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Long-distance Fiber-optic Sensor System

Posted on:2009-03-02Degree:MasterType:Thesis
Country:ChinaCandidate:X D LuoFull Text:PDF
GTID:2208360245960899Subject:Optical Engineering
Abstract/Summary:PDF Full Text Request
With the rapid development of large architecture, long distance pipeline and railroad, oil /gas field etc in China, it is essential to research advanced long distance sensing systems to ensure the security and monitor the breakage of these projects. Compared with traditional electric sensor, fiber sensor has the advantages of corrosion resistance, anti-electromagnetic interference, low attenuation, broad bandwidth etc. Especially, the quasi-distributed and distributed sensing system can easily transmit the sensor signal along a single long distance fiber with many sensors. The thesis researches the quasi-distributed system based on FBG and distributed system based onΦ-OTDR respectively, and realizes their sensing along long distance.Firstly, the principles and application of FBG andΦ-OTDR sensing systems are analyzed, and the existing methods of long distance fiber sensing systems are investigated and compared. Optical fiber amplification technology is analyzed and compared, and then EDFA and FRA are chosen to apply to the long distance sensing system.Secondly, a tunable fiber ring laser and long distance FBG sensing system are designed and constructed. A novel method with EDF amplification and dual-wavelength Raman amplification is proposed. Experimental results show that an excellent optical SNR of ~57dB has been achieved for a 100km transmission distance. Then the temperature sensing and static strain sensing experiments are carried out with sensing system based on a fiber ring laser and swept laser Si720 respectively,and the results demonstrate that the feasibility of the 100km sensing system.Finally, aΦ-OTDR sensing system based EDFA is designed and constructed. The Brillouin threshold power of the sensing fiber is analyzed and measured, fixing on the max-power of sensing signal. Then the disturbing experiments are carried out with different power of EDFA, and the advantage and disadvantage of the sensing system based EDFA are analyzed and compared. TwoΦ-OTDR sensing systems based forward FRA and bi-directionally FRA respectively are designed and constructed. Then the disturbing sensing experiments are carried out ,respectively. Experimental results show that an optical SNR of 6dB has been achieved for a 50km transmission distance.
Keywords/Search Tags:optical fiber sensor, Fiber Bragg Gate, Φ-OTDR, fibere amplification, long distance sensor
PDF Full Text Request
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