JP2005252805A - Optical network node device and optical network system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an optical network node device for improving transmission characteristics of a user signal.
In an optical network node device 10 forming an optical network system 100, a part of a user optical signal (NRZ optical signal) directly accommodated in a wavelength multiplexed signal is extracted to perform clock extraction, and according to the extracted clock. Thus, the user optical signal is intensity-modulated, and the user optical signal (NRZ optical signal) is converted into a CS-RZ optical signal or RZ optical signal suitable for long-distance transmission, so that the transmission characteristics of the user signal can be improved. it can. In addition, since long-distance transmission is possible without making any changes on the user node device side, it is possible to easily construct an economical network, and it is suitable for a wavelength lending service that opens the wavelength of the wavelength multiplexed signal to the user. .
[Selection] Figure 2

Description

  The present invention relates to an optical network node device and an optical network system that transmit a user signal directly accommodated in a wavelength channel.

As is well known, in an optical network system using a wavelength multiplexing technique, a transmission waveform deteriorates due to the influence of chromatic dispersion and nonlinear optical effects in an optical fiber serving as a transmission path. Therefore, conventionally, band compression encoding is performed by reducing RZ (Return to Zero) modulation, which can reduce the influence of nonlinear optical effects on NRZ (Non Return to Zero) modulation, and by further reducing the spectrum spread during RZ modulation. High-speed transmission using CS-RZ (Carrier-Suppressed Return to Zero) modulation is performed. An optical modulation technique using a CS-RZ code is disclosed in, for example, Patent Document 1.
JP 2002-328348 A

By the way, an optical network node device that forms an optical network electrically multiplexes client signals supplied from the user node side, converts them into high-speed wavelength multiplexed signals, and transmits these signals over a long distance using optical fibers. It is common. The long-distance transmission often uses the above-described CS-RZ modulation.
On the other hand, most of the client signals (hereinafter referred to as user signals) supplied from the user node side use NRZ modulation that can be realized by an inexpensive device. As described above, NRZ modulation is a high-speed signal. Not suitable for long distance transmission. For this reason, when a user signal is directly accommodated in the wavelength channel of the optical network node device, there arises a problem that long-distance transmission cannot be compensated.

  On the other hand, from the spread of wavelength division multiplexing transmission in optical networks and the increase in user signal capacity, the concept of wavelength lending service that opens the wavelength of wavelength division multiplexed signals to users is also emerging. There is also a demand for an optical network system that improves the transmission characteristics of user signals and transmits them over long distances without any changes.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an optical network node device and an optical network system capable of improving the transmission characteristics of user signals.

  In order to achieve the above object, in the optical network node device according to claim 1, an optical branching unit for extracting a part of a user optical signal directly accommodated for wavelength multiplexing, and a user light extracted by the optical branching unit A clock extraction unit that extracts a clock signal from the signal, and intensity-modulating the user optical signal according to the clock signal extracted by the clock extraction unit, and encoding the user optical signal into a coding format suitable for long-distance transmission Coding conversion means for converting.

  The optical network node device according to claim 2, wherein an optical branching unit for extracting a part of a user optical signal directly accommodated for wavelength multiplexing and a clock signal are extracted from the user optical signal extracted by the optical branching unit. A clock extraction unit; and an encoding conversion unit that modulates the intensity of the user optical signal according to the clock signal extracted by the clock extraction unit and converts the user optical signal into an encoding format suitable for long-distance transmission. When the transmission distance to the connection destination is short, the directly accommodated user optical signal is wavelength-multiplexed and transmitted as it is. On the other hand, when the transmission distance to the connection destination is long, the encoding conversion means performs a long distance. Transmission means for wavelength-multiplexing and transmitting a user optical signal converted into an encoding format suitable for transmission.

  4. The optical network node apparatus according to claim 3, wherein an optical branching unit for extracting a part of an NRZ code user optical signal directly accommodated for wavelength multiplexing and an NRZ code user optical signal extracted by the optical branching unit. A clock extracting means for extracting a clock signal from the signal, and a coding for intensity-modulating the user optical signal of the NRZ code with a half clock obtained by dividing the clock signal extracted by the clock extracting means and converting it into a CS-RZ code Conversion means.

  5. The optical network node apparatus according to claim 4, wherein an optical branching unit for extracting a part of an NRZ code user optical signal directly accommodated for wavelength multiplexing, and an NRZ code user optical signal extracted by the optical branching unit. A clock extracting means for extracting a clock signal from the signal, and a coding conversion means for intensity-modulating the user optical signal of the NRZ code with the clock signal extracted by the clock extracting means and converting it into an RZ code. Features.

  In the optical network node device according to claim 5, which is dependent on claim 4, the encoding conversion means includes an optical phase modulator that converts a user optical signal converted into an RZ code into a CRZ code. Features.

  An optical network system according to claim 6, comprising: a first optical network node device connected to a transmission side of a user node; and a second optical network node device connected to a reception side of the user node; One optical network node apparatus converts a user optical signal of an NRZ code transmitted from a user node into a CS-RZ code, and performs wavelength division multiplexing transmission to the second optical network node apparatus.

  An optical network system according to claim 7, comprising: a first optical network node device connected to a transmission side of a user node; and a second optical network node device connected to a reception side of the user node, One optical network node apparatus converts a user optical signal of an NRZ code transmitted from a user node into an RZ code, and performs wavelength division multiplexing transmission to the second optical network node apparatus.

  The optical network system according to claim 8, comprising: a first optical network node device connected to a transmission side of a user node; and a second optical network node device connected to a reception side of the user node, The second optical network node device performs optical code conversion opposite to the optical code conversion performed by the first optical network node device.

  In the invention according to claim 9, which is dependent on claim 8, the first optical network node device converts a user optical signal of an NRZ code transmitted from a user node into a CS-RZ code, and wavelength division multiplexing transmission. The second optical network node device converts the user optical signal of the CS-RZ code into an NRZ code and sends it to the user node.

  In the invention according to claim 10, which is dependent on claim 8, the first optical network node device converts a user optical signal of an NRZ code transmitted from a user node into an RZ code, and performs wavelength division multiplexing transmission. The second optical network node device converts the user optical signal of the RZ code into an NRZ code and sends it to the user node.

  According to the first aspect of the present invention, a part of the user optical signal directly accommodated for wavelength multiplexing is extracted, and the intensity of the user optical signal is modulated according to the clock signal extracted from the extracted user optical signal, Since the user optical signal is converted into an encoding format suitable for long-distance transmission, the transmission characteristic of the user signal can be improved. In addition, there is an effect that it is suitable for a wavelength lending service that opens the wavelength of the wavelength multiplexed signal to the user.

  According to the second aspect of the present invention, when the transmission distance to the connection destination is short, the directly accommodated user optical signal is wavelength-multiplexed and transmitted as it is, while the transmission distance to the connection destination is long. Since the user optical signal converted into the encoding format suitable for long-distance transmission is wavelength-multiplexed and transmitted, the transmission characteristics of the user signal can be improved. In addition, there is an effect that it is suitable for a wavelength lending service that opens the wavelength of the wavelength multiplexed signal to the user.

  According to the third aspect of the present invention, a half clock obtained by extracting a part of the user optical signal of the NRZ code directly accommodated for wavelength multiplexing and dividing the clock signal extracted from the extracted user optical signal of the NRZ code Since the user optical signal of NRZ code is intensity-modulated and converted into a CS-RZ code, the transmission characteristics of the user signal can be improved. In addition, there is an effect that it is suitable for a wavelength lending service that opens the wavelength of the wavelength multiplexed signal to the user.

  According to the fourth aspect of the present invention, a part of the user optical signal of the NRZ code directly accommodated for wavelength multiplexing is extracted, and the user of the NRZ code is extracted with the clock signal extracted from the extracted user optical signal of the NRZ code. Since the optical signal is intensity-modulated and converted into an RZ code, the transmission characteristic of the user signal can be improved. In addition, there is an effect that it is suitable for a wavelength lending service that opens the wavelength of the wavelength multiplexed signal to the user.

  According to the sixth and seventh aspects of the invention, the first optical network node device connected to the transmission side of the user node and the second optical network node device connected to the reception side of the user node are provided. The first optical network node device converts the user optical signal of the NRZ code transmitted from the user node into a CS-RZ code and wavelength-multiplexes the signal to the second optical network node device, or the user node The user optical signal of the NRZ code transmitted from is converted into an RZ code and is wavelength-division-multiplexed to the second optical network node device. Long-distance transmission is possible without changing the user node device side. In addition, it is possible to easily construct an economical network and to achieve an effect that it is suitable for a wavelength lending service that opens the wavelength of the wavelength multiplexed signal to the user.

  According to invention of Claims 8-10, it has the 1st optical network node apparatus connected to the transmission side of a user node, and the 2nd optical network node apparatus connected to the reception side of a user node. The second optical network node device performs optical code conversion opposite to the optical code conversion performed by the first optical network node device, so that the longer distance without changing the user node device side. Transmission is possible. In addition, it is possible to easily construct an economical network and to achieve an effect that it is suitable for a wavelength lending service that opens the wavelength of the wavelength multiplexed signal to the user.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an optical network system 100 according to an embodiment of the present invention. The optical network system 100 includes a plurality of optical network node devices 10 that are connected to each other via an optical fiber that is a transmission medium, and a user node 200 that is connected to each optical network node device 10. The optical network node device 10 directly accommodates a user optical signal from the user node 200, transmits it as it is when the connection-destination user node 200 is a short distance, and when the connection-destination user node 200 is a long distance. As will be described later, the optical signal is encoded and converted and transmitted.

  FIG. 2 is a block diagram showing a configuration of the optical network node device 10. An optical network node device 10 includes an electrical multiplexing circuit 11 that electrically multiplexes low-speed client signals and outputs a high-speed optical signal, and an encoding conversion circuit 12 that optically converts a user optical signal that has been NRZ-modulated as a high-speed client signal. And a wavelength multiplexing circuit 13 for converting a high-speed optical signal output from the electrical multiplexing circuit 11 and a user optical signal optically encoded and converted by the encoding conversion circuit 12 into a wavelength multiplexed signal.

  The encoding conversion circuit 12 according to the gist of the present invention includes an optical branch circuit 120, a timing extraction circuit 121 and an optical intensity modulator 122. The optical branching circuit 120 extracts a part of the directly accommodated user optical signal and outputs the main signal side as it is to the next stage. The timing extraction circuit 121 extracts a clock signal from the user optical signal extracted by the optical branching circuit 120. The light intensity modulator 122 converts the sign of the main signal output from the optical branching circuit 120 as light based on the clock signal extracted by the timing extraction circuit 121. The optical intensity modulator 122 uses the extracted clock signal as a full clock, converts the NRZ optical signal into an RZ optical signal, uses the extracted clock signal as a half clock, and converts the NRZ optical signal to CS− A CS-RZ conversion circuit for converting into an RZ optical signal. Further, CRZ conversion can be performed by adding an optical phase modulator to the RZ conversion circuit. These optical code conversions are expected to improve transmission characteristics as compared with conventional NRZ modulation, and can be transmitted to a user node at a longer distance.

  Next, with reference to FIG. 3, the contents of the verification experiment of the optical network node device 10 according to the present invention will be described. FIG. 3A is a block diagram showing the configuration of the demonstration experiment system. As the user node device 200, a 40G terminal device having a transmission / reception function of a 40 Gb / s NRZ optical signal is used. A 40 Gb / s NRZ optical signal transmitted from the 40 G terminal equipment is transmitted through a 25 km optical fiber DSF, and then branched into two in the encoding conversion circuit 12 of the optical network node apparatus 10 according to the present invention. Based on the 20 GHz half clock extracted from one branched NRZ optical signal, intensity modulation is performed on the other branched NRZ optical signal to perform CS-RZ conversion. The CS-RZ optical signal thus obtained is transmitted through an optical amplifier EDFA and transmitted through an 80 km optical fiber DSF that simulates between network nodes and between a network node and a connected user node. Received.

In such an experimental system, the error rate BER with respect to the received light power in the 40G terminal device receiving unit when the NRZ / CS-RZ code conversion is performed and when the NRZ optical signal is transmitted is illustrated in FIG. To do. As is apparent from the graph shown in this figure, when both are compared with the received power that achieves BER = ^10-12 , the NRZ / CS-RZ code conversion is performed compared to the case where the NRZ optical signal is transmitted. It can be seen that a characteristic improvement of about 2 dB is obtained, and long-distance transmission is possible. Although omitted in the configuration of this demonstration experimental system for the principle confirmation, in practice, the network node device 10 after the NRZ / CS-RZ conversion circuit and after transmission has a wavelength demultiplexing circuit. It is common.

In the experimental system described above, an example in which NRZ / CS-RZ code conversion is performed has been described. However, the gist of the present invention is not limited to this, and various modifications can be made. For example, the optical network node apparatus 10 may convert the NRZ optical signal received from the user node apparatus 200 into an RZ optical signal and transmit it by NRZ / RZ code conversion instead of NRZ / CS-RZ code conversion. For example, as illustrated in FIG. 4, a mode of performing NRZ / CS-RZ code conversion and CS-RZ / NRZ code conversion in the transmission of the optical network node device 10 is also possible.
That is, after the 40 Gb / s NRZ optical signal transmitted from the user node device 200 is transmitted through the optical fiber DSF, it is branched into two in the encoding conversion circuit 12-1 of the optical network node device 10, and one of the branched ones. Based on the 20 GHz half clock extracted from the NRZ optical signal, intensity modulation is performed on the other branched NRZ optical signal to perform CS-RZ conversion, thereby converting it into a CS-RZ optical signal.

  The CS-RZ optical signal is amplified by an optical amplifier EDFA and then transmitted to another optical network node device 10 through an optical fiber DSF that simulates between network nodes. In the encoding conversion circuit 12-2 of another optical network node device 10, the CS-RZ optical signal is branched into two, based on a 20 GHz half clock extracted from one of the branched CS-RZ optical signals. Then, intensity modulation is performed on the other branched CS-RZ optical signal to convert it into an RZ optical signal. Thereafter, the RZ optical signal is passed through an optical filter and converted into an NRZ optical signal, and then transmitted to the connected user node device 200 (40G receiving terminal station).

  As shown in FIG. 5, the coding conversion circuit 12-2 that performs CS-RZ / NRZ code conversion includes a CS-RZ / RZ conversion circuit 12-2a and an RZ / NRZ conversion circuit 12-2b. Here, the CS-RZ / RZ conversion circuit 12-2a has the same configuration as that of the encoding conversion circuit 12 shown in FIG. 1, and when a CS-RZ optical signal is input, it is used as a half clock of the input. When the intensity is modulated, RZ conversion is performed. The RZ / NRZ conversion circuit 12-2b is composed of an optical filter having the transmission characteristics shown in FIG. 6, and an NRZ optical signal is obtained by filtering the RZ optical signal with this optical filter.

  Next, FIG. 7 is a block diagram showing a configuration for performing NRZ / RZ code conversion and RZ / NRZ code conversion in the transmission of the optical network node device 10. In this case, after the 40 Gb / s NRZ optical signal transmitted from the user node device 200 is transmitted through the optical fiber DSF, it is branched into two in the encoding conversion circuit 12-1 of the optical network node device 10, and one of the branched signals. Based on the 40 GHz full clock extracted from the NRZ optical signal, the other branched NRZ optical signal is intensity-modulated and converted to an RZ optical signal.

  The RZ optical signal is amplified by an optical amplifier EDFA and then transmitted to another optical network node device 10 through an optical fiber DSF that simulates between network nodes. In an encoding conversion circuit 12-3 of another optical network node device 10, an RZ / NRZ conversion circuit (same as the RZ / NRZ conversion circuit 12-2b in FIG. 5) having the configuration shown in FIG. 8, that is, shown in FIG. The RZ optical signal is filtered and converted into an NRZ optical signal by an optical filter having transmission characteristics to be transmitted, and then transmitted to the connected user node device 200 (40G receiving terminal station).

  As described above, in the present embodiment, in the optical network node device 10 forming the optical network system 100, a part of the user optical signal (NRZ optical signal) directly accommodated in the wavelength multiplexed signal is extracted and clock extraction is performed. The user optical signal is intensity-modulated according to the extracted clock, and the user optical signal (NRZ optical signal) is converted into a CS-RZ optical signal or RZ optical signal suitable for long-distance transmission. Transmission characteristics can be improved. In addition, since long-distance transmission is possible without making any changes on the user node device side, it is possible to easily construct an economical network, and it is suitable for a wavelength lending service that opens the wavelength of the wavelength multiplexed signal to the user. Also has the effect of.

1 is a diagram showing a schematic configuration of an optical network system 100 according to an embodiment of the present invention. 2 is a block diagram showing a configuration of an optical network node device 10. FIG. It is a figure for demonstrating the content of a demonstration experiment system. It is a figure which shows an example which performs NRZ / CS-RZ code conversion and CS-RZ / NRZ code conversion. It is a block diagram which shows the structure of CS-RZ / RZ conversion circuit 12-2a and RZ / NRZ conversion circuit 12-2b. It is a figure which shows the permeation | transmission characteristic of the optical filter with which RZ / NRZ conversion circuit 12-2b is provided. It is a block diagram which shows the structure which performs NRZ / RZ code conversion and RZ / NRZ code conversion. It is a block diagram which shows the structure of the encoding conversion circuit 12-3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical network node apparatus 11 Electric multiplexing circuit 12 Coding conversion circuit 120 Optical branching circuit 121 Timing extraction circuit 122 Optical intensity modulator 13 Wavelength multiplexing circuit 100 Optical network

Claims (10)

An optical branching means for extracting a part of a user optical signal directly accommodated for wavelength multiplexing;
Clock extraction means for extracting a clock signal from the user optical signal extracted by the optical branching means;
Encoding conversion means for intensity-modulating the user optical signal according to the clock signal extracted by the clock extraction means, and converting the user optical signal into an encoding format suitable for long-distance transmission. A characteristic optical network node device. An optical branching means for extracting a part of a user optical signal directly accommodated for wavelength multiplexing;
Clock extraction means for extracting a clock signal from the user optical signal extracted by the optical branching means;
In accordance with the clock signal extracted by the clock extraction means, the user optical signal is intensity-modulated, and the user optical signal is converted into an encoding format suitable for long-distance transmission,
When the transmission distance to the connection destination is short, the directly accommodated user optical signal is wavelength-multiplexed and transmitted as it is, and when the transmission distance to the connection destination is long, long-distance transmission is performed by the encoding conversion means. An optical network node device comprising: transmission means for wavelength-multiplexing and transmitting a user optical signal converted into an encoding format suitable for the optical network. Optical branching means for extracting a part of the user optical signal of the NRZ code directly accommodated for wavelength multiplexing;
A clock extracting means for extracting a clock signal from the user optical signal of the NRZ code extracted by the optical branching means;
And a coding conversion means for modulating the intensity of the user optical signal of the NRZ code with a half clock obtained by dividing the clock signal extracted by the clock extraction means and converting it into a CS-RZ code. Optical network node device. Optical branching means for extracting a part of the user optical signal of the NRZ code directly accommodated for wavelength multiplexing;
A clock extracting means for extracting a clock signal from the user optical signal of the NRZ code extracted by the optical branching means;
An optical network node device comprising: an encoding conversion unit that modulates an intensity of a user optical signal of an NRZ code using the clock signal extracted by the clock extraction unit and converts the optical signal into an RZ code.   5. The optical network node apparatus according to claim 4, wherein the encoding conversion means comprises an optical phase modulator that converts a user optical signal converted into an RZ code into a CRZ code. A first optical network node device connected to the transmission side of the user node;
A second optical network node device connected to the receiving side of the user node,
An optical network characterized in that a first optical network node device converts a user optical signal of an NRZ code transmitted from a user node into a CS-RZ code, and wavelength-division-transmits the signal to the second optical network node device. system. A first optical network node device connected to the transmission side of the user node;
A second optical network node device connected to the receiving side of the user node,
The first optical network node device converts a user optical signal of an NRZ code transmitted from a user node into an RZ code, and wavelength-division-transmits the signal to the second optical network node device. A first optical network node device connected to the transmission side of the user node;
A second optical network node device connected to the receiving side of the user node,
The optical network system, wherein the second optical network node device performs optical code conversion opposite to optical code conversion performed by the first optical network node device. The first optical network node device converts a user optical signal of an NRZ code transmitted from a user node into a CS-RZ code, and performs wavelength division multiplexing transmission.
9. The optical network system according to claim 8, wherein the second optical network node device converts a user optical signal of a CS-RZ code into an NRZ code and transmits the NRZ code to the user node. The first optical network node device converts a user optical signal of an NRZ code transmitted from a user node into an RZ code, and performs wavelength division multiplexing transmission.
9. The optical network system according to claim 8, wherein the second optical network node device converts the user optical signal of the RZ code into an NRZ code and transmits the NRZ code to the user node.

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