Rearch Of Fiber Hydrophone In Wireless Sensor Networks

The technology of information may be the greatest invention in the 21 century and now still progresses rapidly. And meanwhile the requirement for information acquisition is more strictly. So a new approach, which calls wireless sensor networks or WSNs, is developed with the development of sensing technology, micro-electron technology, embedded system technology and network technology. It has been proofed effective to be used to detect and monitor the target area, where is extremely difficult for human being to reach, such as ocean, jungle, battlefield, or highly radioactive and contaminated environment, both in theory and application. Since its representative paper was published in 1999, it has been strongly studied by both foreign and domestic institutes and has getten some principial success. It is sure that it will have promising application future and potential value in the field such as military, public security, environment protection, health care, plant diseases and insect prevention, anti-terrorist, and anti- disaster. In the other hand, fiber hydrophone is the trend of the tomorrow hydrophone. Compared with traditional piezoelectric needle and membrane hydrophone with PVDF (Polyvinylidene Fluoride), the fiber optic hydrophone's sensitivity is 2 or 3 orders higher. Meanwhile, the fiber optic hydrophone has prominent advantages in anti-electromagnetic interference, weight, and volume. Furthermore when taking advantage of modern optical communication technology, it is easy to integrate and form hydrophone array. So long distance monitoring becomes reality. Based on two consideration described above, as well as the principle of the national"863"strategic plan and"11.5"plan that strengthening the research about detecting submarine active target and monitoring the ocean water quality, this project adopts a creative idea that combines their advantages together. In the other word, it uses the fiber optic senor to detect sound signal, and uses wireless sensor network to transfer the sound signal that detected. Hope that from this way, we could continuously monitor the target area. The theoretically analysis and experimental result also suggests that the scheme we present work well.In the paper, we mainly discuss the fiber sensing component. It takes responsibility for providing sound signal which is high SNR (signal and noise ratio) and satisfies the specific electrical demands. This paper includes as follows:Broadly analyze the fiber sensing technology that currently exists. Then we adopt the Mach-Zehnder interferer with 3×3 coupler after full comparion. Meanwhile, we do theoretical analyze for it in detail.Broadly analyze opto-eletronics convert circuit. And then design the specific circuit which satisfies our project's application.Theoretical analyze the two currently and customarily used demodulation arithmetics about 3×3 coupler scheme in detail. And then we present the improved arithmetic, which is more immune to disturbance, and more effective. So that it is suitable for microprocessor (AVR).At last, we get conclusion that: the Mach-Zehnder interferer with 3×3 coupler is a relatively excellent approach for our project. We use software to realize the demodulation, so that it is not only flexible but also stable.