Gain flattening utilizing a two-stage erbium-based amplifier

• US 20070286559A1
• Filed: 10/11/2006
• Published: 12/13/2007
• Est. Priority Date: 06/08/2006
• Status: Active Grant

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: Yeh, Chien-Hung, Chi, Sien
• Granted Patent: US 7,702,201 B2
• Time in Patent Office: Days
• US Class Current: 385/123
• CPC Class Codes: G02B 2006/1208 Rare earths
• CPC Class Codes: G02B 2006/12183 Ion-exchange
• CPC Class Codes: G02B 6/02 Optical fibres with cladding with or without a coating
• CPC Class Codes: G02B 6/30 for use between fibre and thin-film device
• CPC Class Codes: H01S 2301/04 Gain spectral shaping, flattening
• CPC Class Codes: H01S 3/063 Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength waveguide gas lasers H01S3/0315
• CPC Class Codes: H01S 3/06754 Fibre amplifiers H01S3/06708 takes precedence
• CPC Class Codes: H01S 3/094061 Shared pump, i.e. pump light of a single pump source is used to pump plural gain media in parallel
• CPC Class Codes: H01S 3/2316 Cascaded amplifiers
• CPC Class Codes: H04B 10/2941 using an equalising unit, e.g. a filter H04B10/296 takes precedence

Abstract

An optical amplifier is disclosed having a substantially uniform spectral gain. In an exemplary embodiment, the optical amplifier comprises a planar waveguide including a substrate, which includes a region doped with rare earth element. The optical amplifier also comprises an optical fiber including a core doped with the rare earth element. The optical fiber is optically coupled to the planar waveguide.

Claims

1. An optical amplifier comprising:

a planar waveguide including a substrate, the substrate including a region doped with a fluorescent material; and

an optical fiber including a core doped with the fluorescent material, the optical fiber being optically coupled to the planar waveguide.

2. An optical amplifier in accordance with claim 1, further comprising:

a first coupler configured to combine a first input optical signal and a first pump light onto a first optical communication path portion, the first optical communication path portion being coupled to the planar waveguide; and

a second optical coupler being configured to combine a second input optical signal and a second pump light onto a second optical communication path portion, the second optical communication path portion being coupled to the optical fiber.

3. An optical amplifier in accordance with claim 2, further comprising:

an optical source; and

a third optical coupler having an input coupled to the source and first and second outputs, the first output being configured to supply the first pump light to the first optical coupler and the second output being configured to supply the second pump light to the second optical coupler.

4. An optical amplifier in accordance with claim 2, wherein the planar waveguide has an input portion and an output portion, the optical amplifier further comprising:

a first optical isolator coupled to the input portion of the planar waveguide via the first coupler;

an optical filter configured to substantially block transmission of the first pump light, the optical filter being coupled to the output portion of the planar waveguide; and

a second optical isolator coupled to the optical filter.

5. An optical amplifier in accordance with claim 2, further comprising:

a first optical source configured to output the first pump light, the first optical source being coupled to the first optical coupler; and

a second optical source configured to output the second pump light, the second optical source being coupled to the second optical coupler.

6. An optical amplifier in accordance with claim 2, wherein the first and second pump lights include light having a wavelength substantially equal to 980 nm.

7. An optical amplifier in accordance with claim 1, wherein the fluorescent material includes a rare earth element.

8. An optical amplifier in accordance with claim 6, wherein the rare earth element includes erbium.

9. An optical amplifier in accordance with claim 1, wherein the optical amplifier is configured to receive an input optical signal and supply an output optical signal in response to the input optical signal, wherein when the input optical signal has an optical power of −

25 dBm and said input optical signal includes a plurality of optical signals having wavelengths in a range of 1528 nm to 1562 nm, an amount of gain associated with the optical amplifier is greater than or equal to 37 dB, and a variation of the gain is equal to or less than 1.1 dB over the range of 1528 nm to 1562 nm.

10. An optical amplifier in accordance with claim 1, wherein an input signal to the optical amplifier is supplied to the planar waveguide and an output signal of the optical amplifier is supplied from the optical fiber.

11. An optical amplifier in accordance with claim 1, wherein an input signal to the optical amplifier is supplied to the optical fiber and an output signal of the optical amplifier is supplied from the planar waveguide.

12. A wavelength division multiplexing transmission system, comprising:

a plurality of transmitters each of the plurality of transmitters being configured to transmit a respective one of a plurality of optical signals, wherein each of the plurality of optical signals is at a respective one of a plurality of wavelengths;

a multiplexer configured to combine the plurality of optical signals onto an optical communication path;

an optical amplifier comprising;

a planar waveguide including a substrate, the substrate including a region doped with a fluorescent material, and

an optical fiber including a core doped with the fluorescent material, the optical fiber being optically coupled to the planar waveguide;

a demultiplexer configured to separate each of the plurality of optical signals based on their respective wavelength; and

a plurality of receivers configured to receive the separated optical signals and convert the optical signals into corresponding electrical signals.

13. A wavelength division multiplexing transmission system in accordance with claim 12, wherein the optical amplifier further comprises:

a first coupler configured to combine a first input optical signal and a first pump light onto a first optical communication path portion, the first optical communication path portion being coupled to the planar waveguide;

a second optical coupler being configured to combine a second input optical signal and a second pump light onto a second optical communication path portion, the second optical communication path portion being coupled to the optical fiber.

14. A wavelength division multiplexing transmission system in accordance with claim 13, wherein the optical amplifier further comprises:

an optical source; and

a third optical coupler having an input coupled to the source and first and second outputs, the first output being configured to supply the first pump light to the first optical coupler and the second output being configured to supply the second pump light to the second optical coupler.

15. A wavelength division multiplexing transmission system in accordance with claim 13, wherein the planar waveguide of the optical amplifier has an input portion and an output portion, the optical amplifier further comprising:

a first optical isolator coupled to the input portion of the planar waveguide via the first coupler;

an optical filter configured to substantially block transmission of the first pump light, the optical filter being coupled to the output portion of the planar waveguide; and

a second optical isolator coupled to the optical filter.

16. A wavelength division multiplexing transmission system in accordance with claim 13, wherein the optical amplifier further comprises:

a first optical source configured to output the first pump light, the first optical source being coupled to the first optical coupler; and

a second optical source configured to output the second pump light, the second optical source being coupled to the second optical coupler.

17. A wavelength division multiplexing transmission system in accordance with claim 13, wherein the first and second pump lights include light having a wavelength substantially equal to 980 nm.

18. A wavelength division multiplexing transmission system in accordance with claim 12, wherein the fluorescent material includes a rare earth element.

19. A wavelength division multiplexing transmission system in accordance with claim 18, wherein the rare earth element includes erbium.

20. A wavelength division multiplexing transmission system in accordance with claim 12, wherein the optical amplifier is configured to receive an input optical signal and supply an output optical signal in response to the input optical signal, wherein when the input optical signal has an optical power of −

25 dBm and said input optical signal includes a plurality of optical signals having wavelengths in a range of 1528 nm to 1562 nm, an amount of gain associated with the optical amplifier is greater than or equal to 37 dB, and a variation of the gain is equal to or less than 1.1 dB over the range of 1528 nm to 1562 nm.

21. A wavelength division multiplexing transmission system in accordance with claim 12, wherein an input signal to the optical amplifier is supplied to the planar waveguide and an output signal of the optical amplifier is supplied from the optical fiber.

22. A wavelength division multiplexing transmission system in accordance with claim 12, wherein an input signal to the optical amplifier is supplied to the optical fiber and an output signal of the optical amplifier is supplied from the planar waveguide.