KR100432558B1 - Optical amplifier - Google Patents

Abstract

The present invention is configured to perform the first amplification through the Raman amplification means for the input light and the second amplification through the erbium doped optical fiber (EDF) so that the signal strength for each wavelength is uniform even for the intensity change of the input optical signal. An optical amplifier is configured to output an optical signal.

In addition, the optical amplifier according to the present invention is a Raman amplification means for performing the Raman amplification so that the difference in the amplification gain level for each wavelength with respect to the input light, and dispersion compensation for performing the dispersion compensation process for the amplified optical signal applied from the Raman amplification means EDF amplification means for amplifying and outputting the input light by a predetermined level to compensate for the loss caused by the optical signal dispersion compensation process in the dispersion compensation processing means, and amplifying and outputting the same gain level for each wavelength; And a gain leveling filter for equalizing the output intensity for each wavelength of the amplified light applied from the light source.

In addition, in the optical transmission system which performs multi-channel information transmission and provides channel change information according to the ADD / DROP of the channel to the optical amplifier through the wavelength for the control signal, the optical amplifier according to the present invention does not change the channel. When the light intensity is changed, by adjusting the amplification gain of the Raman amplification means to correspond to the change in the input light intensity, it is characterized in that the output for each channel is configured to be constant.

Description

Optical amplifier

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical amplifier, and in particular, to perform first-order amplification through Raman amplification means for input light and second-order amplification through erbium doped fiber (EDF) to change the intensity of an input optical signal. The present invention relates to an optical amplifier configured to always output an optical signal having an equal signal intensity for each wavelength.

The optical transmission system is configured to transmit a predetermined optical signal through an optical fiber transmission path. In this case, the optical signal generally decreases in signal strength due to signal loss such as scattering loss and absorption loss while passing through the optical fiber transmission path, so that the optical receiver cannot receive the optical signal during long distance transmission. In addition, the optical signal is transmitted to the optical fiber transmission path in a waveform of a predetermined pulse shape, and has a dispersion characteristic that the pulse waveform is spread while passing through the optical fiber of a long distance. The dispersion characteristic of the optical signal affects the peripheral pulse waveform, resulting in a problem that the transmission optical signal is distorted.

Accordingly, the optical transmission system is operating by installing an optical amplifier to perform amplification and dispersion compensation of the optical signal by a predetermined distance unit.

1 is a view showing a schematic configuration of a conventional optical amplifier. Conventional optical amplifiers primarily amplify the attenuated and dispersed optical signal through the transmission optical fiber through the first optical amplification means (1), and the first amplified optical signal is a dispersion compensated optical fiber for compensating for dispersion. Dispersion compensation is performed through 2). In this case, as the first amplified optical signal passes through the dispersion compensation optical fiber 2, for example, a loss of about 0.5 dB / km is generated, and to compensate for this, the second optical amplification means 3 performs second amplification. It is composed.

Here, the first and second optical amplification means (1,3) is generally referred to as Erbium-Doped Fiber (Erbium-Doped Fiber: "EDF") to excite the rare earth ions by the pumping light to perform optical signal amplification And amplification gains of the first and second optical amplifiers 1 and 3 are fixed according to the relay position where the optical amplifier is installed.

However, the EDF has different gain characteristics for each wavelength as shown in FIG. 2 with respect to the input light. Accordingly, when an optical signal passes through a plurality of optical amplifiers, the signal having a small amplification gain becomes smaller and the signal having a large amplification gain becomes larger, resulting in an optical signal that is too large or too small at the final receiver. As a result, a large signal above a certain level is not recognized at the receiving end, and a signal below a certain level is treated as noise, causing a problem that reception of an optical signal is not properly performed.

Therefore, the optical amplifier is required so that the optical signal output through the second optical amplifier means has a uniform signal strength for each wavelength. To this end, an optical amplifier in which a gain leveling filter is coupled to the output terminal of the optical amplifier, that is, the output terminal of the second optical amplifier 3 as shown in FIG. 1 is used.

Here, the gain flattening filter is configured such that a gain attenuation value for each wavelength of the input optical signal is fixedly set. That is, since the second optical amplification means 3 is composed of EDF and the 1530 nm wavelength band has a gain characteristic larger than other wavelength bands as shown in Fig. 2, the second optical amplification means 3 is set to have a larger gain attenuation value for the 1530 nm wavelength. The attenuation gain for each wavelength is set so that the optical signal gain output from the flattening filter is always constant. Such an optical amplifier may severely deteriorate gain flatness for each wavelength other than a predetermined gain.

On the other hand, recently, Wavelength Division Multiplexing (WDM) technology, which simultaneously transmits optical signals of various wavelengths through one transmission line, and ADD / which artificially removes or adds multiple wavelength optical signals from the input stage of the optical amplifier, The DROP technology is applied to the optical transmission system, and as the ADD / DROP technology is applied, there is a change in the overall signal strength of the optical signal input to the optical amplifier. In addition, the optical signal input to the optical amplifier changes depending on the transmission path.

However, as shown in FIG. 3, the EDF has a characteristic in which a gain curve changes a lot due to a change in gain level for each wavelength according to input light intensity. That is, in FIG. 3, (A) shows the EDF gain characteristics when the input light intensity is 1 dBm, and (B) shows the EDF gain characteristics when the input light intensity is -3 dBm, where the input light intensity is 1 dBm. In case (A), the gain level at 1535 nm wavelength is about 20.5 dB and the gain level at 1555 nm wavelength is about 23 dB, which is about 2.5 dB difference, but when the input light intensity is -3 dBm, (B) gain at 1535 nm wavelength. Both the level and the gain level at 1555 nm wavelength are about 26.5 dB, resulting in little gain level difference. In other words, the gain level of the EDF varies according to the input light intensity, and thus the EDF has a difference in the gain curve.

Accordingly, in the conventional optical amplifier in which the gain value is fixed according to the transmission distance and the dispersion characteristic, the gain characteristic for each wavelength output from the first and second optical amplifier stages 1 and 3 changes according to the input light intensity. In addition, the optical signal passed through the gain flattening filter having a fixed gain attenuation value for each wavelength coupled to the second optical amplifier stage 3 also has different gain characteristics for each wavelength. As a result, the output intensity of each wavelength output through the optical amplifier is not constant, and thus, the receiver does not properly recognize the received light due to the multi-stage optical amplifier.

Accordingly, the present invention has been made in view of the above circumstances, and the input light signal is primarily amplified through the optical fiber and secondly amplified through the EDF to change the input light intensity due to the ADD / DROP of the optical signal. It is a technical object of the present invention to provide an optical amplifier to output an optical signal having an equivalent output intensity for each wavelength.

Another object of the present invention is to provide an optical amplifier configured to always output an optical signal having a uniform output intensity for each wavelength even with a change in input light intensity due to a problem in a transmission path.

1 shows a schematic configuration of a conventional optical amplifier.

2 shows amplification characteristics of a general EDF.

3 is a diagram illustrating gain characteristics for each wavelength according to input light intensity of a general EDF.

4 and 5 are views for explaining the configuration of a conventional optical amplifier in which the automatic gain control method is employed.

6 is a view for explaining the configuration of a conventional optical amplifier in which the fixed output intensity control method is employed.

7 shows Raman gain characteristics for each wavelength according to the input light intensity of the optical fiber.

8 and 9 illustrate a configuration of an optical amplifier according to the present invention.

10 is a diagram illustrating signal transmission characteristics of a conventional optical amplifier X and an optical amplifier Y according to the present invention.

******* Brief description of the main parts of the drawing ******

50: Raman amplification means, 51: optical fiber,

52: coupler, 53: photodiode,

54: wavelength division multiplexer, 55: pumping light supply means,

56: isolator, 57: control unit,

60: distributed compensation optical fiber, 70: EDF amplification means,

80: gain leveling filter.

The optical amplifier according to the first aspect of the present invention for achieving the above object is a Raman amplification means for performing Raman amplification so that the difference in the amplification gain level for each wavelength with respect to the input light, and an amplified optical signal applied from the Raman amplification means Distributed compensation processing means for performing a distributed compensation process for the compensation, coupled to the output terminal of the distributed compensation processing means for outputting a predetermined level amplified input light to compensate for the loss caused by the optical signal dispersion compensation processing in the distributed compensation processing means, EDF amplifying means for amplifying and outputting the same gain level for each wavelength, and a gain leveling filter for equalizing the output intensity for each wavelength of the amplified light applied from the EDF amplifying means.

In addition, the optical amplifier according to the second aspect of the present invention for achieving the above object performs an optical transmission of the multi-channel and provides the channel change information according to the ADD / DROP of the channel to the optical amplifier through the wavelength for the control signal The optical amplifier comprises a Raman amplifier, a distributed compensation processing device and an EDF amplifier are sequentially coupled, the Raman amplifier is an optical fiber Raman amplifying the input optical signal, the pumping light supply for providing a pumping light Means, optical coupling means for coupling the pumping light as an input of the optical fiber in a reverse excitation manner, and an optical signal coupled between the optical fiber and the optical coupling means and divided from the optical fiber by a predetermined ratio to the first and second output ends. Coupling means for outputting each of the pumping light applied from the optical coupling means to the optical fiber, the first of the coupling means A photodiode for converting an optical signal applied from the output end into an electrical signal, and measuring the output light intensity of the optical fiber based on the signal applied from the photodiode, and the channel provided through the output light intensity and the control channel And control means for controlling the pumping light output intensity of the pumping light supply means based on the change information.

That is, as described above, the Raman amplifier and the EDF amplifier are combined in a hybrid form, and a simple configuration of controlling the amplification gain of the Raman amplifier without combining additional components is provided. It is possible to provide an optical amplifier capable of outputting a signal.

In addition, the optical amplifier combined with the Raman amplifier and the EDF amplifier in a hybrid form according to the present invention has an advantage that the long-distance transmission is easy because the noise characteristics are better than the conventional optical amplifier.

Hereinafter, an optical amplifier according to the present invention will be described.

The optical amplifier according to the present invention is configured to perform Raman amplification and EDF amplification so as to always output an optical signal with a uniform signal intensity for each wavelength in response to a change in the input light intensity.

Of course, as shown in FIG. 1, even in the conventional optical amplifiers in which the first and second optical amplification means are constituted by EDF, a structure for maintaining a constant gain and output intensity is always proposed. Auto Gain Control and Constant Output Power are adopted.

4 is a view for explaining the configuration of a conventional optical amplifier to which the automatic gain control method is applied, and in particular, shows the internal configuration of the first optical amplifier 1.

That is, as shown in FIG. 4, the conventional first optical amplifying means 1 separates the input optical signal through the coupler 11, and for example, separates it into 99: 1 so that the input light corresponding to “99” is wavelength-divided. The output light S corresponding to “1” is output to the multiplexer (WDM) 13 and converted into an electrical signal through the photodiode 12, and then provided to the controller 17. In addition, the wavelength division multiplexer 13 provides the input light S applied from the coupler 11 and the pumped light applied from the pumping light laser diode 14 to the EDF 15 in a forward excitation manner, and the EDF 15 ) Is configured to amplify the input light S by a predetermined level and then output it through the isolator 16. Here, the controller 17 measures the input light intensity based on the signal applied from the photodiode 12 and adjusts the pumping light intensity output from the pumping light laser diode 14 so as to correspond to the input light intensity. The amplification gain of the EDF 15 is adjusted.

That is, when the input light intensity is reduced, the controller 17 recognizes that the change in the input light intensity is caused by the ADD / DROP of the optical signal, and controls to reduce the pumping light intensity by the reduced signal intensity ratio. For example, when the amplification gain of the EDF 15 is 20 dB for the input light intensity of 40 channels, the controller 17 adjusts the pumping light intensity so that the amplification gain of the EDF 15 is 20 dB even for the input light intensity of 20 channels. Thus, the channel output through the EDF 15, that is, the output intensity for each wavelength is controlled to be kept constant at all times. In this case, the second optical amplification means is configured as shown in FIG. 4 to adjust the amplification gain of the EDF with respect to the change in the input light intensity, so that the gain characteristic for each wavelength of the optical signal output to the second optical amplification means, that is, the difference in signal strength between wavelengths You can keep it constant all the time. Therefore, an optical signal having an equal signal intensity for each wavelength is output through the gain flattening filter coupled to the output terminal of the second optical amplifier.

Also, as shown in FIG. 5, the optical amplifier couples the second coupler 18 to the output terminal of the isolator 16, and outputs a predetermined amount of optical signal separated through the second coupler 18. After converting into an electrical signal through the photodiode 19 may be configured to apply to the control unit 17. In this case, the controller 17 is configured to measure the signal strength of the input light and the output light applied from the first and second photodiodes 12 and 19 so as to control to output an optical signal having a constant signal strength. It is possible to provide a more stable optical amplifier than the same optical amplifier.

However, in the optical communication system, the input light intensity can be changed not only by the ADD / DROP of the channel but also due to the loss due to the problem on the transmission path. However, even when the input signal is attenuated due to a problem in the transmission path without changing the channel, when the automatic gain control method as shown in FIG. 4 is adopted, the output strength is also reduced according to the input strength attenuation to maintain the gain constant. Done. This reduces the light intensity per channel of the optical signal used because the output intensity is reduced without changing the number of channels of the optical signal being used.

That is, when the input light intensity is reduced by 3 dB due to a problem in the transmission channel for the 40 channels, if it is recognized as a DROP phenomenon of 20 channels and the amplification gain of the EDF 15 is maintained at 20 dB, the second optical amplification means ( The total input light intensity applied to 3) is reduced by 3 dB, and thus the output intensity output through the EDF 15 is reduced by 3 dB. In this case, the input light intensity of the next transmission section is also all reduced by 3dB. When this phenomenon accumulates in the final receiver, the receiver does not recognize the received light properly due to the decrease in the intensity of the optical signal per channel.

Accordingly, in the optical communication system, the channel change information is provided to the optical amplifier using a wavelength other than the signal transmission band, for example, a 1510 nm or 1625 nm control signal, and the optical amplifier adjusts the amplification gain of the EDF based on the channel change information. The fixed output strength control method is adopted and used to obtain a fixed output strength.

FIG. 6 illustrates a conventional optical amplifier configuration according to a fixed power intensity control method in an optical communication system providing channel change information.

That is, the conventional optical amplifier according to the fixed output intensity control method combines the optical separation unit 21 for separating the wavelength for the control signal from the input optical signal in front of the first optical amplifier 1 as shown in FIG. The control signal wavelength separated from the optical separation unit 21 is applied to the optical reception processing unit 22 to output information on channel change to the control unit 17 of the first optical amplification means 1 as a control signal. . In addition, a voltage control optical attenuater (hereinafter referred to as "VOA") for varying a gain level for an input optical signal according to the voltage level is coupled to the output terminal of the first optical amplifying means 1. It is composed.

Then, the control unit 17 of the first optical amplification means 1 is based on the channel change information applied from the light receiving processing unit 22 and the input light intensity information applied from the photodiode 12 and the EDF 15 and Control to change the gain level of the VOA (23). For example, when the input light intensity is reduced in the state where there is no change in the number of channels, the controller 17 sets the loss value of the VOA 23 to a low level without adjusting the amplification level of the EDF 15, thereby reducing the second light. The input light intensity applied to the amplifying means is adjusted to be constant.

That is, the optical amplifier shown in Fig. 6 is configured to maintain a constant gain by adjusting the output level of the EDF with respect to the change in the input light intensity according to the change in the number of channels, and for the change in the input light intensity due to the problem in the transmission path. It is configured to maintain constant output strength by adjusting the loss level of VOA.

In this case, however, the VOA 23 is further coupled to the output terminal of the first optical amplification means 1, so that signal loss such as insertion loss due to optical component coupling occurs. Therefore, the apparatus for compensating for the loss by physically coupling the VOA to the optical amplifier must be further included in the optical amplifier, thereby making the configuration of the optical amplifier more complicated.

On the other hand, according to the research of the present inventors, using a Raman amplification means that amplifies the optical signal by induced Raman scattering by the pumping light using a quartz-based optical fiber as an amplification medium can not only obtain a constant gain for the change in the input light intensity In addition, even when the amplification gain is changed, it is confirmed that the amplification gain characteristic of each wavelength is almost constant without the difference of the amplification gain (see FIG. 3) generated by using EDF as an amplification medium. 7 shows gain characteristics for each wavelength with respect to the input light intensity. In Fig. 7, (H) to (N) are wavelengths whose gains are adjusted so that the output remains constant when the input light intensity is -16 dBm, -17 dBm, -18 dBm, -19 dBm, -20 dBm, -21 dBm, or -22 dBm, respectively. As shown in FIG. 3, it can be seen that the Raman amplifier has a fixed gain difference between wavelengths without changing the gain characteristic curve even when the gain is changed with respect to the change in the input light intensity.

That is, the optical amplifier according to the present invention uses the gain characteristics of the optical fiber as described above so that the output intensity for each wavelength of the optical amplifier with respect to the input optical intensity is equally maintained in a simpler configuration.

8 illustrates a schematic configuration of an optical amplifier according to the present invention. As shown in FIG. 8, the optical amplifier according to the present invention primarily amplifies the input light applied through the transmission path through the Raman amplification means 50, and the Raman amplification means 50 through the distributed compensation optical fiber 60. The optical compensation signal is applied from the optical compensation signal from the dispersion compensation optical fiber 60 through the EDF amplification means 70, and then amplified the optical signal applied through the gain leveling filter 80 for each wavelength output. It is configured to output an optical signal of equal intensity.

At this time, the amplification gain of the Raman amplification means 50 and the EDF amplification means 70 is fixed. That is, since the gain level for each wavelength is constant even if the input light intensity is changed by the ADD / DROP of the optical signal, the Raman amplification means 50 maintains a difference in the gain level for each wavelength applied to the EDF amplification means 70 thereafter. Since only the overall signal intensity output to the EDF amplification means 70 is changed, it is possible to output an optical signal having a uniform signal intensity for each wavelength through the gain leveling filter 80. In other words, an optical amplifier having a simple configuration that sequentially performs Raman and EDF amplifications on the input light can achieve the same effect as the conventional optical amplifier (see FIG. 4) to which the automatic gain control method is applied.

In addition, the optical amplifier according to the present invention can be configured to adopt a fixed output intensity control method that can cope with changes in the input light intensity due to problems in the transmission path. At this time, the optical transmission system is configured to provide the channel change information to the optical amplifier through the wavelength for the predetermined control signal (see Fig. 6).

9 is a view for explaining the configuration of the optical amplifier when the fixed output intensity control method is applied, the optical amplifier according to the present invention to control the amplification gain of the Raman amplification means 50 to the conventional optical amplifier as shown in FIG. The same effect can be obtained. At this time, the gain of the EDF amplification means 70 is fixed.

That is, the Raman amplification means 50 of the optical amplifier according to the present invention is applied to the coupler 52 through the optical fiber 51 in which the input light S is used as the optical path, as shown in FIG. The coupler 52 divides an optical signal applied from the optical fiber 51 into, for example, 99: 1 to provide input light corresponding to “1” to the photodiode 53, and input light corresponding to “99” is a wavelength. To the division multiplexer 54. In addition, the wavelength division multiplexer 54 reversely excites the pumping light of a predetermined wavelength applied from the pumping light supply means 55 to the optical fiber 1 through the coupler 52. At this time, the optical fiber 51 amplifies the input light and passes through the coupler 52, the wavelength division multiplexer 54, and the isolator 65 in order to output to the distributed compensation optical fiber 60, and the coupler 52 Through the provided amount of amplified light to the photodiode 53. The photodiode 53 converts the amplified light signal applied from the coupler 52 into an electrical signal and provides the converted signal to the controller 57.

On the other hand, the control unit 57 isolator 56 based on the amplified light signal applied through the photodiode 53 and the channel change information (see Fig. 6) applied through the transmission path in front of the Raman amplification means 50. It controls the pumping light level output from the pumping light supply means 55 so that the output intensity of the optical signal output through the constant.

Here, the optical fiber 51 is to amplify the optical signal by induced Raman scattering by the pumping light using a quartz-based optical fiber as an amplification medium, and generally has a characteristic of amplifying light of about 100 nm long wavelength band than the wavelength of the pumping light. . In addition, the pumping light supply means 55 is provided with a plurality of laser diodes 551 having a specific wavelength for amplifying a multi-wavelength optical signal as shown in Figure 9, the control signal applied from the control unit 57 The pumping light supply unit 552 is configured to adjust the signal strength of the pumping light applied from the laser diode 551 based on the.

That is, when only the output light intensity of the optical fiber 51 applied from the photodiode 53 is changed in a state where the channel is not changed, the controller 57 recognizes this as a loss due to a problem in the transmission path and thus the optical fiber 51 The pumping light intensity output from the pumping light supply means 55 is adjusted to correspond to the output light intensity of the. For example, when the output light intensity of the optical fiber 51 is reduced in the absence of a channel change, the amplification gain of the optical fiber 51 is increased, and when the output light intensity of the optical fiber 51 is increased, the amplification gain of the optical fiber 51 is reduced. The pumping light intensity is controlled so that the intensity of the output light amplified from the optical fiber 51 is always kept constant. At this time, the amplification gain varies depending on the input intensity and the output of the optical signal, but since the optical fiber 51 has an amplification characteristic of the gain difference for each wavelength with respect to the input light intensity, the gain difference for each wavelength of the optical signal output from the optical fiber 51 And the signal strength is kept constant. Therefore, since the input light intensity applied to the EDF amplifying means 70 is constant, the output light is always kept constant, and the input to the gain flattening filter 80 coupled to the output terminal of the EDF amplifying means 70 is also constant, thereby gain flattening filter. The output intensity for each wavelength of the optical signal output through 80 is equalized.

That is, in applying the fixed output intensity control method, the optical amplifier according to the present invention has a simple configuration that controls the amplification gain of the Raman amplification means so as to correspond to the input light intensity without the coupling of additional optical elements. It is possible to obtain the same effect.

In addition, when the optical amplifier and the conventional optical amplifier according to the present invention are applied to the actual optical transmission system, each optical amplifier has the optical signal transmission characteristics as shown in FIG.

That is, in Fig. 10, (X) shows the optical signal transmission characteristics of the conventional optical amplifier in which the EDF is composed of primary and secondary amplification means, and (Y) shows the optical signal transmission characteristics of the optical amplifier according to the present invention. For example, the conventional optical amplifier X has a characteristic that the optical signal decreases to a noise level after a certain distance even when amplified to have a high signal strength with respect to the input light. On the other hand, it can be seen that the optical amplifier Y according to the present invention does not set the optical signal lower than the noise level after a certain distance even after amplifying the optical signal with a relatively small signal strength with respect to the input light. In other words, the optical amplifier configured by combining the Raman amplifier and the EDF amplifier in a hybrid form has advantages in that the signal transmission characteristics are better than those in the conventional optical amplifier, so that long-distance transmission is easy.

That is, the optical amplifier according to the present invention outputs an optical signal with an equal output intensity for each wavelength without changing the gain characteristics of the Raman amplifier 50 with respect to the change in the input light intensity due to the change in the number of channels by ADD / DROP. You can do it.

In addition, the optical amplifier according to the present invention controls the amplification gain of the Raman amplification means 50 for a change in the input light intensity due to a problem in the transmission path, not a change in the number of channels, thereby providing an optical signal with an equal output wavelength for each wavelength. You can print it out.

Therefore, according to the present invention, in the optical amplifier for performing the first and second amplification for the input light, the Raman optical fiber amplifier having a constant gain characteristic for each wavelength with respect to the signal strength of the input light by configuring a primary optical amplification stage The simple configuration of controlling the pumping light intensity of the Raman fiber amplifier without adding components enables the provision of an optical amplifier that outputs an optical signal having a specific characteristic of the signal intensity for each wavelength regardless of the input signal strength. .

Meanwhile, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the technical spirit of the present invention.

As described above, according to the present invention, the Raman amplifier and the EDF amplifier are combined in a hybrid form, and the signal strength for each wavelength is changed with respect to the input light intensity change with a simple configuration that controls the amplification gain of the Raman amplifier without combining additional components. An optical amplifier capable of always outputting a constant optical signal can be provided.

Claims (6)

Raman amplification means for performing Raman amplification so that the difference in amplification gain level for each wavelength is constant for the input light, Distributed compensation processing means for performing distributed compensation processing on the amplified optical signal applied from said Raman amplification means; EDF amplification is coupled to the output terminal of the dispersion compensation processing means to amplify and output a predetermined level of the input light to compensate for the loss caused by the optical signal dispersion compensation processing in the dispersion compensation processing means, the same level of gain for each wavelength Means; And a gain flattening filter for equalizing the output intensity for each wavelength of the amplified light applied from the EDF amplifying means. In the optical transmission system that performs the multi-channel information transmission and provides the channel change information according to the ADD / DROP of the channel to the optical amplifier through the wavelength for the control signal, The optical amplifier is configured by sequentially combining the Raman amplifier, distributed compensation processing device and EDF amplifier, The Raman amplification apparatus includes an optical fiber for Raman amplifying an input optical signal, pumping light supply means for providing pumping light, optical coupling means for coupling the pumped light as an input of the optical fiber in a reverse excitation method, the optical fiber and the optical coupling The optical signal coupled between the means and applied from the optical fiber is divided into a predetermined ratio and output to the first and second output terminals, respectively, and the pumping light applied from the optical coupling means is provided to the optical fiber. A photodiode for converting an optical signal applied from the first output stage into an electrical signal, and the output light intensity of the optical fiber is measured based on the signal applied from the photodiode, and provided through the output light intensity and the control channel. And control means for controlling the pumping light output intensity of the pumping light supply means based on the channel change information. An optical amplifier, characterized in that. The method of claim 2, The output amplifier of the EDF amplifying means is an optical amplifier, characterized in that further comprising a gain leveling filter for equalizing the output intensity for each wavelength of the input light. The method according to claim 2 or 3, If only the output light intensity from the optical fiber is changed without changing the channel, the control means adjusts the pumping light output intensity of the pumping light supply means to correspond to the output light intensity so that the output intensity for each wavelength is changed without changing the gain characteristic shape. An optical amplifier, characterized in that for controlling the equal optical signal to be output through the output stage. The method of claim 4, wherein And the control means controls to increase the amplification gain by the reduction ratio when the output light intensity of the optical fiber decreases without changing the channel. The method according to claim 2 or 3, And the EDF amplifying means has a fixed amplification gain for the input light.