JP2007300679A - Optical wavelength multiplex transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To materialize a simple structure in which structures of two networks (transmission lines) are integrated and no joint is present in an optical wavelength multiplex transmission system. <P>SOLUTION: The optical wavelength multiplex transmission system is equipped with: a first optical fiber transmission line for inputting a wavelength multiplex signal; a second optical fiber transmission line having a zero dispersion wavelength different from the first optical fiber transmission line; and an optical repeater which converts wavelengths of the wavelength multiplex signal input from the first optical fiber transmission line by a first wavelength arrangement into a second wavelength arrangement different from the first wavelength arrangement and outputs the signal to the second optical fiber transmission line. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical transmission system, and more particularly to an optical wavelength multiplex transmission system.

  In recent years, expectations for the development of optical communication technology that can provide high-speed and large-capacity transmission lines as an infrastructure of the information society have increased, and research and development of high-speed and large-capacity optical communication systems has become active on a global scale. Is underway.

  On land, optical wavelength division multiplexing transmission systems with a transmission rate of 10 Gb / s using 1.3 μm-band single-mode fiber (SMF) and 1.55 μm-band dispersion-shifted fiber (DSF) transmission lines are researching and progressing from the development stage to the practical stage. .

  On the other hand, on the sea floor, an optical wavelength division multiplexing transmission system with a transmission rate of 10 Gb / s using a non-zero dispersion shifted fiber transmission line having a zero dispersion wavelength in the 1.58 μm band is progressing from a research and development stage to a practical stage.

  In optical fibers, transmission waveform degradation occurs due to the interaction (SPM-GVD effect) between self-phase modulation effect (SPM) and group-velocity dispersion (GVD). It is necessary to set the dispersion (group velocity dispersion) value generated by different propagation times of the signal light in the optical fiber as small as possible.

  However, as each signal light wavelength approaches the zero dispersion wavelength of the transmission path, crosstalk due to four-wave mixing (FWM) between the signal lights occurs, and the transmission characteristics deteriorate. Therefore, in wavelength division multiplexing transmission, it is necessary to perform wavelength arrangement in consideration of the zero dispersion wavelength of the optical fiber.

For example, Japanese Patent Laid-Open No. Hei 8-97777 is disclosed as a transmission method for suppressing the influence of conventional four-wave mixing in an optical wavelength division multiplexing transmission method using a 1.55 μm band dispersion shifted fiber (DSF) transmission line.
FIG. 17 is a diagram for explaining the principle of the system. Wavelength conversion is performed on signals of each wavelength, and the crosstalk light level is set to a predetermined value or less by exchanging the wavelengths.

JP-A-8-97771

  When two different networks (transmission paths) such as land and seabed are connected, they are currently terminated electrically at the network connection point.

  However, in order to put the low-cost system into practical use, it is necessary to realize a simple and seamless structure in which two network structures are integrated.

  However, since the zero-dispersion wavelength of the optical fiber used is different, the SPM-GVD effect and the crosstalk due to FWM become a big problem when transmitting as it is.

  An optical wavelength division multiplexing transmission system according to the present invention includes a first optical fiber transmission line for inputting a wavelength multiplexed signal, a second optical fiber transmission line having a zero dispersion wavelength different from that of the first optical fiber transmission line, Each wavelength of the wavelength multiplexed signal input from the first optical fiber transmission line with the first wavelength arrangement is converted into a second wavelength arrangement different from the first wavelength arrangement and output to the second optical fiber transmission line. And an optical repeater.

  The present invention can realize a simple seamless structure in which two network structures are integrated in an optical wavelength division multiplexing transmission system.

Hereinafter, an embodiment of the present invention will be described.
Embodiment 1 FIG.
FIG. 1 shows a network configuration diagram according to Embodiment 1 of the present invention.
In FIG. 1, 1 is an optical repeater with a wavelength conversion device, 2 is an optical fiber having a zero dispersion wavelength of λ0, and 3 is an optical fiber having a zero dispersion wavelength of λ0 ′.
FIG. 2 shows an example of wavelength arrangement according to this embodiment.
FIG. 2A shows the wavelength arrangement of the optical input signal in the optical repeater 1. With respect to the zero-dispersion wavelength λ0 of the optical fiber 2, the n-wave wavelengths from λ1 to λn are arranged so that the SPM-GVD effect and FWM are minimized.
FIG. 2B shows the wavelength arrangement of the optical output signal in the optical repeater 1. The optical fiber 3 converts the wavelength of the zero dispersion wavelength λ0 ′ so that the SPM-GVD effect and FWM are minimized, and outputs the result.

FIG. 3 is a diagram showing a configuration of the optical repeater 1 according to the present embodiment.
In the figure, 5 is a wavelength selection means, 6 is a wavelength converter, and 7 is a multiplexing means.

Next, the operation will be described.
In the optical repeater 1 shown in FIG. 3, the wavelength selection means 5 to which the signal light multiplexed with the wavelengths λ1 to λn is separated into the signal light of these wavelengths λ1 to λn and provided to the wavelength converter 6.
When the wavelength converter 6 converts the wavelengths λ1 into λ1 ′ and λ2 into λ2 ′ according to the control signal and sends them to the combining means 7, the combining means 7 sends these wavelengths λ1 ′, λ2 ′. λn ′ is multiplexed and output.
Therefore, a seamless seamless structure in which the structures of two networks (transmission paths) are integrated can be realized.
The wavelength selecting means 5 can be easily configured using an optical filter and the multiplexing means 7 using a coupler.

As described above, the first optical fiber transmission line 2 and
Between the first optical fiber transmission line 2 and the second optical fiber transmission line 3 having a different zero dispersion wavelength,
Each wavelength of the wavelength multiplexed signal input from the first optical fiber transmission line 2 is wavelength-converted so that the SPM-GVD effect and FWM in the second optical fiber transmission line 3 are minimized, and the second light. By providing the optical repeater 1 that outputs to the fiber transmission line 3, a simple and seamless structure in which the structures of the two networks (transmission lines) are integrated can be realized.

Embodiment 2. FIG.
In the second embodiment, the wavelength selecting means 5 in FIG. 3 is configured by the demultiplexing means 4 and the wavelength selecting means 5 shown in FIG.
In this case, the signal light multiplexed with the wavelengths λ1, λ2,... Λn is output in the same way for all channels by the demultiplexing means 4 and sent to the wavelength selection means 5. The wavelength selection means 5 receives the wavelengths λ1, λ2,... λn are separated and sent to the wavelength converter 6. Thereafter, the operation is the same as in FIG.
In addition, a simple seamless structure in which the structures of two networks (transmission paths) are integrated can be realized.
For example, a coupler may be used as the demultiplexing unit 4.

Embodiment 3 FIG.
In this embodiment, as shown in FIG. 5, an optical amplifier 8 that compensates for the loss due to the wavelength converter 6 and amplifies the light after multiplexing is provided at the subsequent stage of the multiplexing means 7.

Embodiment 4 FIG.
In the present embodiment, as shown in FIG. 6, an optical amplifier 8 for amplifying each wavelength to a uniform level is provided between each wavelength converter 6 and the multiplexing means 7 for each wavelength.
In this case, as shown in FIG. 6, optical loss is reduced by inserting an optical amplifier 8 for each individual wavelength after the wavelength converter 6 so that the gain can be adjusted according to the wavelength conversion efficiency of each wavelength. Can compensate.

Further, as shown in FIG. 7, both the transmission line loss and the wavelength conversion loss may be compensated.

Embodiment 5 FIG.
The present embodiment relates to the wavelength converter 6 in the first to fourth embodiments.
FIG. 8 shows the configuration of the first wavelength converter 6 according to the fifth embodiment. In this fifth embodiment, the first wavelength converter 6 is composed of the photoelectric conversion means 9 and the photoelectric conversion means 10, and the photoelectric conversion is performed. The means 9 converts the input optical signal having the wavelength λi into an electric signal, and the electric signal is converted into another wavelength λi ′ by the electro-optical conversion means 10 which can be operated by the control signal.

As the photoelectric conversion means 9, a photodiode, an avalanche photodiode, a photocounter, or the like can be used. The electro-optical conversion means 10 can be easily configured using a semiconductor laser.

Embodiment 6 FIG.
FIG. 9 shows a configuration of the second wavelength conversion element according to the sixth embodiment, and a wavelength conversion element 11 having a nonlinear optical effect for converting an input optical signal λi operable by a control signal into another wavelength λi ′. Is used. As the wavelength conversion element 11, a semiconductor optical amplifier, an electroabsorption modulator, an optical fiber, or the like can be used.

Embodiment 7 FIG.
Next, the seventh to ninth embodiments relate to the configuration of the second wavelength conversion element 11 included in the sixth embodiment.
FIG. 10 shows a configuration of the wavelength conversion element 11 using the semiconductor optical amplifier according to the seventh embodiment.
In FIG. 10, 12 is a light source, 13 is an optical coupler, 14 is an optical filter, and 15 is a semiconductor optical amplifier. The optical signal (wavelength: λi) and the pump light (wavelength: λp) are combined by the optical coupler 13 and incident on the semiconductor optical amplifier 15. Newly converted light (wavelength: λi ′) is generated by the four-wave mixing in the semiconductor optical amplifier 15. Only the converted light is filtered and output by the optical filter 14.

Embodiment 8 FIG.
FIG. 11 shows the configuration of the wavelength conversion element 11 using the electroabsorption modulator according to the eighth embodiment.
In FIG. 11, 12 is a light source, 13 is an optical coupler, 14 is an optical filter, and 16 is an electroabsorption modulator. The optical signal (wavelength: λi) and the unmodulated probe light (wavelength: λi ′) from the light source 12 are combined by the optical coupler 13 and incident on the electroabsorption modulator 16. The probe light (wavelength: λi ′) is modulated by the mutual absorption modulation effect of the electroabsorption modulator 16, and only the probe light modulated by the optical filter 14 is filtered and output.

Embodiment 9 FIG.
FIG. 12 shows a configuration of the wavelength conversion element 11 using the optical fiber according to the ninth embodiment.
In FIG. 12, 12 is a light source, 13 is an optical coupler, 14 is an optical filter, and 17 is an optical fiber. The optical signal (wavelength: λi) input to the wavelength conversion element 11 is combined with the excitation light (wavelength: λp) from the light source 12 by the optical coupler 13 and incident on the optical fiber 17. Newly converted light (wavelength: λi ′) is generated by light wave mixing. Only the converted light is filtered and output by the optical filter 14.

  Next, in the tenth to thirteenth embodiments, the wavelength interval of the optical repeater 1 is changed from an equal interval arrangement to an unequal interval arrangement, or from an unequal interval arrangement to an equal interval arrangement.

Embodiment 10 FIG.
In this embodiment, the wavelength interval of the optical repeater 1 is changed from an equal interval arrangement to an unequal interval arrangement.

FIG. 13 shows an example of wavelength arrangement of the optical repeater 1.
FIG. 13A shows the wavelength arrangement of the optical input signal of the optical repeater 1 with a wavelength converter. The n-wavelengths of λ1 to λn are arranged so that the SPM-GVD effect and FWM are minimized with respect to the zero dispersion wavelength λ0 of the fiber.
FIG. 13B shows the wavelength arrangement of the optical output signal of the optical repeater 1 with a wavelength converter. Since the SPM-GVD effect and the FWM are wavelength-converted and arranged at unequal intervals with respect to the zero dispersion wavelength λ0 ′ of the fiber, the same effect as in the first embodiment can be obtained.

Embodiment 11 FIG.
In the present embodiment, the wavelength interval of the optical repeater 1 is changed from an unequal interval arrangement to an equal interval arrangement.

FIG. 14 shows an example of wavelength arrangement.
FIG. 14A shows the wavelength arrangement of the optical input signal of the optical repeater 1 with a wavelength converter. The n-wave wavelengths from λ1 to λn are unequally spaced so that the SPM-GVD effect and FWM are minimized with respect to the zero dispersion wavelength λ0 of the fiber.
FIG. 14B shows the wavelength arrangement of the optical output signal of the optical repeater 1 with a wavelength converter. Since the wavelength conversion is performed so that the SPM-GVD effect and the FWM are minimized with respect to the zero dispersion wavelength λ0 ′ of the fiber, the same effect as in the first embodiment can be obtained.

Embodiment 12 FIG.
In the present embodiment, the wavelength interval of the optical repeater 1 is changed from a constant value Δλ to a constant value Δλ ′.

FIG. 15 shows an example of wavelength arrangement.
FIG. 15A shows the wavelength arrangement of the optical input signal of the optical repeater 1. For the zero-dispersion wavelength λ0 of the optical fiber 2, the wavelengths of n waves from λ1 to λn are arranged at a wavelength interval Δλ so that the SPM-GVD effect and FWM are minimized.
FIG. 15B shows the wavelength arrangement of the optical output signal of the optical repeater 1. Since the wavelength interval is changed to Δλ ′ so as to minimize the SPM-GVD effect and FWM with respect to the zero dispersion wavelength λ0 ′ of the optical fiber 3, the same effect as in the first embodiment can be obtained.

Embodiment 13 FIG.
In this embodiment, the number of wavelengths of the optical repeater input / output is changed by adding / dropping the wavelength.
FIG. 16 shows an example of wavelength arrangement.
FIG. 16A shows the wavelength arrangement of the optical input signal of the optical repeater 1. With respect to the zero dispersion wavelength λ0 of the optical fiber 2, the wavelengths of n waves from λ1 to λn are arranged so that the SPM-GVD effect and FWM are minimized.
FIG. 16B shows the wavelength arrangement of the optical output signal of the optical repeater 1. Since the optical repeater 1 branches and inserts the wavelength so that the SPM-GVD effect and FWM are minimized with respect to the zero dispersion wavelength λ0 ′ of the fiber, the same effect as in the first embodiment can be obtained.

1 is a configuration diagram according to Embodiment 1. FIG. FIG. 3 shows a wavelength arrangement diagram on the input / output side of the first embodiment. 1 is a configuration diagram of an optical repeater 1 according to Embodiment 1. FIG. The block diagram of the optical repeater 1 by Embodiment 2 is shown. 6 is a configuration diagram of an optical repeater 1 according to Embodiment 3. FIG. FIG. 6 is a configuration diagram of an optical repeater 1 according to a fourth embodiment. It is a block diagram of the other optical repeater 1 by Embodiment 4. FIG. FIG. 10 is a configuration diagram of a wavelength converter 6 according to a fifth embodiment. FIG. 10 is a configuration diagram of a wavelength converter 6 according to a sixth embodiment. 10 is a configuration example of a wavelength conversion element 11 according to a seventh embodiment. 10 is a configuration example of a wavelength conversion element 11 according to an eighth embodiment. 10 is a configuration example of a wavelength conversion element 11 according to a ninth embodiment. FIG. 38 is a wavelength arrangement diagram on the input / output side according to the tenth embodiment. FIG. 38 is a wavelength layout diagram on the input / output side of the eleventh embodiment. FIG. 22 is a wavelength layout diagram on the input / output side of the twelfth embodiment. FIG. 38 is a wavelength layout diagram on the input / output side of the thirteenth embodiment. It is a wavelength arrangement | positioning figure of a prior art example.

Explanation of symbols

1 Optical repeater 2 Optical fiber (zero dispersion wavelength: λ0)
3 Optical fiber (zero dispersion wavelength: λ0 ')
4 demultiplexing means 5 wavelength selection means 6 wavelength converter 7 multiplexing means 8 optical amplifier 9 photoelectric conversion means 10 electro-optic conversion means 11 wavelength conversion element 12 light source 13 optical coupler 14 optical filter 15 semiconductor optical amplifier 16 electroabsorption modulation 17 Optical fiber

Claims (10)

A first optical fiber transmission line for inputting a wavelength multiplexed signal;
A second optical fiber transmission line having a zero dispersion wavelength different from that of the first optical fiber transmission line;
Each wavelength of the wavelength multiplexed signal input from the first optical fiber transmission line in the first wavelength arrangement is converted into a second wavelength arrangement different from the first wavelength arrangement, to the second optical fiber transmission line An optical repeater to output,
An optical wavelength division multiplexing transmission system characterized by comprising:   2. The optical repeater according to claim 1, wherein all wavelengths of the wavelength division multiplexed signal input from the first optical fiber transmission line are shifted by a predetermined value and output to the second optical fiber transmission line. Optical wavelength division multiplexing transmission system.   In the optical repeater, the wavelength intervals of the wavelength multiplexed signals input from the first optical fiber transmission path are equal, and the wavelength intervals of the wavelength multiplexed optical signals output to the second optical fiber transmission path are unequal. 2. The optical wavelength division multiplexing transmission system according to claim 1, wherein the distance is an interval.   In the optical repeater, the wavelength intervals of the wavelength multiplexed signals input from the first optical fiber transmission line are unequal, and the wavelength intervals of the wavelength multiplexed optical signals output to the second optical fiber transmission line are equal. 2. The optical wavelength division multiplexing transmission system according to claim 1, wherein the distance is an interval.   In the optical repeater, the wavelength interval of the wavelength multiplexed signal input from the first optical fiber transmission line is a constant value Δλ, and the wavelength interval of the wavelength multiplexed optical signal output to the second optical fiber transmission line is constant. 2. The optical wavelength division multiplexing transmission system according to claim 1, wherein the value is Δλ ′.   In the optical repeater, the wavelength number of the wavelength multiplexed signal input from the first optical fiber transmission line is a natural number n, and the wavelength number output to the second optical fiber transmission line is a natural number m (m ≠ n). The optical wavelength division multiplexing transmission system according to claim 1, wherein   The optical wavelength division multiplexing transmission system according to claim 1, wherein the optical repeater includes a nonlinear element having a wavelength conversion function.   The optical wavelength division multiplexing transmission system according to claim 1, wherein the optical repeater includes one or more semiconductor optical amplifiers.   2. The optical wavelength division multiplexing transmission system according to claim 1, wherein the optical repeater includes one or more electroabsorption optical modulators and one or more light sources.   2. The optical wavelength division multiplex transmission system according to claim 1, wherein the optical repeater includes one or more light sources and an optical fiber having a nonlinear optical effect.

Images