DISTRIBUTED BRILLOUIN SENSING SYSTEMS AND METHODS USING FEW-MODE SENSING OPTICAL FIBER
First Claim
1. A distributed Brillouin optical fiber sensing system, comprising:
- a sensing optical fiber configured to support a fundamental guided mode and at least one higher-order guided mode;
a pump light source configured to introduce pump light into one of the guided modes to define a pump light guided mode, the pump light forming a Brillouin dynamic grating (BDG);
a probe light source configured to introduce input probe light into one or more of the guided modes other than the pump light guided mode to create reflected probe light from the BDG, with the reflected and input probe light shifted in frequency by a Brillouin frequency shift; and
a receiver optically coupled to the sensing optical fiber and configured to detect the reflected probe light to determine a Brillouin frequency shift, a reflection location of the probe light, and the wavelength separation between the probe and pump lights, said receiver being configured to determine simultaneously temperature and strain in the sensing optical fiber as a function of distance along the sensing optical fiber.
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Abstract
Some embodiments of a distributed Brillouin optical fiber sensing system employs a sensing optical fiber that supports two or more (i.e., few) guided modes. Pump light supported by one of the guided modes is used to form a dynamic Brillouin grating (DBG). Probe light supported by at least one of the other guided modes interacts with the DBG to form reflected probe light that is received and analyzed to determine a Brillouin frequency shift, a phase matching wavelength between probe and pump light, a reflection location, which in turn allows for making a measurement of at least one condition along the sensing optical fiber. Supporting the pump and probe light in different guided modes results in the optical fiber sensing system being able to simultaneously measure temperature and strain and having a higher spatial resolution than sensing systems where the pump light and probe light share a common guided mode.
14 Citations
20 Claims
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1. A distributed Brillouin optical fiber sensing system, comprising:
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a sensing optical fiber configured to support a fundamental guided mode and at least one higher-order guided mode; a pump light source configured to introduce pump light into one of the guided modes to define a pump light guided mode, the pump light forming a Brillouin dynamic grating (BDG); a probe light source configured to introduce input probe light into one or more of the guided modes other than the pump light guided mode to create reflected probe light from the BDG, with the reflected and input probe light shifted in frequency by a Brillouin frequency shift; and a receiver optically coupled to the sensing optical fiber and configured to detect the reflected probe light to determine a Brillouin frequency shift, a reflection location of the probe light, and the wavelength separation between the probe and pump lights, said receiver being configured to determine simultaneously temperature and strain in the sensing optical fiber as a function of distance along the sensing optical fiber. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A distributed Brillouin optical fiber sensing system, comprising:
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a sensing optical fiber configured to support at least first and second guided modes; a first pump light source optically coupled to the sensing optical fiber and configured to generate first pump light that travels in the sensing optical fiber in the first guided mode and forms a Brillouin dynamic grating (BDG) that contains information of a local Brillouin frequency of the sensing optical fiber; a probe light source optically coupled to the sensing optical fiber and configured to generate pulsed probe light that travels in the sensing optical fiber in the second guided mode, with the pulsed probe light having a wavelength selected so that at least a portion of the pulsed probe light reflects from the Brillouin dynamic grating and includes information about the local Brillouin frequency and a probe-light reflection location; and a receiver optically coupled to the sensing optical fiber and configured to receive the reflected probe light and determine the local Brillouin frequency, the reflection location, the wavelength separation between pump and probe lights, and at least two condition along the sensing optical fiber wherein the at least two conditions include at of temperature and strain as a function of distance from an input/output end of the sensing optical fiber. - View Dependent Claims (10)
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11. A method of sensing at least two conditions along a sensing optical fiber, comprising:
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sending pump light down the optical fiber in only a first guided mode supported by the sensing optical fiber to create a Brillouin dynamic grating; sending pulsed probe light of a first frequency down the optical fiber in at least a second guided mode supported by the sensing optical fiber to obtain reflected probe light from the Brillouin dynamic grating, the reflected probe light having a second frequency shifted relative to the first frequency by a frequency shift and having a reflection location; and analyzing the reflected probe light shifted frequency, the reflection location, and the wavelength separation between probe pump light to determine the at least two conditions. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A sensing optical fiber comprising:
- a few-moded core with a core radius of 4 μ
m≦
r≦
10 μ
m and F factor (μ
m2) is 76 μ
m2to 306 μ
m2.
- a few-moded core with a core radius of 4 μ
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18. A sensing optical fiber comprising:
- a few-moded core with a core Δ
between 0.25% to 1%, and the core radius r is between 4 to 10 microns the F-factor 100 μ
m 2≦
F-factor≦
200 μ
m2 and effective area Aeff of 50 μ
m2≦
Aeff≦
150 μ
m2.
- a few-moded core with a core Δ
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20. A distributed Brillouin optical fiber sensing system, comprising:
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a sensing optical fiber configured to support a fundamental guided mode and at least one higher-order guided mode, said sensing fiber having core radius of 4 μ
m≧
ro≧
10 μ
m and F factor (μ
m2) of 76 μ
m2to 306 μ
m2;a pump light source configured to introduce pump light into one of the guided modes to define a pump light guided mode, the pump light forming a Brillouin dynamic grating (BDG); and a probe light source configured to introduce input probe light into one or more of the guided modes other than the pump light guided mode to create reflected probe light from the BDG, with the reflected and input probe light shifted in frequency by a Brillouin wavelength shift. - View Dependent Claims (19)
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Specification