from being transmitted through the 1st network over a connection part. Single or plural transmission lines corresponding to the number of transmission lines extracted from the 1st network are extracted from the 2nd network and inserted into the 1st network and the extracted transmission lines are prevented from being transmitted through the 2nd network over the connection part. Consequently the inter- network connection system simply connects a specific channel from the 1st network to the 2nd network and from the 2nd network to the 1st network without generating the competition of channels.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a network connection device utilizing a plurality of transmission lines such as channel (wavelength etc.) multiplexing.

[0002]

2. Description of the Related Art Conventionally, there has been a multi-hop network in which a plurality of parallel transmission lines are used and transmission is performed while switching between transmission lines at a node. For example, JP
There is an example as described in 4-24539. One such network with multiple parallel transmission lines
Considering one network, as a method of connecting these networks, there is a method of electrically transmitting and receiving all wavelengths in the network connection method, selecting a desired wavelength from them, and connecting to the other network. FIG. 8 shows a configuration of a network connection device that connects the first network and the second network, and FIG. 9 shows transmission / reception wavelengths of each node connected to the network.

In FIG. 9, a first network and a second network
Each of the networks is connected in a loop with one optical fiber. The optical signal on the first network is
Eight waves from λ1 to λ8 are multiplexed and transmitted in the direction of the arrow. The optical signal on the second network is four-wave multiplexed from λ1 to λ4 and is similarly transmitted in the direction of the arrow.

In FIG. 9, 502 to 525 and 526
529 are nodes forming a shuffle network,
The dots represent the transmitted and received wavelengths. FIG. 7 shows a node configuration in which transmission / reception wavelengths are λi and λj. In FIG. 7, reference numerals 601 and 602 denote wavelength demultiplexing filters that demultiplex the wavelengths λi and λj, respectively.
Reference numerals 603 and 604 denote wavelength demultiplexing filters 601 and 6 respectively.
OE for converting wavelengths λi and λj from 02 into electric signals
607 is a reception buffer for extracting a signal from the node,
Reference numeral 608 is a switching unit, 609 is a transmission buffer for transmitting a signal from a node, and 610 and 611 are wavelengths λi and λj, respectively.
The EO units 612 and 613 for converting the optical signals of the EO units 612 and 613 respectively into the signals of the EO units 611 and 610 and the wavelength demultiplexing filter 602.
It is a combiner that combines the signals from the.

These nodes perform transmission / reception of two wavelengths in accordance with the rules concerning the routing of the shuffle network, and the data reaches the destination node while changing the wavelength.

In FIG. 8, reference numeral 501 denotes a network connection device for connecting the first network and the second network, which has the following configuration. Optical tree couplers 401 and 402 uniformly distribute an optical signal. Each of the wavelength pass filters 403 to 414 selectively transmits only the wavelengths shown in FIG. 8 and cuts other wavelengths. OE
The conversion units 415 to 426 use the filters 403 to 41.
The transmitted light signal of No. 4 is converted into an electric signal. Exchange unit 441
Is a 12-input and 12-output switch that selects an output wavelength according to the header portion of data that is electrified for each wavelength of both networks. The EO converters 427 to 438 convert the switching unit output signals into wavelengths λ1 to λ8, respectively. The optical tree couplers 439 and 440 combine the wavelength signals.

Next, the above conventional example will be described by taking a data transfer operation from the nodes 517 to 527 as an example. The data transmitted from the node 517 on the first network is the wavelength λ.
8 are used to transfer the nodes 521, 525, and 501 in this order. The node configuration of the transmitting node 517 is i in FIG.
= 7, j = 8. The data transmitted from the transmission buffer 609 is converted into an optical signal of wavelength λ8 by the EO unit 611, combined by the combiner 612, and then the node 521.
Is input to A node 518 next to the transmitting node 517,
In both 519 and 520, both i and j in FIG.
Therefore, the signal of λ8 is the wavelength demultiplexing filter 601,
The light having the same wavelength without being demultiplexed by 602, the combiners 612, 6
Pass the node via 13. The same applies to the nodes 522 to 524.

Since the node 521 corresponds to i = 6 and j = 8 in FIG. 7, the signal from the transmission node 517 is demultiplexed by the wavelength demultiplexing filter 602 and is not subjected to the switching operation by the switch 608. The EO unit 611 transmits again with the wavelength λ8. Similarly, the node 525 operates.

The operation of the network connection device 501 will be described with reference to FIG. The optical signal sent from the node 525 at the wavelength λ8 is distributed by the optical tree coupler 401 to eight wavelength pass filters 403 to 410. Since the wavelength pass filters 403 to 409 do not pass λ8, the data does not proceed to the OE units 415 to 422. Since the wavelength pass filter 410 passes λ8, the data is sent to the OE unit 422, where it is converted into an electric signal. Next, the data is input to the exchange unit 441, and the exchange unit 44
1 indicates that the destination node is the second from the packet header information of the data
5 receiving wavelengths λ3 and λ4 on the network
The data is connected to the EO unit 437 which transmits the wavelength λ3. The data is converted by the EO unit 437 into an optical signal of wavelength λ3, merged with another wavelength signal by the optical multiplexer 440, and sent to the second network. Second
Since the wavelength λ3 is not received by the node 526 of the above network, the data is received by the next node 527.

[0010]

However, in the above-mentioned conventional example, the network connection device requires an EO, an OE converter, a wavelength pass filter, etc. for each wavelength. Further, there is a drawback that the configuration of the network connection device becomes complicated, such as the need for a 12 × 12 exchange unit.

Therefore, an object of the present invention is to provide a network connection device, a connection method, and a network including the same which have a simple structure.

[0012]

A network connection device, a connection method, or a network including the same according to the present invention which achieves the above object comprises a plurality of transmission lines and a number of transmission / reception units smaller than the number of the transmission lines. First consisting of multiple nodes with
And a network connecting device that connects the second network with the second network extracts one or a plurality of transmission lines in the first network and inserts the transmission line into the second network, and the extracted transmission line exceeds the connection device. A first means for preventing transmission on the first network; and a first or a plurality of transmission paths that are the same as the transmission paths extracted by the first means in the second network.
And second means for preventing the transmission path taken out from the connection network from being transmitted over the second network while being inserted into the network.

More specifically, the following modes may be adopted. The plurality of transmission lines are ring-shaped transmission lines in which channels are multiplexed. The plurality of transmission lines are ring-shaped transmission lines wavelength-multiplexed. First extracting means for extracting one or a plurality of transmission paths (wavelengths or the like) in the first network and inserting them in the second network; and transmission paths extracted by the first extracting means. First blocking means (optical blocking means or the like) for preventing transmission of data over the connection device on the first network
And a second means for extracting and inserting into the first network one or a plurality of transmission paths that are the same as the transmission paths extracted by the first extracting means in the second network. And a second cutoff unit for preventing the transmission path extracted by the second extraction unit from being transmitted over the second network over the connection device.

According to the present invention, with the above configuration, the inter-network connecting device or method simply sends a specific channel from the first network to the second network and from the second network to the first network. Since the connection is made without any conflict, the configuration becomes simple.

[0015]

First Embodiment FIG. 1 shows the configuration of a network connection device according to the first embodiment of the present invention. FIG. 2 shows a relationship between transmission / reception wavelengths at nodes of the first network and the second network. The network connection device 105 is connected with a first network that is eight-wave multiplexed and a second network that is four-wave multiplexed. Further, the wavelength λl is used for the inter-network connection in this network connection device.

In FIG. 2, the first network and the second network
Each of the networks is connected in a loop with one optical fiber. The optical signal on the first network is
Eight waves from λ1 to λ8 are multiplexed and transmitted in the direction of the arrow. The optical signal on the second network is four-wave multiplexed from λ1 to λ4 and transmitted in the direction of the arrow.

1 and 2, 106 to 129 and 1
Reference numerals 30 to 133 are nodes forming a shuffle network, and dots in FIG. 1 represent transmission / reception wavelengths. The node configuration is similar to that of FIG. These nodes perform two-wavelength transmission / reception in accordance with the rules regarding the routing of the shuffle net, and data reaches the destination node while changing wavelengths.

The connection relationship between each node and the transmission line depends on the network configuration of the shuffle network as described above, as in the above-mentioned conventional example (Japanese Patent Laid-Open No. 64-24539). That is, 0 is displayed in binary on eight transmission lines.
When transmission line numbers from 00 to 111 are given in order, a set of two transmission lines which differ only in each one-digit digit of this transmission line number is selected and a node connected thereto is set. In this embodiment, the nodes 106 to 109 are in the first digit, the nodes 110 to 113 are in the second digit, and the node 114 is
To 117 are connected to the transmission lines which differ only in the last digit of the third digit. In addition, the nodes 118 to 129 are
The same procedure is repeated twice and set. Although the number of nodes is 24 in this embodiment, the same procedure can be repeated any number of times to increase the number of nodes. The transmission directions of the respective transmission lines in this embodiment are all the same, but they can be determined as follows, for example. That is, it is determined that the transmission lines with the different numbers of the above-mentioned transmission line numbers have the same direction and the transmission lines with the different numbers have the same direction. In detail, the transmission method of each transmission line focuses on the transmission line number by the above-mentioned binary system, counts either 0 or 1 in the number, and it is an odd number and an even number ( (Including 0), the transmission directions are different from each other. Here, 000, 011 and 10
Since the number of 1 becomes 0 or 2 in 1 and 110, the number of 1 becomes 1 or 3 and becomes an odd number in 001, 010, 100 and 111 by using them as the first transmission line group. They are used as a second transmission line group and have different transmission directions.

In FIG. 1, reference numeral 105 denotes a network connection device for connecting the first network and the second network, which has the following configuration. Reference numeral 101 is a wavelength demultiplexing filter that separates the wavelength λl from the first network and passes the remaining wavelengths λ2 to λ8. Reference numeral 102 is a wavelength that separates the wavelength λl from the second network and passes the remaining wavelengths λ2 to λ4. Demultiplexing filter 103 is a wavelength demultiplexing filter 10
2 is a wavelength combiner that combines the wavelength λl from the wavelength demultiplexing filter 101 with the wavelengths λ2 to λ8 from the wavelength demultiplexing filter 101, and 104 is the wavelength λl from the wavelength demultiplexing filter 101 and the wavelength demultiplexing filter 102.
Is a wavelength combiner that combines the wavelengths λ2 to λ4. Here, since the wavelengths to be demultiplexed by the wavelength demultiplexing filters 101 and 102 are equal, the wavelength demultiplexing filter 10l and the wavelength multiplexer 103, and the wavelength demultiplexing filter 102 and the wavelength multiplexer 1 are connected.
There is no λ1 having the same wavelength between 04. As a result, wavelength multiplexing is realized without competition between the data transmitted from the first network using the wavelength λl and the data transmitted from the second network using the wavelength λl.

The structure of the wavelength demultiplexing filter 101 is shown in FIG. The arrow indicates the traveling direction of the optical signal, 701 is an optical waveguide connecting the first network input of the wavelength demultiplexing filter 105 and the wavelength multiplexer 103, and 702 demultiplexes the wavelength λl from the optical signal passing through the waveguide 701. Grating, 70
Reference numeral 3 is a waveguide for extracting the signal of wavelength λl demultiplexed by the grating 702 and inputting it to the wavelength multiplexer 104. The configuration of the wavelength demultiplexing filter 102 also conforms to FIG. 3 except for the connection relationship with the outside of the filter.

Next, a data transfer operation from the node 121 to the node 131 will be described as an example. Since the transmission / reception wavelengths of the node 121 on the first network are λ7 and λ8,
In order to transmit on the second network, it is necessary to transmit to the network connection device 105 at the wavelength λl. Therefore, the node 121 first transmits data at the wavelength λ7.
Since the wavelength λ7 passes through the wavelength demultiplexing filter units of the nodes 122 and 123, it is not received there but is received by the node 124. The node 124 then transmits at λ5 according to the header information of the data. The signal at wavelength λ5 is then received at node 126 and similarly transmitted at wavelength λl. The signal of wavelength λl is then received by the network connection device 105. The operation in the network connection device 105 is as follows.

First, the optical signal received by the network connection device 105 is a waveguide 701 in the wavelength demultiplexing filter 101.
The wavelength λl is demultiplexed into the waveguide 703 by the grating 702 and is input to the wavelength combiner 104.
The other λ2 to λ8 proceed through the waveguide 701 as they are,
It is input to the wavelength multiplexer 103. In this way, the data signal of the wavelength λl from the first network is transmitted to the wavelength combiner 1
03 is not transmitted. Λl input to the wavelength multiplexer 104
Signal is multiplexed with the wavelength from the wavelength demultiplexing filter 102 and transmitted to the second network at the wavelength λl. Second
Data sent to the network at wavelength λl is then received at node 130 and retransmitted at wavelength λl. Next, at node 132, the data signal of wavelength λl is received,
The wavelength is changed to λ3 and is transmitted. Finally, the data will be received by the node 131, which receives the wavelength λ3.

In the above structure, data can be transferred from any node in the first network to any node in the second network. Because the signal transmitted from any node in the first network is
Since it is guaranteed that the wavelength will be the transmission / reception wavelength of the node 106, the network connection device 10
This is because if the data is pulled into the second network at 5, the data can be transferred to any node in the second network after that because it is also the transmission / reception wavelength of the node 130 downstream of the network connection device 105. . Therefore, in the example of FIG. 2, for the same reason, the wavelengths λ2, λ3, and λ4 can be used for the inter-network connection.

Next, a data transfer operation from the node 122 to the node 106 will be described as an example. The transmission and reception wavelengths of the node 122 are λl and λ3, and the transmission and reception wavelengths of the node 106 are λl and λ.
Since it is 2, transmission should be possible if data is always transferred at a wavelength λl common to both. However, the node 122
Since the network connection device 105 exists between the node 106 and the node 106, when the data is transferred at the wavelength λl, the network connection device 105 transfers the data to the second network. Therefore, in the data transfer within the same network, it is necessary not to transmit to the network connection device 105 at the wavelength λl. Therefore, the data transmitted from the node 122 at the wavelength λl is received by the node 126 and transmitted at the wavelength λ5. In the network connection device 105, the data signal of wavelength λ5 is input to the waveguide 701 in the wavelength demultiplexing filter 101. Since the wavelength λ5 is not demultiplexed by the grating 702, the data signal of λ5 travels through the waveguide 701 as it is to the wavelength multiplexer 103 and merges with the signal of wavelength λl from the wavelength demultiplexing filter 102, and at λ5. It is sent to the first network. After that, the wavelength is converted to the wavelength λ6 at the node 108 according to the transmission / reception wavelength of each node. Furthermore, the nodes 113, 115,
After passing through 120 and 125, the wavelength is converted to the wavelength λ2 at the node 127 and received at the node 106. Of course, in the data transfer in the first network, the data transfer may be performed from the node 122 using the wavelength λl. This is because even if the data is transmitted to the network connection device 105 at the wavelength λl, the wavelength λl is transferred in the loop-type second network and then returned to the first network. Therefore, the data transfer in the first network is performed. Is possible.

Data transfer from a node in the second network to a node in the first network, data transfer between nodes in the second network, in the first network not crossing the network connection device 105 Data transfer between nodes may also be considered according to the above-mentioned data transfer operation.

[0026]

Second Embodiment FIG. 4 shows a second embodiment of the present invention. This figure shows the configuration of a network connection device that connects the first network and the second network, and wavelength λl is used for data transfer between the networks. The network configuration other than the network connection device 201 is shown in FIGS.
be equivalent to.

In FIG. 4, 202 is an optical branching device for branching an optical signal from the first network, 205 is an optical branching device for branching an optical signal from the second network, and 203 is an optical branching device 202. A wavelength pass filter that transmits the wavelength λl of the optical signal, 204 is a wavelength pass filter that transmits the wavelength λl of the optical signal from the optical branching device 205, 2
Reference numeral 06 denotes a wavelength cut filter that cuts only the wavelength λl of the optical signal branched by the optical branching device 202, and 207 denotes a wavelength cut filter that cuts only the wavelength λl of the optical signal branched by the optical branching device 205. Reference numeral 208 denotes the optical signal transmitted through the wavelength cut filter 206 and the wavelength pass filter 2
209, an optical multiplexer for multiplexing signals of wavelength λl from 04
Is an optical combiner for combining the optical signal transmitted through the wavelength cut filter 207 and the signal of wavelength λl from the wavelength pass filter 203.

The configuration of the optical branching device 202 is shown in FIG. 80
Reference numeral 1 denotes a waveguide connecting the first network input of the network connection device 201 and the wavelength cut filter 206,
Reference numeral 802 is a coupler for branching the intensity of the optical signal in the waveguide 801, and 803 is a waveguide for inputting the signal branched by the coupler 802 to the wavelength pass filter 203. The configuration of the wavelength cut filter 206 is shown in FIG. Reference numeral 901 is an optical waveguide connecting the optical branching device 202 and the optical combiner 208, and 902 is a grating for separating the wavelength λl. The optical branching device 205 and the wavelength cut filter 207 are also based on FIGS. 5 and 6, except for the connection relationship with the outside of the filter.

Next, the transfer operation from the node 121 to the node 131 in the above configuration will be described as an example. The transfer operation from the node 121 to the node 131 on the first network is the same as that in the first embodiment, and therefore its description is omitted. Therefore, the operation of the network connection device 201 will be described.
The data transmitted at the wavelength λl at the node 126 passes through the waveguide 801 in the optical branching device 202 of the network connection device 201, and the coupler 802 divides the signal intensity into two equal parts. One of them goes through the waveguide 801 as it is, then goes to the waveguide 901 of the wavelength cut filter 206, and is separated by the grating 902. Therefore, the signal of the wavelength λl is not transmitted to the waveguide 901 after the grating 902. The other passes through the wavelength pass filter 203, and the wavelength combiner 209 outputs the wavelengths λ2 and λ3 of the second network.
It merges with λ4 and is sent to the second network. The data transmitted at the wavelength λl is received at the node 130.

Next, in the transfer operation example from the node 122 to the node 106, the operation of the network connection device 201 which is different from the first embodiment will be described. The data transmitted at the wavelength λ5 at the node 126 passes through the waveguide 801 in the optical branching device 202 of the network connection device 201,
The coupler 802 divides the signal intensity into two equal parts. One of them is branched to the waveguide 803, and the signal other than the wavelength λl is cut by the wavelength pass filter 203. The other part proceeds through the waveguide 801 as it is, and proceeds to the waveguide 901 of the wavelength cut filter 206. Then, since the wavelength is not λl in the grating 902, it is not separated, and the grating 902
The signal of wavelength λ5 is transmitted to the subsequent waveguide 901, and proceeds to the optical combiner 208. The optical combiner 208 combines the signal of λl from the wavelength pass filter 204, and the data has a wavelength of λ5.
The output of the network connection device 201 remains unchanged. The subsequent process is similar to that of the first embodiment.

[0031]

Other Embodiments With the contents described above, it is possible to set the wavelength for network connection to a wavelength other than .lambda.l, and further to a plurality of wavelengths. However, in order to prevent wavelength competition at the time of multiplexing, the same wavelength must be separated from both the first and second networks. Furthermore, a wavelength pass filter,
If the wavelength demultiplexing filter and the wavelength cut filter are of variable wavelength type, it is possible to increase the options for wavelength exchange between networks. In addition, when the connection wavelength includes a wavelength in the opposite direction of data transfer, the wavelength demultiplexer for that wavelength,
A wavelength branching / merger, a filter, etc. may be added in the opposite direction. If the loss of the optical signal becomes a problem, an optical amplifier may be used.

Further, in each of the above-mentioned embodiments, the node is connected to two transmission lines, but the present invention is not limited to this, and for example, a node having many signals to be transmitted and received is three.
You may make it connect to the above transmission path. Further, although the present invention is configured to multiplex a plurality of annular transmission lines by wavelength multiplexing, as a multiplexing method, a configuration of spatial multiplexing in which a plurality of cables are bundled is also possible, and a plurality of transmission media are not multiplexed. May be used for. Regarding signals, not only optical signals but also electric signals can be used. At that time, for example, when performing multiplexing by frequency multiplexing, a network connection device and a node may be configured using a frequency filter or the like.

[0033]

As described above, by providing the filter or the like in the network connecting device for connecting the two networks as described above, the structure of the network connecting device is simplified and the power supply is not required. There is.

[Brief description of drawings]

FIG. 1 is a diagram showing a node connection device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing node connections in the embodiment.

FIG. 3 is a diagram showing a configuration of a wavelength demultiplexing filter according to the first embodiment.

FIG. 4 is a diagram showing a node connection device according to a second embodiment of the present invention.

FIG. 5 is a diagram showing an optical branching device according to a second embodiment.

FIG. 6 is a diagram showing a wavelength cut filter according to a second embodiment.

FIG. 7 is a diagram showing a configuration of a node.

FIG. 8 is a diagram showing a network connection device in a conventional example.

FIG. 9 is a diagram showing node connection in a conventional example.

[Explanation of symbols]

 101, 102 Wavelength demultiplexing filter 103, 104, 208, 209 Combiner 105, 201 Network connection device 106-133 node 202, 205 Brancher 203, 204 Wavelength pass filter 206, 207 Wavelength cut filter 701, 703, 801, 803 Waveguide 702,902 Grating 802 Coupler

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location H04L 12/28

Claims (11)

[Claims] 1. A network connection device for connecting a first network and a second network, each of which comprises a plurality of transmission lines and a plurality of nodes each having a number of transmission / reception units smaller than the number of the transmission lines,
To take out one or a plurality of transmission lines in the first network and insert them into the second network, and to prevent the taken out transmission lines from being transmitted over the connection device on the first network. The first means and a single or a plurality of transmission paths that are the same as the transmission path extracted by the first means in the second network are extracted and inserted into the first network, and the extracted transmission path is the connection device. And a second means for preventing transmission over the second network over the network connection device. 2. The network connection device according to claim 1, wherein the plurality of transmission lines are ring-shaped transmission lines in which channels are multiplexed. 3. The network connection device according to claim 2, wherein the plurality of transmission lines are wavelength-multiplexed annular transmission lines. 4. The first extracting means for extracting one or a plurality of transmission paths in the first network and inserting them into the second network, and the transmission extracted by the first extracting means. A first blocking means for preventing a route from being transmitted over the connection device over the first network, the second means comprising:
Second take-out means for taking out one or a plurality of transmission lines identical to the transmission line taken out by the first take-out means in the network and inserting them in the first network; and take-out by the second take-out means. 2. The network connection device according to claim 1, further comprising a second cutoff unit for preventing the transmission path from being transmitted over the connection device over the second network. 5. The first extracting means extracts the wavelength or wavelengths in the first network and inserts the wavelength into the second network, and the wavelength extracted by the first extracting means A first optical blocking means for preventing transmission over the first network over the connection device, and the second means is the first extracting means in the second network. A second extracting unit that extracts a single wavelength or a plurality of wavelengths that are the same as the extracted wavelengths and inserts the wavelengths into the first network, and a wavelength extracted by the second extracting unit exceeds the second connection device. The network connection device according to claim 3, further comprising a second light blocking unit for preventing transmission on the network. 6. A first and second network comprising a plurality of transmission lines and a plurality of nodes having a number of transmission / reception units smaller than the number of the transmission lines, and a network connection device for connecting the first and second networks. In a network with
The network connection device extracts one or a plurality of transmission lines in the first network and inserts the transmission line in the second network, and the extracted transmission line is transmitted over the connection device on the first network. And a first means for preventing the first network in the second network.
A single or a plurality of transmission lines that are the same as the transmission lines extracted by the means are extracted and inserted into the first network, and the extracted transmission paths extend beyond the connection device.
And a second means for preventing transmission over the network. 7. The network according to claim 6, wherein the plurality of transmission lines are ring-shaped transmission lines in which channels are multiplexed. 8. The network according to claim 7, wherein the plurality of transmission lines are ring-shaped transmission lines in which wavelengths are multiplexed. 9. In a network having first and second networks, each of which comprises a plurality of transmission paths and a plurality of nodes having a smaller number of transmission / reception units than the number of the transmission paths, one or more of the first networks. The transmission line is taken out and the second
Or a plurality of transmission lines that are the same as the extracted transmission lines in the second network while being prevented from being transmitted on the first network over the connection part while being inserted into the second network. Of the transmission line is inserted into the first network, and the extracted transmission line is connected to the first and second networks while preventing the transmission line from being transmitted over the second network. A network connection method characterized by: 10. The network connection method according to claim 9, wherein the plurality of transmission lines are ring-shaped transmission lines in which channels are multiplexed. 11. The network connection method according to claim 10, wherein the plurality of transmission lines are wavelength-multiplexed annular transmission lines.