Raman amplifier, optical repeater, and Raman amplification method

Patent metadata

Field	Value
Publication number	US-9281654-B2
Application number	US-201313859133-A
Country	US
Kind code	B2
Filing date	Apr 9, 2013
Priority date	Jul 23, 1998
Publication date	Mar 8, 2016
Grant date	Mar 8, 2016

Abstract

A Raman amplifier using semiconductor lasers of Fabry-Perot, DFB, or DBR type or MOPAs, to output pumping lights having different central wavelengths, an interval between adjacent central wavelengths greater than 6 nm and smaller than 35 nm. An optical repeater is adapted to compensate loss in an optical fiber transmission line by the Raman amplifier. A Raman amplification method wherein the shorter the central wavelength of the pumping light, the higher light power of the pumping light. In the Raman amplifier, a certain pumping 1 wavelength being a first channel, and second to n-th channels are arranged with an interval of about 1 THz toward a longer wavelength side, pumping lights having wavelengths corresponding to the first to n-th channels are multiplexed, and pumping light having a wavelength spaced apart from the n-th channel by 2 THz or more toward the longer wavelength side is combined with the multiplexed light, thereby forming the pumping light source.

First claim

The invention claimed is:

1. A Raman amplifier comprising:
a pump light source; and
an amplifying optical fiber configured to transmit a signal light and amplify the signal light by a pumping light supplied from the pump light source, wherein the pump light source comprising:
a semiconductor laser,
an external resonator arranged to maintain a predetermined central wavelength of laser light emitted from said semiconductor laser notwithstanding fluctuation of a driving current of said semiconductor laser,
a laser light intensity control unit configured to control a gain profile of the Raman amplifier by controlling the driving current of said semiconductor laser, wherein the predetermined central wavelength of the laser light being maintained substantially constant by the external resonator.

2. The Raman amplifier according to claim 1 , wherein said pump light source further comprising:
one or more additional semiconductor lasers,
one or more additional external resonators corresponding to the one or more additional semiconductor lasers respectively, each additional external resonator being configured to maintain a central wavelength of a respective additional semiconductor laser at a different wavelength than the central wavelength of said semiconductor laser, wherein a laser emission bandwidth of each of said semiconductor lasers is as narrow as 3nm.

3. The Raman amplifier according to claim 1 , wherein said pump light source further comprising:
one or more additional semiconductor lasers,
one or more additional external resonators corresponding to the one or more additional semiconductor lasers respectively, each additional external resonator being configured to maintain a central wavelength of a respective additional semiconductor laser at a different wavelength than the central wavelength of said semiconductor laser, the Raman amplifier further comprising:
a monitor light branching coupler configured to branch a part of the signal light transmitted through the amplifying optical fiber;
a wavelength de-multiplexer configured to de-multiplex the branched part of the signal light into a plurality of de-multiplexed signal lights having different wavelengths; and
a plurality of detectors arranged to measure the intensity of each de-multiplexed signals, wherein the laser light intensity control unit controls driving currents of the plurality of semiconductor lasers in response to the measured intensities of the de-multiplexed signal lights by the plurality of detectors.

4. A Raman amplifier according to claim 3 , wherein each of said different wavelengths corresponds to a wavelength of a maximum gain generated by pumping light of a corresponding pumping wavelength.

5. A Raman amplifier according to claim 1 , wherein said pump light source further comprising:
one or more additional semiconductor lasers,
one or more additional external resonators configured to maintain a central wavelength of a respective additional semiconductor laser at a different wavelength than the central wavelength of said semiconductor laser;
an amplifying optical fiber configured to transmit a signal light and amplify the signal light by a pumping light supplied from the pump light source;
a monitor light branching coupler configured to branch a part of the signal light transmitted through the amplifying optical fiber;
a power splitter configured to split the branched signal lights into a plurality of signal lights, the number of which corresponds to a predetermined number of central wavelengths of the pumping light;
a plurality of detectors arranged to measure the intensities of the split signal lights; and
a plurality of bandpass filters arranged between each of the detectors and the power splitter respectively, each bandpass filter having a different permeable central wavelength, wherein the laser light intensity control unit controls the driving currents of the semiconductor laser in response to the intensities of the split signal lights measured by the plurality of detectors.

6. The Raman amplifier according to claim 1 , wherein the external resonator is a fiber Bragg grating.

7. The Raman amplifier according to claim 6 , further comprising a polarization maintaining optical fiber provided as at least part of a connecting optical fiber connecting the semiconductor laser and the external resonator, or as at least part of an output optical fiber of the external resonator, or as at least part of each of the connecting and output optical fibers, wherein the polarization maintaining fibers output linear-polarized light.

8. The Raman amplifier according to claim 1 , wherein said pump light source further comprising:
one or more additional semiconductor lasers,
one or more additional external resonators corresponding to the one or more additional semiconductor lasers respectively, each additional external resonator being configured to maintain a central wavelength of a respective additional semiconductor laser at a different wavelength than the central wavelength of said semiconductor laser, the Raman amplifier further comprising one or more polarization maintaining optical fibers corresponding to the one or more additional semiconductor laser and provided as at least part of a connecting optical fiber connecting the semiconductor laser and the external resonator, or as at least part of an output optical fiber of the external resonator, or as at least part of each of the connecting and output optical fibers, and the polarization maintaining fibers output linear-polarized light.

9. The Raman amplifier according to claim 8 , wherein the external resonator is a fiber Bragg grating.

10. The Raman amplifier according to claim 1 , further comprising a device configured to measure or monitor intensity of input or output signal light, and said control unit is further configured to control said laser current in order to control the gain profile of the Raman amplifier.

11. The Raman amplifier according to claim 10 , wherein said control unit is further configured to control a gain profile of the Raman amplifier based on the intensity of the input or output signal light.

12. The Raman amplifier according to claim 1 , wherein said pump light source further comprising:
one or more additional semiconductor lasers,
one or more additional external resonators corresponding to the one or more additional semiconductor lasers respectively, each additional external resonator being configured to maintain a central wavelength of a respective additional semiconductor laser at a different wavelength than the central wavelength of said semiconductor laser, the Raman amplifier further comprising a device configured to measure or monitor intensity of input or output signal light, and said control unit is further configured to control said laser current in order to control the gain profile of the Raman amplifier.

13. The Raman amplifier according to claim 12 , wherein said control unit is further configured to control a gain profile of the Raman amplifier based on the intensity of the input or output signal light.

14. The Raman amplifier according to claim 1 , wherein the semiconductor laser is Fabry-Perot type.

15. The Raman amplifier according to claim 14 , wherein the central wavelength of the laser light is within 1400 nm band, and a wavelength of the signal light within 1500 nm band.

16. A pump light source for a Raman amplifier, comprising:
a semiconductor laser;
an external resonator arranged to maintain a predetermined central wavelength of laser light emitted from said semiconductor laser notwithstanding fluctuation of a

Assignees

• Furukawa Electric Co Ltd

Inventors

• Akasaka Youichi
• Emori Yoshihiro
• Namiki Shu

Classifications

• H01S3/13013

  by controlling the optical pumping · CPC title

• H01S3/2383

  Parallel arrangements · CPC title

• H04B10/2916

  using Raman or Brillouin amplifiers · CPC title

• H01S3/302 Primary

  in an optical fibre · CPC title

• H01S3/2375

  Hybrid lasers (H01S3/07 takes precedence) · CPC title