JP2003264511A - Light amplifying method and device, and optical amplification relay system using the device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To flatten the gain of each wavelength by controlling the attenuation quantity of an optical variable attenuator so as to have a slope reverse to a gain slope caused by an SRS from detection results of output power. <P>SOLUTION: A correction circuit 51 calculates the correction value of the attenuation quantity of the optical variable attenuator 45 from the total optical output power detected by an optical power detection circuit 49, and a control circuit 50 controls the attenuation quantity of the optical variable attenuator 45 so as to negate the slope of a gain wavelength characteristic caused by the influence of the SRS by a downstream side optical transmission path 30 and thereby makes the gain of each wavelength uniform at an input port of an optical amplifier of the next stage through the optical transmission path 30 to flatten the gain wavelength characteristic. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses an optical amplification method for adjusting the amount of attenuation of an optical variable attenuator in order to make the gain and output of an optical signal constant irrespective of wavelength. The present invention relates to an optical amplification repeater system.

[0002]

2. Description of the Related Art In a conventional optical amplification repeater system, data traffic is rapidly increasing as the transmission distance becomes longer and the transmission capacity increases. This increase in data traffic leads to deterioration in communication performance. Therefore, in order to prevent the deterioration of the communication performance, a wavelength division multiplexing (WDM) system is becoming popular.

Such a WDM system is shown in FIG.
2, the transmitting terminal station device 10 and the receiving terminal station device 2
0, and an optical fiber transmission line for connecting the transmitting terminal device 10 and the receiving terminal device 20 (hereinafter referred to as "optical transmission line")
There is one that is composed of a plurality of optical amplification devices 40 provided on the optical fiber transmission line 30 and several optical signals having different wavelengths are simultaneously transmitted to the optical transmission line 30 of one core.

That is, in this system, each of the optical transmitters 111 to 11n (n is an arbitrary integer) of the transmission terminal station device 10.
A plurality of optical signals transmitted at different wavelengths λ1 to λn by an optical multiplexer 12 including an optical coupler, a WDM coupler, an arrayed waveguide type optical demultiplexer (AWG), etc. After the optical amplification at 13, the single mode optical fiber (SMF) or dispersion shift optical fiber (DS
It is transmitted to one transmission line 30 composed of F). This multiplexed optical signal is, for example, an erbium-doped fiber amplifier (EDFA) or a thulium-doped fiber amplifier (TDF).
A) and a semiconductor optical amplifier (SOA), etc. are passed through several stages of optical amplifying devices 40, and then transmitted to the receiving terminal station device 20, thereby performing high-power optical signal transmission and realizing long-distance and large-capacity transmission. Was.

In the receiving terminal station device 20, the multiplexed optical signal is demultiplexed by the optical demultiplexer 22 via the optical amplifying device 21 and sent to the optical receivers 231 to 23n for each wavelength λ1 to λn. was there.

Optical amplifier 40 used in this system
For example, as shown in FIG. 13, the optical fiber amplifier section (hereinafter referred to as “optical amplifier section”) 41, 42 is provided. The optical amplifying units 41 and 42 include automatic gain control circuits (hereinafter,
"AGC" 43 and automatic light output control circuit (hereinafter,
The transmission loss of the optical transmission line 30 is compensated for by collectively amplifying the multiplexed optical signal controlled by “ALC” 44.

In this optical amplifier 40, the optical amplifiers 41,
An optical variable attenuator 45 is connected between 42. And
In this optical amplifier 40, the optical input power P1 and the optical output power P4 of the optical amplifier in the optical signals demultiplexed by the optical demultiplexers 46 and 47 are detected by the optical power detection circuits 48 and 49, and control is performed. The circuit 50 controls the attenuation amount A of the optical variable attenuator 45 so that the sum of the gain G1 of the optical amplification section 41 and the gain G2 of the optical amplification section 42 becomes constant.

That is, the attenuation amount A of the variable optical attenuator 45
Is obtained by the difference A = P2−P3 (1) between the optical output power P2 of the optical amplifier 41 and the optical input power P3 of the optical amplifier 42, and the gain G1 of the optical amplifier 41 is equal to the optical power of the optical amplifier 41. The difference G1 = P2-P1 (2) between the output power P2 and the optical input power P1 of the optical amplifier 41 is obtained, and the gain G2 of the optical amplifier 42 is equal to the optical output power P4 of the optical amplifier 42 and the optical amplification. The difference of the optical input power P3 of the section 42 is obtained by G2 = P4-P3 (3).

Next, since the gains of the optical amplifiers 41 and 42 are controlled so as to be constant, G1 + G2 = C (constant) (4) Here, by substituting the equations (2) and (3) into the equation (4) to obtain the attenuation amount A of the variable optical attenuator 45, (P2-P1) + (P4-P3) = C (P2- P3) + (P4-P1) = C (P2-P3) = C- (P4-P1). Therefore, A can be obtained from the equation (1) by A = C- (P4-P1) (5).

Here, for example, the total sum of gains G1 + G2 = 2
0 [dB], optical input power P1 = + 2 [dBm], optical output power P4 = + 18 [dBm], and these values are substituted into the equation (5) to obtain the attenuation amount A of the optical variable attenuator 45. Then, A = 20− (18-2) = 4 [dB].

The gain wavelength characteristic and the level diagram in this conventional example are shown in FIGS. 14 (a) to 14 (c) and FIG. That is, FIG. 14A shows the gain wavelength characteristic of the optical amplifying section 41, FIG. 14B shows the gain wavelength characteristic of the optical amplifying section 42, and FIG. 14C shows the optical amplifying section 41,
FIG. 16 is a characteristic diagram showing a gain wavelength characteristic when 42 is connected in multiple stages, and FIG. 15 is a diagram showing a level diagram showing the optical power of each part.

As is clear from these figures, the optical amplifier 4
1 is designed so as to obtain a wavelength characteristic of a downward-sloping gain when the optical power P1 is amplified to P2, and the optical amplification section 42, when amplifying the optical power P3 to P4,
It was designed so as to obtain a wavelength characteristic of a gain that rises to the right, and at the output end, these were designed so that the gain wavelength characteristic was almost flat. Further, the variable optical attenuator does not have a gain wavelength characteristic, and attenuates all wavelengths uniformly from the optical power P2 to P3.

[0013]

However, in the above conventional example, as shown in the gain wavelength characteristic of FIG.
The gain wavelength of the optical signal amplified by the optical amplification section 41 is designed to be substantially flat. However, when this optical signal is transmitted to the optical fiber transmission line 30, SRS which is one of the nonlinear optical phenomena. (Stimulated Raman Sc
attering: stimulated Raman scattering).

That is, since the SRS shifts the optical power on the short wavelength side to the long wavelength side by the interaction with the optical phonon in the optical fiber transmission line, the WDM optical signal incident on the optical fiber transmission line is Due to the influence of this SRS, the optical signal on the long wavelength side receives a gain from the optical signal on the short wavelength side. For this reason, the optical power of the WDM optical signal after being transmitted through the optical fiber transmission line is large in the optical signal on the long wavelength side, and the optical spectrum thereof has a wavelength characteristic that rises to the right.

Therefore, in the optical amplification repeater system in which the optical amplifiers are connected in multiple stages, the difference in optical power between the short wavelength side and the long wavelength side increases as the number of multistage connections increases, and the S / of the optical signal on the short wavelength side increases. There is a problem that N is deteriorated, the transmission efficiency is lowered, and the transmission distance of the optical signal is limited.

Further, as shown in the relationship between the optical output power and the inclination of the optical spectrum of the WDM optical signal in FIG. 16, the higher the optical output power (total optical power incident on the optical fiber transmission line), the more WDM light The slope of the optical spectrum of the signal was large.

The present invention has been made in view of the above problems, and controls the attenuation amount of the optical variable attenuator so as to have a slope opposite to the slope of the gain generated by the SRS from the detection result of the optical power. An object of the present invention is to provide an optical amplification method, an apparatus and an optical amplification repeater system using the apparatus, which can flatten the gain at each wavelength and improve the transmission efficiency.

[0018]

In order to achieve the above object, according to the present invention, at least two optical amplifiers and at least one attenuator are connected to each other, and an optical signal input through an optical transmission line is inputted to the optical amplifier. In the optical amplification method in which the optical power of the optical signal is detected and the attenuation amount is controlled according to the detected optical power, the sum of the gains of the optical amplifiers is the total to the optical transmission line. There is provided an optical amplification method including a control step of controlling an attenuation amount of the attenuator so that a target value depends on an optical input power.

According to the present invention, the gain of each optical amplifier is set to G
1, G2, and the gain G1 is the difference G1 = P2-P1 between the optical output power P2 and the optical input power P1 of the optical amplifier,
This gain G2 is the difference G2 = P4-P3 between the optical output power P4 and the optical input power P3 of the optical amplifier, and the sum (P2-
P1) + (P4-P3) becomes the target value C + ΔL depending on the total optical input power to the optical transmission line (P2-P
1) + (P4−P3) = C + ΔL (see equation (6) described later), and the attenuation amount A = C + ΔL− (P
By controlling 4-P1), a slope opposite to the slope of the gain generated by the SRS is provided, and the gain at each wavelength is flattened.

According to a second aspect of the present invention, in the above invention, in the control step, the total optical input power of the optical signal to the upstream optical transmission line to which the optical signal is input and the optical signal are propagated. It is characterized in that the attenuation amount of the attenuator is controlled so that the target value depends on at least one total optical input power of the total optical input power of the optical signal to the downstream side optical transmission line. .

According to the present invention, the amount of attenuation is the total optical input power of each wavelength of the optical signal to the upstream optical transmission line and / or the total optical input of each wavelength of the optical signal to the downstream optical transmission line. By controlling to a target value that depends on power, the gain is made uniform and stable optical transmission is performed.

According to a third aspect of the present invention, at least two optical amplifiers, at least one attenuator and a dispersion compensating optical transmission line are connected, and an optical signal input via the optical transmission line is amplified by the optical amplifier. In addition, in the optical amplification method of detecting the optical power of the optical signal and controlling the attenuation amount according to the detected optical power, the sum of the gains of the optical amplifiers is the total optical input to the optical transmission line. An optical amplification method is provided, which includes a control step of controlling an attenuation amount of the attenuator so that a target value depends on power and total optical input power to the dispersion-compensated optical transmission line. .

According to the present invention, the sum of the gains of the optical amplifiers becomes a target value that depends on the total optical input power to the dispersion compensation type optical transmission line in addition to the total optical input power to the optical transmission line. In this way, the gain has a slope opposite to the slope of the gain generated by the SRS, and the gain at each wavelength is flattened.

According to a fourth aspect of the present invention, in the above invention, in the control step, the total optical input power of the optical signal to the optical transmission path on the upstream side for inputting the optical signal and the optical signal are propagated. Of the total optical input power of the optical signal to the downstream optical transmission line, the target value depends on at least one total optical input power and the total optical input power to the dispersion-compensated optical transmission line. In addition, the attenuation amount of the attenuator is controlled.

According to the present invention, the amount of attenuation is set to the total optical input power of each wavelength of the optical signal to the upstream side optical transmission line or /
By controlling to a target value that depends on the total optical input power of each wavelength of the optical signal to the downstream side optical transmission line and the total optical input power to the dispersion compensation type optical transmission line, the gain is made uniform and stable optical Make a transmission.

According to a fifth aspect of the present invention, at least two optical amplifiers and at least one attenuator are connected, and an optical signal input through an optical transmission line is amplified by the optical amplifier and at the same time the optical signal of the optical signal is amplified. In an optical amplifying device that controls the attenuation amount according to optical power, a detection unit that detects the optical power of the optical signal, and a predetermined correction value of the attenuation amount of the attenuator based on the detected optical power There is provided an optical amplifying device comprising: a correction unit to be obtained and a control unit to control an attenuation amount of the attenuator based on the obtained correction value.

According to the present invention, in order to correct the slope of the gain caused by the influence of SRS, the optical power is detected, and the correction value of the attenuation amount of the optical variable attenuator is obtained from the detection result of this optical power. , The attenuation amount of the optical variable attenuator is controlled so as to cancel this gain slope.

According to a sixth aspect of the present invention, in the above invention, the detecting means has a total optical input power of the optical signal to an upstream optical transmission line for inputting the optical signal to the own device, and the own device. The total optical input power of at least one of the total optical input power of the optical signal to the downstream side optical transmission line for propagating the optical signal from is detected.

According to the present invention, the object to be detected is detected depending on whether the control target is the slope of the gain generated by the influence of SRS due to the upstream optical transmission line or the downstream optical transmission line, or both. Determine the optical transmission line and detect the total optical input power.

According to a seventh aspect of the present invention, in the above invention, the correcting means sets the gain slope of the optical amplifier based on the detected total optical input power as a gain slope generated by stimulated Raman scattering. It is characterized in that a correction value of the attenuation amount of the attenuator is obtained so as to have an opposite inclination.

According to the present invention, a correction value that causes the gain slope of the optical amplifier to have a slope opposite to the slope of the gain generated by the SRS is obtained, and the slopes cancel each other out, so that the gain wavelength at each wavelength is canceled. Aim to flatten the characteristics.

According to claim 8 of the present invention, at least three optical amplifiers, at least one attenuator, and a dispersion-compensating optical transmission line are connected, and an optical signal input through the optical transmission line is amplified by the optical amplifier. In addition, in the optical amplification device for controlling the attenuation amount according to the optical power of the optical signal,
First for detecting the optical power of the optical signal to the optical transmission line
Detecting means, second detecting means for detecting the optical power of the optical signal to the dispersion compensating optical transmission line, and correction of a predetermined attenuation amount of the attenuator based on each of the detected optical powers. Based on the correction means for obtaining the value and the obtained correction value,
An optical amplifying device is provided, which comprises: a control unit that controls the amount of attenuation of the attenuator.

According to the present invention, when the dispersion compensating optical transmission line for the optical amplifier is connected, the optical power of the optical signal to the dispersion compensating optical transmission line is detected in addition to the optical transmission line. hand,
The correction value of the attenuation amount of the attenuator is obtained to compensate the transmission loss due to the influence of the SRS of the optical transmission line.

According to a ninth aspect of the present invention, in the above invention, the first detecting means has a total optical input power of the optical signal to the upstream side optical transmission line for inputting the optical signal to its own device, and At least one total optical input power of the total optical input power of the optical signal to the downstream side optical transmission line for propagating the optical signal from the own device is detected.

According to the present invention, detection is performed depending on whether the control target is the slope of the gain wavelength characteristic generated by the influence of SRS by the upstream optical transmission line or the downstream optical transmission line, or both of them. Determine the optical transmission line and detect the total optical input power.

According to a tenth aspect of the present invention, in the above invention, the second detecting means detects the total optical input power of the optical signal to the dispersion compensating optical transmission line.

According to the present invention, when the dispersion compensation type optical transmission line is connected in the optical amplifier, the total optical input power of the optical signal to the dispersion compensation type optical transmission line is detected. It is targeted for compensation.

In the eleventh aspect of the present invention, in the above invention, the correction means changes the gain slope of the optical amplifier by the stimulated Raman scattering based on the detected total optical input power. It is characterized in that the correction value of the attenuation amount of the attenuator is obtained so as to have the opposite inclination.

According to the present invention, the slope of the gain of the optical amplifier is SR based on each detected total optical input power.
A correction value that gives an inclination opposite to the inclination of the gain generated by S is obtained, and the inclinations of the two are canceled.

According to a twelfth aspect of the present invention, in the above invention, the optical amplifying device includes transmitting means for transmitting the information on the detected optical power and receiving means for receiving the information on the detected optical power. Is further provided.

According to the present invention, a transmitter and a receiver for transmitting and receiving the information of the detected optical power are provided, the attenuation amount can be controlled in another optical amplifying device, and the optical amplifying device of a plurality of stages is provided. It is possible to control the attenuation by obtaining the detection result of the optical output power from.

According to a thirteenth aspect of the present invention, there is provided an optical amplification repeater system for amplifying and relaying an optical signal propagating through the optical transmission line by an optical amplification device connected in multiple stages to the optical transmission line. An optical amplification repeater system comprising at least one optical amplification device according to any one of claims 1 to 12.

According to the present invention, at least one optical amplifying device according to any one of claims 5 to 12 is connected to the optical amplifying repeater system, and the gain generated by SRS is detected from the detection result of the optical power in each optical amplifying device. The gain wavelength characteristic is flattened by giving an inclination opposite to the inclination and canceling each other.

According to a fourteenth aspect of the present invention, in an optical amplifying device which is connected in multiple stages to at least two optical transmission lines for upstream and downstream, an optical signal propagated to the optical transmission line is amplified to bidirectionally. An optical amplification repeater system for performing the optical repeater according to claim 5, wherein at least one optical amplification device according to any one of claims 5 to 12 is provided.

According to the present invention, an optical amplification repeater system for performing bidirectional transmission using the upstream and downstream optical transmission lines to which at least one optical amplifying device according to claim 5 is connected is constructed. By doing so, the detection result of the optical power on the downstream side can be received together with the optical power on the upstream side.

According to a fifteenth aspect of the present invention, in the above-mentioned invention, in the optical amplification repeater system including the optical amplification device of the twelfth aspect, the optical amplification device is detected from another optical amplification device connected to the optical transmission line. When the optical power information is received, a predetermined correction value of the attenuation amount of the attenuator based on the optical power is obtained, and the attenuation amount of the attenuator is controlled based on the obtained correction value.

According to the present invention, the attenuation amount of the attenuator is adjusted so as to have a slope opposite to the slope of the gain generated by the SRS from the detection result of the optical output power in other optical amplifiers regardless of the upstream or the downstream. By controlling, the gain at each wavelength in the target stage optical amplifier becomes uniform.

[0048]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an optical amplification method, an apparatus therefor and an optical amplification repeater system using the apparatus according to the present invention will be described below with reference to the accompanying drawings. Note that, in the following drawings, the same components as those in FIGS. 12 and 13 are denoted by the same reference numerals for convenience of description.

(Embodiment 1) FIG. 1 is a configuration diagram showing a configuration of Embodiment 1 of an optical amplifier according to the present invention. In this figure, the difference from the conventional example of FIG. 13 is that the correction circuit 51 in which the correction value of the attenuation amount of the variable optical attenuator 45 is set in order to correct the slope of the gain wavelength characteristic caused by the influence of SRS. That is the point. The correction circuit 51 uses the optical amplifier 42 in order to cancel the inclination of the gain wavelength characteristic.
On the basis of the optical output power from, the correction value ΔL of the attenuation amount that has the gain wavelength characteristic having an inclination opposite to the inclination of the gain wavelength characteristic is obtained and output to the control circuit 50. The control circuit 50 obtains the attenuation amount based on the correction value ΔL, the optical input power from the optical transmission line 30 and the optical output power to the optical transmission line 30, and determines the attenuation amount A of the optical variable attenuator 45. Have control.

That is, in this embodiment, the attenuation amount A of the variable optical attenuator 45 is obtained by the equation (1), and the gain G1 of the optical amplification section 41 is obtained by the equation (2), as in the conventional example.
Further, the gain G2 of the optical amplification section 42 is obtained by the equation (3).

The gains of the optical amplifiers 41 and 42 are G1 + G2 = C + ΔL (6) Here, by substituting the equations (2) and (3) into the equation (6) to obtain the attenuation amount A of the variable optical attenuator 45, (P2-P1) + (P4-P3) = C + ΔL (P2 -P3) + (P4-P1) = C + [Delta] L (P2-P3) = C + [Delta] L- (P4-P1) Therefore, A is obtained from the equation (1) by A = C + [Delta] L- (P4-P1) ... (7).

Next, ΔL is obtained. Here, first SRS
Of gain wavelength characteristic SRS (d
G / dλ) is SRS (dG / dλ) = 4.34 · (β · P0 · Leff) [dB / nm] (8) where P0: total of optical signals incident on the optical transmission line 30. Optical power [W] (corresponding to P4 in FIG. 1) β: Optical transmission line 30 on which this total optical power is incident
(Type) -dependent coefficient [1 / W · km · nm] Leff: This total optical power is the effective length [km] of the incident optical transmission line.

The equation (8) is ELECTRON.
ICS LETTERS, 16 ^th April 199
8, Vol. 34, No. 8, M.M. Zirngibl.

Next, in order to cancel the slope of the gain wavelength characteristic generated by the influence of SRS, the slope OFA (dG / dλ) of the gain wavelength characteristic generated by the optical amplifier is S
Since the slope of the gain wavelength characteristic generated due to the influence of RS is the opposite slope, OFA (dG / dλ) = − a · ΔL [dB / nm] (9) where a: in the design of the optical amplifier Dependent proportionality coefficient [1 /
nm] ΔL: It becomes the correction value [dB] of the attenuation amount of the variable optical attenuator.

When the sum of the equations (8) and (9) becomes zero, the gain of each wavelength after being transmitted through the optical transmission line becomes uniform and the gain wavelength characteristic becomes flat. First, the sum of equations (8) and (9) is SRS (dG / dλ) + OFA (dG / dλ) = 4.34 · (β · P0 · Leff) −a · ΔL = 0 (10)

Next, ΔL is obtained by ΔL = 4.34 · (β · P0 · Leff) / a (11). That is, ΔL is the total optical power P0 of the optical signal incident on the optical transmission line, and a coefficient β depending on the type of the optical transmission line on which the total optical power P0 is incident,
This total optical power is a value obtained from the effective length of the optical transmission line on which it is incident.

Here, for example, a = 0.02 [1 / n
m], β = 3.5 × 10 ⁻³ [1 / W · km · nm], P
0 = P4 = + 18 [dBm] = 0.063 [W], Le
If ff = 21 [km], these values are substituted into the equation (11), and the correction value ΔL of the attenuation amount of the optical variable attenuator is calculated. ΔL = {4.34 · (3.5 × 10 ⁻³・ 0.063 ・ 2
1)} / 0.02 = 1 [dB].

Further, the conditions shown in the conventional example, that is, the sum of gains G1 + G2 = 20 [dB], the optical input power P1 =
+2 [dBm], optical output power P4 = + 18 [dBm]
Then, by substituting these values into the equation (7) to obtain the attenuation amount A of the optical variable attenuator, A = C + ΔL− (P4-P1) = 20 + 1− (18-2) = 5 [dB] Become.

The gain wavelength characteristic in the case of this embodiment is shown in FIG.
(A) to (c), and the level diagram is as shown in FIG. In this embodiment, since the optical power of P3 is reduced by the amount of attenuation of the correction value, the gain of the optical amplification section 42 is larger than that of the conventional example (the dotted line portion in FIG. 3).

Further, the slope of the gain wavelength characteristic changes with the magnitude of the gain as shown in FIG. That is, as can be seen from the figure, when the gain increases, the slope increases to the lower right, and when this gain decreases,
The inclination increases to the right.

Here, for example, as shown in FIG. 3, when the gain of the optical amplification section 42 increases, the slope of the wavelength characteristic of the gain increases toward the lower right. Therefore, as shown in FIG. 2C, the gain wavelength characteristic of this embodiment has a lower right slope than the gain wavelength characteristic of the conventional example.

As described above, in this embodiment, the correction value of the attenuation amount of the optical variable attenuator is obtained from the detection result of the total optical output power in order to correct the inclination of the gain wavelength characteristic caused by the influence of SRS. Then, since the attenuation amount of the optical variable attenuator is controlled so as to cancel the inclination of the gain wavelength characteristic, the input of the optical amplifying device 40 of the next stage via the optical transmission line 30 as shown in FIG. The gain wavelength characteristic at each wavelength at the end is flattened, and the transmission efficiency can be improved.

For this reason, in this embodiment, even if the optical power incident on the optical transmission line fluctuates due to an increase or decrease in the number of channels, the slope of the gain of the wavelength-division-multiplexed signal generated by the influence of the SRS is automatically collected. It is possible to correct the deviation of the gain of this wavelength-division multiplexed signal to a minimum, thereby making the optical power at each wavelength uniform, preventing S / N deterioration in the optical signal on the short wavelength side, and stabilizing the optical signal. Optical transmission is possible.

(Embodiment 2) FIG. 5 is a block diagram showing the structure of Embodiment 2 of the optical amplifier according to the present invention. In the figure, in the optical amplifying device 40 of this embodiment, a control / monitoring signal receiving circuit 52 for receiving a control / monitoring signal from the optical amplifying device 40 in the previous stage via the optical transmission line 30, and the optical amplifying device 40 in the next stage. And a control / monitoring signal transmitting circuit 53 for transmitting a control / monitoring signal.

The control / monitoring signal receiving circuit 52 receives the information of the optical output power incident on the upstream optical transmission line as a control / monitoring signal via the optical demultiplexer 54, and the preceding optical amplification. S generated in the optical transmission line 30 between the device 40 and the device itself
The control circuit 50 controls the attenuation amount of the variable optical attenuator 45 so as to have a slope opposite to the slope of the gain due to the influence of RS. In addition, the control / monitoring signal transmission circuit 53
Transmits the optical output power incident on the optical transmission line 30 via the optical multiplexer 55 to the optical amplifier of the next stage (not shown).

Also in this embodiment, as in the case of the first embodiment, the correction value ΔL of the attenuation amount which gives the gain wavelength characteristic having the slope opposite to the wavelength characteristic of the gain, the optical input power from the optical transmission line 30, The attenuation amount A of the variable optical attenuator 45 is controlled by obtaining the attenuation amount based on the optical output power to the optical transmission line 30. In this embodiment, the point different from the first embodiment is that the optical power P01 is the optical output power of the optical amplification device at the preceding stage,
P0 in the equation (11) corresponds to this optical output power P01,
The correction value ΔL is derived from the optical output power P01 and the type and effective length of the upstream optical transmission line through which the optical signal of P01 is transmitted.

The gain wavelength characteristic in the case of this embodiment is shown in FIG.
As shown in (a) and (b). In this embodiment, since the slope of the gain wavelength characteristic of the optical signal input to the optical amplifying device 40 increases to the right as shown in FIG. 6A, the optical variable attenuation is performed so as to cancel this gain wavelength characteristic. Control the amount of attenuation of the vessel.

As a result, in this embodiment, as shown in FIG.
As shown in FIG. 5, the gain at each wavelength at the output end of the optical amplifying device 40 becomes uniform, the gain wavelength characteristic is flattened, the transmission efficiency can be improved, and the same effect as that of the first embodiment is obtained. In addition, it is possible to prevent the influence of SRS on the upstream optical transmission line and further improve the transmission efficiency.

(Embodiment 3) FIG. 7 is a block diagram showing an embodiment in which three optical amplifiers 41, 42, 60 are provided in the optical amplifier 40. The optical amplification section 41 is controlled by an automatic current control circuit (hereinafter referred to as “ACC”), and the optical amplification sections 42 and 60 are controlled by ALCs 44 and 61 to collectively amplify the multiplexed optical signals. Thus, the transmission loss of the optical transmission line 30 is compensated.

Further, in this optical amplifying device 40, a DCF 66 is connected between the optical amplifying parts 42 and 60. And
In this optical amplification device 40, the optical demultiplexers 56, 57, 62,
The optical output power P2 of the optical amplification section 41, the optical input power P3 of the optical amplification section 42, the optical input power P5 and the optical output power P6 of the optical amplification section 60 in the optical signal demultiplexed by 63 are detected by the optical power detection circuit. 58, 59, 64 and 65, the control circuit 50 determines that the sum of the gain G1 of the optical amplification section 41, the gain G2 of the optical amplification section 42 and the gain G3 of the optical amplification section 60 is C.
The attenuation amount A of the optical variable attenuator 45 is set so as to be + ΔL.
Are in control.

In this case, ΔL is ΔL1 which is a correction value of the attenuation amount of the optical variable attenuator for the optical transmission line 30 connected to the optical amplifier of the next stage and the attenuation amount of the optical variable attenuator for the DCF 66. Δ, which is the correction value of ΔL2
It consists of the value of L = ΔL1 + ΔL2.

That is, the gains of the optical amplifiers 41, 42 and 60 are G1 + G2 + G3 = C + ΔL (12) Further, the gain G1 of the optical amplifier 41 is obtained by the equation (2), and the gain G2 of the optical amplifier 42 is obtained by the equation (3), and the gain G3 of the optical amplifier 60 is obtained by the equation 6.
Optical output power P6 of 0 and optical input power P of the optical amplifier 60
5 difference G3 = P6-P5 (13)

Substituting equations (2), (3) and (13) into equation (12), (P2-P1) + (P4-P3) + (P6-P5) = C
It becomes + ΔL. Then, from the above equation, the attenuation amount (P2-P3) of the variable optical attenuator 45 is obtained by (P2-P3) = C + [Delta] L- (P4-P1)-(P6-P5) ... (14). Therefore, from (1) to A, A = C + ΔL- (P4-P1)-(P6-P5) ... (15)

Further, in this embodiment, the correction value ΔL of the attenuation amount of the optical variable attenuator (actually, ΔL1 and ΔL2 are calculated and added) is calculated based on the above-mentioned expressions (8) to (11). be able to. That is, the correction value ΔL1 of the attenuation amount of the optical variable attenuator for the optical transmission line 30 connected to the optical amplifier of the next stage is ΔL1 = 4.34 · (β1 · P6 · Leff1) / a where P6: Total optical power [W] β1 of the optical signal incident on the stage transmission line β1: Coefficient [1 / (W · km · nm)] Leff1: This total light that depends on the optical transmission line on which this total optical power is incident Effective length of optical transmission line on which power is incident [km] a: Proportional coefficient (unit: [1 / nm]) depending on the design of the optical amplifier of the device itself, and attenuation of the optical variable attenuator with respect to this DCF 66 The correction value ΔL2 for the amount is ΔL2 = 4.34 · (β2 · P4 · Leff2) / a where P4: total optical power [W] β2 of the optical signal incident on the DCF: this total optical power is incident. Depends on DCF Coefficient [1 / (W · km · nm)] Leff2: DCF into which this total optical power is incident
Becomes an effective length [km]. Therefore, the correction value ΔL of the attenuation amount of the optical variable attenuator in this embodiment is ΔL = ΔL1 + ΔL2 = 4.34 · (β1 · P6 · Leff1) /a+4.34· (β2 · P4 · Leff2) / a = 4 .34 · {(β1 · P6 · Leff1) + (β2 · P4 · Leff2)} / a.

As described above, in this embodiment, in order to correct the inclination of the gain wavelength characteristic caused by the influence of the DCF and the SRS in the optical transmission line, the attenuation amount of the optical variable attenuator is detected from the detection result of the optical output power. Of the optical variable attenuator so as to cancel the inclination of the gain wavelength characteristic, the wavelength of the wavelength at the input end of the optical amplifier 40 of the next stage via the optical transmission line 30 is calculated. Gain becomes uniform,
The gain wavelength characteristic can be flattened, the transmission efficiency can be improved, the same effect as that of the first embodiment of FIG. 1 can be obtained, and the influence of SRS in the DCF can be prevented, and further transmission can be performed. The efficiency can be improved.

(Embodiment 4) FIG. 8 includes three optical amplifiers 41, 42, and 60 in the optical amplifier 40, and based on the information of the optical output power incident on the upstream optical transmission line. It is a block diagram which shows one Example in the case of controlling the amount of attenuation of the optical variable attenuator 45. In this optical amplifier 40, the control / monitoring signal receiving circuit 52 controls the information of the optical output power P06 incident on the upstream optical transmission line via the optical demultiplexer 54 as in the second embodiment.・ SR received as a supervisory signal and generated in the optical transmission line 30 between the optical amplification device 40 in the previous stage and the device itself
The control circuit 50 controls the attenuation amount of the variable optical attenuator 45 so as to have a slope opposite to the gain slope due to the influence of S. In addition, the control / monitoring signal transmission circuit 53
Is the optical output power incident on the optical transmission line 30 of the next stage,
It is transmitted to the optical amplifier at the next stage (not shown). The optical output power P06 corresponds to the optical output power P01 shown in the second embodiment of FIG.

The control circuit 50 controls the gain G1 of the optical amplifier 41.
The attenuation amount A of the optical variable attenuator 45 is controlled so that the sum of the gain G2 of the optical amplifier 42 and the gain G3 of the optical amplifier 60 is C + ΔL. In this case, ΔL
Is a correction value ΔL1 of the attenuation amount of the optical variable attenuator for the optical transmission line 30 connected to the optical amplification device in the preceding stage, and DCF6.
ΔL2 which is the correction value of the attenuation amount of the optical variable attenuator for 6
And ΔL = ΔL1 + ΔL2.

That is, the gains of the optical amplifiers 41, 42 and 60 are G1 + G2 + G3 = C + ΔL (16) Further, the gain G1 of the optical amplifier 41 is obtained by the equation (2), the gain G2 of the optical amplifier 42 is obtained by the equation (3), and the gain G3 of the optical amplifier 60 is obtained by the equation (13). .

Substituting equations (2), (3) and (13) into equation (16), (P2-P1) + (P4-P3) + (P6-P5) = C
It becomes + ΔL. Then, from the above formula, the attenuation amount (P2-P3) of the variable optical attenuator 45 is obtained by (P2-P3) = C + [Delta] L- (P4-P1)-(P6-P5) ... (17). Therefore, the attenuation amount A is obtained from the equation (1) by A = C + ΔL- (P4-P1)-(P6-P5) ... (18).

Also in this embodiment, the correction value ΔL of the attenuation amount of the optical variable attenuator (actually, ΔL1 and ΔL2 are calculated and added) is calculated based on the above-mentioned expressions (8) to (11). be able to. That is, the correction value ΔL1 of the attenuation amount of the optical variable attenuator for the optical transmission line 30 connected to the optical amplifier of the next stage is ΔL1 = 4.34 · (β1 · P06 · Leff1) / a where P06: the previous stage Optical power [W] β1: of the optical signal incident on the transmission line of the optical fiber [1:] A coefficient [1 / (W · km · nm)] Leff1: the total optical power of which the total optical power depends on the incident optical transmission line Is the effective length [km] a of the incident optical transmission line a: proportional coefficient (unit: [1 / nm]) depending on the design of the optical amplifier of the device itself, and the attenuation of the variable optical attenuator with respect to this DCF 66. Correction value ΔL2 of ΔL2 = 4.34 · (β2 · P4 · Leff2) / a where P4: total optical power [W] β2 of the optical signal incident on the DCF: this total optical power is incident. To DCF Dependent coefficient [1 / (W · km · nm)] Leff2: DCF into which this total optical power is incident
Becomes an effective length [km]. Therefore, the correction value ΔL of the attenuation amount of the optical variable attenuator in this embodiment is ΔL = ΔL1 + ΔL2 = 4.34 · (β1 · P06 · Leff1) /a+4.34· (β2 · P4 · Leff2) / a = It is 4.34 · {(β1 · P06 · Leff1) + (β2 · P4 · Leff2)} / a.

As described above, in this embodiment, in order to correct the slope of the gain wavelength characteristic caused by the influence of the DCF and the SRS in the optical transmission line, the detection result of the optical output power of the upstream optical transmission line is used. Since the correction value of the attenuation amount of the optical variable attenuator is obtained and the attenuation amount of the optical variable attenuator is controlled so as to cancel the inclination of the gain wavelength characteristic, the same effect as that of the second embodiment of FIG. 5 can be obtained. It is possible and S in DCF
The influence of RS can be prevented and the transmission efficiency can be further improved.

(Embodiment 5) Next, referring to FIG. 9, a case will be described in which an optical variable attenuator is not incorporated in the optical amplifier of the preceding stage. Since the manufacturing cost of the control function using the variable optical attenuator is high, an optical amplifying device having an optical variable attenuator may be provided every few units to reduce the manufacturing cost.

Therefore, in this embodiment, the control / monitor signal receiving circuit 52 makes the intermediate optical output power P04 made incident on the DCF 71 transmitted from the optical amplifier 70 on the upstream side and the light made incident on the optical transmission line 30. Output power P06 information,
It is received as a control / monitoring signal via the optical demultiplexer 54, and the gain slope due to the influence of the SRS generated in the DCF 71 of the optical amplification device 70 in the preceding stage and the optical transmission line 30 between this optical amplification device 70 and its own device 40. The control circuit 50 controls the attenuation amount of the optical variable attenuator 45 so as to have the opposite inclination. Here, P04 is the intermediate optical output power of the optical amplifier of the preceding stage, and P06 is the optical output power of the optical amplifier of the preceding stage.

The control circuit 50 has a gain G1 of the optical amplifier 41, a gain G2 of the optical amplifier 42, and a gain G of the optical amplifier 60.
This optical variable attenuator 4 is set so that the sum of 3 becomes C + ΔL.
The attenuation amount A of 5 is controlled. In this case, Δ
L is a correction value of the attenuation amount of the optical variable attenuator with respect to the optical transmission line 30 connected to the optical amplifier of the next stage, ΔL1, and DCF
ΔL which is the correction value of the attenuation amount of the optical variable attenuator for 66
2, ΔL3 which is the correction value of the attenuation amount of the optical variable attenuator for the optical transmission line 30 connected to the optical amplifier device 70 of the previous stage, and the correction value of the attenuation amount of the optical variable attenuator for the DCF 71 of the optical amplifier device 70 of the previous stage. ΔL = ΔL combined with ΔL4
It consists of the value of 1 + ΔL2 + ΔL3 + ΔL4.

In this embodiment, the optical amplifiers 41, 42 and 6 are used.
The gain of 0 is G1 + G2 + G3 = C + ΔL (19)

Substituting equations (2), (3) and (13) into equation (19), (P2-P1) + (P4-P3) + (P6-P5) = C
It becomes + ΔL. Then, from the above equation, the attenuation amount (P2-P3) of the variable optical attenuator 45 is obtained by (P2-P3) = C + [Delta] L- (P4-P1)-(P6-P5) ... (20).

Also in this embodiment, the correction value ΔL of the attenuation amount of the optical variable attenuator (actually, ΔL1 to ΔL4 is calculated and added) is calculated based on the above-mentioned expressions (8) to (11). be able to. That is, the correction value ΔL1 of the attenuation amount of the optical variable attenuator for the optical transmission line 30 connected to the optical amplifier of the next stage is ΔL1 = 4.34 · (β1 · P6 · Leff1) / a where P6: Total optical power [W] β1 of the optical signal incident on the stage transmission line β1: Coefficient [1 / (W · km · nm)] Leff1: This total light that depends on the optical transmission line on which this total optical power is incident Effective length of optical transmission line on which power is incident [km] a: Proportional coefficient (unit: [1 / nm]) depending on the design of the optical amplifier of the own device, and variable optical attenuation for the DCF 66 of the own device The correction value ΔL2 of the attenuation amount of the container is ΔL2 = 4.34 · (β2 · P4 · Leff2) / a where P4: Total optical power [W] β2 of the optical signal incident on the DCF of the own device β2: Total optical power is incident Coefficient depending on the DCF to be generated [1 / (W · km · nm)] Leff2: DCF to which this total optical power is incident
Becomes an effective length [km].

Further, ΔL3, which is the correction value of the attenuation amount of the optical variable attenuator for the optical transmission line 30 connected to the optical amplification device 70 in the preceding stage, is ΔL3 = 4.34 · (β3 · P06 · Leff3) / a where , P06: Total optical power [W] β3 of the optical signal incident on the preceding transmission line β3: Coefficient [1 / (W · km · nm)] Leff3: which this total optical power depends on the incident optical transmission line This total optical power becomes the effective length [km] of the incident optical transmission line, and ΔL4, which is the correction value of the attenuation amount of the variable optical attenuator with respect to the DCF 71 of the optical amplifier 70 in the previous stage, is ΔL4 = 4.34 · ( β4 · P04 · Leff4) / a where P04 is the total optical power [W] of the optical signal incident on the DCF of the optical amplifier at the preceding stage [beta] 4: This total optical power is a coefficient depending on the incident DCF. 1 / (W · km · nm)] Leff4: DCF this total optical power is incident
Becomes an effective length [km].

Therefore, the correction value ΔL of the attenuation amount of the variable optical attenuator in this embodiment is ΔL = ΔL1 + ΔL2 + ΔL3 + ΔL4 = 4.34 · (β1 · P6 · Leff1) /a+4.34· (β2 · P4 · Leff2) / a + 4.34 · (β3 · P06 · Leff3) /a+4.34· (β4 · P04 · Leff4) / a = 4.34 · {(β1 · P6 · Leff1) + (β2 · P4 · Leff2) + (β3 · P06 · Leff3) + (β4 · P04 · Leff4)} / a.

As described above, in this embodiment, the D in the optical amplifier device without the control function in the front stage and the D in the preamplifier in the rear stage is used.
In order to correct the slope of the gain wavelength characteristic caused by the influence of CF and the SRS in the optical transmission line, the correction value of the attenuation amount of the optical variable attenuator is obtained from the detection result of the optical output power of the upstream optical transmission line. Then, since the attenuation amount of the variable optical attenuator in multiple stages is controlled so as to cancel the inclination of the gain wavelength characteristic, it is possible to obtain the same effect as that of the above-described embodiment, and also in the optical amplifier of multiple stages. The gain at each wavelength becomes uniform, the gain wavelength characteristics can be flattened, and the transmission efficiency can be further improved.

(Sixth Embodiment) Next, FIG. 10 shows an embodiment of an optical amplification repeater system using the above-described optical amplification apparatus according to the present invention. In this embodiment, the optical amplifying device 70 which does not include the optical variable attenuator according to the present invention,
71 shows a system in which 71 and the optical amplifier 40 according to the present invention are connected on one optical transmission line 30.

In this system, the optical amplifiers 70, 71 are
Cannot control the slope of the gain wavelength characteristic, so that the optical amplifier 40 also controls the slope of the gain generated there. Optical output power P1 of the optical amplifiers 70 and 71
The information of a, P1b, P2a, and P2b is transmitted to the optical amplification device 40 as a monitoring / control signal from the control / monitoring signal transmission circuit of each optical amplification device 70, 71. The light output powers P1a and P2a correspond to the intermediate light output power P04 shown in FIG. 9, and the light output powers P1b and P2b.
Corresponds to the optical output power P06 shown in FIG.

Optical amplifier 40 used in this system
Is required to be a device capable of transmitting the information of the optical output power, therefore, the device having the control / monitoring signal transmitting circuit and the receiving circuit shown in FIGS. 5, 8 and 9 is essential in the configuration. .

The control / monitoring signal transmission circuit of the optical amplifying device 40 uses the optical amplifying device 7 in response to a polling request, for example.
Information on the optical output power can be obtained from 0 and 71.
The optical amplifying device 4 from another optical amplifying device via the optical transmission line 30.
In the optical amplifying device which does not have the variable optical attenuator which takes in the control / monitoring signal addressed to 0, the control / monitoring signal is again sent to the optical transmission line 30 after passing through the optical amplifying section. In addition,
The control / monitoring signal is an optical signal having a wavelength different from that of the main signal, and may be outside the amplification wavelength band of the optical amplifier or within this band, for example, in the case where it is within the amplification wavelength band of the optical amplifier. , And is transmitted after being optically amplified by the optical amplifier.

As described above, in this embodiment, since at least one optical amplifying device according to the present invention is connected to construct an optical amplifying repeater system, SRS is generated from the detection result of the optical power in each optical amplifying device. The attenuation amount of the variable optical attenuator can be controlled so as to have a slope opposite to the slope of the gain, whereby the gain can be flattened at each wavelength and the transmission efficiency can be improved.

(Embodiment 7) FIG. 11 is a system configuration diagram showing the configuration of another embodiment of the optical amplification repeater system using the above-described optical amplification apparatus according to the present invention. In the figure, in this system, two optical transmission lines 1 and 2 for uplink and downlink are provided, and a plurality of optical amplifiers 40, 70 to 73, 80 to 84 are respectively provided in multiple stages on each optical transmission line 1 and 2. It shows a case where they are connected, and at least one of these optical amplifying devices is provided with the optical amplifying device 40 according to the present invention.

If there are a plurality of optical amplifying devices 70 to 73 that do not have a variable optical attenuator on the upstream side and the downstream side of the optical amplifying device 40, these optical amplifying devices 7
Optical output powers P1a to P5a, P1 generated at 0 to 73
Information of b to P5b is transmitted to the optical amplification device 40.
The optical output power P of the optical amplifiers 72 and 73 on the downstream side is
The information of 4a, P4b, P5a, P5b is transmitted to the optical amplification device 40 via the monitoring module SV and the optical amplification devices 82 to 84.

The optical amplifying device 40 controls the attenuation amount of the optical variable attenuator so as to have a slope opposite to the slope of the gain generated by the SRS from the detection result of the optical output power in these optical amplifying devices.

As described above, in this embodiment, there is constructed an optical amplification repeater system having the upstream and downstream optical transmission lines to which at least one optical amplification device according to the present invention is connected and performing bidirectional transmission. Therefore, it is possible to obtain the same effect as that of the sixth embodiment in FIG. 10, receive the detection result of the optical power on the downstream side, and obtain the slope opposite to the slope of the gain generated by the SRS regardless of the upstream and downstream. It is possible to control the amount of attenuation of the optical variable attenuator so that it has, the gain at each wavelength in the target stage optical amplifier becomes uniform, the gain wavelength characteristics can be flattened, and the transmission efficiency is further improved. You can

The present invention is not limited to these embodiments, and various modifications can be made without departing from the gist of the present invention.

[0101]

As described above, according to the first aspect of the present invention, at least two optical amplifiers and at least one attenuator are connected to each other, and an optical signal input through the optical transmission line is transmitted by the optical amplifier. In the optical amplification method of amplifying and detecting the optical power of the optical signal and controlling the amount of attenuation according to the detected optical power, the sum of the gains of the optical amplifiers is the total optical power to the optical transmission line. Since the attenuation amount of the attenuator is controlled so that the target value depends on the input power, the optical variable attenuator is controlled so as to have a slope opposite to the slope of the gain generated by SRS from the detection result of the optical power. The amount of attenuation can be controlled, the gain at each wavelength can be flattened, and the transmission efficiency can be improved.

According to a second aspect of the present invention, the amount of attenuation of the optical variable attenuator is set to the total optical input power of each wavelength of the optical signal to the upstream optical transmission line or / and the optical signal to the downstream optical transmission line. Since it is controlled to a target value depending on the total optical input power of each wavelength, the gain can be made uniform and stable optical transmission can be performed.

According to the third and fourth aspects of the present invention, at least two optical amplifiers, at least one attenuator, and a dispersion-compensating optical transmission line are connected, and an optical signal input via the optical transmission line is described above. In the optical amplification method of amplifying with an optical amplifier, detecting the optical power of the optical signal, and controlling the amount of attenuation according to the detected optical power, the sum of the gains of the optical amplifiers is upstream or / and In addition to the total optical input power to the optical transmission line on the downstream side, the target value depends on the total optical input power to the dispersion-compensated optical transmission line, so that SRS is generated from the detection result of the optical power. It is possible to have a slope opposite to the slope of gain, and it is possible to flatten the optical power at each wavelength.

According to the fifth and sixth aspects of the present invention, at least two optical amplifiers and at least one attenuator are connected, and an optical signal input via an optical transmission line is amplified by the optical amplifier, and In an optical amplification device that controls the attenuation amount according to the optical power of the optical signal, the upstream side and / or the downstream side optical power is detected, and the attenuation amount of the optical variable attenuator is corrected from the detection result of the optical power. Seeking the value,
Since the attenuation amount of the optical variable attenuator is controlled, the attenuation amount of the optical variable attenuator is controlled so as to have a slope opposite to the slope of the gain generated by SRS from the detection result of the optical power, and the gain at each wavelength is controlled. Can be flattened and the transmission efficiency can be improved.

According to a seventh aspect of the present invention, the correction means causes the gain slope of the optical amplifier to have a slope opposite to the slope of the gain generated by stimulated Raman scattering based on the total optical input power. Since the correction value of the attenuation amount of the attenuator is obtained, the slopes of the gain wavelength characteristics cancel each other out, the gain wavelength characteristics at each wavelength are flattened, and the transmission efficiency can be improved.

According to the eighth to eleventh aspects of the present invention, a dispersion-compensating optical transmission line is connected, the optical signal input through the optical transmission line is amplified by the optical amplifier, and the optical power of the optical signal is increased. In the optical amplifying device for controlling the attenuation amount according to, the total optical input power of the optical signal to the upstream side and / or the downstream side optical transmission line, and the total optical input power of the optical signal to the dispersion compensation type optical transmission line The input power is detected, and a correction value is obtained based on each detected total optical input power so that the gain slope of the optical amplifier has a slope opposite to the slope of the gain generated by stimulated Raman scattering. Since the mutual inclinations are canceled out, the attenuation amount of the variable optical attenuator is controlled so as to have an inclination opposite to the inclination of the gain generated by the SRS from the detection result of the optical power, and the gain of each wavelength is controlled. Achieving tanker, the transmission efficiency can be improved.

According to the twelfth aspect of the present invention, since the transmission means for transmitting the information on the detected optical power and the reception means for receiving the information on the detected optical power are provided, another optical amplifier device is provided. It is possible to control the amount of attenuation at
It is possible to obtain the detection result of the optical output power from the optical amplifiers of a plurality of stages and control the attenuation amount in the optical amplifiers of the target stage.

According to a thirteenth aspect of the present invention, there is provided an optical amplification repeater system for amplifying and relaying an optical signal propagated to the optical transmission line with an optical amplification device connected in multiple stages to the optical transmission line. At least one of the optical amplifying devices according to 5 to 12 is connected, and the gains are made to cancel each other by providing a slope opposite to the slope of the gain generated by SRS from the detection result of the optical power in each optical amplifier. The wavelength characteristics can be flattened and the transmission efficiency can be improved.

Further, according to claims 14 and 15 of the present invention,
In an optical amplification repeater system for amplifying an optical signal propagated to the optical transmission line and performing bidirectional optical relaying, in an optical amplification device connected in multiple stages to at least two optical transmission lines for upstream and downstream. Optical power on the upstream side is constructed by constructing an optical amplification repeater system that performs bidirectional transmission using upstream and downstream optical transmission lines to which at least one optical amplification device according to claim 5 is connected. At the same time, it becomes possible to receive the detection result of the optical power on the downstream side, and the detection result of the optical output power in the other optical amplifying device has a slope opposite to the slope of the gain generated by the SRS so as to cancel each other. The gain wavelength characteristic can be flattened and the transmission efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of a first embodiment of an optical amplification device according to the present invention.

FIG. 2 is a characteristic diagram showing a gain wavelength characteristic of each part shown in FIG.

FIG. 3 is a diagram similarly showing a level diagram showing the optical power in each part.

FIG. 4 is a characteristic diagram showing a gain wavelength characteristic for explaining that the slope of the gain wavelength characteristic changes depending on the magnitude of the gain.

FIG. 5 is a configuration diagram showing a configuration of a second embodiment of the optical amplifying device according to the present invention.

6 is a characteristic diagram showing a gain wavelength characteristic of each part shown in FIG.

FIG. 7 is a configuration diagram showing a configuration of a third embodiment of the optical amplifying device according to the present invention.

FIG. 8 is a configuration diagram showing a configuration of a fourth embodiment of the optical amplifying device according to the present invention.

FIG. 9 is a configuration diagram showing a configuration of a fifth embodiment of the optical amplifying device according to the present invention.

FIG. 10 is a system configuration diagram showing a configuration of an embodiment of an optical amplification repeater system using the optical amplification device according to the present invention.

FIG. 11 is a system configuration diagram showing the configuration of another embodiment of the optical amplification repeater system using the optical amplification device according to the present invention.

FIG. 12 is a configuration diagram showing an example of a configuration of a conventional WDM system.

13 is a configuration diagram showing an example of a configuration of the optical amplification device shown in FIG.

FIG. 14 is a characteristic diagram showing gain wavelength characteristics of each part shown in FIG.

FIG. 15 is a diagram similarly showing a level diagram showing the optical power in each part.

FIG. 16 is a diagram showing the relationship between the optical output power and the slope of the optical spectrum of a WDM signal.

[Explanation of symbols]

1,2,30 Optical fiber transmission line (optical transmission line) 10 Transmission end station device 12,55 Optical multiplexer 13 Optical amplification device 20 Reception end station device 21, 40, 70-73, 80-84 Optical fiber amplification device ( Optical amplification device) 22, 46, 47, 54, 56, 57, 62, 63 Optical demultiplexer 41, 42, 60 Optical amplification unit 45 Optical variable attenuator 48, 49 Optical power detection circuit 50 Control circuit 51 Correction circuit 52 Control / monitor signal receiving circuit 53 Control / monitor signal transmitting circuit 58, 59, 64, 65 Optical power detection circuit 111 to 11n Optical transmitter 231 to 23n Optical receiver

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04J 14/02

Claims (15)

[Claims] 1. At least two optical amplifiers and at least one attenuator are connected, the optical signal input through an optical transmission line is amplified by the optical amplifier, and the optical power of the optical signal is detected, In the optical amplification method of controlling the amount of attenuation according to the detected optical power, the attenuation is performed so that the sum of the gains of the optical amplifiers becomes a target value that depends on the total optical input power to the optical transmission line. An optical amplification method comprising a control step of controlling an attenuation amount of a container. 2. In the control step, the total optical input power of the optical signal to the upstream optical transmission line for inputting the optical signal and the downstream optical transmission line for propagating the optical signal are input. Of the total optical input power of the optical signal,
2. The optical amplification method according to claim 1, wherein the attenuation amount of the attenuator is controlled so that the target value depends on at least one total optical input power. 3. At least two optical amplifiers, at least one attenuator, and a dispersion compensating optical transmission line are connected, and an optical signal input via the optical transmission line is amplified by the optical amplifier and the optical signal is transmitted. In the optical amplification method for detecting the optical power of the optical amplifier and controlling the amount of attenuation according to the detected optical power, the sum of the gains of the optical amplifiers is the total optical input power to the optical transmission line and the dispersion compensation type. An optical amplification method comprising a control step of controlling the attenuation amount of the attenuator so that the target value depends on the total optical input power to the optical transmission line. 4. In the control step, the total optical input power of the optical signal to the upstream optical transmission line for inputting the optical signal and the downstream optical transmission line for propagating the optical signal are input. Of the total optical input power of the optical signal,
4. The attenuation amount of the attenuator is controlled so that the target value depends on at least one of the total optical input power and the total optical input power to the dispersion compensating optical transmission line. Optical amplification method. 5. At least two optical amplifiers and at least one attenuator are connected to amplify an optical signal input via an optical transmission line by the optical amplifier, and according to the optical power of the optical signal, In an optical amplification device that controls an attenuation amount, a detection unit that detects an optical power of the optical signal, a correction unit that obtains a correction value of a predetermined attenuation amount of the attenuator based on the detected optical power, and An optical amplifying device comprising: a control unit that controls the attenuation amount of the attenuator based on the obtained correction value. 6. The detecting means includes a total optical input power of the optical signal to an upstream optical transmission line for inputting the optical signal to the own device and a downstream side for propagating the optical signal from the own device. 6. The optical amplifying device according to claim 5, wherein at least one of the total optical input powers of the optical signals to the optical transmission line is detected. 7. The correcting means sets the slope of the gain of the optical amplifier opposite to the slope of the gain generated by stimulated Raman scattering based on the detected total optical input power. 7. The optical amplification device according to claim 5, wherein a correction value of the attenuation amount of the attenuator is obtained. 8. At least three optical amplifiers, at least one attenuator, and a dispersion-compensating optical transmission line are connected, and an optical signal input via the optical transmission line is amplified by the optical amplifier and the optical signal is transmitted. An optical amplifier that controls the amount of attenuation in accordance with the optical power of the optical signal,
Detecting means, second detecting means for detecting the optical power of the optical signal to the dispersion-compensating optical transmission line, and correction of a predetermined attenuation amount of the attenuator based on each of the detected optical powers. An optical amplifying device comprising: a correction unit that obtains a value; and a control unit that controls the attenuation amount of the attenuator based on the obtained correction value. 9. The first detecting means propagates the total optical input power of the optical signal to the upstream optical transmission line for inputting the optical signal to the own device and the optical signal from the own device. 9. The optical amplifying device according to claim 8, wherein at least one of the total optical input powers of the optical signals to the downstream optical transmission line is detected. 10. The optical amplifying device according to claim 8, wherein the second detecting means detects a total optical input power of the optical signal to the dispersion compensation type optical transmission line. 11. The correcting means, based on each of the detected total optical input powers, causes the slope of the gain of the optical amplifier to have a slope opposite to the slope of the gain generated by stimulated Raman scattering. 11. The correction value of the attenuation amount of the attenuator is obtained, according to claim 8.
The optical amplification device described in 1. 12. The optical amplifying device further comprises: a transmitting unit for transmitting the information on the detected optical power, and a receiving unit for receiving the information on the detected optical power. Item 12. The optical amplifier device according to any one of items 5 to 11. 13. An optical amplification repeater system for amplifying and repeating an optical signal propagating in the optical transmission line in an optical amplifier device connected in multiple stages to the optical transmission line, wherein the optical amplifier according to any one of claims 5 to 12 is used. At least one amplification device
An optical amplification repeater system that has two features. 14. An optical amplifying device, which is connected in multiple stages to at least two optical transmission lines for upstream and downstream, and which amplifies an optical signal propagated to the optical transmission line to perform bidirectional optical relay. In an amplification repeater system, at least one optical amplification device according to any one of claims 5 to 12 is provided.
An optical amplification repeater system that has two features. 15. An optical amplification repeater system including the optical amplification device according to claim 12, wherein when the information of the detected optical power is received from another optical amplification device connected to the optical transmission line, the optical amplification device The optical amplification according to claim 13 or 14, wherein a predetermined correction value of the attenuation amount of the attenuator is obtained based on power, and the attenuation amount of the attenuator is controlled based on the obtained correction value. Relay system.