Intensity distribution type demodulation system and distribution type sensing optical fiber

A technology of sensing optical fiber and demodulation system, which is applied in the direction of transmitting sensing components, cladding optical fibers, optical waveguides and light guides using optical devices, can solve problems such as high cost, avoid fusion splicing loss, high capacity, and ensure long distance. Effect

Active Publication Date: 2014-12-03
LASER RES INST OF SHANDONG ACAD OF SCI
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0005] In order to solve the problems of engineering application convenience, long-distance monitoring, high spatial resolution, and high cost of distributed measurement, we combine the advantages of optical time-domai

Method used

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  • Intensity distribution type demodulation system and distribution type sensing optical fiber
  • Intensity distribution type demodulation system and distribution type sensing optical fiber
  • Intensity distribution type demodulation system and distribution type sensing optical fiber

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Embodiment 1

[0053] like image 3 As shown, a light intensity distributed demodulation system, which includes distributed feedback semiconductor lasers, acousto-optic modulators, circulators, couplers, distributed sensing fibers, photodetectors and light intensity demodulation devices; narrow line A wide (f rep =n / 2Lc, where n is the refractive index of the fiber, L is the length of the fiber, c is the speed of light in vacuum, the pulse width of the pulsed laser is W, and the pulsed laser enters the C of the circulator 1 end, through the C of the circulator 2 The end enters the sensing fiber, traverses the first grating, the second grating, the third grating in turn, until the Nth grating, because the reflectivity of the optical fiber is 0.1%-1%, most of the light passes through the grating and continues to propagate forward , only a small amount of light is reflected by the grating to the C of the circulator 3 end, reflected light from the circulator's C 3 The end enters the unbalan...

Embodiment 2

[0073] The similarities between this embodiment and Embodiment 1 will not be repeated, and the difference is that: Figure 6 As shown, the unbalanced interferometer includes a third coupler and a fourth coupler connected to the third coupler; the reflected light from the C of the circulator 3 terminal into the third coupler's P 31 After the end, it is divided into two paths, one path passes through the P of the third coupler 32 terminal into the fourth coupler’s P 41 end, the other from the P of the third coupler 33 The terminal enters the P of the fourth coupler through a 10m delay fiber 42 end, the two beams of light are at the P of the fourth coupler 43 After the end interference, it is sent to the photodetector.

Embodiment 3

[0075] The similarities between this embodiment and Embodiment 1 will not be repeated, and the difference is that: Figure 7 As shown, the unbalanced interferometer includes a fifth coupler and a third Faraday rotating mirror connected to the fifth coupler; the reflected light from the C of the circulator 3 terminal into the fifth coupler's P 51 After the end, it is divided into two paths, one path passes through the P of the fifth coupler 54 end into the 80m delay fiber and enter the P of the fifth coupler 52 end, the other way through the P of the fifth coupler 55 end reaches the third Faraday rotating mirror and reflects back to the P of the fifth coupler 55 terminal, the P of the fifth coupler 52 The optical signal output from the terminal is connected with the fifth coupler P 55 end of the return light at the fifth coupler P 53 After interference at the end, it is sent to a photodetector.

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Abstract

A distribution type sensing optical fiber is characterized in that thousands of fiber gratings with ultra-low reflectance are carved on a common single-mode fiber, so that the common single-mode fiber and the fiber gratings are integrated; the reflectance R of the fiber gratings is set to be 0.1-1%, and accordingly multi-path reflection is effectively lowered. An intensity distribution type demodulation system comprises a distribution type feedback semiconductor laser device, an acousto-optic modulator, a circulator, a coupler, the distribution type sensing optical fiber, a photoelectric detector and an intensity modulation device. The distribution type feedback semiconductor laser device sends out continuous laser into the acousto-optic modulator, the laser is modulated into pulse laser with the pulse width of W, the pulse laser enters the circulator and sequentially travels through a first grating, a second grating, a third grating to the Nth grating on the distribution type sensing optical fiber, reflected light enters an unbalance interferometer from the C3 end of the circulator for interference, interference light output by the unbalance interferometer enters the photoelectric detector, and the photoelectric detector outputs electric signals to an intensity demodulation device.

Description

technical field [0001] The solution relates to a distributed acoustic wave monitoring technology, in particular to a light intensity distributed demodulation system and a distributed sensing optical fiber. Background technique [0002] At present, fiber optic distributed sensing technology includes fiber optic double interferometer technology, fiber Bragg grating quasi-distributed sensing technology and optical time domain reflectometry technology. Optical fiber double interferometer technology uses Sagnac–Sagnac, Sagnac–MZ, Sagnac–Michelson and other interferometric schemes to realize distributed testing. The optical path design and demodulation algorithm are complex, and there are many difficult problems in engineering practical applications. [0003] Fiber Bragg grating quasi-distributed sensing technology uses the reflection of fiber Bragg grating to realize the distributed monitoring of physical quantities. In previous patents and applications, it mainly uses the wavele...

Claims

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Application Information

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IPC IPC(8): G02B6/02G01D5/26
Inventor 尚盈王昌刘小会王晨宋志强
Owner LASER RES INST OF SHANDONG ACAD OF SCI
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