Study On Fiber-Optic Acoustic Vibration Detection Systems And Distributed Vibration Sensing Technology

Acoustic belongs to the matter wave, and its essence is the particle vibration, stress, pressure, and other diverse forms in the elastic medium. In the research field of acoustics, the generation mechanism, the propagative form and detection method of acoustic wave are jointly involved. Acoustic detection technology is currently using acoustic signals propagate changes in elastic medium to detect the target sounding, accurate identification, location, etc.Fiber optic acoustic detection is a hot research field of fiber optic sensing currently. It can be used as hydrophone in the security systems with real-time detection and pre-warning of oil and natural gas pipe laying in the ocean and land, also can be used as fiber optic microphone made of Fiber Bragg Grating sensing probe primitives to the fiber grating center wavelength modulation to obtain the sensing information. The acoustic sensors not only have the characteristics of all fiber, high sensitivity and anti-jamming, but also have potential features of probe miniaturization, ease of wavelength division multiplexing (WDM) etc. Therefore, this paper studies on an acoustic vibration detection system with simple, stable structure and large range of frequency response, which has high sensitivity to weak vibration signals additionally. Moreover, as multi-point positioning and high sensitivity can be achieved simultaneously, this paper takes research on distributed interferometric fiber optic sensing technology.In this paper, there are several innovative aspects. The first is to propose the acoustic vibration detection system with the simple and stable structure, frequency response range and the faint sound of the vibration signal of high sensitivity. The second is a double-optical-path balanced detection method for the annular structure of the distributed vibration sensing system, combining with ring structure with double optical path balance detection method can be implemented and dc items completely filter out double the range of the interference signal at the same time, can also be a multipoint positioning. Then, the paper puts forward ring structure of distributed vibration sensing system of dual wavelength method by comparing the two light wave interference to obtain the phase of signal spectrum characteristics to implement multipoint positioning, algorithm is implemented easily. At last, the paper puts forward using high birefringence of photonic crystal fiber optic sensing optical fiber ring structure method. Thus, we can improve the sensitivity of optical fiber sensing without temperature compensation.