WO2006085370A1 - 光増幅器,光増幅中継器および励起光供給制御方法 - Google Patents
光増幅器,光増幅中継器および励起光供給制御方法 Download PDFInfo
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- WO2006085370A1 WO2006085370A1 PCT/JP2005/001958 JP2005001958W WO2006085370A1 WO 2006085370 A1 WO2006085370 A1 WO 2006085370A1 JP 2005001958 W JP2005001958 W JP 2005001958W WO 2006085370 A1 WO2006085370 A1 WO 2006085370A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/29—Repeaters
- H04B10/291—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form
- H04B10/2912—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form characterised by the medium used for amplification or processing
- H04B10/2916—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form characterised by the medium used for amplification or processing using Raman or Brillouin amplifiers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/09—Processes or apparatus for excitation, e.g. pumping
- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
- H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
- H01S3/094003—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light the pumped medium being a fibre
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
- H01S3/1301—Stabilisation of laser output parameters, e.g. frequency or amplitude in optical amplifiers
- H01S3/13013—Stabilisation of laser output parameters, e.g. frequency or amplitude in optical amplifiers by controlling the optical pumping
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/23—Arrangements of two or more lasers not provided for in groups H01S3/02 - H01S3/22, e.g. tandem arrangements of separate active media
- H01S3/2375—Hybrid lasers
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/29—Repeaters
- H04B10/291—Repeaters in which processing or amplification is carried out without conversion of the main signal from optical form
- H04B10/293—Signal power control
- H04B10/294—Signal power control in a multiwavelength system, e.g. gain equalisation
- H04B10/2942—Signal power control in a multiwavelength system, e.g. gain equalisation using automatic gain control [AGC]
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S2301/00—Functional characteristics
- H01S2301/04—Gain spectral shaping, flattening
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
- H01S3/06754—Fibre amplifiers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/09—Processes or apparatus for excitation, e.g. pumping
- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
- H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
- H01S3/094061—Shared pump, i.e. pump light of a single pump source is used to pump plural gain media in parallel
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/10007—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers
- H01S3/10015—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating in optical amplifiers by monitoring or controlling, e.g. attenuating, the input signal
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/30—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range using scattering effects, e.g. stimulated Brillouin or Raman effects
- H01S3/302—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range using scattering effects, e.g. stimulated Brillouin or Raman effects in an optical fibre
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B2210/00—Indexing scheme relating to optical transmission systems
- H04B2210/003—Devices including multiple stages, e.g., multi-stage optical amplifiers or dispersion compensators
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J14/00—Optical multiplex systems
- H04J14/02—Wavelength-division multiplex systems
- H04J14/0221—Power control, e.g. to keep the total optical power constant
Definitions
- the present invention relates to an optical amplifier, an optical amplifying repeater, and a pumping light supply control method that are suitable for use in an optical transmission system.
- An optical amplifier directly amplifies a signal to compensate for a loss when an optical signal propagates through an optical fiber transmission line in an optical transmission system or a loss of an optical component 'optical module.
- an optical fiber medium for supplying pumping light The pumping light having a predetermined wavelength is supplied to the optical fiber medium for optical amplification by the means for supplying the pumping light, and the optical fiber medium is activated.
- the signal light is optically amplified and output.
- rare earth-doped optical fiber amplifiers doped with rare earth ions such as erbium and Raman amplifiers utilizing Raman stimulated scattering characteristics of optical fibers are applied as optical fiber amplification media.
- WDM wavelength division multiplexing
- Raman amplification technology has been attracting attention for the purpose of improving performance.
- EDF A Erbium Doped Fiber Amplifier
- Optical repeaters are often configured in combination with rare earth-doped optical fiber amplifiers such as optical fiber amplifiers.
- Raman amplification has a peak at about 13.2 THz low frequency from the excitation light frequency (about lOOnm long wavelength when the excitation wavelength is 1.4um band) when silica-based optical fiber is used as the amplification medium. In many cases, it has an asymmetric optical amplification band. In addition, it is possible to superimpose the optical amplification bands by injecting pumping light with a plurality of different wavelengths into the optical fiber, to ensure flatness of the output light level according to the wavelength, and to expect wideband signal light amplification.
- the mainstream configuration of the Raman amplifier is to mount a large number of excitation wavelengths in order to widen the wavelength band that is an amplification band.
- the optical amplification repeater adds a Raman pumping light source to the EDFA pumping light source, which increases power consumption for the pumping light source and tends to increase the mounting area due to the heat sink for heat dissipation. is there.
- the optical amplifier is required to reduce the power consumption of the excitation light source.
- the transmission distance and transmission path loss of a land-based optical transmission system vary, and the signal level input to the optical amplifying repeater differs for each transmission span.
- designing an optical amplifier designing an optical amplifier that maintains the flatness of the output wavelength according to the range of the signal input level results in a large amount of optical amplifier menus, management costs, This is not desirable because problems such as an increase in inventory occur. For this reason, optical amplifiers are often required to have a wide signal input power dynamic range while maintaining the flatness of the output wavelength.
- the tilt characteristic changes greatly depending on the wavelength arrangement of the input optical signal due to the Raman effect between the optical signals, so that the Raman amplification that applies the excitation light of a plurality of wavelengths as described above is performed. In doing so, it is necessary to supply pumping light having a plurality of wavelengths at a power ratio that maintains the flatness of the output signal light wavelength according to the wavelength arrangement of the input optical signal.
- a rare earth doped fiber amplifier is provided after the Raman amplification medium, it is necessary to consider the tilt characteristics of the output of the rare earth doped fiber amplifier.
- the branching ratio and pumping intensity of this pumping light are controlled while supplying one system of pumping light to the fiber amplifier and the Raman amplifier. And there is something that controls the Raman gain (special (See Permissible Literature 2).
- Patent Document 1 JP 2000-98433 A
- Patent Document 2 JP 2003-283019
- Patent Document 3 Japanese Translation of Special Publication 2004-511004
- Patent Document 4 Japanese Patent Laid-Open No. 11-84440
- the Raman amplifier does not individually change the branching ratio of the excitation light having a plurality of wavelengths, so that the input signal light as described above is used.
- the flatness of the output signal light cannot be ensured according to the wavelength arrangement.
- none of the techniques described in Patent Documents 3 and 4 can ensure the flatness of the output signal light according to the wavelength arrangement of the input signal light, as in the case described above.
- the present invention has been made in view of such a problem, and an object thereof is to ensure flatness of output signal light according to the wavelength arrangement of input signal light.
- Another object is to increase the efficiency of use of excitation light.
- an optical amplifier includes a Raman amplifying medium for inputting wavelength multiplexed signal light, a rare earth-doped fiber provided in a subsequent stage of the Raman amplifier, the Raman amplifying medium, and A first pumping light output unit capable of outputting pumping light having a plurality of wavelengths including a wavelength capable of causing an amplification action on the wavelength multiplexed signal light in both of the rare earth-doped fibers, and the first pumping light output unit.
- a variable distribution element capable of distributing the output excitation light of a plurality of wavelengths to the Raman amplification medium and the rare earth-doped fiber at a variable distribution ratio for each wavelength, and each signal light wavelength-multiplexed with the wavelength multiplexed signal light
- a control unit for individually controlling the distribution ratio for each wavelength in the variable distribution element and the power of the pumping light of the plurality of wavelengths from the first pumping light output unit according to the wavelength arrangement of Configured It is characterized in that was.
- the Raman amplification medium can be used as a dispersion compensating fiber to perform lumped Raman amplification, or the Raman amplification medium can be used as a transmission line fiber to perform distributed constant Raman amplification. .
- a second pumping light output unit for pumping the rare earth-doped fiber may be provided.
- control unit controls a distribution ratio in the variable distribution element
- a pumping control unit controls the pumping light power output from the first pumping light output unit.
- the distribution ratio control unit and the excitation control unit may be controlled according to the wavelength of each signal light multiplexed in wavelength with the wavelength multiplexed signal light.
- the optical amplification repeater of the present invention is an optical amplification repeater that is connected to the input side optical transmission line and the output side optical transmission line and relays wavelength multiplexed light, and includes a rare earth doped fiber and the input side optical transmission line.
- a first pumping light output unit capable of outputting pumping light having a plurality of wavelengths, including a wavelength capable of causing an amplification action on the wavelength-multiplexed signal light in both of the rare earth-doped fiber and the pumping light.
- variable distribution element that can be distributed to the input-side optical transmission line and the rare earth-doped fiber with a variable distribution ratio, and the variable distribution element according to the wavelength arrangement of each signal light wavelength-multiplexed with the wavelength-division multiplexed signal light
- control unit that individually controls the distribution ratio of the pumping light of the plurality of wavelengths and the power of the pumping light of the plurality of wavelengths from the first pumping light output unit. Speak.
- the pumping light supply control method of the present invention includes a Raman amplification medium for inputting a wavelength multiplexed optical signal, a rare earth-doped fiber provided in a subsequent stage of the Raman amplifier, the Raman amplification medium, and the rare earth-doped fiber.
- a first pumping light output unit capable of outputting pumping light of a plurality of wavelengths, including wavelengths that can cause an amplification action on the wavelength-multiplexed signal light on both sides, and a plurality of wavelengths output from the first pumping light output unit Of the pumping light separately from the first pumping light output unit, and a variable distribution element capable of distributing the pumping light to the Raman amplification medium and the rare earth doped fiber at a variable distribution ratio for each wavelength.
- a pumping light supply control method for an optical amplifier comprising: a pumping light output unit; and At the time of raising, the pumping light of the first pumping light output unit force is concentratedly supplied to the Raman amplification medium according to the wavelength arrangement of each signal light wavelength-multiplexed with the wavelength-multiplexed signal light. After setting the distribution ratio in the variable distribution element, the output from the Raman amplification medium can be obtained at the level of the Raman amplification output that is the control target, and the excitation light spectrum is unstable.
- the distribution ratio of the variable distribution element is controlled together with the pumping light power at the first pumping light output unit so as to be equal to or higher than the lower limit value set as an indicator that the The pumping light of the second pumping light output unit force is supplied to the rare earth doped fiber so that the level of the output signal light becomes the target output level of the entire optical amplifier, and the first pumping light output unit
- the variable distribution element together with the pumping light power at As control means controls the distribution ratio, Ru.
- the level of the output signal light of the optical amplifier power is changed to the target output level to be changed.
- the pumping light power at the first pumping light output unit is controlled to be changed, and the Raman amplification output in the Raman amplifying medium is changed by changing the pumping light power at the first pumping light output unit.
- the present invention in order to perform respective optical amplification in the Raman amplifying medium and the rare earth-doped fiber by the first pumping light output unit and the variable distribution element, by appropriately adjusting the distribution ratio of the variable distribution element while using the pumping light in common, the flatness of the output signal light is ensured according to the wavelength arrangement of the input signal light, and the optical characteristics are improved while improving the noise characteristics.
- the power consumption required for pumping light output can be made more efficient.
- FIG. 1 is a diagram showing an optical amplifier that works according to the first embodiment of the present invention.
- FIG. 2 is a diagram showing a configuration of a variable distribution element according to the first embodiment of the present invention.
- FIG. 3 is a flow chart for explaining the start-up operation of the optical amplifier that is effective in the first embodiment.
- FIG. 5 is a diagram for explaining the pumping light supply operation in the case of (a) 1 (d) m, where the deviation is a relatively small Raman amplification gain).
- FIG. 6 is a flowchart for explaining an operation when changing the level of output signal light as a control target in the optical amplifier according to the first embodiment.
- FIG. 7 (a) and (d) are diagrams for explaining the operation when the level of the output signal light as a control target in the optical amplifier is changed.
- FIG. 8 is a diagram illustrating the effect of the present invention.
- FIG. 9 is a diagram showing an optical amplifier according to a second embodiment of the present invention.
- Distribution ratio control circuit (Distribution ratio controller)
- FIG. 1 is a diagram showing an optical amplifier 1 according to a first embodiment of the present invention.
- a dispersion compensating fiber (DCF) 2 as a Raman amplifying medium and an erbium doped optical fiber (EDF) 3 as a rare earth doped fiber are cascaded in this order from the signal input side.
- Amplifier output setting circuit 9 branching force bra 10a-10c, multiplexer 11a-11c, optical isolators 12a-12d, and wavelength filter 13 are configured!
- the optical amplifier 1 according to the first embodiment can be applied as an optical amplifying repeater in a WDM optical transmission system, and outputs pumping light having a plurality of pumping wavelength forces to the first pumping light output.
- the output light from the unit 41 is supplied to the DCF 2 so that the input signal light is Raman-amplified, and a part of the pump light output from the first pump light output unit 41 is also used as the excitation light of the EDF 3. It has a configuration.
- the optical amplifier 1 can set a power distribution ratio for each pump wavelength from the first pump light output unit 41 that allocates a part of the pump light power to the DCF 2 for pumping the EDF 3.
- the variable distribution element 5 is provided.
- the DCF 2 compensates for the dispersion by the wavelength-division multiplexed signal light as the input signal light, and transmits the pump light from the first pump light output unit 41 through the variable distribution element 5 and the multiplexer 11a described later.
- the supplied signal light functions as a Raman amplification medium capable of performing Raman amplification (in a lumped constant manner).
- the EDF 3 supplies a part of the pump light output from the first pump light output unit 41 as backward pump light through the variable distribution element 5 and the multiplexer 11c, and forms the second pump light output unit.
- Light from LD (Laser Diode) 4—2 is supplied as forward pumping light through a multiplexer 1 lb to amplify Raman-amplified signal light by DCF2.
- the first pumping light output unit 41 can output pumping light having a plurality of wavelengths including a wavelength capable of causing an amplification effect on the input wavelength multiplexed signal light to both the DCF2 and the EDF3.
- the excitation light sources 4a and 4b having plural (for example, two) LD forces having different oscillation wavelengths ⁇ 1 and ⁇ 2 are provided. It has a level monitor 4c that monitors the light level output by the excitation light sources 4a and 4b.
- the excitation light wavelengths ⁇ 1 and ⁇ 2 output from the excitation light sources 4a and 4b are used for both the DCF2 Raman amplification and the EDF3 excitation.
- the wavelength can be as short as about lOOnm from the long band (ie 1.45 m band and 1.48 m band).
- the variable distribution element 5 distributes the excitation light output from the two excitation light sources 4a and 4b at a power distribution ratio set for each excitation wavelength.
- the distributed pumping light can be supplied to DCF2 through the multiplexer 11a and supplied as back pumping light to EDF3 through the multiplexer 1 lb. Further, the variable distribution element 5 has a configuration as shown in FIG. 2 to be described later, for example.
- the pumping light output from the first pumping light output unit 41 is used as pumping light to DCF2 and EDF3. Thus, distribution can be performed with a variable distribution ratio.
- the PD 6a monitors the level of the signal light input to the optical amplifier 1 based on the light branched by the branch coupler 10a.
- the PD 6b The level of the output signal light that is also output by 1 force is monitored based on the light branched by the branching force bra 10c.
- the excitation control circuit 7 controls the power of the excitation lights ⁇ 1, 1, ⁇ 2 output from the excitation light sources 4a and 4b by driving and controlling the excitation light sources 4a and 4b.
- a tilt characteristic that can also be obtained as a result of monitoring from the PDs 6a and 6b is determined according to the wavelength arrangement of each signal light wavelength-multiplexed with the wavelength multiplexed signal light. So that the gain of the optical amplifier 1 can be controlled so as to be a gain set by the amplifier output setting circuit 9 described later or a Raman amplification output level (first level) so as to be a control target. 4a, 4b can now be controlled.
- the PDs 6c and 6d monitor the signal light level Raman-amplified by the DCF 2 for each wavelength band.
- PD6c monitors the signal light level on the short wavelength side when the signal light wavelength band is divided into two, and monitors the signal light level on the long wavelength side when the PD6d signal light wavelength band is divided into two.
- the branching coupler 10b branches a part of the signal light Raman-amplified by DCF2, and the wavelength filter 13 branches the branched light from the branching force bra 10b into two signal lights divided into two by the signal light wavelength band. Supply to PD6c and 6d, respectively.
- the distribution ratio control circuit 8 uses the wavelength gain set by the amplifier output setting circuit 9 based on the channel arrangement of the wavelength multiplexed optical signal based on the monitoring result in the PDs 6c and 6d.
- the above distribution ratio in the variable distribution element 5 is variably controlled so that the characteristic (tilt information) and the target output signal level (first level) can be obtained by Raman amplification.
- the circuit 9 functions as a control target providing unit that gives control targets in the distribution ratio control circuit 8 and the excitation control circuit 7 according to the wavelength arrangement of each signal light wavelength-multiplexed with the input wavelength multiplexed signal light. is there. That is, the distribution ratio control circuit 8 and the excitation control circuit 7 are controlled according to the wavelength of each signal light wavelength-multiplexed with the wavelength multiplexed signal light.
- the amplifier output setting circuit 9 includes a Raman output signal level (first level) that is a control target in the above-described excitation control circuit 7 and distribution ratio control circuit 8, and a control target as an optical amplifier output.
- first level a Raman output signal level
- second level a control target in the above-described excitation control circuit 7 and distribution ratio control circuit 8
- This wavelength gain characteristic can be determined based on, for example, wavelength arrangement information that also provides management signal power in the WDM optical transmission system described above. That is, based on this wavelength arrangement information, the wavelength gain characteristic to be controlled and the distribution ratio in the variable distribution element 5 are also determined.
- variable distribution element 5 uses the excitation control circuit 7, the distribution ratio control circuit 8 and the amplifier output setting circuit 9 described above according to the wavelength arrangement of each signal light wavelength-multiplexed with the wavelength multiplexed signal light.
- 2 wavelength pumping light ⁇ ⁇ 1, ⁇ ⁇ 2 distribution ratio and first pumping light output unit 41 Control unit to control power of 2 wavelengths pumping light ⁇ 1, ⁇ 2 individually Make up 40.
- FIG. 2 is a diagram showing the variable distribution element 5.
- the variable distribution element 5 in the first embodiment includes power distribution ratio variable couplers 5a and 5b and WDM couplers 5c and 5d.
- the power distribution ratio variable power bra 5a distributes the pumping light P ⁇ 1 from the LD4a in two directions with a variable distribution ratio
- the power distribution ratio variable power bra 5b has the pumping light of LD4b power ⁇ ⁇ 2 Is distributed in two ways with a variable distribution ratio.
- the distribution ratio variable force bra 5a receives the control from the distribution ratio control circuit 8 and supplies the excitation light P ⁇ 2 from the LD 4b! /, And the distribution ratio b (0 ⁇ b ⁇ 1) and at the distribution ratio (1-b) for EDF3 excitation.
- the WDM coupler 5c combines the pumping light distributed for pumping the DCF2 by the power distribution ratio variable couplers 5a and 5b, and supplies the pumping light aP ⁇ 1 + bP ⁇ 2 to the multiplexer 1 la. Output.
- the WDM coupler 5d combines the pump lights distributed for pumping the EDF3 by the power distribution ratio variable couplers 5a and 5b, and the pump light (1 a) P ⁇ 1 + (1 ⁇ b) P ⁇ 2 Is output to the multiplexer 11c.
- variable distribution element 5 branches the pumping light power, which is also input with the LD 4a and 4b forces, into the ratio set by the control of the distribution ratio control circuit 8 in the power distribution ratio variable couplers 5a and 5b.
- the input signal light is Raman-amplified by the DCF 2 and then amplified by the EDF 3 and output as output signal light.
- the distribution ratio control circuit 8 controls the variable distribution element 5 based on the monitoring results from the PDs 6c and 6d, so that the signal light output from the DCF2 is set by the amplifier output setting circuit 9. It has a light level for each wavelength.
- the distribution ratio control circuit 8 sets the pumping light power of the wavelength ⁇ 2 together with the pumping light power of the wavelength ⁇ 1 that forms the pumping light to be supplied to the DCF 2 by controlling the distribution ratio for the variable distribution element 5.
- the light level (tilt information) for each wavelength can be controlled to have, for example, a substantially flat characteristic according to the wavelength arrangement of the input signal. is there.
- FIGS. 4 (a) to 4 (d) are diagrams for explaining the pumping light supply operation when the Raman amplification gain is relatively large.
- Fig. 4 (a) is a time chart of pumping light power Pp for DCF2, Fig.
- FIG. 4 (b) is a time chart of pumping light power Pp for EDF3
- Fig. 4 (c) is the first and second pumping light output units 41, 42 is a time chart of the pumping light power Pp output at 2
- FIG. 4D is a time chart showing a change in distribution ratio by the variable distribution element 5.
- Fig. 4 (a)-Fig. 4 (d) when the Raman amplification gain of DCF2 is set to be relatively large, for example, when the loss as DCF2 is relatively large, There are cases where the level is relatively small.
- FIGS. 5 (a) to 5 (d) are diagrams for explaining the pumping light supply operation in the case where the Raman amplification gain is made relatively small.
- Fig. 5 (a) is a timing chart of pumping light power Pp for DCF2
- Fig. 5 (b) is a time chart of pumping light power Pp for EDF3
- Fig. 5 (c) is the first and second pumping light output units 41
- 42 is a time chart of the pumping light power Pp output at 42
- FIG. 5 (d) is a time chart showing a change in distribution ratio by the variable distribution element 5.
- FIG. 5 (a)-Fig. 5 (d) when the Raman amplification gain of DCF2 is set to be relatively small, for example, when the loss as DCF2 is relatively small, The level is relatively small!
- the output from the DCF 2 can obtain the level (first level) of the Raman amplification output that is the control target, and the excitation light spectrum is unstable.
- the distribution ratio of the variable distribution element 5 is controlled together with the pumping light power at the first pumping light output unit 41 so as to be equal to or higher than the lower limit value set as an index of not performing the keying (step A1 to A5).
- the excitation power distribution ratios a and b to the DCF 2 by the power distribution ratio variable couplers 5a and 5b of the variable distribution element 5 are both set to “1” as initial values.
- the distribution ratio is set so that the power of the excitation light ⁇ ⁇ ⁇ and ⁇ ⁇ 2 output from the excitation light sources 4a and 4b is concentrated and supplied to the DCF 2 as an initial value! Step A1).
- the pumping light power from the pumping light sources 4 a and 4 b is raised by the pumping control circuit 7. This allows variable distribution in DCF2.
- the input signal light is Raman-amplified by the element 5 and the supplied pumping light power (step A2).
- the power distribution ratio variable couplers 5a and 5b by the distribution ratio control circuit 8 The distribution ratio control and the drive control for the excitation light sources 4a and 4b by the excitation control circuit 7 are performed in cooperation.
- a technique for flattening the signal power characteristic of the Raman amplifier output with respect to the wavelength described in JP-A-2002-72262 can be used.
- the excitation control circuit 7 drives and controls the excitation light sources 4a and 4b so that the Raman-amplified optical signal becomes the target level at the first level set by the amplifier output setting circuit 9.
- the pumping light sources 4a and 4b are driven so that both have the same power output (see time tO-tl in FIG. 4 (c) or FIG. 5 (c)).
- the first level is the target output signal level to be obtained by Raman amplification in DCF2.
- the power distribution ratio variable power brazing is performed so that the signal power wavelength characteristic is flattened by Raman amplification by the DCF2.
- the distribution ratio in 5a and 5b can be controlled (see step A3, time tO-tl in FIG. 4 (d) or FIG. 5 (d)).
- the excitation light level output from the excitation light sources 4 a and 4 b has an unstable waveform. Whether or not the value is equal to or greater than the lower limit value set by using the not functioning as an index is determined based on the value from the level monitor 4c provided in the first excitation light output unit 41 (step A4).
- the distribution ratio control circuit 8 changes the distribution ratio in the power distribution ratio variable force bras 5a and 5b and distributes the excitation power to the EDF 3. In other words, by reducing the values of the distribution ratios a and b, the excitation power distributed to the DCF 2 is reduced (from the No route in step A4 to step A5). In the excitation control circuit 7, the excitation power in the excitation light sources 4a and 4b is further increased and controlled so that the first output signal level can be maintained by the Raman amplification by DC F2 even by changing the distribution ratio (from step A5). (Step A3)
- step A5 after changing the distribution ratios a and b low (in this case, the same change amount for both a and b), the excitation light sources 4a, 4a, Increase the pump light power from 4b.
- the Raman amplifier can adjust the power of the multi-wave excitation light incident on the amplification medium to change the average output level while maintaining the flatness of the signal output wavelength characteristic.
- the excitation wavelength may become unstable near the optical power threshold value of the pumping light output by, which leads to instability of Raman amplification characteristics.
- Step A1 In step A5, by controlling the distribution ratio of the power distribution ratio variable force bras 5a and 5b in cooperation with the pump light power control, the wavelength is higher than the lower limit where the wavelength does not become unstable.
- the Raman amplification output at the target level can be obtained while outputting the pumping light, so that the restriction by the lower limit value on the pumping light power as described above can be eliminated.
- the target Raman amplification output is obtained while the outputs from the excitation light sources 4a and 4b are in a stable output state (Yes route in step A4), the output signal from the optical amplifier 1 is then output.
- the pumping light from the second pumping light output unit 42 is supplied to the EDF 3 so that the light level becomes the target output level (second level) of the optical amplifier 1 as a whole, and the first pumping light output
- the distribution ratio of the variable distribution element 5 is controlled together with the pumping light power in the unit 41 (step A6—step A10).
- the pumping control circuit 7 drives and controls the second pumping light output unit 42 to start up the forward pumping light for the EDF 3 (step A6) and output the second pumping light output. Increase the optical level until the pumping light level output from part 4-2 reaches the upper pumping power limit (from the Yes route of Step A8 to Step A6, Figure 4 (b) or Figure 5 (b) Point tl 1 t2).
- the pumping light power output from the first pumping light output unit 4-1 and the distribution ratio setting in the variable distribution element 5 are constant [FIG. 4 (a). -See Fig. 4 (d) or Fig. 5 (a)-Fig. 5 (d) at time t1 t2.
- the branching ratio control circuit 8 increases the light supplied to the EDF 3 as backward pumping light by changing the distribution ratio of the power distribution ratio variable force bras 5a and 5b to (almost) the same ratio [step No route of A7, No route of step A8 to step A6, see Fig. 4 (a)-Fig. 4 (d) or Fig. 5 (a)-Fig. 5 (d), point t2-3]
- the distribution ratio is changed so that the excitation light to be supplied to the DCF 2 is reduced.
- the excitation control circuit 7 causes the Raman amplification by the DCF 2 to be performed. So that the first output signal level can be maintained by the excitation light sources 4a and 4b.
- the excitation power is further increased and controlled (step A9).
- the distribution ratio is changed at a constant rate that allows the control to keep the Raman amplification output constant, so that the Raman amplification output is set to the first level, and the level of the optical amplifier 1 output is changed. Until the target level is reached to the second level, the distribution ratio is sequentially changed to increase the pumping light power supplied to EDF3 (from No route of step A9 to step A10).
- FIGS. 7A to 7D are diagrams for explaining the excitation light supply control when the output signal light level that is the control target is changed.
- the first pumping light output unit 4 When changing the target output level of the optical amplifier 1 as a whole, first, the first pumping light output unit 4 so that the level of the output signal light from the optical amplifier 1 becomes the changed target output level.
- the pump light power at 1 is changed and controlled (Step B1—Step B3).
- step Bl the control target gain as the optical amplifier 1 is changed so as to obtain a desired output optical signal level
- the gain for Raman amplification of DCF2 (DCFRA gain)! / Is the setting at the completion of startup even when the control target gain as the optical amplifier 1 is changed.
- DCFRA gain the gain to amplify the signal light with EDF3 as EDFA This corresponds to the change of the output signal light level of the control target.
- the pump control circuit 7 controls the change of the pump light power from the pump light sources 4a and 4b, and the output signal light level becomes P2. Like that.
- the pump control circuit 7 in this case, the gain of the optical amplifier 1 becomes the changed control target gain
- the pump light source 4a Change (decrease) the pump light power from 4b (control loop consisting of No route of steps B2 and B3).
- the Raman amplification output in DCF 2 that changes according to the change in the excitation light power at the first excitation light output unit 41 is switched to the Raman amplification output (first level) that is the control target.
- Distribution in the variable distribution element 5 The ratio is changed and controlled (No route of step B4, control loop consisting of step B5 and step B6).
- step B3 when the pumping light power is changed, the distribution ratio in the variable distribution element 5 is not subjected to change control, so as shown in FIG.
- the level of the Raman amplification output has also changed (decreased) from the initial setting level P3 to P4.
- the output signal light level is maintained at P2, while the distribution ratio control circuit 8 controls the distribution ratio in the variable distribution element 5 so that the Raman amplification gain (or DCF2 output) in DCF2 becomes the original setting level P3 [Step B4-B6, Fig. 7 (c) reference ⁇ .
- the Raman amplification gain in the DCF 2 is changed, the gain in the EDF 3 is also reduced by changing the branching ratio so that the gain of the optical amplifier 1 as a whole is kept constant.
- the branching ratio control circuit 8 repeatedly repeats a predetermined unit amount until the Raman amplification gain (or DCF2 output) in DCF2 reaches the original set level P3. b will be increased. Therefore, the pumping at the first pumping light output unit 41 should flatten the slope of the output signal light power wavelength characteristic due to the gain change of the EDF3 by changing and controlling the distribution ratio in the variable distribution element 5.
- the distribution ratio of the variable distribution element 5 is controlled together with the optical power (Step B7—Step B10).
- the slope of the output signal light power wavelength characteristic due to the gain change of EDF3 is calculated from the relational expression between the signal output power and the tilt generated by EDFA, which is obtained in advance as the characteristic of EDF3.
- the pumping light power from the pumping light sources 4a and 4b is changed and controlled by the pumping control circuit 7. Control is performed so that the level of the output signal light from is kept at a constant level P2 (step B9). Thereafter, the first pumping light output unit 41 keeps the slope of the output signal light power wavelength characteristic due to the gain change of EDF3 flat and the gain of the optical amplifier 1 as a whole is kept at a constant level P2.
- the distribution ratio of the variable distribution element 5 is controlled together with the excitation light power (control loop consisting of step B7, No route, step B8, and step B9).
- the pump control circuit 7 and the distribution ratio control circuit 8 cooperate.
- the Raman amplification output level at DCF2 is controlled to follow the first level while maintaining the changed output signal light level, and the output signal light power wavelength characteristics are flattened. (From step B7 Yes route to step B10).
- the first pumping light output unit 41 and the variable distribution element 5 perform the respective optical amplification in the DCF 2 and the EDF 3.
- control unit 40 appropriately adjusts the distribution ratio of the variable distribution element 5 according to the channel arrangement of the wavelength multiplexed signal light while using the pump light from the first pump light output unit 41 in common.
- the optical amplifier output level or the optical amplifier gain can be controlled while improving the noise characteristics.
- the power ratio of the required excitation wavelength varies greatly depending on the number of channels of the input signal light and the channel arrangement, but each pump can be adapted to accommodate any number of channels.
- the wavelength provides a margin of power, and this margin is shared as the pump light for EDFA, so that the power consumption required for pump light output can be reduced according to the number of input signal light channels and the channel arrangement.
- power consumption can be reduced as a whole by efficiently using the optical amplifier.
- the input dynamic range is absorbed by VO A included in the EDFA.
- the excitation control circuit 7 and the distribution ratio control circuit 8 perform gain control of the EDF A itself and excitation power adjustment for Raman amplification, thereby ensuring the gain flatness and the above-described input dynamics.
- the range can be absorbed (that is, it can cope with fluctuations in the input signal light level), and the VOA that was necessary to absorb the input dynamic range is no longer required.
- the characteristics can be improved. For example, as shown in FIG. 8, the noise figure (NF) with respect to the output power per channel can be greatly reduced as compared with the conventional configuration.
- FIG. 9 is a diagram showing an optical amplifying repeater 20 that works according to the second embodiment of the present invention.
- the optical amplifying repeater 20 shown in FIG. 9 is connected to the transmission line fiber 22 that is the input side transmission line and the transmission line fiber 34 that is the output side transmission line, and relays the wavelength multiplexed light.
- EDF23, first and second pumping light output units 24-1, 24- which correspond to the components indicated by reference numerals 3-9, 10a-10c, 11a-11c, and 13 in the optical amplifier 1 in the first embodiment.
- the optical transmission line fiber 21 to be Raman amplified and the optical amplification repeater 20 constitute an optical amplifier 35.
- excitation control circuit 27, the distribution ratio control circuit 28, and the amplifier output setting circuit 29 described above constitute the same control unit 40 as in the first embodiment.
- the signal light is input from the left end of the transmission line, and distributed Raman amplification is performed in a distributed constant manner using the transmission line fiber 22 as an amplifying medium, and EDF3 is optically amplified as an EDFA, and is transmitted to the output side transmission line fiber 34. By outputting, the optical signal can be relayed.
- the pumping light for Raman amplification in the transmission line fiber 22 is obtained by the first pumping light output unit 24-1.
- the pumping light for amplification by EDF23, and the control unit 40 uses the first pumping light output unit 24-1 according to the wavelength arrangement of each signal light wavelength-multiplexed with the wavelength multiplexed signal light. Since the output pumping light can be supplied and controlled to the transmission line fiber 22 and the EDF 23, the same advantage as in the case of the first embodiment can be obtained.
Abstract
Description
Claims
Priority Applications (3)
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PCT/JP2005/001958 WO2006085370A1 (ja) | 2005-02-09 | 2005-02-09 | 光増幅器,光増幅中継器および励起光供給制御方法 |
JP2007502513A JP4399496B2 (ja) | 2005-02-09 | 2005-02-09 | 光増幅器,光増幅中継器および励起光供給制御方法 |
US11/831,252 US7400441B2 (en) | 2005-02-09 | 2007-07-31 | Optical amplifier, optical amplification repeater and pump light supply control method |
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PCT/JP2005/001958 WO2006085370A1 (ja) | 2005-02-09 | 2005-02-09 | 光増幅器,光増幅中継器および励起光供給制御方法 |
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US11/831,252 Continuation US7400441B2 (en) | 2005-02-09 | 2007-07-31 | Optical amplifier, optical amplification repeater and pump light supply control method |
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Cited By (4)
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JP2007094289A (ja) * | 2005-09-30 | 2007-04-12 | Sumitomo Electric Ind Ltd | ラマン増幅器 |
JP2009188110A (ja) * | 2008-02-05 | 2009-08-20 | Nec Corp | 光増幅装置 |
WO2018097074A1 (ja) * | 2016-11-28 | 2018-05-31 | 日本電気株式会社 | 光通信装置および光増幅用の励起光を供給する装置 |
WO2018097281A1 (ja) | 2016-11-28 | 2018-05-31 | 日本電気株式会社 | 光増幅装置、励起光供給方法および回路 |
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US8233214B2 (en) * | 2008-02-13 | 2012-07-31 | Maxim Bolshtyansky | Optical fiber amplifier and a control method therefor |
US8111454B2 (en) * | 2009-02-13 | 2012-02-07 | Xtera Communications, Inc. | Optical communication using shared optical pumps |
JP5304378B2 (ja) * | 2009-03-26 | 2013-10-02 | 富士通株式会社 | 光増幅器 |
US9083142B2 (en) * | 2010-10-22 | 2015-07-14 | Nec Corporation | Excitation light distribution device, excitation light distribution method, optical amplification system and node device |
JP2017017605A (ja) * | 2015-07-03 | 2017-01-19 | 富士通株式会社 | 伝送路損失測定装置、伝送路損失測定方法、及び、光伝送システム |
CN108141283B (zh) * | 2015-09-29 | 2020-07-28 | 日本电气株式会社 | 光中继器和光中继器的控制方法 |
EP3598668A4 (en) * | 2017-03-17 | 2020-03-18 | Nec Corporation | OPTICAL UNDERWATER CABLE SYSTEM AND OPTICAL UNDERWATER RELAY DEVICE |
US20210028590A1 (en) | 2018-04-11 | 2021-01-28 | Nec Corporation | Optical amplifier, optical communication system and optical amplification method |
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WO2018097074A1 (ja) * | 2016-11-28 | 2018-05-31 | 日本電気株式会社 | 光通信装置および光増幅用の励起光を供給する装置 |
WO2018097281A1 (ja) | 2016-11-28 | 2018-05-31 | 日本電気株式会社 | 光増幅装置、励起光供給方法および回路 |
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US7400441B2 (en) | 2008-07-15 |
JP4399496B2 (ja) | 2010-01-13 |
JPWO2006085370A1 (ja) | 2008-06-26 |
US20070268569A1 (en) | 2007-11-22 |
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