JP4630256B2 - Optical amplification method, apparatus thereof, and optical amplification repeater system using the apparatus - Google Patents

Description

  The present invention relates to an optical amplification method for adjusting the attenuation of an optical variable attenuator in order to make the gain and output of an optical signal constant regardless of the wavelength, an apparatus thereof, and an optical amplification repeater system using the apparatus. is there.

  In the conventional optical amplifying and relaying system, data traffic is rapidly increasing as the transmission distance is increased and the transmission capacity is increased. This increase in data traffic causes a decrease in communication performance. Therefore, in order to prevent this deterioration in communication performance, wavelength division multiplexing (WDM) systems are becoming widespread.

  As shown in FIG. 12, for example, such a WDM system includes a transmission terminal station device 10, a reception terminal station device 20, and an optical fiber transmission line (hereinafter referred to as an optical fiber transmission line) that connects the transmission terminal station device 10 and the reception terminal station device 20. And an optical amplifying device 40 provided in several stages on the optical fiber transmission line 30, a plurality of optical signals having different wavelengths are simultaneously transmitted to a single optical transmission line 30. There is something to transmit.

  That is, in this system, each of the optical transmitters 111 to 11n (n is an arbitrary integer) of the transmitting terminal device 10 transmits a plurality of optical signals transmitted at different wavelengths λ1 to λn, to an optical coupler, a WDM coupler, or an array. After being wavelength-multiplexed by an optical multiplexer 12 composed of a waveguide type optical demultiplexer (AWG) or the like and optically amplified by an optical amplifying device 13, it is composed of a single mode optical fiber (SMF) or a dispersion shifted optical fiber (DSF). It is transmitted to a single transmission line 30. The multiplexed optical signal passes through several stages of optical amplifying devices 40 such as an erbium-doped fiber amplifier (EDFA), a thulium-doped fiber amplifier (TDFA), a semiconductor optical amplifier (SOA), etc. By transmitting, high-power optical signal transmission was performed, and long-distance and large-capacity transmission was realized.

  In the receiving terminal device 20, there is a device in which the multiplexed optical signal is demultiplexed by the optical demultiplexer 22 via the optical amplifying device 21, and sent to the optical receivers 231 to 23n for each of the wavelengths λ1 to λn. .

  The optical amplifying device 40 used in this system includes optical fiber amplifying units (hereinafter referred to as “optical amplifying units”) 41 and 42 as shown in FIG. The optical amplifiers 41 and 42 are controlled by an automatic gain control circuit (hereinafter referred to as “AGC”) 43 and an automatic optical output control circuit (hereinafter referred to as “ALC”) 44, and the multiplexed optical signals are collectively displayed. By amplifying, the transmission loss of the optical transmission line 30 is compensated.

  In this optical amplifying apparatus 40, an optical variable attenuator 45 is connected between the optical amplifying units 41 and 42. In this optical amplifying apparatus 40, the optical power detection circuits 48 and 49 detect the optical input power P1 and the optical output power P4 of the optical amplifier in the optical signals demultiplexed by the optical demultiplexers 46 and 47, respectively. The control circuit 50 controls the attenuation amount A of the optical variable attenuator 45 so that the sum of the gain G1 of the optical amplifier 41 and the gain G2 of the optical amplifier 42 is constant.

That is, the attenuation amount A of the optical variable attenuator 45 is the difference between the optical output power P2 of the optical amplifying unit 41 and the optical input power P3 of the optical amplifying unit A = P2-P3 (1)
The gain G1 of the optical amplifying unit 41 is the difference between the optical output power P2 of the optical amplifying unit 41 and the optical input power P1 of the optical amplifying unit G1 = P2−P1 (2)
The gain G2 of the optical amplifying unit 42 is the difference between the optical output power P4 of the optical amplifying unit 42 and the optical input power P3 of the optical amplifying unit G2 = P4-P3 (3)
It is obtained by

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

Here, for example, the sum of gains G1 + G2 = 20 [dB], the optical input power P1 = + 2 [dBm], and the optical output power P4 = + 18 [dBm], and these values are substituted into the equation (5) to change the light. When the attenuation amount A of the attenuator 45 is obtained,
A = 20- (18-2)
= 4 [dB]
It becomes.

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

  As is apparent from these drawings, the optical amplifying unit 41 is designed so as to obtain a wavelength characteristic of a downward-sloping gain when the optical power P1 is amplified to P2. In the optical amplifying unit 42, the optical power P3 is obtained. Is designed to obtain a wavelength characteristic of a gain that rises to the right when the signal is amplified to P4, and at the output end, the gain wavelength characteristic is designed to be almost flat when combined. The optical variable attenuator does not have gain wavelength characteristics and attenuates all wavelengths uniformly from optical power P2 to P3.

  However, in the above conventional example, as shown in the gain wavelength characteristic of FIG. 14C, the gain wavelength of the optical signal amplified by the optical amplifying unit 41 is designed to be substantially flat. Is transmitted to the optical fiber transmission line 30, it is affected by SRS (Stimulated Raman Scattering) which is one of nonlinear optical phenomena.

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

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

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

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

  In order to achieve the above object, in the present invention, at least two optical amplifiers and at least one attenuator are connected, an optical signal input via an optical transmission line is amplified by the optical amplifier, and the optical signal In an optical amplification method for detecting optical power and controlling the amount of attenuation according to the detected optical power, a sum of gains of the optical amplifiers is set to a target value that depends on a total optical input power to the optical transmission line. Thus, there is provided an optical amplification method comprising a control step of controlling the attenuation amount of the attenuator.

  According to the present invention, the gain of each optical amplifier is G1, G2, and this gain G1 is the difference G1 = P2-P1 between the optical output power P2 of the optical amplifier and the optical input power P1, and this gain G2 is the optical power of the optical amplifier. The difference G2 between the output power P4 and the optical input power P3 = P4−P3, and this sum (P2−P1) + (P4−P3) becomes the target value C + ΔL depending on the total optical input power to the optical transmission line ( P2-P1) + (P4-P3) = C + ΔL (refer to equation (6) described later), and the attenuation amount A = C + ΔL− (P4-P1) of the attenuator is controlled to be generated by SRS. The gain at each wavelength is flattened by giving a slope opposite to that of the gain.

  In the present invention, in the above invention, in the control step, the total optical input power of the optical signal to the upstream optical transmission path to which the optical signal is input and the downstream optical transmission path to propagate the optical signal The attenuation amount of the attenuator is controlled so that the target value depends on at least one of the total optical input powers of the optical signal.

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

  In the present invention, at least two optical amplifiers, at least one attenuator, and a dispersion-compensating optical transmission line are connected, an optical signal input through the optical transmission line is amplified by the optical amplifier, and the optical signal In an optical amplification method for detecting optical power and controlling the amount of attenuation according to the detected optical power, a sum of gains of the optical amplifiers is a total optical input power to the optical transmission line and the dispersion compensation type light There is provided an optical amplification method characterized by including a control step of controlling the attenuation amount of the attenuator so that the target value depends on the total optical input power to the transmission line.

  According to the present invention, the sum of the gains of the optical amplifiers is set to a target value that depends on the total optical input power to the dispersion compensating optical transmission line in addition to the total optical input power to the optical transmission line. Therefore, the gain at each wavelength is flattened by giving a slope opposite to that of the gain generated by the SRS.

  In the present invention, in the above invention, in the control step, the total optical input power of the optical signal to the upstream optical transmission path through which the optical signal is input and the downstream optical transmission through which the optical signal is propagated The attenuation of the attenuator so that the target value depends on at least one of the total optical input power of the optical signal to the path and the total optical input power to the dispersion-compensating optical transmission path. It is characterized by controlling the amount.

  According to the present invention, the amount of attenuation is determined based on the total optical input power of each wavelength of the optical signal to the upstream optical transmission path or / and the total optical input power of each wavelength of the optical signal to the downstream optical transmission path and the dispersion compensation type. By controlling the target value depending on the total optical input power to the optical transmission line, the gain is made uniform and stable optical transmission is performed.

  In the present invention, at least two optical amplifiers and at least one attenuator are connected, an optical signal input via an optical transmission line is amplified by the optical amplifier, and the attenuation is performed according to the optical power of the optical signal. In the optical amplifying apparatus for controlling the amount, a detecting means for detecting the optical power of the optical signal, a correcting means for obtaining a correction value for the attenuation amount of the predetermined attenuator based on the detected optical power, and the obtaining There is provided an optical amplifying device comprising control means for controlling the attenuation amount of the attenuator based on the correction value.

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

  In this invention, in the above invention, the detection means propagates the total optical input power of the optical signal to the upstream optical transmission line for inputting the optical signal to the own device and the optical signal from the own device. It is characterized in that at least one of the total optical input powers of the optical signal to the downstream optical transmission line to be detected is detected.

  According to the present invention, the detected optical transmission path is detected depending on whether the control target is the slope of the gain generated by the influence of the SRS by the upstream optical transmission path or the downstream optical transmission path, or both. To detect the total optical input power.

  According to the present invention, in the above invention, the correction means is configured so that the gain inclination of the optical amplifier has a slope opposite to the slope of the gain generated by stimulated Raman scattering based on the detected total optical input power. In addition, a correction value of the attenuation amount of the attenuator is obtained.

  According to the present invention, the correction value for obtaining the slope of the gain of the optical amplifier having a slope opposite to that of the gain generated by the SRS is obtained, and the slopes cancel each other so that the gain wavelength characteristic at each wavelength is flattened. Plan

  In the present invention, at least three optical amplifiers, at least one attenuator, and a dispersion-compensating optical transmission line are connected, and an optical signal input via the optical transmission line is amplified by the optical amplifier, and the optical signal In an optical amplifying apparatus that controls the attenuation amount according to optical power, first detection means for detecting optical power of the optical signal to the optical transmission line, and the optical signal to the dispersion-compensating optical transmission line Second detection means for detecting the optical power of the light, correction means for obtaining a correction value of the attenuation amount of the predetermined attenuator based on each detected optical power, and the attenuation based on the obtained correction value And a control means for controlling the attenuation of the optical device.

  According to the present invention, when the optical amplifying unit dispersion compensation type optical transmission line is connected, the optical power of the optical signal to the dispersion compensation type optical transmission line in addition to the optical transmission line is also detected and attenuated. A correction value for the attenuation of the optical device is obtained to compensate for transmission loss due to the influence of SRS in the optical transmission line.

  In this invention, in the above invention, the first detection means includes a total optical input power of the optical signal to the upstream optical transmission line that inputs the optical signal to the own device, and the optical signal from the own device. It is characterized in that at least one total optical input power is detected from the total optical input power of the optical signal to the downstream optical transmission line for propagating the optical signal.

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

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

  According to the present invention, when a dispersion-compensating optical transmission line is connected in the optical amplifying device, the total optical input power of the optical signal to the dispersion-compensating optical transmission line is detected and compensated for. To do.

  According to the present invention, in the above invention, the correcting means causes the gain gradient of the optical amplifier to have a gradient opposite to the gain gradient generated by stimulated Raman scattering based on each detected total light input power. Thus, the correction value of the attenuation amount of the attenuator is obtained.

  According to the present invention, based on each detected total optical input power, a correction value that makes the slope of the gain of the optical amplifier have a slope opposite to the slope of the gain generated by the SRS is obtained, and the slopes of each other are canceled out. Like that.

  According to the present invention, in the above invention, the optical amplifying device further includes a transmission unit that transmits the information on the detected optical power and a reception unit that receives the information on the detected optical power. And

  According to the present invention, a transmitter and a receiver that transmit and receive information on detected optical power are provided, and it is possible to control the amount of attenuation in another optical amplifying device, and the optical output from a plurality of stages of optical amplifying devices. The power detection result is obtained and the attenuation can be controlled.

  According to the present invention, in an optical amplification repeater system that amplifies and repeats an optical signal propagated to the optical transmission line with an optical amplification apparatus connected in multiple stages to the optical transmission line, the optical amplification apparatus according to the invention described above is at least There is provided an optical amplification repeater system including one.

  According to this invention, at least one optical amplifying device described in the above invention is connected to the optical amplifying relay system, and the slope opposite to the slope of the gain generated by the SRS from the optical power detection result in each optical amplifying device. The gain wavelength characteristics are flattened so as to cancel each other.

  According to the present invention, an optical amplification apparatus that amplifies an optical signal propagated to the optical transmission line and performs bidirectional optical relaying in an optical amplification device that is connected in multiple stages to at least two optical transmission lines for uplink and downlink The relay system includes at least one optical amplifying device according to the invention described above.

  According to this invention, by constructing an optical amplification repeater system that performs bidirectional transmission using an upstream and downstream optical transmission line to which at least one optical amplification device according to the above invention is connected, The detection result of the downstream optical power as well as the optical power on the downstream side can be received.

  According to the present invention, in the above invention, in the optical amplification repeater system including the optical amplifying device according to the above invention, the detected optical power information is received from another optical amplifying device connected to the optical transmission line. Then, a predetermined correction value for the attenuation amount of the attenuator based on the optical power is obtained, and the attenuation amount of the attenuator is controlled based on the obtained correction value.

  According to the present invention, the attenuation amount of the attenuator is controlled so that the slope of the gain generated by the SRS is opposite to the slope of the gain generated by the SRS from the detection result of the optical output power in the other optical amplifying apparatus regardless of whether it is upstream or downstream. The gain at each wavelength in the target stage optical amplifier is uniform.

  As described above, according to the present invention, at least two optical amplifiers and at least one attenuator are connected, an optical signal input via an optical transmission line is amplified by the optical amplifier, and the optical signal of the optical signal is amplified. In the optical amplification method for detecting power and controlling the attenuation amount according to the detected optical power, the sum of gains of the optical amplifiers becomes a target value depending on the total optical input power to the optical transmission line. Thus, since the attenuation amount of the attenuator is controlled, the attenuation amount of the optical variable attenuator can be controlled so as to have a slope opposite to the slope of the gain generated by the SRS from the detection result of the optical power. The gain is flattened and the transmission efficiency can be improved.

  In the present invention, the attenuation amount of the optical variable attenuator is used to determine the total optical input power of each wavelength of the optical signal to the upstream optical transmission path or / and the total optical input of each wavelength of the optical signal to the downstream optical transmission path. Since the target value depending on the power is controlled, the gain can be made uniform and stable optical transmission can be performed.

  In the present invention, at least two optical amplifiers, at least one attenuator, and a dispersion-compensating optical transmission line are connected, and an optical signal input through the optical transmission line is amplified by the optical amplifier, and the optical amplifier In an optical amplification method for detecting optical power of a signal and controlling the attenuation amount according to the detected optical power, a sum of gains of the optical amplifiers is a total to an upstream or / and downstream optical transmission line. In addition to the optical input power, the target value depends on the total optical input power to the dispersion-compensating optical transmission line, and therefore has a slope opposite to the slope of the gain generated by the SRS from the optical power detection result. The optical power at each wavelength can be flattened.

  In the present invention, at least two optical amplifiers and at least one attenuator are connected, and an optical signal input via an optical transmission line is amplified by the optical amplifier, and according to the optical power of the optical signal. In the optical amplifying apparatus for controlling the attenuation amount, optical power on the upstream side and / or downstream side is detected, a correction value for the attenuation amount of the optical variable attenuator is obtained from the detection result of the optical power, and the optical variable attenuator is obtained. Since the attenuation of the optical variable attenuator is controlled so as to have a slope opposite to the slope of the gain generated by the SRS from the optical power detection result, the gain at each wavelength is flattened. And transmission efficiency can be improved.

  Further, according to the present invention, the correction means corrects the attenuation amount of the attenuator based on the total optical input power so that the gain inclination of the optical amplifier has a slope opposite to that of the gain generated by stimulated Raman scattering. Since the value is obtained, the slopes of the gain wavelength characteristics cancel each other, the gain wavelength characteristics at each wavelength are flattened, and the transmission efficiency can be improved.

  In the present invention, a dispersion compensation type optical transmission line is connected, and an optical signal input through the optical transmission line is amplified by the optical amplifier, and the attenuation is controlled according to the optical power of the optical signal. In the optical amplifying device, the total optical input power of the optical signal to the upstream or / and downstream optical transmission line and the total optical input power of the optical signal to the dispersion compensation type optical transmission line are detected and detected. Based on each total optical input power, a correction value is obtained so that the slope of the gain of the optical amplifier has a slope opposite to the slope of the gain generated by stimulated Raman scattering, and the slopes of each other are canceled out. Therefore, the attenuation of the optical variable attenuator is controlled so that the slope of the gain generated by the SRS is opposite from the detection result of the optical power, thereby flattening the gain at each wavelength and improving the transmission efficiency. Kill.

  In addition, since the present invention includes a transmission means for transmitting the detected optical power information and a reception means for receiving the detected optical power information, the attenuation amount in other optical amplifiers can be controlled. In addition, the detection result of the optical output power is obtained from a plurality of stages of optical amplifying apparatuses, and the attenuation amount can be controlled in the target stage of the optical amplifying apparatus.

  According to the present invention, there is provided an optical amplifying apparatus according to the above invention in an optical amplifying and relaying system for amplifying and relaying an optical signal propagated to the optical transmission path with an optical amplifying apparatus connected in multiple stages to the optical transmission path. Are connected to each other, and the gain wavelength characteristics are flattened so as to cancel each other with a slope opposite to the gain slope generated by the SRS from the detection result of the optical power in each optical amplifying device. Efficiency can be improved.

  In the present invention, the optical signal propagated to the optical transmission line is amplified and bidirectionally relayed by an optical amplifying apparatus connected in multiple stages to at least two optical transmission lines for upstream and downstream. In the optical amplification repeater system, by constructing an optical amplification repeater system that performs bidirectional transmission using the upstream and downstream optical transmission lines to which at least one optical amplification device according to the above invention is connected, In addition to the optical power on the side, the downstream optical power detection result can also be received, and the optical output power detection results in other optical amplifying devices cancel each other with a slope opposite to that of the gain generated by the SRS. As a result, the gain wavelength characteristic can be flattened to improve the transmission efficiency.

  Exemplary embodiments of an optical amplification method, an apparatus thereof, and an optical amplification repeater system using the apparatus according to the present invention will be described below with reference to the accompanying drawings. In the following drawings, the same components as those in FIGS. 12 and 13 are denoted by the same reference numerals for convenience of explanation.

Example 1
1 is a configuration diagram showing the configuration of a first embodiment of an optical amplifying device according to the present invention. In this figure, the difference from the conventional example of FIG. 13 is that a correction circuit 51 in which a correction value of the attenuation amount of the optical variable attenuator 45 is set in order to correct the slope of the gain wavelength characteristic caused by the influence of SRS. This is the point. In order to cancel the slope of the gain wavelength characteristic, the correction circuit 51 corrects the attenuation amount that becomes the gain wavelength characteristic having a slope opposite to the slope of the gain wavelength characteristic based on the optical output power from the optical amplifying unit 42. A value ΔL is obtained and output to the control circuit 50. The control circuit 50 obtains an attenuation amount based on the correction value ΔL, the optical input power from the optical transmission line 30, and the optical output power to the optical transmission line 30, and determines the attenuation amount A of the optical variable attenuator 45. I have control.

  That is, in this embodiment, the attenuation amount A of the optical variable attenuator 45 is obtained by the equation (1), and the gain G1 of the optical amplifying unit 41 is obtained by the equation (2). The gain G2 of the unit 42 is obtained by the equation (3).

The gains of the optical amplifying units 41 and 42 are
G1 + G2 = C + ΔL (6)
It becomes. Here, by substituting the equations (2) and (3) into the equation (6) and obtaining the attenuation amount A of the optical variable attenuator 45,
(P2-P1) + (P4-P3) = C + ΔL
(P2-P3) + (P4-P1) = C + ΔL
(P2−P3) = C + ΔL− (P4−P1)
Therefore, from equation (1), A is
A = C + ΔL− (P4−P1) (7)
It is obtained by

Next, ΔL is obtained. Here, the slope SRS (dG / dλ) of the gain wavelength characteristic generated by the influence of SRS is
SRS (dG / dλ) = 4.34 · (β · P0 · Leff) [dB / nm]
(8)
Here, P0: Total optical power [W] of the optical signal incident on the optical transmission line 30
(Equivalent to P4 in FIG. 1)
β: Depends on the optical transmission line 30 (type) on which this total optical power is incident
Existing coefficient [1 / W · km · nm]
Leff: Effective length [km] of the optical transmission line on which this total optical power is incident
It becomes.

Incidentally, the expression ^{(8), ELECTRONICS LETTERS, 16 th April 1998} , Vol. 34, no. 8, M.M. It is described in the Zirngib literature.

Next, in order to cancel the slope of the gain wavelength characteristic generated by the influence of the SRS, the slope OFA (dG / dλ) of the gain wavelength characteristic generated by the optical amplifier is equal to the slope of the gain wavelength characteristic generated by the influence of the SRS. Is the opposite slope,
OFA (dG / dλ) = − a · ΔL [dB / nm] (9)
Where, a: proportional coefficient [1 / nm] depending on the design of the optical amplifier
ΔL: Correction value [dB] of attenuation of the optical variable attenuator
It becomes.

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

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

Here, for example, a = 0.02 [1 / nm], β = 3.5 × 10 ⁻³ [1 / W · km · nm], P0 = P4 = + 18 [dBm] = 0.063 [W], When Leff = 21 [km], these numerical values are substituted into the equation (11), and the attenuation value correction value ΔL of the optical variable attenuator is obtained.
ΔL = {4.34 · (3.5 × 10 ⁻³ · 0.063 · 21)} / 0.02 = 1 [dB]
It becomes.

Further, the conditions shown in the conventional example, that is, the total gain G1 + G2 = 20 [dBm], the optical input power P1 = + 2 [dBm], and the optical output power P4 = + 18 [dBm], and these values are expressed by the equation (7). Substituting and obtaining the attenuation amount A of the optical variable attenuator,
A = C + ΔL− (P4−P1)
= 20 + 1- (18-2)
= 5 [dB]
It becomes.

  The gain wavelength characteristics in this embodiment are as shown in FIGS. 2A to 2C, and the level diagram is as shown in FIG. In this embodiment, since the optical power of P3 is reduced by the attenuation amount of the correction value, the gain of the optical amplifying unit 42 becomes larger than that of the conventional example (dotted line portion in FIG. 3).

  In addition, the slope of the gain wavelength characteristic varies depending on the magnitude of the gain, as shown in FIG. That is, as shown in the figure, when the gain increases, the slope increases toward the lower right, and when the gain decreases, the slope increases toward the upper right.

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

  As described above, in this embodiment, in order to correct the slope of the gain wavelength characteristic caused by the influence of SRS, the correction value of the attenuation amount of the optical variable attenuator is obtained from the detection result of the total optical output power. Since the amount of attenuation of the optical variable attenuator is controlled so as to cancel the slope of the gain wavelength characteristic, as shown in FIG. 2D, at the input end of the optical amplifying apparatus 40 of the next stage via the optical transmission line 30 The gain wavelength characteristic at each wavelength is flattened, and the transmission efficiency can be improved.

  For this reason, in this embodiment, even if the optical power incident on the optical transmission line fluctuates due to an increase or decrease in the number of channels, the slope of the gain of the wavelength multiplexed signal generated by the influence of SRS is automatically corrected collectively. The deviation of the gain of this wavelength division multiplexed signal can be minimized, so that the optical power at each wavelength becomes uniform, the S / N deterioration in the optical signal on the short wavelength side is prevented, and stable optical transmission is achieved. Yes.

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

  The control / monitoring signal receiving circuit 52 receives information on the optical output power incident on the upstream optical transmission line as a control / monitoring signal via the optical demultiplexer 54, and The amount of attenuation of the optical variable attenuator 45 is controlled by the control circuit 50 so as to have a slope opposite to that of the gain due to the influence of the SRS generated in the optical transmission line 30 between the own apparatuses. Further, the control / monitor signal transmission circuit 53 transmits the optical output power incident on the optical transmission line 30 via the optical multiplexer 55 to an optical amplification device at the next stage (not shown).

  In this embodiment as well, as in the first embodiment, the attenuation correction value ΔL having a gain wavelength characteristic having a slope opposite to that of the gain wavelength characteristic, the optical input power from the optical transmission line 30, and the optical transmission line The attenuation amount A of the optical variable attenuator 45 is controlled by obtaining the attenuation amount based on the optical output power to 30. In this embodiment, the difference from the first embodiment is that the optical power P01 is the optical output power of the optical amplifying apparatus in the previous stage, P0 in the equation (11) corresponds to the optical output power P01, and the correction value ΔL is This is derived from the optical output power P01 and the type and effective length of the upstream optical transmission line through which the optical signal of P01 is transmitted.

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

  As a result, in this embodiment, as shown in FIG. 6B, the gain at each wavelength at the output end of the optical amplifying device 40 becomes uniform, the gain wavelength characteristic is flattened, and the transmission efficiency is improved. Thus, the same effects as in the first embodiment can be obtained, the influence of the SRS in the upstream optical transmission line can be prevented, and the transmission efficiency can be further improved.

(Example 3)
FIG. 7 is a configuration diagram showing an embodiment in the case where three optical amplifying units 41, 42, 60 are provided in the optical amplifying device 40. The optical amplifying unit 41 is controlled by an automatic current control circuit (hereinafter referred to as “ACC”), and the optical amplifying units 42 and 60 are controlled by the ALCs 44 and 61 to amplify the multiplexed optical signals at once. Thus, the transmission loss of the optical transmission line 30 is compensated.

  In this optical amplifying device 40, a DCF 66 is connected between the optical amplifying units 42 and 60. In this optical amplifying device 40, the optical output power P2 of the optical amplifying unit 41 in the optical signal demultiplexed by the optical demultiplexers 56, 57, 62, 63, the optical input power P3 of the optical amplifying unit 42, The optical input power P5 and the optical output power P6 of the optical amplifying unit 60 are detected by the optical power detection circuits 58, 59, 64 and 65, and the control circuit 50 detects the gain G1 of the optical amplifying unit 41 and the optical amplifying unit 42. The attenuation amount A of the optical variable attenuator 45 is controlled so that the sum of the gain G2 and the gain G3 of the optical amplifying unit 60 becomes C + ΔL.

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

That is, the gains of the optical amplifiers 41, 42, and 60 are
G1 + G2 + G3 = C + ΔL (12)
It becomes. Further, the gain G1 of the optical amplifying unit 41 is obtained by equation (2), the gain G2 of the optical amplifying unit 42 is also obtained by equation (3), and the gain G3 of the optical amplifying unit 60 is obtained by the optical amplifying unit 60. Difference between the optical output power P6 of the optical amplifier and the optical input power P5 of the optical amplifying unit 60 G3 = P6-P5 (13)
It is obtained by

Here, substituting (2), (3), and (13) into (12),
(P2-P1) + (P4-P3) + (P6-P5) = C + ΔL
It becomes. From the above equation, the attenuation amount (P2-P3) of the optical variable attenuator 45 is
(P2−P3) = C + ΔL− (P4−P1) − (P6−P5) (14)
It is obtained by Therefore, from (1) to A,
A = C + ΔL− (P4−P1) − (P6−P5) (15)

Further, in this embodiment, the correction value ΔL (actually, ΔL1 and ΔL2 are obtained and added) of the attenuation amount of the optical variable attenuator can be obtained based on the above-described equations (8) to (11). . That is, the correction value ΔL1 of the attenuation amount of the optical variable attenuator with respect to the optical transmission line 30 connected to the optical amplifier of the next stage is
ΔL1 = 4.34 · (β1 · P6 · Leff1) / a
Here, P6: Total optical power [W] of the optical signal incident on the transmission path of the next stage
β1: Coefficient [1 depending on the optical transmission line on which this total optical power is incident
/ (W · km · nm)]
Leff1: Effective length [km] of an optical transmission line on which this total optical power is incident
a: Proportional coefficient depending on the design of its own optical amplifier
(Unit: [1 / nm])
Further, the correction value ΔL2 of the attenuation amount of the optical variable attenuator for the DCF 66 is
ΔL2 = 4.34 · (β2 · P4 · Leff2) / a
Here, P4: Total optical power [W] of the optical signal incident on the DCF
β2: Coefficient [1 / of the total optical power depending on the incident DCF
(W / km / nm)]
Leff2: Effective length [km] of DCF to which this total optical power is incident
It becomes. Therefore, the correction value ΔL of the attenuation of the optical variable attenuator in this embodiment is
ΔL = ΔL1 + ΔL2
= 4.34 · (β1 · P6 · Leff1) /a+4.34· (β2 · P4 · Leff2) / a
= 4.34 · {(β1 · P6 · Leff1) + (β2 · P4 · Leff2)} / a
It becomes.

  As described above, in this embodiment, in order to correct the slope of the gain wavelength characteristic generated by the influence of the DCS and the SRS in the optical transmission line, the correction value of the attenuation amount of the optical variable attenuator from the detection result of the optical output power. Therefore, the attenuation amount of the optical variable attenuator is controlled so as to cancel the slope of the gain wavelength characteristic, so that the gain at each wavelength at the input end of the optical amplifier 40 at the next stage via the optical transmission line 30 is It becomes uniform, flattening the gain wavelength characteristics, improving the transmission efficiency, obtaining the same effect as the first embodiment of FIG. 1, and preventing the influence of SRS in the DCF. Further, transmission efficiency can be improved.

Example 4
FIG. 8 shows the amount of attenuation of the optical variable attenuator 45 based on the information of the optical output power that is provided with three optical amplifying units 41, 42, and 60 in the optical amplifying device 40 and is incident on the upstream optical transmission line. It is a block diagram which shows one Example in the case of controlling. In this optical amplifying apparatus 40, as in the second embodiment, the control / monitor signal receiving circuit 52 controls the information of the optical output power P06 incident on the upstream optical transmission line via the optical demultiplexer 54. An optical variable attenuator is received by the control circuit 50 so as to have a slope opposite to that of the gain due to the influence of the SRS generated in the optical transmission line 30 between the preceding optical amplifying apparatus 40 and the own apparatus. The amount of attenuation of 45 is controlled. Further, the control / monitoring signal transmission circuit 53 transmits the optical output power incident on the optical transmission line 30 at the next stage to an optical amplification apparatus at the next stage (not shown). The optical output power P06 corresponds to the optical output power P01 shown in Example 2 in FIG.

  The control circuit 50 controls the attenuation amount A of the optical variable attenuator 45 so that the sum of the gain G1 of the optical amplifier 41, the gain G2 of the optical amplifier 42, and the gain G3 of the optical amplifier 60 becomes C + ΔL. ing. In this case, ΔL is a correction value of the attenuation amount of the optical variable attenuator with respect to the optical transmission line 30 connected to the optical amplifier of the previous stage, and a correction value of the attenuation amount of the optical variable attenuator with respect to the DCF 66. It consists of a value of ΔL = ΔL1 + ΔL2 that is combined with a certain ΔL2.

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

Here, substituting (2), (3), and (13) into (16),
(P2-P1) + (P4-P3) + (P6-P5) = C + ΔL
It becomes. From the above equation, the attenuation amount (P2-P3) of the optical variable attenuator 45 is
(P2−P3) = C + ΔL− (P4−P1) − (P6−P5) (17)
It is obtained by Therefore, the attenuation amount A from the equation (1) is
A = C + ΔL− (P4−P1) − (P6−P5) (18)
It is obtained by

Also in this embodiment, the correction value ΔL (actually, ΔL1 and ΔL2 are obtained and added) of the attenuation amount of the optical variable attenuator can be obtained based on the above-described equations (8) to (11). . That is, the correction value ΔL1 of the attenuation amount of the optical variable attenuator with respect to the optical transmission line 30 connected to the optical amplifier of the next stage is
ΔL1 = 4.34 · (β1 · P06 · Leff1) / a
Here, P06: Total optical power [W] of the optical signal incident on the previous transmission line
β1: Coefficient depending on the optical transmission line on which this total optical power is incident
[1 / (W · km · nm)]
Leff1: Effective length [km] of an optical transmission line on which this total optical power is incident
a: Proportional coefficient depending on the design of its own optical amplifier
(Unit: [1 / nm])
Further, the correction value ΔL2 of the attenuation amount of the optical variable attenuator for the DCF 66 is
ΔL2 = 4.34 · (β2 · P4 · Leff2) / a
Here, P4: Total optical power [W] of the optical signal incident on the DCF
β2: Coefficient [1 / of the total optical power depending on the incident DCF
(W / km / nm)]
Leff2: Effective length [km] of DCF to which this total optical power is incident
It becomes. Therefore, the correction value ΔL of the attenuation of the optical variable attenuator in this embodiment is
ΔL = ΔL1 + ΔL2
= 4.34 · (β1 · P06 · Leff1) /a+4.34· (β2 · P4 · Leff2) / a
= 4.34 · {(β1 · P06 · Leff1) + (β2 · P4 · Leff2)} / a
It becomes.

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

(Example 5)
Next, the case where the optical variable attenuator is not built in the preceding stage optical amplifying device in FIG. 9 will be described. Since a control function using an optical variable attenuator increases the manufacturing cost, an optical amplifying device provided with several optical variable attenuators is usually provided to reduce the manufacturing cost.

  Therefore, in this embodiment, the control / monitoring signal receiving circuit 52 receives the intermediate optical output power P04 incident on the DCF 71 transmitted from the upstream optical amplifying device 70 and the optical output power P06 incident on the optical transmission line 30. Is received as a control / monitoring signal via the optical demultiplexer 54, and the influence of the SRS generated in the optical transmission line 30 between the DCF 71 of the optical amplification device 70 in the previous stage and the optical amplification device 70 and its own device 40 is received. The amount of attenuation of the optical variable attenuator 45 is controlled by the control circuit 50 so as to have a slope opposite to the slope of the gain due to. Here, P04 is the intermediate optical output power of the preceding optical amplifying device, and P06 is the optical output power of the preceding optical amplifying device.

  The control circuit 50 controls the attenuation amount A of the optical variable attenuator 45 so that the sum of the gain G1 of the optical amplifier 41, the gain G2 of the optical amplifier 42, and the gain G3 of the optical amplifier 60 becomes C + ΔL. is doing. In this case, ΔL is ΔL1, which is a correction value of the attenuation amount of the optical variable attenuator for the optical transmission line 30 connected to the optical amplifier of the next stage, and a correction value of the attenuation amount of the optical variable attenuator with respect to the DCF 66. ΔL2, which is a correction value of the attenuation amount of the optical variable attenuator with respect to the optical transmission line 30 connected to the optical amplifier 70 in the previous stage, and the attenuation amount of the optical variable attenuator with respect to the DCF 71 of the optical amplifier 70 in the previous stage. It consists of a value of ΔL = ΔL1 + ΔL2 + ΔL3 + ΔL4, which is a sum of correction value ΔL4.

In this embodiment, the gains of the optical amplifiers 41, 42 and 60 are
G1 + G2 + G3 = C + ΔL (19)
It becomes.

Here, substituting (2), (3), and (13) into (19),
(P2-P1) + (P4-P3) + (P6-P5) = C + ΔL
It becomes. From the above equation, the attenuation amount (P2-P3) of the optical variable attenuator 45 is
(P2−P3) = C + ΔL− (P4−P1) − (P6−P5) (20)
It is obtained by

Also in this embodiment, the correction value ΔL (actually, ΔL1 to ΔL4 is obtained and added) of the attenuation amount of the optical variable attenuator can be obtained based on the above-described equations (8) to (11). . That is, the correction value ΔL1 of the attenuation amount of the optical variable attenuator with respect to the optical transmission line 30 connected to the optical amplifier of the next stage is
ΔL1 = 4.34 · (β1 · P6 · Leff1) / a
Here, P6: Total optical power [W] of the optical signal incident on the transmission path of the next stage
β1: Coefficient [1 depending on the optical transmission line on which this total optical power is incident
/ (W · km · nm)]
Leff1: Effective length [km] of an optical transmission line on which this total optical power is incident
a: Proportional coefficient depending on the design of its own optical amplifier
(Unit: [1 / nm])
In addition, the correction value ΔL2 of the attenuation amount of the optical variable attenuator with respect to the DCF 66 of this apparatus is
ΔL2 = 4.34 · (β2 · P4 · Leff2) / a
Here, P4: Total optical power [W] of the optical signal incident on the DCF of its own device
β2: Coefficient [1 / of the total optical power depending on the incident DCF
(W / km / nm)]
Leff2: Effective length [km] of DCF to which this total optical power is incident
It becomes.

Further, ΔL3, which is a correction value of the attenuation amount of the optical variable attenuator with respect to the optical transmission line 30 connected to the optical amplifier 70 in the previous stage,
ΔL3 = 4.34 · (β3 · P06 · Leff3) / a
Here, P06: Total optical power [W] of the optical signal incident on the previous transmission line
β3: Coefficient [1 depending on the optical transmission line on which the total optical power is incident
/ (W · km · nm)]
Leff3: Effective length [km] of the optical transmission line on which this total optical power is incident
ΔL4, which is a correction value of the attenuation amount of the optical variable attenuator with respect to the DCF 71 of the optical amplifier 70 in the previous stage,
ΔL4 = 4.34 · (β4 · P04 · Leff4) / a
Here, P04: Total optical power [W] of the optical signal incident on the DCF of the preceding stage optical amplifying device
β4: Coefficient [1 / of the total optical power depending on the incident DCF
(W / km / nm)]
Leff4: Effective length [km] of DCF to which this total optical power is incident
It becomes.

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

  As described above, in this embodiment, in order to correct the slope of the gain wavelength characteristic generated by the influence of the DCS and the SRS in the optical transmission line in the optical amplifier having no control function in the front stage and the preamplifier in the rear stage, Since the attenuation value of the optical variable attenuator is calculated from the detection result of the optical output power of the optical transmission line, the attenuation amount of the optical variable attenuator in multiple stages is controlled so as to cancel the slope of the gain wavelength characteristic. In addition to obtaining the same effects as in the above embodiments, the gain at each wavelength in the multi-stage optical amplifying device is uniform, the gain wavelength characteristic can be flattened, and the transmission efficiency can be further improved. it can.

(Example 6)
Next, FIG. 10 shows an embodiment of an optical amplification repeater system using the above-described optical amplification apparatus according to the present invention. In this embodiment, the optical amplifying devices 70 and 71 not including the variable optical attenuator according to the present invention and the optical amplifying device 40 according to the present invention are connected on one optical transmission line 30. It is shown.

  In this system, since the optical amplifying devices 70 and 71 cannot control the slope of the wavelength characteristic of the gain, the optical amplifier 40 also controls the slope of the gain generated there. Information on the optical output powers P1a, P1b, P2a, and P2b of the optical amplifying devices 70 and 71 is transmitted from the control / monitoring signal transmission circuit of each of the optical amplifying devices 70 and 71 to the optical amplifying device 40 as a monitoring / control signal. The optical output powers P1a and P2a correspond to the intermediate optical output power P04 shown in FIG. 9, and the optical output powers P1b and P2b correspond to the optical output power P06 shown in FIG.

  Since the optical amplifying device 40 used in this system needs to be a device capable of transmitting optical output power information, the optical amplifying device 40 includes the control / monitoring signal transmission circuit and the reception circuit shown in FIGS. Is essential for the configuration.

  The control / monitor signal transmission circuit of the optical amplifying device 40 can obtain information on the optical output power from the optical amplifying devices 70 and 71 by, for example, a polling request. In an optical amplifying apparatus that does not have an optical variable attenuator that takes in a control / monitoring signal addressed to the optical amplifying apparatus 40 from another optical amplifying apparatus via the optical transmission line 30, the optical transmission is performed again after passing through the optical amplifying unit. The control / monitoring signal is sent to the path 30. The control / monitoring signal is an optical signal having a wavelength different from that of the main signal, and may be outside or within the amplification wavelength band of the optical amplification device. For example, the control / monitoring signal is within the amplification wavelength band of the optical amplification device. Is transmitted after being optically amplified by the optical amplifier.

  Thus, in this embodiment, since an optical amplification repeater system is constructed by connecting at least one optical amplification device according to the present invention, the slope of the gain generated by the SRS from the detection result of the optical power in each optical amplification device. The amount of attenuation of the optical variable attenuator can be controlled so as to have a slope opposite to the above, thereby flattening the gain at each wavelength and improving the transmission efficiency.

(Example 7)
FIG. 11 is a system configuration diagram showing the configuration of another embodiment of the optical amplification repeater system using the above-described optical amplification apparatus according to the present invention. In the figure, in this system, two optical transmission paths 1 and 2 for upstream and downstream are provided, and a plurality of optical amplifying devices 40, 70 to 73 and 80 to 84 are provided in each of the optical transmission paths 1 and 2, respectively. The case where it connects is shown, The optical amplifier 40 concerning this invention is provided in at least one of these optical amplifiers.

  When there are a plurality of optical amplifying devices 70 to 73 that do not have an optical variable attenuator on either the upstream side or the downstream side of the optical amplifying device 40, the optical amplifying devices 70 to 73 are generated. Information of the optical output powers P1a to P5a and P1b to P5b is transmitted to the optical amplifying device 40. Information on the optical output powers P4a, P4b, P5a, and P5b of the downstream optical amplifying devices 72 and 73 is transmitted to the optical amplifying device 40 via the monitoring module SV and the optical amplifying devices 82 to 84.

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

  As described above, in this embodiment, since an optical amplification relay system that performs bidirectional transmission has been constructed having an optical transmission path for upstream and downstream to which at least one optical amplification device according to the present invention is connected, The effect similar to that of the sixth embodiment of FIG. 10 can be obtained, and the downstream optical power detection result can be received, so that the slope of the gain generated by the SRS is opposite to that of the upstream and downstream. In addition, the attenuation of the optical variable attenuator can be controlled, the gain at each wavelength in the target stage optical amplifying device becomes uniform, the gain wavelength characteristic can be flattened, and the transmission efficiency can be further improved.

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

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the structure of Example 1 of the optical amplifier concerning this invention. It is a characteristic view which shows the gain wavelength characteristic of each part shown in FIG. Similarly, it is a figure which shows the level diagram which shows the optical power in each part. It is a characteristic view showing a gain wavelength characteristic for explaining that the slope of the gain wavelength characteristic changes depending on the magnitude of the gain. It is a block diagram which shows the structure of Example 2 of the optical amplifier concerning this invention. It is a characteristic view which shows the gain wavelength characteristic of each part shown in FIG. It is a block diagram which shows the structure of Example 3 of the optical amplifier concerning this invention. It is a block diagram which shows the structure of Example 4 of the optical amplifier concerning this invention. It is a block diagram which shows the structure of Example 5 of the optical amplifier concerning this invention. 1 is a system configuration diagram showing the configuration of an embodiment of an optical amplification repeater system using an optical amplification apparatus according to the present invention. It is a system block diagram which shows the structure of the other Example of the optical amplification relay system using the optical amplifier concerning this invention. It is a block diagram which shows an example of a structure of the conventional WDM system. It is a block diagram which shows an example of a structure of the optical amplification apparatus shown by FIG. It is a characteristic view which shows the gain wavelength characteristic of each part shown in FIG. Similarly, it is a figure which shows the level diagram which shows the optical power in each part. It is a figure which shows the relationship between the optical output power and the inclination of the optical spectrum of a WDM signal.

Explanation of symbols

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

Claims (3)

In an optical amplifying and relaying system that amplifies and repeats a wavelength multiplexed optical signal propagated to the optical transmission line in an optical amplifying apparatus connected in multiple stages to the optical transmission line,
Each optical amplifier is
A control monitoring signal transmission circuit for transmitting at least the optical output power output to the optical transmission line connected to the lower stage side as a control monitoring signal to the lower stage optical amplification device via the optical transmission line;
At least one of the light amplifying devices is:
At least two optical amplifying units for amplifying a wavelength multiplexed optical signal input via the optical transmission line;
At least one variable attenuator connected between the two optical amplification units;
A dispersion-compensating optical transmission line connected between the two optical amplification units;
The output power of the other device light that is the optical output power indicated by the control monitoring signal transmitted from the control monitoring signal transmission circuit, the dispersion-compensating optical transmission line optical output power to be output to the dispersion-compensating optical transmission line, and at least one of them Detecting means for detecting the optical output power of the own device to be output to the optical transmission line connected to the latter stage side of the two optical amplifying devices;
The optical output power, a coefficient indicating a slope of a gain generated by stimulated Raman scattering generated in the optical transmission path to which the optical output power is input, an effective length of the optical transmission path to which the optical output power is input, The coefficient indicating the magnitude of the gain gradient when the gain of the optical amplification unit is varied in the design stage, the dispersion-compensated optical transmission line optical output power, and the dispersion-compensated optical transmission line optical output power are output. The optical transmission line and the dispersion-compensating optical transmission line based on a coefficient indicating a slope of gain generated by stimulated Raman scattering generated in the dispersion-compensating optical transmission line and the effective length of the dispersion-compensating optical transmission line And a control means for obtaining a correction value ΔL of the attenuation amount of the variable attenuator for canceling the slope of the gain wavelength characteristic due to stimulated Raman scattering generated by both , and controlling the variable attenuation amount using the ΔL. The concerned An optical amplification repeater system characterized in that an optical power output from an optical transmission line connected to a rear stage side of at least one optical amplification device is kept constant. An optical amplification repeater system that amplifies a wavelength-multiplexed optical signal propagated to the optical transmission line and performs bidirectional optical relay in an optical amplification device connected in multiple stages to at least two optical transmission lines for upstream and downstream In
Each optical amplifier is
A control monitoring signal transmission circuit for transmitting the optical output power to be output to the optical transmission line as a control monitoring signal to the lower-stage optical amplifying device via the optical transmission line;
Between each stage of each optical amplifying device on the two optical transmission lines, a monitoring module that transmits at least the control monitoring signal in both directions is provided,
Among the optical amplification devices, at least one optical amplification device provided on each of the two optical transmission lines is:
At least two optical amplifying units for amplifying a wavelength multiplexed optical signal input via the optical transmission line;
At least one variable attenuator connected between the two optical amplification units;
A dispersion-compensating optical transmission line connected between the two optical amplification units;
The optical output power of the other device, which is the optical output power indicated by the control monitoring signal transmitted from the control monitoring signal transmission circuit and received via the monitoring module, and the dispersion compensated light output to the dispersion compensated optical transmission line Detecting means for detecting the optical output power of the transmission line and the optical output power of the own apparatus output to the optical transmission line connected to the rear stage side of the at least one optical amplifying device;
The optical output power, a coefficient indicating a slope of a gain generated by stimulated Raman scattering generated in the optical transmission path to which the optical output power is input, an effective length of the optical transmission path to which the optical output power is input, The coefficient indicating the magnitude of the gain gradient when the gain of the optical amplification unit is varied in the design stage, the dispersion-compensated optical transmission line optical output power, and the dispersion-compensated optical transmission line optical output power are output. Based on the coefficient indicating the gain gradient generated by stimulated Raman scattering generated in the dispersion-compensating optical transmission line and the effective length of the dispersion-compensating optical transmission line , the optical transmission line and the dispersion-compensating optical transmission line A control means for obtaining a correction value ΔL of the attenuation amount of the variable attenuator for canceling the slope of the gain wavelength characteristic due to stimulated Raman scattering generated by both , and controlling the variable attenuation amount using the ΔL; 2 above An optical amplification repeater system characterized in that the optical power output from the final output end of the optical transmission line is kept constant. At least one of the other optical amplifying devices other than the at least one optical amplifying device has a dispersion-compensating optical transmission line,
The control monitoring signal transmission circuit of the other optical amplifying device includes the dispersion-compensating optical transmission line optical output power output to the dispersion-compensating optical transmission line in the other optical amplifying device as the control monitoring signal. Send
2. The control unit according to claim 1, wherein the control unit controls the variable attenuation amount in consideration of a slope of a gain generated by stimulated Raman scattering generated in a dispersion compensation type optical transmission line in the other optical amplifying device. Or the optical amplification repeater system of 2.

Images