The Research And Design Of Fiber Microphone

As a communication device, microphone works on the condition of electric signals. It is widely used in many aspect due to its low cost. However, in certain circumstance such as strong magnetic field, underwater condition, the traditional device has some limitations. Fiber microphone which is corrosion resistant and anti-magnetic is theoretically and practically suitable for these harsh circumstance.This dissertation designs a Fiber Bragg Grating microphone and Fabry-Perot fiber white light interferometric microphone based on optical fiber sensing technology. The working principle of these two microphones are interprtated and the system structure are designed. Virtual hardware platform of voice sensing system is built by LabVIWE. Simulation of voice signal is accomplished by the software Matlab.In the Fiber Bragg Grating microphone, speech signal is generated in voice port. Sound field works on Fiber Bragg Grating through distilled water, thus, optic signal scatters on the surface of Fiber Bragg Grating. Once the Bragg condition is achieved, optic signal scattered from the Fiber Bragg Grating gradually accumulated to a reflection peak whose center wavelength is decided by Grating parameters. The wavelength is demodulated by building the virtual hardware platform.In the Fabry-Perot fiber white light interferometric microphone, the vibration mode of voice port is highly reflected. Even a small vibration could change the length of Fabry cavity. The light reflected from the Fabry cavity goes into the white light interferometer. The optic path difference of interferometer sensing arm and the Fabry-Perot cavity length is obtained for demodulation. For more accurate signal, peak-valley hybrid striped counting method is used to reduce the mutation of zigzag period. The voice signal acquired by virtual hardware platforms has better reliability.Figure[50] Table[4] parameters[56]...