JPH10304407A - Optical exchange and optical network system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the configuration of a reception section of the optical exchange by providing a variable wavelength light source to a transmission section and providing a fixed filter for receiving a main signal that passes only an optical signal with a fixed wavelength assigned to its own exchange and a variable wavelength filter that detects an operating state of a transmission line to the reception section, to detect whether or not a wavelength of a signal going to be transmitted causes collisions. SOLUTION: A transmission section 110 of the optical exchange is provided with a variable wavelength light source, whose generated wavelength is switched depending on a destination of an optical signal. At optical filter 103 selectively passes an optical signal with a fixed wavelength, assigned to a receiver of the optical exchange. An optical filter 104 is a band-pass filter the frequency band of which is variable and selectively passes a wavelength of a signal transmitted from its own exchange, based on an instruction from a light source section 107. A transfer control section 109 discriminates whether or not a wavelength of the optical signal to be transmitted collides with a wavelength of an optical signal sent from other node and allows a transmission buffer 108 to be in standby with a transmission packet, in the case where there may be a possibility of collisions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical switching device and an optical network system, and more particularly, to an optical network system for exchanging optical packet signals and an optical switching device constituting the same.

[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.

FIG. 2 shows a configuration example of a system currently proposed as such an optical network system. FIG. 3 shows a configuration example of an optical switching device (node) used in this optical network system. In this optical network system, different transmission wavelengths are assigned to each node.

Therefore, in this optical network system, optical signals transmitted from each node at a unique transmission wavelength are multiplexed by one star coupler and transmitted to all nodes. On the other hand, the receiving unit
Pass filters corresponding to all transmission wavelengths allocated to other nodes except the own device are prepared, and optical signals of each optical wavelength are separated from a received signal.

[0005]

However, in the case of the above-described system, when the optical wavelength is separated on the receiving side, the number of nodes excluding its own device (that is, the number of optical wavelengths, and the system configuration of FIG. In this case, as shown in FIG.
) And an optical-to-electrical converter.
For this reason, when the scale of the network is increased (that is, when the number of nodes is increased), the circuit configuration such as a pass filter to be provided in each node is increased in proportion to the size, and the nodes themselves are increased in size and the product cost is increased. was there.

[0006]

[Means for Solving the Problems]

(A) In order to solve this problem, in the present invention,
An optical switching device of a wavelength division multiplexing type optical network system that multiplexes and transmits wavelength-divided optical signals has the following configuration.

[0007] That is, (1) a variable wavelength light source for switching the generation wavelength according to the destination of the optical signal is provided in the transmission unit, and (2) the fixed wavelength of the fixed wavelength allocated to the own device is provided in the reception unit. A fixed filter for receiving a main signal that passes only an optical signal and a variable wavelength filter for detecting a state of use of a transmission line that can vary the wavelength of the optical signal to be passed are provided.

As described above, since each optical switching device has a variable wavelength filter capable of selectively transmitting an optical signal of an arbitrary wavelength in its receiving section, the light passing through the variable wavelength filter can be selectively used. If the wavelength of the signal is set to the same wavelength as that used by the own device for transmission or used at the time of transmission, whether the wavelength to be used is currently used or whether the transmitted signal has a collision. Whether or not it can be identified.

As a result, in each optical switching device, the configuration of the device portion used for receiving the signal addressed to the own device can be made only the configuration for selectively receiving one wavelength assigned to the own device, The device configuration can be downsized.

(B) In order to solve such a problem,
In the present invention, an optical switching device of a wavelength division multiplexing type optical network system that multiplexes and transmits wavelength-divided optical signals has the following configuration.

That is, (1) an optical signal having a wavelength corresponding to the destination of the optical signal is generated in the transmitting section for communication, and an optical signal having a wavelength different from the wavelength assigned to each of the destinations is received. Provide a variable wavelength light source generated for the notification of the state, (2) in its receiving unit, a fixed filter for the main signal that passes only the optical signal of the fixed wavelength assigned to its own device, for notification of the reception state A fixed filter for notifying the reception state that allows only the optical signal of the assigned fixed wavelength to pass is provided.

As described above, each optical switching apparatus transmits to its receiving section whether or not the optical signal previously transmitted by itself has arrived at the destination in a normal state. By confirming by monitoring, it is possible to simplify the configuration of components necessary for detecting whether or not transmission has been performed normally.

(C) In order to solve such a problem, in the present invention, an optical network system is configured by the optical switching devices described in (A) and (B), so that the configuration of the entire system is also improved. An optical network system that can be simplified can be realized.

[0014]

[Problems to be solved by the invention]

(A) First Embodiment Hereinafter, an embodiment of an optical network system according to the present invention and an optical switching device constituting the same will be described with reference to the drawings. Here, an optical network system that wavelength-multiplexes and transmits an optical packet signal will be described.

(A-1) Network Configuration First, the configuration of the optical network system according to the embodiment will be described. FIG. 4 illustrates a configuration example of the optical network system according to the embodiment. This optical network system also has a configuration in which an optical signal output from each node 201 is input to one star coupler 202, multiplexed, and transmitted to all nodes.

This has the characteristic that the optical signal is attenuated when it is multiplexed / demultiplexed. If multiplexing / demultiplexing is performed for each node, the optical power varies and the bit This is because it causes an error.

(A-2) Wavelength Assignment Next, an optical wavelength assignment method will be described. In general, optical wavelength allocation methods include a method of allocating to a transmission wavelength (that is, a method in which the wavelength depends on the transmitting device) and a method of allocating to the receiving wavelength (that is, a method in which the wavelength depends on the receiving device). is there. In this embodiment, as shown in FIG.

However, if a wavelength is assigned to a transmission wavelength, the wavelength transmitted at each node becomes a different wavelength, so that there is an advantage that it is not necessary to consider collision with a received signal. However, in this case, the receiving unit has to monitor all optical wavelengths used in the network, and there is a disadvantage that the configuration of the receiving unit becomes large.

On the other hand, when the wavelength is allocated to the reception wavelength, the wavelength received on the reception unit side can be fixed, so that there is an advantage that the configuration of the reception unit can be simplified. However,
In this case, when signals are transmitted from different nodes to the same destination, there is a problem that signal collision occurs.

However, since signal collisions rarely occur, the optical network system according to the present embodiment employs a method of adding a means for detecting signal collision to each node and assigning it to a reception wavelength. For example, in the case of FIG. 4, a wavelength is assigned to a signal transmitted to the node 1, λ1 is assigned to a signal transmitted to the node 2, and so on.

(A-3) Node Configuration Next, the configuration of the node according to the embodiment will be described with reference to FIG.

First, the configuration of the transmitting section will be described. The transmission unit includes a light source control unit 107, a transmission buffer 108, a transfer control unit 109, an electro-optical converter (TLD) 110,
An output port 111 is provided.

Here, the transmission buffer 108 is means for adjusting the transmission timing of the transmission packet input from the packet processing unit 112. It is also used to hold a transmission packet until a collision is determined in preparation for a collision of transmission signals.

The electro-optical converter 110 is provided in the light source controller 10.
7 is a means for converting an input transmission packet into an optical signal of a wavelength assigned to the transmission destination node based on the control of 7. That is, the electro-optical converter 110 includes:
Supports all transmission wavelengths used in the network,
The wavelength can be changed according to the transmission destination.

The transfer control unit 109 determines whether the wavelength of the optical signal to be transmitted is already in use or whether a collision occurs between the transmitted optical signal and the optical signal transmitted from another node. This is a means for determining whether or not the operation is performed. Here, when there is a possibility of collision, a command is issued to cause the transmission buffer 108 to wait for the transmission packet until there is no possibility of collision.

When the occurrence of a collision is confirmed, the transfer control unit 109 instructs retransmission of the optical signal. As described above, the transmission node checks the presence / absence of the collision in the transfer control unit 109. The presence / absence of a collision is determined by the transfer control unit 109 based on whether or not the transmission packet fetched from the transmission buffer 108 and the corresponding reception packet match each other.

Next, the configuration of the receiving section will be described. The receiving unit includes an input port 101, a coupler 102, optical filters 103 and 104, optical-electrical converters 105 and 106,
It comprises a packet processing unit 112.

Here, the coupler 102 is means for splitting the received optical packet signal into two systems, a main signal addressed to the own device and a signal for collision detection. Thus, in the case of this embodiment, the number of branches is always set to two regardless of the number of nodes located on the network.

The optical filter 103 is a band-pass filter used to selectively pass an optical signal of a main signal wavelength (wavelength assigned to the own device) from optical signals of a received wavelength. . The passing characteristic is set to a characteristic unique to each node.

The optical filter 104 is a variable band-pass filter provided for monitoring the transfer state (that is, for monitoring the presence or absence of collision). That is, the optical filter 104 is a means for adjusting the pass characteristic to the same wavelength as that transmitted by the own device or the same wavelength as that transmitted, and selectively extracting the same based on an instruction from the light source control unit 107.

The packet processing unit 106 is a means for processing a received packet and a means for specifying a transmission destination and forming a transmission packet.

<A-4) Switching Operation Next, how the nodes exchange optical packet signals in the optical network system having the above configuration will be specifically described.

First, the operation performed by the transmitting node at the time of transmission will be described.

When each node functions as a transmission side, it gives the transmission packet generated by the packet processing unit 112 to the transmission buffer 108 and holds the information until the transmission control unit 109 issues a transmission start instruction.

At this time, since information on the destination to which the transmission packet is to be transmitted is given from the packet processing unit 112 to the light source control unit 107, the wavelength to be used at the time of transmission is specified based on the information. Do. The information on the wavelength is transmitted from the light source control unit 107 to the electro-optical converter 110.
Is sent to At this time, the light source control unit 107
Thus, the information of the specified wavelength is also given to the optical filter 104, and the pass band is changed to the wavelength band of the optical signal to be transmitted.

As a result, if a signal having the same wavelength as the wavelength to be transmitted (same destination) already exists on the network, the corresponding packet signal is transmitted from the optical filter 104 to the transfer control unit 109. The input state is entered, and the occurrence of a collision before transmission is prevented.

The following operation is specifically performed. For example, in the case of FIG. 4, when the node 1 transmits an optical packet signal to the node 3, the light source control unit 109 instructs both the electro-optical converter 110 and the optical filter 104 to switch the wavelength to λ3. And the wavelength is changed. Thereafter, the presence or absence of another node using the wavelength λ3 is confirmed, and if it is confirmed that the node is unused, the transmission packet is transferred from the transmission buffer 108 to the electro-optical converter 110. , The optical wavelength λ3 is converted into an optical packet signal.

Next, the operation performed by the receiving node at the time of reception will be described.

Each node always takes in the optical packet signal transmitted on the network via the input port 101 and converts the taken optical packet signal into the coupler 1.
At 02, it branches into two. Of these, one optical packet signal is input to the optical filter 103 for reception, and the other optical packet signal is input to the optical filter 104 for collision detection.

Here, in the optical filter 103, only the optical wavelength addressed to the own device passes as described above, and in the optical filter 104, only the optical wavelength immediately before or during transmission by the own device passes. . The node converts the optical packet signal thus selectively extracted into an electric signal in the corresponding optical-to-electrical converters 105 and 106, and converts the received sequence signal into a packet processing unit 112.
On the other hand, for the signal of the inspection sequence, the transfer control unit 109
Give to.

The transfer control unit 109 determines whether the received data
The data is compared with the data in the transmission buffer to determine whether the data is correct or incorrect. If the data is incorrect, it is determined that a collision has occurred, and retransmission is instructed.

(A-5) Effects of the First Embodiment As described above, according to the present embodiment, it is determined whether or not a signal of an optical wavelength to be transmitted is already used in the transmitting node. Or, by providing means for checking whether the signal content of the optical wavelength currently being transmitted is different between the time of transmission and the time of reception, it is possible to realize communication in which the optical wavelength is allocated to the reception wavelength. it can.

That is, although a variable wavelength light source is used for the transmission unit, the configuration of the reception unit only needs to select one fixed wavelength, so that the configuration of the reception unit can be simplified. Therefore, the configuration of the node itself is also simplified.

(B) Second Embodiment Next, a second embodiment of the optical network system according to the present invention and the optical switching apparatus constituting the same will be described with reference to the drawings. Note that this embodiment also relates to an optical network system that wavelength-multiplexes and transmits an optical packet signal. The difference between this embodiment and the first embodiment lies in a signal collision detection method. That is, an ACK packet signal transmitted from the receiving side to the transmitting side is used. Hereinafter, each item will be described.

(B-1) Network Configuration First, the configuration of the optical network according to this embodiment is the same as that of the first embodiment, and the description is omitted. That is, the present invention is applied to the star network configuration shown in FIG.

(B-2) Wavelength Assignment Next, an optical wavelength assignment method will be described. Also in this case, as in the case of the first embodiment, a method of allocating an optical wavelength to a reception wavelength is adopted to simplify the node configuration on the reception side.

The difference is that one wavelength is allocated for an ACK packet. The ACK packet is a packet that is notified to the sending side of a packet that has been normally received on the receiving side, and has a data length set to be extremely shorter than a packet used for communication.

(B-3) ACK Packet As described above, the ACK packet is a packet transmitted from the receiving side to the transmitting side of the optical packet when the optical packet signal arrives at the receiving side in a normal state. is there. Therefore, when the ACK packet does not arrive within a predetermined period from the transmission (when the ACK packet does not return within the timeout), it can be determined that a collision has occurred in the previously transmitted optical packet signal.

However, since the same wavelength is used for the ACK packet when the ACK packet is addressed to any node, if no care is taken, this is identified and used by the transmitting node that has received the ACK packet. Can not do it. Therefore, in the ACK packet, the serial number, the transmission address, and the destination address attached to the received optical packet signal are written as packet data, and the received ACK packet is addressed to the own device. And which data it is related to.

(B-4) Node Configuration Next, the configuration of the node according to the present embodiment will be described with reference to FIG. 5 corresponds to FIG. 1 and corresponds to the same part, and is denoted by the same reference numeral.

First, the configuration of the transmitting section will be described. The transmission unit includes a light source control unit 107, a transmission buffer 108, an electro-optical converter (TLD) 110, and an ACK processing unit 201.
And an output port 111.

The ACK processing unit 201 determines whether the transmission of the optical packet signal has been completed normally based on whether the ACK packet has been returned within a predetermined time after the transmission. The ACK processing 201 executes A
If the CK packet is not returned, it is regarded as a signal collision and the transmission buffer 108 is instructed to retransmit the signal.

Next, the configuration of the receiving section will be described. The receiving unit includes an input port 101, a coupler 102, optical filters 103 and 202, optical-electrical converters 105 and 106,
It comprises a packet processing unit 203.

The optical filter 103 selectively selects an optical signal of the main signal wavelength (wavelength assigned to the own device) from among the received optical signals of the wavelength, as in the first embodiment. It is a bandpass filter used to pass.

On the other hand, the optical filter 202 is a band-pass filter for confirming an ACK packet to which an optical wavelength is allocated separately from that for communication. Therefore, this pass characteristic
Unlike the example of the first embodiment, it is fixed.

As described above, the configuration of the node according to the present embodiment has a simple configuration as the first embodiment does not require processing such as wavelength control and data comparison. I have.

(B-5) Switching Operation Next, how the nodes exchange optical packet signals in the optical network system having the above configuration will be specifically described.

First, a transmission node generates a transmission packet. The transmission packet generated by the packet processing unit 203 is temporarily stored in the transmission buffer 108, and then, at the same time as the transmission start instruction, is transmitted to the electro-optical converter (TL).
D) Read out to 110. The electro-optical converter 110 includes
Based on the control of the light source control unit 107, the input transmission packet is converted into an optical signal of the wavelength assigned to the transmission destination node and output. The transmission packet corresponding to the optical packet signal transmitted at this time is held in the transmission buffer 108 in preparation for a later retransmission request.

On the other hand, the receiving node is connected to the input port 10
The optical packet signal received via the
, The signal is branched into two systems, one for the main signal and the other for the ACK.

Here, the optical packet signal addressed to the own device (of the wavelength assigned to the own device) is
After that, the signal is supplied to the optical-electrical converter 105 and converted into an electric signal. After this, the packet signal
The packet is processed in the packet processing unit 203, and it is determined whether or not there is an error in the received data.

Here, the packet processing unit 203 executes a process to discard a packet having an error due to a collision, and to transmit an ACK packet to a transmitting side for a normally received packet. Since the packet processing unit 203 manages the serial number of the received packet, when the same data comes (when the same serial number comes), the packet is discarded even if the reception is normal. Is performed.

By the way, at this time, the wavelength of the ACK packet transmitted from the receiving node to the transmitting node has a common wavelength for all nodes as described above. Therefore, if no allowance is made, ACK packets output from each node may collide with each other on the transmission path, and the target transmitting node may not be able to recognize the ACK packet.

Therefore, in the case of this embodiment, a method of transmitting a plurality of ACK packets at arbitrary intervals within the timeout period is adopted. For example, as shown in FIG.
Four ACK packets are notified at an arbitrary timing within a predetermined time. As a result, even if collision of ACK packets partially occurs, a transmission timing may be shifted because the interval between ACK packets is arbitrary, and at least one collision can be prevented.

However, even in this case, if a collision occurs for all ACK packets, it is assumed that no ACK packet is returned, and the corresponding data is retransmitted.

(B-6) Effects of the Second Embodiment As described above, according to the present embodiment, A
An optical wavelength is assigned to the CK packet, and the AC
Realizing communication that allocates a reception wavelength to an optical packet signal to be transmitted by checking whether or not there is a response of a K packet and determining whether or not signal collision has occurred in the optical packet signal transmitted earlier. Can be.

That is, since only two fixed wavelength filters are used on the receiving side, the configuration of the receiving unit can be simplified, and the configuration of the node itself can be simplified.

(C) Other Embodiments In the above-described embodiment, the switching system of the optical signal to be transmitted is the packet switching system. However, the present invention is applicable to both the cell switching system and the frame switching system. I can do it.

Further, in the above-described embodiment, a case has been described in which the buffer is provided only on the transmitting side and the buffer is not used on the receiving side. However, the present invention is not limited to this, and the buffer may be used on the receiving side. If the present invention
It can be applied to multi-hop networks.

[0069]

As described above, according to the present invention, in an optical switching device constituting a wavelength division multiplexing type optical network system for multiplexing and transmitting wavelength-division multiplexed optical signals, the use state of a communication path is transmitted. Side receives the optical signal transmitted by its own device again, or detects it based on the reception state signal notified from the receiving side, so that the configuration of the receiving unit is assigned to its own device. A simple configuration for receiving only the optical signal of the wavelength can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of an optical switching device used in a first embodiment.

FIG. 2 is a diagram showing a conventional network configuration.

FIG. 3 is a block diagram showing a conventional example of an optical switching device.

FIG. 4 is a diagram illustrating a network configuration according to the embodiment.

FIG. 5 is a block diagram illustrating a configuration example of an optical switching device used in a second embodiment.

FIG. 6 is a diagram illustrating transmission timing of an ACK packet.

[Explanation of symbols]

101: input port, 102: coupler, 103, 10
4, 202: optical filter, 105, 106: optical-electrical converter, 107: light source control unit, 108: transmission buffer, 1
09: transfer control unit, 110: electric-optical converter, 111:
Output ports, 112, 203 ... Packet processing unit, 201
... An ACK processing unit.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04B 10/02

Claims (6)

[Claims] In a wavelength division type optical network system for multiplexing and transmitting wavelength-divided optical signals, each optical switching device constituting a network transmits its generated wavelength to its transmission unit in accordance with the destination of the optical signal. A fixed filter for receiving a main signal that passes only an optical signal of a fixed wavelength assigned to its own device.
An optical network system, comprising: a variable wavelength filter for detecting a use state of a transmission line capable of changing a wavelength of an optical signal to be passed. 2. The optical switching device according to claim 1, wherein the optical switching device passes the tunable wavelength filter to the same wavelength as the wavelength of the optical signal to be transmitted from the tunable wavelength light source of the optical switching device or the wavelength of the optical signal transmitted immediately before. An optical network system comprising wavelength control means for controlling a band. 3. In a wavelength division type optical network system for multiplexing transmission of wavelength-divided optical signals, each optical switching device constituting a network transmits an optical signal of a wavelength corresponding to the destination of the optical signal to its transmission unit. And a variable wavelength light source that generates an optical signal having a wavelength different from the wavelength assigned to each of these destinations for notification of a reception state. Having a fixed filter for the main signal that passes only the optical signal of the fixed wavelength, and a fixed filter for the reception state notification that allows only the optical signal of the fixed wavelength allocated for the notification of the reception state. Optical network system. 4. An optical switching device of a wavelength division multiplexing type optical network system for multiplexing and transmitting wavelength-division multiplexed optical signals, a variable wavelength light source for switching its generation wavelength according to the destination of the optical signal in its transmission unit. Having a fixed filter for receiving a main signal that passes only an optical signal of a fixed wavelength assigned to the own device,
An optical switching device, comprising: a variable wavelength filter for detecting a use state of a transmission line capable of changing a wavelength of an optical signal to be passed. 5. The wavelength control according to claim 4, wherein the variable wavelength light source of the own device controls the pass band of the variable wavelength filter to the same wavelength as the wavelength of the optical signal to be transmitted or the wavelength of the optical signal transmitted immediately before. An optical switching device comprising means. 6. An optical switching device of a wavelength division multiplexing type optical network system for multiplexing and transmitting wavelength division multiplexed optical signals, wherein an optical signal having a wavelength corresponding to a destination of the optical signal is generated in a transmission unit for communication. And a variable wavelength light source that generates an optical signal having a wavelength different from the wavelength assigned to each of these destinations for notification of the reception state. An optical switching device comprising: a fixed filter for a main signal that allows only an optical signal to pass; and a fixed filter for notifying a reception state that allows only an optical signal of a fixed wavelength allocated for notification of a reception state.