JP2001015845A - Wavelength multiplex optical transmission system utilizing raman distribution amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a wavelength multiplex optical transmission system which copes with the fluctuation of the number of channels and the fluctuation of a span loss without using a variable optical attenuator for adjusting the gain of the system, and is very good in noise characteristic while maintaining the flatness of the gain. SOLUTION: This system is a wavelength multiple optical transmission system which is provided with one excitation laser 9 or a plurality of excitation lasers 9 injecting an optical power in an optical fiber transmission line of a transmission medium for a wavelength division multiplexed light signal, and generating a Raman distribution amplification action, an optical multiplexing means 5 which is arranged on the latter step of the above optical fiber transmission line and is used for injecting light sent out from the above laser 9 in the above optical fiber transmission line, a light branching means 2 which is arranged on the latter step of the above means 5 and takes out one part of a multiple wavelength light signal, and a gain control means which utilizes light taken out by the above means 2 to exercise a control of the output power of the above excitation laser 9 for the Raman distribution amplification action and exercises a constant control of the automatic output level of the above multitude wavelength light signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extremely low-noise wavelength multiplexing optical transmission system using a Raman distribution amplifier.

[0002]

2. Description of the Related Art Rare-earth-doped optical fiber amplifiers are widely used in optical communication systems. In a wavelength division multiplexing optical transmission system, an optical signal transmitted through an optical fiber and weakened is collectively amplified as an optical signal without being converted into an electric signal by an optical fiber amplifier, and is transmitted to the next transmission optical fiber. Generally, such an optical fiber amplifier has a gain control function for always keeping the output power of an optical signal constant in order to maintain desired transmission quality. In a wavelength division multiplexing optical transmission system, the number of channels passing through an optical fiber amplifier may change due to branching / addition of a channel at a relay node or a node failure. Even when the number of channels fluctuates, the output power of the signal must be kept constant. Therefore,
As a gain control method suitable for such a wavelength division multiplexing optical transmission system, a gain constant control method for keeping the gain constant even when the total input power changes has been proposed.

FIG. 20 is a schematic diagram showing an example of the constant gain control optical fiber amplifier. In FIG. 20, 100 is a constant gain control optical fiber amplifier, 1A and 1B are optical fiber transmission lines, 2A and 2B are optical couplers, 3A and 3B are optical isolators, 4 is a rare earth doped optical fiber, 5 is an optical multiplexer, and 6
A and 6B are light receivers, 7 is a logarithmic calculator, 8 is a comparator, 9 is an excitation laser, ML is a wavelength-multiplexed optical signal, LS is laser light, and SS is a reference value.

In the configuration shown in FIG. 20, the total power of the input and the total power of the output are monitored, and the power of the pump laser is controlled so that the ratio becomes constant.
Even when the number of channels fluctuates, the signal gain (the ratio of the output level to the input level of the signal) can always be kept constant. At this time, the output level per channel output from the optical fiber amplifier is constant regardless of the number of channels.

On the other hand, the loss value (span loss) of an optical fiber actually laid in the field is not always constant due to a difference in a relay interval, a loss variation at the time of connecting the fiber, and aging. In the configuration shown in FIG. 20, since only a predetermined gain is obtained, the output level per channel of the optical signal output from the optical fiber amplifier also varies due to such a span loss variation. Accordingly, a gain control method has been proposed which compensates not only for the variation in the number of channels but also for the variation in span loss and always keeps the output level constant. FIG. 21 and FIG. 22 show examples.

FIG. 21 is a schematic diagram of a conventional optical fiber amplifier 200 for controlling the output level of a wavelength multiplexed optical signal.
The optical bandpass filter 10 extracts only signal light of a certain wavelength, monitors its power, and controls the power of the pump laser so that its value is always constant. This method can cope with both channel number fluctuation and span loss fluctuation (the output level per channel can be kept constant), but with the gain change of the optical fiber amplifier,
There is a problem that the gain flatness (the wavelength dependence of the gain) greatly changes. The system design is based on a predetermined gain flatness, and if this value changes greatly, in a multi-repeater wavelength-multiplexed optical transmission system in which optical amplifiers are connected in multiple stages, deviations from the design state accumulate, The optical signal will not be transmitted correctly. FIG. 22 shows an example of a control method for solving such a problem. In FIG. 22, 2A, 2
B and 2C are optical couplers, 11 is a variable optical attenuator, 12
Is a differential amplifier.

The basic configuration is composed of an optical fiber amplifier whose gain is controlled to be constant as shown in FIG. 20, a variable optical attenuator, and a feedback control circuit of the variable optical attenuator.
The feedback control circuit has the same configuration as in FIG.
Only the signal light that is the optical bandpass filter 10 is extracted, its power is monitored, and the attenuation of the variable optical attenuator 11 is controlled so that its value is always constant. The gain is adjusted by changing the attenuation of the variable attenuator instead of the power of the pump laser, so that the output level can be kept constant even with fluctuations in the number of channels and fluctuations in span loss. The gain flatness is also maintained because the gain does not change. Generally, when such gain control is performed, a desired output power is obtained by compensating for excess loss caused by the variable optical attenuator.
As shown in FIG. 3, two stages of constant gain control optical amplifiers (optical fiber amplifiers) are connected, and a variable optical attenuator is arranged in the middle stage. As shown in FIG. 24, the optical coupler may be disposed after the constant gain control optical fiber amplifier in the subsequent stage.

[0008]

FIG. 23 and FIG.
In the configuration (1), since a variable optical attenuator for gain adjustment is inserted in the middle stage in advance, there is a problem that the loss is excessive and the noise characteristic of the wavelength division multiplexing optical transmission system is reduced.

Normally, these optical fiber amplifiers are connected in multiple stages to construct an optical transmission system.
There is also a problem that deviations from design values gradually accumulate due to polarization dependence, wavelength dependence, and the like of the variable optical attenuator. Therefore, it is desirable from the viewpoint of system design that such optical components should not be inserted into the transmission line as much as possible.However, as described above, when an attempt is made to adjust the gain of an optical fiber amplifier without using a variable optical attenuator for gain adjustment. In addition, there is a problem that the gain flatness cannot be suppressed small.

It is an object of the present invention to provide a Raman distributed amplifier by performing automatic output level control so as not to use a variable optical attenuator for gain adjustment, to cope with fluctuations in the number of channels, fluctuations in span loss, etc. It is an object of the present invention to provide a wavelength division multiplexing optical transmission system that can maintain flatness and has extremely good noise characteristics.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0012]

The outline of a typical invention among the inventions disclosed in the present application will be briefly described as follows.

(1) A wavelength division multiplexing optical transmission system including an optical amplifier for amplifying a plurality of optical signals which are wavelength division multiplexed and propagate in one optical fiber, wherein a part or all of the optical amplifier is provided. A Raman distribution amplifier, wherein the Raman distribution amplifier injects optical power into the optical fiber transmission line as a transmission medium of the wavelength division multiplexed optical signal and Raman distribution amplification. One or two pumping lasers having the same pumping wavelength to generate an action, and a pumping laser disposed downstream of the optical fiber transmission line for injecting light emitted from the pumping laser into the optical fiber transmission line. An optical multiplexing unit, an optical branching unit disposed downstream of the optical multiplexing unit, for extracting a part of the wavelength multiplexed optical signal, and using the light extracted by the optical branching unit, And controls the output power of the amplifier pump laser comprises a gain control means for automatic output level control of the wavelength-multiplexed optical signal.

(2) The gain control means includes an optical filter for extracting light having a desired wavelength from the light extracted by the optical branching means, and a light intensity detection means for detecting the power of the light extracted by the optical filter. And feedback control means for controlling the power of the Raman distribution amplification pumping laser so that the light power obtained by the light intensity detection means is at a desired level.

(3) The gain control means includes a wavelength number detecting means for detecting a wavelength number of the optical signal from the light extracted by the optical branching means, and a total of the optical signal from the light extracted by the optical branching means. Light intensity detecting means for detecting power, calculating means for calculating an average light power per wavelength from the number of wavelengths and the total power obtained from the wavelength number detecting means and the light intensity detecting means, and the calculating means There is feedback control means for controlling the power of the Raman distribution amplification pump laser so that the obtained average optical power is at a desired level.

(4) The gain control means includes a wavelength number detecting means for detecting the number of wavelengths of the optical signal from the light extracted by the optical splitting means, and a total of the optical signal from the light extracted by the optical splitting means. Light intensity detection means for detecting power, feedback control means for controlling the power of the Raman distribution amplification pumping laser such that the total power obtained from the light intensity detection means is at a desired level, and the wavelength number detection means Adjusting means for adjusting a desired level in the feedback control means according to the number of wavelengths obtained by the above.

(5) The gain control means comprises: an optical demultiplexing means for demultiplexing the wavelength-division multiplexed optical signal extracted by the optical branching means for each wavelength; and a demultiplexing means for each wavelength obtained by the optical demultiplexing means. A plurality of light intensity detection means for individually detecting the power of the optical signal, and a maximum value selection means for selecting only the maximum detection signal from among the plurality of detection signals obtained from the plurality of light intensity detection means, There is provided feedback control means for controlling the power of the Raman distribution amplification pump laser so that the detection signal selected by the maximum value selection means has a desired level.

(6) A wavelength division multiplexing optical transmission system including an optical amplifier for amplifying a plurality of optical signals which are wavelength division multiplexed and propagate in one optical fiber, wherein a part or all of the optical amplifier is provided. A Raman distribution amplifier, wherein the Raman distribution amplifier is an optical fiber transmission line that is a transmission medium of the wavelength division multiplexed optical signal, and an optical fiber that is a transmission medium of the optical wavelength division multiplexed optical signal. A plurality of pump lasers having different pump wavelengths for injecting optical power into a transmission path and generating a Raman distribution amplifying action, and a second optical coupler for multiplexing lights having different wavelengths obtained from the plurality of pump lasers. A first optical multiplexing means disposed downstream of the optical fiber transmission line for injecting light transmitted from the second optical multiplexing means into the optical fiber transmission line; of An optical branching unit that is disposed at a stage subsequent to the multiplexing unit and extracts a part of the wavelength multiplexed optical signal, and controls the output power of the Raman distribution amplification pumping laser by using the light extracted by the optical branching unit. And a gain control means for performing automatic output level constant control of the wavelength multiplexed optical signal.

(7) In the wavelength-division multiplexing optical transmission system of the means 6, the gain control means comprises N (N is a natural number of 2 or more) light having a desired wavelength from the light extracted by the optical branching means. Optical demultiplexing means for extracting light, and N for individually detecting the power of the light extracted by the optical demultiplexing means.
M (M is a natural number of 2 or more) feedback control signals are extracted using the N light intensity detection means and the N detection signals obtained by the N light intensity detection means, and A plurality of feedback control means for controlling the power of a plurality of Raman distribution amplification pump lasers having different excitation wavelengths, wherein the gain control means comprises a plurality of Raman distribution amplification pump lasers having different excitation wavelength numbers. Is L (L
Is a natural number of 2 or more), the number N of detection signals and the number M of feedback control signals satisfy N = M = L.

(8) In the wavelength division multiplexing optical transmission system of the means 7, the gain control means comprises N (N is a natural number of 2 or more) light having a desired wavelength from the light extracted by the optical branching means. Optical demultiplexing means for extracting light, and N for individually detecting the power of the light extracted by the optical demultiplexing means.
Light intensity detection means and N light powers obtained by the N light intensity detection means are used as M (M = N) feedback control signals, and the levels of the M feedback control signals are all It has L (L = M = N) feedback control means for individually controlling a plurality of pumping lasers for Raman distribution amplification so as to have a set desired level.

(9) In the wavelength-division multiplexing optical transmission system of the means 6, the gain control means comprises N (N is a natural number of 2 or more) light of a desired wavelength from the light extracted by the optical branching means. Light demultiplexing means for extracting light, N light intensity detection means for individually detecting the intensity of light extracted by the light demultiplexing means, and N detection lights obtained by the N light intensity detection means Control signal generating means for extracting M (M is a natural number of 2 or more) feedback control signals using a signal; and a plurality of pump signals having different excitation wavelengths using the M feedback control signals obtained from the control signal generating means. A plurality of feedback control means for controlling the power of the Raman distribution amplification pumping laser, wherein the gain control means comprises: (L is a natural number of 2 or more) when the detection signal number N and the feedback control signal number M is N> M =
L is satisfied.

(10) In the wavelength-division multiplexing optical transmission system of the means 9, the gain control means comprises N (N is a natural number of 2 or more) light of a desired wavelength from the light extracted by the optical branching means. Light demultiplexing means for extracting light, N light intensity detection means for individually detecting the power of the light extracted by the light demultiplexing means, and N light beams obtained by the N light intensity detection means One or M total power / wavelength number detecting means for detecting the total power of the optical signal in each wavelength region and the number of wavelengths of the optical signal in each wavelength region in a predetermined different wavelength region from the power; , Said 1
One or M calculating means for calculating an average optical power per wavelength in each wavelength region from the total power and the number of wavelengths obtained by one or M total power / wavelength number detecting means; L (L = M) for individually controlling the power of a plurality of Raman distribution amplification pumping lasers so that the average optical power in each of the M wavelength regions obtained by the means is at a set desired level. Feedback control means.

(11) In the wavelength-division multiplexing optical transmission system of the means 9, the gain control means comprises N (N is a natural number of 2 or more) light of a desired wavelength from the light extracted by the optical branching means. Light demultiplexing means for extracting light, N light intensity detection means for individually detecting the power of the light extracted by the light demultiplexing means, and N light beams obtained by the N light intensity detection means One or M total power / wavelength number detecting means for detecting the total power of the optical signal in each wavelength region and the number of wavelengths of the optical signal in each wavelength region in a predetermined different wavelength region from the power; The powers of a plurality of Raman distribution amplification pump lasers are individually controlled such that the total power of the optical signal in each wavelength region obtained by the total power / wavelength number detecting means is all the desired level set. L (L = M) feedback control means, and the L feedback means according to the number of wavelengths of the optical signal in each wavelength region obtained by the one or M total power / wavelength number detection means. And one or L adjusting means for individually adjusting a desired level in the control means.

(12) In the wavelength division multiplexing optical transmission system of the means 9, the gain control means comprises N (N is a natural number of 2 or more) light of a desired wavelength from the light extracted by the optical branching means. Light demultiplexing means for extracting light, N light intensity detection means for individually detecting the power of the light extracted by the light demultiplexing means, and N light beams obtained by the N light intensity detection means One or M maximum optical power selecting means for selecting only the maximum optical power in each wavelength region in a predetermined different wavelength region from the power;
The powers of a plurality of Raman distribution amplification pump lasers are individually adjusted so that the maximum optical powers in each of the M wavelength regions obtained by the one or M maximum optical power selecting means are all at the set desired levels. L (L = M) feedback control means.

That is, the first feature of the wavelength division multiplexing optical transmission system of the present invention is that a Raman distribution amplifier is used.

FIGS. 1 and 2 show a conventional configuration of a Raman distributed amplifier according to the present invention. In FIG. 1 and FIG.
0 is a conventional Raman distribution amplifier, 301 is a conventional gain stabilized Raman distribution amplifier, 1 is an optical fiber transmission line, 5 is an optical multiplexer, 6 is a photodetector, 9 is a pump laser, 9M is a laser drive circuit, and 12 is A differential amplifier (drive circuit), ML is a wavelength multiplexed optical signal, LS is a laser beam, and SS is a reference value.

The Raman distribution amplification is, as shown in FIG.
This is a technique in which pumping light is injected into the optical fiber transmission line 1 so that the optical fiber transmission line 1 is also used as an amplification medium to amplify optical signals in a distributed manner. This Raman distribution amplifier 3
The advantage of 00 is that it has much lower noise than the optical fiber amplifier described above. Therefore, using the Raman distribution amplifier 300 can construct a wavelength multiplexing optical transmission system having much better noise characteristics than using the conventional optical fiber amplifier (constant gain control optical fiber amplifier) 100.

A second feature of the present invention is that the Raman distributed amplifier 300 is subjected to automatic output level control. Since the gain of the Raman distributed amplifier 300 is proportional to the power of the pump laser 9, generally, as shown in FIG. 2, the power of the pump laser 9 is monitored and the gain is stabilized by keeping the power constant. Raman distributed amplifier 301 can be constructed. However, the gain actually obtained greatly depends on the spectrum shape of the pump laser 9, the length of the optical fiber transmission line, the variation in the core diameter of the optical fiber, and the like. Therefore, as shown in FIG. Even if a certain reference value is set, the same gain is not always obtained. Further, even if the reference value is set so that a desired gain is obtained when the system is introduced, it is not possible to cope with a dynamic loss fluctuation due to a temperature change, a secular change or a bending of the transmission line.

In the present invention, such fluctuations are automatically compensated by monitoring the output level of the wavelength multiplexed optical signal and performing feedback control on the output power of the pump laser 9 of the Raman distribution amplifier, so that the desired optical signal is always obtained. A wavelength division multiplexing optical transmission system for obtaining a signal output can be constructed. This is because the Raman distribution amplifier has a wider gain band than the optical fiber amplifier, and the gain flatness is kept almost constant even if the gain is changed by changing the output power of the pump laser 9. Is to make effective use of the features that are not available (references:
Hansen et al., “Capacity upgrades of transmission syst
ems by Raman amplification, ”IEEE Photon.Technol.L
ett., vol. 9, no2, 1997, pp. 262-264.).

Further, since the output level is controlled to be constant, the variable optical attenuator described in the conventional example of the optical fiber amplifier is not required, and the deterioration of the noise characteristic due to this can be avoided.

As described above, by performing the automatic output level constant control on the Raman distribution amplifier, the flatness of the gain can be maintained, and the variable number of channels and the span loss can be dealt with without using the variable optical attenuator for the gain adjustment. Thus, it is possible to construct a wavelength division multiplexing optical transmission system having extremely good noise characteristics. Further, the Raman distribution amplifier has a feature that the gain band can be freely selected according to the wavelength of the pump light source.

Hereinafter, the present invention will be described with reference to the drawings.
Both embodiments (examples) will be described in detail.

In all the drawings for describing the embodiments (examples), those having the same functions are denoted by the same reference numerals, and their repeated description will be omitted.

[0034]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIGS.
FIG. 1 is a schematic diagram illustrating a schematic configuration of a Raman distributed amplifier with automatic output level constant control used in a wavelength division multiplexing optical transmission system according to a first embodiment of the present invention. 3 to 6, 100
Is a constant gain control optical fiber amplifier, 302 is an automatic output level constant control Raman distribution amplifier (Raman distribution amplifier),
1 is an optical fiber transmission line, 2 is an optical coupler, 5 is an optical multiplexer,
6 is a photodetector, 9, 9A and 9B are pump lasers, 10 is an optical bandpass filter, 12 is a differential amplifier, 13 is a gain equalizer, 14 is a polarization combining module, ML is a wavelength multiplexed optical signal, LS is a laser beam, and SS is a reference value.

As shown in FIG. 3, the Raman distributed amplifier 302 with the automatic output level constant control according to the first embodiment includes an optical fiber transmission line 1, an optical coupler 2, an optical multiplexer 5, an optical receiver 6, an excitation laser 9, an optical laser 9, It comprises a bandpass filter 10 and a differential amplifier 12.

In FIG. 3, the wavelength-multiplexed optical signal ML that has passed through the optical fiber transmission line 1 is extracted by the optical coupler 2 and guided to the optical bandpass filter 10. An optical signal having a desired wavelength is extracted by the optical bandpass filter 10, and its power is detected by the optical receiver 6. The difference between the detected value and the reference value SS is detected by the differential amplifier 12, and the power of the pump laser 9 is controlled to change the gain of the Raman distribution amplifier so that the difference becomes zero (0). With this configuration, the output level of the optical signal of a desired wavelength extracted by the optical bandpass filter 10 can be always kept constant without depending on the optical fiber transmission line length, variation in the core diameter, temperature change, and the like.

The Raman distribution amplifier is a pump laser 9
Even if the gain is changed by changing the power of the optical fiber amplifier, the gain flatness is substantially constant, which is not a feature of the optical fiber amplifier. Therefore, even if such feedback control is performed, the gain flatness can be maintained.

A control signal may be transmitted simultaneously with the wavelength-multiplexed optical signal ML, and the control signal may be extracted by the optical bandpass filter 10 to control the excitation laser 9. Further, the optical bandpass filter 10 may have any configuration as long as it can extract an optical signal of a desired wavelength.
As shown in FIG. 7, a circulator 21 and a fiber grating 22 may be combined.

FIG. 3 shows an automatic output level control Raman distribution amplifier 302 and a gain control optical fiber amplifier 10.
0, and the optical coupler 2 includes an optical multiplexer 5 for injecting pump power into the optical fiber transmission line 1.
And the constant gain control optical fiber amplifier 100. However, as shown in FIG. Further, as shown in FIG. 5, a gain equalizer 13 may be used to improve gain flatness. Further, if the loss of the optical fiber transmission line 1 and the gain of the automatic output level constant control Raman distribution amplifier 302 can be made equal by using the pump laser 9 having high output power, the gain control optical fiber amplifier 10
By removing 0, a wavelength division multiplexing optical transmission system using only the Raman distribution amplifier may be constructed.

Even when two pump lasers are polarization multiplexed as one means for obtaining high pump power, if the pump wavelengths are the same, the control circuit is not changed at all,
As shown in FIG. 6, the powers of the two pump lasers 9A and 9B may be controlled so that the value obtained from one differential amplifier 12 becomes zero (0).

In the following embodiments, the position of the optical coupler 2 may be any position, the gain equalizer 13 may be used, and the automatic output level may be kept constant unless otherwise specified. When the gain of the control Raman distributed amplifier 302 is sufficiently large, the post-stage constant gain control optical fiber amplifier 100 may be omitted, and even when two pump lasers having the same pump wavelength are polarization multiplexed,
One differential amplifier 1 without changing the control circuit
The powers of the two pump lasers 9A and 9B may be controlled so that the value obtained from 2 becomes zero (0).

(Embodiment 2) FIG. 8 is a schematic diagram showing a schematic configuration of an automatic output level constant control Raman distribution amplifier according to Embodiment 2 of the present invention.

As shown in FIG. 8, the automatic output level constant control Raman distribution amplifier (Raman distribution amplifier) 303 according to the second embodiment includes an optical fiber transmission line 1, optical couplers 2A and 2A.
B, an optical multiplexer 5, a light receiver 6, an excitation laser 9, a differential amplifier 12, a wavelength number detection circuit 14, and a divider 16. The optical coupler 2B, the light receiver 6, and the wavelength number detecting circuit 14 constitute a total power / wavelength number detecting means 15.

In FIG. 8, the optical signal extracted by the optical coupler 2A is branched again by the optical coupler 2B, one of which is sent to the light receiver 6 of the total power / wavelength number detecting means 15 and the other is sent to the wavelength number detecting circuit 14. Then, the total optical signal power Psig and the number of wavelengths n are detected. Divider 16
The average optical signal power per channel Psig / n
Is calculated, and the excitation laser 9 is controlled so that the value is always constant. Therefore, with this configuration, the average optical signal power per channel can always be kept constant.

The total power / wavelength number detecting means 15
Is not limited to this configuration at all, and it goes without saying that it may be realized using an optical spectrum analyzer or the like.

(Embodiment 3) FIG. 9 is a schematic diagram showing a schematic configuration of a Raman distributed amplifier with constant output level control according to Embodiment 3 of the present invention.

As shown in FIG. 9, the automatic output level control Raman distribution amplifier (Raman distribution amplifier) 304 according to the third embodiment includes an optical fiber transmission line 1, optical couplers 2A and 2A.
B, an optical multiplexer 5, a light receiver 6, an excitation laser 9, a differential amplifier 12, a wavelength number detection circuit 14A, a switch 17, and a memory 18. The optical coupler 2B, the light receiver 6, and the wavelength number detecting circuit 14A constitute a total power / wavelength number detecting means 15.

In FIG. 9, the total power / wavelength number detecting means 15 is the same as that of the second embodiment, but the method of using the detected value is different. The detected total power is guided to the differential amplifier 12, and the power of the pump laser 9 is controlled so that the value becomes constant. At that time, for example,
When the number of wavelengths n is halved, the total optical power must also be halved to keep the average optical signal power per channel constant. This means that the reference value referred to by the differential amplifier 12 differs according to the number of wavelengths n.

In the third embodiment, the memory 18 (memory areas A1, A2,..., An) stores a reference value SS corresponding to the number of wavelengths in advance, and switches the switch 17 according to the detected number of wavelengths. The reference value SS is read according to the number of switching wavelengths (so that the output power per channel becomes constant). With such a configuration, the average optical signal power per channel can always be kept constant, as in the second embodiment.

The total power / wavelength number detecting means 15
Is not limited to this configuration at all, and it goes without saying that it may be realized using an optical spectrum analyzer or the like.

(Embodiment 4) FIG. 10 is a schematic diagram showing a schematic configuration of an automatic output level constant control Raman distribution amplifier according to Embodiment 4 of the present invention.

As shown in FIG. 10, the automatic output level constant control Raman distribution amplifier (Raman distribution amplifier) 305 of the fourth embodiment includes an optical fiber transmission line 1, an optical coupler 2, an optical multiplexer 5, an optical receiver 6A1, ..., 6An, pump laser 9, differential amplifier 12, optical demultiplexer 19, maximum optical power selection circuit 2
0.

In FIG. 10, the wavelength-division multiplexed optical signal extracted by the optical coupler 2 is demultiplexed into each wavelength, and
Each optical power is detected by A1,..., 6An. The maximum light power selection circuit 20 selects only the largest value from the detected light powers. The difference between the selected maximum value and the reference value SS (corresponding to the desired output power in the optical fiber amplifier) is detected by the differential amplifier 12, and the power of the pump laser 9 is set so that the difference becomes zero (0). Control. By employing this method, the maximum power of the wavelength multiplexed signal light can be always kept constant.

(Embodiment 5) FIG. 11 is a schematic diagram showing a schematic configuration of a Raman distributed amplifier with constant output level control according to Embodiment 5 of the present invention, and FIG. 12 is a multi-wavelength pump Raman realized by Embodiment 5 of the present invention. FIG. 3 is a diagram schematically illustrating a gain profile and a gain control method of the distributed amplifier.

As shown in FIG. 11, an automatic output level constant control Raman distribution amplifier (Raman distribution amplifier) 306 according to the fifth embodiment includes an optical fiber transmission line 1, an optical coupler 2, optical multiplexers 5A and 5B, a light receiver. 6A, 6B, excitation laser 9A,
9B, the differential amplifiers 12A and 12B, and the optical demultiplexer 19.

As shown in FIG. 11, the Raman distributed amplifier (Raman distributed amplifier) 306 of the fifth embodiment differs from the first to fourth embodiments in that a plurality of pump wavelengths are different. Excitation lasers 9A, 9
B, and individually controls the powers of a plurality of pump lasers 9A and 9B having different wavelengths.

In general, one of the great features of the Raman distribution amplifier is that the gain band can be arbitrarily selected, that is, a gain peak appears on the long wavelength side about 100 nm away from the pump wavelength. Accordingly, FIG. 12 schematically shows a gain profile when pumping is performed at multiple wavelengths. In FIG. 12, as an example, the case where the number of excitation wavelengths is 2 and the center wavelength of excitation is 10 nm away is assumed. A method of controlling the gain of such a multi-wavelength pumped Raman distribution amplifier will be described below with reference to FIGS.

Here, a case where N = M = L = 2 will be described as an example. Here, N is the number of optical signals (the number of detection signals) monitored to perform gain control from the wavelength multiplexed optical signals, and M is the number of feedback control signals actually used as feedback signals to the pump laser. And L is the number of excitation wavelengths of the excitation laser (N,
M and L are natural numbers of 2 or more). As shown in FIG. 11, the wavelength division multiplexed optical signal branched by the optical coupler 2 is
9, where two optical signals (wavelengths λa1, λa
2) is taken out.

The optical signal of the wavelength λa1 is
The optical signal of wavelength λa2 is located near the peak of the gain profile by the pump laser 9B (FIG. 12).
reference). The strengths of the extracted optical signals of the wavelengths λa1 and λa2 are individually detected by the two light receivers 6A and 6B. These two detected values and the reference values SS1 and SS2
Is detected by the two differential amplifiers 12A and 12B, and the pump laser 9A is set so that the difference becomes zero (0).
And 9B are controlled independently.

With this configuration, even when pumping is performed at multiple wavelengths, the output levels of the optical signals of the wavelengths λa1 and λa2 can be constantly maintained while maintaining gain flatness.

The optical demultiplexer 19 may be anything as long as it can extract a desired wavelength. For example, as shown in FIG. 13, a circulator 21A, 21B and a fiber grating 22A, 22B are combined. Is also good.

In FIGS. 11 to 13, N = M = L
Although the case of = 2 has been described, the present invention is not limited to this and can be extended to the case of N = M = L = k (k is a natural number of 3 or more) as shown in FIG. 11 to 13 are that light of k wavelengths is extracted by the optical demultiplexer 19, and that each of the optical demultiplexer 19 includes k light receivers, differential amplifiers, and pump lasers. , The operating principle is the same.

Of course, the optical demultiplexer 19 may be of any type as long as it can extract k desired wavelengths, and may be configured using k circulators and k fiber gratings. In addition, as shown in FIG. 15, not only the wavelength multiplexing of the pumping laser to improve the pumping power, but also the polarization multiplexing of two pumping lasers having the same pumping wavelength as described in the first embodiment. There may be additional configurations. Even in such a case, as described in the first embodiment, without changing the control circuit at all, two signals having the same pumping wavelength can be used.
One pump laser can be driven and controlled by one differential amplifier. FIG. 15 can naturally be extended to the case of N = M = L = k.

(Embodiment 6) FIG. 16 is a schematic diagram showing a schematic configuration of a Raman distributed amplifier of constant output level control according to Embodiment 6 of the present invention.

The automatic output level constant control Raman distribution amplifier 309 of the sixth embodiment is different from that of the fifth embodiment in that the relationship between the number N of detection signals, the number M of feedback control signals, and the number L of excitation wavelengths is N = N. Not M = L, N> M
= L. That is, each of the excitation lasers 9A, 9A
A major feature is that a plurality of optical signals are used to obtain one feedback control signal for controlling the power of B,..., 9L.

FIG. 17 is a schematic diagram of a method for controlling the gain profile and gain of a Raman distributed amplifier using L pump lasers. In FIG. 17, pump lasers 9A, 9B,
,..., 9L (i, j, k are natural numbers) are used to obtain the respective feedback control signals. If any one of i, j,..., k is 2 or more, N
> M (all 1s correspond to the fifth embodiment).

In FIG. 17, it is assumed that the optical signals to be detected do not overlap, but they may overlap if necessary. Also, not all optical signals need be used. The method shown in FIG. 16 basically uses the method shown in the second embodiment. The wavelength division multiplexed optical signal split by the optical coupler 2 is split by the optical splitter 19 into a plurality of light beams having desired wavelengths. .., 6Ai, 6B1,...
, 6Bj, 6L1,..., 6Lk are individually detected.

In order to obtain a feedback control signal for controlling the pump laser 9A, the total power / wavelength number detecting means 15A calculates the total power, which is the sum of the powers of the respective lights obtained by the photodetectors 6A1 to 6Ai. The power and the number (wavelength number) of the i light receivers 6A1,..., 6Ai to which the optical signal is input are calculated.
An average power obtained by dividing the total power by the number of wavelengths is calculated by the divider 16A, and the pump laser 9A is driven and controlled by the differential amplifier 12A so that the average power is constant.

The same control is performed for the other excitation lasers 9B,..., 9L by using j,. By such means, even in the case of multi-wavelength pumping, it is possible to realize an automatic output level constant control Raman distribution amplifier 309 in which the average optical signal power is substantially the same as in the case of single wavelength pumping. FIG.
As described in 5, it is also possible to add a pump laser having the same pump wavelength by polarization multiplexing, and to adopt a configuration in which two differentially multiplexed pump lasers are controlled by one differential amplifier. Of course.

FIG. 16 shows a case where L (= M) total power / wavelength detectors and L dividers are used. However, by sharing the total power / wavelength detector and dividers, Of course, a configuration in which the same function is realized by one total power / wavelength number detecting means and one divider may be used.

(Embodiment 7) FIG. 18 is a schematic diagram showing a schematic configuration of an automatic output level constant control Raman distribution amplifier according to Embodiment 7 of the present invention, wherein 15A, 15B,.
15L is a total power / wavelength number detecting means, 17A, 1
, 17L are switches, 18A, 18B, ...,
Reference numeral 18L denotes a memory, and 310 denotes a Raman distribution amplifier of the seventh embodiment.

The seventh embodiment also relates to the case where N> M = L, and relates to a means for realizing a control method for keeping the average optical signal power constant, similar to the sixth embodiment. The automatic output level constant control Raman distribution amplifier 310 of the seventh embodiment is exactly the same as the sixth embodiment up to the point where the total power and the number of wavelengths are detected.
Use of the two values is different. The method described here basically applies the third embodiment, and has a configuration in which the switches 17A,..., 17L are switched according to the number of wavelengths to change the reference value. 6 and different.

By changing the reference value according to the number of wavelengths in this manner, even when the number of wavelengths changes, the same automatic output level control Raman as in the sixth embodiment, in which the average optical signal power is constant. The distributed hat 310 can be realized. As described with reference to FIG. 15, pump lasers having the same pump wavelength can be added by polarization multiplexing. Two pump lasers to be polarization multiplexed can be controlled by one differential amplifier. Of course, it is also possible to adopt a configuration that performs the above.

FIG. 18 shows the case where L (= M) total power / wavelength detecting means, switches and memories are used, respectively. Means, one switch, and one memory may of course be configured to realize the same function.

(Embodiment 8) FIG. 19 is a schematic diagram showing a schematic configuration of a Raman distributed amplifier with constant automatic output level control according to Embodiment 8 of the present invention, wherein 6A1,..., 6Ai,
6B1, 6Bj, 6L1,..., 6Lk are light receivers,
, 9L are pump lasers, 12A, 12
, 12L are differential amplifiers, 20A, 20B,.
20L is a maximum optical power selection circuit.

The principle of the control according to the eighth embodiment will be described with reference to FIG. The method shown here basically employs the method of keeping the maximum optical signal power described in the fourth embodiment constant. The wavelength division multiplexed optical signal split by the optical coupler 2 is split by the optical splitter 19 into a plurality of light beams having desired wavelengths. .., 6Bi, 6L1,..., 6Bj, 6L1,
.., Individually detected at 6Lk. In order to obtain a feedback control signal for controlling the excitation laser 9A, the maximum optical power selection circuit 20A selects the light receiver 6A1 from the i wavelengths near the peak of the gain profile of the excitation laser 9A (see FIG. 17). ,..., 6Ai, only the maximum optical power is extracted from the optical power detected.
The value is used as a feedback control signal for the differential amplifier 12.
A, and controls the excitation laser 9A so that the value becomes constant. Similarly, for the other pump lasers 9B,..., 9L, from the j,..., K wavelengths near the peak of the gain profile of each pump laser, each of the maximum optical power selection circuits 20B,. , 20L, only the maximum optical power is extracted as a control signal for each of the excitation lasers 9B,..., 9L. Then, the control signal is guided to each of the differential amplifiers 12B,..., 12L, and the respective excitation lasers 9B,.
By such means, even in the case of multi-wavelength excitation,
It is possible to realize a Raman distribution amplifier that keeps the maximum optical signal power constant, almost the same as in the case of single wavelength pumping.

As described with reference to FIG. 15, a pump laser having the same pump wavelength can be added by polarization multiplexing, and one differential pump is used for two pump lasers to be polarization multiplexed. A configuration controlled by an amplifier may be adopted.

FIG. 19 shows that the maximum optical power selection circuit is set to L (=
Although the case of using M) is shown, it is of course possible to adopt a configuration in which the same function is realized by one maximum optical power selection circuit by sharing this.

Embodiments (Examples) of the Present Invention
However, the present invention is not limited to the above-described embodiment, but may be variously modified without departing from the gist of the invention.

[0080]

The effects obtained by typical aspects of the invention disclosed in the present application will be briefly described as follows.

(1) By applying a Raman distribution amplifier to a wavelength division multiplexing optical transmission system, a wavelength having much better noise characteristics than a wavelength division multiplexing optical transmission system comprising a conventional optical fiber amplifier not using a Raman distribution amplifier. A multiplex optical transmission system can be constructed.

(2) By performing gain control on the Raman distribution amplifier, fluctuations such as fluctuations in the number of channels and fluctuations in span loss can be compensated. Therefore, it is possible to construct a wavelength division multiplexing optical transmission system capable of always obtaining a constant optical signal output. it can.

(3) Since the Raman distribution amplifier has a characteristic that the gain flatness is kept almost constant even when the gain is changed, which is not included in the conventional optical fiber amplifier, the wavelength multiplexed signal is added to the Raman distribution amplifier. By performing automatic power level control that monitors and controls the power of the pump laser,
A variable optical attenuator for gain adjustment, which was conventionally required, can be reduced, and deterioration of noise characteristics due to this can be avoided. Also, by reducing the number of variable optical attenuators, it is not necessary to consider the polarization dependence and wavelength dependence of the variable optical attenuator, which is desirable from the viewpoint of system design.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a conventional Raman distributed amplifier according to the present invention.

FIG. 2 is a schematic diagram showing another configuration of the conventional Raman distributed amplifier according to the present invention.

FIG. 3 is a schematic diagram showing a schematic configuration of a Raman distributed amplifier with constant automatic output level control used in the wavelength division multiplexing optical transmission system according to the first embodiment of the present invention.

FIG. 4 is a schematic diagram showing a schematic configuration of another automatic output level constant control Raman distribution amplifier according to the first embodiment.

FIG. 5 is a schematic diagram showing a schematic configuration of another automatic output level constant control Raman distribution amplifier according to the first embodiment.

FIG. 6 is a schematic diagram showing a schematic configuration of another automatic output level constant control Raman distribution amplifier of the first embodiment.

FIG. 7 is a diagram illustrating an example of an optical bandpass filter according to the first embodiment.

FIG. 8 is a schematic diagram illustrating a schematic configuration of a Raman distributed amplifier with constant automatic output level control according to a second embodiment of the present invention.

FIG. 9 is a schematic diagram showing a schematic configuration of a Raman distributed amplifier with constant automatic output level control according to a third embodiment of the present invention.

FIG. 10 is a schematic diagram showing a schematic configuration of a Raman distributed amplifier with constant output level control according to a fourth embodiment of the present invention.

FIG. 11 is a schematic diagram showing a schematic configuration of a Raman distributed amplifier with constant automatic output level control according to a fifth embodiment of the present invention.

FIG. 12 is a diagram schematically illustrating a gain profile and a gain control method when pumping at multiple wavelengths according to the fifth embodiment.

FIG. 13 is a diagram showing a configuration in which a circulator and a fiber grating are combined as an optical demultiplexer according to the fifth embodiment.

FIG. 14 is a schematic diagram showing a schematic configuration of another automatic output level constant control Raman distributed amplifier according to Embodiment 5 of the present invention.

FIG. 15 is a schematic diagram showing a schematic configuration of another automatic output level constant control Raman distribution amplifier according to Embodiment 5 of the present invention.

FIG. 16 is a schematic diagram illustrating a schematic configuration of a Raman distributed amplifier with constant automatic output level control according to a sixth embodiment of the present invention.

FIG. 17 is a diagram schematically illustrating a gain profile and a gain control method of a Raman distributed amplifier using L pump lasers according to the sixth, seventh, and eighth embodiments.

FIG. 18 is a schematic diagram showing a schematic configuration of a Raman distributed amplifier having constant automatic output level control according to a seventh embodiment of the present invention.

FIG. 19 is a schematic diagram showing a schematic configuration of a Raman distributed amplifier with constant automatic output level control according to an eighth embodiment of the present invention.

FIG. 20 is a schematic diagram showing a schematic configuration of an optical fiber amplifier used in a conventional wavelength division multiplexing optical transmission system.

FIG. 21 is a schematic diagram showing a schematic configuration of another optical fiber amplifier used in a conventional wavelength division multiplexing optical transmission system.

FIG. 22 is a schematic diagram showing a schematic configuration of another optical fiber amplifier used in a conventional wavelength division multiplexing optical transmission system.

FIG. 23 is a schematic diagram showing a schematic configuration of another optical fiber amplifier used in a conventional wavelength division multiplexing optical transmission system.

FIG. 24 is a schematic diagram showing a schematic configuration of another optical fiber amplifier used in a conventional wavelength division multiplexing optical transmission system.

[Explanation of symbols]

100: constant gain control optical amplifier; 300: Raman distributed amplifier; 301: gain stabilized Raman distributed amplifier;
311 ... Raman distributed amplifier with automatic output level constant control,
1, 1A, 1B ... optical fiber transmission line, 2, 2A, 2B ...
Optical coupler, 3A, 3B: optical isolator, 4: rare earth-doped optical fiber, 5, 5A, 5B: optical multiplexer, 6, 6A,
6A1, 6Ai, 6An, 6B, 6B1, 6Bj, 6
K, 6L1, 6Lk: photodetector, 7: logarithmic calculator, 8: comparator, 9, 9A, 9B, 9A ', 9B', 9K, 9L ...
Excitation laser, 9M laser drive circuit, 10 optical bandpass filter, 11 variable optical attenuator, 12, 12
A, 12B, 12K, 12L: differential amplifier, 13: gain equalizer, 14, 14A: wavelength number detection circuit, 15, 15
A, 15B, 15L: total power / wavelength number detecting means, 16, 16A, 16B, 16L: divider, 17,
17A, 17B to 17L: Switch, 18, 18A to 1
8L: memory, 19: optical demultiplexer, 20, 20A, 20
B, 20L... Maximum optical power selection circuit, 21, 21A, 2
1B: circulator, 22, 22A, 22B: fiber grating, 23, 23A, 23B: polarization combining module, ML: wavelength multiplexed optical signal, LS: laser light, SS, SS1, SS2, SSK, SSL: reference value .

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04B 10/17 10/16 H04J 14/00 14/02 (72) Inventor Koji Masuda Nishi-Shinjuku, Shinjuku-ku, Tokyo 3-19-2 Nippon Telegraph and Telephone Corporation (72) Inventor Shingo Kawai 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo F-term within Nippon Telegraph and Telephone Corporation 2K002 AA02 AB12 BA01 CA15 HA23 5F072 HH02 HH04 JJ20 QQ07 YY17 5K002 AA06 BA02 BA04 BA05 BA13 CA09 CA13 DA02 FA01

Claims (12)

[Claims] 1. A wavelength division multiplexing optical transmission system comprising an optical amplifier for amplifying a plurality of optical signals which are wavelength division multiplexed and propagate in one optical fiber, wherein a part or all of said optical amplifier is provided. Using a Raman distribution amplifier, the Raman distribution amplifier injects optical power into the optical fiber transmission line as a transmission medium of the wavelength division multiplexed optical signal, and a Raman distribution amplification function. One or two pumping lasers having the same pumping wavelength for generating a laser beam, and an optical combiner disposed downstream of the optical fiber transmission line for injecting light emitted from the excitation laser into the optical fiber transmission line. Wave means, disposed after the optical multiplexing means, an optical branching means for extracting a part of the wavelength multiplexed optical signal, using light extracted by the optical branching means,
A wavelength-division multiplexing optical transmission system, comprising: gain control means for controlling the output power of the Raman distribution amplification pumping laser and performing automatic output level control of the wavelength-division multiplexing optical signal. 2. An optical filter for extracting light having a desired wavelength from the light extracted by the optical branching means, and a light intensity detecting means for detecting the power of the light extracted by the optical filter. 2. A wavelength division multiplexing optical transmission according to claim 1, further comprising feedback control means for controlling the power of the Raman distribution amplification pumping laser so that the optical power obtained by said light intensity detecting means is at a desired level. system. 3. The gain control means includes: a wavelength number detecting means for detecting a wavelength number of an optical signal from the light extracted by the optical splitting means; and a total power of an optical signal from the light extracted by the optical splitting means. Light intensity detecting means for detecting the number of wavelengths, calculating means for calculating the average light power per wavelength from the number of wavelengths and the total power obtained from the light intensity detecting means, 2. The wavelength division multiplexing optical transmission system according to claim 1, further comprising feedback control means for controlling the power of the Raman distribution amplification pumping laser so that the obtained average optical power becomes a desired level. 4. The gain control means includes: a wavelength number detecting means for detecting a wavelength number of an optical signal from the light extracted by the optical splitting means; and a total power of an optical signal from the light extracted by the optical splitting means. Light intensity detecting means for detecting the power, the feedback control means for controlling the power of the Raman distribution amplification pumping laser so that the total power obtained from the light intensity detecting means is at a desired level, and the wavelength number detecting means 2. The wavelength division multiplexing optical transmission system according to claim 1, further comprising an adjusting unit that adjusts a desired level in said feedback control unit according to the obtained number of wavelengths. 5. The gain control means comprises: an optical demultiplexing means for demultiplexing the wavelength division multiplexed optical signal extracted by the optical branching means for each wavelength; and a light of each wavelength obtained by the optical demultiplexing means. A plurality of light intensity detection means for individually detecting signal power; a maximum value selection means for selecting only a maximum detection signal from a plurality of detection signals obtained from the plurality of light intensity detection means; and 2. The Raman distribution amplifier according to claim 1, further comprising feedback control means for controlling the power of the Raman distribution amplification pump laser so that the detection signal selected by the value selection means has a desired level. 6. A wavelength division multiplexing optical transmission system comprising an optical amplifier for amplifying a plurality of optical signals which are wavelength division multiplexed and propagate in one optical fiber, wherein a part or all of said optical amplifier is provided. A Raman distributed amplifier, wherein the Raman distributed amplifier comprises: an optical fiber transmission line that is a transmission medium of the wavelength division multiplexed optical signal; and an optical fiber transmission line that is a transmission medium of the optical wavelength division multiplexed optical signal. A plurality of pump lasers having different pump wavelengths for injecting optical power into a path and generating a Raman distribution amplifying function, and a second optical multiplexing device for multiplexing light having different wavelengths obtained from the plurality of pump lasers Means, a first optical multiplexing means disposed after the optical fiber transmission path, for injecting light transmitted from the second optical multiplexing means into the optical fiber transmission path, the first optical multiplexing means; Optical multiplexing An optical branching unit that is disposed at a stage subsequent to the unit and extracts a part of the wavelength multiplexed optical signal, and using the light extracted by the optical branching unit, controls the output power of the Raman distribution amplification pumping laser, A wavelength division multiplexing optical transmission system comprising a gain control means for performing automatic output level control of the wavelength division multiplexing optical signal. 7. The light demultiplexing means for extracting N (N is a natural number of 2 or more) light having a desired wavelength from the light extracted by the optical branching means, and the optical demultiplexing means. N light intensity detection means for individually detecting the power of the light extracted by the means, and M light intensity detection means (M is 2 or more) using the N detection signals obtained by the N light intensity detection means. A natural number), and a plurality of feedback control means for controlling the power of a plurality of pumping lasers for Raman distribution amplification having different pumping wavelengths by using the feedback control signal. In the Raman distribution amplification pump lasers, when the number of different pump wavelengths is L (L is a natural number of 2 or more), the number N of detection signals and the number M of feedback control signals satisfy N = M = L. Claim 6 WDM optical transmission system. 8. The optical demultiplexing means for extracting N (N is a natural number of 2 or more) light having a desired wavelength from the light extracted by the optical branching means, and the optical demultiplexing means. N light intensity detecting means for individually detecting the power of the light extracted by the means, and M (M = N) feedback control of the N light powers obtained by the N light intensity detecting means L (L = M = N) feedback control means for individually controlling a plurality of pumping lasers for Raman distribution amplification so that the levels of the M feedback control signals are all set to desired levels. The wavelength division multiplexing optical transmission system according to claim 7, comprising: 9. The light demultiplexing means for extracting N (N is a natural number of 2 or more) light having a desired wavelength from the light extracted by the optical branching means, and the optical demultiplexing means. N for individually detecting the intensity of light extracted by the means
Light intensity detecting means, and control signal generating means for extracting M (M is a natural number of 2 or more) feedback control signals using the N detection signals obtained by the N light intensity detecting means. A plurality of feedback control means for controlling the powers of a plurality of pumping lasers for Raman distribution amplification having different pumping wavelengths using M feedback control signals obtained from the control signal generating means; Is
In the plurality of Raman distribution amplification pump lasers, when the number of different pump wavelengths is L (L is a natural number of 2 or more),
The number N of detection signals and the number M of feedback control signals are N> M
7. The wavelength division multiplexing optical transmission system according to claim 6, wherein = L is satisfied. 10. The gain control means includes N light sources (N is a natural number of 2 or more) from the light taken out by the light branching means.
Light demultiplexing means for extracting light having a desired wavelength, N light intensity detection means for individually detecting the power of the light extracted by the light demultiplexing means, and N light intensity detection means From the obtained N optical powers, one or M total optical powers for detecting the total power of the optical signal in each wavelength region and the number of wavelengths of the optical signal in each wavelength region in a predetermined different wavelength region. A power / wavelength number detecting means, and a total power and wavelength number obtained by the one or M total power / wavelength number detecting means.
One or M arithmetic means for calculating the average optical power per wavelength, and a plurality of arithmetic means so that the average optical power in each of the M wavelength regions obtained by the arithmetic means are all at the set desired level. 10. The wavelength division multiplexed optical transmission system according to claim 9, further comprising L (L = M) feedback control means for individually controlling the power of the Raman distribution amplification pump laser. 11. The gain control means includes N light sources (N is a natural number of 2 or more) from the light extracted by the light branching means.
Light demultiplexing means for extracting light having a desired wavelength, N light intensity detection means for individually detecting the power of the light extracted by the light demultiplexing means, and N light intensity detection means From the obtained N optical powers, one or M total optical powers for detecting the total power of the optical signal in each wavelength region and the number of wavelengths of the optical signal in each wavelength region in a predetermined different wavelength region. Power / wavelength number detecting means, and a plurality of Raman distribution amplification pumping lasers so that the total power of the optical signal in each wavelength region obtained by the total power / wavelength number detecting means is all set to a desired level. L (L = M) feedback control means for individually controlling the powers of the optical signals, and according to the number of wavelengths of the optical signal in each wavelength region obtained by the one or M total power / wavelength number detecting means. L feedback One or L-number of adjusting means and the wavelength-multiplexed optical transmission system according to claim 9, wherein that it comprises the individually adjusted a desired level in the control means. 12. The gain control means comprises N light sources (N is a natural number of 2 or more) from the light taken out by the light branching means.
Light demultiplexing means for extracting light having a desired wavelength, N light intensity detection means for individually detecting the power of the light extracted by the light demultiplexing means, and N light intensity detection means One or M maximum optical power selecting means for selecting only the maximum optical power in each wavelength region in a certain different wavelength region from the obtained N optical powers; L individually controlling the powers of a plurality of pumping lasers for Raman distribution amplification so that the maximum optical powers in each of the M wavelength regions obtained by the maximum optical power selecting means are all at the set desired level. (L =
The wavelength division multiplexing optical transmission system according to claim 9, further comprising: M) feedback control means.