Raman-based utility optical amplifier

• US 6,433,920 B1
• Filed: 09/18/2000
• Issued: 08/13/2002
• Est. Priority Date: 04/27/2000
• Status: Expired due to Fees

• Current Assignee: JDS Uniphase Corporation (Lumentum Holdings Inc.)
• Original Assignee: JDS Uniphase Corporation (Lumentum Holdings Inc.)
• Inventors: Welch, David F., Ziari, Mehrdad, Lang, Robert J., Vail, Edward C.
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US09/664,986
• Time in Patent Office: 694 Days
• Field of Search: 359/334, 359/337, 359/337.1
• US Class Current: 359/334
• CPC Class Codes: H01S 2301/04 Gain spectral shaping, flattening
• CPC Class Codes: H01S 3/005 Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B
• CPC Class Codes: H01S 3/0078 Frequency filtering
• CPC Class Codes: H01S 3/094003 the pumped medium being a fibre
• CPC Class Codes: H01S 3/094073 Non-polarized pump, e.g. depolarizing the pump light for Raman lasers
• CPC Class Codes: H01S 3/09415 the pumping beam being parallel to the lasing mode of the pumped medium, e.g. end-pumping
• CPC Class Codes: H01S 3/302 in an optical fibre
• CPC Class Codes: H01S 5/1096 in a single cavity
• CPC Class Codes: H01S 5/146 using a fiber as external cavity
• CPC Class Codes: H01S 5/4025 Array arrangements, e.g. constituted by discrete laser diodes or laser bar H01S5/42 takes precedence

Abstract

An optical amplifier with a flattened wideband response is obtained by coupling counter-propagating pumping energy into an optical waveguide to cause Raman amplification in the optical waveguide, and by reflecting an amplified signal received from the optical waveguide into an output waveguide using a reflector having a spectral characteristic that is complementary to the spectral gain characteristic of the Raman amplification.

Claims

1. An optical amplifier comprising:

an optical waveguide having a first end and a second end, wherein a signal is received through the first end, is amplified by Raman amplification as it propagates within the optical waveguide from the first end to the second end, and is transmitted through the second end;

a pumping energy source optically coupled to the optical waveguide to provide pumping energy that causes the Raman amplification to have a spectral gain characteristic; and

a reflector having an input optically coupled to the second end of the optical waveguide and having an output, wherein the reflector receives the amplified signal through the input and reflects it through the output, and wherein the reflector has a continuous response property that is complementary to the spectral gain characteristic of the Raman amplification for modifying the amplified signal.

2. An optical amplifier according to claim 1 wherein the pumping energy has a plurality of wavelengths.

3. An optical amplifier according to claim 1 wherein the pumping energy source comprises one or more pump lasers that provide pumping energy that is substantially depolarized.

4. An optical amplifier according to claim 3 wherein the pumping energy source comprises a combiner that combines pumping energy having a plurality of polarization orientations received from the one or more pump lasers.

5. An optical amplifier according to claim 3 that comprises a depolarizer interposed between the optical waveguide and the one or more pump lasers.

6. An optical amplifier according to claim 3 that comprises a polarization rotator, and wherein at least part of the pumping energy from one pump laser passes through the polarization rotator.

7. An optical amplifier according to any one of claims 3 through 6 wherein the one or more pump lasers operate in a coherence collapse mode.

8. An optical amplifier according to claim 1 wherein the reflector comprises an optical filter with transmissive properties that cause, at least in part, the property of the reflector that is complementary to the spectral gain characteristic of the Raman amplification.

9. An optical amplifier according to claim 1 wherein the reflector comprises a multilayer dielectric material.

10. An optical amplifier according to claim 1 wherein the reflector comprises a reflective fiber grating and an optical circulator.

11. An optical amplifier according to claim 1 wherein the reflector comprises a fused coupler with a respective reflective grating in each output arm of the coupler.

12. An optical amplifier according to claim 1 wherein the reflector comprises one or more reflective gratings.