Optical amplifier, light source module and optical system

• US 20020039227A1
• Filed: 07/02/2001
• Published: 04/04/2002
• Est. Priority Date: 06/30/2000
• Status: Active Grant

• Current Assignee: Furukawa Electric Company Limited
• Original Assignee: Furukawa Electric Company Limited
• Inventors: Shimizu, Takeo, Katayama, Etsuji, Tsuda, Toshiaki, Yamaguchi, Takeharu, Aoyagi, Hideo, Irie, Yuichiro
• Granted Patent: US 6,532,107 B2
• Time in Patent Office: Days
• US Class Current: 359/341.3
• CPC Class Codes: H01S 3/094003 the pumped medium being a fibre
• CPC Class Codes: H01S 3/0941 of a laser diode

Abstract

An optical amplifier of the present invention comprises a pumping light source configured to output a pumping light, an amplifier unit configured to receive the pumping light from said pumping light source and amplify an optical signal that passes therethrough, and an optical fiber disposed between said pumping light source and said amplifier unit, said optical fiber including an optical filter that is configured to attenuate the optical signal from said amplifier unit.

Claims

1. An optical amplifier comprising:

a pumping light source configured to output a pumping light;

an amplifier unit configured to receive the pumping light from said pumping light source and amplify an optical signal that passes therethrough; and

an optical fiber disposed between said pumping light source and said amplifier unit;

said optical fiber including an optical filter that is configured to attenuate the optical signal from said amplifier unit.

2. The optical amplifier according to claim 1 wherein:

said amplifier unit is configured to amplify the optical signal, said optical signal having a first wavelength band;

said pumping light having a second wavelength band different from said first wavelength band, and

said optical filter being configured to emit the optical signal having said first wavelength band to a clad mode of said optical fiber so as to attenuate the first wavelength band, said optical filter being configured to permit the second wavelength band of the pumping light to pass therethrough.

3. The optical amplifier according to claim 1 wherein said optical filter is configured as a long-period grating.

4. The optical amplifier according to claim 1 wherein said optical filter includes at least one of a plurality of long-period gratings arranged in series, said long-period gratings having respective central wavelengths different from one another, at each of which a loss of light transmission is at a peak, and a chirped grating in which a grating period is continuously varied from one end of the optical fiber to the other end.

5. The optical amplifier according to claim 1 wherein said amplifier unit includes an optical fiber doped with Er as an amplifying medium.

6. The optical amplifier according to claim 1 wherein the wavelength band of said pumping light is 980 nm and the wavelength band of said optical signal is 1550 nm.

7. The optical amplifier according to claim 1 further comprising a protecting member configured to house said optical filter.

8. A light source module comprising:

a light source configured to output a laser beam;

an optical fiber configured to have said laser beam propagate therethrough; and

an optical filter disposed in said optical fiber and configured to attenuate light having a first wavelength band that is different from a second wavelength band in said laser beam.

9. The light source module according to claim 8 wherein the light having said second wavelength band is an optical signal amplified by an optical amplifier pumped by said laser beam.

10. The light source module according to claim 8 wherein said optical filter is configured to emit the light having the second wavelength band to a clad mode of the optical fiber.

11. The light source module according to claim 8 wherein said optical filter is a long-period grating.

12. The light source module according to claim 8 wherein said optical filter includes at least one of a plurality of long-period gratings arranged in series, said long-period gratings having respective central wavelengths different from one another, at each of which a loss of light transmission is at a peak, and a chirped grating in which a grating period is continuously varied from one end of the optical fiber to the other end.

13. The light source module according to claim 8 wherein the wavelength band of the laser beam from said light source is 980 nm.

14. The light source module according to claim 8 further comprising a protecting member configured to house said optical filter.

15. An optical system comprising:

a first optical device configured to emit a light having a first wavelength band;

a second optical device configured to emit a light having a second wavelength band;

means for connecting said first and second optical devices; and

an optical part configured to propagate the light having the second wavelength band from said second optical device to said first optical device through said connecting means, said optical part being configured to prevent the light having the first wavelength band from said first optical device to enter said second optical device through said connecting means and also to return from said connecting means or said second optical device back to said first optical device.

16. A method for generating pump light for an optical amplifier, comprising steps of;

emitting a light in a first optical bandwidth from a first optical device;

emitting another light in a second optical bandwidth from a second optical device;

passing the another light through a connecting portion from said first optical device to said second optical device, including sub-steps of,

preventing light in the first optical bandwidth from said first optical device from entering said second optical device, and also returning to said first optical device from at least one of said second optical device and the connecting portion.

17. A light source for an optical amplifier, comprising:

means for emitting a light in a first optical bandwidth;

means for emitting another light in a second optical bandwidth;

means for passing the another light to said means for emitting a light, including,

means for preventing light in said first optical bandwidth from entering said means for emitting the another light, and also returning to said means for emitting a light from at least one of said means for emitting the another light and said means for passing.