JPH06104868A - Wavelength multiplexed optical relay transmission system - Google Patents

Abstract

PURPOSE:To improve transmission quality at the time of transmitting the respective optical signals of plural wavelengths through an optical fiber transmission line. CONSTITUTION:This system is provided with the plural optical fiber transmission lines 31-3n for respectively transmitting one optical signal or plural optical signals provided with wavelength intervals for which the influence of four light wave mixture is less. Repeaters 4 provided on the transmission lines are provided with optical multiplexers 5 for multiplexing the respective optical signals transmitted through the respective optical fiber transmission lines, batch optical amplifiers 7 for amplifying the output of the optical multiplexers 5 in the lump and optical demultiplexers 6 for demultiplexing the amplified output of the batch optical amplifiers 7 to be transmitted to the respective optical fiber transmission lines.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength division multiplexing optical repeater transmission system for repeating and transmitting optical signals of a plurality of waves.

[0002]

2. Description of the Related Art FIG. 4 is a configuration diagram showing a configuration of a conventional wavelength division multiplexing optical repeater transmission system. The system shown in this figure is a one-way transmission system with multiplex number n. In the figure, reference numerals 110 and 210 denote a transmitting terminal station and a receiving terminal station connected by one optical fiber transmission line 31, and a collective light for collectively amplifying wavelength-multiplexed optical signals on the optical fiber transmission line 31. The amplifier 7 is provided as a repeater.

[0003] In the transmitting end station 110, n the information signal is converted into an optical signal of wavelength lambda ₁ to [lambda] _n in the optical transmitter ₁ 1 to 1 _n, respectively. The n-wave optical signal is wavelength-multiplexed by the optical multiplexer 5 and sent to the optical fiber transmission line 31. The transmitted optical signal is transmitted to the receiving terminal station 210 while being collectively amplified by the collective optical amplifier 7 for compensating for the loss in the optical fiber transmission line 31.

In the receiving terminal station 210, the optical demultiplexer 6 is
Divided one optical signal transmitted wavelength multiplexed optical fiber transmission path 31 to an optical signal of wavelength lambda ₁ to [lambda] _n, the corresponding supply to the optical receiver 2 ₁ to 2 _n, respectively. Each optical receiver 2
_{1 to} 2 _n output an information signal corresponding to each optical signal.

By the way, in general, when a plurality of optical signals of different wavelengths propagate in one optical fiber, the wavelengths corresponding to the sum frequency and the difference frequency of those optical signals are changed due to the nonlinear response of the material of the optical fiber. A large light wave is generated. This phenomenon is known as four-wave mixing. When the new light wave matches the original wavelength of the optical signal, crosstalk occurs, and the SN ratio of the optical signal deteriorates. That is, the transmission quality deteriorates. This can be found in the literature ("LIMITA
TIONS OF WDM TRANSMISSION OVER 560Km DUE TODEGENER
ATE FOUR WAVE MIXING ", Electronics Letters, No. 28
Vol. 3, 1992, p.307-p.309).

[0006]

Since the conventional wavelength-multiplexed optical repeater transmission system is constructed as described above, when a wavelength-multiplexed signal is transmitted over a long distance through one optical fiber transmission line 31, four-wave mixing is performed. There was a problem that the transmission quality deteriorates.

Therefore, an object of the present invention is to provide a wavelength division multiplexing optical repeater transmission system capable of improving the transmission quality when transmitting signals of a plurality of wavelengths through an optical fiber transmission line, compared to the conventional system. .

[0008]

A wavelength division multiplexing optical repeater transmission system according to the present invention has one optical signal or four optical signals, respectively.
Each optical signal transmitted through the optical fiber transmission line is a repeater equipped with a plurality of optical fiber transmission lines that transmit a plurality of optical signals having wavelength intervals that are not easily affected by light wave mixing. An optical multiplexer that multiplexes the optical multiplexer, a collective optical amplifier that collectively amplifies the output of this optical multiplexer, and an optical demultiplexer that demultiplexes the amplified output of this collective optical amplifier and sends it to each optical fiber transmission line. It is a structure having.

[0009]

Each of the optical fiber transmission lines in the present invention transmits an optical signal having a combination of wavelengths which is less affected by the light waves due to the four-wave mixing. The repeater, which is provided on the transmission path and amplifies each optical signal, collectively amplifies each transmitted optical signal.

[0010]

1 is a block diagram showing the structure of a wavelength division multiplexing optical repeater transmission system according to a first embodiment of the present invention. In the figure, 101 and 201 are a transmission terminal station and a reception terminal station connected by _n optical fiber transmission lines 3 _{1 to} 3 _n corresponding to n-wave optical signals, respectively, and a repeater 4 is used for each optical fiber transmission. Amplifies the optical signal on the paths 3 _{1 to} 3 _n .

In this case, the optical fiber transmission lines 3 _{1 to} 3
_n is _integrated into one optical fiber cable 30. Usually, one optical fiber cable is formed by assembling about 10 to 100 optical fiber transmission lines. At present,
It is also possible to combine 1000 or more cables into one optical fiber cable.

In the transmitting terminal station 101, each optical transmitter 1 ₁
To 1 _n is transmitted to the optical fiber transmission line 3 ₁ to 3 _n which corresponds to the optical signal of the wavelength lambda ₁ to [lambda] _n. n optical signals of each wavelength transmitted by the optical fiber transmission line 3 ₁ to 3 _n of the book, while being amplified by the repeater 4 to compensate for losses in the optical fiber transmission line 3 ₁ to 3 _n, the receiving terminal station 201 is transmitted.

In the repeater 4, first, the n-wave optical signal is wavelength-multiplexed by the optical multiplexer 5. Therefore, it becomes possible to carry out collective amplification by the collective optical amplifier 7. The amplified wavelength-multiplexed optical signal is demultiplexed by the optical demultiplexer 6 into optical signals of respective wavelengths and sent to the optical fiber transmission lines 3 _{1 to} 3 _n . By sequentially performing such amplification by the repeater, it is possible to prevent the generation of a new light wave due to the four-wave mixing in the optical fiber even in the long-distance multi-stage relay transmission.

In the receiving terminal station 201, each optical receiver 2 ₁
To 2 _n receives the optical signals of transmission wavelength lambda ₁ to [lambda] _n in n optical fiber transmission path 3 ₁ to 3 _n, and outputs an information signal corresponding to each optical signal.

By the way, even in the case where the wavelength-multiplexed optical signal is transmitted through the optical fiber, there is no problem as long as the influences of the four-wave mixing can be ignored for each wavelength.
For example, the fact that the intensity of the four-wave mixed light is approximately inversely proportional to the square of the wavelength interval of the original optical signal is used. Ie 4
For each wavelength that is separated by a wavelength enough to ignore the effect of lightwave mixing, even if the wavelength of the four lightwave mixed light and the wavelength of the optical signal overlap, the original optical signal is obtained when wavelength-multiplexed. The influence of the four-wave mixing given is small.

FIG. 2 is a block diagram showing the construction of a wavelength division multiplexing optical repeater transmission system according to the second embodiment of the present invention based on such a viewpoint. In this case, the transmitting terminal station 102
The optical coupler 8, with each other multiplexes sufficiently what wavelength interval apart among the optical signal of the wavelength lambda ₁ to [lambda] _n to the optical transmitter 1 ₁ to 1 _n is transmitted, are respectively wavelength-multiplexed m wave (m <
n) Create an optical signal. Then, the optical multiplexer 8 sends a light signal of m waves in the optical fiber transmission line 3 ₁ to 3 _m which corresponds.

In the repeater 41, the optical multiplexer 51 is
Wavelength λ₁~ Λ _nEach optical signal of wavelength
It is a multiplexed optical signal. The collective optical amplifier 7 has its wavelength
Collectively amplifies the multiplexed optical signals. Amplified wavelength division multiplexing
The optical signal is demultiplexed into an m-wave optical signal by the optical demultiplexer 61,
Fiber transmission line 3₁~ 3_mSent to. Like this
The original optical signal is affected by the four-wave mixing of the optical fiber.
System and the system according to the first embodiment.
Reduces the number of optical fibers compared to the
The stem is built. For example, the wavelength λ₁~ Λ_nEach light of
If two signals are combined by m = n / 2, the optical fiber
The number is 1/2 as compared with the case of the first embodiment. Mochiro
However, m is not limited to 1/2 and can be any natural number smaller than n.
You can

In the configuration shown in FIG. 2, the wavelengths of the m-wavelength optical signals that are wavelength-multiplexed are different from the wavelengths of the optical signals in the wavelengths corresponding to the sum / difference frequencies of the wavelengths. May be selected. In that case, the wavelength of the light wave resulting from the four-wave mixing can be made different from the wavelength of the original optical signal, which is effective in preventing the influence of the four-wave mixing.

FIG. 3 shows a configuration example of the optical multiplexer 5 and the optical demultiplexer 6 used in each embodiment.
The one shown in the figure is an example of a 5-wave multiplexer / demultiplexer, but each wavelength is multiplexed with other wavelengths by the optical multiplexer / demultiplexer 53 via the wavelength determining unit 52, and finally the 5-wavelength multiplex is performed. The optical signal thus obtained is obtained in the waveguide 51. Alternatively, the five-wavelength wavelength-multiplexed optical signal guided to the waveguide 51 is demultiplexed into each wavelength λ _{1 to} λ ₅ via each optical multiplexing / demultiplexing unit 53 and wavelength determining unit 52. The multiplexer / demultiplexer can also be configured with an interference film filter or the like.

[0020]

As described above, the present invention provides a wavelength division multiplexing optical repeater transmission system in which each optical fiber transmission line has a single optical signal or a plurality of optical signals with wavelength intervals less affected by four-wave mixing. Since it is configured to transmit, the effect of four-wave mixing can be eliminated and a system with good transmission quality can be provided. Further, since the optical amplification is performed collectively by the repeater, it is possible to provide a system suitable for a submarine repeater transmission system in which the size of the repeater is severely limited without increasing the size of the repeater.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of a wavelength division multiplexing optical repeater transmission system according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing a configuration of a wavelength division multiplexing optical repeater transmission system according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram showing a configuration example of a multiplexer / demultiplexer.

FIG. 4 is a configuration diagram showing a configuration of a conventional wavelength division multiplexing optical repeater transmission system.

[Explanation of symbols]

101,102 Transmitting terminal station 201,202 Receiving terminal station 3 _{1 to} 3 _n Optical fiber transmission line 4,41 Repeater 5,51 Optical multiplexer 6,61 Optical demultiplexer 7 Collective optical amplifier 8 Optical multiplexer 9 Optical demultiplexer Wave instrument

Claims (1)

[Claims] 1. A wavelength division multiplexing optical repeater transmission system for repeating transmission of a plurality of optical signals having different wavelengths, each transmitting a single optical signal or a plurality of optical signals having wavelength intervals less affected by four-wave mixing. A plurality of optical fiber transmission lines, an optical multiplexer that multiplexes the optical signals transmitted through the optical fiber transmission lines, a collective optical amplifier that collectively amplifies the output of the optical multiplexer, and a collective optical amplifier An optical repeater transmission system comprising: a repeater having an optical demultiplexer for demultiplexing an amplified output and sending the demultiplexed signal to each optical fiber transmission line.