JP2002319896A - Optical packet withdrawal/insertion method in optical network and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light wave merging/branching method for optical wavelength division multiplex communication capable of the withdrawal of a packet unit at an ultra high speed in a WDM network, and a device therefor. SOLUTION: An optical label selector 11 and an optical switch 12 are provided, the optical label selector 11 is constituted of an optical correlation device, a time gate, an optic/electric converter and a threshold setting device and a fiber diffraction grating is used as the optical correlation device. By making the optical label of the packet be incident on the fiber diffraction grating of which the grating interval is set so as to generate an optical code sequence equivalent to the identification label of a node and detecting reflected waves, correlation calculation on a time base is performed by the principle of a matched filter. The maximum value of an autocorrelation value is extracted by the time gate, optical signals are converted to electronic signals and only the maximum value is extracted in the threshold setting device. Thus, the matching/non-matching of the optical label are identified and the packet to be withdrawn is decided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for dropping / inserting an optical packet in an optical network.
In particular, the present invention relates to a method and an apparatus for selectively debiting an optical packet in an optical network.

[0002]

2. Description of the Related Art FIG. 11 shows wavelength division multiplexing optical communication (WDM).
FIG. 2 is a basic configuration diagram of a transmission system.

In FIG. 11A, 101 is a plurality of optical transmitters (Tx), 102 and 108 are optical filters, 10
3 and 106 are optical fibers, 104 and 107 are amplifiers, 1
05 is a repeater (3R), 109 is a plurality of optical receivers (R
x). As shown in FIG. 11B, the optical transmitter (Tx) 101 includes a TDM multiplexing unit 101A and a light source modulator 101B, and as shown in FIG. 11C, an optical receiver (Rx) 109. Denotes a light receiving element 109A, a demodulator 109
B, TDM demultiplexing section 109C.

[0004] In recent years, the WDM network has been commercialized as a large-capacity information communication infrastructure. The withdrawal of the optical packet causes only the traffic to be terminated to be dropped at the node of the optical network and the remaining traffic to be bypassed.

Hereinafter, the prior art will be described in detail.

In recent years, with the spread of the Internet,
2. Description of the Related Art Although the demand for communication has exploded, an optical network system is expected as a technology for achieving a dramatic increase in the capacity and speed of transmission in response to a rapid increase in the amount of information. To increase the capacity of the optical network system, methods such as time division multiplexing and wavelength multiplexing are used. Therefore, the signal form is basically an ultra-high-speed time-series optical signal, and it is necessary to perform processing on transmission information at an ultra-high speed with a great increase in signal time density. 2. Description of the Related Art In a current processing system for optical communication, a node of an optical network, such as a router or a switch, temporarily converts an optical signal into an electric signal to perform electric processing, and converts the signal into an optical signal again to control a transmission path.

On the other hand, in traffic of optical communication, a stream type in which bits like a telephone are intermittently transmitted, a burst transfer type such as a transaction file, an IP (Inter).
net Protocol). The optical channel is used properly according to these types. In the case of the stream type, an optical channel is set in advance on a necessary route according to the amount of traffic, thereby bypassing a node in the middle and ending.
-To-end can be transferred with minimum delay. In a relatively large-capacity burst type, a wavelength is reserved and transmitted at a stretch. IP
Occupying a wavelength for short bit information such as a packet wastes wavelength resources.

In a router that processes an optical signal packet transmitted by an optical signal, it is necessary to identify information such as an address included in a header of the packet and determine a destination of the packet. In the header address identification processing, a method is mainly employed in which an optical signal is converted into an electric signal and then electrically processed. In order to dramatically improve the processing capability of the rapidly increasing fine-grained IP packets, processing using optical signals as they are is desired.

[0009]

However, there is no ultra-high-speed packet-based withdrawal technique in an optical network.

Here, a comparison with SONET will be described.

A conventional SONET (synchronous optical network: referred to as SDH in the ITU-T standard) ADM (Ad
d / drop multiplexers can process traffic at a finer granularity, extract slower streams from faster streams, and add slower streams to faster streams.

However, as the bit rate of the network increases, the speed of electronic processing becomes increasingly a bottleneck. Therefore, in the future optical data network, the demand for a high-speed and multifunctional ADM capable of handling finer-grained traffic is expected to increase.

In view of the above circumstances, an object of the present invention is to provide an optical packet withdrawal / insertion method and apparatus in an optical network capable of ultrahigh-speed packet-by-packet withdrawal in an optical network.

[0014]

According to the present invention, there is provided a method for dropping / inserting an optical packet in an optical network, comprising the steps of: A time waveform representing an optical code sequence is added as an optical label indicating a source, and by identifying the optical label, only predetermined optical packets are withdrawn from the arrived optical packets, and the rest are bypassed.
Further, when there is no optical packet to be bypassed, an optical packet is inserted from the node.

[2] In the optical packet withdrawing / inserting method in the optical network according to the above [1], an optical label selector and an optical switch are provided, and the optical label selector is an optical correlator, a time gate, an optical-electrical converter. A fiber grating or an optical waveguide encoder is used as the optical correlator, and a grating interval of the fiber grating or a tap interval of the optical waveguide encoder is used to identify the node. The optical label of the optical packet is incident on the fiber grating or the optical waveguide type encoder set so as to generate an optical code sequence corresponding to a label, and a reflected wave is detected. Calculate the correlation on the axis, extract the maximum value of the autocorrelation value by the time gate, convert the optical signal into an electronic signal, and By extracting only the maximum value, it is determined whether the optical labels match or not, and an optical packet to be dropped is determined. In the case of a match, a control signal is sent to the optical switch, and the setting of the optical switch is changed to a cross state. To send the optical packet to a predetermined port,
Only when there is a mismatch, the optical packet is passed while the state of the optical switch is kept in the bar state.

[3] In the optical packet withdrawing / inserting method in the optical network according to [2], when there is no bypass packet in which the optical switch is in the cross state, the setting of the optical switch is set to the cross state. The optical packet is inserted from the node through an optical switch and transmitted.

[4] An optical packet withdrawing / inserting device in an optical network, comprising, in a node of the optical network system, an optical label selector and an optical switch,
An add / drop multiplexer that inserts or drops an input optical packet into or from a main line, wherein the optical label selector includes an optical correlator, a time gate, an optical-electrical converter, and a threshold value determiner.

[5] In the optical packet withdrawing / inserting device in the optical network according to the above [4], the light amount of a part of the input optical packet is sent to the optical label selector,
An optical code consisting of an optical pulse train having source and destination information is added to the header of this input optical packet, and the optical pulse is 0 or π, and each node is set to a unique similar optical code. It is characterized by.

[6] In the optical packet withdrawing / inserting apparatus in the optical network according to the above [4], the signal waveform is discriminated by the optical correlator, and the optical code of the header of the input optical packet and the optical code of each node are determined. Is performed by matched filtering.

[0020]

Embodiments of the present invention will be described below in detail.

FIG. 1 shows a packet-selective optical ADM (PADM: Photonic Add / d) showing an embodiment of the present invention.
FIG. 2 is a schematic diagram of a (r.o.

Packet Selective Optical ADM (PADM) 10
Is installed at the node and deducts packet 2 from incoming input packet 1 or bypasses input packet 1 and adds packet 3 from the node. Where 4
Is a WDM demultiplexer for demultiplexing, 5 is a WDM multiplexer for multiplexing, and 6 is a bypass and insertion packet.

This is performed for each packet on one WDM link.

FIG. 2 is a basic configuration diagram of a packet-selective optical ADM (PADM) module showing an embodiment of the present invention.

In this figure, 10 is a PADM,
The basic functions of the PADM 10 are optical label selection by an optical label selector 11 and an optical space switch (1 × 2 optical switch) 1
2 is a withdrawal function. I / O port is one W
Connected to DM link. The optical label added to the header of the arriving packet 14 is processed, and a control signal operates the optical space switch 12 based on the optical label, and the input packet 14 is dropped or bypassed to the output port. Here, 13 is an optical delay element, and 15 is a bypass and insertion packet.

Next, the optical label selector 11 will be described.

FIG. 3 is a diagram showing the structure of an optical packet. 20 is a header, 21 is a destination / source optical label, 22 is other information, 23 is a packet body, 24 is a termination flag,
25 is a space (guard time).

As shown in this figure, the optical label 21 of the header 20 is simply a relatively short fixed-length identifier having information on the source and destination. A flag 24 indicating the end is attached to the end of the packet. Other management information can be added to the label as needed. The rest of the network control information is encapsulated in a higher layer frame.

FIG. 4 is a diagram showing a 4-chip optical code group and its autocorrelation waveform according to an embodiment of the present invention. For example, FIG. 4 shows a 4-bit optical code group and its autocorrelation waveform. It is.

As shown in this figure, each node (I, J,
K) are assigned unique labels, and each label is mapped to an optical code (i, j, k). Optical cord (i,
(j, k) is an optical pulse train. The pulse train is shorter than one bit time interval. The optical label selection is performed based on the optical correlation between the optical code (i, j, k) of the arriving packet and the assigned code of the node. Optical correlation is performed by a matched filter in the time domain. The code is bipolar and the phases of the optical carrier of the individual pulses are 0 and π representing 1 and -1. This is the key to ultra-high-speed processing of PADM since the label selector does not perform optical logic operations.

Next, main components of the PADM module will be described.

The basic functions of the PADM are implemented by an optoelectronic conversion device.

As shown in FIG. 5, the optical label selector comprises an optical correlator 31, a time gate 32, an opto-electronic converter (O / E).
33, a threshold value judging device 34. Further, the optical correlator 31 includes a fiber diffraction grating (FB) as shown in FIG.
G) 35, or an optical waveguide type correlator 36 as shown in FIG.
Consists of The same device is used for optical encoding.

The optical waveguide correlator 36 shown in FIG.
Is an optical encoder / decoder 36A, a selection tap 36
B, a phase shifter 36C, and a combiner 36D, and are composed of a planar lightwave circuit (PLC).

If the lattice spacing is set to a desired wavelength by one FBG 35, there is an advantage that the optical label can be selected simultaneously with the wavelength. The high-definition FBG 35 can generate a bipolar optical code.

On the other hand, a high-speed general-purpose optical space switch is commercially available. The switching speed of a semiconductor optical amplifier (SOA) is a few nanoseconds, exceeding the required speed. However, since there is no random access optical memory comparable to the RAM of an electronic memory, an optical fiber is used as a buffer for temporarily storing optical packets.

Next, the asynchronous packet transmission of the transmission rate control will be described.

The operating mechanism proposes a transmission rate control line access method for changing a band and transmitting a large amount of data in a MAN or LAN. this is,
Implemented using PADM. A "leak bucket mechanism" is used for control of packet insertion at each node. A "leak bucket mechanism" is a virtual device that controls a large amount of flow.

As shown in FIG. 8, tokens are introduced at a fixed rate into a fixed amount of a token pool 42, and if the token pool 42 is not full, the tokens are stored.・ Pool 4
When the packet 43 arrives when there is an empty space in the buffer 41, the packet is stored in the buffer 41. When the token pool 42 is full, the packet 43 is output immediately after the packet 43 arrives, and at the same time, one token is deleted from the token pool. When the packet 43 arrives when the packet is empty, the packet 43 is discarded. When a token is input to the token pool 42, if the packet 43 is present in the buffer 41, the packet 43 at the head of the matrix is output from the buffer 41 and at the same time. Have one token deleted. The capacity of the token pool 42 is determined based on the burstiness of a large number of packets. The large token pool 42 allows for the transmission of large amounts of packets. In addition, 44 is a coupling part.

Next, optical mounting will be described.

FIG. 9 shows the access protocol. If the packet arriving at node j has the destination label of node j, the packet is dropped from optical space switch sw1. When the arriving packet has a different destination label than node j and the token pool is not empty, it is bypassed to downstream nodes. However, when the arriving packet has a different destination label than node j and the token pool is empty, the packet is discarded. The bypassed packet is given a higher priority than the packet added at the node j. As a result, packet transmission from node j is delayed until a large amount of packets from node i (i <j) pass through node j.

The PADM implementation is shown in FIG. This is an optical label selector 11, three 1 × 2 optical space switches s
w1, sw2, sw3, two optical delay elements 13A, 13
B, an electronic leakage bucket controller 51 and the like. In addition, 52 is a photoelectric converter.

The optical label selector 11 directly controls the optical space switch sw 1, and the control signal from the optical label selector 11 is supplied to the leak bucket controller 51. The leak bucket controller 51 controls the optical space switches sw2 and sw3. The delay time τ of the optical delay line is set equal to the processing time of the optical label selector 11.

On the other hand, τ ₁ is set equal to the processing time of the leak bucket controller 51. The optical space switch sw1 drops the arriving packet when it enters the cross state, and stays in the bar state in other states to bypass the packet. The optical space switch sw3 is in a bar state for bypassing the arriving packet, and is in a cross state for discarding the arriving packet.

The optical space switch sw2 is controlled by the leak bucket controller 51, and enters a cross state to add a packet from the buffer 53 only when there is no bypass packet. At other times, it is always in a bar state to bypass the packet. In order to avoid collision between the bypass packet and the additional packet, the first optical delay line buffers the bypass packet for one packet section.

Leakage bucket control is very simple, and implementing a leaky bucket mechanism involves only fetching and adding operations to registers.

A transmission circuit of 100 Gbit / s and 1000
Considering a packet of bits, the packet transmission time is 1
0 ns. This time is sufficient for several lines of instructions to execute the leaky bucket algorithm, even with current processor technology.

The ultimate performance of a fixed rate control access system can be predicted from an optical packaging point of view. The processing performance of the PADM depends on the performance of the optical label selector. This is determined by the propagation delay required for optical correlation. An experiment was performed in which an 8-bit optical code was processed, and a load of 64 bits long was routed by an optical space switch at 10 Gbit / s. 35ps
The processing capacity reached 29 Gbit / s at the time interval of the optical label.

As described above, according to the present invention, there is provided an add / drop multiplexer which includes an optical label selector and an optical space switch in a node of an optical network system and inserts or drops an input optical packet into or from a trunk. The label selector is an optical correlator, a time gate, a photoelectric converter,
(1) A part of an input packet (about 1 /
Send the light quantity of 10) to the optical label selector. An optical code consisting of an optical pulse train having information on the source and destination is added to the header of the packet. The light pulse is either 0 or π (corresponding to 0 and 1 in the computer). Each node has a unique similar optical code.

(2) A signal waveform is identified by an optical correlator. The correlation between the optical code of the header portion of the packet and the optical code of each node is performed by matched filtering.

(3) On the basis of this, a signal is sent to the optical space switch, and the corresponding node either drops or returns to the original packet (bypass).

The optical correlator is a fiber diffraction grating or an optical waveguide type diffraction grating.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

[0054]

As described above, according to the present invention, the following effects can be obtained.

(A) In a WDM network, it is possible to withdraw packets at ultra-high speed in packet units.

(B) A high-speed multi-function A capable of processing finer-grained traffic in an optical data network
DM can be obtained.

(C) Since no logic element is used, high speed operation can be realized.

(D) Short information such as an IP packet is
It is possible to transmit at high speed with nd-to-end.

(E) There is a possibility of being installed not only in a large-capacity, ultra-high-speed trunk WDM network, but also in any WDM network node, such as a metropolitan WAN (wide area network) and an access LAN. However, the market size will continue to expand in the future.

[Brief description of the drawings]

FIG. 1 shows a packet-selective optical ADM showing an embodiment of the present invention.
It is a schematic diagram of (PADM).

FIG. 2 is a packet-selective optical ADM showing an embodiment of the present invention.
It is a basic block diagram of a (PADM) module.

FIG. 3 is a configuration diagram of an optical packet showing an embodiment of the present invention.

FIG. 4 shows an optical code having a 4-chip length according to an embodiment of the present invention.
It is a figure which shows a group and its autocorrelation waveform.

FIG. 5 is a configuration diagram of an optical label selector showing an embodiment of the present invention.

FIG. 6 shows a fiber grating (FB) showing an embodiment of the present invention.
It is a block diagram of G).

FIG. 7 is a configuration diagram of an optical waveguide type correlator showing an embodiment of the present invention.

FIG. 8 is a diagram illustrating a logical structure of a leakage bucket according to the embodiment of the present invention.

FIG. 9 is a diagram illustrating an access protocol of packet transmission controlled at an asynchronous ratio according to an embodiment of the present invention.

FIG. 10 is a configuration diagram of an optically-mounted PADM for packet transmission controlled at an asynchronous ratio according to an embodiment of the present invention.

FIG. 11 is a basic configuration diagram of a wavelength division multiplexing optical communication (WDM) transmission system.

[Explanation of symbols]

 1, 14 input packet 2 withdrawn packet 3 packet to be added 4 WDM demultiplexer for demultiplexing 5 WDM multiplexer for multiplexing 6, 15 bypass and insertion packet 10 packet selective optical ADM (PADM) 11 optical label selection Device 12, sw1, sw2, sw3 Optical space switch 13, 13A, 13B Optical delay element 20 Header 21 Destination / source optical label 22 Other information 23 Packet body 24 Termination flag 25 Space (guard time) 31 Optical correlator 32 Time gate 33 photoelectric converter (O / E) 34 threshold value judging device 35 fiber grating (FBG) 36 optical waveguide correlator 36A optical encoder / decoder 36B selection tap 36C phase shifter 36D combiner 41,53 buffer 42 fixed amount token・ Pool 43 Packet 44 Coupling part 51 Electronic leak bucket controller 52 Photoelectric converter

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) H04Q 3/52 H04B 9/00 N (72) Inventor Masayuki Murata 4-8-18-406 F, Eirakuso, Toyonaka-shi, Osaka Terms (reference) 2K002 AA02 AB05 AB22 DA07 EA07 EA14 EB14 EB15 5K002 AA05 BA04 BA06 BA21 CA12 DA02 DA13 5K030 HA08 HB09 JL03 KX20 LA17 LC04 5K069 BA09 BA10 CB10 DB33 DB41 EA22 EA25 EA30

Claims (6)

[Claims] 1. A node of an optical network, a time waveform representing an optical code sequence is added to a header of an optical packet as an optical label indicating a destination and a source, and the optical label arrives by identifying the optical label. Only predetermined optical packets are dropped from the packets, and the rest are bypassed.
Further, when there is no optical packet to be bypassed,
An optical packet withdrawal / insertion method in an optical network, wherein an optical packet is inserted from the node. 2. The method for dropping / inserting an optical packet in an optical network according to claim 1, further comprising an optical label selector and an optical switch, wherein the optical label selector is an optical correlator, a time gate, a photoelectric converter, It is composed of a threshold value judging device,
A fiber diffraction grating or an optical waveguide encoder is used as the optical correlator, and a grating interval of the fiber diffraction grating or a tap interval of the optical waveguide encoder is used to generate an optical code sequence corresponding to a label for identifying the node. The fiber diffraction grating or optical waveguide type encoder set so as to make the optical label of the optical packet incident and detect a reflected wave to perform a correlation calculation on the time axis by the principle of a matched filter, The maximum value of the autocorrelation value is extracted by the time gate, the optical signal is converted into an electronic signal, and the optical label is identified and matched by extracting only the maximum value in the threshold value judging device. Determine an optical packet, and in the case of a match, send a control signal to the optical switch;
The setting of the optical switch is set to a cross state, and the optical packet is sent to a predetermined port. On the other hand, only when there is a mismatch, the optical packet is passed while keeping the state of the optical switch in a bar state. An optical packet withdrawal / insertion method in an optical network. 3. The optical packet withdrawal / insertion method in an optical network according to claim 2, wherein when there is no bypass packet in which the optical switch is in a cross state, the setting of the optical switch is set to a cross state, and the node is set to a cross state. And inserting and transmitting said optical packet through an optical switch. 4. An add / drop multiplexer for an optical network system node, comprising an optical label selector and an optical switch, for inserting or dropping an input optical packet into or from a trunk, wherein the optical label selector is an optical correlator. ,
An optical packet withdrawing / inserting device in an optical network, comprising a time gate, an optical-electrical converter, and a threshold value judging device. 5. The optical packet withdrawing / inserting device in an optical network according to claim 4, wherein a light amount of a part of the input optical packet is sent to the optical label selector, and a source of the input optical packet is included in a header of the input optical packet. An optical packet consisting of an optical pulse train having information of a transmission destination is added, the optical pulse is 0 or π, and each node is set to a unique similar optical code. Insertion and insertion device. 6. An optical packet withdrawing / inserting apparatus in an optical network according to claim 4, wherein said optical correlator discriminates a signal waveform and correlates an optical code of a header of said input optical packet with an optical code of each node. The optical packet debiting / inserting device in an optical network, characterized in that: