JP2006287696A - Dispersion compensation device, optical communication equipment using the same, and optical communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain miniaturization and cost reduction of a dispersion compensation device by reducing the number of dispersion compensation means used in the dispersion compensation device. <P>SOLUTION: Dispersion of optical signals with two different wavelength is compensated by one dispersion compensation means by constituting the dispersion compensation device so as to input an optical signal with first wavelength in one end of an input/output terminal of the dispersion compensation means, to output the optical signal from the other end, to input an optical signal with second wavelength in the other end and to output the optical signal from one end by connecting directional couplers to both ends of the dispersion compensation means, respectively. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to compensation for chromatic dispersion generated in an optical signal transmission line of a DWDM (Dense Wavelength Division Multiplexing) optical communication system, and in particular, chromatic dispersion can be compensated with fewer dispersion compensation means than before. The present invention relates to a dispersion compensator, an optical communication apparatus using the same, and an optical communication system.

  With the rapid growth of the information and communication industry in recent years, the demand for high-speed and large-capacity optical communication systems is increasing. For example, the basic communication systems of Internet connection services such as ADSL (Asymmetric Digital Subscriber Line), FTTH (Fiber To The Home), and wireless, which have been rapidly spreading for general households in recent years, are composed of optical communication systems. With the increase of subscribers and the amount of data transmitted, the demand for communication traffic is rapidly increasing. In addition, fixed telephones and the like that conventionally use analog signals are also being accommodated in the optical communication system (core communication system) due to the progress of IP (Internet Protocol). Thus, there is a growing need for high speed and large capacity for optical communication systems.

  Along with the need for higher speed and higher capacity of optical communication, an increase in the bit rate of optical signals and an increase in the number of wavelength multiplexing (hereinafter referred to as high multiplexing) are rapidly progressing. With a higher bit rate, the transmission speed of a general optical communication system has increased from 2.5 Gbps to 10 Gbps over the past few years, and development is now underway toward the spread of the 40 Gbps level. Also, with high multiplexing, the number of multiplexing in a general optical communication system has increased from about 4 waves to over 100 waves in the last few years, and development for further higher multiplexing is now underway. .

  By the way, in a system that transmits long distances such as between major metropolitan cities among the basic communication systems, as the bit rate of the optical signal is increased, it becomes difficult to identify each bit received at the receiving end of the optical signal, A reception error occurs. This is due to a phenomenon called chromatic dispersion. This is because the signal waveform is distorted in proportion to the transmission distance because the propagation speed of light in the medium differs depending on the wavelength. When the distortion becomes large, a certain bit received at the receiving end of the optical signal cannot be distinguished from the preceding and succeeding bits.

  As a solution to this problem, a method of compensating for chromatic dispersion using a dispersion compensator is known (see, for example, Patent Document 1). The dispersion compensator compensates for chromatic dispersion generated in the transmission line using a dispersion compensation fiber or the like having a dispersion characteristic tendency opposite to that of the optical fiber used in the transmission line.

  However, when the wavelength band becomes wide due to high multiplexing, it becomes difficult for one dispersion compensator to appropriately compensate dispersion over the entire wavelength band. This is because it is difficult to precisely reverse the dispersion characteristics of the dispersion compensator and the dispersion characteristics of the optical fiber or the like used in the transmission line over a wide band, and thus chromatic dispersion cannot be accurately compensated over the entire area. In order to accurately compensate chromatic dispersion over a wide band, it is necessary to divide the band and use a plurality of dispersion compensators. Specifically, a technique is known in which a wavelength-multiplexed optical signal is demultiplexed for each wavelength (channel), and dispersion is compensated by separate dispersion compensators (see, for example, Patent Document 2 and Patent Document 3). In Patent Document 2, as shown in FIG. 11, a wavelength multiplexed optical signal propagated through a transmission line is demultiplexed into optical signals of respective wavelengths by a demultiplexer 4, and a dispersion compensator 1 is provided for each wavelength. A configuration in which dispersion is compensated and received by the optical receiver 5 is disclosed. In Patent Document 3, as shown in FIG. 12, first, the dispersion of all wavelengths is compensated in a lump and then demultiplexed to each wavelength, and the remaining dispersion of each wavelength is compensated by a separate dispersion compensator. The structure to perform is disclosed.

JP-A-62-65529 JP 09-116493 A JP-A-11-103286

In the method of using a dispersion compensator for each channel as in the above-described conventional example, there is a problem that the optical communication apparatus that accommodates the dispersion compensator is increased in size and cost. Generally, a dispersion compensator is configured by winding a dispersion compensation fiber (dispersion compensation means) around a reel and housing the case in a case. Since this reel has an outer diameter and a width of several tens of centimeters, for example, when configuring an optical communication system that transmits 500 km by 64-wave multiplexing, 64 dispersion compensators are 30 cm deep × 60 cm wide × high It is the size of two 200cm equipment storage racks. This is about half of the total of four station devices.
In view of the above problems, an object of the present invention is to reduce the required number of dispersion compensators and reduce the size and cost of an optical communication device.

  The present invention is characterized in that the dispersion of two optical signals is compensated by one dispersion compensation means.

  According to the present invention, since the number of dispersion compensators to be accommodated in the optical communication apparatus can be halved, the optical communication apparatus can be significantly reduced in size and cost.

  In the dispersion compensator of the present invention, an optical signal having the first wavelength is input to one end of the input / output terminal of the dispersion compensating means and output from the other end, and an optical signal having the second wavelength is input to the other end. Configure to output from one end. Preferably, two signals of adjacent channels are compensated by a single dispersion compensator so that the dispersion becomes substantially zero.

  FIG. 1 shows a first embodiment of the present invention, and is a configuration diagram of a dispersion compensator that compensates for dispersion of two optical signals by one dispersion compensation means. In the figure, 10 is a dispersion compensation means, and 20 and 30 are directional couplers. The directional coupler is an optical branching and coupling device, and the directional coupler used in this embodiment outputs, for example, an optical signal input from the port 21 of FIG. Is output to 23.

Here, the operation when the optical signal of wavelength λ ₁ is input from input 1 and the optical signal of wavelength λ ₂ is input from input 2 will be described. First, an optical signal having a wavelength λ ₁ is input to the dispersion compensation means 10 via the directional coupler 20 (input to the port 21 and output from the port 22). Then, the dispersion is compensated by the dispersion compensation means 10 and outputted from the output 1 through the directional coupler 30 (input to the port 31 and output from the port 32).

On the other hand, the optical signal having the wavelength λ ₂ is input to the dispersion compensation means 10 through the directional coupler 30 (input to the port 33 and output from the port 31) in the direction opposite to the wavelength λ ₁ . Then, the dispersion is compensated by the dispersion compensating means 10 and outputted from the output 2 through the directional coupler 20 (input to the port 22 and output from the port 23).

  In this way, dispersion compensation of two signals having different wavelengths is performed by one dispersion compensator. Preferably, two signals of adjacent channels are compensated by a single dispersion compensator so that the dispersion becomes substantially zero. Since the two signals have different wavelengths, it is not possible to optimally compensate for the respective dispersions, but the difference in dispersion amount between adjacent channels is small and within the error range in the system design. By adopting a configuration in which the dispersion of two signals having different wavelengths is compensated by one dispersion compensation means, the number of dispersion compensation means can be halved in the present invention.

  In this embodiment, directional couplers are added to both ends of the dispersion compensation means, but this directional coupler is much smaller and less expensive than the dispersion compensation fiber. Therefore, by adding two directional couplers and reducing one dispersion compensation means, the dispersion compensation device can be greatly reduced in size and cost, and an exceptional effect can be achieved.

  FIG. 2 shows a second embodiment of the present invention, in which the directional couplers 20 and 30 in the first embodiment are replaced with an optical circulator 200 and an optical circulator 300, respectively. The insertion loss of an optical circulator is generally about 1 dB, and the insertion loss can be reduced compared to the first embodiment using a directional coupler (generally the insertion loss is 3 dB or more).

  In this embodiment, an optical circulator is added to both ends of the dispersion compensation means, but this optical circulator is much smaller and less expensive than the dispersion compensation fiber. Therefore, by adding two optical circulators and reducing one dispersion compensation means, the dispersion compensation device can be greatly reduced in size and cost, and an exceptional effect can be achieved.

  FIG. 3 shows a third embodiment of the present invention, in which the directional couplers 20 and 30 in the first embodiment are configured by a 3 dB optical coupler 201 (301) and an optical isolator 202 (302), respectively. . A 3 dB optical coupler is an optical device that equally divides incident light into two ports (equal power).

Here, an operation when an optical signal having the wavelength λ ₁ is input from the input 1 will be described. The optical signal having the wavelength λ ₁ is input from the port 21 of the directional coupler 20, passes through the optical isolator 202, is input to the optical coupler 201, and is equally distributed to the port 22 side and the optical coupler open end. Therefore, the optical signal of wavelength λ ₁ output from the port 22 side is input to the dispersion compensation means 10 with a loss of about 3 dB. The optical signal having the wavelength λ ₁ that is dispersion-compensated by the dispersion compensation means 10 enters from the port 31 of the directional coupler 30 and is equally distributed to the port 32 side and the port 33 side by the optical coupler 301. Here, since the optical signal having the wavelength λ ₁ branched to the port 33 side is blocked by the optical isolator 302, it is output only from the port 32. Therefore, it outputs only from port 32 with a loss of 3 dB. As described above, in this embodiment, the insertion loss (3 dB) of the directional coupler 20 (30) is larger than that of the optical circulator 200 (300) (insertion loss 1 dB). It is characterized by using a cheaper device. Accordingly, the cost can be further reduced as compared with the dispersion compensator configured using the directional coupler and the optical circulator as disclosed in the first and second embodiments. In addition, both the optical isolator and the optical coupler are significantly smaller than the dispersion compensating fiber, and the dispersion compensating apparatus can be greatly reduced in size. Therefore, by adding two directional couplers having the configuration shown in the present embodiment and reducing one dispersion compensation means, the dispersion compensation device can be greatly reduced in size and cost, and an exceptional effect can be achieved. I was able to.

FIG. 4 shows a fourth embodiment of the present invention, and is a configuration diagram of an optical communication apparatus on the reception side of a 64-wavelength multiplexed optical signal using the dispersion compensators 1-1 to 1-32 of the present invention. The demultiplexer 4 demultiplexes the wavelength-multiplexed optical signal into wavelengths λ ₁ to λ ₆₄ , and optical signals of two adjacent wavelengths (for example, λ ₁ and λ _{2 in} FIG. 4) among the demultiplexed optical signals. Is input to each input port (λ ₁ → input 1, λ ₂ → input 2) of the dispersion compensator 1-1. Then, the optical signals of wavelengths λ ₁ and λ ₂ that have been dispersion-compensated by the dispersion compensator are output from the output ports (output 1 → λ ₁ , output 2 → λ ₂ ) of the dispersion compensator 1-1. These optical signals are converted into electrical signals by the optical receiver 5-1 and the optical receiver 5-2, respectively. In this figure, the configuration of the subsequent stage from the demultiplexer 4 is the same regardless of whether or not the dispersion compensator for all-wavelength collective compensation is arranged before the demultiplexer 4, so that the dispersion compensation for collective compensation is the same. The vessel is not shown. Needless to say, this embodiment can also be applied to the case where a dispersion compensator for all-wavelength collective compensation is arranged in front of the duplexer 4. Even if the number of wavelengths to be multiplexed changes (for example, 32 waves, 128 waves, etc.), there is no particular change in the configuration of this embodiment in which dispersion of two types of optical signals can be compensated simultaneously by one dispersion compensation means. .

  According to the present embodiment, the required amount of the dispersion compensator is halved compared with the prior art, and the optical communication apparatus can be significantly reduced in size and cost, and an exceptional effect can be achieved.

FIG. 5 shows a fifth embodiment of the present invention, which is a configuration of an optical communication apparatus on the transmission side of a 64-wavelength multiplexed optical signal using the dispersion compensators 1-1 to 1-32 of the present invention. In the fourth embodiment, the system for compensating for the dispersion of the optical signal of each wavelength after the optical signal propagates through the transmission line is disclosed. However, in this embodiment, before the optical signal propagates through the transmission line, the transmission line This is an embodiment in which the amount corresponding to the amount of dispersion generated by propagating is compensated in advance. Of the optical signals of wavelengths λ _{1 to} λ ₆₄ output from the optical transmitters 8-1 to 8-64, optical signals of two adjacent wavelengths (for example, λ ₁ and λ ₂ ) are converted into dispersion compensators 1-1. To each input port (λ ₁ → input 1, λ ₂ → input 2). The optical signal dispersion compensation wavelength lambda ₁ and lambda ₂ in the dispersion compensator is output from the dispersion compensator 1 ₁ output port (output 1 → lambda _1, the output ₂ → λ 2). Similarly, after passing optical signals of two adjacent wavelengths through one dispersion compensator, the optical signals of wavelengths λ _{1 to} λ ₆₄ output from the respective dispersion compensators are input to the multiplexer 9. After being converted into a wavelength multiplexed optical signal, it is output to the transmission line. In this figure, since the configuration of the preceding stage of the multiplexer 9 is the same regardless of whether or not the dispersion compensator for all-wavelength collective compensation is arranged at the subsequent stage of the multiplexer 9, the dispersion compensation for collective compensation is the same. The vessel is not shown. Needless to say, this embodiment can also be applied to the case where a dispersion compensator for all-wavelength collective compensation is arranged at the subsequent stage of the multiplexer 9. Even if the number of wavelengths to be multiplexed changes (for example, 32 waves, 128 waves, etc.), there is no particular change in the configuration of this embodiment in which dispersion of two types of optical signals can be compensated simultaneously by one dispersion compensation means. .

  According to the present embodiment, the required amount of the dispersion compensator is halved compared with the prior art, and the optical communication apparatus can be significantly reduced in size and cost, and an exceptional effect can be achieved.

FIG. 6 shows a sixth embodiment of the present invention, which is a configuration example of an optical repeater for 64-wavelength multiplexed optical signals using the dispersion compensators 1-1 to 1-32 of the present invention. In the fourth and fifth embodiments, the example of dispersion compensation at the receiving terminal station and the transmitting terminal station of the optical signal is disclosed. However, the present embodiment is an example of compensating the dispersion of the optical signal in the optical repeater. The wavelength multiplexed optical signal propagated through the transmission line is demultiplexed into wavelengths λ _{1 to} λ ₆₄ by the demultiplexer 4, and two adjacent wavelengths (for example, λ ₁ and λ ₂ ) among the demultiplexed optical signals. of the optical signal, inputted to the input port of the dispersion compensator ₁ 1 (λ 1 → input 1, lambda ₂ → input 2). The optical signal dispersion compensation wavelength lambda ₁ and lambda ₂ in the dispersion compensator is output from the dispersion compensator 1 ₁ output port (output 1 → lambda _1, the output ₂ → λ 2). Similarly, after passing optical signals of two adjacent wavelengths through one dispersion compensator, the optical signals of wavelengths λ _{1 to} λ ₆₄ output from the respective dispersion compensators are input to the multiplexer 9. After being converted into a wavelength multiplexed optical signal, it is output to the transmission line. This figure shows the configuration from the demultiplexer 4 to the multiplexer 9 regardless of whether or not the dispersion compensator for collective compensation of all wavelengths is arranged before the demultiplexer 4 and after the multiplexer 9. For the same reason, the dispersion compensator for collective compensation is not shown. Needless to say, this embodiment can also be applied to the case where a dispersion compensator for all-wavelength collective compensation is arranged at the front stage of the duplexer 4 or the rear stage of the multiplexer 9. Even if the number of wavelengths to be multiplexed changes (for example, 32 waves, 128 waves, etc.), there is no particular change in the configuration of this embodiment in which dispersion of two types of optical signals can be compensated simultaneously by one dispersion compensation means. .

  According to the present embodiment, the required amount of the dispersion compensator is halved compared with the prior art, and the optical communication apparatus can be significantly reduced in size and cost, and an exceptional effect can be achieved.

FIG. 7 shows a seventh embodiment of the present invention, which is an optical communication device in which the duplexer 4 in the fourth embodiment is configured using an interleaver 6 and an AWG (Arrayed Waveguide Grating) 7. An interleaver demultiplexes a wavelength-multiplexed optical signal into two sets of signal sequences whose wavelength interval is twice, or conversely combines two sets of wavelength-multiplexed optical signals into one signal sequence whose wavelength interval is half. It is a device having a function to perform. In a DWDM optical transmission system that multiplexes wavelengths at small intervals such as 0.4 nm intervals, the demultiplexer is often composed of the interleaver 6 and demultiplexers having double wavelength intervals. In this embodiment, the wavelength multiplexed optical signal is converted into an odd channel wavelength (λ ₁ , λ ₃ ,... Λ ₆₃ ) and an even channel wavelength (λ ₂ , λ ₄ ,...) By an interleaver 6 in the demultiplexer ₄ .・ Demultiplex to λ ₆₄ ), and then demultiplex each by AWG7 for each wavelength. Thereafter, similarly to the fourth embodiment, the dispersion compensation of the optical signals having adjacent wavelengths is performed by one dispersion compensator. In this figure, as in FIG. 4, the configuration of the subsequent stage from the demultiplexer 4 is the same regardless of whether or not the dispersion compensator for all-wavelength collective compensation is arranged in the previous stage of the demultiplexer 4. A compensating dispersion compensator is not shown. Needless to say, this embodiment can also be applied to the case where a dispersion compensator for all-wavelength collective compensation is arranged in front of the duplexer 4. Even if the number of wavelengths to be multiplexed changes (for example, 32 waves, 128 waves, etc.), there is no particular change in the configuration of this embodiment in which dispersion of two types of optical signals can be compensated simultaneously by one dispersion compensation means. .

FIG. 8 shows an eighth embodiment of the present invention, which is an optical communication apparatus in which a multiplexer 9 in the fifth embodiment is configured using an interleaver 6 and an AWG 7. Similar to the fifth embodiment, dispersion compensation is performed on optical signals having adjacent wavelengths by using one dispersion compensator. Then, the odd channel wavelengths (λ ₁ , λ ₃ ,..., Λ ₆₃ ) and the even channel wavelengths (λ ₂ , λ ₄ ,... Λ ₆₄ ) are respectively multiplexed by the AWG 7 in the multiplexer 9. After that, they are made incident on the interleaver 6 and output to the transmission line as wavelength multiplexed optical signals of wavelengths λ _{1 to} λ ₆₄ that combine the odd channels and the even channels. In this figure, as in FIG. 5, the configuration of the preceding stage of the multiplexer 9 is the same regardless of whether or not the dispersion compensator for all-wavelength collective compensation is arranged after the multiplexer 9. A compensating dispersion compensator is not shown. Needless to say, this embodiment can also be applied to the case where a dispersion compensator for all-wavelength collective compensation is arranged at the subsequent stage of the multiplexer 9. Even if the number of wavelengths to be multiplexed changes (for example, 32 waves, 128 waves, etc.), there is no particular change in the configuration of this embodiment in which dispersion of two types of optical signals can be compensated simultaneously by one dispersion compensation means. .

FIG. 9 shows a ninth embodiment of the present invention, which is an optical repeater in which at least one of the duplexer 4 and the multiplexer 9 in the sixth embodiment is constituted by an interleaver 6 and an AWG 7. . In the present embodiment, the duplexer 4 and the multiplexer 9 are both configured by the interleaver 6 and the AWG 7, but only the duplexer may be configured by the interleaver 6 and the AWG 7. Only a multiplexer may be used. A wavelength multiplexed optical signal is converted into an odd channel wavelength (λ ₁ , λ ₃ ,..., Λ ₆₃ ) and an even channel wavelength (λ ₂ , λ ₄ ,... Λ ₆₄ ) by an interleaver 6 in the duplexer 4. Then, each is demultiplexed to each wavelength by AWG7. Thereafter, similarly to the sixth embodiment, the dispersion compensation is performed on the optical signals having adjacent wavelengths by using one dispersion compensator. Thereafter, the optical signals of the wavelengths λ _{1 to} λ ₆₄ output from the respective dispersion compensators are set to odd channel wavelengths (λ ₁ , λ ₃ ,... Λ ₆₃ ) and even numbers by the AWG 7 in the multiplexer 9. The channel wavelengths (λ ₂ , λ ₄ ,... Λ λ ₆₄ ) are combined and then incident on the interleaver 6, and wavelength multiplexing of wavelengths λ _{1 to} λ ₆₄ , which combines the odd channel and the even channel. Output to the transmission line as an optical signal. In this figure, similarly to FIG. 6, regardless of whether or not a dispersion compensator for all-wavelength collective compensation is arranged before the duplexer 4 and after the multiplexer 9, the duplexer 4 to the multiplexer Since the configuration up to 9 is the same, the dispersion compensator for collective compensation is not shown. Needless to say, this embodiment can also be applied to the case where a dispersion compensator for all-wavelength collective compensation is arranged at the front stage of the duplexer 4 or the rear stage of the multiplexer 9. Even if the number of wavelengths to be multiplexed changes (for example, 32 waves, 128 waves, etc.), there is no particular change in the configuration of this embodiment in which dispersion of two types of optical signals can be compensated simultaneously by one dispersion compensation means. .

  FIG. 10 shows a tenth embodiment of the present invention. In an optical communication system applied to a submarine system or a land-based trunk medium-to-long distance optical communication transmission line, the optical communication apparatus according to any of the fourth to ninth embodiments. It is an example of the optical communication system characterized by using at least 1 among these. As described above, by halving the number of dispersion compensators mounted in the optical communication apparatus, it was possible to achieve a special effect of significantly reducing the cost for configuring the optical communication system.

The figure which shows the 1st Example of this invention The figure which shows the 2nd Example of this invention The figure which shows the 3rd Example of this invention The figure which shows the 4th Example of this invention The figure which shows the 5th Example of this invention The figure which shows the 6th Example of this invention The figure which shows the 7th Example of this invention The figure which shows the 8th Example of this invention The figure which shows the 9th Example of this invention The figure which shows the 10th Example of this invention The figure which shows the conventional dispersion compensation method with respect to a wavelength multiplexing optical signal The figure which shows the conventional dispersion compensation method with respect to a wavelength multiplexing optical signal

Explanation of symbols

1: dispersion compensator 10: dispersion compensation means 20, 30: directional couplers 21, 22, 23,
31, 32, 33: input / output terminals 200, 300: optical circulator 201, 301: 3 dB optical coupler 202, 302: optical isolator 4: duplexer 5: optical receiver 6: interleaver 7: AWG (Arrayed Waveguide Grating)
8: Optical transmitter 9: Multiplexer 11: Optical communication device (transmission side)
12: Optical repeater 13: Optical communication device (receiving side)

Claims (11)

In a dispersion compensator having one or a plurality of dispersion compensation means used in an optical communication system, an optical signal having a first wavelength is inputted to one end of an input / output terminal of at least one dispersion compensation means and outputted from the other end. The dispersion compensator is characterized in that an optical signal having a second wavelength is input to the other end and output from the one end. 2. The dispersion compensator according to claim 1, wherein directional couplers are connected to both input and output ends of the dispersion compensation means. 2. The dispersion compensator according to claim 1, wherein optical circulators are connected to both input and output ends of the dispersion compensation means. The dispersion compensator according to claim 2, wherein the directional coupler includes an optical coupler and an optical isolator. A demultiplexer for demultiplexing the wavelength-multiplexed optical signal; a dispersion compensation device for compensating for dispersion of the optical signal output from the demultiplexer; and an optical receiver for receiving the optical signal output from the dispersion compensation device. An optical communication apparatus, wherein the dispersion compensator is configured by using at least one dispersion compensator according to any one of claims 1 to 4. In the optical communication device comprising: a light source; a dispersion compensation device that compensates for dispersion of an optical signal output from the light source; and a multiplexer that combines the optical signals output from the dispersion compensation device and outputs the multiplexed signals to a transmission path. An optical communication apparatus, wherein the dispersion compensator is configured by using at least one dispersion compensator according to claim 1. A demultiplexer for demultiplexing a wavelength-multiplexed optical signal, a dispersion compensation device for compensating for dispersion of the optical signal output from the demultiplexer, and an optical signal output from the dispersion compensation device are combined and output to a transmission line. 5. An optical communication apparatus including a multiplexer, wherein the dispersion compensation apparatus is configured using at least one dispersion compensator according to claim 1. 6. The optical communication apparatus according to claim 5, wherein the duplexer includes an arrayed waveguide grating (AWG) and an interleaver. The optical communication apparatus according to claim 6, wherein the multiplexer includes an AWG and an interleaver. 8. The optical communication apparatus according to claim 7, wherein at least one of the multiplexer and the duplexer includes an AWG and an interleaver. A wavelength division multiplexing optical communication system using at least one of the optical communication apparatuses according to claim 5.

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