The Research Of Theory And Application Of Distributed Mach-Zehnder Interferometer

Optical fibre sensing technology has been expanding rapidly in the latest decades, and is playing an important role in the area of military, industry and scientific research. It possessed the outstanding advantages based on its high sensitivity, widely dynamic range and immunity to electromagnetic interference. In various kinds of fiber sensor including intensity, frequency, wavelength and polarization modulation, the optical fiber interferometer sensor had the most sensitive. Moreover, the distributed optical fiber interferometer vibration sensor could achieve continuous and high sensitive detecting and locating of the vibration signals, so it has the broad application prospect. This paper conducted research and discussion on several fundmental problems of optical fibre sensing. The paper is composed of 7 parts as listed below:(1) Introduction.(2) The status and trends of real-time monitoring system for pipeline leakage. The simple explanation of distributed optical fiber sensor.(3) The design for accurately controlling output and frequency of the laser diode was invented in interferometic optical fibre sensing.(4) The modulation and demodulation theory of the optical fiber interferometer sensor had been deduced through theoretical and experimental analysis.(5) Research on detection and signal processing system of optical fiber sensor.(6) Conclusion.In the first part, the project was introduced simply from background and task. In the second part, on the basis of referneces, the author gave an overview of status and trends of real-time monitoring system for pipeline leakage. In the third part, after a simple explanation of Optical fiber sensor, emphasis was given on research of important technology of distributed optical fiber interferometer sensor. In the fourth part, through theoretical and experimental analysis, the operation amplifier with high S/N, and a semiconductor cooler were used. A laser power driving system was invented. The experimental data indicate the method is not only simple, but also highly accurate and stable in terms of temperature control. The application maintains the output wavelength of the laser diode at a constant level and assures the measure accuracy in optical fiber interferometer sensor (OFIS). In the fifth part of the paper, the modulation and demodulation theory of the optical fiber interferometer sensor had been deduced and analyzed. Designed the scheme of signal demodulation, and illuminated the characteristic of 3×3 couplers demodulation method by this experiment. Introduced and discussed the effects of the phase demodulation methods using the Labview software. In the sixth part, the author had paid much concern on the hardware realization of the data processing system, which consists of high performance DSP chips, CPLD and USB2.0 interface. Also, each part of the realization is introduced particularly, including chip choosing, circuit connecting and the software program. On the basis of the hardware platform, the author realized signal processing of the child system of output optical power detection. At the end of this paper, a roughly conclusion was given based on the experimental result and corresponding theoretical analysis.