JP2006121725A - Optical repeater, optical repeating method, optical transmission system and optical transmission method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To readily compensate for deterioration of waveform due to SPM-GVD effect without designing/manufacturing a light dispersion compensator depending on individual transmission lines, to reduce labor and time required for configuring an optical communication, and to also reduce the cost. <P>SOLUTION: The optical repeater is provided with: a first unit including an optical demultiplexing section for demultiplexing the waveform of a wavelength-division multiplexed optical signal including a plurality of optical signals having different wavelengths into first optical signals and second optical signals having wavelengths longer than wavelengths of the first optical signals, and a first dispersion compensator for compensating the dispersion of the first optical signals; and a second unit including a second dispersion compensator for compensating the dispersion of the second optical signals. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical wavelength multiplex transmission system using a band around the zero dispersion wavelength of an optical fiber, and a long distance and ultrahigh speed using, for example, an erbium doped optical fiber amplifier (hereinafter referred to as EDFA). In an optical communication system, a technique for compensating for waveform deterioration due to a mutual effect (hereinafter referred to as SPM-GVD effect) between self-phase modulation and chromatic dispersion (group velocity dispersion), which is one of the limiting factors of transmission distance and transmission speed. About.

As the amount of information has increased dramatically in recent years, a large-capacity communication system has become necessary. Currently, research for constructing this communication system is being actively conducted.
In order to realize such a large capacity communication system, realization by an optical communication system is most promising. For example, along with an optical communication system of 2.4 Gb / s, an optical amplification system using an EDFA is currently used. Although relay systems are being put into practical use, the amount of information is expected to increase with the progress of computerization in the future, and an optical communication system whose capacity has been increased in response to the increase in the amount of information. Construction is desired.

As a method for increasing the capacity of an optical communication system, a time division multiplexing (TDM) system that multiplexes on the time axis in the sense of increasing the transmission speed, or a WDM that performs multiplexing on the optical frequency axis [ (Wavelength division multiplexing; generally, a relatively wide wavelength interval is called a WDM system, and a high density multiplexed one is called an FDM (frequency division multiplexing) system).
Among them, in multiplexing such as TDM, in order to increase the transmission speed, it is necessary to increase the speed of the electronic circuits in the transmitter and the receiver, and at present, tens of Gb / s is considered the limit.

On the other hand, in the WDM (FDM) system using the broadband property of the optical fiber, the capacity can be increased to several tens to several hundreds Gb / s by using it together with the increase in transmission speed. By using an optical multiplexing device and an optical demultiplexing device (MUX / DEMUX) using the above, multiplexing and demultiplexing can be easily performed in the optical region, thereby reducing the burden on the electronic circuit.
Here, in the WDM (FDM) system in which wavelength division multiplexing is performed on the optical frequency axis, there is a gain band dependency of an optical amplifier and a wavelength dependency of an optical component, so that a usable band is limited. Therefore, in order to increase the capacity by multiplexing, it is necessary to narrow the channel interval and narrow the band indicated by all channels. Further, in multi-gigabit optical transmission, waveform degradation occurs due to dispersion of the optical fiber, so that the wavelength of the optical signal needs to be set around the zero dispersion wavelength of the optical fiber.

  However, in an optical communication system using the WDM (FDM) method for increasing the capacity as described above, the channel spacing is narrowed in consideration of the band, and the zero dispersion wavelength of the optical fiber is considered in consideration of chromatic dispersion. If optical signals are arranged in the vicinity, the nonlinear effect of the optical fiber, particularly the influence of four-wave mixing (hereinafter referred to as FWM (Four Wave Mixing)) becomes significant, and transmission is impossible due to crosstalk from other channels due to this FWM. There is a problem of becoming. Further, there is a similar problem even when wavelength multiplex transmission has to be performed in a band around the zero dispersion wavelength due to upgrade of an existing transmission line or the like.

In particular, the crosstalk caused by the above-mentioned FWM has been pointed out as a cause of deterioration of transmission characteristics in an optical amplification multi-relay WDM system using a band near the zero dispersion wavelength of an optical fiber. The generation efficiency of this FWM is determined by the relationship between the zero dispersion wavelength of the optical fiber transmission line and the channel arrangement.
The required characteristics of optical fibers in the WDM system include (1) zero dispersion wavelength, (2) dispersion of zero dispersion wavelength, and (3) dispersion slope (secondary dispersion). Multiple signal band, (b) Gain band of EDFA among optical amplifiers, (c) Guard band for FWM suppression according to the present invention, (d) Limit band due to SPM-GVD effect, (e) Insertion of optical dispersion compensator This is closely related to the above five elements.

By the way, there are a loss limitation due to optical fiber loss and a bandwidth limitation due to chromatic dispersion as factors that limit the increase in distance and speed of the optical communication system. Loss control is almost solved by the advent of EDFA, and it has become possible to construct an ultra-long-distance optical communication system of several thousand km or more.
However, the repeat interval in the multi-repeating optical amplification system mainly includes (1) optical SNR (Signal to Noise Ratio) degradation due to ASE (Spontaneous Emission) accumulation in each optical amplification repeater, and (2) It is limited by two factors, waveform deterioration due to the SPM-GVD effect via the Kerr effect.

  Among these, it is known that the waveform degradation due to the SPM-GVD effect of (2) can be compensated by using an optical dispersion compensator having a dispersion value of the opposite sign of the optical fiber transmission line, and the waveform degradation due to the SPM-GVD effect. The dispersion compensation effect can be easily simulated by solving the nonlinear Schroedinger equation using the split step Fourier method.

  The optical dispersion compensator used for the above-mentioned purpose can cope with the optical fiber dispersion amount of each relay section, reduces the man-hours and time required to realize the optimum dispersion compensation amount, and reduces the cost. It is required to be possible. The optical dispersion compensation technology uses not only the currently installed 1.55 μm dispersion-shifted fiber (hereinafter referred to as DSF) transmission line network but also the existing 1.3 μm single mode fiber (hereinafter referred to as SMF) transmission line network. This is also important in the long-distance / ultra-high-speed optical communication system and the WDM (FDM) optical communication system.

For ultra-long-distance optical communication systems over several thousand kilometers, use the zero-dispersion wavelength λ ₀ of the optical fiber transmission line to avoid dispersion penalties, and the normal dispersion region of the optical fiber to minimize nonlinear effects ( It is desirable to use a dispersion value D <0). In order to satisfy these contradictory conditions, means has been proposed in which the normal dispersion region is used as the transmission line and the optical dispersion compensator is used to make the apparent dispersion value zero. This optical dispersion compensation technique is effective not only for DSF transmission but also for SMF transmission having a large dispersion value of about 18 ps / nm / km.

As an optical dispersion compensator, a dispersion compensating fiber, a transversal filter type, an optical resonator type, and the like have been proposed so far. At present, the dispersion compensation fiber is regarded as promising because of the advantage that the dispersion compensation amount can be easily adjusted by changing the fiber length. By devising the core shape, the dispersion value is −100 ps / (nm · km). The above is obtained.
The actual zero-dispersion wavelength of the optical fiber transmission line varies in the longitudinal direction. Further, in a land-based optical communication system, it is difficult to set the relay interval constant as in a submarine optical communication system. The amount of dispersion is not necessarily constant. For this reason, ideally, it is desirable to insert an optical dispersion compensator having an optimum dispersion compensation amount after measuring the actual dispersion amount for each relay section. In addition, there is a problem that it takes too much man-hours, time and cost to realize an optimum optical dispersion compensator.

The present invention has been devised in view of such problems. First, the first object of the present invention is to affect the influence of bandwidth, chromatic dispersion, and FWM when using a bandwidth around the zero dispersion wavelength of an optical fiber. In consideration of this, by arranging optical signals at an efficient channel interval, the capacity of the optical communication system can be increased without being affected by crosstalk caused by FWM.
The second object of the present invention is to clarify the relationship between the required characteristics of the optical fiber (especially the zero dispersion wavelength and its variation) and the five elements, and the signal light in the optical amplification multi-relay WDM system. It is to be able to establish a channel arrangement method and a transmission path design method.

  Furthermore, the third object of the present invention is to make it possible to easily compensate for the waveform deterioration due to the SPM-GVD effect without designing and manufacturing an optical dispersion compensator corresponding to each transmission line, and to reduce the optical power. If it is not very large, SPM does not occur so much and only waveform degradation due to chromatic dispersion (GVD) may occur, but in this case as well, dispersion compensation can be performed effectively, reducing the man-hours until construction of an optical communication system. The aim is to reduce the cost as well as to reduce the time.

  For this reason, the optical repeater of the present invention (Claim 1) uses a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths as a wavelength longer than the wavelength of the first optical signal and the first optical signal. And a second unit that compensates for the dispersion of the second optical signal, a first unit that includes a first dispersion compensation unit that compensates for dispersion of the first optical signal, and a second unit that compensates for dispersion of the second optical signal. It is characterized by comprising a second unit including a dispersion compensator.

  The optical repeater of the present invention (Claim 2) is configured to convert a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a wavelength longer than the wavelength of the first optical signal. An optical separation unit that separates the wavelength into two optical signals, a first optical amplification unit that amplifies the first optical signal, and dispersion of the first optical signal amplified by the first optical amplification unit, and outputs the result A first unit including a first dispersion compensation unit, a second optical amplification unit that amplifies the second optical signal, and dispersion of the second optical signal amplified by the second optical amplification unit are compensated and output. And a second unit including a second dispersion compensation unit.

  The optical repeater according to the present invention (Claim 3) converts a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a wavelength longer than the wavelength of the first optical signal. An optical separation unit that separates the wavelength into two optical signals; a first dispersion compensation unit that compensates for dispersion of the first optical signal; and the first optical signal that has been dispersion-compensated by the first dispersion compensation unit is amplified and output. A first unit including a first optical amplifying unit, a second dispersion compensating unit for compensating for dispersion of the second optical signal, and amplifying the second optical signal dispersion-compensated by the second dispersion compensating unit It is characterized by comprising a second unit including a second optical amplification section that outputs.

According to an optical repeater of the present invention (Claim 4), a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths is converted into a first optical signal and a wavelength longer than the wavelength of the first optical signal. Wavelength separation into two optical signals is performed, and dispersion of the first optical signal and the second optical signal is separately compensated.
According to an optical repeater of the present invention (Claim 5), a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths is converted into a first optical signal and a wavelength longer than the wavelength of the first optical signal. The wavelength is separated into two optical signals, the first optical signal and the second optical signal are separately amplified, and the dispersion of the amplified first optical signal and the second optical signal is separately compensated and output. It is characterized by that.

According to an optical repeater of the present invention (Claim 6), a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths is converted into a first optical signal and a wavelength longer than the wavelength of the first optical signal. Wavelength-separated into two optical signals, separately compensate for dispersion of the first optical signal and the second optical signal, and separately amplify and output the dispersion-compensated first optical signal and the second optical signal It is characterized by doing.
The optical repeater according to the present invention (Claim 7) converts a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a wavelength longer than the wavelength of the first optical signal. Compensates for dispersion of the first optical signal amplified by the optical separation unit that separates the wavelength into two optical signals, the input-side first optical amplification unit that amplifies the first optical signal, and the input-side first optical amplification unit A first dispersion compensation unit that outputs the first optical signal, and an output-side first optical amplification unit that amplifies and outputs the first optical signal dispersion-compensated by the first dispersion compensation unit, and the second unit An input-side second optical amplifying unit that amplifies an optical signal, a second dispersion compensating unit that compensates and outputs the dispersion of the second optical signal amplified by the input-side second optical amplifying unit, and the second dispersion compensating unit And a second unit including an output-side second optical amplification unit that amplifies and outputs the second optical signal that has been dispersion-compensated by It is characterized in that it is configured.

  An optical repeater according to the present invention (Claim 8) is configured to convert a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a wavelength longer than the wavelength of the first optical signal. Compensates for dispersion of the first optical signal amplified by the optical separation unit that separates the wavelength into two optical signals, the input-side first optical amplification unit that amplifies the first optical signal, and the input-side first optical amplification unit A first dispersion compensation unit that outputs the first optical signal, and an output-side first optical amplification unit that amplifies and outputs the first optical signal dispersion-compensated by the first dispersion compensation unit, and the second unit A second unit including an input-side second optical amplification unit that amplifies the optical signal, and a second dispersion compensation unit that compensates and outputs the dispersion of the second optical signal amplified by the input-side second optical amplification unit; It is characterized by having been configured.

  The optical repeater according to the present invention (claim 9) converts a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a wavelength longer than the wavelength of the first optical signal. Compensates for dispersion of the first optical signal amplified by the optical separation unit that separates the wavelength into two optical signals, the input-side first optical amplification unit that amplifies the first optical signal, and the input-side first optical amplification unit A first dispersion compensation unit that outputs the first optical signal, and an output-side first optical amplification unit that amplifies and outputs the first optical signal dispersion-compensated by the first dispersion compensation unit, and the second unit A second unit including a second dispersion compensation unit that compensates for dispersion of the optical signal and an output-side second optical amplification unit that amplifies and outputs the second optical signal dispersion-compensated by the second dispersion compensation unit; It is characterized by being composed.

  An optical repeater according to the present invention (claim 10) converts a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a wavelength longer than the wavelength of the first optical signal. Compensates for dispersion of the first optical signal amplified by the optical separation unit that separates the wavelength into two optical signals, the input-side first optical amplification unit that amplifies the first optical signal, and the input-side first optical amplification unit The first dispersion compensation unit that outputs the first dispersion compensation, the second dispersion compensation unit that compensates and outputs the dispersion of the second optical signal, and the second dispersion compensated by the second dispersion compensation unit. A second unit including an output-side second optical amplifying unit that amplifies and outputs an optical signal is provided.

An optical repeater according to the present invention (claim 11) converts a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a wavelength longer than the wavelength of the first optical signal. An optical separation unit that separates a wavelength into two optical signals; a first means for processing the first optical signal; and a second means for processing the second optical signal. It is a feature.
An optical repeater according to the present invention (claim 12) converts a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a wavelength longer than the wavelength of the first optical signal. An optical separation unit that separates a wavelength into two optical signals, a first means for compensating and outputting the first optical signal, a second means for compensating and outputting the second optical signal, It is characterized by comprising an optical multiplexing section for wavelength multiplexing the first optical signal compensated by the first means and the second optical signal compensated by the second means.

According to an optical repeater of the present invention (claim 13), a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths is converted into a first optical signal and a wavelength longer than the wavelength of the first optical signal. The method includes a step of wavelength separation into two optical signals, a step of compensating the first optical signal, and a step of compensating the second optical signal.
According to an optical repeater of the present invention (Claim 14), a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths is converted into a first optical signal and a wavelength longer than the wavelength of the first optical signal. Two optical signals, a step of compensating and outputting the first optical signal, a step of compensating and outputting the second optical signal, and the compensated first optical signal. And a step of wavelength multiplexing the second optical signal.

  An optical transmission system of the present invention (Claim 15) includes an optical transmitter that transmits a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths, and relays the wavelength-multiplexed optical signal from the optical transmitter. A second optical signal having a wavelength longer than that of the first optical signal and the wavelength of the first optical signal, the optical repeater receiving the wavelength-multiplexed optical signal received from the optical transmission device. An optical separation unit for wavelength-separating into signals, a first unit including a first dispersion compensation unit for compensating for dispersion of the first optical signal, and a second dispersion compensation unit for compensating for dispersion of the second optical signal. It is characterized by having a second unit.

  An optical transmission system according to the present invention (claim 16) includes an optical transmitter that transmits a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths, and relays the wavelength-multiplexed optical signal from the optical transmitter. A second optical signal having a wavelength longer than that of the first optical signal and the wavelength of the first optical signal, the optical repeater receiving the wavelength-multiplexed optical signal received from the optical transmission device. A first optical amplifying unit that amplifies the first optical signal, and a first optical amplifying unit that compensates for dispersion of the first optical signal amplified by the first optical amplifying unit and outputs the first optical signal. A first unit including a dispersion compensator; a second optical amplifier that amplifies the second optical signal; and a second optical amplifier that compensates for the dispersion of the second optical signal amplified by the second optical amplifier and outputs the second optical signal. And a second unit including a dispersion compensation unit.

  An optical transmission system according to the present invention (Claim 17) relays the wavelength-multiplexed optical signal from the optical transmitter that transmits a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths. A second optical signal having a wavelength longer than that of the first optical signal and the wavelength of the first optical signal, the optical repeater receiving the wavelength-multiplexed optical signal received from the optical transmission device. A first optical signal that is wavelength-separated into a signal, a first dispersion compensation unit that compensates for dispersion of the first optical signal, and the first optical signal that has been dispersion-compensated by the first dispersion compensation unit; A first unit including one optical amplifying unit; a second dispersion compensating unit that compensates for dispersion of the second optical signal; and the second optical signal that is dispersion-compensated by the second dispersion compensating unit is amplified and output. And a second unit including a second optical amplification unit. That.

According to an optical transmission method of the present invention (claim 18), a wavelength multiplexed optical signal including a plurality of optical signals having different wavelengths is transmitted, and the wavelength division multiplexed optical signal is transmitted as the first optical signal and the first optical Wavelength separation is performed on a second optical signal having a wavelength longer than the wavelength of the signal, and dispersion of the first optical signal and the second optical signal is separately compensated.
According to an optical transmission method of the present invention (claim 19), a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths is transmitted. Wavelength separation into a second optical signal having a wavelength longer than the wavelength of the signal, amplifying the first optical signal and the second optical signal separately, and amplifying the first optical signal and the second optical signal It is characterized in that the dispersion is separately compensated and output.

  According to an optical transmission method (claim 20) of the present invention, a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths is transmitted, and the wavelength-division multiplexed optical signal is transmitted as the first optical signal and the first optical signal. Wavelength-separated into a second optical signal having a wavelength longer than the wavelength of the signal, separately compensates for dispersion of the first optical signal and the second optical signal, and the dispersion-compensated first optical signal and the first optical signal It is characterized by amplifying and outputting two optical signals separately.

  An optical transmission system according to the present invention (claim 21) includes an optical transmitter that transmits a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths, and relays the wavelength-multiplexed optical signal from the optical transmitter. A second optical signal having a wavelength longer than that of the first optical signal and the wavelength of the first optical signal, the optical repeater receiving the wavelength-multiplexed optical signal received from the optical transmission device. Compensating for dispersion of the first optical signal amplified by the optical separation unit that separates the signal into wavelengths, the input-side first optical amplification unit that amplifies the first optical signal, and the input-side first optical amplification unit A first unit including a first dispersion compensator for output and an output first optical amplifier for amplifying and outputting the first optical signal dispersion-compensated by the first dispersion compensator; and the second optical signal. Of the second optical signal amplified by the input-side second optical amplification unit and the input-side second optical amplification unit A second unit including a second dispersion compensation unit that compensates and outputs the dispersion, and an output second optical amplification unit that amplifies and outputs the second optical signal that has been dispersion-compensated by the second dispersion compensation unit. It is characterized by being configured.

  An optical transmission system according to the present invention (claim 22) includes an optical transmitter that transmits a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths, and relays the wavelength-multiplexed optical signal from the optical transmitter. A second optical signal having a wavelength longer than that of the first optical signal and the wavelength of the first optical signal, the optical repeater receiving the wavelength-multiplexed optical signal received from the optical transmission device. Compensating for dispersion of the first optical signal amplified by the optical separation unit that separates the signal into wavelengths, the input-side first optical amplification unit that amplifies the first optical signal, and the input-side first optical amplification unit A first unit including a first dispersion compensator for output and an output first optical amplifier for amplifying and outputting the first optical signal dispersion-compensated by the first dispersion compensator; and the second optical signal. Of the second optical signal amplified by the input-side second optical amplification unit and the input-side second optical amplification unit That is configured to include a second unit and a second dispersion compensator for the dispersion in the compensation output is characterized in.

  An optical transmission system according to the present invention (claim 23) includes an optical transmitter that transmits a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths, and relays the wavelength-multiplexed optical signal from the optical transmitter. A second optical signal having a wavelength longer than that of the first optical signal and the wavelength of the first optical signal, the optical repeater receiving the wavelength-multiplexed optical signal received from the optical transmission device. Compensating for dispersion of the first optical signal amplified by the optical separation unit that separates the signal into wavelengths, the input-side first optical amplification unit that amplifies the first optical signal, and the input-side first optical amplification unit A first unit including a first dispersion compensator for output and an output first optical amplifier for amplifying and outputting the first optical signal dispersion-compensated by the first dispersion compensator; and the second optical signal. A second dispersion compensation unit that compensates for the dispersion of the second optical signal, and the second optical signal that is dispersion-compensated by the second dispersion compensation unit To a second unit which amplifies and and an output-side second optical amplifying section for outputting is configured it is characterized in.

  An optical transmission system according to the present invention (claim 24) includes an optical transmitter that transmits a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths, and relays the wavelength-multiplexed optical signal from the optical transmitter. A second optical signal having a wavelength longer than that of the first optical signal and the wavelength of the first optical signal, the optical repeater receiving the wavelength-multiplexed optical signal received from the optical transmission device. Compensating for dispersion of the first optical signal amplified by the optical separation unit that separates the signal into wavelengths, the input-side first optical amplification unit that amplifies the first optical signal, and the input-side first optical amplification unit A first unit including a first dispersion compensator for output, a second dispersion compensator for compensating and outputting dispersion of the second optical signal, and the second optical signal dispersion-compensated by the second dispersion compensator And a second unit including an output side second optical amplifying unit for amplifying and outputting It is characterized in Rukoto.

  An optical transmission system according to the present invention (claim 25) includes a transmission means for wavelength-multiplexing a plurality of optical signals having different wavelengths to generate a wavelength-multiplexed optical signal, and the wavelength-multiplexed light from the transmission means. Relay means for relaying a signal, and the relay means sends the wavelength-multiplexed optical signal received from the transmission means to a first optical signal and a wavelength longer than the wavelength of the first optical signal. An optical separation unit that separates the wavelength of the optical signal into two optical signals; a first unit that compensates the first optical signal; and a second unit that compensates the second optical signal. It is characterized by.

  An optical transmission system according to the present invention (claim 26) includes a transmission means for wavelength-multiplexing a plurality of optical signals having different wavelengths to generate a wavelength-multiplexed optical signal, and the wavelength-multiplexed light from the transmission means. Relay means for relaying a signal, and the relay means sends the wavelength-multiplexed optical signal received from the transmission means to a first optical signal and a wavelength longer than the wavelength of the first optical signal. An optical demultiplexing unit for wavelength-separating into two optical signals, first means for compensating and outputting the first optical signal, second means for compensating and outputting the second optical signal, It is characterized by comprising an optical multiplexing unit that wavelength-multiplexes the first optical signal compensated by the first means and the second optical signal compensated by the second means.

  An optical transmission method (Claim 27) of the present invention includes a step of wavelength multiplexing a plurality of optical signals having different wavelengths to generate a wavelength multiplexed optical signal, and the wavelength division multiplexed optical signal is converted into a first optical signal. Wavelength separating the signal into a second optical signal having a wavelength longer than the wavelength of the first optical signal, compensating the first optical signal, and compensating the second optical signal. It is characterized by that.

  The optical transmission method of the present invention (Claim 28) includes a step of wavelength multiplexing a plurality of optical signals having different wavelengths to generate a wavelength multiplexed optical signal, and the wavelength division multiplexed optical signal as a first optical signal. Wavelength separation into a signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal, a step of compensating and outputting the first optical signal, and a compensation of the second optical signal And a step of wavelength multiplexing the compensated first optical signal and the compensated second optical signal.

  An optical transmission system according to the present invention (claim 29) includes an optical repeater that relays a wavelength multiplexed optical signal including a plurality of optical signals having different wavelengths and outputs the optical signal as a post-relay wavelength multiplexed optical signal, and the optical repeater And an optical receiver that receives each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal. An optical demultiplexer for wavelength-separating the multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal; and a first that compensates for dispersion of the first optical signal A first unit including a dispersion compensator; a second unit including a second dispersion compensator for compensating for dispersion of the second optical signal; the first optical signal compensated by the first unit; and the second unit. And wavelength-multiplexing the second optical signal compensated by the wavelength-multiplexed optical signal after relaying It is characterized by being configured to include an optical multiplexing unit for outputting as.

  An optical transmission system according to the present invention (claim 30) includes an optical repeater that relays a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths and outputs the signal as a post-relay wavelength-multiplexed optical signal, and the optical repeater And an optical receiver that receives each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal. An optical demultiplexing unit that demultiplexes the multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal, and a first optical amplification that amplifies the first optical signal A first unit including a first dispersion compensation unit that compensates and outputs the dispersion of the first optical signal amplified by the first optical amplification unit, and a second optical amplification that amplifies the second optical signal And the second optical signal amplified by the second optical amplifying unit compensates for dispersion and outputs the second optical signal. A second unit including a dispersion compensation unit, the first optical signal from the first unit, and the second optical signal from the second unit are wavelength-multiplexed and output as a post-relay wavelength-multiplexed optical signal It is characterized by having an optical multiplexing unit.

  An optical transmission system according to the present invention (claim 31) repeats a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths, and outputs the signal as a wavelength-multiplexed optical signal after relaying, and the optical repeater And an optical receiver that receives each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal. An optical demultiplexer for wavelength-separating the multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal; and a first that compensates for dispersion of the first optical signal A first unit including a dispersion compensation unit and a first optical amplification unit that amplifies and outputs the first optical signal that has been dispersion-compensated by the first dispersion compensation unit; and a first unit that compensates for dispersion of the second optical signal. Amplifies the second optical signal dispersion-compensated by the two dispersion compensator and the second dispersion compensator A second unit including a second optical amplifying unit that outputs the first optical signal, and the first optical signal from the first unit and the second optical signal from the second unit are wavelength-multiplexed and post-relay wavelength-multiplexed It is characterized by having an optical multiplexing unit that outputs as an optical signal.

  According to an optical transmission method of the present invention (claim 32), a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths is received from a first optical transmission line, and the first optical signal and the first optical signal are received. Wavelength-separated into a second optical signal having a wavelength longer than the wavelength of the first optical signal, the dispersion of the first optical signal and the second optical signal is separately compensated, and the dispersion-compensated first optical signal and dispersion compensated The second optical signal is wavelength-multiplexed and output to the second optical transmission line as a post-relay wavelength-multiplexed optical signal, and the post-relay wavelength-multiplexed optical signal from the second optical transmission line is wavelength-separated and relayed Each of the plurality of optical signals included in the post-wavelength multiplexed optical signal is received.

  According to an optical transmission method of the present invention (claim 33), a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths is received from a first optical transmission line, and the first optical signal and the first optical signal are received. Wavelength-separated into a second optical signal having a longer wavelength than the first optical signal, separately compensating dispersion of the first optical signal and the second optical signal, and dispersion-compensated first optical signal and second Optical signals are separately amplified and output, and the amplified first optical signal and the amplified second optical signal are wavelength-multiplexed and output to the second optical transmission line as a post-relay wavelength-multiplexed optical signal, The post-relay wavelength-multiplexed optical signal from the second optical transmission line is wavelength-separated and each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal is received.

  According to an optical transmission method of the present invention (claim 34), a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths is received from a first optical transmission line, and the first optical signal and the first optical signal are received. Wavelength-separated into a second optical signal having a longer wavelength than the first optical signal, amplifying the first optical signal and the second optical signal separately, and the amplified first optical signal and the second optical signal Dispersion is compensated separately, the dispersion-compensated first optical signal and the dispersion-compensated second optical signal are wavelength-multiplexed, and output as a wavelength-multiplexed optical signal after relay to the second optical transmission line. The post-relay wavelength-multiplexed optical signal from two optical transmission lines is wavelength-separated, and each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal is received.

  According to an optical transmission method of the present invention (claim 35), a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths is received from a first optical transmission line, and the first optical signal and the first optical signal are received. Wavelength-separated into a second optical signal having a longer wavelength than the first optical signal, amplifying the first optical signal and the second optical signal separately, and the amplified first optical signal and the second optical signal Dispersion is separately compensated, and the dispersion-compensated first optical signal and the second optical signal are separately amplified and output, and the amplified first optical signal and the amplified second optical signal are Wavelength-multiplexed and output as a post-relay wavelength-multiplexed optical signal to the second optical transmission line, wavelength-separated the post-relay wavelength-multiplexed optical signal from the second optical transmission line, and included in the post-relay wavelength-multiplexed optical signal Each of the plurality of optical signals is received.

  An optical transmission system according to the present invention (Claim 36) repeats a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths and outputs the signal as a wavelength-multiplexed optical signal after relaying, and the optical repeater And an optical receiver that receives each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal. An optical demultiplexing unit that demultiplexes the multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal, and a first optical amplification that amplifies the first optical signal And a first dispersion compensation unit for compensating and outputting dispersion of the first optical signal amplified by the first optical amplification unit, and amplifying the first optical signal dispersion-compensated by the first dispersion compensation unit A first unit including a first optical amplifying unit for outputting and a second optical signal for amplifying the second optical signal A second dispersion compensation unit that compensates and outputs the dispersion of the second optical signal amplified by the optical amplification unit and the second optical amplification unit, and the second optical signal that has been dispersion compensated by the second dispersion compensation unit A second unit including a second optical amplifying unit that amplifies and outputs; the first optical signal from the first unit and the second optical signal from the second unit are wavelength-multiplexed and the post-relay wavelength It is characterized by comprising an optical multiplexing unit that outputs as a multiplexed optical signal.

  An optical transmission system according to the present invention (claim 37) includes an optical repeater that relays a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths and outputs the optical signal as a post-relay wavelength-multiplexed optical signal, and the optical repeater And an optical receiver that receives each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal. An optical demultiplexing unit that demultiplexes the multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal, and a first optical amplification that amplifies the first optical signal And a first dispersion compensation unit for compensating and outputting dispersion of the first optical signal amplified by the first optical amplification unit, and amplifying the first optical signal dispersion-compensated by the first dispersion compensation unit A first unit including a first optical amplifying unit for outputting and a second optical signal for amplifying the second optical signal A second unit including an optical amplification unit and a second dispersion compensation unit that compensates and outputs the dispersion of the second optical signal amplified by the second optical amplification unit; and the first light from the first unit An optical multiplexing unit is provided that wavelength-multiplexes the signal and the second optical signal from the second unit and outputs the signal as a wavelength-multiplexed optical signal after relay.

  An optical transmission system according to the present invention (claim 38) includes an optical repeater that relays a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths and outputs as a post-relay wavelength-multiplexed optical signal, and the optical repeater And an optical receiver that receives each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal. An optical demultiplexing unit that demultiplexes the multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal, and a first optical amplification that amplifies the first optical signal And a first dispersion compensation unit for compensating and outputting dispersion of the first optical signal amplified by the first optical amplification unit, and amplifying the first optical signal dispersion-compensated by the first dispersion compensation unit A first unit including a first optical amplifying unit for outputting and compensating for dispersion of the second optical signal A second dispersion compensation unit and a second optical amplification unit that amplifies and outputs the second optical signal dispersion-compensated by the second dispersion compensation unit, and the second unit from the first unit. It is characterized by comprising an optical multiplexing unit that wavelength-multiplexes one optical signal and the second optical signal from the second unit and outputs the result as a post-relay wavelength-multiplexed optical signal.

  An optical transmission system according to the present invention (claim 39) repeats a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths and outputs the signal as a wavelength-multiplexed optical signal after relay, and the optical repeater And an optical receiver that receives each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal. An optical demultiplexing unit that demultiplexes the multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal, and a first optical amplification that amplifies the first optical signal A first unit including a first dispersion compensation unit that compensates and outputs the dispersion of the first optical signal amplified by the first optical amplification unit, and a second unit that compensates for the dispersion of the second optical signal The second optical signal that has been dispersion-compensated by the dispersion compensator and the second dispersion compensator is amplified and output. A second unit including a second optical amplification unit that performs wavelength multiplexing of the first optical signal from the first unit and the second optical signal from the second unit, and the post-relay wavelength multiplexed optical signal It is characterized by comprising an optical multiplexing unit that outputs as follows.

  An optical transmission system according to the present invention (claim 40) repeats a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths and outputs the optical signal as a post-relay wavelength-multiplexed optical signal, and the optical repeater And an optical receiver that receives each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal. An optical demultiplexing unit for wavelength-separating the multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal, and a first for compensating the first optical signal Means, second means for compensating the second optical signal, wavelength multiplexing of the first optical signal compensated by the first means and the second optical signal compensated by the second means And an optical multiplexing unit that outputs the wavelength multiplexed optical signal after the relay. It is characterized in that.

  An optical transmission system according to the present invention (claim 41) includes a transmission means for wavelength-multiplexing a plurality of optical signals having different wavelengths to generate a wavelength-multiplexed optical signal, and the wavelength-multiplexed light from the transmission means. A relay means for relaying a signal and outputting it as a post-relay wavelength multiplexed optical signal; and a plurality of the plurality of optical signals included in the post-relay wavelength multiplexed optical signal after wavelength separation of the post-relay wavelength multiplexed optical signal from the relay means And receiving means for receiving each of the optical signals, and the repeater means that the wavelength-multiplexed optical signal received from the transmitting means is longer than the wavelengths of the first optical signal and the first optical signal. An optical separation unit that separates a wavelength into a second optical signal having a wavelength; a first unit that compensates and outputs the first optical signal; and a second unit that compensates and outputs the second optical signal. Means, the first optical signal compensated by the first means and the second hand And a wavelength multiplexing and the second optical signal compensated is characterized by being configured to include an optical multiplexer for outputting the wavelength-multiplexed optical signal after the relay by.

  The optical transmission method of the present invention (Claim 42) includes a step of wavelength multiplexing a plurality of optical signals having different wavelengths to generate a wavelength multiplexed optical signal, and the wavelength division multiplexed optical signal as a first optical signal. Wavelength separation into a signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal, compensating the first optical signal, compensating the second optical signal, and compensation Wavelength-multiplexing the first optical signal thus compensated and the compensated second optical signal to output as a wavelength-multiplexed optical signal after relay, wavelength-separating the wavelength-multiplexed optical signal after relay, and wavelength after relay Receiving each of the plurality of optical signals included in the multiplexed optical signal.

  According to an optical transmission method of the present invention (claim 43), a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths is converted into a first optical signal and a wavelength longer than the wavelength of the first optical signal. Two optical signals, a step of compensating and outputting the first optical signal, a step of compensating and outputting the second optical signal, and the compensated first optical signal. A step of wavelength-multiplexing the second optical signal and outputting as a post-relay wavelength-multiplexed optical signal, a wavelength separation of the post-relay wavelength-multiplexed optical signal, and a plurality of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal Receiving each of the optical signals.

According to the present invention described above, there are the following effects and advantages.
(1) The influence of the FWM can be suppressed, and the band can be used efficiently by arranging the signal light efficiently, so that the capacity of the optical communication system can be increased while maintaining high transmission quality.
(2) Even when the zero-dispersion wavelength is located within the band of the optical amplifier or within the band of the optical component, the signal light can be efficiently and compactly arranged while suppressing the effect of the FWM within the limited band. There are advantages.

(3) Channel spacing on the transmitting side can be controlled by one or two Fabry-Perot interferometers, and the receiving side can use an interferometer having the same characteristics as the transmitting side, so that the transmitting side can be controlled easily. And selective reception becomes easy.
(4) In the WDM system using the band around the zero dispersion wavelength λ ₀ of the optical fiber, the signal light of each channel can be arranged without being affected by the FWM, and at the same time, the zero dispersion wavelength of the optical fiber transmission line to be laid There is an advantage that required characteristics regarding λ ₀ can be clarified, and a channel arrangement method and a transmission path design method for signal light in the optical amplification multi-relay WDM system can be established.

(5) The dispersion of the zero dispersion wavelength in the longitudinal direction of the optical fiber is considered and managed, and at the same time, the influence of FWM is suppressed, the influence of other channels due to crosstalk is suppressed, and there is an advantage that high transmission accuracy can be maintained. .
(6) In addition to performing signal light arrangement in consideration of waveform degradation due to the SPM-GVD effect, by arranging the signal light of each channel within the gain band Δλ _{EDFA of the EDFA} , the signal light power can be made equal, The light reception characteristics can be made equal.

  (7) By expanding and setting the signal light band according to the optical wavelength variation of the signal light of each channel, the variation of each signal light due to the manufacturability and wavelength control accuracy of the signal light source such as a semiconductor laser is taken into consideration In the case of using an optical dispersion compensator, the dispersion of the optical dispersion compensator is set by extending the signal optical band by the dispersion compensation amount variation range on both the long wavelength side and the short wavelength side. Considering variation in quantity, more reliable optical transmission can be performed.

  (8) Without designing or manufacturing an optical dispersion compensator corresponding to each transmission line, it becomes possible to easily compensate for waveform degradation due to the SPM-GVD effect and dispersion amount for guard bands, and to construct an optical communication system. There is an advantage that the man-hour reduction and the time reduction can be realized.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(A) Description of First Embodiment FIGS. 1 to 4 show an optical wavelength division multiplexing transmission system as a first embodiment of the present invention, and FIG. 1 is a diagram showing the arrangement of signal light of a plurality of channels, FIG. FIG. 3 is a block diagram showing the configuration of an optical WDM (FDM) distributed transmission system to which the optical wavelength division multiplexing transmission system is applied, and FIGS. 3 and 4 are diagrams for explaining the operation.

First, an optical WDM distributed transmission system to which the optical wavelength division multiplexing transmission system of the present embodiment is applied will be described with reference to FIG. 2. In FIG. 2, 1 is a transmission circuit, Signals are multiplexed with high density as signal lights having different frequencies (wavelengths).
The transmission circuit 1 receives laser light (LD-1 to LD-n) 1a provided for each channel (CH-1 to CH-n) and signal light from the laser diode 1a for each channel. It is configured with a multiplexing 1b for multiplexing these signal lights.

  2 is an optical fiber for transmitting multiplexed signal light from the transmission circuit 1, 3 is a distributor for distributing the signal from the optical fiber 2 to each channel, 4 is each channel CH-i (i = 1 to 1). n) each receiving circuit that receives signal light of a corresponding frequency (wavelength), and each receiving circuit 4 extracts and outputs a corresponding signal from the multiplexed signal light, and an optical filter A control circuit 4b for controlling the filter 4a and a detector 4c for detecting signal light from the optical filter 4a are provided.

By the way, the FWM as the nonlinear effect of the optical fiber 2 uses the band around the zero dispersion wavelength of the optical fiber 2 to multiplex signal lights having different frequencies (wavelengths) by the transmission circuit 1 and input them to the optical fiber 2. In this case, the phenomenon occurs due to optical frequency mixing between signal lights, which causes crosstalk from other channels and degrades signal transmission characteristics.
In optical WDM (FDM) transmission using a band around the zero-dispersion wavelength of the optical fiber 2, FWM is the nonlinear effect of the optical fiber 2 that has the most severe effect. In order to explain this FWM in more detail, the design of a system that needs to be performed in consideration of the influence of the FWM, in particular, channel spacing, channel arrangement, and input power will be described below.

For example, when signal light having a frequency f _{1 to} f _n (wavelengths λ _{1 to} λ _n ) is input, any three waves f _i , f _j , f _k (λ _i , λ _j , λ _k ) are used. The fourth light of the frequency f _ijk (wavelength λ _ijk ; i ≠ k, j ≠ k) generated through the third-order nonlinear susceptibility χ _llll of the optical fiber 2 is the FWM. This frequency f _ijk (wavelength λ _ijk ) is generated at the position of the optical frequency satisfying the relationship of the following equation (1). When the interval is equal and the number of channels is large, the frequency is a combination of i, j, and k. Since several FWMs are generated at the position of f _ijk (wavelength λ _ijk ) and superimposed on the signal light, the crosstalk is further deteriorated.

f _ijk = f _i + f _j −f _k (λ _ijk = λ _i + λ _j −λ _k ) (1)
Also, the zero-dispersion wavelength near the generation efficiency of the frequency f _ijk (wavelength lambda _ijk) is increased, the frequency _{f i, f j, f k} , f ijk ( each wavelength _{λ i, λ j, λ k} , λ _The efficiency changes according to the phase relationship of _ijk ) (the efficiency increases as the phase mismatch amount Δβ described later decreases).
In general, when the polarizations of the three signal channels match, the optical power (optical power) P _ijk of the FWM is expressed by the following equation (2).

P _ijk =
η _ijk · {(1024π ⁶ · χ _llll ² · d ² ) / (n ⁴ · λ ² · c ² )}
(L _eff / A _eff ) ² · P _i · P _j · P _k · exp (-αL) (2)
Where η _ijk is the generation efficiency of the frequency f _ijk (wavelength λ _ijk ), χ _llll is the third-order nonlinear susceptibility, and d is the degeneracy coefficient (when i ≠ j ≠ k, d = 6, i = j ≠ k Where d = 3), n is the refractive index of the core, λ is the signal wavelength, c is the speed of light, L _eff is the effective optical fiber length given by the following equation (3), and A _eff is the effective cross section (= πW ² , W is the mode field diameter), α is the attenuation coefficient of the optical fiber, P _i , P _j , and P _k are the input signals of frequencies f _i , f _j , f _k (wavelengths λ _i , λ _j , λ _k ), respectively. Power.

L _eff = {1−exp (−αL)} / α (3)
Here, the generation efficiency η _ijk (= η) is expressed by the following equation (4).
η = α ² · [1 + 4exp (−αL) · sin ² (ΔβL / 2) / {1-exp (−αL)} ² ]
/ (Α ² + Δβ ² ) (4)
L is the optical fiber length, and Δβ is the phase mismatch amount. If the dispersion slope dD / dλ of the optical fiber 2 is constant with respect to the wavelength, the phase mismatch amount Δβ is expressed by the following equations (5) and (6).

(A) When f _i ≠ f _j ≠ f _k (λ _i ≠ λ _j ≠ λ _k ) Δβ = (πλ ⁴ / 3c ² ) · (dD / dλ)
{(F _i + f _j −f _k −f ₀ ) ³ − (f _i −f ₀ ) ³
-(F _j -f ₀ ) ³ + (f _k -f ₀ ) ³ )} (5)
(B) When f _i = f _j ≠ f _k (λ _i = λ _j ≠ λ _k ) Δβ = (πλ ⁴ / c ² ) · (dD / dλ)
2 (f _i -f ₀ ) (f _i -f _k ) ² (6)
Here, D is the chromatic dispersion of the optical fiber, dD / dλ is the chromatic dispersion of the secondary optical fiber, and f ₀ is the zero dispersion optical frequency. However, the case where the frequencies f _i , f _j , f _k , and f ₀ in the above equations (5) and (6) are replaced with the wavelengths λ _i , λ _j , λ _k , and λ ₀ is also established in the same manner as the above equation. To do.

In the case of multiple channels, a combination of FWM i, j and k generated at a position of frequency f _ijk (wavelength λ _ijk ) is obtained, and optical power P _ijk is obtained for each. The sum is the optical power of the FWM generated at the position of the frequency f _ijk (wavelength λ _ijk ). The crosstalk amount CR is given by the following equation (7) using the sum of the optical powers.
CR = 10 · log {(sum of all FWM optical powers generated at the position of f _ijk )
/ (Signal light power at the position of f _ijk )} (7)
If the above equations (2) and (4) to (7) are used, the influence of FWM can be estimated, and the values of system parameters such as channel spacing, channel arrangement, and input power can be designed. In the description of the operational effects of the first to sixth embodiments described below, the influence of the FWM obtained by the above-described formula is appropriately estimated (see FIGS. 3, 4, 7, 11, and 12). Is used.

  As described above, in order to prevent waveform degradation due to dispersion of the optical fiber 2, it is necessary to use the band around the zero dispersion wavelength of the optical fiber, and the FWM that becomes noticeable when multiplexed in the above band. The channel spacing and the signal channel arrangement taking into account the influence of the above are necessary. In response to these, in the optical wavelength division multiplexing transmission system according to the first embodiment of the present invention, for example, as shown in FIG. Signal light is arranged.

According to the channel arrangement as shown in FIG. 1, an FWM suppression guard band 5 having a certain width from the zero dispersion wavelength λ ₀ is provided, and the outside of the guard band 5 is longer than the zero dispersion wavelength λ _0. 6, signal light is arranged.
With the above configuration, in the optical wavelength division multiplex transmission system according to the first embodiment of the present invention, signals from each channel are multiplexed with high density as signal lights having different frequencies (wavelengths) in the transmission circuit 1. It is transmitted via the optical fiber 2.

The signal light transmitted through the optical fiber 2 is separated by the distributor 3 and input to the receiving circuit 4 corresponding to each channel, and detected as signal light having a frequency (wavelength) corresponding to the input channel.
At this time, for example, in the case of a system in which the number of channels of the transmission circuit 1 is 16 (n = 16), the channel interval is 150 GHz, the length L of the optical fiber 2 is 90 km, and the optical input power P per channel is +3 dBm. The calculation result of the crosstalk amount of each channel is as shown in FIG. The parameters used in this calculation are χ _llll = 5.0 × 10 ^-15 cm ³ / erg (esu), A _eff = 4.6 × 10 ^-11 m ² , α = 5.2958 × 10 ^-5 m ^-1 (0.23 dB / km ), DD / dλ = 0.065 ps / (km · nm ² ).

In FIG. 3, the description such as “0.0 ps” in the figure is the value of dispersion in CH1 (channel number 1). As the channel number (CH No.) increases, the dispersion value increases according to the dispersion slope dD / dλ. From the results shown in FIG. 3, the amount of crosstalk in CH2, CH3, and CH4 is the largest.
FIG. 4 shows the results calculated by paying attention to these CH2, CH3, and CH4. As shown in FIG. 4, for example, in order to suppress the crosstalk amount to 30 dB or less, the dispersion value of CH1 may be set to 0.64 ps / nm / km or more. For example, dD / dλ = 0.065 ps / (km · nm ² ), CH1 may be separated from the zero dispersion wavelength λ ₀ by about 10 nm, and a guard band 5 of 10 nm may be set.

As described above, according to the optical wavelength division multiplex transmission system of the first embodiment, the signal light of each channel is arranged from the zero dispersion wavelength λ ₀ of the optical fiber 2 through the guard band 5, thereby suppressing the influence of FWM. In addition, the influence of crosstalk from other channels can be suppressed, and the band can be used efficiently. Therefore, the capacity of the optical communication system can be increased while maintaining high transmission accuracy.

In the present embodiment, the signal light than the zero-dispersion wavelength lambda ₀ are arranged on the longer wavelength side 6, the signal light through the guard band 5 on the shorter wavelength side 7 than the zero-dispersion wavelength lambda ₀ You may arrange.
(B) Description of Second Embodiment Next, a description will be given of an optical wavelength division multiplex transmission system as a second embodiment of the present invention. FIG. 5 is a diagram showing the signal light arrangement of a plurality of channels. Note that the optical wavelength division multiplexing transmission system as the second embodiment is also applied to the same optical WDM (FDM) distributed transmission system described with reference to FIG.

In the optical wavelength division multiplex transmission system according to the present embodiment, as shown in FIG. 5, the FWM suppression guard bands 5 are provided on both sides of the zero dispersion wavelength λ ₀ , the short wavelength side 7 outside the guard band 5, The signal light of each channel is arranged on each wavelength side 6.
By performing the channel arrangement as described above, according to the optical wavelength multiplex transmission system of the second embodiment, even when the zero dispersion wavelength λ ₀ is located in the band of the optical amplifier or in the band of the optical component, Signal light can be placed efficiently and compactly while suppressing the effect of FWM in a limited band and suppressing the influence of other channels due to crosstalk, increasing the capacity of the system while maintaining high transmission accuracy There is an advantage that can be realized.

(C) Description of Third Embodiment Next, a description will be given of an optical wavelength division multiplexing transmission system as a third embodiment of the present invention. FIG. It is a figure explaining. The optical wavelength division multiplex transmission system of the third embodiment is also applied to the same optical WDM (FDM) distributed transmission system described with reference to FIG.

In the optical wavelength division multiplex transmission system of the third embodiment, as shown in FIG. 6, the FWM suppression guard band 5 is centered on the zero dispersion wavelength λ ₀ , on the short wavelength side 7 and the long wavelength side 6. It is provided so as to be asymmetric, and the channel spacing of the multiplexed signal light is set differently on the short wavelength side 7 (Δf) and the long wavelength side 6 (Δf ′). ing.

  By changing the channel spacing on each of the short wavelength and long wavelength sides of the guard band 5, the generation position of the FWM light generated between the signal light on the short wavelength side and the signal light on the long wavelength side of the guard band is any signal. It is possible to prevent coincidence with the optical wavelength, and the influence from other channels due to crosstalk is suppressed. Here, the width for shifting the band in which the FWM light is generated from the band of the signal light is desirably within a range that can be suppressed by the optical filter 4a on the reception side.

For example, as shown in FIG. 7, the left and right channel spacing is changed to 200 GHz on the short wavelength side 7 and 150 GHz on the long wavelength side 6, and the width of the guard band 5 is 1.6 nm on the short wavelength side 7. When 6 is set to 4 nm, FWM light is generated between channels, but generation of FWM light is reduced in the band of signal light, and the amount of crosstalk is also reduced.
Thus, by the optical wavelength multiplex transmission method of the third embodiment, by disposing the signal light of each channel from the zero dispersion wavelength lambda ₀ on either side of the zero-dispersion wavelength lambda ₀ through a guard band 5, the FWM Since the influence can be suppressed and the influence from other channels due to crosstalk can be suppressed, and the band can be used efficiently, there is an advantage that the capacity of the system can be increased while maintaining high transmission accuracy.

(D) Description of Fourth Embodiment Next, a description will be given of an optical wavelength division multiplexing transmission system as a fourth embodiment of the present invention. FIG. The optical wavelength division multiplex transmission system of the fourth embodiment is also applied to the same optical WDM (FDM) distributed transmission system described with reference to FIG.

In the optical wavelength division multiplex transmission system of the fourth embodiment, as shown in FIG. 8, the channel interval on each of the short wavelength side 7 and the long wavelength side 6 is set to a fixed number of integral multiples.
For example, if the channel spacing Δf is Δf = A · X, the channel spacing between the channel n + 4 and the channel n + 5 is Δf ′ = B · X, and the channel spacing between the channel n + m−1 and the channel n + m is Δf ″ = C -Let X be. Here, X is a fixed number, and A, B, and C are integers.

As shown in FIG. 8, also in this embodiment, the FWM suppression guard band 5 is provided so as to be asymmetric between the short wavelength side 7 and the long wavelength side 6 with the zero dispersion wavelength λ ₀ as the center. It has been.
In the transmission circuit 1, it is necessary to stabilize the wavelengths of the plurality of laser diodes 1a with a desired channel arrangement and channel spacing, and in the reception circuit 4, it is necessary to select and extract channels. It is desired that the channel arrangement and the channel interval required for suppressing the influence of the FWM as described above are easily controlled by the transmission circuit 1 and easily extracted by the reception circuit 4.

  In general, the channel spacing is controlled by utilizing the periodic characteristics of the optical interferometer. For example, when the channel spacing is controlled using a Fabry-Perot interferometer, the desired channel spacing is equal to the transmission peak spacing of the Fabry-Perot interferometer or is an integral multiple of the transmission peak spacing. If the wavelength of each laser diode 1a is stabilized at the position of its transmission peak with reference to the Fabry-Perot interferometer, control of all channels can be easily realized. Becomes complicated.

From such a viewpoint, the channel interval between the short wavelength side 7 and the long wavelength side 6 of the zero dispersion wavelength λ ₀ is set to an integer multiple of a fixed number (one cycle interval of the transmission peak of the optical interferometer or an integral multiple thereof). Thus, the control of the channels on the short wavelength side 7 and the long wavelength side 6 can be controlled by one or two Fabry-Perot interferometers having the same characteristics. The same applies to the receiving circuit 4, and an interferometer having the same characteristics can be used by setting the channel interval to an integer multiple of a certain number.

As described above, according to the optical wavelength division multiplex transmission system of the fourth embodiment, the control of the channel interval on the transmission side can be controlled by one or two Fabry-Perot interferometers. There are advantages that can be made.
The same applies to the reception side. By setting the channel interval to an integer multiple of a fixed number, it becomes possible to use an interferometer having the same characteristics as the transmission side, facilitating selective reception and simplifying the apparatus. There are advantages that can be made.

In this embodiment, it is also possible to set adjacent channel intervals of signal light of a plurality of channels so that the short wavelength side 7 and the long wavelength side 6 outside the guard band 5 are different from each other.
(E) Description of Fifth Embodiment Next, a description will be given of an optical wavelength division multiplexing transmission system as a fifth embodiment of the present invention. FIG. 9 is a diagram showing the arrangement of signal light of a plurality of channels. The optical wavelength division multiplexing transmission system of the fifth embodiment is also applied to the same optical WDM (FDM) distributed transmission system described with reference to FIG.

In the optical wavelength division multiplexing transmission system of the fifth embodiment, as shown in FIG. 9, the interval between the signal lights of the respective channels arranged on both sides of the FWM suppressing guard band 5 The frequency (wavelength) of the signal light of each channel is set so as to satisfy the relationship that is separated by a constant integer multiple.
Specifically, if the optical frequency of channel (CH) i is f, the optical frequency of an arbitrary channel j is set to satisfy f ± A · X (A: integer, X: constant).

  By performing the channel arrangement as described above, according to the optical wavelength division multiplexing transmission system of the fifth embodiment, each channel interval across the guard band 5 is a fixed number (one cycle interval of the transmission peak of the optical interferometer). Or an integer multiple thereof), the channel spacing on the transmission side can be controlled with only one optical interferometer, and an interferometer with the same characteristics can be used on the reception side. There is an advantage that the apparatus is simplified and the apparatus is further simplified.

(F) Description of Sixth Embodiment Next, a description will be given of an optical wavelength division multiplexing transmission system as a sixth embodiment of the present invention. FIG. Both are diagrams for explaining the operation. The optical wavelength division multiplexing transmission system of the sixth embodiment is also applied to the same optical WDM (FDM) distributed transmission system described with reference to FIG.

In the optical wavelength division multiplex transmission system of the sixth embodiment, as shown in FIG. 10, two or more channels overlap when viewed at the zero dispersion wavelength λ ₀ on the optical frequency (optical wavelength) axis. The channels are arranged so as not to be (arranged so that the number of pairs having the same absolute value of the dispersion value is 1 or less). In the example shown in FIG. 10, only one set of CH3 and CH8 overlaps.
For example, in the case of a system in which the number of channels of the transmission circuit 1 is 16, the channel spacing is 150 GHz, 200 GHz, 250 GHz, the length L of the optical fiber 2 is 90 km, and the optical input power P per channel is 0 dBm, The calculation result of the talk is as shown in FIG. 11. The number of channels of the transmission circuit 1 is 16, the channel spacing is 150 GHz, 200 GHz, 300 GHz, the length L of the optical fiber 2 is 90 km, and the optical input power P per channel. In the case of a system with 0 dBm, the calculation result of the crosstalk of each channel is as shown in FIG. As shown in FIG. 11 or FIG. 12, the crosstalk of all channels shows a good value around -30 dB.

In FIG. 7 shown in the third embodiment, the influence of the crosstalk of CH2, CH5, CH11, and CH15 appears. However, in the channel arrangement of FIG. 7, when turning back at the zero dispersion wavelength λ ₀ , CH2 and CH15 Overlap, and CH5 and CH11 overlap. In other words, these two sets have the same absolute value of the variance value. On the other hand, in this embodiment, as shown in FIGS. 11 and 12, only one set having the same absolute value of the dispersion value is used, and as described above, all channels are good at about −30 dB. The value is shown.

If there are two or more pairs having the same absolute value across the zero dispersion wavelength λ _0, as can be seen from the equation (5), the phase mismatch amount Δβ in the combination of the three channels in the two sets. Becomes 0, and FWM light is generated with high efficiency in the remaining one channel position. Eventually, FWM light is generated at the optical frequency positions of all the two sets of four channels, thereby deteriorating crosstalk. Therefore, as in the present embodiment shown in FIGS. 11 and 12, it is necessary that the same absolute value of the dispersion value does not become two or more sets (below one set).

As described above, according to the optical wavelength division multiplex transmission system of the sixth embodiment, since there is no absolute value of two or more sets of dispersion values across the zero dispersion wavelength λ ₀ , the generation of FWM light can be suppressed. In addition to being able to more reliably suppress the effects of crosstalk from other channels, as in the previous embodiments, the bandwidth can be used efficiently, increasing the capacity of the system while maintaining high transmission accuracy. There is an advantage that can be realized.

In the first to sixth embodiments described above, the channel interval is set according to the frequency. However, the channel interval may be set according to the wavelength, and in this case, the same effect as that of the above-described embodiment can be obtained. .
(G) Description of Seventh Embodiment Now, a WDM optical transmission system using a band around the zero dispersion wavelength of an optical fiber [in the seventh embodiment, an optical amplification multiple repeater system (regenerative repeater as described later with reference to FIG. 15). In order to suppress and avoid crosstalk caused by FWM between signal lights, it is necessary to separate the signal light band from the zero dispersion wavelength of the optical fiber as described above. The channel arrangement at this time is mainly determined by a guard band for FWM suppression (guard band 5 described in the first to sixth embodiments), a limited band due to the SPM-GVD effect, and an EDFA gain band. In addition, the zero dispersion wavelength of an actual optical fiber varies in the longitudinal direction, and it is extremely important for system design to manage the zero dispersion wavelength and its variation. Furthermore, by using an optical dispersion compensator, the apparent zero dispersion wavelength can be shifted, and this has the effect of allowing zero dispersion wavelength variation, as will be described later.

In the seventh embodiment and the eighth embodiment to be described below, a channel arrangement method in the WDM system when the above factors are taken into account will be described. In other words, this can be considered as a method of defining the zero dispersion wavelength of the optical fiber and its variation under the condition that the number of channels and the channel interval are determined.
In the following description, first, (a) wavelength multiplexed signal band, (b) EDFA gain band, (c) guard band for FWM suppression, and (d) SPM-GVD effect, which are limiting factors of signal light band After describing the limited band, the relationship between the channel arrangement and the required characteristics of the optical fiber will be described in consideration of whether or not the optical dispersion compensator is inserted.

Restriction Factors (a) Wavelength-multiplexed signal band When n-wave signal light is arranged at an equal wavelength interval Δλ _S , the wavelength-multiplexed signal light band Δλ _WDM is represented by Δλ _S × (n−1). In the case of the equal wavelength interval arrangement, the FWM light in the signal light band tends to be large, but the wavelength stabilization control is facilitated as described in the fourth and fifth embodiments.

(B) EDFA gain band In the case of WDM optical transmission, in order to equalize the reception characteristics of each wave, it is necessary to equalize the optical power of each signal. Must be used. For example, FIG. 16 shows an example of an ASE spectrum after four stages of EDFAs are connected (the ASE spectrum distribution is substantially equal to the gain distribution of EDFA). In this frequency band, the gain is flat, and it is desirable to arrange the signal light of all channels within this bandwidth (Δλ _EDFA = 10 nm).

Note that frequency bands other than those described above include the vicinity of 1535 nm with the same gain. Factors that determine the channel spacing at this time include wavelength selection filter characteristics and wavelength stability of the semiconductor laser. Further, as means for expanding the gain bandwidth Δλ _EDFA of the EDFA, optimization of the EDFA operating point, optimization of the EDF composition, insertion of an optical notch filter, and the like can be considered.

(C) Guard Band for FWM Suppression As described in the first embodiment, in optical WDM (FDM) transmission using a band around the zero dispersion wavelength of an optical fiber, the channel spacing is considered in consideration of the effect of FWM. , Channel allocation and input power need to be set. For example, when signal light of wavelengths λ _{1 to} λ _n is input, the wavelength λ is transmitted through the third-order nonlinear susceptibility χ _llll of the optical fiber by arbitrary three waves λ _i , λ _j , λ _k among them. _A fourth light (FWM) of _ijk (i ≠ k, j ≠ k) is generated.

This wavelength λ _ijk satisfies the relationship of the above equation (1), and when there is signal light at that position, it becomes crosstalk and degrades transmission characteristics. In particular, when the channel interval is equal and the number of channels is large, a plurality of FWMs are superimposed at the position of the wavelength λ _{ijk by} the combination of i, j, k, and the amount of crosstalk increases. Also, the generation efficiency eta _ijk wavelength lambda _ijk each wavelength _{λ i, λ j, λ k} , changed by the phase relationship of lambda _ijk, increases in zero-dispersion wavelength lambda ₀ the vicinity of the optical fiber.

In general, when the polarization of the three signal lights and the phase at the input end of the optical fiber coincide with each other, the FWM optical power P _ijk and the generation efficiency η _{ij k} are the above-described equations (2), (3) and It is represented by the equations (4) to (6).
For example, as shown in FIG. 17, when 16 wave signal lights are arranged at an equal interval of wavelength interval Δλ _S = 1.2 nm, the cross to each channel when the dispersion value D _ch1 of channel 1 is changed FIG. 18 shows a calculation example of the talk amount [see the above-described equation (7)]. The parameters used in this calculation are: λ = 1.55 _μm , χ _llll = 5.0 × 10 ⁻¹⁵ esu, A _eff = 4.6 × 10 ⁻¹¹ m ² , α = 5.3 × 10 ⁻⁵ m ⁻¹ (0.23 dB / km) , DD / dλ = 0.065 ps / (km · nm ² ), L = 90 km, and P _i = 0 dBm / ch.

As shown in FIG. 18, the number of combinations of FWM light superimposed on each channel is the maximum in the center 7 and 8 channels, but since the dispersion value in each channel is different, crossing in channels 2 to 4 The amount of talk is maximized (this is the same result as that described in FIG. 3 in the first embodiment). If the required crosstalk amount is −30 dB, the dispersion value D _ch1 of channel 1 needs to be 0.25 ps / (km · nm) or more. That is, the wavelength interval between the zero-dispersion wavelength λ ₀ and the wavelength λ _{1 of the} channel 1 needs to be 3.8 nm or more, and this is called the FWM suppression guard band Δλ _g of this embodiment.

(D) Limited Band Due to SPM-GVD Effect FIG. 15 is a block diagram showing the configuration of a regenerative repeater system (optical transmission system) to which the optical wavelength division multiplexing transmission system as the seventh embodiment of the present invention is applied. , 11 is a transmitter that converts an electrical signal into an optical signal (signal light) and performs optical wavelength multiplexing using the configuration described above with reference to FIG. 2 (transmission circuit 1), and 12 is substantially in the optical transmission line (optical fiber 2). It is an in-line repeater (In-line amplifier) that amplifies a signal inserted at a constant interval L _In-line and attenuated due to line loss.

_{Reference numeral} 13 denotes a regenerative repeater (Regenerative-repeater) inserted into the optical transmission line (optical fiber 2) at a substantially constant interval L _R-rep (interval wider than the interval L _{In-line of the in-line} repeater 12). This regenerative repeater 13 is used to regenerate and transmit the signal light deteriorated by the influence of noise depending on the line characteristics before it becomes indistinguishable. Reshaping, Retiming, and Regenerating have a function of three Rs and are also called 3R repeaters.

Further, reference numeral 14 denotes a receiver that separates the signal light multiplexed by the configuration (reception circuit 4) described above with reference to FIG. 2 and converts each signal light into an electric signal.
In this embodiment, the transmitter 11 and the receiver 14 described above are connected by the optical fiber 2 through the plurality of in-line repeaters 12 and the regenerative repeaters 13, so that the optical amplification multi-relay WDM system can be used. A transmission system (regenerative relay system) 10 is configured.

In the case of the optical transmission system 10 as described above, the interval L _R-rep of the regenerative repeater 13 mainly includes (1) optical SNR degradation due to ASE accumulation in the inline repeater 12, and (2) optical fiber. 2 is limited by two factors such as waveform deterioration due to the SPM-GVD effect via the Kerr effect. At the same time, the lower limit of the input power into the optical fiber 2 is limited by the optical SNR, and the upper limit is limited by the SPM-GVD effect. For the evaluation of the waveform deterioration due to the SPM-GVD effect, as described above, generally, simulation by solving the nonlinear Schrodinger equation using the split step Fourier method is effective.

FIG. 19 shows the relationship between the input power to the optical fiber 2 and the interval L _R-rep of the regenerative repeater 13 when only one wave is transmitted at a transmission rate of 10 Gbps and the interval L _In-line of the in _-line repeater 12 is 70 km. An example relationship is shown. Assuming that the fluctuation of the optical output from each optical amplifier (in-line repeater 12) is ± 2 dB, when the allowable dispersion value D _allow = ± 1 ps / (nm · km), the interval L _R-rep of the regenerative repeater 13 When the allowable dispersion value D _allow = ± 2 ps / (nm · km), the maximum value of the interval L _R-rep of the regenerative repeater 13 is 210 km. In order to realize long-distance transmission, it is necessary to set the allowable dispersion value small and the input power to the optical fiber 2 large.

-Relationship between channel arrangement and required characteristics of optical fiber As described above, the required characteristics of DSF (optical fiber 2) that must be taken into consideration when performing optical transmission by the WDM method are as follows: (1) Zero dispersion wavelength λ ₀ , (2) Zero dispersion wavelength variation ± Δλ ₀ , (3) Dispersion slope (secondary dispersion) dD / dλ. Here, the zero dispersion wavelength variation ± Δλ ₀ is not only the variation in DSF manufacturing, but also the maximum variation of the zero dispersion wavelength λ _{0 in} the longitudinal direction of the optical fiber 2 within the interval L _R-rep of the regenerative repeater 13. It means width.

FIG. 20 shows the measurement result of the FWM generation efficiency η when _two wavelengths of signal light are input to an actual DSF, one wavelength λ ₂ is fixed at 1557 nm, and the other wavelength λ ₁ is changed (FIG. 20). 20, white circles connected by solid lines). At this time, the optical fiber length was 60 km, and each signal light power was +4 dBm. Compared with the calculation result (dotted line in FIG. 20) when the zero dispersion wavelength λ ₀ is fixed to a constant value, the measured values are distributed over a wide wavelength range, which is the actual zero dispersion wavelength λ ₀ of the DSF. Means that it varies in the longitudinal direction.

Considering the above points, in the optical wavelength division multiplexing transmission system of the seventh embodiment of the present invention, for example, as shown in FIG. 13, the signal light of each channel is arranged. In the present embodiment, a case will be described in which signal light of four channels is wavelength-multiplexed and optically transmitted.
That is, as shown in FIG. 13, considering the zero dispersion wavelength λ ₀ of the optical fiber 2 and the zero dispersion wavelength variation ± Δλ _{0 in} the longitudinal direction of the optical fiber 2, the zero dispersion wavelength variation range of the optical fiber 2 is short. On the shorter wavelength side than the wavelength end (λ ₀ −Δλ ₀ ), the signal lights of the four channels to be multiplexed are arranged at equal intervals Δλ _S.

At this time, the short wavelength end (λ ₀ of the zero dispersion wavelength variation range of the optical fiber 2 is
The shorter wavelength side than -.DELTA..lambda _0), provided the guard band [Delta] [lambda] _g for FWM suppressing the wavelength (λ _{0 -Δλ 0 -Δλ g)} further shorter wavelength side than the four-channel optical signal (channel 1 ˜4 and wavelengths λ _{1 to} λ ₄ ) are arranged. In the present embodiment, the wavelength λ _{1 of the} channel 1 is set at a position away from the zero dispersion wavelength λ ₀ of the DSF (optical fiber 2) by (Δλ ₀ + Δλ ₀ ) on the short wavelength side [wavelength (λ ₀ −Δλ ₀ −Δλ _g ) is set to match the wavelength λ _{1 of} channel 1].

In the present embodiment, four channels of signal light are arranged in the transmittable band Δλ _SPM-GVD defined by the allowable dispersion value D _allow determined by the SPM-GVD effect in the optical fiber 2. Yes. That is, as shown in FIG. 13, the transmittable signal light wavelength range is Δλ _SPM-GVD = | from the long wavelength end (λ ₀ + Δλ ₀ ) of the zero dispersion wavelength variation range for the optical fiber 2 to the short wavelength side. D _allow | / (dD / dλ). At this time, the wavelength λ _SPM-GVD [= (λ ₀ + Δλ ₀ ) −Δλ _SPM-GVD ] and the wavelength λ _{4 of the} channel 4 in order to allow transmission of all four waves and allow the zero dispersion wavelength variation Δλ ₀ as large as possible. Are set to match.

Furthermore, in the present embodiment, within the gain band Δλ _EDFA (for example, in the range of 1550 to 1560 nm as shown in FIG. 16) of the EDFA connected to the optical fiber 2 (optical amplifier arranged in the inline repeater 12), 4 Signal light of one channel is arranged.
Although not shown in FIG. 13, when considering the variation in the optical wavelength of each signal light due to the manufacturability of the semiconductor laser (signal light source) and the wavelength control accuracy, a plurality of variations are made depending on the variation. The band Δλ _{WDM in} which the channel signal light is arranged is set to be extended.

Here, the signal light arrangement example shown in FIG. 13 will be described more specifically with a numerical example. For example, four signal lights with a transmission rate of 10 Gbps are arranged at equal wavelength intervals of Δλ _S = 2 nm on the shorter wavelength side than the zero dispersion wavelength λ ₀ of the DSF (optical fiber 2), and the distance L between the inline repeaters 12 The relationship between the channel arrangement and the required characteristics of the DSF will be described in the case where the in _-line is 70 km and the interval L _R-rep of the regenerative repeater 13 is 280 km.

First, FIG. 21 shows the relationship of the guard band Δλ _g where the crosstalk amount in all channels is −30 dB or less with respect to the wavelength interval Δλ _S when the optical fiber length is 70 km and the input power of each channel is +6 dBm. . As can be seen from FIG. 21, when the wavelength interval Δλ _S = 2 nm (signal light band Δλ _WDM = 6 nm), the guard band Δλ _g = 3 nm is necessary.
As shown in FIG. 13, in order to effectively use the gain band (1550 to 1560 nm) of the EDFA, the wavelength λ _{1 of the} channel 1 is set to 1560 nm, which is the long wavelength end of the gain band. At this time, the wavelength λ ₁ is a wavelength separated from the zero dispersion wavelength λ _{0 of the} DSF by (Δλ ₀ + Δλ _g ) on the short wavelength side as described above.

Further, from FIG. 19, since the allowable dispersion value D _allow for the interval L _R-rep = 280 km of the regenerative repeater 13 is −1 ps / (nm · km), the transmittable signal light wavelength range is as described above. As described above, from the wavelength (λ ₀ + Δλ ₀ ) to the short wavelength side, it is a region within Δλ _SPM-GVD = | D _allow | / (dD / dλ), and all four waves can be transmitted and zero dispersion wavelength variation Δλ _0. Is set so that the wavelength (λ ₀ + Δλ ₀ ) −Δλ _SPM-GVD and the wavelength λ _{4 of the} channel 4 coincide with each other. From these conditions, each value of Δλ _SPM-GVD , Δλ ₀ , and λ ₀ is defined as follows.

Δλ _SPM-GVD = | D _allow | / (dD / dλ)
= 1 (ps / (nm · km)) / 0.08 (ps / (nm 2 · km)) = 12.5nm
Δλ ₀ = (Δλ _SPM-GVD −Δλ _WDM −Δλ _g ) /2=1.75 nm
λ ₀ = λ ₁ + Δλ ₀ + Δλ _g = 1564.75 nm
The above numerical values are those when the variation Δλ ₀ is minimum. Note that, as the dispersion slope dD / dλ is smaller, Δλ _SPM-GVD becomes larger and the variation Δλ ₀ can be allowed to be larger.

  Although the case where the optical dispersion compensator is not used has been described with reference to FIG. 13, the case where the signal light arrangement of each channel is performed using the optical dispersion compensator will be described next. That is, in the optical wavelength division multiplex transmission system according to the seventh embodiment of the present invention, the signal light of each channel can be arranged by using an optical dispersion compensator, for example, as shown in FIG. In this case as well, a case will be described in which signal light of four channels is wavelength-multiplexed and optically transmitted.

That is, first, as shown in the upper part of FIG. 14, in addition to the transmittable band Δλ _SPM-GVD defined by the allowable dispersion value D _allow determined by the SPM-GVD effect in the optical fiber 2, After the signal light is arranged, the zero-dispersion wavelength λ ₀ of the optical fiber 2 is shifted to λ ₀ ′ using an optical dispersion compensator as shown in the lower part of FIG. Apparently, it is arranged in the transmittable band Δλ _SPM-GVD .

At this time, the signal light of the four channels is shifted to a shorter wavelength side than the wavelength (λ ₀ −Δλ ₀ −Δλ _g ), similarly to the arrangement example described in FIG. Arranged at equal intervals Δλ _S and within the gain band Δλ _{EDFA of the EDFA} . Note that the wavelength λ _{1 of the} channel 1 is set to coincide with a wavelength (λ ₀ −Δλ ₀ −Δλ _g ) that is separated from the zero dispersion wavelength λ ₀ by (Δλ ₀ + Δλ _g ) on the short wavelength side.

By shifting the actual zero-dispersion wavelength lambda ₀ by the optical dispersion compensator only [Delta] [lambda] _DC to the short wavelength side, as shown in the lower part of FIG. 14, the signal light of four channels, apparently, the transmittable band It is arranged in Δλ _SPM-GVD .
Although not shown in FIG. 14, when considering the variation in the optical wavelength of each signal light due to the manufacturability of the semiconductor laser (signal light source) and the wavelength control accuracy, a plurality of variations are made depending on the variation. The band Δλ _{WDM in} which the channel signal light is arranged is set to be extended.

Although not shown in FIG. 14, when the optical dispersion compensator is used as described above, the signal light band Δλ _{WDM is changed} to the long wavelength side in consideration of the dispersion compensation amount variation range ± δλ _DC of the optical dispersion compensator. Further, the dispersion compensation amount variation range δλ _{DC is} extended and set on both sides on the short wavelength side. Furthermore, as an optical dispersion compensator, what is demonstrated below by 9th-15th embodiment can be used, for example.

Here, the signal light arrangement example shown in FIG. 14 will be described more specifically with a numerical example. In this case, the zero dispersion wavelength variation Δλ ₀ for the optical fiber 2 can be maximized by using an optical dispersion compensator having a transmission line in the signal band and a dispersion value of the opposite sign, and the optical Consider the case where the dispersion compensation wavelength shift amount Δλ _DC is minimized in view of the size of the dispersion compensator and the optical loss. Each numerical value is the same as that described with reference to FIG.

As shown in the lower part of FIG. 14, a zero from the lower limit of the dispersion wavelength variation and scope of the [Delta] [lambda] _SPM-GVD from the lower limit to the short wavelength side of the range and the zero dispersion wavelength deviation of [Delta] [lambda] _SPM-GVD to the long wavelength side are overlapped region When the signal light band Δλ _WDM coincides, the zero dispersion wavelength variation Δλ ₀ can be allowed to the maximum. That means
Δλ _{0 (max)} = (2 ・ Δλ _SPM-GVD −Δλ _WDM ) / 2
= (2 x 12.5-6) / 2 = 9.5nm
At this time, the apparent zero dispersion wavelength λ ₀ ′ after dispersion compensation is located at the center of the signal light band Δλ _WDM .

Before dispersion compensation, as shown in the upper part of FIG. 14, the wavelength λ _{1 of the} channel ₁ is separated from the zero dispersion wavelength λ ₀ by Δλ ₀ + Δλ _g to the short wavelength side due to the FWM suppression condition. Therefore,
λ ₀ = λ ₁ + Δλ ₀ + Δλ _g = 1572.5 nm
Thus, λ ₀ ± Δλ ₀ = 1572.5 ± 9.5 nm.
At this time, the dispersion compensation wavelength shift amount Δλ _DC is λ ₀ −λ ₀ ′, and is obtained as follows.

Δλ _DC = (2 ・ Δλ ₀ −Δλ _SPM-GVD ) + Δλ _g + Δλ _WDM
= (2 × 9.5-12.5) + 3 + 6 = 15.5nm
As an optical dispersion compensator, high dispersion, low loss, and downsizing are demanded. Dispersion compensation fibers, transversal filter types, optical resonator types, and the like have been proposed so far. A device to which an optical dispersion compensation method described later according to the ninth to fifteenth embodiments is applied is used.

In the example shown in FIG. 14, an optical dispersion compensator having a positive dispersion value is required. For example, if a normal single mode fiber [dispersion value D _DC = 18 ps / (nm · km)] is used, it is necessary. The fiber length L _DC is given as follows.
L _DC = (Δλ _DC · dD / dλ · L _R-rep ) / D _DC
= (15.5 × 0.08 × 280) /18=19.3km
In the examples of FIGS. 13 and 14 described above, the case where the zero dispersion wavelength variation Δλ ₀ is minimum and maximum has been specifically described, but FIG. 22 shows that the signal light is placed on the short wavelength side of the zero dispersion wavelength λ _0. In the case of the arrangement, the relationship between the zero dispersion wavelength λ ₀ and the dispersion compensation wavelength shift amount Δλ _DC with respect to the variation Δλ ₀ is shown. In FIG. 22, a solid line indicates a case where the wavelength interval Δλ _S = 2 nm and the guard band Δλ _g = 3 nm. The case of the wavelength interval Δλ _S = 3 nm is indicated by a dotted line. At this time, as shown in FIG. 13, since the zero dispersion wavelength λ ₀ and the wavelength λ _{1 of the} channel 1 do not have to coincide with each other, the guard band Δλ _g = 1 nm is obtained. did.

Thus, according to the optical wavelength division multiplexing transmission system of the seventh embodiment, in the optical amplification multi-relay WDM system using the band around the zero dispersion wavelength λ ₀ of the optical fiber 2, each channel is not affected by the FWM. Of the signal light in the optical amplification multi-relay WDM system, and the required characteristics regarding the zero dispersion wavelength λ ₀ of the optical fiber transmission line to be laid can be clarified simultaneously. A transmission line design method can be established.

In particular, according to the present embodiment, the signal light of each channel is arranged on the shorter wavelength side than the wavelength (λ ₀ −Δλ ₀ −Δλ _g ) in consideration of the zero dispersion wavelength variation range and the FWM suppression guard band. Thus, the dispersion of the zero dispersion wavelength in the longitudinal direction of the optical fiber 2 is considered and managed, and at the same time, the influence of FWM is suppressed, the influence of crosstalk from other channels is suppressed, and high transmission accuracy can be maintained. .

Further, according to the present embodiment, the signal light can be arranged in consideration of the waveform deterioration due to the SPM-GVD effect, and the signal light power of each channel can be obtained by arranging the signal light of each channel within the gain band Δλ _{EDFA of the EDFA} . And the reception characteristics of each signal light can be made equal.
Furthermore, by expanding and setting the band Δλ _WDM where the signal light is arranged according to the variation in the optical wavelength of the signal light of each channel, each signal light can be determined according to the manufacturability and wavelength control accuracy of the signal light source such as a semiconductor laser. In the case where an optical dispersion compensator is used, the band Δλ _{WDM in} which the signal light is arranged is changed to a dispersion compensation amount variation range δλ _DC of the optical dispersion compensator on both the long wavelength side and the short wavelength side. By setting only an extension, it is possible to take into account dispersion variations in the optical dispersion compensator and to perform more reliable optical transmission.

In the seventh embodiment described above, the case where signal light of four channels is arranged has been described, but the present invention is not limited to this.
(H) Description of Eighth Embodiment Next, a description will be given of an optical wavelength division multiplexing transmission system as an eighth embodiment of the present invention. FIG. 23 is a diagram showing the signal light arrangement of the plurality of channels, and FIG. FIG. 25 is a graph showing the relationship between the zero dispersion wavelength and the dispersion compensation amount with respect to the zero dispersion wavelength variation. Note that the optical wavelength division multiplex transmission system of the eighth embodiment is also applied to the same system as the regenerative repeater system (optical transmission system) described with reference to FIG.

In the seventh embodiment described above, the case where the signal light of each channel is arranged on the shorter wavelength side than the zero dispersion wavelength λ ₀ of the optical fiber 2 has been described. However, in the eighth embodiment, the signal light of each channel is optically transmitted. The fiber 2 is arranged on the longer wavelength side than the zero dispersion wavelength λ ₀ , and the wavelength λ _{1 of the} channel 1 is set to the short wavelength end 1550 nm of the gain band of the EDFA, and then in FIG. 13 of the seventh embodiment. The relationship between the channel arrangement and the required characteristics of the DSF (optical fiber 2) is determined by exactly the same means as described.

That is, as shown in FIG. 23, considering the zero dispersion wavelength λ ₀ of the optical fiber 2 and the zero dispersion wavelength variation ± Δλ _{0 in} the longitudinal direction of the optical fiber 2, the length of the zero dispersion wavelength variation range for the optical fiber 2 is considered. On the longer wavelength side than the wavelength end (λ ₀ + Δλ ₀ ), signal light of four channels to be multiplexed is arranged at equal intervals Δλ _S.
At this time, an FWM suppression guard band Δλ _g is provided on the long wavelength side of the long wavelength end (λ ₀ + Δλ ₀ ) of the zero dispersion wavelength variation range for the optical fiber 2, and the wavelength (λ ₀ + Δλ ₀ + Δλ _g ) is provided. Further, signal light of four channels (wavelengths λ _{1 to} λ 4 for channels 1 to ₄ ) are arranged on the longer wavelength side. In the present embodiment, the wavelength λ _{1 of the} channel 1 is set at a position away from the zero dispersion wavelength λ ₀ of the DSF (optical fiber 2) by (Δλ ₀ + Δλ _g ) on the long wavelength side [wavelength (λ ₀ + Δλ ₀ + Δλ _g ) is set to match the wavelength λ _{1 of} channel 1].

In the present embodiment, four channels of signal light are arranged in the transmittable band Δλ _SPM-GVD defined by the allowable dispersion value D _allow determined by the SPM-GVD effect in the optical fiber 2. Yes. That is, as shown in FIG. 23, the transmittable signal light wavelength range is Δλ _SPM-GVD = from the short wavelength end (λ ₀ −Δλ ₀ ) of the zero dispersion wavelength variation range for the optical fiber 2 to the long wavelength side. | D _allow | / (dD / dλ). At this time, the wavelength λ _SPM-GVD [= (λ ₀ −Δλ ₀ ) + Δλ _SPM-GVD ] and the wavelength λ _{4 of the} channel 4 in order to allow transmission of all four waves and allow the zero dispersion wavelength variation Δλ ₀ as large as possible. Is set to match.

Furthermore, in the present embodiment, four channels of signal light are arranged within a gain band Δλ _EDFA (for example, a range of 1550 to 1560 nm as shown in FIG. 16) of the EDFA connected to the optical fiber 2.
Although not shown in FIG. 23, in the present embodiment as well, when the variation in the optical wavelength of each signal light due to the manufacturability of the semiconductor laser (signal light source) and the wavelength control accuracy is taken into account, the variation is considered. Depending on the minutes, the band Δλ _{WDM in} which signal lights of a plurality of channels are arranged is extended and set.

Incidentally, although the case where the optical dispersion compensator is not used has been described with reference to FIG. 23, the case where the signal light arrangement of each channel is performed using the optical dispersion compensator will be described next. That is, in the optical wavelength division multiplex transmission system according to the eighth embodiment of the present invention, the signal light of each channel can be arranged by using an optical dispersion compensator, for example, as shown in FIG.
That is, first, as shown in the upper part of FIG. 24, in addition to the transmittable band Δλ _SPM-GVD defined by the allowable dispersion value D _allow determined by the SPM-GVD effect in the optical fiber 2, After the signal light is arranged, the zero-dispersion wavelength λ ₀ of the optical fiber 2 is shifted to λ ₀ ′ using an optical dispersion compensator as shown in the lower part of FIG. Apparently, it is arranged in the transmittable band Δλ _SPM-GVD .

At this time, before shifting by the optical dispersion compensator, the signal light of the four channels is equally spaced on the longer wavelength side than the wavelength (λ ₀ + Δλ ₀ + Δλ _g ), as in the arrangement example described in FIG. Arranged at Δλ _S and within the gain band Δλ _{EDFA of the EDFA} . Note that the wavelength λ _{1 of the} channel 1 is set to coincide with a wavelength (λ ₀ + Δλ ₀ + Δλ _g ) separated from the zero dispersion wavelength λ ₀ by (Δλ ₀ + Δλ _g ) on the long wavelength side.

Then, by shifting the actual zero dispersion wavelength λ ₀ by Δλ _DC (= λ ₀ ′ −λ ₀ ) to the long wavelength side by the optical dispersion compensator, as shown in the lower part of FIG. The light is apparently arranged in the transmittable band Δλ _SPM-GVD .
Also in FIG. 24, as described in FIG. 14 of the seventh embodiment, from the lower limit of the zero dispersion wavelength variation to the longer wavelength side, the range of Δλ _SPM-GVD and from the lower limit of the zero dispersion wavelength variation to the shorter wavelength side. The case where the region where the range of Δλ _SPM-GVD overlaps and the signal light band Δλ _WDM are made coincident and the zero dispersion wavelength variation Δλ ₀ can be allowed to the maximum is illustrated.

In addition, although not shown in FIG. 24, when considering the variation in the optical wavelength of each signal light due to the manufacturability of the semiconductor laser (signal light source) and the wavelength control accuracy, a plurality of variations are made depending on the variation. The band Δλ _{WDM in} which the channel signal light is arranged is set to be extended.
Further, although not shown in FIG. 24, when the optical dispersion compensator is used as described above, the signal light band Δλ _{WDM is changed} to the long wavelength side in consideration of the dispersion compensation amount variation range ± δλ _DC of the optical dispersion compensator. The dispersion compensation amount variation range δλ _{DC is} extended and set on both sides on the short wavelength side. Furthermore, as an optical dispersion compensator, what is demonstrated below by 9th-15th embodiment can be used, for example.

In the example of FIG. 23 and FIG. 24 described above, the case where the zero dispersion wavelength variation Δλ ₀ is the minimum and the maximum is described, but FIG. 25 shows the case where the signal light is arranged on the long wavelength side of the zero dispersion wavelength λ _0. The relationship between the zero dispersion wavelength λ ₀ and the dispersion compensation wavelength shift amount Δλ _DC with respect to the variation Δλ ₀ is shown. In FIG. 25, the same numerical values as those in FIG. 22 described above according to the seventh embodiment are applied. In FIG. 25, since the signal light is arranged on the longer wavelength side than the zero dispersion wavelength λ ₀ , there is a variation. slopes for the zero-dispersion wavelength lambda ₀ for [Delta] [lambda] ₀ are reversed from that shown in FIG. 22.

As described above, even by the optical wavelength division multiplex transmission system of the eighth embodiment, it is possible to obtain the same effects as those of the seventh embodiment described above.
In the above-described eighth embodiment, the case where signal light of four channels is arranged has been described, but the present invention is not limited to this.
In the seventh embodiment and the eighth embodiment described above, the case where the signal light of each channel is arranged on either the short wavelength side or the long wavelength side of the zero dispersion wavelength λ ₀ has been described. The present invention is not limited to this, and the signal light of each channel can be arranged on both sides of the zero dispersion wavelength λ ₀ . At this time, when performing optical dispersion compensation, it is necessary to use different optical dispersion compensators for the short wavelength side and the long wavelength side of the zero dispersion wavelength λ ₀ separately.

(I) Description of Ninth Embodiment Next, an optical dispersion compensation system according to a ninth embodiment of the present invention will be described. FIG. 26 is a block diagram thereof. In FIG. A transmitter 22 that converts the signal into a transmission and a repeater 22 are inserted into the optical transmission line (optical fiber 2). Examples of the repeater 22 include the in-line repeater and the regenerative repeater described above.

Reference numeral 23 denotes a receiver that converts a received optical signal into an electrical signal. The transmitter 21 and the receiver 23 described above are connected by an optical fiber 2 through a plurality of repeaters 22, so that an optical transmission system can be obtained. In this optical transmission system 20, signal light from the transmitter 21 is transmitted to the receiver 23 via the repeater 22 and the optical fiber 2.
24A and 24B are two types of optical dispersion compensator units each having a positive dispersion amount + B and a negative dispersion amount −B. These two types of optical dispersion compensator units 24A and 24B are prepared in advance. As described later, it is inserted into the optical transmission system 20 (any part of the optical fiber 2, the transmitter 21, the repeater 22, and the receiver 23).

When the optical transmission system 20 is an optical amplification regenerative repeater system as described above with reference to FIG. 15, the allowable dispersion value decreases as the regenerative repeater interval increases as described above with reference to FIG. An optical dispersion compensator for keeping the (signal light) arrangement position within the allowable dispersion value is indispensable.
In the first to eighth embodiments described above, the zero dispersion wavelength and the signal light wavelength of the optical fiber 2 are used to avoid crosstalk due to the FWM in the WDM system using the band around the zero dispersion wavelength of the optical fiber 2. However, dispersion compensation for that amount (especially, refer to the examples of FIGS. 14 and 24 in the seventh and eighth embodiments) is required. Such dispersion compensation is also necessary for single-wave transmission and SMF transmission.

In particular, in the case of a land optical communication system, the repeat interval is not constant, and the actual zero dispersion wavelength of the optical fiber 2 varies in the longitudinal direction. Therefore, it is difficult to equalize the dispersion amount in each repeat section. . Therefore, when the signal light wavelength is set in the vicinity of the zero dispersion wavelength of the DSF (optical fiber 2), there is a possibility that the positive and negative dispersion amounts differ for each relay section.
Therefore, in the ninth embodiment, in order to compensate for the amount of dispersion of the optical transmission system 20, two types of optical dispersion compensator units 24A and 24B prepared in advance are inserted into the optical transmission system 20 respectively. The optical dispersion compensator unit 24A or 24B with the better transmission characteristics of the system 20 is selected and inserted into the optical transmission system 20.

Thereby, when the accurate dispersion amount cannot be measured and the dispersion of the zero dispersion wavelength can be grasped to some extent, the dispersion amount of the optical transmission system 20 can be easily compensated.
Further, when the dispersion amount of the optical transmission system 20 can be measured, the optical transmission system 20 can be more reliably selected by selecting the optical dispersion compensator unit 24A or 24B having a sign opposite to the sign of the measured dispersion quantity. Can be compensated for.

As described above, according to the optical dispersion compensation method of the ninth embodiment, the waveform deterioration due to the SPM-GVD effect and the amount of dispersion with respect to the guard band can be achieved without designing and manufacturing an optical dispersion compensator corresponding to each transmission path. Can be easily compensated, and man-hour reduction and time reduction until construction of the optical communication system can be realized.
Here, specific numerical examples of the ninth embodiment will be described. Assuming that the transmission speed is 10 Gbps, the in-line repeater interval L _In-line is 70 km, and the fluctuation of the optical output from each optical amplifier is ± 2 dB, the allowable dispersion value D _allow = ± 1 ps / (nm · km) from FIG. The maximum regenerative repeater interval is 280 km, and dispersion of signal light after 280 km transmission requires dispersion compensation of ± 280 ps / nm. Therefore, for example, when the transmission line dispersion is +1200 ps / nm, when the optical dispersion compensator units 24A and 24B with dispersion +1000 ps / nm and −1000 ps / nm are prepared, the optical dispersion compensation with the dispersion −1000 ps / nm If the unit 24B is inserted into the transmission line, the total dispersion amount becomes +200 ps / nm and transmission is possible.

(J) Description of Tenth Embodiment Next, the optical dispersion compensation system as the tenth embodiment of the present invention will be described. FIG. 27 is a block diagram thereof, and in FIG. Since the reference numerals indicate the same parts, the description thereof is omitted.
In the ninth embodiment described above, two types of optical dispersion compensator units having a positive dispersion amount + B and a negative dispersion amount −B are prepared in advance, whereas in the tenth embodiment, positive and negative. A plurality of types of optical dispersion compensator units 25A and 25B having different codes and dispersion amounts are prepared in advance.

Here, a plurality of two types of optical dispersion compensator units 25A and 25B having dispersion amounts B1 and B2 are prepared, and an optical dispersion compensator unit 25 configured by combining these optical dispersion compensator units 25A and 25B is provided. The optical transmission system 20 is inserted into one of the optical fiber 2, the transmitter 21, the repeater 22, and the receiver 23.
In this embodiment, at the site where the optical communication system is installed, two types of optical dispersion compensator units 25A and 25B are inserted into the optical transmission system 20 while changing the number and combination of the units, and the transmission of the optical transmission system 20 is performed. The optical dispersion compensator unit 25 having a combination of the number of installations and the combination in which the transmission characteristic is good while measuring the characteristics, particularly the code error rate (in FIG. 27, three optical dispersion compensator units 25A and one optical dispersion compensator The combination of the optical unit 25B and the optical unit 25B is selected and determined from the two types of optical dispersion compensator units 25A and 25B, and is inserted and installed in the optical transmission system 20.

Thereby, the dispersion amount of the optical transmission system 20 can be simply and optimally compensated when the dispersion of the zero dispersion wavelength is unknown or when the zero dispersion wavelength and the signal light wavelength are largely separated from each other. Can do.
Further, when the dispersion amount of the optical transmission system 20 can be measured, the dispersion amount is measured, and based on the measured dispersion amount, the number of installations and combinations in which the dispersion value of the signal light is within the dispersible dispersion value The optical dispersion compensator unit 25 is selected and determined from the two types of optical dispersion compensator units 25A and 25B, and is inserted and installed in the optical transmission system 20, so that the amount of dispersion of the optical transmission system 20 is ensured. Compensation can be made so as to be within an allowable dispersion value.

As described above, even with the optical dispersion compensation method of the tenth embodiment, the waveform dispersion due to the SPM-GVD effect and the dispersion amount for the guard band can be reduced without designing and manufacturing an optical dispersion compensator corresponding to each transmission path. Compensation can be easily performed, and man-hours and time required for constructing an optical communication system can be reduced.
In the tenth embodiment described above, the case where two types of optical dispersion compensator units prepared in advance are described, but the present invention is not limited to this.

  Here, specific numerical examples of the tenth embodiment will be described. Similar to the numerical example of the ninth embodiment, when dispersion compensation of ± 280 ps / nm is required as the dispersion amount of the signal light after 280 km transmission, for example, +300 ps as dispersion amounts A1, A2, B1, and B2, respectively. Assuming that optical dispersion compensator units of / nm, + 100ps / nm, -300ps / nm, and -100ps / nm are prepared, the optical dispersion compensator units are transmitted in combination of B1 x 3 + B2 x 1 If inserted in the path, the total dispersion becomes +200 ps / nm and transmission is possible.

(K) Description of Eleventh Embodiment Next, an optical dispersion compensation system as an eleventh embodiment of the present invention will be described. FIG. 28 is a block diagram thereof, FIG. 29 and FIG. It is a block diagram which shows 2 modifications. In the ninth and tenth embodiments described above, the case where only one wave of signal light is transmitted has been described, but in this embodiment, four channels of signal light (wavelengths λ _{1 to} λ ₄ ) are wavelength-multiplexed. Will be described.

  As shown in FIG. 28, also in this embodiment, the optical transmission system 20 is configured by connecting a transmitter 21, a repeater 22, and a receiver 23 with an optical fiber 2, but in this eleventh embodiment, The transmitter 21 converts the electrical signals of the respective channels into signal lights having different wavelengths (frequencies), and then performs optical wavelength multiplexing on these signal lights, and is provided for each channel. Is converted into signal light of a predetermined wavelength, and the signal light from the electric / optical conversion unit 21a for each channel is received and multiplexed. And an optical multiplexing unit 21b for this purpose.

  The receiver 23 separates multiplexed signal light transmitted from the transmitter 21 via the optical fiber 2 and the repeater 22 and converts each signal light into an electrical signal. An optical separation unit 23a that separates and distributes the signal light into each channel, and an optical / electrical conversion unit (O) that converts the signal light of the channel that is provided for each channel and is distributed from the optical separation unit 23a into an electrical signal. / E1 to O / E4) 23b.

In this embodiment, an optical dispersion compensator unit 25 is provided between each electrical / optical converter 21a and the optical multiplexer 21b of the transmitter 21. That is, an appropriate number and combination of optical dispersion compensator units 25A and 25B are installed for each channel of signal light having wavelengths λ _{1 to} λ ₄ before wavelength multiplexing.
For example, in Figure 28, it is provided only one optical dispersion compensator units 25A amount of dispersion B1 is the wavelength lambda ₁ of the channel, the dispersion amount and the optical dispersion compensator units 25A amount of dispersion B1 is the wavelength lambda ₂ of the channel and B2 of the optical dispersion compensator unit 25B is provided by one, to the channel of the wavelength lambda ₃ is provided with two optical dispersion compensator unit 25B of the optical dispersion compensator unit 25A has one and dispersion amount B2 of dispersion amount B1 In addition, one optical dispersion compensator unit 25A with a dispersion amount B1 and three optical dispersion compensator units 25B with a dispersion amount B2 are provided in the channel of wavelength λ ₄ .

  At this time, when selecting the number and combination of the optical dispersion compensator units 25A and 25B arranged in each channel, as described in the ninth and tenth embodiments, the transmission characteristics of each channel are good. May be selected by trial and error, or if the amount of dispersion of the optical transmission system 20 can be measured, the one in which the dispersion value of the signal light falls within the dispersible value based on the measurement result is selected. May be.

In FIG. 28, the case where the optical dispersion compensator unit 25 is provided in the transmitter 21 has been described. However, as shown in FIGS. 29 and 30, the optical dispersion compensator unit 25 includes the repeater 22 and the receiver. 23 may be provided.
As shown in FIG. 29, when the optical dispersion compensator unit 25 is provided in the repeater 22, the amplified signal light is transmitted to the repeater 22 after the optical amplifier 22a constituting the repeater 22 at each wavelength λ. ₁ and the optical separating unit 22b for wavelength separation by one wavelength to to [lambda] every _four, each wavelength λ suitable installation number for each channel of ₁ to [lambda] ₄ of the signal light separated by the light separating portion 22b, a combination of optical dispersion An optical dispersion compensator unit 25 in which compensator units 25A and 25B are installed, and optical multiplexing for again wavelength-multiplexing the signal light for each channel, which has been dispersion-compensated by the optical dispersion compensator unit 25, and sending it to the transmission line The part 22c is arranged. Note that the above-described optical separation unit 22b, optical dispersion compensator unit 25, and optical multiplexing unit 22c may be provided before the optical amplifier 22a.

In addition, as shown in FIG. 30, when the optical dispersion compensator unit 25 is provided in the receiver 23, the optical dispersion compensator unit 25 is provided between the optical separation unit 23a of the receiver 23 and each optical / electrical conversion unit 23b. Is provided. That is, an appropriate number and combination of optical dispersion compensator units 25A and 25B are installed for each channel of signal light having wavelengths λ _{1 to} λ ₄ after wavelength separation.
As described above, according to the optical dispersion compensation system of the eleventh embodiment, even when the optical transmission system 20 performs optical wavelength multiplexing transmission in which signal lights having different wavelengths are multiplexed and transmitted, it is appropriate for each wavelength. By installing the light dispersion compensator units 25A and 25B having the same number and combination, the same operational effects as those of the ninth and tenth embodiments described above can be obtained.

In the above-described embodiment, the case where the number of channels of signal light to be multiplexed is four and there are two types of optical dispersion compensator units prepared in advance for dispersion compensation for each channel has been described. Is not limited to this.
(L) Description of Twelfth Embodiment Next, an optical dispersion compensation system according to a twelfth embodiment of the present invention will be described. FIG. 31 is a block diagram thereof, and FIGS. It is a block diagram which shows 2 modifications. In addition, since the same code | symbol as already described has shown the same part, the description is abbreviate | omitted.

In the eleventh embodiment described above, the case where an appropriate number and combination of optical dispersion compensator units 25A and 25B are installed for each wavelength has been described. In the twelfth embodiment, in the optical transmission system 20, An appropriate number and combination of optical dispersion compensator units 25A and 25B are installed for each channel group composed of a plurality of wave signals (two waves in this embodiment).
That is, FIGS. 31 to 33 show examples in which the optical dispersion compensator unit 25 is provided in the transmitter 21, the repeater 22, and the receiver 23. As shown in FIG. When the dispersion compensator unit 25 is provided, the optical multiplexing unit 21b in the transmitter 21 described above includes an optical multiplexing unit 21c that multiplexes the signal lights having the wavelengths λ ₁ and λ ₂ from the electrical / optical conversion unit 21a. , An optical multiplexing unit 21d that multiplexes the signal light of the wavelengths λ ₃ and λ ₄ from the electrical / optical conversion unit 21a, and two signal lights multiplexed by these optical multiplexing units 21c and 21d It is divided into an optical multiplexing unit 21e for multiplexing.

An optical dispersion compensator unit 25 is provided between the optical multiplexing units 21c and 21d and the optical multiplexing unit 21e. That is, an appropriate number and combination of optical dispersion compensator units 25A and 25B are installed for each channel group composed of two signal lights.
For example, in FIG. 31, only one optical dispersion compensator unit 25A with a dispersion amount B1 is provided in the channel group of wavelengths λ ₁ and λ _2, and the dispersion amount B1 is provided in the channel group of wavelengths λ ₃ and λ _4. One optical dispersion compensator unit 25A and one optical dispersion compensator unit 25B with a dispersion amount B2 are provided.

  At this time, when selecting the number and combination of the optical dispersion compensator units 25A and 25B arranged in each channel group, the transmission characteristics of each channel are good as described in the ninth and tenth embodiments. May be selected by trial and error, or if the dispersion amount of the optical transmission system 20 can be measured, the dispersion value of the signal light is within the dispersible dispersion value based on the measurement result. You may choose.

Further, as shown in FIG. 32, when the optical dispersion compensator unit 25 is provided in the repeater 22, the amplified signal light is supplied to the repeater 22 after the optical amplifier 22a constituting the repeater 22. An optical separation unit 22d that performs wavelength separation into two channel groups (a group of wavelengths λ ₁ and λ _{2 and} a group of wavelengths λ ₃ and λ ₄ ), and an appropriate number of installations for each channel group separated by the light separation unit 22d. , A combination optical dispersion compensator unit 25A, 25B, and an optical dispersion compensator unit 25, and the signal light for each channel group dispersion-compensated by the optical dispersion compensator unit 25 is wavelength-multiplexed again to obtain a transmission line. And an optical multiplexing unit 22e that transmits the data to the network. The optical demultiplexing unit 22d, the optical dispersion compensator unit 25, and the optical multiplexing unit 22e described above may be provided before the optical amplifier 22a.

Further, as shown in FIG. 33, when the optical dispersion compensator unit 25 is provided in the receiver 23, the optical demultiplexing unit 23a in the receiver 23 described above includes the channel groups of the wavelengths λ ₁ and λ ₂ and the wavelengths λ ₃ and λ. ₄ and the optical separation unit 23c for separating the channel group, the wavelength lambda _1, lambda and each wavelength lambda ₁ a channel group _2, the light separating portion 23d which separates the lambda ₂ of the signal light, the wavelength lambda _3, lambda ₄ Are further divided into an optical separator 23e that separates the signal light of λ ₃ and λ ₄ .

An optical dispersion compensator unit 25 is provided between the light separation unit 23c and the light separation units 23d and 23e. That is, an appropriate number and combination of optical dispersion compensator units 25A and 25B are installed for each channel group composed of two signal lights.
As described above, according to the optical dispersion compensation system of the twelfth embodiment, even when the optical transmission system 20 performs optical wavelength multiplexing transmission in which signal lights having different wavelengths are multiplexed and transmitted, it is appropriate for each channel group. By installing the light dispersion compensator units 25A and 25B having the same number and combination, the same operational effects as those of the ninth and tenth embodiments described above can be obtained.

In the above-described embodiment, the number of channels of signal light to be multiplexed is 4, two types of optical dispersion compensator units prepared in advance for dispersion compensation for each channel, and divided into two channel groups. Although the case has been described, the present invention is not limited to this.
(M) Description of Thirteenth Embodiment Next, an optical dispersion compensation system as a thirteenth embodiment of the present invention will be described. FIG. 34 is a block diagram thereof, and FIG. 35 and FIG. It is a block diagram which shows 2 modifications. In addition, since the same code | symbol as already described has shown the same part, the description is abbreviate | omitted.

  In the eleventh and twelfth embodiments described above, the case where the appropriate number and combination of optical dispersion compensator units 25A and 25B are installed for each wavelength and for each channel group has been described. In this thirteenth embodiment, however. In the optical transmission system 20, optical dispersion compensator units 25A and 25B having an appropriate number and combination are installed for a plurality of channels (four channels in the present embodiment) of signal light.

  34 to 36 each show an example in which the optical dispersion compensator unit 25 is provided in the transmitter 21, the repeater 22, and the receiver 23. As shown in FIG. In the case where the dispersion compensator unit 25 is provided, an optical dispersion compensator unit 25 in which an appropriate number and combination of optical dispersion compensator units 25A and 25B are installed in the subsequent stage of the optical multiplexing unit 21b in the transmitter 21 is provided. It has been. For example, in FIG. 34, one optical dispersion compensator unit 25A with a dispersion amount B1 and one optical dispersion compensator unit 25B with a dispersion amount B2 are provided.

  At this time, when selecting the number and combination of the optical dispersion compensator units 25A and 25B arranged in a lump, the transmission characteristics of each channel are good as described in the ninth and tenth embodiments. May be selected by trial and error, or if the amount of dispersion of the optical transmission system 20 can be measured, the one in which the dispersion value of the signal light falls within the dispersible value based on the measurement result is selected. May be.

  Further, as shown in FIG. 35, when the optical dispersion compensator unit 25 is provided in the repeater 22, the repeater 22 has an appropriate number and combination in the subsequent stage of the optical amplifier 22a constituting the repeater 22. An optical dispersion compensator unit 25 in which the optical dispersion compensator units 25A and 25B are installed is disposed. The optical dispersion compensator unit 25 may be provided in front of the optical amplifier 22a.

Furthermore, as shown in FIG. 36, when the optical dispersion compensator unit 25 is provided in the receiver 23, an appropriate number and combination of optical dispersion compensator units 25A and 25B are installed in the preceding stage of the optical separator 23a in the receiver 23. An optical dispersion compensator unit 25 is provided.
As described above, according to the optical dispersion compensation system of the thirteenth embodiment, even when the optical transmission system 20 performs optical wavelength multiplexing transmission in which signal lights having different wavelengths are multiplexed and transmitted, On the other hand, by installing the appropriate number and combination of optical dispersion compensator units 25A and 25B collectively, the same effects as those of the ninth and tenth embodiments described above can be obtained.

In the above-described embodiment, the case where the number of channels of signal light to be multiplexed is four and there are two types of optical dispersion compensator units prepared in advance for dispersion compensation for each channel has been described. Is not limited to this.
In the tenth to thirteenth embodiments described above, the dispersion value of each optical dispersion compensator unit is designed in consideration of the wavelength interval of each channel and the dispersion slope dD / dλ of the transmission line, and the optical dispersion compensator It is important to have as few unit types as possible.

(N) Description of Fourteenth Embodiment Next, an optical dispersion compensation system as the fourteenth embodiment of the present invention will be described. FIG. 37 is a block diagram thereof, and FIGS. FIG. 39 is a block diagram showing a second modification, FIG. 39 is a block diagram showing a second modification, and FIG. 40 is a diagram showing a package configuration example according to the second modification. In addition, since the same code | symbol as already described has shown the same part, the description is abbreviate | omitted.

In the ninth to thirteenth embodiments described above, the arrangement means of the light dispersion compensation units 24A, 24B, 25, 25A, and 25B has been described. In the fourteenth embodiment, each light dispersion compensation unit 25, 25A, A specific configuration example of 25B itself and insertion / installation means will be described.
For example, as shown in FIG. 37, an optical amplifier 26 that can compensate for optical loss caused by the optical dispersion compensator units 25A and 25B before or after the optical dispersion compensation units 25A and 25B constituting the optical dispersion compensation unit 25. Is added.

By the way, as an optical dispersion compensator, a dispersion compensating fiber, a transversal filter type, an optical resonator type, and the like have been proposed so far. At present, a dispersion compensation fiber with a dispersion value of -100 ps / (nm · km) or more is manufactured by devising the core shape, but the dispersion compensation amount can be easily adjusted by the fiber length, but the optical loss increases. End up.
Therefore, as in the fourteenth embodiment, by integrating the optical dispersion compensator units 25A and 25B with the optical amplifier 26 such as an EDFA, the optical loss of the dispersion compensating fiber can be compensated.

In FIG. 37, the optical amplifier 26 is added to each of the optical dispersion compensation units 25A and 25B. However, as shown in FIGS. 38A and 38B, the group of the optical dispersion compensator units 25A and 25B (optical dispersion). One optical amplifier 26 may be added to the compensator unit 25).
As shown in FIG. 39, optical amplifiers 26A and 26B may be added to the front and rear stages of the group of optical dispersion compensator units 25A and 25B (optical dispersion compensator unit 25), respectively.

  If the optical amplifier has only one stage, not only a large gain is required to compensate both the transmission line loss and the optical loss in the optical dispersion compensator unit 25, but also the optical dispersion compensator unit 25 having a large optical loss. Is placed in front of the optical amplifier 26, it causes a great deterioration of NF. This must be avoided particularly when the optical dispersion compensator unit 25 is inserted into the 1R repeater in the optical amplification multiple repeater system.

Therefore, as shown in FIG. 39, the front and rear of the optical dispersion compensator unit 25 are sandwiched between two optical amplifiers 26A and 26B, thereby reducing the NF of the preceding optical amplifier, thereby reducing the 1R repeater. The overall NF can be kept small, and a sufficient gain can be secured by the two-stage optical amplifiers 26A and 26B.
On the other hand, insertion / installation of the optical dispersion compensator unit 25 as described above into the transmitter 21, the repeater 22, or the receiver 23 is performed, for example, in the following manner. Space for inserting the optical dispersion compensator unit 25 in advance in the transmitter 21, repeater 22 or receiver 23, and after the system is installed, the optimum optical dispersion according to the transmission path (optical transmission system 20) The optical dispersion compensator unit 25 is inserted and installed in the optical transmission system 20 by adding the compensator unit 25 additionally.

In addition, the electronic component and the optical component in the optical transmission device are generally mounted on a printed circuit board (the form mounted on the printed circuit board is called a package) and can be inserted into and removed from the device rack. In many cases.
Therefore, a dispersion compensation package in which the optical dispersion compensator unit is mounted may be provided, and the entire dispersion compensation package may be inserted and removed. For example, FIG. 40 shows a package of the optical dispersion compensator unit 25 shown in FIG. In FIG. 40, reference numeral 27 denotes a printed circuit board, on which an optical dispersion compensator unit 25 including two front and rear optical amplifiers 26A and 26B and two types of three optical dispersion compensator units 25A and 25B are provided. As a result, the dispersion compensation package 28 is configured. Each of the optical dispersion compensator units 25A and 25B is configured by winding a dispersion compensating fiber (optical fiber 2) on a small bobbin provided on the printed board 27 for a predetermined length.

By using such a dispersion compensation package 28, the optical dispersion compensator unit 25 can be easily replaced and incorporated in a package unit, and the dispersion compensation amount can be easily changed.
(O) Description of Fifteenth Embodiment Next, an optical dispersion compensation system as a fifteenth embodiment of the present invention will be described. FIG. 41 is a block diagram thereof, and FIG. 42 and FIG. It is a block diagram which shows the example of 2 application. In addition, since the same code | symbol as already described has shown the same part, the description is abbreviate | omitted.

In the fifteenth embodiment, an optical dispersion compensator unit 32 as shown in FIG. 41 is incorporated in each of the transmitter 21, the repeater 22, and the receiver 23 that constitute the optical transmission system 20.
As shown in FIG. 41, the optical dispersion compensator unit 32 includes a plurality of types of optical dispersion compensator units 25A to 25D having different positive and negative signs and different amounts of dispersion (four types in this embodiment, each of which has a dispersion amount of B1 to B4). Are connected in a switchable / changeable state through a switch (switching means) 29A-29C in a combination of the optical dispersion compensator units 25A-25D.

In the optical dispersion compensator unit 32 shown in FIG. 41, four types of optical dispersion compensator units 25A to 25D are provided in three stages. The units 25 </ b> A to 25 </ b> D can be selected and inserted into the optical transmission system 20.
The switches 29A to 29C include means for wiring the optical dispersion compensator units 25A to 25D with optical fibers [mechanical connection (mechanical switch)], means for selecting a connection path with an optical switch, and the like. . Examples of the optical switch include an optical waveguide switch and a space switching switch.

As the switching operation means for the switches 29A to 29C, means for simply changing the wiring of the optical fiber or turning on / off the optical switch by external human work, or an electric or optical control signal from the outside There is a means to do it automatically.
Next, more specific application examples in the case where the switches 29A to 29C are switched by an external control signal to select the appropriate combination of the three optical dispersion compensator units 25A to 25D are shown in FIGS. 43.

As a means for performing the switching operation automatically by the control signal, in addition to the method of sending the control signal from the transmission / reception terminal station to each repeater 22, in the application example shown in FIG. Control signals are sent to the switches 29A to 29C of the optical dispersion compensator unit 32 in the transmitter 21, the repeater 22, and the receiver 23.
In the application example shown in FIG. 43, a function of outputting a control signal for switching to each switch 29A to 29C of the optical dispersion compensator unit 32 in each transmitter 21 and repeater 22 on the receiver 23 side, Transmission characteristic measuring means 31 for measuring transmission characteristics (error rate, waveform, etc.) in the transmission system 20 is provided.

  Then, each of the switches 29A to 29C is operated by a control signal from the receiver 23 side to switch the combination of the optical dispersion compensator units 25A to 25D in the optical dispersion compensator unit 32 in order, while the transmission characteristic measuring unit 31 performs optical switching. The transmission characteristics of the transmission system 20 are measured to determine the optical dispersion compensator units 25A to 25D of the combination in which the transmission characteristics of the optical transmission system 20 are optimal, and the switches 29A to 29C are controlled by the control signal from the receiver 23 side. To switch the combination of the optical dispersion compensator units 25 </ b> A to 25 </ b> D to a combination that optimizes the determined transmission characteristics of the optical transmission system 20.

  Thus, according to the optical dispersion compensation system of the fifteenth embodiment, a plurality of types of optical dispersion compensator units 25A to 25D are connected to the switch 29A in the transmitter 21, repeater 22, and receiver 23 in the optical transmission system 20. Are connected in a switchable and changeable state through the combination of the optical dispersion compensator units 25A to 25D through the switch 29C, and are previously built in, so that the switch 29A to 29C is operated, whereby the optical dispersion compensator unit 25A. An appropriate combination of the optical dispersion compensator units 25A to 25D is selected from ˜25D. In particular, by configuring as shown in FIG. 43, the combination of the optical dispersion compensator units 25A to 25D can be automatically switched to a combination that optimizes the transmission characteristics of the optical transmission system 20.

  In the above-described embodiment, the case where the optical dispersion compensator unit 32 is incorporated in each of the transmitter 21, the repeater 22, and the receiver 23 included in the optical transmission system 20 has been described. It goes without saying that the same effect as that of the above-described embodiment can be obtained as long as 32 is incorporated in at least one of the transmitter 21, the repeater 22, and the receiver 23.

It is a figure which shows the signal light arrangement | positioning of the multiple channels in the optical wavelength division multiplex transmission system as 1st Embodiment of this invention. 1 is a block diagram showing a configuration of an optical WDM distributed transmission system to which an optical wavelength division multiplexing transmission system as a first embodiment of the present invention is applied. FIG. It is a figure explaining operation | movement of 1st Embodiment of this invention. It is a figure explaining operation | movement of 1st Embodiment of this invention. It is a figure which shows signal light arrangement | positioning of the multiple channels in the optical wavelength division multiplex transmission system as 2nd Embodiment of this invention. It is a figure which shows the signal light arrangement | positioning of the multiple channels in the optical wavelength division multiplex transmission system as 3rd Embodiment of this invention. It is a figure explaining operation | movement of 3rd Embodiment of this invention. It is a figure which shows signal light arrangement | positioning of the multiple channels in the optical wavelength division multiplex transmission system as 4th Embodiment of this invention. It is a figure which shows signal light arrangement | positioning of the multiple channels in the optical wavelength division multiplex transmission system as 5th Embodiment of this invention. It is a figure which shows signal light arrangement | positioning of the multiple channels in the optical wavelength division multiplex transmission system as 6th Embodiment of this invention. It is a figure explaining operation | movement of 6th Embodiment of this invention. It is a figure explaining operation | movement of 6th Embodiment of this invention. It is a figure which shows signal light arrangement | positioning of the multiple channels in the optical wavelength division multiplex transmission system as 7th Embodiment of this invention. It is a figure which shows the modification of the signal light arrangement | positioning of several channels in the optical wavelength division multiplex transmission system as 7th Embodiment of this invention. It is a block diagram which shows the structure of the regenerative repeater system to which the optical wavelength division multiplex transmission system as 7th Embodiment of this invention is applied. It is a graph which shows the ASE spectrum (gain distribution of EDFA) after EDFA four-stage connection in order to explain the gain band of EDFA. It is a figure which shows the guard band for FWM suppression, and channel arrangement | positioning. It is a graph which shows the relationship between the dispersion value of channel 1, and crosstalk. It is a graph which shows the relationship between optical fiber input power and a regenerative repeater space | interval. It is a graph which shows the signal light wavelength dependence of FWM generation efficiency. It is a graph which shows the relationship between a channel space | interval and a guard band. It is a graph which shows the relationship between the zero dispersion wavelength with respect to the zero dispersion wavelength dispersion | variation in 7th Embodiment of this invention, and a dispersion compensation amount. It is a figure which shows signal light arrangement | positioning of the multiple channels in the optical wavelength division multiplex transmission system as 8th Embodiment of this invention. It is a figure which shows the modification of the signal light arrangement | positioning of several channels in the optical wavelength division multiplex transmission system as 8th Embodiment of this invention. It is a graph which shows the relationship between the zero dispersion wavelength with respect to the zero dispersion wavelength dispersion | variation in 8th Embodiment of this invention, and a dispersion compensation amount. It is a block diagram which shows the optical dispersion compensation system as 9th Embodiment of this invention. It is a block diagram which shows the optical dispersion compensation system as 10th Embodiment of this invention. It is a block diagram which shows the optical dispersion compensation system as 11th Embodiment of this invention. It is a block diagram which shows the 1st modification of the optical dispersion compensation system as 11th Embodiment of this invention. It is a block diagram which shows the 2nd modification of the optical dispersion compensation system as 11th Embodiment of this invention. It is a block diagram which shows the optical dispersion compensation system as 12th Embodiment of this invention. It is a block diagram which shows the 1st modification of the optical dispersion compensation system as 12th Embodiment of this invention. It is a block diagram which shows the 2nd modification of the optical dispersion compensation system as 12th Embodiment of this invention. It is a block diagram which shows the optical dispersion compensation system as 13th Embodiment of this invention. It is a block diagram which shows the 1st modification of the optical dispersion compensation system as 13th Embodiment of this invention. It is a block diagram which shows the 2nd modification of the optical dispersion compensation system as 13th Embodiment of this invention. It is a block diagram which shows the optical dispersion compensation system as 14th Embodiment of this invention. (A), (b) is a block diagram which shows the 1st modification of the optical dispersion compensation system as 14th Embodiment of this invention. It is a block diagram which shows the 2nd modification of the optical dispersion compensation system as 14th Embodiment of this invention. It is a figure which shows the package structural example by the 2nd modification of 14th Embodiment of this invention. It is a block diagram which shows the optical dispersion compensation system as 15th Embodiment of this invention. It is a block diagram which shows the 1st example of application of the optical dispersion compensation system as 15th Embodiment of this invention. It is a block diagram which shows the 2nd application example of the optical dispersion compensation system as 15th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission circuit 1a Laser diode 1b Multiplexer 2 Optical fiber 3 Divider 4 Receiver circuit 4a Optical filter 4b Control circuit 4c Detector 5 Four-wave mixing (FWM) suppression guard band 6 Long wavelength side 7 Short wavelength side 10 Optical transmission System (regenerative relay system)
DESCRIPTION OF SYMBOLS 11 Transmitter 12 In-line repeater 13 Regenerative repeater 14 Receiver 20 Optical transmission system 21 Transmitter 21a Electrical / optical conversion part 21b-21e Optical multiplexing part 22 Repeater 22a Optical amplifier 22b, 22d Optical separation part 22c, 22e Light Multiplexer 23 Receiver 23a, 23c-23e Optical separator 23b Optical / electric converter 24A, 24B, 25, 25A-25D Optical dispersion compensator unit 25a Bobbin 26, 26A, 26B Optical amplifier 27 Printed circuit board 28 Dispersion compensation package 29A-29C switch (switching means)
30 Center Office (CO)
31 Transmission characteristic measuring means 32 Optical dispersion compensator unit

Claims (43)

An optical separation unit for wavelength-separating a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
A first unit including a first dispersion compensation unit for compensating for dispersion of the first optical signal;
An optical repeater comprising: a second unit including a second dispersion compensation unit that compensates for dispersion of the second optical signal. An optical separation unit for wavelength-separating a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
A first unit including a first optical amplification unit that amplifies the first optical signal and a first dispersion compensation unit that compensates and outputs the dispersion of the first optical signal amplified by the first optical amplification unit;
A second unit including a second optical amplifying unit for amplifying the second optical signal and a second dispersion compensating unit for compensating and outputting the dispersion of the second optical signal amplified by the second optical amplifying unit; An optical repeater characterized in that it is configured. An optical separation unit for wavelength-separating a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
A first unit comprising: a first dispersion compensation unit that compensates for dispersion of the first optical signal; and a first optical amplification unit that amplifies and outputs the first optical signal dispersion-compensated by the first dispersion compensation unit; ,
A second unit comprising: a second dispersion compensation unit that compensates for dispersion of the second optical signal; and a second optical amplification unit that amplifies and outputs the second optical signal dispersion-compensated by the second dispersion compensation unit; An optical repeater characterized by comprising: Wavelength-division-multiplexed optical signal including a plurality of optical signals having different wavelengths is wavelength-separated into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
An optical repeater method comprising separately compensating for dispersion of the first optical signal and the second optical signal. Wavelength-division-multiplexed optical signal including a plurality of optical signals having different wavelengths is wavelength-separated into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
Amplifying the first optical signal and the second optical signal separately;
An optical relay method, comprising: separately compensating and outputting dispersion of the amplified first optical signal and second optical signal. Wavelength-division-multiplexed optical signal including a plurality of optical signals having different wavelengths is wavelength-separated into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
Separately compensating for dispersion of the first optical signal and the second optical signal;
An optical relay method, wherein the dispersion-compensated first optical signal and the second optical signal are separately amplified and output. An optical separation unit for wavelength-separating a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
An input-side first optical amplification unit that amplifies the first optical signal, a first dispersion compensation unit that compensates and outputs the dispersion of the first optical signal amplified by the input-side first optical amplification unit, and the first A first unit including an output-side first optical amplification unit that amplifies and outputs the first optical signal that has been dispersion-compensated by the dispersion compensation unit;
An input-side second optical amplification unit that amplifies the second optical signal, a second dispersion compensation unit that compensates for and outputs the dispersion of the second optical signal amplified by the input-side second optical amplification unit, and the second An optical repeater comprising: a second unit including an output-side second optical amplification unit that amplifies and outputs the second optical signal dispersion-compensated by the dispersion compensation unit. An optical separation unit for wavelength-separating a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
An input-side first optical amplification unit that amplifies the first optical signal, a first dispersion compensation unit that compensates and outputs the dispersion of the first optical signal amplified by the input-side first optical amplification unit, and the first A first unit including an output-side first optical amplification unit that amplifies and outputs the first optical signal that has been dispersion-compensated by the dispersion compensation unit;
A second dispersion compensator for amplifying the second optical signal; and a second dispersion compensator for compensating and outputting the dispersion of the second optical signal amplified by the input second optical amplifier. An optical repeater comprising two units. An optical separation unit for wavelength-separating a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
An input-side first optical amplification unit that amplifies the first optical signal, a first dispersion compensation unit that compensates and outputs the dispersion of the first optical signal amplified by the input-side first optical amplification unit, and the first A first unit including an output-side first optical amplification unit that amplifies and outputs the first optical signal that has been dispersion-compensated by the dispersion compensation unit;
A second dispersion compensation unit that compensates for dispersion of the second optical signal, and an output-side second optical amplification unit that amplifies and outputs the second optical signal dispersion-compensated by the second dispersion compensation unit. An optical repeater characterized by comprising a unit. An optical separation unit for wavelength-separating a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
A first dispersion compensation section that amplifies the first optical signal and a first dispersion compensation section that compensates and outputs the dispersion of the first optical signal amplified by the input first optical amplification section; 1 unit,
A second dispersion compensation unit that compensates and outputs the dispersion of the second optical signal, and an output-side second optical amplification unit that amplifies and outputs the second optical signal that has been dispersion-compensated by the second dispersion compensation unit. An optical repeater comprising a second unit including the optical repeater. An optical separation unit for wavelength-separating a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
First means for processing the first optical signal;
An optical repeater comprising: a second means for processing the second optical signal. An optical separation unit for wavelength-separating a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
First means for compensating and outputting the first optical signal;
Second means for compensating and outputting the second optical signal;
An optical multiplexing unit configured to wavelength multiplex the first optical signal compensated by the first means and the second optical signal compensated by the second means, Optical repeater. Wavelength-separating a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
Compensating the first optical signal;
And compensating the second optical signal. Wavelength-separating a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
Compensating and outputting the first optical signal;
Compensating and outputting the second optical signal;
A method of wavelength multiplexing the compensated first optical signal and the compensated second optical signal. An optical transmitter for transmitting a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths;
An optical repeater that relays the wavelength-multiplexed optical signal from the optical transmitter;
The optical repeater is
An optical separation unit for wavelength-separating the wavelength-multiplexed optical signal received from the optical transmission device into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
A first unit including a first dispersion compensation unit for compensating for dispersion of the first optical signal;
An optical transmission system comprising: a second unit including a second dispersion compensation unit that compensates for dispersion of the second optical signal. An optical transmitter for transmitting a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths;
An optical repeater that relays the wavelength-multiplexed optical signal from the optical transmitter;
The optical repeater is
An optical separation unit for wavelength-separating the wavelength-multiplexed optical signal received from the optical transmission device into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
A first unit including a first optical amplification unit that amplifies the first optical signal and a first dispersion compensation unit that compensates and outputs the dispersion of the first optical signal amplified by the first optical amplification unit;
A second unit including a second optical amplifying unit for amplifying the second optical signal and a second dispersion compensating unit for compensating and outputting the dispersion of the second optical signal amplified by the second optical amplifying unit; An optical transmission system characterized by being configured. An optical transmitter for transmitting a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths;
An optical repeater that relays the wavelength-multiplexed optical signal from the optical transmitter;
The optical repeater is
An optical separation unit for wavelength-separating the wavelength-multiplexed optical signal received from the optical transmission device into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
A first unit comprising: a first dispersion compensation unit that compensates for dispersion of the first optical signal; and a first optical amplification unit that amplifies and outputs the first optical signal dispersion-compensated by the first dispersion compensation unit; ,
A second unit comprising: a second dispersion compensation unit that compensates for dispersion of the second optical signal; and a second optical amplification unit that amplifies and outputs the second optical signal dispersion-compensated by the second dispersion compensation unit; An optical transmission system characterized by comprising: Transmitting a wavelength multiplexed optical signal including a plurality of optical signals having different wavelengths;
Wavelength-separating the wavelength division multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
An optical transmission method comprising separately compensating for dispersion of the first optical signal and the second optical signal. Transmitting a wavelength multiplexed optical signal including a plurality of optical signals having different wavelengths;
Wavelength-separating the wavelength division multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
Amplifying the first optical signal and the second optical signal separately;
An optical transmission method characterized by separately compensating and outputting dispersion of the amplified first optical signal and the second optical signal. Transmitting a wavelength multiplexed optical signal including a plurality of optical signals having different wavelengths;
Wavelength-separating the wavelength division multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
Separately compensating for dispersion of the first optical signal and the second optical signal;
An optical transmission method characterized in that the dispersion-compensated first optical signal and the second optical signal are separately amplified and output. An optical transmitter for transmitting a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths;
An optical repeater that relays the wavelength-multiplexed optical signal from the optical transmitter;
The optical repeater is
An optical separation unit for wavelength-separating the wavelength-multiplexed optical signal received from the optical transmission device into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
An input-side first optical amplification unit that amplifies the first optical signal, a first dispersion compensation unit that compensates and outputs the dispersion of the first optical signal amplified by the input-side first optical amplification unit, and the first A first unit including an output-side first optical amplification unit that amplifies and outputs the first optical signal that has been dispersion-compensated by the dispersion compensation unit;
An input-side second optical amplification unit that amplifies the second optical signal, a second dispersion compensation unit that compensates for and outputs the dispersion of the second optical signal amplified by the input-side second optical amplification unit, and the second An optical transmission system comprising: a second unit including an output-side second optical amplification unit that amplifies and outputs the second optical signal that has been dispersion-compensated by the dispersion compensation unit. An optical transmitter for transmitting a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths;
An optical repeater that relays the wavelength-multiplexed optical signal from the optical transmitter;
The optical repeater is
An optical separation unit for wavelength-separating the wavelength-multiplexed optical signal received from the optical transmission device into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
An input-side first optical amplification unit that amplifies the first optical signal, a first dispersion compensation unit that compensates and outputs the dispersion of the first optical signal amplified by the input-side first optical amplification unit, and the first A first unit including an output-side first optical amplification unit that amplifies and outputs the first optical signal that has been dispersion-compensated by the dispersion compensation unit;
A second dispersion compensator for amplifying the second optical signal; and a second dispersion compensator for compensating and outputting the dispersion of the second optical signal amplified by the input second optical amplifier. An optical transmission system comprising two units. An optical transmitter for transmitting a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths;
An optical repeater that relays the wavelength-multiplexed optical signal from the optical transmitter;
The optical repeater is
An optical separation unit for wavelength-separating the wavelength-multiplexed optical signal received from the optical transmission device into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
An input-side first optical amplification unit that amplifies the first optical signal, a first dispersion compensation unit that compensates and outputs the dispersion of the first optical signal amplified by the input-side first optical amplification unit, and the first A first unit including an output-side first optical amplification unit that amplifies and outputs the first optical signal that has been dispersion-compensated by the dispersion compensation unit;
A second dispersion compensation unit that compensates for dispersion of the second optical signal, and an output-side second optical amplification unit that amplifies and outputs the second optical signal dispersion-compensated by the second dispersion compensation unit. An optical transmission system comprising a unit and an optical transmission system. An optical transmitter for transmitting a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths;
An optical repeater that relays the wavelength-multiplexed optical signal from the optical transmitter;
The optical repeater is
An optical separation unit for wavelength-separating the wavelength-multiplexed optical signal received from the optical transmission device into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
A first dispersion compensation section that amplifies the first optical signal and a first dispersion compensation section that compensates and outputs the dispersion of the first optical signal amplified by the input first optical amplification section; 1 unit,
A second dispersion compensation unit that compensates and outputs the dispersion of the second optical signal, and an output-side second optical amplification unit that amplifies and outputs the second optical signal that has been dispersion-compensated by the second dispersion compensation unit. An optical transmission system comprising a second unit including the second unit. A transmission means for wavelength-multiplexing a plurality of optical signals having different wavelengths to generate a wavelength-multiplexed optical signal;
Relay means for relaying the wavelength multiplexed optical signal from the transmission means,
The relay means
An optical demultiplexing unit that wavelength-separates the wavelength-multiplexed optical signal received from the transmission unit into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
First means for compensating the first optical signal;
An optical transmission system comprising: a second means for compensating the second optical signal. A transmission means for wavelength-multiplexing a plurality of optical signals having different wavelengths to generate a wavelength-multiplexed optical signal;
Relay means for relaying the wavelength multiplexed optical signal from the transmission means,
The relay means
An optical demultiplexing unit that wavelength-separates the wavelength-multiplexed optical signal received from the transmission unit into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
First means for compensating and outputting the first optical signal;
Second means for compensating and outputting the second optical signal;
And an optical multiplexing unit configured to wavelength-multiplex the first optical signal compensated by the first means and the second optical signal compensated by the second means. , Optical transmission system. Wavelength multiplexing a plurality of optical signals having different wavelengths to generate a wavelength multiplexed optical signal;
Wavelength-separating the wavelength division multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
Compensating the first optical signal;
Compensating the second optical signal. An optical transmission method comprising: Wavelength multiplexing a plurality of optical signals having different wavelengths to generate a wavelength multiplexed optical signal;
Wavelength-separating the wavelength division multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
Compensating and outputting the first optical signal;
Compensating and outputting the second optical signal;
A method of wavelength multiplexing the compensated first optical signal and the compensated second optical signal. An optical repeater that relays a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths and outputs as a wavelength-multiplexed optical signal after relay;
An optical receiver that wavelength-separates the post-relay wavelength-multiplexed optical signal from the optical repeater and receives each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal;
The optical repeater is
An optical separation unit for wavelength-separating the wavelength-multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
A first unit including a first dispersion compensation unit for compensating for dispersion of the first optical signal;
A second unit including a second dispersion compensation unit that compensates for dispersion of the second optical signal;
And an optical multiplexing unit that wavelength-multiplexes the first optical signal compensated by the first unit and the second optical signal compensated by the second unit and outputs the wavelength-multiplexed optical signal after the relay. An optical transmission system characterized by being configured as described above. An optical repeater that relays a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths and outputs as a wavelength-multiplexed optical signal after relay;
An optical receiver that wavelength-separates the post-relay wavelength-multiplexed optical signal from the optical repeater and receives each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal;
The optical repeater is
An optical separation unit for wavelength-separating the wavelength-multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
A first unit including a first optical amplification unit that amplifies the first optical signal and a first dispersion compensation unit that compensates and outputs the dispersion of the first optical signal amplified by the first optical amplification unit;
A second unit including a second optical amplification unit that amplifies the second optical signal and a second dispersion compensation unit that compensates and outputs the dispersion of the second optical signal amplified by the second optical amplification unit;
An optical multiplexing unit configured to wavelength-multiplex the first optical signal from the first unit and the second optical signal from the second unit and output the wavelength-multiplexed optical signal after the relay; An optical transmission system characterized by comprising: An optical repeater that relays a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths and outputs as a wavelength-multiplexed optical signal after relay;
An optical receiver that wavelength-separates the post-relay wavelength-multiplexed optical signal from the optical repeater and receives each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal;
The optical repeater is
An optical separation unit for wavelength-separating the wavelength-multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
A first unit comprising: a first dispersion compensation unit that compensates for dispersion of the first optical signal; and a first optical amplification unit that amplifies and outputs the first optical signal dispersion-compensated by the first dispersion compensation unit; ,
A second unit comprising: a second dispersion compensation unit that compensates for dispersion of the second optical signal; and a second optical amplification unit that amplifies and outputs the second optical signal dispersion-compensated by the second dispersion compensation unit; ,
An optical multiplexing unit configured to wavelength-multiplex the first optical signal from the first unit and the second optical signal from the second unit and output the wavelength-multiplexed optical signal after the relay; An optical transmission system characterized by comprising: A wavelength multiplexed optical signal including a plurality of optical signals having different wavelengths is received from the first optical transmission line, and the first optical signal and the second optical signal having a wavelength longer than the wavelength of the first optical signal; Wavelength separation into
Separately compensating for dispersion of the first optical signal and the second optical signal;
Disperse-compensated first optical signal and dispersion-compensated second optical signal are wavelength-multiplexed and output to the second optical transmission line as a post-relay wavelength-multiplexed optical signal,
An optical transmission method characterized by wavelength-separating the post-relay wavelength-multiplexed optical signal from the second optical transmission line and receiving each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal . A wavelength multiplexed optical signal including a plurality of optical signals having different wavelengths is received from the first optical transmission line, and the first optical signal and the second optical signal having a wavelength longer than the wavelength of the first optical signal; Wavelength separation into
Separately compensating for dispersion of the first optical signal and the second optical signal;
The dispersion-compensated first optical signal and the second optical signal are separately amplified and output,
Wavelength-division-multiplexing the amplified first optical signal and the amplified second optical signal, and outputting as a wavelength-multiplexed optical signal after relay to the second optical transmission line;
An optical transmission method characterized by wavelength-separating the post-relay wavelength-multiplexed optical signal from the second optical transmission line and receiving each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal . A wavelength multiplexed optical signal including a plurality of optical signals having different wavelengths is received from the first optical transmission line, and the first optical signal and the second optical signal having a wavelength longer than the wavelength of the first optical signal; Wavelength separation into
Amplifying the first optical signal and the second optical signal separately;
Separately compensating for the dispersion of the amplified first and second optical signals;
Disperse-compensated first optical signal and dispersion-compensated second optical signal are wavelength-multiplexed and output to the second optical transmission line as a post-relay wavelength-multiplexed optical signal,
An optical transmission method characterized by wavelength-separating the post-relay wavelength-multiplexed optical signal from the second optical transmission line and receiving each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal . A wavelength multiplexed optical signal including a plurality of optical signals having different wavelengths is received from the first optical transmission line, and the first optical signal and the second optical signal having a wavelength longer than the wavelength of the first optical signal; Wavelength separation into
Amplifying the first optical signal and the second optical signal separately;
Separately compensating for the dispersion of the amplified first and second optical signals;
The dispersion-compensated first optical signal and the second optical signal are separately amplified and output,
Wavelength-division-multiplexing the amplified first optical signal and the amplified second optical signal, and outputting as a wavelength-multiplexed optical signal after relay to the second optical transmission line;
An optical transmission method characterized by wavelength-separating the post-relay wavelength-multiplexed optical signal from the second optical transmission line and receiving each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal . An optical repeater that relays a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths and outputs as a wavelength-multiplexed optical signal after relay;
An optical receiver that wavelength-separates the post-relay wavelength-multiplexed optical signal from the optical repeater and receives each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal;
The optical repeater is
An optical separation unit for wavelength-separating the wavelength-multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
A first optical amplifying unit for amplifying the first optical signal; a first dispersion compensating unit for compensating and outputting dispersion of the first optical signal amplified by the first optical amplifying unit; and the first dispersion compensating unit. A first unit including a first optical amplification unit that amplifies and outputs the first optical signal that has been dispersion-compensated;
A second optical amplifying unit for amplifying the second optical signal; a second dispersion compensating unit for compensating and outputting dispersion of the second optical signal amplified by the second optical amplifying unit; and the second dispersion compensating unit. A second unit including a second optical amplification unit that amplifies and outputs the second optical signal that has been dispersion-compensated;
An optical multiplexing unit configured to wavelength-multiplex the first optical signal from the first unit and the second optical signal from the second unit and output the wavelength-multiplexed optical signal after the relay; An optical transmission system characterized by comprising: An optical repeater that relays a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths and outputs as a wavelength-multiplexed optical signal after relay;
An optical receiver that wavelength-separates the post-relay wavelength-multiplexed optical signal from the optical repeater and receives each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal;
The optical repeater is
An optical separation unit for wavelength-separating the wavelength-multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
A first optical amplifying unit for amplifying the first optical signal; a first dispersion compensating unit for compensating and outputting dispersion of the first optical signal amplified by the first optical amplifying unit; and the first dispersion compensating unit. A first unit including a first optical amplification unit that amplifies and outputs the first optical signal that has been dispersion-compensated;
A second unit including a second optical amplification unit that amplifies the second optical signal and a second dispersion compensation unit that compensates and outputs the dispersion of the second optical signal amplified by the second optical amplification unit;
An optical multiplexing unit configured to wavelength-multiplex the first optical signal from the first unit and the second optical signal from the second unit and output the wavelength-multiplexed optical signal after the relay; An optical transmission system characterized by comprising: An optical repeater that relays a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths and outputs as a wavelength-multiplexed optical signal after relay;
An optical receiver that wavelength-separates the post-relay wavelength-multiplexed optical signal from the optical repeater and receives each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal;
The optical repeater is
An optical separation unit for wavelength-separating the wavelength-multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
A first optical amplifying unit for amplifying the first optical signal; a first dispersion compensating unit for compensating and outputting dispersion of the first optical signal amplified by the first optical amplifying unit; and the first dispersion compensating unit. A first unit including a first optical amplification unit that amplifies and outputs the first optical signal that has been dispersion-compensated;
A second unit comprising: a second dispersion compensation unit that compensates for dispersion of the second optical signal; and a second optical amplification unit that amplifies and outputs the second optical signal dispersion-compensated by the second dispersion compensation unit; ,
An optical multiplexing unit configured to wavelength-multiplex the first optical signal from the first unit and the second optical signal from the second unit and output the wavelength-multiplexed optical signal after the relay; An optical transmission system characterized by comprising: An optical repeater that relays a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths and outputs as a wavelength-multiplexed optical signal after relay;
An optical receiver that wavelength-separates the post-relay wavelength-multiplexed optical signal from the optical repeater and receives each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal;
The optical repeater is
An optical separation unit for wavelength-separating the wavelength-multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
A first unit including a first optical amplification unit that amplifies the first optical signal and a first dispersion compensation unit that compensates and outputs the dispersion of the first optical signal amplified by the first optical amplification unit;
A second unit comprising: a second dispersion compensation unit that compensates for dispersion of the second optical signal; and a second optical amplification unit that amplifies and outputs the second optical signal dispersion-compensated by the second dispersion compensation unit; ,
An optical multiplexing unit configured to wavelength-multiplex the first optical signal from the first unit and the second optical signal from the second unit and output the wavelength-multiplexed optical signal after the relay; An optical transmission system characterized by comprising: An optical repeater that relays a wavelength-multiplexed optical signal including a plurality of optical signals having different wavelengths and outputs as a wavelength-multiplexed optical signal after relay;
An optical receiver that wavelength-separates the post-relay wavelength-multiplexed optical signal from the optical repeater and receives each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal;
The optical repeater is
An optical separation unit for wavelength-separating the wavelength-multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
First means for compensating the first optical signal;
Second means for compensating the second optical signal;
And an optical multiplexing unit that wavelength-multiplexes the first optical signal compensated by the first means and the second optical signal compensated by the second means and outputs the wavelength-multiplexed optical signal after the relay. An optical transmission system characterized by being configured as described above. A transmission means for wavelength-multiplexing a plurality of optical signals having different wavelengths to generate a wavelength-multiplexed optical signal;
Relay means for relaying the wavelength-multiplexed optical signal from the transmission means and outputting it as a wavelength-multiplexed optical signal after relay;
Receiving means for wavelength-separating the post-relay wavelength-multiplexed optical signal from the relay means and receiving each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal;
The relay means
An optical demultiplexing unit that wavelength-separates the wavelength-multiplexed optical signal received from the transmission unit into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
First means for compensating and outputting the first optical signal;
Second means for compensating and outputting the second optical signal;
An optical multiplexing unit that wavelength-multiplexes the first optical signal compensated by the first means and the second optical signal compensated by the second means, and outputs the result as a post-relay wavelength-multiplexed optical signal; An optical transmission system characterized by being configured. Wavelength multiplexing a plurality of optical signals having different wavelengths to generate a wavelength multiplexed optical signal;
Wavelength-separating the wavelength division multiplexed optical signal into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
Compensating the first optical signal;
Compensating the second optical signal;
Wavelength-multiplexing the compensated first optical signal and the compensated second optical signal and outputting as a post-relay wavelength-multiplexed optical signal;
And a step of wavelength-separating the post-relay wavelength-multiplexed optical signal and receiving each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal. Wavelength-separating a wavelength division multiplexed optical signal including a plurality of optical signals having different wavelengths into a first optical signal and a second optical signal having a wavelength longer than the wavelength of the first optical signal;
Compensating and outputting the first optical signal;
Compensating and outputting the second optical signal;
Wavelength-multiplexing the compensated first optical signal and the compensated second optical signal and outputting as a post-relay wavelength-multiplexed optical signal;
And a step of wavelength-separating the post-relay wavelength-multiplexed optical signal and receiving each of the plurality of optical signals included in the post-relay wavelength-multiplexed optical signal.

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