Apparatus for characterizing fiber bragg gratings

• US 7,480,034 B2
• Filed: 05/07/2008
• Issued: 01/20/2009
• Est. Priority Date: 05/15/2004
• Status: Expired due to Fees

• Current Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Original Assignee: Board of Trustees of the Leland Stanford Junior University (Stanford University)
• Inventors: Kino, Gordon S., Digonnet, Michel J. F., Ozcan, Aydogan
• Primary Examiner(s): Chowdhury; Tarifur
• Assistant Examiner(s): COOK, JONATHON
• Application Number:
  US12/116,871
• Publication Number:
  US 20080204726A1
• Time in Patent Office: 258 Days
• Field of Search: 356/73.1, 356/364
• US Class Current: 356/73.1
• CPC Class Codes: G01M 11/3145 Details of the optoelectronics or data analysis
• CPC Class Codes: G01M 11/3172 Reflectometers detecting the back-scattered light in the frequency-domain, e.g. OFDR, FMCW, heterodyne detection
• CPC Class Codes: G02B 2006/02166 Methods of designing the gratings, i.e. calculating the structure, e.g. algorithms, numerical methods
• CPC Class Codes: G02B 6/0208 characterised by their structure, wavelength response G02B6/02114, G02B6/02171, G02B6/02195 take precedence; multiple layer cores or claddings G02B6/036, protective coverings G02B6/4429

Abstract

An apparatus characterizes at least one fiber Bragg grating. The apparatus includes a laser pulse source, an optical spectrum analyzer, and multiple optical paths. A first optical path includes a pulse stretcher and an attenuator. A second optical path optically coupled to the first optical path includes a mirror. A third optical path optically coupled to the first optical path includes a first fiber Bragg grating. A fourth optical path is optically coupled to the second optical path, the third optical path, and the optical spectrum analyzer. A fifth optical path optically coupled to the laser pulse source and the optical spectrum analyzer includes a delay line.

Claims

1. An apparatus for characterizing at least one fiber Bragg grating, the apparatus comprising:

a laser pulse source, the laser pulse source generating at least one input laser pulse;

an optical spectrum analyzer;

a first optical path optically coupled to the laser pulse source, the first optical path comprising a pulse stretcher and an attenuator, wherein a first portion of the input laser pulse propagates from the laser pulse source and is stretched by the pulse stretcher and is attenuated by the attenuator;

a second optical path optically coupled to the first optical path and comprising a mirror, wherein a first portion of the stretched and attenuated laser pulse from the first optical path is reflected from the mirror;

a third optical path optically coupled to the first optical path and comprising a first fiber Bragg grating, wherein a second portion of the stretched and attenuated laser pulse from the first optical path is reflected from the first fiber Bragg grating;

a fourth optical path optically coupled to the second optical path, the third optical path, and the optical spectrum analyzer, wherein the reflected pulse from the mirror and the reflected pulse from the first fiber Bragg grating propagate to the optical spectrum analyzer; and

a fifth optical path optically coupled to the laser pulse source and the optical spectrum analyzer, the fifth optical path comprising a delay line, wherein a second portion of the input laser pulse propagates from the laser pulse source along the fifth optical path to the optical spectrum analyzer.

2. The apparatus of claim 1, further comprising a sixth optical path optically coupled to the first optical path and the fourth optical path, the sixth optical path comprising a second fiber Bragg grating, wherein a third portion of the stretched and attenuated laser pulse from the first optical path is reflected from the second fiber Bragg grating, the reflected pulse from the second fiber Bragg grating propagating to the optical spectrum analyzer.

3. The apparatus of claim 1, wherein the laser pulse source comprises a mode-locked laser with a temporal width between approximately 2 picoseconds and approximately 4 picoseconds.

4. The apparatus of claim 1, wherein the optical spectrum analyzer has a resolution less than or equal to 10 picometers.

5. The apparatus of claim 1, wherein the pulse stretcher comprises a single-mode fiber optic cable which broadens the temporal width of a pulse propagating therethrough by a factor of approximately 2 to 5.

6. The apparatus of claim 1, wherein the attenuator is greater than approximately 20 dB.

7. The apparatus of claim 1, wherein the mirror comprises a bare fiber end.

8. The apparatus of claim 1, wherein the mirror comprises a mirrored fiber end.