Study on Ammonia-N Degradation Monitoring by Analyzing Long-Period Fiber Grating Spectrum Character
LIU Hong-yue1, LIANG Da-kai1, ZENG Jie1, CAO Zhi-bin2, ZENG Jian-min3
1. Ministry of Education Key Laboratory of Vehicle Structure and Control, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China 2. College of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China 3. Ministry of Education Key Laboratory of New Processing Technology for Nonferrous Metals and Materials, Guangxi University, Nanning 530004, China
Abstract：In the present paper, the principle of a long-period fiber grating (LPFG) ammonia-nitrogen degradation monitoring sensor was discussed in detail firstly based on a sensitive characteristic that the resonance spectrum of long-period fiber grating changes with refractive index in external environment. The relationship between the resonance peaking wavelength of long-period fiber grating and the concentration of ammonia-nitrogen solutions was also analyzed detailedly. Then, the long-period fiber grating spectrum measurement technology was selected to obtain long-period fiber grating spectrum curves corresponding to seven different kinds of concentration of ammonia-nitrogen solutions, and the resonance wavelengths increased with the increase in the concentration of ammonia-nitrogen solutions. The variations of the resonance wavelength decreased from 2.707 to 0.068 nm and had a relatively good corresponding relationship with the concentration values of ammonia-nitrogen solutions. The responsivity of this correlation is 52.78 pm·mg-1·L. The concentration of ammonia-nitrogen solutions was acquired exactly through the way of monitoring the changes of the spectrum attribute, at the same time, the process and the extent of ammonia-nitrogen wastewater degradation were estimated. This method, which can directly monitor the concentration of ammonia-nitrogen solutions, is simple and easy to operate. The measurement and transmission section of the system are completely composed of optical fiber, which can avoid the electronic interference. There is no necessary to use chemic reagent to sign the solutions, which are going to be degraded. In conclusion, the late-model long-period fiber grating ammonia-nitrogen degradation monitoring system could achieve a real time, rapid, accurate and long distance measurement.
