JP2000022667A - Optical amplification device and optical communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical amplification device capable of improving the S/N characteristics of main signal components and reducing the scale of an optical transmitter. SOLUTION: This device is provided with an optical amplifier 20 for amplifying optical signals S42 inputted through an optical fiber cable 4 by an amplification factor indicated by an amplification factor control signal S52, an optical spectrum analyzer 51 for detecting the optical intensity of the optical signals branched from the amplified optical signals S45 while changing a detection wavelength and holding the peak value of the detected light intensity and an amplification factor decision device 52 for deciding the amplification factor so as to make the held peak value be more than a reference value and generating the amplification factor control signal S52 for indicating the decided amplification factor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical amplifier and an optical communication system for amplifying an optical signal transmitted through an optical fiber cable or the like.

[0002]

2. Description of the Related Art As shown in FIG. 16, an optical signal generated by an optical transmitting device 2 provided on a transmitting side is transmitted through an optical fiber cable 4, and an optical receiving device 3 provided on a receiving side is transmitted.
There is an optical communication system 1 for receiving the data. In such an optical communication system 1, an optical amplifying device 5 ₁ , which amplifies an attenuated optical signal, is usually provided at a plurality of locations on an optical fiber cable 4.
5 _2, 5 ₃ are provided.

[0003] Each component shown in FIG. 16 will be described below. FIG. 17 is a configuration diagram of the optical transmission device 2. FIG.
As shown in FIG. 7, the optical transmitter 2 includes a transmission signal source 10, a control signal source 11, a multiplexer 12, and a light source 13.
In the optical transmission device 2, the control signal S11 for level adjustment having a predetermined frequency is superimposed on the main signal S10 generated by the transmission signal source 10 in the multiplexer 12, and the transmission signal S1
2 is generated. This transmission signal S12 is output to the light source 13. In the light source 13, the transmission signal S is transmitted by a semiconductor laser or the like.
12 is modulated to generate an optical signal S2. This optical signal S2 is output to the optical fiber cable 4.

[0004] Figure 18 is a configuration diagram of an optical amplifying device 5 _1. As shown in FIG. 18, the optical amplifying device 5 _1, an optical amplifier 20, an optical coupler 21, O / E converter 22, a filter 23
And a comparator 24. In the optical amplifying device 5 _1, a portion of the optical signal S5 which is optically amplified by the optical amplifier 20,
The signal is output to the O / E converter 22 via the optical coupler 21 and is converted into an electric signal S22. The electric signal S22 is output to the filter 23, and the filter 23 extracts the component of the control signal S11 included in the electric signal S22. Then, the extracted component of the control signal S11 is output to the comparator 24. The comparator 24 compares the level of the component of the control signal S11 with a previously stored reference level, and indicates a comparison result indicating the comparison result. The signal S24 is output to the optical amplifier 20.

In the optical amplifier 20, the amplification factor is controlled based on the comparison signal S24 so as to reduce the difference between the level of the component of the control signal S11 and the reference level.
The input optical signal S4 is amplified and output as an optical signal S5. When the optical amplifier 20 is of a semiconductor type, the amplification factor is determined by a current value, and when the optical amplifier is of a doped fiber type, the amplification factor is determined by optical power from an excitation light source.

The optical receiving device 3 converts an optical signal received via the optical fiber cable 4 into an electric signal by an O / E converter and outputs the electric signal. In this way optical communication system 1, so that the optical amplifying device 5 _1, 5 _2, 5 ₃ signal light power output from the constant reference value, by superimposing a control signal for level adjustment to the optical signal transmission and, by performing the control in each of the optical amplifying device 5 _1, 5 _2, 5 ₃ levels based on the control signal, noise light generated in the optical amplifier 20 (ASE: amplified Spontanaous Emission)
The control of the optical amplifier which was not affected by the power was realized.

[0007]

In the modulation at the light source 13 of the optical transmitter 2 shown in FIG. 17, the sum of the maximum modulation degrees of the multiplexed signals exceeds the maximum modulation degree of the semiconductor laser of the light source 13. There is a restriction that can not be. That is, if the maximum modulation degree of the semiconductor laser is exceeded, in the case of the light intensity modulation, the waveform of the optical signal S2 is distorted, or the component of the control signal S11 included in the optical signal S2 becomes the main signal S1.
Problems such as interference with the zero component occur. However, in the above-described conventional optical communication system 1, the main signal S1
Since the control signal S11 is superimposed on 0, the maximum degree of modulation that can be assigned to the main signal S10 is smaller than in the case where the control signal S11 is not superimposed.
2 has a problem that the component S / N characteristic of the main signal S10 included in No. 2 is not good.

Further, in the optical communication system 1 described above, as shown in FIG. 17, it is necessary to provide a control signal source 11 in the optical transmission device 2, and there is a problem that the optical transmission device 2 becomes large-scale. In particular, wavelength-division multiplexing (Wave-length Divisio
n Multiplexing (WDM) transmission, light source 1
It is necessary to provide the number of control signal sources 11 by the number of 3, and there is a problem that the optical transmission device 2 becomes extremely large in scale.

An object of the present invention is to provide an optical communication system capable of improving the S / N characteristic of a main signal component in view of the above-mentioned problems of the prior art. Another object of the present invention is to provide an optical communication system capable of reducing the size of an optical transmission device.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems of the prior art and to achieve the above-mentioned object, an optical amplifying apparatus according to a first aspect of the present invention receives an input signal via an optical communication cable. An optical amplifying device for amplifying an optical signal, comprising: an optical amplifying unit configured to amplify the input optical signal at a designated amplification factor; a branching unit configured to branch a part of the amplified optical signal; The light intensity of the optical signal is detected for each wavelength,
A light intensity detecting unit that generates an electric signal corresponding to the detected light intensity, a light intensity peak holding unit that holds a peak value of the detected light intensity, and the held peak value is equal to or more than a reference value. And an amplification factor determining unit that determines the amplification factor and designates the determined amplification factor to the optical amplification unit.

In the optical amplifying device according to the first aspect of the present invention, the optical signal input to the optical amplifying means via the optical communication cable is amplified by the optical amplifying means at a designated amplification factor. Then, a part of the amplified optical signal is branched by the optical branching unit and output to the light intensity detecting unit. Then, in the light intensity detecting means, the light intensity of the branched optical signal is detected for each wavelength, and an electric signal corresponding to the detected light intensity is generated. Then, the detected peak value of the light intensity is held in the light intensity peak holding means. Then, the amplification factor is determined by the amplification factor determining means so that the held peak value is equal to or higher than the reference value, and the determined amplification factor is designated to the optical amplification means.

Further, in the optical amplifier according to the first aspect of the present invention, preferably, the light intensity detecting means detects the light intensity of the branched optical signal while changing a detection wavelength,
This is an opto-electric means for generating an electric signal corresponding to the detected light intensity.

An optical amplifying apparatus according to a second aspect of the present invention is an optical amplifying apparatus for inputting and amplifying an optical signal obtained by multiplexing a plurality of optical signals having different wavelengths through an optical communication cable, The input optical signal, an optical amplification unit that amplifies at a specified amplification factor, a branching unit that branches a part of the amplified optical signal, and a plurality of wavelengths included in the branched optical signal. Light intensity detecting means for sequentially detecting the light intensity for each wavelength, and generating an electric signal corresponding to the detected light intensity, and holding the peak value of the detected light intensity for each of the plurality of different wavelength optical signals. Light intensity peak holding means,
Amplification factor control means for designating the amplification factor of the optical amplification means such that the peak values of the light intensity of the optical signals of the plurality of different wavelengths are equal to or higher than a reference value.

In the optical amplifying apparatus according to the second aspect of the present invention, the optical signal input to the optical amplifying means via the optical communication cable is amplified by the optical amplifying means at a designated amplification factor. Then, a part of the amplified optical signal is split by the splitter, and the split optical signal is output to the light intensity detector. In the light intensity detecting means, the light intensities of the plurality of wavelengths included in the branched optical signal are sequentially detected for each wavelength, and an electric signal corresponding to the detected light intensity is generated by the light intensity detecting means. You. Then, the detected peak value of the light intensity is held in the light intensity peak holding means for each of the plurality of optical signals having different wavelengths. Then, in the gain control means, the gain of the optical amplifying means is specified so that the peak value of the light intensity of the optical signals of the plurality of different wavelengths is equal to or more than a reference value.

Further, in the optical amplifying apparatus according to the second aspect of the present invention, preferably, the plurality of different optical signals on the transmitting side of the optical signal correspond to peak values of the optical intensities of the optical signals having the different wavelengths. There is further provided an attenuation rate control signal generating means for generating an attenuation rate control signal for controlling the attenuation rate of the optical signal having the wavelength.

Further, in the optical amplifying apparatus according to the second aspect of the present invention, preferably, the attenuation rate control signal generating means causes a difference between peak values of the plurality of optical signals having different wavelengths to be equal to or less than a reference value. And generating an attenuation rate control signal for controlling an attenuation rate of the optical signals of the plurality of different wavelengths on the transmission side of the optical signal.

Further, in the optical amplifying apparatus according to the second aspect of the present invention, preferably, the attenuation rate control signal generating means includes a minimum peak value among the held peak values of the optical signals of the plurality of different wavelengths. Attenuation rate control for controlling attenuation rates of the optical signals of the plurality of different wavelengths on the transmission side of the optical signal so that a value falls within a predetermined allowable range with respect to the total power of the optical signal including noise light. Generate a signal.

Further, in the optical amplifying apparatus according to the second aspect of the present invention, preferably, the attenuation rate control signal generating means is configured such that a difference between peak values of light intensities of the plurality of optical signals having different wavelengths is equal to or less than a reference value. Generating an attenuation rate control signal for controlling the attenuation rate of the optical signals of the plurality of different wavelengths on the transmission side of the optical signal; and holding the light of the optical signals of the plurality of different wavelengths held. The optical signals of the plurality of different wavelengths on the transmission side of the optical signal such that the minimum peak value among the intensity peak values is within a predetermined allowable range with respect to the total power of the optical signal including noise light. And a process of generating an attenuation rate control signal for controlling the attenuation rate.

Further, in the optical amplifying apparatus according to the second aspect of the present invention, preferably, the light intensity detecting means detects the light intensity of the split optical signal while changing a detection wavelength.
It is an opto-electric means for generating an electric signal according to the light intensity of the detected optical signal.

An optical communication system according to a first aspect of the present invention is an optical communication system for transmitting an optical signal from an optical transmitting device to an optical receiving device via an optical communication cable, wherein the optical transmitting device comprises: A transmission signal source for generating a main signal; and a light source for modulating the main signal to generate an optical signal. Also,
An optical amplifier for optically amplifying the optical signal is provided on the optical communication cable. The optical amplifying device may further include an optical amplifying unit configured to amplify the input optical signal at a designated amplification factor, a branching unit configured to branch a part of the amplified optical signal, and the branched optical signal. Light intensity for each of a plurality of wavelengths, a light intensity detection unit that generates an electric signal corresponding to the detected light intensity, a light intensity peak holding unit that holds a peak value of the detected light intensity, An amplification factor determining unit that determines the amplification factor so that the held peak value is equal to or more than a reference value, and specifies the determined amplification factor to the optical amplification unit.

Further, an optical communication system according to a second aspect of the present invention is an optical communication system for transmitting an optical signal from an optical transmitting device to an optical receiving device via an optical communication cable, wherein the optical transmitting device comprises: A plurality of transmission signal sources each generating a main signal, and provided corresponding to each of the plurality of transmission signal sources, modulating the main signal from the corresponding transmission signal source at a different wavelength from the other main signals. A plurality of light sources that generate optical signals, and generate optical signals that are provided corresponding to the plurality of light sources and attenuate the optical signals from the corresponding light sources at an attenuation rate according to the input attenuation rate control signal. And a multiplexing unit that multiplexes the optical signals generated by the plurality of optical attenuation units and outputs the multiplexed optical signals to the optical communication cable. The optical communication cable further includes an optical amplifier that optically amplifies the optical signal. Further, the optical amplifying device, optical amplifying means for amplifying an optical signal input via the optical communication cable at a specified amplification factor, and a branching means for branching a part of the amplified optical signal, Light intensity detecting means for sequentially detecting the light intensities of the plurality of different wavelengths included in the branched optical signal for each wavelength, and generating an electric signal according to the detected light intensity; and A light intensity peak value holding unit for holding a light intensity peak value of the optical signal for each optical signal, and the light intensity peak value of the light signals of the plurality of different wavelengths being equal to or more than a reference value. Amplifying means for specifying the amplifying rate of the amplifying means; and an attenuating rate control signal generating means for generating the attenuating rate control signal in accordance with the peak values of the held optical signals having the different wavelengths.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described.
The optical amplifier and the optical communication system will be described.First embodiment FIG. 1 is a configuration diagram of an optical communication system 41 of the present embodiment.
You. As shown in FIG. 1, the optical communication system 41
Device 42, optical amplifying device 45 ₁, 45_Two, 45_Three, Light fa
It has an optical cable 4 and an optical receiver 3. Optical communication system
In the stem 41, the optical transmitting device 42 and the optical receiving device 3
Connected via fiber cable 4
Optical amplifier 45 at a predetermined interval on₁, 4
5_Two, 45_ThreeIs incorporated. Optical communication system 41
Then, the optical signal attenuated during transmission through the optical fiber cable 4
The light intensity of the signal is₁, 45_Two, 45_ThreeIncrease in
It is width.

[Optical Transmitter 42] As shown in FIG. 1, the optical transmitter 42 has a transmission signal source 10 and a light source 13. The configuration of the optical transmitter 42 is the same as that of FIG. 16 except that the control signal source 11 and the multiplexer 12 are not provided.
Is the same as the optical transmission device 2 of the conventional optical communication system 1 shown in FIG. In the optical transmitter 42, the main signal S10 generated by the transmission signal source 10 is output to the light source 13 as it is. Then, in the light source 13, the main signal S is output by a semiconductor laser or the like.
10 is light-intensity-modulated, for example, to generate an optical signal S42. This optical signal S2 is output to the optical fiber cable 4. That is, the optical transmitter 42 does not superimpose the control signal S11 on the main signal S10. Therefore, the optical transmission device 42
Can reduce the device scale as compared with the optical transmission device 2.

[0024] [optical amplifier 45 _1] FIG 2 is a configuration diagram of an optical amplifying device 45 _1. 2, the optical amplifier device 45 ₁ has an optical amplifier 20, an optical coupler 21, an optical spectrum analyzer 51 and gain determiner 52. The optical amplifier 20 optically amplifies the optical signal S42 input via the optical fiber cable 4 with an amplification factor according to the amplification factor control signal S52 from the amplification factor determiner 52, and converts the optically amplified optical signal S45 into Output to the downstream side of the optical fiber cable 4. The optical amplifier 20 controls the current value in the case of a semiconductor type, and controls the optical power from an excitation light source in the case of a doped fiber type, based on the amplification factor control signal S52. The optical amplifying device 45 ₂ and 45 _3, the optical amplifier 45
It has the same configuration as ₁ .

The optical coupler 21 extracts a part of the optical signal S 45 output from the optical amplifier 20 to the downstream side of the optical fiber cable 4 and outputs the extracted signal to the optical spectrum analyzer 51.

As shown in FIG. 3, for example, the optical spectrum analyzer 51 includes a diffraction grating 60, an O / E converter 61,
It has a peak value storage unit 62 and a lens 63. The optical signal incident on the diffraction grating 60 is reflected by the diffraction grating 60,
After being condensed by the lens 63, the O / E converter (photoelectric) 61
Is received at. Since the wavelength of the reflected light changes according to the change in the angle of incidence on the diffraction grating 60, it is possible to extract an optical signal for each wavelength component by rotating the diffraction grating 60. At this time, peak level information for each wavelength is obtained based on the rotation angle information, that is, the reflection wavelength information, and the electric signal level obtained from the O / E converter 61 photoelectric converter.

The O / E converter 61 receives the optical signal reflected by the diffraction grating 60 and generates a voltage or a current corresponding to the intensity of the received light, thereby converting the optical signal into an electric signal. , And outputs the electric signal to the peak value storage unit 62. The peak value storage unit 62 compares the light intensity indicated by the electric signal from the O / E conversion unit 61 with the already stored peak value of the light intensity, and indicates the electric signal from the O / E conversion unit 61. If the light intensity is higher, the previously stored peak value is updated with the light intensity. Peak value storage unit 62
Outputs the stored light intensity peak value S51 to the amplification factor determiner 52.

The amplification factor determiner 52 compares the peak value S51 of the light intensity input from the peak value storage unit 62 of the optical spectrum analyzer 51 with a reference value stored in advance, so that the difference between them is reduced. Next, the amplification factor of the optical amplifier 20 is determined. Then, the amplification factor determiner 52 outputs the amplification factor control signal S52 indicating the determined amplification factor to the optical amplifier 20.
Output to

[0029] Hereinafter, the operation of the optical amplifying apparatus 45 ₁ shown in FIG. Figure 5 is a flow chart for explaining the operation of the optical amplifier 45 _1. Step S1: In the optical spectrum analyzer 51, while rotating the diffraction grating 60 to change the wavelength of the reflected optical signal, the optical signal reflected by the diffraction grating 60
The signal is converted into an electric signal by the E converter 61. Step S2: The electric signal indicating the light intensity generated by the O / E conversion unit 61 is input to the peak value storage unit 62, and the peak value S51 of the light intensity of the optical signal S45 is converted to the amplification factor determiner 52.
Is output to

Step S3: The amplification factor determiner 52 compares the input peak value S51 with the reference value. If the peak value S51 is larger, the process of step S6 is performed, and the peak value S51 is compared with the reference value. If smaller, step S4
Is performed. Step S6: This is executed when it is determined in step S3 that the peak value S51 is larger, and an amplification factor control signal S52 indicating that the amplification factor is to be reduced is output from the amplification factor determiner 52 to the optical amplifier 20.

Step S4: Peak value S at step S3
This is executed when it is determined that 51 is smaller, and the amplification factor determiner 52 determines whether or not the peak value S51 matches the reference value. When it is determined that the peak value S51 matches the reference value, the process ends,
If it is determined that they do not match, the process of step S5 is performed.

Step S5: Peak value S at step S4
This is executed when it is determined that the reference value 51 does not match the reference value, and an amplification factor control signal S52 indicating that the amplification factor is to be increased is output from the amplification factor determiner 52 to the optical amplifier 20.

As described above, in the optical communication system 41 shown in FIG. 1, a control signal is applied to the optical signal S42 output from the optical transmission device 42 to the optical fiber cable 4 as in the conventional optical communication system 1 described above. There is no need to overlap.
Therefore, the component of the main signal S10 included in the optical signal S42 does not receive the interference of the control signal as in the related art.
Further, the degree of modulation of the optical signal S42 can be increased. Therefore, the optical signal S42 transmitted through the optical fiber cable 4
Can improve the S / N characteristics.

Further, according to the optical communication system 41, an optical spectrum analyzer 51 of the optical amplifier 45 ₁ to 45 ₃
Thus, in addition to the light intensity of the optical signal S42, the optical signal S42
It allows the wavelength or spectrum observations, by outputting these observations, it is possible to monitor the entire or state of the optical amplifier 45 ₁ to 45 ₃ of the optical communication system 41.

Second Embodiment FIG. 6 is a configuration diagram of an optical communication system 101 according to this embodiment. As shown in FIG. 6, the optical communication system 101 includes an optical transmitting device 102, optical amplifying devices 145 ₁ , 145 ₂ , and 14
6. It has an optical fiber cable 4 and an optical receiver 103, and employs a wavelength division multiplexing (WDM) system in which optical signals of four wavelengths are transmitted by one optical fiber cable 4.

In the optical communication system 101, the optical transmitter 1
02 and the optical receiver 103 are connected via the optical fiber cable 4, and the optical amplifiers 145 ₁ , 145 ₂ , and 146 are incorporated in the optical fiber cable 4 at predetermined intervals. In the optical communication system 101, the light intensities of the optical signals of a plurality of wavelengths attenuated during transmission through the optical fiber cable 4 are amplified by the optical amplifiers 145 ₁ , 145 ₂ , 146 ₃ and the optical signals of the plurality of wavelengths are also amplified. Optical transmission device 1 such that the difference between the light intensity peak values for
In 02, the optical attenuation rates of the optical signals of a plurality of wavelengths are adjusted.

[Optical Transmitter 102] As shown in FIG.
The optical transmission device 102 includes a transmission signal source 10 ₁ 10 ₂ , 1
0 ₃ , 10 ₄ , light sources 13 ₁ , 13 ₂ , 13 ₃ , 13 ₄ ,
It has optical attenuators 110 ₁ , 110 ₂ , 110 ₃ , 110 ₄ , an optical coupler 112, an optical attenuator controller 114, and a control signal receiver 116. Similarly to the first embodiment, the optical transmission device 102 does not include a control signal source. However, unlike the first embodiment, four transmission signal sources and four light sources are provided.

The transmission signal source 10 ₁ to 10 ₄ each main signal S10 ₁ ~S10 _4, respectively source _131-134
Output to ₄ . Light sources 13 ₁ , 13 ₂ , 13 ₃ , 13
₄ respectively converts the main signals S10 ₁ , S10 ₂ , S10 ₃ and 10 ₄ into a first wavelength, a second wavelength,
And optical intensity modulation in wavelength and the fourth wavelength of the optical signal corresponding to the respective _{S13 1, S13 2, S13 3} , S13 4
To the optical attenuators 110 ₁ , 110 ₂ , 110 ₃ ,
Output to 110 ₄ .

Optical attenuator 110₁~ 110_FourRespectively
Optical attenuation rate control signal S114 from optical attenuator controller 114
₁~ S114_FourAnd the optical signal S
13 ₁~ S13_FourSignal S110 attenuated₁~ S11
0_FourIs output to the optical coupler 112. The optical coupler 112 is
Optical signal S110₁~ S110_FourAre optically coupled to form an optical signal S1.
02 is output to the optical fiber cable 4.

The control signal receiver 116 receives attenuation rate control signals S146 _{1 to} S146 ₄ from the optical amplifier 146 shown in FIG.
And, for example, the attenuation rate control signals S146 _{1 to} S146
₄ is demodulated if they are modulated, and if they are optical signals, O / E conversion is performed.
And outputs an attenuation factor control signal S116 ₁ -116 ₄ that E converts the optical attenuator controller 114. Optical attenuator controller 114
Is optionally an attenuation factor control signal S116 ₁ -116 _4, optical attenuator _{1101 4} converts the processable signal, the attenuation factor control signal generated by the conversion S1
14 _{1 to} 114 ₄ are respectively assigned to optical attenuators 110 _{1 to} 110
Output to ₄ .

[Optical Receiver 103] FIG. 8 shows an optical receiver.
FIG. As shown in FIG.
103 denotes an optical coupler 119, an optical filter 120 ₁~ 12
0_FourAnd O / E converter 121₁~ 121_FourHaving.
In the optical receiving device 103, the
The input optical signal S102 is branched by the optical coupler 119,
Optical coupler 120₁~ 120_FourIs output to And light
Of the signal S102, the first wavelength component and the second wavelength component
Component, the third wavelength component, and the fourth wavelength component.
Each optical filter 120₁, 120 _Two, 120_Three, 12
0_FourThrough the optical signal S120₁, S120_Two, S1
20 _Three, S120_FourO / E converter 121₁, 12
1_Two, 121_Three, 121_FourIs output to And Koshin
No.S120₁, S120_Two, S120_Three, S120
_FourAre respectively O / E converters 121₁, 121_Two, 12
1_Three, 121_FourIn each of the electric signals S121₁, S1
21_Two, S121_Three, S121_FourIs converted to

[Optical Amplifier 145 ₁ ] FIG. 9 is a configuration diagram of the optical amplifier 145 ₁ . As shown in FIG. 9, the optical amplifier 145 ₁ includes an optical amplifier 20, an optical coupler 21, an optical spectrum analyzer 161, and an amplification factor determiner 162. The optical amplifier 145 ₂ is an optical amplifier 14
5 is ₁ with the same configuration. Optical amplifier 145 _1, basically has the same configuration as the optical amplifying apparatus 45 ₁ shown in FIG. 2 described in the first embodiment, the function of the optical spectrum analyzer 161 and the amplification factor determiner 162, Optical spectrum analyzer 51 and amplification factor determiner 5 shown in FIG.
Somewhat different from 2.

FIG. 10 shows an optical spectrum analyzer 16.
1 is a configuration example diagram of FIG. As shown in FIG. 10, the optical spectrum analyzer 161 has a diffraction grating 60, an O / E converter 61, a lens 63, and a peak value storage 164. In FIG. 10, the components denoted by the same reference numerals as those in FIG. 3 are basically the same as those described in the first embodiment. The diffraction grating 60 rotates as described above,
The wavelength of the reflected light is changed according to the change in the incident angle of the optical signal. At this time, the reflected light is reflected such that the first wavelength, the second wavelength, the third wavelength, and the fourth wavelength are sequentially reflected. Is changed.

The peak value storage section 164 stores the optical signal S102
The peak value of the light intensity is detected and stored for each of the first wavelength, the second wavelength, the third wavelength, and the fourth wavelength included in. Note that the peak value storage unit 164
Indicates which of the first to fourth wavelength components the electric signal input from the optical spectrum analyzer 61 indicates, based on, for example, rotational position information input from a motor that drives the rotation of the diffraction grating 60. to decide.

The amplification factor determiner 162 reads the optical signal S from the peak value storage 164 of the optical spectrum analyzer 161.
The peak value of the light intensity of each component of the first wavelength, the second wavelength, the third wavelength, and the fourth wavelength included in 102 is input, and the smallest peak value among these is stored in advance. The amplification factor of the optical amplifier 20 is determined so as to reduce these differences by comparing with a reference value. And
The amplification factor determiner 162 outputs an amplification factor control signal S162 indicating the determined amplification factor to the optical amplifier 20. As described above, by amplifying the optical amplifier 20 based on the smallest peak value, the first wavelength included in the optical signal S102,
The peak values of the light intensity of the components of the second, third and fourth wavelengths can all be amplified above the reference value.

FIG. 11 is a flowchart of the processing in the amplification factor determiner 162. As shown in FIG. 11, in the amplification factor determiner 162, the optical spectrum analyzer 161 is used.
Whether the smallest peak value among the light intensity peak values of the first, second, third, and fourth wavelength components input from the peak value storage unit 164 is larger than the reference value. It is determined whether or not the gain is large (step S11). When it is determined that the gain is large, for example, an amplification factor control signal S162 indicating that the amplification factor is to be reduced is output to the optical amplifier 20 (step S14). On the other hand, in the amplification factor determiner 162,
If it is determined that the smallest peak value is smaller than the reference value, then it is determined whether the smallest peak value matches the reference value (step S12). When the processing is completed and it is determined that they do not match, for example, an amplification control signal S162 indicating that the amplification is to be increased is output to the optical amplifier 20 (step S13).

[Optical Amplifier 146] FIG. 12 is a configuration diagram of the optical amplifier 146 disposed immediately before the optical receiver 103. As shown in FIG. 12, the optical amplifying device 146
It has an optical amplifier 20, an optical coupler 21, an optical spectrum analyzer 161, an amplification rate / decay rate determiner 172, and an attenuation rate control signal transmitter 173. The optical amplifier 20 and the optical coupler 21 are the same as those shown in FIG. 2, and the optical spectrum analyzer 161 is the same as that shown in FIG.

The gain / decay rate determiner 172 has a function of controlling the gain of the optical amplifier 20 and a function of controlling the attenuation rate of the optical attenuator of the optical transmitter 102. Here, the function of controlling the amplification factor of the optical amplifier 20 is the same as the function described above with reference to FIG. On the other hand, the control of the attenuation rate of the optical attenuator of the optical transmitter 102 by the amplification rate / attenuation rate determiner 172 is performed as follows.

That is, as shown in FIG. 13, the light intensities of the first, second, third, and fourth wavelength components input from the peak value storage unit 164 of the optical spectrum analyzer 161. When there is a difference between the peak value 1, the peak value 2, the peak value 3 and the peak value 4 of the above, and the difference between the maximum peak value 2 and the minimum peak value 3 exceeds a predetermined allowable range, Or the minimum peak value is
When the total power of the optical signal including the noise light exceeds a predetermined allowable range, the optical transmitter 102 shown in FIG.
Of the optical attenuators 110 _{1 to} 110 ₄ are controlled so that the difference falls within an allowable range. The amplification factor
When the minimum peak value of the optical signal output from the optical amplifier 20 exceeds a predetermined allowable value with respect to the total power of the optical signal including noise light,
By controlling the attenuation factor of the optical attenuator _{1101 4} shown in FIG. 7, increase the light intensity of the optical signal S110 ₁ ~S110 _4.

FIG. 14 is a flowchart for controlling the attenuation factor of the optical attenuator of the optical transmitter 102 in the amplification factor / decay factor determiner 172. Step S21: The light of the first wavelength, the second wavelength, the third wavelength, and the fourth wavelength component input from the peak value storage unit 164 of the optical spectrum analyzer 161 in the amplification rate / decay rate determiner 172. It is determined whether the difference between the maximum peak value and the minimum peak value among the peak values 1, 2, 3, and 4 of the intensity is within a predetermined allowable range. . If it is determined that the value falls within the permissible range, the process proceeds to step S23.
Is performed, and if it is determined that the value is not within the permissible range, the process of step S22 is performed.

Step S22: Amplification rate / decay rate determiner 1
At 72, a first wavelength, a second wavelength, a third wavelength, and the like.
And peak value 1 of the light intensity of the component of the fourth wavelength
2, so that the peak value 3 and the peak value 4 are almost the same
The optical attenuator 110 shown in FIG. ₁~ 110_ThreeLight decay rate
Is determined respectively, and the optical attenuation rate control indicating the optical attenuation rate is determined.
Signal S172₁~ S172_FourIs the damping rate system shown in FIG.
It is output to the control signal transmitter 173.

Step S23: Amplification rate / decay rate determiner 1
At 72, the minimum peak value among the peak value 1, the peak value 2, the peak value 3, and the peak value 4 of the light intensity of the first wavelength, the second wavelength, the third wavelength, and the fourth wavelength component is Then, it is determined whether or not the power is within a predetermined allowable range by comparing with the total power including the ASE of the optical signal S102. If it is determined that the power is within the allowable range, the process is terminated, and if it is not within the allowable range. If it is determined, the process of step S24 is performed.

Step S24: Amplification rate / decay rate determiner 1
At 72, the minimum peak value is within a predetermined tolerance, as compared to the total power including ASE,
The attenuation factors of the optical attenuators 110 _{1 to} 110 ₄ shown in FIG. 7 are controlled. When the ratio of the ASE included in the optical signal S102 is large, the optical attenuators 110 _{1 to} 110 ₄ reduce the ratio of the ASE by increasing the light intensity of the optical signal input to the optical amplifier. Optical attenuation rate control signals S172 _{1 to} S172 ₄ indicating that the attenuation rate is reduced uniformly are output to the attenuation rate control signal transmitter 173 shown in FIG.

The attenuation rate control signal transmitter 173 has an amplification factor
Optical attenuation rate control signal S1 input from attenuation rate determiner 172
72 ₁ ~S172 ₄ as needed to generate an attenuation factor control signal S146 ₁ ~S146 ₄ performs modulation and E / O conversion, the control signal receiver 116 of the optical transmitter 102 of this
Output to

Further, in the optical amplifying device 146, the peak values of the light intensities of the optical signals of the plurality of different wavelengths are all equal to or greater than the reference value, and the difference between the peak values of the optical signals of the plurality of different wavelengths is equal to or less than the reference value. 14 and until the minimum peak value is within a predetermined allowable range with respect to the total power of the optical signal including noise light.
Control of the attenuation rate of the optical attenuators 110 _{1 to} 110 ₄ shown in
The control of the optical amplification factor of the optical amplifier 20 shown in FIG. 11 is alternately repeated.

As described above, the optical communication system 10
According to No. 1, the peak values of the light intensity of the first, second, third and fourth wavelength components included in the optical signal S102 by the optical amplifiers 145 ₁ , 145 ₂ and 146. Can all be amplified above the reference value. Therefore, the optical signal S 102 arriving at the optical receiving device 103 via the optical fiber cable 4 can have a light intensity sufficient to be accurately detected by the optical receiving device 103.

In the optical communication system 101, the WDM
By transmission, optical signals of multiple wavelengths are multiplexed and transmitted,
Since taken out a plurality of components of wavelengths included in the optical signal received by the optical receiver 103 separates an optical filter 120 _{1-120 4} shown in FIG. 8, included in the optical signal received by the optical receiving apparatus 103 If the difference in light intensity between each other components of the plurality of wavelengths is large, between an optical signal cross separated by the optical filter 120 _{1-120 4,} leakage component of the wavelength of the next, accurate detection of the components of each wavelength There are things you can't do. However, according to the optical communication system 101 of the present embodiment, the light of the first wavelength, the second wavelength, the third wavelength, and the fourth wavelength component included in the optical signal S102 is generated by the optical amplifier 146. When the difference between the peak value 1, the peak value 2, the peak value 3, and the peak value 4 of the intensity exceeds a predetermined allowable range, the optical attenuator 11 of the optical transmitter 102 shown in FIG.
0 _1-110 to control the _fourth attenuation rate, it is possible to make the difference within the allowable range. Accordingly, it is possible to prevent the leakage of the light of the adjacent wavelength and improve the transmission quality of the optical signal S102.

If the optical signal S102 contains a large amount of ASE, the optical signal received by the optical receiving device 103 may be deteriorated due to the influence of noise, and may not be accurately detected by the optical receiving device 103. . In particular, when there is a large difference in light intensity among a plurality of wavelength components included in the optical signal S102, the optical signal having the minimum peak value among the optical signals received by the optical receiver 103 is affected by noise. Deterioration is likely to occur, and the optical receiving device 103 cannot accurately detect. Therefore, as described above, the transmission quality of all optical signals can be improved by controlling the optical amplifier 146 to reduce the difference between the peak values of the light intensity of each wavelength and reduce the ratio of ASE. Can be.

The present invention also relates to, for example, an optical communication system 101 shown in FIG.
Instead of using the optical receiver 3 shown in FIG.
The optical signal S102 is received by one O / E converter 221.
The distinction between the main signal S10 ₁ ~S10 ₄ shown in FIG. 7, it is also useful for determining the frequency of the transmission signal source 10 ₁ to 10 _4. In this case, the transmission signal source 10 ₁ to 10 ₄ outputs a modulated signal having different carrier frequencies respectively. FIG.
In 5, the distributor 219 is a distributor of an electric signal that distributes the electric signal output from the O / E converter 221, and the RF filters 220 _{1 to} 220 ₄ are RF filters that extract only selected frequency components. . In such a system, the electric signal output from the O / E conversion unit 221, since the various frequency components having the transmission signal source 10 ₁ to 10 ₄ is contained at the same time, transmits the necessary frequency components, not required Filter 2 that does not allow transmission of various frequencies
20 220 ₁ -220 ₄ is required. In such a system, of the attenuation rate control method shown in FIG. That is, in such a system, since a plurality of optical signals are received by one O / E converter 221, if the ratio of the total power including ASE to the minimum peak value is large, the minimum peak value is reduced. The transmission quality of the transmission signal transmitted from the optical transmitting device with the indicated signal light deteriorates due to the influence of noise, and the optical receiving device 203 cannot detect it accurately. Such a problem can be dealt with by reducing the ratio of the total power including the ASE by performing the control of FIG. 14, and it is possible to prevent the deterioration of the transmission quality.

Further, according to the optical communication system 101,
The optical spectrum analyzer 161 of each of the optical amplifiers 145 ₁ , 145 _2, and 146 enables observation of the wavelength and spectrum of the optical signal S 102 in addition to the light intensity of the optical signal S 102, and outputs the observation results. so,
The whole optical communication system 41 and the optical amplifiers 145 ₁ , 14 ₁
5 the state of ₂ and 146 makes it possible to monitor.

The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the optical spectrum analyzer 51 illustrated in FIG. 2 is illustrated as the light transmitting unit, the light receiving unit, and the peak value holding unit, but the light intensity of the optical signal is detected for each wavelength, and the detected light There is no particular limitation as long as it has a light intensity detecting means for generating an electric signal corresponding to the intensity and a light intensity peak holding means for holding the peak value of the light intensity of the detected optical signal. In the above embodiment, the light spectrum analyzer 161 shown in FIG.
The light intensity detection means for detecting the light intensity of the optical signal of a plurality of different wavelengths for each wavelength, and generating an electric signal according to the detected light intensity, and the light intensity of the detected optical signal There is no particular limitation as long as it has a light intensity peak holding means for holding the peak value.

Further, in this embodiment, the case where the light reflection type diffraction grating 60 is used has been described as an example, but the present invention may use a light transmission type.

In the above-described embodiment, as shown in FIG. 6, the optical amplifier 146 shown in FIG. 12 is provided at the last stage on the optical fiber cable 4, and the optical amplifier 145 shown in FIG. _Although the case where ₁ and 145 ₂ are provided has been exemplified, the optical amplifier 1 shown in FIG.
46 may be provided. In that case, the optical attenuator 110 of FIG.
_{For 1-110} control signal indicating different control contents to ₄ from a plurality of optical amplifying apparatus is likely to be sent, previously negotiated or to prioritize control content from which the optical amplifying device. For example, control is performed by giving priority to the optical attenuator control signal in order from the optical amplifier closer to the optical receiver 103. Note that a plurality of optical amplifiers 1
When 46 is provided, the transmission path of the attenuation rate control signal is
As many as the number of optical amplifiers 146 may be provided, or FDM (Frequency Divisiton Multiplexing) using a common transmission path.
Alternatively, multiplex transmission may be performed by a time division multiplexing (TDM) method.

In the above-described optical communication system 101 shown in FIG. 6, a case where four different wavelengths of optical signals are multiplex-transmitted has been exemplified. However, the number of optical signals having different wavelengths for multiplex transmission is arbitrary.

[0065]

As described above, according to the optical amplifier and the optical communication system of the present invention, the transmission quality of an optical signal can be improved. According to the optical communication system of the present invention,
The optical transmitter can be downsized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical communication system according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of the optical amplifying device shown in FIG.

FIG. 3 is a configuration diagram of the optical spectrum analyzer shown in FIG. 2;

FIG. 4 is a diagram for explaining a relationship between a wavelength of a light signal transmitted through the diffraction grating shown in FIG. 3 and light intensity;

FIG. 5 is a flowchart for explaining the operation of the optical amplifier shown in FIG. 2;

FIG. 6 is a configuration diagram of an optical communication system according to a second embodiment of the present invention.

FIG. 7 is a configuration diagram of the optical transmission device shown in FIG. 6;

FIG. 8 is a configuration diagram of the optical receiver shown in FIG. 6;

FIG. 9 is a configuration diagram of the first-stage and second-stage optical amplifiers shown in FIG. 6;

FIG. 10 is a configuration diagram of the optical spectrum analyzer shown in FIG. 9;

FIG. 11 is a flowchart for explaining a process of an amplification factor determiner shown in FIG. 9;

FIG. 12 is a configuration diagram of a third-stage optical amplification device shown in FIG. 6;

FIG. 13 is a diagram for explaining processing in an amplification factor / attenuation factor determiner shown in FIG. 12;

FIG. 14 is a flowchart of a process in an amplification factor / decay factor determiner shown in FIG. 12;

FIG. 15 is a configuration diagram of a modification of the optical receiver shown in FIG. 6;

FIG. 16 is a configuration diagram of a conventional optical communication system.

FIG. 17 is a configuration diagram of the optical transmitter illustrated in FIG. 16;

FIG. 18 is a configuration diagram of the optical amplifying device shown in FIG.

[Explanation of symbols]

 3,103 ... optical receiving device, 10,10₁, 10_Two, 10
_Three... Transmission signal sources 13, 13₁, 13_Two, 13_Three, 13
_Four... light source, 20 ... optical amplifier, 21 ... optical coupler, 41,1
01: Optical communication system, 42, 102: Optical transmission device, 4
5₁, 45_Two, 45_Three, 145₁, 145_Two, 146 ...
Optical amplifying device, 51, 61, 161 ... optical spectrum analyzer
Riser, 52, 162: amplification rate determiner, 60: diffraction grating
Child, 62, 164... Peak value storage unit, 110₁, 110
_Two, 110_Three, 110_Four... optical attenuators, 112, 119 ...
Optical coupler, 114: optical attenuator controller, 116: control signal
Receiver, 120₁, 120_Two, 120_Three, 120_Four…light
Filter, 121₁, 121 _Two, 121_Three, 121_Four…
O / E converter, 172... Amplification rate / attenuation rate determiner, 173
... Attenuation rate control signal transmitter

Continuation of front page (72) Inventor Hideyuki Omura 2-6-1 Marunouchi, Chiyoda-ku, Tokyo F-term in Furukawa Electric Co., Ltd. F-term (reference) 5K002 AA06 BA02 BA04 BA05 CA09 CA10 CA13 DA02 EA05 FA01

Claims (12)

[Claims] 1. An optical amplifying device for amplifying an optical signal input via an optical communication cable, comprising: an optical amplifier for amplifying the input optical signal at a specified amplification factor; Branching means for partially branching, light intensity detecting means for detecting the light intensity of the branched optical signal for each wavelength, and generating an electric signal corresponding to the detected light intensity; and Light intensity peak holding means for holding a peak value, and an amplification factor determining means for determining the amplification factor so that the held peak value is equal to or more than a reference value, and designating the determined amplification factor to the optical amplification means. An optical amplifier having: 2. The photoelectric intensity detecting means according to claim 1, wherein the optical intensity detecting means detects an optical intensity of the split optical signal while changing a detection wavelength, and generates an electric signal corresponding to the detected optical intensity. Item 2. The optical amplifying device according to item 1. 3. An optical amplifier for inputting and amplifying an optical signal obtained by multiplexing a plurality of optical signals having different wavelengths through an optical communication cable, wherein the input optical signal is amplified at a designated amplification factor. An optical amplifying unit, a branching unit that branches a part of the amplified optical signal, and sequentially detects light intensities of the plurality of wavelengths included in the branched optical signal for each wavelength, and the detected light intensity A light intensity detecting unit that generates an electric signal corresponding to the above, a light intensity peak holding unit that holds a peak value of the detected light intensity for each of the plurality of different wavelength optical signals, and a light of the plurality of different wavelengths. An amplification control unit that specifies the amplification factor of the optical amplification unit so that the peak value of the light intensity of the signal is equal to or higher than a reference value. 4. An attenuation rate control signal for controlling an attenuation rate of the plurality of different wavelength optical signals on the transmitting side of the optical signal according to a peak value of the light intensity of the plurality of different wavelength optical signals. 4. The optical amplifying device according to claim 3, further comprising an attenuation rate control signal generating unit that performs the control. 5. The light source apparatus according to claim 1, wherein said attenuation rate control signal generating means includes a light source for transmitting said optical signals having different wavelengths on a transmission side of said optical signal such that a difference between peak values of said optical signals having different wavelengths is equal to or less than a reference value. 5. The optical amplifying device according to claim 4, wherein an attenuation rate control signal for controlling an attenuation rate of the signal is generated. 6. The attenuation rate control signal generating means, wherein a minimum peak value of the held peak values of the plurality of optical signals having different wavelengths is determined with respect to a total power of the optical signal including noise light. The optical amplifying device according to claim 4, wherein an attenuation rate control signal for controlling an attenuation rate of the optical signals of the plurality of different wavelengths on the transmission side of the optical signal is generated so as to be within a predetermined allowable range. 7. The attenuating rate control signal generating means, wherein the difference between the peak values of the light intensities of the plurality of optical signals having different wavelengths is equal to or less than a reference value. A process of generating an attenuation rate control signal for controlling an attenuation rate of an optical signal of a wavelength; and a minimum peak value among light intensity peak values of the held optical signals of the different wavelengths includes noise light. A process of generating an attenuation rate control signal that controls an attenuation rate of the optical signals of the plurality of different wavelengths on the transmission side of the optical signal so that the total power of the optical signal falls within a predetermined allowable range. The optical amplifying device according to claim 4, wherein the light amplification is performed in order. 8. An optical / electrical means for detecting the light intensity of the split optical signal while changing the detection wavelength, and generating an electric signal corresponding to the detected light intensity of the detected optical signal. The optical amplifying device according to any one of claims 3 to 7, wherein 9. An optical communication system for transmitting an optical signal from an optical transmitting device to an optical receiving device via an optical communication cable, the optical transmitting device comprising: a transmission signal source for generating a main signal; And a light source that generates an optical signal by performing the above operation. The optical communication cable further includes an optical amplifier that optically amplifies the optical signal on the optical communication cable. Optical amplification means for amplifying the amplified optical signal, branching means for branching a part of the amplified optical signal, detecting the light intensity of the branched optical signal for each of a plurality of wavelengths, and detecting the detected light intensity Light intensity detecting means for generating an electric signal according to the following; light intensity peak holding means for holding the peak value of the detected light intensity; and the amplification factor such that the held peak value becomes a reference value or more. Determined, and determines the determined amplification factor with the light An optical communication system having an amplification factor determining unit designated as an amplifying unit. 10. An optical communication system for transmitting an optical signal from an optical transmitting device to an optical receiving device via an optical communication cable, wherein the optical transmitting device comprises: a plurality of transmission signal sources each generating a main signal; A plurality of light sources that are provided corresponding to the transmission signal sources, respectively, and that generate the optical signal by modulating the main signal from the corresponding transmission signal source at a different wavelength from the other main signals; A plurality of light attenuating means for generating an optical signal attenuated at an attenuation rate according to the input attenuation rate control signal, and a plurality of optical attenuating means, Multiplexing means for multiplexing the generated optical signal and outputting the multiplexed optical signal to the optical communication cable; and a light for optically amplifying the optical signal on the optical communication cable. With amplification device An optical amplification unit that amplifies an optical signal input via the optical communication cable at a designated amplification factor; a branching unit that branches a part of the amplified optical signal; Light intensity detecting means for sequentially detecting the light intensities of the plurality of different wavelengths included in the branched optical signal for each wavelength, and generating an electric signal corresponding to the detected light intensity; and the light of the plurality of different wavelengths. Light intensity peak value holding means for holding a peak value of the light intensity of the optical signal for each signal; and the optical amplification so that the light intensity peak values of the optical signals of the plurality of different wavelengths are equal to or more than a reference value. Optical communication comprising: amplification factor control means for designating the amplification factor of the means; and attenuation factor control signal generation means for generating the attenuation factor control signal in accordance with the peak values of the held optical signals of the plurality of different wavelengths. system. 11. An optical amplifier for amplifying an optical signal input through the optical communication cable at a designated amplification factor; a branching unit for branching a part of the amplified optical signal; Light intensity detecting means for detecting the light intensity of the detected optical signal for each of a plurality of wavelengths, and generating an electric signal corresponding to the detected light intensity, and light intensity peak holding means for holding the peak value of the detected light intensity A single or a plurality of optical amplifying devices comprising: an amplification factor determining unit that determines the amplification factor so that the held peak value is equal to or greater than a reference value, and specifies the determined amplification factor to the optical amplification unit. The optical communication system according to claim 10, further comprising: 12. The optical amplifying device having the attenuation rate control signal generating means is provided immediately before the optical receiving device on the optical communication cable.
2. The optical communication system according to 1.