Narrow bandwidth reflectors for reducing stimulated Brillouin scattering in optical cavities

Patent metadata

Field	Value
Publication number	US-9252559-B2
Application number	US-201213545497-A
Country	US
Kind code	B2
Filing date	Jul 10, 2012
Priority date	Jul 10, 2012
Publication date	Feb 2, 2016
Grant date	Feb 2, 2016

Abstract

An optical-fiber filter system to narrow a linewidth and to reduce noise fluctuations of an optical beam is provided. The optical-fiber filter system includes an optical fiber having a first end-face and an opposing second end-face, the first end-face and the second end-face setting a fiber length; a fiber Bragg grating having a first reflectivity positioned at the first end-face; and a reflector having a second reflectivity positioned at the second end-face. When the optical beam at a first frequency is coupled from a laser into one of the first end-face or the second end-face, a resonant cavity is established at the first frequency between the fiber Bragg grating and the reflector while Brillouin scattered light shifted from the first frequency within the optical fiber is transmitted through the fiber Bragg grating.

First claim

What is claimed is:

1. An optical-fiber filter system to narrow a linewidth and to reduce noise fluctuations of an optical beam, the optical-fiber filter system comprising:
an optical fiber having a first end-face and an opposing second end-face, the first end-face and the second end-face setting a fiber length;
a fiber Bragg grating having a first reflectivity positioned at the first end-face; and
a reflector having a second reflectivity positioned at the second end-face, wherein, when the optical beam at a first frequency is coupled from a laser into one of the first end-face or the second end-face, a resonant cavity is established at the first frequency between the fiber Bragg grating and the reflector while Brillouin scattered light shifted from the first frequency within the optical fiber is transmitted through the fiber Bragg grating.

2. The optical-fiber filter system of claim 1 , wherein the optical beam from the laser is configured to couple into the first end-face, the first end-face being an input end-face, the optical-fiber filter system further comprising:
a photodiode;
a circulator to direct the optical beam from the laser to the input end-face, and to direct an optical beam from the input end-face of the optical fiber to the photodiode;
a resonance tracking servo communicatively coupled to input a signal from the photodiode and to output a control signal to a phase controller; and
the phase controller configured to input the control signal from the resonance tracking servo and to modify the phase of the optical beam in the optical fiber based on the control signal.

3. The optical-fiber filter system of claim 1 , wherein the optical beam from the laser is configured to couple into the first end-face, the first end-face being an input end-face, the optical-fiber filter system further comprising:
an optical isolator to direct the optical beam from the laser to the input end-face;
a tap coupler to input the optical beam output from the second end-face of the optical fiber;
a photodiode to input a first portion of the optical beam from the tap coupler, wherein a second portion of the optical beam is output from the optical-fiber filter system;
a resonance tracking servo communicatively coupled to input a signal from the photodiode and to output a control signal to a phase controller; and
the phase controller configured to input the control signal from the resonance tracking servo and to modify the phase of the optical beam in the optical fiber based on the control signal.

4. The optical-fiber filter system of claim 1 , wherein the optical fiber is a first optical fiber having a first fiber length, wherein the fiber Bragg grating is a first fiber Bragg grating, the reflector is a first reflector, and the resonance cavity is a first resonance cavity, the optical-fiber filter system further comprising:
a second optical fiber having a first end-face and an opposing second end-face, the first end-face and the second end-face of the second optical fiber setting a second fiber length;
a second fiber Bragg grating having a third reflectivity and positioned at the first end-face of the second optical fiber; and
a second reflector having a fourth reflectivity and positioned at the second end-face of the second optical fiber, wherein, when an optical beam at the first frequency is coupled from the first optical fiber into one of the first end-face or the second end-face of the second optical fiber, a second resonant cavity at the first frequency is established between the second fiber Bragg grating and the second reflector, while Brillouin scattered light shifted from the first frequency within the second optical fiber is transmitted through the second fiber Bragg grating.

5. The optical-fiber filter system of claim 1 , wherein the fiber Bragg grating is a first fiber Bragg grating and the reflector is a second fiber Bragg grating, wherein when the optical beam is coupled from the laser into one of the first end-face or the second end-face, the resonant cavity at the first frequency is established between the first fiber Bragg grating and the second fiber Bragg grating, while the Brillouin scattered light shifted from the first frequency within the optical fiber is transmitted through the first fiber Bragg grating and the second fiber Bragg grating.

6. The optical-fiber filter system of claim 5 , wherein the optical fiber is a first optical fiber having a first fiber length, and the resonance cavity is a first resonance cavity, the optical-fiber filter system further comprising:
a second optical fiber having a first end-face and an opposing second end-face, the first end-face and the second end-face of the second optical fiber setting a second fiber length;
a third fiber Bragg grating having a third reflectivity and positioned at the first end-face of the second optical fiber; and
a second reflector having a fourth reflectivity and positioned at the second end-face of the second optical fiber, wherein, when an optical beam from the first optical fiber is coupled into one of the first end-face or the second end-face of the second optical fiber, a second resonant cavity is established at the first frequency between the third fiber Bragg grating and the second reflector, and Brillouin scattered light shifted from the first frequency within the second optical fiber is transmitted through the third fiber Bragg grating.

7. The optical-fiber filter system of claim 6 , wherein the optical beam from the laser is configured to couple into the first end-face of the first optical fiber, the first end-face being a first input end-face, wherein the optical beam from the first optical fiber is configured to couple into the first end-face of the second optical fiber, the first end-face of the second optical fiber being a second input end-face, the optical-fiber filter system further comprising:
a first photodiode;
a first circulator to direct the optical beam from the laser to the first input end-face, and to direct an optical beam from the first input end-face to the first photodiode;
a first resonance tracking servo communicatively coupled to input a signal from the first photodiode and to output a control signal to a first phase controller; and
the first phase controller configured to input the control signal from the first resonance tracking servo and configured to adjust a strain on the first optical fiber based on the control signal;
a second photodiode;
a second circulator to direct the optical beam from an output end-face of the first optical fiber to the second input end-face, and to direct an optical beam from the second input end-face to the second photodiode;
a second resonance tracking servo communicatively coupled to input a signal from the second photodiode and to output a control signal to a second phase controller; and
the second phase controller configured to input the control signal from the second resonance tracking servo and configured to adjust a strain on the second optical fiber based on the control signal.

8. The optical-fiber filter system of claim 6 , wherein the second reflector is a fourth fiber Bragg grating positioned at the second end-face of the second optical fiber, wherein when an optical beam from the first optical fiber is coupled into one of the first end-face or the second end-face of the second optical fiber, the second resonant cavity is established at the first frequency between the third fiber Bragg grating and the fourth fiber Bragg grating while the Brillouin scattered light shifted from the first frequency in the second optical fiber is also transmitted through the fourth Bragg grating.

9. The optical-fiber filter system of claim 8 , wherein the optical beam from the laser is configur

Assignees

• Narayanan Chellappan
• Sanders Glen A
• Strandjord Lee K
• Wu Jianfeng
• Honeywell Int Inc

Inventors

• Narayanan Chellappan
• Sanders Glen A
• Strandjord Lee K
• Wu Jianfeng

Classifications

• G01C19/727 Primary

  using a passive ring resonator · CPC title

• G01C19/721

  Details, e.g. optical or electronical details · CPC title

• H01S3/10023 Primary

  by functional association of additional optical elements, e.g. filters, gratings, reflectors · CPC title

• G02B6/29322

  Diffractive elements of the tunable type (G02B6/02195 takes precedence; optical modulation devices based on a change of the optical properties of the medium G02F1/00) · CPC title

• G02B6/02195

  characterised by means for tuning the grating · CPC title