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Research On Directional Characteristics Of Dual-Frequency Interferometric Fiber Laser Acoustic Vector Sensor

Posted on:2017-12-10Degree:MasterType:Thesis
Country:ChinaCandidate:Y Q ZhaoFull Text:PDF
GTID:2348330503467111Subject:Engineering, optical communication and optical sensing
Abstract/Summary:PDF Full Text Request
The vector hydrophone is usually composed of a particle velocity(acceleration)sensor with a dipole directivity and a traditional nondirectional sound pressure sensor.The particle acceleration sensor with vector detection capability is the core component. Dual-polarization fiber laser has been shown to be easy for demodulation implementation and reuse, compact in structure and high sensitive for optical fiber sensing applications. However, so far, there are few reports on their ability for vector detection.This thesis focuses on dual-polarization fiber laser sensors, which has carried out the following research, and achieved certain results:First, according to the requirement of experiments, a dual-polarization fiber laser with length of 10.5 mm is fabricated.Under the condition of near field sound source,the directivity characteristics of a dual-polarization fiber laser based acoustic pressure sensor is tested. The results show that, the directivity of acoustic pressure sensor is more omnidirectional when the frequency is lower.Second, a dual-polarization fiber laser based acceleration sensor is proposed and realized. Through lateral displacement restriction of the mass block, the measurement of acceleration vector is demonstrated. As the core component of the optical fiber acoustic vector sensor, although there is no special optimization design for the structure, the directional performance is similar to that of commonly used standard acceleration meter(4384V, B & K). It shows a good "8"- shaped directivity and a flat frequency response of 39.24 kHz/(m/s2) below 1 kHz.Third, MATLAB based simulation of minimum variance distortionless response(MVDR) algorithm is employed to sharpen the directivity of the fiber-optic vector sensor and estimate the direction of arrival(DOA). The natural directivity of an acoustic vector sensor is in "8" shape and the main beam width is around 90?, which only allows a rough estimation of DOA. Sharpened by the MVDR algorithm, the main beam width of the directivity is about 10? with a directivity index of 43.7 dB,making two uncorrelated signals with horizontal angle greater than 20?distinguishable.
Keywords/Search Tags:vector sensor, fiber laser, acceleration sensor, directivity
PDF Full Text Request
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