No abstract

In this paper a new fiber-optic Microelectromechanical System (MEMS) acoustic sensor system for gunship acoustic detecting is developed. A novel MEMS acoustic sensor used in the system is designed. The sensor is based on extrinsic Fabry-Perot (FP) interferometer coupled to an external membrane for modulating the FP cavity length and a light--emitting diode (LED) as light source. The relation expression between displacement of cavity length and light intensity is deduced. Theoretical signal of the sensor is simulated.

The underwater opto-acoustic communication system for directional acoustic communication between an in-air platform and a submerged platform operating is important. The paper presents a new method to solve this problem with opto-acoustic technology, which combines high-energy laser, the opto-acoustic transmitter that optical energy is converted to acoustic energy at the water surface. The laser-based transmitter provides a versatile method for generating underwater sound. The acoustic pressure is linearly proportional to the laser power. The paper designed an experimental measurement system for the opto-acoustic communication. It made experiments for study on the waveform and spectrum characteristics of opto-acoustic signals. The paper also discuss the acoustic wave after optical breakdown in water with Nd:YAG laser pulses. The opto-acoustic signals can controll by adjusting the laser's parameters. The conclusion is that the opto-acoustic communication has some technical advantages. This system presents a change in the way communicational from the air.

Introducing a new intensity modulated optic microphone theory model, it can be used in infrasound sensor field. Single-mode optical fiber to transmit and receive light and optical lens to collimate is used to realize light intensity modulation, the system also contains MEMS membrane to be compatible with vibration displacement. Through the analysis of membrane size and the change of pressure, the related parameters about the sensitivity of fiber optic displacement sensor could be acquired. Simulation results show that the proper choice of parameters can make the sensitivity of sensor improve in orders of magnitude than traditional light intensity modulated methods.

Aiming at how to detect evaporation duct environment accurately in real time, method of detecting atmospheric duct by using laser technique was put forward. From the model of air refractive index of radar band, theoretical relationship between laser scattering properties of aerosol over the ocean and vertical change characteristics of the air humidity was established; judge whether to produce evaporation duct, through using laser to detect the echo signal characteristics of aerosol. The research content is an important complement for methods of atmospheric duct detection, and it can solve several common problems that atmospheric duct forecasting methods needs rigorous measuring conditions, its measurement results delay, it need be estimated by experience and detecting precision is not high, which has higher military application value.