Research On The Driving Control System Of Steady-frequency For Light Source In Optical Fiber Gas Sensing

Optical fiber gas sensor is an emerging integrated detection technology. Because light-source decides its working patterns, signal processing methods, resolution, sensitivity and measurement precision, it is vital for the entire project to choose a suitable light-source and design the driving-control system of steady frequency in fiber-optic sensing. In this paper, The Distributed Feed-Back Laser Diode (DFB LD) is chosen as a light-source of the sensor, the analysis, research and design for its driving-control system of steady frequency and the correlative signal processing system is carried out in the text.Firstly, the article introduces the technique of optical fiber gas sensor, the development of the steady frequency light-source, and gives a detailed description of the development and status of the light-source's driving-control technology through the extensive reading and in-depth summarizing relevant documentation. After choosing the light-source, the article analyzes the theory and research content of the driving-control system of steady frequency.Secondly, by the analyzing in detail of the operation principles and characteristics of DFB LD, the article focuses on the framework of its driving-control system for technical analysis, and details lasers security strategy. It also analyzes the theory of Modulation technique and Harmonic Detection technique which involves in gas sensing.According to previous theoretical and technical analysis, the article proposes the whole framework of the driving-control system of steady frequency and the technical programmer of important function modular, and completes the design and development of the system circuit. The driving-control system of steady frequency includes several core module circuits, such as constant current (CC) source, automatic power control (APC) circuit, and automatic temperature control (ATC) circuit. It also includes some other security circuits such as slow-start circuit, current limit protection circuit and so on, which enhance the security and reliability of the entire driving-control system of steady frequency. Furthermore, according to the characteristics of optical fiber gas sensing, the paper analyzes and designs AC modulation circuit of LD, and signal processing circuit for gas detection.Finally, experiments and tests are made to validate the performance of the driving- control system of steady frequency and relevant signal processing circuit, which designed and developed in this paper. And then, chart of the relevant conduct data can be given and it shows that the design of driving-control system of steady frequency met requirements.