Distributed Fiber Bragg Grating Sensor System Research Based On TDM

Fiber Bragg grating (FBG) sensors has become the focus in sensors study field. It has many special advantages such as immunity of electromagnetic interference, high accuracy, good stability, reusability, and so on. In particular, the reusability is particularly prominent. The use of multiple fiber Bragg grating sensors, distributing sensor networks, enabling multi-point detection, plays an important role in monitoring of large and complex structures in practical applications. In time-division multiplexing sensor network, the number of sensors is no longer limited by light source bandwidth and dynamic range of the measured object. In theory the number of reusable sensor is very considerable, and the series topology makes power efficiency high. In this paper, based on time division multiplexing fiber grating distributed sensing system is studied. The primary achievements in this paper are as follows:1. The characteristics, classification of FBG and its application in the field of sensor is summarized. The demodulation and multiplexing of FBG sensor and current research directions are introduced too.2. The theory of fiber grating sensor is expounded. The coupled mode theory of FBG, the transmission characteristics and characteristics of chirped fiber Bragg grating are analyzed; the sensing principle of FBG is analyzed theoretically; the demodulation technique of FBG sensor and distributed multiplexing fiber Bragg grating sensor network are also introduced.3. The characteristics of ultra-low reflectivity FBG with series topology is analyzed theoretically and simulated. Then a TDM distributed fiber Bragg grating sensor system is designed. The using matched FBG demodulation technique effectively avoids FBG stress, temperature cross-sensitivity effect. The simulation proves the program can be used for long-distance, high-density sensor measurement. In the case of the first FBG sensor probe peak reflectivity R=-40dB, the distance between adjacent sensor probes d=1km, the system can multiplexed128sensor probes, and the sensing distance can achieve128km.4. Matched FBG demodulation technique is studied in-depth. Then the demodulation technique is analyzed theoretically and simulated in the principle and structure. The experiments show that the demodulation technical has feasibility and good linearity effects.