KR100785290B1 - Wavelength division multiplexing packet transfer system of ring structure - Google Patents

Abstract

The present invention relates to a WDM packet transmission system having a ring structure suitable for packet data transmission. The wavelength division multiplex packet transmission system having a ring structure according to the present invention includes an optical tap coupler for separating a received optical signal at a predetermined ratio, and a packet data is received by dropping an allocated wavelength of a magnetic node among received optical signals passed through the optical tap coupler. The remaining wavelengths are read by the signal receiver passing through the received optical signal separated from the optical tap coupler, and the presence or absence of packet data for each destination node transmitted is determined to determine whether packet data can be transmitted for each destination node, and thus randomly transmitted from the own node. A reception reader for controlling the transmission of packet data to a destination node, and modulating the packet data to be transmitted to a destination node that can be transmitted under the control of the reception reader, into an assigned subcarrier of the destination node, and putting the packet data on an allocated optical wavelength to receive the signal receiver. And a signal transmitter which adds to the optical signal which has passed.

Description

Wavelength division multiplexing packet transfer system of ring structure

1 is a block diagram of a WDM optical transmission network having a general ring structure for transmitting time division multiplexed data;

2 is a block diagram illustrating a state in which a single wavelength is allocated to the same destination in a WDM packet transmission network according to the present invention;

3 is a block diagram of a WDM packet transmission system having a ring structure according to the present invention;

4 is a view showing an optical signal after passing through the broadband pass filter of FIG.

FIG. 5 is a diagram illustrating a signal passing through the bandpass filters of FIG. 3 and input to a transmission determiner. FIG.

※ Explanation of code about main part of drawing ※

10: signal receiving unit 11: optical circulator

12: Fiber Bragg Grating (FBG) 13: Optical / Electric Converter

14 peak value detector 15 offset value adjuster

16: amplifier 17: CDR

20: reception reader 21: broadband pass filter                 

22: optical / electric converter 23, 24, 25: bandpass filter

26: transmission determiner 30: signal transmission unit

31: Buffer 32: Destination Node Controller

33: voltage controlled oscillator 34: mixer

35 variable laser diode 36 optical multiplexer

40: optical tap coupler

The present invention relates to a wavelength division multiplex (WDM) optical transmission system of a ring structure, and more particularly, to a WDM packet transmission system of a ring structure suitable for packet data transmission.

The wavelength division multiplex (hereinafter, referred to as WDM) method is an optical communication method for multiplexing and transmitting optical signals having different wavelengths to one strand of optical fiber, thereby maximizing data transmission capacity. The network constituting the WDM scheme may be configured in various forms such as a forming structure, a bus structure, a mesh structure, and a ring structure. However, most WDM networks use a ring structure.

A general ring structured WDM optical transmission network is designed as a system for transmitting time division multiplexed (TDM) data. An example of such a ring structured WDM optical transmission network is shown in FIG. 1. 1 is a configuration diagram of a WDM optical transmission network in which four nodes (Node A, Node B, Node C, and Node D) are connected to a ring network and data flow is unidirectional. Each node has a logical connection with several other nodes, which are made by assigning one wavelength between the two nodes. That is, the first wavelength λ ₁ is used for communication from node A to node B, the second wavelength λ ₂ is used for communication from node A to node C, and the third wavelength is used for communication from node A to node D. The wavelength λ ₃ is used. Similarly, three wavelengths are required for communication from node B to node C, from node B to node D, and from node B to node A. In addition, three wavelengths are required for communication at node C, and three wavelengths are required for communication at node D, respectively. That is, in the case of a unidirectional WDM optical transmission network in which four nodes are connected, a total of 12 dedicated channels (optical wavelengths) are required.

When designing a WDM transmission system for packet data transmission based on the WDM optical transmission network having such a structure, transmission efficiency is deteriorated because one optical wavelength must be allocated assuming a maximum yield between nodes. In other words, unlike the time division multiplexing (TDM) data, the packet data has a burst data transmission characteristic in which the data is temporarily concentrated and remaining idle at other times. Therefore, a dedicated channel between two nodes has a longer idle state in which no data is transmitted than a busy state in which packet data is transmitted. Since the channel cannot be used for communication between other nodes, the efficiency of using the channel is reduced.

In addition, as shown in FIG. 1, when a link using a dedicated channel is configured in a ring structure in which four nodes are connected, three optical wavelengths are processed for each source when the corresponding node is a destination for each node's optical transmission system. If the configuration is for a node and the node is a starting point, the system configuration is complicated because all of the configurations for processing three optical wavelengths must be included for each destination.

An object of the present invention is to assign one wavelength to each node connected in a ring structure and to share the wavelength allocated to the node when the other nodes transmit packet data to the node, thereby increasing the channel transmission efficiency and To provide a wavelength division multiple packet transmission system having a ring structure that can reduce the number of optical wavelengths used.

In the WDM packet transmission system of the ring structure of the present invention for achieving the above object, the optical signal transmitted to the magnetic node of the optical signal received from the previous node connected to the ring network drop and the remaining optical signal passes to the next node, The packet data to be transmitted from the node to another node connected through the ring network is converted into an optical signal using subcarriers and optical wavelengths allocated to the destination node, added to the passed optical signal, and transmitted to the next node.

A wavelength division multiplex packet transmission system having a ring structure includes: an optical tap coupler for separating a received optical signal at a predetermined ratio; A signal receiver which receives packet data by dropping an allocated wavelength of a magnetic node among received optical signals passing through the optical tap coupler, and passes the remaining wavelengths; By reading the presence or absence of packet data for each destination node carried on the received optical signal separated by the optical tap coupler, it is possible to determine whether packet data can be transmitted for each destination node, and to transmit packet data from its own node to any destination node. A reception reader for controlling; And a signal transmitter which modulates packet data to be transmitted to a destination node which can be transmitted under the control of the reception reader, and modulates the packet data into an allocated subcarrier of the destination node, and adds it to an optical signal which has passed through the signal receiver. do.

Hereinafter, the WDM packet transmission system of the present invention will be described with reference to the accompanying drawings.

2 is a diagram illustrating a state in which a single wavelength is allocated to the same destination in the WDM packet transmission network according to the present invention. Referring to FIG. 2, four nodes (node A, node B, node C, and node D) are connected in a ring shape. In this case, one wavelength is allocated to each node, the first wavelength λ _{1 at} node A, the second wavelength λ ₂ at node B, the third wavelength λ ₃ at node C, and at node D. Fourth wavelengths λ ₄ are assigned, respectively. When each node wants to transmit the packet data, the node loads the packet data on the wavelength allocated to the destination node and transmits the packet data. In this case, the packet data is not directly carried on the assigned wavelength of the destination node, but is first modulated by the subcarriers assigned to the destination node and then on the assigned wavelength of the corresponding destination node.

When all nodes transmit packet data using the same wavelength only to the same destination node, collisions may occur on the optical path if two or more nodes simultaneously transmit the packet data to the same destination node. To prevent this, each node first reads whether there is packet data currently transmitted to the destination node to which the packet data is to be transmitted, before transmitting the packet data. That is, if the packet data is not loaded on the wavelength allocated to the corresponding destination node among the optical signals received from the previous node and is empty, the packet data is transmitted on the wavelength. If the packet data is loaded on the wavelength, the channel is empty. Suspend data transmission.

3 is a configuration diagram of a WDM packet transmission system according to the present invention at each node performing the above function. Different wavelengths and subcarriers are allocated to each node. In this embodiment, a first wavelength λ ₁ and a first subcarrier f ₁ are allocated to node A, and a second wavelength λ ₂ and a second node are assigned to node B. A second subcarrier f ₂ is assigned, a third wavelength λ ₃ and a third subcarrier f ₃ are assigned to a node C, and a fourth wavelength λ ₄ and a fourth subcarrier are assigned to a node D (not shown). Assume (f ₄ ) is assigned.

3 is a block diagram of a WDM packet transmission system of a node D, which is a signal receiving unit 10 which drops an allocated wavelength of its own node and passes a remaining wavelength among the received optical signals, and the received light A reception readout unit 20 for determining whether packet data for each destination node is transmitted on the signal, and determining whether packet data can be transmitted for each destination node; and modulating the data to be transmitted to the transmittable destination node with subcarriers of the corresponding node. And a signal transmitter 30 that adds to the optical signal passed by the signal receiver 10 on the assigned wavelength of the node. In addition, an optical tap coupler 40 for branching the received optical signal to the signal receiving unit 10 and the receiving reading unit 20 at a predetermined ratio.

The signal receiving unit 10 receives the optical signal branched from the optical tap coupler 40 to the a terminal and outputs it to the b terminal, and the optical circulator 11 to output the optical signal input through the b terminal to the c terminal, and the optical Among the optical signals output to the b terminal of the circulator 11, the assigned wavelength of the magnetic node is reflected to the b terminal of the optical circulator 11, and the remaining wavelength is passed through the fiber Bragg grating (FBG). (12), an optical / electric converter (13) for converting an optical signal of an assigned wavelength of the magnetic node output to the c terminal of the optical circulator (11) into an electrical signal, and output from the optical / electric converter (13). Amplifying a peak value detector 14 for detecting a peak value from the electrical signal to be converted, an offset value adjuster 15 for adjusting an offset value based on the detected peak value, and an electrical signal output from the optical / electric converter 13 The amplifier 16 and the offset value using the And a clock and data recovery (CDR) 17 for recovering the clock and data of the electrical signal output from the amplifier.

The reception reader 20 includes an optical band pass filter (OBPF) 21 for removing optical signal noise excluding transmission bands from the optical signal branched from the optical tap coupler 40, and the broadband pass filter 21. An optical / electric converter 22 for converting the optical signal passing through the signal into an electrical signal, and a plurality of band pass filters for detecting the allocated subcarriers for each destination node by receiving the electrical signal from the optical / electric converter 22. Filter 23, 24, 25, and sub-carrier detection information detected through each band pass filter 23, 24, 25 and a destination node selection signal to transmit packet data in a self-node. Detects whether data is loaded in the assigned wavelength of the destination node, and outputs a frequency selection signal and a transmit enable signal to the signal transmitter 30 when there is no packet data transmitted to the destination node to which the packet data is transmitted from its own node.And a new machine (26).

The signal transmitter 30 receives and temporarily stores the packet data to be transmitted. When the transmit enable signal is input from the transmission determiner 26, the signal transmitter 30 outputs the packet data from the buffer 31 and the transmission determiner 26. A voltage controlled oscillator (VCO) 33 for receiving an input frequency selection signal and oscillating a subcarrier of a corresponding frequency and the packet data output from the buffer 31 are output from the voltage controlled oscillator 33. The destination node controller 32 which receives the destination node selection signal of the packet data stored in the buffer 31, the wavelength control of the destination node controller 32, and the mixed signal from the mixer 34; In a variable laser diode (LD) 35 which is mounted on an optical signal of a wavelength controlled by the control beam) and outputs, an optical signal and a variable laser diode which have passed the FBG 12 of the signal receiver 10 An optical multiplexer 36 for multiplexing the variable optical signal is provided.

The operation of the WDM packet transmission system according to the present invention configured as described above is as follows.                     

When the optical signal transmitted from the previous node is input, the optical signal of four wavelengths (when four nodes are connected as in this embodiment) is multiplexed on the optical signal. The optical signal of each wavelength may be transmitted by carrying packet data modulated by a subcarrier according to the corresponding wavelength or in an empty state in which packet data is not loaded.

When the magnetic node is the node D, the optical signal of the fourth wavelength λ ₄ is dropped to the magnetic node, and the optical signal of the first wavelength λ ₁ to the third wavelength λ ₃ is passed. The packet data to be transmitted from node D to another node is added to the optical signal which is passed after being loaded on the assigned subcarrier and wavelength of the corresponding destination node. At this time, the node D detects whether the packet data is loaded on the assigned wavelength of the destination node to which the packet data is to be transmitted, and waits if it is already loaded, and adds the packet data if not.

That is, if there is packet data to be transmitted from node D to node A, it is detected whether the first wavelength λ ₁ is empty. If the packet data is empty, the packet data is modulated to the first subcarrier f and then the first wavelength λ is detected. ₁ ) to add. If there is packet data to be transmitted from node D to node B, it is detected whether the second wavelength λ ₂ is empty, and if it is empty, the packet data is modulated to the second subcarrier f ₂ and then the second wavelength ( λ ₂ ) to add. If there is packet data to be transmitted from node D to node C, it is detected whether the third wavelength λ ₃ is empty, and if it is empty, the packet data is modulated to the third subcarrier f ₃ and then the third wavelength ( λ ₃ ) to add.

Hereinafter, an operation of a signal receiver which drops an optical signal wavelength transmitted to its own node and passes the remaining wavelengths, and an operation of a reception reader which detects a subcarrier being transmitted to the optical signal to determine whether to transmit packet data, and packet data. The operation of the signal transmission unit which adds to the allocated subcarrier of the destination node and the optical signal carried on the wavelength will be described in detail.

First, the optical signal input from the previous node is branched at a specific ratio in the optical tap coupler 40 and input to the signal receiving unit 10 and the receiving reading unit 20, respectively.

The optical signal branched from the optical tap coupler 40 is input to the a terminal of the optical circulator 11, output to the b terminal, and input to the FBG 12. The FBG 12 is an optical fiber device that periodically modulates the refractive index of the optical fiber core to reflect light of a specific wavelength. The FBG 12 reflects the fourth wavelength λ ₄ and reflects the first wavelength λ ₁ to the third wavelength λ _3. ) Pass. The fourth wavelength λ ₄ reflected by the FBG 12 is converted into an electrical signal in the photoelectric converter 13 and input to the peak detector 14 and the amplifier 16, respectively. The peak detector 14 detects the maximum value of the electrical signal, and the offset value adjuster 15 adjusts the offset value, which is a criterion for determining the data value, based on the maximum value. On the other hand, the electrical signal output from the photoelectric converter 13 is amplified by the amplifier 16 and input to the CDR (17). The CDR 17 recovers clock and packet data from an electrical signal output from the amplifier 16 using the offset value.

On the other hand, the optical signal branched from the optical tap coupler 40 and input to the reception readout unit 20 has noise removed except for the transmission band by the optical band pass filter (OBPF) 21, thereby removing the noise as shown in FIG. An optical signal of a transmission band including one wavelength λ ₁ to a third wavelength λ ₃ is passed. The optical signal passing through the broadband pass filter 21 is converted into an electrical signal by the opto-electric converter 22, and the electrical signal is input to the three band pass filters 23, 24, and 25, respectively.

The bandpass filter 23 passes only the first subcarrier f ₁ as shown in FIG. 5, the bandpass filter 24 passes only the second subcarrier f ₂ , and the bandpass filter 25 passes through the third filter. Pass only the subcarrier f ₃ . For example, if the optical signal includes packet data transmitted to node A and node C, but no packet data transmitted to node B, the packet data transmitted to node C and the first subcarrier carrying packet data transmitted to node A are stored. In fact, the third subcarrier will be detected and the second subcarrier carrying the packet data sent to Node B will not be detected. That is, as shown in FIG. 5, the band pass filters 23 and 25 output the first subcarrier f ₁ and the third sub carrier f _3, respectively, but the band pass filter 24 outputs no output value. Will not.

The output values of the band pass filters 23, 24 and 25 are input to the transmission determiner 26. When the first subcarrier f ₁ and the third subcarrier f ₃ are input, the transmission determiner 26 reads that there is packet data transmitted to the node A and the node C in the corresponding optical signal, and the second subcarrier f ₂ If) is not input, it reads that there is no packet data transmitted to Node B in the corresponding optical signal. Accordingly, the packet data to be transmitted from the own node to the node B can be added at present, and the packet data to be transmitted from the node to the node A or the node C cannot be added at present, and the necessary signal is transmitted to the signal transmitter ( Output to 30).

For example, if there is packet data to be transmitted from node D to node A, the transmission determiner 26 detects this through the node selection signal. Since the current optical signal includes packet data transmitted to the node A, the signal transmission unit ( Do not output the transmit enable signal to 30).

However, if there is packet data to be transmitted from node D to node B, the transmission determiner 26 detects this through the node selection signal, and there is no packet data transmitted to node B in the current optical signal and the second wavelength λ ₂ is empty. Therefore, the subcarrier f control signal and the transmit enable signal are output to the signal transmitter 30.

When the packet data to be transmitted to another node is input, the signal transmitter 30 stores the packet data in the buffer 31. When the transmit enable signal is input from the transmission determiner 26 of the reception reader 20, the signal data is stored. Is output to the mixer 34. On the other hand, the voltage controlled oscillator 33 oscillates a subcarrier of the corresponding frequency when the frequency selection signal and the transmit enable signal are simultaneously input from the transmission determiner 26 to provide the mixer 34. The mixer 34 modulates the packet data provided from the buffer 31 by using the subcarrier provided from the voltage controlled oscillator 33 and inputs them to the variable laser diode 35. Meanwhile, the destination node controller 32 receives the destination node selection signal and outputs the assigned wavelength control signal of the corresponding destination node to the variable laser diode 35, and the variable laser diode 35 outputs the mixed signal to the corresponding wavelength. It is loaded to the optical multiplexer 36. Then, the optical multiplexer 36 multiplexes the optical signal passed by the signal receiver 10 and the optical signal output from the variable laser diode 35 and transmits the multiplexed optical signal to the next node.

At this time, since the wavelength of the optical signal to be added is not included in the optical signal passing through the signal receiving unit 10, the collision of the optical signal does not occur.

As described above, since the link can be configured using the optical wavelength of the number of nodes connected to the ring network by using the characteristics of the packet data, it is possible to drastically reduce the optical wavelength used, thus simplifying the system configuration and reducing the unit cost according to the system configuration. There is an advantage to being lowered.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims (5)

In a wavelength division multiple packet transmission system having a ring structure, An optical tap coupler for separating the received optical signal at a predetermined ratio; A signal receiving unit for receiving packet data by dropping an allocated wavelength of a magnetic node among the received optical signals passing through the optical tap coupler, and passing the remaining wavelengths; Controls the transmission of packet data from its own node to any destination node by determining whether the packet data can be transmitted for each destination node according to the presence or absence of packet data for each destination node carried on the received optical signal separated by the optical tap coupler. A reception reading unit; And a signal transmitter configured to modulate the packet data to be transmitted to a destination node that can be transmitted under the control of the reception readout unit into an allocated subcarrier of the destination node, and then add the signal data to an optical signal passed through the signal receiver. A wavelength division multiple packet transmission system having a ring structure. The method of claim 1, wherein the signal receiving unit, An optical circulator for receiving the optical signal passing through the optical tap coupler to the a terminal and outputting it to the b terminal and the optical signal input through the b terminal to the c terminal; An optical fiber Bragg grating for reflecting the assigned wavelength of the magnetic node among the optical signals output to the b terminal of the optical circulator and passing the remaining wavelength to the b terminal of the optical circulator; An optical / electric converter for converting an optical signal of an assigned wavelength of the magnetic node output to the c terminal of the optical circulator into an electrical signal; And a data detection means for detecting packet data in the electrical signal. The method of claim 2, wherein the data detection means, A peak value detector for detecting peaks in an electrical signal output from the photoelectric converter; An offset value adjuster for adjusting an offset value for determining a data value based on the detected peak value; An amplifier for amplifying an electrical signal output from the photoelectric converter; And a clock and data recovery (CDR) for recovering clock and data of an electrical signal output from the amplifier by using the offset value. The method of claim 1, wherein the reception reading unit, A wideband pass filter for removing noise included in the received optical signal branched from the optical tap coupler; An optical / electric converter for converting the optical signal passing through the broadband pass filter into an electrical signal; A plurality of band pass filters for detecting subcarriers included in an electrical signal output from the optical / electric converter; The subcarrier detection information detected through the plurality of bandpass filters is used to detect whether packet data is included in an allocated optical wavelength of a destination node to which packet data is to be transmitted from its own node, and if there is no packet data transmitted to the destination node. And a transmission determiner for outputting a frequency selection signal and a transmission enable signal to the signal transmission unit. The method of claim 4, wherein the signal transmission unit, A packet data buffer which temporarily stores packet data to be transmitted to the destination node and outputs the signal when the transmit enable signal is input from the transmission determiner; A voltage controlled oscillator for oscillating a subcarrier of the frequency when a frequency selection signal and a transmit enable signal are input from the transmission determiner; A mixer for modulating packet data output from the packet data buffer into subcarriers output from the voltage controlled oscillator; A destination node controller for outputting an optical wavelength selection signal allocated to the destination node of the packet data to be transmitted; A variable laser diode which loads the signal output from the mixer into an optical wavelength according to the optical wavelength selection signal and converts the signal into an optical signal; And an optical multiplexer for multiplexing the optical signal passing through the signal receiving unit and the optical signal output from the variable laser diode to the next node.

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