KR100249775B1 - A novel all-optical header structure and detection method for photonic packet switch - Google Patents

Abstract

The present invention relates to a novel all-optical header detection method for an optical packet switch, wherein two pairs of pulses generated at 1.5T time intervals at the forefront of an optical packet serve to remove the correlation between the header and the payload. The result shows only two optical pulses in the PITD header, and the time between the two pulses represents the header information.

In order to perform PITD header detection, an optical header is generated that is configured so that the time between two pairs of optical pulses having a 1.5T time interval is separated by a time indicating information of the header.

The optical header detector consists of two optical AND logics and an optical delay line. The input of the leading optical AND is input after passing the 0T and 1.5T optical delay lines, and the second optical AND input is connected to the 0T and hT optical delay lines. It is configured to be input after coarse, so that only two optical AND logics are connected in series, so that a full optical header can be detected without a separate device.

Description

Fully Optical Header Structure and Detection Method for Optical Packet Switch

The present invention relates to a novel method for detecting a full optical header for an optical packet switch.

With the development of high speed optical transmission related technology, there is a demand for the implementation of an optical packet switch that maintains optical transparency without optical / electrical / electrical / optical conversion.

One of the important parts of the high speed optical packet switch is the full optical header encoding / decoding part, and therefore several schemes have been proposed.

The first method is incoherent code-division (ICD) header encoding / decoding, where the number of '1's in the header of length N are equally included and the headers Create a header by encoding it so it doesn't matter.

Header decoding in this manner is achieved by constructing a fiber-optic delay lines matching filter from the information of the header to be detected and obtaining a maximum optical peak using a discriminator.

The second method is the 'keyword' header encoding / decoding method.

The header of length N has a corresponding Boolean complement, and when the AND operation is performed on the two bit streams arranged in bits, the output of "00000 ....." is used.

That is, if at least one '1' is detected in the AND operation result, it is determined that the keyword does not match.

A third method is the PITD header encoding / decoding scheme, which represents each header as the time between two optical pulses and detects the header by measuring the time in the decoding part.

The first method described above has an advantage that it is easy to optically configure the header encoding / decoding portion, but it is not an encoding method that efficiently uses bandwidth.

The second method is an efficient use of bandwidth, but requires a separate packet-level sync detector and is difficult to implement because it requires generating a complementary 'keyword' light pattern from the detected packet-based optical sync pulse signals. .

On the other hand, since the third PITD method detects the time between two optical pulses, the implementation can be simplified similarly to the first method, and has the advantage that the bandwidth utilization efficiency of the header is better than that of the first method. .

However, in addition to the two pulses constituting the header, having a data and optical correlation value in the payload may cause an error, requiring a separate device to prevent it.

Therefore, the PITD method of simply coding a header with a time between two optical pulses has a lot of difficulties in the actual packet switch configuration, and requires a separate device to prevent the optical header and the payload from correlating with each other. there was.

1 is a packet configuration diagram of a conventional PITD method, and it can be seen that the header 10 is encoded at _a time T _a 80 between two pulses.

If the reference clock pulse is always placed in the N-th position and the pulse representing the address is placed in the i-th, as shown in FIG. 2, the optical delay 50 is as much as T _a (80) ignoring the common optical delay. Only if is the peak of the correlation value is obtained.

However, in this method, the payload 20 data and the pulse of the header 10 may have a correlation value. For example, if the correlation between the i th pulse and the N + 1 th pulse shows a wrong header detection result. In order to prevent this, a separate device is required.

In order to solve the above problems, an object of the present invention is to propose a method capable of simply detecting a full optical header with two optical AND logics by improving the existing PITD method.

1 is a packet configuration diagram of a conventional PITD scheme;

2 is a characteristic diagram of a header decoding timing diagram using a conventional PITD scheme;

3 is a packet configuration diagram of a proposed PITD scheme according to the present invention;

4 is a proposed header decoding optical block diagram to which the present invention is applied;

5A through 5B are timing diagram characteristic diagrams of header decoding for the proposed scheme according to the present invention.

6 illustrates an embodiment of the proposed scheme according to the present invention.

<Description of the code | symbol about the principal part of drawing>

10: header 20: payload

30: packet-address pulse 40: clock pulse

50: common light delay 60: threshold

70: optocoupler 80: time between two pulses (T _a )

90 optical AND logic 100 optical fiber delay line

110,174: Optocouplers

120: Gain Switching-LD Module

130,173: polarization controller (PC) 140: packet generator

150,171: semiconductor optical amplifier (SOA) 160,172: band pass filter (BPF)

170: header decoder 180: detector

In order to achieve the above object, the present invention is characterized in that the packet is passed through the first optical AND, and the second optical AND input is characterized in that it consists of a step after passing through the optical delay line.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

3 is a packet diagram of the proposed PITD method according to the present invention, and data uses a return-to zero (hereinafter, referred to as RZ) signal.

The header is 4 bits, the most front part of the product is a 2-bit is 1.5 T _b have a gap packet is always located at the beginning, 1.5 T _b the other two pulses with intervals are positioned T _a (80) hours after the separation indicates an address .

4 is a proposed header decoding optical configuration diagram to which the present invention is applied, and the header decoding portion includes two logics 90 passing through optical AND, an optical fiber delay line 100, and an optical coupler 110.

5A through 5B are timing diagram characteristic diagrams of header decoding for the proposed scheme according to the present invention.

FIG. 5A shows the result of the packet passing through the first optical AND 90, and FIG. 5B shows the result after the second optical AND.

The first optical AND 90 extracts the packet synchronous optical pulse signal and the optical pulse representing the address, and the second AND detects the address.

As can be seen in FIG. 5, this configuration has an advantage that a separate device is not required because the structure does not have a correlation value between the payload 20 and the header 10 of the packet.

The light AND logic 90 may be comprised of a nonlinear optical loop mirror (hereinafter referred to as NOLM), four-wave mixing, or the like.

6 is an exemplary view of the proposed scheme according to the present invention, which uses a SLALOM for easily obtaining a time correlation between two pulses.

This obtains the time correlation between the optical pulses by shifting the SOA 150 and 171 positions by the time corresponding to the time to be detected from the center point in the optical loop mirror.

As described above, the present invention has a structure in which only two optical AND logics are connected in series, so that a full optical header can be detected without a separate device.

Claims (5)

A method for processing header detection of an optical header detector of an optical packet switch composed of two optical end logics and an optical delay line as full light, A first step in which the packet passes the first optical AND; And a second optical AND input comprises a second step which is input after passing through the optical delay line. The method of claim 1, wherein the first step A method for detecting a complete optical header for an optical packet switch, comprising extracting an optical unit pulse signal and an optical pulse indicating an address. The method of claim 1, wherein the second step A method for detecting a full optical header for an optical packet switch, characterized by detecting an address of an optical header. In full optical header detection of a packet having a header structure, The header of an optical packet consists of certain bits, so that two are paired, A full optical header structure for an optical packet switch, wherein the spacing between two pulses is a certain multiple of the spacing between data pulses in the payload. The method of claim 4, wherein Two optical AND logics, Each input of the optical AND logic is just input to one side via an optical coupler, The other is a complete optical header structure for the optical packet switch, characterized in that the two are connected in series through the optical delay line.

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