Raman or erbium-doped fiber laser using few-mode fiber grating, and long-distance remote sensor for simultaneously measuring temperature and strain by separating temperature and strain components using the same

• US 20050259697A1
• Filed: 12/29/2004
• Published: 11/24/2005
• Est. Priority Date: 05/24/2004
• Status: Abandoned Application

• Current Assignee: Korea Advanced Institute of Science and Technology
• Original Assignee: Korea Advanced Institute of Science and Technology
• Inventors: Lee, Ju-Han, Han, Young-Geun, Lee, Sang-Bae, Kim, Sang-Hyuck
• Application Number:
  US11/024,991
• Publication Number:
  US 20050259697A1
• Time in Patent Office: Days
• US Class Current: 372/6
• CPC Class Codes: H01S 3/302 in an optical fibre

Abstract

Disclosed are a Raman or erbium-doped fiber laser using a few-mode fiber grating, and a long-distance remote sensor using the same that can simultaneously measure temperature and strain by separating temperature and strain components using Raman amplification or erbium amplification. When a multi-wavelength Raman or erbium-doped laser is configured by means of a short-period fiber grating serving as a few-mode fiber grating at one side of a resonator and a chirped fiber Bragg grating or tunable chirped fiber Bragg grating at the other side of the resonator, multi-wavelength laser signals are generated in different modes. Because wavelength shift and reflectivity vary with a change in temperature and strain, temperature and strain components can be simultaneously measured. Because an optical fiber of several tens of kilometers is used, it can be utilized as a sensing probe of the long-distance remote sensor.

Claims

1. A Raman or erbium-doped fiber laser using a few-mode fiber grating, comprising:

a resonator based on multi-wavelength Raman or erbium amplification using an optical fiber grating with at least two modes.

2. The Raman or erbium-doped fiber laser of claim 1, wherein the resonator comprises:

an optical fiber serving as a gain medium;

a mirror fiber grating formed at one end of the gain medium, the mirror fiber grating being configured by a chirped fiber Bragg grating or tunable chirped fiber Bragg grating of a wide wavelength band for performing a mirror function; and

at least one few-mode fiber grating formed at the other end of the gain medium, the few-mode grating being configured by a short-period or variable-period fiber grating for performing a mirror function and a temperature and strain sensing function.

3. The Raman or erbium-doped fiber laser of claim 2, wherein the optical fiber serving as a Raman gain medium is any one selected from a typical optical fiber, single mode fiber, dispersion shifted fiber, dispersion compensated fiber, PCF (Photonic Crystal Fiber), and HNLF (Highly Nonlinear Fiber).

4. The Raman or erbium-doped fiber laser of claim 2, wherein the length of the optical fiber serving as the gain medium is selected within the range between several kilometers and several hundred kilometers or more.

5. A long-distance remote sensor for simultaneously measuring temperature and strain by separating temperature and strain components using a Raman or erbium-doped fiber laser that uses a few-mode fiber grating, comprising:

a coupler connected to an output stage for receiving Raman laser pumping light;

an optical fiber serving as a gain medium extended from the coupler;

a mirror fiber grating formed between one end of the gain medium and the coupler, the mirror fiber grating being configured by a chirped fiber Bragg grating or tunable chirped fiber Bragg grating of a wide wavelength band for performing a mirror function; and

at least one few-mode fiber grating formed at the other end of the gain medium, the few-mode fiber grating being configured by a short-period or variable-period fiber grating for performing a mirror function and a temperature and strain sensing function.

6. The long-distance remote sensor of claim 5, wherein the optical fiber serving as a Raman gain medium is any one selected from a typical optical fiber, single mode fiber, dispersion shifted fiber, dispersion compensated fiber, PCF (Photonic Crystal Fiber), and HNLF (Highly Nonlinear Fiber).

7. The long-distance remote sensor of claim 5, wherein the length of the optical fiber serving as the gain medium is selected within the range between several kilometers and several hundred kilometers or more.

8. The long-distance remote sensor of claim 5, wherein the few-mode fiber grating with several resonant peaks in a wavelength range of the gain medium is repeatedly formed in an extension state so that Raman laser outputs having different wavelengths at different positions can be acquired.

9. The long-distance remote sensor of claim 5, wherein the few-mode fiber grating is configured so that a center wavelength of the few-mode fiber grating varies with a change in temperature and strain, and a Raman laser'"'"'s resonance wavelength varies with the few-mode fiber grating'"'"'s center wavelength and hence the Raman laser'"'"'s center wavelength varies at the output stage.