A Fiber Bragg Grating Wavelength Demodulation Technique Based On High Birefringence Fiber Sagnac Interferometer

Fiber Bragg grating has been applied broader and broader because of its many advantages. To facilitate the broad use of this class of sensors, compact, rugged, wide range and low cost interrogation systems are required. The edge filter demodulation technic in which the FBG is interrogated by measuring the power of the output light has the advantages such as high demodulation speed, low cost, convenience and suitable for both static and dynamic measurement. In this paper, high birefringence fiber Sagnac interferometer is used as edge filter to interrogate both static and dynamic signal of FBG sensors. Moreover, by using wavelength multiplexer, a system has the ability of multi-wavelength interrogation and the advantages of all fiber design, wide demodulation range and high speed, has been designed and constructed. The main context includes: 1. The filtering character of high birefringence fiber Sagnac interferometer(high birefringence fiber loop mirror,i.e. Hi-Bi FLM) is studied theoretically and experimentally 2. Based on Hi-Bi FLM, a FBG interrogation system is built and applied to sense static and dynamic measuring object. 3. Based on Hi-Bi FLM and WDM, a FBG interrogation system with the ability of interrogate multi-wavelength is proposed and demonstrated. It is verified experimentally that both static and vibrating measurements can be achieved. 4. The temperature characteristic of Hi-Bi FLM is studied and several methods of temperature compensation is analyzed are proposed and studied.