JPH1141270A - Optical wavelength multiple network system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evade the discontinuation of a network even against the occurrence of a fault, to improve the using efficiency of wavelength and to easily increase the nodes by setting properly the pass bands of variable length filters placed at the nodes which are arranged in a star shape around a star coupler and forming the network in a ring shape. SOLUTION: When an optical signal is inputted to a certain node device 2 from an ATM switch 3 of a lower order hierarchy, the optical signal is converted into an electric signal by an O/E(optical/electric) converter 2a. The electric signal is converted into an optical signal of the prescribed wavelength set for each node by an electric/optical modulator LD1 2b and outputted to a star coupler 1. The optical signals which are multiplexed by the coupler 1 are inputted to all nodes 2, and every variable wavelength filter 2C having the pass wavelength inherent to each node 2 processes only the optical signal that is coincident with the pass wavelength. The selected optical signal is converted into an electric signal by an O/E converter O/E 2d ana then converted again into an optical signal by an electric/optical modulator LD2 2e. This optical signal is outputted to the switch 3. Thus, it is not required to use the different wavelengths for the transmission and reception respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wavelength division multiplexing network system for realizing packet communication using optical signals.

[0002]

2. Description of the Related Art In recent years, a wavelength division multiplexing network system has attracted attention as an optical network system suitable for high speed and large scale. Here, a wavelength multiplexing network system that has been conventionally proposed will be described by taking the system of Document 1 as an example.

Reference 1: "Optically Restorable WDM Rin
g Network Using Simple Add / Drop Circuitry '' Bernard Glance, et al, Journal of Lightwave Techno
logy, vol.14, no.1, pp.2453-2456, nov 1996. This wavelength division multiplexing network system consists of two ring-shaped transmission lines with different transmission directions, and the two transmission lines and an optical switch. ATM (Asynchronous Transfer Mode) for distributing transmission cells to node devices connected via
It comprises a switch and an optical coupler for branching the output of the ATM switch.

[0004] The feature of this network system is that even if a failure or the like occurs, the network system can be used without stopping by switching the connection relationship between each node device and the ring transmission line before and after the failure. What you can do.

[0005]

However, in the wavelength-division multiplexing network system having the above-described configuration, the number of connectable nodes is limited to the number of ATM switch lines, so that the system scale is increased and the number of node devices is increased. Not suitable.

For example, if the switching capability of an ATM switch is 2.5 Gbps and the transmission speed per connected line is 155 Mbps, only 16 node devices can be connected.

Further, in this network system, different wavelengths are used for the transmission wavelength and the reception wavelength, so that the number of wavelengths is twice as large as the number of nodes, and the number of wavelengths used is increased. , A multiplicity of about 32 waves is required).

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and proposes a wavelength division multiplexing network system in which the system can be easily scaled up and the number of wavelengths to be used does not need to be greater than the number of nodes. It is assumed that.

[0009]

According to the present invention, there is provided an optical fiber having a star-like physical network configuration in which a plurality of node devices are arranged in a star shape around a star coupler. The wavelength multiplexing network system is provided with the following means.

That is, each of the plurality of node devices converts (1) an electric signal into an optical signal having a wavelength unique to each node device and outputs the converted signal; (2)
Filter means for passing only an optical signal of a specific wavelength set in advance so that the logical network configuration is ring-shaped among optical signals output from the electrical / optical conversion means in each node device and multiplexed in the star coupler; (3)
An optical / electrical conversion means for converting an optical signal passing through the filter means into an electric signal is provided.

As described above, according to the present invention, a network system having a physically star configuration is logically constructed by appropriately setting a wavelength to be passed through the filter means. Thus, even if a failure occurs in a node device or the like, it is possible to avoid a communication failure only by changing the passing wavelength of the filter means.

[0012] In addition, since optical signals having the same wavelength are used for communication both upstream and downstream, the wavelength utilization efficiency is higher than in the past, and the number of node devices that can be connected to the network system is reduced due to the limitation of multiplexable wavelengths. Many can be applied to large network systems.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

(A) First Embodiment Hereinafter, a first embodiment of a wavelength division multiplexing network system according to the present invention will be described with reference to the drawings. In the following description, it is assumed that an ATM network system is connected to a lower hierarchy of each node device.

(A-1) Configuration of Wavelength Division Multiplexing Network System and Node Device Constituting It The wavelength division multiplexing network system according to the present embodiment comprises:
It is characterized in that a network system that is physically configured in a star configuration is used as a logical configuration in a ring configuration.

Hereinafter, the configuration of a wavelength division multiplexing network system having such a configuration will be described. FIG. 1 shows the first
FIG. 3 is a block diagram illustrating a physical configuration of a wavelength division multiplexing network system according to the embodiment.

As shown in FIG. 1, this wavelength division multiplexing network system comprises an optical branching circuit (hereinafter, referred to as a star coupler) 1, a plurality of node devices 2 arranged in a star shape around the optical branching circuit, and each node. It comprises a plurality of ATM switches 3 connected below the device.

The node device 2 has a configuration unique to this embodiment. The input / output terminals a and b used for connection to the ATM switch 3 and the input / output terminals c and c used for connection to the star coupler 1 are provided. d and optical / electrical converter (O / E) 2
a and 2d and an electric / optical converter (LD1, LD2) 2b
And 2e, and a variable wavelength filter 2c.

The transmission system of the node device 2 includes an input terminal a, an optical / electrical converter (O / E) 2
a, an electric / optical converter (LD1), and an output terminal 2c, and a receiving system includes an input terminal d, a tunable wavelength filter 2
a, an optical / electrical converter (O / E) 2d, and an electric / optical converter (LD2) 2e.

The optical / electrical converter (O / E) 2a and the electric / optical converter (LD2) 2e are interface circuits for connecting the node device 2 to the ATM switch 3, respectively.

The former means is used to convert an optical signal input from the input terminal a into an electric signal. On the other hand, the latter is a means used to convert an electric signal into an optical signal and output it to the output terminal b,
It oscillates a light wavelength in the band.

Incidentally, this interface circuit is a circuit used when the node device 2 and the ATM switch 3 are connected by an optical signal, and is used when the node device 2 and the ATM switch 3 are connected by an electric signal interface. Is unnecessary.

However, when an electric signal is used for the interface, the error rate increases when the transmission speed of the interface portion is high. Therefore, in the case of the present embodiment, the connection between the ATM switch 3 and each node device 2 is made. Optical signals are used for the interface.

The electric / optical converter (LD1) 2b has 155
A light emitting unit that oscillates at a predetermined optical wavelength in the 0 nm band, and has a unique wavelength W1 to Wn assigned to each node device.
Oscillates at

The variable wavelength filter 2c is a filter that allows only an optical signal having an arbitrarily set wavelength to pass, and has a configuration in which the passing wavelength can be changed as appropriate. In addition,
In this embodiment, the passing wavelength of the tunable wavelength filter 2c is set so that the logical network configuration has a ring shape.
The passing wavelength of each node device is set so as not to overlap with the passing wavelength of another node device.

The optical / electrical converter (O / E) 2d is a variable wavelength filter 2c of the optical signal input from the input terminal d.
This is a means used to convert an optical signal that has passed through to an electrical signal.

(A-2) Cell switching operation as viewed from the physical network Next, the cell switching operation in the wavelength multiplexing network system having the above configuration will be described. Here, a description will be given assuming that an optical signal of the 1310 nm band is input to a certain node device from the ATM switch 3 located in the lower hierarchy.

When this optical signal is inputted from the input terminal a, it is converted into an electric signal in the optical / electrical converter (O / E) 2a. This electric signal is converted to an electric / optical converter (LD)
1) converted into an optical signal of 1550 nm band in 2b,
The signal is output from the output terminal c to the star coupler 1.

Each output wavelength of the optical signal differs depending on the node device 2 from which the signal is output. Here, the wavelength interval differs depending on the wavelength multiplexing technology, but in the case of the current system, the interval is 0.8 nm. In this way, optical signals having wavelengths slightly shifted from each node device are output and multiplexed by the star coupler 1.

Each of the optical signals multiplexed by the star coupler 1 is input to all the node devices 2 connected to the star coupler 1. However, since the variable wavelength filters 2c of the respective node devices 2 each have a unique pass wavelength, only the optical signal having the wavelength that matches the pass wavelength is actually processed in the node device 2.

The selected optical signal is supplied to an optical / electrical converter (O
/ E) After being converted into an electric signal in 2d, it is input to an electric / optical converter (LD2) 2c located in the next stage, and
It is converted to an optical signal in the 10 nm band.

Finally, the data is output from the output terminal b to the ATM switch 3 located below the output terminal b. As described above, in the wavelength division multiplexing network system having this configuration, it is not necessary to use separate wavelengths for the transmission wavelength and the reception wavelength, so that it is possible to connect as many node devices as the number of wavelengths to be multiplexed to the network system. is there.

In the optical network system, since an optical signal is attenuated in each of the optical devices constituting the system, a method of compensating for the attenuation by an optical amplifier is adopted. However, an optical amplifier has a limitation on an optical wavelength band that can be amplified, and is currently about 30 nm.

Therefore, within this range, the wavelength interval is 0.8 n
If wavelength multiplexing is performed with m, the multiplicity is about 32 waves. That is, 32 node devices can be connected to the network.

(A-3) Method of Setting Variable Wavelength Filter Next, a specific method of setting the passing wavelength of the variable wavelength filter 2c used in this embodiment will be described. As described above, in this embodiment, by setting the passing wavelength of each variable wavelength filter 2c so as not to overlap with the passing wavelength of another node device, the logical structure is changed to the ring shape shown in FIG. I am trying to become.

For example, in the case of the ring configuration of FIG. 2, in order to make the transmission direction clockwise (clockwise), the transmission wavelength of the tunable wavelength filter 2c of each node device 2 is set counterclockwise with respect to each node device. Is set to the wavelength at which the node device located on the side (left side) oscillates. As described above, by uniquely setting the selected wavelength, the order of the ring-shaped node devices can be freely changed without changing the physical configuration.

(A-4) Cell Switching Operation Seen from the Logical Network Next, the data transfer operation between node devices will be specifically described with reference to FIG. Here, a case where data is transferred from terminal # 1 connected to node device # 2 to terminal # 2 connected to node device # 4 will be described.

First, the destination of the cell output from the terminal # 1 is determined by the ATM switch 3 of the node device # 2, and is output to the transmission side of the node device # 2.

Next, this cell is transferred from the node device # 2 to the node device # 3, and output to the ATM switch 3 connected to the node device # 3.

The cell whose destination is determined by the ATM switch 3 is returned to the node device # 3 (output to the transmission side).

Further, the cell is transferred from the node device # 3 to the node device # 4, and is output to the ATM switch 3 connected to the node device # 4.

The cell whose destination is determined by the ATM switch 3 is finally output to the terminal # 2.

As described above, in the data transfer, the data reaches the target terminal via the node device and the ATM switch.

(A-5) Method of Switching Path (Optical Bus) Next, a method of switching paths when a failure or the like occurs will be described. There are two kinds of causes for the path switching. One is due to node failure and the other is due to traffic (load) concentration.

First, a method of switching paths in the case of a node failure will be described with reference to FIGS. For example, when a failure occurs in the node device # 3 in FIG. 4, the communication path from the node device # 2 to the node device # 4 is interrupted. That is, the network stops.

In this case, the problem can be solved if the node device # 3 can be removed from the transfer path. As for the method of removal, the passing wavelength of the variable wavelength filter 2c of the node device # 4 is simply switched to the wavelength oscillated by the node device # 2 without changing the passing wavelength of the node device # 2.

When the switching is performed in this manner, it appears that the data is physically transferred from the node device # 2 to the node device # 3 and from the node device # 3 to the node device # 4. Device # 3 as shown in FIG.
2 to node device # 4.

Next, a method of switching paths when traffic is concentrated will be described with reference to FIGS. In FIG. 6, when communication from node device # 1 to node device # 7, communication from node device # 2 to node device # 6, and further communication from node device # 3 to node device # 5 occur (however, It is assumed that each communication has a high load.), And the load concentrates on the node device # 5. In this case, depending on the processing capacity of the ATM switch 3, there is a possibility that all communications cannot be processed (packet loss occurs).

To avoid such load concentration,
A method of changing the order (transfer order) of the node devices is adopted. That is, as shown in FIG. 7B, node device # 1 → node device # 7 → node device # 2 → node device # 6 → node device # 3 → node device # 4 → node device # 5 → node device # Change the order to 8. In this way, if the transfer order between the node devices is changed, concentration of the load can be avoided.

This switching is performed by setting the passing wavelength of the variable wavelength filter 2c forming the node device # 7 to the oscillation wavelength W1 of the node device # 1, and changing the passing wavelength of the variable wavelength filter 2c forming the node device # 2 to the node device # 7 oscillation wavelength W7
It just needs to be set in such a way.

(A-6) Effects of the First Embodiment As described above, according to the first embodiment, the light passes through the variable wavelength filters 2c of the respective node devices arranged in a star shape with the star coupler as the center. By setting the wavelength appropriately and making the logical network configuration ring-shaped,
Even if a failure occurs, the logical network configuration can be changed to prevent the network from being stopped.

Further, it is possible to realize a large-scale wavelength-division multiplexing network system in which node devices corresponding to the number of wavelength-division multiplexes can be connected.

This makes it possible to realize a system which can be applied to a high-speed and large-scale network, and which can be easily added if the number of multiplexed wavelengths is limited.

(B) Second Embodiment Next, a wavelength multiplexing network system according to a second embodiment of the present invention will be described with reference to the drawings.

In the network system according to the first embodiment described above, there is a problem of who switches the variable wavelength filter. For example, if each user performs the packet separately, a packet passing through the node device may be lost (it does not arrive at the destination node device by any time). Therefore, it is necessary to switch all of them at once.

Therefore, in the second embodiment,
A server is provided on the network system, and the server switches the passing wavelengths of all the variable wavelength filters 2c.

(B-1) Configuration of Wavelength Division Multiplexing Network System and Node Units Constituting It In FIG. 8, the same parts as those in FIG. 1 are assigned the same reference numerals as those in FIG. The configuration of the node device and the configuration of the network system will be described. As can be seen from FIG. 8, in the second embodiment, the server
It has a configuration in addition to the configuration of the embodiment.

First, the configuration of the server is as follows.
It is composed of a terminal 5 for performing software processing and a node device 4 for performing hardware processing. Since the software configuration and algorithm are not directly related to the present invention, the description of the internal configuration of the terminal 5 and the software is omitted.

Here, the configuration of the node device (S) 4 used by the server will be described. As shown in FIG.
The node device (S) 4 is an electric / optical converter (LD2) 4
a, variable wavelength filter 4b, optical / electrical converter (O / E)
4c and a demultiplexer (DEMUX) 4d.

Among them, the electric / optical converter (LD2)
The electric / optical converter (LD) described in the first embodiment
Similar to 2), it is a light emitting unit that oscillates at a light wavelength in the 1310 nm band. The variable wavelength filter 4b is filter means provided for receiving an optical signal from each node device, and its passing wavelength can be periodically switched. This is different from the first embodiment.

A demultiplexer (DEMUX) 4
d is means for separating and extracting cells multiplexed in the ATM switch 3. Although not shown in the figure, a selector is provided at the subsequent stage of the demultiplexer (DEMUX) 4d, and the demultiplexer (DE
MUX), the separated cells are selected for each channel.

FIG. 9 shows the receiving operation of the server. As shown in FIG. 9, the server includes wavelengths W1 to Wn of each node device.
By periodically selecting (scanning) a channel allocated to each terminal, the terminal device operates to receive information on all terminals belonging to a lower layer of each node device.

Here, there is no special rule for the order of selection. For example, a frequently selected item may be selected a plurality of times during one cycle. Conversely, the infrequent one may be selected once every two cycles. That is, the efficiency of the network can be improved by adjusting the number of selections in one cycle according to the respective frequencies.

Next, the configuration of the node device 2 provided on the user side will be described. The configuration of the node device 2 is basically the same as the configuration of the first embodiment, but differs in that a circuit that enables collective control from a server is added to the configuration.

That is, in the node device 2 of this embodiment, in addition to the configuration of the first embodiment, a splitter 2f, an optical / electrical converter (O / E) 2g,
The configuration includes a control circuit 2h and an electric / optical converter (LD2).

Of these, the splitter 2f is 1310n
This is a spectral unit for separating the light wavelength in the m band from the light wavelength in the 1550 nm band. Here, the optical wavelength in the 1310 nm band is a signal for a control system, and the optical wavelength in the 1550 nm band is a signal for a data system.

The control circuit 2h is configured to change the setting of the passing wavelength of the variable wavelength filter 2c and control the switching of the ATM switch 3 based on a control signal from the server. Therefore, the control circuit 2h has a function of dividing the input signal into a control signal for the variable wavelength filter 2c and a control signal for the ATM switch 3 based on the header information.

FIG. 10 shows the internal configuration of the control circuit 2h.
The control circuit 2h includes a header determination circuit 2h1, a selector 2h
2. It is composed of four circuits, a cell (packet) separation circuit 2h3 and a switching control circuit 2h4.

Here, the header determination circuit 2h1 is a means for transmitting the input cell to the subsequent selector 2h2 and controlling the selector 2h2 based on the header information of the cell.

The selector 2h2 includes a header determination circuit 2h1
Is a means for switching the output destination of an input cell based on the above control. If the input cell is a cell for controlling the variable wavelength filter 2c, the output is output to the cell separation circuit 2h3 and the ATM switch 3 is controlled. If it is a cell,
The signal is output to an electric / optical converter (LD2) 2i. The converted optical signal is provided to the ATM switch 3.

The cell separation circuit 2h3 is a circuit for extracting control data from control cells of the variable wavelength filter 2c.
The switching control circuit 2h4 generates a switching signal for switching and controlling the passing wavelength of the variable wavelength filter 2c based on the extracted control data, and outputs this.

With the above configuration, the logical system configuration of this wavelength division multiplexing network system is as shown in FIG. As can be seen from a comparison with FIG. 2 showing the logical configuration of the network system according to the first embodiment, in the case of the network system according to the second embodiment, the user-side nodes connected in a ring shape Each of the devices # 1 to # 8 has a configuration in which all of the devices are connected to the node device (S) 4 on the server side.

(B-2) Switching Operation of Passing Wavelength Subsequently, the switching operation of the wavelength by the wavelength division multiplexing network system according to the second embodiment will be described. The operation of exchanging optical cells is the same as in the first embodiment, and a description thereof will be omitted.

Here, it is assumed that the server has received an alarm signal from the node device and has detected an abnormality in the node device.
In this case, the server periodically scans all channels of each wavelength based on FIG. 9 to grasp the traffic situation at that time, and at the timing when communication is interrupted,
The variable wavelength filter 2c is provided to the node device 2 on the user side.
The control cell for instructing the switching of the passing wavelength is transmitted. In the case of the ATM network system, data transfer is performed after setting up a call.
A control cell for controlling the passing wavelength of the variable wavelength filter 2c is transmitted.

Here, the data of the control cell to be transmitted includes information of the node device to be switched and wavelength information to be switched by the node device.

FIG. 12 shows a case where a failure has occurred in the node device # 3. The node device # 3 outputs an alarm signal, and the server receives this signal. Then, the traffic is confirmed by scanning, and a switching signal is output to the node device # 4 at an appropriate timing. The node device # 4 changes the passing wavelength of the tunable wavelength filter 2c from W3 to W2 according to a signal from the server. This avoids a network outage.

It is difficult to switch the route (optical bus) according to the traffic situation. This is because the transmission path is momentarily interrupted at the time of switching. Therefore, switching based on traffic concentration must be performed with some prediction.

(B-3) Advantages of the Second Embodiment As described above, according to the second embodiment, the server manages the entire network system, and when an abnormality occurs, the server operates on the user side. , The passing wavelength of the tunable wavelength filter 2c of the node device 2 is switched under the management thereof, so that a node device failure can be quickly and accurately avoided.

(C) Third Embodiment Next, a third embodiment of the wavelength division multiplexing network system according to the present invention will be described with reference to the drawings. Note that this embodiment is an embodiment based on the system configuration according to the above-described second embodiment, and specifically, is an embodiment regarding a communication method for realizing communication between arbitrary user terminals. . Therefore, the basic configuration and operation contents are the same as those of the second embodiment.

(C-1) Communication System Here, a communication procedure between user terminals will be described with reference to FIGS. 20 and 21. FIG. 20 shows a communication path formed between the server and the user terminal.
Reference numeral 1 denotes an outline of a communication procedure executed when the user 1 transfers data to the user 2.

The server periodically switches the combination of the node device (wavelength) and the channel to be received by periodically switching the selectors of the variable wavelength filter 4b and the demultiplexer (DEMUX) 4d, and is specified by the combination. Scans for communication data from the user terminal to the server.

The user terminal 1 keeps transmitting the requested cell repeatedly until the server notifies the server that the requested cell has been received.

Eventually, the channel received by the server matches the channel of the user terminal 1, and the requested cell of the user terminal 1 is received.

Then, while continuing the scanning operation, the server sends an ACK (reception response) notifying the user terminal 1 that the request cell from the terminal has been normally received to the user terminal 1 in a multicast manner. Respond to 1.

Upon receiving this ACK, the user terminal 1 stops transmitting the requested cell.

On the other hand, following the transmission of the ACK, the server transmits a setting cell (notification of request and setting of the ATM switch) necessary for setting a call by a multicast method. When these arrive at both user terminals 1 and 2, a call is set up between them.

After that, the user terminal 1 starts transferring data to the user terminal 2. The communication procedure executed at the time of communication between users has been described above.

(C-2) Effect of Third Embodiment As described above, according to the third embodiment, all user terminals can access the server, so that a call can be set prior to the start of communication. Becomes

Further, since communication with the server can be performed within the same network, installation of the network is simplified.

(D) Fourth Embodiment Next, a wavelength multiplexing network system according to a fourth embodiment of the present invention will be described with reference to the drawings. Note that this embodiment is also an embodiment based on the system configuration according to the above-described second embodiment, and other configurations except for the difference in the configuration of the server node device are described in the second embodiment.
This is the same as the configuration of the embodiment. Therefore, in the following description, only the differences will be described.

(D-1) Configuration of Server Node Device FIG. 15 shows the server node device (S) according to the present embodiment.
4 'is shown. FIG. 15 shows the same or corresponding parts in FIG. 8 with the same or corresponding reference numerals.

As can be seen from FIG. 15, the server node device (S) 4 'according to this embodiment identifies the cell header in addition to the configuration of the server node device (S) described in the second embodiment. The difference is that a virtual channel (VC) filter 4e, a buffer 4f, a selector 4g, and a monitor circuit 4h for monitoring a traffic situation are newly provided.

The demultiplexer (DEMUX) 4
The cell of each channel branched in d is connected to the VC filter 4e and the selector 4 via the corresponding signal line.
g.

The buffer 4f is provided to prevent cell discard when a plurality of cells addressed to the server arrive at the same time.

(D-2) Reception Operation of Server Node Device Next, the operation in the wavelength multiplexing network system having the server node device having the above configuration will be described. However, the operation contents other than the server node device 4 'are the same as those of the second embodiment, and therefore, only the differences will be described here.

A plurality of wavelengths multiplexed on the star coupler 1 are input to the variable wavelength filter 4b constituting the server node device 4 '. Here, the variable wavelength filter 4
Since the passing wavelength b is periodically switched by a control signal provided from the server terminal 5, only one of the multiplexed wavelengths is periodically switched to the subsequent optical / electrical converter ( O / E) 4c.

By the way, at each wavelength, cells of a plurality of channels corresponding to each terminal belonging to a lower layer of the node device corresponding to the wavelength are multiplexed.
These are separated in a demultiplexer (DEMUX) 4d.

The multiplex cells separated by the demultiplexer (DEMUX) are provided to the VC filters 4e and 4g. Here, the VC filter 4e passes only cells destined for the server from the cell header. That is, as can be seen from FIG. 16, only necessary cells are extracted from a large amount of data (cells “1”, “2”, “3”, “4”) are extracted, and cells indicated by oblique lines are discarded. .).

This means that in the case of the fourth embodiment, it is not necessary to scan all the channels as in the second embodiment. Therefore,
The scan time is only the time of the wavelength scan performed by the variable wavelength filter 4b, and higher-speed operation can be guaranteed as compared with the second embodiment. For example, if the wavelength used in the network is 16 wavelengths and the read time per wavelength is 2 ms, the time required for one cycle is 32 m
s is good.

Next, the operation of monitoring the traffic situation will be described. As described above, in the present embodiment, the multiplexed cells separated by the demultiplexer (DEMUX) 4d are input to the selector 4g. The selector 4g periodically selects each channel and selects the channel. The monitor circuit 4h counts the cells of the channel that has been set. The count result is passed from the monitor circuit 4h to the server terminal, so that the server terminal can monitor the traffic situation.

In FIG. 15, the switching signal of the selector 4g is provided from the server terminal. However, the switching signal may be provided using a timer generated in the node device. However, if provided from the server terminal, there is an advantage that the selection interval can be set flexibly.

(D-3) Effect of Fourth Embodiment As described above, according to the fourth embodiment, the scan operation in the server node device 4 'is limited to the scan of the selected wavelength, and the scan operation of the channel is performed. Since it is unnecessary to perform the scanning, the total time required for scanning can be shortened. That is, the time required for call connection can be reduced.

(E) Fifth Embodiment Next, a fifth embodiment of the wavelength division multiplexing network system according to the present invention will be described with reference to the drawings.

The wavelength division multiplexing network system according to the fifth embodiment is characterized in that the network configuration according to the first embodiment is doubled. In other words, by making the network configuration double, it is possible to achieve efficient communication by dispersing the concentration of the load, and if one system fails, the communication efficiency is improved if the other system is normal. Although it may fall, it allows access to other node devices.

(E-1) Configuration of Wavelength Division Multiplexing Network System and Node Device Constituting The Same FIG. 17 in which the same parts as those in FIG. And the configuration of the network system.

As can be seen from the above description and FIG.
The network system according to the fifth embodiment includes a double star network (on a physical network) centered on two star couplers 1.

For this reason, each node device 2 is provided with two systems of the configuration of the node device described in the first embodiment corresponding to each star network. That is,
The transmission system of the node device 2 according to the present embodiment includes a pair of optical /
It comprises electric converters (O / E) 2a1 and 2a2 and electric / optical converters (LD1, LD2) 2b1 and 2b2. The reception system of the node device 2 includes a pair of variable wavelength filters 2c1 and 2c2 and an optical / electrical converter (O /
E) 2d1 and 2d2 and an electric / optical converter (LD3, L
D4) 2e1 and 2e2.

The transmission-system electric / optical converter (LD1, LD1,
LD2) 2b1 and 2b2 are light emitting means for oscillating a light wavelength in the 1550 nm band, and the electric / optical converters (LD3, LD4) 2e1 and 2e2 in the receiving system each oscillate a light wavelength in the 1310 nm band. It is a light emitting means.

By the way, the optical / electrical converter (O /
E) 2a1 and 2a2 and an electric / optical converter (L
D3, LD4) 2e1 and 2e2 are interface circuits necessary when the interface between the node device 2 and the ATM switch 3 is an optical signal, as described in the first embodiment. This is not necessary when using an interface.

Note that also in the case of this embodiment, the interface between the node device 2 and the ATM switch 3 includes:
Description will be made assuming that an optical signal is used. This is because if the transmission speed of the interface part is high, the error rate increases.

(E-2) Cell Switching Operation Seen from the Physical Network Next, an optical cell switching operation performed in the wavelength division multiplexing network system having the above configuration will be described.

[0111] Optical signals of the 1310 nm band are independently input to the respective node devices from the ATM switches 3 located in the lower hierarchy via different systems. The optical signal is transmitted to an optical / electrical converter (O /
E) Once converted into an electrical signal using 2a1 and 2a2, the electrical / optical converters (LD1, LD2) 2b1 and 2
The light signal is converted into an optical signal in the 1550 nm band by b2 and output to the star coupler 1.

Here, the electric / optical converters (LD1, LD
2) The wavelengths of the optical signals output from each of 2b1 and 2b2 are the same. The wavelength of the optical signal is assigned a unique wavelength for each node device. The wavelength interval of the optical signal output from each of the node devices 2 is 0.8 nm at present, although it depends on the wavelength multiplexing technology.

As described above, each node device outputs an optical signal having a slightly different wavelength, and the two star couplers 1
Multiplexed separately above.

As described above, the optical signals W1 to Wn multiplexed on the star coupler 1 are input from the star coupler 1 to the node device 2, but as in the case of the first embodiment, each node Variable wavelength filter 2c1 constituting device
And 2c2, only the optical signal having the wavelength matching the passing wavelength is selected and passed through the filter.

Then, the selected optical signal is converted into an electric signal by the optical / electrical converters (O / E) 2d1 and 2d2, and the electric / optical converters (LD3, LD4) 2e respectively.
At 1 and 2e2, the optical signal is converted into an optical signal of the 1310 nm band and output to the ATM switch 3. As a matter of course, also in the third embodiment, it is possible to connect the node devices for the number of wavelength multiplexing.

In the optical network system, since an optical signal is attenuated in each optical device constituting the system, a method of compensating for the attenuation by an optical amplifier is adopted. However, the optical amplifier has an optical wavelength band limit that can be amplified, and is currently about 30 nm.

Therefore, within this range, the wavelength interval is 0.8 n
If wavelength multiplexing is performed with m, the multiplicity is about 32 waves. That is, 32 node devices can be connected to the network.

(E-3) Setting Method of Variable Wavelength Filter As described in the first embodiment, the network system according to this embodiment includes a transmission wavelength of the variable wavelength filter 2c constituting each node device. Is appropriately selected, each node device can be logically connected in a ring shape.

In other words, in the case of the third embodiment, as shown in FIG.
It has a double ring shape. However, in the case of FIG. 18, two variable wavelength filters 2 constituting each node device are used.
Different wavelengths are set as the passing wavelengths of c1 and 2c2 so that the transmission directions in the logical network are opposite to each other.

Of course, the selection of the passing wavelength is optional, and the two variable wavelength filters 2c1 and 2c2 may have the same passing wavelength. In any case, the variable wavelength filter 2
If the passing wavelengths of c1 and 2c2 are changed, the logical network configuration can be changed freely without changing the physical network configuration.

(E-4) Cell Switching Operation Seen from the Logical Network Next, a data transfer operation between node devices will be described with reference to FIG. Here, terminal # 1 connected to node apparatus # 2 and terminal # 1 connected to node apparatus # 4
A case in which data is transferred bi-directionally between the two will be described.

First, the cell output from the terminal # 1 has its destination determined by the ATM switch 3 of the node device # 2, and is output clockwise (clockwise) to the node device # 2. The destination of the cell output from one terminal # 2 is determined by the ATM switch 3 of the node device # 4, and the cell is output counterclockwise (counterclockwise) to the node device # 4.

As described above, the cell output from the terminal # 1 is transferred from the node device # 2 to the node device # 3, and is transferred to the ATM switch 3 connected to the node device # 3.
Is output to On the other hand, the cell output from terminal # 2 also
The data is transferred from the node device # 4 to the node device # 3, and output to the ATM switch 3 connected to the node device # 3.

At the ATM switch 3 of the node device # 3,
When the destination is determined from the header of each cell, the cell is returned to the corresponding transmission system of the node device # 3 (the cell output from the terminal # 1 is transmitted clockwise (clockwise) to the transmission system of the node # 3, The output cell is output to the counterclockwise (counterclockwise) transmission system.)

Further, the cell output from terminal # 1 is
The data is transferred from the node device # 3 to the node device # 4, and output to the ATM switch 3 connected to the node device # 4. The cell output from the terminal # 2 is transferred from the node device # 3 to the node device # 2, and output to the ATM switch 3 connected to the node device # 2.

Then, the cell output from terminal # 1 is
Finally, the destination is determined by the ATM switch 3 connected to the node device # 4, and reaches the terminal # 2. on the other hand,
The destination of the cell output from the terminal # 2 is finally determined by the ATM switch 3 connected to the node device # 2, and reaches the terminal # 1.

Thus, the cell output from the terminal is
A desired terminal is reached via one or more node devices 2 and the ATM switch 3. Note that the above-described bidirectional data transfer can be performed simultaneously between different node devices in the double ring as between the terminals 3 and 4 shown in FIG.

(E-5) Method of Switching Path (Optical Bus) Next, a method of switching paths when a failure or the like occurs will be described. There are two kinds of causes for the path switching. One is due to node failure, the other is traffic (load)
Is due to the concentration of

First, a method of switching paths in the case of a node failure will be described with reference to FIGS. For example, if the clockwise (clockwise) reception system or transmission system of the node device # 7 in FIG.
6 to the node device # 8 is interrupted.
That is, the clockwise (clockwise) network stops.

In this case, if the node device # 7 can be removed from the transfer path, the problem can be solved. To remove, if no change is made to the passing wavelength of the node device # 6 and the selected wavelength of the clockwise (clockwise) variable wavelength filter 2c of the node device # 8 is switched to the wavelength oscillated by the node device # 6. good.

When switching is performed in this manner, it looks as if it is physically transferred from node device # 6 to node device # 7 and from node device # 7 to node device # 8, but is logically shown in FIG. Thus, the node device # 7 is removed from the clockwise (clockwise) ring, and the data is transferred from the node device # 6 to the node device # 8.

Since no failure has occurred in the counterclockwise (counterclockwise) ring, the terminal connected to the node device # 7 is not disconnected from the network.

Next, a method of switching paths when traffic is concentrated will be described with reference to FIGS. 22 and 23. In FIG. 22, node devices # 1 and #
6, communication from node device # 8 to node device #
7, and from node device # 5 to node device # 8.
When the communication to the network device occurs (however, each communication has a high load), the load is concentrated between the node device # 7 and the node device # 8 whose paths are overlapped, and a cell loss may occur. .

In order to avoid such load concentration,
A method of changing the order (transfer order) of the node devices is adopted. That is, as shown in FIG. 23, the clockwise (clockwise) route is routed from the node device # 1 to the node device # 2 to the node device # 3.
→ Node device # 4 → Node device # 5 → Node device # 7 →
Node device # 8 → node device # 6, and the counterclockwise (counterclockwise) route is routed from node device # 1 → node device # 6 → node device # 8 → node device # 7 → node device # 5 → node device # 4 → node device # 3 → node device # 2. In this way, if the transfer order between the node devices is changed, concentration of the load can be avoided.

This switching is performed in the clockwise (clockwise) ring by the variable wavelength filter 2 forming the node device # 7.
c to the oscillation wavelength W5 of the node device # 5 and the node device # 6
May be set to the oscillation wavelength W8 of the node device # 8, and the passing wavelength of the variable wavelength filter 2c forming the node device # 1 may be set to the oscillation wavelength W6 of the node device # 6.

In the counterclockwise (counterclockwise) ring, the passing wavelength of the variable wavelength filter 2c forming the node device # 6 is set to the oscillation wavelength W1 of the node device # 1, and the variable wavelength forming the node device # 8. The passing wavelength of the filter 2c is set to the oscillation wavelength W6 of the node device # 6, and the passing wavelength of the variable wavelength filter 2c constituting the node device # 5 is set to the node device # 7.
May be set to the oscillation wavelength W7. At this time, the transfer order between the node devices is as shown in FIG.

(E-6) Effects of the Fifth Embodiment As described above, according to the fifth embodiment, the ring configuration is doubled, and the cell configuration is set based on the individually set transfer paths. By enabling the transfer, it is possible to further increase the degree of freedom in changing the logical network when a failure occurs in a node device or the like.

As a result, the terminal connected to the failed node device can avoid the failure without being disconnected from the network.

In addition, even when bidirectional high-load communication occurs, traffic concentration can be similarly avoided by reconfiguring an optimal logical network.

Further, since the connection of the node devices corresponding to the number of wavelength multiplexing is possible, a high-speed and large-scale network can be constructed.

(F) Other Embodiments In the above-described fifth embodiment, the case where the network system according to the first embodiment is doubled has been described. However, the present invention is not limited to this. The present invention can also be applied to a case where the network system according to the fourth embodiment is provided twice. In this case, a terminal that controls the two servers may be prepared.

In the fifth embodiment described above,
Although the network system has a double configuration, it is needless to say that the network system is not limited to this, and three or more network systems may be multiplexed.

Further, in the first to fifth embodiments described above, the case where cells are transferred has been described. However, the present invention can be applied to the case of transferring packets, the case of transferring frames, and the like.

[0144]

As described above, according to the present invention, (1) an electric signal is transmitted to each of a plurality of node devices constituting an optical wavelength division multiplexing network system by an optical signal having a wavelength unique to each node device. And (2) the optical signal output from the electric / optical conversion means in each node device and multiplexed in the star coupler in advance so that the logical network configuration becomes ring-shaped. Physically a star-type configuration comprising: filter means for passing only an optical signal of a set specific wavelength, and (3) optical / electrical conversion means for converting the optical signal passing through the filter means to an electric signal. The use of a network system that adopts a ring-type network system makes it easy to change the communication path and is suitable for large-scale network systems. It is possible to realize a heavy network system.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a physical network configuration of a wavelength division multiplexing network system according to a first embodiment.

FIG. 2 is a block diagram illustrating a logical network configuration of the wavelength division multiplexing network system according to the first embodiment.

FIG. 3 is a block diagram showing a communication path during data transfer.

FIG. 4 is a diagram illustrating an example of occurrence of a failure.

FIG. 5 is a diagram illustrating a configuration of a logical network after a selected wavelength is changed.

FIG. 6 is a diagram showing an example of load concentration.

FIG. 7 is a diagram illustrating a change in a selected wavelength and a configuration of a logical network after the change.

FIG. 8 is a block diagram illustrating a physical network configuration of a wavelength division multiplexing network system according to a second embodiment.

FIG. 9 is a chart showing the order of wavelength and channel scanning executed in the server node device.

FIG. 10 is a block diagram illustrating an internal configuration of a control circuit.

FIG. 11 is a block diagram illustrating a logical network configuration of a wavelength division multiplexing network system according to a second embodiment.

FIG. 12 is a diagram provided for conceptual description of an automatic switching operation of a logical network configuration by a server node device.

FIG. 13 is a block diagram illustrating a physical network configuration of a wavelength division multiplexing network system according to a third embodiment and a communication path between a terminal and a server.

FIG. 14 is a diagram illustrating a communication procedure executed when communication between user terminals is started.

FIG. 15 is a block diagram illustrating a configuration of a server node device used in a wavelength division multiplexing network system according to a fourth embodiment.

FIG. 16 is a diagram provided for describing operations of a VC filter and a buffer.

FIG. 17 is a block diagram illustrating a physical network configuration of a wavelength division multiplexing network system according to a fifth embodiment.

FIG. 18 is a block diagram illustrating a logical network configuration of a wavelength division multiplexing network system according to a fifth embodiment.

FIG. 19 is a diagram illustrating a communication path during two-way communication between user terminals.

FIG. 20 is a diagram illustrating an example of occurrence of a failure.

FIG. 21 is a diagram illustrating a configuration of a logical network after a selected wavelength is changed.

FIG. 22 is a diagram illustrating an example of load concentration.

FIG. 23 is a diagram illustrating an example of changing a selected wavelength.

FIG. 24 is a diagram illustrating a configuration of a logical network after a selected wavelength is changed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Star coupler, 2 ... Node device, 3 ... ATM switch, 2a, 2a1, 2a2, 2d, 2d1, 2d2, 4
c ... optical / electrical converter, 2b, 2b1, 2b2, 2e, 2
e1, 2e2, 4a ... electric / optical converters, 2c, 2c1,
2c2, 4b: variable wavelength filter, 3: ATM switch, 4, 4 ': server node device, 4d: demultiplexer, 4e: VC filter, 4f: buffer, 4g: selector, 4h: monitor circuit, 5: terminal.

Claims (7)

[Claims] 1. An optical wavelength-division multiplexing network system having a star-like physical network configuration in which a plurality of node devices are arranged in a star shape around a star coupler, wherein each of the plurality of node devices is An electrical / optical converter for converting a signal into an optical signal having a wavelength unique to each node device and outputting the optical signal; and an optical signal output from the electrical / optical converter in each node device and multiplexed in the star coupler. home,
Filter means for passing only an optical signal of a specific wavelength set in advance so that the logical network configuration has a ring shape, and optical / electrical converting means for converting the optical signal passing through the filter means to an electric signal. An optical wavelength division multiplexing network system, comprising: 2. The optical wavelength division multiplexing network system according to claim 1, wherein a packet path switching device is connected to said node device, and each node device executes routing based only on wavelength, while said packet path switching device. In the optical wavelength division multiplexing network system, switching is performed in packet units. 3. The optical wavelength-division multiplexing network system according to claim 1, wherein when there are a plurality of said star couplers, said node device includes said electric / optical conversion means, said filter means, and said optical / electric conversion means. , A plurality of sets are provided for each star coupler. 4. The optical wavelength division multiplexing network system according to claim 1, wherein the passing wavelength of said filter means can be arbitrarily changed as needed. 5. The optical wavelength division multiplexing network system according to claim 4, wherein a passing wavelength of said filter means is:
An optical wavelength division multiplexing network system, which can be appropriately changed based on a control signal from a server device connected to the star coupler similarly to the node device having the filter means. 6. The optical wavelength division multiplexing network system according to claim 5, wherein the node device converts the optical signal input from the star coupler into a user data signal and a control signal from a server device based on the wavelength. An optical wavelength division multiplexing network system comprising splitter means for distributing and outputting only a user data signal to the filter means. 7. The optical wavelength division multiplexing network system according to claim 5, wherein the server device sequentially passes an optical signal of a specific wavelength that is periodically changed from an optical signal multiplexed by the star coupler. A filter means, an optical / electrical conversion means for converting an optical signal passed through the filter means into an electric signal, and an electric signal for outputting an optical signal having a wavelength different from that of the optical signal output from each node device. And / or an optical conversion unit.